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F Gremo

Publications and source records attributed to F Gremo.

52 records · Page 3Linked to original sources
PubMed1983

Origin of axoplasmic RNA in the squid giant fiber.

The origin of axoplasmic RNA in the squid giant fiber was investigated after exposure of the giant axon or of the giant fiber lobe to [3H]uridine. The occurrence of a local process of synthesis was indicated by the accumulation of labeled axoplasmic RNA in isolated axons incubated with the radioactive precursor. Similar results were obtained in vivo after injection of [3H]uridine near the stellate nerve at a sizable distance from the ganglion. Exposure of the giant fiber lobe to [3H]uridine under in vivo and in vitro conditions was followed by the appearance of labeled RNA in the axoplasm and in the axonal sheath. While the latter process is attributed to incorporation of precursor by sheath cells, a sizable fraction of the radioactive RNA accumulating in the axoplasmic is likely to originate from neuronal perikarya by a process of axonal transport.

Animals↗
PubMed1982

Development of neuronal connections in chick embryonic retino-tectal system: an overview.

Synaptogenesis has been examined in the retino-tectal system of the chick embryo both biochemically and morphologically. We have evaluated the amount and the rate transport of glycoproteins synthetized in retinal ganglion cells and axonally transported to retinal nerve endings. The distribution of glycoproteins inside the tectum shows that they are part of the synaptosomal membrane either because they are incorporated in it "en route" or because they flow through an axolemmal flow. The role they might play in the building up of the synaptic membrane is discussed in relation to the maturation of synaptic contacts, observed either with E-PTA staining method or with routine fixation methods. The distribution of a carbohydrate binding protein was followed with histochemical techniques. This protein is synthesized by the matching tectal neurons, and its synthesis is developmentally regulated. It distribution is affected by innervation. All of these findings are discussed in relation to the hypothesis that three different steps are involved in embryonic synaptogenesis. These three steps are: 1) interneuronal recognition; 2) formation of initial contact, and 3) formation of synapses. The possibility that different kinds of cell surface macromolecules might play a different role is also discussed.

Animals↗
PubMed1981

Preferential accumulation of [3H] corticosterone in chick brain during embryonic development.

In the present study, we examined the distribution of [3H]corticosterone ([3H]B) in chick embryonic brain during development using two different routes of administration: intracerebral and intraocular. After injection of 1 microCi into the brain of 8-day embryos, [3H]B was preferentially accumulated in the retinas, whereas regions such as cerebral hemispheres, optic tecta, and midbrain showed lower amounts of [3H]B. In 14-day embryos, a slightly higher amount of [3H]B was found in retinas and midbrain in comparison with other regions of the brain. After injection into the eye, [3H]B seemed to easily diffuse to brain regions and toe preferentially accumulate in the opposite eye and very slowly diffused to other brain areas. The accumulation of the hormone in the retina parallels the presence of hormone receptors reported by others. A correlation between the preferential accumulation of hormone and its action is proposed.

Animals↗
PubMed1978

Distribution of an endogenous lectin in the developing chick optic tectum.

We determined the cellular localization of an endogenous lectin at various times during the development of a well-characterized region of chick brain, the optic tectum. This lectin is a carbohydrate-binding protein that interacts with lactose and other saccharides, undergoes striking changes in specific activity with development, and has previously been purified by affinity chromatography from extracts of embryonic chick brain and muscle. Cellular localization in the tectum was done by indirect immunofluoresecent staining, using immunoglobulin G derived from an antiserum raised against pure lectin. No lectin was detectable in the optic tectum examined at 5 days of embryonic development. From approximately 7 days of development, neuronal cell bodies and fibers were labeled by the antibody; and extracts of tectum contained hemagglutination activity that could be inhibited by lactose or by the antiserum. Lectin remained present in many tectal neuronal layers after hatching; but in 2-month-old chicks it was sparse or absent in most of the tectum except for prominent labeling of fibers in the stratum album centrale. The initial appearance of lectin in the optic tectum was not dependent on innervation by optic nerve fibers since bilateral enucleation during embryogenesis did not affect it. Lectin was detectable on the surface of embryonic optic tectal neurons dissociated with a buffer containing EDTA.

Animals↗
PubMed1975

Dynamic properties of axonal transport of proteins and glycoproteins: a study based on the effects of metaphase blocking drugs in the developing optic pathway of chick embryos.

Some properties of the axonal transport of proteins and glycoproteins along the optic pathway of chick embryos and newly hatched chicks were studied by labelling retinal ganglion cells with 3H-proline or 3H-fucose. A study of the effects of colchicine (COL) and vinblastine (VLB) on embryonic axonal transport was also carried out. Marked changes in the efficiency of axonal transport were found throughout development. In particular, the fraction of retinal ganglion cell proteins which is rapidly exported toward tectal terminals increases during embryonic life but steadily decreases after hatching. Glycoprotein transport behaves similarly except that its efficiency is relatively higher at stages when critical events of synaptic maturation in the tectum are reported to occur. Embryonic axonal transport is blocked by COL and VLB at very low intravitreal concentrations. Retinal protein synthesis and the morphology of ganglion cells are profoundly altered by the drugs: in general, COL and VLB effects were much more marked in embryonic than in mature neurons. An analysis of the time course of rapid transport along embryonic optic axons was carried out by reducing the efflux of labelled proteins from the eye by giving VLB intravitreally 2 h after the pulse. It revealed some peculiar features in the retino-tectal migration of glycoproteins and confirmed their progressive accumulation within terminals as previously described by radioautography. These results suggest that axonal transport of proteins during embryonic life undergoes changes in parallel with synaptic maturation. It may thus be considered as one of the factors controlling the genesis of neuronal networks.

Animals↗
PubMedDate not supplied

Platelet-activating factor production by human fetal microglia. Effect of lipopolysaccharides and tumor necrosis factor-alpha.

Since platelet-activating factor (PAF) exerts neurotoxic effects on brain cells, we explored the possibility of PAF production by human fetal microglial cells in vitro. PAF content in pure cultures was assayed and characterized in basic conditions, and after stimulation with growth factors and cytokines. Results showed that microglia cells synthesized PAF when challenged with tumor necrosis factor-alpha and lipopolysaccharides, whereas other molecules, such as gamma-interferon or basic fibroblast growth factor, were ineffective. The induced PAF production was concentration- and time-dependent. These results are in line with the hypothesis that microglia can start a cascade of events leading to tissue damage, thus playing a central role in the pathogenesis of several central nervous system diseases.

Brain↗
PubMedDate not supplied

Role of fibroblast growth factor-2 in human brain: a focus on development.

Trophic factors have gained a great degree of attention as regulators of neural cells proliferation and differentiation as well as of brain maturation. Very little is known, however, about their effects on human immature nervous system. In this paper, data on expression of fibroblast-growth factor-2 and its receptors are reviewed and discussed in the light of its possible role in human brain development.

Brain↗
PubMedDate not supplied

Platelet-activating factor production occurs through stimulation of cholinergic and dopaminergic receptors in the chick retina.

In previous work we showed that platelet-activating factor (PAF) was produced upon stimulation of the chick retina with acetylcholine (ACh) and dopamine (DA), via a dithiothreitol-insensitive cholinephosphotransferase (DTT-CPT). Other neurotransmitters were ineffective. Since ACh and DA stimulated PAF production at different stages of development, we advanced the hypothesis that selected cholinergic and dopaminergic receptors were involved. In this paper we demonstrate that only muscarinic or D2 (and not D1 and nicotinic) receptor stimulation induced PAF production in the chick retina either before or after hatching. Moreover, our data show that PAF production was completely prevented by blockage of these receptors by specific antagonists. These data further substantiate the hypothesis that PAF synthesis could be physiologically associated with synapse stimulation.

Acetylcholine↗