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Biomedical subjects

R Neuhaus

Publications and source records attributed to R Neuhaus.

At least 19 recordsLinked to original sources
PubMed1992

Inhibition of protein kinases in rat pheochromocytoma (PC12) cells promotes morphological differentiation and down-regulates ion channel expression.

We have studied morphological differentiation and ion channel expression in PC12 cells under different culture conditions. Differentiation mediated by nerve growth factor (NGF) was compared with that induced by depletion and inhibition of protein kinases (phorbol ester beta-PMA plus staurosporine). Morphological differentiation was similar under both conditions. However, ion channel densities, studied by means of the patch-clamp technique, were enhanced by NGF and reduced by beta-PMA+staurosporine. Similar changes were also observed for omega-conotoxin-sensitive Ca2+ channels by measuring radioligand binding. The decrease in Ca2+ channel density, after treatment of the cells with beta-PMA+staurosporine, resulted in a reduced increase in the intracellular Ca2+ concentration during K+ depolarization. We conclude that morphological differentiation, but not ion channel expression, can occur during depression of protein kinase activities in PC12 cells.

Alkaloids↗
PubMed1992

Inhibition of membrane currents and rises of intracellular Ca2+ in PC12 cells by CGS 9343B, a calmodulin inhibitor.

The calmodulin inhibitor 1,3-dihydro-1-[1-((4-methyl-4H,6H-pyrrolo[1,2-a]-[4,1]benzoxazepin - 4-yl)methyl)-4-piperidinyl]-2H-benzimidazol-2-one maleate (CGS 9343B) caused a reversible block of voltage-activated Ca2+, Na+, and K+ currents in differentiated rat pheochromocytoma (PC12) cells. The drug also inhibited nicotinic acetylcholine receptor (nAChR) channel currents but not inward currents evoked by extracellular ATP. Depolarization-induced intracellular Ca2+ transients were almost completely inhibited in growth cones and cell bodies by CGS 9343B. Our results suggest actions of CGS 9343B on ion fluxes unrelated to calmodulin inhibition.

Adenosine Triphosphate↗
PubMed1992

Hepatitis C virus reinfection in allografts after orthotopic liver transplantation.

From September 1988 to May 1991, 160 orthotopic liver transplantations were performed in our hospital. Twenty-four patients had end-stage cirrhosis caused by chronic non-A, non-B hepatitis. Antibodies against hepatitis C virus were documented before and after orthotopic liver transplantation in 13 patients. Studies using the polymerase chain reaction demonstrated hepatitis C virus RNA in the serum and liver tissue of 17 patients (10 of whom tested positive for hepatitis C virus antibodies) before orthotopic liver transplantation. Tissue samples taken from liver grafts during the operation were hepatitis C virus RNA negative in every case. Ten of these 17 patients had positive hepatitis C virus RNA findings in serum and liver biopsy specimens within the first month after surgery. One patient died of Mucor sepsis 2 mo after orthotopic liver transplantation. Another patient died of multi-organ failure 3 mo after a retransplantation. Two patients underwent retransplantation for graft rejection at 2 and 3 mo, respectively. One year after orthotopic liver transplantation, hepatitis C virus RNA was demonstrated in allograft biopsy specimens in 13 of 15 patients. Two patients remained hepatitis C virus RNA negative in repeated biopsies up to 12 mo. Mild portal and lobular hepatitis developed within 6 months of orthotopic liver transplantation in four patients and within 1 yr in five additional patients. The data suggest that persistent hepatitis C virus reinfects the allograft in most cases, but the risk of acute organ damage caused by hepatitis C virus reinfection is low.

Adult↗
PubMed1992

Activation of different pathways for calcium elevation by bradykinin and ATP in rat pheochromocytoma (PC 12) cells.

We have studied the pathways by which extracellular bradykinin and adenosine 5'-triphosphate (ATP) elicit changes in intracellular free calcium ([Ca2+]i) in nerve-growth-factor(NGF)- treated rat pheochromocytoma (PC 12) cells. Both substances caused a significant rise in [Ca2+]i as assessed by fura-2 based microfluorimetry. The bradykinin-induced response consisted of an initial Ca2+ mobilization from an internal pool followed by a sustained increase in [Ca2+]i, which was due to activation of a small inward current. The initial response always started at a localized site opposite to the cell nucleus. The inward current was partially carried by Ca2+ and began with a time lag of about 4 s after the start of the initial transient signal. Stepwise hyperpolarization of the plasma membrane, after activation of the inward current by bradykinin, caused a simultaneous increase in current amplitude and in [Ca2+]i, due to an increase in the driving force for Ca2+ influx. With ATP as an agonist the onset of inward current coincided with an increase in [Ca2+]i. Inward current and [Ca2+]i were enhanced during hyperpolarizing steps indicating a substantial Ca2+ influx through ATP-activated channels. No release of Ca2+ from internal stores, but a large Na+ inward current, was observed in Ca(2+)-free external solution after addition of ATP. While the bradykinin-induced responses were much more pronounced in cell bodies than in growth cones, the ATP effects were somewhat variable in cell bodies and more homogeneous in growth cones.

Adenosine Triphosphate↗
PubMed1992

[Orthotopic liver transplantation in hepatic cirrhosis: on the problem of infection of the transplant with persistent hepatitis viruses].

269 orthotopic liver transplantations (OLT) were performed in 253 patients at our institution from September 1988 to May 1992. 121 patients had end-stage cirrhosis secondary to viral hepatitis type B, delta, or type non-A non-B and C respectively. Reinfection of the graft by persistent viruses is a potential complication in these cases. Passive immunization with anti-HBs hyperimmunoglobulin (HIg) can prevent clinically relevant reinfection of the graft in patients with hepatitis B virus (HBV) infection and low replication rates. Patients with high replication rates will rarely benefit from OLT. Patients with hepatitis delta virus (HDV) infection usually experience HDV reinfection of the graft with subsequent chronic hepatitis although prophylaxis with anti-HBs-HIg was performed. Treatment with interferon alpha had no apparent effect on the incidence of graft reinfection with HBV in this series, but the replication rate of HDV was reduced. Persistent hepatitis C viruses (HCV) usually infect the graft; this was demonstrated in 17 patients by means of the polymerase chain reaction. HCV infection usually causes a mild form of acute hepatitis with transition to a chronic course. Therefore the significance of persistent viral infection lies in the potential for chronic hepatitis in the transplanted organ rather than in the danger of acute injury of the allograft.

Biopsy, Needle↗
PubMed1991

[Randomized, double-blind comparison of isosorbide-5-mononitrate and delayed-action nifedipine in patients with stable exertional angina. Multicenter Study Group].

The therapeutic effects of IS-5-MN and s.r. nifedipine were investigated in this double-blind, randomized, group-comparative, multicenter study over 2 weeks, in 251 patients with stable reproducible exercise-induced angina. After 2 weeks' treatment with IS-5-MN 20 mg b.i.d. or t.i.d., 61% of the patients were responders who showed an increase in total exercise time (to moderately severe angina) of greater than or equal to 20% in comparison with placebo in the run-in phase. The corresponding responder rate after s.r. nifedipine 20 mg b.i.d. or 40 mg b.i.d. was 53%. Both IS-5-MN and s.r. nifedipine significantly increased the total exercise time, the time to angina onset and to greater than or equal to 1 mm ST-depression, and significantly reduced the rate pressure product and the ST-segment depression at peak exercise in comparison with placebo in the run-in phase. The improvement in quality of life as indicated by the reduction in anginal episodes and intake of short-acting nitrates was comparable with both drugs. The pattern and incidence of all AEs were as expected in the two active treatment groups. The daily treatment costs for a 20 mg b.i.d. dosing regimen for both drugs in the Federal Republic of Germany was 64% higher for s.r. nifedipine than with IS-5-MN.

Angina Pectoris↗
PubMed1991

Follow-up of recurrent hepatitis B and delta infection in liver allograft recipients after treatment with recombinant interferon-alpha.

Reinfection of the graft with hepatitis B virus (HBV) and hepatitis delta virus (HDV) is a potential complication in patients undergoing orthotopic liver transplantation (OLT). Therefore, we added recombinant interferon-alpha (rIFNa) to the standard immunosuppressive regimen in 11 patients who received transplants following liver failure attributed to cirrhosis B (n = 10, with HDV co-infection in four cases) or fulminant hepatitis B (n = 1). Patients were treated with rIFNa for periods ranging from 2 to 3 months between the first and the 13th month after OLT. All patients received immunosuppressive treatment with low-dose corticosteroids, azathioprine and cyclosporine. Anti-HBs hyperimmune globulin was also administered. None of the patients showed evidence of severe allograft rejection. Seven patients suffered HBV reinfection of the graft with histological signs of acute hepatitis in five cases and transition to chronic hepatitis in one patient. Treatment with rIFNa did not prevent or reduce HBV replication. Reinfection of the graft with HDV was demonstrated by PCR in four patients co-infected with HDV. During treatment with rIFNa liver biopsy specimens from three reinfected patients were transiently negative for HDV antigen but not for HDV RNA, and the sera from two patients were transiently negative for HDV RNA. The data indicate that rIFNa can reduce HDV replication in reinfected liver allografts.

Adrenal Cortex Hormones↗
PubMed1991

Regulation of bradykinin- and ATP-activated Ca(2+)-permeable channels in rat pheochromocytoma (PC12) cells.

Membrane currents activated by bradykinin (500 nM) and by extracellular ATP (50 microM) were studied in voltage-clamped, NGF-treated rat pheochromocytoma (PC12) cells. Under quasiphysiological ionic conditions, both substances caused an outward current due to opening of Ca(2+)-activated K+ channels. Bradykinin caused an additional inward current that could be studied after blockade by internal Cs+ of the initial transient outward current. The inward current became larger when the extracellular Ca2+ concentration was increased. Neither inositol-1,4,5-trisphosphate, dioctanoylglycerol, phorbol 12-myristat 13-acetate, forskolin, GTP, GTP-gamma-S, or pretreatment with pertussis toxin affected this current component. Increasing the internal Ca buffer concentration [EGTA or bis-(o-aminophenoxy)-ethane-N,N,N',N'-tetra-acetic acid] from 1 to 10 mM had no effect on the inward current as long as the free [Ca2+]i was kept constant. However, it was modulated by the resting free [Ca2+]i. Elevation of [Ca2+]i from nominally 0 to 60 or to 180 nM increased the bradykinin-induced average peak current density from 0.14 to 1.04 or to 2.29 pA/pF, respectively. This regulation may depend on a calmodulin-dependent pathway, since CGS 9343B, a calmodulin inhibitor, blocked the effect of elevated [Ca2+]i. With ATP as an agonist, outward current was preceded by a large inward current that was partially blocked by extracellular Ca2+ in the millimolar range. Extracellular Ca2+ was also found to reduce the single-channel conductance estimated from outside-out patches treated with ATP.

Adenosine Triphosphate↗
PubMed1990

Changes in the conductance of the neuronal nicotinic acetylcholine receptor channel induced by magnesium.

We have investigated the effect of magnesium on the single-channel conductance of neuronal nicotinic acetylcholine receptors (nAChRs) in nerve growth-factor treated rat pheochromocytoma (PC12) cells. The patch-clamp technique was used to record single-channel currents from cell attached and excised, outside-out patches in the presence of various internal and external Mg2+ concentrations. Mg2+ reduced the single-channel conductance in a concentration-dependent manner with an IC50 of 9.2 mM for external Mg2+ (inward conductance) and 0.69 mM for external Mg2+ (outward conductance). Both estimated and measured conductances for divalent cation-free CsCl solutions were around 60 pS. We also find that divalent cations are not involved in the inward rectification of whole-cell ACh-induced currents in these cells. Our results imply that the amino acids screened by divalent cations sense electric fields only weakly and are presumably outside the lipid bilayer. They also suggest that the density and the number of charges (or both) differ on either side of the ion pore.

Acetylcholine↗
PubMed1990

The effects of dihydropyridine derivatives on force and Ca2+ current in frog skeletal muscle fibres.

1. The effects of dihydropyridine (DHP) derivatives on current through the slow Ca2+ channel and on isometric force were investigated in short toe muscle fibres of the frog (Rana temporaria). The experiments were performed under voltage-clamp conditions with two flexible internal microelectrodes. 2. The non-chiral DHP derivative nifedipine was used mainly because it allowed control measurements after the inactivation of the drug with UV light. 3. In a TEA sulphate solution containing 4 mM-free Ca2+, nifedipine (1 microM) caused no relevant alterations in the time course of successive contractures induced by depolarizing steps to 0 mV of 3.5 min duration followed by a restoration time at -90 mV of 1.5 min. 4. When external Ca2+ was replaced by Mg2+, nifedipine caused a dose-dependent shortening of contractures. The effect reached saturation at about 50% of shortening with 1-5 microM-nifedipine. In the absence of divalent cations and with Na+ being the only metallic cation in the solution, shortening became more pronounced and maximum force decreased. 5. The application of 2 microM-nifedipine to a Ca2(+)-free, Mg2(+)-containing solution shifted the voltage dependence of force inactivation by 5-10 mV to more negative potentials. 6. Force activation was facilitated by nifedipine. In the presence of 2 microM-nifedipine in a Ca2(+)-containing solution, threshold potentials (rheobase) as negative as -75 mV were measured under microscopical observation. UV irradiation shifted the threshold potential back to the normal value of about -50 mV. 7. The slow Ca2+ inward current was blocked almost completely by approximately 5 microM-nifedipine, even when induced from negative holding potentials (-90 to -120 mV), i.e. under conditions where normal phasic contractures could still be observed. 8. Nifedipine (0.8 microM) caused a shift of the voltage dependence of current inactivation (V0.5) by 4 mV from -26 to -30 mV and at negative holding potentials (-90 mV), a reduction of maximum current by 35%. 9. The voltage dependence of current activation was not significantly altered by nifedipine (2 microM). 10. It is assumed that nifedipine binds with low affinity to the resting state of the DHP receptor (KD 0.8 microM) and with high affinity (KD 1 nM) to the inactivated and the active state (or to a precursor of this state). These assumptions could explain the relatively small shift of the inactivation curves (points 5 and 8) to more negative potentials and the facilitation of force activation (point 6).

Animals↗
PubMed1986

Comparative clinical trial of isosorbide 5-mononitrate and sustained-release isosorbide dinitrate in ischaemic heart disease.

A double-blind crossover study, with placebo periods preceding each active treatment, was carried out in 29 patients with ischaemic heart disease to compare the clinical efficacy of isosorbide 5-mononitrate 40 mg twice daily and the same regimen of sustained-release isosorbide dinitrate. Assessment was by bicycle ergometry, symptomatology and blood nitrate level measurements. After 2-weeks' therapy with isosorbide 5-mononitrate, mean ST segment depression at the highest comparable exercise level for each patient was reduced by 32.5% (p less than 0.01), the mean maximum exercise level was increased from 87 to 102 Watts (17.8%, p less than 0.01), and mean work capacity was increased from 581 Watts-minutes to 783 Watts-minutes (34.6%, p less than 0.01). With sustained-release isosorbide dinitrate, ST segment depression was reduced by 16.5% (p less than 0.05); maximum exercise level showed only a small non-significant increase, from 89 to 97 Watts (8.6%), but work capacity increased (p less than 0.05) from 593 Watts-minutes to 705 Watts-minutes (18.9%). There was no significant difference between drugs as regards ST segment reduction but a slight difference in favour of isosorbide 5-mononitrate (p less than 0.05) in terms of maximal exercise level and work capacity. Both drugs resulted in very small reductions in blood pressure (p less than 0.001 for systolic with isosorbide 5-mononitrate; p less than 0.01 for systolic and p less than 0.05 for diastolic with sustained-release isosorbide dinitrate). Heart rate and rate-pressure product changed little with either drug.(ABSTRACT TRUNCATED AT 250 WORDS)

Angina Pectoris↗
PubMed1978

[Risk of general anaesthesia (author's transl)].

95 506 patients who received general anesthesia during the period of 1964--1977 were studied. The account of all actual or possible life threatening complications during the anesthesia is given: oedema of the glottis, air embolism, accidental injection of the wrong drug, respiratory insufficiency, hypoxia, pulmonary oedema, airway occlusion by the cuff, vomiting and aspiration, anaphylactoid reaction, death within 24 hours, death on the table. Deaths not attributable to anaesthesia are listed separately. We have found that in one of every 139 anaesthetics given there was a life threatening complication to the patient. In every 197th anaesthetic there was a clear connection with the anaesthetic technique used. In contrast with the great number of near fatal complications the rate of irreversible damage or mortality connected with general anaesthesia was low.

Adolescent↗