Polybrominated biphenyls (PBBs) cause a mixed-type (phenobarbital- plus 3-methylcholanthrene-like) induction of liver microsomal drug metabolizing enzymes in rats. However, 2,2',4,4',5,5'-hexabromobiphenyl and 2,2',3,4,4',5,5'-heptabromobiphenyl, which together comprise less than 80% of PBBs (FireMaster), were shown to be strictly phenobarbital-type inducers. Other components (unidentified) must therefore cause the 3-methylcholanthrene-like effects. The potential for PBBs to exert effects on neonates through milk was examined. Lactating rats were fed 0, 0.1, 1.0, or 10 ppm FireMaster for the 18 days following delivery, at which time mothers and most pups were sacrificed. Pups nursing from mothers fed 10 ppm PBBs showed significant increases in liver weights and microsomal protein, and both mothers and pups had increased cytochrome P-450, aminopyrine demethylation, benzo[a]pyrene hydroxylation, and UDP-glucuronyltransferase. Pups nursing from rats fed 1.0 ppm had increases in microsomal protein, cytochrome P-450, aminopyrine demethylation, and benzo[a]pyrene hydroxylation, while their mothers were unaffected. Several pups from the 0, 0.1, and 1.0 ppm groups were maintained on their mother's diets, raised, and allowed to mate. Their pups showed much the same responses to PBBs as did the original group of pups. The effects on both generations of adult female rats were also comparable. PBBs cause a mixed-type induction in both lactating rats and their nursing pups; PBB components responsible for both aspects of this induction must be transmitted through milk. Nursing rats are approximately tenfold more sensitive to the effects of PBBs in their mother's diets than are the dams. The approximate no-effect level for microsomal induction in nursing rats is 0.1 ppm PBBs in the diet of the adult.

Animal Feed↗

PubMed1978

Studies on the microsomal metabolism and binding of polybrominated biphenyls (PBBs).

The metabolism of polybrominated biphenyls (PBBs) was studied in vitro by using rat liver microsomes in the presence of NADPH and atmospheric O2. Quantitative recoveries of all PBBs were obtained after incubations with control or 3-methylcholanthrene (MC) induced microsomes. Of the twelve major components, losses of only peaks 1 (2,4,5,2',5'-pentabromobiphenyl) and 3 (a hexabromobiphenyl) were observed following incubations with microsomes from phenobarbital (PB)- or PBBS- pretreated rats. Of seven structurally identified PBB components, only peak 1 has a bromine-free para position. Peaks 1, 2, and 5 all have two adjacent unsubstituted carbons, yet only peak 1 is metabolized. Of two dibromobiphenyl model compounds studied, the 2,2'-congener was very rapidly metabolized by PB-induced microsomes whereas its 4,4'-isomer was not. These results suggest that the presence of a free para position is required for the metabolism of brominated biphenyls. Of lesser importance appears to be the number of bromines or the availability of two adjacent unsubstituted carbons. In vivo evidence for the metabolism of peaks 1 and 3 was also provided by their drastically diminished levels in liver and milk extracts. When a 14C-PBB mixture consisting almost exclusively of peaks 4 (2,4,5,2',4',5'-hexabromobiphenyl) and 8 (2,3,4,5,2',4',5'-heptabromobiphenyl) was incubated with PB- or PBBs- induced microsomes and NADPH, only traces of radioactivity remained with the microsomes after extensive extraction. However, less radioactivity was bound to microsomes from MC pretreated or especially control rats. No radioactivity was bound to exogenous DNA included in similar microsomal incubations, regardless of the type of microsomes used. Under the same conditions, [3H]-benzo[a]pyrene metabolites were bound to DNA, and PBB-induced microsomes enhanced this binding more than six-fold.

Animals↗

PubMed1978

Effects of sexual stimulation on plasma levels of LH and testosterone in rams from high- and low-fertility flocks.

Plasma LH and testosterone levels did not differ significantly between high and low fertility rams before or after sexual stimulation (ejaculation or teasing). Repeated stimulation caused significant elevation of mean plasma LH and an almost significant rise in testosterone concentration. Plasma testosterone peaks followed those of LH after 30-60 min. A single sexual stimulation did not always cause an LH peak or increase the mean LH level.

Animals↗

PubMed1977

Atopic eczema: a clinical psychiatric study.

Twenty subject (including patients with atopic eczema and normal matched controls) were subjected to extensive psychiatric interviewing and psychological testing. The atopic eczema patients were found to differ from the controls in early childhood experiences, in adaptation to aggressive conflicts, in themes of dreams and first memories as well as in conflicts and relationships to their extended families. A precipitant stress could be identified at the time of onset and exacerbation of the eczema. Significant psychiatric pathology was found in 60% of the atopic eczema patients. Psychological test results also indicated differences between the two groups with the MMPI being the most discriminating test of those used.

Adolescent↗

PubMed1976