The effect of a nutritionally-balanced cassava (Manihot esculenta Crantz) diet on endocrine function using the dog as a model 2. Thyroid

Abstract

_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _Growing dogs were divided into three groups and were fed on nutritionally-balanced diets. Control dogs were fed on a rice diet, the cassava (gari) group ate a diet in which gari provided the carbohydrate source, while the rice +cyanide group consumed the rice diet to which hydrocyanic acid (equivalent to that present in gari) was added. Each group consumed its diet for 14 weeks, during which plasma thiocyanate concentration and total serum triiodothyronine (T3) were monitored. At the end of the experiment the concentrations of the plasma free amino acids phenylalanine and tyrosine, the thyroid weights and histology were determined. While plasma thiocyanate remained undetectable in control dogs, animals consuming both gari and rice +cyanide generated significant amounts. In the control dogs and the gari group, total serum T, increased 40 and 38.8 % respectively from the basal level by the end of the period (P < 0.02). In contrast there was a decrease in T, by 36 % in the dogs fed on rice + cyanide (P < 0.05).This group also showed significant thyroid enlargement and a histological picture consistent with parenchymatous goitre, whereas the gari group was essentially normal. The relatively low mean thyroid weight, the rise in total serum T, level and the normal histological appearance of the gland indicate that dogs that consumed the gari diet were essentially normal with respect to their thyroid function, in spite of their high blood thiocyanate content. In contrast, dogs that consumed rice with cyanide suffered from hypothyroidism and goitre. It is suggested that the gari diet, despite generating thiocyanate endogenously, when taken in a nutritionally-balanced diet with high-quality animal protein, has no deleterious effects on thyroid function.Thyroid: Cassava diet: Dog

Comparison of the effects of cassava (Manihot esculenta Crantz) organic cyanide and inorganic cyanide on muscle and bone development in a Nigerian breed of dog

“…Gluconeogenesis from protein was five and two times greater in the gari-fed and rice plus cyanide-fed dogs respectively, relative to the rice-fed control dogs (Kamalu, 1991). Although the reasons for the differences observed in the responses of the different muscles to either the gari or rice plus cyanide diets are not known for sure, the present findings, as well as the biochemical and histopathological differences previously reported in the gari-and rice plus cyanide-fed dogs (Kamalu, 1991;Kamalu & Agharanya, 1991), suggest that the metabolic fate and effects on muscle development of organic and inorganic dietary cyanide in the dog may differ. This agrees with the observations of Tewe & Maner (1981) on the effects of organic and inorganic cyanide on muscle development, but is contrary to the observations of Ermans et al (1973) who reported that the metabolic fate of hydrocyanic acid closely resembles that of inorganic cyanide in single-stomached animals.…”

“…A decrease in thyroid hormone level is also associated with a decrease in the levels of various lysosomal proteases like cathepsin B ( E C 3.4.22.1) and D ( E C 3.4.23.5) in the liver and muscles (DeMartino & Goldberg, 1978). However, the hypothyroidism observed in the rice plus cyanide-fed dogs was not associated with reduction in muscle mass suggesting that the rice plus cyanide diet probably contained enough dietary protein for both cyanide detoxification and other body needs as indicated by findings of the highest level of free plasma amino acids (phenylalanine and tyrosine) in this group (Kamalu & Agharanya, 1991). In addition, Goldberg et al (1980) reported that an alteration of thyroid hormone level is usually associated with synchronous 2-3-fold alteration in the levels of a variety of lysosomal enzymes, and suggested that this may be responsible for the various unexplained effects of the thyroid hormone in disease conditions.…”

Clinical and pathological effects of short-term cyanide repeated dosing to goats

“…Another possibility is a neuronal accumulation of cyanide, which was observed earlier in in vitro studies (Borowitz et al, 1994). Long-term cyanogenic plant consumption by both men (Adewusi and Akindahunsi, 1994) and animals (Bahri, 1987;Kamalu and Agharanya, 1991) has been associated with the development of hypothyroidism. Thiocyanate, the main cyanide metabolite, is thought to be responsible because it competes with iodide in the thyroid gland (Delange and Ermans, 1996).…”

Comparative effects of prolonged administration of cyanide, thiocyanate and chokecherry (Prunus virginiana) to goats

“…Long-term cyanogenic plant consumption by both humans (Adewusi and Akindahunsi, 1994) and animals (Bahri, 1987;Kamalu and Agharanya, 1991) has been linked to the development of hypothyroidism and goiter. In the present work, goats treated with chokecherry and thiocyanate had an increased number of vacuoles in the colloid of thyroid glands, which was similar to earlier studies (Soto-Blanco et al, 2001a; Means for each day in the same column preceded by different superscript letters are significantly different (P < 0.05).…”