Differences in GH secretion from individual somatotropes in rats genetically selected for fast and slow growth.

A reverse hemolytic plaque assay was used to examine effects of selection for fast (F) and slow (S) growth on growth hormone (GH) secretion by individual somatotropes. Anterior pituitaries (AP) from 32 male Charles River CD strain rats selected for F and S growth for 20 generations were used. Four rats per line were used at 4, 6, 8, or 10 wk of age. Body weight (P < 0.0001) of F rats was greater compared with S rats. AP (P < 0.05) were heavier at 8 and 10 wk of age in F compared with S line rats. Percentages of GH-secreting cells were unaffected by age (range = 32.7-35.5%) and line [F = 33.1 +/- 1.2% (SE) vs. S = 34.5 +/- 1.2%] or by human GH-releasing factor (hGRF). At 8 and 10 wk, mean plaque-forming area was greater (P < 0.0001) in F compared with S rats under both nonstimulated (2,704 +/- 202 vs. 1,648 +/- 202 microns2) and hGRF-stimulated secretion (4,503 +/- 202 vs. 2,682 +/- 202 microns2). Results indicate that differences in growth observed in the two lines may be due to a greater secretory capacity of individual somatotropes rather than to a greater percentage of somatotropes or sensitivity of somatotropes to secretagogue.

Effect of the beta-agonist cimaterol on growth and composition of neonatal rats selected for large and small body size.

The effect of subcutaneous injection of the beta-agonist cimaterol on growth and body composition of neonatal rats differing in growth potential was examined. Rats that represented substrain populations of Charles River CD rats selected for either large or small body size were used. Cimaterol administration resulted in a greater reduction in body weight gain in the Large strain rats. Body growth rate declined linearly with increasing doses of cimaterol in both strains. Percent carcass fat and protein were unchanged with cimaterol treatment. Administration of cimaterol inhibited skeletal muscle growth but caused cardiac hypertrophy. These results suggest that the effectiveness of beta-agonists is influenced by animal genotype.

Papillomas on fish exposed to chlorinated wastewater effluent.

The presence of carcinogenic and mutagenic chemical(s) in the effluent of a wastewater treatment plant was indicated by papillomas developing on caged black bullheads (Ictalurus melas), hepatic enzyme induction in exposed fish, and Ames test mutagenicity of organic extracts of the wastewater. Although virus-like particles have been reported in papillomas of several other fish species, no evidence was obtained for the presence of viruses in the black bullhead papillomas. Mutagenic and carcinogenic chemicals were not identified in the wastewater, but chlorination was implicated as a factor contributing to the induction of the papillomas. The prevalence of papillomas on wild black bullheads exposed to the effluent decreased from 73 to 23% after the amount of residual chlorine (CAS: 7782-50-5) in the effluent leaving the chlorine contact chamber was reduced from 1.3-3.1 mg/liter to 0.25-1.2 mg/liter.

Characterization of a lectin from cowpeas.

A lectin without blood group specificity was isolated from cowpeas (Vigna unguiculata (L.) Walp.). This lectin was prepared from a crude saline extract by acid precipitation and Sephadex gel filtration. Purification steps generally resulted in increased agglutination activity. Homogeneity was demonstrated by polyacrylamide gel electrophoresis, and ultracentrifugation. The native lectin had a molecular weight of approximately 55,000 as shown by gel filtration, polyacrylamide electrophoresis, and analytical ultracentrifugation. Amino acid analysis showed a very low sulfur amino acid content and relatively high content of aspartic and glutamic acids. Total neutral sugar analysis indicated less than 1% of saccharides. The lectin interacted with several saccharides.