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Biomedical subjects

B Baumann

Publications and source records attributed to B Baumann.

At least 73 records · Page 4Linked to original sources
PubMed1996

Dynamics of denitrification activity of Paracoccus denitrificans in continuous culture during aerobic-anaerobic changes.

Induction and repression of denitrification activity were studied in a continuous culture of Paracoccus denitrificans during changes from aerobic to anaerobic growth conditions and vice versa. The denitrification activity of the cells was monitored by measuring the formation of denitrification products (nitrite, nitric oxide, nitrous oxide, and dinitrogen), individual mRNA levels for the nitrate, nitrite, and nitrous oxide reductases, and the concentration of the nitrite reductase enzyme with polyclonal antibodies against the cd1-type nitrite reductase. On a change from aerobic to anaerobic respiration, the culture entered an unstable transition phase during which the denitrification pathway became induced. The onset of this phase was formed by a 15- to 45-fold increase of the mRNA levels for the individual denitrification enzymes. All mRNAs accumulated during a short period, after which their overall concentration declined to reach a stable value slightly higher than that observed under aerobic steady-state conditions. Interestingly, the first mRNAs to be formed were those for nitrate and nitrous oxide reductase. The nitrite reductase mRNA appeared significantly later, suggesting different modes of regulation for the three genes. Unlike the mRNA levels, the level of the nitrite reductase protein increased slowly during the anaerobic period, reaching a stable value about 30 h after the switch. All denitrification intermediates could be observed transiently, but when the new anaerobic steady state was reached, dinitrogen was the main product. When the anaerobic cultures were switched back to aerobic respiration, denitrification of the cells stopped at once, although sufficient nitrite reductase was still present. We could observe that the mRNA levels for the individual denitrification enzymes decreased slightly to their aerobic, uninduced levels. The nitrite reductase protein was not actively degraded during the aerobic period.

Aerobiosis↗
PubMed1996

Leber's hereditary optic neuropathy: clinical and molecular genetic results obtained in a family with a new point mutation at nucleotide position 14498 in the ND 6 gene.

Mitochondrial DNA mutations at nucleotide position (np) 3460 in the ND 1 gene, np 11778 in the ND 4 gene, and np 14484 in the ND 6 gene are commonly considered to be associated with the clinical features of Leber's hereditary optic neuropathy (LHON) and account for the majority of LHON cases. Recently, a further mutation in the mtDNA at np 14459 was detected. Herein we report the clinical and the most relevant molecular genetic findings obtained in a LHON family with a new mitochondrial DNA mutations at np 14498 in the ND 6 gene. Clinical and historical data were collected over four generations on three affected and five yet unaffected relatives of the maternal line in this family. All three patients and four of their relatives underwent molecular genetic examination. Two patients and five relatives were also studied clinically. All patients exhibited typical clinical features of LHON. In all yet unaffected relatives, various degrees of peripapillary microangiopathy were found. Molecular analysis did not reveal any of the common LHON mutations. Sequence analysis of the mtDNA of one patient was performed and showed a thymine-to-cytosine exchange at np 14498 in the ND 6 gene, leading to the replacement of an evolutionary highly conserved tyrosine by a cysteine residue. The mutation was not found among 70 other LHON lineages and 180 controls. The new mutation at np 14498 lies in the vicinity of the LHON-related mutations at np 14484 and of the recently described mutation at np 14459, in a region constituting the most evolutionarily conserved part of this polypeptide. That the new mutation at np 14498 is found within this highly conserved region and was not present in any controls implies that this mutation is responsible for LHON in this family.

Adolescent↗
PubMed1995

Fos is an essential component of the mammalian UV response.

Mouse 3T3 fibroblasts lacking c-fos were employed to demonstrate an essential function of the UV-inducible transcription factor AP-1 (Fos/Jun) in the response to the cytotoxic effects of short-wavelength ultraviolet (UVC) radiation. Clonogenic survival and proliferation of cells lacking c-fos were drastically reduced following UV irradiation. This UV hypersensitivity manifests itself primarily in increased cell death, partly by apoptosis, and prolonged recovery time from UV-induced cell cycle arrest. Co-culture with wild-type cells did not ameliorate the hypersensitivity of mutant cells. Transcriptional induction of the c-Fos target genes collagenase I, stromelysin-1 and stromelysin-2 by UV is almost absent in cells lacking c-fos which correlates with a reduced UV induction of AP-1 DNA-binding and transactivation activity. The repair of UV-induced DNA lesions was not affected, as shown by unscheduled DNA synthesis and host cell reactivation assays. These data demonstrate that c-Fos is involved in a novel protective function other than DNA repair against the harmful consequences of UVC.

3T3 Cells↗
PubMed1993

Murine clusterin: molecular cloning and mRNA localization of a gene associated with epithelial differentiation processes during embryogenesis.

Clusterin is a broadly distributed glycoprotein constitutively expressed by various tissues and cell types, that has been shown to be involved in cell-cell adhesion and expressed during cellular differentiation in vitro. To assess the suggested participation of clusterin in these processes in vivo, we have cloned the cDNA encoding murine clusterin and studied the cellular distribution of clusterin mRNA during murine embryogenesis. Sequence analysis of the cDNA encoding murine clusterin revealed 92 and 75% sequence identity with the rat and human cDNAs, respectively, and conservation of the predicted structural features which include alpha-helical regions and heparin-binding domains. From 12.5 d of development onwards, the clusterin gene is widely expressed in developing epithelia, and selectively localized within the differentiating cell layers of tissues such as the developing skin, tooth, and duodenum where proliferating and differentiating compartments are readily distinguished. In addition, transient and localized clusterin gene expression was detected in certain morphogenetically active epithelia. In the lung, abundant gene transcripts were detected in cuboidal epithelial cells of the terminal lung buds during branching morphogenesis, and in the kidney, clusterin gene expression in the epithelial cells of comma and S-shaped bodies coincided with the process of polarization. Our results demonstrate the in vivo expression of the clusterin gene by differentiating epithelial cells during murine embryogenesis, and provide novel evidence suggesting that clusterin may be involved in the differentiation and morphogenesis of certain epithelia.

Amino Acid Sequence↗
PubMed1991

[Effect of alfa-2b interferon on prognostic parameters and clinical events in HIV positive patients in the LAS/ARC stage].

A number of in vivo and in vitro results suggest that interferons have an antiretroviral effect on HIV. To check this, 15 HIV-positive patients who had no full-blown AIDS, were treated with recombinant interferon alpha 2b (5 mill. IU s. c. three times a week) over a period of six months. Twelve to 16 weeks after the initiation of treatment, an increase in CD 4 lymphocytes (+16%), NK cells (+16%), lymphocytes stimulation by con A (+ 176%), neopterin (+66%), and beta-2-microglobulin (+19%) was observed. By the end of the study, all these parameters had slightly decreased again. In all patients with CD4 lymphocytes greater than 0.2 c/nl, we observed a decrease in p24 antigen levels, but in patients with CD4 lymphocytes less than 0.2 c/nl, an increase. It would thus seem that any antiretroviral effect of IFN (as shown by the p24 antigen parameter) is more pronounced in patients with superior immune parameters.

AIDS-Related Complex↗
PubMed1990

[Equipment for respiratory gas conditioning under hygienic conditions].

The significance of respiratory gas conditioning systems as sources of germ colonization and infection of the respiratory tract results from the principle of operation and the temperature. Six respiratory air humidifiers were tested for their hygienic risk in experiments with test germs. Contrary to several reports, some humidifiers were shown to accumulate microorganisms, whereas others do not promote germ population in the respiratory tract even though the water of the humidifier is heavily contaminated. It could be confirmed that basic differences exist between "blow over" and "blow through" humidifiers in the accumulation of microorganisms in respiratory air. Moreover, our investigations revealed that even "blow over" humidifiers should not be considered completely harmless. The "blow over" apparatuses Hydrotrop 200, Aquapor and VH 620 (infant) did not cause any germ propagation in the resuscitation tubes, whereas in the "blow through" apparatuses Bennett Cascade and VH 620 (adult) germ propagation is quite considerable. The mortality kinetics of the germs differ depending on the temperature and the type of apparatus used and should be taken into account when it comes to choosing or developing respiratory gas conditioning devices. Constant heating of the water in the humidifier to a minimum of 50 degrees C provokes a bactericide behaviour of the problem germs. Therefore, it is quite justifiable to do without expensive internationally recommended measures if the humidifier is well chosen. The requirement to replace the humidifier every 24 hours in long-term artificial respiration need not be observed for devices classified as harmless if aseptic handling is guaranteed, i.e. if manual germ transmission by the staff is avoided.

Cross Infection↗
PubMed1989

M2 muscarinic receptors on the iris sphincter muscle differ from those on iris noradrenergic nerves.

The pre- and postjunctional affinity constants of a series of muscarinic antagonists were determined in guinea pig and rabbit irises. Field stimulation-evoked [3H]noradrenaline release from superfused isolated irises was concentration dependently inhibited by (+/-)-methacholine, confirming the presence on the iris noradrenergic nerves of prejunctional inhibitory muscarinic receptors. The affinity constants of the antagonists at the pre- and postjunctional receptors are compatible with the coexistence in the iris of two different M2 receptors: the cardiac (M2 alpha) subtype on the noradrenergic nerves and the smooth muscle (M2 beta) subtype on the iris sphincter muscle. The rank order of potency of the antagonists studied at the prejunctional site was: atropine greater than himbacine greater than AF-DX 116 greater than pirenzepine greater than hexahydrosiladifenidol. The order of potency at the postjunctional receptors mediating the methacholine-induced isotonic contraction of the isolated rabbit iris sphincter was: atropine greater than hexahydrosiladifenidol greater than pirenzepine greater than himbacine greater than AF-DX 116.

Animals↗
PubMed1989

[Influence of antiseptic measures on the flora of the oral cavity. 2. In vivo examinations].

For prophylactic antisepsis of the oral cavity 12 antiseptic solutions and 4 antiseptically acting tablets were examined in vivo. A total of 720 samples were evaluated after indirect contact sampling and 80 after direct contact sampling. After the evaluation of the in vivo findings the following antiseptic agents can be recommended for prophylactic antisepsis of the oral cavity in stomatological practice: the 0.2% chlorhexidine solution, the 0.1% aqueous solution of Tosyl-chloramid-Sodium, and Sulfachin.

Anti-Infective Agents, Local↗
PubMed1989

[Nosocomial infections caused by multi-resistant Serratia marcescens at a university clinic--clinical aspects and drug resistance].

Serratia marcescens (S.m.) has become increasingly important as a nosocomial pathogen and displayed an increasing resistance to antimicrobial agents in the past decade. We recently studied in 1985 and 1986 an epidemic caused by multi resistant S.m. strains that involved 27 infants and 1 adult patient. 14 neonates (in most cases very low birth weight infants) in a neonatal intensive care unit developed a S.m.-septicemia and/or meningitis, 11 of them died. In a ward for young infants with congenital heart diseases 13 patients suffered a S.m. infection and one patient died in the adult intensive care unit in consequence of a S.m. septicemia.

Anti-Bacterial Agents↗
PubMed1988

Essential thrombocythemia. Clinical characteristics and course of 61 cases.

Sixty-one patients with essential thrombocythemia (ET) were followed from 1974 through 1987 at the Medizinische Poliklinik. Fifty-one patients (84%) presented with thromboembolic complications, and eight patients (13%) with hemorrhages. In seven patients (12%), a thrombocytosis was detected accidentally. Disturbances of the microcirculation (67%), mainly of the fingers and toes (53%), were the most frequent thromboembolic symptoms. The mean age of all patients was 58 years (male patients, 61 years; female patients, 56 years). The average platelet count at diagnosis was 897,000/microliter. The average maximal platelet count was 1.231 X 10(6)/microliter (range, 500,000/microliter to 4 X 10(6)/microliter). Seventy-two percent had a moderate leukocytosis (average, 12,400/microliter), 34% a splenomegaly, 29% a hepatomegaly. Signs of hypermetabolism were infrequent, lactate dehydrogenase (LDH) and uric acid elevations, if present, were moderate. Bleeding time and viscosity were normal in most patients. Spontaneous platelet aggregation was increased in 81% of patients (n = 40). Platelet aggregation studies with the aggregation inducing substances adenosine diphosphonate (ADP), platelet activating factor (PAF), thrombin, collagen, and adrenalin showed hypoaggregation in most patients. Adrenalin-induced aggregation distinguished best between ET-patients and reactive thrombocytosis showing hypoaggregation in all ET-patients tested (n = 16) and in none of 22 controls. Bone marrow studies were performed in 57 patients. The histologic studies (done in 49 patients) were consistent with a chronic myeloproliferative disorder in all cases. In 41 cases (84%) the picture of a megakaryocytic myelosis was found, in 12 of these a granulocyte-rich form of megakaryocytic myelosis. Cytologic studies only (eight patients) did not differentiate ET well from reactive thrombocytosis. Platelet aggregation studies and bone marrow histology may be of help in the diagnosis of difficult cases of thrombocytosis. The Philadelphia status was negative in all cases studied (14 patients). Fourteen patients died. The causes of death were thromboembolic complications in probably 11 and acute leukemia in two patients. The probability of 10-year survival is 64% after a mean follow-up time of approximately 5 years. It appears that considering the average age of ET patients at diagnosis, life expectancy is close to normal.

Bone Marrow↗
PubMed1988

[Thrombocyte function in essential thrombocythemia and reactive thrombocytosis].

Blood of 16 patients with essential thrombocythemia (ET), 9 patients with reactive thrombocytosis (RT) and 13 healthy persons was used for platelet aggregation studies. When the aggregation was induced with adenosine diphosphate (0.01 microM), collagen (0.1 micrograms/ml) or platelet activating factor (PAF 0.5 microM) the plasma of the patients with ET showed significantly decreased aggregation (35%-44% of the value for the control groups). Independent of inhibitors of platelet aggregation, thrombin (0.05 U/ml) caused similar aggregation in healthy controls and patients with ET; patients with RT showed an increase aggregation. Adrenalin-induced aggregation discriminated best between patients with ET and controls. Adrenalin in concentrations ranging from 0.01 micrograms/ml to 100 micrograms/ml caused comparable dose-related amounts of aggregation in healthy controls and patients with RT. Over the whole concentration range, patients with ET showed significantly decreased aggregation (28%-34% of the value for the control groups). This difference proved to be independent of the influence of inhibitors of platelet aggregation. Though concentrations of alpha1-acid glycoprotein never reached inhibitory levels in the plasma of patients with ET (n = 12) they were significantly higher compared with those in normal plasma (n = 12). Fibrinogen concentrations in plasma of ET-patients (n = 12) were in the normal range. Cellular adenosine 3'-5'-cyclic monophosphate concentrations in ET (n = 10) are comparable with normal values (n = 5). The significance of the results for diagnosis and better pathophysiological understanding of ET is discussed.

Blood Platelets↗
PubMed1985

Consequences of frameshift mutations at the immunoglobulin heavy chain locus of the mouse.

From an IgM secreting hybridoma line we have isolated 16 spontaneous mutants that produce truncated IgM polypeptides. The size of the mu-mRNAs produced by these mutants is normal, but they express 3- to 100-fold less mu-mRNA and mutant mu-protein than the parental cell line. Nucleotide sequence analysis of cloned mu-genes and/or their mRNAs show frameshift mutations that generate in-phase chain termination codons. The extent of the reduction in mu-mRNA levels depends on the position of the nonsense codon within the gene.

Amino Acid Sequence↗