Biomedical subjects

M Oertle

Publications and source records attributed to M Oertle.

13 recordsLinked to original sources

PubMed2006

[Electromagnetic fields in hospitals: wireless-LAN as a risk factor?].

The actual level of exposure to non-ionizing radiation in Swiss hospitals is not well known. Therefore, the electromagnetic field of wireless LAN (WLAN) and other non-ionizing radiation sources in the publicly funded Hospital Thun (Switzerland), where WLAN supports bedside access to the computerized patient record for more than three years, has been measured. The results are compared to the international and national exposure limits for the general public. Nurse workplaces as well as patient rooms show exposure levels well below the legal (national and international) exposure limits. In the investigated patients' room the electromagnetic field of GSM and broadband cellular phone networks are dominant, whereas at the nurse workplace WLAN exposure is the most important source of exposure. The results of a questionnaire survey emphasize, that the hospital staff does not worry much about electromagnetic fields of new ICT technologies.

Attitude of Health Personnel↗

PubMed1998

Discrepancy of clinical and angiographic results in the follow-up of percutaneous transluminal renal angioplasty (PTRA).

BACKGROUND: To investigate the value of recurrent hypertension as indicator for renal artery patency after PTRA clinical and angiographic follow-up results were analysed. PATIENTS AND METHODS: results of 66 follow-up angiographies and blood pressure measurements were available in 55 patients after technically and clinically successful PTRA. Out of 43 patients with atherosclerosis, in 33 was recurrent hypertension present, and in ten patients none. Of 12 angiographies in patients with fibromuscular dysplasia nine were done because of recurrent hypertension. RESULTS: In atherosclerosis, 21 (64%) out of 33 patients with recurrent hypertension showed a re-stenosis by > 70%, and 12 (36%) none. Out of the ten follow-up angiographies performed in patients with no recurrence, two showed an unexpected stenosis. In fibromuscular dysplasia, stenoses were present in seven cases (77%). Four of them were at the site of PTRA (44%), while three were at a new site (33%). The follow-up angiographies in three patients with no recurrence showed patent arteries. Out of 11 further angiographies carried out because of hypertension after repeated PTRA, only three revealed re-stenosis. CONCLUSIONS: In only about 35% of all patients with recurrent hypertension re-stenosis was shown in angiography but in 15% of asymptomatic patients. Recurrence of hypertension after PTRA and renal artery stenosis is not well correlated. Thus, follow-up should be performed not only clinically but also by direct examination of renal artery patency such as by ultrasound.

Adult↗

PubMed1996

Potassium induces multiple steroidogenic enzymes in cultured rat zona glomerulosa cells.

The effects of the extracellular potassium concentration on the expression of four steroidogenic cytochromes P-450 (CYP11B2, CYP11B1, CYP11A1, and CYP21A1) in cultured rat adrenal zona glomerulosa cells were studied by Northern blot analysis. At a potassium concentration of 6.4 mM, the CYP11B2 messenger RNA (mRNA) level and aldosterone production were undetectable. Upon increasing the potassium concentration to 18 mM, CYP11B2 mRNA and aldosterone production became measurable and reached a plateau within 4 days. The high potassium concentration also caused distinct increases in the levels of CYP11B1, CYP11A1, and CYP21A1 mRNA, comparable to those induced by ACTH. ACTH did not affect the CYP11B2 mRNA level at the lower potassium concentration. In zona fasciculata cells, CYP11B2 expression was not inducible by potassium; CYP11B1, CYP11A1, and CYP21A1 mRNA levels increased in response to ACTH, but not in response to a high potassium concentration. According to these results, potassium initiates CYP11B2 biosynthesis most likely at the level of transcription or by increasing mRNA stability. Potassium also has a zona glomerulosa-specific inductive effect on three other steroidogenic enzymes.

Adrenal Cortex Hormones↗

PubMed1993

Two types of cytochrome P-450(11 beta) in rat adrenals: separate regulation of gene expression.

Northern blot hybridization with specific oligonucleotide probes was used for assaying steady state concentrations of the mRNAs encoding the two types of rat cytochrome P-450(11 beta), i.e. CYP11B1 (non-aldosterone-producing) and CYP11B2 (aldosterone-producing). The zona glomerulosa level of CYP11B2 mRNA was raised by potassium repletion or sodium restriction and was lowered by potassium depletion or by the administration of deoxycorticosterone, ACTH or dexamethasone. In all zones of the adrenal cortex, the CYP11B1 mRNA level was decreased upon dexamethasone treatment. Only in the zona glomerulosa it was increased upon mineralocorticoid treatment and decreased upon potassium repletion or sodium restriction. According to this evidence, the expression of the two genes encoding the two isozymes (CYP11B1 and CYP11B2) in rat zona glomerulosa cells is separately regulated. Whereas CYP11B2 expression is controlled mainly by angiotensin II and extracellular potassium, ACTH is the major but not the only factor controlling CYP11B1 expression in these cells.

Adrenal Cortex↗

PubMed1993

Separate induction of the two isozymes of cytochrome P-450(11) beta in rat adrenal zona glomerulosa cells.

In the rat adrenal cortex, two isozymes of cytochrome P-450(11) beta (CYP11B1 and CYP11B2) have been identified. They are encoded by two different genes with a homology much higher in their coding than in their 5'-flanking regions. CYP11B1 is found in all the zones of the gland and catalyzes a single hydroxylation of deoxycorticosterone (DOC) in the 11 beta- or the 18-position. CYP11B2 is produced exclusively in the zona glomerulosa and catalyzes all three reactions involved in the conversion of DOC to aldosterone. In vivo and in vitro, the expression of the genes encoding CYP11B1 and CYP11B2 is regulated by two separate control systems which appear to operate both independently and interdependently. In vivo zona glomerulosa expression of CYP11B1 was enhanced by ACTH treatment or potassium depletion and was lowered by potassium repletion. CYP11B2 expression disappeared upon potassium depletion or ACTH treatment, but reappeared during potassium repletion. In vitro, only CYP11B1 activity was detectable and responsive to ACTH treatment in zona glomerulosa cells cultured at a potassium concentration of 6.4 mmol/l. Aldosterone biosynthetic activity and mRNA encoding CYP11B2 could be detected only after at least 1 day of exposure to a high extracellular potassium concentration (> or = 12 mmol/l).

Adrenocorticotropic Hormone↗

PubMed1991

Isoelectric focusing of cytochrome P450: isolation of six phenobarbital-inducible rat liver microsomal isoenzymes.

A procedure for the isolation of native proteins from membranes by isoelectric focusing is described. It was used to resolve into six components the major fraction of cytochrome P450, obtained from liver microsomes of phenobarbital-treated rats, after chromatography on DE-52 cellulose. When eluted from the gel, these proteins are in a native form as shown by (a) the light absorption spectra of the Soret region of their reduced carbonyl derivatives, all characterized by maxima around 450 nm, and (b) their enzymatic activities toward three different substrates. Characterization by a monoclonal antibody and partial sequence analysis of tryptic peptides reveal that three of the IEF-purified proteins have P450IIB1 character, whereas the other three are related to P450IIB2.

Amino Acids↗

PubMed1991

Mechanism of monoclonal antibody inhibition/stimulation of reactions catalyzed by cytochrome P450IIB1.

We describe two monoclonal antibodies (MAbs) against rat cytochrome P450IIB1 and investigate the mechanisms by which they influence P450IIB1-mediated catalysis. MAb ce9 partially inhibits the activities toward p-nitroanisole, 7-ethoxycoumarin, and benzphetamine as well as NADPH oxidation. These findings can be explained by the observation that ce9 cross-links P450 to form large aggregates resulting in the inhibition of the functional interaction with NADPH cytochrome P450 reductase. Binding of ce9 to P450IIB1 does not affect the spin state of the P450 heme, as revealed by comparing the magnetic circular dichroism (MCD) spectra of free and antibody-bound P450IIB1. On the other hand, the second antibody tested, MAb 14E10, induces a remarkable low to high spin transition upon binding to P450IIB1, as shown by MCD difference spectroscopy. This MAb stimulates activities toward p-nitroanisole and 7-ethoxycoumarin without affecting the rate of NADPH oxidation. This observation indicates that MAb 14E10 may increase the efficiency of electron utilization by P450IIB1. Benzphetamine metabolism remains unchanged in the presence of MAb 14E10.

Animals↗

PubMed1990

Ca2(+)-binding site of carp parvalbumin recognized by monoclonal antibody.

Monoclonal antibody 235 which was used for immunohistochemical staining of parvalbumin in tissue sections partially protects Lys-54 of carp muscle parvalbumin from reaction with acetic anhydride in the parvalbumin-antibody complex. Lys-54 is located in the CD-loop of parvalbumin and is flanked by the Ca2(+)-ligands Asp-53 and Ser-55 of the Ca2(+)-site I. Another monoclonal antibody against carp parvalbumin, mca 239, partially protects lysine residues 27, 32, 87 and 107, indicating that this antibody is directed against a discontinuous epitope distant from the two Ca2(+)-binding sites of parvalbumin.

Amino Acid Sequence↗

PubMed1989

Mapping of four discontiguous antigenic determinants on horse cytochrome c.

The epitopes (antigenic determinants) recognized by four different monoclonal antibodies on horse cytochrome c have been partially characterized by differential acetylation of lysine residues of free and antibody-bound cytochrome c. The degree of acetylation in the bound and free antigen molecule was assessed by a double-labeling procedure with [3H]acetic anhydride and [14C]acetic anhydride. Out of the 19 lysine residues of cytochrome c only very few were less reactive in the antigen-antibody complex, i.e. presumably located at the epitope for the antibody under study. The protection varied from 1.5-fold to over 20-fold lower reactivity in antibody-bound cytochrome c. The present results are complemented by previous data obtained by cross-reactivity analysis with cytochromes c from different species, with chemically modified cytochrome c derivatives, and by inhibition of proteolysis of cytochrome c in the presence of the antibodies. From the combined data we conclude that each of the four epitopes depends on the precise spatial folding of the antigen and contains residues which are brought together by the folding of the polypeptide chain. This work exemplifies that mapping of conformation-dependent epitopes can be achieved by applying a combination of mapping procedures of which each by itself provides partial information.

Acetylation↗

PubMed1985

Kinetics of carbon monoxide binding to phenobarbital-induced cytochrome P-450 from rat liver microsomes: a simple bimolecular process.

The kinetics of carbon monoxide binding to phenobarbital-induced cytochrome P-450 (P-450PB) and to its enzymatically inactive form P-420PB have been investigated by both stopped-flow and flash-photolysis spectrophotometry. When the simultaneous presence of both forms of the enzyme is taken into account, the binding of CO to these two proteins can be described in terms of two bimolecular processes with rate constants of 4.5 X 10(6) M-1.S-1 and 4.7 X 10(5) M-1.S-1 for P-450PB and 1.7 X 10(7) M-1.S-1 and 1.5 X 10(6) M-1.S-1 for P-420PB. From kinetic studies of the binding of CO to P-450PB under different experimental conditions, investigations of the homogeneity of our P-450PB preparations, and comparative kinetic investigations of P-450s from different sources, we conclude that CO binding to reduced P-450PB is a simple bimolecular process and that the observed biphasic traces are due to heterogeneity of the proteins. This conclusion is in contrast with previous reports of complex reaction mechanisms for the binding of CO to P-450PB. Optical spectroscopy studies indicate the existence of an equilibrium between P-450PB and P-420PB, at least for the reduced carbonyl derivatives of the enzymes. The interconversion is strongly influenced by the aggregation state of the protein. Large differences between the CO binding properties of P-450PB and those of P-420PB are found. These are discussed in terms of possible effects of the proximal ligation state of the iron on heme reactivity.

Animals↗

PubMed1984

Characterization of the ouabain-insensitive ATPase activity of rat liver plasma membranes.

Very little is currently known about the ouabain-insensitive ATPase activity of the liver plasma membrane; we have therefore characterized it in plasma membranes from rat liver prepared using two different isolation techniques. Greater than 85% of ATPase activity in both preparations was ouabain-insensitive. Based on the effects of multiple inhibitors, including dicyclohexylcarbodiimide (DCCD), N-ethylmaleimide (NEM), vanadate, and oligomycin, the ouabain-insensitive ATPase activity of rat liver plasma membranes consists of a family of ATP-hydrolysing enzymes. Ouabain-insensitive ATPase activity was stimulated by HCO3-in both plasma membranes (13%) and mitochondria (69%) over the range of 7.5 to 9.0, and HCO3--stimulation was similarly inhibited by oligomycin in both preparations. A fraction of the ouabain-insensitive ATPase of liver plasma membranes is inhibited by DCCD and is resistent to inhibition by oligomycin; these characteristics are similar to those of the non-mitochondrial H+-ATPases recently described in lysosomes, endosomes, clathrin-coated vesicles, and Golgi from liver and other cell types.

Adenosine Triphosphatases↗

PubMed1983

Kinetic properties of cobalt--iron hybrid hemoglobins.

The replacement of O2 with CO was studied on cobalt-iron hemoglobin hybrids. Both proto- and mesocobalt hemes were used for the reconstitution. In the oxy quaternary conformation no difference is observed between alpha- and beta-subunits when only proto hemes are present in the hybrid (k4 = 30 s-1, k'4/l'4 = 2.5). If Co-meso heme is present on the beta-chains the binding properties of the partner subunit are modified (k'4/l'4 = 4).

Carbon Monoxide↗

PubMedDate not supplied

Identification of cytochrome P-450IIB1 as a cocaine-bioactivating isoform in rat hepatic microsomes and in cultured rat hepatocytes.

Induction of cytochrome P-450-dependent monooxygenases with phenobarbital (PB) or other hepatic drug-metabolizing enzyme inducers in the rat is associated with enhanced cocaine hepatotoxicity both in vivo and in cultured rat hepatocytes. To demonstrate whether the major PB-inducible P-450 subfamily (P-450IIB) could be involved in the metabolic activation of cocaine, rates of cocaine N-demethylation (the first step of cocaine bioactivation) and the rate of irreversible (covalent) binding of tritiated cocaine to hepatic microsomal proteins (a measure for the overall bioactivation) were determined in microsomes from saline or PB-pretreated rats. PB pretreatment augmented Vmax (6-fold), but not KM, of cocaine N-demethylation. Similarly, the rate of irreversible protein binding was 3-fold increased in microsomes from PB-pretreated rats as compared with those from saline controls. Addition of benzphetamine, a substrate of P-450IIB, markedly inhibited cocaine irreversible binding. In addition, various concentrations of cocaine inhibited microsomal pentoxyresorufin O-depentylase activity in a competitive-type pattern. A polyclonal antibody raised against purified rat P-450IIB1 markedly inhibited cocaine N-demethylation as compared with control incubations with preimmune IgG. Finally, pretreatment of rats with PB potentiated cocaine-induced cytotoxicity in primary, short-term cultured hepatocytes, assessed as lactate dehydrogenase release into the culture medium. This enhancing effect of PB became even more evident in glutathione-depleted cells. These results suggest that cocaine is metabolized and bioactivated by P-450IIB1 in the rat liver, and that induction of this isoform with various agents may be associated with enhanced lethal hepatocyte injury in the rat.

Animals↗