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Biomedical subjects

P Bayer

Publications and source records attributed to P Bayer.

53 records · Page 3Linked to original sources
PubMed1993

Equine infectious anemia virus Tat is a predominantly helical protein.

Nuclear magnetic resonance (NMR) spectroscopy revealed features of the secondary structure of the equine infectious anemia virus (EIAV) Tat protein in solution. We could show that this protein, which is required in the replication cycle of lentiviruses, forms a predominantly helical structure in trifluoroethanol/water (40% by vol.) solution. In particular, the basic RNA-binding region and the adjacent core domain, which are highly conserved among lentiviral Tat proteins, show helix-type secondary structure under these conditions. Our observations, in concert with recent biochemical data from other laboratories, suggest that the core sequence region and the basic sequence region form interdependent structural domains, both possibly necessary for correct RNA binding.

Amino Acid Sequence↗
PubMed1993

Effect of human native low-density and high-density lipoproteins on prostaglandin production by mouse macrophage cell line P388D1: possible implications in pathogenesis of atherosclerosis.

Macrophages have been shown to play a key-role in the development of atherosclerotic lesions. Monocyte attraction and activation in the arterial wall lead to foam cell formation, cholesterol accumulation and secretion of inflammation mediators. Among macrophage secretions, prostacyclin and thromboxane are prostaglandins involved in the regulation of coagulation and vascular permeability. In this study, we have evaluated the effects of human native low-density and high-density lipoproteins on macrophage prostaglandin production (P388D1 mouse cell line). Lipoprotein fractions were purified from venous blood of healthy volunteers by sequential ultracentrifugation. After lipoprotein incubation with cells, supernatants were extracted and prostaglandins quantified by high-performance liquid chromatography. Our technique allows the determination of the main classes of prostaglandins. In the presence of low-density lipoproteins, time-course study showed an increase in total prostaglandin production within 10 min (50 times basal secretion level). This increase was dose-dependent. A steady-state was obtained at 20 mg protein LDL/1. Stimulation of thromboxane B2 and prostacyclin was predominant, with a main effect on the proaggregant thromboxane. Production of the proinflammatory PGF2 alpha and the immunoregulatory PGE2 was lower. In the presence of high-density lipoproteins, P388D1 cells also increased their total prostaglandin secretion at 30 min, in a dose-dependent manner. This increase was directly related to a stimulation of prostacyclin, with no significant effect on thromboxane. Our results demonstrate that normal low-density lipoproteins can stimulate macrophage prostaglandin secretions, with putative deleterious effects on the arterial wall, in particular thrombus formation. On the other hand, high-density lipoproteins, by mainly stimulating prostacyclin, could theoretically have a beneficial influence.

Animals↗
PubMed1993

[Serum magnesium, serum potassium and arrhythmia profile in patients with acute myocardial infarct].

In 176 patients with acute myocardial infarction (AMI) serum magnesium concentration (MGK) and serum potassium concentration (KK) were analysed during the first 48 hours after AMI. The patients rhythm was continuously recorded. In a subgroup of 70 patients a signal averaging-ECG was performed. 4.5% of the patients had a low, 55.7% a normal and 39.8% a high MGK. 14.8% of the patients had a low, 80.1% a normal and 5.1% a high KK. Ventricular arrhythmias > or = Lown IV b were found in 25% of the patients with low MGK, in 38.8% with normal and in 52.9% with high MGK. 50% of the patients with low, 62.2% with normal and 61.3% with high MGK had late potentials. There was no relation between hypomagnesemia and ventricular arrhythmias as between hypomagnesemia and late potentials. Thus, hypomagnesemia in AMI patients is rare and does not correlate with ventricular arrhythmia or delayed ventricular potentials.

Aged↗
PubMed1981

Determination of plasma catecholamines by means of radioenzymatic labelling and high pressure liquid chromatographic separation.

0.05 ml plasma samples are incubated with 3H-S-adenosylmethionine and catechol-O-methyl-transferase. The resulting methodoxy derivatives are extracted, the extracts separated by high pressure liquid chromatography and the metanephrine fractions collected. Evaluation is performed by liquid scintillation counting of radioactivity in the respective fractions. The following performance criteria are presented: precision, accuracy, detectability (40 pg/ml for adrenaline and noradrenaline, 130 pg/ml for dopamine), linearity and day-by-day variation. Comparison with a standard method shows an excellent correlation for adrenaline and noradrenaline.

Adult↗
PubMedDate not supplied

Determination of the structure of the RNA complex of a double-stranded RNA-binding domain from Drosophila Staufen protein.

We have determined using NMR the structure of the complex between the third double-stranded RNA-binding domain (dsRBD3) of Drosophila Staufen protein and a RNA stem-loop with optimal binding properties in vitro. This work was designed to understand how dsRBD proteins bind RNA and to investigate the role of Staufen dsRBDs in the localization of maternal RNAs during early embryonic development. The structure determination was challenging, because of weak, nonsequence specific binding and residual conformational flexibility at the RNA-protein interface. In order to overcome the problems originated by the weak interaction, we used both new and more traditional approaches to obtain distance and orientation information for the protein and RNA components of the complex. The resulting structure allowed the verification of aspects of RNA recognition by dsRBDs matching the information obtained by a related crystallographic study. We were also able to generate new observations that are likely to be relevant to dsRBD-RNA binding and to the physiological role of Staufen protein.

Animals↗
PubMedDate not supplied

[Multicenter evaluation of four homogenous LDL-cholesterol assays].

International guidelines emphasize the importance of LDL cholesterol (LDL-C) assay in the care and follow-up of patients with cardiovascular risk. Most studies and common practice use Friedewald's formula for LDL-C calculation. The accuracy of the result depends closely on the precision of the input parameters (total cholesterol, triglycerides (TG) and HDL cholesterol), and discrepancies between calculated LDL-C and measurement by reference methods appear when TG exceed 4.5 mmol/L, or in the presence of abnormal lipoproteins. These restrictions and uncertainties in calculations have prompted the recent development of direct and homogeneous methods that fit all analyzers. A multicenter evaluation of four direct assays of LDL-C (Daiichi, Denka Seiken, Kyowa, Wako) was carried out on 45 serum samples (TG below 3.1 mmol/L) in eight laboratories using different analyzers. For three methods (Daiichi, Kyowa, Wako), the interlaboratory reproducibility was markedly improved relative to that of calculation. A strong correlation was found for all new methods when compared with a beta-quantification assay. Average bias in Denka Seiken assays was greater than Kyowa's and Daiichi's (although less dispersed for the latter) and for Wako all bias were positive. The relationship between bias variations and the lipid parameters of the samples was studied. Three methods, Daiichi, Kyowa and Wako, revealed a significant positive correlation between bias and serum VLDL-C/TG ratio, clearly indicating that cholesterol enrichment of VLDL was a source of variability in these assays. Specificity of the four methods was tested in situation of dyslipidemia by spiking isolated lipoproteins (chylomicrons, VLDL and HDL). This experiment revealed differences in behavior, most evidently upon addition of VLDL. No method was truly specific, but up to 8 mmol/L of TG the variations were acceptable. In the presence of type III hyperlipoproteinemia, however, only the Denka Seiken method was reliable. Linearity up to 20 mmol/L (Daiichi, Denka Seiken) or 14 mmol/L (Kyowa, Wako) of LDL-C allows these tests to be used in main routine cases. New direct assays are an obvious technological advance in terms of analytical performance and conveniency. Their use for the diagnosis and follow-up of hyperlipidemic patients offers an alternative that overcomes the limitations of the Friedewald calculation.

Blood Chemical Analysis↗