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Biomedical subjects

M Schuster

Publications and source records attributed to M Schuster.

At least 91 records · Page 5Linked to original sources
PubMed1998

Chemotactic response regulator mutant CheY95IV exhibits enhanced binding to the flagellar switch and phosphorylation-dependent constitutive signalling.

CheY, a response regulator protein in bacterial chemotaxis, mediates swimming behaviour through interaction with the flagellar switch protein, FliM. In its active, phosphorylated state, CheY binds to the motor switch complex and induces a change from counterclockwise (CCW) to clockwise (CW) flagellar rotation. The conformation of a conserved aromatic residue, tyrosine 106, has been proposed to play an important role in this signalling process. Here, we show that an isoleucine to valine substitution in CheY at position 95--in close proximity to residue 106--results in an extremely CW, hyperactive phenotype that is dependent on phosphorylation. Further biochemical characterization of this mutant protein revealed phosphorylation and dephosphorylation rates that were indistinguishable from those of wild-type CheY. CheY95IV, however, exhibited an increased binding affinity to FliM. Taken together, these results show for the first time a correlation between enhanced switch binding and constitutive signalling in bacterial chemotaxis. Considering present structural information, we also propose possible models for the role of residue 95 in the mechanism of CheY signal transduction.

Bacterial Proteins↗
PubMed1998

Importance of CD49d-VCAM interactions in human monocyte adhesion to porcine endothelium.

By using a primate model of natural antibody depletion, we have previously shown that delayed rejection of porcine cardiac xenografts in unmodified primate recipients resulted from xenograft infiltration with monocyte/macrophage lineage cells. In the present study, we initially showed that human monocytes/macrophages demonstrated significantly greater adherence to unstimulated pig aortic endothelial cells (PAEC) than to human umbilical vein endothelial cells (HUVEC). Human TNF-alpha augmented monocyte adhesion to HUVEC by 5-fold higher levels than to PAEC. This effect could not be explained on the basis of incompatibility between human TNF-alpha and its receptor on PAEC since porcine VCAM expression increased by 75-85% after stimulation with TNF-alpha. TNF-augmented monocyte adherence was abrogated by either treatment of PAEC with an anti-VCAM Mab or monocytes with an anti-CD49d Mab. These results suggest that VCAM-CD49d interactions are important in adhesion of human monocytes to PAEC but may not be as effective as those between human monocytes and allogeneic endothelium, perhaps because of structural differences across species. Other interactions, as yet undefined, must explain the relative increase in adhesiveness of human monocytes for unstimulated PAEC versus HUVEC. In experiments investigating the functional consequences of this enhanced monocyte adherence, PAEC stimulation induced 10-fold higher levels of macrophage-derived IL-1 beta and 3-fold higher levels of T cell proliferation compared with HUVEC. Using an anti-DR Mab to interrupt antigen presentation by autologous macrophages markedly reduced the T cell proliferative response to PAEC. Together, these results indicate that the enhanced adherence of human monocytes to PAEC contributes to xenograft rejection beyond the hyperacute period by leading to tissue infiltration, elaboration of cytokines, and an augmented indirect pathway of T cell xenoantigen recognition.

Animals↗
PubMed1998

Computer-aided resolution of an experimental paradox in bacterial chemotaxis.

Escherichia coli responds to its environment by means of a network of intracellular reactions which process signals from membrane-bound receptors and relay them to the flagellar motors. Although characterization of the reactions in the chemotaxis signaling pathway is sufficiently complete to construct computer simulations that predict the phenotypes of mutant strains with a high degree of accuracy, two previous experimental investigations of the activity remaining upon genetic deletion of multiple signaling components yielded several contradictory results (M. P. Conley, A. J. Wolfe, D. F. Blair, and H. C. Berg, J. Bacteriol. 171:5190-5193, 1989; J. D. Liu and J. S. Parkinson, Proc. Natl. Acad. Sci. USA 86:8703-8707, 1989). For example, "building up" the pathway by adding back CheA and CheY to a gutted strain lacking chemotaxis genes resulted in counterclockwise flagellar rotation whereas "breaking down" the pathway by deleting chemotaxis genes except cheA and cheY resulted in alternating episodes of clockwise and counterclockwise flagellar rotation. Our computer simulation predicts that trace amounts of CheZ expressed in the gutted strain could account for this difference. We tested this explanation experimentally by constructing a mutant containing a new deletion of the che genes that cannot express CheZ and verified that the behavior of strains built up from the new deletion does in fact conform to both the phenotypes observed for breakdown strains and computer-generated predictions. Our findings consolidate the present view of the chemotaxis signaling pathway and highlight the utility of molecularly based computer models in the analysis of complex biochemical networks.

Acetates↗
PubMed1998

Improving the quality of healthcare for children: implementing the results of the AHSR research agenda conference.

OBJECTIVE: To describe the rationale, development, content, and results of the AHSR-sponsored conference on developing a research agenda focused on improving the quality of care for children. DATA SOURCES AND METHODS: Planning documents, background papers, and conference proceedings. PRINCIPAL FINDINGS: The conference developed the research agenda focused on (1) monitoring the health of children; (2) evaluating the efficacy and effectiveness of health services for children; (3) assessing the quality of healthcare provided to children; (4) improving the quality of healthcare within health systems; (5) assessing the performance of community systems for children; (6) exploring the impact of different financial incentives on the provision of pediatric healthcare; and (7) developing and disseminating clinical practice guidelines and other information to physicians, families, and consumers. Specific issues and research questions in each area are also presented. Strategies for implementing the research agenda are presented and include: (1) expanding the child health services research workforce; (2) developing child healthcare quality improvement research centers; (3) conducting research in specific high-priority areas; (4) focusing research on improving the health of vulnerable populations; (5) improving child health data and collection systems at the national level; (6) developing better community health monitoring for children; (7) building and supporting research networks and a consortium of research users; and (8) developing a coordinated interagency federal effort to advance this agenda and to provide accountability for its completion. CONCLUSION: The proposed research agenda should be a national priority so that all Americans can be assured that children are receiving the best quality of care that the United States can provide.

Child↗
PubMed1997

Endometrial resection and late reoperation in the treatment of menorrhagia.

STUDY OBJECTIVE: To evaluate the effectiveness of transcervical resection of the endometrium and indications for late reoperation. DESIGN: Retrospective study. SETTING: Central hospital in northern Norway. PATIENTS: Two hundred fifty women (age 30-59 yrs) with dysfunctional bleeding. INTERVENTIONS: Hysteroscopic transcervical resection of the endometrium. MEASUREMENTS AND MAIN RESULTS: Success as measured by patient satisfaction at 3-month follow-up was 97% and at 4 to 48 months was 91.6%. Mean observation time was 24 months. Twenty-one women required further surgery. Repeat resection was performed in eight women (3.2%), of whom 95% were satisfied. Thirteen women (5.2%) had a hysterectomy. Late reoperation was performed in 7 patients (2.8%) due to recurrent unacceptable vaginal bleeding and in 14 (5.6%) due to late onset of pain. CONCLUSION: After endometrial resection, a definite subgroup (8.4%) of women developed late onset of pain or bleeding requiring reoperation.

Adult↗
PubMed1996

Examples of in vivo isotype class switching in IgM+ chronic lymphocytic leukemia B cells.

Chronic lymphocytic leukemia (CLL) usually involves the expansion of a clone of CD5+ B cells synthesizing IgM antibodies. These B cells appear to be blocked at the antigen receptor-expressing stage of B cell differentiation and are thought not to undergo an isotype class switch to IgG or IgA production. In vivo and in vitro studies suggest, however, that in some instances terminal differentiation and isotype switching can occur. To test the hypothesis that in vivo isotype class switching occurs in IgM+ B-type CLL cells, we analyzed the PBMC of 19 CLL patients for the presence of transcripts encoding the rearranged CLL V(H)DJ(H) associated with either gamma or alpha H chains. The molecular data indicate that approximately 50% of B-CLL patients have amplifications of IgM+ B cells that undergo an isotype class switch. Switching to IgA appears to occur more often than to IgG; also, switching can involve different IgG subclasses in individual patients. In many instances, these CLL-related gamma and alpha transcripts are much more plentiful than those of normal B cells that produce the same isotype. These switched transcripts do not reveal evidence for the accumulation of significant numbers of new V(H) gene mutations. The cellular data indicate that B cells with lesser amounts of surface membrane IgD and higher IgM/IgD ratios are more likely to undergo this switching process. Furthermore, B cells expressing IgG and IgA of the same idiotype or V(H) family and the same CDR3 length as those of the CLL IgM+ clone can be identified in the blood of patients studied using multiparameter immunofluorescence analyses. Collectively, these data suggest that not all members of a B-CLL clone are frozen at the surface membrane Ig-expressing stage of B cell maturation, and that some members can switch to the production of non-IgM isotypes. The occurrence of switching without the accumulation of V gene mutations indicates that the processes of differentiation and diversification are not linked.

Adult↗
PubMed1996

N-Dansyl-N'-ethylthiourea for the fluorometric detection of heavy metal ions.

N-Dansyl-N'-ethylthiourea (DET) forms fluorescent chelates with a large number of heavy metal ions. The influence of the pH-value on the luminescence of DET and its metal chelates was investigated. The addition of Cu(II) to DET causes a bathochromic shift of the emission maximum, which is linearly dependent on the Cu(II) concentration. Low detection limits and a wide linear range of detection are achieved by HPLC using RP 18 columns as stationary phase. Also presented are first measurements of fluorescence decay times of the ligand as well as some complexes.

Journal Article↗
PubMed1996

Endometrial Resection and Late Reoperation in the Treatment of Menorrhagia

We evaluated the effectiveness of transcervical resection of the endometrium (TCRE) and the indications of late reoperations in 250 women with dysfunctional bleeding. The women were questioned about symptoms and levels of satisfaction 3, 12, 24, 36, and 48 months after the procedure. Average follow-up was 24 months (range 4-48 mo). Repeat resection was performed in 8 women (3.2%) and hysterectomy in 13 (5.2%). Seven women (2.8%) had reoperation because of recurrent unacceptable vaginal bleeding. Late onset of pain occurred in 14 (5.6%). The success rate at 3 months as measured by patient satisfaction was 97% and at 4 to 45 months 91%. A definite subgroup of women developed late onset of pain with or without bleeding after endometrial resection. Results at 3 months did not necessarily correlate with longer-term outcomes. Provided that the surgeon has extensive training, few women will be dissatisfied with the procedure.

Journal Article↗
PubMed1995

[Continuous flow hysteroscopy. An improved endoscopic method for examination of the uterine cavity].

A new technique for hysteroscopic visualisation of the uterine cavity has significantly increased the accuracy of diagnosing intrauterine disorders. Major breakthroughs in this field have been the introduction of the use of continuous flow hysteroscopy. We describe the recent development of the new generation continuous flow hysteroscope and our experience of the first 91 continuous flow hysteroscopies in paracervical block at our outpatient clinic. The problems of mucus, blood and debris, which earlier could disturbingly blur the vision when using CO2 as distension medium, have now been overcome with the new generation continuous flow hysteroscope. During the period from 1 February to 31 July 1994 we performed in paracervical block 91 continuous flow hysteroscopies at our outpatient clinic. We experienced no failure in the examinations, and had no complications. We found normal uterine cavity in 53% of the patients, macroscopic pathology in 44% and in 3% of the patients a missed intrauterine device was located in the uterine cavity.

Evaluation Studies as Topic↗
PubMed1992

Contributions to the S'-subsite specificity of papain.

The product ratio was analyzed for the papain-catalyzed acyl transfer from the specific acyl donor Mal-Phe-Ala-OEtCl to various nucleophilic amino components, ranging from amino acid amides to tripeptide amides. The data obtained are discussed in terms of binding specificity. From the structure-activity relationships for the S'1-P'1 interaction it follows that only three methyl(ene) groups can be accommodated in the S'1 subsite. Hydrophilic side chains are bound better to S'1 than indicated by their hydrophobicities. Negatively charged amino components are inefficient deacylating agents. However, there was no evidence for electrostatic contributions to the nucleophile binding. Amino components with bulky hydrophobic amino acid residues in the P'2 and in the P'3 position, respectively, are preferentially bound to Mal-Phe-Ala-papain. The results of this study can be applied to the planning of papain-catalyzed peptide synthesis reactions.

Acyltransferases↗