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Biomedical subjects

G Gerber

Publications and source records attributed to G Gerber.

At least 91 records · Page 5Linked to original sources
PubMed1988

Optimization of the ion-pair high-performance liquid chromatographic separation of purine derivatives in erythrocytes, thymocytes and liver mitochondria.

Various methods are described for the analysis of purine derivatives in biological samples by ion-pair high-performance liquid chromatography (HPLC) with both gradient and isocratic systems. A new approach is proposed that is suitable for the separation of nuclei acid constituents in different cells with a specific enzymatic activity pattern. The ion-pair HPLC methods were developed for the analysis of erythrocytes, lymphocytes and mitochondria acid-soluble fractions in clinical and experimental studies of normal and altered nucleotide metabolism. The results of studies of purine metabolite redistribution in mouse liver mitochondria during a 30-min incubation at 37 degrees C and data on purine metabolic alterations in mouse thymocytes during hepatoma growth are discussed.

Animals↗
PubMed1988

Calcitonin gene-related peptide enhances calcium current of rat dorsal root ganglion neurons and spinal excitatory synaptic transmission.

The actions of calcitonin gene-related peptide (CGRP) were examined on Ca2+-dependent action potentials and voltage-dependent Ca2+ currents in rat dorsal root ganglion (DRG) neurons in vitro. In addition, we tested the effect of CGRP on excitatory synaptic transmission in the rat spinal dorsal horn. CGRP produced a reversible increase in the amplitude and the duration of the Ca2+ spike of DRG neurons and directly increased the voltage-dependent Ca2+ current by enhancing both the transient and the sustained components of the current. The increase in the Ca2+ current is likely to be responsible for the increase in the Ca2+ spike and facilitation of excitatory synaptic transmission.

Action Potentials↗
PubMed1988

Actions of calcitonin gene-related peptide on rat spinal dorsal horn neurons.

The membrane actions of calcitonin gene-related peptide (CGRP) and the effect on the Ca-dependent action potential of dorsal horn neurons have been investigated by means of an intracellular recording technique in the immature rat in vitro spinal cord slice-dorsal root ganglion preparation. Bath application of CGRP (10(-8)-10(-6) M for 1-10 min) produced a slow reversible depolarization in about one-third of the cells examined. Biphasic membrane response consisting of an initial hyperpolarization followed by a late prolonged depolarization was seen in a smaller proportion of tested cells. Both membrane responses were present, and even enhanced, when synaptic transmission and Na spikes were blocked by perfusing the slice with a TTX-containing Krebs solution. The CGRP-induced membrane changes were also present in media containing TTX and TEA. The CGRP-evoked depolarization was associated with an increase in the input resistance, and enhanced excitability in a majority of neurons tested. In addition, CGRP modified the duration of Ca-dependent action potentials of dorsal horn neurons, the most consistent change being a prolonged increase in the spike duration. Our results are consistent with a neurotransmitter or neuromodulator role for CGRP in the rat spinal dorsal horn.

Action Potentials↗
PubMed1988

Purine and pyridine nucleotides in rabbit red blood cells of different maturity.

Using reversed-phase high-performance liquid chromatography purine nucleotides, nucleosides and nucleobases as well as pyridine nucleotides were determined in extracts of reticulocytes and mature red blood cells of rabbits. The concentrations of almost all compounds measured decrease during the last phase of red blood cell maturation. These changes were interpreted with respect to the loss of mitochondria, accompanied by shifting the energy production from the preferentially oxidative mode to the exclusively glycolytic one and variations in the concentrations of purine compounds in blood plasma during reticulocytosis.

Adenine Nucleotides↗
PubMed1988

Actions of calcitonin gene-related peptide on rat sensory ganglion neurones.

The membrane actions of calcitonin gene-related peptide (CGRP) and the effect of CGRP on the Ca-dependent action potential of rat dorsal root ganglion (DRG) neurons have been studied by means of an intracellular recording technique in isolated DRG of 2-3-week-old rats in vitro. Bath application of CGRP (10(-8)-10(-6) M for 1-5 min) elicited a slow reversible hyperpolarization and this hyperpolarizing effect was still observed in the medium containing TTX and TEA. However, about half of the large cells, classified by duration of action potential, were depolarized by CGRP. These membrane effects of CGRP were associated with an increase in membrane input resistance (about 20%). In addition, CGRP increased the duration of Ca-dependent action potentials. Our results are consistent with the role of CGRP as an excitatory neurotransmitter or neuromodulator in DRG-spinal cord.

Animals↗
PubMed1987

Determination of nucleotides, nucleosides and nucleobases in cells of different complexity by reversed-phase and ion-pair high-performance liquid chromatography.

Procedures are presented for the analysis of profiles of purine and pyridine compounds in human and rabbit red blood cells by reversed-phase high-performance liquid chromatography and in Ehrlich ascites tumour cells of mouse by ion-pair high-performance liquid chromatography. These compounds are present in rabbit erythrocytes in higher concentrations than in human blood cells, and in rabbit reticulocytes the concentration of purine compounds is still higher. During glucose-free incubation, human red cells accumulate adenosine and adenine in the presence of coformycin owing to the inhibition of adenosine and AMP deamination. Ehrlich ascites tumour cells lose major portions of purine mono-, di- and triphosphates between the seventh and eleventh day after inoculation into mouse peritoneal cavities.

Animals↗
PubMed1987

Damage of erythrocytes by activated oxygen generated in hypoxic rat liver.

The implication of activated oxygen in the interaction between hypoxic rat liver and circulating erythrocytes was investigated. Reduced species of oxygen generated in hypoxic liver owing to accelerated purine nucleotide degradation via xanthine oxidase initiate alterations of plasma membrane and glutathione system of erythrocytes. Osmotic fragility, hemolysis rate and erythrocytic GSSG:GSH ratio may be considered as appropriate indicators of oxidative load in liver and other tissues. Addition of erythrocytes to the perfusion medium attenuates the GSSG efflux of hypoxic liver from 2.7 +/- 0.5 nmol x g w.w.-1 x min-1 to 1.4 +/- 0.2 nmol x g w.w.-1 x min-1 Thus, circulating erythrocytes protect the liver against oxidative attack.

Animals↗
PubMed1987

Identification and characteristics of a novel mitochondrial ATPase in rat liver.

A novel ATPase is postulated for isolated mitochondria and mitoblasts of rat liver. The enzyme is active in the presence of oligomycin and carboxyatractyloside. It can be distinguished from other well-known mitochondrial and non-mitochondrial ATPases by its insensitivity to common ATPase inhibitors and effectors and by digitonin treatment. The ATPase is localized on the outer side of the inner mitochondrial membrane. It is activated by Mg2+ in the alkaline pH range and exhibits a biphasic kinetics. The novel external ATPase of rat liver mitochondria possesses similar properties with respect to ATP-dependent protease.

Adenosine Triphosphatases↗
PubMed1987

Degradation of AMP in erythrocytes of man. Evidence for a cytosolic phosphatase activity.

By means of selective inhibitors of adenosine deaminase and adenosine kinase, the contributions of two competing pathways for the breakdown of adenosine nucleotides in erythrocytes of man were examined. Under nearly physiological conditions in vitro the main pathway for the irreversible breakdown proceeds from AMP via IMP and inosine to hypoxanthine. Its rate amounts to 12 mumol AMP/l cells X h. At the same time about three times as much AMP, about 40 mumol/l cells X h, are degraded by way of dephosphorylation to adenosine. However, this pathway does not contribute significantly to the production of hypoxanthine, since the adenosine formed is rephosphorylated by adenosine kinase. Both AMP and IMP are dephosphorylated by an unspecific cytosolic acid phosphatase, the maximal activity of which amounts to 660 mumol nucleotide/l cells X h.

Acid Phosphatase↗
PubMed1986

H2O2 formation during nucleotide degradation in the hypoxic rat liver: a quantitative approach.

In the hypoxic liver an increased rate of cytosolic and peroxisomal H2O2 generation is due to the accelerated purine nucleotide degradation. The relative contribution of the oxidase type of xanthine oxidoreductase activity increases in hypoxia by less than 10%, the dehydrogenase type of this enzyme is hardly inhibited by the increased concentration of free NADH. Nevertheless, due to the high hypoxanthine supply the xanthine oxidase related H2O2 formation is increased six-fold and together with the peroxisomal uricase-mediated share it accounts for half of the oxygen consumption.

Animals↗
PubMed1986

Influence of postnatal hypoxia on 32P-labeling of polyphosphoinositides and phosphatidic acid in striatum synaptosomes from rat brain.

Striatum synaptosomes prepared from adult rats which had been exposed to postnatal hypoxia incorporate 32P-phosphate into phosphatidylinositol-4,5-trisphosphate (PI-4,5-P2) with decreased rate. 32P-incorporation amounted to 57% of the control for PI-4,5-P2 labeling and was slightly diminished for phosphatidic acid and PI-4-P. Exposure to hypoxia of adult rats did not affect inositol phospholipid labeling. The inhibitory effect of dopamine on 32P-phosphate incorporation was reduced only after postnatal hypoxia. 32P-incorporation rates and the dopamine inhibitory effect were not influenced by external calcium. A working hypothesis is suggested for the dopamine action on specific receptors which may be linked to the polyphosphoinositide metabolism and membrane calcium release. The long lasting effects of an early postnatal hypoxia on 32P-incorporation rates into polyphosphoinositides and phosphatidic acid could reflect the role of the proposed dopamine receptor interaction.

Animals↗
PubMed1986

[The central retinal artery of the white laboratory mouse].

The white laboratory mouse has an Arteria centralis retinae which differs from the Arteria centralis retinae of the human in the following points being: The origin of this artery hies in the region where the Arteria bulbi comes through the Sclera and therefore does not enter the Nervus opticus until she is in the wall of the Bulbus oculi. In the retina the Arteria centralis retinae divides into 6 radiating branches.

Animals↗
PubMed1985

A mathematical model to study short-term regulation of mitochondrial energy transduction.

A mathematical model is presented which includes the following elementary process of mitochondrial energy transduction: hydrogen supply, proton translocation by the respiratory chain, proton-driven ATP synthesis by the F0F1-ATPase, passive back-flow of protons (leak) and carrier-mediated exchange of adenine nucleotides and phosphate. For these processes empirical rate laws are used. The model is applied to calculate time-dependent states of energy transduction in isolated rat liver mitochondria. From the general agreement of the computational results with experimental data (Ogawa, S. and Lee, T.M. (1984) J. Biol. Chem. 259, 10004-10011) the following conclusions can be drawn. (1) The length of the time interval during which mitochondria are able to maintain a relatively high and constant delta pH in the absence of oxygen (anaerobiosis) is limited by the availability of intramitochondrial ATP. (2) The overshoot kinetics of delta pH which appear when reoxigenating mitochondria after a preceeding anaerobiosis might be due to a lag phase kinetics of the F0F1-ATPase. (3) In phosphorylating mitochondria the homeostasis of delta pH is brought about by a high sensitivity of the respiration rate and the rate of the F0F1-ATPase as to changes of delta pH. (4) Analysis of the mean transient times shows that the rate of ATP synthesis in State 3 is controlled to almost the same extent by the hydrogen supply, the respiratory chain, the adenine nucleotide translocator and the proton leak.

Adenine Nucleotides↗