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Biomedical subjects

D Giulian

Publications and source records attributed to D Giulian.

51 records · Page 3Linked to original sources
PubMed1984

Target regulation of protein biosynthesis in retinal ganglion cells during regeneration of the goldfish visual system.

Transected ganglion cells of the goldfish retina demonstrate a marked increase in protein biosynthesis as their axons regrow into a primary target tissue, the optic tectum. In order to examine what role the target tissue may play in regulating the pattern of neuronal protein biosynthesis, the tectum is removed at the time of axotomy. By 10 days after surgery, the production of specific polypeptides including the structural proteins, tubulin and actin, are not affected by tectal ablation. However, during a later phase of regeneration when axons would normally begin to re-connect with the tectum, the appearance of a radiolabeled polypeptide of 300 kDaltons is blocked by tectal ablation. These data suggest that ganglion cells are regulated by target tissues late in the regenerative process perhaps by contact between axons and cells of the tectum.

Animals↗
PubMed1984

Peptides from the regenerating central nervous system of goldfish stimulate glia.

Severed ganglion cell axons of the goldfish retina regrow and form new synaptic connections within their primary target tissue, the optic tectum. During axonal regeneration, optic tract glia show increased incorporation of both thymidine and amino acids. Ablation of the tectum reduces the biosynthetic activity of cells in the optic tract, suggesting that humoral factors released from the tectum may stimulate neighboring glia. A soluble fraction isolated from denervated tecta increases glial incorporation of both thymidine and amino acids by 2- to 3-fold when compared to control cells treated with soluble material from intact tecta. One glial promoting factor, designated GPF -1, is a trypsin-sensitive peptide of about 14,000 daltons. Peptides released from target tissues may help to regulate growth of glial cells during neuronal regeneration.

Animals↗
PubMed1983

Localization of 2',3'-cyclic nucleotide-3'-phosphohydrolase within the vertebrate retina.

Histochemical and immunochemical techniques are used to locate 2',3'-cyclic nucleotide-3'-phosphohydrolase (2',3'-cNMP-3'ase) within cells of the vertebrate retina. A new histochemical method is described which links the hydrolysis of 2',3'-cNADP to the formation of a reduced, insoluble tetrazolium formazan. Photoreceptors from fish, bovine, and rat retinas are stained by this procedure. The reaction is blocked by 2'-AMP, a known inhibitor of 2',3'-cNMP-3'ase. Rabbit antibodies prepared against 2',3'-cNMP-3'ase from bovine brain are found to cross-react with bovine and rat retinal enzymes. Peroxidase-labeled antibody shows by light microscopy the greatest staining along the inner segments of the photoreceptors. Electron microscopy of the same preparations confirms binding to the plasma membrane of the inner segments of both rods and cones. Retinal 2',3'-cNMP-3'ase is thus predominantly associated with the photoreceptors, suggesting some role for 2',3'-cyclic nucleotides as substrates in visual function.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗
PubMed1980

Identification of 2':3'-cyclic nucleotide 3'-phosphodiesterase in the vertebrate retina.

The enzyme, 2':3'-cyclic nucleotide 3'-phosphodiesterase (2':3'-cNMP-3'-ase) has been used as a marker in the nervous system for the presence of myelin membrane or myelin-producing glial cells. In this study, goldfish and bovine neural retinas are found to have high levels of such a diesterase activity. Analysis of retinal tissue incubated with 2':3'-cAMP shows only 2'-AMP as the reaction product, indicating the selective hydrolysis of the cyclic nucleotide. Microdissection of the goldfish retina demonstrates the highest 2':3'-cNMP-3'-ase activity in the region of the photoreceptors. A fraction enriched in bovine rod outer segments has about a 5-fold increase in specific enzyme activity when compared to whole retina preparations. These data suggest that 2':3'-cNMP-3'-ase is either closely associated with or is an intrinsic feature of vertebrate photoreceptor elements. The retina, which contains this enzyme, may serve as a model to investigate the influence of 2':3'-cyclic nucleotides on a function of the nervous system.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗
PubMed1977

The electrophysiological mapping of compartments within a mammalian cell.

The electrical properties of structures within an intact cell were examined by impalement with micropipette electrodes. Mean potential differences (PDs) measured from interphase HeLa cells showed that internal membrane-bounded compartments such as the nucleus, Golgi region, and the mitochondria were more negative than the cytoplasm with respect to an external grounding electrode. The nuclear PDs, unlike Golgi and cytoplasmic PDs, shifted during interphase and reached a peak value shortly before mitosis. The positioning of micropipettes was confirmed by electron microscope examination of marker solutions that were microinjected into specific intracellular regions. The combination of methods described here offers a new approach for the study of physiological events within intact, living cells.

Cell Division↗
PubMed1974

Altered development of the rat brain serotonergic system after disruptive neonatal experience.

A single disruptive experience, a cold treatment, on postnatal day 1 elevated open-field activity and reduced reaction to handling in rats tested more than 240 days later. Neurochemical mechanisms underlying these behavioral phenomena were examined by monitoring the development of the rat brain serotonergic system. After cold treatment, elevations in 5-hydroxytryptamine levels of a preparation of forebrain plus midbrain could be first detected on postnatal day 16 in both sexes. A more detailed regional dissection of the brain showed that such increases occurred in the cerebrum, midbrain, septum-thalamus, and hypothalamus-preoptic area. Rats treated on postnatal days 1 or 6 showed increased 5-hydroxytryptamine levels, whereas animals treated on postnatal day 10 did not, a finding that points to a possible "critical period" of sensitivity. Results of adrenalectomy and corticosterone injections suggest that the influence of the adrenal gland cannot account for the elevation in brain serotonin. Furthermore, the gonadal steroids, estradiol and testosterone, alter brain 5-hydroxytryptamine independently of early experience, as distinguished by the time of appearance, periods of sensitivity, and the direction of monoamine changes. These findings are discussed in relation to the maturation of the neuroendocrine systems governing adrenal and gonadal function.

Adrenal Glands↗
PubMedDate not supplied

Secreted peptides as regulators of neuron-glia and glia-glia interactions in the developing nervous system.

Secreted peptides of the nervous system help to regulate neuron-glia and glia-glia interactions during development. These regulatory factors, referred to as glia-promoting factors (GPFs), act on specific classes of glia and include oligodendroglia-stimulating peptides, interleukin-1 (IL-1), colony-stimulating factors (CSF), and fibroblast growth factor (FGF). The maturity of secretory and target cells determines, in part, the ability of a factor to influence glial proliferation, activation, or differentiation. During neural development, GPFs help to control such fundamentally important events as cell movement, neurite outgrowth, and myelination.

Animals↗