Abstracts of the Fourth Northern Lkhts Neuroscience SvmDosium: Pathobiohzv of Mental Retardation, Annual Meeting, Septemvder 12- 14, 1991, Gothenburg, Sweden J

I

Photochemically induced cortical infarction in rats: the cerebrovascular consequences and the significance of nimodipine on the infarct size Laursen* H , Hansen** AJ, Sheardown"'

M

* Institute of Neuropathology, University of Copenhagen, ** Novo Nordisk CNS S ~ b o r g Denmark , Photochemical cortical infarction and related changes of blood-brain barricr permeability (BBB) and brain specific gravity (SG) were investigated in rats. The influence of nimodipine on the infarct volume was also measured. Cortical infarction was induced by a 2 mm argon lascr beam (0.1 watts, 10 min) positioned on the parietal bone in animals given 20 mg/kg Rose-Bengal i.v. Histology and permeability of the BBB to serum proteins were evaluated in paraffin sections from 2 h to 3 wccks after thc insult. Thc infarcts consolidated after 7 days. Infarct volumes were measurcd in a group of laser treated animals givcn nimodipine 1 mg/kg i.p. 30 min after the laser treatment and once daily for thc subsequent 6 days. The area of damaged tissue was mcasurcd on a Lcitz texture analyzing system and the inParct volume was calculated by multiplying the sum of areas with the distance between sections measured, i.e. 200 pm. The serum proteins were demonstrated by an immunoperoxidasc technique. The specific gravity

was measured in a kerosene-nionobromobenLcnc gradient column. Al 2 h a necrotic center surrounded by a vacuolated border had formed in the cortex. The neurons were distorted at the border. At 24 h the lesion was infiltrated with granulocytes and thc center digcstcd by macrophages. After 3 weeks a cyst had formed. The blood-brain barrier was permeable to proteins at 2 h and protein extravasation and brain oedema reached a maximum at 24 h. On day 7, the serum proteins were confined to the center of the lesion and the specific gravity had normalized except for the very center. The volumcs of the infarcts were 3.5 mm3 i 0.35 and 2.93 mm3 f 0.29 (mean f s.e.) in controls and nimodipine treated animals respectively (n = 5 in each group, p = 0.30, t-test). The photochcmical infarction is inorphologically similar to the ischemic stroke lesion in man. In this study nimodipine did not seem to decrease infarct volume.

Cysteine sulfinate (CSA) is an unlikely mediator of cysteine (CYS) neurotoxicity in the immature rat brain Lehmann A, Orwar 0, Sandberg M Institute of Neurobiology, University of Gothenburg, S w e d e n Amino acids carrying two acidic groups arc excitatory and neurotoxic (excitotoxic). CYS is an exception to this rule? but it has been speculated that CYS excitotoxicity is mediated by the oxidized CYS analogucs CSA and/or cysteate. Dcspite the fact that this proposal was made two decades ago, it has nevcr been experimentally vcrified. The present study was thercfore initiated to determine the role of CSA and cysteatc in CYS toxicity. Four-days old rats were injected with CYS ( 1 mg/g; s.c.) and the cortical lcvcls of CYS, CSA an< cysleate were determined with reccntly developcd HPLC techniques. Ncuropathological changes induced by CYS, and the effects of the selective NMDA antagonist MK-801 (1 pg/g) or the specific non-NMDA antagonist NBQX (15 pg/g). were evaluated in animals fixed 24 h after injection. These were compared with the toxicity of CSA (3 mg/g; s.c.) which in some cases was administered after injection of MK-801 ( 1 pg/g). Within one h, [CYS] reached peak levels 19 times of control (absolute lcvelsz 10 pmol/g prot.). Cortical [CSA] increased in a delayed Fashion and was increased 17-fold (corresponding to approx. 0.1 pmol/g prot.) 6 h after CYS administration, but [cysteate] was not clcvated. CYS produced widespread damage which was most severe in the dorsolateral cortex and hippocampus. The distribution of the lesion appeared to relate to some extent to the pathways for bulk transport of fluids, i.c. to the ventricles and major bundles of axons. In this respect, CYS partly reproduced hypoglycemic injury. In agree-

ment with a recent report, MK-801 afforded complete protection against CYS toxicity. The notion that CYS toxicity is exclusively mediated by NMDA receptors is supported by the finding that NBQX failed to prevent the lesion. CSA caused a considerably more limited damage than CYS, and although CSA-induced lesions partly overlapped those produced by CYS, many disparities existed. For instance, CYS damaged the entire dorsolateral cortex, while CSA inflicted injury more specifically localized in the frontomedial, parahippocampal and temporal cortices. The medial habcnular nucleus, tectum, hypothalamus and cerebellum were lesioncd by CSA but not by CYS. Most importantly, in spite of the observation that CYS induced amuch more severedamage that could be totally blocked by MK-801, CSA toxicity was consistently ameliorated but nevcr abolished by this antagonist, indicating that CSA is a mixed receptor agonist. The biochemical findings suggest that although [CSA] was pronouncedly elcvated by CYS administration, the absolute levels were probably too low to produce toxicity. The differences in the distribution of damagc caused by thc toxins, as well as the diffcrcntial effects of MK-801, further indicate that CSA does not mediate CYS toxicity. The idcntity of the molecule mediating CYS cxcitotoxicity is unknown, but candidates include CY S-carbamate, S-carboxyCYS, S-sulfo-CYS and CYS itself.

95

Abstracts

Laminin p l - and collagen type IV gene expression in peripheral nerve: reinnervation compared to denervation

’ J, Sandberg’ M, Vuorinen3 V, Roytta ’ M Departments of ’ Pathology, Medical Biochemistry, Univer-

Siironen

sity of Turku, Left sciatic nerves of total number of 122 rats wcrc transected. In half of the animals, rcgencration was allowed to take place freely, whereas in the other half regeneration was prevented by suturing the transected ncrvc ends. The expression of basement membrane (BM) components; B 1 laminin and type IV collagen in the endoneurium was followed proximally and distally to the sitc of transection from 3 days until 8 weeks. For this purpose, thc cndoneuriums of the nerves were niicrosurically isolated from surrounding pcri- and epineurium, and studicd by Northern hybridization. In the proximal stumps of the dcncrvatcd as well as the freely regenerating nerves the expression of laminin and type 1V collagen was markedly increased and lasted from 3 days until 8 weeks. In the distal stump, close to the site of transection (2-7 mm) the expression of laminin and somewhat also that of type IV collagen was enhanced if frec axonal reinnervation was allowed and two major peaks of expression was observed, first on day 14, then on day 56. Further distally (10-15 nim), the expression of B 1 laminin and type IV collagen was similar in both experimental groups.

Neurosurgery, University of Helsinki, Finland

The cxprcssion was observed during the first two weeks. The prcscnt results show that laminin and type IV collagen cxprcssion wcrc markedly different in parts of rat sciatic nerve. Sincc the expression was strong also in the proximal stump it seems that losing the axonal contact is not essential to the expression of the B M components at mRNA level and that there is a continuing need for the BM components also in the proximal stump during peripheral ncrvc rcgcncration. The factors causing the peaks or cxprcssion due t o frcc axonal reinnervation may bc related to the axonal maturation. The first peak (on Day 7) may coincide with the arrival of the first axonal sprouts, while the other peak (on day 56) may coincide with the myclinisation of axons. Further distally, the cndoneurial cclls rcact in a similar fashion in both experimcntal groups. Thus, pcriphcral nerve reaction to an injury may he a stereotyphic one with onetime production of growthpromoting factors and axonal reinnervation is not essential to the expression of B1 l a n i i h and type IV collagen.

Brain malformation without mental retardation. I. Cerebral migration anomaly (heterotopic grey matter) Hori A Institute of Neuropathology, Medizinische Hochschule, Hannover, Germany Brains with nodular hctcrotopic grey matter were found in 0.72, (preliminary calculation) of a routine necropsy series. Rcvicw of the clinical files of thcsc patients’ histories rcvealed neither mental retardation nor epileptic fils; there was also n o evidence of disturbed social intcraction. Nccropsy rcvealed multiple heterotopic nodules located in the subcpendymal area of the posterior horn of the lateral ventricle, usually unilaterally, of an average size of about 1 cm in di-

ameter. They contained well differentiated magnoccllular and parvocellular neurons. The arrangement of the neurons occasionally siniulated, though irregular, cortical laminar structure. The favorable location of the heterotopias may explain heir clinical silence.

Hydrolethalus syndrome: brain pathology

’ A, Salonen’ R, Herva3 R, Haltia ’ M Departments of ’ Pathology, University of Helsinki,

Paetau

Obstetrics a n d Gynaecology, Helsinki University Central Hospi tal, 3Pathology, University of Oulu, Finland Hydrolethalus syndrome is an autosomal recessive lethal malformation syndrome with hydrocephalus, micrognathia, polydactyly, congenital heart defects and genitourinary anomalies as main features. It was recognized during a study on Mcckcl syndrome in Finland (Clin Genet 19: 321-330, 1981; J med Genet 27: 756-759, 1990). Almost 60 patients havc been detected in Finland, and only a few cases havc been reported from elsewhere. All cases havc a severe malformation of the central nervous system. Most of them display a massive intracranial accumulation of cerebrospinal fluid. Widely separated cerebral hemispheres, without midline structures (corpus callosum, septum pellucidum, fornices), are found at the base of the skull. The wide space betwcen the hemispheres is covered by a distended and teared

96

arachnoid membrane and secms to communicate with the subdural space. Primitive basal ganglia and thalami are partly fused in the midline. A cleft at the position of the third ventricle is open dorsally and communicates with the aqueduct. The olfactory bulbs and tracts are absent. A polypoid mass protruding from the maniillary region is observed in some cases. The posterior fossa is small, wjith hypoplastic brain stcm and cerebellum. A midline defect in the occipitcil bonc results in a “kcyholeshaped” foranicn magnum. This pattern of brain pathology seems unique for the hydrolethalus syndrome. Thcrc is evidence of disturbance of both dorsal and ventral induction, combined with and resulting in a very spccial type of severc hydrocephalus.

Abstracts

Presence of Alzheimer and Lewy body pathology in a middle-aged case of Down’s syndrome: Aetiopathological implications for Alzheimer’s and Parkinson’s diseases Raghavan R , Khin-Nu C, Manners T, Day K, Tyrer S, Irving D, Perry R H Neuropathology Department, Newcastle General Hospital, Newcastle upon Tyne, Ashington, Northgate, and Prudhoe Hospitals, Northumberland, England The cxtcnt of neurodegenerative pathology in a 62 year old man with Down’s syndrome is presented. The brain was mildly atrophic with a mean neocortical plaque density of 21.2/mm2. Numerous small plaques without aniyloid cores were observed in the hippocampus, particularly within the hyppocampal gyrus. Ncocortical and archicortical ncurofibrillary tangles were, however, scanty although neurofibrillary tangles were present in periaqueductal grey matter in the mid brain, pons and medulla. Lewy bodies were observed in catechola-

minergic nuclei (locus coeruleus). These findings will be presented in relation to: 1. the prevalence of Alzheimer-type and Lcwy body pathology in (a) the normal aging brain and (b) a series of 20 cases of Down’s syndrome: 2. the spectrum of Parkinson’s Disease and Lewy body disorders; 3. the chromosome 21 amyloid gcnc abnormality described in sonic pedigrees of familial Alzheimer’s Disease.

Brain abnormalities in the carbohydrate deficient glycoprotein syndrome severe mental retardation

-

a new disorder with

S t r o m m e ’ P, MEhlen’ J, S t r 0 m 2 EH, Torvik’ A



Departments of Pediatrics, Rikshospitalet, Ullevi5l Hospital, Oslo, Norway The carbohydrate deficient glycoprotcin (CDG) syndrome is a metabolic disorder with severe mental retardation and extensive neurological abnormalities. We here present the neuropathological findings in two male twins both affected by this syndrome. Patient I . Muscular hypotonia was noted at the age of three months. He died one month later of Pneumocystis carinii pneumonia. The brain was normal on gross examination. Microscopically there were signs of an early olivopontocerebellar atrophy with nerve cell loss and gliosis of the inferior olives, pontine nuclei and ccrcbellum. Patient 2. Severe mental retardation, epilepsy and progressive cerebellar ataxia developed within the first year. At the age of three years he became acutely hemiplegic on his right side. He died at the age of six years due to acute pneumonia. Gross examination of the brain showcd an old ischemic cortical lesion in the left parietal lobe and extreme atrophy of the entire cer-

Pathology,

ebellum. Histological examination showed advanced olivopontoccrebellar atrophy with cxtcnsivc gliosis and complete loss of Purkinje cells and subtotal loss of granule cells throughout the cercbcllar cortex and anterior vermis. Nerve cell loss and marked gliosis was also observed in the pontine nuclei and inferior olives. The retina was very thin and showed degenerative changes with loss of photorcceptors and migration of pigment cells in a retinitis pigmentosa-like pattern. Cmclusions. Based on these observations we conclude that the ataxia in the CDG syndrome is caused by olivopontoccrcbellar atrophy with a neonatal onset. It may progress rapidly to an end stagc atrophy which corresponds well with the clinical observation that the ataxia stabilizes after some years. Cerebral infarction and retinitis pigmcntosa were associated findings.

Acute polyneuropathy due to primary hyperoxaluria: a case report Nennesmo

’ I,

Solders‘ G, Samuelsson M



Departments of Pathology, Neurology and Neurophysiology, Huddinge Hospital, Stockholm, Regionssjukhuset i Orebro, S w e d e n A 22-year-old man, who had suffered from kidney stones since the age of 7, suddenly developed end stagc uremia. Bilateral nephrectomy was performed and ii renal transplantation was planncd. One week after the operation he developed a flaccid tetraparesis with ncurophysiological signs of a combined axonal and demyelinating neuropathy. Analysis of cerebrospinal fluid was normal. A diagnosis of acute

polyradiculitis was made. No improvement was seen after plasmapheresis. Crystals containing calcium were dctcctcd in biopsics from different tissues including nerve and muscle, and thc diagnosis was changed to primary hyperoxaluria with polyneuropathy. A livcr transplantation was performed, but the patient died in a cardial iirrythmia at the end of this operation.

97

Abstracts

Structural aspects of monkey brain Radu I Faculty of Medicine, Craiova, Romania Wc studied 10 nionkcy brains (Macaca Rhesus, Cercopithccus aetiops. Macaca ncmcstrina) with general methods of histology and neurohistology as well as histoenrymology. The removed fragments wcrc embedded in celloidin and paraffin or processed at cryotome. The injection with ink, sometimes with an overstaining for connective tissue showed a vcry fine and well ramified network. Vcry clear results uppearcd in the cerebclluni. ATP-asc activity is marked in vessel

walls. Brain parenchyma, astroglia and inicroglia are evidenced by thc fine prolongations. Succinate dehydrogenase is very activc in neurons, marked in astroglial vascular pcdiclcs and absent in vascular walls. Lactate dehydrogenase also gives a vcry rich demonstration of microvascular networks, mainly the white substancc. NADH- and NADPH-tetrazolium rcductasc appeared very activc in the elastic tissue of vessels.

Parachordoma of the sacrococcygeal region is a glial tumor Wiebe 6, Laursen H Department of Pathology, Sundby Hospital, Institute of Neuropathology, University of Copenhagen, Denmark The parachordoma is a benign tumor of uncertain histogenesis. The tumor is infrequent. The immunochcmical rcactivity in a case from a 25 ycar old man has been scrutinized. The parachordoma presented with positive reactions to antibodies to Glial Fibrillary Acid protein (GFA), S-100. Neurone Specific Enolasc and Vimentin but not with antibodies to Epithelial Membrane Antigen (EMA), keratin and Neurotilamcnt 200 KD. Differential diagnoses are the chordoma and thc cxtraskcletal myxoid chondrosarcomo. These tumors reacted with

antibodies to S-100 and Vimentin. The chordoma reacted also with antibodics to keratin and EMA and none of thcrn reacted with antibodies to GFA. The prcscnt parachordonia diflcrs immunologically from the chordomas and the extraskelctal myxoid chondrosarcomas. The parachordoma, thcrcfore, seems to be an entity of its own. Thc immunohistochemical rcactions indicate that the parachordnma is a neuroepithelial tumor of glial origin.

Mental retardation: recent trends in epidemiology and neuropediatric research Hagberg Bengt Department of Pediatrics, Gothenburg, S w e d e n Mental retardation (MR) is the grcatcst handicap complex in childhood and adolescence. Prevalence figures for severe MR (SMR = I Q 5 50) remain relatively static around 3-4 per 1000 in most wcstcrn world countries. Mild MR (MMR = IQ 50-70) is more controvcrsial as to definition, prevalence, and proportions of biological c~uscA . recent U K survey supports our findings from the late '70s of a biological defect behind MMR in over 40"/0 of cases: prenatal in 15-25'!;,; pcrinat:il in 15-20~,~,:postnatal in 2-5';,. Constitutional oligophrenia represents only 30-40"" in these MMR series. - SMR

98

mainly contains a broad diversity of early prenatal causes, likely in 80-85";. Chromosomal and other early multiple congenital anomaly syndromes together sland for 2/3 of all prenatal SMR. High actunlity has thc 5-10yo of SMR due to inborn errors of brain cell mctaholism, some with potential preventive aspects. Recent research advances related to the origin of Rctt syndrome and thc new carbohydrate deficient glycoprotein (CDG/DDD) disease will be prcscnted. The worrying increase in very and extremely prctcrni multiimpaircd babics with perinatally acquired brain damage will be discusscd.

Abstracts

Synaptic remodelling as an integral process of synaptogenesis Wolff JR Department of Anatomy, University of Gottingen, Germany Synaptic junctions to a great extent determine the functional role each neuron plays in nervous systems. Apart from the frequency of activation, synaptic influences are based on qualitative and quantitative characteristics of the afferent and efferent synaptic spectrum; i.e. on the types of transmitters, receptors and effectors used by subpopulalions of synapses; on the size and/or number of synapses, and on their microtopography on the neural surface. Synaptogenesis ( S G ) may then be defined as a set of morphogcnetic processes which provides each ncuron with appropriate synaptic connections. Primarily SG was idcntificd with progressive processes involved in synapse formation either during ontogenesis (primary SG) or as a consequence of partial deaffcrention of neurons (reactive SG). Later on, it became clear that pre- and postsynaptic elements may be formed independently of each other and, at least temporally, make contact with inappropriate partners (c.g. transient axo-glial synapses and diffuse projections as a precursor of focalized innervation patterns). Synapse removal revealed that regressive processes may participate in the production of normal adult innervation patterns, irrcspectively of whether these transient synapses were regarded as “developmental errors” or as synapses which serve transient functions in development. We are still far from understanding the devclopinental role of transient synaptic

connections. Their removal is based on, e.g. physiological ccll death of isolated populations of neurons, removal of axon branches, reorganization of dendrites, especially spines, etc. Usually, these regressive processes are not included in the concept of SG, but rather rcgarded as separate phenomena, e.g. as a part of neuroplastic reorganization during metamorphosis, critical periods, etc. Until now, four types of synaptic regression have been described: synapse removal as a consequence of a degcncrating presynaptic (I)or postsynaptic element (2), disconnection of a possibly persisting prc- and postsynaptic elements, e.g. as a retrograde reaction to axotoniy of afferent synapses on rnotoneurons ( 3 ) , autophagy and lysosomal degradation of presynaptic components or elements (4). It will be demonstrated that lysosomal degradation of synapses and synaptic cornponcnts cannot be separated from the process of synapse formation. It occurs during characteristic phases of primary and reactive synaptogenesis in ncocortex and hippocampus, respectively, whcrc it apparently marks changes in the velocity of synapse formation. This suggests that remodelling and replacement of synapses are integral (may be essential) processes during SG. Hence, factors inducing mental retardation may not only interfere with synapse formation, but also with the physiological reorganisation of synaptic connectivity.

99

Abstracts

The relevance of synaptic plasticity for an understanding of abnormal synaptic organization J o n e s DG Department of A n at o my , University of O t ag o , Dunedin, New Zealand Morphological approaches to synaptic organization have tended to concentrate on either the normal or abnormal, as though these constitute quite distinct facets of the organization of synapses. While this has been an understandable approach, it is probably also a simplistic way of looking at what is undoubtedly a continuum. The question confronting us is how best to tackle this continuum. The thesis of this presentation is that a possible means open to us is via the notion of synaptic plasticity. The concept that synapses are being continuously rcinodelled and then replaced, as part of the normal functioning of ncurons, is fundamental to thc idea of plasticity and is the basis for current thinking rcgarding regeneration and homeostatic maintenance orthe post-dcvclopmcntal CNS. Considerable ctrort has been put into cxamining processes involved in the reactive replacement of existing synapses with newly-formed connections. However, it is possible that the restructuring of existing synapses during normal life may have equally significant implications. This latter form of naturally-occurring plasticity is an ongoing process in the CNS, and has been reported in a wide variety of experimental paradigms, including changes in both the internal and external environments, and from other non-invasive cvcnts of normal life such as aging. Inevitably, plastic changes result in morphological changes that may cause synaptic organization to deviate considerably from what is generally regarded as normal. Morphological changes consequent on synaptic plasticity affcct dendritic spines, various synaptic parameters, and the synaptic junctional zone itself. Of the synaptic characteristics that may play a role in synaptic plasticity, thc postsynaptic density, synaptic curvature, the spinulc, coatcd vesicles, polyribosonics, and the spine apparatus havc all been implicated. An aspect of the junctional zone that has emerged as of especial interest is the perforation or discontinuity found in a surprisingly high percentage of ncocortical synapses. These arc the perforated synapses, the role of which has bccn expressed using a number

100

of models, all of which revolve around the central theme of synaptic plasticity. A question that will be addressed is whether this synaptic type plays a role in the replacement of synapses or in the rcstructuring of existing synapses, or whether it represents a deviation froni normal synaptic maturation. In order to do this, emphasis will be placed on recent unbiased stereological and three-dimensional computer reconstruction investigations of rat ncocortical synapses froni late gestation to late adulthood. These dcmonstratc that the frequency of perforated synapses ranges from 120.:, at 7 days postnatal to a peak of 37% at 10 months, with values of around 34% up t o 19 months of age. It appears that non-perforated and perforated synapses havc many different characteristics, throughout the age-range of thcsc studies. These include the following: i) the size of synapses increases with age, with perforated synapses being about twice the size of nonperforated synapses; ii) the size and structural complexity of the postsynaptic density of the perforated synapses increase considerably with age; iii) the proportion of the synaptic contact zone occupied by the postsynaptic density increases for non-perforated synapses, but decreases for perforated connections over the period of the study; iv) the total surface density of postsynaptic densities in mid-adulthood is maintained above the lcvcl found during early development, despite a large decrease in the number of non-perforated synapses; v) the postsynaptic density surface of perforated synapses per unit volunic increases with increasing age. It is tentatively proposcd that pcrforatcd synapses constitute a separate, enduring component of thc synaptic population, with a major part to play in the maintenance of synaptic activity in the mature CNS. If this is correct, it suggcsts that perforated synapses play a crucial role in ongoing synaptic plasticity in the neocortex, and that any interference with this role will result in the emergence of synaptic pathologies.

Abstracts

Neurotransmitters as morphogens in neural and non-neural development Lauder JM, Shuey DL, Yavarone

M, Liu J

Department of Cell Biology & Anatomy, University of North Carolina at Chapel Hill, USA I n primitive organisms and early embryos, neurotransmillcrs such as the nionoaniines are present during periods of active morphogcnesis. Neurotransmitters may have evolved from primitive signalling devices to thcir present functions as mediators ofchemical neurotransmission. These phylogcnctically old functions appear to be reiterated in the embryo, since psychoactive drugs such as synthesis inhibitors, receptor ligands and uptakc inhibitors can disturb structural or functional devclopment of neural and non-neural tissues. High lcvcls of serotonin (5-HT) are present in serum and placenta of mammalian species. In the mouse embryo, 5-HT is taken up by the ectoplaccntal cone and placenta during thc period of ncurulation and craniofacial development. Culturcd mouse embryos exhibit low affinity uptake sites for 5-HT in epithelia of the craniofacial region, hindbrain neuromeres, myocardium, gut, thyroid and kidney. Craniofacial and cardiac mcscnchynie (cushion tissue) cells express serotonin binding protein (SBP), the storage protein for 5-HT in synaptic vesicles of adult neurons. Uptake sites arc correlated with regions of low proliferative activity, and with segmental development of thc hindbrain. SBP becorncs localizcd in neural crest-dcrivcd mesenchyma in register with epithclial 5-HT uptake sites during the period of epithelialnicsenchymal interactions prior to chondrogenesis and osteogenesis, and is found in chondrogenesis sites at later stages together with 5HT receptor-like proteins. Treatment of cultured mouse embryos with 5-HT uptakc inhibitors, receptor antagonists or 5-HT producc sitespecific malformations of craniofacial and cardiac structures, as well as gradients of altered proliferative activity. I n vitro, 5-HT either stimulatcs or inhibits migration of cardiac or craniofacial mesenchymal cells towards a chemotactic stimulus, depending on dosc. These structural and functional studies suggest that 5-HT may act as a morphogcn or regulator of other morphogenic substances during critical periods of ncural and non-neural development in the mouse. In the rat

brain, 5-HT is one of the earliest ncuronal phenotypes to be expressed during cmbryogenesis. 5-HT neurons of thc rostra1 raphc complex (RR) rapidly extend axons towards the forebrain, passing through the analgen of subsequent synaptic targets such as the dopamincrgic (DA) substantia nigra (SN). Treatment of pregnant rats with the 5-HT synthesis inhibitor pCPA produces delayed neurogcncsis in thcsc regions, suggesting that 5-HT may act as a regulator of differentiation of its embryonic tsrget cells. Maternal treatmcnt with pCPA or the 5-HTl agonist 5-MT produces long-lasting altcrations in expression of 5-HT1 receptors in brains of offspring, suggesting that thcsc receptors become hnctionally regulated prenatally and could mcdiatc the effects of 5-HT on ncurogenesis. I n situ hybridization and irnmunocytochcmical studies of 5-HT receptor expression support this view. The effects of 5-HT on early neurogencsis could be direct, or indirect via effects on glia. In vitro studies with embryonic radial glia/astrocytcs and 5-HT (RR) or D A (SN) neurons indicate that 5-HT is inhibitory to neurite outgrowth at doses where glial uptakc occurs, but stiniulatory at lower doses, suggesting mediation by receptors. Glia from both regions express mRNAs and irnniunorcactivily for 5-HTIA and 1C receptors, but produce different types of neuronotrophic activities in response to 5-HT. Moreover, 5-HT and DA neurons respond differently to growth regulatory factors present in glial cultures (S100B, IGF-11). These results raise the possibility that 5-HT affects neuronal differentiation by receptor-mediated release of glial-derived growth factors, which exert specific effects on particular transmitter phcnotypes. In summary, 5-HT appears to regulate the morphogenesis of ncural and non-neural tissues cxprcssing appropriate signal transduction mechanisms. Psychoactive drugs which intcrfcrc wilh these mechanisms may produce cascades of tcratologic effects on thcsc tissues and their ontogenic cohorts.

101

Abstracts

Functional changes induced after pre- and postnatal treatments Archer T Department of Psychology, University of Gothenburg, Sweden The effects of different perinatal treatments upon various parameters of lcarncd and spontaneous behaviours have been investigated. These treatments appear, in common and either by design or discovery, to have caused some alteration of dopaminergic receptor activity in forebrain regions. These investigations can be summarised: 1) A series of experiments were performed to study the cffeets of neonatally-induced dopamine (DA) depletions upon the development of spontaneous motor activity and instrumental learning. Microinjections of 6hydroxydopaminc (6-OHDA), on Day 1 after birth, were administered at either 100 ug, 75 ug or 50 ug doses. The extent of DA depletion in the striatum and substantia nigra corresponded closely to the dose 6-OHDA injected. The behavioural effects of neonatal 6-OHDA treatment were also related to the degree of depletion: Both the 100 and 75 ug doses caused a retardation of acquisition performance in the radial arm maze (an appetitively reinforced task) but only the 100 ug dose caused an impairment of spatial navigation in the circular swim maze (essentially an aversive task requiring rats to escape to a submerged platform); this impairment was quite permanent. All three doses caused denervation-induced hyperactivity although this effect was obtained at an earlier age as the dose and severity of DA depletion was increased. Concomitant with the hyperactivity, indexed as an increase in ambulatory or locomotor behaviour, a decrease in exploratory bchaviour was observed, measured by hcad-dips and rearings in a modified opcnfield/holeboard. In all the cases of 6-OHDA induced hyperactivity a transient reversal could be obtained after acute treatment with stimulant compounds, e.g. d-amphetamine, niethylphenidatc or apomorphine. 2) The effects of prenatal exposure to organotin compounds (tributyltin, 1 and 5 mg/kg, and trihexyltin, 5 nig/kg) upon the development and bchavioural repertoire of rats were studied also. Dose levels were sclccted so as not to induce maternal toxicity. No consistent delay upon the occurrence of various markers of the organotin-treated offspring was observed, nor were any changes of regional CNS concentrations of monoamines and monoa m h e metabolites in the adult male offspring obtained. As adults, thc tributyltin-treated offspring showed a considerable degree of hyperactivity (i.e. the locomotion and total activity parameters) in automated test cages following the initial habituation period (60 min), whereas trihexyltin-treated offspring were hyperactive to a lesser cxtent. Curiously, rearing behaviour was decreased in these animals. In the spatial learning tasks applied, the radial arm maze and the circular

102

swim maze, a significant rctardation of acquisition was indicated by Ihe tributyltin offspring in the former. whereas the trihexyltin offspring did not differ from controls. No diffcrcnces were obtained in the lattcr, swim maze, task. Tributyltin-treated offspring showed a drastic potentiation of d-amphetamine (1 .0 mg/kg)-induced hyperactivity; the tributyltin offspring showed only a marginal increase. 3 ) the effects of prenatal and postnatal treatment with metallic mercury upon the dcvelopment of similar behavioural tests to those applied above were studied. Again, dose levels were selected so as not to induce toxicity in the mothers. In the prenatal administration study, tests of spontaneous activity showed in a dose-related manner that the offspring were hypoactive at 3 months of age but hyperactive at 14 months. In the spatial learning tasks applied, the radial arm maze and the circular swim maze, the metallic mercury treated offspring indicated a doserelated retardation of acquisition of the former test but no differences were obtained in the latter. Interestingly, a quite similar pattern was obtained in the postnatal treatment study, i.c. spontaneous motor activity and radial arm maze performanee being the only parameters affected. No induction of delay in the occurrcncc of various maturational markers of development were observed. 4) Thc effects of prenatal administration of a low dose of haloperidol (2.5 umol) and three doses (10, 40, 150 umol/kg) of the novel, atypical, neuroleptic compound, remoxipride, upon developmental and behavioural parameters was studies in rats. None of the doses induced any signs of maternal toxicity. The highest dose of remoxipride ( I 50 umol/kg) and haloperidol were shown to produce behavioural changes in thc offspring. The offspring of haloperidol treated dams showed a clear rctardation of acquisition in the radial arm maze task. Additionally, these offspring and those of the remoxipride (150 umol/kg) darns showed permanent increases in basal activity levels. All five groups wcrc tested for the effects of d-amphetamine stimulation (0.25 mg/kg). It was found that the haloperidol and remoxipride (1 50 umol/kg) offspring showed a potentiation of the stimulatory cffccts of d-amphetamine on motor activity. This effect was the opposite of that produced in 6-OHDA induced dencrvation, neonatally, where d-aniphctamine decreased activity levels of hyperactive rats, and suggests perhaps a functional hyperinnervation. These diverse studies demonstrate that the bchavioural alterations described commonly derive from alterations to catecholamine pathways and in particular dopamine.

Abstracts

Association of phenotypic neural abnormalities of Down syndrome with an imbalance of genes on chromosome 2 1 Becker LE Division of Neuropathology, Department of Pathology, University of Toronto and The Hospital for Sick Children, Toronto, Ontario, Canada The phenotype of the brain in Down Syndrome is different from that of a normal child both in its reduction in sizc and altered gyral configuration. Uiiderlying the mental retardation are neuronal abnormalities including alterations of cortical lamination, reduced dendritic ramifications and diminished synaptic formation. However, cholincrgic enzymes such as choline acetyl transferase and acetyl cholinestcrasc have shown no abnormalities in young children with Down Syndrome. The pace of dendritic maturation is altered in Down Syndrome. In infancy, the normal dendritic tree continuously expands. In Down Syndrome, at four months of age, the neurons show a relatively expanded dendritic tree, but during the first year, the dendrites stop growing and become atrophic relative to control neurons. In order to relate these phenotypic alterations to chromosome 21, we examined the gene products of several genes localized to chromosome 21. The

identification of such gcncs and the determination of their gene product allow the production of specific antibodies and through immunohistochcmical techniques, the identification of the expression of these proteins in both normal development and Down Syndrome. Specifically, the localization and appearance during development of proteins such as P-subunit of S 100, P-amyloid, superoxide dismutasc and OK2 are providing links between genotype and phenotype. S 100 protein is of particular interest because of its effect in vitm on neuritic outgrowth and its increased expression in the temporal lobe in Down Syndrome. The brains of transgenic mice bearing multiple copies of the human Sl00 gene show some comparable changes to those in Down Syndrome. Thcsc experimental approaches provide the nicans for better understanding the cellular and molecular basis for the mcntal retardation in Down Syndrome.

Molecular definition of a small region of chromosome 21 that causes Down’s syndrome Anneren G Department of Clinical Genetics, University Hospital, Uppsala, S w e d e n Down syndrome (DS), the most common postnatally viable human autosornal chromosomal abnormality is caused by trisomy for chromosome 2 1. The mechanism whereby the supernumerary chromosome 21 contribute to the pathology of DS remains elusive. There are, however, several evidences that D S is a gene dosrrge di,sease. This means that over-production of certain proteins encoded by normal genes on the extra chromosonic 21 distorts the delicate balance of sonic biochemical pathways that are important for proper dcvelopmcnt and function of the organs affected in DS. It has also been shown that only the distal segment of the long arm of chromosome 21 is involvcd in thc pathogenesis of DS. I t is suggested that as few as 10 gcncs might be responsible for the D S phenotype. Great research efforts to define this “DSspecifc sep2ent” are made today, with the aini to define the segments and thc genes within it, in order to be able to explain thc effects from one single supernumerary gcnc in D S

patients. I will report from a world-wide collaboration study and specially our results from one single paticnt. It is a woman. born 1957 with a characteristic phenotype of DS. She had a sister with DS. who is dead. Repeated cytogenetic investigations (G-banding and Prophasc banding) of the patient, her sister and parents revealed normal karyotypes. Autoradiograms of quantitative Southern blots of DNAs from the patient and her parents were analyzed after hybridimtion with unique DNA sequences regionally mapped on chromosome 2 I . The patient has three alleles at the VNTR-polymorphism in the Col6A I gcnc, one copy from the father and two from thc mother. The Col6A I gene is mapped at the very distal segment of the long arm of chromosome 21 (21~22.3).She has only two alleles of all loci analysed proximal to Col6A1. This indicates that the patient has trisomy for the very distal part of the band 21q22.3, a segment of about 2000 k B . The “DS spccific segment” might contain only 5‘1, of chromosonic 21.

Carl Hammarberg (1865- 1893) founder of the research on the relationship between development of the cerebral cortex and mental retardation Sourander P Institute of Pathology, University of Gothenburg, S w e d e n Hammarberg ( 1893) was the first to apply carefully controlled, quantitativc histological studies on the cytoarchitectural and developmental characteristics of a great number of different cortical regions of the h u m i n brain. His studies wcrc performed on 12 brains ofnormal and 0 brains of inentally retarded individuals of varying ages. The morphomctric determinations were made on 10 or 20 pin thick celloidin embcddcd sections stained with mcthylen blue for microscopic visualization of ncuronal cell bodies. Their size and number per unit volume and the thickness of the diff‘erent cortical layers were calcu-

lated. The results supported the following conclusions. Mental retardation may be associated with microscopic structural changes of the cerebral cortex. A relationship between thc dcgrcc of hchnvioural and structural changes was noticed and interpreted as the consequence of inhibited development of different cortical regions cxamincd. Hammarberg’s thcsis was written in Swcdish and posthumously published in German (Studien abcr die Klinik und Patologic dcr Idiotic, Uppsala, 1895).

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Abstracts

Hemimegalencephaly: a case with severe disorder of neuronal migration confined to one cerebral hemisphere Paljarvi L, Airaksinen E Departments of Pathology and Pediatrics, University Hospital of Kuopio, Finland

Unilateral enlargcmcnt of the brain or a large part of it (hemimegalcncephaly) is a rare disorder often associated with phacomatoses or hypertrophy in other viscera. We present a case with enlarged left cerebral hemisphere as the only anomaly. Following an uneventful prenatal history, a boy started to have seizures on his first day of life. Later on, mental retardation and right spastic paraplegia were noted. CT showed asymmetry of hemispheres and altered structures consistent with hemimegalcncephaly. The partial, generalizing seizures originating from foci in the left anterior hemisphere proved drug-resistant. He died of bronchopneumonia at the age of 22 months. Post mortem, the left hemisphere was found to be largcr than the right (by 20% in linear measurements) and partly micropolygyric. It was rubbery hard

on palpation. The distinction of gray and white matter was blurred. Microscopically, the layering of cortical structurcs was severely disorganized, and deep gray matter was also poorly defined with nodular heterotopialike features. Enlarged, strongly argyrophilic neurons appeared. Astroglia was proliferating and often consisted of gemistocytes. No corresponding changes were found in the right cerebral hemisphere, brain stem or cerebellum. In our case - as in somc others - pathology shows features of both neuronal migration problem and neoplasia resembling ganglioglioma. Quantitative studies are necded to prove the suggestioIi that overproduction - or deficient elimination - of neurons during development are at the core of pathogenesis of this curious phenomenon.

Familial mental deficiency and schizo-affective disorder associated with temporal lobe cortical dysgenesis Raghavan R, Smith PEM, Smith DA, Day K, Perini RF, Perry RH Neuropathology Department, Newcastle General Hospital. Newcastle Upon Tyne, Ashington, Northgate and Prudhoe Hospitals, Northumberland, England

The clinical and neuropathological features of a 29-year-old male who presented with mental dcficieney at an early age and developed an atypical schizo-affective disorder at the age of 13 years accompanied by a dystonic movement disorder are presented. The neuropatholog-

ical findings of abnormal cortical architectonics in the temporal lobe (occipitotemporal gyrus) of this individual will be discussed within the context of a positive history of mental subnormality and affective disorders in the family.

Chromosomal aberrations in the mildly mentally retarded. A population based study Wahlstrom D

’ J, Gostason

R , Johannesson

’ T, Holmqvist ’



Department of Clinical Genetics, East Hospital, Gothenburg, Sweden, Social Board of the Kopparberg County Council, Falun, Sweden

Chroinosomc analyses were performed on 52 mildly mentally retarded adults and a control group representing the non-retarded population. Chromosomal aberrations were found in 19.2% of the mentally rctarded and in 1.9:; of the controls. The aberrations in the retarded group consisted of three cases with trisomy 21, two males with fragilc X, thrcc cases had sex- chromosome aberrations and two case with

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balanced translocations. The index group included a man with a fragile site Xp22.1. The aberration in thc control group consisted of a karyotype with an extra marker chromosome. Thcsc results support the hypothesis that intelligence and mild mental retardation are not determined by polygenes.

Abstracts

Potential hazards of benzodiazepines for the foetus Laegreid Hagberg

’ L, Olegerd ’ R, Conradi’ N, Wahlstrom3 J, ’ G, Lundberg ’ A, Hedner4 T



Departments of Pediatrics, Pathology, Genetics, macology, University of Gothenburg, S w e d e n Eight children excessively exposed to benzodiazepine (BZD) in utero had similar facial features and CNS dysfunction from birth. One child had an aplasia of one kidney and 2 a cleft palate. One infant died and at autopsy had varying degrces of distortion of neuronal migration with concomitant heterotopias. Two children were severely mentally retarded and 5 mildly so. This generated the hypothesis of a teratogcnic BZD syndrome which was tested in 3 case-control studies. In the first study 4 particular operational diagnoses of congenital malformation were chosen as the inclusion criteria. The diagnoses were: a) unspecified embryopathy and fetopathy, b) unspecified congcnilal malformations of the nervous system, c) cleft palate and cleft lip and d) congenital malformations of the urinary tract. Stored serum, taken from the mother at around gestational week 12, was screened for BZD. The association between a BZD-positive serum test and these particular malformations was highly significant. In the second study, pcrinatal death was the inclusion criterion. Maternal drug use in pregnancies resulting in 73 perinatally dead infants was compared with thosc resulting in 73 surviving infants. The association between psy-

Phar-

chotropic drug usc, including BZD, and perinatal death was significant. In the third study 17 children born to mothers who had used BZD in therapeutic doses throughout pregnancy were compared with 29 newborns with no known drug exposure (reference group). InPmts exposed to BZD had an impaired intrauterine growth as compared with the reference group. They also had significantly more pre- and perinatal complications and deviating neurobchaviour in the newborn period. The neurodevelopment was studied at 6 , 10 and 18 months of age. The gross motor development in BZD-cxposed children was significantly retarded at 6 and 10 months but was,ncarly norrnal at 18 months. Impaired fine motor function was found on all the follow-up occasions. A cluster of craniofacial anomalies was found in 5 infants. The BZD-exposed children demonstrated significantly delayed devclopmental quotients at 10 and 18 months. Conclu.sions - The significant association between maternal BZD use and minor and major anomalies supports the hypothesis of the teratogenicity of BZD, especially when taken in large doses. A long-lasting etfcct of BZD on the CNS and its functions cannot be excluded.

Down’s syndrome complicated with brain tumors. Case report and review of the literature Hori’ A, Walter’ GF, Haas* J



Institute of Neuropathology, Department of Neurology, Medizinische Hochschule Hannover, Germany This report concerns a 34-year-old patient with Down syndrome complicatcd with a differentiated plexus papilloma. The mixed neoplastic and dysgenetic character of the tumor is described. Brain tumors,

though rare, are not a coincidental finding but onc of the possible complications in Down syndrome.

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Abstracts

Clinical, biochemical and molecular studies on lysosomal disorders W e n g e r DA Jefferson Medical College, Philadelphia, Pennsylvania, USA Lysosomal disorders result from mutations in genes coding for lysosoma1 enzymes, activator proteins, protector proteins, packaging enzymes, transport proteins and other unknown proteins. At this time the products of over 30 genes have been shown to be implicated in lysosomal diseases. For each gene that has been cloned, and patients examined, a number of different mutations have been found. This probably will explain the wide range of clinical features found in patients with a deficiency of a common protein. At this time, and for the foresecablc future, the diagnosis of a patient with an unknown dcgenerative disorder will rest with protein based testing and/or examination of urinary excretion products. The identification of carriers among family members and prenatal diagnosis may increasingly rely on examination of DNA for mutations once they have been identified in the patient. I t is also probable that better tests for prognosis will be developed through identification of mutations (types, location, etc.) in well described patients. While the classic patients can usually be recognized clinically and diagnosed by simple testing, the diagnosis of variant patients requires interaction between the clinician and the laboratory. The identification of patients with a variant form of metachromatic leukodystrophy caused by mutations in the gene coding for sphingolipid activator protein- 1 (SAP- 1) illustrates the need for additional testing in patients with evidence of a lcukodystrophy and normal enzyme values. At least 6 patients with SAP-I deficiency havc been diagnosed and their mutations havc been identified. This gene, called prosaposin, codes for 4 potential SAP with different specificities, and, therefore, mutations in this one gene could lead to differ-

ent lysosomal disorders (depending on where the mutation was located). Three patients from two families of Mexican ancestry were found to have a single nucleotide change in the SAP-I domain. This substitution of C by T changes the codon from threoninc to isolcucine, and, more important, eliminates the only glycosylation site in maturc SAP-I. Another patient with this disorder was found to havc a 33 nucleotide insertion in her mRNA. The mature SAP-I was unstable due to the presence of 11 extra amino acids. A single base change (C to A) in the middle of a 4 kb intron produces a new splice junction in the patient, leaving 33 extra nucleotides in her mRN.4. A severely affected patient has been shown to be missing one exon in the SAP-I domain but the exact mutation has not been identified. One other patient from the literature also has a single base change in the SAP1 domain. All of these patients have defects i n the metabolism of sulfatide, a major component of myelin. A patient with subacutc neuronopathic Gauchcr disease and normal beta-glucosidase activity was found to have a mutation in domain 3 (SAP-2) of prosaposin. SAP-2 has been shown to activate the enzymatic hydrolysis of glucosylccramide and galactosylceramide. Late onset forms of lysosomal disease, including Krabbe disease, presenting after 20 years of age, have been diagnosed in this laboratory. These will be discussed as wcll as our recent research efforts to purify galactocerebrosidasc, the cnzyme missing in Krabbe disease. As more is understood about these genes and their products new attempts at therapy will bc attempted with a reasonable chance for success.

Peroxisomal disorders: facts and concepts Barth PG, W a n d e r s RJA, S c h u t g e n s RBH Department of Pediatrics, University Hospital, Amsterdam, Netherlands Peroxisomcs arc organelles bounded by a single rncmbrane, present in all vertebrate cells except red blood cells. Their relevance to human genetic disease was discovered relatively late (Goldfisher et al., 1973) by their apparent absence on routine electronmiscroscopy in tissues of patients with the cerebrohepatorenal (Zellweger) syndrome, later also the infantile Refsum syndrome and neonatal adrenoleukodystrophy. This triad is now collectively known as generahed peroxisonial disorders (group 1). In these disorders all the known peroxisomal metabolic pathways are either deficient or have become cytosolic rather than organelle-bound. In group 2, confined to rhizomelic chondrodysplasia calcificans punctata, peroxisomes are morphologically preserved and at least two peroxisomal metabolic pathways arc clin-

106

ically affected. In group 3, only one peroxisomal cnzynic is dcficicnr. The latter group, includes the important x-linked adrcnoleukodystrophy/adrcnomycloneuropathy coniplcx as well as a number of rare but important isolated peroxisomal p-oxidation defects. This group is still expanding. From the viewpoint of pediatric neurology and devclopmental neuropathology peroxisomal disorders are important causcs of disrupted brain development, especially neocortical dysgenesis, and progressive myelin disordcrs. In this paper two main problems of genetic peroxisomal disorders will be addressed: 1) tlic different expression of the generalized peroxisonial disorders with respect to brain involvement; 2) the significance of impaired peroxisonial bela oxidation to prenatal and postnatal pathology of the brain.

Abstracts

Neurological consequences of mitochondrial dysfunction De Vivo DC Division of Pediatric Neurology, Neurological Institute, Columbia-Presbyterian Medical Center, New York, N Y 10032, USA The subject of mitochondrial discases was poorly understood and hopclcssly confused prior to 1980. A diversity of clinical and morphological observations had been madc, but defects of mitochondrial function were considered rare and largely incompatible with postnatal life. Toxicological studies had cstablishcd a hierarchy of tissue dysfunction resulting from respiratory chain failure. The brain was most vulnerable to energy failure followed by the oxidative rich type I skeletal musclc fibers, heart, kidncy and liver. W. King Engel and colleagues recognized mitochondrial abnormalities in skeletal muscle using the modified Gomori trichrome stain and introduced the term ragged-red fibers (RRF) in 1963. The importance of this observation as the histopathological signature of mitochondrial diseases, however, would not be appreciated for many years. Also, in 1963, investigators recognized that mitochondria contained DNA (mtDNA). In 1977, Shapira and colleagues introduced the clinical term “mitochondrial encephalomyopathy” to accent thc vulnerability of brain and skeletal muscle but the scope of this disease category awaited future discoveries. In 1980, Giles and colleagues documented the maternal nonMendelian inheritance of human mtDNA and further validated the basic biological principle that mitochondria in the fertilized gamete derive exclusively from the ovum. In the decade that followed, we have witnessed an explosion of new information that relates mitochondrial pathobiology and a diversity of human diseases. The mitochondrion is the only extranuclear organcllc containing DNA. As such, genetically-determined mitochondrial diseases may result from a molccular dcfcct involving the mitochondrial genome or the nuclear genonic. The first is characterized by maternal inheritance, and the second by Mendelian inheritance. The mitochondrial genome reprcsents the molecular genetics of oxidation-phosphorylation. Each mitochondrion contains 2-10 copies of mtDNA, a small circular doublestrandcd molecule containing 16569 bp and 37 genes. These genes code for 22 transfer RNAs, 2 ribosomal RNAs, and 13 of the 67 proteins located in the respiratory chain. Seven subunits in complex I , 1 in complex 111, 3 in complex IV, and 2 in complex V arc encoded by mtDNA. Of note, complcx 11 contains no mtDNA gene products. Thus, complex I1 defects would be inherited according to Mendelian patterns. R R F commonly are scen with primary lcsions of mtDNA. But this association is not invariant. Conversely, R R F are seldom associated with primary lesions of nuclear DNA. Deletions, duplications, and point mutations of mtDNA commonly are associated with RRF and lactic acidosis, witness Kcarns-Sayre syndrome (major mtDNA deletions or duplications). Pearson’s syndrome (major mtDNA deletions), myoclonus epilepsy with R R F (MERRF) (point mutation affecting tRNA”*), and mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS) (point mutation ~ R N A I ~ [ J [ J R, )However, RRF and lactic acidosis are absent in Lebcr’s hereditary optic neuropathy (LHON) (point mutation affccting intDNA nuclcotidc 11778), and the newly described condition associatcd with maternally-inherited retinitis pigmentosa, develop-

mental delay, dementia, seizures, ataxia, sensory ncuropathy, and limb weakness (Queen Square disease) (point mutation affecting mtDNA nucleotide 8993). The point mutation in LHON affccts a subunit in complex 1. The point mutation in Queen square disease affects subunit 6 of complex V. The point mutations in MELAS and MERRF, and the major mtDNA deletions in KSS have a broader biochemical impact, since these molecular defects involve the translational process of mitochondrial protein synthesis. The nuclear defects involving mitochondrial function generally are not associated with RRF. The current biochemical classification of mitochondrial diseases principally catalogues these nuclear defects. This classification divides mitochondrial diseases into five categories: 1. Defects of substrate transport. 2. Defects of substrate utilization. 3. Defects of Krebs cycle. 4. Defects of oxidation-phosphorylation coupling. 5 . Defects of respiratory chain function. Primary and secondary deficiencies of carnitine are examples of a substrate transport defect. A lipid storage myopathy often is present. Disturbances of pyruvate or fatty acid metabolism are examples of substrate utilization defects. Only two defects of thc Krebs cycle are known: fumarase deficiency and dihydrolipoyl dehydrogenasc deficiency. Luft’s disease is the singular cxamplc of a dcfcct in oxidationphosphorylation coupling. Defects of respiratory chain function are manifold. Two clinical syndromes predominate - one involving limb weakness, the other primarily affccting brain function. Defects involving cytochrome c oxidase (complex IV) are most common. Thcsc defects are associated with several clinical phenotypes ranging from a benign, rcversiblc limb weakness to an inexorably progressive, ultimately fatal disease of brain (Leigh syndrome). Leigh syndrome may result from different enzyme defects, most notably pyruvate dchydrogenase complex deficiency and cytochrome c oxidasc deficiency. The neuropathology is distinctive with topographically discreet abnormalities manifested by vascular proliferation, demyclination, neuronal loss, cystic cavitation and spongy degeneration. Reccntly, a new group of mitochondrial diseases has cmcrgcd that rcsult from defective interaction between the nuclear and mitochondrial genomcs. The first example is an autosomal dominant condition associated with multiple mtDNA deletions. The second example is a fatal infantile disorder associated with reduced abundance of mtDNA - tcrnicd the mitochondrial DNA depletion syndrome. It is presumed in both instances that the primary molecular defects involve the nuclear genome. The lesions disturb thc biological integrity or the abundance of the mitochondrial genome. An interaction between the two genomes also has been proposed to explain the preponderance of affected males with LHON. Ultimately, a genetic classification of mitochondrial diseases may be more parsimonious than the current biochemical classification.

107

Abstracts

Perinatal hypoxic-ischemic brain damage: clinical and experimental aspects Vannucci RC Pennsylvania State University College of Medicine, Milton S. Hershey Medical Center; Hershey, PA, USA

Pcrinatal hypoxic-ischemic brain damage is a frequent contributor to the chronic neurologic conditions of cerebral palsy, mental retardation and epilepsy. Ccrebral hypoxia-ischcmia occurs eithcr prepartum, intrapartum or postpartum; the latter occurring most frequently in the prematurely born infant. The severity and distribution of the neuropathologic lesions arising from hypoxia-ischemia are dependent upon several factors; including gcstational age at the time of the insult, extent and duration of systemic hypoxia/acidosis, severity of arterial hypotension, and associatcd metabolic derangements. Hypoxicischemic brain damage occurring antenatally (i.c. prior to labor and delivery) usually results from occlusive vascular disease (thrombotic or embolic), while intrapartum brain damage is typically the consequence of asphyxia. Early postnatal brain damage in the premature infant occurs either as an accompaniment to scvcre intraventricular hcmorrhage, as a result of intrapartum asphyxia, or as the consequence of repeated episodes of hypoxia/hypotension in the newborn period. In general, pathologic changes reflccting hypoxia-ischemia in fulltcrrn infants arc located predominantly in the gray matter structurcs of the brain; including the cercbral cortex, hippocampus, basal ganglia and thalamus, brainstem and cercbcllar hemispheres. Lesions in the ccrebral cortex take the form of selcctive neuronal necrosis or infarction usually in a laminar distribution but also occasionally in a columnar distribution which is oricnted perpendicular to the pial SUP face. In premature infants, the lesions arc focused primarily on white matter structures, especially of the cerebral hemispheres. In small

premature infants, white matter necrosis usually occurs bilaterally and situated adjacent to the latcral ventricles, hencc thc tcrm pcrivcntricular leukomalacia. In infants born closer to tcrin, the topography of the necrotic foci shifts from subepcndymal to subcortical arcas, oftcn with associated selective neuronal necrosis or inparction of the ovcrlying cerebral cortex. The necrotic lesions oftcn contain a hemorrhagic component, especially when associatcd with intraventricular hcniorrhage. Hypoxic-ischemic brain damage has been produccd cxpcrimentally in fetal and developing postnatal animals; including rats, dogs, sheep and monkeys. Of the available models, that of thc inimature rat is the m.ost widely acccptcd to investigatc pathogcnctic mechanisms, neuropathologic altcrations and the cffcct of thcrapcutic manipulations. The model is based on thc Levine preparation in the adult rat, whcrcupon the animal is subjcctcd to unilateral common carotid artery ligation followed by exposure to hypoxia wit S'?o oxygen. Pathologic reactions include both selectivc ncuronal necrosis and infarction of the cerebral cortcx in both a laminar and columnar distribution in association with neuronal necrosis of vulnerable scctors of the hippocampus and of the basal ganglia and thalamus. White matter nccrosis originates in so-called myelinogenic foci as wcll as in the subcpendymal regions. Accordingly, the acute and chronic ncuropathologic alterations mimic closely those observed in fctal and newborn human infants sustaining cerebral hypoxia-ischemia betwcen 34 and 38 weeks of gestation.

On pathogenesis of germinal layer hemorrhage (GLH) in the premature infant Lou H JF Kennedy Institute, Glostrup, Denmark

G L H originate in thc rich capillary network in the germinal matrix of the premature infant. The risk of hemorrhage is influenced by thc pressure gradient across the capillary wall and its resistance. In its turn, the pressure gradient is determined by the systemic artcrial blood pressure, the presencc or absence of autoregulatory mechanisms with protective arteriolar constriction, and the extravascular pressure in thc cranial cavity. Experimental and clinical evidence indicate that the arterial pressure is low and stable in utcro, the extravascular pressure high, and GLH rarc. After birth, the systemic arterial blood pressure

108

rises. This rise is particularly dramatic after an initial pcriod of hypotension in hypoxia, and may bc superimposed by prcssurc increments during motor activity and stress. Continuous ultrasound monitoring has shown G L H to occur at the time of such pressure pcaks. A prerequisite for arterial pressure pcaks to be transmitted to thc capillary wall is absent autoregulation, and our recent data have shown that severe G L H is in fact preceded by a state of pressure passive ccrcbral circulation. Loss of autoregulation may occur at arterial oxygen saturation bclow 50%.

Abstracts

Perinatal brain injury as investigated by magnetic resonance and near infrared spectroscopy Edwards AD University College a n d Middlesex School of Medicine, London, England Magnetic resonance and near infrared spectroscopy are non-invasive tools which provide complimentary information about cerebral oxidative mctabolism and hacmodynamics in the newborn infant. Magnetic resonance spectroscopy (MRS). "Phosphorus MRS measures ATP, phosphocreatinc (PCr) and inorganic orthophosphate (Pi) as well as other key metabolites. The concentration ration PCr/Pi can be used as a direct index of cellular energy metabolism: a hypoxicischaemic insult is rapidly followed by a decline in PCr/Pi, but only when this has fallen to very low levels does the ATP concentration fall appreciably. If substrate supply is reestablished before death occurs PCi-/Pi rapidly returns to nornial. However, in a proportion of the survivors of this priwury energyfuilurr, a decline in PCr/Pi occurs some hours later demonstrating a secondary energyfailure which leads to cell death and significant loss of brain tissue. MRS studies in ncwborn infants who have suffered perinatal hypoxic-ischaemic injury show that the severity of the secondary energy failure is closely relatcd to adversc neurodevclopmcntal outcomc. The mechanisms of the secondary energy failure are being investigated. Near infrared spectroscopy (NIRS) depends on the absorption of light in the near infrared rcgion of the spectrum (700- 1000 nm). Light at these wavelengths can penetrate 8 em of tissue and the attenuation of light is related to the concentrations of absorbing chroinophores in the tissue. This can be

used to quantify changes in the concentration of oxy and dcoxyhacmoglobin ( H b 0 2 and Hb) and oxidised cytochrome aa3, the terminal element of the mitochondria1 electron transport chain (cytaa,). From these data cerebral blood flow (CBF) and cerebral blood volume (CBV) can be derived and the response of CBV and cytaa, to stinuli such as changes in arterial carbon dioxide tension (CO,) measured. Normal ranges have been defined, and preliminary data gathered from full term infants suffering pcrinatal brain injury. CBF and CBV were raised, and the response of CBV to changes in CO, reduced; the extent of these hacmodynamic abnormalities correlated with the severity of adverse outcome. The changes occurred before secondary energy Failure could be detected by MRS. NIRS has also been used to investigate the effects of therapeutic interventions in preterni infants. Adminislcring morphine and surfactant had no effect on CBF or CBV, but indomethacin caused a significant Fall in both, together with a loss of the response of CBV to changes in CO,; in some infants there was also fall in the concentration of oxidised cytaa,, dcmonstrating a relative intracellular oxygen deficiency. NIRS has recently been extended to the investigation of the fetus during labour, and it was shown that during uterine contractions associated with fetal heart rate decelerations there was a clear fall in average cerebral oxygen saturation which did not occur with normal contractions.

Role of excitotoxins in developmental neuropathology Olney J W Washington University Medical School, St. Louis, MO, USA Significant progress has been made recently in understanding the neurotoxic (cxcitotoxic) properties of glutamate (Glu) and related excitatory amino acids (EAA). Three EAA receptor subtypes that convey excitotoxicity [ N-methyl-D-aspartate (NMDA), kainic acid (KA), quisqualic acid (Quis)] have been identified, drugs with antiexcitotoxic actions have been discovered and cvidcncc for the potcntial complicity of both exogenous and endogenous cxcitotoxins in neurodcgcnerative disorders has begun to unfold. Thcrc now is substantial cvidcncc for the involvement of each EAA receptor subtype in one or more human neurodegenerative syndrome, and recent findings suggest that EAA rcccplors arc sensitive mediators of excitotoxicity at both ends of the age spectrum. Recent evidence suggests that during dcvcloprncnt NMDA receptors are hypersensitive to excitotoxic stimulation (relative to other dcvcloping EAA receptor subtypes or to morc maturc NMDA receptors). In addition, NMDA receptors on diffcrcnt ncuronal groups rcach peak scnsitivity at different developnicntal agcs. Thcrcforc, during development it may not require a vcry strong excitotoxic stimulus to trigger NMDA receptor-mediated brain damage, and an excitotoxin acting at NMDA receptors [c.g., endogenous Glu or cysteine] might induce various patterns of ncuronal degeneration depending on which NMDA rcccptor-bearing neu-

ronal populations are at peak sensitivity at the time of insult. It follows that different clinical syndromes might ensue (c.g. ranging from cerebral palsy to schizophrenia) depending on developmental age at the time of injury. Involvcmcnt of EAA receptor systems in neuropsychiatric disorders of old age may also be postulated based on evidence pertaining to domoic acid poisoning. Although individuals poisoned by donioic acid ranged in age from 20 to 89, severe neuropsychological impairment (profound anterograde amnesia) occurred primarily in those over 60 years of age. This suggests that KA reccptors are scnsitive mediators of excitoloxic neuropathology in the aging human brain. It is noteworthy, however, that domoic acid, likc KA, is a powerful convulsant that induces brain damage primarily by a seizure mechanism, and that seizure-mediated brain damage of the type induced by KA can be largely prevented by blockade of NMDA receptors. The postulated basis for this is that, although KA rcccptor activation is the mechanism by which domoic acid induces persistent seizure activity, much of the ensuing brain damage stems from seizure-mediated release of endogenous Glu at NMDA rcccptors. Thus, the domoic acid poisoning incident teaches that both NMDA and KA rcccptors may be sensitive mediators of excitotoxic pathology in the aged human brain.

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Abstracts

PEHO syndrome: neuropathological findings Haltia

' M, Sorner '

M

Departments of Pathology, Medical Genetics, University of Helsinki, and Department of Medical Genetics, t h e Finnish Population a n d Family Welfare Federation, Helsinki, Finland The PEHO syndrome (Progrcssive encephalopathy with Edema Hypsarrhythmia, and Optic atrophy) is a new clinically dcfined entity with infantile spasms, carly arrest in psychomotor development, severe hypotonia, transicnt or persistent subcutaneous cdcma, and blindness (Salonen ct al.: Clinical Genetics 39: 287-293, 1991). The onset of symptoms is from 2 weeks to 4 months; pregnancy and delivery arc normal, and most patients arc considered healthy during thc first weeks of life. The basic etiological defect is unknown, but the typical clinical course and characteristic dysmorphic facial features allow recognition of thcse patients. About 20 sporadic cases and 6 families with more than one affected child have been found in Finland. The

patients may livc in a vegetative state up t o an agc of 15 ycars. Uniform neuropathological changes were seen in 7 autopsicd patients. including two sisters. There was severe cerebral and cxtrcme cerebellar atrophy, which was most pronounced in thc vcrmis. Thc rnolccular layer of the cerebellar cortex was abnormally thin, and the Purkinje cells were reduced in number and sizc, dcformcd and disoriented. The inner granular layer was cithcr totally absent or showed a sparse population of scattered neurons. This combination of clinical and histopathological findings does not seem to be compatible with any prcviously known disease and suggests a new autosomal recessive disorder with distinctive neuropathological findings.

Aicardi syndrome. A neuropathological study Billette d e Villemeur T, Robain 0 INSERM U29. Laboratoire de neuropathologie, Hospital d e Saint Vincent d e Paul, Paris Aicardi syndrome includes infantile spasmes, agensis of the corpus callosum and chorioretinal lacunae. Aicardi syndrome have been rcported in girls only, (and in a 47XXY boy). Thc main troubles are mcntal arrieration and severe epilepsia. Both arc the consequences of the brain malformation. This girl died at three months. The brain weigh 600 g (normal), the leptomeninges arc thin, the malformation includes complete agenesis of the corpus callosum and an embosscd surface of the gyri. This polymicrogyric aspects predominates in right frontal and parietal lobes. On coronal section, there are Probst bundle, agenesis of anterior pilars of the fornix; antcrior commissure is present. To the microgyric superficial creasing corresponds a deep folding. The cortical mantle is invaginated and mcrgcd face to face. Numerous hcterotopias are present in the paraventricular regions and in the white matter of the centrum semi ovale. On niicroscopical cxamination, the facing molccular layers are fused, lined by vessels. The

cortex is unlaycrcd and large pyramidal cells arc sccn in thc wholc thickness ofthe cortex. The radial disposition ofthe neurons is present. In laycr I large neurons are present and Cajal-Rctzius cclls arc recogniziblc. A persistant subpial layer of granule cclls is present. Scattered neurons blur the inner limit of the cortex, many ncurons invadc molecular layer and meninges, nodular hcterotopias arc numerous. This cerebral malformation combincs agcncsis of the corpus callosum with a peculiar cortical dysplasia, and heterotopias. The abnormal cortical organisation includes an absence of horizontal laycring and persistancc of Cajal-Retzius cells and subpial granular laycr which normally are regressivc. Thc abnormal migration is both in excess and in shortage. Thc microgyric folding is a late manifestation of thc cortical disorder. Mental arricration and epilepsia are both the consequences of the cortical disordcrs.

Epilepsies among mentally retarded children. Prevalence, pathogenesis and drug resistance Steffenburg U, Kyllerrnan M, Hagberg G Ped.klin. II Barnklinikerna, Ostra Sjukhuset, Gothenburg, Sweden A population based prcvalence study of epilepsy (EP) in 6-13 year old children with mental retardation (MR) was performed in the city of Gothenburg, with the prcvalcnce day of 3 1 of deccmber 1988. MR was dcfincd as those attending education for mentally rctarded, corresponding to IQ 50-70 in mild mental rctardation (MMR) and IQ < 50 in severe mcntal retardation (SMR). EP was considered with 2 or more non-febrile seizures of cerebral origin. The prevalence rate of MR was 7.5/1000, and 20?

Abstracts of the 4th Northern Lights Neuroscience Symposium: Pathobiology of Mental Retardation, annual meeting. Gothenburg, Sweden, September 12-14, 1991.

Abstracts of the Fourth Northern Lkhts Neuroscience SvmDosium: Pathobiohzv of Mental Retardation, Annual Meeting, Septemvder 12- 14, 1991, Gothenburg,...
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