Comparative biochemistry and physiology. Part C, Pharmacology, toxicology & endocrinology最新文献

Lindane (gamma-hexachlorocyclohexane) influence on the in vitro intestinal transport of D-galactose and L-leucine has been studied in isolated chicken enterocytes. Animals were injected i.p. with 30 mg/kg b.w. of the pesticide over 7 days. Total uptake of D-galactose and L-leucine was significantly decreased by lindane action. There was no alteration in the non-mediated component, but the mediated transport was markedly inhibited in both cases. Furthermore, the exit of D-galactose across the basolateral membrane, as well as (Na(+)-K+)-ATPase activity, was significantly decreased in pesticide-treated chickens.

The effects of potassium (K+), noradrenaline (NA), serotonin (5-HR), histamine (Hi) and prostaglandin F2 alpha (PGF2 alpha) were studied on isolated pudendal arteries from non-lactating goats. K+, NA, 5-HT, Hi and PGF2 alpha had concentration-dependent contractile effects on the arteries. The developed tensions were, in order of potencies, 5-HT > NA > PGF2 alpha > Hi > K+. NA induced a significantly higher maximal contractile force than K+, 5-HT, PGF2 alpha and Hi. Pretreatment with cocaine was without significant effect on the contractile response to NA. The contractile response to Hi was totally eliminated by mepyramine. Ca2+ had a concentration-dependent contractile effect on arteries depolarized by 125 mM K+. The results indicate that NA, 5-HT and PGF2 alpha may play essential roles in the regulation of goat mammary blood flow. The response to K+ is highly dependent on extracellular Ca2+. The contractile response to histamine may be mediated via H1-receptors. The in vitro method used is well suited to study the vascular reactivity in different regions of the mammary vascular bed.

The effect of oral KCN administration on Na(+)-K(+)-ATPase, Ca(2+)-ATPase and Mg(2+)-ATPase activities was studied in some rabbit tissues. Generally, the order of activity of the enzymes was kidney > liver > ileum > colon. There were significant decreases (P < 0.05) in the activities of all the ATPases in the tissues of KCN-treated rabbits relative to controls. The decreases in Na(+)-K(+)-ATPase and Ca(2+)-ATPase activities were most pronounced in liver and kidney. The decreases in ATPases suggest impairment of membrane function as a result of the toxic effect of cyanide.

Complementary DNA (cDNA) of insulin-like growth factor-I (IGF-I) of Japanese quail was cloned. The nucleotide sequence analysis of the cDNA showed that only seven bases differed from those of chicken IGF-I cDNA in the 440 bases of the cloned region. This difference in nucleotide sequence did not cause changes in the amino acid sequence. Using this cloned cDNA, the changes in IGF-I mRNA content in the tissues of female quail during growth and development were investigated. In the oviduct, IGF-I mRNA was high about 5 weeks after hatching, concomitant with the rapid increase in total DNA content in this tissue (and the increases in total RNA content and RNA/DNA ratio). It decreased after 6 weeks, in accordance with the appearance of ovalbumin mRNA. When immature quails (6-day-old) were injected with diethylstilbestrol (DES), induction of IGF-I mRNA was observed after 24 hr. A few days later, there was a strong induction of ovalbumin mRNA. These two inductions were dependent on the dose of DES. The sequential inductions of these two mRNAs were also noted when DES was re-administered to the immature quail to which it had been first administered and from which then withdrawn. The present results showed that IGF-I gene is expressed extensively during development of the oviduct, probably in accordance with the activity of DNA replication, because the highest IGF-I mRNA content was observed when the total DNA content of the tissues increased extensively. The results suggest that IGF-I in the oviduct of Japanese quail works in an autocrinal or paracrinal mode during the development of this tissue.

Caffeine is a methylxanthine whose primary biological effect is the competitive antagonism of the adenosine receptor. Its presence in coffee, tea, soda beverages, chocolate and many prescription and over-the-counter drugs makes it a commonly consumed stimulant. Coffee and/or caffeine consumption has been linked to many human diseases in epidemiologic studies. Causal relationships have been difficult to substantiate. Initial investigations, showing an association between coffee and coronary heart disease, suffer from confounding variables and have been difficult to replicate. Recent studies, showing a significant effect over long follow-up periods and with high coffee intake, have again raised the question of a role for coffee and/or caffeine consumption in the pathogenesis of atherosclerotic heart disease. Contrary to common belief, the published literature provides little evidence that coffee and/or caffeine in typical dosages increases the risk of infarction, sudden death or arrhythmia.

Lactation in seals is characterized by a rapid and enormous lipid transfer from mother to pups within a milk rich in lipids. Since grey seals do not feed during lactation, all milk constituents are solely derived from body stores. Monitoring levels of fat-soluble vitamins as well as PCBs in blubber and milk may give an insight into the mechanisms involved in their mobilization from blubber, transfer into milk and deposition in the blubber of pups. During lactation, total lipids in milk increased from 261 to 601 g/l. While the level of PCBs in milk per g lipid remained constant throughout lactation, vitamin E, as well as vitamin A and cholesterol, showed a marked decrease during lactation when expressed as quantity per unit lipid. An incomplete transfer of all components from maternal blubber to milk was observed, except for vitamin E. The milk of pregnant females had vitamin E levels per unit which were three times higher than that in blubber, indicating a mobilization of vitamin E from the liver. During the later stages of lactation, there were no differences between the levels of vitamins A and E per unit lipid in the milk and the blubber of suckling pups. The close correlation of PCBs with total milk lipids and the drastic decrease in all other monitored fat-soluble components in seal milk with the progress of lactation point to different mechanisms of mobilization and transport for triglycerides and PCBs compared to fat-soluble vitamins and cholesterol.

BHA (2(3)-tert-butyl-4-hydroxyanisole) produced inhibition of both culture growth and oxygen consumption, NAD(P) reduction and cytochrome b oxidation, on intact epimastigotes of Trypanosoma cruzi. BHA inhibited respiration and reduced NAD(P) in intact T. cruzi trypomastigotes. Oxidative phosphorylation of in situ mitochondria of epimastigotes was inhibited by BHA and this effect was liberated by the addition of ascorbate+TMPD. The incorporation of rhodamine-123 to mitochondria of living epimastigotes was diminished by BHA. These results suggest that the basis of the trypanocidal effects of BHA could be due to the blockage of the mitochondrial electron transport chain on the segment previous to cytochrome c. We postulate that the mechanism of action of BHA could be by mimicking coenzyme-Q (ubiquinone).

Inhibitory effects of neomycin administration (10-80 mg/kg body weight/day, s.c. for 7 days) on several enzyme activities of kidney and duodenal mucosa were compared between male rats and mice. In Wistar rat kidney, tubular brush border Mg(2+)-dependent, HCO3(-)-stimulated ATPase activity was inhibited by neomycin in a dose-dependent manner, while microsomal Mg(2+)-Na(+)-K(+)-ATPase activity and cytosol carbonic anhydrase (CA) activity were inhibited only by larger doses. In rat duodenal mucosa, Mg(2+)-HCO3(-)-ATPase and CA activities were also inhibited only by larger doses. Serum urea nitrogen (UN) concentration and urinary N-acetyl-beta-D-glucosaminidase (NAG) activity were increased in a dose-dependent manner. In ddY and C57black mice, however, all enzyme activities in kidney and duodenal mucosa were almost unaffected by any dose of neomycin and showed no changes in serum UN concentration and urinary NAG activity except for ddY mice in which NAG activity was only increased by the largest dose of neomycin. In light microscopic analysis, 80 mg neomycin/kg produced necrosis in the greater part of rat proximal tubuli with no changes in duodenal brush border. On the other hand, no histological changes were produced in the renal cortex or duodenal mucosa of mice by any dosage. In conclusion, there are organ-specific and species differences in the effects of neomycin between rats and mice.

Female turkey poults were hypophysectomized at 4-5 weeks of age. Beginning at 6 weeks of age, 20 hypophysectomized and 20 intact birds received a daily intramuscular injection of natural chicken growth hormone (cGH, 100 micrograms/kg body weight) or vehicle for 12 days. Blood samples were taken from each bird just before injection and 4 hr post-injection at 6 and 12 days of treatment. Hypophysectomy reduced the growth rate of turkey poults to 75% of that of intact controls, significantly reduced carcass protein and ash percentages, and significantly lower plasma concentrations of GH, insulin-like growth factor-I, triiodothyronine, thyroxine, insulin, glucose, triglycerides, and non-esterified fatty acids. Hypophysectomy was without effect on liver GH receptor binding activity, but increased liver 5'-monodeiodinase activity. Daily cGH injection had no effect on the average daily gain of either hypophysectomized or intact poults when compared to vehicle-injected controls over 12 days of treatment. Daily cGH administration increased plasma insulin-like growth factor-I levels in intact and hypophysectomized turkeys, and increased plasma triiodothyronine, insulin, glucose, and triglyceride concentrations in hypophysectomized birds, but not in intact birds. Responses of young turkeys to hypophysectomy and GH replacement were consistent with the known metabolic role of GH in other species, but the influence of GH on growth appears to be of less importance in poultry than in mammals.