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Biomedical subjects

M Schmidt

Publications and source records attributed to M Schmidt.

At least 739 records · Page 41Linked to original sources
PubMed1988

Macro-prostatic acid phosphatase in a patient's serum.

A patient without prostatic carcinoma had a high concentration of prostatic acid phosphatase (PAP; EC 3.1.3.2) in his serum. This PAP was bound to IgG ("macro-PAP"), and IgG autoantibodies against PAP were demonstrated in serum. The patient's IgG prolonged the biological half-life of radiolabeled PAP in rats, suggesting that the formation of IgG-PAP complexes was responsible for decreased PAP catabolism. Furthermore, macro-PAP was inactivated in serum more slowly than PAP. These factors accounted for the increases in the enzymatic activity and antigenic concentration of PAP measured in the patient's serum. Inappropriate therapy was prescribed on the basis of this laboratory result. The diagnosis of prostatic carcinoma requires clinical or histological evidence of malignant disease, and should not rely solely on PAP measurements.

Acid Phosphatase↗
PubMed1988

Renal function in patients with obstructive sleep apnea. Effects of nasal continuous positive airway pressure.

Patients with obstructive sleep apnea (OSA) often exhibit nocturnal polyuria, which disappears with nasal continuous positive airway pressure (CPAP) treatment. We measured water and electrolyte urinary excretion, creatinine and osmolal clearances, and water transport during sleep in 13 polygraphically monitored patients with OSA during two consecutive nights, either untreated or treated with nasal CPAP, and in eight normal subjects. Untreated patients with OSA had greater urinary flows and greater urinary sodium, chloride, and potassium excretions than did controls. Nasal CPAP treatment in patients with OSA resulted in a reduction in urinary flow and in sodium and chloride excretion, with a concomitant increase in sodium resorption. None of these effects was observed in CPAP-treated normal subjects. The only effect of nasal CPAP common to normal subjects and patients was a trend toward decreased glomerular filtration rate.

Adult↗
PubMed1987

A monoclonal antibody directed against the head region of vimentin.

The production and identification of a monoclonal antibody directed against an epitope in the aminoterminal head region of vimentin is described. Enzyme-linked immunosorbent assay, protein blotting and indirect immunofluorescence were used. The wide range of cross-reactivity within cytoskeletal proteins observed for this antibody gives evidence for a determinant in an evolutionarily conserved region. Computer comparison of aminoacid sequences of the immunoreactive proteins and biochemical cleavage of vimentin provide possible clues to some antigenic determinants.

Animals↗
PubMed1987

Renal and iliac vascular effects of dopamine in the anaesthetized rat.

The renal and iliac vascular effects of dopamine were compared in pentobarbital anaesthetized rats. Local vascular resistances were calculated from simultaneous measurement of blood pressure, renal and iliac blood flow. Without pretreatment, dopamine increased renal and iliac vascular resistance. After pretreatment with prazosin, dopamine decreased the renal vascular resistance while the iliac vascular resistance was still increased. After a combination of yohimbine and prazosin pretreatment, dopamine lowered both the renal and iliac vascular resistance by 30%. These responses were not modified by the beta-adrenoceptor antagonist, sotalol, or by pretreating the rats with reserpine. The renal but not the iliac vascular response to dopamine was abolished by (+)-butaclamol, a stereoselective dopamine receptor antagonist, and by SCH 23390, the DA1-selective dopamine receptor antagonist. The decrease in iliac vascular resistance was not modified by indomethacin or the non-selective 5-HT receptor antagonist, metitepin. These results show that after blockade of alpha 1 and alpha 2-adrenoceptors, dopamine induces iliac vasodilation by a postsynaptic mechanism independent of an interaction with beta-adrenoceptors, dopamine or serotonin receptors. They also confirm in the rat in vivo the existence of renal vasodilation mediated by DA1 dopamine receptors.

Adrenergic alpha-Antagonists↗
PubMed1987

Disintegration of isolated cells.

A simple device has been developed for the disintegration of isolated cells in isotonic or hypertonic media. It is based on the extrusion of a cell suspension through a small orifice under controlled pressure. The diameter of this interchangeable orifice has to be adapted to the cell type to be disrupted. The conditions fulfill the requirements for an efficient disruption of the plasma membranes and for good preservation of the particularly fragile subcellular components, lysosomes and peroxisomes, of rat hepatocytes and rat Leydig cells.

Animals↗
PubMed1987

Production and characterization of monoclonal antibodies specific for pathogenic serogroups O:3, O:8, and O:9 of Yersinia enterocolitica.

A panel of 7 murine hybridoma derived monoclonal antibodies (MAbs) to Yersinia enterocolitica were produced and characterized by indirect fluorescence assay (IFA) and agglutination reactions. One MAb designated 2D8 (IgG 3) showed specific reactivity both in the IFA and agglutination assays with 70 of the 70 strains belonging to serogroup O:3 of Y. enterocolitica. Three MAbs, 8E9 (IgG 3b), 10G11 (IgG3) and 11G2 (IgG 3), gave unequivocal positive reactions in the IFA and agglutination tests with all the strains representing serogroup O:9 (56/56), but not with serogroup O:3 or O:8 strains. Another MAb coded 1G2 (IgG 1) reacted specially in the IFA test (but not in the agglutination test) with all the strains representing serogroup O:3 (70/70) and O:9 (56/56) indicating that this antibody recognizes an immunodeterminant shared by serogroups O:3 and O:9. Finally, 2 MAbs 4C2 (IgM) and 6G5 (IgM), showed reactivity both in IFA and agglutination assays with "esculin negative" biogroups 1 (pathogenic American strains) strains of serogroup O:8 (12/12), whereas the strains assigned to "esculin positive" biogroup 1 (nonpathogenic) failed to react (6/6). However, 4C2 and 6G5 exhibited narrow cross reactivity with type strains assigned to serogroups O:18, O:20, and O:22. The results of absorption tests and the clear out cell wall immunofluorescence imply that the antigenic molecule(s) recognized by these MAbs are exposed on the bacterial cell surfaces. Some of the MAbs described in this report are useful reagents for precise serotyping of clinical isolates of Y. enterocolitica by simple and rapid slide agglutination assay. They may also allow the development of specific and sensitive tests for probing the presence of pathogenic Y. enterocolitica organism in clinical and food materials.

Agglutination Tests↗
PubMed1987

Tissue converting enzyme activity is low in the kidney of spontaneously hypertensive rats.

Angiotensin-converting enzyme (ACE) activity was measured in the plasma, the kidney, and other organs of 5-, 8-, and 11-week-old spontaneously hypertensive male rats (SHR) of the Okamoto-Aoki strain and compared with that of age-matched Wistar-Kyoto (WKY, bred by Iffa-Credo) or normotensive Wistar rats. ACE activity was measured spectrofluorometrically, using the artificial substrate N-CBZ-L-phe-L-his-L-leu. ACE activity was constantly lower in the plasma and renal cortex of SHR from 5 weeks on than in WKY rats. This difference in the renal cortex ACE activity persisted after 1 h of open circuit perfusion of the isolated kidney with Krebs-Henseleit medium. On the other hand, there lung, the brain occipital cortex, or the abdominal aorta of hypertensive or normotensive rats. The percentage inhibition of ACE activity provoked by 7 days of oral administration of ramipril (Hoe 498, 1 mg/kg/day) was analogous in the kidneys and lungs of WKY rats and SHR. Enalapril (MK 421, 30 mg/kg/day) was equipotent to ramipril in the kidney but had lower inhibitory effects on the pulmonary ACE activities of WKY rats and SHR.

Aging↗
PubMed1987

Characterisation of the alpha-adrenoceptors of the rat renal vascular bed.

Postjunctional renal alpha-adrenoceptors were studied (1) in vivo, on the renal vasculature of the anaesthesized rat and compared with those in the femoral vasculature, and (2) in vitro, on the renal vascular bed of isolated perfused rat kidney. In vivo, renal and iliac blood flows were measured with an electromagnetic flow meter. The i.v. injection of (-)-phenylephrine (1-16 micrograms/kg) and B-HT 920 (0.6-600 micrograms/kg) induced an increase in both renal and iliac vascular resistance, inhibited respectively with prazosin (300 micrograms/kg) or yohimbine (300 micrograms/kg). In the kidney, maximum response to B-HT 920 was equivalent to 64% of that to (-)-phenylephrine; on the iliac vasculature, vasoconstrictor responses to both drugs were identical, but only corresponded to 50% of the maximum renal response to (-)-phenylephrine. This indicates the predominance of alpha 1- over alpha 2-adrenoceptors in the renal vascular bed. In vitro, on the isolated perfused rat kidney, vasoconstriction was induced by the preferential alpha 1-adrenoceptor agonists [(-)-phenylephrine, cirazoline and methoxamine] and the preferential alpha 2-adrenoceptor agonists (alpha-methylnoradrenaline, dopamine and clonidine) at concentrations at which they lose their selectivity for the alpha 2-adrenoceptors; all responses were antagonised by prazosin but not by yohimbine. B-HT 920, the selective alpha 2-adrenoceptor agonist, only induced renal vasoconstriction in vitro under concomitant infusion of rabbit plasma.

Animals↗
PubMed1987

Action and localization of acetylcholine in the cat retina.

1. Retinal ganglion cells were recorded extracellularly in the intact eye of anesthetized adult cats. The effects of acetylcholine (ACh), the muscarinic antagonist scopolamine (Sco), the nicotinic antagonist dihydro-beta-erythroidine (DBE), and the acetylcholinesterase inhibitor physostigmine (Phy) on maintained and light-evoked ganglion cell discharge was examined using iontophoresis techniques. 2. A monoclonal antibody directed against the ACh synthesizing enzyme choline acetyltransferase (ChAT) was used to label cholinergic cells in retinal wholemounts. The topographical distribution of these cells was studied. 3. Intracellular filling with the fluorescent dye lucifer yellow (LY) was performed to identify the dendritic morphology of putative cholinergic neurons. 4. ACh increased and Sco decreased neuronal activity of all brisk ganglion cell types under all stimulus conditions tested in this study. The action of ACh was abolished during simultaneous application of Sco. 5. DBE raised the firing rate of ON-center brisk cells and decreased activity of OFF-center brisk cells. Again there was no difference under different stimulus conditions. During DBE application the ACh action on OFF-center cells was completely blocked. The ACh action on ON-center cells was diminished. 6. Phy prolonged and enhanced ACh action on all ganglion cell types. During simultaneous stimulation of the receptive-field center and the surround, Phy caused an activity shift in favor of the center response. 7. Immunocytochemical staining revealed two populations of amacrine cells, one in the inner nuclear layer, and the other in the ganglion cell layer. Their total density increased from 250 cells/mm2 in the periphery to 2,700 cells/mm2 in the central area. Analysis of the distribution pattern indicated a functional independence of the two subpopulations. 8. The dendritic morphology of putative cholinergic amacrine cells in the cat retina resembled that of rabbit and rat "starburst" amacrines, which are known to be cholinergic. 9. The possible function of cholinergic amacrine cells in the cat retina is discussed in view of the present findings and compared with results from other mammalian species.

Acetylcholine↗