INFLUENCE OF DIETARY INORGANIC CYANIDE (KCN) ON PLACENTAL THIOCYANATE TRANSFER, TISSUE RIIODANESE ACTIVITY AND PERFORMANCE OF RATS DURING GESTATION

Thirty two bred rats were allotted to two diets to investigate the influence of non-addition or addition of 1000 ppm KCN to cassava — soybean diets on thiocyanate concentrations, tissue rhodanese activity and performance parameters. KCN caus­ed a non-significant (P>0.05) depres­sion in body weight gain but had no effect on weights of liver, kidney and placenta, nor on number and weight of 19 day old foetus. High (1000 ppm) KCN level caused a significant (P<0.05) increase in urinary thiocyanate excretion of thiocyanate. It however had no marked effect on serum protein bound 'iodine, ammiotic fluid thiocyanitte, rhodanese activity of foetal and material tissues nor on foetal thio­cyanate concentration.

Pathological changes in growing dogs fed on a balanced cassava (Manihot esculenta Crantz) diet

Studies were carried out to determine the effects of the toxic principle linamarin, a cyanogenic glucoside, in a diet containing cassava (Manihot esculenta Crantz) in the form of gari fed to growing dogs for 14 weeks. There were three groups of dogs, each comprising six animals. One group was fed on a control diet with rice as the carbohydrate source, the second group was fed on cassava (gari) as the carbohydrate source and which was expected to release 10.8 mg HCN/kg cooked food, the third group was fed on the control diet to which enough NaCN was added at feeding time to release 10.8 mg HCN/kg cooked food in order to monitor the effects of the HCN released from gari. All diets contained 130 g erude protein (N × 6.25)/kg and were supplemented with vitamins and minerals. Each animal was given approximately 100 g diet/kg body weight for the duration of the experifnent. The biochemical variables investigated were plasma electrolytes, serum proteins, plasma-free amino acids, plasma enzymes and urine protein, and the histology of some metabolically active tissues, namely liver, kidney, myocardium, testis and adrenal gland, was studied. The gari diet caused an elevated plasma thiocyanate concentration (P < 0.01), elevated 24 h urinary thiocyanate excretion and elevated urinary protein excretion (P < 0.01), lowered serum albumin (P < 0.05), a plasma-free amino acid profile which resembled that found in kwashiorkor, lowered plasma K and Ca (P < 0.05). The rice + cyanide diet caused an elevated plasma thiocyanate (P < 0.01) and a 24 h urinary thiocyanate excretion that was significantly higher (P < 0.01) than that of the dogs fed on gari, but caused a urinary protein excretion that was significantly lower than that of the dogs fed on gari (P < 0.01), lowered serum albumin (P < 0.05), a plasma-free amino acid profile that indicated that the amino acids were not being utilized to the same extent as in the control (rice) group but were accumulating. Neither diet had an effect on plasma γ-glutamyltransferase (EC 2.3.2.2), alanine aminotransferase (EC2.6.1.2) or isocitrate dehydrogenase (EC 1.1.1.42) activities, plasma Na, Mg, and P concentrations. The gari diet caused generalized congestion and haemorrhage, periportal vacuolation of the liver, swelling, vacuolation and rupture of the epithelial cells of the proximal convoluted tubules of the kidney, myocardial degeneration and adrenal gland degeneration. In the testes there were occasional abnormal germ cells in the seminiferous tubules, and occasional seminiferous tubules denuded to basement membrane of germ cells but with remnants of Sertoli cells. Spermatogenesis, however, appeared to be normal since the percentage of round tubules in stage 8 of the spermatogenic cycle was not significantly different from that of the control dogs. The rice + cyanide diet caused nephrosis and a significantly reduced relative frequency of testicular tubules in stage 8 of the spermatogenic cycle (P < 0.01). There was also marked testicular germ cell sloughing and degeneration. There was adrenal gland hyperplasia and hypertrophy. It was concluded that the observed changes which occurred when the gari diet was consumed were not entirely due to cyanide.

High α-linolenic acid flaxseed (Linum usitatissimum):some nutritional properties in humans

Although high α-linolenic acid flaxseed (Linum usitatissitmum) is one of the richest dietary sources of α- linolenic acid and is also a good source of soluble fibre mucilage, it is relatively unstudied in human nutrition. Healthy female volunteers consumed 50 g ground, raw flaxseed/d for 4 weeks which provided 12–13% of energy intake (24–25 g/100 g total fat). Flaxseed raised α-linolenic acid and long-chain n-3 fatty acids in both plasma and erythrocyte lipids, as well as raising urinary thiocyanate excretion 2.2- fold. Flaxseed also lowered serum total cholesterol by 9 % and low-density-lipoprotein-cholesterol by 18%. Changes in plasma α-linolenic acid were equivalent when 12 g α-linolenic acid/d was provided as raw flaxseed flour (50 g/d) or flaxseed oil (20 g/d) suggesting high bioavailability of α-linolenic acid from ground flaxseed. Test meals containing 50 g carbohydrate from flaxseed or 25 g flaxseed mucilage each significantly decreased postprandial blood glucose responses by 27%. Malondialdehyde levels in muffins containing 15 g flaxseed oil or flour/kg were similar to those in wheat-flour muffins. Cyanogenic glycosides (linamarin, linustatin, neolinustatin) were highest in extracted flaxseed mucilage but were not detected in baked muffins containing 150 g flaxseed/kg. We conclude that up to 50 g high-α-linolenic acid flaxseed/d is palatable, safe and may be nutritionally beneficial in humans by raising n-3 fatty acids in plasma and erythrocytes and by decreasing postprandial glucose responses.

THE EFFECT OF SODIUM THIOSULFATE AND HYDROXO-COBALAMIN ON RATS FED NITRILE-RICH OR GOITRIN-RICH RAPESEED MEALS

Three experiments were conducted with rats to study the effect of feeding rapeseed preparations supplemented with sodium thiosulfate (Na2S2O3∙5H2O) and hydroxo-cobalamin (vitamin B12a). A significant antidotal effect of 0.1% sodium thiosulfate supplementation was observed with pre-hydrolyzed, freeze-dried (PHFD) raw Midas meal which is rich in nitrile content, but not with Midas meal that was not hydrolyzed. The antidotal effect of sodium thiosulfate was less conspicuous with Tower meal, but addition of 0.1% sodium thiosulfate to PHFD raw Tower meal resulted in slightly improved performance. Addition of sodium thiosulfate to heated Midas or heated Tower meal had no effect on weight gain whether they were pre-hydrolyzed or not. No antidotal effect of hydroxo-cobalamin was observed with meals of high-nitrile or high-goitrin content. The addition of sodium thiosulfate or hydroxo-cobalamin had no significant effect on the weight of thyroid glands. Increased kidney weight was observed in treatments in which meal of high nitrile content (raw Midas meals) was fed. The addition of hydroxo-cobalamin resulted in an increase in kidney weight in some treatments while the addition of sodium thiosulfate caused a decrease in kidney and liver weight in the high-nitrile treatments. A significantly higher thiocyanate content was observed in the serum of rats fed high-nitrile meals supplemented with sodium thiosulfate. Thiocyanate excretion in the urine was reduced when Midas meals were pre-hydrolyzed and freeze-dried, but remained much higher than for the control group.