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Biomedical subjects

H Hahn

Publications and source records attributed to H Hahn.

At least 199 records · Page 11Linked to original sources
PubMed1986

Characterization of three different rat T-cell clones with specificity to Listeria monocytogenes: phenotype, specific proliferation, lymphokine production, and protective capacity in vivo.

Splenic T lymphocytes from rats immunized with the facultative intracellular bacterium, Listeria monocytogenes, were cloned by the limiting-dilution technique. From several clones obtained, three have been scrutinized in detail. As demonstrated by their reactivity to the monoclonal antibodies, W3/25 and MRC OX8, the clones RVIIC2 and R23D6 are of helper cell phenotype, whereas cells from clone R30D5 express both the helper and the cytotoxic/suppressor cell markers. Proliferation of all three clones critically depends on antigen-presenting cells, exogenous interleukin 2, Listeria antigen, and on class II-restricted antigen presentation by accessory cells. There are differences between cells from different clones with respect to the degree of production of migration inhibitory and macrophage-activating factors. Thus, T lymphocytes of clones R23D6 and R30D5 are highly active, whereas cells of clone RVIIC2 showed markedly less production of these factors. In vivo studies, analyzing the capacity of cells to transfer systemic protection, showed a positive correlation between the production of migration inhibitory factor, macrophage-activating factor, and systemic protection.

Animals↗
PubMed1986

Effects of anti-Bacteroides-antibodies on Escherichia coli and different Bacteroides species in vitro and vivo.

Bacteroides species are known to cause synergistic pathogenicity in mixed infections with Enterobacteriaceae. In vitro studies showed that anaerobes may compete with aerobes for opsonisation thus interfering with the phagocytosis and killing of the latter by leukocytes. The present study investigated the effect of anti-Bacteroides-antibodies on in vitro phagocytosis of E. coli and on experimental mixed infections. It was shown that in vitro, B. fragilis suppressed the phagocytosis of E. coli by leukocytes only moderately. The addition of specific antibodies to the phagocytosis mixture could enhance this effect. However, antibodies in the absence of B. fragilis were also active suggesting a nonspecific mechanism such as blockade of Fc receptors. Prophylactic treatment with the immunoglobulin preparations failed to protect mice from experimental infections with E. coli and Bacteroides species.

Animals↗
PubMed1986

Comparative efficacy of different beta-lactam antibiotics and gentamicin in Klebsiella pneumoniae septicaemia in neutropenic mice.

The in-vivo activity of ceftazidime, cefotetan, imipenem/cilastatin, piperacillin and gentamicin against two strains of Klebsiella pneumoniae was evaluated in a model of experimental septicaemia in neuropenic mice. Single agent therapy with the aminoglycoside was highly effective against both strains. Among the beta-lactams, ceftazidime and cefotetan were nearly as active as gentamicin, whereas imipenem/cilastatin was slightly less effective, and the results achieved with piperacillin were markedly inferior.

Animals↗
PubMed1986

Inhibition of macrophage phagocytosis by Bacteroides fragilis in vivo and in vitro.

A number of investigators have provided experimental evidence for synergistic effects in mixed infections with Escherichia coli and Bacteroides fragilis. In vitro studies have suggested that competition for serum opsonins and diminished subsequent phagocytosis by polymorphonuclear leukocytes might explain these effects. In the present study we evaluated the effect of B. fragilis on macrophage phagocytosis. It was shown that peritoneal macrophages from mice injected intravenously 6 to 12 h earlier with 10(8) CFU of encapsulated B. fragilis were markedly suppressed in their phagocytic ability. Injections of laboratory-passaged, less-encapsulated B. fragilis, other bacteria, or latex particles were either not suppressive of macrophage phagocytosis or less effective. When peritoneal macrophages were treated in vitro for 24 h with the same challenge organisms prior to assessing their phagocytic capacity, encapsulated B. fragilis also proved significantly more suppressive than challenges with other organisms or latex particles. We conclude that suppression of macrophage phagocytosis by B. fragilis seems to be an important mechanism contributing to synergistic effects described for mixed aerobic and anaerobic infections.

Animals↗
PubMed1986

Ciprofloxacin: a comparative evaluation of its bactericidal activity in human serum against four enterobacterial species.

Serum bactericidal titres following a 200 mg i.v. dose of ciprofloxacin were measured in healthy volunteers and compared with those achieved with standard doses of ceftazidime, piperacillin and gentamicin, given alone or in combination. Five strains of each of four enterobacterial species were included in the study. Bactericidal titres 1 h after infusion of ciprofloxacin exceeded 1:16 for Escherichia coli, Klebsiella pneumoniae, Proteus vulgaris and Enterobacter cloacae. While ceftazidime produced higher peak bactericidal titres against the Enterobacteriaceae, piperacillin was less effective than ciprofloxacin against three of the four enterobacterial species tested. Among the combinations, only piperacillin/gentamicin showed synergistic activity against some strains. Studies of bacterial killing kinetics again confirmed the high bactericidal activity of ciprofloxacin for the Enterobacteriaceae. The combination of ciprofloxacin with gentamicin resulted in more rapid killing of some strains of Klebsiella pneumoniae and Proteus vulgaris.

Adult↗
PubMed1985

[Bacterial colonization of the rat jejunum in long-term nutrition with an elemental diet].

Elemental diets and peptide diets are increasingly used in the treatment of enteral diseases and as alternatives to parenteral nutrition. Though multiple influences of these diets on the small intestinal bacteria seem possible no long-term studies were hitherto carried out to clarify their actions on the intestinal flora. Therefore, the jejunal flora was assessed qualitatively and quantitatively in a group of rats fed an elemental diet over a period of 60 days and a control group receiving standard pellet food. In both sets of animals similar numbers of colony forming bacteria/ml jejunal juice of the aerobic and anaerobic growing flora were observed. In parallel, the individual genera did not exhibit significant differences in control and experimental animals. According to these findings long-term feeding of a peptide diet to rats does not influence the small intestinal flora.

Animals↗
PubMed1985

[Significance of deficient bacterial colonization in the pathogenesis of mucosal lesions in experimental blind loop syndrome].

A complete evaluation of the bacterial flora in jejunal self-filling blind loops was performed. The results show a significant increase in bacteria of the genera E. coli, Streptococcus and Bacteroides. In further experiments, jejunal self-filling blind loops were created in germ-free animals. In spite of the germ-free state the mucosa displayed marked hyperplasia. The same was true when the blind loops had been contaminated with aerobic bacteria. These results demonstrate that other factors in addition to bacterial overgrowth contribute to the mucosal damage observed in self-filling blind loops.

Animals↗
PubMed1985

[Quantitative and qualitative determination of the bacterial colonization of the rat jejunum following long-term feeding with an elemental diet].

Elemental diets are increasingly used in the treatment of enteral diseases, but only limited studies have been hitherto carried out to clarify their actions on the intestinal flora. Therefore, the jejunal flora was assessed in rats fed an elemental diet or standard pellet food over a period of 60 days. In both sets of animals similar numbers of colony-forming bacteria per ml intestinal content of the aerobic and anaerobic flora were found. In addition, the individual genera did not exhibit significant differences in control and experimental animals. Thus, long-term feeding with an elemental diet does not influence the jejunal flora of rats.

Animals↗
PubMed1985

An adoptive transfer system for the investigation of granuloma formation in murine listeriosis.

A system is described for studying adoptive transfer of granuloma formation in infection of mice with the facultative intracellular bacterium, Listeria monocytogenes. Intravenous injection of graded numbers of L. monocytogenes-immune peritoneal exudate T-enriched cells (PETLEs) together with 5 X 10(4) living L. monocytogenes resulted in dose-dependent accelerated granuloma formation in the livers of recipient mice. The lymphoid cells conferring granuloma formation were T cells by virtue of their nonadherence to nylon wool and sensitivity to anti-Thy 1.2 antiserum plus complement. Since granuloma formation could not be transferred from C57B1/6J donors to BALB/c recepients it is concluded that adoptive transfer of granuloma formation is genetically restricted.

Animals↗
PubMed1985

Influence of different immunoglobulin G preparations on phagocytosis of Pseudomonas aeruginosa by polymorphonuclear granulocytes.

Commercially available immunoglobulin products suitable for intravenous application in humans are made by enzymatic or chemical modification of the IgG molecule. In order to examine, to which extent in vitro biologic functions of the IgG molecule are preserved in such preparations, specific antipseudomonal IgG from the rabbit was modified according to some of these procedures. The opsonizing activity of the different IgG preparations was evaluated in an in vitro system measuring the phagocytosis of Pseudomonas aeruginosa by rabbit granulocytes. The results demonstrated that the product Fab/Fc, which is made by papain or plasmin degradation of the IgG molecule, was still able to enhance phagocytosis but not to activate complement. The smaller papain- or plasmin-derived fragments Fab and Fc had no opsonizing activity. The pepsin-derived product F(ab')2 which possesses a divalent antigen binding site but lacks the Fc part, only enhanced phagocytosis when complement concentrations of more than 20% were present in the phagocytic system. Since the F(ab')2 fragment is not able to interact with Fc receptors or to activate complement via the classical pathway, the phagocytosis-enhancing activity of this molecule must be attributed to alternative complement pathway activation. In contrast to the enzymatically derived IgG preparations, a newly developed S-sulphonated IgG product was as efficient as unmodified IgG both in Fc- and complement-mediated opsonization.

Animals↗
PubMed1985

In vitro and in vivo activities of different immunoglobulin G preparations from the rabbit against Enterobacteriaceae.

Specific rabbit IgG, prepared against three enterobacterial strains, was modified according to procedures used for the production of human IgG preparations suitable for intravenous infusion. The resulting products were examined for their in vitro opsonic and in vivo protective activity against the respective bacterial strains. A sulfonated IgG preparation (S-sIgG) and the enzymatically derived fragments F(ab')2 and Fab/Fc were opsonic in vitro and provided in vivo protection against lethal enterobacterial infection in mice. Protection by Fab fragments varied in the different in vivo models.

Animals↗
PubMed1985

Production of Listeria-specific rat T-cell clones and role of interleukin-2 receptors in regulation of Listeria-dependent T-cell clone growth in vitro.

Splenic T lymphocytes from rats immunized with the facultative intracellular bacterium Listeria monocytogenes were cloned by the limiting-dilution technique in the presence of accessory cells, heat-killed L. monocytogenes as antigen, and conditioned medium containing interleukin-2. The cloned rat T-cells were Listeria-specific cells, and their proliferation depended on class II-restricted antigen presentation by accessory cells. As demonstrated by their reactivity to the monoclonal antibody W3/25, the clones were of helper cell phenotype. Cloned-cell proliferation depended on repeated (or continuous) exposure to antigen. When antigen was omitted from the system, cell growth subsided over time, and cells finally ceased to grow. By the use of the monoclonal antibody ART-18, which recognizes the interleukin-2 receptor, it was shown that cessation of growth was accompanied by the disappearance of interleukin-2 receptors from the cell surface. The addition of antigen to the culture resulted in the reexpression of interleukin-2 receptors and concomitant resumption of proliferation.

Animals↗
PubMed1985

Multiple cotton wool spots following bone marrow transplantation for treatment of acute lymphatic leukaemia.

Three patients with acute lymphatic leukaemia developed visual impairment due to occlusion of small retinal vessels with multiple cotton wool spots after treatment which included whole body and skull irradiation followed by bone marrow transplantation and cyclosporin A. Withdrawal of cyclosporin A and treatment with corticosteroids was followed by recovery of visual acuity. This retinopathy and the retinal changes seen in the immunodeficiency syndrome are thought to be closely related. The possible role of cyclosporin A is discussed, though cotton wool spots and retinal haemorrhages have never been described in renal transplant patients during treatment with this drug. Withdrawal of cyclosporin A, which is highly effective in preventing graft-versus-host disease, can be fatal. Irradiation of the skull prior to bone marrow transplantation and intrathecal administration of methotrexate may be the most important factors causing the retinal ischaemic signs described here. The inclusion of an ophthalmologist in the team monitoring transplant patients would lead to increased documentation and a better understanding of this disease.

Adult↗
PubMed1985

Metabolic products of microorganisms. 228. New nikkomycins produced by mutants of Streptomyces tendae.

Four new dipeptidyl nikkomycins of the Z- and the X-series with a variation in the amino acid moiety of the molecule were isolated from the mutant Streptomyces tendae 901/395 and characterized. Nikkomycins Kz and Kx contain 2-amino-4-hydroxy-4-(2-pyridyl)butyric acid, and nikkomycins Oz and Ox 2-amino-4-hydroxy-4-(5-hydroxy-2-pyridyl)butyric acid. In contrast to nikkomycins Z and X, nikkomycins Kx and Ox are quite stable at alkaline pH and exhibit a lower biological activity against various test organisms. From the mutant S. tendae 901/C37, which is auxotrophic for methionine and threonine, enhanced amounts of two tripeptidyl nikkomycins, Qz and Qx, were produced which are analogues of nikkomycins J and I and contain a homoserine residue instead of glutamic acid. These nikkomycins exhibit a high pH instability.

Aminoglycosides↗