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Biomedical subjects

B Meier

Publications and source records attributed to B Meier.

At least 487 records · Page 27Linked to original sources
PubMed1977

The role of macrophages in the generation of T helper cells. V. Evidence for differential activation of short-lived T1 and long-lived T2 lymphocytes by the macrophage factors GRF and NMF.

The generation of T helper cells in vitro requires macrophages or macrophage-derived factors such as genetically related macrophage factor (GRF) or nonspecific macrophage factor (NMF). However, there is a basic difference of T helper cell induction when using particulate antigens. The present study demonstrates that this difference is based on the activation of two different T cell subsets. GRF activates short-lived 'T1' cells which amplify the induction of T2 cells, which are the helper cell precursors. Thus, the genetic restriction of T helper cell induction seen with soluble antigen or GRF lies on the level of macrophage or GRF interaction with T1 cells. NMF (or macrophages) and particulate antigens directly activate the helper cell precursor (T2) indicating no requirement for T1-T2 cooperation. The direct activation of the helper cell precursor with particulate antigens does not require histocompatible macrophages or NMF from histocompatible macrophages. The present results may explain some of the discrepancies reported in the literature concerning the genetic requirements and specificity of T cell activation.

Animals↗
PubMedDate not supplied

Two-dimensional echocardiographic evaluation of intracardiac transvenous pacemaker leads.

A two-dimensional (2-D) echocardiographic study was performed on 40 consecutive patients presenting for a routine check-up of their transvenous pacemaker devices, in order to assess the visibility of the intracardiac portion of the pacemaker lead. In 34 patients (85%) the presence of the lead could be demonstrated satisfactorily. In 4 of these 34 patients the entire intracardiac portion of the pacing wire was imaged, in 20 the distal fragment bearing the electrode(s) was seen, and in 10 an intermediate segment was visible. In 6 of the 40 patients (15%) the lead was not visible. In 3 of these 40 patients it was virtually impossible to image any cardiac structure. The less than 100% visibility of the pacing wire may be due to our randomized patient group with a high mean age of 75 years. We conclude that during follow-up examinations or when problems arise in patients with transvenous pacemakers, 2-D echocardiography may be an alternative to roentgenograms, especially if simultaneous information about heart function is desired or septal perforation is suspected. However, chest roentgenograms are still more accurate and remain the technique of choice under normal circumstances.

Aged↗
PubMedDate not supplied

Proximal coronary artery stenosis: three-dimensional MRI with fat saturation and navigator echo.

The purpose of this study was to compare the diagnostic value of MR angiography (MRA) with conventional contrast angiography in coronary artery disease. Thirty-five patients underwent MRA and coronary angiography within 4 hours. Of these, three patients were investigated twice: once before and once after balloon angioplasty. The pulse sequence was a cardiac-triggered, single-slab, three-dimensional gradient-echo sequence, employing a spin-echo navigator echo measurement to track the variation of the diaphragm during the scan. The following segments of the coronary arteries were included in this prospective study: left main coronary artery, proximal and middle left anterior descending, proximal and middle left circumflex, proximal and middle right coronary artery, and intermediate branch, if present. In total, 176 segments were classified as normal or having a stenosis of less than 50% and as having a stenosis of more than 50%. Five patients were excluded because of lack of cooperation. Over all, 45 of 54 stenoses were detected and interpretable by MRA. Sensitivity, specificity, and positive and negative predictive values of MRA for detecting significant stenoses were 83%, 94%, 87%, and 93%, respectively. MRA identified significant stenoses within the major coronary arteries with a high degree of accuracy. Sensitivity and specificity are higher compared with exercise tests or scintigraphy or top of the precise localization.

Coronary Angiography↗
PubMedDate not supplied

Comparing phytopharmaceuticals: the example of St. John's Wort.

At present, dosage in phytotherapy often falls victim to an undifferentiated point of view. In the case of St. John's Wort, for example, 900 mg of extract has become the standard dosage; however, no studies have investigated the dose-effect ratio, even though there are numerous indications that smaller amounts, particularly of ethanolic extracts, are sufficient to achieve the desired effect. Moreover, listing extract dosages is of no use unless other identifying characteristics are also specified. If phytopharmaceuticals are to be compared with one another, the scope of consideration cannot be limited to single components. The comparison must be carried out comprehensively.

Chromatography, High Pressure Liquid↗
PubMedDate not supplied

Direct peripheral effects of ghrelin include suppression of adiponectin expression.

The stomach-derived peptide, ghrelin, has recently been discovered as an important regulator of energy homeostasis. Central nervous system pathways involving stimulation of hypothalamic neuropeptides play a prominent role in mediating ghrelin's orexigenic effects. However, potential direct peripheral effects remain poorly understood. Using a brown adipocyte model, we tested ghrelin-mediated influences on adipose tissue. Chronic ghrelin stimulation of differentiating adipocytes did not affect the pattern or extent of fat accumulation. Furthermore, insulin-induced glucose uptake as a hallmark of adipocyte function was not altered by ghrelin pre-treatment. However, acute ghrelin treatment resulted in a significant time-dependent increase in p44/42 mitogen-activated protein kinase phosphorylation. There was no stimulation of phosphatidylinositol 3-kinase, JAK/STAT, or stress kinase signaling pathways. Furthermore, ghrelin did not significantly alter gene expression of the thermogenic uncoupling protein-1. By contrast, expression of the novel adipokine adiponectin, which has been implicated in the pathogenesis of insulin resistance and obesity, was strongly impaired. This inhibition occurred acutely, and was sustained for several hours. In summary, our data provide evidence for selective effects of ghrelin on adipocyte signaling and function and thus propose a role for adipose tissue as a novel mediator of ghrelin's effects on energy balance and glucose homeostasis.

Adipocytes↗
PubMedDate not supplied

Management and outcome of stents in 1998: long-term outcome.

In the first 20 years of its existence, percutaneous transluminal coronary angioplasty (PTCA) has emerged to become the most common major medical intervention. In the meantime, many different adjunctive devices, such as drills, lasers, cutters, and suckers, have been invented, but only stents (introduced in 1986) have become a major asset to PTCA. Their main benefit is reducing the incidence of acute occlusions caused by dissection and, thus, the need for emergency bypass grafting. The approximate 30% restenosis rate of PTCA between 3 and 6 months after the intervention is also reduced to approximately 20% by stents. In the long term, ie, after 6 months, the stented or nonstented lesion is stable and needs a revascularization procedure in only 4% of the lesions. After PTCA, progression of coronary artery disease plays a dominant role, necessitating subsequent interventions for new stenoses in as many as 10% of patients.

Angioplasty, Balloon, Coronary↗
PubMedDate not supplied

Superoxide release in human fibroblasts upon treatment with culture supernatants of the arthritogenic bacteria Erysipelothrix rhusiopathiae and Mycoplasma arthritidis.

Culture supernatants of the arthritogenic bacteria Mycoplasma pneumonia, Mycoplasma arthritidis, Borrelia burgdorferi and Erysipelothrix rhusiopathiae stimulated primary cultures of human fibroblasts to release reactive oxygen species into the environment, whereas cell walls and membranes of these bacteria had no effects. Lipopolysaccharides of various gram-negative bacteria and lipid A, the lipid moiety of endotoxines, also failed to stimulate the release of reactive oxygen species by fibroblasts. The stimulatory fractions of the culture supernatants of Mycoplasma arthritidis and Erysipelothrix rhusiopathiae exhibited a molecular weight of about 9.5 kDa. After an induction period of 5 min the presence of the stimulant was not necessary any more. The primary radical released by the fibroblasts was the superoxide anion O2-. Radical formation took place continuously over some hours. Additionally, low-level chemiluminescence of fibroblasts was increased upon stimulation with culture supernatants of Mycoplasma arthritidis and Erysipelothrix rhusiopathiae. No irreversible injury of the fibroblast was caused upon stimulation and the cells exhibited normal proliferation pattern after replacing them to the culture medium.

Arthritis, Infectious↗