Cyclic AMP-independent, dual regulation of voltage-dependent Ca2+ currents by LHRH and somatostatin in a pituitary cell line.

Voltage-dependent Ca2+ currents appear to be involved in the actions of hormones that regulate pituitary secretion. In order to investigate modulation of Ca2+ currents by release-inducing and release-inhibiting hormones, we performed whole-cell clamp experiments in the pituitary cell line GH3. The resting potential was approximately -40 mV; spontaneous action potentials were observed in the majority of cells. Superfusion of cells with the stimulatory hormone, LHRH, depolarized the plasma membrane to approximately -10 mV, whereas the inhibitory hormone, somatostatin, caused hyperpolarization to approximately -60 mV; both hormones suppressed spontaneous action potentials. Under voltage clamp conditions, GH3 cells exhibited slowly and fast inactivating Ca2+ currents. LHRH increased whereas somatostatin decreased the slowly inactivating currents; fast inactivating currents were not affected by these hormones. The stimulatory effect of LHRH was not mimicked by intracellularly applied cAMP. In contrast to vasoactive intestinal peptide and forskolin, LHRH did not activate adenylate cyclase in membranes of GH3 cells, but rather appeared to cause inhibition of the enzyme. Hormonal stimulation and inhibition of inward currents were abolished by pretreatment of the cells with pertussis toxin. In membranes of GH3 cells, we identified a pertussis toxin-sensitive G-protein of the Gi-type and Go. We conclude that LHRH and somatostatin modulate voltage-dependent Ca2+ currents via cAMP-independent mechanisms involving pertussis toxin-sensitive G-proteins. The occurrence of both pertussis toxin-sensitive hormonal stimulation and inhibition of voltage-dependent Ca2+ currents in one cell type suggest that these opposite regulations are mediated by distinct G-proteins.     

Lack of a relationship between immune function and chemically induced hepatocarcinogenesis in B6C3F1 mice

Summary The relationship between immune function and chemically induced hepatocarcinogenesis was studied employing an in vivo murine model. Neonatal B6C3F₁ mice were given a single carcinogenic dose of diethylnitrosamine (DEN) and the time-response kinetics for the early (foci of alteration) and late (adenomas/carcinomas) phases of hepatocellular carcinogenesis were compared to changes in hematopoiesis and immune functions associated with immune surveillance and natural resistance. Increases in hematopoiesis occurred just prior to or concurrent with the appearance of hepatocellular carcinomas, while increased macrophage and natural killer cell cytotoxicity and suppression of cell-mediated immunity occurred following tumor appearance and progressed with increasing tumor burden. Neither immunological nor hematopoietic changes were associated with early phases of hepatocarcinogenesis, as monitored by the appearance of altered hepatocellular foci. Although changes in hematopoiesis may represent an early indicator for hepatocarcinogenesis in the mouse tumor model, the data suggest that altered immune surveillance and natural resistance are not factors in the development of chemically induced hepatocellular tumors, and the changes in immune function are probably secondary to tumor development.     

Effects of spinal anesthesia on response to main pulmonary arterial distension

Nonocclusive main pulmonary arterial distension produces peripheral pulmonary hypertension. The mechanism of this response is unknown. The effects of total spinal anesthesia on the response were studied in halothane-anesthetized dogs. Before total spinal anesthesia, main pulmonary arterial balloon inflation increased pulmonary arterial pressure and resistance without affecting systemic hemodynamic variables. Both right and left pulmonary arterial pressures were monitored to exclude unilateral obstruction with main pulmonary arterial balloon inflation. Total spinal anesthesia decreased cardiac output and systemic arterial pressures. After total spinal anesthesia, main pulmonary arterial distension still increased pulmonary arterial pressure and resistance. Right atrial pacing, discontinuation of halothane anesthesia, and norepinephrine infusion during total spinal anesthesia partially reversed the hemodynamic changes caused by total spinal anesthesia. The percent increase in pulmonary vascular resistance due to main pulmonary arterial distension was similar before total spinal anesthesia and during all experimental conditions during total spinal anesthesia. The pulmonary hypertensive response is therefore not dependent on central synaptic connections.     

Efficacy and safety of foscarnet for recurrent orolabial herpes: a multicentre randomized double-blind study.

Foscarnet sodium (trisodium phosphonoformate hexahydrate) has been shown to inhibit herpes simplex virus (HSV) in vitro and to be efficacious for topical treatment of experimental HSV infection in animals. To assess its clinical efficacy in the treatment of recurrent orolabial herpes a multicentre collaborative, double-blind, placebo-controlled trial was conducted. The study patients were randomly assigned to receive either 3% foscarnet cream (78 patients) or placebo (cream vehicle) (75 patients) and were asked to start treatment at the earliest indication of a recurrence. Efficacy was evaluated in 143 patients (74 in the foscarnet group and 69 in the placebo group). There was no significant difference in time to healing or duration of virus shedding between the two groups. However, in the subgroup of patients who started treatment before vesicles appeared, the duration of virus shedding was shorter in the foscarnet group than in the placebo group (p = 0.04), and the proportion of lesions that evolved to the vesicular stage was smaller (p = 0.03). No significant difference in the incidence of local or systemic adverse effects was noted between the two groups. We conclude that the beneficial effect of foscarnet was limited to a subgroup of patients who started treatment in the prevesicular stage.     

Photosensitized formation of ascorbate radicals by chloroaluminum phthalocyanine tetrasulfonate: an electron spin resonance study.

The chloroaluminum phthalocyanine tetrasulfonate sensitized photooxidation of ascorbic acid to ascorbate radical (A.-) was followed by electron spin resonance (ESR) spectroscopy. In air saturated aqueous media, steady-state amounts of A.- are rapidly established upon irradiation. The ESR signal disappears within a few seconds after the light is extinguished--more slowly under constant irradiation as oxygen is depleted. No photooxidation was observed in deaerated media. The effect of added superoxide dismutase, catalase, desferrioxamine, and singlet oxygen scavengers (NaN3 and tryptophan) was studied, as was replacement of water by D2O and saturation with O2. The results are indicative of free radical production by direct reaction between ascorbate ion and sensitized phthalocyanine (a Type I mechanism) in competition with the (Type II) reaction of HA- with singlet oxygen, a reaction which does not produce ascorbate radical intermediates.     

The changes in the dominance hierarchy over time of a complete field-captured colony of Cryptomys hottentotus hottentotus

The common mole-rat, Cryptomys h. hottentotus , is a social subterranean rodent occurring in colonies in which one female and one to three males are involved in reproduction and the remaining colony members are non-reproductive. Within each sex the reproductive animals are usually the largest and most dominant animals.
The dominance hierarchy amongst a field-captured colony was linear ( h = 0.95, calculated from Landau's linearity index) soon after capture. The non-reproductive females were ranked low in the dominance hierarchy; many were subordinate to non-reproductive males. The order of capture of mole-rats was not related to the position in the dominance hierarchy. The hierarchy became non-linear ( h = 0.56) after six months in captivity during which two juvenile animals became adult. The breakdown in the hierarchy may result from the lack of opportunity in captivity for animals to disperse and establish satellite colonies, or from colony members becoming co-dominant in the hierarchy as a result of a rise in rank by young animals.
Dominant mole-rats are involved in a greater proportion of interactive behaviours than subordinates. Popularity studies show that females tend to be more popular animals than males. The largest reproductive male was the least popular animal in the first study, whereas a beta male was the least popular animal in the second study period. The reproductive female was the most popular in both periods.     

Immunochemical detection of the alpha-subunit of the G-protein, GZ, in membranes and cytosols of mammalian cells

An antiserum (AS 98) was raised against a synthetic peptide deduced from published cDNA sequences of the alpha-subunit of the putative G-protein, GZ (Fong et al. Proc. Natl. Acad. Sci. USA 85, 3066-3070, 1988; Matsuoka et al. Proc. Natl. Acad. Sci. USA 85, 5384-5388, 1988). In membrane and cytosol preparations of many but not all tested mammalian tissues, AS 98 predominantly recognized two proteins of 40 and 43 kDa Mr. Whereas high levels of a 40 kDa GZ alpha-subunit were found in rat liver membranes and in brain cytosol, AS 98 failed to detect the alpha-subunit of GZ in brain membranes.     

Elongation of C20 polyunsaturated fatty acids by human skin fibroblasts

Human skin fibroblasts actively elongate a portion of incorporated C20 polyunsaturated fatty acids to their respective C22 derivatives. As much as 40% of incorporated [14C]eicosapentaenoate is elongated within 8 h and 85% by 48 h. Elongation of [14C]arachidonate is initially less than half that of [14C]eicosapentaenoate and plateaus at 20-30% of incorporated 14C-labeled fatty acid. The elongation of 5,8,11-[14C]eicosatrienoate is intermediate between that of 20:4(n-6) and 20:5(n-3). Docosatetraenoate is not an effective inhibitor of the elongation of arachidonate, thus suggesting that the observed plateau is not due to product inhibition. When concentrations of exogenous fatty acids are increased, these cells elongate substantial quantities of C20 polyunsaturated fatty acids; elongation of eicosapentaenoate is consistently more extensive than that of arachidonate. Eicosapentaenoate is also an effective inhibitor of the elongation of [14C]arachidonate. Increases in exogenous arachidonate up to 10 microM result in an increase in elongation of [14C]arachidonate both in absolute quantities and as a percentage of that incorporated; the arachidonate thus acts as a positive modulator of its own elongation. Increased eicosapentaenoate also enhances the elongation of [14C]eicosapentaenoate, but only at lower concentrations (0.02-0.15 microM). The factors which regulate the elongation of C20 polyunsaturated fatty acids in human skin fibroblasts serve to permit extensive elongation of eicosapentaenoate while retaining incorporated arachidonate primarily in its C20 form.     

Persistence of vesicular stomatitis virus in cloned interleukin-2-dependent natural killer cell lines.

We have investigated virus-lymphocyte interactions by using cloned subpopulations of interleukin-2-dependent effector lymphocytes maintained in vitro. Cloned lines of H-2-restricted hapten- or virus-specific cytotoxic T lymphocytes (CTL) and alloantigen-specific CTL were resistant to productive infection by vesicular stomatitis virus (VSV). In contrast, cloned lines of natural killer (NK) cells were readily and persistently infected by VSV, a virus which is normally highly cytolytic. VSV-infected NK cells continued to proliferate, express viral surface antigen, and produce infectious virus. Furthermore, persistently infected NK cells showed no marked alteration of normal cellular morphology and continued to lyse NK-sensitive target cells albeit at a slightly but significantly reduced level. The persistence of VSV in NK cells did not appear to be caused by the generation of temperature-sensitive viral mutants, defective interfering particles, or interferon. Consequently, studies comparing the intracellular synthesis and maturation of VSV proteins in infected NK and mouse L cells were conducted. In contrast to L cells, in which host cell protein synthesis was essentially totally inhibited by infection, the infection of NK cells caused no marked diminution in the synthesis of host cell proteins. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of immunoprecipitates of viral proteins from infected cells showed that the maturation rate and size of VSV surface G glycoprotein were comparable in L cells and NK cells. Nucleocapsid (N) protein synthesis also appeared to be unaffected in NK cells. In contrast, the viral proteins NS and M appeared to be selectively degraded in NK cell extracts. Mixing experiments suggested that a protease in NK cells was responsible for the selective breakdown of VSV NS protein. Finally, VSV-infected NK cells were resistant to lysis by virus-specific CTL, suggesting that persistently infected NK cells may harbor virus and avoid cell-mediated immune destruction in an immunocompetent host.