Search PubMed⌕ Search

Biomedical subjects

R Haas

Publications and source records attributed to R Haas.

At least 289 records · Page 16Linked to original sources
PubMed1989

Reassortment of pilin genes in Neisseria gonorrhoeae occurs by two distinct mechanisms.

Phase and antigenic variation of pilin expression in Neisseria gonorrhoeae result from recombination events in which variant sequences from one of the silent loci (pilS) are transferred to the expression locus (pilE). Such rearrangements were originally thought to be gene conversions, but findings showing that phase variation is partially inhibited by DNase I, that piliated (P+) cells are highly competent for DNA uptake and that gonococci readily undergo autolysis in culture, led to the suggestion that pilin variation occurs through transformation by exogenous DNA. We have developed a simple method for the selection of non-piliated (P-) cells and have evaluated naturally occurring P+ to P- transitions. Two primary pathways of pilin variation can be distinguished--transformation-mediated recombination, which is influenced by culture conditions and inhibited by DNase I, and intragenomic reciprocal recombination, which is unaffected by DNase I. Furthermore, we demonstrate that both piliated and revertible P- cells are competent for DNA uptake, an essential prerequisite of the first pathway.

Bacterial Outer Membrane Proteins↗
PubMed1989

Effect of recombinant human granulocyte-macrophage colony-stimulating factor (rhuGM-CSF) on normal peripheral B lymphocytes and B lymphoblastoid cell lines.

The role of the granulocyte-macrophage colony-stimulating factor (GM-CSF) for the proliferation and differentiation of normal and leukemic myeloid cells has been extensively investigated. We examined whether rhuGM-CSF has any functional effect on normal purified B cells and cell lines from patients with B cell non-Hodgkin's lymphomas (NHL). Normal B cells were prepared by combining E-rosetting followed by two non-adherence procedures. Further B cell enrichment was achieved by complement-mediated lysis with a panel of antibodies directed against various T cell antigens. Alternatively, we incubated the cells with monoclonal antibodies recognizing specific antigens on monocytes/macrophages and T cells followed by a separation with immunomagnetic beads coated with sheep anti-mouse IgG. With these different separation procedures B cell populations with a various content of monocytes/macrophages were obtained. An optimal enrichment of B cells up to 80-90% was achieved by combining E-rosetting, non-adherence, and separation with immunomagnetic beads. The proliferative response to rhuGM-CSF (0.01-1000 ng/ml) was assessed in a [3H]-thymidine uptake assay. RhuGM-CSF alone or in combination with anti-IgM or SAC did not cause any proliferative effect in normal B cells. Even in the presence of 35% monocytes (CD11+) as accessory cells no stimulatory effect could be measured. Similarly, the malignant B lymphoma cells did not show any proliferative response to rhuGM-CSF. To assess a potential differentiation-inducing capacity the Ig production was measured.(ABSTRACT TRUNCATED AT 250 WORDS)

B-Lymphocytes↗
PubMed1989

Mouse thymidine kinase: the promoter sequence and the gene and pseudogene structures in normal cells and in thymidine kinase deficient mutants.

The mouse genome carries one gene and two pseudogenes for cytoplasmic thymidine kinase. The overall structure of these genes was determined with the help of cosmids and lambda phage clones and the upstream sequence containing the promoter was determined. The data allow an allocation of bands seen in the complex patterns of genomic Southern blots obtained from the DNA of wild type cells and of thymidine kinase deficient mutants to the gene as well as to the two pseudogenes. The much used LTK cell line was found to lack the entire gene but to retain the pseudogenes. Two other TK cell lines had DNA patterns indistinguishable from the wild type. Whereas the LTK line did not produce any TKmRNA, the two other mutants had normal amounts of TKmRNA but no cytoplasmic TK activity.

Animals↗
PubMed1989

Effect of recombinant human interleukin 2 (rIL-2) on normal peripheral blood B cells and B lymphoblastoid cell lines.

The role of interleukin 2 (IL-2) for growth and differentiation of normal and malignant B cells still remains controversial. We assessed normal peripheral blood B cells and cell lines derived from patients with B non-Hodgkin's lymphomas (NHLs) with respect to their responsiveness to recombinant human IL-2 (rIL-2). The NHL cell lines used in our experiments expressed the Tac antigen (CD25)--a compound of the IL-2 receptor (IL-2R)--in a percentage ranging from 28 to 57%. As measured in a [3H]thymidine uptake assay, the normal peripheral blood B cells demonstrated a dose-dependent proliferative response to rIL-2, whereas the NHL cells did not show any responsiveness to rIL-2. In a clonogenic culture assay we evaluated the colony formation of the NHL cells and found a decrease of 28 to 41% on average in the presence of rIL-2 (10-50 U/ml). This moderate inhibitory effect on the clonal growth of the NHL cells was not due to a differentiation inducing effect of rIL-2, as studied by measuring the Ig production under increasing doses of rIL-2 (1 to 100 U/ml). Thus, malignant NHL B cells may express the CD25 compound of the IL-2 receptor on their surface, demonstrating a different functional responsiveness to rIL-2 compared to normal peripheral blood B cells.

B-Lymphocytes↗
PubMed1989

HLA-DP antigens in patients with chronic autoimmune thrombocytopenia (AITP).

AITP, a disease with well-defined autoimmune character, has been previously studied for a possible HLA association. However, no such association with antigens of the A, B, C or DR loci was found. As this does not exclude a possible association with HLA-DP antigens, we have investigated 36 patients with AITP for DP w1, w2, w3, w4 and w5 by primed lymphocyte typing using locally derived as well as the original DP reagents as used in the 9th International Histocompatibility Workshop. Comparison of antigen frequencies with those of 254 healthy controls revealed an increased frequency of DPw5 in the patient group which, however, was not statistically significant. Other discrepancies were not observed.

Adolescent↗
PubMed1989

Deficiency of carnitine palmitoyltransferase I.

Defective activity of carnitine palmitoyltransferase I was demonstrated in fibroblasts derived from a patient with hypoketotic hypoglycemia. The level of activity observed was approximately 10% of the control mean. Oxidation of palmitate by intact fibroblasts was reduced to 5% of control values. The patient presented at age 14 months with seizures and was found to have marked hypoglycemia and no ketones in the urine. In response to fasting, she developed hypoglycemia, but the curves for acetoacetate and 3-hydroxybutyrate were flat. Administration of medium-chain triglycerides relieved the hypoglycemia and generated a brisk ketogenesis.

Acyltransferases↗
PubMed1989

Enhanced myelopoiesis in long-term cultures of human bone marrow pretreated with recombinant granulocyte-macrophage colony-stimulating factor.

Long-term bone marrow culture (LTBMC) for human hemopoiesis supports continuous proliferation and differentiation within the myeloid progenitor population by the formation of an adherent stromal monolayer. LTBMC represents the most suitable in vitro model for the study of regulatory mechanisms in human hemopoiesis. We investigated the effect of recombinant human granulocyte-macrophage colony-stimulating factor (rhuGM-CSF) on bone marrow of normal donors in LTBMC. The cells (2 x 10(6)/ml) were incubated with 100 ng/ml rhuGM-CSF for 24 h in culture medium supplemented with 10% fetal calf serum. After the preincubation, LTBMCs were started and maintained over a period of 10 weeks. After 1 week in culture we observed a statistically significant difference with a 1.5-fold higher number of nonadherent cells in the LTBMCs containing the bone marrow preincubated with rhuGM-CSF (p less than 0.05). This increase was due to an expansion of the mature myeloid cells. At the same time point the number of GM colony-forming units (CFU-GM)/ml in the LTBMCs with rhuGM-CSF-preincubated bone marrow was slightly increased compared to the controls without reaching a statistically significant level. We conclude that rhuGM-CSF at a saturation dose is a potent stimulator of in vitro myelopoiesis stem cell pool. This in vitro result is of relevance for the clinical use of rhuGM-CSF in patients undergoing bone marrow transplantation. The incubation of donor bone marrow prior to transplantation might be a new approach to facilitate the engraftment and to shorten the phase of pancytopenia.

Bone Marrow↗
PubMed1988

Myxothiazol resistance in human mitochondria.

We have investigated electron transfer activities of respiratory chain complexes in platelet mitochondria of a patient with intermittent ataxia and lactic acidosis who was previously reported to be deficient in the E1 (decarboxylase) component of the pyruvate dehydrogenase complex. Electron transfer from succinate to cytochrome c was normal, but the mitochondria exhibited moderately decreased (63% of control) quinol: cytochrome-c oxidoreductase activity, suggesting a defect in complex III. Consistent with some perturbation in complex III, electron flux through complex III was resistant to inhibition by myxothiazol compared to normal controls. In contrast, titration with antimycin revealed a less abnormal pattern of inhibition. The extreme specificity of myxothiazol binding at or near the quinol oxidase domain of mitochondrial cytochrome b, i.e., b-566, suggests a defect in this region of complex III which may perturb the kinetics or thermodynamics of quinol oxidation in the complex. These data suggest that the patient's illness results from a mutation in the quinol oxidase domain of mitochondrial cytochrome b (b-566).

Acidosis, Lactic↗
PubMed1988

Synthesis and properties of novel psoralen derivatives.

We have synthesized a set of new trimethylpsoralen derivatives that are characterized by a chain extending from the 4'-position of the furan ring and linked to this ring by an aminomethylene group. The nature of the side chain can be varied widely. In these derivatives, the chains contain either amino or ethylene oxide units for enhanced water solubility and allow the introduction of a thiol or amine group to nucleic acids. These compounds represent the first set of thiolated psoralen derivatives, and their usefulness is demonstrated in several nucleic acid cross-linking experiments. The reagents can be used to create both intraduplex reversible cross-links between the two single-strand partners in a DNA double helix and interduplex reversible cross-links between two DNA double helices.

Cross-Linking Reagents↗
PubMed1988

Drosophila acetylcholinesterase: demonstration of a glycoinositol phospholipid anchor and an endogenous proteolytic cleavage.

The presence of a glycoinositol phospholipid anchor in Drosophila acetylcholinesterase (AChE) was shown by several criteria. Chemical analysis of highly purified Drosophila AChE demonstrated approximately one residue of inositol per enzyme subunit. Selective cleavage by Staphylococcus aureus phosphatidylinositol-specific phospholipase C (PI-PLC) was tested with Drosophila AChE radiolabeled by the photoactivatable affinity probe 3-(trifluoromethyl)-3-(m-[125I]iodophenyl)diazirine [( 125I]TID), a reagent that specifically labels the lipid moiety of glycoinositol phospholipid-anchored proteins. Digestion with PI-PLC released 75% of this radiolabel from the protein. Gel electrophoresis of Drosophila AChE in sodium dodecyl sulfate indicated prominent 55- and 16-kDa bands and a faint 70-kDa band. The [125I]TID label was localized on the 55-kDa fragment, suggesting that this fragment is the C-terminal portion of the protein. In support of this conclusion, a sensitive microsequencing procedure that involved manual Edman degradation combined with radiomethylation was used to determine residues 2-5 of the 16-kDa fragment. Comparison with the Drosophila AChE cDNA sequence [Hall, L.M.C., & Spierer, P. (1986) EMBO J. 5, 2949-2954] confirmed that the 16-kDa fragment includes the N-terminus of AChE. Furthermore, the position of the N-terminal amino acid of the mature Drosophila AChE is closely homologous to that of Torpedo AChE. The presence of radiomethylatable ethanolamine in both 16- and 55-kDa fragments was also confirmed. Thus, Drosophila AChE may include a second posttranslational modification involving ethanolamine.

Acetylcholinesterase↗
PubMed1988

Complement-mediated cytolysis: quantification of B cell surface antigen molecules and role of cell cycle.

Complement (C')-mediated cytolysis is currently used for the purging of autografts in autologous bone marrow transplantation (ABMT). However, a number of factors influencing the efficiency of lysis remain to be explored. In this report, firstly using a Scatchard analysis, the number of surface antigen molecules for CD19 and CD20 on 3 B cell lines has been quantified. This demonstrated that with CD20 a higher number of antigen molecules was required as compared to CD19 to produce an equally effective cytolysis. Secondly, the role of cell cycle has been investigated: cytolysis was not affected by cell phase. Moreover, CD19- and CD20-deficient cells escaping lysis displayed no difference in cell phase and possessed an identical growth pattern as controls.

Antigens, CD19↗
PubMed1988

Distal anterior choroidal artery aneurysm: intraoperative localization and treatment.

Distal anterior choroidal artery aneurysms with intraventricular hemorrhage are rare and difficult to treat. We report the case of a 46-year-old woman with a left distal anterior choroidal artery aneurysm presenting as a typical subarachnoid hemorrhage from which she had no focal neurological signs. Because the aneurysm was located within the dominant deep temporal lobe, we used intraoperative computed tomography to guide a probe to the aneurysm to allow minimal dissection. This is the first report of a successfully treated distal anterior choroidal artery aneurysm. Reports of this unusual aneurysm and methods of approaching deep temporal lesions are reviewed.

Female↗
PubMed1988

B-cell proliferative and differentiative responses after autologous peripheral blood stem cell or bone marrow transplantation.

In this study the authors have evaluated B-cell function after autologous peripheral-blood stem cell transplantation (ABSCT) and autologous bone marrow (ABMT) transplantation. The B-enriched fractions of peripheral blood from ten normal subjects and 22 autografted patients (11 patients after ABMT, eight patients after ABSCT, and three patients after ABSCT followed by ABMT) were investigated. Time postgrafting ranged from 1 to 34 months. Proliferative responses to anti-mu antibody, Staphylococcus aureus Cowan 1 (SAC), and low molecular weight (mol wt) 12-Kd B-cell growth factor (BCGF) were measured. Differentiative responses to the same factors were assessed by quantifying in vitro immunoglobulin (IgG/IgM) production. The authors found no difference in B-cell function between the ABMT and the ABSCT patient groups. Compared to the B cells of normal subjects, only five out of 22 autografted patients showed a normal proliferative response to all agents used, while nine out of 22 did not respond to any signals. Eight out of 22 patients displayed various defects of B-cell response. However, in vitro IgG/IgM secretion of predominantly IgG subclass was normal in 19 out of 22 patients. This in vitro ability to produce Ig was reflected by the patients' normal serum IgG/IgM levels, whereas serum IgA levels were low. The authors speculate that there may be 2 B-cell populations: the normal in vitro Ig production and in vivo serum IgG may come from the stimulation of a small number of re-infused pre-committed memory B cells while, in parallel, immature B cells develop from autografted hematopoietic progenitor cells.

Adult↗