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P Weber

Publications and source records attributed to P Weber.

At least 145 records · Page 8Linked to original sources
PubMed1995

Translocation of gliadin into HLA-DR antigen containing lysosomes in coeliac disease enterocytes.

Coeliac disease is triggered by ingestion of wheat gliadin and is probably immune mediated. There is evidence by light microscopy that expression of class II major histocompatibility complex (MHC) molecules is increased in the small intestinal epithelium of patients with untreated coeliac disease and that gliadin can be taken up by small intestinal enterocytes. The pathway by which gliadin is transported to class II MHC proteins has not been demonstrated. Using an immunogold technique and thin frozen sections of jejunal biopsy specimens, gliadin, HLA-DR antigens, and IgA were localised at an ultrastructural level in the jejunal epithelium of patients with both untreated and treated coeliac disease and controls. Cathepsin D was used as a marker for late endosomes or lysosomes. The results show that gliadin is translocated into vacuoles positive for HLA-DR antigens as well as cathepsin D in jejunal enterocytes of patients with untreated coeliac disease. Secretory IgA may have a role in this translocation of gliadin, which is a specific event that occurred only in jejunal enterocytes from patients with untreated coeliac disease but not in a patient maintained on a gluten free diet or in controls. These results support a central role for epithelial cells of the human intestinal mucosa in the transport of gliadin to an HLA-DR positive compartment which precedes antigen presentation of gliadin to antigen sensitive T lymphocytes.

Antigen Presentation↗
PubMed1994

A protein kinase isolated from porcine brain microvessels is similar to a class of heat-shock proteins.

To further characterize a protein kinase present in porcine brain microvessels, a cDNA library using porcine microvessel poly(A) RNA was screened with polyclonal antibodies raised against the native protein kinase. Since no full-length cDNA clone could be obtained, the missing sequence information was completed using two subsequent polymerase chain reactions. The amplified transcripts were cloned and the sequence determined. Additionally, a genomic DNA library from porcine kidney was screened to substantiate the results obtained from the polymerase chain reaction. Earlier hints of a relation to a subclass of the family of heat-shock proteins (HSPs) based upon a close sequence similarity at its amino-terminus could be confirmed by comparison of the full-length cDNA sequences. Common protein kinase consensus sequences, a targeting sequence for proteins of the endoplasmic reticulum at the carboxy-terminus as well as a hydrophobic leader sequence in the amino-terminal region of the protein could also be identified. Furthermore, a set of membrane-associated substrate proteins of this enzyme could be detected in brain capillaries. The results indicate that at least some members of the HSP 90 subfamily undergo autophosphorylation and show protein kinase activity by phosphorylating substrate proteins in vitro.

Amino Acid Sequence↗
PubMed1994

[Hepatitis-B-associated vasculitis. Clinical course with glucocorticoid and alpha-interferon therapy].

A 31-year-old women with chronic active hepatitis B (HBs antigen-positive, HBe antigen-negative) developed a painful petechia rash on both lower legs and the inner surface of the thighs. Histology of a skin biopsy revealed leucocytoclastic vasculitis. The affected skin areas contained HBs antigen and immunoglobulins. Immunosuppressive treatment with initially 60mg/d prednisolone improved the skin condition but activated the chronic hepatitis, GPT rising up to 240 U/l. The steroid treatment had to be discontinued. Subsequently the transaminases became normal but the vasculitis foci recurred. The patient was therefore given alpha-interferon, three times 5 mill. IU weekly subcutaneously for 6 months. The skin lesions disappeared and the circulating HBV-DNA decreased. But the HBs antigen could not be eliminated. It is to be noted that 12 months after the end of the alpha-interferon treatment the vasculitis has not recurred. - This case and published reports indicate that interferon treatment is effective against HBV-associated and immunoglobulin-complex mediated disease.

Adult↗
PubMed1994

Methods for reconstructing phase sensitive slice profiles in magnetic resonance imaging.

The experimental determination of slice profiles excited by applying radiofrequency pulses in the presence of a gradient generally results in magnitude profiles. The conditions necessary to obtain a phase-sensitive picture of the profile of a slice are discussed. A distinction is made between the "excitation profile" (distribution of the transverse magnetization immediately after the RF pulse) and the "slice profile" (distribution after refocusing by gradient reversal and/or imperfect gradient switching). Methods are presented that allow one to obtain either the excitation profile or the slice profile. It is shown that phase encoding along the direction of the slice selection gradient provides a convenient protocol for obtaining the distribution of both the real and imaginary parts of the slice profile. The phase sensitive excitation profile can be obtained by frequency encoding. These methods were used to evaluate the performance of various shaped pulses.

Algorithms↗
PubMed1994

A nonradioactive assay for microsomal cysteine-S-conjugate N-acetyltransferase activity by high-pressure liquid chromatography.

Microsomal cysteine-S-conjugate N-acetyltransferase, an enzyme specific for S-substituted cysteines, plays an important role in the detoxicative metabolism of xenobiotics by catalyzing the N-acetylation of cysteine-S-conjugates. Cysteine-S-conjugate N-acetyl-transferase activity is generally assayed by measuring the amount of N-[14C]acetyl-S-benzyl-L-cysteine generated from the model compound S-benzyl-L-cysteine and [14C]acetyl-CoA and subsequent extraction of the product. Although sensitive, this method is costly and time consuming. For safety and environmental reasons we developed a nonradioactive assay for cysteine-S-conjugate N-acetyltransferase activity. Our method depends upon the acetylation of the uv-sensitive model compound 4-nitro-S-benzyl-L-cysteine. The test mixture is separated by HPLC, guaranteeing that no by-products interfere with the determination of product formation. Radioactive and nonradioactive methods were compared using different porcine kidney samples. With the nonradioactive test we determined values of Km and Vmax of both 4-nitro-S-benzyl-L-cysteine and acetyl-CoA. In summary, this new nonradioactive assay is sensitive, less costly, safer, less time-consuming, and less laborious than radioactive assays for cysteine-S-conjugate N-acetyltransferase.

Acetyl Coenzyme A↗
PubMed1994

Cytomegalovirus in liver biopsies of marrow transplant recipients: detection methods, clinical, histological and immunohistological features.

In a retrospective analysis liver biopsy specimens obtained from 44 marrow transplant recipients were studied to evaluate the frequency of local presence of human cytomegalovirus (CMV) and graft-versus-host disease (GvHD)-like histological and immunohistological alterations in patients with and without liver dysfunction following bone marrow transplantation (BMT). In 22 of 28 patients with marked liver dysfunction after BMT and histopathological alterations described as typical for acute GvHD CMV could be detected in the liver biopsy specimen. The polymerase chain reaction (PCR) technique revealed the highest sensitivity for CMV detection in liver biopsy samples, but in 20 of 22 PCR-positive specimens CMV infection could be confirmed by at least one additional technique. All the liver biopsies obtained from 16 patients with normal liver function lacking histopathological signs of GvHD were CMV negative. In all 3 patients with CMV-positive liver biopsy started on antiviral therapy liver function improved and no generalized CMV disease occurred. All the 4 patients without local presence of CMV started on severe immunosuppressive therapy showed an improvement of liver dysfunction without occurrence of CMV infection. Local CMV infection of the liver could not be differentiated from hepatic GvHD by clinical and histopathological features, nor by immunohistological analysis of the bile duct epithelium. In contrast, only in liver biopsy with local viral presence could an increase in HLA class II- and ICAM-1 expression be demonstrated on hepatocytes. Thus, especially the high negative predictive value of the PCR technique helps to manage the patient with liver dysfunction after BMT.

Adolescent↗
PubMed1994

Neutrophil autoantibodies: a genetic marker in primary sclerosing cholangitis and ulcerative colitis.

BACKGROUND/AIMS: Perinuclear antineutrophil cytoplasmic antibodies (pANCA) were found at high frequency in patients with primary sclerosing cholangitis and ulcerative colitis. In this study, to accumulate further evidence for the importance of genetic factors in pathogenesis of inflammatory bowel disease, sera of patients with inflammatory bowel disease and primary sclerosing cholangitis and their unaffected family members were tested for pANCA. METHODS: Three hundred twenty-seven sera from 11 families of patients with primary sclerosing cholangitis, 43 families of patients with ulcerative colitis, 11 families of patients with Crohn's disease, and 11 healthy families were tested for pANCA in immunofluorescence on cytospin slides with isolated neutrophils. RESULTS: pANCA were found in 82% of the patients with primary sclerosing cholangitis and in 25% of their relatives. In ulcerative colitis, 70% of the patients and 30% of their relatives had pANCA. pANCA were found only in low titers in 27% of patients with Crohn's disease and in 6% of their relatives. pANCA were not detected in members of healthy families. Only 16% of the patients with ulcerative colitis and their families and none of the patients with primary sclerosing cholangitis and their families were completely negative for pANCA. CONCLUSIONS: These data show that pANCA may be a genetic marker in families of patients with ulcerative colitis and primary sclerosing cholangitis.

Adolescent↗
PubMed1994

Induction of autoimmune phenomena in patients with chronic hepatitis B treated with gamma-interferon.

All interferons display antiviral properties, but gamma-interferon especially has an immunomodulatory effect and may induce autoimmune phenomena. Therefore the formation of autoantibodies was investigated in patients with chronic hepatitis B treated with gamma-interferon. Eleven patients (all HBs-Ag and HBe-Ag positive) were treated for 6 months with recombinant gamma-interferon. The following antibodies were tested: anti-nuclear antibodies, smooth muscle antibodies, anti-actin, anti-mitochondrial antibodies of subgroup anti-M2 and anti-M9 as well as naturally occurring antibodies, antibodies to liver-kidney microsomes, vascular endothelial cell antibodies, sarcolemmal antibodies, parietal cell antibodies, thyroglobulin antibodies and antibodies to laminin and keratin. All patients produced autoantibodies during therapy. The maximum antibody formation and the highest titres were observed in the period between the 3rd and 6th month after therapy began. The cumulative frequencies of the different antibody specificities were as follows: n = 6 anti-nuclear antibodies, n = 7 smooth muscle antibodies, n = 1 anti-actin, n = 12 antibodies to laminin or keratin, n = 6 endothelial cell antibodies/sarcolemmal antibodies, n = 6 anti-mitochondrial antibodies, n = 1 antibodies to liver-kidney microsomes, n = 2 thyroglobulin antibodies, n = 4 parietal cell antibodies. Antibodies persisted in six patients over a period of 3 months (two cases of parietal cell antibodies and one case of antibodies to liver-kidney microsomes) and were still detectable in three patients 6 months after therapy. In three patients new antibody formation occurred 1 month after therapy. So far, clinical signs of an autoimmune disorder have not appeared in any of the patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Actins↗
PubMed1994

Restored heptad pattern continuity does not alter the folding of a four-alpha-helix bundle.

The sequences of alpha-helical coiled-coils and bundles are characterized by a specific pattern of hydrophobic and hydrophilic residues which is repeated every seven residues. Highly conserved breaks in this pattern frequently occur in segments of otherwise continuous heptad substructures. The hairpin bend of the ROP protein coincides with such a break and provides a model system for the study of the structural effects induced by heptad discontinuities. The structure of a ROP mutant which re-establishes a continuous heptad pattern, shows insignificant changes relative to the wild-type protein, as is also reflected in its conformational stability, spectroscopic properties and unfolding behaviour. Thus, formation of alpha-alpha-hairpin bends may occur both in the presence and absence of heptad breaks.

Amino Acid Sequence↗
PubMed1994

Tenascin-contactin/F11 interactions: a clue for a developmental role?

To understand how the extracellular matrix glycoprotein tenascin modifies cell adhesion and neurite outgrowth, we sought to isolate cellular receptors for tenascin. So far, two completely different cell surface ligands for tenascin have been detected. This we achieved by affinity chromatography of tissue extracts and of isolated proteins over tenascin-Sepharose and by solid-phase assays using the individual proteins. The first receptor, the neuronal cell adhesion molecule contactin/F11, a member of the immunoglobulin superfamily, binds to tenascin via a site in the N-terminal immunoglobulin-like domains. The binding site is within the fibronectin type III homology region at the boundary of the alternatively spliced region of tenascin, requiring that fibronectin type III homology domains 5 and 9 be adjacent, as they are in the 190 kD tenascin isoform. The close similarity in tertiary structure between type III domains and immunoglobulin-like repeats raises the possibility that we are observing a side-by-side interaction between the two molecules in a manner closely analogous to that between paired immunoglobulin domains. The second receptor is the heparan sulfate proteoglycan, glypican, which, similarly to contactin/F11, is anchored to the membrane via glycosylphosphatidylinositol. Glypican bound to a column of tenascin-Sepharose cannot be dissociated by chondroitin sulfate or dermatan sulfate, but elutes in a broad peak with a gradient of heparan sulfate and in a sharper peak with heparin. By means of fusion proteins, we have identified a potential binding site on the fifth fibronectin type III homology domain of tenascin. We are trying to define these sites more closely by means of site-directed mutagenesis. It will be interesting to see whether the interaction between tenascin and cell surface contactin/F11, and possibly cellular heparan sulfate proteoglycans, contributes to the prominent role played by tenascin in pattern formation during development of the nervous system. In a first step, we have examined the distribution of tenascin isoforms and contactin/F11 during retinal development by means of immunohistochemistry and in situ hybridization with tenascin isoform-specific probes. Tenascin isoforms 190/200 along with contactin/F11 are particularly prominent in the inner and outer plexiform layers of embryonic day 8 retina in the chick. This coordinate up-regulation was confirmed both by immunoblots and Northern blots of retinal extracts. A speculative model is presented to suggest how the unique hexabrachion may signal the cell via contactin/F11.

Amino Acid Sequence↗
PubMed1994

[Disseminated peritoneal leiomyomatosis: an exceptionally misleading disease. A case report].

Peritoneal leiomyomatosis disseminata is an exceptional benign disease with characteristic multifocal subperitoneal smooth muscle cell growth. We report and exceptional case associating pelvic endometriosis and mimicking cancer of the ovary. Surgery was performed and was found a posteriori to be excessive in light of the good prognosis of this disease. Positive hormone receptor assays on the surgical specimen favoured ovarian steroid hormone involvement in the aetiopathology of this strange disease.

Diagnosis, Differential↗
PubMed1994

Incidence of local CMV infection and acute intestinal GVHD in marrow transplant recipients with severe diarrhoea.

Intestinal biopsy samples derived from 22 consecutive patients with severe diarrhoea (> 1.5 1/day for 3 or more consecutive days) following allogeneic BMT were analysed for the local presence of cytomegalovirus (CMV) and histological and immunohistological alterations described as typical for acute graft-versus-host disease (GVHD). Seventeen patients showed extensive histopathological lesions typical for acute intestinal GVHD grade > I, 14 marked GVHD-related immunohistological alterations. In intestinal biopsies from 10 of these 22 patients CMV-DNA was detected using PCR- and in situ hybridisation techniques. In 7 of these 10 CMV-DNA positive samples CMV protein expression and in 5 cytomegalic cells were demonstrated. CMV could predominantly be shown in biopsies obtained from the ascending colon and/or the terminal ileum. All 10 patients with local CMV infection showed severe histopathological and immunohistological alterations described as typical for acute intestinal GVHD. Five of seven patients with a CMV-positive intestinal biopsy showed marked improvement of lower gastrointestinal tract disease on antiviral therapy. Five of seven patients lacking local presence of CMV but with severe histopathological lesions responded to therapy with high-dose steroids. Thus, PCR screening for CMV and histopathological analysis may help to treat lower intestinal disease in the marrow transplant recipient early and effectively.

Adolescent↗