Biomedical subjects

M Müller

Publications and source records attributed to M Müller.

At least 1,009 records · Page 56Linked to original sources

PubMed1992

ConA induced changes in energy metabolism of rat thymocytes.

The influence of ConA on the energy metabolism of quiescent rat thymocytes was investigated by measuring the effects of inhibitors of protein synthesis, proteolysis, RNA/DNA synthesis, Na+K(+)-ATPase, Ca(2+)-ATPase and mitochondrial ATP synthesis on respiration. Only about 50% of the coupled oxygen consumption of quiescent thymocytes could be assigned to specific processes using two different media. Under these conditions the oxygen is mainly used to drive mitochondrial proton leak and to provide ATP for protein synthesis and cation transport, whereas oxygen consumption to provide ATP for RNA/DNA synthesis and ATP-dependent proteolysis was not measurable. The mitogen ConA produced a persistent increase in oxygen consumption by about 30% within seconds. After stimulation more than 80% of respiration could be assigned to specific processes. The major oxygen consuming processes of ConA-stimulated thymocytes are mitochondrial proton leak, protein synthesis and Na+K(+)-ATPase with about 20% each of total oxygen consumption, while Ca(2+)-ATPase and RNA/DNA synthesis contribute about 10% each. Quiescent thymocytes resemble resting hepatocytes in that most of the oxygen consumption remains unexplained. In contrast, the pattern of energy metabolism in stimulated thymocytes is similar to that described for Ehrlich Ascites tumour cells and splenocytes, which may also be in an activated state. Most of the oxygen consumption is accounted for, so the unexplained process(es) in unstimulated cells shut(s) off on stimulation.

Animals↗

PubMed1992

Immunohistological detection of tissue factor in normal and abnormal human mammary glands using monoclonal antibodies.

Tissue factor (TF) is the primary cell-bound initiator of the coagulation protease cascade. The cytological distribution of TF in various tissues may be described on the basis of immunohistochemistry with epitope-defined monoclonal antibodies and the extravascular distribution of TF apparently represents a haemostatic envelope ready to activate coagulation when vascular integrity is disrupted. The present study localized TF in human breast cancer tissues when compared with normal breast gland tissues and benign disorders of the mammary gland. By use of a cocktail of three epitope-defined monoclonal antibodies, TF was detected only in the myoepithelia of the resting breast gland. In proliferating disorders like fibrocystic disease or in fibroadenomas, both myoepithelia and luminal epithelia showed TF expression. Of 115 breast cancers 93 reacted with anti-TF, in an inhomogeneous manner in terms of intensity and number of positive cells. There was a tendency for more positive and intensely stained cells to be found in well-differentiated structures such as tubules. Invasive ductal carcinomas exhibiting more positive and more strongly stained cells were less commonly metastatic to lymph nodes when compared with the tumours with no detectable or very low TF immunostaining. A semi-quantitatively recorded score of TF immunostaining correlated with the procoagulatory activity measured (7 fibroadenomas and 24 carcinomas). The results of this study suggest that proliferation and differentiation of the mammary gland is associated with enhanced TF expression in the epithelia which are negative for TF staining in the resting gland. Malignant growth is characterized by randomly expressed epithelial TF, which expression is enhanced and more frequent in well-differentiated tumour cells.

Antibodies, Monoclonal↗

PubMed1992

ConA induced changes in energy metabolism of rat thymocytes.

Adenosine Triphosphate↗

PubMed1992

PCR amplification of large genomic fragments from human and simian immunodeficiency virus infected cell lines.

Polymerase chain reaction (PCR) has been used to amplify the large fragments from viral genomic DNA of SIV from wild caught, asymptomatic Erythrocebus monkeys from Western Africa (Senegal) and also from HIV-2 infected cell lines. By using consensus primer sequences from highly conserved stretches of gag, pol and env genes, two halves of the viral genome of HIV-2 and SIV (isolated from west African Erythrocebus monkeys) have amplified by PCR. One half spans 5200 bp from within the U3 region of the 5' long terminal repeat (LTR) into pol gene and an overlapping fragment spans 3700 bp from the pol gene into U5 region of 3' LTR. Also fragments ranging from 1-2.3 kb from gag pol and env genes have been successfully amplified. Our data demonstrate that primers used to amplify large segments from viral DNA yield better results if they are derived from a consensus sequence of a highly conserved stretch of the viral genome.

Animals↗

PubMed1992

Antibodies to HPV-16 E6 and E7 proteins as markers for HPV-16-associated invasive cervical cancer.

Transforming proteins E6 and E7 of human papillomaviruses (HPVs) are consistently expressed in HPV-associated cervical cancers. In ELISA with four HPV-16 E6-E7 peptides, patients with HPV-16-associated invasive cervical cancer (group 1) had a greater seroreactivity than all other groups, which included patients with HPV-16-associated cervical intraepithelial neoplasia, invasive cervical cancer patients without HPVs, and unaffected controls. A larger proportion of group 1 sera, as compared to sera of all other groups, was reactive with at least one peptide (49% vs 17-27%), and with two or more peptides (22% vs 0-6%). A clear difference between group 1 and all other groups was also found for high ELISA absorbance values to at least one peptide (22% vs 0-8%). This high seroreactivity of group 1 sera was confirmed by a radioimmunoprecipitation assay with in vitro transcribed and translated HPV-16 E7 protein. Sera from 50% of group 1 but only 3% of controls were reactive in this test. Antibodies to HPV-16 E6 and E7 proteins appear to be virus-specific and disease state-specific markers of HPV-associated cervical cancer.

Amino Acid Sequence↗

PubMed1992

Transport and in vivo elimination of cysteinyl leukotrienes.

Transport processes control not only synthesis and release of LTC4 but also the elimination and excretion of LTC4 and its metabolites. (i) A primary-active ATP-dependent export carrier mediates the release of LTC4 from a leukotriene-generating cell, as exemplified by mastocytoma cells, and as measured in mastocytoma plasma membrane vesicles (2). (ii) Release of cysteinyl leukotrienes into the blood circulation is followed by a rapid elimination with an initial half-life of 38 sec in rats and 4.0 min in man, as measured with the labeled, representative LTC4 catabolite, N-acetyl-LTE4. (iii) 11C-labeled N-acetyl-LTE4 can serve for non-invasive studies on cysteinyl leukotriene elimination and excretion by the liver and kidney in the intact organism using positron emission tomography. An impairment of leukotriene transport from the liver across the canalicular membrane into bile, studied in mutant rats and in extrahepatic cholestasis, leads to a compensatory diversion of cysteinyl leukotriene elimination to the kidney. N-Acetyl-LTE4 labeled with a short-lived positron-emitting isotope provides quantitative insight into the pathways of cysteinyl leukotriene elimination in vivo. (iv) Cysteinyl leukotriene export from the liver into bile is mediated by an ATP-dependent primary-active export carrier. This decisive step in cysteinyl leukotriene elimination has been characterized in hepatocyte canalicular membrane vesicles (3). The leukotriene exporter is deficient in transport mutant rats. The leukotriene carrier is distinct from other ATP-dependent export carriers identified in this membrane domain, such as the ATP-dependent bile salt export carrier (25) and the multidrug export carrier (27).

Adenosine Triphosphate↗

PubMed1992

Pyruvate kinase from Trichomonas vaginalis, an allosteric enzyme stimulated by ribose 5-phosphate and glycerate 3-phosphate.

Trichomonas vaginalis pyruvate kinase was purified over 1750 fold to a specific activity greater than 100 mumol min-1 (mg protein)-1. The enzyme is a tetramer of M(r) 266,000, consisting of subunits of M(r) 53,000 and 56,000 in equivalent amounts. Its activity was dependent on the presence of magnesium but was not stimulated by potassium or ammonium. The enzyme exhibited positive cooperativity towards phosphoenolpyruvate and was inhibited by inorganic phosphate, which increased the sigmoidicity of the saturation curve for phosphoenolpyruvate without affecting maximal activity. It was heterotropically stimulated by ribose 5-phosphate and glycerate 3-phosphate, not previously known to act on eukaryotic pyruvate kinases, but was unaffected by known effectors of most pyruvate kinases, including fructose 1,6-bisphosphate and fructose 2,6-bisphosphate.

Allosteric Regulation↗

PubMed1992

Energy metabolism of ancestral eukaryotes: a hypothesis based on the biochemistry of amitochondriate parasitic protists.

Parasitic amitochondriate protists, representatives of early branches of eukaryote evolution, differ considerably in their central, energy metabolism from mitochondrion-bearing cells. These differences are: significant metabolic functions of inorganic pyrophosphate, major role of iron-sulfur proteins in key metabolic steps and in hydrogenosome-bearing organisms the disposal of electrons by H2 formation. Cytochrome-mediated electron transport and electron transport-linked phosphorylation are absent. All proteins which have been sequenced so far were found to be homologous to isofunctional proteins from other organisms. A few reactions, however, are catabolized by proteins which are not homologous to enzymes performing similar reactions in other eukaryotes. Two significantly different types of metabolism of amitochondriate protists can be distinguished: (a) without compartmentation and (b) with cytosol/hydrogenosome compartmentation. It is likely that these metabolic types have conserved certain traits present in ancestral eukaryotes before mitochondria became established.

Animals↗

PubMed1992

Constitutive tissue factor expression of human breast cancer cell line MCF-7 is modulated by growth factors.

Expression of tissue factor, the initiator of the extrinsic coagulation protease cascade, is a feature of certain malignant tumours. To study the modulation of tissue factor expression we incubated the breast cancer cell line MCF-7 with several growth factors. Epidermal growth factor (EGF), transforming growth factor alpha (TGF alpha) and interleukin-1 (IL-1) rapidly increased tissue factor expression of MCF-7 cells peaking at 6-8 h after starting point of incubation, as determined by clotting test, enzyme linked immunosorbent assay and flow cytometry. The data presented support the hypothesis that modulation of constitutive tissue factor expression in tumour cells by TGF alpha and IL-1 could also occur in vivo possibly resulting from interactions of stromal and cancer cells. The meaning for tumour biology, however, remains unclear.

Blood Coagulation Tests↗

PubMed1992

[CO2 test with transcranial Doppler sonography in cerebral ischemia].

We evaluated the CO2-induced vasomotor reactivity of the cerebral vasculature in 48 patients with high degree stenosis or occlusion of the internal carotid artery by transcranial Doppler ultrasonography measuring changes of flow velocities in the middle cerebral artery. Further, the vasomotor reactivity of the basilar artery was measured in 48 patients with vertebro-basilar ischemia. These results were compared with the findings in normal individuals. The vasomotor reactivity was significantly reduced in patients with stenosis or occlusion of the internal carotid artery as compared to normal controls. In patients with high degree ICA stenoses, undergoing to carotid surgery, CO2-test showed a significant improvement of the pathological vasomotor reactivity 6 month after the operation. In the group of patients with vertebro-basilar ischemia, the vasomotor reactivity measured in the basilar artery, was significantly reduced in patients with completed brainstem infarctions but not in patients with transient brainstem ischemia or infarctions in the posterior cerebral artery territory. We conclude that evaluation of the cerebral vasomotor reactivity by transcranial Doppler ultrasound is able to identify an inadequate cerebral blood supply and may help to estimate the hemodynamic effect of stenosis or occlusion of the extracranial brain supplying arteries.

Adult↗

PubMed1992

[Intraoperatively-induced astigmatism after "small incision cataract extraction". An analysis of 4.0 mm, 5.0 mm and 6.5 mm incisions].

Surgically induced astigmatism in three series of cataract surgical procedures were compared. The three series comprised 120 eyes having phacoemulsification and implantation of: a) a foldable silicon lens through a 4.0 mm incision (32 eyes), b) a 5.0 mm PMMA lens through a 5.0 mm incision (48 eyes) and c) a 6.5 mm diameter PMMA lens through a 6.5 mm incision (40 eyes). There were no significant differences in surgically induced cylinder between the three groups after one month or 6 months postoperatively. No differences between these three groups with respect to visual rehabilitation were seen. We concluded that small diameter PMMA implants inserted through a 5.0 mm or 6.5 mm incision minimized surgically induced cylinder in a way comparable to the use of foldable silicone implants inserted through a 4.0 mm incision.

Adult↗

PubMed1992

Echinococcus granulosus infection of the liver and lung in an 8 1/2-year-old boy.

We report on an 8 1/2-year-old boy with an echinococcus granulosus infection of the liver and lung, drawing particular attention to the therapy applied. This therapy consists on the one hand of medicinal treatment with Mebendazol and on the other hand of two subsequent operations with resection of the cysts. The course of the illness is illustrated by means of the most important laboratory parameters; an indication of the present serological diagnostic is also given.

Child↗

PubMed1992

Molecular cloning of porcine Mx cDNAs: new members of a family of interferon-inducible proteins with homology to GTP-binding proteins.

Porcine cells treated with interferon (IFN) or double-stranded RNA synthesize two proteins that exhibit high homology of the amino acid sequence to mouse Mx1 protein involved in selective resistance to influenza virus. A full-length cDNA clone (poMx1) encoding the porcine Mx1 protein was isolated and sequenced. It contained an open reading frame of 663 amino acids. The predicted molecular weight of 75.6 kD is in good agreement with the apparent molecular mass of the two immunoprecipitable proteins of 76 kD and 73 kD determined by SDS polyacrylamide gel electrophoresis. A second cDNA (poMx2) was characterized which was incomplete in the 5' region. A comparison of all known Mx proteins revealed an average homology of 67.5%. The porcine Mx1 polypeptide is most closely related to human MxA (p78), murine Mx2, rat Mx2, and rat Mx3 proteins. The amino-terminal halves of all Mx proteins are highly conserved and possess three consensus elements in proper spacing, characteristic of GTP-binding domains. The Mx family shows in their amino termini striking homology to previously characterized Mx-related proteins playing roles in the intracellular vectorial transport of proteins--the products of the yeast Vps1 locus and the dynamins.

Amino Acid Sequence↗

PubMed1992

An ELISA for tissue factor using monoclonal antibodies.

Whereas tissue factor, a high-affinity cell-surface receptor and essential cofactor for the serine protease factor VII is constitutively present in certain tissues such as epithelial tissue, brain and placenta, it is not normally expressed by cells within the vasculature. However, the stimulation of monocytes and endothelial cells by a variety of inflammatory and immunological reactions results in the induction of cell surface tissue factor (TF) expression. TF is also expressed on tumour cells, and may play a role in tumour growth and metastasis formation. To examine the role of TF in these processes we developed monoclonal antibodies to human tissue factor apoprotein. The antibodies were characterized by neutralization of the procoagulant activity and by immunoblotting. With two of these monoclonal antibodies a sandwich ELISA was developed for the rapid quantitation of TF. The sensitivity of the assay permits extensive studies involving the modulation of TF expression on small numbers of cells. The results are comparable to the functional clotting assay as evaluated with unpurified TF and with the tumour cell line MCF-7. For certain applications, monitoring of cellular TF expression by ELISA using anti-TF monoclonal antibodies is preferable because it is not influenced by other coagulation factors or by inhibitors of procoagulant activity on the cells.

Animals↗

PubMed1992

Histochemistry of guanylate cyclase, phosphodiesterase, and NADPH-diaphorase (nitric oxide synthase) in rat brain vasculature.

The distribution of guanylate cyclase, phosphodiesterase, and NADPH-diaphorase [nitric oxide (NO) synthase] was studied in rat brain both at the light and electron microscopic level with special emphasis on the vascular system. We showed that the cGMP-generating enzyme is located in cells (glial cells and pericytes) surrounding cerebral vessels, but not in the endothelium. For NO synthase, a dual localization was observed. The enzyme is present in parts of the endothelium and in nerve endings apparently innervating larger brain vessels. We propose, therefore, that NO acts on guanylate cyclase both from a "synaptic" and endothelial source.

Amino Acid Oxidoreductases↗

PubMed1992

In vivo analysis of the helix-turn-helix motif of the fushi tarazu homeo domain of Drosophila melanogaster.

We report a systematic mutational analysis of the helix-turn-helix motif (HTH) of the fushi tarazu (ftz) homeo domain (HD) of Drosophila. We started out by testing the function of chimeric ftz proteins containing either a part of the Sex combs reduced (Scr) or the muscle segment homeobox (msh) HDs. By complementation tests in transgenic flies, cotransfection assays in cultured Drosophila cells and in vitro DNA-binding assays, we have found that the ftz activity is retained in the ftz-Scr chimera but is lost in the ftz-msh chimera, which is defective in binding to an Antennapedia (Antp)-class target site. Further studies with a series of back-mutants of the ftz-msh chimera have revealed that a set of class-specific DNA backbone-contacting residues in the HTH, particularly Arg-28 and Arg-43, are required for efficient target site recognition and, hence, full ftz activity both in vitro and in vivo.

Amino Acid Sequence↗

PubMed1992

Effect on dentinal adhesives on marginal adaptation and cavity sealing with resin restorations in vitro.

In a companion article in this issue and a previous article in this journal, two experimental enamel dentin adhesive systems were evaluated and compared with four commercially available resin bonding agents by SEM investigation of the tooth adhesive interfaces and by determination of bond strengths to enamel and dentin under various conditions. In continuation of these screening investigations, the present article describes the results of cavity tests for assessment of marginal adaptation by measurement of gap dimensions, and of cavity sealing by rating of microleakage, when standardized dentin cavities were treated with the adhesive restorative systems. Both tests resulted in the same ranking of the six materials. Gluma, Clearfil Photo Bond, and two experimental compounds showed very narrow gaps and moderate microleakage. In contrast, Prisma Universal Bond 2 (the material has been replaced in the market by Prisma Universal Bond 3) and Scotchbond 2 showed significantly wider marginal gaps and more pronounced microleakage. Final discrimination between the efficacy of adhesive restorative materials by any of the currently used in vitro tests is disputable and prediction of long-term clinical performance by laboratory test data remains questionable.

Adhesives↗

PubMed1992

Comparative in vitro evaluation of recent enamel and dentin adhesive materials.

In this in vitro study, two experimental and four commercially available enamel-dentin bonding agents are characterized by shear bond strengths to human teeth following storage of the specimens for 2 minutes, 15 minutes, and 24 hours, respectively, or after stressing of the bonds by 5000 thermal cycles between 5 degrees and 55 degrees C. It is assumed that the experimental compounds are clinically adequate materials to mediate long-term retention of resin restorations placed without reliance on mechanical undercuts. The limitations of such in vitro strength data regarding clinical performance are discussed and emphasized.

Analysis of Variance↗