443

involved are likely to be very small, this could wellaccount for the failure to recover virus from spontaneoustumours, even in chickens. Moreover, sometimes anappreciable amount of virus can be recovered fromtumour tissue, even when it is of a low-dose type; henceit is still worth while to search for virus in all possiblelesions. If virus can be recovered, the technique ofserial and selective passage can be utilised to enhancevirulence and so aid identification. Finally BRYAN drawsattention to the detection in cultures of naturally occur-ring lesions of a hitherto unknown agent " of herpes-like ultrastructural morphology, which differs both bio-logically and antigenically from all of the known agentsof the herpes group ". This agent, which has beendetected by new technical methods, appears to be

present at low levels in normal and cancerous cells;whether it, in its turn, is a

"

passenger "

or is associatedin some way with the cause of malignancy, remains tobe seen.The search for possible leukaemic viruses in human

tissue is clearly being actively prosecuted, and workersare not discouraged by recent failures and contradictions.This work is becoming increasingly technical and

specialised, and the clinician can do no more than followthe results with hopeful interest. Although a propertrial must be given to new agents, such as asparaginase,16for control of leukaemia, these can never offer more thana second-rate chance compared with treatment firmlybased on knowledge of xtiology.

16. Lancet, 1968, i, 1075.

Annotations

LEAF PROTEINS

SOMETHING like a fifth of the people of the world areadequately fed: for the rest, protein deficiency is a

common, and sometimes serious, problem. I Educationcan do much to ease today’s food problems: wars anddrought apart, most people get enough food to assuagetheir hunger, and lack of protein is often due to dietarytraditions which demand that they eat the wrong kindsof food, even though it would be possible for them togrow crops that are rich in protein. But the long-termoutlook is grim: by the end of the century the world’sfood production will have to be trebled at least, to keeppace with population expansion, and unconventionalsources of protein will sooner or later have to be exploited.Greater use will have to be made of plant protein, forthe dry-weight yield per acre can be as much as tentimes higher than that obtainable from the livestockthat can be supported by the same area of land.2Oleaginous seeds have already been successfuly marketedin many parts of the world. For instance, soya-beanflour, containing 55% protein, is widely used in manu-factured foods in the U.S.A., and bottled soy milk is

produced on a commercial scale in several countries. IThe extraction of protein from fresh leaf crops, thoughit has attracted considerable interest, has not yet beendeveloped on a practical scale. The nutritional value ofleaf protein-better than most seed proteins and as

good as many animal proteins-has been known for

many years: the trouble is that the alimentary system ofnon-ruminants like man is ill equipped to deal with largeamounts of vegetable matter.3At Rothamsted Experimental Station Mr. N. W. Pirie,

F.R.S., head of the biochemistry department, whose inter-est in leaf proteins extends back some 30 years, hasdeveloped a machine which makes their extraction afeasible proposition for agricultural communities in de-veloping countries.4 Fresh leaves grown for the purpose(e.g., wheat or clover) or byproduct leaves (e.g., frompeas, potatoes, or sugar-beet) are fed into a horizontalcylinder 0-9 m. long and 0-6 m. in diameter, where theyare reduced to a pulp by a set of rotating beaters. Whendriven by a 25 h.p. motor the machine can handle a ton

1. DeMaeyer, E. M. Wld Hlth Org. Chron. 1968, 22, 225.2. Pearsall, W. H. New Biol. 1954, 17, 9.3. Pirie, N. W. Science, N.Y. 1966, 152, 1701.4. Times, July 19.

of leaves per hour, from which is extracted about 40 lb.of protein. Some of the beaters are wedge-shaped, tomove the crop along the cylinder, and crops of differenttexture can be accommodated by changing the speed ofrotation and the ratio of plain and wedge-shaped beaters.The pulp passes to a conveyor belt of adjustable tension,which presses it against a perforated pulley. The protein-rich juice then flows through the perforations, into thepulley, and out over its edges. The juice is heated

quickly to at least 70°C (usually by steam injection) tocoagulate the protein, which, after washing, appears asa dark-green cheese-like substance. Protein could alsobe separated by drying the whole leaf juice, but the pro-duct would contain other substances besides protein-salts, sugars, and aminoacids that are nutritionally usefulbut that could be supplied economically in other ways;some polysaccharides and nitrogen compounds of novalue to non-ruminants; and various other substancesthat may be toxic or unpleasant to taste. The extractionobviously produces a large amount of fibrous material,but since cattle will readily eat the residue, leaf-proteinextraction could be made to form part of a programmeof forage conservation.Machines that pulp and press in one operation do not

extract satisfactorily unless the material is passed throughseveral times, but for an unsophisticated communitysimplicity is probably more important than efficiency,and in Pirie’s small " village unit " the two operationsare combined. 100-200 kg. lots of leaf are pulped by aheavy ribbed roller driven round on a horizontal bed,and as the juice is released it is pressed through perfora-tions in the bed. This machine uses less power per tonof crop than the larger version, but it extracts only 40-50%protein, compared with 50-70% in the larger machine.It may be possible to improve the extraction by modify-ing the design of the ribs.One obstacle to the introduction of any novel food is

the attitude of the well-fed people who, both nationallyand internationally, control research policy. They oftenassume that the only foods that are acceptable are thosewith which they are familiar, though slight concessionsare made in favour of bland pale powders with anindefinite shelf-life. As normally made, leaf protein isdark green and has a slight flavour of tea or spinach.People become accustomed to its undisguised appearanceand taste in one or two weeks; with a little skill in pre-sentation it proves acceptable to nearly all the visitorsto Rothamsted to whom it is offered.

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Leaf-protein extraction is especially suitable for thewet tropics, where vegetation grows luxuriantly. Intrials in England the annual yield of dry extracted

protein is roughly 1-4 tons per hectare: in Mysore it isabout 3 tons per hectare. Leaf extractors have been usedat various times in Jamaica, India, Nigeria, and NewGuinea, but so far no programmes have been financedwell enough to allow large-scale production. Leaf pro-tein can be extracted from local crops, for local con-

sumption, without elaborate machinery. If the extractorreceives the interest and support it deserves, the wetterparts of the tropics, where protein shortage is most

acute, might eventually be made nutritionally self-sufficient.

OCCUPATIONAL MEDICINE WITHIN THE N.H.S.

THE rising figures for absenteeism and the costs, directand indirect, of illness suggest that some new thinking isneeded about the health of the working population, and itis at least possible that the experience of doctors specialis-ing in occupational medicine might be more effectivelyused in the national interest. In the light of the Ministryof Health green-paper on the administration of the HealthService,! it is timely to suggest that, instead of confiningits interest in occupational medicine to the part played bydoctors in the enforcement of regulations designed toprevent illnesses due to employment, the State, havingassumed responsibility for virtually all medical care, shouldpay more attention to the contribution existing occupa-tional health services, voluntarily provided and financedby employers, could make to community health.The Ministry of Health has no responsibility for, and

no official cognisance of, occupational health services, andhas never attempted to compute the extent to which theylighten the burden on the public Service by preventingdisease and injury and by providing immediate treatmentfor injuries and minor ailments presenting at work. TheDepartment of Employment and Productivity is interestedonly in the effects of work on health (i.e., in diseasesspecifically due to occupation) but no Ministry is con-cerned with the effects of health on work: Dr. Tyrer andDr. Murray (p. 445) think that they are equally important,and advocate making the Ministry of Health responsible,through the proposed area health boards, for dealing withboth. They suggest that these boards might consider thesetting up of publicly provided occupational health ser-vices, coexisting with the private ones.The Ministry of Labour’s report on the Appointed

Factory Doctor Service,2 now two years old, was preparedat a time when the possibilities opened up by the green-paper were not foreseeable. Some of its proposals metwith qualified approval as an attempt to remedy the defectsof the present system, which is at once inadequate andwasteful; but they would affect only the management ofindustrial diseases, and the more professional service it

proposed would be directed by the Department of Employ-ment and Productivity. It would seem wise to defer givingstatutory effect to the report’s proposals until the possi-bilities of integrating occupational medicine with theNational Health Service have been fully explored.1. National Health Service: the Administrative Structure of the Medical

and Related Services in England and Wales. H.M. Stationery Office,1968.

2. The Appointed Factory Doctor Service. Report by a subcommittee ofthe Industrial Health Advisory Committee. London, 1966. See Lancet,1966, i, 884, 915.

CHOLESTYRAMINE

CHOLESTYRAMINE resin is an insoluble chloride salt ofa basic anion-exchange resin which has a strong affinityfor bile-salts in the intestine. It exchanges chloride forcholates, which it binds into an insoluble complex that isexcreted in the faeces, so preventing their reabsorptionfrom the intestine and re-excretion in the bile. Since theliver synthesises less than 10% of the bile-salts which itnormally secretes, but depends on the enterohepaticcirculation to maintain the supply, the interruption of thiscirculation by cholestyramine results in a decrease in theblood-level of bile-salts.l

The pruritus of obstructive jaundice has been thoughtto be due to an increased blood-level of bile-salts, eventhough a good statistical correlation has not been shownbetween them.2 On this hypothesis, however, chole-

styramine has been given to patients with severe pruritusassociated with partial biliary obstruction, and has beenshown to relieve itching in 4-7 days.3 4 Serum-bile-acidlevels fall and faecal bile-acid values increase. Continuedtreatment can control the pruritus for years, but itchingreturns 10-14 days after treatment is stopped. Chole-styramine is of no value in complete biliary obstruction,presumably because no bile-salts are getting through tothe small intestine to be bound by the resin.More severe forms of biliary cirrhosis associated with

xanthomatosis have been treated successfully with chole-styramine. Such cases require larger doses of the resin,which produce a fall, not only of serum bile-acids but alsoof total lipids, cholesterol, and phospholipids.5 6 At suchdose-levels there is malabsorption of fat, which may beassociated with deficiencies of vitamins A, D, and K.These should be given by intramuscular injection,therefore, if treatment is to be continued for any lengthof time.

The possibility that cholestyramine might be used in thetreatment of hyperlipoproteinsemia has been investigatedby Fallon and Woods. They studied 21 patients, of whom14 with essential hyperlipoproteinxmia (type 2) showeda 24% decline in serum-cholesterol after treatment withcholestyramine, while the other 7 with other forms ofhyperlipoproteinaemia had no significant decrease. Serum-triglyceride levels remained unchanged in all patients atthe dose-level used. There was a high incidence of

gastrointestinal side-effects, but only 2 patients dis-continued therapy on this account.Another suggested indication for cholestyramine is

porphyria cutanea tarda. Stathers showed that uro-

porphyrin and coproporphyrin were bound by the resinin vitro, and found that 3 patients with this condition wereimproved clinically with a decrease in the formation ofphotosensitive blisters and in skin fragility. There was noclear alteration in porphyrin excretion patterns, but theresin apparently bind porphyrins in the gastrointestinaltract. Lischner 9 has described similar clinical improve-ment in a patient with erythropoietic protoporphyrintreated with cholestyramine.1. J. Am. med. Ass. 1966, 197, 261.2. Osborn, E. C., Wootton, I. D. P., Da Silva, L. C., Sherlock, S. Lancet,

1959, ii, 1049.3. Carey, J. B., and Williams, G. J. Am. med. Ass. 1961, 176, 432.4. Datta, D. V., Sherlock, S. Br. med. J. 1963, i, 216.5. Ahrens, E. H., Kunkel, G. H. J. clin. Invest. 1949, 28, 1665.6. Keczkes, K., Goldberg, D. M., Fergusson, A. G. Archs intern. Med.,

1964, 114, 321.7. Fallon, H. J., Woods, J. W. J. Am. med. Ass. 1968, 204, 1161.8. Stathers, G. M. Lancet, 1966, ii, 780.9. Lischner, H. W. ibid. p. 1079.