Biomedical subjects
Publications and source records attributed to M Köhler.
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.
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.
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.
A double-labeling approach was applied to nonisotopic in situ hybridization with individual cosmid and plasmid clones, using digoxigenin or biotin as label and a combination of two separate enzymatic labeling methods. Probe labeling was achieved by nick translation, followed by tailing of the probe by terminal deoxynucleotidyl transferase. The double-labeling method, in conjunction with an improved detection protocol, provides for a higher signal intensity than that obtainable with single-labeled probes.
In human pancreatic islets an increase in the glucose concentration from 3 to 20 mM raised the free cytoplasmic Ca2+ concentration [( Ca2+]i), an effect being reversible upon withdrawal of the sugar. Depolarization with a high concentration of K+ or the sulphonylurea tolbutamide also raised [Ca2+]i. Addition of extracellular ATP produced a transient rapid rise in [Ca2+]i. Oscillations in [Ca2+]i were observed in the presence of 10 mM glucose. Insulinoma cells responded to glucose and tolbutamide with increases in [Ca2+]i, whereas the sulphonamide diazoxide caused a decrease in [Ca2+]i. These findings confirm previous results obtained in rodent beta-cells.
L-glutamate, the principal excitatory transmitter in the brain, gates ion channels mediating fast neurotransmission. Subunit components of two related classes of glutamate receptor channels have been characterized by cDNA cloning and shown to carry either an arginine or a glutamine residue in a defined position of their putative channel-forming segment. The arginine residue in this segment profoundly alters, and dominates, the properties of ion flow, as demonstrated for one channel class. We now show that the genomic DNA sequences encoding the particular channel segment of all subunits harbor a glutamine codon (CAG), even though an arginine codon (CGG) is found in mRNAs of three subunits. Multiple genes and alternative exons were excluded as sources for the arginine codon; hence, we propose that transcripts for three subunits are altered by RNA editing. This process apparently edits subunit transcripts of the two glutamate receptor classes with different efficiency and selectivity.
An experimental approach towards the molecular analysis of the male fertility function, located in interval 6 of the human Y chromosome, is presented. This approach is not based on the knowledge of any gene product but on the assumption that the functional DNA structure of male fertility genes, evolutionary conserved with their position on the Y chromosome, may contain an evolutionary conserved frame structure or at least conserved sequence elements. We tested this hypothesis by using dhMiF1, a fertility gene sequence of the Y chromosome of Drosophila hydei, as a screening probe on a pool of cloned human Y-DNA sequences. We were able to select 10 human Y-DNA sequences of which 7 could be mapped to Y interval 6 (the pY6H sequence family). Since the only fertility gene of the human Y chromosome is mapped to the same Y interval, our working hypothesis seems to be strongly supported. Most interesting in this respect is the isolation of the Y-specific repetitive pY6H65 sequence. The pY6H65 locus extends to a length of at least 300 kb in Y interval 6 and has a locus-specific repetitive sequence organization, reminiscent of the functional DNA structure of Y chromosomal fertility genes of Drosophila. We identified the simple sequence family (CA)n as one sequence element conserved between the Drosophila dhMiFi fertility gene sequence and the homologous human Y-DNA sequences.
The pharmacokinetics of urokinase (two-chain urokinase-type plasminogen activator, tcu-PA) and single-chain urokinase-type plasminogen activator (scu-PA) were studied in 20 patients with acute myocardial infarction (AMI). Ten consecutive patients received 2.5 million units tcu-PA by bolus injection within 5 min during the first 6 h after AMI (group I). Ten further consecutive patients received 250,000 U tcu-PA within 5 min, followed by 4.5 million U scu-PA by intravenous infusion over 40 min (group II). An enzyme immunoassay was developed for urokinase antigen determinations, and a fibrin plate assay for determinations of fibrinolytic activity was applied. Using a 3-compartment model, in group I 98% of urokinase antigen were cleared with a half-life of 60.8 min. After scu-PA, urokinase antigen was cleared with half-lives (area under the curve in parentheses) of 6.9 min (74.8%), 26.5 min (23.6%), and 329.7 min (2.2%). The half-disappearance times of fibrinolytic activity were 18 and 8 min in group I and II, respectively. A more pronounced decrease of plasminogen was observed after tcu-PA.
1. The effects of several phenols, anilines and aliphatic alcohols on yeast plasma membrane H(+)-ATPase and purine transport system as well as on Na+, K(+)-ATPase and adenosine uptake by Chinese hamster ovary cells (CHO) were investigated. 2. In all cases an inhibition was observed, which could be correlated with the octanol/water partition coefficients of the substances tested, thus making quantitative structure-activity predictions possible. 3. The observed effects correlated well with the influence of the chemicals on cell growth. 4. The results suggest a common mechanism of toxicity by the action of hydrophobic xenobiotics on biomembranes.
Organic psychosyndromes may be classified 1) by the state of vigilance (agitated or reduced), 2) by the progress in time (episodic versus progressive), 3) by the presence or absence of brain-local or vegetative accompanying phenomena, 4) by etiology. The most frequent forms are: multi-infarct-dementia and primary degenerative dementia of Alzheimer's type. We must be aware that this didactic differential diagnosis in reality mostly shows overlapping criteria. Either more to the one side or more to the other. Etiological therapy (as well "vasoactive" as "nootropic") should in most cases be combined with therapy of underlying internistic (cardiac for example) and accompanying (infection for example) symptoms. Depression as a special frequent dimension needs special attention. Furthermore there are complex therapeutic possibilities in the social, recreative, psychologic, rehabilitative, psychotherapeutic etc. field. Relatives need to be treated concommitantly. Only thus scientific as well as human implications for rehabilitation can meet.
Among 126 patients in neurorehabilitation, most of them suffering from cerebral vascular disease, 78 were afflicted by a disturbance of urinary excretion, which could be alleviated in 42 cases (54%) during the first 3 weeks of therapy. In more than half of catheterized patients the catheter could eventually be abandoned. In terms of our rehabilitation scale, we could observe an improvement of 53% in scale points during the period of treatment. We adhere to a scheme of consistent cooperation between urologists and neurologists with respect to optimal and economical care for the catheterized patient with regular training of the vesical sphincter. Rational medication can in some cases take advantage of side-effects of drugs which are indicated for the primary disorder anyway. Permanent communication between the medical specialist in rehabilitation, the neurologist and the nurse is an essential requirement. Psychological and environmental aspects have to be considered in order to treat the patient as a complex entity.
The influence of several temperatures on the wild strain Pichia guilliermondii Pg 0799 and a selected fusion product fp 3/9 was studied in batch- and continuous cultures. Growth and substrate utilization of both strains were compared by determination of specific growth rates, yield coefficients and biomass production. The results showed, that strain fp 3/9 has in general a higher optimum of temperature for biomass production.
The potency and tests for thrombogenicity were studied prospectively in 7 different (two lots of each brand, A-G) prothrombin complex concentrates (PCC). Human albumine (H) and a factor IX concentrate (I), served as controls. The potency of coagulation factors and inhibitors varied considerably. Two brands (E, F) contained no protein S, additionally one brand contained no protein C. Two preparations exhibited high amidolytic activities, especially towards the thrombin-sensitive chromogenic substrate S-2238, in vitro. These activities could be quenched in part by the addition of hirudin or antithrombin III. The heparin and antithrombin III content of the PCCs was significantly different, and, after addition of antithrombin III an increase of thrombin-antithrombin III complexes in 2 preparations (B, D) was observed in vitro. Additionally, three brands (B, D, F) caused more severe cardio-pulmonary reactions in rabbits, associated with an increase of fibrin split products for brands B and D. We conclude that the use of these preparations in patients, in whom an acquired protein C or S defect, or a hypercoagulable state, can be suspected, cannot be recommended.
In the central nervous system (CNS), the principal mediators of fast synaptic excitatory neurotransmission are L-glutamate-gated ion channels that are responsive to the glutamate agonist alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA). In each member of a family of four abundant AMPA receptors, a small segment preceding the predicted fourth transmembrane region has been shown to exist in two versions with different amino acid sequences. These modules, designated "flip" and "flop," are encoded by adjacent exons of the receptor genes and impart different pharmacological and kinetic properties on currents evoked by L-glutamate or AMPA, but not those evoked by kainate. For each receptor, the alternatively spliced messenger RNAs show distinct expression patterns in rat brain, particularly in the CA1 and CA3 fields of the hippocampus. These results identify a switch in the molecular and functional properties of glutamate receptors operated by alternative splicing.
Benzodiazepines are widely prescribed anxiolytics and anticonvulsants which bind with high affinity to sites on the GABAA receptor/Cl- channel complex and potentiate the effect of the neurotransmitter GABA (gamma-aminobutyric acid). The heterogeneity of benzodiazepine recognition sites in the central nervous system was revealed by studies showing different classes of GABAA receptor subunits (classes alpha, beta and gamma) and variant subunits in these classes, particularly in the alpha-class. Expression of recombinant subunits produces functional receptors; when certain alpha-variants are coexpressed with beta- and gamma-subunits the resulting receptors have pharmacological properties characteristic of GABAA-benzodiazepine type I or type II receptors. The alpha-variants are differentially expressed in the central nervous system and can be photoaffinity-labelled with benzodiazepines. Here we report a novel alpha-subunit (alpha 6) of cerebellar granule cells. We show that recombinant receptors composed of alpha 6, beta 2 and gamma 2 subunits bind with high affinity to the GABA agonist [3H]muscimol and the benzodiazepine [3H]Ro15-4513 but not the other benzodiazepines or beta-carboniles. The same distinctive pharmacology is observed with GABAA receptors from rat cerebellum immunoprecipitated by an antiserum specific for the alpha 6 subunit. We conclude that this alpha-subunit is part of a cerebellar receptor subtype, selective for Ro15-4513, an antagonist of alcohol-induced motor incoordination and ataxia.
Desmopressin (DDAVP) is an effective tool for increasing factor VIII (FVIII)/von Willebrand factor (vWF) in normal subjects and in patients with haemophilia A and von Willebrand's disease. There are a few studies utilizing DDAVP to increase the FVIII/vWF yield in plasmapheresis donors. In these studies, DDAVP was given either by intranasal administration or intravenous infusion. The aim of our pilot study was to investigate the subcutaneous (s.c.) injection of DDAVP in combination with double bag plasmapheresis. 8 donors with blood group A and 5 with O were given 0.4 micrograms/kg body weight DDAVP as a s.c. injection 30 min prior to the first donation. FVIII increased 3.7 and ristocetin cofactor 2.5 the initial value in the donors. In the plasma bags, a 3 (1st bag) and 3.5 (2nd bag) fold higher FVIII level was found, when compared with baseline levels. There was only a mild decrease of blood pressure, and serious adverse effects were not observed. Our data suggest that s.c. DDAVP may be more effective and especially suited for increasing FVIII/vWF yield in plasmapheresis donors.
Prothrombin complex concentrates (PCC) are frequently used for the treatment of acquired coagulation factor deficiencies. However, a major problem when using these preparations is their thrombogenic potential. Thus, the potency and tests for thrombogenicity were studied prospectively in 7 different PCC's. Human albumine and a factor IX concentrate served as controls. The potency of coagulation factors and inhibitors varied considerably, especially for proteins S and C. Two preparations exhibited high amidolytic activities in vitro. These activities could be quenched in part by the addition of hirudin or antithrombin III. Additionally, these two preparations caused more severe cardiopulmonary reactions in rabbits and an increase of fibrin split products. We conclude that the use of these preparations in patients, in whom an acquired protein C or S defect, or a hypercoagulable state, can be suspected, cannot be recommended.
Recombinant human erythropoietin (rh-EPO) has been shown to be effective in the treatment of renal anemia. Additionally, rh-EPO improves the hemostatic defect of uremia. On the other hand, a hypertensinogen effect and an increased risk for thrombosis have been reported in hemodialysis (HD) patients with rh-EPO. 20 HD patients in Homburg were recruited for a multicenter, placebo-controlled study (MF 3981), aiming to assess the risk of rh-EPO. Initially, 10 patients received rh-EPO at a dose of 3 x 80 U/kg body weight and week which was subsequently adjusted according to the hematocrit. After 6 months, the patients receiving placebo were changed to rh-EPO therapy. Clinical and laboratory data were obtained before, as well as 1, 3, 6 and 12 months after beginning of the study. Erythrocyte counts increased significantly in the rh-EPO group. Also, an increase of platelet count, fibrinogen and plasma viscosity was observed during rh-EPO. Tissue type plasminogen activator and plasminogen activator inhibitor as well as von-Willebrand-factor remained unchanged, although a shortening of the bleeding time was observed. Blood pressure and arterial blood flow were not influenced by rh-EPO.