Search PubMed⌕ Search

Biomedical subjects

M C Giess

Publications and source records attributed to M C Giess.

At least 19 recordsLinked to original sources
PubMed1995

Notochord and floor plate stimulate oligodendrocyte differentiation in cultures of the chick dorsal neural tube.

The regionalization of oligodendrocyte potentialities and the cellular interactions leading to the expression of the oligodendrocyte phenotype have been analyzed in the embryonic chick spinal cord. Dorsal and ventral regions of the spinal cord of 4-day-old embryos (E4) were cultivated separately. Oligodendrocyte differentiation was monitored at various times after explantation, using specific oligodendrocyte markers. After 2 weeks, several hundreds of differentiated oligodendrocytes were invariably observed in ventral cultures whereas significant numbers of oligodendrocytes failed to develop in dorsal spinal cord cultures. However, the E7 dorsal spinal cord was found to produce large numbers of oligodendrocytes, indicating that the ventral restriction of oligodendrocyte potentialities is transient. To test whether ventrally derived signals might influence oligodendrocyte differentiation, E4 dorsal spinal cord microexplants were cocultivated with notochord segments or with floor plate tissue. Numerous oligodendrocytes were found in dorsal explants associated with either tissue, notochord or floor plate, but not in dorsal explants cultivated alone, indicating that cells competent to be induced along the oligodendrocyte phenotype exist in the dorsal spinal cord. These results show that oligodendrocyte differentiation potentialities are initially restricted to the ventral spinal cord and suggest that ventrally derived signals from notochord and floor plate influence oligodendrocyte differentiation in the embryonic spinal cord.

Animals↗
PubMed1995

[Oligodendrocyte lineage].

The mechanisms leading to cell diversification in the Vertebrate central nervous system are still poorly understood. We have analyzed neural differentiation potentialities of the embryonic chick optic nerve. In the adult, the optic nerve is made up of astrocytes and oligodendrocytes ensheathing retinal axons, but it is entirely devoid of neuronal cell bodies. Using explant cultures and specific cell type markers, we demonstrate that in fact the embryonic optic nerve contains cells endowed with neuronal potentialities but is initially devoid of a potential for oligodendrogenesis. Studies by other groups in rodents suggest that oligodendrocyte precursors may be initially restricted to the ventral region of the developing spinal cord. Taken together, these results indicate that early in development, oligodendrocyte precursors are not distributed homogeneously in the neuroepithelium. Preliminary results in our laboratory show that the specification of the oligodendrocyte lineage in the chick spinal cord may depend on ventral signals from the notochord.

Animals↗
PubMed1992

Cells from the early chick optic nerve generate neurons but not oligodendrocytes in vitro.

We have recently described neuronal potentialities in neuroepithelial cells of the embryonic chicken optic nerve (Giess et al., Proc. Natl. Acad. Sci. USA, 87 (1990), 1643-1647). To further investigate the developmental repertoire of optic nerve cells, oligodendroglial development was studied in cultures of optic nerve explanted at various developmental stages. Oligodendrocyte differentiation was analyzed using antibodies directed against galactocerebrosides (Gal-C) and against sulfatides. Optic nerves removed at embryonic days 5 and 6 (E5-E6) never gave rise in culture to differentiated oligodendrocytes, even after 3 weeks in vitro. In contrast, in cultures of optic nerves removed from E7 or older embryos, cells expressing both oligodendrocyte markers were rapidly and invariably observed. Absence of oligodendrocytes before E7 was not due to culture conditions being inadequate to support the differentiation of early precursors along this pathway, since neuroepithelial cells from E2 and E4 trunk neural tube cultivated in the same conditions expressed Gal-C after respectively 16 and 10 days. These results demonstrate that the optic nerve territory is initially devoid of oligodendrocyte potentialities. Whether oligodendrocyte precursors that, around E7, populate the optic nerve are induced by a specific developmental signal occurring at this stage or migrate from outside the optic nerve remains to be determined.

Animals↗
PubMed1990

Neuronal potentialities of cells in the optic nerve of the chicken embryo are revealed in culture.

Neuronal potentialities in neuroepithelial cells of the chicken embryonic optic nerve were studied in culture by using neurofilament antibodies as neuronal markers. Embryonic day-4 and -5 (E4 and E5) optic stalks were explanted in vitro. Within the first few days of culture, numerous morphologically identifiable neurons extending long neurites developed. These neurons and their processes were specifically labeled with neurofilament antibodies. Similar results were obtained by explanting only the medial portion of E7 optic stalks away from possibly contaminating cerebral or retinal tissue. To determine whether neuronal potentialities persisted at later embryonic stages, cultures of dissociated optic stalks were established at E11, E15, and E18. Neurons labeled with the various neurofilament antibodies appeared in all cultures of E11 and E15 optic stalks. However, typical neurons could not be recognized in cultures of E18 optic nerves. These results indicate that cells with neuronal potentialities are present in the embryonic optic nerve from early stages of development and persist until at least E15. Since the adult optic nerve is devoid of nerve cell bodies, our observations are consistent with the hypothesis that axons of retinal ganglion cells, which course through the optic stalk, repress neuronal potentialities within a subpopulation of precursor cells during normal development.

Animals↗
PubMed1985

The role of extracellular signals in the differentiation of cholinergic neurons from the CNS and PNS in culture.

Rat skeletal muscle cells release in culture a macromolecule which stimulates by 25-100 fold the development of choline acetyltransferase (CAT) in cultures of new-born rat sympathetic neurons. This "cholinergic factor" impaired the development of three norepinephrine synthesizing enzymes and of acetylcholinesterase (AChE) in these cultures. The 16S form of AChE failed to develop in cultures grown with the factor, but amounted to 30-40% in 3-week old cultures grown in its absence. Using the development of CAT activity in sympathetic neuron cultures as an assay, the cholinergic factor has been partially purified in 6 steps, and its hydrodynamic parameters determined. The effects of this factor on sympathetic neurotransmitter choice were qualitatively reproduced by 1-10 mM Na butyrate. The cholinergic factor increased CAT activity and decreased AChE in neuron cultures from new-born rat nodose ganglia. The factor also stimulated CAT activity in rat embryo (E14) spinal cord cultures, but stimulated the development of AChE in these cultures.

Animals↗
PubMed1984

Acetylcholine metabolism in rat spinal cord cultures: regulation by a factor involved in the determination of the neurotransmitter phenotype of sympathetic neurons.

Acetylcholine metabolism has been studied in sister cultures of E13 rat spinal cord cells cultured for 1 to 3 weeks with or without conditioned medium (CM) from rat skeletal muscle cells. Spinal cord cells grown with CM synthesized and accumulated 3 to 4 times more [3H]ACh from [3H]choline than cultures grown without CM. This effect of CM was accompanied by a comparable increase in CAT activity and could not be mimicked by increasing the density of the spinal cord cultures. A 2- to 3-fold increase in AChE activity was also observed in 2- to 3-week-old CM cultures, whereas the activity of lactate dehydrogenase was identical in cultures grown with and without CM. We have compared the effects of CMs from various non-neuronal cell cultures on [3H]ACh synthesis and storage by spinal cord cultures and by sympathetic neuron cultures. CM by skeletal muscle greater than skin fibroblasts greater than rat heart muscle greater than C6 glioma cells were the most active on both types of neuron cultures, whereas CM from rat brain, L6 myoblasts, mouse 3T3, and PYT21 fibroblasts was inactive on spinal cord cultures and only weakly active on sympathetic neurons. Serum-free CM from skeletal muscle was inactive on both types of neuron cultures. The CM factor active on spinal cord cultures has been purified several thousand-fold by using a four-step fractionation scheme which has previously led to a partial purification of the CM factor involved in the regulation of CAT, AChE, and catecholamine-synthesizing enzymes in sympathetic neuron cultures ( Swerts , J. P., A. Le Van Thai, A. Vigny , and M. J. Weber (1983) Dev. Biol. 100: 1-11). Moreover, a comparison of dose-response curves established with this purified material showed that it exerted its effects on spinal cord and on sympathetic neuron cultures in the same range of concentration. Thus, these results suggest that the same macromolecule is involved in the regulation of neurotransmitter phenotype in both types of cultures despite their different embryological origins.

Acetylcholine↗
PubMed1980

Variations in the recombination rate of Drosophila melanogaster induced by balloon flight.

Drosophila males, heterozygous for b, pr, cn and en genes, were submitted to balloon flights, ceiling time ranging from about 8 hours (flights performed in France) to 22 hours (transmediterranean flight). Effects on recombination were investigated on progeny after breeding with females homozygous for the same genes. The transmediterranean flight and one flight performed in France resulted in a significantly higher recombination rate.

Animals↗
PubMed1980

Differences between natural ageing and radio-induced shortening of the life expectancy in Drosophila melanogaster.

Adult Drosophila aged 1,4 or 8 days were irradiated with a 60Co source, supplying 1,000 rpm, at doses of 0, 15, 20, 25, 50 and 75 kr. In either sex, radio-induced death seems to arise from different mechanisms to those of natural death. The post-radiative response, however, is different for the two sexes, radiosensitivity in females is dependent on their state of physiological maturity i.e. at 20 and 25 kr sensitivity decreased with age. In males, in return, radiosensitivity is not directly correlated to age, death occurs at a fixed period after irradiation.

Aging↗
PubMed1979

[Involution of genital function with age studied as an index aging in Drosophila melanogaster].

Reproductive system in Drosophila estimated by fertility in female and fertilizing power in male gradually decreased with age. Physiological changes as a function of age occur slowly in virgin females and their ageing seems really slower than those observed in inseminated ones. On the other hand, genital function involution is the same in virgin and mated males and seems independent of aging.

Aging↗
PubMed1977

Influence of sex on the radiation-induced life span modifications in Drosophila melanogaster.

Drosophila melanogaster is exposed to 0, 25, 50, 75 kr of 60Co gamma-irradiation at 1,000 r/min, on the 4th day of its imaginal life. As a result, the life span of the flies is reduced for both sexes. Females, however, are more radiosensitive than males. In females, the radiation-induced life span shortening does not vary with the doses administered; in males, on the contrary, the life expectancy decreases as the dose is increased.

Aging↗