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Biomedical subjects

A Foldes

Publications and source records attributed to A Foldes.

29 records · Page 2Linked to original sources
PubMed1981

In vitro noradrenaline accumulation by sheep skin: partial characterization and localization.

Previous studies from this laboratory have implicated the sympathetic neurotransmitter noradrenaline (NA) in regulation of wool growth. The current study was undertaken to investigate [3H]NA accumulation and its localization by Merino skin, and to determine the effects of gonadal and glucocorticoid steroids on such uptake. The presence of an active uptake system was demonstrated and the process was partially characterized in terms of its magnitude, time course, concentration dependence and requirement for various nutrient and ionic factors. The uptake was seen to occur predominantly into cocaine- and 6-hydroxydopamine-sensitive sites in skin from various body regions of Merino sheep. None of three steroids tested in vivo or in vitro was seen to influence the uptake process. These results do not enable us to correlate the observed [3H]NA uptake process with the previously reported effects of NA on wool growth.

Aging↗
PubMed1979

The effects of histamine on responses of the rabbit ear artery to electrical stimulation and to exogenous noradrenaline.

1 The effects of a subconstrictor dose of histamine (9 x 10(-7) mol/l) on the responses of the isolated perfused ear artery of the rabbit to electrical stimulation (E.S.) and to exogenous noradrenaline (NA) were investigated.2 Both intraluminal (I/L) and extraluminal (E/L) histamine potentiated responses to E.S. and to I/L NA to the same extent.3 Mepyramine alone (2.5 x 10(-6) mol/l) had no effect on the response of the ear artery to either stimulus, but in the presence of this concentration of mepyramine, the potentiation by histamine of the response to I/L NA was significantly decreased and that to E.S. was replaced by inhibition.4 The H(1)-receptor agonist, 2(2-pyridyl) ethylamine, applied I/L potentiated responses to I/L NA at both concentrations used (5.1 and 51 x 10(-7) mol/l), but only potentiated the effects of E.S. at the higher concentration.5 The H(2)-receptor antagonist, metiamide (4 x 10(-6) mol/l), alone did not alter the extent of potentiation of responses to either E.S. or I/L NA by histamine. This suggests relatively weak H(2)-receptor activity in the rabbit ear artery. In the presence, but not the absence of metiamide, the potentiation by histamine of the I/L NA response was reversible, an observation suggesting an interaction between metiamide and the non-reversible component of the potentiating effect of histamine.6 These results are interpreted in terms of postsynaptic H(1)-receptors which potentiate and presynaptic H(2)-receptors which inhibit contractile responses in the ear artery.

Animals↗
PubMed1977

The metabolism of exogenous histamine by aortic tissues.

A thin layer chromatographic system is presented for the separation of histamine (H), 1,4-methylhistamine (M), acid metabolites comprising imidazole and methylimidazole acetic acids (A) and N-acetylhistamine (N). The system was applied to separation of the histamine metabolites formed following incubation of rabbit and guinea-pig thoracic aorta segments with labelled histamine. The effects of various agents known to affect histamine uptake, storage and metabolism in vascular tissue were studied on the disposition of histamine metabolites.

Amodiaquine↗
PubMed1977

Endogenous histamine in rabbit thoracic aorta.

A sensitive automated assay was developed for the determination of histamine. The endogenous histamine content of intact rabbit thoracic aorta, and of its separated adventitial and medial layers was determined. The histamine content of the intact aorta was found to be only partially sensitive to compound 48/80. The isolated aorta accumulated labelled histamine against a concentration gradient. The uptake was abolished by cooling to 1 degree, but was unaffected by oxygen lack. The uptake process was sensitive to a variety of agents including extraneuronal catecholamine uptake inhibitors (deoxycorticosterone acetate, normetanephrine) as well as inhibitors of catecholamine and histamine metabolism (tranylcypromine, hydrallazine). The uptake was not affected by amodiaquin, a histamine N-methyl-transferase inhibitor, by the metabolites 1,4-methylhistamine or imidazole acetic acid, by compound 48/80 or by the basic amino acid arginine.

Animals↗
PubMed1972

Dopamine -hydroxylase of bovine adrenal medullae. A rapid purification procedure.

1. A rapid purification procedure for dopamine beta-hydroxylase from bovine adrenal-medulla chromaffin granules is presented. The homogeneity of the purified enzyme was demonstrated by means of three independent criteria. The specific activity of the enzyme compares favourably with that obtained by more involved procedures. 2. The stability of the enzyme was investigated and storage in polypropylene tubes was found preferable to storage in glass. 3. The soluble and particulate forms of dopamine beta-hydroxylase appear to be identical, since membrane-bound and membrane-enclosed forms of the enzyme exhibit similar properties as regards size, charge and amino acid composition. 4. Ca(2+) was found to stimulate the release of dopamine beta-hydroxylase from bovine chromaffin granules in vitro. 5. An endogenous inhibitor of the enzyme was found in the chromaffin granules. This inhibitor was not inactivated either by heating at 100 degrees C or by pretreatment with p-chloromercuribenzoate or Cu(2+) ions.

Adrenal Medulla↗
PubMedDate not supplied

Identification of a seasonal elevation in daytime melatonin levels associated with the rut in fallow bucks (Dama dama): the effect of day length and exogenous melatonin.

The timing of the seasonal reduction in voluntary food intake and hormonal changes associated with the rut were investigated in mature fallow bucks subjected to artificial long-day exposure with and without superimposed melatonin-releasing implants. Circulating testosterone profiles and the period of inappetence, signalling the onset of the period of reproductive activity in untreated bucks under natural photoperiod, were phase-advanced in both treatment groups. In the long-day treated group, these profiles were phase-advanced by 1 week, while in the long-day + melatonin group, the phase advance was 6 weeks compared to the controls. Circulating daytime melatonin, elevated in all three groups, corresponds with seasonal changes in circulating testosterone levels associated with the rut. Prolactin profiles followed ambient photoperiod, being high during natural or artificial long days and low during natural short days. Exogenous melatonin administered during long-day exposure initiated a rapid and reversible decrease in circulating prolactin levels. The elevation in plasma melatonin could not be separated temporally from the seasonal testosterone peak by exposure to long days or to exogenous melatonin. However, this daytime melatonin profile was abolished by the ablation of circulating testosterone following immunization against luteinizing hormone releasing hormone (LHRH). The presence of this endogenous melatonin during daylight was observed only during the rut, as measured in two radioimmunoassays and confirmed by mass spectrometry. It is likely that both testosterone and melatonin influence the onset of the seasonal rut in fallow bucks.

Animals↗