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Biomedical subjects

B Schmidt

Publications and source records attributed to B Schmidt.

At least 505 records · Page 28Linked to original sources
PubMed1983

Transport of the precursor to neurospora ATPase subunit 9 into yeast mitochondria. Implications on the diversity of the transport mechanism.

Isolated yeast mitochondria were able to take up Neurospora ATPase subunit 9 in vitro although the homologous yeast protein is synthesized within the mitochondria and inserted into the membrane from the matrix side (Tzagoloff, A., and Meagher, P. (1972) J. Biol. Chem. 247, 594-603). The transfer of the protein was dependent on an energized mitochondrial inner membrane. It was accompanied by proteolytic processing of the precursor to the mature protein with the correct NH2 terminus as determined by Edman degradation of the transferred protein. The possibility is discussed that there are common features in the uptake machinery neither specific for one species nor specific for individual precursor proteins in the same species.

Adenosine Triphosphatases↗
PubMed1983

Micro-enzyme-linked immunoassay for the quantitation of platelet-associated IgG (PAIgG).

An enzyme linked immunoassay was developed using the microtiter system to measure platelet-associated IgG (PAIgG). One single determination needs 2 x 10(6) platelets usually obtained from 3 ml blood anticoagulated with EDTA. Platelets are incubated with peroxidase-conjugated anti-human IgG. Its unbound fraction is adsorbed to an IgG coated microtiter plate, quantitated by a colour reaction and found to be inversely related to the amount of PAIgG. Healthy donors (n = 40, aged 1 day to 35 years) possessed 3.6 +/- 2.0 (mean +/- S.D.) fg IgG/platelet. Increased levels of PAIgG were found in patients with acute (n = 16) and chronic (n = 5) idiopathic thrombocytopenic purpura. Postrecovery platelets had normal values of PAIgG. Widely varying levels of PAIgG were found in patients with freshly diagnosed acute lymphocytic leukemia.

Blood Platelets↗
PubMed1983

Computed tomography in the evaluation of plexopathies and proximal neuropathies.

We describe nine patients with plexopathies or proximal mononeuropathies due to mass lesions. In four, computed tomography (CT) was the only radiological technique to show the cause of the neuropathy. In five patients, CT either unequivocally confirmed the presence of an abnormality or was superior to other imaging techniques in showing its full anatomical extent. CT scanning is a valuable aid in the assessment of lesions of the peripheral nervous system, particularly plexopathies and mononeuropathies caused by retroperitoneal, pelvic or superior pulmonary sulcus tumors.

Adolescent↗
PubMed1983

Biosynthetic pathway of mitochondrial ATPase subunit 9 in Neurospora crassa.

Subunit 9 of mitochondrial ATPase (Su9) is synthesized in reticulocyte lysates programmed with Neurospora poly A-RNA, and in a Neurospora cell free system as a precursor with a higher apparent molecular weight than the mature protein (Mr 16,400 vs. 10,500). The RNA which directs the synthesis of Su9 precursor is associated with free polysomes. The precursor occurs as a high molecular weight aggregate in the postribosomal supernatant of reticulocyte lysates. Transfer in vitro of the precursor into isolated mitochondria is demonstrated. This process includes the correct proteolytic cleavage of the precursor to the mature form. After transfer, the protein acquires the following properties of the assembled subunit: it is resistant to added protease, it is soluble in chloroform/methanol, and it can be immunoprecipitated with antibodies to F1-ATPase. The precursor to Su9 is also detected in intact cells after pulse labeling. Processing in vivo takes place posttranslationally. It is inhibited by the uncoupler carbonylcyanide m-chlorophenylhydrazone (CCCP). A hypothetical mechanism is discussed for the intracellular transfer of Su9. It entails synthesis on free polysomes, release of the precursor into the cytosol, recognition by a receptor on the mitochondrial surface, and transfer into the inner mitochondrial membrane, which is accompanied by proteolytic cleavage and which depends on an electrical potential across the inner mitochondrial membrane.

Adenosine Triphosphatases↗
PubMed1983

[Use of an immunoenzyme microtechnic for quantitative determination of platelet-associated IgG in pediatrics. Acute idiopathic thrombocytopenia purpura and thrombocytopenia following exchange transfusion].

An enzyme linked immunoassay was developed using the microtiter system to measure platelet-associated IgG (PAIgG). The specificity of the assay was demonstrated in 6 children with acute idiopathic thrombocytopenic purpura (ITP): Elevated values of PAIgG (25-800 fg IgG/platelet) corresponded with low platelet counts. Complete remission was accompanied by normalization of PAIgG levels. Since immune destruction of platelets may be encountered in the development of neonatal postexchange thrombocytopenia, platelet counts and PAIgG levels were determined in pre- and postexchange samples from the recipient and in samples from the donor's blood. Eight double-volume exchange transfusions were studied in 7 newborns. Various patterns of interaction between donor and recipient were observed. Five donors proved to be thrombocytopenic, 3 of them had correspondingly high PAIgG levels, indicating immune destruction of donor platelets prior to transfusion. Three newborns had pre-existing immune thrombocytopenia before the exchange. Significant falls in platelet counts with concomitant rises in PAIgG were found following 2 out of 8 exchange transfusions. The quantitation of PAIgG by means of a micro enzyme linked immuno-assay is reliable and helpful in the detection of immune-mediated thrombocytopenia in all pediatric age-groups.

Acute Disease↗
PubMed1982

Requirement of a membrane potential for the posttranslational transfer of proteins into mitochondria.

Posttranslational transfer of most precursor proteins into mitochondria is dependent on energization of the mitochondria. Experiments were carried out to determine whether the membrane potential or the intramitochondrial ATP is the immediate energy source. Transfer in vitro of precursors to the ADP/ATP carrier and to ATPase subunit 9 into isolated Neurospora mitochondria was investigated. Under conditions where the level of intramitochondrial ATP was high and the membrane potential was dissipated, import and processing of these precursor proteins did not take place. On the other hand, precursors were taken up and processed when the intramitochondrial ATP level was low, but the membrane potential was not dissipated. We conclude that a membrane potential is involved in the import of those mitochondrial precursor proteins which require energy for intracellular translocation.

Adenosine Triphosphatases↗
PubMed1982

Acyltransferase-catalyzed cleavage of arachidonic acid from phospholipids and transfer to lysophosphatides in lymphocytes and macrophages.

The cleavage of fatty acyl moieties from phospholipids was compared in intact cells and homogenates of mouse lymphocytes (thymocytes, spleen cells) and macrophages. Liberation of free arachidonic acid during incubations of intact cells was only detectable in the presence of albumin. Homogenization of prelabeled thymocytes and further incubation of these homogenates at 37 degrees C resulted in a pronounced decrease of phospholipid degradation and cleavage of arachidonoyl residues, while further incubation of homogenates from prelabeled macrophages produced a greatly increased phospholipid degradation. Homogenates of macrophages but not those of thymocytes contain substantial activities of phospholipase A2 detectable using exogenous radiolabeled substrates. These findings indicate that in thymocytes cleavage of arachidonic acid from phosphatidylcholine is an active process that is not catalyzed by phospholipase A2. Addition of CoA and lysophosphatidylethanolamine to prelabeled thymocyte homogenates induced a fast breakdown of phosphatidylcholine and transfer of arachidonic acid to phosphatidylethanolamine, as in seen during incubations of intact thymocytes or macrophages. The transfer is restricted to arachidonic acid and does not require addition of ATP. Sodium cholate, a known inhibitor of the acyl-CoA:lysophosphatide acyltransferase, completely inhibited this transfer reaction. These results suggest that the CoA-mediated, ATP-independent breakdown of phosphatidylcholine and transfer of arachidonic acid is catalyzed by the acyl-CoA:lysophosphatide acyltransferase operating in reverse.

Acyltransferases↗
PubMed1982

Action spectra for 8-methoxypsoralen and 3-carbethoxypsoralen in skin fibroblasts in vitro.

8-methoxypsoralen (8-MOP) and 3-Carbethoxypsoralen (3-CPs) are known photoreagents which have been employed in the treatment of psoriasis. Using skin fibroblasts grown in vitro we have determined the action spectra of both compounds in the long ultraviolet range. Narrow-band interference filters were applied to a Xenon lamp. Reduction in methyl-3H-thymidine (3H-TdR) uptake served as a parameter for photoinhibited cells. The results show a linear increate of 8-MOP-mediated photoinhibition with increasing wavelengths; 3-CPs showed comparatively weak inhibitory rates at the lower wavelength range (349-365 nm). Possibly this is due to the formation of 3-CPs photoproducts which are unreactive with DNA. Compared to 8-MOP, the monofunctional photoreagent 3-CPs is a weak photoinhibitor.

Animals↗
PubMed1982

[Inhibition of platelet function in pediatric medicine (author's transl)].

The postulated importance of platelets in the pathogenesis of thromboembolic events has stimulated interest in drugs that inhibit platelet function. Clinical trials of antiplatelet agents in the secondary prevention of myocardial infarction and transient ischaemic attacks have so far been inconclusive. In children antiplatelet drugs area used on the evidence of nothing but anecdote. Optimum drug or combination of drugs and dosage are still controversial. Possible fruitful applications of platelet modifying agents such as aspirin and dipyridamole in paediatric nephrology and cardiology await further evaluation in prospective trials.

Age Factors↗
PubMed1982

Mass transfer in membrane plasma exchange.

In vitro and in vivo sieving coefficients (SC) have been determined for a spectrum of proteins ranging in molecular weight from 66,500 daltons (albumin) to 2.4 million (beta-lipoprotein) daltons for three commercially available membrane plasma separation devices: the Plasmaflo 0.1, Plasmaflo 02, and Plasmaflux. A model relating serum level of a protein to pretherapy level, plasma volume, plasma filtration rate, membrane SC, and duration of treatment has been used to investigate the influence of SC on exchange efficiency. Comparison of predicted and clinically obtained reductions in serum solute levels demonstrated the validity of the model. The results of the analysis suggest that all three plasma separators are capable of delivering equally acceptable therapy. The model further demonstrates the decreasing effectiveness, and increased cost in terms of replacement fluid per unit of solute removed, with prolonged treatment times.

Biological Transport↗
PubMed1982

Sorbent membrane dialysis in uremia.

The inclusion of activated charcoal within hemodialysis membranes offers potentially improved plasma clearance of creatinine and middle molecules. However, the carbon becomes saturated with continued use and beyond 1 h removal of solutes is by dialysis alone. Two independently conducted crossover studies, to assess the efficacy of sorbent membrane dialysis (SMD) in the treatment of uremia, found predialysis urea levels increased by approximately 15%, creatinine by 10-15%, and inorganic phosphate levels by 10-18% on SMD compared to conventional hemodialysis. One study also observed "middle molecule' (peak "b') levels elevated. No differences were observable in the clinical status of patients. The results suggest that the charcoal content of the SMD device is too small to effect any advantages over conventional dialysis.

Adsorption↗
PubMed1982

Arterial occlusion in a preterm infant. Successful non-surgical treatment with urokinase and low-dose heparin.

Neonatal arterial occlusion is a rare condition of obscure aetiology, when not associated with catheterization of the umbilical artery. Embolic occlusion of the left iliac artery was diagnosed in a preterm baby weighing 1000 g, who presented with a cold, pale and pulseless left leg on the 6th day of life. Surgical embolectomy was contraindicated in this very small baby. Fibrinolytic therapy with urokinase and administration of low-dose heparin resulted in a complete recovery of skin colour, skin temperature and blood pressure. After three weeks of urokinase therapy, no pulse differences could be detected between right and left femoral and popliteal arteries by Doppler examination, and only minimal differences were present between right and left tibial arteries.

Blood Pressure↗
PubMed1981

Decreased production or increased turnover of antithrombin III in severe acquired coagulopathy?

During the course of severe coagulopathy in an infant suffering from septicaemia and shock, antithrombin III levels were determined repeatedly before and during substitution therapy with human antithrombin. By mathematical analysis of these data, using a biexponential function, the plasma elimination half-life of the antithrombin III was estimated to be 7.5-10.5 h. Compared with known plasma half-lives of radioactively labelled antithrombin III in adults the increase was five-to ten-fold. This indicates that the significantly decreased levels of antithrombin III in this case of coagulopathy were at least partly due to an accelerated consumption of antithrombin III. The estimation of the plasma elimination half-life of antithrombin III helps to differentiate decreased production from increased consumption in cases of severe coagulopathy. Thus, a more precise diagnosis of disseminated intravascular coagulation can be made whilst taking advantage of substitution therapy and avoiding the hazards of radioactive tracer proteins.

Antithrombin III↗
PubMed1981

[Circulatory regulation during orthostatic test in young hypertensive patients].

The recognition of orthostatic circulatory dysregulations the usual circulation test were critically analysed concerning their valency. The results of our examinations show that all tests are only a supplementing diagnostics to the comprehensive directed anamnesis and clinical examination. The importance of the orthostasis in the therapy of hypertension is known. Taking into consideration the complex approach, the frequency of orthostatic circulatory dysregulations is also evident in untreated juvenile hypertensive patients. Juvenile hypertensive patients with orthasthenia should be treated with a basis therapy with beta-receptor blockers.

Adult↗