Brabz Research, 593 (1992) 159-167

159

© 1992 Elsevier Science Publishers B.V. All rights reserved 110116-8993/92/$115.110

BRES 18158

Graded postischemic reoxygenation reduces lipid peroxidation and reperfusion injury in the rabbit spinal cord A. Fercakova, G. Halat, M. Marsala, N. Lukacova and J. Marsala Institute of Neurobiology, SIocak Academy of Sciences, Kosice (Czechoslocakia) (Accepted 19 May 1992)

Key words: Spinal cord; lschemia; Graded reoxygenation;Rabbit

The effect of graded postischemic reo~genation on lipid peroxioation, neurological recovery and the degree of spinal cord damage after 20 min abdominal aorta ligature was teste.I in the rabbit. In comparison with normoxic recirculation, the graded postischemic reoxygenation (GPIR) during early phase of reperfusion (30 rain) significantly reduced the level of lipid peroxidation products (LPP) in rive and in vitro aher 1 h survival. Neuropathological changes in animals with normoxic reperfusion showed gradual deterioration ranging from appearance of heavy argyrophilic neurons after 1 h reperfusion followed by neuronal necroses after 12 h survival to the development of an extensive spongy lesion reaching ventral horn and intermediate zone 2 days postoperatively. The neuroprotective effect of graded postischemic reoxygenation was evident even after 2 days survivalwith preserved structural integrity of the gray matter as confirmed by light and electron microscopy. The results indicate that graded postischemic reo~genation during I h reperfusion can reduce lipid peroxidation and suppress i,Teversibleneuronal damage using developing during the early reperfusion phase.

INTRODUCTION Histopathology of ischemic neuronal damage using the rabbit spinal cord ischemic model has been widely studied ~,~2'24-~''~°. Recently, protective effects against ischemic injury in the spinal cord have been reported after hypothermia4°, hypoglycemia4l, calcium u' and glutamate antagonists 2"~'a2'4~ or free radical scavanger administration'~,26. This wide scale of different therapeutical interventions indicates that several pathogenetic mechanisms are involved in the development of ischemic and reperfusion tissue damage. It is known that ischemic injury is linked with the generation of oxygen free-radicals5'a4. Free-radical formation has been demonstrated both during ischemia3'~3 and the reperfusion phase 5'44. However, involvement of free radicals in the pathogenesis of early neuronal ischemic damage is still controversial. It has been suggested that free radicals do not play a pivotal role in the pathophysiology of ischemic injury after a brief period (15 min) of cerebral ischemiaI. On the other hand a significant enhancement of free-radical formation has been reported after 10 min of brain ischemia followed by 1 h

survival t'. It has been shown that these uneatable radicals are powerful initiators of lipid an0 protein degradation 4x. The protective effect of antio;idants and free-radical scavengers provides indirect evidence for the role of oxygen free-radicals and lipid i~eroxidation in the outcome of ischemia2a'4a. Recent studies have revealed an increase in lipid peroxidation after cerebral ischemia in rats and gerbils 4'2°. It has been shown that lipid peroxidation inhibitors such as tocopherol z~ or 21-aminosteroid U74006F 2" can prevent formation of the brain edema and neuronal damage, in the present study we investigated the influence of graded postischemic reoxygenation in the early reperfusion phase on the lipid peroxidation, neurological recovery and the degree of tissue damage alter transient spinal cord ischemia. MATERIAL AND METHODS

Experimental procedures Sixty-four adult male rabbits weighing 2.5-3 kg were used in this study. The animals were anesthetized with pentobarbital (30 mg/kg, i.e.) and maintained with 75% nitrous oxide and 25% oxygen. A Teflon cannula (Portex 0.5-0.9) was introduced into the right femoral

Correspondence: A. Fercakova, Institute of Neurobiology, Sroharova 57, 04001 Kosice, Czechoslovakia.

160 TABLE I

Ah,asured i,hysioh',tical ~hlta (mean +_S.D. ) All animals subjected to normoxic or graded postischemic reoxygenation were tested

Control

Before release

10 rain

20 rain

30 min

Group NR

pH (units) p,,CO_, (mmHg) p,,O: (mmHg)

7.40 5:0.03 40.87 5:2.25 93.15 _4-6.75

7.39 _+0.02 41.25 5:1.50 89.85 __5.25

7.43 + 0.03 38.25 + 3.01 90.22 + 6.01

7.38 5:0.04 40.50_+ 5.25 92.25 5:8.25

7.42 + 0.04 41.17 +_0.60 90.07 + 6.75

Group GPIR

pH (units) p a c e , (mmHg) p,,O, (mmHg)

7.43 + 0.03 39.37+3.75 93.22 ± 4.25

7.43 +_0.02 41.175:3.01 38.2 t) _+5.32 +

7.38 5:0.03 41.405:3.75 53. I 0 5:6.01 +

7.39 + 0.03 38.70+_6.01 61.80 5:0.75 +

7.41 _+0.02 41.17+3.75 90.52 5:5.25

" Statistically significant difference between the normoxic reoxygenation (NR) and graded postischemic reox3,genation (GPIR) group; P < 0.01.

artery for monitoring the distal blood pressure (LDP-102, Tesla, CSFR). A tracheostomy was performed and the animals were intubated with an ¢ndotracheal cannula (Portex, 2.5-3.5) connected to a volume-cycled ventilator (Chirolog 3, Fluidic vcntila~.or, Chirana, CSFR} The rate of ventilation was adjusted to maintain pO, between 91} and II0 mmHg and pCO., between 35 and 40 mmHg. Artcri:d blood gases were periodically recast, red to ensure that pCO z and pO 2 were between these ranges (AVL 995-Hb, Table I). A small subcostal inciskm on the right side was performed, providing access to the abdominal aorta at the level of the renal arteries. A sn~re ligature t-" with a long file was then placed around the aorta, distal to the left renal artery and subsequently tightened for 20 rain. Shortly bob)re tightening, the first blood sample was taken from the central car artery, fl~llowed by one taken immediately before the release. Subsequent samples were taken nt 5 rain intervals up to 30 rain, when animals were extubated, Body temperature was monitored with a rectal prohe and maintained between 38 ~,nd 39°C with a heating pad. The animtds were divided into three groups. In group A, surviving with normoxi¢ repcrfusion (NR), the respi. ratory gases remained uncltanged during ischemic and recircnlation period (roont air). The animals survivt~d [ h (subgroup A I, n ,~ 4), 6 I1 (subgroup A2, n ~ 2), 12 h (subgroup A3, n ~ 2) and 2 days (sub. ~roup A4, n **8), respectively, ht ~roup B, survivb'~ with ~raded postischemic reoxygenatitm (CiPlR), the 0 2 content of file insuflated gas mixture was lowered from 25r.~ to 10% approximately 3 rain bcflw~: the ligatur~ relettse which corresponded with reducing the poe,, to the 48± 12 mnttlg, Nitrnus oxide was added to the inhahttion mixture to maintain the inspiratory volume. Gradual normaliz:Ltion of the arterial pO, to the

original level was animals were then h (subgroup B2, (subgroup B4, n =

then achieved during 30 min recirculation. The allowed to survive for I h (subgroup BI, n = 4), 6 n = 2 ) , 12 h (subgroup B3, n = 2 ) and 2 days 8), respectively (Table 1I).

Neurological erahmtion Six hours following the procedure and then three times daily until the end of 2nd postoperative day, an observer unaware of the experimental groups graded the neurological status in groups A4 and B4 (2 days surviving period) using the following criteria: grade 1) = complete neurological deficit, animals were paraplegic and insensitive to noxious stimulation; grade I = partial neurological deficit, animals were able to stand but unable to hop, with variable response to noxious stimulation; grade I I = no neurological loss of function, animals were able to hop with normal physiological responses to noxious stimulation (Table III). The Fisher's exact test was used to determine the differences in neurological recovery.

Neunqmthologieal analysis After predetermined survival periods, the animals from subgroups AI~A4 and BI=B4 w~r¢ rean~sthctized and IrunscardiaUy perfllsed with saline (3(111ml/kg) followed by fixative containing 2% glutaraldehyde and 3% hwmaldehyd¢ in 0.1 M phosphate buffer, pll 7,4,

For the electron microscopy study the lumbar spinal cords were removed 12-18 h after perfusion fixation was accomplished and stored in the same fixative overnight at 4"C, Samples dissected from L4-L7 segments were postfixed in 2% OsO~ for 2 h. The specimens

TABLE II

Schematic representation of the erperbnental groups E.~perimental grcmps

Surt'it'al time

Histopathok~gk'al analysis

Et'ahmtion qf twu~tdogical status

Lipid peroxidation nzeasurt,nlents

Al(n = 4) A 2 ( n - - 2) A3 (n -- 2) A4 (n = 8)

+LM +LM, EM + LM + LM

-

-

NR

Ih 6h 12 h 2 days

-+

--

+LM

-

-

GPIR

+LM +LM + LM, EM

-+

--

B4 (n = 8)

6h 12 h 2 days

CI

control

-

-

+

-

-

+

-

-

+

-

-

+

Ill ( . = 4 ) B2tn = 2) B3 (n = 2)

(n

=

8)

C2 (n = 8) C3 (n = 8) (?4 (n -- 8)

I h

20 rain ischemia without reperfusion I h NR 1h (GPIR)

NR, normoxic postisehemic reoxygenation; GPIR, graded postisehemic reoxygenation.

-

f--

TABLE II1 Neurological status during recirculation period m gaoup A ~ (NR) and B4 (GPIR) Experimental grou~,

Grade

Time of recircularion 6h

12h

24h *

48b *

A4 (NR)

0

4

5

7

7

(n = 8)

!

2

2

0

0

ll

2

!

1

1

0

2 2 4

I 2 5

1 I

1 I 6

B4 (GPIR) (n = 8)

I

II

6

NR, normoxic postischemic rcoxygenation; GPIR, graded postischemic rcoxygenation; * P < 0.05 vs. group B4.

were dehydrated in alcohols and embedded in Durcupan. Semithin ! p.m sections were stained with Cresyl violet. Ultrathin sections were then analyzed using a Tesla BS 500 electron microscope. In addition to semithin sections and electron microscopic analysis, separate samples in groups AI and Bi (1 h surviving period)were taken from lumbar spinal cords and p~tfixed in 10% buffered formaline for at least 14 days. Then standard transverse sections (20 p,m thick) from LA-L6 segments were prepared and impregnated using the suppressive Nauta method, permitting the visualization of the early neuronal changes manifested by somatic and dendritic argyrophilia ~s'2~. The numbers of neurons damaged by ischemia-reperfusion were then counted with respect to their laminar distribution •~'~ and divided into 3 areas for statistical analysis: area I (interneurons localized in laminae I-VI), area II (interneurons localized in laminae VII and X) and area Ill (laminae VIII and IX). The mean values of impregnated neurons from each of L4-L6 segnlents were evaluated and compared using Student's t-test (Table IV). Bita'hemk'al analysis From the total of 64 rabbits, 32 animals were used (group C) for the endogenous and exogenous lipid pcroxidution measurement and were divided into 4 subgroups: (I) sham control (subgroup CI, n - 8 ) ; (2) animals with 20 rain ischemia without recirculation (subgroup C2, n ® 8); (3) 60 min of normoxic rueirculaiion (subgroup C3, n ~ 8); (4) 60 rain of graded poslischemic reoxygenation (subgroup C4, n - 8, Table It). Frozen spinal cord homogenales prepared from lumbosacral segments were used for determination of lipid peroxidation products (LPP) in rive and in vitro, The level of LPP in rive was measured as thiobarbituric acid.reactive substrates (TBA-RS) as reported by Hal a t e t al. za. Homogenates prepared from LA-L7 spinal cord segments were used for in vitro peroxidation and were incubated in a water bath at 37°C with ferrous sulphate (0.01 mM. l - z) and ascorbic acid (0.25 raM.I-I). Incubated samp]es were continuously equilibrated (for I h) with a gas mixture consisting of 95% 0 2 and 5% CO 2. Formation of LPP represented by TBA.RS in rive and during stimulated pemxidation in vitro was determined by the method of

1 |

I c 2 0 H I N ISCH.

RESULTS

Tightening of the snare ligature caused an immediate drop in distal blood pressure to 10 + 3 mmHg measured in right femoral artery in all animals. The appearance of distal blood pressure was detected immediately after the ligature release and preischemic level was reached in 2 - 3 rain postocclusion. No significant differences between the groups were detected (Fig. 1),

Lipid peroxidation The results presented in Fig. 2 show that 20 rain spinal cord ischemia did not result in detectable changes in concentration of TBA-RS. Ischemia fol-

1.0 0.9

0.8 G7 0.6 ...

0.4

Distribution of heacy argyrophilic neurons after i h o f normoxic (NR) or graded postischemic (GPIR) reoxygenation

0.3

...

0.2

---

0.1

"';

Group AI (NR) (n = 4) Group BI (GPIR) (n = 4)

area I *

area !1 *

area Iii

15.6_+3.7

22.3_+8.3

4.2-+ 1.2

6.14:3.7

8.9_+7.8

2.2-+ 1.7

area I, laminae 1-VI; area II, laminae VII and X; area I11, lamina ViII and IX. * P < 0.05 vs. group BI.

1p 20min I RECIRCULATION

Ushiyama and Mihara 4.. Results from analyses were expressed as nmol TBA-RS.mg protein. Protein concentn:tion was determined by the method of Lowry el al. 27. Results were st ~ti~lically evaluated by Student's t-test, analysis of variance and have been given as means + S.E.M.

0.5

Number of argyrophilic neurons

I

Fig. I. Time-course of arterial blood pressure changes during aortic occlusion and early rcperfusion phase measured in the femoral artery.

TABLE IV

Experimental group

161

Z~ C!

C2

C3

C4

Fig. 2. Effect of graded postischemic reoxygenation on formation of TBA-RS in spinal cord tissue from lumbosacral segments following 20 rain ischemia and 60 min reoxygenation. Cj: control; C2:2(1 rain ischemia; C;: 60 rain of normoxic recirculation, and C 4 : 6 0 rain graded reoxygenation; data are means of 8 experiments _+S.EM.

162

*'1" , • F.o'"

,,!

. /4...V ,,g

It

3

Fig. 4. Argyrophilic neurons (arrows) in the anterior horn (LIX) and intermediate zone (L VII) after 20 rain isehemia and 1 h of normoxic reperfusion; Nauta method, 120 x .

I i ~t t e

g

b

(5

fi)

Ks

6'o ml,

Fig. 3. Time-course of TBA-RS prodtlction (measured as TBA) in spinal cord homogenales from h, mbosacral segmenls in vitro following 2(I rain ischcmia :rod 61) rain rcoxygcnation. ~ control; . . . . . 20 rain ischcmia and 6(1 rain reoxygenation; - - - - - - 20 rain ischemia and 61) rain graded reoxygenation. Homogenates were incubated at 37°C in the presence of 0.01 mM FeSO4, 0,25 mM ascorbic acid. 95r~ O: +5¢~ CO, for 61) nlin. D,'lta arc me:ms of 8 experimcnts±S,E.M. *P < I),0=l with respect to incubated etmtml, o p < I),0l, ' P < IL02 with respect to 21) rnin ischemia and 6(1 min grqded reoxyg~ll;ltit)ll,

lowed by 6(1 rain of normoxic recirculation was manifested by a significant increase of TBA-RS in spinal c,,w; :issue, TBA-RS values were by 29% higher in comparison with the control tissue. After 60 rain of graded reoxygenation TBA-RS formation was suppressed and remained close to control or ischemic level. Different postischemic susceptibility of spinal cord lipids to stimulated peroxidation in vitro is shown in Fig. 3. The addition of ferrous sulphate and ascorbic acid to homogenates increased TBA-RS content nearly to 50%. The rapid increase in the concentration of TBA-RS was found during incubation of these homogenates in the presence of 95% O: and 5% CO 2. The susceptibility of tissue lipids to stimulated peroxidation in vitro was lower after graded reoxygenation in comparison to normoxic recirculation,

Postoperatice neurological status b~ group A4 and B4 After 6 h reperfusion no significant differences were found. Statistical analysis revealed significantly better functional recovery in group B4 when compared with group A4 and was clearly apparent after 24 h reperfusion and remained unchanged until the end of the 2nd postoperative day (Table Ill).

Histopathological findings after 1 h reperfusion In group A1 histopathological analysis using the suppressive Nauta method revealed high density of heavy argyrophilic interneurons localized in area II (interneurons localized in laminae Vll and X) which was significantly different if compared with group B1 (Figs. 4 and 5). Significant differences between area I and III were detected (Table IV). Neuronal damage after 6 h reperfusion Light microscopic observation (Cresyl violet) revealed most ~f motoneurons with normal appearance and no signs of ischemic changes in bt~th A2 and B2 groups were found. However, evident interneuronal loss with initial formation of n~crotLc loci localized mostly between laminae V-VII was detected in group A2. This finding was in contrast with group B2 in which only occasional loss of interneurons was found during this period. Electron microscopy in group A2 showed perineuronal edema accompanied by alteration of synaptic terminals and swelling of astrocyte foot processes (Fig, 6),

Fig. 5. Normal-appearing motoneurons (arrows) in the medial part of the anterior horn tL IX) after 1 h survival with GPIR, Nauta method, 250 X.

163

Fig. 6. Electron micrograph depicting perineuronal edema and enlarged astrocyticprocesses (arrows), 20 rain ischemia and 6 I! of normoxic reperfusionlC = cytoplasmof motoneuroncontaininglargedenselystainedNisslbodies, 2,4{)1)x,

Neuropathological findings after 12 h reperfusion Within 12 h survival various degrees of neuronal alteration were observed in group A3. ~, number of motoneurons localized in the central and lateral parts of ventral horns were already necrotic or disintegrated and those in the marginal zone became dark and shrunken. The neuropil displayed clear signs of vacuolization affecting predominantly the central part of the gray matter (Fig. 7). Dark and shrunken neurons detected in semithin sections corresponded with neurons displaying a higher density of cytoplasm which are generally described as the electron-dense form of neuronal damage. In these neurons the mitoehondria were swollen, combined with disruption or complete loss of their internal membranes. Although fine vacuolization in the intermediate zone (lamina VII) was also found in group B3, anterior horns remained almost entirely protected. Motoneurons seen in semithin sections showed cytoplasm, nucleus and nucleolus of normal appearance (Fig. 8).

Neuronal damage after 2 days survival The degree of gray matter damage showed clear correlation with loss of neurological function in both

A4 and B4 groups. In paraplegic animals the extent of the multifocal liquefactive necrosis, affecting 40-80% of the gray matter was detected and only occasionally small neurons of normal appearance located in lami-

Fig. 7. Light micrograph taken from section of an I..5 segment subjected to 20 rain ischemiaand 12 h of normoxicreperfusion.Dark shrunken and necrotic neurons (asterisks) and vacuolizationof the neuropil can be seen,semithinsection,Cresylviolet,200×.

164

Fig. 8. Light micrograph taken from section of an 1.5 segment subjected to 20 rain ischemia and 12 h of graded postischemic reoxygenation. Normal-appearing motoneurons (arrowheads); no signs of vaculizalion in the neuropil can be seen, semithin section, Cresyl violet, 200 ×.

nae I-Ill were detected (Fig. 9). However these neurons were found in close vicinity to dense macrophage proliferation combined with polymorphonuclear infil-

Fig. tO. Light micrograph taken from section of an !.5 segment subjected to 20 min ischemia and 2 days survival after graded postischemie reoxygenation, No signs of infarction can be seen, Cresyl violet, 63 x .

tration usually creating the borders between necrotic and relatively unaffected tissue, in animals which regained their neurological functions histopathological analysis revealed almost fully preserved motoneurons containing coarse-granulated Nissl substance and round centrally placed nuclei with conspicuous nucleoli (Fig, 10), In animals with GPIR only few neurons were detected in ultrathin sections displaying high density of cytoplasm and containing a large number of neurofilaments and lysosomes scattered among Nissl bodies. Edema of dendrites and astrocytes occurring in close vicinity of these neurons was quite apparent (Fig. 11). DISCUSSION

Fig, 9, Light micrograph taken from section of an [.5 segment subjected to 20 rain ischemia and 2 days survival with normoxic reperfusion. Extensive necrotic area in the anterior horn, intermediate zone and in the deep portion of the posterior horn can be seen, Cresyl violet, 63 x .

Our results obtained from a highly reproducible rabbit spinal cord ischemia model demonstrate a significant protective effect of graded postischemic reoxygenation (GPIR) on lipid peroxidation and the degree of ischemie tissue damage. We have shown that 30 rain

165

Fig, I !. Electron micrographtaken from ultrathin section of an L5 segment subjected to 20 min ischemiafollowedby graded postischemic

reoxygenation and 2 days survival. The cytoplasm of a motoneuron contains scattered Nissl bodies (asterisks) and a higher amount of neurofilaments(arrowhead),2,400×.

of GPIR instituted immediately after 20 min of spinal

cord ischemia present an efficient neuroprotective intervention which markedly reduces the level of lipid peroxidation products (TBA-RS) in comparison with normoxic reoxygenation (NR) after 1 h survival. Measurement of TBA-RS has been suggested as being a non-specific index of lipid peroxidation but under controlled conditions the method can adequately reflect peroxidative tissue reactions 2. The protective effect of GPIR was also apparent after a longer survival period, i.e. 2 days, as confirmed by neurological and neuropathological analysis. The concept of reperfusion injury is based on the evidence that the availability of oxygen in the previously ischemic tissue triggers a series of reactions leading to the generation of oxygen free-radicals 2~'~4. Our results are in agreement with the evidence indicating that during ischemia and particularly in the reperfusion phase, enhanced formation of oxygen free-radicals occurs 44'47. During aortic occlusion in the rabbit spinal cord a residual circulation reaching 2% of normal blood flow remains n. It has been estimated that 5% of

the tissue 0 2 level may be sufficient for free-radical generation ~3. Reperfusion spinal cord injury is related in part to the tissue hyperoxia due to postischemic hypermia 2x, Previous experiments in our laboratory have shown that graded postischemic reoxygenation prevented postischemic rise in tissue pO 2, improved the energy metabolism and functional spinal cord recovery H~'2~, and had a highly protective effect on blood-brain barrier permeability a6. Oxygen radicals arising during recirculation are known to attack any compartment of the cell with preferential activity on lipids and proteins 3s. Free-radicals can react with the polyunsaturated fatty acids in the cell membrane and thereby alter its structural integrity and functional activity 34. It has been demonstrated that spinal cord ischemia leads to free fatty acid accumulation thus providing a substrate for oxidative pathways ~s. The cell injury produced by lipid peroxidation of cell membranes can range from increased membrane permeability to cell lysis 35. The study of neuronal membrane permeability to horseradish peroxi-

166 dase following 10 rain of brain ischen':~ in the rat demonstrated the presence of membrane discontinuities after 60 min of recirculation t4. The membrane perturbations may be the result of phospholipid changes leading to the opening of C a 2+ channels and increased cytoplasmic concentration of this ion followed by enhanced phospholipase and protease activity that can digest membranous and cytoplasmic components 43. The changes in vascular permeability indicate that endothelial capillary cells may be the primary target affected by oxygen free-radicals. The present study shows a different vulnerability of membrane systems to reperfusion injury. Inside the cell, the membranez of the endoplasmic reticulum appeared to be highly sensitive and were partly disintegrated 6 h after normoxic reoxygenation, while the mitochondria remained well ~,cserved. The most susceptible seemed to be the synap(i¢ and cell membranes, a phenomenon probably connected with glutamate release. Excitatory amino acids (EAA) glutamate and aspartate are of particular importance in the development of ischemic spinal cord injury 32'33 and there is physiological evidence indicating that EAA are involved in the excitation of some spinal cord neurons it. Recently, it has been suggested that the neurotoxic effect of EAA can be mediated by, or is mutually i¢lated to the free-radical formation leading to ischemic neuronal death "~7 which is supported by the evidence that excitotoxin-induced neuronal damage may be reduced by free-radical scavangers ts. Our results indicate the GPIR can reduce or partly abolish the glutamate neurotoxicity in the spinal cord gray matter during the early reo~genation period, Recent evidence suggests that enhanced Ca 2+ influx may occur as a result of lipid peroxidation after ischemia ~s. Therefore, stabilizing of membranes by preventing free-radical formation may reduce Ca 2+ overload in neurons and thereby ameliorate the outcome of ischemia 22. The role of postischemie oxygen free-radical production has been suggested to occur also during the late postischemic recirculation period i.e., 2-3 days postocclusion as a result of the mononuclear's infiltration and due to their metabolic and phagocytic activity. The first increase of non-specific esterase in the spinal cord gray matter has been detected 3 h after 20 min ischemia, being in contrast with first signs of irreversible neuronal damage detected several hours after ischemia using light microscopy and standard staining methods s'~. However, using the suppressive Nauta method, unambiguous irreversible neuronal damage was clearly detected after 60 rain postischemia thus preceding the phase of postischemic mononuclear infiltration. The results from our study indicate that G P I R

can significantly suppress the number of irreversibly damaged neurons during the early reperfusion phase in accordance with a better motor score if graded 2 days postocclusion. The efficacy of different therapeutic interventions aimed at preventing early postisehemic neuronal damage thus appears to play a pivotal role, influencing the recovery of neurological functions developing several days after ischemic insult. In conclusion, the protective effect of graded postischemic reoxygenation can effectively reduce lipid peroxidation and early postischemic neuronal damage if instituted at the very beginning of the recirculation phase. Moreover, this protective effect was confirmed also after 2 days survival and was manifested as reduced gray matter damage accompanied by neurological recovery. Acknowledgements. The authors wish to thank Dr. J. Taxi for his

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Graded postischemic reoxygenation reduces lipid peroxidation and reperfusion injury in the rabbit spinal cord.

The effect of graded postischemic reoxygenation on lipid peroxidation, neurological recovery and the degree of spinal cord damage after 20 min abdomin...
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