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Biomedical subjects

M Steffen

Publications and source records attributed to M Steffen.

At least 37 records · Page 2Linked to original sources
PubMed1995

Successful transformation of yeast mitochondria with RPM1: an approach for in vivo studies of mitochondrial RNase P RNA structure, function and biosynthesis.

Mitochondrial RNase P RNA (Rpm1r) is coded by the RPM1 gene of mitochondrial DNA in many yeasts. As an initial step to developing a genetic approach to the structure and biogenesis of yeast mitochondrial RNase P, biolistic transformation has been used to introduce wild type and altered RPM1 genes into strains containing no mitochondrial DNA. The introduced wild type gene does support RNase P activity demonstrating that pre-existing RNase P activity is not necessary for the biosynthesis of the enzyme. Mutations introduced into RPM1 in vitro result in reduced accumulation of mature tRNA and in an alteration of the processing of Rpm1r in vivo.

Base Sequence↗
PubMed1993

Increased secretion of tumor necrosis factor-alpha, interleukin-1-beta, and interleukin-6 by alveolar macrophages from patients with sarcoidosis.

BACKGROUND: Alveolar macrophages from patients with sarcoidosis were analyzed for their ability to secrete tumor necrosis factor-alpha (TNF-alpha), interleukin-1-beta (IL-1-beta), and interleukin-6 (IL-6). RESULTS: Constitutive release of all three monokines in these patients was concomitantly increased in the active state of disease in comparison with inactive sarcoidosis or healthy control subjects. Alveolar macrophages from patients with inactive sarcoidosis compared with cells from healthy subjects showed increased spontaneous secretion of TNF-alpha and IL-6 only, whereas the constitutive release of IL-1-beta was similar as in healthy volunteers. In vitro stimulation of alveolar macrophages from healthy control subjects with lipopolysaccharide or pokeweed mitogen led to a time- and dose-dependent enhanced secretion of TNF-alpha, IL-1-beta, and IL-6. In a similar manner, with corresponding cells from patients with sarcoidosis the secretion of all three cytokines could be further increased by stimulation with lipopolysaccharide or pokeweed mitogen. CONCLUSIONS: The data presented indicate that an increased release of TNF-alpha, IL-1-beta, and IL-6 correlates to disease activity and may play a critical part in the pathogenesis of sarcoidosis.

Adult↗
PubMed1993

Differences in cytokine secretion by intestinal mononuclear cells, peripheral blood monocytes and alveolar macrophages from HIV-infected patients.

Mononuclear cells of the lamina propria (LpMNC), isolated from endoscopically taken biopsies of the large bowel from AIDS patients, were analysed for their ability to secrete tumour necrosis factor-alpha (TNF-alpha), IL-1 beta and IL-6. Stimulation of LpMNC from normal controls with pokeweed mitogen (PWM) led to a time- and dose-dependent enhancement of TNF-alpha, IL-1 beta and IL-6 secretion. In contrast, PWM stimulation of LpMNC from AIDS patients resulted in only a small increase in TNF-alpha release. Constitutive secretion of IL-1 beta and IL-6 in these patients was already increased to the concentration range of stimulated cells from normal controls and could not be further increased, probably due to maximal in vivo stimulation. Secretion of TNF-alpha, IL-1 beta and IL-6 by peripheral blood monocytes (PBM) and alveolar macrophages from AIDS patients was elevated with or without stimulation compared with normal controls. Obviously, the regulation of TNF-alpha secretion is dependent on the microenvironment. Since it is known that interferon-gamma (IFN-gamma) may induce the production of TNF-alpha, the secretion of this cytokine was examined. Release of IFN-gamma was constitutively and under stimulation lowered in LpMNC from AIDS patients compared with normal controls. Addition of IFN-gamma to LpMNC did not result in enhanced TNF-alpha secretion. Our data indicate a defective function of intestinal mononuclear cells in AIDS patients as shown by the diminished TNF-alpha secretion.

HIV Infections↗
PubMed1993

Enhanced secretion of tumour necrosis factor-alpha, IL-6, and IL-1 beta by isolated lamina propria mononuclear cells from patients with ulcerative colitis and Crohn's disease.

The perpetuation of inflammation in ulcerative colitis and Crohn's disease may be regulated in part by an increased secretion of proinflammatory cytokines due to either an appropriate response to initial stimulating agents, and/or due to an impaired down-regulation of cytokine secretion. The aim of this study was to determine the secretion patterns of the proinflammatory cytokines tumour necrosis factor-alpha (TNF-alpha), IL-6 and IL-1 beta, from isolated lamina propria mononuclear cells (LPMNC) isolated from colonic biopsies from patients with untreated ulcerative colitis or Crohn's disease. LPMNC isolated from involved inflammatory bowel disease (IBD) mucosa spontaneously produced increased amounts of TNF-alpha, and IL-6, and IL-1 beta. The TNF-alpha secretion from IBD LPMNC could be further enhanced by pokeweed mitogen stimulation. The secretion patterns of TNF-alpha and IL-1 beta by LPMNC from patients with either ulcerative colitis or Crohn's disease demonstrated a close correlation with the degree of tissue involvement and mucosal inflammation. LPMNC from non-involved ulcerative colitis mucosa secreted markedly increased levels of IL-6 compared with non-involved Crohn's disease mucosa or control mucosa. The heightened IL-6 secretion from LPMNC from non-involved ulcerative colitis mucosa without visible or microscopic signs of inflammation indicates that the pathophysiologic mechanisms involved in the initiation of inflammation may differ between ulcerative colitis and Crohn's disease. The determination of proinflammatory cytokine secretion by isolated LPMNC from colonoscopic biopsies may be a sensitive method for monitoring the severity of mucosal inflammation in IBD patients.

Adult↗
PubMed1992

Karyotype instability and altered differentiation of rat sarcoma cells after retroviral infection.

The karyotypic and phenotypic stability of cultured rat fibrosarcoma cells was challenged by infection with Moloney murine sarcoma virus (MoMuSV). After transformation, the spindle-like morphology of the parental HH-16 cl.2/1 cells had altered to a rounded phenotype, which was maintained in tumors produced by inoculating transformed cells into congenic animals. In contrast to the parental cells, transformed cells lacked cables of cytokeratins 14-16 and 19 and showed reduction of the mesenchymal marker protein vimentin. Additionally, the morphologically altered cell clones tf-1 to tf-3 had lost growth arrest in the presence of dexamethasone. The DNA of the transformed cells contained between four and six randomly integrated proviral copies. Karyotypic alterations were manifested by reduction of morphologically intact chromosomes in the MoMuSV-transformed cells together with increase of structural aberrations. Three additional markers were identified in the virus-transformed cell clones. Karyotypic instability induced by MoMuSV infection appeared closely related to reduction of the cellular differentiation status, although only cells of clone tf-1 had increased metastatic potential.

Age Factors↗
PubMed1992

Transforming growth factor-alpha and epidermal growth factor messenger ribonucleic acid and protein levels in human placentas from early, mid, and late gestation.

OBJECTIVE: Human placenta expresses receptors for transforming growth factor-alpha and epidermal growth factor throughout pregnancy. Experiments were performed to determine whether epidermal growth factor or transforming growth factor-alpha might be synthesized by placental cells and act through an autocrine mechanism to influence functioning of placental cells in vivo. STUDY DESIGN: Human placentas from early, mid, and late gestations were analyzed for transforming growth factor-alpha and epidermal growth factor messenger ribonucleic acid and proteins. Polyadenylic acid-positive ribonucleic acid was isolated from placentas from 10, 11, 13, 21, 32, 38, 39, and 40 weeks of gestation and analyzed by Northern analysis for hybridization with complementary deoxyribonucleic acid probes specific for epidermal growth factor or transforming growth factor-alpha. Levels of immunoreactive epidermal growth factor and transforming growth factor-alpha were measured by specific radioimmunoassays in pools of placentas from early, mid, and late gestations, and levels of epidermal growth factor and transforming growth factor-alpha receptor-active protein were measured by radioreceptor assay. RESULTS: All placentas had a strong transforming growth factor-alpha hybridization band at 4.5 kb and a weak epidermal growth factor hybridization band at 5.2 kb. High levels of transforming growth factor-alpha immunoreactive protein (90 to 180 ng/mg protein) and low levels of immunoreactive epidermal growth factor (3 to 9 pg/mg protein) were detected in pools of placentas from early, mid, and late gestations. High levels of epidermal growth factor and transforming growth factor-alpha receptor-active protein (250 ng/mg protein) were also detected. CONCLUSION: Human placentas contain relatively high levels of immunoreactive and receptor-active transforming growth factor-alpha, as well as transforming growth factor-alpha messenger ribonucleic acid, throughout gestation. This finding suggests that transforming growth factor-alpha may act by an autocrine system to influence human placental cell function in vivo.

Blotting, Northern↗
PubMed1992

Modulation of leukemic cell growth by tumor necrosis factor: action and expression in myeloid leukemia.

Normal and leukemic bone marrow cells were studied in the presence of tumor necrosis factor alpha (TNF) together with granulocyte colony-stimulating factor (G-CSF) or granulocyte-macrophage colony-stimulating factor (GM-CSF) in clonogenic assays. Cells of four normal volunteers, three patients with chronic myeloid leukemia, 16 patients with acute non-lymphocytic leukemia (ANLL), and six patients with myelodysplastic disorders were compared. Our results show four patterns of response to TNF in the presence of G-CSF or GM-CSF: (a) increased sensitivity to inhibition by TNF relative to the response of normal bone marrow cells; (b) response indistinguishable from normal bone marrow cells; (c) refractoriness to TNF at all doses; (d) synergistic growth stimulation with both G-CSF and GM-CSF. Leukemic cells of eight additional ANLL patients were incubated in a 3H-thymidine incorporation assay, and three patterns of reactivity to TNF were observed: (a) decreased 3H-thymidine uptake in the presence of TNF; (b) no response to TNF at all doses; and (c) increased 3H-thymidine uptake in response to TNF. Leukemic cells of 26 ANLL patients of various FAB-types were examined for the production of TNF mRNA by Northern blot analysis. TNF mRNA could be detected in cells of eight patients, predominantly in the M5B FAB type. Our data show that the growth response of leukemic cells to TNF is not uniform and was not determined by FAB category.

Cell Division↗
PubMed1992

[Antiphospholipid syndrome].

Antibodies against phospholipids in serum, lupus anticoagulant and anticardiolipin antibodies, are strongly associated with venous and arterial thrombosis. A syndrome characterized by these symptoms and the autoantibodies, the antiphospholipid syndrome, is found mostly in patients with systemic lupus erythematosus or related autoimmune disease, but is also found primary without a systemic disease.

Antibodies, Anticardiolipin↗
PubMed1990

Elevated expression of v-mos is correlated with altered differentiation of carcinoma cells.

Permanent alterations of the epithelial differentiation pattern were investigated after infection of HH-16 cl. 4 adenocarcinoma cells with Moloney murine sarcoma virus (MoMuSV). Transformed cell clones with fibroblastoid morphology were isolated and compared with clones of unchanged epithelioid phenotype. Southern blot analyses showed intact MoMuSV proviral genomes in copy numbers between 4 and 9 in the DNA of the morphologically transformed cell clones as well as in the clones with unaltered morphology. The fibroblastoid cells produced sarcomas after inoculation of newborn rats, whereas MoMuSV-infected cell clones with unaltered epithelioid morphology yielded adenocarcinomas. Immunocytochemical analyses revealed that morphological transformation into the fibroblastoid phenotype was accompanied by loss of cytokeratin expression and appearance of the mesenchymal marker protein vimentin. Proviral DNA was transcribed in the infected cell clones irrespective of their phenotype; however, transcription was significantly higher in cells with fibroblastoid morphology than in epithelioid cells.

Adenocarcinoma↗
PubMed1989

[Assessment of nutritional status--a part of routine clinical diagnosis: cholinesterase activity as a nutritional indicator].

Nutritional assessment has not yet been established as integral part of basic clinical diagnostic procedures everywhere, eventhough the prognostic relevance of malnutrition is well known. One of the reasons is the lack of nutritional indicators, which are specific of and sensitive for changes of the nutritional status on the one hand, and routinely analyzed on the other. We report on the utility of serum cholinesterase, which has the shortest half-life of all plasma proteins, to identify malnourished patients. 54 internal inpatients with malignant diseases or in septic state were followed up prospectively with respect to courses of cholinesterase (CHE), albumin (ALB), transferrin (TRA), and body weight over periods of 4 weeks. A correct correlation to malnutrition was defined as plasma concentrations less than reference ranges or continuous concentr. fall greater than 10%. Based on 132 observations (65 with continuous weight loss, mean: -5.5% of original w.; 54 w. gain, mean +4.6%, 13 constant w.), changes of CHE had the highest correlation to weight changes (r = 0.79, p less than 0.001), compared to the courses of TRA- or ALB-levels (r = 0.65/0.68). Incorrect positive results (conc. fall or conc. less than ref. range without weight loss): absolute levels - CHE 4%, ALB 4%, TRA 22%; conc. courses - CHE 0%, ALB 0%, TRA 6%. Incorrect negative: absolute c. - CHE 63%, ALB 30%, TRA 28%; courses - CHE 15%, ALB 19%, TRA 17%. The common determination of CHE and ALB-courses allowed a correct identification of malnutrition in 96% of all observations, with the same result as the courses of ALB + TRA.(ABSTRACT TRUNCATED AT 250 WORDS)

Body Weight↗
PubMed1989

Management and efficacy of intensified insulin therapy--starting in outpatients.

Diabetic patients under multiple injection insulin therapy (i.e., intensified insulin therapy, IIT) usually start this treatment during hospitalization. We report here on the logistics, efficacy, and safety of IIT, started in outpatients. Over 8 months, 52 type I and type II diabetics were followed up whose insulin regimens consecutively had been changed from conventional therapy to IIT. Two different IIT strategies were compared: free mixtures of regular and intermediate (12 hrs)-acting insulin versus the basal and prandial insulin treatment with preprandial injections of regular insulin, and ultralente (24 hrs-acting) or intermediate insulin for the basal demand. After 8 months HbA1 levels had decreased from 10.6% +/- 2.4% to 8.0% +/- 1.3% (mean +/- SD). There was no difference between the two regimens with respect to metabolic control; but type II patients maintained the lowered HbA1 levels better than type I patients. Only two patients were hospitalized during the follow-up time because of severe hypoglycemia. An increase of body weight due to the diet liberalization during IIT became a problem in one-third of the patients. Our results suggest that outpatient initiation of IIT is safe and efficacious with respect to near-normoglycemic control. Weight control may become a problem in IIT patients.

Blood Glucose↗
PubMed1989

Privatization in French health politics: few projects and little outcome.

The author presents the main features of the organization of the French health care system, revealing an important mixture of public and private actors and institutions and a large number of political restraints that oppose resistance to privatization. In spite of traditional references to "liberal medicine" and recurrent debates opposing public and private intervention, neither the doctors nor the political decision makers have really supported the few projects that have been proposed for privatization or liberalization of health care. On the contrary, the cost-control policy introduced growing State intervention and new management methods into the health care sector, whose actors were not used to it. The privatization and liberalization debates appear as a rhetoric necessary to accommodate these difficult changes.

Cost Control↗
PubMed1989

Presence of tumour necrosis factor or a related factor in human basophil/mast cells.

The observation that mast cell products and cachectin/tumour necrosis factor (TNF) mediate similar responses suggested an investigation of cultured human basophil/mast cells for production of TNF. Using in situ hybridization and the avidin biotin-complex (ABC) immunoperoxidase method, we have demonstrated the presence of TNF mRNA in the cytoplasm and TNF protein in the granules of individual human basophil/mast cells. The production of TNF by these cells could explain many of their reported functions.

Basophils↗