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Biomedical subjects

M Schirmer

Publications and source records attributed to M Schirmer.

At least 19 recordsLinked to original sources
PubMed2003

Glutathione reductase of the malarial parasite Plasmodium falciparum: crystal structure and inhibitor development.

The malarial parasite Plasmodium falciparum is known to be sensitive to oxidative stress, and thus the antioxidant enzyme glutathione reductase (GR; NADPH+GSSG+H(+) <==> NADP(+)+2 GSH) has become an attractive drug target for antimalarial drug development. Here, we report the 2.6A resolution crystal structure of P.falciparum GR. The homodimeric flavoenzyme is compared to the related human GR with focus on structural aspects relevant for drug design. The most pronounced differences between the two enzymes concern the shape and electrostatics of a large (450A(3)) cavity at the dimer interface. This cavity binds numerous non-competitive inhibitors and is a target for selective drug design. A 34-residue insertion specific for the GRs of malarial parasites shows no density, implying that it is disordered. The precise location of this insertion along the sequence allows us to explain the deleterious effects of a mutant in this region and suggests new functional studies. To complement the structural comparisons, we report the relative susceptibility of human and plasmodial GRs to a series of tricyclic inhibitors as well as to peptides designed to interfere with protein folding and dimerization. Enzyme-kinetic studies on GRs from chloroquine-resistant and chloroquine-sensitive parasite strains were performed and indicate that the structure reported here represents GR of P.falciparum strains in general and thus is a highly relevant target for drug development.

Amino Acid Sequence↗
PubMed2003

Prospective evaluation of the epidemiology, microbiology, and outcome of bloodstream infections in hematologic patients in a single cancer center.

Bloodstream infections (BSIs) have an important impact on the outcome of cancer patients. A prospective cohort study was undertaken at a referral cancer center in order to describe the clinical and microbiological characteristics of patients with hematologic malignancies and BSIs and to identify independent predictors associated with mortality. The study enrolled 110 consecutive BSI episodes during an 18-month period. Patients were monitored for 30 days after the last positive blood culture. There were 10.24 BSI episodes per 1,000 patient-days. The median age of the patients was 25 years. Most patients had acute leukemia ( n=72). The origin of the BSI was unknown in 43.6% of the episodes and was associated with known sites in 32.7%. There were 58 concomitant infectious sites (lungs, 43%, and soft tissue, 22.4%) and 195 noninfectious comorbid factors (poor performance status, 30.2%; undernourishment, 14.3%). The median neutrophil count was 215 cells/mm(3). Indwelling catheters were present in 70% of the episodes. The majority of isolates obtained within the first 48 h of the BSI episode (61%) were gram-negative rods. Overall mortality was 24.5%. Multivariate analysis using logistic regression showed relapsed leukemia, poor performance status, recent weight loss, and ventilatory failure requiring ventilatory support as independent predictors of mortality. Hematologic cancer patients with BSIs should be regarded as a distinct group of patients at high risk of death. The knowledge of variables amenable to intervention would help diminish or prevent serious medical complications.

Bacteremia↗
PubMed2003

18F-fluorodeoxyglucose-positron emission tomography: a new explorative perspective.

18F-Fluorodeoxyglucose-positron emission tomography (18F-FDG-PET) is a new functional imaging technique available for clinical and experimental use. 18F-FDG-PET studies can be used for screening, localization and follow-up of hypermetabolic processes including malignancies, infections and autoimmune processes. For several years it has been applied in oncological, cardiological and neurological patients, but nowadays an increasing number of studies favours its use in patients with autoimmune diseases including large vessel arteritis. From the experimental view, this technique has even become more important since the introduction of a small PET scanner for the use in animal models. This review focuses on technical aspects, clinical experiences and experimental and future perspectives of 18F-FDG-PET, with a special emphasis on large vessel vasculitis and other autoimmune diseases.

Aged↗
PubMed2002

Vascular endothelial growth factor (VEGF) in ankylosing spondylitis--a pilot study.

INTRODUCTION: Angiogenesis is important for the pathogenesis of chronic inflammatory diseases in joints. Inflammation itself may upregulate the expression of VEGF in rheumatic diseases. Angiogenesis may become a new target for therapeutic intervention in inflammatory joint disease. AIM OF THE STUDY: To examine plasma levels of VEGF in AS patients and to test a possible correlation with serological and/or clinical parameters. PATIENTS AND METHODS: Sixteen consecutive patients with definite AS were recruited from the Gasteiner Heilstollen Hospital and compared to eight healthy probands as controls. VEGF was determined in EDTA plasma samples by using an ELISA kit. Data are given as mean values (+/- SEM). The Spearman two-sided test was used to test possible correlations. RESULTS: EDTA-plasma levels of VEGF were 75.3 +/- 19.0 pg/ml, compared to 13.8 +/- 4.7 pg/ml measured in the control group (P = 0.001). A significant correlation was found between plasma VEGF of AS patients and the BASMI score (r = 0.665, P = 0.013). Whereas VEGF was elevated in patients without treatment or NSAIDs (88.9 +/- 24.2 pg/ml), lower levels up to 43.8 pg/ml were found in patients treated with corticosteroids (34.7 +/- 4.0 pg/ml, P = 0.039). CONCLUSIONS: Disease status of AS appears to be associated with elevated VEGF plasma levels. Whether this reflects inflammation or a truly angiogenic pathomechanism requires further investigation.

Adrenal Cortex Hormones↗
PubMed2000

Clonality and longevity of CD4+CD28null T cells are associated with defects in apoptotic pathways.

CD4(+)CD28(null) T cells are oligoclonal lymphocytes rarely found in healthy individuals younger than 40 yr, but are found in high frequencies in elderly individuals and in patients with chronic inflammatory diseases. Contrary to paradigm, they are functionally active and persist over many years. Such clonogenic potential and longevity suggest altered responses to apoptosis-inducing signals. In this study, we show that CD4(+)CD28(null) T cells are protected from undergoing activation-induced cell death. Whereas CD28(+) T cells underwent Fas-mediated apoptosis upon cross-linking of CD3, CD28(null) T cells were highly resistant. CD28(null) T cells were found to progress through the cell cycle, and cells at all stages of the cell cycle were resistant to apoptosis, unlike their CD28(+) counterparts. Neither the activation-induced up-regulation of the IL-2R alpha-chain (CD25) nor the addition of exogenous IL-2 renders them susceptible to Fas-mediated apoptosis. These properties of CD28(null) T cells were related to high levels of Fas-associated death domain-like IL-1-converting enzyme-like inhibitory protein, an inhibitor of Fas signaling that is normally degraded in T cells following activation in the presence of IL-2. Consistent with previous data showing protection of CD28(null) cells from spontaneous cell death, the present studies unequivocally show dysregulation of apoptotic pathways in CD4(+)CD28(null) T cells that favor their clonal outgrowth and maintenance in vivo.

Adult↗
PubMed2000

Divergence of mucosal and motor effects of insulin-like growth factor (IGF)-I and LR3IGF-I on rat isolated ileum following abdominal irradiation.

BACKGROUND AND AIMS: In addition to its beneficial effects on small intestinal mucosal development and repair, insulin-like growth factor (IGF)-I has also been reported to improve neural function in toxic neuropathies. It has recently been recognized that enteric neural abnormalities contribute to the small intestinal dysmotility observed during and after abdominal radiotherapy for gynecological and pelvic malignancy. The aim of the present study was to evaluate the effects of IGF-I (5 mg/kg per day) and the more potent analog LR3IGF-I (5 mg/kg per day) on neurally mediated ileal dysmotility following irradiation. METHODS: Intestinal motor activity was recorded from 6-8 cm segments of explanted rat ileum using a miniaturized manometric technique during arterial perfusion with oxygenated fluorocarbon solution. Studies were performed 4 days after treatment with 10 Gy abdominal irradiation. At the time of irradiation, all rats underwent implantation of an osmotic mini-pump that contained 100 mmol/L acetic acid vehicle (n = 8), IGF-I (n = 8) or LR3IGF-I (n = 7). For each experiment, the total number of pressure waves, high-amplitude long-duration (defined as > 20 mmHg, > 6 s; HALD) pressure waves and long bursts (> 20) of pressure waves were determined. Ileal segments from 12 non-irradiated rats were used as controls for manometric studies. In radiotherapy treated animals, the degree of mucosal damage was determined using a standardized histologic scoring system. RESULTS: The HALD pressure waves were infrequent in non-irradiated rats but occurred in all irradiated animals. Insulin-like growth factor-I and LR3IGF-I had no effect on the frequency, amplitude or migration characteristics of HALD pressure waves compared with vehicle. Histologic damage was reduced in animals that received IGF-I and LR3IGF-I compared with vehicle-treated animals. CONCLUSIONS: In radiation enteritis, IGF-I has no effect on neurally mediated small intestinal dysmotility while improving mucosal histology. The disparity between these results suggests that parallel but separate pathologic processes underlie mucosal and motor abnormalities in radiation enteritis.

Animals↗
PubMed2000

New rearrangement pattern after treatment of hairy-cell leukemia with 2-chlorodeoxyadenosine.

Leukemic hairy cells are clonally proliferating B-lymphoid cells with clonal rearrangements of genes for immunoglobulin chains. We describe a patient with a new hairy-cell clone after treatment with 2-chlorodeoxyadenosine (2-CdA). In this patient, a single course of 2-CdA resulted in good partial remission of hairy-cell leukemia, but Southern blot analysis of bone marrow biopsies and polymerase chain reaction using seminested amplifications with consensus primers revealed a new rearranged band 4 months after therapy with 2-CdA. Four years after therapy, the patient is in complete clinical remission and both bands disappeared during follow-up. The new rearranged band might have been related to prior treatment of hairy-cell leukemia with 2-CdA.

Antimetabolites, Antineoplastic↗
PubMed2000

Medicaid-eligible children who don't enroll: health status, access to care, and implications for Medicaid enrollment.

We estimate that 17% of Medicaid-eligible children in the United States are uninsured, with 27% covered by private insurance. Uninsured children have become a target for state outreach and enrollment efforts. However, the effort may not be a worthwhile use of resources if these children have sufficient access to primary care and are able to enroll in Medicaid should serious health problems arise. This analysis of health status, access to care, and use of preventive and other services suggests otherwise. Although the uninsured Medicaid-eligible children are slightly healthier than their enrolled counterparts, they face reduced access to care and lower rates of service use. After controlling for health status and other characteristics, we find that being uninsured increases the likelihood of being without a usual source of care by eight percentage points, and increases reporting of unmet needs by seven percentage points. Being uninsured also decreases by nine percentage points the proportion of children with any health provider visits, and increases by 12 percentage points the proportion with family out-of-pocket expenses exceeding $500. These findings lend support to the hypothesis that the enrollment process is onerous for some families. Targeted efforts to enroll uninsured Medicaid-eligible children could help in reducing the effect of barriers and reducing differences in access to care.

Adolescent↗
PubMed1999

Gemcitabine--a novel immunosuppressive agent--prevents rejection in a rat cardiac transplantation model.

BACKGROUND: 2',2' -difluorodeoxycytidine (dFdC, gemcitabine) is a pyrimidine antimetabolite with antineoplastic activity against a wide range of solid tumors. The immunosuppressive activities of this compound have not been described to date. METHODS: The in vitro effects on activated T lymphocytes were studied with a lymphocyte colony-forming assay in a microagar culture system. Heart transplantations were performed in the fully allogeneic Lewis/ Brown Norway combination. dFdC was administered once daily at various dosages from the time of surgery until day 50. RESULTS: Phytohemagglutinin-induced lymphocyte proliferation was inhibited 50% by dFdC at a concentration of 3.25+/-0.9 nmol/L. Allografts of untreated animals survived for 7.5 (7-8) days and those with 25, 50, and 75 microg/kg body weight dFdC for 7.3 (7-8), 9.3 (8-10), and 16.3 (10-38) days, respectively. Treatment with 100 or 125 microg/kg body weight of dFdC, however, prolonged allograft survival until day 152.8 (129-178). Dose-dependent leukopenia was the main toxicity. CONCLUSIONS: DFdC is a new immunosuppressive agent that can successfully prevent cardiac rejection in a rat transplantation model.

Animals↗
PubMed1999

Differential effects of cladribine and gemcitabine on erythroid and granulocytic progenitors from patients with chronic myeloid leukemia.

Chronic myeloid leukemia (CML) is a clonal neoplastic disease that originates in a pluripotent stem cell. Selection of normal progenitors by graft-purging may improve the outcome after autologous transplantation. In our methylcellulose assays, the nucleoside analogs cladribine (2-CdA) and gemcitabine (dFdC) showed more prominent inhibitory effects on CML than normal bone marrow (BM) progenitors. For dFdC, however, long-term incubations were necessary to achieve complete inhibition. Deoxycytidine kinase, the key enzyme of both 2-CdA and dFdC metabolisms, was only partially responsible for this differential sensitivity. We suggest that 2-CdA and dFdC might be helpful in purging of CML BM cells before autologous BM transplantation. Further studies on more primitive cells are warranted.

Antimetabolites, Antineoplastic↗
PubMed1998

Resistance to apoptosis and elevated expression of Bcl-2 in clonally expanded CD4+CD28- T cells from rheumatoid arthritis patients.

Patients with rheumatoid arthritis have a subset of CD4+ T lymphocytes that are characterized by a defect in CD28 expression. CD4+CD28- T cells frequently undergo clonal expansion in vivo. These clonotypes include autoreactive cells and persist over many years. The clonogenic potential and longevity of these T cells could be related to an altered response to apoptosis-inducing signals. To explore this possibility, CD4+CD28- T cell lines and clones were examined for their response pattern to stimuli inducing physiologic cell death. CD4+CD28- T cells were found to be resistant to apoptosis upon withdrawal of the growth factor, IL-2. To examine whether the altered sensitivity to this apoptotic signal was correlated with the expression of proteins of the bcl-2 family, the expression of bcl-2, bcl-x, and bax proteins was determined. CD28+ and CD28-CD4+ T cells could not be distinguished by the levels of bax or bcl-xL protein; however, CD4+CD28- T cells expressed higher amounts of bcl-2 protein than did CD4+CD28+ T cells. The increased bcl-2 expression in CD4+CD28- T cells was relatively independent of signals provided by exogenous IL-2. In CD28-deficient CD4+ T cells, bcl-2 was not significantly up-regulated by the addition of exogenous IL-2 and was maintained despite IL-2 withdrawal, as opposed to CD28-expressing CD4+ T cells. We propose that CD4+CD28- T cells are characterized by a dysregulation of the survival protein, bcl-2, which may favor the clonal outgrowth of autoreactive T cells and thus contribute to the pathogenesis of rheumatoid arthritis.

Apoptosis↗
PubMed1998

Aging-related deficiency of CD28 expression in CD4+ T cells is associated with the loss of gene-specific nuclear factor binding activity.

Changes in T cell populations and concomitant perturbation of T cell effector functions have been postulated to account for many aging-related immune dysfunctions. Here, we report that high frequencies of CD28(null) CD4+ T cells were found in elderly individuals. Because deviations in the function of these unusual CD4+ T cells might be directly related to CD28 deficiency, we examined the molecular basis for the loss of CD28 expression in CD4+ T cells. In reporter gene bioassays, the minimal promoter of the CD28 gene was mapped to the proximal 400 base pairs (bp) of the 5' untranslated region. CD28 deficiency was associated with the loss of two noncompeting binding activities within a 67-bp segment of the minimal promoter. These binding activities were not competed by consensus Ets, Elk, or AP3 motifs that were found within the sequence stretch. The DNA-protein complexes were also not recognized by antibodies to Ets-related transcription factors. Furthermore, introduction of mutations into the 67-bp segment at positions corresponding to the two DNA-protein interaction sites, i.e. nucleotides spanning -206 to -179 and -171 to -148, resulted in the loss of specific nuclear factor binding activities and the abrogation of promoter activity. These observations implicate at least two regulatory motifs in the constitutive expression of CD28. The loss of binding activity of trans-acting factors specific for these sequences may contribute to the accumulation CD4+CD28(null) T cells during aging.

Aging↗