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creatinine ratios. Jenkins et al believe that insulin-induced enhancement of hepatic cholesterol synthesis through hydroxymethylglutarylcoenzyme A reductase may be the basis of the

urinary C-peptide

TELL US A STORY

to

changes. What is the relevance of these findings? The Toronto researchers feel that their approach will lead to better understanding of the metabolic adaptations to measures-eg, a-glucosidase inhibitors, fibre, and diets with a low glycaemic index that decrease serum lipid concentrations and improve carbohydrate metabolism—designed to smooth out the absorption of nutrients through the day. Whilst no-one is seriously going to propose a seventeen meal a day eating pattern, this sort of work strengthens earlier suggestionsZ,4-6 that little and often may be better than the single meal a day which is becoming increasingly common. The results also give further credence to the practice of advising patients with insulin-dependent diabetes to eat more than three small meals a day. Finally, this type of research provides new insights into the metabolic adaptations one can expect during continuous artificial parenteral or enteral feeding.16,17 carbohydrate tolerance in diabetics following the hourly administration of glucose and insulin over long periods. Q J Med

1. Ellis A. Increased

1934; NS3: 137-53. 2. Hollifield G, Parson W. Metabolic adaptations to a "stuff and starve" feeding program. II. Obesity and the persistence of adaptive changes in adipose tissue and liver occurring in rats limited to a short daily feeding period. J Clin Invest 1962; 41: 250-53. 3. Cohn C, Joseph D, Bell L, Oler A. Feeding frequency and protein metabolism. Am J Physiol 1961; 205: 71-78. 4. Gwinup G, Byron RC, Roush W, Kruger F, Hamwi GJ. Effect of nibbling versus gorging on glucose tolerance. Lancet 1963; ii: 165-67. 5. Gwinup G, Byron RC, Roush WH, Kruger FA, Hamwi GJ. Effect of nibbling versus gorging on serum lipids in man. Am J Clin Nutr 1963; 13: 209. 6. Irwin MI, Feeley RM. Frequency and size of meals and serum lipids, nitrogen and mineral retention, fat digestibility and urinary thiamine and riboflavin in young women. Am J Clin Nutr 1967; 20: 816-24. 7. Cohn C, Joseph D. Effect of rate of ingestion of diet on hexose monophosphate shunt activity. Am J Physiol 1959; 197: 1347-49. 8. Tepperman J, Tepperman HM. Metabolism of glucose-1-14C and glucose-6-14C by liver slices of refed rats. Am J Physiol 1961; 200: 1069-73. 9. Bray GA. Lipogenesis in human adipose tissue: some effects of nibbling and gorging. J Clin Invest 1972; 51: 537-48. 10. Sugden MC, Holness J, Palmer N. Fuel selection and carbon flux during the starved to fed transition. Biochem J 1989; 263: 313-23. 11. Pallardo FV, Williamson DH. Comparison of the flux of carbon to hepatic glycogen deposition and fatty acid and cholesterol synthesis on refeeding rats fed ad libitum or meal fed rats with a chow diet meal. Biochem J 1989; 257: 607-10. 12. Holness MJ, Sugden MC. Comparison of tissue pyruvate dehydrogenase activities on refeeding rats ad libitum or meal-fed rats with a chow-diet meal. Biochem J 1989; 262: 321-25. 13. Dallosso HM, Murgatroyd PR, James WPT. Feeding frequency and energy balance in adult males. Hum Nutr Clin Nutr 1982; 36c: 25-39. 14. Garrow JS, Durrant ML, Blaza S, Wilkins D, Royston P, Sunkin S. The effect of meal frequency and protein concentration on the composition of the weight lost by obese subjects. Br J Nutr 1981; 45: 5-16. 15. Jenkins DJA, Wolever TMS, Vuksan V, et al. Nibbling versus gorging: metabolic advantages of increased meal frequency. N Engl J Med 1989; 321: 929-34. 16. Messing B, Pontal PJ, Bernier JJ. Metabolic study during cyclic total parenteral nutrition in adult patients with and without corticosteroid induced hypercatabolism: comparison with standard total parenteral nutrition. J Parenter Enter Nutr 1983; 7: 21-25. 17. Lerebours E, Rimbert A, Hecketsweiler B, Hellot M-F, Denis P, Colin R. Comparison of the effects of continuous and cyclic nocturnal parenteral nutrition on energy expenditure and protein metabolism. J Parenter Enter Nutr 1988; 12: 360-64.

Sighted people dramatise any narrative, especially the extended tales found in books, with their own visual imagery. The physiological response to reading is uniquea high narrative input must be processed while the visual system is busy decoding the text. By contrast, the storyteller’s audience uses the performer’s gestures rather than the listener’s own vision to create awareness of anything. In both cases, however, the scene is being created internally. If we make the effort to ponder the source of what we are seeing in the mind’s eye, it becomes apparent that we often use a repertoire of internal scenes or mappings that refer to real places but have nothing to do with the story. These we use a little like chessboards or sand tables. Thus, a passage from Vanity Fair is set in a landscape where the position of trees, buildings, and so forth is in fact the landscape of the old school playing field or a street adjacent to the family home-shorn of all mnemonic detail, but acting as a stage set. Even when, as in Victorian novels, the author’s description is detailed, we still impose it on such a scene. Closer introspection will often show that the same treatment is used with other thought processes and with certain tasks, especially those that involve dissociative concentration. Many will recognise the slightly hypnotic effect of hours spent on a circuit board, which itself becomes a landscape or map in small. Very little attention has been paid to these "mental models in narrative comprehension".’ Although Bower and Morrow1 concentrate on the influence of the map, relevant or irrelevant, on comprehension of the story, the way in which these spatial models are activated is perhaps more thought-provoking. Neurologists are bound to be interested not so much in the fact that mental mapping takes place, but in the aura-like character of some of these inner-visual archetypes that are often imprinted early in life or in the distant past. In dealing with these compulsive images the choice of map seems to be arbitrary, and not, as in Bower and Morrow’s experiments, based on characters’ goals. In those experiments "if the protagonist is hungry images of places and objects associated with eating will be activated". In relation to the imprinted map, however, the restaurant will take on the spatial characters of the wholly irrelevant street or playing field. It is by no means clear whether everyone experiences these overriding spatial mappings, or why certain scenes are imprinted in this way. One immediate association is with the mnemonic auras, in which sudden recollection of an unremarkable scene presages a fit; the seizure can sometimes be aborted if the patient can suppress the mental image. Another very similar experience characterises the "dream scintillations"2,3 of temporal lobe migraine-the scene comes to mind together with a sense of meaningful association with something that cannot be recalled, plus an unpleasant affect. Since these symptomatic effects are apparently active processes, the storage of the images is probably active too, and they may well have a profound if unrecognised function in providing the scaffolding on which our continuous sequence of inner visualisation is erected. They certainly have a considerable bearing on the programming of dreams, but they are also active, if we look for them, in the substance of many waking thought processes.

Creation of coherent, usually memory-based, by electrical stimulation goes back to

images and Hughlings Jackson, and one can see why any complex organism should scenes

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have circuitry to compile a set of mappings at an early stage. The point of interest is that once these are formed some of us seem to hang onto them for life. For those who wish to pursue "introspective neurology", the entire range of these preferred maps is most easily recalled, as are sequences of previously forgotten dreams, in the period when one is falling asleep. The possible association between mapping and dreaming may well be the most interesting feature of all. GH, Morrow DG. Mental models in narrative comprehension. Science 1990; 247: 44-48. 2. Forbes A. Dream scintillations. Psychosom Med 1949; 2: 160. 3. Saul LJ. Dream scintillations. Psychosom Med 1965; 27: 286. 1. Bower

WALRUS WITHOUT TEARS The hazards of infection associated with several culinary practices-notably, the inadequate cooking of poultry and eggsl and the preparation of "cook-chill" food2-have been widely publicised. Other infections contracted as a result of injudicious eating habits are less well appreciated. Trichinella spiralis is a nematode parasite of many species of carnivorous animals. Man becomes infected by eating encysted larvae in raw or poorly cooked meat from these animals, principally pigs, wild boar, and bears. Although the number of cases of trichinosis reported to the public health authorities has declined sharply both in the UK3and in the USA,4 these figures probably represent only a fraction of the total. Trichinosis is often symptomless or misdiagnosed, and the disease is still endemic in many areas of the world. In the USA there are now very few cases of trichinosis caused by commercial pork products,4largely because contacts between commercially farmed pigs and wild animals such as rats have been eliminated and there are regulations forbidding the feeding of garbage to pigs unless it has first been boiled. Almost all the reported cases are caused by the consumption (often as homemade sausage) of wild animal meat or of pork obtained direct from small farms.4 Trichinosis is especially common in the Arctica between 1970 and 1985 the annual rate in Alaska was 1-8/100 000 population compared with 0-05 cases/ 100 000 for the entire USA.6 Similarly, between 1973 and 1982, the northernmost regions of Canada reported 11-0 cases/ 100 000 per year, a rate almost 200-fold higher than that in the country as a whole.’ These high rates are related to the consumption of polar bear and walrus meat by the Inuit (Eskimo) population8 and most cases are caused by a distinct strain (and possibly a different species) of Trichinella.9 Elsewhere, other meat may be hazardous. Outbreaks of trichinosis in FrancelO,l1 and Italy12 have been attributed to the consumption of horse meat, which is apparently typically eaten raw (as steak tartare or minced into soups) or rare. Two such outbreaks, affecting at least 1073 persons with 5 deaths, occurred in 1985." Although thirteen localities in France reported cases, all could be traced to meat from two horse carcasses. The horse is, of course, herbivorous, and for the animals to have become infected presumablv the foodstuffs must have been contaminated with animal remains-either rodents accidentally ground into the grain used as fodder or pork offal mixed into prepared food. After encysted Trichinella larvae are ingested, they are liberated in the small intestine and develop into adult worms. Within a few days adult females produce larvae,

which enter the circulation and begin to invade striated muscle. During the few days of adult worm development the patient may notice gastrointestinal symptoms, chiefly diarrhoea. The classic clinical features of the infectionfever, myalgia, and periorbital oedema--are caused by the encystment of larvae. The diagnosis may be suggested during the muscle phase by a pronounced eosinophilia and increased serum concentrations of muscle enzymes; it can be established by finding the larvae in a muscle biopsy specimen. Canadian workers have now described a new clinical syndrome caused by trichinosis in the Arctic .7,13 There were 49 patients, most of whom had illnesses characterised by diarrhoea without fever and only minor and transient muscular symptoms. The diarrhoea lasted for a mean of 6 weeks and was watery, non-bloody, and often associated with abdominal pain; it was especially likely to occur in those who had become infected as a result of eating walrus meat. Trichinellae are known to cause bowel hypermotility in mice14 but the reason for this different form of illness in the Arctic is unknown. It may be the result of Trichinella reinfections in individuals with existing immunity or of different virulence of the Arctic strains of the

parasite? Trichinosis is a preventable disease. Ready-to-eat pork are safe becuase they must be heated or frozen to kill the larvae before they are sold to consumers. Fresh pork and all wild animal meat should be assumed to be infected and must be heated to 77°C to kill the parasite. Microwave ovens must be used correctly. Improper cooking of wild boar sausage in a microwave has been associated with trichinosis15 and recommendations for the safe microwave cooking of pork have been published.16 Although the Inuit delicacies of igunaq (raw walrus left to ferment in a skin bag for several weeks) or polar bear meat are unlikely to appeal to others, the increase in travel and hence the consumption of more exotic foods and the fashion for "naturally reared" rather than intensively farmed meat make it important to obtain a detailed dietary history in patients who present with clinical illnesses accompanied by eosinophilia. The injunction "never eat pink pork" should be equally rigorously applied to several other forms of meat.

products

1. Cowden JM, Lynch D, Joseph CA, et al. Case-control study of infections with Salmonella enteritidis phage type 4 in England. Br Med J 1989; 299: 771-73. 2. Editorial. Listeriosis. Lancet 1989; i: 83-84. 3. PHLS Communicable Disease Surveillance Centre. Communicable Disease Report quarterly and annual tabulations, 1986. London: Public Health Laboratory Service, 1989: 28. 4. Bailey TM, Schantz PM. Trichinosis surveillance, United States, 1986. MMWR 1988; 37 SS-5: 1-8. 5. Tanner CE, Staudt M, Lussier M, Bertrand S, Prichard RK. Seroepidemiological study for five different zoonotic parasites in northern Quebec. Can J Publ Health 1987; 78: 262-66. 6. Centers for Disease Control. Annual summary 1984: reported morbidity and mortality in the United States. MMWR 1986; 32: 125-27. 7. MacLean JD, Viallet J, Law C, Staudt M. Trichinosis in the Canadian Arctic: report of five outbreaks and a new clinical syndrome. J Infect Dis 1989; 160: 513-20. 8. Margolis HS, Middaugh JP, Burgess RD. Arctic trichinosis: two Alaskan outbreaks from walrus meat. J Infect Dis 1979; 139: 102-05. 9. Dick TA. Species and infraspecific variation. In: Campbell WC, ed. Tnchinella and trichinosis. New York: Plenum, 1983: 31-73. 10. Bourée P, Bouvier JB, Passerson J, Galanaud P, Dormont J. Outbreak of trichinosis near Paris. Br Med J 1979; i: 1047-49. 11. Ancelle T, Dupouy-Camet J, Bougnoux M-E, et al. Two outbreaks of trichinosis caused by horsemeat in France in 1985. Am J Epidemiol 1988; 127: 1302-11. 12. Mantovani A, Filippini I, Bergomi S. Indagini su un’ epidemia di trichinellosi umana verificatasi in Italia. Parassitologia 1980; 22: 107-34.