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Biomedical subjects

G Mayer

Publications and source records attributed to G Mayer.

At least 73 records · Page 4Linked to original sources
PubMed2001

Anaphylactic reactions to aprotinin reexposure in cardiac surgery: relation to antiaprotinin immunoglobulin G and E antibodies.

BACKGROUND: Aprotinin, a serine proteinase inhibitor, reduces bleeding during cardiac surgery. As aprotinin is derived from bovine lung, it has antigenic properties. This investigation examined the incidence of anaphylactic reactions in patients reexposed to aprotinin and the relation to preformed antiaprotinin immunoglobulin (Ig)G and IgE antibodies. METHODS: This prospective observational study conducted at five centers in Germany evaluated patients undergoing repeat cardiac surgery reexposed to aprotinin between 1995 and 1996. Antiaprotinin IgG and IgE antibody measurements, using a noncommercial enzyme-linked immunosorbent assay and an immunofluorescence assay, respectively, were performed preoperatively and postoperatively. An anaphylactic reaction was defined as major changes from baseline within 10 min of aprotinin administration of systolic pressure 20% or greater, heart rate 20% or greater, inspiratory pressure greater than 5 cm H2O, or a skin reaction. RESULTS: In 121 cases (71 adults, 46 children), a mean aprotinin reexposure interval of 1,654 days (range, 16-7,136 days) was observed. Preoperative antiaprotinin IgG (optical density ratio > 3) and IgE antibodies (radioallergosorbent test [RAST] score < 3) were detected in 18 and 9 patients, respectively. High concentrations of each (IgG, optical density ratio > 10; IgE, RAST score > or = 3) were detected in five patients. Three patients (2.5%; 95% confidence interval, 0.51-7.1%) experienced an anaphylactic reaction after aprotinin exposure, followed by full recovery; these patients had reexposure intervals less than 6 months (22, 25, and 25 days) and the highest preoperative IgG concentrations of all patients (P < 0.05). Assay sensitivity was 100%, as no anaphylactic reactions occurred in IgG-negative patients (95% confidence interval, 0.0-3.1%); assay specificity was 98%. Preoperative IgE measurements were quantifiable in two of three reactive patients and in three nonreacting patients. CONCLUSIONS: Quantitative detection of antiaprotinin IgE and IgG lacks specificity for predictive purposes; however, quantitation of antiaprotinin IgG may identify patients at risk for developing an anaphylactic reaction to aprotinin reexposure.

Adolescent↗
PubMed2001

Reduction in mean glomerular pore size coincides with the development of large shunt pores in patients with diabetic nephropathy.

The glomerular size selectivity was determined by neutral dextran clearance sieving technique and plasma cystatin C levels in two groups of patients with long-standing type I diabetes mellitus and different stages of albuminuria but normal glomerular filtration rate and in a group of healthy controls. The sieving characteristics of the glomerular filter were determined using a mathematical model of log normal pore size distribution. Patients with albuminuria above 200 microg/min exhibited a significant increase of cystatin c plasma concentrations and a significant reduction in mean glomerular filtration slit size. Only these patients exhibited large, unrestrictive pores in the glomerular filter (shunt). The plasma cystatin c levels correlated significantly with 26-angstrom neutral dextran plasma levels in microalbuminuric patients and in patients with albuminuria above 200 microg/min. We conclude that a reduction in average pore size of the glomerular filter does not occur earlier than the development of large shunt pores. The renal clearance of cystatin c in patients with proteinuric diabetic nephropathy but a normal glomerular filtration rate is reduced due to its molecular size.

Adult↗
PubMed2000

Hypothyroidism as a cause of tacrolimus intoxication and acute renal failure: a case report.

The nephrotoxic side effects of cyclophilin-binding agents like cyclosporine A and tacrolimus are well characterized. In severe cases nephrotoxicity may profoundly deteriorate kidney function and even induce acute renal failure. In this report we describe the first case of excessive tacrolimus intoxication caused by hypothyroidism. The patient had undergone single-lung transplantation 6 months earlier, developed hypothyroidism, and was admitted with acute anuric renal failure. Thyroxin is a potent activator of the cytochrome P-450- CYP 3A enzyme system, which is crucial for tacrolimus metabolism. Hence, hypothyroidism reduces cytochrome P-450 activity and may result in drug accumulation. Rapid reversal of toxic drug levels could be achieved by reducing drug intake and increasing thyroxin levels by substitution therapy. In conclusion, it is important to consider thyroid function when prescribing medications with a narrow therapeutic range, which are metabolized by the cytochrome P-450 system such as tacrolimus, and the possible devastating effect of impaired drug metabolism during hypothyroidism.

Acute Kidney Injury↗
PubMed2000

Thymosin alpha(1) application augments immune response and down-regulates tumor weight and organ colonization in BALB/c-mice.

The immunomodulatory and antimetastatic/antitumor activity of thymosin alpha(1) (Talpha(1)) was evaluated in BALB/c-mice. Daily subcutaneous application (7 consecutive days, 0.01-10 microg of Talpha(1)/injection per mouse) upregulated the number of thymocytes and peripheral blood cells in tumor bearing mice. To check the influence of Talpha(1) treatment on growth of experimental metastases, RAW H10 lymphosarcoma cells or L-1 sarcoma cells were intravenously injected into BALB/c-mice to establish liver or lung metastases. Local tumor growth was induced by subcutaneous injection of L-1 sarcoma cells. Talpha(1) was subcutaneously administered daily for 7 consecutive days starting 24 h after tumor cell challenge. Organ colonization, as well as local tumor growth, were investigated on day 14 after tumor cell inoculation, and demonstrated a statistically significant (P<0.05) reduction of experimental liver and lung metastases and local tumor growth for Talpha(1) treated mice.

Adjuvants, Immunologic↗
PubMed2000

High-performance liquid chromatographic determination of p-aminohippuric acid and iothalamate in human serum and urine: comparison of two sample preparation methods.

A high-performance liquid chromatography method applied to determine p-aminohippuric acid (PAH) and iothalamate (IOT) in serum and urine samples of patients was evaluated according to recovery, reproducibility and linearity utilizing narrow-bore columns. The mobile phase consisted of 0.15 M sodium dihydrogenphosphate with 1.2 mM tetrabutylammonium sulphate, the pH was adjusted to pH 4.6, acetonitrile was added to a final ratio of 95:5 (v/v), the flow-rate was set at 0.3 ml/min. The separation was achieved on a ODS Hypersil column (200 x 2.1 mm I.D.). The UV detector was set at 254 nm. PAH and IOT are used for evaluation of kidney function [effective renal plasma flow (ERPF) and glomerular filtration rate (GFR)]). Under the described chromatographic conditions two sample preparation techniques, ultrafiltration and acetonitrile precipitation were compared. The results demonstrate the accuracy of both methods in evaluation of ERPF and GFR. Due to its cost-effectiveness we recommend the acetonitrile precipitation method in clinical routine.

Chromatography, High Pressure Liquid↗
PubMed2000

Endoscopic mucosal resection of early cancer and high-grade dysplasia in Barrett's esophagus.

BACKGROUND & AIMS: In view of the mortality and morbidity rates of esophagectomy and the relatively large group of inoperable patients, local therapeutic techniques are required for high-grade dysplasia and early Barrett's cancer. METHODS: A prospective investigation of endoscopic mucosal resection was conducted in 64 patients (mean age, 65 +/- 10 years) who had early carcinoma (61 patients) or high-grade dysplasia (3 patients) in Barrett's esophagus. Thirty-five patients met the criteria for low risk: macroscopic types I, IIa, IIb, and IIc; lesion diameter up to 20 mm; mucosal lesion; and histological grades G1 and G2 and/or high-grade dysplasia (group A). The remaining 29 patients were included in group B (high risk). RESULTS: A total of 120 resections were performed, with no technical problems encountered. The mean number of treatment sessions per patient was 1. 3 +/- 0.6 in group A and 2.8 +/- 2.0 in group B (P < 0.0005). Only one major complication occurred, a case of spurting bleeding, which was managed endoscopically. Complete local remission was achieved significantly earlier (P = 0.008) in group A than in group B. In May 1999, complete remission had been achieved in 97% of the patients in group A and in 59% of those in group B; however, 1 patient in group A and 9 in group B are still undergoing treatment or awaiting the first check-up. During a mean follow-up of 12 +/- 8 months, recurrent or metachronous carcinomas were found in 14%. CONCLUSIONS: Endoscopic mucosal resection of early carcinoma in Barrett's esophagus is associated with promisingly low morbidity and mortality rates. The procedure may offer a new minimally invasive therapeutic alternative to esophagectomy, especially in low-risk situations. Comparisons with surgical results will need to be done when the long-term results of this procedure become available.

Adult↗
PubMed2000

Nucleic acid aptamers-from selection in vitro to applications in vivo.

Aptamers are nucleic acid ligands which are isolated from combinatorial oligonucleotide libraries by in vitro selection. They exhibit highly complex and sophisticated molecular recognition properties and are capable of binding tightly and specifically to targets ranging from small molecules to complex multimeric structures. Besides their promising application as molecular sensors, many aptamers targeted against proteins are also able to interfere with the proteins' biological function. Recently developed techniques facilitate the intracellular application of aptamers and their use as in vivo modulators of cellular physiology. Using these approaches, one can quickly obtain highly specific research reagents that act on defined intracellular targets in the context of the living cell.

Animals↗
PubMed2000

The Erlangen Endo-Trainer: life-like simulation for diagnostic and interventional endoscopic retrograde cholangiography.

The Erlanger Endo-Trainer offers a large spectrum of training possibilities in endoscopic techniques using life-like biological specimens. We organised the first pilot study of interventions at the papilla and the bile duct under x-ray control. Specially prepared upper visceral porcine organ packages including the esophagus, stomach, duodenum, liver, gallbladder and bile ducts were implanted into the Endo-Trainer. Furthermore, small stones were introduced into the bile duct. The test study was carried out by a senior endoscopist assisted by his endoscopy nurse. The following steps could therefore be carried out as a structured team-training scheme: Introduction of the side-viewing endoscope and passage into the duodenum; identification and adjustment at the papilla; cannulation of the papilla; selective bile duct imaging with contrast application under x-ray vision; placement of a guidewire; papillotomy; stone extraction and finally placement of a plastic stent. The special value of this type of simulation is the fact that endoscopic techniques can be trained in the usual manner with real tissue-feeling using regular commercial instruments. Although there is general consent that individual practice on the patient cannot be completely replaced by simulator training, a suitable and realistic simulation model can be of great value, for initial steps prior to "real" patient contact as well as for refining techniques and tactics.

Animals↗
PubMed2000

Mechanisms of hypertension after renal transplantation.

Hypertension is extremely prevalent after renal transplantation, affecting up to 70% of all patients. An elevation in blood pressure is associated with an increased cardiovascular risk and may also contribute to chronic allograft failure. Renal transplantation provides interesting insights into the pathogenesis of hypertension. Experimental and human data show that the kidney is an essential organ for blood pressure regulation. In clinical practice a differential diagnosis that is based on excretory allograft function has proved useful.

Animals↗
PubMed2000

Bacteriological and serological findings in a further case of transfusion-mediated Yersinia enterocolitica sepsis.

A 13-year-old patient developed severe shock due to administration of a Yersinia enterocolitica-contaminated red blood cell concentrate. Y. enterocolitica (serotype O:9, biotype II) was cultivated from the residual blood in the blood bag and from a stool sample of the blood donor. In the donor's plasma immunoglobulin M (IgM), IgA, and IgG antibodies against Yersinia outer proteins (YopM, -H, -D, and -E) were found. Since the donor remembered a short-lasting, mild diarrhea 14 days prior to blood donation, a transient attack of Yersinia enteritis may be associated with a longer than expected period of asymptomatic bacteremia that causes contamination of donor blood. Serological screening for IgM antibodies against Yersinia outer proteins might offer a way to reduce the risk of transfusion-associated Y. enterocolitica sepsis.

Adolescent↗
PubMed2000

Introduction of a novel HRP substrate-Nanogold probe for signal amplification in immunocytochemistry.

Amplification of immunological signals with catalyzed reporter deposition (CARD) allows improved detection of scarce tissue antigens in light and electron microscopy. The technique takes advantage of the oxidation ability of horseradish peroxidase (HRP), in the presence of hydrogen peroxide, to yield the accumulation of one of its specific reporter-tagged substrates. This immunocytochemical approach continues to be improved by the introduction of new reporter molecules tagged to tyramine or to other HRP substrates. In this study we introduced a novel HRP substrate tagged to Nanogold particles. The amplification protocol is based on the application of a specific primary antibody, a biotinylated secondary antibody, streptavidin-HRP, and an HRP substrate coupled to Nanogold, followed by silver intensification. In addition to amplification of immunological signals of high resolution, direct accumulation of Nanogold particles at target sites by enzymatic activity of HRP improves the efficiency of the technique compared to other amplification protocols. Moreover, this approach combines the CARD amplification potentials with the ultrasmall gold probe and the silver intensification method. Immunolabeling obtained by light and electron microscopy, as well as immunodot assay using this new amplification strategy, appear to be highly sensitive, specific, and of enhanced intensity.

Animals↗
PubMed2000

Colocalization of chaperone Cpn60, proinsulin and convertase PC1 within immature secretory granules of insulin-secreting cells suggests a role for Cpn60 in insulin processing.

Many of the mechanisms that control insulin processing and packaging by interaction with different elements along the secretory pathway remain poorly understood. We have investigated the possibility that Cpn60, a member of the heat shock protein family, may be present in rat insulin-secreting cells, participating in the proinsulin-insulin maturation process. Immunofluorescence and high resolution immunocytochemical studies revealed the presence of the Cpn60 protein all along the insulin secretory pathway, being particularly abundant over the proinsulin-containing immature secretory granules. Double-labeling experiments showed associations between Cpn60 and proinsulin, as well as between Cpn60 and PC1 convertase, with a preferential binding to proinsulin. These findings paralleled those of coimmunoprecipitation studies showing the Cpn60 chaperone and the mature form of the PC1 convertase in proinsulin immunoprecipitates, as well as the PC1 in Cpn60 immunoprecipitates from total islet cell extracts. In vitro binding of Cpn60 to proinsulin, insulin and glucagon was also documented. Cpn60, significantly abundant in proinsulin-containing secretory granules where conversion of proinsulin to insulin takes place, and the colocalization of the chaperone with proinsulin and PC1 convertase suggest that the Cpn60 protein may play a role directing precise molecular interactions during insulin processing and/or packaging.

Animals↗
PubMed2000

Sleep atlas and multimedia database.

The ENN sleep atlas and database was set up on a dedicated server connected to the internet thus providing all services such as WWW, ftp and telnet access. The database serves as a platform to promote the goals of the European Neurological Network, to exchange patient cases for second opinion between experts and to create a case-oriented multimedia sleep atlas with descriptive text, images and video-clips of all known sleep disorders. The sleep atlas consists of a small public and a large private part for members of the consortium. 20 patient cases were collected and presented with educational information similar to published case reports. Case reports are complemented with images, video-clips and biosignal recordings. A Java based viewer for biosignals provided in EDF format was installed in order to move free within the sleep recordings without the need to download the full recording on the client.

CD-ROM↗
PubMed1999

Biomonitoring of human genotoxicity induced by complex occupational exposures.

Sensitivity, specificity and correlations among several biomarkers for monitoring occupational exposure to complex mixtures of genotoxic agents were assessed in occupational environments in Hungarian study populations. The studies have been focused on DNA adduct formation, urinary metabolites, mutations and micronuclei induced by exposures to complex organic mixtures. In two Hungarian aluminium plants, increased DNA adduct and 1-hydroxypyrene (1-OH-PY) levels were observed in workers as compared to controls. However, no association between the biomarker levels was evident on an individual basis. In Hungarian garage mechanics, DNA adduct determinations did not show increased genotoxic exposure as compared to the controls. However, ambient air measurements, significantly enhanced 1-OH-PY levels, and slightly enhanced frequency of micronuclei indicated increased polycyclic aromatic hydrocarbon (PAH) exposure in the garages, as compared to the general environment. In a Hungarian vulcanizing plant, DNA adduct determinations and 1-OH-PY did not show significantly elevated exposure levels as compared to controls. The glycophorin A (GPA) somatic mutation assay was also negative for this occupational exposure. The results support previous observations of a lack of correlation between DNA adducts detectable by 32P-postlabelling and those measured by the PAH-DNA immunoassay in the same DNA sample. These studies also demonstrate a lack of close correlation between levels of DNA adducts and urinary 1-OH-PY in the same individual.

Air Pollutants, Occupational↗
PubMed1999

Dual reporter systems in yeast and mammalian cells for assessing progesterone receptor modulators.

In the present study we describe the set-up of a new one-hybrid reporter gene assay in Saccharomyces cerevisiae composed of the human progesterone receptor fused to the DNA-binding domain of the yeast transcriptional activator Gal4. This assay allows the convenient estimation of receptor mediated progestogenic as well as antiprogestogenic actions of compounds. The induction of the beta-galactosidase reporter gene expression correlated well with the progesterone receptor affinity and the concentration of the progestins tested. The results corresponded to those obtained from a reporter gene assay in the cancer cell line CV-1 and in vitro binding experiments using rabbit uterus cytosol. In both the yeast and CV-1 cells the activity of antiprogestins was detectable by inhibition of the progestin-induced reporter gene expression. Secondary reporter genes under the transcriptional control of receptor unrelated promoters have been introduced into yeast and mammalian test strains to distinguish between specific receptor mediated antihormone actions and nonspecific effects on cellular metabolism.

Amino Acid Sequence↗
PubMed1999

Cloning of a second nm23-M1 cDNA: expression in the central nervous system of adult mouse and comparison with nm23-M2 mRNA distribution.

Nm23 has been identified as a gene family encoding different isoforms of the nucleoside diphosphate kinase. This protein is a key enzyme in the control of cellular concentrations of nucleoside triphosphates. Moreover, it has been shown to play important roles in various cellular functions such as differentiation and metastasis. In the present study, a second cDNA for nucleoside diphosphate kinase A (Nm23-M1) was isolated from a cDNA library of mouse embryonic stem cells. This clone encodes the same putative 152 aminoacids long protein as an already published cDNA but is longer in both its 5' and 3' untranslated regions. Tissue and cellular distribution of nm23-M1 mRNA was investigated by using Northern blot analysis and in situ hybridization. Nm23-M1 transcripts were found to be widely distributed throughout the mouse central nervous system with prominent expression in several restricted areas. No differences were noticed between the distribution of long and short transcripts. Furthermore, a similar pattern of expression was described in the central nervous system for nm23-M2 mRNA, encoding a second isoform of the nucleoside diphosphate kinase. However, the transcript of this isoform displayed a wider distribution and was expressed in all organs analysed by northern blotting. The possible involvement of nm23-M1 in differentiation of mouse nervous system is further discussed.

Animals↗