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Biomedical subjects

B Bauer

Publications and source records attributed to B Bauer.

At least 217 records · Page 12Linked to original sources
PubMed1980

[3H]-dopamine release from the rabbit retina.

[3H]-Dopamine was found to be released from the rabbit retina in vitro by light stimulation, by 40 mM K+, and by alpha-MSH (alpha-Melanocyte-Stimulating Hormone) down to about 10(-7) M. The effect of alpha-MSH was dose-dependent. A number of known and putative retinal neurotransmitters and agonists (GABA, muscimol, glutamic acid, kainic acid, glycine, and carbachol, all 10(-4) M) were without significant effect. The results show that it is unlikely that there are excitatory receptors on the retinal dopaminergic neurons to any of the conventional transmitters. Further, alpha-MSH seems of interest as a possible neuroactive retinal substance, which was previously not been suspected.

Animals↗
PubMed1979

[Reaction performance, motor coordination performance and findings in hypertensive patients under diisopropylamine and reserpine therapy].

In 64 male hypertonics the reaction and coordination functions and the condition were standardized and compared before and after a four weeks ambulatory treatment with diisopropylamine (3 times 200 mg a day) and reserpine (3 times 0.25 mg a day). The two medicaments achieved good blood pressure reducing effects. Since in reserpine the therapeutic effect later appeared, fatigue and need for sleep were more frequent and continuous, in older patients still after a treatment of four weeks right and temporary reactions decreased, wrong reaction increased and the aim accelerated, is concluded that here in particular in the behaviour of older people more frequently a longer lasting disturbance is probable.

Adult↗
PubMed1979

Effect of pentobarbitone on the spontaneous efflux of gamma-amino acids from rabbit retina.

The effect of pentobarbitone on the spontaneous release of radioactivity from rabbit retinas preloaded with [3H]GABA, [3H]DABA, [3H]beta-alanine and [3H]glycine was studied. In high concentration of pentobarbitone (10(-3)M) the rate of spontaneous efflux of neuronal [3H]GABA, [3H]DABA and [3H]beta-alanine was reduced but not that of [3H]glycine. Glial release of [3H]GABA was much less influenced. At lower concentrations (10(-4)-10(-5)M) there was an initial increase in the release of [3H]GABA, [3H]DABA and [oH]beta-alanine followed by a decrease, indicating several components in the release system for the amino acids.

Alanine↗
PubMed1978

Effect of prolonged low-dose infusions of ile5-angiotensin ii on blood pressure, aldosterone and electrolyte excretion in sodium replete man.

Two healthy young males on a constant normal sodium diet (135 mM/day) were infused for 132 h with 3 ng/kg/min of angiotensin II. Plasma angiotensin II levels were therby raised to the range of moderate sodium depletion. Plasma aldosterone and the urinary excretion rate of aldosterone-18-glucuronide were markedly increased during the whole infusion period and returned to control levels after the infusion was stopped. A slight tendency of aldosterone secretion to decrease towards the end of infusion was probably due to sodium retention (appr. 200 mM and 350 mM respectively) and to a fall in plasma potassium by approximately 0.5 mM/1. Plasma aldosterone during infusion, maintained circadian variations similar to those of cortisol. Plasma cortisol patterns were unaffected by angiotensin II. Blood pressure increased gradually during angiotensin II infusion, reflecting changes in sodium balance. The results, differing from those of studies in dog and sheep, support the assumption that angiotensin II is an important regulator of aldosterone secretion in man rather than a merely permissive factor.

Adult↗
PubMed1978

Photic release of radioactivity from rabbit retina preloaded with [3H]GABA.

The in vitro release of radioactivity by light from rabbit retina was studied after intravitreal injection of [3H]GABA (gamma-aminobutyric acid). The site of uptake of [3H]GABA into the retina after intravitreal injection was checked by autoradiography and was localized at 2 h after the injection mainly in glia but at 4 h in amacrine cells and some ganglion cells. If the retina loaded with [3H]GABA was stimulated by light flashes the efflux of radioactivity increased significantly. Chromatographic analysis of the superfusate demonstrated that [3H]GABA was released by light stimulation. However, the efflux was not elicited by constant light, and was abolished in a medium containing 20 mM Mg++ and 0.2 mM++. When the metabolism of GABA was inhibited by amino-oxyacetic acid, light flashes no longer increased the efflux of radioactivity significantly. No light-evoked release of radioactivity could be demonstrated from glia. Pentobarbitone inhibited the spontaneous efflux and prior anaesthetization with pentobarbitone abolished the light-evoked release. These results support the view that GABA is a retinal neurotransmitter in the rabbit.

Aminobutyrates↗
PubMed1978

Prolonged infusions of Ile5-angiotensin-II in sodium replete and deplete man: effects on aldosterone, ACTH, cortisol, blood pressure, and electrolyte balance.

Angiotensin II (Ile5) was infused for 72 h into 4 sodium replete (3 ng/kg/min) and 8 sodium deplete (3 or 6 ng/kg/min) healthy young men after appropriate control periods, and the effects on aldosterone secretion, plasma cortisol, ACTH, renin activity, plasma and urinary electrolytes, and blood pressure were assessed. Sustained contrived elevation of plasma angiotensin II levels in sodium replete subjects to the range of moderate sodium depletion led to a sustained increase in plasma and urinary aldosterone levels, which further and significantly increased between the 1st and 2nd days of angiotensin II infusion, when gross sodium retention during infusion was prevented. This additional increase may be explained as the expression of a "trophic" effect of angiotension II on the zona glomerulosa. In the sodium deplete state, the absolute increment of aldosterone secretion for a given elevation of angiotensin II levels diring infusion was larger than in sodium replete subjects. This confirms the conclusions from previous short-term angiotensin II infusion experiments that sodium deficiency sensitizes the zona glomerulosa against angiotensin II. The "trophic" effect of angiotensin II on the adrenal gland seems to be one mechanism by which the sensitization is brought about, but insufficient for its full explanation. Since plasma ACTH and cortisol, plasma sodium and potassium concentrations, and potassium blance did not change significantly across sodium depletion or angiotensin II infusion, the mechanism of sensitization awaits its full elucidation. The effect of angiotensin II on blood pressure was blunted by soidum depletion. The opposite shifts in sensitivity against angiotensin II of the zona glomerulosa and of resistance blood vessels with changes in the sodium state seem to be an effective and important means in the regulation of body sodium.

Adrenocorticotropic Hormone↗
PubMed1977

Light evoked release of radioactivity from rabbit retinas preloaded with (3H)-GABA.

Light flashes evoke an increased release of radioactivity in vitro from rabbit retinas preloaded with (3H)-GABA in vivo. Constant light does not affect the release. No light evoked release can be demonstrated from the glia. Pentobarbitone and AOAA depress the evoked release. The results are consistent with GABA being a retinal neuro-transmitter, most likely in a class of amacrines.

Aminobutyrates↗
PubMed1977

Stimulated release of [3H]beta-alanine from the rabbit retina.

The efflux of [3H]beta-alanine from rabbit retina after intravitreal injection has been studied. The site of uptake of [3H]beta-alanine into retina was checked by autoradiography and was found mainly in the inner plexiform layer and in cells with the position of amacrines and in some ganglion cells. When the preloaded retina was stimulated by light flashes and release of radioactivity increased significantly. Chromatography of the superfusate demonstrated a single radioactive spot which cochromatographed with authentic beta-alanine. The efflux of [3H]beta-alanine was affected by raising the K+ concentration. The rate of efflux was also immediately increased when unlabelled beta-alanine or GABA was added to the superfusion medium. Glycine was much less effective. The present study shows that light stimulation releases [3H]beta-alanine from the retina and that beta-alanine may use the same transport system as GABA. This further supports the suggestion that beta-alanine may act as a "false transmitter" replacing GABA in the retina.

Alanine↗
PubMed1977

Factors affecting the spontaneous release of (3H)glycine from rabbit retina.

The efflux of [3H]glycine was studied in superfused rabbit retina in the presence of various amino acids, ouabain, or high K+ or low Ca2+ concentrations in the superfusion medium. Unlabelled glycine evoked an accelerated efflux as did the structurally similar neutral alpha-amino acids. beta-alanine and GABA were ineffective. The results demonstrate a homoexchange of glycine, and a heteroexchange with the neutral alpha-amino acids. A low concentration of glutamic acid (10(-5) M) will release glycine from the retina. This is an ATPase dependent process which is partially blocked by a high Mg2+/Ca2+ ratio and which may be related to a retinal transmitter function of glutamic acid. A high concentration of K+ or the presence of ouabain in the superfusing medium greatly increases the rate at which glycine is lost from the retina.

Amino Acids↗
PubMed1975

Plasmid-determined tetracycline resistance in Streptococcus faecalis: evidence for gene amplification during growth in presence of tetracycline.

The tetracycline (TG)-resistant Streptococcus faecalis strain DS-5Cl harbors two plasmids designated alpha and gamma with molecular masses of approximately 6 and 35 million daltons, respectively. TC-sensitive variants were derived by storing cells at 45 degrees for 2-3 weeks. Analysis of covalently closed circular DNA from five such variants (derived independently) revealed that in each variant the alpha-plasmid, which normally sediments at 28 S (supercoiled) in a sucrose density gradient, was replaced by a 22S substance. Growth of DS-5Cl in the presence of 150 mug/ml of TC (minimum inhibitory concentration is 250 mug/ml in liquid broth) for a prolonged period of time (50-60 generations) resulted in the disappearance of 28S DNA and the appearance of a heterogeneous covalently-closed circular DNA sedimenting at about 40-48 S. This phenomenon was accompanied by an increase in the level of bacterial TC-resistance, whereby tells were subsequently grown in the absence of TC for 70-80 generations, the heterogeneous DNA disappeared and a typical 28S alpha-plasmid reappeared. The cells also became less resistant to TC, i.e., the minimum inhibitory concentration returned to 250 mug/ml. These data suggest that bacterial growth in the presence of TC results in a reversible gene amplification with respect to a TC-resistant determinant residing on the alpha-plasmid.

Cell Division↗