Absence of therapeutic blood concentrations of tetracycline in rats after administration in drinking water

Because of ease of administration and broad antibacterial spectrum, tetracycline often is administered in drinking water to control infectious diseases of rats. Assay of serum after a gavage bolus of tetracycline (300 mg/kg body weight) revealed little absorption of tetracycline by this route. Rats were given water containing tetracycline at several concentrations (400 mg/liter, 4g/liter, and 4 g tetracycline plus 50 g sucrose/liter) ad libitum and serum concentrations of tetracycline were monitored. Bioassay of serum samples from these animals, taken during 72 hours of water medication, revealed no detectable tetracycline concentrations (greater than 0.2 mcg/ml) in the 400 mg and 4 g/liter groups. Two of eighteen serum samples from the group given 4 g tetracycline with 50 g sucrose/liter had minimal therapeutic tetracycline concentrations (0.3 mcg/ml) effective for Mycoplasma pulmonis. Some of the animals given tetracycline ad libitum in drinking water drank very little and lost weight compared to control animals. These findings indicate that the practice of adding tetracycline to drinking water of rats may be ineffective in controlling systemic diseases, and also be detrimental to the treated animals.     

Species-specific antigens ofMycoplasma hyopneumoniae and cross-reactions with other porcine mycoplasmas

Cell proteins from the porcine mycoplasmasMycoplasma hyorhinis, M. hyopneumoniae, andM. flocculare have been analyzed by SDS-gel electrophoresis and immunoblotting. The protein profiles ofM. hyopneumoniae andM. flocculare were similar, but the protein profile ofM. hyorhinis was quite different from the others. Antisera prepared against whole cells of the above three mycoplasmas were used in immunoblotting of electrophoretically separated antigens and in enzyme-linked immunosorbent assay. One major antigen, which had a molecular weight of 73 k, was found to be common to all three mycoplasmas. Another major antigen, with a molecular weight of 41 k, was common toM. hyopneumoniae andM. flocculare and may also be present inM. hyorhinis. Several antigens of comparatively high molecular weights (108 k, 102 k, 93 k, 89 k, and 87 k) seemed to be specific forM. hyopneumoniae. Three antisera prepared by immunization of rabbits with immunoprecipitates obtained by crossed immunoelectrophoresis ofM. hyopneumoniae were also used in blotting experiments. One of these antisera was found to be directed against the 73 k antigen common to the three porcine mycoplasmas investigated. The other two antisera were directed againstM. hyopneumoniae-specific antigens with molecular weights of 74 k, 58 k, 45 k, 44 k, and 38 k.     

Lipopolysaccharide and lipoteichoic acid induce different innate immune responses in bovine mammary epithelial cells

The objective of the present study was to characterize the innate immune responses induced by in vitro stimulation of bovine primary mammary epithelial cells (bMEC) using gram-negative lipopolysaccharide (LPS) and gram-positive lipoteichoic acid (LTA) bacterial cell wall components. Quantitative real-time PCR (qRT-PCR) was employed to examine the mRNA expression of a panel of 22 cytokines, chemokines, beta-defensins and components of the Toll-Like Receptor signaling pathway. Stimulation of bMEC with LPS for 24h elicited a marked increase in mRNA expression for IL-1beta, IL-8, TNFalpha, CXCL6 and beta-defensin while members of the Toll-Like Receptor pathway, although present, were largely unaffected. Surprisingly, stimulation of these cells with LTA for 24 h did not significantly alter the expression of these genes. A time course of the expression of IL-1beta, IL-8, TNFalpha, CXCL6 and beta-defensin was subsequently performed. The mRNA levels of all genes increased rapidly after stimulation for 2-4 h with both LPS and LTA but only the former treatment resulted in sustained responses. In contrast, the increased gene expression for LTA stimulated cells returned to resting levels after 8-16 h with the exception of beta-defensin, which remained up-regulated. The limited and unsustained cytokine response to LTA may explain why mastitis caused by gram-positive bacteria has greater potential for chronic intra-mammary infection than gram-negative infection. It was concluded that bovine mammary epithelial cells have a strong but differential capacity to mount innate immune responses to bacterial cell wall components.     

The terpene-producing glands of a Phasmid insect. Cell morphology and histochemistry

The defensive glands of Anisomorpha buprestoides produce the terpene toxicant anisomorphal. Each gland consists of a cuticular secretion reservoir surrounded by the secretory epithelium and the musculature which serves to compress the gland and expel the secretion. Two types of cells make up the secretory epithelium: a squamous layer next to the cuticular reservoir and a layer of larger secretory cells responsible for production of the toxicant. The microvilli-laden plasma membrane of each secretory cell is invaginated to form a central cavity. It appears that secretory products pass into the central cavity and then flow out to the gland reservoir via an efferent cuticular ductule contained within the squamous epithelial cell. Histochemical techniques demonstrate lipid reserves, carboxylic esterases, a variety of phosphatases, and an alcohol dehydrogenase, within the secretory cells. It is suggested that the lipid reserves are precursors of the terpenoid toxicant, that a mevalonic kinase has been histochemically demonstrated by the phosphatase test, and that an unusual alcohol dehydrogenase is active in the final steps of toxicant synthesis. The histochemical evidence is consistent with the hypothesis that anisomorphal is produced via the mevalonic acid pathway.     

Effect of aromatase inhibition on prostatic growth and pathology, prostatic and serum androgen concentrations, and testicular androgen secretion in beagles[Poster 29]

Treatment of dogs with an oral nonsteroidal aromatase inhibitor for 25 weeks increased (P<.01) serum testosterone concentration and testicular androgen secretion over controls. No effect (P>0.10) upon prostatic growth, histology, or androgen concentrations was observed.     

Metabolic variables of cholesterol during squalene feeding in humans: comparison with cholestyramine treatment

Squalene, a key intermediate of cholesterol synthesis, is present especially in olive oil. Regulation of cholesterol metabolism by dietary squalene in man is unknown, even though olive oil users in Mediterranean areas have low serum cholesterol levels. We have investigated absorption and serum levels of squalene and cholesterol and cholesterol synthesis with the sterol balance technique and serum levels of cholesterol precursors in humans during squalene feeding (900 mg/d for 7-30 days). The results were compared with those during cholestyramine treatment. Fecal analysis suggested that about 60% of dietary squalene was absorbed. Serum squalene levels were increased 17 times, but serum triglyceride and cholesterol contents were unchanged. The squalene feeding significantly (P less than 0.05) increased serum levels of free (1.7-2.3 times) and esterified (1.9-2.4 times) methyl sterol contents, while elevations of free and esterified delta 8-cholesterol and lathosterol levels were inconsistent. Cholestyramine treatment modestly augmented free methyl sterol levels (1.3-1.7 times), less consistently than those of esterified ones, while, in contrast to the squalene feeding, serum contents of free and esterified delta 8-cholesterol and lathosterol were dramatically increased (3.3-8 times). Neither of the treatments significantly affected serum plant sterol and cholestanol levels. The squalene feeding had no consistent effect on absorption efficiency of cholesterol, but significantly increased (paired t-test, P less than 0.05) the fecal excretions of cholesterol and its nonpolar derivatives coprostanol, epicoprostanol, and coprostanone (655 +/- 83 SE to 856 +/- 146 mg/d) and bile acids (212 +/- 24 to 255 +/- 24 mg/d), indicating an increase of cholesterol synthesis by about 50%. We suggest that a substantial amount of dietary squalene is absorbed and converted to cholesterol in humans, but this squalene-induced increase in synthesis is not associated with consistent increases of serum cholesterol levels. The clearly increased serum contents of esterified methyl sterols may reflect stimulated tissue acyl CoA: cholesterol acyltransferase (ACAT, EC 2.3.1.26) activity during squalene feeding as these sterols are not esterified in serum.