E. C. Onyeneke

Changes in carboxypeptidase A, dipeptidase and Na+/K+ ATPase activities in the intestine of rats orally exposed to different doses of cadmium.

The purpose of the present study was to evaluate the effect of cadmium on some protein digestive and absorption enzymes in rats. Thirty-six rats were grouped into three groups of 12 animals each; one group received deionised water and acted as control. One group received 445 µM Cd and the last group received 890 µM Cd in their drinking water for a period of one month. The results obtained indicate that increasing the level of cadmium from 445 µM to 890 µM in the drinking water of the rats led to 29 and 23 increase in accumulated cadmium in the proximal and distal small intestine respectively. The body weight gain of rats exposed to 445 µM and 890 µMCd was decreased by about 24 and 43 respectively when compared with the control. The activities of carboxypeptidase A, dipeptidase and Na+/K+ ATPase were reduced in the mucosa of the proximal end of the small intestine of cadmium exposed rats. The reduction was dose dependent; with the 890 µM Cd exposed rats displaying the least activities. In the distal small intestine, the activities of these enzymes were restored in the 445 µM Cd exposed rats to levels that were not statistically different (P>0.05) from those observed in the controls. In the 890 µMCd exposed rats, dipeptidase activity improved by about 80 compared with the activity of the enzyme in the proximal small intestine. Likewise, Na+/K+ ATPase activity increased by about 125 compared with the observed level in the proximal small intestine. The study suggests that cadmium given to rats in drinking water compromise protein digestion and absorption of nutrients particularly in the proximal region of small intestine and could account for weight reduction associated with cadmium toxicity.

Effect of soy protein on serum lipid profile and some lipid-metabolizing enzymes in cholesterol fed rats

The effect of soy protein on serum lipid profile and some lipid metabolizing enzymes in rats fed with cholesterol diets was examined in this study. Rats were subjected to feeding trial over a period of six weeks on formulated diets containing: 20% soy protein with 0% cholesterol (group A), 20% soy protein with 5% cholesterol (group B), 20% soy protein with 10% cholesterol (group C), 0% soy protein with 20% cholesterol (group D), and 5% soy protein with 20% cholesterol (group E). Serum total, VLDL, LDL, and HDL-cholesterol and triglyceride concentrations were found to be reduced significantly in Groups B and C when compared with Groups D and E (p 0.05). Groups D and E showed significant increased levels (p < 0.01) when compared to other groups. Lipoprotein lipase (LPL), lecithin:cholesterol acyl transferase (LCAT), and triglyceride lipase (TGL) activities were found to be significantly reduced (p< 0.05) in groups B and C when compared with groups D and E. Though groups B, C, D, and E rats all showed significant elevation (p < 0.05) in the enzyme activities when compared to the control.

Regulation of tyrosine aminotransferase activity by glucagon and cAMP analogues in chick embryos in ovo

Glucagon, dibutyryl cAMP (Bt2cAMP) and 8-(4-chlorophenylthio) cAMP (CptcAMP), singly or when combined, stimulated tyrosine aminotransferase (TAT) activity in 17-day-old chick embryos in ovo. Maximal induction was produced within 4 hr of injection of the inducers. The effects of glucagon and the cAMP analogues were not additive. Glucagon administration was accompanied by a rapid increase in hepatic cAMP concentration which remained elevated for at least 4 hr. The stimulated increase in TAT activity elicited by the hormone or cyclic nucleotide was prevented by injection of cycloheximide or cordycepin. These results are discussed vis-à-vis the possible regulation of TAT in ovo by physiological concentrations of glucagon and the likely role of cAMP as a second messenger in this process during chick embryogenesis.

Effect of sucrose supplementation on aflatoxin production by Aspergillus parasiticus 2999 cultures in soybeans and cashew fruit juice

The aflatoxigenic potential ofAspergillus parasiticus 2999 on soybeans (raw and cooked) and cashew fruit juice (ripe, unripe, raw and cooked) variously supplemented with sucrose (0–20g) has been evaluated. Aflatoxin production showed a dual increase with increasing sucrose (0–20g) and soybeans (0.1–2.0g) concentrations which probably indicates the limited availability of suitable carbon sources in soybeans. This may be partly responsible for its resistance to aflatoxin synthesis. Two to five per cent (w/v) sucrose supplementation was optimal for maximal toxin production in cashew juice. Above this range aflatoxin production dropped steeply. Cooked soybeans supported higher yields of toxin than raw, in direct contrast with cashew fruit juice. Ripe cashew juice produced a greater quantity of toxin than the unripe. More fluorescent metabolites were synthesized in cashew fruit media than in soybeans. These results have been discussed in relation to the limiting role of the carbon source and the resistance to aflatoxin production on natural substrates.