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L Bologa

Publications and source records attributed to L Bologa.

6 recordsLinked to original sources
PubMed1989

In vitro hormonal regulation of astrocyte proliferation.

Previously, we showed that purified myelin basic protein (MBP) induces a two-fold increase in the proliferation rate of astrocytes in culture. This observation allowed us to hipothesize that MBP-induced astroglial proliferation might be one of the causes of astrogliosis and astroglial scar formation in case of in vivo myelin breakdown. Also, we observed that dehydroepiandrosterone (DHEA) and its sulfated derivative (DHEA-S) reduce the amount of 3H-Thymidine incorporated by cultured astrocytes. In the present study, we investigated by a combined 3H-Thymidine autoradiography/immunocytochemistry technique whether the mitogenic effect that MBP exerts upon astrocytes in vitro can be prevented by DHEA and DHEA-S. Results showed that a treatment of the cells with MBP only induces approximately a two-fold increase in the number of silver grains overlaying the nuclei of astrocytes. In cultures treated with both MBP and DHEA there was a 2.5-3 fold reduction in the number of silver grains, while DHEA-S provoked a 3-4 fold reduction. These results allow us to speculate that DHEA and DHEA-S could modulate the astrogliosis that usually accompanies myelin breakdown.

Animals↗
PubMed1986

Regulation of myelin basic protein in oligodendrocytes by a soluble neuronal factor.

Myelin basic protein (MBP) is one of the most important myelin components. Based on our previous studies, we hypothesized that neurons might have regulatory effects on the production of MBP by oligodendrocytes, and we conducted studies designed to verify this hypothesis. Oligodendroglia-rich cultures from total brain of neonatal rats or mice and pure cultures of embryonic rats or chicks were prepared. Cultures of mouse fibroblasts and astrocytes were prepared as well. We show here that MBP production by oligodendrocytes was greatly enhanced by treatment with either pure neurons, rat neuronal conditioned medium, or chick neuronal conditioned medium, while chemically defined, hormonally supplemented medium or medium conditioned by astrocytes and fibroblasts had no effect on MBP expression. We conclude that the production of MBP by oligodendrocytes is regulated by a nonspecies specific soluble neuronal factor. The conservation of this phenomenon from avian to rodent species implies its critical role in myelination and suggests its potential application as a treatment in demyelination.

Animals↗
PubMed1985

Myelin basic protein stimulates the proliferation of astrocytes: possible explanation for multiple sclerosis plaque formation.

In dissociated mouse brain cell cultures we frequently observed an association between myelin basic protein (MBP) positive oligodendrocytes and proliferating astrocytes. When MBP was added in a purified form to the culture medium, it greatly stimulated the proliferation of astrocytes, while other proteins tested did not. This finding allows us to speculate that the gliosis observed in demyelinating diseases or/and in central nervous system (CNS) injury would be due to the mitogenic effect exerted by MBP or its fragments when there is myelin breakdown.

Animals↗
PubMed1985

Cellular development and myelin production in primary cultures of embryonic mouse brain.

The development of cell cultures from embryonic mouse cerebral hemispheres has been followed in detail for periods up to 40 days in culture using a variety of approaches. Functionally well differentiated neurons (shown by receptor binding studies, immunocytochemistry and morphological examination) were found to be abundant early in culture and to form cell contacts with oligodendrocytes characterized both immunocytochemically and morphologically. Myelin-like membranes with the periodicity of classical myelin elaborated by oligodendrocytes were detected only after 30 days in culture when neurones were no longer present. These results are discussed with regard to possible mechanisms of initiation of myelin synthesis.

Animals↗
PubMed1977

Some data concerning immune processes in concomitant tumor immunity experimental models. Comparative in vivo and in vitro investigations II. In vitro experiments.

The humoral and cellular immune status of C57BL/6 male mice and "R" male rats bearing MC-induced sarcomas were investigated in vitro, using 51Cr-releasing and mixed hemadsorption assays. Analysis was performed on mice subjected to concomitant tumor immunity (CTI) model experiments or bearing primary tumors of different sizes, that was done also in rats. Chromatographic fractions, assumed to contain tumor specific antigens, antibodies or antigen-antibody complexes were identified by their absorption capacity upon specially prepared syngeneic immune sera. Free antibody and antigen-antibody complexes, accompanied with a weak cell mediated immunity (CMI) were correlated with efficient CTI in 2--3% TW/TBW tumor bearers. Homoral immunity (HI) showed sometimes an important increase after challenge administration. High levels of free antigen and antigen-antibody complexes, lack of antibodies and CMI were correlated with CTI absence in huge tumor bearers, representing 30--37% of total body weight. Conditions determining variability of results reported by different authors and the possible mechanisms by which serum immune factor may impair the tumor bearer's immune status are discussed.

Animals↗