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Biomedical subjects

D Roth

Publications and source records attributed to D Roth.

At least 19 recordsLinked to original sources
PubMed2000

In vivo regulation of protein synthesis by phosphorylation of the alpha subunit of wheat eukaryotic initiation factor 2.

The regulation of protein synthesis is a critical component in the maintenance of cellular homeostasis. A major mechanism of translational control in response to diverse abiotic and biotic stress signals involves the phosphorylation of the alpha subunit of eukaryotic initiation factor 2 (eIF2alpha). The pathway has been demonstrated in all eukaryotes except plants, although components of a putative plant pathway have been characterized. To evaluate the in vivo capability of plant eIF2alpha to participate in the translation pathway, we have used vaccinia virus recombinants that constitutively express wheat eIF2alpha and inducibly express the eIF2alpha dsRNA-stimulated protein kinase, PKR, in BSC-40 cells. Activation of PKR in cells expressing wild-type wheat eIF2alpha resulted in an inhibition of cellular and viral protein synthesis and an induction of cellular apoptosis correlating with phosphorylation of eIF2alpha on serine 51. Expression of a nonphosphorylatable mutant (51A) of plant eIF2alpha reversed the PKR-mediated translational block as well as the PKR-induced apoptosis. A direct interaction of the plant proteins with the mammalian translational initiation apparatus is supported by coimmunoprecipitation of wild-type plant eIF2alpha and the 51A mutant with mammalian eIF2gamma and the localization of the plant proteins in ribosome fractions. These findings suggest that plant eIF2alpha is capable of interacting with the guanine nucleotide exchange factor eIF2B within the context of the eIF2 holoenzyme and provide direct evidence for its ability to participate in phosphorylation-mediated translational control in vivo.

Amino Acid Sequence↗
PubMed2000

Oral 5-aminosalicylic acid for inducing remission in ulcerative colitis.

OBJECTIVES: To assess the efficacy, dose-responsiveness and safety of the newer release formulations of 5-aminosalicylic acid (5-ASA) compared to placebo or sulfasalazine (SASP) for the induction of remission in active ulcerative colitis. SEARCH STRATEGY: A computer-assisted literature search for relevant studies (1981-1998) was performed using MEDLINE, BIOS, the Cochrane Controlled Trials Register and the Science Citation Index, followed by a manual search of reference lists from previously retrieved articles, review articles, symposia proceedings, and abstracts from major gastrointestinal conferences. SELECTION CRITERIA: Studies were accepted for analysis if they were randomized, double-blinded, and controlled clinical trials of parallel design, with treatment durations of a minimum of four weeks. DATA COLLECTION AND ANALYSIS: Based on an intention to treat principle, the outcomes of interest in the treatment of active disease were the failure to induce global/clinical remission, global/clinical improvement, endoscopic remission, or endoscopic improvement. MAIN RESULTS: 5-ASA was superior to placebo with regard to all measured outcome variables. For the failure to induce global/clinical improvement or remission, the pooled Peto odds ratio was 0.51 (95% CI, 0.35 to 0.76). A dose-response trend for 5-ASA was also observed. When 5-ASA was compared to SASP, the pooled Peto odds ratio was 0.87 (CI, 0.63 to 1.21) for the failure to induce global/clinical improvement or remission, and 0.66 (CI, 0.42 to 1.04) for the failure to induce endoscopic improvement. SASP was not as well tolerated as 5-ASA. REVIEWER'S CONCLUSIONS: The newer 5-ASA preparations were superior to placebo and tended towards therapeutic benefit over SASP. However, considering their relative costs, a clinical advantage to using the newer 5-ASA preparations in place of SASP appears unlikely.

Aminosalicylic Acids↗
PubMed2000

Oral 5-aminosalicylic acid for maintaining remission in ulcerative colitis.

OBJECTIVES: To assess the efficacy, dose-responsiveness and safety of the newer release formulations of 5-aminosalicylic acid (5-ASA) compared to placebo or sulfasalazine (SASP) in the maintenance of remission in ulcerative colitis. SEARCH STRATEGY: A computer-assisted literature search for relevant studies (1981-1998) was performed using MEDLINE, BIOS, the Cochrane Controlled Trials Register, the Inflammatory Bowel Disease Trials Register, and Science Citation Index, followed by a manual search of reference lists from previously retrieved articles, review articles, symposia proceedings, and abstracts from major gastrointestinal conferences. SELECTION CRITERIA: Studies were accepted for analysis if they were prospective, randomized, double-blinded, and placebo- or SASP-controlled clinical trials of parallel design with treatment duration of at least six months. DATA COLLECTION AND ANALYSIS: Based on an intention to treat principle, the primary outcome was the failure to maintain clinical or endoscopic remission. Secondary outcomes were the number of patients experiencing adverse events, the number of patients withdrawn due to adverse events, and exclusions or withdrawals after entry into the study (not due to relapse). All data were analyzed using the Peto odds ratio and corresponding 95% confidence intervals (CI). MAIN RESULTS: The Peto odds ratio for the failure to maintain clinical or endoscopic remission (withdrawals and relapses) for 5-ASA versus placebo was 0. 47 (95% CI, 0.36 to 0.62) with an NNT of 6. These values were also calculated for the trials in which SASP and 5-ASA were compared, revealing an odds ratio of 1.29 (95% CI, 1.05 to 1.57), with a negative NNT value (-19), suggesting a higher degree of therapeutic effectiveness for SASP. SASP and 5-ASA had similar adverse event profiles, with odds ratios of 1.16(0.62 to 2.16), and 1.31(0.86 to 1.99), respectively. The NNH values were determined to be 171 and 78 respectively. REVIEWER'S CONCLUSIONS: The newer 5-ASA preparations were superior to placebo in maintenance therapy. However, the newer preparations had a statistically significant therapeutic inferiority relative to SASP.

Administration, Oral↗
PubMed2000

De novo ANCA-associated vasculitis occurring 14 years after kidney transplantation.

A cadaveric kidney transplant recipient, with no history of a connective tissue disease, was admitted with malaise, arthralgias, diplopia, mild headache, and a painful left eye. The patient was on maintenance immunosuppression for 14 years with cyclosporine and methylprednisolone. Initial laboratory data indicated an elevated serum creatinine from baseline, 2+ proteinuria, and 50 to 100 red blood cells (RBCs)/high-power field (HPF) in the urine. Renal biopsy was consistent with necrotizing vasculitis involving glomerular capillaries, with crescent formation and an absence of immune complexes. Perinuclear antineutrophil cytoplasmic autoantibodies (P-ANCA) and anti-myeloperoxidase (MPO) were found to be elevated. To the best of our knowledge, this is the first reported case of an ANCA-associated small vessel vasculitis (SVV) developing in a renal transplant recipient without history of connective tissue disease.

Antibodies, Antineutrophil Cytoplasmic↗
PubMed2000

Consumers' and case managers' perceptions of mental health and community support service needs.

Consumers with serious and persistent mental illness (N = 385) and their case managers rated the amount of help needed and the amount of help received with mental health and community support services. Consumers also identified their primary source of help with each type of need. Results highlighted areas of agreement and disagreement between consumers' and case managers' perceptions. Consumers' reports revealed a strong reliance on sources of support outside the mental health system (e.g., family and friends) for many community support service needs, interpersonal needs, and crisis-related needs. In general, correlations between consumers' and case managers' ratings of help needed and help received were low. Consumers perceived the majority of their needs to be unmet; case managers perceived the majority of consumer needs to be overly met. Discussion focuses on the importance of increasing consensus between consumers and case managers regarding needs by including consumers in treatment planning and providing them with more information about available services. It is recommended that researchers and evaluators examine perceptions of help needed, help received, and sources of help when assessing service needs.

Adult↗
PubMed2000

Attitudes toward mental illness in medical students: does personal and professional experience with mental illness make a difference?

PURPOSE: Medical students may be susceptible to emotional difficulties because of the high levels of both academic and interpersonal stress associated with their training. This study examined attitudes toward mental illness in medical students. It was expected that people who had experience of mental illness, either in their personal lives or through their professional experience, would have more positive attitudes toward students with mental health problems than would people who had not had such experience. METHOD: Faculty and staff employed by a large American university medical centre completed a questionnaire package including several measures designed to assess specific attitudes toward medical students with emotional problems. Data were also collected on the degree to which specific mental disorders were thought to interfere with the performance of medical students. RESULTS: In general, prior experience with mental illness, either through personal or professional activities, was associated with more positive attitudes about students with mental illness. However, the pattern of findings was complex. CONCLUSION: Future research should examine the extent to which specific mental illnesses actually affect the performance of medical students.

Adult↗
PubMed1999

Microangiopathy in kidney and simultaneous pancreas/kidney recipients treated with tacrolimus: evidence of endothelin and cytokine involvement.

BACKGROUND: In the past 3 years, three transplant recipients [one kidney, two simultaneous pancreas/kidney (SPK)] developed a thrombotic thrombocytopenic purpura-like clinical syndrome. This was characterized by an abrupt fall in the hematocrit and platelet count with evidence of hemolysis (fragmented red blood cells and schistocytes) and transplant kidney dysfunction during the first 2 weeks after transplantation. This was also associated with pancreatic dysfunction in the two SPK recipients. In all three patients, elevated tacrolimus levels (>24 ng/ml) occurred. METHODS: Serum cytokine and endothelin levels were determined retrospectively from stored (-70 degrees C) sera. RESULTS: In each case tacrolimus was discontinued, and treatment with plasmapheresis, fresh frozen plasma, steroids, and OKT3 was begun. The clinical courses varied from mild (one patient), to moderate (one patient), to severe (one patient), complicated with seizures and coma. Each patient responded clinically and ultimately was converted to cyclosporine A, and/or mycophenolate mofetil. These clinical events were associated with a rise in serum levels of endothelin and several cytokines. Levels of endothelin were elevated at 209+/-137 pg/ml, particularly in the severe episode where peak levels reached 480 pg/ml (normal 0-20 pg/ml). Peak levels of IL-8 (104+/-36 pg/ml), interleukin- (IL) 10 (238+/-105 pg/ml), and/or IL-12 (306+/-119 pg(ml) mean+/-SE, occurred during or before the clinical event. Serum levels of tumor necrosis factor-a and interferon-gamma were elevated in 2 patients while levels of IL-2, IL-4, and IL-6 were not elevated during the acute phase. CONCLUSIONS: These data are consistent with a mechanism of microangiopathy involving endothelial cell injury (associated with tacrolimus treatment), and accompanied by cytokines (IL-10, IL-12, tumor necrosis factor-a, interferon-gamma) that affect expression of adhesion molecules, chemokines (IL-8) that direct the influx of white blood cells and endothelins that may exacerbate underlying hypertension and increase shear force-related red blood cell destruction.

Adult↗
PubMed1999

Dominant-negative alleles of 14-3-3 proteins cause defects in actin organization and vesicle targeting in the yeast Saccharomyces cerevisiae.

14-3-3 Proteins are thought to function as adapters in signaling complexes [1,2], thereby participating in cellular processes including vesicle trafficking and exocytosis [3,4]. To delineate further the function of 14-3-3 proteins during vesicle trafficking, we generated dominant-negative alleles of the two 14-3-3 homologues, Bmh1p and Bmh2p, in budding yeast and analyzed their phenotype in respect to exocytosis. Cells overexpressing the carboxy-terminal region of Bmh2p failed to polarize vesicular transport although bulk exocytosis remained unaffected and showed a disrupted actin cytoskeleton. Our data suggest that 14-3-3 proteins may act primarily on the actin cytoskeleton to regulate vesicle targeting.

14-3-3 Proteins↗
PubMed1999

A more accurate method to estimate glomerular filtration rate from serum creatinine: a new prediction equation. Modification of Diet in Renal Disease Study Group.

BACKGROUND: Serum creatinine concentration is widely used as an index of renal function, but this concentration is affected by factors other than glomerular filtration rate (GFR). OBJECTIVE: To develop an equation to predict GFR from serum creatinine concentration and other factors. DESIGN: Cross-sectional study of GFR, creatinine clearance, serum creatinine concentration, and demographic and clinical characteristics in patients with chronic renal disease. PATIENTS: 1628 patients enrolled in the baseline period of the Modification of Diet in Renal Disease (MDRD) Study, of whom 1070 were randomly selected as the training sample; the remaining 558 patients constituted the validation sample. METHODS: The prediction equation was developed by stepwise regression applied to the training sample. The equation was then tested and compared with other prediction equations in the validation sample. RESULTS: To simplify prediction of GFR, the equation included only demographic and serum variables. Independent factors associated with a lower GFR included a higher serum creatinine concentration, older age, female sex, nonblack ethnicity, higher serum urea nitrogen levels, and lower serum albumin levels (P < 0.001 for all factors). The multiple regression model explained 90.3% of the variance in the logarithm of GFR in the validation sample. Measured creatinine clearance overestimated GFR by 19%, and creatinine clearance predicted by the Cockcroft-Gault formula overestimated GFR by 16%. After adjustment for this overestimation, the percentage of variance of the logarithm of GFR predicted by measured creatinine clearance or the Cockcroft-Gault formula was 86.6% and 84.2%, respectively. CONCLUSION: The equation developed from the MDRD Study provided a more accurate estimate of GFR in our study group than measured creatinine clearance or other commonly used equations.

Age Factors↗
PubMed1999

The exocyst is an effector for Sec4p, targeting secretory vesicles to sites of exocytosis.

Polarized secretion requires proper targeting of secretory vesicles to specific sites on the plasma membrane. Here we report that the exocyst complex plays a key role in vesicle targeting. Sec15p, an exocyst component, can associate with secretory vesicles and interact specifically with the rab GTPase, Sec4p, in its GTP-bound form. A chain of protein-protein interactions leads from Sec4p and Sec15p on the vesicle, through various subunits of the exocyst, to Sec3p, which marks the sites of exocytosis on the plasma membrane. Sec4p may control the assembly of the exocyst. The exocyst may therefore function as a rab effector system for targeted secretion.

Cell Membrane↗
PubMed1999

Signal joint formation is inhibited in murine scid preB cells and fibroblasts in substrates with homopolymeric coding ends.

During B and T lymphocyte development, immunoglobulin and T cell receptor genes are assembled from the germline V, (D) and J gene segments (Lewis, S.M., 1994. The mechanism of V(D)J joining: lessons from molecular, immunological and comparative analyses. Adv. Immunol. 56, 27-150). These DNA rearrangements, responsible for immune system diversity, are mediated by a site specific recombination machinery via recognition signal sequences (RSSs) composed of conserved heptamers and nonamers separated by spacers of 12 or 23 nucleotides (Lewis, S.M., 1994. The mechanism of V(D)J joining: lessons from molecular, immunological and comparative analyses. Adv. Immunol. 56, 27-150). Recombination occurs only between a RSS with a 12mer spacer and a RSS with a 23mer spacer (Lewis, S.M., 1994. The mechanism of V(D)J joining: lessons from molecular, immunological and comparative analyses. Adv. Immunol. 56, 27-150). RAG1 and RAG2 proteins cleave precisely at the RSS-coding sequence border leading to flush signal ends and coding ends with a hairpin structure (Eastman, M., Leu, T., Schatz, D., 1996. Initiation of V(D)J recombination in vitro obeying the 12/23 rule. Nature 380, 85-88; Roth, D.B., Menetski, J.P., Nakajima, P.B., Bosma, M.J., Gellert, M., 1992. V(D)J recombination: broken DNA molecules with covalently sealed (hairpin) coding ends in scid mouse thymocytes. Cell 983-991: Roth, D.B., Zhu, C., Gellert. M., 1993. Characterization of broken DNA molecules associated with V(D)J recombination. Proc. Natl. Acad. Sci. USA 90, 10,788-10,792; van Gent, D., McBlane, J.. Sadofsky, M., Hesse, J., Gellert, M., 1995. Initiation of V(D)J recombination in a cell-free system. Cell 81, 925-934). Signal ends join, forming a signal joint. The hairpin coding ends are opened by a yet unknown endonuclease, and are further processed to form the coding joint (Lewis, S.M., 1994. The mechanism of V(D)J joining: lessons from molecular, immunological and comparative analyses. Ad. Immunol. 56, 27-150.) The murine scid mutation has been shown to affect coding joints, but much less signal joint formation. In this study we demonstrate that the murine scid mutation inhibits correct signal joint formation when both coding ends contain homopolymeric sequences. We suggest that this finding may be due to the function of the SCID protein as an assembly component in V(D)J recombination.

Animals↗
PubMed1999

Specific in vitro phosphorylation of plant eIF2alpha by eukaryotic eIF2alpha kinases.

Phosphorylation of the alpha subunit of eukaryotic initiation factor 2 (eIF2alpha) is known to be an important translational control mechanism in all eukaryotes with the major exception of plants. Regulation of mammalian and yeast eIF2alpha activity is directly governed by specific phosphorylation on Ser-51. We now demonstrate that recombinant wheat wild-type (51S) but not mutant 51-Ala (51A) protein is phosphorylated by human PKR and yeast GCN2, which are defined eIF2alpha kinases. Further, only wheat wild-type eIF2alpha is a substrate for plant-encoded, double-stranded RNA-dependent kinase (pPKR) activity. Plant PKR and GCN2 phosphorylate recombinant yeast eIF2alpha 51S but not the 51A mutant demonstrating that pPKR has recognition site capability similar to established eIF2alpha kinases. A truncated version of wild-type wheat eIF2alpha containing 51S but not the KGYID motif is not phosphorylated by either hPKR or pPKR suggesting that this putative eIF2alpha kinase docking domain is essential for phosphorylation. Taken together, these results demonstrate the homology among eukaryotic eIF2alpha species and eIF2alpha kinases and support the presence of a plant eIF2alpha phosphorylation pathway.

Eukaryotic Cells↗
PubMed1998

Continuing observations on the regulatory effects of donor-specific bone marrow cell infusions and chimerism in kidney transplant recipients.

BACKGROUND: Continued follow-up of a series of donor bone marrow cell (DBMC)-infused first cadaver renal transplant recipients is described (n=58), now at a 36-month actuarial time point postoperatively. Serial polymerase chain reaction-flow cytometry (PCR-Flow) and cellular immune assays of iliac crest bone marrow aspirates and peripheral blood have begun to be compared with concomitantly transplanted recipients of living-related donor (LRD) kidneys and donor marrow infusions given the same immunosuppressive regimen (n=16). There have also been comparisons (36 months) with 188 controls transplanted concomitantly, i.e., recipients of first cadaver kidney transplants, who did not receive bone marrow. METHODS: Each group was given equivalent immunosuppressive regimens of OKT3 anti-T cell induction and maintenance tacrolimus, mycophenolate mofetil, and methylprednisolone. Actuarial patient and graft survival have been 96% and 93%, respectively, in the controls and 91% and 91%, respectively, in the DBMC-infused recipients. Trough levels of tacrolimus were significantly lower in the DBMC-infused group. RESULTS: In PCR-Flow measurements, in peripheral blood up to 6 months postoperatively, there were higher levels of chimerism, i.e., in the total number of donor cells, as well as the donor CD3+ and CD34+ subsets in the LRD recipients administered DBMC infusions, compared with cadaver DBMC recipients, supporting the notion of a positive effect of histocompatibility on chimerism levels. In PCR-Flow measurements of recipient iliac crest bone marrow aspirates as in previous studies on peripheral blood, early acute rejection episodes (<1 month) were found to be associated with a later (6-14 months) decrease in donor cell lineage chimerism. However, a trend toward recovery of chimeric levels occurred by 21-28 months in a second iliac crest marrow aspirate 1 year after the first aspirate in the DBMC-infused recipients who experienced such early rejection episodes. This was in contrast to the controls in whom there were sustained low levels of iliac crest bone marrow chimerism at both the earlier and later intervals (i.e., no chimeric recovery), with 17/183 surviving controls progressing into chronic rejection. This has not yet been seen in the DBMC-infused group (0/54). In in vitro observations on cellular immune reactivity at 1 year postoperatively, decreased peripheral blood lymphocyte proliferative reactions were seen in response to phytohemagglutinin and Staph-A mitogens, as well as to cytomegalovirus and Epstein-Barr viral protein antigens in the DBMC-infused group versus the controls. Chronic immunosuppression did not seem to effect a vigorous in vitro inhibitory (regulatory) activity of bone marrow taken from these transplant recipients 2 years postoperatively in mixed lymphocyte culture and cell-mediated lympholysis reactions, using allogeneic responding cells from "normal" laboratory volunteers. Autologous peripheral blood lymphoproliferative responses to phytohemagglutinin and Staph-A mitogens, as well as to cytomegalovirus and Epstein-Barr virus protein antigens, were also regulated by either organ donor (non-immunosuppressed) bone marrow cells or by transplant recipient (immunosuppressed) bone marrow cells. What appeared to be disparate between the DBMC-infused and control groups (both immunosuppressed) was the trend for the (autologous) bone marrow suppressive effect on antiviral lymphoproliferative responses, to be stronger in the DBMC-infused group, who also had significantly (>one order of magnitude) higher levels of chimerism (P=0.01). CONCLUSIONS: It is concluded that the establishment of a chimeric state in DBMC-infused recipients, albeit of relatively low magnitude (approximately 1% at 2 years in recipient iliac crest bone marrow), has had a definite regulatory effect on immune responses. These results, therefore, add weight to the "causal" horn of the dilemma as to whether donor cell chimerism is a cause or an effect of

Bone Marrow Cells↗
PubMed1998

Primary immunosuppression with tacrolimus and mycophenolate mofetil for renal allograft recipients.

BACKGROUND: Studies using tacrolimus and corticosteroids or the combination of cyclosporine, mycophenolate mofetil, and corticosteroids have been shown to reduce the incidence of biopsy-proven acute rejection episodes in cadaveric kidney recipients compared with cyclosporine-based immunosuppression. The current study is a retrospective analysis of our experience with tacrolimus combined with mycophenolate mofetil and steroids as primary immunosuppression for kidney transplant recipients. METHODS: In a retrospective analysis, 72 patients who received primary therapy with tacrolimus, mycophenolate mofetil, and corticosteroids (triple therapy) were compared with a control group of 98 kidney recipients who received tacrolimus and corticosteroids (double therapy). RESULTS: There was a significant reduction in the incidence of biopsy-confirmed acute rejection in the triple therapy group (8.2%) compared with the double therapy group (21%; P=0.003). One-year patient and graft survival did not differ between groups. The incidence of posttransplant diabetes mellitus was 18% and 21% in the triple and double therapy groups, respectively. Leukopenia and gastrointestinal side effects were the most common cause for discontinuation of mycophenolate mofetil. CONCLUSIONS: The combination of tacrolimus with mycophenolate mofetil and corticosteroids is more effective at preventing early acute rejection than tacrolimus and corticosteroids alone. The use of mycophenolate mofetil was associated with a higher incidence of leukopenia and diarrhea, often leading to discontinuation of the drug.

Actuarial Analysis↗
PubMed1998

Solving belief problems: toward a task analysis.

Solving belief problems develops as a skill in normal children during the preschool years. To understand this process of development, it is necessary to provide an analysis of the tasks used to test preschool 'theory of mind' skills. This analysis should allow us to relate the structure of a given task to the underlying cognitive mechanisms that the task engages. In two experiments, we find that 3-year-old children show a pattern of success and failure on belief tasks that is not consistent with 'conceptual deficit' accounts. Young children possess the concept, BELIEF, but have certain characteristic difficulties with correctly calculating the contents of beliefs. In childhood autism, by contrast, the mechanisms that in normal development bestow conceptual competence in this domain are impaired. In the first experiment, parallel task structures are used to show that 3-year-olds are no better at predicting behavior from a partially true belief than they are at predicting behavior from an entirely false belief. We develop specific proposals about task structural factors that either facilitate or hinder success in belief-content calculation. These proposals are supported in a second experiment. We compare two false-belief tasks, one of which has helpful structural factors, the other of which has hampering factors, with a third task which exemplifies a hampering task structure but without any theory of mind content. We compare 3- and 4-year-olds' patterns of performance with that of autistic children. Each of the three groups shows a distinct performance profile across the three tasks, as predicted for each case by our model. Innate attentional mechanisms provide the conceptual foundations for 'theory of mind' but must be supplemented by a robust executive process that allows false beliefs to achieve 'conceptual pop-out.' Our approach has general implications for the study of conceptual development.

Autistic Disorder↗