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Biomedical subjects

G Mercier

Publications and source records attributed to G Mercier.

At least 91 records · Page 5Linked to original sources
PubMed1984

Induction of natural killer cells and interferon during mouse hepatitis virus infection of resistant and susceptible inbred mouse strains.

Following infection by mouse hepatitis virus (JHM strain), an induction of natural killer (NK) cell activity was observed in C3H mice, which are considered to be sensitive to JHM virus infection. In contrast, mice of the resistant SJL strain did not show any increase of NK cell activity after JHM virus infection. However, infection of both SJL and C3H mice with mouse hepatitis virus type 3 (MHV3) resulted in an increase of NK level, comparable to that observed with the JHM virus infection in the C3H strain. No significant differences were observed in the NK cell activity of the peritoneal exudate or spleen cells of infected mice. Low levels of interferon were detected in serum or peritoneal exudate of C3H mice infected with JHM virus 18 or 24 hours before, but no detectable early interferon production was found. Also no interferon could be detected in the resistant SJL mice. After JHM virus infection, the number of peritoneal exudate cells (PEC) was increased significantly in C3H mice but not in SJL mice. Macrophages obtained from the C3H mice supported virus replication, whereas SJL macrophages did not. Our data suggest that NK cells do not play a role in the resistance of SJL mice against JHM virus infection but may participate in the defence mechanisms against this virus in C3H mice.

Animals↗
PubMed1982

[Effects of electric stimulation of the para-ventricular nucleus on corticotropin function in Long-Evans and Brattleboro rats].

Two peptides have a strong corticotropin releasing factor (CRF) activity: arginine vasopressine (AVP) and a 41-residue peptide (41-CRF). Both peptides are present in high concentration in the PVN of the Rat, a zone of the hypothalamus at which electrical stimulation elicits ACTH release. Since homozygous Brattleboro Rats (Di/Di) congenitally lack endogenous AVP, it was of interest to compare the ACTH and corticosterone release after electrical stimulation of the PVN in Long-Evans (L.E.) and Di/Di Rats. In both L.E. and Di/Di Rats, there is a significant increase in plasma ACTH and corticosterone after electrical stimulation of the PVN. However, corticosterone levels are significantly lower in Di/Di than in L.E. Rats whether the Rats have been stimulated or not. It is concluded that a physiological CRF activity is present in the PVN of Di/Di Rats independently of the CRF like activity of AVP.

Adrenocorticotropic Hormone↗
PubMed1982

The nylon wool adherence marker of the B cell lineage appears at the resting pre-B cell stage.

The proliferative state of functionally defined populations of size-separated pre-B cells was investigated. The results presented here support the hypothesis that pre-B cells are in the G2 phase when stable membrane IgM is first expressed. Small resting precursor cells significantly adhere to nylon wool columns, unlike larger cycling cells which can be enriched in the nonadherent fraction. These results suggest that the nylon wool "receptor' is a useful early B cell marker. Since the in vitro recruitment of both cycling and resting precursors was shown to be essentially dependent on agar mitogen(s), cumulative data suggest that the receptors for agar mitogen(s) appear shortly before surface IgM on proliferating pre-B cells. Nylon wool adherence potential develops next on their resting progeny, followed by full lipopolysaccharide reactivity as cells further mature.

Animals↗
PubMed1982

Pre-B cell differentiation in the bone marrow: a proliferative pathway parallels the post-mitotic maturation of early B cells.

Considerable heterogeneity was found in bone marrow B cell progenitors as functionally defined, size-separated populations were analyzed for their density of membrane IgM receptors, their adherence potential to nylon wool fibers and their susceptibility to lipopolysaccharide-induced differentiation to IgM secretion. The investigation of their cycling status with tritiated thymidine further permitted definition of resting and actively proliferating populations. Heterogeneity was found in the fraction of resting small cells as expected for early B cells progressing through postmitotic maturation. However, the data suggest that part of the pre-B cell progeny can also mature during a proliferative phase.

Animals↗
PubMed1982

Light-chain diversification during pre-B cell differentiation.

The possibility that a committed normal pre-B cell can generate progeny expressing more than one light chain was studied by isoelectric focusing of supernatants from pre-B cells cultured at limiting dilution. Supernatants from mitogen-stimulated mature spleen B-cells analysed on day 6 have shown the presence of a rather homogeneous IgM spectrotype profile. Supernatants from the 8-10-day cultures were usually negative. Isoelectric focusing profiles of supernatants from cultures of bone marrow pre-B cells were different from those of mature spleen cells. Many IgM spectrotypes appeared in the culture supernatants of bone marrow pre-B cells between days 6 and 13, whether the cultures were negative or restricted in their IgM profiles on day 6. These results support the idea that normal pre-B cells, during differentiation, can associate a variety of light chains with an already chosen mu heavy chain.

Animals↗
PubMed1982

Abundant messenger RNA sequences common to transplanted mouse tumours of different tissue origins.

Radioactive cDNA, cell-free-synthesised on poly(A)-rich mRNAs from mouse FLS-ascites tumour cells, were separated into two fractions corresponding to abundant mRNA species and to rare mRNA species respectively, the former being nearly 100-times more abundant per cell than the latter. Aliquots of each fraction were hybridized to a large excess of RNA of different origins; three ascites tumours (the FLS, Krebs 2 and Ehrlich tumours) all transplanted in animals; one established line of Friend erythroleukemia cells serially passaged in culture; adult organs and whole mouse embryos. It was shown that all or nearly all the mRNA species, in particular the abundant ones, were present and similarly distributed in the three transplanted tumour strains studied, despite their different tissue origins. The great majority of abundant mRNA species were also present in Friend erythroleukemia cells but about two-times less frequent relative to transplanted tumours. Much greater differences were found as compared with non-malignant cells. In particular, although the majority of the abundant mRNA species were also found in all normal tissues studied, they were on the average 7-8-times less abundant in adult liver or in 10-days-old embryos, and 10-times less abundant in adult brain, than in tumour cells. Finally about 10% of the abundant RNA species common to all transplanted tumours appeared to be absent in normal cells, whatever their growth rates or stage of differentiation. The possible implications of these findings are discussed.

Animals↗
PubMed1980

Size separation and polyclonal activation to immunoglobulin secretion of early precursors of B lymphocytes.

In adult mammals the bone marrow is a major site of B lymphocyte production, which occurs through the differentiation of pluripotent stem cells. In vivo studies have permitted the description of intermediate stages of differentiation. Following the recent development of culture conditions and the discovery of many polyclonal activators, it is now possible to carry out in vitro a finer analysis of B lymphocyte precursors differentiation. Because in vivo studies have shown that precursors vary in size, adult murine bone marrow cells were separated according to size. Fractions were cultured with polyclonal mitogens and tested for their capacity to develop into Ig-secreting cells. With this assay system, up to six populations were detected in adult bone marrow that can differentiate along the B cell lineage. The characterization of those populations was made according to size, mitogen(s) responsiveness, and kinetics of maturation. Precursor frequencies estimated by limiting dilution analysis further suggest that in cultures of some fractions of the gradient, new lymphocytes are produced through differentiation of immature precursors, although in cultures of some other fractions B lymphocytes may arise by self-renewal of mature cells.

Animals↗