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Biomedical subjects

R Schmidt

Publications and source records attributed to R Schmidt.

At least 649 records · Page 36Linked to original sources
PubMed1984

Identification of a 140-kDa activation antigen as a target structure for a series of human cloned natural killer cell lines.

In the present study, we have developed a monoclonal antibody termed anti-TNKTAR, able to block cytotoxicity mediated by a human natural killer (NK) clone termed JT9. Analysis of the functional effects of anti-TNKTAR indicated that alteration of the cytotoxic reactions resulted from the binding of the antibody to the membrane of target cells. In addition, it was shown that inhibition of cytotoxicity induced by anti-TNKTAR could be abolished by lectin approximation. Immunoprecipitation experiments indicated that TNKTAR antigen is a heterodimeric structure which resolves as a single band at 140 kDa under nonreducing conditions and as two bands at approximately 97 kDa and 40 kDa under reducing conditions in sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis. This heterodimer is present on lymphocytes and monocytes in human peripheral blood and perhaps more importantly, the membrane density of TNKTAR antigen increases very early and strongly following lymphocyte activation. In addition, it was shown that TNKTAR is expressed on each single cultured cell line which has been tested, although the density of the antigen varies strongly from one cell line to another. Even though the 140-kDa molecule was found to be widely distributed on activated cells, anti-TNKTAR had no blocking effects on cytotoxic reactions mediated by a series of either NK or cytotoxic T lymphocyte clones unrelated to JT9. In contrast, anti-TNKTAR blocked, in an identical fashion, cytotoxicity of JT9 and two additional clones, JT10 and JT11, against a series of 8 sensitive targets. JT9, JT10 and JT11 human cloned NK cell lines have been derived from peripheral blood of one individual donor drawn on month 0 (JT9), 12 (JT10) and 18 (JT11). Most importantly, these three clones initially selected for their capacity to kill K562 cells have been found to express the same 90-kDa clonotypic antigen receptor structure (termed NKTa) and display identical specificity when tested against a panel of randomly selected target cell lines. We have previously demonstrated that a unique subset of NK active mature T lymphocytes interact with target cells via 90-kDa clonotypic determinants in a major histocompatibility complex-independent fashion. Taken together, the present data strongly supports the view that a surface antigen of 140 kDa, linked to cell activation, serves as a specific recognition structure at the target cell level for these NK-active T lymphocytes.

Antibodies↗
PubMed1984

Antigenic cross-reactions between Mycoplasma arthritidis and rat tissues.

An antigenic relationship between Mycoplasma arthritidis and rat tissues could be demonstrated using the enzyme-immune assay and the agar gel double diffusion test. Cross-reactions were observed with joint homogenates as well as with muscle, lung, liver, kidney, spleen and brain tissue from rats. In addition, antibodies against joint homogenate were found in the sera of rats infected with M. arthritidis ISR 1 using the indirect hemagglutination test. The significance of common antigens between M. arthritidis and rat tissues for the pathogenesis of the M. arthritidis polyarthritis in rats is discussed.

Animals↗
PubMed1984

Photoaffinity labeling and characterization of the cloned purine-cytosine transport system in Saccharomyces cerevisiae.

8-Azido[2-3H]adenine was used as a photoaffinity label for the purine-cytosine transport system. After irradiation in the presence of the photoaffinity label, the cells were converted into protoplasts, their plasma membranes were purified, and the membrane proteins were extracted and separated by NaDodSO4/PAGE. The radioactivity was specifically incorporated into a protein with a molecular weight of 120,000. Photoaffinity labeling of this protein could be blocked by irradiation in the presence of natural substrates for the transport system. The molecular weight as determined by NaDod-SO4/PAGE was found to be twice the value calculated from mRNA analysis of the cloned gene. Incubation of exponentially growing cells with tunicamycin, an antibiotic that inhibits glycosylation of proteins, resulted in a 40% decrease in the overall initial uptake rate, which correlates with the reduction of the labeled Mr 120,000 protein. Treatment of the extracted labeled plasma membrane proteins with glycosidic enzymes resulted in disappearance of the Mr 120,000 peak and the appearance of new peaks at Mr 60,000 and Mr 73,000. These findings indicate that the purine-cytosine transport protein is a glycoprotein.

Adenine↗
PubMed1984

A comparative study of guanine N7-alkylation in mice in vivo by the organophosphorus insecticides trichlorphon, dimethoate, phosmet and bromophos.

Following intraperitoneal administration to male mice (strain AB Jena/Halle) of 14C-methyl-labelled trichlorphon, dimethoate, phosmet and bromophos, 10-20 Ci/mol, in dosages of 0.06-0.55 mmol/kg, DNA from liver and kidneys was analyzed for 14C in N-7 methylguanine (7-MeG). The extents of methylation were in the range of 5-10 mumol 7-MeG/mol guanine for trichlorphon and dimethoate and of 0.2-0.4 for phosmet and bromophos, for high doses, respectively Excretion half-lives of 7-MeG were differing between trichlorphon (5 hrs, high dose, and 15-17 hrs, low dose) and dimethoate (23-160 hrs, high dose). The extents of methylation at 0-6 of guanine were estimated to be around 0.01 mumol 0-6 MeG/mol guanine for high doses of organophosphates of sufficient water solubility. Factors associated with the partition of organophosphates in mammalian systems are useful for estimating DNA attack by organophosphates in mammals in vivo.

Alkylation↗
PubMed1984

Pulmonary fat embolism after intralipid therapy--a post-mortem artefact? Light and electron microscopic investigations in low-birth-weight infants.

The lungs of 22 low-birth-weight infants were investigated, mean gestational age 29 weeks (range 25 to 35). Thirteen of the 22 newborns had been treated with Intralipid--10% for an average of 20 days (range 3 hours to 75 days). The mean maximum rate of fat infusion was 2.0 g/kg/day (range 0.5 to 3.6). Nine of the 22 newborns had been fed formula and given supplemental amounts of amino acids and glucose intravenously, but no Intralipid. The lungs were fixated in situ immediately after death with glutaraldehyde. Neither in the Intralipid group nor in the non-Intralipid controls was intravascular fat accumulation identified, either by light microscopy or by electron microscopy. It is speculated that an agglomeration of lipoprotein globules to larger stainable lipid droplets cannot take place in the short interval between the actual time of death and the time of fixation of the lung tissue. Thus, fat globules found in lungs of premature infants and described as fat embolism might have been post mortem artefacts.

Autopsy↗
PubMed1984

Ultrastructural alteration of intrapulmonary nerves after exposure to organic solvents. A contribution to 'sniffers disease'.

The effects of the solvents n-hexane, butanone (methyl-ethyl-ketone, MEK) and a mixture of both in the intrapulmonary nerve system of rats were studied by light and electron microscopy. The alteration in the fine structures of the tissue consisted in a disseminated swelling of axons due to a striking multiplication of neurofilaments. Nonspecific axonal alterations could be demonstrated as well. The latter consisted in clusters of phospholipid material within the axoplasm of nerve fibers and the cytoplasm of Schwann cells plus an accumulation of glycogen granules in the axoplasm. Additionally, single degenerative changes of Schwann cells were observed. An enzyme-associated metabolic damage with a concomitant impairment of axonal flow is discussed as a possible underlying pathomechanism.

Animals↗
PubMed1984

[Light and electron microscopic studies of the brain, heart and pancreas in mice infected with MengoM virus].

Infection of ABAF hybride mice with MengoM viruses prepared as a suspension of mouse brain tissue (0.1 ml 10 LD50) after a series of more than 90 animal passages produced a severe panencephalitis and pancreatitis 60 h after inoculation. Histological examinations of the brain, pancreas, and heart revealed damage to the central nervous system and the acinar cells of the pancreas, consisting of a degeneration of the specific cells and their organelles, with little involvement of the heart muscle cells detectable with the electron microscope. This was consistent with high virus titers in the tissues in the period immediately following infection. The acute damage of exocrine tissues was without evidence of diabetes-like changes in the islets of Langerhans.

Animals↗
PubMed1984

[Stress reduction by i.m. premedication with 6 different single substances].

In three prospective randomized studies six substances for intramuscular premedication were investigated and compared to placebo (NaCl 0.9%): diazepam (10-20 mg), flunitrazepam (1-2 mg), droperidol (2.5-5 mg), triflupromazin (10-20 mg), pethidin (50-100 mg) and buprenorphin (0.15-0.3 mg). The effects on preoperative stress were evaluated with psychometrical methods (ESB), heart rate, blood pressure and plasma-cortisol levels. Degree of sedation and side effects were recorded. Good effects on anxiety were found after flunitrazepam, diazepam and triflupromazin. The worst effects were found after droperidol and pethidin. Good effects on depression were found after pethidin, buprenorphin, diazepam and triflupromazin. The worst effects were found after droperidol. Asthenic patients were improved with diazepam and flunitrazepam, but deteriorated after placebo, pethidin, triflupromazin and droperidol. The physiological stress parameters were positively influenced by diazepam and flunitrazepam, but not after placebo and droperidol. Nausea and vomitus were found after buprenorphin, pethidin and droperidol; psychological and neurological problems occurred after droperidol. The highest degree of sedation was found after flunitrazepam, diazepam and droperidol. The day after surgery the patients found placebo, flunitrazepam, diazepam and triflupromazin to be the best premedications, pethidin and buprenorphin were inferior and droperidol was the poorest premedication.

Adolescent↗
PubMed1984

[High-dose thalamonal-rohypnol for premedication. A randomized double-blind study].

The combination of fentanyl and droperidol, Innovar, was compared to flunitrazepam (1-2 mg) in a higher dosage (2.5-5 ml) for i.m. premedication. We measured psychological (ESB) and physiological (blood pressure, heart rate, p.cortisol) stress parameters before and after premedication. Side effects were registered. The day after surgery the patients were asked about the quality of premedication. Flunitrazepam reduced anxiety; Innovar did not. After Innovar the feeling of weakness increased significantly compared to flunitrazepam. Two patients panicked and refused operation. Other severe side effects were not observed. There were slight advantages for flunitrazepam on physiological stress. Patients were more satisfied with flunitrazepam than with Innovar premedication. The results show that Innovar also in a higher dosage cannot be recommended for premedication.

Adolescent↗
PubMed1984

[Biochemical and morphologic studies on the effect of bile acids on the epithelium of the rat jejunum].

The influence of bile salts on the mucosal surface of rat jejunum was tested with an in vivo technique of segmental perfusion. Sodium taurocholate and chenodesoxycholate were applied in a concentration of 3 mmol/l. The release of 5 brush border membrane enzymes, 5 cytosolic, 1 mitochondrial, and 2 lysosomal enzymes during a perfusion time of 150 min as well as morphological alterations after bile salt treatment were investigated. Among the membrane enzymes, due to their superficial localization, the solubilization of enteropeptidase and alpha-1,4-glucosidase was highest both in the control perfusion and in the presence of bile salts. At the same time, cytoplasmic enzyme activities were liberated extensively whereas lysosomal and mitochondrial enzymes were scarcely detectable. This disproves any serious injury of the enterocytes. Electronmicroscopic results supported this suggestion. After administration of taurocholate (in physiological concentration), only an occasional diminution of the glycocalyx was observed and even chenodeoxycholate (in an unphysiological concentration) caused only negligible destructions of intestinal brush borders. Investigations with ruthenium red to contrast the glycocalyx showed a partially unchanged structure. Microvesiculation from the microvilli was observed in many electron microscopic photographs. That is a possibility for the release of membrane-bound and cytosolic enzymes without destruction of enterocytes.

Animals↗
PubMed1984

[Preoperative stress. Study of the mental behavior and parameters of physiological stress in non-premedicated patients during the preoperative period].

In 29 male patients undergoing arterial bypass operations of the lower limb, psychological and physiological stress parameters were investigated. They received no premedication. We found an increase of heart rate (HR), arterial blood pressure (BP), plasma cortisol (Cort), free fatty acids (FFA), ventricular ectopic beats (VEB) and supra-ventricular ectopic beats (SVEB) (registered with a 24 hour ECG). The physiological dynamics were different, depending on the results of the psychological tests (MMQ and ESB): Repressor had higher HR and increased significantly more than sensitizer. Depressive patients had higher Cort levels the day before surgery compared to hopeful ones, but remained at these levels, whereas hopeful patients had a significant increase of Cort immediately before operation. They had also higher BP's and HR's. Patients with sthenic affections increased significantly more with FFA levels than asthenic ones. Anxious and asthenic patients had significantly more VEB than non anxious and sthenic ones. These results can well be interpreted in terms of dynamic psychophysiological stress reactions. We propose the use of psychological and physiological stress parameters for investigations of methods for the reduction of preoperative stress.

Blood Pressure↗
PubMed1984

[Profundaplasty in older persons].

The profunda femoris artery has become the most important collateral vessel for compensating femoro-popliteal arterial occlusion. The circulation of the ischaemic limb can be obtained by profundaplasty. From 1972 to 1982, 70 patients with a mean age of 75,7 years underwent surgery. Good results were obtained in 75,9%.

Aged↗
PubMed1983

Fast and efficient purification of yeast plasma membranes using cationic silica microbeads.

A fast and efficient procedure for the purification of plasma membranes of Saccharomyces cerevisiae is described. Protoplasts served as starting material. They were coated with cationic silica microbeads. After lysis, the plasma membranes were washed free from debris and cell organelles. This procedure resulted in a high yield (about 85%) of plasma membranes, as judged by measuring vanadate-sensitive ATPase as a plasma membrane marker. The enzyme was enriched 12-fold relative to the homogenate after lysis. Its specific activity was 1.5--2.0 micromol/min per mg protein, the pH optimum was 6.5, and 10 microM vanadate was sufficient to obtain maximum inhibition. Based on the assay of internal markers and electron microscopic studies, we found our preparation essentially free of contamination from other cell organelles.

Adenosine Triphosphatases↗