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Biomedical subjects

C Barth

Publications and source records attributed to C Barth.

At least 55 records · Page 3Linked to original sources
PubMed1994

Non-responsiveness to hepatitis B vaccination in haemodialysis patients: association with impaired TCR/CD3 antigen receptor expression regulating co-stimulatory processes in antigen presentation and recognition.

The study was undertaken to evaluate the relationship between non-responsiveness to hepatitis B (HBV) vaccination in haemodialysed patients and HBs antigen (Ag) presentation and recognition depending on TCR/CD3 receptors expression. We have found that the cause of the blunted response to HBV vaccination is multifactorial and seems to be associated with the following: (1) A reduced number of TCR/CD3 antigen receptor complexes on freshly isolated uraemic CD4 T cells, especially in non-responders. (2) The blunted proliferative response of uraemic CD4 T cells isolated from non-responders and stimulated for 6 days by autologous monocytes presenting HBsAg was associated with the decreased density of the TCR/CD3 receptors. (3) Moreover, in uraemic non-responders the expression of adhesion and accessory molecules on monocytes (intercellular adhesion molecule-1/ICAM-1, HLA-DR/Ia/) was significantly decreased following the culture with autologous monocytes serving as HBsAg-presenting cells. CD4 molecules and lymphocyte function antigen-1 beta/LFA-1 beta/ on helper-inducer T cells were increased before and after the culture. (4) These findings were also associated with a diminished binding capacity of IL-1 beta and IL-6 to their receptors on helper-inducer T cells. (5) IL-2, IFN-gamma and IL-4 production was decreased in uraemic non-responders, especially after 72 h of the culture. (6) Inhibited proliferation of helper-inducer T cells in uraemic non-responders was only partially reversible in the presence of exogenous IL-1 beta, IL-6, IL-2 and IFN-gamma. (7) HLA typing of uraemic non-responders was associated with extended haplotype: HLA A1,B8,DR3,DR7,DQ2.

Adult↗
PubMed1993

Inactivation by ionizing radiation of ion channels formed by polyene antibiotics amphotericin B and nystatin in lipid membranes: an inverse dose-rate behavior.

The phenomena reported are part of a study about the effects of ionizing radiation on membrane transport. We found that the conductance of lipid membranes in the presence of the polyene-antibiotics nystatin or amphotericin B is reduced to virtually zero following irradiation. Ion channels formed by these substances seem to represent extremely sensitive structures being inactivated by radiation doses in the range of a few Centigray (1 cGy = 1 rad) at sufficiently small dose rates. Inactivation shows a so-called inverse dose-rate behavior, i.e., at constant radiation dose the effect increases with decreasing dose rate. Similar to radiation-induced lipid peroxidation the phenomenon may be understood on the basis of a radical chain mechanism initiated by free radicals of water radiolysis. The process--via peroxidation of the polyene part of the molecules--is suggested to modify the hydrophobic exterior and to destabilize the barrel-like structure of the ion channels.

Amphotericin B↗
PubMed1991

Radiation inactivation of ion channels formed by gramicidin A. Protection by lipid double bonds and by alpha-tocopherol.

The conductance induced by the channel-forming peptide gramicidin A in lipid membranes is reduced by many orders of magnitude on exposure of the membrane and its aqueous environment to ionizing radiation. This results from an interaction of free radicals of water radiolysis with the tryptophan residues of gramicidin A. The sensitivity of the ion channels towards irradiation is strongly reduced in the presence of either vitamin E or of highly unsaturated lipids. An increase of the D37 dose up to a factor of 50 was found. The phenomena are interpreted via a reduction of the effective concentration of free radicals (such as OH.) in the membrane by reaction with unsaturated fatty acid residues or with vitamin E.

Electric Conductivity↗
PubMed1991

Estimation of carrier density and turnover rate of the Na+/H+ exchanger in human platelets using 5-(N-methyl-N-[3H]isobutyl)- amiloride.

We used the radiolabelled inhibitor of Na+/H+ exchange 5-(N-methyl-N-[3H]isobutyl)amiloride ([3H]-MIA) for assessment of the amount of Na+/H+ exchanger in intact human blood platelets. The inhibition constant, KI, of unlabelled MIA toward the antiport was determined at 100 nM. Washed platelets were incubated for 5 s with different concentrations of [3H]-MIA in the presence or absence of an excess concentration of unlabelled amiloride (400 microM). The platelets were rapidly centrifuged and the radioactivity in the pellet was determined. Scatchard analysis revealed one single class of specific binding sites (KD = 63 nM) and a maximum binding capacity of 500 sites/cell. The turnover rate of the Na+/H(+)-exchanger in unstimulated platelets was estimated at 800/s at 25 degrees C.

Amiloride↗
PubMed1991

Attenuation of myocardial ischemia during coronary occlusion by ultrashort-acting beta adrenergic blockade.

To assess the effect of the ultrashort-acting beta blocker esmolol on ischemia induced by acute coronary occlusion, we studied 16 patients undergoing coronary angioplasty. Doppler echocardiography and ECG monitoring were performed continuously before, during, and after balloon occlusion in the drug-free state and during esmolol infusion. Fourteen of the 16 patients had ST segment elevation during balloon inflation. However, maximal ST segment elevation (2.1 +/- 1.5 mm vs 1.7 +/- 1.3 mm, p less than 0.001) and duration of ST segment elevation (68 +/- 20 seconds vs 54 +/- 19 seconds, p less than 0.05) were both significantly reduced during esmolol infusion. Furthermore, the decrease in ejection fraction seen during drug-free balloon occlusions was significantly blunted during esmolol infusion. In the baseline state ejection fraction decreased from 55% to 38% (p less than 0.05) during coronary occlusion compared with a decrease from 52% to 49% (p = NS) during esmolol infusion. In addition, esmolol appeared to delay the onset of segmental wall motion abnormalities after coronary occlusion, occurring at a mean of 40 seconds after balloon inflation versus a mean of 31 seconds in the absence of beta blockade (p less than 0.05). Thus the use of ultrashort-acting beta blockade appears to diminish the extent and delay the onset of myocardial ischemia during acute coronary occlusion.

Adrenergic beta-Antagonists↗
PubMed1991

Ultra short-acting intravenous beta-adrenergic blockade as add-on therapy in acute unstable angina.

To assess the efficacy and safety of the ultra short-acting beta-blocking agent, esmolol, in acute unstable angina, we administered esmolol to 21 patients who had persistent angina despite conventional medical therapy. Following a baseline Doppler echocardiographic examination, esmolol was titrated to reduce the rate-pressure product by at least 20%. Once the patients had been receiving a maintenance dosage for 30 minutes, Doppler echocardiographic studies were repeated. Mean esmolol dose at target response was 17 +/- 16 mg/min, with the dosage range of 8 to 24 mg/min. Esmolol was effective in alleviating anginal chest pain in 18 of the 21 patients. Seven patients eventually underwent percutaneous transluminal coronary angioplasty (PTCA) and eight had coronary bypass surgery. The remainder were discharged receiving medical therapy including oral beta-blockade. During esmolol therapy, heart rate and blood pressure decreased significantly (86 +/- 14 to 68 +/- 12 beats/min and 125 +/- 16 to 103 +/- 20 mm Hg, both p less than 0.001). Cardiac output decreased from 5.4 +/- 1.3 to 4.5 +/- 1.1 L/min (p less than 0.001) secondary to a decrease in heart rate as stroke volume remained unchanged. Left ventricular ejection fraction increased from 47 +/- 12 to 49 +/- 13 with esmolol therapy, although this change was not statistically significant. Both the one third filling fraction as well as E/A ratio (ratio of early-to-late diastolic filling velocities) increased with esmolol therapy (35 +/- 8% to 38 +/- 8% and 0.73 +/- 0.2 to 0.85 +/- 0.23, both p less than 0.005), indicating improvement in left ventricular diastolic function.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Antagonists↗
PubMed1990

Transcriptional modulation of human IL-6 gene expression by verapamil.

Calcium channel-blocking agents interfere with the initial increase of cytosolic calcium that follows mitogenic stimulation of T lymphocytes. In cultures of mitogen-stimulated PBMC, verapamil also blocked T cell accumulation of cytoplasmic IL-2-encoding mRNA. In sharp contrast, the addition of verapamil to PHA and PMA-stimulated PBMC augmented the mitogen-stimulated increases in nuclear transcription of IL-6-encoding mRNA, steady state levels of IL-6 encoding mRNA, and release of IL-6 bioactivity. These experiments indicated that an increased IL-6 transcriptional rate rather than stabilization of transcripts accounted for the increased cytoplasmic IL-6 mRNA levels and subsequent expression of IL-6 bioactivity. These effects were not produced by nicardipine, another potent calcium channel blocker, or EGTA. We suggest that a non-calcium-dependent, IL-6 regulatory factor, absent or inactive in verapamil-treated cultures, inhibits IL-6 gene activation in mitogen-stimulated PBMC. Failure to express this inhibitory factor would result in IL-6 gene superinduction at a transcriptional level.

Blotting, Northern↗
PubMed1990

[Ultraviolet exposure in the environment of welding work sites].

It has been checked if the "limits of the acceptable doses of ultraviolet radiation of monochromatic radiation at the workplace" (NIOSH-standard of USA) are adhered to in the vicinity of welders' work stations in a factory hall. For recording of UV-doses polysulphon films have been used. According to these investigations non-welders are exposed to doses of UV-radiation which exceed the limits recommended by about eight times. Clinical examinations of these persons showed chronic damage of the external parts of the eyes in a higher percentage than in a control group. It is pointed to the necessity of taking protective measures to shield persons working in the vicinity of welding job sites from ultraviolet radiation.

Dose-Response Relationship, Radiation↗
PubMed1989

[Tissue expanders in plastic surgery of the head and neck. Indications and use].

Tissue expansion allows a functional as well as an aesthetic reconstruction of local defects and thus corresponds to the actual state of the art in plastic surgery.-Tissue expansion provides tissue of the same quality for the repair of defects without leaving deformities on the donor site. It creates local flaps with skin of the same texture, colour and preserved sensitivity.-The use of tissue expanders has grown enormously during the last few years.-A higher rate of complications on the cheek and on the neck must be taken into account.

Head and Neck Neoplasms↗
PubMed1989

Iron, zinc, folate and vitamin B12 nutritional status and milk composition of low-income Brazilian mothers.

The purpose of this study was to assess the nutritional status of low-income Brazilian mothers, who were supplemented with iron and vitamin B12 during pregnancy, in terms of iron, zinc, folate and vitamin B12, in different stages of lactation and to determine the influence of the maternal nutritional status on milk composition. The effect of folate supplementation during pregnancy on folate status of the nursing mothers and milk composition was investigated. The effect of partial weaning on maternal status and milk composition was also studied. In general, the nutritional status of iron, zinc, folate and vitamin B12 of the mothers appears adequate. However, some of the mothers had indices of status lower than normal limits for non-pregnant women. These values, particularly after 30 d post-partum, indicate that these mothers might be at nutritional risk and that the nutrient supplementation received during pregnancy was insufficient to meet demands. There was an increase with the stage of lactation for haematocrit, serum vitamin B12, serum zinc, serum albumin, milk folate and saturation of its binding protein, but there was a decrease for milk protein, total and whey-bound iron and zinc, and lactoferrin. Mothers who took folate supplements during pregnancy had higher serum folate levels immediately after birth than those not taking the supplements but no differences were found at later stages of lactation. Milk composition was not affected. Partial weaning did not affect the maternal nutritional status or the milk composition except for iron which was higher in milk from mothers who were partially breastfeeding.(ABSTRACT TRUNCATED AT 250 WORDS)

Brazil↗
PubMed1988

Correlation of beta-2-microglobulin concentration changes to changes of distribution volume.

Plasma and ultrafiltrate beta-2-microglobulin (B2M) concentrations were determined during hemofiltration (HF) and hemodialysis (HD) in order to evaluate elimination kinetics of B2M. Calculations were done on the basis of plasma-water-concentrations (PWC). Elimination of B2M during HF follows first order kinetics (r = 0.97) and the volume of B2M distribution was calculated to be 17 +/- 2% of body weight. This reflects extracellular volume (ECV). Changes of ECV in HD were induced by weight loss and further provoked by fluid shifts from intra- to extracellular volume and vice versa induced by varying dialysate sodium concentration. These ECV changes were followed by determining inuline in plasma and total dialysate. Changes of B2M concentration correlate well to changes of ECV (r = 0.98). Thus intratreatment concentration changes of B2M in cuprophane dialysis reflect simultaneous changes of B2M distribution volume. This does not exclude the possibility of B2M generation stimulated by dialysis, but proving such effects in vivo will be difficult because of multiple variants, that must be controlled.

Adult↗
PubMed1983

Significance of neutrophils in cerebrospinal fluid samples processed by cytocentrifugation.

We reviewed medical records of 155 pediatric patients whose cerebrospinal fluid (CSF) samples contained an increased proportion of neutrophils when processed by cytocentrifugation, despite normal CSF total white blood cell count. It was determined that these CSF findings occurred more commonly in patients with bacteremia, peripheral leukocytosis, and increased numbers of red blood cells in the CSF. Pulmonary infiltrates in infants and otitis media in children were also significantly associated. Cytocentrifugation allows the identification of neutrophils in the CSF, even in the absence of central nervous system infection. Infants and children with more than 10 per cent neutrophils in CSF require evaluations for focal and bacteremic infections.

Adolescent↗
PubMed1981

[Serum cholesterol and triglyceride levels in a Munich population group: relations to age and sex (author's transl)].

Serum cholesterol and triglyceride levels were determined in 814 subjects and the relation to age, sex and body weight evaluated. In 568 persons the body mass index (BMI) and the relative body weight according to Broca were calculated. Normal values for each age group were established. Serum cholesterol, serum triglycerides and the body mass index showed an age dependent rise in the male and the female population. The body mass index showed a positive correlation with the serum triglycerides, but did not correlate with the serum cholesterol levels. The correlation between body mass index and serum triglycerides was not age dependent. Thus, our data stress the relation between overweight and hypertriglyceridaemia.

Adult↗