HeLa cell plasma membranes : IV. Iodination of membrane proteins in synchronized cells

Intact HeLa cells and isolated HeLa cell plasma membranes were subjected to lactoperoxidase-catalysed iodination. The ¹²⁵I-labelled proteins were separated by SDS-polyacrylamide gel electrophoresis. Six protein species with apparent molecular weights from 32 000 to 200 000 were accessible to labelling from the outer cell surface, while most of the proteins present in the plasma membrane were labelled when isolated plasma membranes were iodinated. Iodination of synchronized intact cells revealed that the labelling obtained was cell cycle dependent with maximal labelling at mitosis. No changes in the distribution of radioactivity among the labelled proteins were observed when cells from different phases were iodinated.     

Sex steroids, growth and condition of Arctic charr broodstock during an annual cycle

Changes in plasma concentrations of sex steroids, growth rate and condition of repeat spawning (3+) male and female Arctic charr were studied throughout an annual reproductive cycle. Individually marked fish (mean weight approx. 500 g) were held under conditions of liberal food supply, constant temperature (4° C) and simulated natural photoperiod (Tromsø, 70° N). Once each month fish were weighed, measured and blood samples taken for steroid analysis. Plasma concentrations of testosterone (T), 11-ketotestosterone (11-KT) and oestradiol-17β (E₂) were determined using radioimmunoassay (RIA). Both male and female fish displayed distinct seasonal changes in plasma concentrations of sex steroids, growth rate and condition. From February (minimal concentrations) to March all sex steroids increased slightly and these elevated concentrations were maintained until May. Thereafter, there was a second, and far more pronounced, increase in plasma steroid concentrations which culminated in peak steroid concentrations in September–October. There was then a rapid decline during the spawning period. In winter, growth rate and condition were generally low, then increased during the spring, reached a peak during the summer, and then declined with the onset of autumn. During spring (March–May), the frequency distributions of plasma testosterone concentrations in both male and female fish were bimodal. The fish of the upper modal group of the distribution had significantly higher growth rates and condition than those in the lower modal group. In summer and early autumn (June–September) the association between T and growth rate changed. Significant negative correlations between T and growth rates were observed in females. There was an increase in endocrine activity, indicated by elevated plasma sex steroid concentrations in March, 7–8 months prior to maturation. It is suggested that this may be one factor influencing the onset of spring growth and energy deposition among maturing charr.     

Pairing for Recombination in Lgv of Caenorhabditis Elegans: A Model Based on Recombination in Deficiency Heterozygotes

The effect of deficiencies on recombination was studied in Caenorhabditis elegans. Heterozygous deficiencies in the left half of linkage group V [LGV(left)] were shown to inhibit recombination to their right. Fourteen deficiencies, all to the left of unc-46, were analyzed for their effect on recombination along LGV. The deficiencies fell into two groups: 10 "major inhibitors" which reduce recombination to less than 11% of the expected rate between themselves and unc-46; and four "minor inhibitors" which reduce recombination, but to a much lesser extent. All four minor inhibitors delete the left-most known gene on the chromosome, while six of the ten major inhibitors do not (i.e., these are "internal" deficiencies). Where recombination could be measured on both sides of a deficiency, recombination was inhibited to the right but not to the left. In order to explain these results we have erected a model for the manner in which pairing for recombination takes place. In doing so, we identify a new region of LGV, near the left terminus, that is important for the pairing process.     

Temperature-dependent development of parthenogenetic embryos in Daphnia pulex de Geer

An in vitro study of the embryonic stages of Daphnia pulex deGeer was carried out by way of removing and isolating eggs fromthe females. The temperature-dependent development rates andthe developmental features were recorded photographically. Thetotal development time was 351 h at 5°C, 161 h at 10°Cand 87 h at 15°C. The relative times of development of embryonic‘stages’ also showed significant variation betweentemperatures. The observed variations in relative developmenttime of D.pulex embryos at different temperatures will questionthe accuracy of previously used methods for estimations of populationbirth rates using egg age determinations. ¹Present address: Akvaforsk, N-6600 Sunndalsøra, Norway ²Present address: Raadgivende Biologer as., Ladegaardsgaten9, 5035 Sandviken, Norway     

Galanin in the porcine pancreas.

Galanin, a 29 amino acid neuropeptide, was recently isolated from pig intestine. We studied the localization, nature and effect of galanin in pig pancreas. Galanin immunoreactive nerve fibers were regularly found in the pancreas. A peptide chromatographically similar to synthetic galanin was identified in pancreas extracts. The effect of galanin on the endocrine and exocrine secretion was studied in isolated pancreases, perfused with a synthetic medium containing 3.5, 5 or 8 mmol/l glucose and synthetic galanin (10(-10)-10(-8) mol/l). There was no effect on the basal exocrine secretion. The output of insulin, glucagon, somatostatin and pancreatic polypeptide (PP) was measured in the effluent. There was no effect on PP secretion. At a perfusate glucose concentration of 5 mmol/l, galanin at 10(-9) mol/l increased insulin secretion by 55 +/- 14% (mean +/- S.E.M., n = 5) of basal secretion, and at 10(-8) mol/l by 58 +/- 27% (n = 6). At 8 mmol/l glucose, insulin secretion increased by 25 +/- 10% (n = 6) and 62 +/- 17% (n = 8). At 5 mmol/l glucose glucagon secretion was increased by 15 +/- 3% (n = 5) by galanin at 10(-9) mol/l and by 29 +/- 11% (n = 5) by galanin at 10(-8) mol/l, and at 8 mmol/l glucose by 66 +/- 27% and 41 +/- 25%. Somatostatin secretion was inhibited to 72 +/- 2% (n = 5) of basal secretion by galanin at 10(-9) mol/l and to 65 +/- 7% (n = 7) at galanin at 10(-8) mol/l, both at 5 mmol/l glucose. At 8 mmol/l the figures were 83 +/- 6% and 70 +/- 10%. Insulin secretion in response to square wave increases in glucose concentration from 3.5 to 11 mmol/l (n = 5) increased 2-fold during simultaneous perfusion with galanin (10(-8) mol/l).     

Contrasting effects of enalapril and metoprolol on proteinuria in diabetic nephropathy.

OBJECTIVE--To assess whether angiotensin converting enzyme inhibition reduces proteinuria in diabetic nephropathy more than blood pressure reduction with other antihypertensive treatment. DESIGN--Prospective, open randomised study lasting eight weeks in patients with diabetic nephropathy. SETTING--Outpatient nephrology clinics. PATIENTS--40 Patients with type I diabetes and diabetic nephropathy with reduced renal function. INTERVENTION--Antihypertensive treatment with enalapril or metoprolol, usually combined with frusemide. MAIN OUTCOME MEASURES--Arterial blood pressure and urinary excretion of albumin and protein. RESULTS--Arterial blood pressure after eight weeks was 135/82 (SD 13/7) mm Hg in the group given enalapril and 136/86 (16/12) mm Hg in the group given metoprolol. Proteinuria and albuminuria were similar in both groups before randomisation. After eight weeks'' treatment, the geometric mean albumin excretion was 0.7 (95% confidence interval 0.5 to 1.2) g/24 h in the patients given enalapril and 1.6 (1.1 to 2.5) g/24 h in the patients given metoprolol (p less than 0.02). The proteinuria was 1.1 (0.7 to 1.7) and 2.4 (1.6 to 3.6) g/24 h respectively (p less than 0.02). CONCLUSIONS--Antihypertensive treatment with enalapril reduced proteinuria in patients with diabetic nephropathy more than an equally effective antihypertensive treatment with metoprolol. This points to a specific antiproteinuric effect of the angiotensin converting enzyme inhibitor independent of the effect on systemic blood pressure.     

Flavobacterium sp. strain 4221 and Pedobacter sp. strain 4236 beta-1,3-glucanases that are active at low temperatures

Secretion of beta-1,3-glucanases by the arctic bacterial isolates 4221 and 4236, related to the genera Flavobacterium and Pedobacter, was discovered. Escherichia coli and Lactococcus lactis expression of beta-1,3-glucanases Glc4221-1 and Glc4236-1 from the respective isolates was achieved. The enzymes hydrolyzed fungal cell walls and retained activity at low temperatures.