Endothelin-1 and insulin activate the steady-state voltage dependent R-type Ca2+ channel in aortic smooth muscle cells via a pertussis toxin and cholera toxin sensitive G-protein

In single rabbit aortic smooth muscle cells, and at a concentration known to induce a maximum sustained increase of intracellular Ca²⁺ via activation of the steady-state voltage dependent R-type Ca²⁺ channels, endothelin-1 (10^-7 M) and insulin (80 U/ml) were found to induce a sustained increase in cytosolic free Ca²⁺ ([Ca]_i) levels that was significantly attenuated by pre-treatment with either pertussis toxin (PTX), cholera toxin (CTX) or removal of extracellular Ca²⁺.However, both PTX and CTX failed to inhibit the sustained depolarization-evoked sustained Ca²⁺ influx and [Ca]_i elevation via activation of the R-type Ca²⁺ channels. Moreover, ET-1 and insulin-evoked sustained increases in Ca²⁺ influx were not attenuated by the selective PKC inhibitor, bisindolylmaleimide (BIS), or the specific L-type Ca²⁺ channel blocker, nifedipine, but were completely reversed by the R-type Ca²⁺ channel blocker, (-) PN 200-110 (isradipine). These data suggest that both insulin and ET-1 activate the nifedipine-insensitive but isradipine-sensitive steady state voltage dependent R-type Ca²⁺ channels present on rabbit VSMCs and these channels are directly coupled to PTX and CTX sensitive G protein(s).     

Binding of α-galactosidase I from vicia faba to potato starch granules and sheep erythrocytes

α-Galactosidase I from Vicia faba seeds binds to potato starch and sheep erythrocytes. With the aid of fluorescence microscopy and using 4-methylumbelliferyl α-D-galactoside as the substrate it has been demonstrated that the binding is via the lectin sites of the enzyme leaving catalytic sites free and detectable. The lectin site is specific for D-glucose/D-mannose residues.     

Acceptor specificity of the human leukocyte alpha3 fucosyltransferase: role of FucT-VII in the generation of selectin ligands

The alpha3 fucosyltransferase, FucT-VII, is one of the key glycosyltransferases involved in the biosynthesis of the sialyl Lewis X (sLex) antigen on human leukocytes. The sialyl Lewis X antigen (NeuAcalpha(2-3)Galbeta(1-4)[Fucalpha(1-3)]GlcNAc-R) is an essential component of the recruitment of leukocytes to sites of inflammation, mediating the primary interaction between circulating leukocytes and activated endothelium. In order to characterize the enzymatic properties of the leukocyte alpha3 fucosyltransferase FucT-VII, the enzyme has been expressed in Trichoplusia ni insect cells. The enzyme is capable of synthesizing both sLexand sialyl-dimeric-Lexstructures in vitro , from 3'-sialyl-lacNAc and VIM-2 structures, respectively, with only low levels of fucose transfer observed to neutral or 3'-sulfated acceptors. Studies using fucosylated NeuAcalpha(2-3)-(Galbeta(1- 4)GlcNAc)3-Me acceptors demonstrate that FucT-VII is able to synthesize both di-fucosylated and tri-fucosylated structures from mono- fucosylated precursors, but preferentially fucosylates the distal GlcNAc within a polylactosamine chain. Furthermore, the rate of fucosylation of the internal GlcNAc residues is reduced once fucose has been added to the distal GlcNAc. These results indicate that FucT-VII is capable of generating complex selectin ligands, in vitro , however the order of fucose addition to the lactosamine chain affects the rate of selectin ligand synthesis.      

Transfer of broad-host-range antibiotic resistance plasmids in soil microcosms

Broad-host-range plasmids, belonging to IncP (RP4 and pUPI102) and IncC (R57.b), were studied for intrageneric and intergeneric gene transfer in three different soil microcosms. RP4 was transferred intragenerically in clay loam, sandy loam, and sandy microcosms at frequencies of 0.71×10^–2, 0.83×10^–2, and 0.41×10^–2 respectively, optimally at 37°C and at 100% vol/wt moisture content. Under similar conditions, R57.b was also transferred at frequencies of 0.38×10^–2, 0.58×10^–2, and 0.80×10^–5 respectively at 30°C. Both RP4 and R57.b were transferred at low frequency at 20°C. Kinetics of plasmid transfer revealed that 48 h was the optimum time for intrageneric conjugal gene transfer. Gene transfer frequency was tenfold higher in all nutrient-amended soil microcosms than in the absence of nutrient amendment. RP4 was transferred to an indigenous soil bacteriumBeijerinckia indica in a nonsterile soil microcosm and to other indigenous soil bacteria, viz.Xanthomonas campestris, Azotobacter chroococcum, Acinetobacter calcoaceticus, Achromobacter agili, andRhizobium meliloti in sterile soil microcosms. pUPI102 was transferred fromA. calcoaceticus BD413 toEscherichia coli K12 J53 at a frequency of 0.75×10^–6 and 1.1×10^–6 in clay loam and sandy loam microcosms respectively. However, no gene transfer was observed in any soil microcosm when strains ofA. calcoaceticus BD413 (pUPI102) andE. coli K12 J53.2 (RP4) were used for conjugal mating. Plasmid RP4 was found to be 100% stable in all the above microorganisms.     

Comparison of tissue culture and whole plant responses to salinity in potato

Salt sensitivities of six potato cultivars using six levels of sodium chloride (0.0 to 0.25M) were studied in a greenhouse. Responses of these cultivars were also determined in tissue culture by studying rooting of stem segments, increase in length of cultured roots and inhibition of growth of cell suspension cultures using similar salt concentrations. Responses of cultured stem segments and cell suspensions differed from those expressed by whole plants. A close similarity was observed between the salt stress response of whole plants and of cultured roots. The latter technique may provide a preliminary screening method for assessing salt tolerance in potato genotypes.     

Changes in protein fractions and leucine-[14C] incorporation during Sorghum grain development

Incorporation of leucine and changes in different protein fractions have been studied during Sorghum grain development. Most of the label from the injected leucine-[¹⁴C] was found in glutelin and residue fraction towards later stages of maturity. The label in albumin, globulin and prolamin decreased with a concomitant increase in label in glutelin and residue proteins. The concentration of lysine, aspartic acid and glycine decreased while that of leucine, proline, alanine, tyrosine, phenylalanine, and cystine increased during grain development. Increase in serine, methionine, valine and isoleucine was only marginal. The proportion of glutamic acid was high at all stages of grain development. Glutelin fraction resolved into two peaks on gel chromatography, only one of which with higher MW was labelled, while in albumin both the peaks were found to be labelled. Tannin content also increased during grain development.     

Rapid detection and quantitation of Clostridium perfringens enterostoxin by counterimmunoelectrophoresis.

Conditions for detection and quantitation of Clostridium perfringens enterotoxin by counterimmunoelectrophoresis are described. As little as 0.2 microgram of enterotoxin per ml could be detected. The test was found to be rapid, sensitive, specific and easy for the detection and quantitation of enterotoxin.     

Differential carbon monoxide sensitivity of cytochrome C oxidase in the leaves of c(3) and c(4) plants

CO sensitivity of cytochrome a₃ in the leaves of a number of C₃ and C₄ plants was monitored by the nitrate reductase assay under differing CO to O₂ ratios. All the C₃ plants were relatively insensitive to CO and required a high CO to O₂ ratio of 40 to promote significant nitrate reductase activity. However, when treated with 2 millimolar 2,4-dinitrophenol, these leaves readily responded to CO even at low CO to O₂ ratios of 10 or less. On the other hand, the leaves of all C₄ plants tested, belonging to the three subgroups, were highly sensitive to CO, even at CO to O₂ ratios of 5 or less. In these leaves, the uncoupler was without any effect, probably because the mitochondria, either from mesophyll or bundle sheath cells or both, lacked tight respiratory control.     

Effect of phenolics on plant amine oxidases

Phenolic compounds at low concentrations decrease pea diamine oxidase activity without affecting growth, but they have no effect on barley polyamine oxidase in spite of a decrease in growth.     

Regulation of nitrate reduction in wheat leaves

Wheat leaves exposed to 710 nm monochromatic light, when only photosystem 1 operates, reduced small but significant amount of nitrate to nitrite. This could be due to partial inhibition of mitochondrial oxidation of NADH, brought about by cyclic photo-phosphorylation. Under dark aerobic conditions, citric acid cycle intermediates only slightly stimulated nitrate reduction. Under dark anaerobic conditions, when maximum reduction of nitrate occurred, the time course showed a 1:1 stoichiometry between nitrite and CO₂. It is suggested that for maximum reduction of nitrate under physiological conditions, CO₂ fixation and export of ATP via triose phosphate shuttle is essential.