Search PubMed⌕ Search

Biomedical subjects

J Schmidt

Publications and source records attributed to J Schmidt.

At least 613 records · Page 34Linked to original sources
PubMed1988

Description and error evaluation of an in vitro knee joint testing system.

An experimental system for the analysis of knee joint biomechanics is presented. The system provides for the simultaneous recording of ligament forces using buckle transducers and three-dimensional joint motion using an instrumented spatial linkage, as in vitro specimens are subjected to a variety of external loads by a pneumatic loading apparatus with associated force transducers. The system components are described, and results of an evaluation of system errors and accuracy are presented. The experimental setup has been successfully used in the analysis of normal knee ligament mechanics, as well as surgical reconstructions of the anterior cruciate ligament. The system can also be adapted to test other human or animal in vitro joints.

Biomechanical Phenomena↗
PubMed1988

Pharmacokinetics of cyproterone acetate and its main metabolite 15 beta-hydroxy-cyproterone acetate in young healthy women.

Cyproterone acetate (CPA) and 15 beta-hydroxy-cyproterone acetate (15 beta-OH-CPA) have been quantitated in human plasma by a selective, automated HPLC assay in 8 young female subjects. Subjects received a single oral dose of 100 mg CPA and four weeks later, a single intramuscular dose of 300 mg CPA. Plasma levels in seven subjects could be evaluated pharmacokinetically. After intramuscular administration maximum CPA serum levels of 191 +/- 49 ng/ml were reached between 2 and 3 days. Postmaximal levels declined with a half-life of 4.3 +/- 0.7 days. After oral administration maximal serum levels of 255 +/- 110 ng/ml were measured between 2 and 3 h. CPA levels decayed biphasically with a terminal half-life of 3.6 +/- 1.3 days. Bioavailability after oral administration was nearly complete (88 +/- 20%). Metabolite levels were below CPA levels until 4 days (i.m.) and 6 h (p.o.) and exceeded CPA levels later on. 15 beta-OH-CPA levels declined with half-lives similar to those of corresponding CPA levels, indicating that terminal half-life of the metabolite in serum reflects its rate of formation rather than its rate of elimination. Areas under the metabolite serum level curves after intramuscular and oral administration were 10 to 15% higher than the corresponding areas for unchanged CPA. Since CPA and 15 beta-OH-CPA contribute to the antiandrogenetic efficacy there is good reason to assume that the intramuscular administration of CPA might be equally effective in the therapeutical use as the oral administration.

Administration, Oral↗
PubMed1988

[Peroxidative vulnerability of synaptosomal high affinity Ca++-ATPase and pharmacologic effects].

The high affinity Ca++-ATPase participates essentially in the regulation of intrasynaptosomal calcium homeostasis. Related to posthypoxically restricted transmitter release, we examined the influence of newly-generated free radicals (ascorbic acid-ferric salt mixture) or sodium dodecyl sulfate in vitro and of a mild hypobaric hypoxia in vivo on the activity of synaptosomal high affinity Ca++-ATPase. Moreover we tested the effectiveness of piracetam, meclofenoxate hydrochloride, pyritinol and verapamil on the changed enzyme activity subsequent to a hypoxic exposure. The activity of synaptosomal high affinity Ca++-ATPase (1.04 +/- 0.03 mumol Pi/mg.h) is reduced by not more than 40% depending on the concentration of the ascorbic acid-ferric salt mixture used but is nearly totally inhibited by sodium dodecyl sulfate (0.2 mg/ml). Hypobaric hypoxia (18 h, 8.7 kPa) decreases the enzyme activity to 0.79 +/- 0.03 mumol Pi/mg.h. Piracetam, meclofenoxate hydrochloride and pyritinol are protectively effective on the decrease of enzyme activity induced by hypoxia. The results emphasize the importance of intact protein-phospholipid interactions for the enzyme activity and support relations between synaptosomal high affinity Ca++-ATPase and transmitter release.

Animals↗
PubMed1988

[Investigations on the tissue compatibility of silicon rubber materials using experimental animals].

The reaction of subcutaneous tissue in guinea-pigs at implants of six kinds of silicone rubber materials (VEB Chemiewerk Nünchritz) was investigated by semiquantitative and quantitative methods. These based on the "Programme to the Assessment of Subcutaneous Tissue Reactions at Implants" by Knöfler, Keller etc. The histocompatibility of the tested materials can be compared with that of titanium. One of the silicone rubbers differs from both the reference material and the other silicone rubber materials significantly and is assessed to be more suitable than the alloy Gisadent KCM 83 (chromium cobalt molybdenum alloy).

Animals↗
PubMed1988

[Colonization of pregnant females and their newborn infants with group B streptococci at the Gondar College of Medical Sciences].

The importance of neonatal septicemia and meningitis caused by group B streptococci (GBS) has risen worldwide in the last ten years. Between January and June 1987 200 nonselected intrapartum women at Gondar College of Medical Sciences were examined for GBS colonization. One rectal and vaginal swab was collected from each woman and cultured in 5% sheepblood agar. Cultures also from 80 newborns were obtained from throat and ear. The colonization rate of women was 9.0%. 5% of the newborns were positive for GBS. The most frequent isolated GBS-type was I b/c, this result is different from those in Europe and the USA. The authors believe, that GBS infections of newborns in development countries are also possible. These severe infections should be included in the diagnostic and therapeutic measures in future.

Ethiopia↗
PubMed1988

[Cholinergic effects of nootropics].

With respect to the enhancing effect of nootropics on learning and memory, the influence of some of these drugs on the high affinity choline uptake has been investigated. Meclofenoxate competes with choline uptake in vitro because of its similar side chain; other nootropics are without in vitro effects. A single dose of pramiracetam enhances the choline uptake in cortex and hippocampus. Application of meclofenoxate decreases the uptake of choline. Other nootropics lack acute effects. Possible increases of uptake after repeated dosage disappear within 24 h.

Animals↗
PubMed1987

15N labeling of oligodeoxynucleotides for NMR studies of DNA-ligand interactions.

The amino protons of 15N-labeled DNA were studied as a possible structural probe in NMR investigations of the interaction of DNA with various ligands. Since the imino protons are located in the center of the double helix, and variations of their chemical shift values are difficult to interpret in terms of structural changes, these probes are not very useful. Instead, amino protons are located in the major or minor groove of the DNA and are often directly involved in the binding of a ligand. For a selective probing 4-15NH2-2'-deoxycytidine and 6-15NH2-2'-deoxyadenosine were obtained by chemical synthesis. The labeled nucleosides were introduced in distinct positions of oligodeoxynucleotides by large-scale DNA synthesis. Direct 15N NMR and 1H-15N multiple quantum NMR were applied to detect the corresponding 15N labels or protons attached to the 15N labels. Chemical shift values for the cytidine and the adenosine amino nitrogen and proton resonances of a symmetric 18 base pair lac operator sequence are reported.

Adenine↗
PubMed1987

Separation strategies for o-phthalaldehyde-mercaptoethanol derivatives of amino acids for reversed-phase high-performance liquid chromatography.

Twenty-three o-phthalaldehyde-mercaptoethanol derivatives of primary amino acids in serum were separated with Waters C18 5-microns Radial-Pak Resolve columns, using aqueous phosphate-methanol mobile phase with acetate and tetrahydrofuran as modifiers. Resolution is critical in this system for glutamine/histidine, citrulline/glycine/threonine/3-methylhistidine, and tryptophan/methionine derivatives, and is affected by small changes in column properties or mobile phase. However, pre-run adjustments in gradient scheme and/or mobile phase composition can usually be used to obtain chromatograms in which all derivatives can be quantitated. For this purpose, and for general method development, we have written two very fast, interactive programs for the Zenith Z-100 Microsoft BASIC compiler: RTGRAPH, for retention, separation, and resolution plots; and LCSIM for simulations of multisegment binary gradient elution. These programs are shown here to be useful and accurate in most aspects required for developing strategies for this method.

Amino Acids↗
PubMed1987

Localization of glycoconjugates at the tegument of the tapeworms Hymenolepis nana and H. microstoma with gold labelled lectins.

Gold labelled lectins were used for electron microscopic localization of carbohydrate components of the tegument surface of two tapeworm species, Hymenolepis nana and H. microstoma. WGA, succinylated WGA, SBA, APA, PNA and, to a lesser extent, Con A were preferentially bound to the spines of the microtrichs. UEA-I and DBA were not adsorbed. The results indicate that the surface coat of both species has exposed N-acetylglucosamine, galactose and perhaps glucose and/or mannose residues. The location of lectin-binding glycoconjugates within the tegument and parenchyma was found using the light microscope on sections of material embedded in Lowikryl K4M after lectin-gold labelling and silver enhancement of the gold grains. The tegument selectively adsorbs WGA and SBA and strongly; adsorbtion of PNA and Con A is less intense. Strong adsorbtion of DBA and PNA was confined to the basal lamina. The parenchyma adsorbed Con A, PNA and DBA, but little WGA and SBA. The results indicate that many glycoconjugates are present in the tegument. They have similar terminal sugar residues to those of the surface coat. The significance of these carbohydrates for host-parasite interactions is discussed.

Animals↗