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Biomedical subjects

C Neumann

Publications and source records attributed to C Neumann.

At least 199 records · Page 11Linked to original sources
PubMed1980

Sequential expression of functions during macrophage differentiation in murine bone marrow liquid cultures.

In the presence of a colony-stimulating factor, murine bone marrow cells proliferate and differentiate into macrophages. This culture system was taken as a model to study the expression of various functions by macrophages in the course of maturation. Several tests were performed daily and in parallel from the same batch of cells. It was found that certain functions were expressed early and were also characteristic for mature macrophages such as Fc receptors, phagocytosis of latex beads and unspecific esterase activity. Other functions appeared and disappeared in an ordered sequence, such as the response to macrophage migration inhibitory factor and chemotactic factor as well as the production of interferon and of plasminogen activator. The time course of functional expression was strongly dependent on proliferation of precursor cells as well as proliferation of differentiated macrophages. It is suggested that the phenotypic expression of functions during differentiation is the basis for the functional heterogeneity of macrophages.

Animals↗
PubMed1980

Interferon production by Corynebacterium parvum and BCG-activated murine spleen macrophages.

Macrophages were identified to be a major source of interferon produced in murine spleen cell cultures after intravenous injection of Corynebacterium parvum (C. parvum), strain CN 6134 or Bacille Calmette Guérin (BCG). Another strain of C. parvum, CN 5888, which lacks RES stimulating activity and adjuvant activity in vivo, was not effective when injected intravenously. Protein synthesis was required for interferon activity to be produced and protein synthesis was also required for the antiviral state to be expressed. The antiviral activity was relatively stable to pH 2 and neutralized by an antiserum against virus-induced fibroblast interferon, thus exhibiting some properties of type I interferon. In vitro only CN 6134, the biologically active strain, could induce small amounts of interferon in spleen macrophage cultures. Macrophages from CN 6134 or BCG-infected athymic nu/nu mice produced similar interferon titers as their controls. It is concluded that infection with certain immunomodulators can activate splenic macrophages via a predominantly T-cell independent mechanism. Interferon in turn may operate locally as a mediator of immunoregulation.

Animals↗
PubMed1980

Detection of plasminogen activator in macrophage culture supernatants by a photometric assay.

Plasminogen activator is usually detected indirectly through the lysis of radioiodinated fibrin. Here, it was investigated whether the fibrinolysis test may be substituted by a photometric assay using a synthetic chromogenic substrate (H-D-Val-Leu-Lys-p-nitroanilide; S-2251). Supernatants from cultured murine macrophages served as source of plasminogen activator. It is shown that under standard conditions the photometric assay is about twice as fast and 2--4-fold more sensitive than the fibrinolysis assay. Furthermore, reproducibility of the photometric test was found within 1.5--3.5% standard deviation compared to the fibrinolysis test which was found between 10--20% standard deviation.

Animals↗
PubMed1978

Immune interferon. II. Different cellular site for the production of murine macrophage migration inhibitory factor and interferon.

The production of macrophage migration inhibitory factor (MIF) and immune interferon (IF) by concanavalin A (Con A)-stimulated cultures of thymus, lymph node and spleen cells was investigated. It was found that all cultures produced MIF activity, whereas only spleen cells produced marked IF activity. The capacity to produce IF was found to be correlated with the macrophage content of a cell preparation as evidenced by staining for esterase-positive cells. Furthermore, column-purified spleen T cells produced MIF but no IF. Migration inhibition caused by residual mitogen could be ruled out. On the other hand, when macrophages grown from bone marrow cells were pre-exposed to supernatants of mitogen-stimulated lymphocytes, IF activity was released into freshly added medium while no significant MIF activity was found. IF was also found in supernatants of macrophage cultures after exposure to conventional inducers in vitro (polyinosinic-polycytidylic acid, Corynebacterium parvum) or in vivo (C. parvum), whereas no MIF was detected. An anti-Type I IF serum neutralized IF in supernatants from Con A-stimulated spleen cells but did not affect MIF in the same supernatants. This indicates that IF and MIF activity are associated with different molecules. It is, therefore, concluded that under the described conditions, IF and MIF are produced by different cells. T cells are the prime producers of MIF while IF is released by macrophages following induction by lymphokines.

Animals↗
PubMed1978

Mutations that alter the covalent modification of glutamine synthetase in Salmonella typhimurium.

glnD and glnE mutant strains of Salmonella typhimurium lack three of the four activities required for reversible covalent modification of glutamine synthetase (GS; EC 6.3.1.2). The glnD strains, which are unable to deadenylylate GS and therefore accumulate the adenylylated or less active form of the enzyme, were isolated as glutamine bradytrophs. They lack the activity of PIIA uridylyl-transferase, one of the proteins required for deadenylylation of GS; in addition, they lack PIID uridylyl-removing activity. Mutations in glnD are suppressed by second-site mutations in glnE that eliminate the activity of GS adenylyltransferase (EC 2.7.7.42) and thus prevent adenylylation of GS. The glnD and glnE strains have one-third to one-half as much total GS as the wild-type strain when they are grown in a medium containing a high concentration of NH4+. The wild-type strain derepresses synthesis of GS fourfold in response to nitrogen limitation; glnD and glnE strains derepress synthesis of the enzyme fourfold and sevenfold, respectively. Thus, mutations that alter covalent modification of GS in Salmonella do not significantly affect derepression of its synthesis. The glnD gene lies at 7 min on the Salmonella chromosome and is 50% linked to pyrH by P22-mediated transduction.

Chromosome Mapping↗
PubMed1976

Mutant strains (nit) of Salmonella typhimurium with a pleiotropic defect in nitrogen metabolism.

We have isolated mutant strains (nit) of Salmonella typhimurium that are defective in nitrogen metabolism. They have a reduced ability to use a variety of compounds including glutamate, proline, arginine, N-acetyl-glucosamine, alanine, and adenosine as sole nitrogen source. In addition, although they grow normally on high concentrations of ammonium chloride (greater than 1 mM) as nitrogen source, they grow substantially more slowly than wild type at low concentrations (less than 1 mM). We postulated that the inability of these strains to utilize low concentrations of ammonium chloride accounts for their poor growth on other nitrogen sources. The specific biochemical lesion in strains with a nit mutation is not known; however, mutant strains have no detectable alteration in the activities of glutamine synthetase, glutamate synthetase, or glutamate dehydrogenase, the enzymes known to be involved in assimilation of ammonia. A nit mutation is suppressed by second-site mutations in the structural gene for glutamine synthetase (glnA) that decrease glutamine synthetase activity.

Acetylglucosamine↗