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J R Sparrow

Publications and source records attributed to J R Sparrow.

33 records · Page 2Linked to original sources
PubMed1991

Experimental studies of tolerance to intravitreal perfluoro-n-octane liquid.

Low viscosity perfluorocarbon liquids are useful adjuncts during vitreoretinal surgery. This study evaluates perfluoro-n-octane (PFnO) for intraoperative use by examining ocular tolerance in rabbits and pigs. Rabbits were treated with intravitreal placement of PFnO for 48 hours and were examined during a period of 2 months following treatment. No clinical, electroretinographic, or light and electron microscopic evidence of adverse effects on the retina were observed. Small residual amounts of PFnO produced no adverse histologic changes 6 months after treatment. In pigs treated with mechanical vitrectomy and placement of PFnO for 3 hours, electron microscopic evaluation of the retina confirmed that the liquid had been well tolerated. These findings indicate that PFnO is safe for intraoperative use. When PFnO remained in the vitreous cavity of rabbits for longer than 1 week, varying degrees of globule dispersion occurred. Furthermore, histologic examination revealed changes in the inferior retina: photoreceptor outer segments were distorted, the outer plexiform layer was narrowed, and preretinal accumulation of macrophages had occurred.

Animals↗
PubMed1990

Cell commitment and differentiation in explants of embryonic rat neural retina. Comparison with the developmental potential of dissociated retina.

The differentiation of presumptive neural retina following its isolation from rat embryos and growth in explant and monolayer culture has been studied to obtain information regarding the extent to which factors extrinsic and intrinsic to the retina participate in determining molecular and cytological differentiation. Explanted retinal epithelium retained the capacity for mitosis, as shown by [3H]thymidine incorporation, and from the undifferentiated neuroepithelium, retinal cell-types emerged and acquired a laminar organization resembling that in vivo. Characterization of rod photoreceptor cells at both the light and electron microscopic level showed that these cells exhibit differentiated structural features including inner segments, connecting cilia and membranous expansions suggestive of forming outer segments. Immunofluorescent labeling with an antibody to a synaptic vesicle protein, and electron microscopic identification of synaptic elements showed formation of synapses by the photoreceptor cells within the explant. Neurites extending from the explants exhibited growth on laminin, fibronectin and collagen substrates. Since the neurites immunolabeled with antibodies to the 140 kDa subunit of neurofilament and with antibodies to Thy-1, they could be identified as axons of ganglion cells. Antibodies to a variety of cell-type specific antigens showed that the cells expressed molecules associated with the fully differentiated cell. Furthermore, since our approach has been to explant embryonic retina at an age when the antigens are not yet expressed in vivo, the appearance of the antigens in culture represented de novo expression. In contrast, neural retinal cells in dissociated cultures did not exhibit de novo expression of differentiated molecular properties.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Fibroblast behavior at aqueous interfaces with perfluorocarbon, silicone, and fluorosilicone liquids.

Perfluorocarbon, silicone, and fluorosilicone liquids with potential for use as vitreous substitutes in the management of complex retinal detachment were evaluated for surface reactivity by assessing the behavior of anchorage-dependent fibroblasts plated at the phase boundary between these compounds and culture medium. Low-viscosity perfluorcarbons were alumina-treated to remove polar impurities. On perfluorodecalin, perfluorodimethylcyclohexane, perfluorotrimethylcyclohexane, perfluoroethylcyclohexane, perfluorooctane, perfluoroperhydrophenanthrene, perfluoromethyladamantane, perfluorodimethyladamantane, the highly viscous perfluoropolyether liquids Krytox TLF7067 and 6354, and dimethylsiloxane liquids of a variety of viscosities, most cells did not attach; the few that did attach exhibited minimal spreading behavior and did not achieve the flattened spindle-shape morphology which is a prerequisite to normal proliferative activity. Conversely, on perfluoromethyldecaline, perfluorofluorene, perfluorotributylamine, the perfluoropolyether K-6 hexamer, trifluoropropylmethylsiloxane (fluorosilicone), and diphenyldimethylsiloxane, some cells became fusiform-shaped and exhibited proliferation, the extent of which varied with the compound. The association of alumina treatment of perfluorocarbon liquids with a reduction in cell growth was indicative of a relationship between the presence of residual hydrogen-containing impurities and the capacity for cellular attachment and growth. This correlation was demonstrated also in experiments in which cell attachment and growth was facilitated by the addition of hydrogen-rich monohydroperfluorooctane to alumina-treated perfluorooctane. In conclusion, evidence for the presence of surface active impurities in liquid vitreous substitute materials can be obtained by observing the behavior of attachment-dependent cells plated at the boundary between these compounds and culture medium.

Aluminum Oxide↗
PubMed1984

Antibodies to gangliosides inhibit goldfish optic nerve regeneration in vivo.

Intraocular injection of antiserum to mixed ganglioside or to GM1 inhibited the regeneration of goldfish optic axons following an optic nerve crush. For example, injections of antiserum on 5 consecutive days beginning the day before the crush resulted in a decrease of about 40% in the axonal outgrowth distance measured at 10 days after the crush. The inhibition was observed even when the treatment was begun a few days after the lesion, and greater degrees of inhibition were observed when the treatment was given later in regeneration. This indicates that the antiganglioside serum interfered with axonal elongation more than with the initial sprout formation. The antiganglioside treatment did not impair the enlargement of the cell bodies and nucleoli that accompanies regeneration, nor did it affect fast axonal transport of protein, glycoprotein, or glycolipid in regenerating nerves. Thus inhibition of outgrowth by antiganglioside treatment was not mediated by a gross change in the metabolism of the regenerating neurons. Treatment of normal neurons with the antiserum produced a 20-30% increase in the amount of 3H-glucosamine-labeled glycoproteins and glycolipids conveyed by fast axonal transport. These results suggest that membrane gangliosides may normally influence the supply of axonally transported glycosylated macromolecules. However, the effect of antiganglioside on axonal transport of glycosylated molecules and on axonal outgrowth are not necessarily related to each other.

Animals↗
PubMed1981

Immunocytochemical localization of plasma proteins in neuronal perikarya.

The presence of naturally occurring plasma proteins in the cell bodies of some neurons whose axons project outside the central nervous system was sought using the peroxidase-antiperoxidase (PAP) immunocytochemical technique. Rabbit antisera to whole rat serum and rat albumin were used as the primary antisera. The finding of immunoperoxidase reaction product within the perikarya is indicative of the presence of plasma proteins. It is suggested that the endocytosis and retrograde transport of exogenous protein tracers by neurons is paralleled by the neuronal incorporation of naturally occurring plasma proteins.

Animals↗
PubMed1980

Immunohistochemical study of the blood-brain barrier. Production of an artifact.

The permeability to normal serum proteins of blood vessels in the central nervous system (CNS) was studied by means of the peroxidase-antiperoxidase immunohistochemical technique. Frozen sections were cut in a cryostat and then fixed briefly in 95% ethanol. The localization of serum proteins outside blood vessels in the brain was shown to be an artifact produced during the preparation of cryostat sections. It was concluded that such cryostat sections are unsuitable for studies of vascular permeability in the CNS.

Animals↗
PubMedDate not supplied

A gradient molecule in developing rat retina: expression of 9-O-acetyl GD3 in relation to cell type, developmental age, and GD3 ganglioside.

In the embryonic and postnatal rat retina a cell surface antigen that is detected by monoclonal antibody JONES is distributed in a dorsoventral gradient. Biochemical analysis has determined that the antigen is a modified ganglioside, 9-O-acetyl GD3. In the present study, the distributions of 9-O-acetyl GD3 and its possible precursor GD3 in developing rat retina were compared immunocytochemically using specific monoclonal antibodies JONES and R24. On embryonic day 13 (E13) immunoreactivity to JONES was localized to central retina; however, R24 stained throughout the retinal epithelium. By E20, when JONES binding was distributed in a gradient along the dorsoventral axis, R24 again stained dorsal and ventral regions with uniform intensity. Analysis of freshly dissociated retinal cells further revealed that GD3 and 9-O-acetyl GD3 expressions do not necessarily coincide. At E15 and postnatal day 2 (PN2), the majority of cells (78 and 92%, respectively) were immunolabeled by antibody to GD3, while between E15 and PN2 the percentage of cells immunolabeled by antibody to 9-O-acetyl GD3 rose from 19 to 68%. By PN4, labeling decreased for both molecules; however, the rate of decline in 9-O-acetyl GD3 labeling was more pronounced. Regulation of the numbers of JONES-positive cells does not appear to depend on interaction with the extraretinal environment, for in neural retina explanted at E15 the proportions of 9-O-acetyl GD3-bearing cells was found to be similar to the percentage observed in neural retina developing to an equivalent age in vivo. Experiments to identify the retinal cell types bearing 9-O-acetyl GD3 revealed that it is expressed by both neurons and glia growing in monolayer cultures of rat perinatal neural retina. Examination of freshly dissociated retinal cells following simultaneous labeling for some specific cell types and 9-O-acetyl GD3 demonstrated that the latter determinant is present on photoreceptor, amacrine, and ganglion cells. For each neuronal cell type, however, not all of the cells were immunoreactive with JONES. We conclude that the differences in the percentages of JONES- and R24-positive cells, and in particular the different rates at which JONES and R24 staining declined with age, indicate that the expression of the JONES epitope is regulated with some independence from parent ganglioside GD3.(ABSTRACT TRUNCATED AT 400 WORDS)

Aging↗
PubMedDate not supplied

Inducible nitric oxide synthase in the central nervous system.

There is an accumulation of evidence indicating that induction of the calcium-independent isoform of nitric oxide synthase (iNOS) in glial cells can contribute to nitric oxide-mediated neural-cell damage. Elucidation of iNOS inducing signals and mechanisms regulating its augmentation and suppression may have implications for our understanding of basic processes underlying some forms of central nervous system disease.

AIDS Dementia Complex↗
PubMedDate not supplied

Immunohistochemical analysis of the neurotrophins BDNF and NT-3 and their receptors trk B, trk C, and p75 in the developing chick retina.

The neurotrophins are trophic and mitogenic factors critical for the development of specific classes of neurons in the central and peripheral nervous systems. In the retina, BDNF and NT-3 have been shown to promote the survival of differentiated ganglion cells (Rodriguez-Tebar et al., 1989; De La Rosa et al., 1994). NT-3 has also been demonstrated to support the survival of amacrine cells and facilitates the differentiation of retinal neurons in culture (De La Rosa et al., 1994). Here, we examine immunohistochemically the expression of BDNF and NT-3 proteins, their cognate receptors, trk B and trk C, respectively, and the p75 neurotrophin receptor in the developing chick retina. At E8, the earliest stage of retinal development examined, all of these proteins exhibit diffuse expression throughout the width of the retina, with the strongest reactivity in the innermost layers. A gradual restriction in expression to ganglion cells and amacrine cells, the staining of which is most prominent at E15, is followed by a downregulation of expression with the strongest immunoreactivity persisting in the ganglion cell layer. Overlapping patterns of expression throughout embryonic development indicate a colocalization of the neurotrophins and their receptors, although NT-3 and p75 alone are present in the inner plexiform layer and only p75 is observed in the outer plexiform layer. Although some of the immunoreactivity for BDNF, NT-3, and their receptors in retina may reflect trophic mechanisms operating in association with the optic tectum and isthmo-optic nucleus, the colocalization of ligands and receptors in retina strengthens the assertion that these neurotrophins function locally during development.

Animals↗