Basolateral plasma membrane localization of ouabain-sensitive sodium transport sites in the secretory epithelium of the avian salt gland

The distribution of Na+ pump sites (Na+-K+-ATPase) in the secretory epithelium of the avian salt gland was demonstrated by freeze-dry autoradiographic analysis of [(3)H] ouabain binding sites. Kinetic studies indicated that near saturation of tissue binding sites occurred when slices of salt glands from salt-stressed ducks were exposed to 2.2 μM ouabain (containing 5 μCi/ml [(3)H]ouabain) for 90 min. Washing with label-free Ringer's solution for 90 min extracted only 10% of the inhibitor, an amount which corresponded to ouabain present in the tissue spaces labeled by [(14)C]insulin. Increasing the KCl concentration of the incubation medium reduced the rate of ouabain binding but not the maximal amount bound. In contrast to the low level of ouabain binding to salt glands of ducks maintained on a freshwater regimen, exposure to a salt water diet led to a more than threefold increase in binding within 9-11 days. This increase paralleled the similar increment in Na+-K+-ATPase activity described previously. [(3)H]ouabain binding sites were localized autoradiographically to the folded basolateral plasma membrane of the principal secretory cells. The luminal surfaces of these cells were unlabeled. Mitotically active peripheral cells were also unlabeled. The cell-specific pattern of [(3)H]ouabain binding to principal secretory cells and the membrane-specific localization of binding sites to the nonluminal surfaces of these cells were identical to the distribution of Na+-K+-ATPase as reflected by the cytochemical localization of ouabain-sensitive and K+-dependent nitrophenyl phosphatase activity. The relationship between the nonluminal localization of Na+-K+-ATPase and the possible role of the enzyme n NaCl secretion is considered in the light of physiological data on electrolyte transport in salt glands and other secretory epithelia.     

Acclimation of different strains of the olive fly, Dacus oleae, to low temperatures

Male and female D. oleae have similar powers of acclimation when exposed to low temperatures. Their torpor thresholds depend upon the temperature to which they have been acclimatised. During slow cooling (i.e. less than 1°C per min) they are capable of some rapid acclimation which enables them to lower their torpor threshold by almost 1°C degree, as compared with when they are chilled quickly. After abrupt transfer from 25°C to a different temperature, acclimation takes some time to be accomplished. At 15°C and above it occurs within 10 days but at temperatures below this, progressive acclimation lowers the torpor thresholds to the very low levels typical of flies overwintering under natural conditions. During this long term acclimation torpor thresholds may change by almost 0.5°C per 1°C change of acclimation temperature.No differences were observed in the ability of either flies from northern and southern Greece, or normal and γ-irradiated laboratory reared flies to acclimate to winter conditions in the field. In all cases, torpor thresholds were progressively lowered in advance of the decline in weekly minimum temperatures.     

Isolation of plasma membrane glycoprotein from bovine thymocytes

Glycoprotein was isolated from a purified thymocyte membrane preparation by two methods: lithium diiodosalicylate-phenol extraction and hot 75% ethanol extraction. A higher yield of membrane sialic acid was obtained by the latter method. The preparations had similar apparent molecular weights on sodium dodecyl sulfate gel electrophoresis. Both had similar receptor activities against a panel of hemagglutinins, although the 75% ethanol extract was more active on a weight basis. However, there were significant differences in carbohydrate and amino acid compositions of the two thymocyte extracts. The lithium diiodosalicylate-extracted material had much more glucose, ribose, and glycine than the ethanol extract. The glycoprotein preparations from thymocytes were quite distinct from the glycoprotein of bovine erythrocytes in both composition and receptor properties.     

Effects of fusicoccin on Fresh Weight and Chlorophyll Levels in Cucumber Cotyledons

Incubation of cucumber cotyledons with fusicoccin increasedtheir fresh weights and chlorophyll levels and this effect wasenhanced by KCl. Addition of fusicoccin to this combinationincreased fresh weights but decreased chlorophyll levels. Thissuggests that the effects of fusiccocin on these two processesare probably mediated via different mechanisms. (Received January 4, 1982; Accepted March 25, 1982)     

Vertebrate lectins, Comparison of properties of beta-galactoside- binding lectins from tissues of calf and chicken

Beta-galactoside-binding lectins were isolated from various calf tissues and from chicken hearts by affinity chromatography on asialofetuin-Sepharose, and were compared with respect to biochemical characteristics, binding properties, antigenic cross-reactivity, and cellular localization. The lectins are all thiol group-requiring, divalent cation-independent dimers, of apparent monomer mol wt 12,000 (calf lectins) or 13,000 (chicken lectin), and acidic pI. The calf lectins appear essentially identical by dodecyl sulfate-polyacrylamide gel electrophoresis, isoelectric focusing, amino acid composition, and radioimmunoassay, while the chicken lectin is distinctly different by these criteria. However, all of the lectins competed for the same binding sites on rabbit erythrocytes, and could be inhibited by the same saccharide haptens (notably lactose and thiodigalactoside). Immuno-fluorescence studies on several cultured cell lines revealed that the bovine and chicken lectins had primarily an intracellular cytoplasmic localization. The beta-galactoside-binding lectins of vertebrates appear to be species-specific rather than tissue-specific.     

Prostaglandin E1 effects on resting and cholinergically stimulated lower esophageal sphincter pressure in cats

Intraluminal esophageal manometry with a sleeve catheter was used to compare the magnitude of decrease in lower esophageal spincter (LES) pressure produced by an arterial or venous infusion of prostaglandin E₁ in cats. Arterial PGE₁ produced significantly lower LES pressures than venous PGE₁ (p < 0.05). Maximal decrease of 75% in basal LES pressure occurred with an associated 15% decrease in systolic blood pressure. The site of action of PGE₁ in producing LES hypotension was studied by injection of either edrophonium, or bethanechol during the maximal PGE₁ effects. Bethanechol, which acts directly on sphincteric smooth muscle, produced an increase in LES pressure during both saline and PGE₁ infusion, while the increases in LES pressure seen with edrophonium during saline infusion were blocked during the PGE₁ infusion. From these studies, we conclude that PGE₁ produces LES hypotension in the cat by an inhibitory effect on the cholinergic pathway responsible for maintaining LES tone. These studies pharmacologically reproduce the LES pressure abnormality previously reported in the cat during acid-induced esophagitis and support the hypothesis that PGE₁ may be involved in the pathogenesis of acute acid-induced lower esophageal sphincter abnormalities.     

THE NATURE OF THE TWO PROTEINS OF BRAIN SPECIFIC ANTIGEN 14-3-2

The three isoenzymes of rat brain enolase (2-phospho d -glycerate hydrolase EC 4.2.1.11.) χχ, χγ and γγ were separated by ion-exchange chromatography and were tested for reaction with an antiserum against brain specific antigen 14-3-2. This monospecific antiserum affects the enolase activity of only the χγ and γγ isoenzymes. Immunoelectrophoretic experiments show that the two proteins which react as 14-3-2 both contain γ enolase subunits, and one of these also contains χ enolase subunits. It is concluded that the 14-3-2 antigen and the γ enolase subunit are identical, and that the two proteins which react immunologically as 14-3-2 are the χγ and γγ enolase isoenzymes.     

Purification and properties of mammalian toxins from the venom of the Brazilian scorpion Tityus serrulatus Lutz and Mello

The water-soluble part of the dried venom from the scorpion, Tityus serrulatus Lutz and Mello (range, Southeastern Brazil), showed 16 polypeptide bands on polyacrylamide gel electrophoresis. This material exhibited toxic and hyaluronidase activity but no phospholipase, phosphodiesterase, protease, or fibrinolytic activity. Fractionation on glycinamide-treated Sephadex G-50 afforded three protein fractions, which were non-toxic, equitoxic, and three times more toxic than the water-soluble venom. Subsequent separation of the toxic fractions on carboxymethyl-cellulose with phosphate buffers furnished five toxic components, which were further purified on carboxymethyl-cellulose with a salt gradient in acetate buffer. Toxin γ, the major and most basic toxin, is a 62-residue protein that, unlike other scorpion toxins, contains methionine. Automated Edman degradation showed the amino-terminal sequence to be H-Lys-Glu-Gly-Tyr-Leu-Met-Asp-His-Glu-Gly-Cys-Lys-Leu-Ser-Cys-Phe-Ile-Arg-Pro-Ser-Gly-Tyr-Cys-Gly-Arg-Glu-Cys-Gly-Ile-. Toxin γ is the first example of a fifth structural type of mammalian toxin from scorpion venom. Its amino-terminal sequence shows greater homology with toxins similar to Centruroides suffusus suffusus toxin III and Androctonus australis toxin II than with toxins similar to A. australis toxin I or Bhutus occitanus tunetanus toxin I.     

Effect of metformin on insulin receptor binding and glycaemic control in type II diabetes.

To investigate the effect of metformin on insulin receptor binding and diabetic control, eight obese type II diabetic patients were studied before treatment, after one and four weeks of taking metformin (500 mg thrice daily), and four weeks after withdrawal of the drug. After one and four weeks of treatment the number of erythrocyte insulin receptors had increased by 116% and 184% respectively. This was due almost entirely to an increase in the number of low affinity binding sites. The number of receptors was still raised four weeks after metformin had been withdrawn. Diabetic control as assessed by urinary glucose, glycosylated haemoglobin (HbA1), and glucose tolerance values was significantly improved during metformin treatment, while plasma insulin concentrations were not altered. These results indicate that metformin produces a rapid and protracted increase in low affinity insulin receptors in type II diabetes, associated with greater insulin sensitivity and improved diabetic control.