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Biomedical subjects

M Zimmer

Publications and source records attributed to M Zimmer.

At least 127 records · Page 7Linked to original sources
PubMed1985

Relaxation of skinned coronary arteries depends on the relative concentrations of Ca2+, calmodulin and active cAMP-dependent protein kinase.

Maximally contracted detergent skinned coronary smooth muscle fibres are relaxed by lowering the concentration of free Ca2+. The extent and rate of relaxation depends on the concentration of free Ca2+ and calmodulin (CaM) suggesting that it is the Ca2+ X CaM complex which is responsible for maintaining tension. At a fixed concentration of Ca2+ and CaM further relaxation can be achieved by addition of the catalytic subunit of the cAMP-dependent protein kinase (cAMP-kinase). The extent as well as the relaxation rate depend on the concentration of cAMP-kinase (0.01-0.5 microM) and both are antagonized by high concentrations of Ca2+ and CaM. The Ca2+-requirement for obtaining half maximal concentration is shifted from 1.1 microM to 6.3 microM Ca2+ in the presence of 0.5 microM cAMP-kinase. These data indicate that the response of the contractile apparatus to a change in the free [Ca2+] can be modulated by cAMP-kinase at the level of the contractile proteins. It is further suggested that the tone of coronary smooth muscle is determined by the relative and not by the absolute concentrations of Ca2+, CaM and cAMP-kinase.

Animals↗
PubMed1984

Calmodulin antagonists inhibit activity of myosin light-chain kinase independent of calmodulin.

The calmodulin antagonists W-7, trifluoperazine and R24571 in vitro inhibited calmodulin-dependent and independent myosin light chain kinase activity with IC50 values of about 300 microM, 140 microM and 18 microM in the presence of 8 mg/ml myosin light chains. These IC50 values decreased to 15 microM, 6 microM and 2.5 microM when the concentration of myosin light chains was decreased to 0.4 mg/ml in the presence of saturating concentrations of calmodulin. Endogeneous tyrosine fluorescence of myosin light chain measured at 334 nm was quenched concentration dependently by trifluoperazine and R24571. In addition, fluorescence of W-7 measured at 370 nm was quenched concentration dependently by myosin light chains. The quenching of fluorescence which was independent of calcium, suggested that all three compounds bound to myosin light chain. The IC50 values for trifluoperazine obtained from fluorescence quench curves at different concentrations of myosin light chain were almost identical with those obtained under similar conditions from inhibition curves of myosin light chain kinase. These results indicate that 'calmodulin antagonists' inhibit the activity of myosin light chain kinase independent of calmodulin by binding to myosin light chain. The implication of this finding for the interpretation of results obtained in vivo by the use of 'calmodulin antagonists' is discussed.

Animals↗
PubMed1984

The effect of nucleotide analogs on cell-free gene expression.

The effects of the following pyrimidine nucleoside 5'-triphosphates: f5 UTP, br5 UTP, rTTP, s2 UTP, s4 UTP and s2 CTP on cell-free expression of the beta-galactosidase gene in lambda h80dlac DNA as well as the galactokinase gene in plasmid 01-14 were investigated. Only rTTP could substitute UTP in cell-free gene expression without restriction. Combinations of the other analogs with their respective natural congeners led to inhibition of gene expression. All analogs were found to inhibit transcription. Whereas br5 UTP and s4 UTP did not affect translation, mRNA containing s2 UMP or s2 CMP residues respectively was found to function poorly in translation. Only in the case of f5 UTP could ambiguitive behaviour be demonstrated. Whether mispairing of f5 UMP residues, responsible for this ambiguity takes place in transcription or in translation, could not be decided.

Cell-Free System↗
PubMed1984

Calmodulin activates bovine-cardiac myosin light-chain kinase by increasing the affinity for myosin light-chain 2.

The basic mechanism by which calmodulin activates bovine-cardiac muscle myosin light-chain kinase was investigated using highly purified preparations of mixed bovine-cardiac myosin light chains or isolated myosin light chain 2. The apparent contamination of these substrate proteins by calmodulin, as detected by activation of calmodulin-sensitive phosphodiesterase, was less than 4 parts/million and was undetectable by antibodies against calmodulin. The apparent KA for calmodulin was 2 nM and 20 nM in the presence of isolated myosin light-chain 2 and mixed myosin light chains, respectively. Purified bovine cardiac troponin C activated myosin light-chain kinase by about 10% at a concentration of 2 microM. Mixed myosin light chains were phosphorylated in the absence and presence of calmodulin and in the presence of calcium with a V of 11.1 and 11.0 mumol phosphate transferred min-1 (mg enzyme)-1, respectively. The apparent Km values for mixed myosin light chains were 8.0 and 0.35 mg/ml in the absence and presence of calmodulin, respectively. Similarly calmodulin lowered the Km value for isolated myosin light-chain 2 over 20-fold and increased the V value only about 1.5-fold. Activity observed in the absence of calmodulin was dependent on the presence of calcium and was suppressed by chelating free calcium either before or during a phosphorylation reaction. The apparent KA for calcium was 1.2 microM and 0.4 microM in the absence and presence of calmodulin. Activity in the absence of calmodulin was inhibited at very high concentrations of the 'specific' calmodulin antagonists W-7, trifluoperazine and R24571 with apparent IC50 values of 0.3 mM, 0.2 mM and 0.02 mM. Antibiotics raised against calmodulin suppressed completely the kinase activity in the presence of calmodulin but had no effect on the activity measured in its absence. These results suggest that calmodulin stimulates the activity of bovine-cardiac myosin light-chain kinase by increasing over 20-fold the affinity for its substrate myosin light-chain 2.

Animals↗
PubMed1984

Seminal plasmin, an antimicrobial protein from bull semen, inhibits gene expression in E. coli.

RNA synthesis in Escherichia coli was immediately inhibited after addition of seminal plasmin, an antimicrobial protein from bull semen. RNA synthesis progressively decreased within 12 min and then ceased completely. In contrast, protein synthesis was not affected within the first 12 min, but thereafter became progressively inhibited. Inhibition of RNA synthesis by seminal plasmin in E. coli interfered with induction of beta-galactosidase by isopropyl-beta-D-thiogalactoside (IPTG). This implied inhibition of beta-galactosidase mRNA synthesis by seminal plasmin in vivo. The sensitivities of total in vivo RNA synthesis and beta-galactosidase mRNA synthesis against seminal plasmin were found to be similar. Seminal plasmin had no effect on the uptake of the inducer IPTG by E. coli cells.

Animals↗
PubMed1984

The mitochondrial genome of the fission yeast Schizosaccharomyces pombe. 3. Gene mapping in strain EF1 (CBS 356) and analysis of hybrids between the strains EF1 and ade7-50h-.

The Schizosaccharomyces pombe strain EF1 (CBS 356) is haploid, prototrophic, respiratory competent, and of homothallic mating type. From restriction enzyme analysis the length of the mitochondrial genome is 17.3 kilobase pairs, which is in good agreement with the value of 17.1 kilobase pairs determined by electron microscopy. The mitochondrial genome of strain EF1 is thus about 2.3 kilobase pairs shorter than that of strain ade7-50h- (about 19.4 kilobase pairs). A restriction map was constructed for 11 enzymes: For most, but not all of them, the pattern is nearly identical to that of strain ade7-50h-. The genes for the large ribosomal RNA, the subunits 1, 2, and 3 of cytochrome c oxidase, subunits 6 and 9 of ATP synthetase, and cytochrome b were localized by hybridization with mitochondrial DNA probes from Saccharomyces cerevisiae. The gene order was found to be the same in both yeast strains. From Southern hybridization of strain ade7-50h- with nick-translated mitochondrial DNA from strain EF1 it is evident that strain EF1 does not possess the intron, which is present in the cytochrome b gene of Schizosaccharomyces pombe strain ade7-50h-. Crosses between strain ade7-50h- and EF1 demonstrate that both the nuclear and the mitochondrial genomes are able to recombine. The mitochondrial genomes of 2 out of 30 independently isolated hybrids between the two strains are described as the result of recombination between the two parental mitochondrial genomes.

Adenosine Triphosphatases↗
PubMed1984

Distribution of portal blood flow in the liver of the rat: a microsphere study.

We sought to determine whether streamlining of portal venous blood occurs in normal anaesthetized rats under basal conditions and with variations in hepatic blood flow. We catheterized the ileocolic vein and injected 15 micron microspheres labeled with 85Sr and 141Ce into this vein and into the spleen, respectively. The hepatic lobar distribution of microspheres was studied in a group under basal conditions and after hepatic blood flow was increased (infusions of nitroglycerin or glucagon) or decreased (infusion of vasopressin or ligation of the superior mesenteric artery); this blood flow was measured with a constant infusion of indocyanine green. Measured results (expressed as proportion of total liver counts per minute) were compared with a reference group in which the portal vein of rats had been partially ligated 10 days prior to study and in which similarly injected microspheres that lodged in the liver were assumed to be completely mixed with portal blood. No differences were seen within groups and between the reference and experimental groups. We conclude that under these experimental conditions, portal venous blood flow appears to be distributed homogeneously between hepatic lobes.

Animals↗
PubMed1983

Volume regulation and metabolism of suspended C6 glioma cells: an in vitro model to study cytotoxic brain edema.

The in vitro model presented provides an approach to study the nature of cell volume control as well as of swelling mechanisms under pathophysiological conditions. Pertinent parameters of cell volume control can be analyzed in isolation due to a virtually infinite extracellular environment precluding secondary effects of the suspended cells. Exposure of C6 glial cells to hypotonic medium was investigated as a model to study fundamental aspects of cell volume control. In confirmation of studies on other cell types glial cells suspended in hypotonic medium recover cell volume after transient swelling. Normalization of cell volume is associated with stimulation of respiration. Moreover, normalization of cell volume in hypotonic medium can be pharmacologically influenced. Addition of naftidrofuryl which enhances cellular O2-consumption led to acceleration of cell volume recovery. On the other hand, inhibition of Na+-K+-ATPase by ouabain did not prevent regulatory volume decrease ruling out a major role of the Na+-transport enzyme in this process. Contrary to hypotonic suspension, hypertonic exposure did not result in volume regulation during an observation period of 3 h. However, this may not necessarily exclude a capability of cell volume to normalize in hypertonic conditions as observed in vivo. Volume control of glial cells in abnormal osmotic medium may--on a cellular basis--reflect fundamental adaptive processes of central nervous tissue. Knowledge of the physiological and biochemical basis of cell volume control is not only of scientific interest but also of therapeutical significance in patients suffering from cytotoxic brain edema.

Brain Edema↗
PubMed1983

Assessment of motor blockade during epidural anesthesia.

Motor blockade during epidural anesthesia was assessed using dynamometry to measure the maximum force of plantar flexion, and the Bromage score method. In a randomized double-blind study, 40 orthopedic patients received one of the following four local anesthetics epidurally: 0.5% bupivacaine-HCl (n = 10), 0.5% bupivacaine-CO2 (n = 10), 1.0% etidocaine (n = 10), and 1.5% etidocaine (n = 10), all without addition of a vasoconstrictor. The decrease of force, measured by dynamometry, followed an e function. This function permits the description of motor blockade development using one single number, its half-life. This finding corresponds to the increase of motor nerve fiber blockade due to diffusion of the local anesthetic into the nerve. Dynamometry was more precise than the Bromage score in describing motor blockade. Both the Bromage score and dynamometry produced roughly comparable results of onset, rate of development, and maximum intensity of motor blockade. These parameters of motor blockade were superior after both etidocaine solutions compared to both bupivacaine solutions. Neither carbonization of bupivacaine nor increased concentration of etidocaine significantly improved motor blockade produced by these drugs. Dynamometry is a time consuming and costly method for accurate quantification of motor blockade during epidural anesthesia; the Bromage score is more practical under clinical considerations and provides useful information.

Adolescent↗
PubMed1982

The immunoperoxidase method for rapid diagnosis of Herpes simplex encephalitis (HSE) using touch preparations.

Ten rats were inoculated intracerebrally with Herpes simplex virus type I to study the possibility of establishing a rapid diagnosis of Herpes simplex encephalitis through examination of touch preparations of brain tissue stained by the immunoperoxidase method. All except one of the animals died within four days of the developing encephalitis. The surviving animal was killed on the fourth day. Touch preparations were shortly fixed in 4% buffered formalin, cold acetone, or alcohol. The indirect immunoperoxidase method was used to identify viral antigen. The authors found that formalin serves as a good fixative and sensitivity as well as specificity is high. The diagnosis could be made within 4 hours. The cellular morphology is retained. The reaction product is stable and background staining no problem. The results of this study imply to use this method also for rapid diagnosis of brain biopsy tissue in human infections.

Animals↗
PubMed1982

Assessment of affect in schizophrenia. Reliability data.

Pathological affect--impairment of facial expressiveness and demeanor--is a common manifestation of the schizophrenic process. In this study, empirically defined and statistically independent concepts of affectual range, mobility, appropriateness, and communicability were rated by 30 professionals and paraprofessionals from special videotapes of 22 chronic schizophrenics. Reliability of the ratings, measured by correlations among and across parameters and rater types, averaged r = .70, notably better than that of the same raters using traditional subjective clinical judgment (r = .54). There was little disagreement among psychiatrists, psychology interns, junior medical students, or social workers/nurses, nor were any of those groups significantly more reliable than the average for all raters. Significant trends toward low reliability of the appropriateness parameter are pointed out and possible clinical relevance is discussed.

Adolescent↗
PubMed1982

An interaction study between benoxaprofen and digoxin.

The influence of maintenance therapy with benoxaprofen, 600 mg daily, on digoxin steady-state plasma levels was studied in 12 patients with rheumatic disease. No difference could be shown during concomitant therapy or after withdrawal of benoxaprofen (p greater than 0.10 and p greater than 0.90, respectively). Toxic concentrations were not observed. There were no changes in renal function values.

Anti-Inflammatory Agents↗
PubMed1981

Herpes simplex encephalitis. A modified indirect immunoperoxidase technique for rapid diagnosis in paraffin-embedded tissue.

A modification of a reliable and simple method of the indirect immunoperoxidase technique was used to identify herpesvirus antigen in paraffin-embedded tissue of patients with herpes simplex encephalitis (HSE), as well as in rats and mice. So far we have studied five cases in humans and six in mice and rats. With preincubation, we increased antigenicity and accomplished high specificity. Brown reaction product was found mainly at the periphery of the areas of necrotizing encephalitis. Here it was present in different types of glial cells, as well as in neurons. In the animals, it was found in the leptomeninx in cells of the basal cortex and in the ependymal cells of the third ventricle and the cells around it. This method should be of great value for the study of human pathology because new drugs are available for treatment of HSE and a tissue diagnosis is necessary. It is also a useful technique for studying viral CNS infections in experimental animals.

Animals↗
PubMed1981

Cell-free expression of the beta-galactosidase gene: a model system to study the effects of nucleotide analogs on transcription-translation.

A cell-free system for the expression of the beta-galactosidase gene was employed to study the effects of the UTP and CTP analogs: s2UTP, s2CTP, f5UTP and rTTP on transcription-translation. From the analogs investigated, only rTTP turned out to be able to substitute UTP in the cell-free synthesis of beta-galactosidase. In case of the other analogs listed above, the incorporation of even a small fraction of analog into rRNA resulted in drastic inhibition of beta-galactosidase synthesis.

Escherichia coli↗
PubMed1977

In vivo labeling of red blood cells with 99mTc: a new approach to blood pool visualization.

A simple and rapid procedure for in vivo labeling of red blood cells (RBC) is presented. The labeling is done with two consecutive intravenous injections, first of "cold" stannous pyrophosphate (Sn-PYP) and then of 99mTc-pertechnetate. Experimentally, a lag time of 30 min between the two injections was found to result in a mean RBC labeling of greater than 95% during the first hour after pertechnetate injection. A total of 75 patients have been explored by scintillation camera imaging of brain, heart, great vessels, aortic bifurcation, testicles, and lower extremities using the technique outlined. High-quality images were obtained.

Erythrocytes↗