Search PubMed⌕ Search

Biomedical subjects

U Zimmermann

Publications and source records attributed to U Zimmermann.

At least 127 records · Page 7Linked to original sources
PubMed1995

Synaptophysin and GAP-43 proteins in efferent fibers of the inner ear during postnatal development.

A rearrangement of afferent and efferent fibers occurs in the postnatal development of the inner ear. Growth and synaptogenesis was explored during this critical period by immunohistochemically monitoring the expression of GAP-43 and synaptophysin. Both proteins were colocalized in efferent fibers beyond postnatal day 3 (pn3). Two distinct synaptophysin- and GAP-43-positive fibers innervated different parts of inner hair cells in the first and second postnatal weeks, respectively. GAP-43-positive efferents projecting to outer hair cells upregulated synaptophysin with base to apex gradient between postnatal day 5 and postnatal day 14. In efferents projecting to outer hair cells GAP-43 was downregulated about 6 days beyond synaptogenesis. In efferents projecting to inner hair cells, however, GAP-43 remained upregulated even beyond pn18, indicating continuous synapse replacement of this fiber type. Both proteins thus improved as excellent markers for growth and synaptogenesis of distinct postnatal efferent fibers.

Animals↗
PubMed1995

Does bright-light therapy influence autonomic heart-rate parameters?

30 inpatients suffering from major depression (DSM-III-R), who did not fulfill the criteria of seasonal affective disorder (SAD), were treated with either doxepin or amitripytyline as monotherapy and supportively with bright light for 14 days. From days 15 to 19, bright light was replaced by dim light. 18 drug-free control subjects underwent an analogous sequence of bright- and dim-light applications. Phototherapy was applied between 06:00 and 07:30. Heart-rate (HR) analysis was performed in the patients and control subjects before and after the 5th session of bright and dim lights, respectively. 12 patients (40%) experienced improvement of mood during bright-light therapy (group I) while 18 (60%) did not (group II). Patients of group I, who reached significantly higher scores in the seasonal pattern assessment questionnaire than patients of group II, showed an increase of the coefficient of HR variation (HRV) during deep breathing as well as an increment of the high-frequency (HF) peak of spectral analysis exclusively after the bright-light sessions. Patients of group II did not show a significant alteration of these parameters, neither under the conditions of bright-light treatment nor under dim light. The control subjects experienced an increment of the HF power exclusively after bright light. The results suggest that a distinct subgroup of patients with non-SAD major depression shows a more pronounced light-associated increment of parasympathetically controlled cardiac functions than the other depressed patients and the controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Effects of light and inhibitors of ATP-synthesis on the chloride carrier of the alga Valonia utricularis: is the carrier a chloride pump?

The effect of metabolic inhibitors, such as cyanide, antimycin A and azide was studied on the chloride transport system of the giant marine alga Valonia utricularis by using the charge pulse relaxation method. Two clearly defined voltage relaxations were resolved. The addition of 10-30 microM cyanide to the artificial sea water (ASW) bathing the algal cells increased the time constants of the slow voltage relaxation, tau 2, significantly when the algal cells were kept in the dark. The cyanide-effect reached a plateau value at 100-300 microM and was fully reversible when cyanide was removed from the ASW. Analysis of the charge pulse data in terms of the Läuger-model demonstrated that the translocation rates of the free, kS, and the charged carrier, kAS, decreased. The decrease of kS was more pronounced than that of kAS. 10 microM antimycin A and 3 mM azide had similar effects on the rate constants when the light was switched off. Upon illumination the cyanide- and antimycin A-, but not the azide-mediated effects disappeared. At concentrations higher than 1 mM cyanide caused a further, dramatic decrease of kS and kAS, while the surface concentration of the carrier molecules, N0, was not affected. This cyanide-effect was also reversible, but not light-dependent. Measurements of the ATP level showed that 3 mM cyanide reduced the ATP level by about 70% both under light and dark conditions. In the presence of 30 microM cyanide (or 10 microM antimycin A) the ATP level decreased by about 50%, but only in the dark. These results suggest two different effects of cyanide on the Cl(-)-carrier system: in the micromolar concentration range cyanide (and antimycin A) reduced predominantly the translocation of the free carrier by inhibition of ATP synthesis by oxidative phosphorylation, whereas in the millimolar concentration range cyanide apparently inhibits the translocation rates of both the free and charged carriers by its binding to the carrier. The results provide some evidence that the chloride transport of V. utricularis could be coupled to metabolic energy but it is an open question whether it is a pump or not.

Adenosine Triphosphate↗
PubMed1995

Adrenomedullin and calcitonin gene-related peptide interact with the same receptor in cultured human neuroblastoma SK-N-MC cells.

Inhibition of human [125I]calcitonin gene-related peptide-I ([125I]hCGRP-I) binding by human adrenomedullin (hADM), its N-terminal truncated fragments, CGRP and amylin, and cyclic AMP accumulation were examined in the human neuroblastoma cell line SK-N-MC. Binding of [125I]hCGRP-I (125 pM) was inhibited by hCGRP-I, hADM(1-52), hADM(13-52), and human amylin with IC50 of 0.32 +/- 0.06, 2.11 +/- 0.26, 3.45 +/- 0.54, and 68.8 +/- 6.6 nM, respectively. hCGRP-I(8-37) and hADM(22-52), which lack the N-terminal ring structure, inhibited [125I]hCGRP-I binding with IC50 of 2.35 +/- 0.45 and > 1000 nM. hCGRP-I, hADM(1-52), hADM(13-52) and human amylin stimulated cAMP accumulation with EC50 of 0.40 +/- 0.05, 18.1 +/- 2.6, 51.3 +/- 9.0 and 925 +/- 159 nM, respectively. hCGRP-I(8-37) (100 nM) antagonized hCGRP-I and hADM(1-52) stimulated cAMP production with the same Ki of 16.6 +/- 1.2 and 16.8 +/- 1.1 nM. In conclusion, human ADM, which is more distantly related to CGRP than amylin, interacts more potently with the CGRP receptor in SK-N-MC cells than amylin. The N-terminal ring structure of hADM, unlike that of hCGRP, is essential for binding to the CGRP receptor. Coupling of hADM binding to cAMP stimulation is less efficient than for hCGRP-I and is reduced by deletion of the unique 12 amino acid sequence of hADM N-terminal to the ring structure.

Adrenomedullin↗
PubMed1995

Immunological identification of candidate proteins involved in regulating active shape changes of outer hair cells.

By employing immunological methods, it has been demonstrated that myosin, myosin light chain (MLC) and myosin light chain kinase (MLCK) proteins in outer hair cells (OHC) are immunologically different from isoforms in platelets, smooth muscle and heart muscle, and are probably more related to isoforms found in red blood cells (RBC). Moreover, proteins related to band 3 protein (b3p) and protein 4.1 (p 4.1), ankyrin as well as fodrin and spectrin, but not glycophorin, have been identified in isolated OHCs. Both OHCs and RBC differ from other motile non-muscle cells in their lack of smooth muscle isoforms of actin, their common high levels of spectrin-, ankyrin- and band 3-like proteins, as well as the expression of the 80 kDa protein 4.1 isoform. The data support the notion that motility of OHC may be based upon regulation of the b3p/p 4.1/ankyrin complex, and thus may be reminiscent to the active shape changes in RBC.

Actins↗
PubMed1995

Quantitative NMR microscopy on intact plants.

Quantitative high resolution images on intact young maize plants were acquired by using magnetization-prepared NMR microscopy. Although the spatial resolution is low compared with that of light microscopy, the calculated spin density and T1 maps exhibit contrasts that are in excellent agreement with photomicrographic images. The T2 map gives image contrasts that are not visible in a usual light microscopic image. The diffusion images show an anisotropic behavior of the water self-diffusion coefficient in the vascular bundles, which can be understood by the cell morphology in this plant section. This work demonstrates that quantitative imaging on intact plant systems is possible and that long total acquisition times are no obstacle. Furthermore, the different single parameter maps give a better insight into the morphology of plants under in vivo conditions.

Magnetic Resonance Spectroscopy↗
PubMed1995

A simple device for serial blood collection in human subjects and animals.

A simple system for the continuos withdrawal of blood and the serial collection of blood samples in human subjects and experimental animals is described. It consists of heparin-coated tubing, a connector attached to an indwelling cannula that allows flushing of the i.v. catheter, a peristaltic pump and a fraction collector and an alarm system which is activated when blood flow through the system is interrupted. It can be assembled from parts available in every laboratory or hospital.

Animals↗
PubMed1995

Caloric evoked motile responses of mammalian vestibular sensory cells.

Evokation of caloric nystagmus in microgravity argues against thermal convection as a sufficient explanation for a caloric nystagmic response. By contrast, caloric nystagmus observed in weightlessness suggests a gravity independent mechanism. Here we demonstrate that direct caloric stimulation of isolated living vestibular hair cells from the guinea pig evoked mechanical responses of the sensory cells. Heating of the mechanoreceptor cells from 37 degrees C to 42 degrees C resulted in elongation cooling of the cells from 37 degrees C to 30 degrees C induced shortening of vestibular hair cells. The observed mechanism might contribute to the caloric evokation of a nystagmus both on earth and in orbit.

Animals↗
PubMed1995

Efficient immortalization of rheumatoid synovial tissue B-lymphocytes. A comparison between the techniques of electric field-induced and PEG fusion.

In this study, B-cells isolated from rheumatoid synovial tissue were immortalized, without prior in vitro stimulation, by means of electric-field induced fusion and conventional PEG fusion in order to compare the efficiency of these methods. Two myeloma cell lines were used as fusion partners, the murine myeloma Ag8 and the murine-human heteromyeloma HAB-1. The results of seven fusion experiments performed simultaneously with identical cell populations showed that fusion frequencies obtained by electrofusion were 4 to 35 times higher than by the PEG fusion technique. The morphological and immunohistochemical evaluation of synovial tissues used for fusion showed that only tissues exhibiting a follicular distribution of B-cells with a high percentage of CD 22-positive lymphocytes gave rise to high fusion yields and produced B-cell clones, whereas synovial tissues with the same percentage of plasma cells but lower percentages of CD 22 lymphocytes yielded very low fusion rates. In conclusion, electrofusion is more efficient for immortalizing small amounts of synovial tissue B-lymphocytes than PEG fusion, since high fusion frequencies could be obtained by this technique without the need for prior in vitro stimulation. Synovial tissue exhibiting a follicular distribution of B-lymphocytes with high percentages of CD 22-positive lymphocytes gave rise to high hybridoma yields and therefore an ideal source of human rheumatoid B-cell clones.

Animals↗
PubMed1995

Generation of a human monoclonal antibody to hepatitis C virus, JRA1 by activation of peripheral blood lymphocytes and hypo-osmolar electrofusion.

We have generated a human monoclonal antibody with binding specificity for hepatitis C virus (HCV)-specific peptides using peripheral blood lymphocytes isolated from a HCV antibody positive patient. The B-lymphocytes were stimulated with lipopolysaccharide (LPS) for 72 hours prior to the fusion. A recently described high efficiency hypo-osmolar electrofusion technique was employed, allowing generation of a large number of human hybridomas. The hybridomas were screened for human immunoglobulin and HCV-specific peptide binding by EIA. A single HCV-positive clone, JRA1, was detected and sub-cloned. Isotype analysis showed it to secrete an IgM lambda monoclonal antibody. The antibody was positive on both first and second generation HCV antibody analysis. This study confirms that viable pathogen-specific B-cells may be recovered from the peripheral blood. Although such cells are likely to be relatively uncommon in the circulating B-cell pool, they may be successfully immortalized by high efficiency electrofusion techniques. This technique might be valuable for the generation of human monoclonal antibodies with specificity for other human pathogens.

Adult↗
PubMed1995

[Glutathione-SH as protection from cytotoxic side-effects of gentamycin. Studies with isolated outer hair cells].

Hearing loss with irreversible cochlear damage can be the consequence of aminoglycoside treatment. The present investigation found that metabolized gentamicin (mG) but not native gentamicin (G) was cytotoxic for isolated guinea pig outer hair cells (OHC). Glutathione-SH (GSH), a detoxifying agent, completely inhibited the cytotoxic effects of mG. Using FURA-2 fluorescence, both G and mG were found to reduce intracellular Ca2+ concentrations in unstimulated OHC and inhibit increases in Ca2+ concentrations during K(+)-induced depolarization. GSH did not interfere with G and mG effects on intracellular Ca2+ concentrations. In unstimulated OHC, mG but not G induced pathological OHC depolarization, indicating opening of transduction channels to allow influx of K+ ions. GSH inhibited this effect, suggesting that GSH probably inhibits mG-induced pathological opening of transduction channels. In so doing GSH may inhibit ototoxic side-effects of mG.

Animals↗
PubMed1994

Acute gentamicin ototoxicity in cochlear outer hair cells of the guinea pig.

The acute effects of the aminoglycoside antibiotics gentamicin on isolated cochlear outer hair cells (OHC) was investigated by whole-cell patch-clamp and measurements of the intracellular potassium level by means of the potassium-sensitive dye PBFI. In addition, the accompanying length changes of OHC are described. It could be shown that gentamicin at different concentrations reversibly induces a hyperpolarization by about 5-10 mV, potassium outflow from the cytoplasm (by about 22 mM) and a cellular elongation (by about 10%). It is suggested that these effects are the result of an interaction between gentamicin and the cochlear transduction channels in OHC as suggested earlier. These acute effects are distinctly different from the chronic gentamicin effects which are based on the metabolization of the antibiotics to cause the death of the OHC by interaction with the phosphoinositide signalling cascade.

Animals↗
PubMed1994

Effect of electric field pulses on the viability and on the membrane-bound immunoglobulins of LPS-activated murine B-lymphocytes: correlation with the cell cycle.

The effects of microsecond electropulses (1-5 kV/cm) on the viability of murine B lymphocytes and on their binding of antibodies by surface immunoglobulin (Ig) were studied in relation to the cell cycle. Before electropulsing, cultures given 48 h mitogenic stimulation showed at least two cell subpopulations, which were distinguishable by their levels of surface-Ig expression as assessed with FITC-labelled antibodies against mouse Ig. The immunofluorescence intensity of cells in S and G2/M phases was higher than that of G0/G1 cells. After exposure of the mitogen-stimulated lymphocytes to three exponentially decaying (time constant tau = 5-40 microseconds) electric field pulses, dye exclusion assay showed that pulsing at 1 or 2 kV/cm (at 4 degrees C or 20 degrees C) did not cause permeabilization. Field strengths of 3, 4, or 5 kV/cm resulted in 20%, 45%, or 70% of dye-permeable cells, respectively, if the pulsed cells were transferred to phosphate-buffered saline on ice for 30 min. Incubation in full medium at 37 degrees C for 30 min ("resealing") significantly decreased the percentage of permeabilized cells. Electropulsed G0/G1 cells were not only more resistant to direct electric exposure (tolerated higher field strengths) than S + G2/M cells but also responded better to resealing. The surface Ig of lymphocytes pulsed at higher fields and low temperature (4 or 5 kV/cm, tau = 5 microseconds, three pulses, 4 degrees C) was less easily immunostained than in controls or in cells pulsed at 2 kV/cm or less. At 5 kV/cm those cells that were not permeabilized showed a greater reduction in immunostaining, especially if resealed.

Animals↗
PubMed1994

Production of purified alginates suitable for use in immunoisolated transplantation.

Alginate is used as a matrix for immunoisolation of cells and tissues in vivo. We have demonstrated previously that commercial alginates contain various fractions of mitogenic impurities and that they can be removed by free flow electrophoresis. The use of purified material is a necessity in order to reveal the parameters that control biocompatibility of the implanted material (such as stability, size, surface charge and curvature, etc.). In this study, we present a protocol for the chemical purification of alginates on a large-scale. Beads made from alginates purified by this multi-step chemical extraction procedure did not induce a significant foreign body reaction when implanted for 3 weeks either intraperitoneally or beneath the kidney capsule of Lewis or non-diabetic BB/Gi rats.

Alginates↗