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Notes on the results of feeding rats exclusively on tannia
458 TRANSACTIONS OF THE ROYAL SOCIETY OF TROPICAL MEDICINE AND HYGIENE.
Vol. XXII.
No. 5.
March,1929.
N O T E S ON T H E R E S U L T S OF F E E D I N G
RATS EXCLUSIVELY
ON T A N N I A . BY
A. CLARK, F.R.C.S. (From the Bacteriological Laboratory, Trinidad, British West Indies.)
BOTANICAL. T h e tannia belongs to the natural order of the Aracea~ and is related to the " Lords and Ladies " of the English ditches as well as to the taro, dasheen and Chinese eddoe. These plants all possess acrid properties due, according to BLACK(1918),* to the presence in their cells of needle-like crystals of calcium oxalate. YOUNC. (1924)t writes : " The corms . . . and all the lateral tubers that send up leaf shoots are extremely acrid and require boiling for at least two hours to become edible." The tubers are very rich in starch and play an important part in the diet of the tropics in the Pacific Is|ands, Central America, West Indies, West Africa, East Africa, East Indies, China and Japan. T h e English representative is cultivated on the Isle of Portland for the sake of its starch, which is still sold as a substitute for arrowroot under the name of " Portland Sago." Queen Elizabeth's laundry used it to stiffen the royal ruffles. # Amer. ffl. Bot., v, (5), 447. f U.S. Dept. Agri. Bull., (1247), 16,
454
RESULTS OF FEEDING RATS ON TANNIA
Chemical. I am indebted to Professor HURST, of the Biochemical Labor~tory of the Imperial College of Tropical Agriculture in Trinidad, for the analysis of the tannia and, for purposes of comparison, of the yam and sweet potato. He reports upon the protein content and amino-acid constitution of these tubers as follows :--Oven-dried t a n n i a c o n t a i n s 3.5 p e r cent. to 4.0 p e r c e n t . o f p r o t e i n . Oven-dried yam contains 6.5 per cent. to 7.0 per cent. of protein. Oven-dried sweet potato contains 1.5 per cent. to 2 per cent. of protein. (Vegetable protein = total nitrogen × 5.68. PLIMMER.) All contain sulphur, phosphorus and tyrosine. Tryptophane is very prominent in tannia, slight in yarn and sweet potato. The sulphur shows that cystine is present. The phospho-proteins are predominantly acid in character, not only because of their phosphoric acid content but also because of the large amount of dicarboxylic acids--aspartic and glutamic. On extracting tannia with dry chloroform and filtering, the filtrate yields on evaporation an oily residue. The addition of strong sulphuric acid or of iodine to this causes no colouration. It is probable, therefore, that no notable quantity of any phytosterol is present.
Physiological. UNDERH1LL showed that sodium tartrate injected subcutaneously causes destruction of the epithelium of the renal tubules, especially that of the convoluted tubules. CUSHNY states that similar lesions are met with in oxalate nephritis. With regard to inflammation in general, it appears that in order to excite it the reagent must be both fat-soluble and positively chemotactic.
Experiments and Their Results. Twenty-two rats have so far been used in this investigation of the food value of tannia. Of these, eight were fully grown animals weighing about 200 g. The remaining were vigorous young rats of 49 g. to 80 g. All the animals consumed the raw tannia with a good appetite, the average daily consumption being at least as large as that of animals on the normal diet (31 g. for an adult). The first rat experimented with was No'. 31. He was put on the diet on 10th July, 1928. He died on 7th August, 1928. Postmortem the c~ecum was found to be enormously distended with a putty-like mass of partly-digested tannia. The bladder was full of urine which gave a heavy precipitate of albumin with the cold nitric acid test. This finding was of such interest that I placed as many suitable rats as I could spare on the same regimen. The results in eighteen rats fed on uncooked tannia showed that death ensued rapidly, in the case of vigorous adult rats in twenty-eight to forty days, in the case of healthy ratlings in five to nine days.
A. CLARK.
455
The postmortem conditions were striking :--
Ccecum.--Usually much enlarged and loaded with a putty-like mass of undigested tannia; generally acid and sometimes highly acid. Rarely the c~ecum was ballooned and empty. Bladder.--Usually distended with urine and loaded with albumin. This was not due to pressure of the c~ecum. Peritoneum and Pericardium.--Usually much fluid in peritoneum and occasionally fluid in the pericardium also. Kidneys.--Usually a glomerulo-tubular nephritis with hmmorrhages. Four rats on the same uncooked tannia diet with the addition of 1 g. of yellow cheese daily showed generally the same postmortem results, but life was considerably prolonged, the ratlings dying in twenty-one to forty-eight days instead of five to nine days. In order to test the possibility of existence upon other tuberous foods, three rats have been on a diet of sweet potato alone for the period from 8th August to l lth November--ninety-two days. Two are still alive and in fair health though they have lost weight considerably, on an average 88.3 g. or 48 per cent. of weight each, and are partly bald as to the body. They are now below CHOSSAT'S starvation death point and no doubt will soon die. In order to test the presence of vitamin B in tannia six pigeons were used. These were given a diet of polished rice, white flour, white sugar and 25 per cent. of tannia. They were put on this diet on 6th July, 1928, and on l l t h November, are still in good health, though they have lost on an average 18.9 per cent. of their original weight. One pigeon was stolen on 10th September, having lost 10.6 per cent. of its weight. It appears, therefore, that vitamin B is present in adequate quantity in tannia. The presence of vitamin A is probable, as one rat lived forty-eight days on tannia alone without developing any signs of xerophthalmia. CONCLUSIONS.
These experiments on a diet of raw tannia alone seem to show that :-(a) It is incompatible with the life of a particularly vigorous young adult rat for much longer than forty-eight days. (b) In healthy ratlings it is incompatible with more than nine days of life. (c) Such a diet almost constantly causes albuminuria and acute glomerulotubular nephritis. (d) Coprostasis with acid contents of the c~ecum is constantly present. (e) The addition of a small amount of yellow cheese prolongs life considerably. Questions suggested by the results of these experiments are :(a) Is there a causal connection between the consumption of tannia in the tropics and the occurrence of chronic nephritis amongst native populations ?
456
RESULTS OF FEEDING RATS ON TANNIA.
(b) Is there present in tannia a poison cumulative or otherwise which causes acute nephritis and paresis of the bowel ? (c) In what way does cheese in small quantities serve to prolong life when added to the tannia diet ? If ketosis were the cause of death it would appear probable that the fat of the cheese would not retard but rather accelerate death. : Experiments are proceeding in Trinidad and this brief note is published in'order to make known these results with the hope that studies in this subject may be undertaken in other parts of the tropics.
Vol. XXII.
No. 5.
March,1929.
N O T E S ON T H E R E S U L T S OF F E E D I N G
RATS EXCLUSIVELY
ON T A N N I A . BY
A. CLARK, F.R.C.S. (From the Bacteriological Laboratory, Trinidad, British West Indies.)
BOTANICAL. T h e tannia belongs to the natural order of the Aracea~ and is related to the " Lords and Ladies " of the English ditches as well as to the taro, dasheen and Chinese eddoe. These plants all possess acrid properties due, according to BLACK(1918),* to the presence in their cells of needle-like crystals of calcium oxalate. YOUNC. (1924)t writes : " The corms . . . and all the lateral tubers that send up leaf shoots are extremely acrid and require boiling for at least two hours to become edible." The tubers are very rich in starch and play an important part in the diet of the tropics in the Pacific Is|ands, Central America, West Indies, West Africa, East Africa, East Indies, China and Japan. T h e English representative is cultivated on the Isle of Portland for the sake of its starch, which is still sold as a substitute for arrowroot under the name of " Portland Sago." Queen Elizabeth's laundry used it to stiffen the royal ruffles. # Amer. ffl. Bot., v, (5), 447. f U.S. Dept. Agri. Bull., (1247), 16,
454
RESULTS OF FEEDING RATS ON TANNIA
Chemical. I am indebted to Professor HURST, of the Biochemical Labor~tory of the Imperial College of Tropical Agriculture in Trinidad, for the analysis of the tannia and, for purposes of comparison, of the yam and sweet potato. He reports upon the protein content and amino-acid constitution of these tubers as follows :--Oven-dried t a n n i a c o n t a i n s 3.5 p e r cent. to 4.0 p e r c e n t . o f p r o t e i n . Oven-dried yam contains 6.5 per cent. to 7.0 per cent. of protein. Oven-dried sweet potato contains 1.5 per cent. to 2 per cent. of protein. (Vegetable protein = total nitrogen × 5.68. PLIMMER.) All contain sulphur, phosphorus and tyrosine. Tryptophane is very prominent in tannia, slight in yarn and sweet potato. The sulphur shows that cystine is present. The phospho-proteins are predominantly acid in character, not only because of their phosphoric acid content but also because of the large amount of dicarboxylic acids--aspartic and glutamic. On extracting tannia with dry chloroform and filtering, the filtrate yields on evaporation an oily residue. The addition of strong sulphuric acid or of iodine to this causes no colouration. It is probable, therefore, that no notable quantity of any phytosterol is present.
Physiological. UNDERH1LL showed that sodium tartrate injected subcutaneously causes destruction of the epithelium of the renal tubules, especially that of the convoluted tubules. CUSHNY states that similar lesions are met with in oxalate nephritis. With regard to inflammation in general, it appears that in order to excite it the reagent must be both fat-soluble and positively chemotactic.
Experiments and Their Results. Twenty-two rats have so far been used in this investigation of the food value of tannia. Of these, eight were fully grown animals weighing about 200 g. The remaining were vigorous young rats of 49 g. to 80 g. All the animals consumed the raw tannia with a good appetite, the average daily consumption being at least as large as that of animals on the normal diet (31 g. for an adult). The first rat experimented with was No'. 31. He was put on the diet on 10th July, 1928. He died on 7th August, 1928. Postmortem the c~ecum was found to be enormously distended with a putty-like mass of partly-digested tannia. The bladder was full of urine which gave a heavy precipitate of albumin with the cold nitric acid test. This finding was of such interest that I placed as many suitable rats as I could spare on the same regimen. The results in eighteen rats fed on uncooked tannia showed that death ensued rapidly, in the case of vigorous adult rats in twenty-eight to forty days, in the case of healthy ratlings in five to nine days.
A. CLARK.
455
The postmortem conditions were striking :--
Ccecum.--Usually much enlarged and loaded with a putty-like mass of undigested tannia; generally acid and sometimes highly acid. Rarely the c~ecum was ballooned and empty. Bladder.--Usually distended with urine and loaded with albumin. This was not due to pressure of the c~ecum. Peritoneum and Pericardium.--Usually much fluid in peritoneum and occasionally fluid in the pericardium also. Kidneys.--Usually a glomerulo-tubular nephritis with hmmorrhages. Four rats on the same uncooked tannia diet with the addition of 1 g. of yellow cheese daily showed generally the same postmortem results, but life was considerably prolonged, the ratlings dying in twenty-one to forty-eight days instead of five to nine days. In order to test the possibility of existence upon other tuberous foods, three rats have been on a diet of sweet potato alone for the period from 8th August to l lth November--ninety-two days. Two are still alive and in fair health though they have lost weight considerably, on an average 88.3 g. or 48 per cent. of weight each, and are partly bald as to the body. They are now below CHOSSAT'S starvation death point and no doubt will soon die. In order to test the presence of vitamin B in tannia six pigeons were used. These were given a diet of polished rice, white flour, white sugar and 25 per cent. of tannia. They were put on this diet on 6th July, 1928, and on l l t h November, are still in good health, though they have lost on an average 18.9 per cent. of their original weight. One pigeon was stolen on 10th September, having lost 10.6 per cent. of its weight. It appears, therefore, that vitamin B is present in adequate quantity in tannia. The presence of vitamin A is probable, as one rat lived forty-eight days on tannia alone without developing any signs of xerophthalmia. CONCLUSIONS.
These experiments on a diet of raw tannia alone seem to show that :-(a) It is incompatible with the life of a particularly vigorous young adult rat for much longer than forty-eight days. (b) In healthy ratlings it is incompatible with more than nine days of life. (c) Such a diet almost constantly causes albuminuria and acute glomerulotubular nephritis. (d) Coprostasis with acid contents of the c~ecum is constantly present. (e) The addition of a small amount of yellow cheese prolongs life considerably. Questions suggested by the results of these experiments are :(a) Is there a causal connection between the consumption of tannia in the tropics and the occurrence of chronic nephritis amongst native populations ?
456
RESULTS OF FEEDING RATS ON TANNIA.
(b) Is there present in tannia a poison cumulative or otherwise which causes acute nephritis and paresis of the bowel ? (c) In what way does cheese in small quantities serve to prolong life when added to the tannia diet ? If ketosis were the cause of death it would appear probable that the fat of the cheese would not retard but rather accelerate death. : Experiments are proceeding in Trinidad and this brief note is published in'order to make known these results with the hope that studies in this subject may be undertaken in other parts of the tropics.