PubMed · 4915722
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
G D Christian. 1969. Medicine, trace elements, and atomic absorption spectroscopy.. https://pubmed.ncbi.nlm.nih.gov/4915722/
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
The devastating impact of human immunodeficiency virus (HIV) infection during pregnancy has made the pharmacologic evaluation of potentially therapeutic agents of high priority. The results presented here are the maternal pharmacokinetics from a series of experiments to delineate more clearly the complex maternal-fetal pharmacokinetics and the effects of AZT in the chronically instrumented maternal and fetal baboon during both steady state intravenous infusion and oral bolus dosage regimens. Two results of major clinical importance were found. First, during pregnancy, both the clearance and volume of distribution of AZT were increased. Plasma clearance in the pregnant animals was 51 +/- 10 ml/min/kg compared with 37 +/- 2 ml/min/kg in the nonpregnant animals, and steady state volume of distribution was 3.7 +/- 1.21/kg compared with 2.2 +/- 0.61/kg. Second, with continuous intravenous infusion plasma drug concentrations were easily maintained in the therapeutic range, whereas with oral administration plasma concentration fell below therapeutic levels within 2 h of the dose being given. Because maternal plasma concentrations are a major determinant of drug concentration achieved in the fetus, an understanding of drug kinetics in pregnancy is of vital importance when making recommendations regarding optimal drug therapy during pregnancy to maximize the beneficial effect--the prevention of HIV infection in children.
Tissue concentrations of 2,3,7,8-tetrabromodibenzo-p-dioxin (TBDD) and induction of ethoxyresorufin O-deethylase (EROD) were determined in female Wistar rats following a single subcutaneous (s.c.) injection of TBDD. Two sets of experiments were performed in order to study (a) the time course after a single s.c. administration of 600 ng TBDD/kg body wt up to 78 days, and (b) the dose-response seven days after a single s.c. injection of different doses of TBDD (3 to 3,000 ng/kg body wt). The results obtained on toxicokinetics and enzyme induction were compared with those following a single s.c. administration of 300 ng/kg body wt 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Three days after the injection, approximately 93% of TBDD and 90% of TCDD had been absorbed. Fourteen days after s.c. injection less than 1% of the administered dose of both substances remained at the injection site. Three days after a single s.c. injection of 600 ng TBDD/kg body wt and 300 ng TCDD/kg body wt, the maximum tissue concentrations in the liver amounted to (M +/- S.D.) 5.7 +/- 0.8 and 4.7 +/- 0.9 ng/g wet weight, respectively. In adipose tissue, the peak concentration was 3.2 +/- 0.2 ng/g wet weight for TBDD on day 14, and 0.8 +/- 0.1 ng/g for TCDD on day 7. Throughout the study, the concentration ratio in the TCDD-treated group was always at least twice as high as that in the TBDD-treated group. The elimination half-life (t1/2) of TBDD and of TCDD in the liver was 13.3 and 13.6 days, respectively. In the adipose tissue the t1/2 of TCDD was 24.5 days but no reliable t1/2 could be calculated for TBDD (t1/2 = 39.4 days with a 95% confidence interval of 25.9 to 82.4 days). Tissue content of TBDD and TCDD in liver and adipose tissue increased dose-dependently, and the linear regression in a double-logarithmic plot showed a straight line. Time course of the induction of hepatic EROD activity after treatment with 600 ng TBDD/kg body wt was almost identical with that observed following a single dose of 300 ng TCDD/kg body wt. The induction of hepatic EROD activity was linearly correlated in a double-logarithmic plot to the hepatic concentrations of the congeners (both TBDD and TCDD). The slopes of the dose-response curves after administration of TBDD and TCDD were almost parallel for tissue concentrations ranging from 0.1 to 30 ng/g wet weight.
The inhibiting effect of phytate on nonheme-iron absorption from different protein sources was examined in human subjects using extrinsic radioiron labeling. A drink containing maltodextrose and corn oil was used as a control meal to which was added sufficient sodium phytate to provide 300 mg phytic acid and/or various protein sources. The proteins were selected to cover a broad range of effects on bioavailability and included egg white, meat, and phytate-free soy protein. When sodium phytate alone was added, there was a pronounced 83-90% reduction in mean absorption in separate studies with a composite average decline of 86%. Despite a wide range in absorption from meals containing the three protein sources, a remarkably similar relative inhibition was observed when sodium phytate was added. No significant difference in the inhibiting effect of phytate could be detected with additions ranging from the equivalent of 50-300 mg phytic acid to a meal containing egg white as the protein source. Our studies found no evidence that the inhibiting effect of phytate depends on the protein composition of the meal.