Plasma somatostatin-like immunoreactivity during growth-hormone-releasing hormone therapy in non-growth-hormone-deficient children

To date, the effects of long-term growth hormone (GH)-releasing hormone [GHRH(1-29)-NH2] treatment on the plasma concentrations of somatostatin-like immunoreactivity (SLI) remain undefined. In the present study, the effect of GHRH(1-29)-NH2 therapy on plasma SLI levels has been studied in 11 non-GH-deficient children. The pattern of administration was 5 micrograms/kg body weight, given subcutaneously once every day. There was no significant change in plasma SLI levels after bolus injection of GHRH(1-29)-NH2 before and during GHRH(1-29)-NH2 therapy. However, plasma SLI rose in basal plasma and nocturnal sleep after 3 months of GHRH(1-29)-NH2 therapy and remained the same during 6 months of treatment with GHRH(1-29)-NH2. The reason for this finding is uncertain, but an increase in SLI release from the enteroinsular axis is a possible explanation. The association of our findings with the role of the circulating SLI on nutrient homeostasis and the effects of GNRH on growth velocity is discussed.     

Cloning ofCandida boidinii DNA fragments promoting autonomous replication of plasmids inSaccharomyces cerevisiae

Fragments of Candida boidinii chromosomal DNA were inserted into the integrative vector YIp-kanr and examined for the presence of sequences promoting autonomous replication of plasmids in Saccharomyces cerevisiae. Restriction maps of two plasmids, designated S6/4 and S6/5, originating from the same S. cerevisiae transformant, were constructed. Southern hybridization data confirmed that the plasmids carry sequences from the C. boidinii chromosome. Both plasmids transform S. cerevisiae strains at 4-5-fold higher frequency than cloning vectors based on the replication origin of the 2 microns plasmid. Mitotic stability of the constructed plasmids is similar to that of the 2 mu-based vector pNF2 in S. cerevisiae.     

Influence of lipid headgroup on the specificity and exchange dynamics in lipid-protein interactions. A spin-label study of myelin proteolipid apoprotein-phospholipid complexes

The pH and salt dependences of the interaction of phosphatidic acid, phosphatidylserine, and stearic acid with myelin proteolipid apoprotein (PLP) in dimyristoylphosphatidylcholine (DMPC) recombinants have been studied by electron spin resonance spectroscopy, using spin-labeled lipids. The two-component spin-label spectra have been analyzed both by spectral subtraction and by simulation using the exchange-coupled Bloch equations to give the fraction of lipids motionally restricted by the protein and the rate of lipid exchange between the fluid and motionally restricted lipid populations. For stearic acid, phosphatidic acid, and phosphatidylserine, the fraction of motionally restricted spin-label increases with increasing pH, with pKa's of 7.7, 7.6, and ca. 9.4, respectively. The corresponding pKa's for the bulk lipid regions of the bilayer are estimated, from changes in the ESR spectra, to be 6.7, 7.4, and 11, respectively. In the dissociated state at pH 9.0, the fraction of motionally restricted component decreases with increasing salt concentration, reaching an approximately constant value at [NaCl] = 0.5-1.0 M for all three negatively charged lipids. The net decreases for stearic acid and phosphatidic acid are considerably smaller (by ca. 30%) than those obtained on protonating the two lipids, whereas for phosphatidylserine the fraction of motionally restricted lipid in high salt is reduced to that corresponding to phosphatidylcholine. For a fixed lipid/protein ratio, the on-rate for exchange at the lipid-protein interface is independent of the degree of selectivity and has a shallow temperature dependence, as expected for a diffusion-controlled process.(ABSTRACT TRUNCATED AT 250 WORDS)     

Monoclonal antibodies to the hydrogenase ofThiocapsa roseopersicina

Monoclonal antibodies were produced to electrophoretically pure hydrogenase fromThiocapsa roseopersicina. Protein immunoelectroblotting was used to identify the hydrogenase-specific antibodies. Among the 18 monoclonal antibodies selected by enzyme immunoassay, three were found to react with highly immunogenic trace contaminating proteins. One cell line produced antibody that inhibitied hydrogenase activity. This was the first specific inhibitor of the hydrogenase function. The results suggest that monoclonal antibodies could provide valuable new informations about the enzyme structure as well.     

Hyperpolarization of mouse skeletal muscle plasma membrane induced by extracellular NADH

Extracellularly applied NADH, but not NAD or NADPH, increases the resting membrane potential from -74.1 to -76.6 mV in freshly isolated muscles in the presence of K+ in the incubation medium and from -64.6 to -72.9 mV in muscles equilibrated for 4-6 h in a K+-free solution. The NADH-induced hyperpolarization is blocked by pretreatment of muscles with ouabain, and the inhibitors of plasma membrane NADH dehydrogenase (adriamycin, azide, PCMB, atebrine, DIDS and bleomycin). The effect of NADH is accompanied by the disappearance of NADH from the incubation medium and by decreased membrane resistance. We conclude that NADH hyperpolarization is due to the enhancement of passive membrane permeability, apparently for K+, which might result from the conformational changes in the plasma membrane during the NADH dehydrogenase reaction. The possibility is discussed that NADH dehydrogenase mediates transport of K+ out from the cell using a pathway connected with the transmembrane Na+/K+ pump.