Search PubMed⌕ Search

Biomedical subjects

S Mayer

Publications and source records attributed to S Mayer.

At least 19 recordsLinked to original sources
PubMed1999

Attachment of cultured human bone cells to novel polymers.

The initial attachment of human bone-derived cells (HBDC) to several polymer systems has been studied in vitro. A novel polymer system based on poly(ethyl methacrylate) polymer and tetrahydrofurfuryl methacrylate monomer (PEMA/THFMA) was compared with a variant in which THFMA was replaced by 2-hydroxyethyl methacrylate (PEMA/HEMA). Tissue culture polystyrene (TCPS) and polystyrene (PS) were used as reference materials. The ability of the substrates to adsorb the attachment glycoproteins fibronectin (Fn) and vitronectin (Vn) from serum and the subsequent effect on radiolabeled HBDC attachment were examined. Initial cell attachment from the medium containing 10% (v/v) serum was highest on TCPS; on PEMA/THFMA and PEMA/HEMA substrates it was about 25% of this level, and on PS it was only 10% of that on TCPS. Attachment of HBDC to all substrates was dependent on the presence of Vn, which, unlike Fn, was able to adsorb in the face of competition from other serum components. Both Vn and Fn were able to support cell attachment when precoated onto all substrates. In comparison to TCPS, PEMA/THFMA did not show enhanced adsorption of either Fn or Vn from serum, and this was reflected in the level of cell attachment. Interestingly, the potency of preadsorbed Fn for cell attachment was much higher on this substrate than on any other: 45 ng/cm2 Fn when adsorbed to PEMA/THFMA gave a level of cell attachment 1.6-fold higher than the same density of Fn on PS or TCPS. The maximum Fn surface density achieved on HEMA/PEMA was 16 ng/cm2. Cells on PEMA/THFMA showed typical clustering of the alpha5 beta1 Fn receptor, but this was not evident in cells attached to PEMA/HEMA even when precoated with Fn. This study indicates that the initial attachment of HBDC to all substrates was Vn dependent. It also indicates that on PEMA/THFMA the favorable presentation of subsequently adsorbed Fn may assist matrix assembly.

Biocompatible Materials↗
PubMed1999

Kinetic study of CD34+ cells during peripheral blood stem cell collections.

The impact of the separated volume on the yield of CD34+ cells during peripheral blood stem cell collections (PBSCC) remains controversial. We therefore studied the CD34+ cell concentration in the peripheral blood of patients (pts) during PBSCC as well as the total amount of CD34+ cells collected after each blood volume (BV) processed and engraftment data for each cycle of high dose chemotherapy (HD Ctx). A total of 21 PBSCC from 20 patients with different malignancies were analyzed. Stem cells were mobilized by chemotherapy and G-CSF (14 pts) or GM-CSF (6 pts). Samples from the pts peripheral blood and the collection bag were taken after each BV processed and analyzed for CD34+ cells, WBC, platelets (plt), and hemoglobin (Hb). The total volume processed was two to five times the pts calculated BV (mean value 17.4 L, range 9.0-24.0 L). Sixteen pts could be evaluated for engraftment. The mean peripheral blood CD34+ cell count was 116+/-103.5/microl at the start of PBSCC and decreased to 57+/-61.6/microl after processing of four times the pts BV. The mean number of CD34+ cells collected after each BV was 2.3+/-2.4, 5.8+/-5.2, 8.5+/-7.2, and 11.8+/-10.3x10(6) per kg body weight, respectively. The mean plt count decreased by 53+/-40.2/nl, Hb by 1.+/-0.5 g/dl and WBC by 0.+/-6.1/nl after separation of 4 BV. All but two pts reached the target value of 1.5x10(6) CD34+ cells/kg body weight and planned cycle of HD Ctx with 1 PBSCC. All pts engrafted and reached neutrophils>500/microl and plt>20,000/microl at a median of 11 and 13 days, respectively. We could demonstrate, that the yield of CD34+ cells during PBSCC increased continuously with the volume of the separated BV and that up to 5x the patients' BV could be processed safely without serious side effects. Most pts had to undergo only 1 PBSCC to collect sufficient numbers of CD34+ cells to support sequential courses of HD Ctx without delayed engraftment.

Adult↗
PubMed1999

Investigation of transport mechanism and uptake kinetics of O-(2-[18F]fluoroethyl)-L-tyrosine in vitro and in vivo.

UNLABELLED: The aim of the study was to investigate the transport mechanism and uptake kinetics of the new 18F-labeled amino acid O-(2-[18F]fluoroethyl)-L-tyrosine (L-[18F]FET) and D-[18F]FET in human SW 707 colon carcinoma cells and the in vivo biodistribution of this tracer in SW 707 tumor-bearing mice. METHODS: SW 707 cells were incubated with L- and D-[18F]FET under physiologic amino acid concentrations with and without the competitive transport inhibitors 2-amino-2 norbornane-carboxylic acid and a-(methylamino)isobutyric acid plus serine. For the investigation of the transport capacity, unlabeled L-FET was added to the samples. In addition, xenotransplanted mice were injected intravenously with L-[18F]FET; killed 10, 30, 60 and 120 min after injection; and the radioactivity concentration in different organs was measured in a gamma counter. RESULTS: The in vitro kinetic experiments showed a fast initial uptake of L-[18F]FET into the cells up to 6 min, followed by a nearly constant tracer concentration. The accumulation factor, calculated as the ratio between intracellular and extracellular tracer concentration, ranged from 3.0 to 5.0. In comparison, D-[18F]FET did not accumulate in the cells. Washing the cells in medium at 37 degrees C, after a 30-min incubation with L-[F-18]FET, led to a rapid decrease of radioactivity, which demonstrates the bidirectional transport. In addition, experiments with increasing concentrations of unlabeled L-FET indicated a linear correlation between L-FET uptake rate and the extracellular concentration. Results of transport inhibition experiments with the specific competitive inhibitors demonstrated that the uptake of L-FET into SW 707 cells was caused mainly (>80%) by the transport system L. In the in vivo studies, the half-life (t1/2 beta) of L-[18F]FET in the plasma was determined to be 94 min and the uptake into the brain increased to 120 min with a brain-to-blood ratio of 0.86. The xenotransplanted tumor showed higher uptake of L-[18F]FET (>6 %ID/g) at 30 and 60 min than all other organs, except the pancreas. The tumor-to-blood ratio reached about 2 between 30 and 120 min. CONCLUSION: L-[18F]FET, which is transported by the specific amino acid transport system L, seems to be a potential amino acid tracer for tumor imaging and therapy monitoring with PET.

Animals↗
PubMed1998

Prinzmetal's variant angina.

Although the prevalence of variant angina pectoris is unknown, it appears to be substantially less common than typical, exertional angina and unstable angina at rest. The patient with variant angina typically complains of a pressure-like, squeezing retrosternal chest discomfort of several minutes duration. The diagnosis is secured by the occurrence of transient ST-segment elevation in association with chest pain, both of which resolve spontaneously or with nitroglycerin. After the diagnosis is made, the patient usually becomes symptom-free on calcium-channel blockers with or without long-acting nitrates. Although the long-term survival of these patients is excellent, an occasional individual with variant angina sustains a complication, most often myocardial infarction, a life-threatening arrhythmia, or sudden cardiac death.

Angina Pectoris, Variant↗
PubMed1998

Spleno-caval shunt in children using internal jugular vein graft: a case report.

Several techniques for decompression of portal hypertension have been described. The spleno-caval shunt is an easy and safe technique described in adult patients. However, the procedures described in adults are not adapted to children. We report an adaptation of this technique in a child, using the internal jugular vein as an interposition graft for relief of portal hypertension.

Child, Preschool↗
PubMed1997

Influence of advanced glycation end-products and AGE-inhibitors on nucleation-dependent polymerization of beta-amyloid peptide.

Nucleation-dependent polymerization of beta-amyloid peptide, the major component of plaques in patients with Alzheimer's disease, is significantly accelerated by crosslinking through Advanced Glycation End-products (AGEs) in vitro. During the polymerization process, both nucleus formation and aggregate growth are accelerated by AGE-mediated crosslinking. Formation of the AGE-crosslinked amyloid peptide aggregates could be attenuated by the AGE-inhibitors Tenilsetam, aminoguanidine and carnosine. These experimental data, and clinical studies, reporting a marked improvement in cognition and memory in Alzheimer's disease patients after Tenilsetam treatment, suggest that AGEs might play an important role in the etiology or progression of the disease. Thus AGE-inhibitors may generally become a promising drug class for the treatment of Alzheimer's disease.

Alzheimer Disease↗
PubMed1997

Minimally invasive direct coronary artery bypass surgery.

Traditional coronary artery bypass surgery involves a median sternotomy and the use of a heart-lung machine to stabilize the heart during suturing. Minimally invasive coronary artery surgery employs small incisions directly over the target vessels and avoids the use of a heart-lung machine, which can cause postoperative complications. The target coronary vessels are stabilized in alternative ways, potentially hazardous manipulation of the ascending aorta is avoided, and the subclavian and axillary arteries provide alternative inflow sources. Other new techniques used in minimally invasive procedures include a coronary artery cannula to avoid intraoperative ischemia and wound irrigation catheters to administer postoperative bupivacaine hydrochloride. Perioperative nurses need to become familiar with these new techniques to be able to plan and implement effective patient care.

Coronary Artery Bypass↗
PubMed1997

A sensitive ELISPOT assay for detection of CD8+ T lymphocytes specific for HLA class I-binding peptide epitopes derived from influenza proteins in the blood of healthy donors and melanoma patients.

An enzyme-linked immunospot (ELISPOT) assay was adapted to detect peptide-specific CD8+ T lymphocytes in peripheral blood mononuclear cells (PBMCs). In HLA-A1-, HLA-A2-, and/or HLA-A3-positive individuals, we determined the release of IFN-gamma on a single cell level in response to three different peptide epitopes derived from the influenza matrix protein and nuclear protein containing the HLA-A2.1- and HLA-A1- or HLA-A3-binding motif, respectively. Comparison of the ELISPOT assay with the standard chromium release assay revealed a close correlation between the number of peptide-specific IFN-gamma-releasing T cells in PBMCs and the level of specific cytotoxicity after 14 days of in vitro expansion. The ELISPOT assay detected T cells with specificity for the HLA-A2. 1-binding epitope derived from the matrix protein in 76% of HLA-A2-positive healthy individuals (n = 25); the median frequency was 41 in 10(6) PBMCs. We also detected peptide-specific T cells in 10 of 12 HLA-A2-positive patients with metastatic melanoma with a median frequency of 20.5 in 10(6) PBMCs. In 10 of 24 HLA-A3-positive individuals and in 2 of 14 HLA-A1-positive individuals, peptide-specific T cells for a HLA-A3- and a HLA-A1-binding epitope derived from the nucleoprotein, respectively, were present. In conclusion, the ELISPOT assay may be suitable to monitor a peptide-specific T-cell response in vaccination protocols using peptides derived from tumor or viral antigens.

CD8-Positive T-Lymphocytes↗
PubMed1996

A sensitive proliferation assay to determine the specific T cell response against HLA-A2.1-binding peptides.

A proliferation assay to detect a specific T cell response against HLA class I-binding peptides is reported. To establish the specificity and sensitivity of the assay we used a synthetic peptide derived from the CMV glycoprotein B containing the HLA-A2.1 ligand motif. Lymphocyte proliferation was measured following culture of PBMC in the presence or absence of peptide by BrdU uptake. Differing culture conditions were compared (cell number, time in culture, peptide concentration, +/- IL-2). A peptide-specific response was detected in 11 of 23 HLA-A2-positive and CMV IgG-positive donors (47.8%), and in 4 of 36 HLA-A2-positive and CMV IgG-negative donors (11.1%, p = 0.019) tested under optimized conditions. None of 22 HLA-A2-negative individuals tested showed a peptide-specific response and the reproducibility was high. Peptide-specific IFN-gamma-secreting T cells could be demonstrated in responding donors with the ELISPOT assay. This proliferation assay may be suitable for monitoring induction of a specific T cell response against known HLA class I-binding peptides following vaccination with tumor or viral antigens.

Antibodies, Viral↗
PubMed1996

Quantitative determination of heparinoid mimetics in human and rat plasma by micellar electrokinetic chromatography.

The investigated new class of heparinoid mimetics are spaced persulfated carbohydrates designed to increase the success rate of angioplasty and bypass surgery by preventing restenosis without increasing the risk of bleeding. Due to the presence of sulfate groups, these compounds are highly charged and, for preclinical kinetic investigations only small sample volumes of rat plasma were available. Therefore, capillary electrophoresis (CE) was applied. A bioanalytical method based on micellar elektrokinetic chromatography (MEKC) with UV-detection was developed for the selective quantitation of heparinoid mimetics (e.g., Ro 48-0843, Ro 48-3151, Ro 47-6199 and Ro 48-8722) in plasma. Using this method, only small volumes of plasma were required, which could be introduced directly into the separation capillary after 1:1 dilution with 100 mM aqueous sodium dodecyl sulfate (SDS). For increased sample throughput, an additional ultrafiltration step was performed after SDS-dilution of the plasma sample, improving both reproducibility and robustness of the method considerably. The sensitivity of the new method (3 micrograms/ml) was sufficient to follow plasma levels in pharmacokinetic studies. The practicability of this easy and rapid assay was demonstrated by the analysis of more than 350 plasma samples from pharmacokinetic studies performed in rats.

Animals↗
PubMed1996

On the pressure and flow-rate distributions in tree-like and arterial-venous networks.

A solution algorithm yielding the pressure and flow-rate distributions for steady flow in an arbitrary, tree-like network is provided. Given the tree topology, the conductance of each segment and the pressure distribution at the boundary nodes, the solution is obtained from a simple recursion based on perfect Gauss elimination. An iterative solution method using this algorithm is suggested to solve for the pressure and flow-rate distributions in an arbitrary diverging-converging (arterial-venous) network consisting of two tree-like networks which are connected to each other at the capillary nodes. A number of special solutions for tree-like networks are obtained for which the general algorithm is either simplified or can be replaced by closed form solutions of the pressure and flow-rate distributions. These special solutions can also be obtained for each tree of diverging-converging networks having particular topologies and conductance distributions. Sample numerical results are provided.

Algorithms↗
PubMed1995

Unified enantioselective capillary chromatography on a Chirasil-DEX stationary phase. Advantages of column miniaturization.

Immobilized Chirasil-DEX (mono-6-O-octamethylenepermethyl-beta-cyclodextrin chemically linked to dimethylpolysiloxane) can be employed as a versatile chiral stationary phase in chromatography. The chiral polymer has a long lifetime and is configurationally and thermally stable. The concept of unified enantioselective chromatography has been demonstrated for the enantiomer separation of hexobarbital by gas chromatography, supercritical fluid chromatography, liquid chromatography and capillary electrochromatography on a single open-tubular column (1 m x 50 microns I.D.) coated with Chirasil-DEX. The advantages of miniaturization in contemporary chromatographic enantiomer separation are demonstrated. Chirasil-DEX coated on porous silica is also useful for enantiomer separation in high-performance liquid chromatography.

Carbohydrate Sequence↗
PubMed1995

Lipid profile with paternal history of coronary heart disease before age 40.

Serum lipids were measured in children and their parents from 40 families in which the father had a myocardial infarction or coronary heart disease (CHD) before age 40 years. The relationship between physical activity and serum lipid concentrations in the children was also evaluated. Twenty six men had one or more abnormal lipid value (in mmol/l): total venous cholesterol (TVC) > 6.24, triglycerides < 2.55, low density lipoprotein cholesterol (LDL-C) > 4.42, or high density lipoprotein cholesterol (HDL-C) < 0.91. There were 15 spouses with significant hyperlipidaemia (values above). In the 107 children examined, TVC mean (SD) was 4.68 (1.17), triglycerides 1.4 (0.8), LDL-C 3.0 (1.0), and HDL-C 1.18 (0.28). Altogether 42% of the children had significant hyperlipidaemia. No significant correlation was found between the degree of physical activity of the children and their LDL-C and TVC concentrations. However, a significant positive correlation was found between the degree of physical activity and HDL-C and a significant negative one with triglyceride concentrations. It is concluded that screening the progeny of young CHD patients is highly productive in identifying young people at excessive risk for future CHD. The data also suggest that promoting high degrees of activity among these children may have a positive influence on risk factors for adult onset CHD.

Adolescent↗