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Biomedical subjects

L R Shull

Publications and source records attributed to L R Shull.

30 records · Page 2Linked to original sources
PubMed1978

Effect of technical grade pentachlorophenol on rumen microorganisms.

The toxicity of technical grade pentachlorophenol to rumen microorganisms was tested by an in vitro fermentation procedure. Rumen fluid was collected from a fistulated mature steer fed a diet of all alfalfa hay. The compound was dissolved in absolute ethanol and added in vitro at concentrations ranging from 0 to 100 ppm. Digestion of cellulose and production of volatile fatty acids over 24 and 48 h of incubation was used to assess toxicity. Both cellulose digestion and propionic acid production were decreased at the 10 ppm concentration. The results suggest that technical grade pentachlorophenol has the potential to interfere with utilization of cellulose in ruminants.

Animals↗
PubMed1977

Dietary selenium status and pyrrolizidine alkaloid metabolism in vitro by rat liver microsomes.

The effect of dietary selenium status on the metabolism of pyrrolizidine alkaloids (monocrotaline, and mixed pyrrolizidine alkaloid from Senecio jacobaea) by rat liver microsomes in vitro was studied. In two experiments, there was no difference in the rate of metabolism of alkaloid by microsomes from selenium deficient or selenium supplemented rats. Selenium deficiency was confirmed by measurement of erythrocyte glutathione peroxidase. Administration of excess selenium by i.p. injection did not affect alkaloid metabolism. It was concluded that dietary selenium status was unlikely to influence the metabolism of pyrrolizidine alkaloids.

Animals↗
PubMedDate not supplied

Chromatographic determination of dicofol and metabolites in egg yolks.

Egg yolk was spiked with p,p'-dicofol (p,p'-DCF) (0.1-2.0 micrograms/gm), p,p'-dichlorobenzophenone (p,p'-DCBP) (0.1-2.0 micrograms/gm), and 1,1-bis(4-chlorophenyl)-2,2-dichloroethylene (p,p'-DDE) (0.05-1.0 micrograms/gm). The fortified egg yolk (2-5 g) was mixed with acetonitrile to extract non-fat organic materials. After removal of acetonitrile, the spiked chemicals were separated with a column chromatograph packed with acid alumina. Recovery efficiencies for p,p'-DCBP and p,p'-DDE were determined by gas chromatography, and for p,p'-dicofol by high performance liquid chromatography. The recovery efficiencies for p,p'-dicofol, p,p'-DCBP and p,p'-DDE were 77.2-93.8%, 84.1-101.1%, and 88.5-96.0%, respectively.

Animals↗
PubMedDate not supplied

Microsomal enzyme induction, egg production, and reproduction in three lines of Japanese quail fed polybrominated biphenyls.

The sensitivity of three genetic lines of Japanese quail to polybrominated biphenyls (PBBs) was evaluated using criteria of egg production, reproduction, and induction of the hepatic microsomal mixed-function oxidase (MFO) system. Two genetic lines of quail, developed to diverge in their plasma cholesterol response to exogenous adrenocorticotropin (ACTH) (a "Low" line and a "High" line), were compared to a random-bred line ("Random"). ACTH administration caused increases in plasma cholesterol in the Low line that were 15 and 39% below the Random-line values in males and females, respectively, while High-line values were 31% higher in males and 36% higher in females when compared to the respective Random-line values. Hepatic activities of aryl hydrocarbon hydroxylase (AHH) and hexobarbital hydroxylase (HxH) were not significantly influenced by ACTH administration or by genetic line in either sex. PBBs fed at 40 or 80 mg/kg diet for 5 wk resulted in significant increases in hepatic AHH and aminopyrine N-demethylase (APND) activities and cytochrome P-450 concentrations. The induction of AHH, APND, and cytochrome P-450 was significantly less in Low-line males in comparison to Random- and High-line males, while the induction of AHH was less in Low-line females when compared to females from the other two lines, based on covariance analysis. In terms of reproductive parameters, there was a greater adverse effect on egg production at 80 ppm PBBs in Low-line females when compared to the Random and High lines. These data indicate an example in which the biological toxicity of a compound and the induction of a 3-methylcholanthrene-type hepatic enzyme are not directly correlated.

Adrenocorticotropic Hormone↗
PubMedDate not supplied

Xenobiotic metabolizing enzyme activities in rat, mouse, monkey, and human testes.

The capacity of the testis to metabolize xenobiotics has been proposed to play a role in the susceptibility of different species to testicular toxicity. Since species differences in testicular xenobiotic metabolizing enzyme activities are not well documented, the primary objective of the present study was to compare enzyme activities in subcellular fractions prepared from rat, mouse, monkey, and human testes. In microsomal fractions, enzyme activities measured were pentoxyresorufin O-dealkylase (PROD), ethoxyresorufin O-dealkylase (EROD), and epoxide hydrolase (mEH). In cytosolic preparations, epoxide hydrolase (cEH) and glutathione S-transferase (cGST) activities were measured. PROD activity was not detectable in any of the species studied, while it was readily detected in liver microsomes used as a positive control. Although EROD activity was low, it was measurable in testicular microsomes from rat and mouse, but not monkey or human. No marked species differences in cEH activity were found. In contrast, mEH activity was low in the monkey, intermediate in the rat, and highest in the human and mouse. cGST activity was significantly lower in the two primate species compared with the rat and the mouse. The levels of activity of the xenobiotic metabolizing enzymes studied were generally more than an order of magnitude lower in the testis as compared to the liver. However, in rat and mouse, the levels of mEH and cGST activities in testis were relatively similar to hepatic levels. Overall, these data indicate that species differences in capacity to metabolize xenobiotics may play a role in differential sensitivity to testicular toxicants.

Adult↗
PubMedDate not supplied

Biological and induction effects of phenobarbital and 3-methylcholanthrene in mink (Mustela vison).

Mink were injected (ip) daily with 20 mg/kg of 3-methylcholanthrene (MC) or 40 mg/kg of phenobarbital (PB) for 3 days and killed 48 hr after the last injection. The duration of anesthetic action of PB increased after each injection. MC-treated mink became anorexic and lost substantial body weight. PB caused enlargement of liver and lungs, whereas MC caused liver atrophy. No major treatment-related morphologic changes including amount of endoplasmic reticulum (ER) in liver were revealed by electron microscopic examination. Microsomal protein content was not increased and NADPH cytochrome P-450 reductase was not induced in liver by either PB or MC. Cytochrome P-450 (448) was increased 3.2-fold by PB and 2.5-fold by MC. Cytochrome b5 was increased 2.3-fold by MC but was not affected by PB. Aminopyrine N-demethylase was enhanced 5.1-fold in activity by PB whereas hexobarbital hydroxylase was not induced. MC-treatment moderately increased the activities of benzo(a)pyrene hydroxylase (1.7-fold) and ethoxyresorufin O-deethylase (2.1-fold) but had no effect on ethoxycoumarin O-deethylase. The most distinctive features of the mink revealed by this study are a) lack of PB induction of the ER, microsomal protein content, NADPH-cytochrome P-450 reductase, and hexobarbital hydroxylase, and b) lack of MC induction of cytochrome P-448-associated mixed function oxidases that are known to be highly responsive to MC in other species.

Animals↗