Search PubMed⌕ Search

Biomedical subjects

A Mayer

Publications and source records attributed to A Mayer.

At least 181 records · Page 10Linked to original sources
PubMed1988

Transmitter release patterns of noradrenergic, dopaminergic and cholinergic axons in rabbit brain slices during short pulse trains, and the operation of presynaptic autoreceptors.

Slices of rabbit brain were field-stimulated either by single electrical pulses or by trains of 4 or 8 pulses at 1 or 100 Hz in order to study transmitter release patterns and the autoinhibition of transmitter release. The slices were preincubated with 3H-noradrenaline (cortex), 3H-dopamine (caudate nucleus) or 3H-choline (caudate nucleus). Slices preincubated with 3H-noradrenaline were superfused with medium containing desipramine 1 mumol/l. The overflow of tritium elicited by single pulses amounted to 0.19% of the tritium content of the tissue. The overflow elicited by 4 pulses/1 Hz was similar, whereas that elicited by 4 pulses/100 Hz was 5.1-fold higher. Yohimbine 10-1000 nmol/l increased up to 2.5-fold the overflow evoked by 4 pulses/1 Hz but did not change the overflow evoked by single pulses or 4 pulses/100 Hz. - Slices preincubated with 3H-dopamine were superfused with medium containing nomifensine 1 mumol/l. The overflow of tritium elicited by single pulses was 0.39% of the tritium content of the tissue. The overflow elicited by 4 pulses/1 Hz was 1.3-fold and the overflow elicited by 4 pulses/100 Hz 1.4-fold higher. Domperidone 1-100 nmol/l and sulpiride 10-1000 nmol/l increased up to 2.4-fold the overflow evoked by 4 pulses/1 Hz but increased only slightly the overflow evoked by single pulses or 4 pulses/100 Hz. - Slices preincubated with 3H-choline were superfused either with physostigmine-free medium or with medium containing physostigmine 1 mumol/l. In physostigmine-free medium, atropine did not increase the evoked overflow of tritium at any stimulation condition. In physostigmine-containing medium, the overflow elicited by single pulses was 0.18% of the tritium content of the tissue. The overflow elicited by 8 pulses/1 Hz was 2.0-fold and the overflow elicited by 8 pulses/100 Hz 2.2-fold higher. Atropine 2-200 nmol/l increased up to 2.4-fold the overflow evoked by 8 pulses/1 Hz but increased only slightly the overflow evoked by single pulses or 8 pulses/100 Hz. In physostigmine-free medium, sulpiride 10-1000 nmol/l did not change the single-pulse-evoked overflow of tritium in the absence but increased it in the presence of nomifensine 1 mumol/l. Single pulses elicit a large release of 3H-noradrenaline, 3H-dopamine and 3H-acetylcholine under the conditions of these experiments. Release elicited by single pulses is not subject to autoinhibition except for a small inhibition by spontaneously released transmitter in the case of dopaminergic and cholinergic axons.(ABSTRACT TRUNCATED AT 400 WORDS)

Acetylcholine↗
PubMed1987

Sodium binding to and protonation of ATP: a multinuclear magnetic double resonance study at 8.46 tesla.

We show that the interaction of ATP with Na+ and H+, whether binding or dissociation, gives rise to exchange broadened 31P-NMR spectra at 8.4 T, pH 6.7 and 310 K. We interpret the effect as being due to a two-step conversion between two NMR-differentiated ATP pools. A quantitative analysis yields all involved equilibrium constants and some of the dynamic parameters. Our results help to understand previous studies of magnesium binding to ATP and the appearance of high-field in vivo 31P-NMR spectra.

Adenosine Triphosphate↗
PubMed1987

[Sonographic diagnosis of holoacardius].

In the 28th week of gestation a normal foetus and a holoacardius were diagnosed via sonography in a biamnotic monochoriatic twin pregnancy. The growth of the foetuses was observed under continuous sonographic control up to the 40th week of pregnancy. The patient delivered a healthy twin by Caesarean section and the acardius was subjected to a postmortem. Macroscopic and histological findings in the foetus, the placenta and the umbilical cords are demonstrated. The pathogenesis of the holoacardius is discussed as being due to chromosomal aberrations and foeto-foetal transfusion syndrome.

Abnormalities, Multiple↗
PubMed1987

Metabolic effects of a low-glycemic-index diet.

Six healthy male volunteers underwent 2-wk metabolically controlled high-glycemic-index (GI) and low-GI diets in random order. Over the low-GI diet significant reductions were seen in serum fructosamine (7.0 +/- 1.0%, p less than 0.01), 12-h blood glucose profile (37 +/- 7%, p less than 0.01), and total serum cholesterol (15 +/- 3%, p less than 0.01). As a measure of insulin secretion, 24-h urinary C-peptide levels were 32 +/- 10% lower (p less than 0.05) after the low-GI than after the high-GI diet. Lower C-peptide levels were maintained after a standard carbohydrate challenge after the low-GI diet despite higher blood glucose levels. Differences in blood glucose were not seen after a 5-g intravenous glucose challenge. These results are of interest with respect to the effect that prolonged postprandial reductions in nutrient fluxes and insulin secretion may have on carbohydrate and lipid metabolism and renal function.

Adult↗
PubMed1984

A molecular approach to leukemogenesis: mouse lymphomas contain an activated c-ras oncogene.

By inducing mouse thymomas with carcinogens and gamma-radiation, we have studied the potential of tumor DNA to induce foci in rodent fibroblasts. A high percentage of the tumors used transformed the cultured cells, and the oncogenic phenotype segregated with extra copies of the c-ras gene family. There appears to be selectivity in the activated gene because so far all analyzed tumors induced by carcinogen have activated the N-ras gene, and those induced by radiation have activated the K-ras gene. The K-ras gene is the cellular counterpart of the viral ras oncogene in Kirsten murine sarcoma virus, but the N-ras has not yet been found in a retrovirus. The transformed cells have a marked increase in expression of the oncogene at the RNA and protein level. This model system might be a powerful tool in the study of leukemogenesis.

Animals↗
PubMed1983

Ecotropic MuLV expression in radiation-induced lymphomas of the RF, BALB/c and (BALB/c X RF)F1 mouse strains.

Endogenous ecotropic viruses isolated from radiation-induced lymphomatous tissue of BALB/c mice have been shown to consist of a collection of variants as assayed by the mobility of virion structural proteins p30, p15, p12 and gp70 on SDS-polyacrylamide gel electrophoresis (SDS-PAGE) (Ellis et al., 1980 a). In this study we show that a similar phenomenon occurs in RF mice, but only with regard to p15 and gp70, and not p30 and p12. Using the distinct and unvarying mobility of the RF viral p12 protein on SDS-PAGE as a marker, we show that the RF-derived ecotropic murine leukemia virus (MuLV) is expressed to the exclusion of the BALB/c-derived ecotropic MuLV in F1 hybrid mice of the BALB/c X RF cross, and that variant viruses expressed in F1 radiation-induced lymphomatous tissue display the pattern of variation characteristic of the RF, and not of the BALB/c, strain.

Animals↗
PubMed1983

Properties of [3H]flunitrazepam binding to different benzodiazepine binding proteins.

Membranes from cerebellum or hippocampus were incubated with various concentrations of [3H]flunitrazepam in the absence or presence of diazepam, Cl 218 872 or ethyl-beta-carboline-3-carboxylate (beta-CCE). After binding equilibrium of [3H]flunitrazepam had been established, the membranes were either filtered for determination of reversible binding or were irradiated with UV light for determination of irreversible binding. Irradiated membranes were then subjected to SDS-polyacrylamide gel electrophoresis and fluorography. Individual photolabeled proteins were identified, appropriate sections cut out of the gel, and the radioactivity in the gel pieces measured. The results indicate that [3H]flunitrazepam binding to individual benzodiazepine binding proteins and its inhibition by various drugs can be measured by the present technique and support previous evidence for the independent existence of various proteins irreversibly labeled by [3H]flunitrazepam and their possible association with different benzodiazepine receptors.

Animals↗
PubMed1983

On the statistics of 32P enrichment in skin tumours.

The authors have determined the distribution of 32P in normal skin and in the case of certain skin tumours (basalioma and spinalioma). In both groups a lognormal distribution was found. It may be assumed that the enrichment is governed by similar distribution in the case of melanoma malignum.

Basal Cell Carcinoma↗
PubMed1982

Postnatal development of proteins irreversibly labeled by [3H]flunitrazepam.

The irreversible labeling by [3H]flunitrazepam of three proteins with apparent molecular weights of 51,000 (P51), 55,000 (P55) and 59,000 (P59) was investigated using hippocampal membranes isolated from rats at various timepoints after birth. The present results indicate that [3H]flunitrazepam predominantly labels P55 and P59 in the early days after birth whereas labeling of P51 starts to increase significantly in the second postnatal week. A possible association of P55 and P59 with type 2 and of P51 with type 1 benzodiazepine receptors is suggested.

Aging↗
PubMed1981

Lithium induces rapid relief of depression in tricyclic antidepressant drug non-responders.

Eight patients suffering from a major unipolar depression and having field to respond to treatment for three weeks or more with tricyclic antidepressants were given lithium. All eight patients experienced a remarkable relief of their depression within 48 hours. This rapid antidepressant effect of lithium in "treatment-resistant' patients might be due to the enhancement of the efficacy of the central serotoninergic system, unveiling the tricyclic antidepressant-induced sensitization of the serotoninergic postsynaptic receptors.

Adult↗