Search PubMed⌕ Search

Biomedical subjects

C Richter

Publications and source records attributed to C Richter.

234 records · Page 13Linked to original sources
PubMed1976

[Loss of blood and carbon tetrachloride poisoning].

In rats the induced enhancement of glutamic-pyruvic transaminase and leucine aminopeptidase activity in plasma to 5.2 mMol CC14/kg (per 05) is potentiated after repeated drawing of blood. The DL50 of CC14 following oral application in rats after loss of blood is reduced significant comparatively to controls and to animals with increased content of haemoglobin in blood.

Alanine Transaminase↗
PubMed1973

Synthesis of bacteriophage and host DNA in toluene-treated cells prepared from T4-infected Escherichia coli: role of bacteriophage gene D2a.

We investigated the synthesis of DNA in toluene-treated cells prepared from Escherichia coli infected with bacteriophage T4. If the phage carry certain rII deletion mutations, those which extend into the nearby D2a region, the following results are obtained: (i) phage DNA synthesis occurs unless the phage carries certain DNA-negative mutations; and (ii) host DNA synthesis occurs even though the phage infection has already resulted in the cessation of host DNA synthesis in vivo. The latter result indicates that the phage-induced cessation of host DNA synthesis is not due to an irreversible inactivation of an essential component of the replication apparatus. If the phage are D2a(+), host DNA synthesis in toluene-treated infected cells is markedly reduced; phage DNA synthesis is probably also reduced somewhat. These D2a effects, considered along with our earlier work, suggest that a D2a-controlled nuclease, specific for cytosine-containing DNA, is active in toluene-treated cells.

Coliphages↗
PubMedDate not supplied

Biophysical consequences of lipid peroxidation in membranes.

This article reviews the biophysical consequences of lipid peroxidation in biological membranes. In the lipid domain, lipid peroxidation (a) causes an increase in the order and "viscosity" of the membrane bilayer, particularly at the depth around acyl-carbon 12, (b) changes the thermotropic phase behaviour, (c) decreases the electrical resistance, and (d) facilitates phospholipid exchange between the two monolayers. Upon lipid peroxidation membrane proteins are crosslinked, and their rotational and lateral mobility is decreased. Studies with microsomal cytochrome P-450 suggest protein aggregation but not the increased lipid order to be the major cause of protein immobilization in peroxidized membranes.

Lipid Bilayers↗
PubMedDate not supplied

Hyperhomocysteinaemia and adverse events complicating coronary catheter interventions.

BACKGROUND: Since hyperhomocysteinaemia is an independent risk factor for development of atherosclerosis as well as for arterial and venous thrombosis we investigated whether elevated homocysteine levels are associated with procedural excess risk which complicates coronary interventions including coronary angioplasty (PTCA), stenting, or directional coronary atherectomy (DCA). DESIGN: Consecutive cases receiving coronary catheter interventions. SETTING: Tertiary referral centre in Germany. METHODS: Fasting total plasma homocysteine levels (tHcy) were determined in 648 consecutive coronary artery disease patients who underwent catheter interventions (272 PTCA, 102 DCA, and 274 stenting). Hyperhomocysteinaemia was defined as tHcy >/=15 micromol/l. The patients were investigated for a 30-day composite endpoint, including need for target-vessel revascularization, myocardial infarction, and death. RESULTS: Among the 648 patients, 78 (12%) demonstrated elevated tHcy levels. The composite endpoint occurred in 41 patients (6.3%). For the entire intervention group there was no evidence that hyperhomocysteinaemia was associated with excess procedural risk (odds ratio [OR]: 1.27; 95% confidence interval [CI]=0.52 to -3.13; P=0.62). In further analyses according to device, hyperhomocysteinaemia also failed to predict complications in the device related subgroups. CONCLUSION: The results indicate that hyperhomocysteinaemia is not a major risk factor for 30-day adverse events complicating PTCA, DCA, or stenting.

Aged↗
PubMedDate not supplied

t-Butylhydroperoxide and gliotoxin stimulate Ca2+ release from rat skeletal muscle mitochondria.

Rat liver mitochondria have a specific Ca2+ release pathway which operates when NAD+ is hydrolysed to nicotinamide and ADPribose. NAD+ hydrolysis is Ca(2+)-dependent and inhibited by cyclosporine A (CSA). Mitochondrial Ca2+ release can be activated by the prooxidant t-butylhydroperoxide (tbh) or by gliotoxin (GT), a fungal metabolite of the epipolythiodioxopiperazine group. Tbh oxidizes NADH to NAD+ through an enzyme cascade consisting of glutathione peroxidase, glutathione reductase, and the energy linked transhydrogenase, whereas GT oxidizes some vicinal thiols to the disulfide form, a prerequisite for NAD+ hydrolysis. We report now that rat skeletal muscle mitochondria also contain a specific Ca2+ release pathway activated by both tbh and GT. Ca2+ release increases with the mitochondrial Ca2+ load, is completely inhibited in the presence of CSA, and is paralleled by pyridine nucleotide oxidation. In the presence of tbh and GT, mitochondria do not lose their membrane potential and do not swell, provided continuous release and re-uptake of Ca2+ ('Ca2+ cycling') is prevented. These data support the notion that both tbh- and GT-induced Ca2+ release are not the consequence of an unspecific increase of the inner membrane permeability ('pore' formation). Tbh induces Ca2+ release from rat skeletal muscle less efficiently than from liver mitochondria indicating that the coupling between tbh and NADH oxidation is much weaker in skeletal muscle mitochondria. This conclusion is corroborated by a much lower glutathione peroxidase activity in skeletal muscle than in liver mitochondria. The prooxidant-dependent pathway promotes, under drastic conditions (high mitochondrial Ca2+ loads and high tbh concentrations), Ca2+ release to about the same extent and rate as the Na+/Ca2+ exchanger. This renders the prooxidant-dependent pathway relevant in the pathophysiology of mitochondrial myopathies where its activation by an increased generation of reactive oxygen species probably results in excessive Ca2+ cycling and damage to mitochondria.

Animals↗
PubMedDate not supplied

Mitochondrial nitric oxide synthase, oxidative stress and apoptosis.

Nitric oxide (NO) exerts a wide range of its biological properties via its interaction with mitochondria. By competing with O(2), physiologically relevant concentrations of NO reversibly inhibit cytochrome oxidase and decrease O(2) consumption, in a manner resembling a pharmacological competitive antagonism. The inhibition regulates many cellular functions, by e.g., regulating the synthesis of ATP and the formation of mitochondrial transmembrane potential (Delta Psi). NO regulates the oxygen consumption of both the NO-producing and the neighboring cells; thus, it can serve as autoregulator and paracrine modulator of the respiration. On the other hand, NO reacts avidly with superoxide anion (O(2)(-)) to produce the powerful oxidizing agent, peroxynitrite (ONOO(-)) which affects mitochondrial functions mostly in an irreversible manner. How mitochondria and cells harmonize the reversible effects of NO versus the irreversible effects of ONOO(-) will be discussed in this review article. The exciting recent finding of mitochondrial NO synthase will also be discussed.

Apoptosis↗
PubMedDate not supplied

Comparison of two once-daily regimens with a regimen consisting of nelfinavir, didanosine, and stavudine in antiretroviral therapy-naïve adults: 48-week results from the Antiretroviral Regimen Evaluation Study (ARES).

BACKGROUND: To improve the dosing frequency and pill burden of antiretroviral therapy, we compared two once-daily dosed regimens to a twice-daily dosed regimen. METHOD: HIV-1-infected, antiretroviral drug-naïve adults were randomized to either twice-daily nelfinavir and stavudine and once-daily didanosine (regimen A) or simplified once-daily dosed antiretroviral regimens consisting of nevirapine, didanosine, and lamivudine (regimen B) or saquinavir, ritonavir, didanosine, and lamivudine (regimen C). RESULTS: At 48 weeks of therapy, the proportion of patients with a blood plasma HIV-1 RNA concentration (pVL) <50 copies/mL by intention-to treat analysis was 42.3%, 50.0%, and 56.5% for regimens A (n = 26), B (n = 22), and C (n = 23), respectively. The time to a pVL <50 copies/mL for the first time was significantly shorter in regimen C, and there was significantly more progression to CDC events in regimen B. These differences are possibly due to differences in baseline characteristics. Adverse events were lowest for regimen C; more signs associated with mitochondrial toxicity occurred in regimen A. Increase in CD4 count was comparable between arms. CONCLUSION: No statistically significant difference in efficacy was found between the two investigated once-daily dosed treatment regimens (B and C) and the reference (A). Regimen C possibly had a better virological response and less toxicity than regimens A and B.

Adult↗
PubMedDate not supplied

Mitochondrial nitric oxide synthase regulates mitochondrial matrix pH.

Nitric oxide (nitrogen monoxide, NO) exerts a wide profile of its biological activities via regulation of respiration and respiration-dependent functions. The presence of nitric oxide synthase (NOS) in mitochondria (mtNOS) was recently reported by us (Ghafourifar and Richter, FEBS Lett. 418, 291-296, 1997) and others (Giulivi et al., J. Biol. Chem. 273, 11038-11043, 1998). Here we report that NO, provided by an NO donor as well as by mtNOS stimulation, regulates mitochondrial matrix pH, transmembrane potential and Ca2+ buffering capacity. Exogenously-added NO causes a dose-dependent matrix acidification. Also mtNOS stimulation, induced by loading mitochondria with Ca2+, causes mitochondrial matrix acidification and a drop in mitochondrial transmembrane potential. Inhibition of mtNOS's basal activity causes mitochondrial matrix alkalinization and provides a resistance to the sudden drop of mitochondrial transmembrane potential induced by mitochondrial Ca2+ uptake. We conclude that mtNOS plays a critical role in regulating mitochondrial delta(pH).

Calcium↗