Search PubMed⌕ Search

Biomedical subjects

J Schmidt

Publications and source records attributed to J Schmidt.

At least 685 records · Page 38Linked to original sources
PubMed1985

Antigens and circulating immune complexes related to the primate retroviral glycoprotein SiSV gp70: prevalence and distribution in human sera.

We have shown previously that antigens and also circulating immune complexes related to the primate retroviral envelope glycoprotein SiSV gp70 correlate with early mortality and survival of 56 patients with acute leukemias and chronic myelogenous leukemia in blast crisis. The prevalence and general distribution of these antigens and immune complexes in human sera was therefore of obvious interest. We now report an analysis of a total of 200 sera from 166 patients. Of these 113 sera were obtained from 84 patients with acute or chronic leukemias and 87 from 82 non-leukemic subjects, including laboratory workers and patients with non-leukemic neoplasias. Antigens and immune complexes were determined by enzyme-linked immunosorbent assays (ELISA). The anti-SiSV gp70 antiserum used predominantly recognized the protein moieties of the glycoproteins. The distribution of SiSV gp70-related antigens and immune complexes was similar among leukemic and non-leukemic sera. The prevalence of SiSV gp70-related antigens was 53% and of SiSV gp70-related immune complexes 49% in all sera. SiSV gp70-related antigens were detected in a somewhat higher proportion of non-leukemic (69%) than leukemic sera (40%), whereas SiSV gp70-related immune complexes and cross-reactive antibodies were more evenly distributed in leukemic and non-leukemic sera (in 46 and 51% of leukemic and 54 and 51% of non-leukemic sera). Presence of antigens correlated with presence of SiSV gp70-related immune complexes in 71% of all sera, but in 13% of all sera antigens were detectable only by determining SiSV gp70-related immune complexes. Total circulating immune complexes did not correlate with SiSV gp70-related immune complexes. The origin and pathophysiological role of the antigens are discussed.

Acute Disease↗
PubMed1985

A large intracellular pool of inactive Na channel alpha subunits in developing rat brain.

An intracellular pool of Na channel alpha subunits has been detected in developing brain cells in vivo and in vitro by phosphorylation with cAMP-dependent protein kinase, immunoprecipitation with specific antiserum, and NaDodSO4 gel electrophoresis or by radioimmunoassay. These alpha subunits are membrane-bound, contain complex carbohydrate chains, and have an apparent molecular weight of 260,000 like mature alpha subunits. In contrast to mature alpha subunits, the intracellular subunits are not covalently attached to a beta 2 subunit, and they do not bind saxitoxin with high affinity. They comprise 67-77% of the total immunoreactive alpha subunit in developing rat brain cells but are not a prominent component in the adult brain. It is proposed that this intracellular pool of alpha subunits forms a ready reserve of preformed subunits for incorporation into the surface membrane during periods of active membrane biogenesis. The results suggest that disulfide linkage of the alpha and beta 2 subunits, insertion into the cell surface membrane, and attainment of a functional conformation are closely related late events in the biogenesis of the Na channel. These processes may regulate the number of functional Na channels in the developing brain.

Animals↗
PubMed1985

Posthypoxic transmitter release from brain slices and behavioural consequences of hypoxia in rats and mice.

Subsequent to a hypoxic exposure of adult rats and mice the stimulus induced release of dopamine from striatum slices is inhibited for several days. The posthypoxic release inhibition is not restricted to the striatal dopaminergic transmission system especially, but hypoxia causes comparable changes also in other brain regions regarding further transmitter systems. The transmitter release inhibition reflects a significant caudo-rostral gradient of increasing vulnerability of phylogenetically younger brain regions. The consequences of these biochemical changes in the brain following cessation of hypoxia are investigated with regard to behavioural manifestations. Corresponding in time with the inhibition of transmitter release and its restitution the seizure susceptibility is increased when pentetrazol is given in subconvulsive doses. On the other hand, the results of further tests (climbing behaviour, open field, rotarod test, forced-swimming test) do not point to behavioural changes induced particularly by a mild hypoxia.

Animals↗
PubMed1985

Proteolysis during in vitro-maturation of rabbit reticulocytes.

We investigated the ATP-dependent proteolysis, cytochrome oxidase and the succinate-cytochrome c-oxidoreductase in reticulocytes under different conditions of incubation in vitro at 37 degrees C. Under standard conditions the proteolysis virtually stops after 4 h. The degradation of the stroma proteins amounted to 30-65% depending on the percentage of reticulocytes. The decrease of the cytochrome oxidase amounted to 70% after 20 h of incubation. Inhibition of the cytosolic reticulocyte lipoxygenase (LOX) by the reversible inhibitor salicylhydroxamate (SHAM) leads to an inhibition of both proteolysis and cytochrome oxidase activity by about two-thirds after 20 h of incubation. In the presence of a Ca++-ionophore the rate of proteolysis was increased by 33%, while the cytochrome oxidase and succinate-cytochrome c-oxidoreductase activities both decreased more rapidly than in the control experiments.

Adenosine Triphosphate↗
PubMed1985

[In vitro malondialdehyde formation in brain structure: a method to characterize antihypoxic properties].

In vitro generated free radicals (ascorbic acid-ferric salt-mixture or hydrogen-peroxide) result in lipid peroxidation on brain cellular fractions and striatum slices an decrease of the stimulated dopamine release from rat striatum slices. Besides cysteamine, alpha-tocopherol, pyrogallol and chelating agents also tisochromide shows an antioxidative activity on lipid peroxidation induced by ascorbic acid-ferric salt-mixture. Nootropic drugs like piracetam, methylglucamine orotate, meclofenoxate hydrochloride and nicergoline are ineffective to mitochondrial malondialdehyde generation. On the other hand, piracetam exhibits a limited effect on oxidative damage of striatum slices. For that reason, the antihypoxic activity of these drugs is not accompanied by any antioxidative component and presumes a relatively high degree of tissular organization.

Animals↗
PubMed1985

[Effect of lithium, carbamazepine, ca-valproate and diazepam on changes in social isolation-induced behavior in mice].

Neurobiological changes induced by social isolation of mice are used to characterize pharmacological influences of lithium and several other drugs. Lithium is able to prevent not only early serotoninergic changes but also enhanced aggressiveness and enhanced spontaneous locomotion, seen after long term isolation. Very similar to lithium are the effects of carbamazepine, whereas Ca-valproat and diazepam prevent the early serotoninergic (stress like) changes, but not later changes in aggressivity and locomotion.

Aggression↗
PubMed1985

[Experimental studies on the problem of improving the myocardial blood circulation in an intraoperatively resuscitated heart].

A pumping system for supporting an intraoperatively failured heart is presented. This system consists of a bell-shaped receptacle for the heart and a pump with a working volume of 49 ml and a working pressure of 220 Torr. The pumping power is transmitted to the heart by means of an external pneumatic pressure line. The efficacy of the pump in the high pressure system amounted to 20-30 per cent. An effective coronary perfusion in case of a cardiac failure is guaranteed by a venous underpressure pump of this pumping system. A favourable influence was also observed in case of the low pressure system.

Animals↗
PubMed1985

[Facilitation of evoked transcallosal responses by nootropic agents].

The effect of nootropic drugs was investigated by studying their influences on transcallosal responses in rats. Piracetam, meclofenoxate, vinpocetin, pyritinol, orotic acid and dihydroergotoxine as well as its components dihydroergocornine and dihydroergocrytpine enhance in a dose dependent manner the amplitudes of transcallosal responses. The evoked potentials remain unchanged after dihydroergocristine and nicergoline by the dosage used.

Animals↗
PubMed1985

[The dynamics of behavioral changes in mice induced by social isolation].

Various behavioural patterns such as spontaneous locomotion, open-field behaviour and aggressivity undergo typical changes in socially isolated mice. Each of them shows a specific course depending on the duration of isolation. Differences in time courses and quantitative changes demonstrate that not only a general mechanism such as decreased arousal threshold is responsible for the complex alterations. It seems that many different mechanisms in the CNS underly the isolation syndrome, but the functional connections between the different alterations are unknown.

Aggression↗
PubMed1985

[Expectorants].

Explore the source record for details and available documents.

Expectorants↗
PubMed1985

The functional importance of cerebral noradrenergic processes for the activating action of nootropic drugs in the behavioural despair test in mice.

The influence of substances with a known modifying effect on cerebral noradrenergic transmission processes on the activating effect of the nootropics piracetam, pyritinol, meclofenoxat, methylglucamine orotate and dihydroergotoxine in comparison to desipramine and d-amphetamine in the behavioural despair test was investigated in mice. Clonidine, an agonist of presynaptic alpha-adrenoceptor, and prazosin, a postsynaptic alpha-adrenoceptor blocker, in doses without own effect on the swimming behaviour counteracted the activating effect of nootropics in the behaviour despair test. On the other hand, yohimbine, a presynaptic alpha-adrenoceptor blocker, resulting itself in activation, did not change the effect of piracetam additionally. The results confirm the functional importance of noradrenergic processes for the state of immobility and support the possible participation of an influence on the cerebral noradrenergic system in the mechanisms of action of nootropic drugs.

Animals↗
PubMed1985

Characterization of the antihypoxic activity of tisochromid.

The antihypoxic activity of tisochromid is compared with the well-known restituting effect of piracetam on posthypoxic dopamine release inhibition. In addition to a distinct restituting effect which accelerates the normalization of dopamine release highly, tisochromid exhibits obviously an antioxidative potency which is responsible for a greater effectiveness of the drug when given prehypoxically. Therefore, tisochromid acts simultaneously as a protective and a restituting drug.

Animals↗
PubMed1985

Influence of nootropic drugs on drinking behaviour in ethanol-preferring mice and ethanol-induced increase of seizure susceptibility.

The influence of several nootropic drugs (piracetam, pyritinol, meclofenoxat, methylglucamine orotate (MGO) and dihydroergotoxine (DHET) on both the ethanol preference and the enhanced seizure susceptibility after a single dose of ethanol was studied. Piracetam, MGO and DHET reduce the ethanol drinking in ethanol-preferring mice. The enhanced seizure susceptibility after a single dose of ethanol was abolished by piracetam and MGO.

Alcohol Drinking↗
PubMed1985

[Effect of hypobaric hypoxia on motor behavior in rats].

Hypobaric hypoxic exposure for 18 h (pO2 8.7 kPa) effects characteristic changes of motoric behaviour in adult rats. We observed a posthypoxic increase of spontaneous locomotion and of open-field activity. 24 h after hypoxic exposure the locomotion stimulated by dopaminergic agonists apomorphine or amphetamine was strengthened. Dopaminergic nuclei showed a different sensitivity to unilaterally applied dopamine after hypoxic exposure. Rotational behaviour was facilitated in the nucleus accumbens but significantly decreased in the substantia nigra. In the nucleus caudatoputamen we could not prove changes in comparison to controls. These results indicate that central dopaminergic processes are influenced by hypobaric hypoxic exposure. Besides the sensitization of dopaminergic receptor populations these changes of motoric behaviour may be connected with interactions between different transmitter systems or displacement of central regulation systems.

Amphetamine↗
PubMed1984

Destruction of acetylcholine receptor by decaying 125I-alpha-bungarotoxin.

Decay of 125I in 125I-alpha-bungarotoxin bound to detergent-solubilized acetylcholine receptor from Torpedo californica electric tissue results in the inactivation of virtually all of the directly occupied and of the second toxin-binding sites. This finding establishes the usefulness of 125I-labeled ligands for binding-site multiplicity analysis of proteins.

Animals↗