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Biomedical subjects

J Schmidt

Publications and source records attributed to J Schmidt.

At least 865 records · Page 48Linked to original sources
PubMed1976

[Relationship between the changes of spontaneous activity and responses of cortical neurons under microiontophoretic administration of glutamic acid].

In neurons of the gyrus sigmoideus posterior of cats, the influence of microiontophoretic application of varying doses of glutamic acid upon the reaction of those neurons to stimulations of the ischiadic nerve and clicks, and the changes of spontaneous activity were studied. The application of glutamic acid led, in 97% of the 90 neurons studied, to a dose-dependent increase in the mean firing rate; in 34% of neurons, to effectuation of click responses, and affected the reaction to stimulation of the ischiadic nerve to a varying extent. With increasing doses of glutamic acid, there was a linear correlation between the logarithm of spontaneous activity and the activity of excitatory responses with considerable differences in the steepness of the resulting straight lines for the individual neurons.

Action Potentials↗
PubMed1976

[Effect of psychopharmaceutic agents on cortical potentials and long-lasting post-tetanic changes in excitability released through stimulation of the dental pulp].

Short-time tetanic stimulation of the tooth pulp with square pulses affords, depending on the stimulation parameters selected, a long-lasting facilitation in the response of subsequently applied test stimuli in the sensomotor cortex of rabbits. The benzodiazepin derivatives, chlorodiazepoxide, nitrazepam (10 mg/kg i.p.) and clonazepam (1 mg/kg i.p.) caused suppression of posttetanic facilitation with partly different influences on cortical potentials following individual stimulation. Meprobamate (200 mg/kg i.p.) had no effect on the processes of posttetanic facilitation, while the amplitudes of sensomotor potentials showed a long-lasting reduction on single stimulation. Chloropromazine (2 mg/kg i.p.) showed a rapid and transient inhibition of posttetanic facilitation and reduced the amplitudes of evoked potentials following single stimulation.

Animals↗
PubMed1976

[Lyophilized vein as an arterial substitution].

The use of homologous preserved veins for replacing seems to have special importance in the surgery on peripheric and coronary arteries. Preliminary results from animal experiments are discussed in which lyophilized veins replaced arteries. Within 8 weeks after implantation into dog aorta develops a functionally satisfactory substitute. No immune reactions can be found histologically. The destruction of the graft and its replacement by host's tissue are temporally balanced. The experiments are to be continued.

Angiography↗
PubMed1975

RNA-dependent DNA polymerase from a cell line derived from the bone marrow of a patient with polycythemia vera.

A RNA-dependent DNA polymerase was isolated from a human cell line derived from the bone marrow of a patient with polycythemia vera. The purification procedure included chromatography on phosphocellulose and oligo(dT)-cellulose, and glycerol gradient centrifugation. The enzyme could be distinguished from polymerase A by salt elution from phosphocellulose, utilization of poly(rC) - oligo(dG) and its molecular size of about 70000, as determined by centrifugation. Throughout the purification procedure ribonuclease H activity was co-purified. Upon dodecylsulfate-polyacrylamide electrophoresis on microgradient gels two main bands with molecular weights of 68000 and 66000 and three minor bands were detected. The enzyme preferentially used poly(rA) - oligo(dT) as template-primer compared with poly(dA) - oligo(dT). It incorporated dGMP into polymer on poly(rC) - oligo(dG).

Bone Marrow↗
PubMed1975

Recurrent inhibition of individual Ia inhibitory interneurones and disinhibition of their target alpha-motoneurones during muscle stretches.

The effects of ramp stretches applied to triceps surae muscle on the discharge patterns of single Ia inhibitory interneurones, monosynaptically invaded from various nerves, were studied in either decerebrate or anesthetized cats. Interneurones which received direct excitatory Ia input from the stretched muscle exhibited augmented activity both during the dynamic and static phase of stretch, which was, however, interrupted by a transient inhibitory influence during the dynamic phase of stretch. The influences on Ia inhibitory interneurones, monosynaptically invaded from hamstring or tibial nerve, were exclusively inhibitory. These stretch-induced inhibitions were better demonstrable in decerebrate than in anesthetized preparations. The timing of the discharge patterns of additionally recorded Renshaw cells during stretch, and the disappearance or reduction of the above described inhibitory effects after administration of DHE, strongly support the idea that these inhibitory actions are caused by Renshaw inhibition. In Ia inhibitory interneurones, monosynaptically activated from the antagonistic peroneal nerve, stretch induced also pronounced inhibitory effects, which were most probably caused by mutual inhibition between Ia inhibitory interneurones. The suppression of agonistic Ia inhibitory interneurone activity below the tonic resting activity corresponded to an enhancement of the monosynaptic reflex amplitude of the antagonistic motoneurone pool. The findings suggest that normal orthodromic activation of Renshaw cells, and consequently the recurrent inhibition of the Ia inhibitory interneurones, is predominantly linked with rapid phasic, rather than slow tonic, motoneuronal firing. The functional role of this mechanism for the performance of rapidly alternating movements and the damping of ballistic agonist contractions is discussed.

Animals↗
PubMed1975

[Activation of the fibrinolytic system by furosemide (author's transl)].

Intravenously administered furosemide induces besides its well known diuretic effect a significant activation of the fibrinolytic system. This fibrinolytic effect, however, is only seen in persons with an intact renal system, not in nephrectomized patients and not in patients with chronic renal insufficiency. From this finding the conclusion is drawn that furosemide needs for its fibrinolytic effect the intact renal tissue. It is discussed that the beneficial therapeutic value of high-dose furosemide in acute renal insufficiency following shock or septic abortion might at least partially be due to furosemide-induced fibrinolysis of the microthrombi of the glomerula.

Abortion, Septic↗
PubMed1975

Correlation of the dynamic behaviour of deefferented primary muscle spindle endings with their static behaviour.

20 deefferented primary muscle spindle endings, 8 afferents from the extensor digitorum longus muscle (EDL) and 12 from the tibialis anterior muscle (TA), were investigated in 12 anesthetized cats. Dynamic responses of muscle spindles to ramp stretches were correlated with their static responses. The variation in the state and dynamic behaviour was found to be interdependent. The correlation coefficients were higher for EDL spindles than for TA spindles. The correlation coefficients depended upon the definition of the dynamic responses.

Animals↗
PubMed1975

Diamine oxydase in rabbit small intestine: separations from a soluble monoamine oxidase, properties and pathophysiological significance in intestinal ischemia.

From all mammals investigated so far only in rabbits diamine oxidase could not be detected in any tissue except the gut. Thus this species was chosen for studying the physiological and pathophysiological function of this enzyme in the gastrointestinal tract. By gel filtration on Sephadex G 50 and G 200 the enzyme was purified 100-fold, separated from a soluble monoamine oxidase, and the properties of the two enzymes were determined. Diamine oxidase from rabbit small intestine deaminated putrecine (Km = 1.3 times 10(-4) M, pH-optimum 6.4-6.9) and histamine (Km = 8 times 10(-5) M, pH-optimum 7.5), but not serotonin, and was inhibited by aminoguanidine, but not by pargyline. Soluble monoamine oxidase from rabbit small intestine catabolized serotonin (Km = 1.8 times 10(-4) M, pH-optimum 8.8) but not putrescine and histamine, and was inhibited by pargyline, but not by aminoguanidine. Based on its properties in vitro intestinal diamine oxidase could inactivate the vasoactive biogenic amine histamine in vivo. To confirm this hypothesis, in rabbits the small intestine was damaged severely by inducing total intestinal ischemia, which occurs as mesenteric infarction also in human subjects and is accompanied by histamine release. Treatment with aminoguanidine and ischemia killed the animals 3-times faster than ischemia alone, which supported our hypothesis on a protective role of intestinal diamine oxidase against histamine.

Animals↗
PubMed1975

Oxidative deamination of biogenic amines by intestinal amine oxidases: histamine is specifically inactivated by diamine oxidase.

The ability of the gut to inactivate various amines by oxidative deamination was tested with a 130-fold purified amine oxidase preparation from dog small intestine. Of 34 amines tested, putrescine, benzylamine, cadaverine, and serotonin were the most favourable substrates. Histamine was inactivated rapidly by this enzyme preparation, too. Histamine derivatives methylated at the imidazole nucleus were also deaminated, whereas Nalpha-methylhistamine was only a poor substrate and Nalpha, Nalpha-dimethylhistamine was not a substrate at all. Using a second procedure for the purification of amine oxidases from gut, the separation of a soluble monoamine oxidase from diamine oxidase was achieved by gel filtration on Sephadex G-200. The diamine oxidase deaminated putrescine (Km = 1.3 x 10(-4)M) and histamine (Km = 6.6 x 10(-5)M), but not serotonin, and was inhibited by aminoguanidine, but not by pargyline. The soluble monoamine oxidase inactivated serotonin (Km = 4.5 x 10(-4)M), but not histamine and putrescine and was inhibited by pargyline, but not by aminoguanidine. It was concluded that in dog small intestine (as well as in rabbit small intestine) only diamine oxidase was capable of inactivating histamine by oxidative deamination.

Amine Oxidase (Copper-Containing)↗
PubMed1975

[Facial manifestations of suppurative trichophytosis].

Several cases of facial suppurative Trichophytia described by the authors lead to a review of the clinical, mycological and pathological features of this disorder which is on the increase in the region of Nantes.

Animals↗