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Biomedical subjects

R Keller

Publications and source records attributed to R Keller.

At least 55 records · Page 3Linked to original sources
PubMed2000

Human colostrum and serum contain antibodies reactive to the intimin-binding region of the enteropathogenic Escherichia coli translocated intimin receptor.

BACKGROUND: In Brazil, enteropathogenic Escherichia coli (EPEC) diarrhoea is endemic in young infants. A characteristic feature of EPEC adhesion to host cells is intimate attachment leading to the formation of distinctive "attaching and effacing" (A/E) lesions on mammalian cells. Two genes directly involved in intimate adhesion, eae and tir, encode the adhesion molecule intimin and its translocated receptor Tir, respectively. The intimin-binding domain of Tir was recently mapped to the middle part of the polypeptide (Tir-M), and the amino (Tir-N) and carboxy (Tir-C) termini were found to be located within infected host cells. Recently, it was shown that colostrum samples from mothers living in Sao Paulo contain IgA-class antibodies reactive with a number of proteins associated with EPEC virulence. It has also been shown that patients infected with verocytotoxin-producing E. coli O157 can produce antibodies to Tir. In the current study antibody responses to the different Tir domains were analyzed in sera and colostrum samples collected in an EPEC-endemic area of Brazil. METHODS: Recombinant Tir, Tir-N, Tir-M, and Tir-C were expressed as His-tagged protein in E. coli BL21a and purified on nickel columns. Western blot analysis was used to investigate colostrum IgA- and serum IgG-class antibodies reactive with the Tir fragments. RESULTS: Anti-Tir IgG antibodies were detected in the serum of children, with (63%) or without (50%) diarrhoea. Anti-Tir IgA-class antibodies were detected in all the colostrum pools tested. With the use of both serum IgG- and colostrum IgA-class antibodies, an immunodominant domain of the Tir-polypeptide, Tir M, was identified. CONCLUSION: The intimin-binding region of Tir (Tir-M) is the immunodominant region of the polypeptide in humans. Both serum IgG-class and colostrum IgA-class antibodies reacted predominantly with the Tir-M domain.

Adhesins, Bacterial↗
PubMed2000

Seroprevalence of human herpesvirus 8 and its association with Kaposi sarcoma in Brazil.

BACKGROUND: Epidemiologic studies have indicated that human herpesvirus 8 is implicated in the development of Kaposi sarcoma in different geographic areas worldwide. GOAL: To provide information on the prevalence of human herpesvirus 8 in Brazil and its association with Kaposi sarcoma. STUDY DESIGN: An immunofluorescence assay was performed to test 1,044 serum samples from 747 blood donors, 73 patients presenting to casualty departments, and 224 patients attending sexually transmitted disease/AIDS clinics. The sexually transmitted disease group was composed of 88 patients with HIV (40 Kaposi sarcoma positive, 48 Kaposi sarcoma negative) and 136 patients without HIV. RESULTS: Antibodies to human herpesvirus 8-latent nuclear antigens were found in 34 blood donors (4.6%), and in seven casualty patients (9.6%). The highest frequency of human herpesvirus 8 antibodies was found in the sexually transmitted disease group: 32 HIV-positive patients with Kaposi sarcoma (80%) and seven patients without Kaposi sarcoma (14.6%). CONCLUSION: The presence of human herpesvirus 8 in patients with HIV was strongly associated with Kaposi sarcoma (odds ratio, 23.4; 95% CI, 7.7-71.4), male gender, homosexual or bisexual orientation, and hepatitis B virus infection, but not with the other sexually transmitted diseases that were investigated.

Adult↗
PubMed2000

Two orcokinins and the novel octapeptide orcomyotropin in the hindgut of the crayfish Orconectes limosus: identified myostimulatory neuropeptides originating together in neurones of the terminal abdominal ganglion.

The tridecapeptides Asn(13)-orcokinin and Val(13)-orcokinin, two known members of the orcokinin neuropeptide family native to crustaceans, and a novel octapeptide, orcomyotropin, FDAFTTGFamide, have been identified from extracts of hindguts of the crayfish Orconectes limosus using an isolated hindgut contractility bioassay, high-performance liquid chromatography, microsequencing and mass spectrometry. All three peptides display strong inotropic actions on crayfish hindguts. Orcomyotropin showed higher potency than the two orcokinins. Threshold concentration was approximately 5 x 10(-12)mol l(-1)versus 10(-10)mol l(-1) for the two orcokinins. An approximately fivefold increase in contraction amplitude was observed with 10(-9)mol l(-1) orcomyotropin and 10(-7)mol l(-1) of the orcokinins. Asn(13)- and Val(13)-orcokinin did not differ significantly with regard to their biological effects. Semi-isolated crayfish hearts and locust oviducts did not respond to the three peptides. Immunocytochemistry using antisera against Asn(13)-orcokinin and orcomyotropin showed that these neuropeptides are co-localized in approximately 80-90 neurones of the terminal abdominal ganglion that have been shown to innervate the entire hindgut muscularis via the intestinal nerve. The neurones form elaborate terminal branches preferentially on longitudinal hindgut muscles. Orcomyotropin is a novel crustacean member of the GF-amide family of myotropic and/or allatotropic neuropeptides from annelids, molluscs and insects.

Amino Acid Sequence↗
PubMed2000

Occupational exposure to inhalative irritants and methacholine responsiveness.

OBJECTIVES: Occupational exposures to inhalative irritants have been associated with an increased reporting of respiratory symptoms in previous studies. Methacholine responsiveness represents a continuous measure of airway responsiveness. As such, it may be less subject to recall bias and more sensitive to detecting effects of occupational exposure on airways. Such effects may be stronger among atopic persons. The objective of the study was to examine the relationship between self-reports of occupational exposure to dusts, gases, vapors, aerosols, and fumes and methacholine responsiveness. METHODS: A sample was studied of never smokers (N=3044) chosen randomly from 8 areas in Switzerland. Atopy was defined as any positive skin test to 8 inhalative allergens. Nonspecific bronchial reactivity was tested using methacholine chloride and quantified by calculating the slope of the dose-response. RESULTS: The methacholine slopes were 19% [95% confidence interval (95% CI) 6-32] higher for never smokers with exposure to dusts, fumes, vapors, gases, or aerosols than for the unexposed group. When only atopic never smokers were examined. the increase was larger (37%, 95% CI 7-75), and for persons with >2 positive skin prick tests the effect was still higher (42%, 95% CI -1.5-104). Exposure to vapors and aerosols was strongly associated with increased methacholine slopes among the atopic subjects. CONCLUSIONS: Occupational exposure, particularly to dusts and fumes, was associated with increased bronchial reactivity in never smokers in this study. The magnitude of the effect was larger among atopic subjects.

Adolescent↗
PubMed1999

An evaluation of two-photon excitation versus confocal and digital deconvolution fluorescence microscopy imaging in Xenopus morphogenesis.

The ability to visualize cell motility occurring deep in the context of opaque tissues will allow many currently intractable issues in developmental biology and organogenesis to be addressed. In this study, we compare two-photon excitation with laser scanning confocal and conventional digital deconvolution fluorescence microscopy, using the same optical configuration, for their ability to resolve cell shape deep in Xenopus gastrula and neurula tissues. The two-photon microscope offers better depth penetration and less autofluorescence compared to confocal and conventional deconvolution imaging. Both two-photon excitation and confocal microscopy also provide improved rejection of "out-of-focus" noise and better lateral and axial resolution than conventional digital deconvolution microscopy. Deep Xenopus cells are best resolved by applying the digital deconvolution method on the two-photon images. We have also found that the two-photon has better depth penetration without any degradation in the image quality of interior sections compared to the other two techniques. Also, we have demonstrated that the quality of the image changes at different depths for various excitation powers.

Animals↗
PubMed1999

[Inoperable non-small-cell bronchial carcinoma: macroscopic and microscopic tumor behavior during and after radiotherapy with curative intent].

The supervision of the efficacy of therapy with curative aim in inoperable NSCLC focus on clinical and radiological parameters and the survival rate. But the decision about the local tumour elimination lies in the microscopic area, which cannot be controlled neither by laboratory tests nor by radiological examinations. About twenty years ago with support of our pneumologist we carried out bronchoscopies and biopsies depending on the applied radiation dose. It was our intention to take the remission noted by endoscopy as measure for the reaction of the whole irradiated target volume. The bronchoscopies and biopsies were provided at dose levels of 60 and 80 Gy. 90.9% (340/374) of repeated bronchoscopies were realized after a dose of 60 to 80 Gy. The analysis covers 253 bronchoscopies before and 374 between or after radiotherapy with 623 histological or cytological examinations on a total of 253 patients. At the begin of the radiotherapy 50.2% (127/253) had tumour between trachea and a lobar bronchus, after 60 Gy only 13% and after 80 Gy still 1.2% (1/81) had tumour in this area. The macroscopical tumour elimination rose from 41.4% (80/193) after 60 Gy to 79.3% (65/82) after 80 Gy. In contrast and unexpectedly the microscopic negativity decreased from 73.4% (141/192) to 71.6% (58/82). Partially this result is a consequence of the fact that "necrosis" may be either a part of an untreated malignoma or an effect of an irradiation. The combination of macro- and microscopic tumour elimination rose from 20.5% (7/34) after a dose of 60 Gy to 64% (16/25) after total doses of 80 Gy. Only combined negativity had a consequence for local relapse free survival (p = 0.034) and overall survival (p = 0.0002) in comparison with the patients with persistent macro- and/or microscopically detected endoluminal tumour at the final bronchoscopy. The assessment of endoluminal tumour regression as part of the whole irradiated malignoma permits conclusions about the total dose needed. This is a new approach providing at least more local security without augmentation of side effects in comparison with the conventional guidelines.

Adult↗
PubMed1999

Lack of expression of bundle-forming pili in some clinical isolates of enteropathogenic Escherichia coli (EPEC) is due to a conserved large deletion in the bfp operon.

Enteropathogenic Escherichia coli (EPEC) produces a plasmid-encoded type IV pilus, called the bundle-forming pilus (BFP), involved in the formation of the localized adhesion onto epithelial cells. In this study, we demonstrate that clinical isolates of serotypes O128ab:H2 and O119:H2 contain a ca. 13-kb deletion in the bfp operon, resulting in a lack of expression of these pili. An IS sequence with homology to the IS66 of Agrobacterium tumefaciens replaced the deleted bfp genes. These results suggest that the bfp operon was deleted through a transpositional event and that other adherence factors may mediate attachment of these bacteria to the host cells.

Agrobacterium tumefaciens↗
PubMed1999

Psychiatric symptoms as late onset of Wilson's disease: neuroradiological findings, clinical features and treatment.

We describe a case of Wilson's disease with late psychiatric onset. Major depressive disorder was the first clinical manifestation at the age of 38 years. After pharmacotherapy with antidepressive agents, a manic episode was observed. Extrapyramidal hand tremor and micrography were the first neurological signs. Emotional lability occurred during worsening of extrapyramidal signs. Diagnosis was based on urinary and serum copper levels, ceruloplasmin serum level, Kayser-Fleischer ring, and liver biopsy that detected cirrhosis. Magnetic resonance imaging revealed basal ganglia hyperintensity on T1-weighted images, and hypodensity in the central part and hyperintensity in the peripheral part of the lentiform nucleus on T2-weighted images. Hyperintensity on T2-weighted images was also observed in the dorsal part of the midbrain. 123I-iodobenzamide single photon emission computed tomography (IBZM-SPECT) detected a normal distribution of the drug in the brain, with better signal in the right side and deficit of D2-dopaminergic receptors in the basal ganglia. Abnormal manganese erythrocyte level was observed. Treatment was based on penicillamine, zinc salts, low-copper diet, antidepressant agents, interpersonal psychotherapy and neurorehabilitation.

Adult↗
PubMed1999

Quantitative electron spectroscopic imaging studies of microelectronic metallization layers.

The combination of focused ion beam (FIB) sample preparation and quantitative electron spectroscopic imaging is an ideal tool for the investigation of layered structures used in microelectronic metallization schemes. In the present work, Si3N4/Cu/Si3N4/SiO2/Si and Al/TiN/Ti/SiO2/Si metallization layers produced by physical vapour deposition are investigated. We apply series of energy filtered images in the low loss region for a mapping of the sample thickness which makes it possible to refine the parameters of the FIB process. We also show how series of energy filtered images in the core loss region can be used to obtain elemental distribution images and chemical bonding information on these samples on a nanometre scale. For materials with a small grain size and/or a strong variation in Bragg orientation, the intensity distribution of the elemental map is strongly influenced by the superimposed Bragg contrast. This detrimental effect can be reduced greatly by using hollow cone illumination, as is demonstrated for polycrystalline Cu. One striking feature observed in Cu layers prepared with FIB is strong, regularly arranged contrast variations caused by subsurface defects in the Cu grains. We suppose that these defects are a consequence of a strong interaction of Ga atoms from the FIB with Cu.

Journal Article↗
PubMed1999

Antisense inhibition of the GDP-mannose pyrophosphorylase reduces the ascorbate content in transgenic plants leading to developmental changes during senescence.

GDP-mannose pyrophosphorylase (GMPase, EC 2.7.7.22) catalyses the synthesis of GDP-D-mannose and represents the first committed step in the formation of all guanosin-containing sugar nucleotides found in plants which are precursors for cell wall biosynthesis and, probably more important, the synthesis of ascorbate. A full-length cDNA encoding GMPase from S. tuberosum was isolated. Transgenic potato plants were generated in which the GMPase cDNA was introduced in antisense orientation to the 35S promoter. Transformants with reduced GMPase activity were selected. Transgenic plants were indistinguishable from the wild-type when held under tissue culture conditions, however, a major change was seen 10 weeks after transfer into soil. Transgenic plants showed dark spots on leaf veins and stems with this phenotype developing from the bottom to the top of the plant. In case of the line with the strongest reduction, all aerial parts finally dried out after 3 months in soil, in contrast to the wild-type plants which did not start to senesce at this time. This coincides with a reduction of ascorbate contents in the transgenic plants, which is in agreement with the recently proposed pathway of ascorbate biosynthesis. Furthermore, leaf cell walls of the transgenic potato plants had mannose contents that were reduced to 30-50% of the wild-type levels, whereas the composition of tuber cell walls was unchanged. The glycosylation pattern of proteins was unaffected by GMPase inhibition, as studied by affinoblot analysis.

Amino Acid Sequence↗
PubMed1999

Density gradient centrifugation of colonic fluid after segmental lavage: a method of purification of exfoliative epithelial colonic cells for cytological interpretation and image cytometry in patients with long-standing ulcerative colitis.

OBJECTIVES: Patients with extensive, long-standing ulcerative colitis (UC) have an increased risk for developing colorectal cancer. In this study, we wanted to establish a method for retrieving cytological material after segmental colonic lavage for further cytopathological investigations and for performing DNA image cytometry. METHODS: Ten patients with long-standing and extensive ulcerative colitis and 10 patients without macroscopic abnormalities were investigated. After segmental colonic lavage during routine colonoscopy a three-layer (1.146, 1.075, and 1.046 g/ml, respectively) density gradient centrifugation of the retrieved colonic fluid was performed for isolation and purification of the epithelial cells. For identification of the epithelial cells flow cytometry with monoclonal antibody against cytokeratin and counterstaining with propidium iodine was performed. The smears obtained were stained for routine cytopathological interpretation and for DNA image cytometry. RESULTS: In eight of 10 UC patients and in nine of 10 control group patients adequate cytological material could be obtained. The band on top of the density gradient at 1.046 g/ml could be identified as the epithelial cells. Atypical cells were found in smears of three UC patients. In these patients and in one additional patient aneuploid stemlines could be detected. In smears of control group patients neither atypical cells nor aneuploidy were present. CONCLUSIONS: Isolation and purification of epithelial cells after segmental colonic lavage by using density gradient centrifugation was performed. This cytological material is adequate for cytopathological interpretation and for DNA image cytometry. Information about atypical cells and DNA aneuploidy as an additional marker of malignant transformation in UC patients was obtained. The combination of cytological examination and DNA image cytometry might improve the detection of UC patients with high risk for colorectal cancer.

Aneuploidy↗
PubMed1999

Patient Outcomes Research Teams: contribution to outcomes and effectiveness research.

This paper describes the key methodological and substantive findings of Patient Outcomes Research Teams, the first outcomes and effectiveness research centers funded by the Agency for Health Care Policy and Research. Patient Outcomes Research Teams contributed to our increased understanding of how to perform meta analysis on nontrial data, use administrative data to characterize patterns of care, develop general and disease-specific outcome measures, and disseminate important outcome information to patients and physicians to reduce practice variation. Patient Outcomes Research Teams also influenced the development of outcomes measurement in the private sector.

Health Services Research↗
PubMed1999

Long-term ambient air pollution and respiratory symptoms in adults (SAPALDIA study). The SAPALDIA Team.

The association between long-term exposure to ambient air pollution and respiratory symptoms was investigated in a cross-sectional study in random population samples of adults (aged 18 to 60 yr, n = 9,651) at eight study sites in Switzerland. Information on respiratory symptoms was obtained with an extended version of the European Community Respiratory Health Survey questionnaire. The impact of annual mean concentrations of air pollutants was analyzed separately for never-, former, and current smokers. After controlling for age, body mass index, gender, parental asthma, parental atopy, low education, and foreign citizenship, we found positive associations between annual mean concentrations of NO2, total suspended particulates, and particulates of less than 10 micrometers in aerodynamic diameter (PM10) and reported prevalences of chronic phlegm production, chronic cough or phlegm production, breathlessness at rest during the day, breathlessness during the day or at night, and dyspnea on exertion. We found no associations with wheezing without cold, current asthma, chest tightness, or chronic cough. Among never-smokers, the odds ratio (95% confidence interval) for a 10 micrograms/ m3 increase in the annual mean concentration of PM10 was 1. 35 (1.11 to 1.65) for chronic phlegm production, 1.27 (1.08 to 1.50) for chronic cough or phlegm production, 1.48 (1.23 to 1.78) for breathlessness during the day, 1.33 (1.14 to 1.55) for breathlessness during the day or at night, and 1.32 (1.18 to 1.46) for dyspnea on exertion. No associations were found with annual mean concentrations of O3. Similar associations were also found for former and current smokers, except for chronic phlegm production. The observed associations remained stable when further control was applied for environmental tobacco smoke exposure, past and current occupational exposures, atopy, and early childhood respiratory infections when restricting the analysis to long-term residents and to non- alpine areas, and when excluding subjects with physician-diagnosed asthma. The high correlation between the pollutants makes it difficult to sort out the effect of one single pollutant. This study provides further evidence that long-term exposure to air pollution of rather low levels is associated with higher prevalences of respiratory symptoms in adults.

Adolescent↗