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Biomedical subjects

M Fuchs

Publications and source records attributed to M Fuchs.

At least 73 records · Page 4Linked to original sources
PubMed1996

Pituitary adenylate cyclase-activating polypeptide: a potent activator of human intestinal ion transport.

To investigate the effects of PACAP-27 on electrolyte transport across the isolated human intestinal mucosa, changes in short-circuit current (Isc) were measured in Ussing chamber experiments. Serosally added PACAP-27 increased Isc in a concentration-dependent manner, eliciting a similar maximal effect in both the jejunal and the colonic mucosa. Bumetanide inhibited Isc responses, indicating stimulation of Cl- secretion. The potency and efficacy of PACAP-27 were comparable to those of VIP, suggesting that both peptides activate intestinal secretion by way of a common receptor located in the basolateral membrane of the intestinal epithelium.

Colon↗
PubMed1996

Peptide nucleic acid pre-gel hybridization: an alternative to southern hybridization.

We have found that it is possible to use labeled peptide nucleic acid (PNA)-oligomers as probes in pre-gel hybridization experiments, as an alternative for Southern hybridization. In this technique, the PNA probe is hybridized to a denatured DNA sample at low ionic strength and the mixture is loaded directly on to an electrophoresis system for size separation. Ensuing gel electrophoresis separates the single-stranded DNA fragments by length. The neutral backbone of PNA allows for hybridization at low ionic strength and imparts very low mobility to excess PNA. Detection of the bound PNA is possible by direct fluorescence detection with capillary electrophoresis, or the DNA/PNA hybrids can be blotted onto a membrane and detected with standard chemiluminescent techniques. Efficient single bp discrimination was achieved routinely using both capillary and slab-gel electrophoresis.

Blotting, Southern↗
PubMed1996

Rapid course radiation therapy vs. more standard treatment: a randomized trial for bone metastases.

PURPOSE: In a prospective randomized trial we examined whether radiotherapy of painful bone metastases can be shortened using larger single doses without impairing effectivity. METHODS AND MATERIALS: One hundred patients with painful bone metastases having no prior surgical intervention or treatment with x-ray therapy and had a median follow-up of 12 months were analyzed. The primary tumor was located in the breast in 43%, in the lung in 24%, and in the prostate in 14%. The most frequent sites of metastases were the pelvis (31%), the vertebral column (30%), and the ribs (20%). Further percentages of sites were: lower extremity 11%, upper extremity 6%, and skull 2%. Fifty-one patients received a short course radiotherapy with a total dose of 20 Gy in 1 week (daily dose 4 Gy), and 49 patients received 30 Gy in 3 weeks (daily dose 2 Gy). RESULTS: There were no significant differences in frequency, duration of pain relief, improvement of mobility, recalcification, frequency of pathologic fractures nor survival. There was a light trend favoring 30 Gy in frequency of pain relief and recalcification. Survival was mostly influenced by primary tumor site, Karnofsky performance status, and possibly by the response to radiotherapy (pain relief). CONCLUSIONS: Because of the very short life expectancy of patients with metastatic bone disease, we now use 20 Gy in 1 week as our standard to reduce hospital stay.

Adult↗
PubMed1996

Gene cloning and cellular localization of a membrane-bound acid phosphatase of Leishmania mexicana.

In a previous publication, we described the purification of a membrane-bound acid phosphatase of Leishmania mexicana as a heterogeneously N-glycosylated protein of an apparent molecular mass of 70000-72000 expressed in both the promastigote and the amastigote stage of the parasite [19]. Screening of a genomic DNA library of L. mexicana with degenerate oligonucleotides designed according to the NH2-terminus of the protein led to the cloning of the lmmbap gene, which is present in one copy per haploid genome. The open reading frame predicts a protein of 516 amino acids composed of a signal sequence, a large hydrophilic region, a trans-membrane alpha-helix and a short cytoplasmic tail. The sequence of the hydrophilic region is homologous to acid phosphatases from other organisms. While in wild-type promastigotes, the acid phosphatase is located in the endosomal/lysosomal compartment between the flagellar pocket and the nucleus, overexpression leads to its abundant exposure on the cell surface. In cells transfected with a construct lacking the region corresponding to the trans-membrane and the cytoplasmic parts, the resulting altered acid phosphatase is efficiently secreted into the culture medium. The potential of this system for studies on membrane trafficking in kinetoplastid organisms is discussed.

Acid Phosphatase↗
PubMed1996

Is a clinical application of hybrid liver support systems limited by an initial disorder in cellular amino acid and alpha-keto acid metabolism, rather than by later gradual loss of primary hepatocyte function?

The in-vitro amino acid (AA) and alpha-keto acid (KA) metabolism of bioreactors initially seeded with 2.5 x 10(9) pig hepatocytes was investigated with a perfusion technique. Considerable changes in the culture medium concentrations of AA and KA were measured during the first days in culture. This is indicative of dynamic cellular metabolism in the initial phase. While the concentration of pyruvate decreased starting on the first day, alpha-ketoglutarate, alpha-ketoisocaproate, alpha-ketoisovalerate, and alpha-keto-beta-methyl-n-valerate were synthesized. The long term use of hepatocyte cultures in bioreactors and thus a desirable clinical hybrid liver support therapy appears to be possible since the hepatocytes switched, after 15 days in culture, to steady-state conditions with a stable amino acid turnover featuring general AA uptake accompanied by KA release. The release of branched chain KA, in particular that of alpha-ketoisocaproate, reflects an effective transamination activity in the bioreactor system. Primary pig hepatocytes cultivated in hybrid liver support systems for therapy of acute liver failure or as devices for bridging to liver transplantation can sustain amino acid metabolism for at least 30 days in vitro. However, an initial disorder following the cell isolation that is demonstrated may limit immediate utilization of the systems prior to the reorganisation of the cells to tissue-like structures in bioreactors.

Amino Acids↗
PubMed1996

Association of human protein-tyrosine phosphatase kappa with members of the armadillo family.

We have identified a human receptor-like protein-tyrosine phosphatase (PTP) in the mammary carcinoma cell line SK-BR-3, which represents the human homolog of murine PTPkappa (Jiang, Y.-P., Wang, H., D'Eustachio, P., Musacchio, J. M., Schlessinger, J., and Sap, J. (1993) Mol. Cell. Biol. 13, 2942-2951) and was therefore termed hPTPkappa. We show here that hPTPkappa expression is dependent on cell density and find it colocalized with two members of the arm family of proteins, beta-catenin and gamma-catenin/plakoglobin, at adherens junctions. Using both in vitro and in vivo binding assays, we demonstrate specific complex formation between endogenous hPTPkappa and beta- and gamma-catenin/plakoglobin. In addition, we present evidence that suggests that beta-catenin may represent a substrate for the catalytic activity of hPTPkappa. The identification of specific binding partners for this receptor-like PTP provides insight into the mechanisms of its biological action and suggests a role for hPTPkappa in the regulation of processes involving cell contact and adhesion such as growth control, tumor invasion, and metastasis.

Amino Acid Sequence↗
PubMed1996

Microchip electrophoretic immunoassay for serum cortisol.

An immunoassay performed using a microchip electrophoretic system is described. Separation and quantitation of free and bound labeled antigen in a competitive assay are carried out in channels micromachined into fused silica substrates. Such microchips are attractive because of their small size, ruggedness, and amenability to automated handling. The assay achieves the determination of cortisol in blood serum over the range of clinical interest (1-60 micrograms/dL) without the need for extraction or other sample preparation steps. The separation is performed in less than 30 s. Very high throughput is possible by operating the assay in multiple channels in parallel. These characteristics make microchip electrophoretic systems a promising technology for the rapid analysis of clinical samples.

Electrophoresis↗
PubMed1996

Antigen presentation by Leishmania mexicana-infected macrophages: activation of helper T cells by a model parasite antigen secreted into the parasitophorous vacuole or expressed on the amastigote surface.

Leishmania are protozoan parasites which invade mammalian macrophages and multiply as amastigotes in phagolysosomes (parasitophorous vacuoles). Using L. mexicana and bone marrow-derived macrophages (BMM), the question is addressed whether infected BMM induced to express major histocompatibility complex class II molecules can present defined antigens to specific T helper type 1 cells. As a model antigen, a membrane-bound acid phosphatase (MAP), a minor protein associated with intracellular vesicles in amastigotes, was either overexpressed at the surface of the parasites or overexpressed in a soluble form leading to antigen secretion into the parasitophorous vacuole. Presentation of MAP epitopes by these three types of amastigotes was then compared for macrophages containing live parasites or amastigotes inactivated by drug treatment. It is shown that surface-exposed and secreted MAP can be efficiently presented to T cells by macrophages harboring live amastigotes. Therefore, the parasitophorous vacuole communicates by vesicular membrane traffic with the plasmalemma of the host cell. The intracellular MAP of wild-type cells or the abundant lysosomal cysteine proteinases are not or only inefficiently presented, respectively. After killing of the parasites, abundant proteins such as overexpressed MAP and the cysteine proteinases efficiently stimulate T cells, while wild-type MAP levels are not effective. We conclude that intracellular proteins of intact amastigotes are not available for presentation, while after parasite inactivation, presentation depends on antigen abundance and possibly stability. The cell biological and possible immunological consequences of these results are discussed.

Animals↗
PubMed1996

[Women in dermatology. German and other European clinics in a comparison].

The situation of women in dermatology was evaluated with the aid of questionnaires in spring 1994. A questionnaire was sent to 33 clinics in Germany and 46 in other European countries, asking about the proportions of male and female physicians in each department. In addition, individual department members were asked in another questionnaire about their reasons for choosing dermatology and about possible sex discrimination. The clinic questionnaires were returned from 22 German and 37 other European clinics and the individual questionnaires by 548 German physicians and 1164 physicians from the other countries (overall 52% women). We found that 41.8% of the dermatologists in German clinics were women, as against 43.4% in the other countries. Women made up about half of the fully qualified specialists, but accounted for only a small percentage of those in higher positions (10.8% in Germany, 27.9% in other countries). Of the 1712 physicians who answered the individual questionnaire, the majority had chosen dermatology because of their interest in the specialty. Slightly more women than men gave other reasons, such as more free time--mostly for family matters--or less physical strain. Clearly more women than men felt they were discriminated against professionally because of their sex. The reasons for this related primarily to the biological and social role of women in society. Overall, women are thus well represented in our specialty, except in leading positions.

Career Choice↗
PubMed1996

[HPV-5 typing with nested PCR and sequencing in epidermodysplasia verruciformis].

We report a case of epidermodysplasia verruciformis (EV) with typical cutaneous manifestations in light-exposed areas. The diagnostic criteria were the characteristic macular lesions, the virus transformed keratinocytes on histological examination and the detection of human papillomavirus (HPV) DNA by a nested-PCR approach for EV-associated types. In this case we found HPV-type 5, the most common type of HPV in EV, directly by sequencing and sequence analysis.

Adult↗
PubMed1996

Isolation and developmental expression analysis of Enx-1, a novel mouse Polycomb group gene.

Members of the Polycomb group (Pc-G) of genes encode transcriptional regulators that control the expression of key developmental effector genes in Drosophila melanogaster. Although multiple Pc-G genes have been identified and characterized in Drosophila, information about these important regulatory proteins in vertebrates, including their precise expression patterns, has remained scarce. We report here the cloning of Enx-1, a novel vertebrate Pc-G gene, which encodes the murine homolog of the Drosophila Enhancer of zeste (E(z)) gene. Drosophila E(z) controls the expression of several homeobox genes as well as some segmentation genes and its disruption causes multiple phenotypes in Drosophila development. Analysis of the primary structure of murine Enx-1 reveals the conservation of several regions, including the previously described SET domain and a newly defined CXC domain. In addition, we find the SET domain to be conserved in evolutionarily distant species ranging from vertebrates to plants and fungi. The expression pattern analysis of Enx-1 reveals ubiquitous expression throughout early embryogenesis, while in later embryonic development Enx-1 expression becomes restricted to specific sites within the central and peripheral nervous system and to the major sites of fetal hematopoiesis. In adult stages we also find Enx-1 expression to be restricted to specific tissues, including spleen, testis and placenta.

Amino Acid Sequence↗
PubMed1996

Feedback regulation of bile acid synthesis measured by stable isotope kinetics in humans.

OBJECTIVE: To investigate the effect of a low dose of exogenous bile acids and a non-absorbable antibiotic on bile acid kinetics in healthy human subjects. METHODS: Pool size, synthesis rate and fractional turnover rate of the three main bile acids were determined simultaneously with stable isotope labelled bile acids in volunteers before and during intake of 500 mg cholic acid (n = 6), chenodeoxycholic acid (n = 6) or deoxycholic acid (n = 5) per day for 4 weeks or 1 g of paromomycin (n = 6) per day for 2 weeks. RESULTS: Administration of cholic acid nearly doubled the input and pool of deoxycholic acid; chenodeoxycholic acid synthesis was inhibited by 38% and pool size was reduced by 50%. Deoxycholic acid administration resulted in a suppression of both cholic acid and chenodeoxycholic acid synthesis by 53%; the corresponding pool sizes were reduced by 64% and 57%, respectively. The degree of suppression of chenodeoxycholic acid synthesis correlated significantly (P < 0.001) with the relative change of deoxycholic acid input and pool size. Oral chenodeoxycholic acid resulted in an inhibition of cholic acid synthesis (65%) and deoxycholic acid input (67%). The effects of the antibiotic were variable. CONCLUSION: The suppressive effect of cholic acid may be mediated by deoxycholic acid, which is nearly as effective as chenodeoxycholate.

Administration, Oral↗
PubMed1995

GCAP-II: isolation and characterization of the circulating form of human uroguanylin.

The systematic isolation of circulating regulatory peptides which generate cGMP as second messenger resulted in the identification of a novel member of the guanylin family. In the present study we describe the purification and amino acid sequence of a new guanylate cyclase C activating peptide (GCAP-II). GCAP-II contains 24 amino acids in the following sequence: FKTLRTIANDDCELCVNVACTGCL. Its molecular mass is 2597.7 Da. The 16 C-terminal amino acids are identical to uroguanylin from human urine. native and synthetic GCAP-II activate GC-C, the specific guanylate cyclase receptor, of cultured human colon carcinoma (T84) cells. GCAP-II stimulates chloride secretion in isolated human intestinal mucosa mediated by intracellular cGMP increase. GCAP-II specific antibodies were used to localize the peptide by immunohistochemistry in entero-endocrine cells of the colonic mucosa.

Amino Acid Sequence↗