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M Köhler

Publications and source records attributed to M Köhler.

At least 145 records · Page 8Linked to original sources
PubMed1994

[Leukocyte filtration of stored whole blood for preparation of components].

Prophylaxis of infection and alloimmunisation is the main reason for leucocyte depletion by filtration of blood components. The question is whether all red cell concentrates (RCC) should be filtered and whether plasma has to be filtered, too. For leucocyte-poor units whole blood was filtered before preparation using the 'top and bottom' system. These units of buffy-coat-poor RCC and plasma were compared with components filtered after preparation. Non-filtered RCCs and plasmas served as a control. By prefiltration of whole blood and filtration of components we obtained RCCs and plasmas with less than 1 x 10(5) leucocytes in every unit. In conclusion, leucocyte filtration before preparation seems to be an easy and cost-effective method in order to get two filtered components (RCC and plasma) with one filter.

Blood Component Transfusion↗
PubMed1994

[Flow cytometry analysis of IGG subclasses of auto- and alloantibodies in autoimmune hemolytic anemia and hemolytic disease of the newborn].

Red cell IgG antibodies capable of causing hemolytic disease of the newborn (HDN) or autoimmune hemolytic anemia (AIHA) have been analyzed concerning their IgG subclasses using flow cytometry. The results were always in agreement with those of the direct Coombs test. Anti-A and/or anti-B able to cause HDN belonged to the IgG1 subclass (4/8 cases) or to the subclasses IgG1 and IgG2 (4/8 cases). In 3 out of 4 cases of HDN caused by Rh antibodies the antibodies belonged to the subclasses IgG1 and IgG3. In patients with lymphoma but without AIHA, red cell autoantibodies were often found to be IgG1 only (n = 10), in low concentrations. In cases of acute AIHA in adults caused by IgG autoantibodies the subclass IgG3 was found in addition to IgG1 in 4/5 cases. In our opinion flow cytometry should become substantial for immunohematological diagnostics.

Adult↗
PubMed1994

[Platelet membrane glycoproteins in thrombocytapheresis and platelet concentrates].

Membrane glycoprotein (GP) expression on platelets changes during preparation of concentrates and storage. Recent studies proved that the increased expression of the GMP-140 (CD 62), a GP appearing on platelets after activation, correlates with the in vivo recovery of transfused platelets. We therefore investigated the expression of this and three other GP (GP IIb/IIIa, GP, Ib, GP 53), detected by flow cytometry, in normal controls and in platelet concentrates prepared by four different methods (apheresis, preparation from buffy coat, from pooled buffy coat and platelet-rich plasma) after preparation and during storage. Furthermore we investigated the influence of filtration, radiation and washing platelet concentrates on the expression of GP. The results can be summarized as follows: (1) The mean surface fluorescence (MF) is a better parameter for the evaluation of preparation and storage lesions than the total number of positive cells. (2) The mean fluorescence of GP Ib in platelet concentrates is generally lower than in normal controls and decreases continuously during storage; there is a small loss of GP Ib through washing and filtration. (3) GP IIb/IIIa fluctuates during preparation and storage, therefore it is not suitable for evaluation of quality. (4) The percentage of CD 62 positive cells and their mean fluorescence is higher in platelet concentrates than in normal controls and increases during storage continuously. There is a weak correlation of CD 62 with CD 63. (5) The changes of GP in apheresis concentrates and concentrates obtained from whole blood are similar after preparation and during storage.

Blood Platelets↗
PubMed1993

RNA editing of AMPA receptor subunit GluR-B: a base-paired intron-exon structure determines position and efficiency.

A functionally critical position (Q/R site) of the AMPA receptor subunit GluR-B is controlled by RNA editing that operates in the nucleus, since in brain and clonal cell lines of neural origin, unspliced GluR-B transcripts occur edited in the Q/R site CAG codon and, additionally, in intronic adenosines. Transfection of GluR-B gene constructs into PC12 cells revealed that the proximal part of the intron downstream of the unedited exonic site is required for Q/R site editing. This intron portion contains an imperfect inverted repeat preceding a 10 nt sequence with exact complementarity to the exon centered on the unedited codon. Single nucleotide substitutions in this short intronic sequence or its exonic complement curtailed Q/R site editing, which was recovered by restoring complementarity in the respective partner strand. Base conversion in the channel-coding region of GluR-B directed by base paired sequences may be executed by a ubiquitous nuclear adenosine deaminase specific for double-stranded RNA.

Adenosine Deaminase↗
PubMed1993

Recent discoveries of Dryopithecus shed new light on evolution of great apes.

The origin and early evolution of the great ape/human clade (Hominidae) is currently a subject of debate. The controversy is fuelled by the fragmentary nature of the fossils which renders it difficult to determine clearly derived features that permit the recognition of fossil members of this clade. We report here the recent discovery of a facial skeleton and a temporal fragment with the petrosal bone of Dryopithecus laietanus, which provides a way out of an impasse. The lack of the fossa subarcuata is a great ape and human clade synapomorphy, and proves unequivocally that Dryopithecus belongs to this clade. The zygomatic possesses derived characters which reveal that Dryopithecus is related to the Ponginae and not to the African apes/humans, as recently suggested. The remaining morphological features are plesiomorphic and thus provide a good model of a common ancestor of all Hominidae.

Africa↗
PubMed1993

Inactivation of viruses in fresh-frozen plasma.

Methylene blue (MB) or solvent/detergent (SD) treatment is used for the inactivation of lipid-enveloped viruses in plasma. One important characteristic of the SD treatment is the necessity to pool plasma from different donors, thus inducing the risk of spreading infectious particles. MB treatment can be applied to single-donor plasma, causing no greater infectious risk than conventional fresh-frozen plasma (FFP). However, the virucidal efficacy of the SD method regarding HIV, HBV and HCV has been significantly better examined and proven than the MB treatment. Most of the therapeutic constituents of both plasma products are well maintained; coagulation factors decrease by roughly 5-20%. SD treatment reduces protein S and alpha 2-antiplasmin by approximately 40%, whereas MB treatment leads to a significant photooxidative alteration of fibrinogen with a disturbance of fibrin polymerization. As current studies show, the use of either plasma product is obviously not limited by acute or chronic toxicity. Several studies are in progress to evaluate the relevance of alterations in FFP quality which may affect the clinical efficacy of virus-inactivated plasma.

Antiviral Agents↗
PubMed1993

Determinants of Ca2+ permeability in both TM1 and TM2 of high affinity kainate receptor channels: diversity by RNA editing.

GluR6, a subunit of high affinity kainate receptor channels in the mammalian CNS, carries a glutamine (Q) or arginine (R) residue in a critical position (Q/R site) of the putative channel-forming segment TM2. One form, GluR6(Q), is encoded by the GluR6 gene; the other, GluR6(R), is generated by RNA editing. Further analysis of cloned GluR6 cDNA revealed that two additional positions, located in transmembrane segment TM1, are diversified by RNA editing to generate either isoleucine (I) or valine (V) in one and tyrosine (Y) or cysteine (C) in the other TM1 position. In GluR6 channels, in contrast with AMPA receptor channels, the presence of Q in the TM2 Q/R site determines channels with low Ca2+ permeability, whereas an R determines a higher Ca2+ permeability if TM1 is fully edited. In the TM1 unedited form of GluR6, Ca2+ permeability is less dependent on the presence of either Q or R in TM2. Thus Ca2+ permeability of kainate receptor channels can vary, depending on editing of both TM1 and TM2.

Amino Acid Sequence↗
PubMed1993

Divergent effects of arginine vasopressin and angiotensin II on proliferation and expression of the immediate early genes c-fos, c-jun and Egr-1 in cultured rat glomerular mesangial cells.

OBJECTIVE: The vasoactive peptides arginine vasopressin (AVP) and angiotensin II (Ang II) induce similar second messengers in cultured glomerular mesangial cells, as shown by the rise in intracellular calcium and the activation of phospholipases C and A2. In contrast, AVP is a strong mitogen for cultured rat mesangial cells while Ang II is not. To elucidate the level of signal divergence, we examined the effects of AVP and Ang II on the expression of the immediate early genes c-fos, c-jun and Egr-1, which have been associated with cell growth. We also tested the effect of AVP and Ang II on the induction of the ornithine decarboxylase gene and enzyme in order to examine a process that is induced in cell activation, e.g. it has been associated with the G1 phase after mitogen-receptor binding. DESIGN AND METHODS: Cellular effects of Ang II and AVP were studied in rat mesangial cells in conventional two-dimensional culture. Proliferation of the mesangial cells was measured by cell-counting and by [3H]-thymidine uptake. The presence of receptors for Ang II and AVP was assessed by measurement of prostaglandin E2 by a radioimmunoassay following stimulation with vasoactive peptides and a receptor-binding assay for Ang II. Messenger (m)RNA levels of c-fos, c-jun Egr-1 and ornithine decarboxylase were determined by Northern blot analysis. Ornithine decarboxylase activity was measured by an enzyme substrate assay. RESULTS: AVP (10(-7) mol/l) stimulated [3H]-thymidine uptake by 3.7-fold after 48 h and increased mesangial cell counts by 42% (P < 0.05), while Ang II was not mitogenic. Stimulation of resting mesangial cells with AVP (10(-9) to 10(-6) mol/l) caused maximal expression of the immediate early genes after 0.5-1 h, which disappeared after 2-4 h. The relative increases were: c-fos, 15-fold; c-jun, 12-fold; Egr-1, sixfold. Ang II (10(-9) to 10(-6) mol/l) did not induce these genes at any time. In contrast, ornithine decarboxylase mRNA and enzyme activity were induced by both AVP and Ang II. CONCLUSIONS: The results demonstrate that AVP, but not Ang II, is a strong inducer of the immediate early genes c-fos, c-jun and Egr-1 in cultured mesangial cells. We conclude that signalling pathways activated by AVP and Ang II in mesangial cells diverge within 30 min after ligand-receptor binding and proximal to the transient expression of immediate early genes. While mitogenesis of cultured mesangial cells, as effected by AVP, involves the expression of immediate early genes, Ang II-induced non-mitogenic changes in the mesangial cell phenotype do not. The increase in ornithine decarboxylase mRNA and enzyme activity following stimulation with both AVP and Ang II indicates that its induction can occur independently of the immediate early gene expression and mitogenesis.

Angiotensin II↗
PubMed1993

[Initial results of a prospective study with automated solid phase and column/agglutination techniques in screening for transfusion relevant IgG antibodies].

We report the first results of a prospective study concerning antibody screening in transfusion recipients. We compared the standard tube test (Liss Coombs) with two commercial tests for the detection of red cell IgG antibodies: (1) a column/agglutination test and (2) a microplate/solid-phase system. The results of the study demonstrate several significant advantages of the two methods as compared with the standard tube test. The new methods, especially the microplate test, are superior in determining red cell antibodies which are relevant to transfusion. The two methods are more sensitive and, when automated, more efficient and safer as compared with the standard tube test.

Blood Grouping and Crossmatching↗
PubMed1993

Comparison of low molecular weight heparins and unfractionated heparin after successive subcutaneous administration. A randomized controlled study in healthy volunteers.

The biological response to 4 different heparins after successive subcutaneous administration once daily for 5 days at a dose used for primary prophylaxis of deep vein thrombosis was investigated in a randomized cross-over study in 12 volunteers. Three different preparations of low molecular weight heparins (LMWH) were administered, 10,000 U unfractionated heparin (UFH) was used as a control. The anticoagulant properties in terms of anti-Xa activities, as measured by a chromogenic substrate assay or Heptest, showed high interindividual variations with peak levels 2 to 4 h following injections. There was a significantly higher increase of anti-Xa activities 3 h after administration at day 5, when compared with day 1, for two LMWH's, suggesting an accumulation of the anticoagulatory effect. The anticoagulant activity, especially when measured by Heptest, was significantly influenced by the body weight. This could be observed for all LMWH's. For the assessment of anticoagulant activity in LMWH-treated individuals, the chromogenic substrate assay and Heptest revealed maximal correlation (r = 0.51), while in UFH-treated individuals, peak correlation (r = 0.75) was observed between the partial thromboplastin time and thrombin clotting time. The chromogenic substrate method was the most sensitive anti-Xa assay, showing also the smallest interindividual variation. No significant influence of heparins neither on platelet count and function nor on fibrinolysis were recognized. Enhanced lipolytic activities were not observed. There was an increase of alanine aminotransferases induced by UFH as well as LMWH's, which, however, was most pronounced after UFH.

Adult↗
PubMed1992

High-affinity kainate and domoate receptors in rat brain.

Mammalian brain expresses receptors which bind the potent neurotoxins, kainate and domoate, with high affinity, and which form a subclass of ionotropic glutamate receptors. A new member of these receptors, expressed in both adult and embryonic CNS is compared in its ligand binding properties to its closely sequence-related homologs.

Amino Acid Sequence↗
PubMed1992

Protein kinase C activity affects glucose-induced oscillations in cytoplasmic free Ca2+ in the pancreatic B-cell.

Acute stimulation of protein kinase C (PKC) inhibited glucose-induced slow oscillations in cytoplasmic free Ca(2+)-concentration, [Ca2+]i, in mouse pancreatic B-cells. In PKC-depleted cells glucose induced rapid transients in [Ca2+]i, lasting for approximately 10 s, superimposed on the slow oscillations in [Ca2+]i. It was demonstrated that the transients did not occur in the absence of extracellular Ca2+. Each transient typically was preceded by a slow increase in [Ca2+]i, representing the rising phase of an ordinary glucose-induced slow oscillation, and the [Ca2+]i, immediately after a transient was lower than just before the spike. These data further emphasize the interplay between voltage-dependent Ca(2+)-channels and the phospholipase C system in the regulation of B-cell [Ca2+]i-oscillations.

Animals↗
PubMed1992

Efficacy and tolerability of moclobemide compared with fluvoxamine in depressive disorder (DSM III). A French/Swiss double-blind trial.

The efficacy and tolerability of moclobemide and fluvoxamine, two new types of antidepressant agents, were compared in a multicentre, double-blind prospective study of patients with a diagnosis of major depressive episode (DSM III). Patients were randomized to receive either moclobemide (150 mg) or fluvoxamine (50 mg) twice daily for 7 days, immediately following a washout period of at least 1 week. Dosages were increased where necessary on day 8, to a maximum of moclobemide 450 mg or fluvoxamine 200 mg and in most cases were maintained at these levels for the remainder of the study period (4-6 weeks). Both treatment groups showed a marked antidepressant effect. While both treatments were well tolerated, moclobemide showed a more favourable side-effect profile than fluvoxamine. Of the 126 patients eligible for evaluation, 34 withdrew from therapy, 22% in the moclobemide group and 30% in the fluvoxamine group. Adverse events were reported in 41.8% of patients treated with moclobemide compared to 60.3% of patients in the fluvoxamine group. Reports of dry mouth and other anticholinergic effects were more frequent among those treated with fluvoxamine. A greater number of gastrointestinal complaints, especially nausea, also occurred in the fluvoxamine-treated patients.

Adult↗