Biomedical subjects

C L Zucker

Publications and source records attributed to C L Zucker.

At least 19 recordsLinked to original sources

PubMed1998

Gamma-aminobutyric acidA receptors on a bistratified amacrine cell type in the rabbit retina.

Gamma-Aminobutyric acid (GABA) is considered to be a major inhibitory neurotransmitter in the inner plexiform layer of the retinas of all vertebrate species. It is contained in and released from nearly 40% of the amacrine cells and is known to play a major role in many aspects of visual processing. By using well-characterized antibodies to several subunits of the GABA(A) receptor, we have analyzed their localization on the cell bodies and dendritic trees of two amacrine cell populations in the rabbit retina, which have been either filled intracellularly with Lucifer yellow or stained immunohistochemically. Both populations are selectively stained by intravitreal injection of the fluorescent nuclear dye 4',6-diaminidin-2-phenylindoldihydrochloride (DAPI). We have found that the most significant concentration of the alpha1 and beta2/3 GABA(A) receptor subunits is localized to the DAPI-3 type amacrine cell. The perikarya of the DAPI-3 cells are found in the proximal inner nuclear layer and send their processes into two sublayers in sublaminae a and b of the inner plexiform layer. These processes abut but do not directly overlap those of the two mirror-symmetric populations of starburst amacrine cells. Because the cell bodies of the DAPI-3 cells are the only ones in the inner nuclear layer that stain strongly for either the alpha1 or beta2/3 subunits, such staining is a diagnostic feature of these cells. Their processes also constitute the most strongly staining ones found within the inner plexiform layer. The dendritic trees of DAPI-3 cells, which range from about 150 microm up to about 300 microm, exhibit recurvate looping processes reminiscent of those described for directionally selective ganglion cells. In contrast to the DAPI-3 cell, we have also shown that the starburst amacrine cells exhibit no immunoreactivity for the alpha1 GABA(A) receptor subunit and very little for the beta2/3 subunit. Thus, we have shown that the DAPI-3 cells contain the highest concentrations of the alpha1 and beta2/3 GABA(A) receptor subunits in the rabbit retina. These cells, which costratify near the processes of both the starburst amacrine cells and the ON-OFF directionally selective ganglion cells, thus, are situated both anatomically and by virtue of their receptor content to potentially interact.

Animals↗

PubMed1998

Expression of vascular endothelial growth factor in the human retina and in nonproliferative diabetic retinopathy.

Vascular endothelial growth factor (VEGF)/vascular permeability factor is a likely angiogenic mediator in proliferative diabetic retinopathy, and its role is under scrutiny in the pathogenesis of the capillary leakage characteristic of background diabetic retinopathy. To examine whether the diabetic milieu induces or increases retinal VEGF expression in humans, we examined retinas from nondiabetic eye donors and donors with 9 +/- 5 years of diabetes and documented microangiopathy. To identify possible confounding effects of the postmortem period, we also studied the postmortem stability of the VEGF transcript and the expression of the VEGF protein in rat retinas. In both human and rat retina we detected by Northern analysis a 4.2-kb VEGF mRNA species and by reverse transcriptase polymerase chain reaction the transcripts encoding VEGF165 (the most abundant), VEGF121, and VEGF189. By in situ hybridization and immunohistochemistry VEGF mRNA and protein co-localized at the ganglion cell, inner nuclear, and outer plexiform layers and in the walls of the blood vessels (where mRNA was scarce). The protein was additionally detected in photoreceptors. The abundance and distribution of VEGF mRNA and protein were not altered in the diabetic retinas, indicating that the diabetic environment is not sufficient to increase retinal VEGF expression. The demonstration that VEGF is constitutively expressed in the adult retina and is localized to discrete neural cells and their processes proposes a role for the cytokine in retinal homeostasis and/or function.

Aged↗

PubMed1994

In vivo staining of oligodendroglia in the rabbit retina.

We have discovered that a strongly fluorescent dye, sulforhodamine 101, when injected intravitreally in vivo, very effectively stains a class of star-shaped cells in the innermost layers of the rabbit retina. The cells were strictly confined to the region containing medullated fibers and emitted dichotomously branching processes that ended up running some distance along the myelinated fibers. In favorable cases they could be seen to ensheath the fibers in a tube-like fashion. No other retinal cells were stained. Shortly (hours) after the injection, the stain appeared in the cell cytoplasm, but it later became progressively more localized to intracellular granules. Most of the dye had disappeared after 2 days. Oligodendrocytes and astrocytes are the only cells known to be confined to the region of the medullated fibers in the rabbit retina, and hence the sulforhodamine 101-stained cells should be one of these two types. Sulforhodamine 101-stained cells were indistinguishable from oligodendrocytes identified by 2',3'-cyclic nucleotide phosphodiesterase (CNP) immunohistochemistry, and sequential staining showed them to be the same. Sulforhodamine 101-stained cells were microinjected with lucifer yellow after lightly fixing rabbit retinas with formaldehyde and were found to be indistinguishable from oligodendrocytes. Glial fibrillary acidic protein staining for astrocytes showed fiber bundles that to some extent were similar to the bundles stained by sulforhodamine 101, but at the level of individual fibers, it was impossible to establish any concordance. Sulforhodamine 101 thus appears to stain oligodendrocytes rather than astrocytes in the rabbit retina. A related dye, rhodamine 123, also stained rabbit oligodendrocytes, but with poor contrast because many other cells and structures were also stained.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1994

Development of cell markers in subretinal rabbit retinal transplants.

Retinas from embryonic rabbits at day E15 were transplanted to the subretinal space in adult rabbits. After survival times between 7 and 193 days, the rabbits were killed, and the transplants were processed for immunohistochemistry. The results show that subretinal transplants from embryonic rabbit retinas develop many, if not all, retinal neuronal types. The cells show approximately normal morphology and express a variety of cell-type-specific markers: photoreceptor cells express visual pigment proteins as identified by antibodies against rhodopsin (R2-15), color-specific cone pigments (COS-1, OS-2) and the cone specific antigen 50-1B11, rod bipolar cells express PKC, horizontal cells HPC-1 antigen and neurofilament 160 kDa, amacrine cells HPC-1 antigen, GABA and neurofilament 160 kDa, and glial cells express vimentin and glial fibrillary acidic protein. The high degree of rosette formation seen in many young grafts, diminishes with time; many transplant cells disappear, and the remaining cells present a less prominent formation of rosettes.

Animals↗

PubMed1992

Heterogeneity of receptor immunoreactivity at synapses of glycine-utilizing neurons.

Neurons often contain, and probably release, more than one neuroactive substance that may have diverse or opposite actions on the postsynaptic cell. It remains unexplained how these neurons utilize their multiple neuroactive substances while maintaining appropriate resolution of neurotransmitter functions. Here, we have examined the ultrastructural localization of glycine receptors by using a monoclonal antibody directed to the intracellular domain of the strychnine-sensitive glycine receptor. We have found that glycine receptors are only localized to 56% of the synapses made by presumed 'glycinergic' (more accurately, glycine-utilizing) amacrine cells in the turtle retina. The remaining synapses made by these same boutons show no evidence of glycine receptors. As there is no evidence to suggest the presence of a second type of glycine receptor, these data indicate that only a portion of the postsynaptic sites contacted by the glycine-utilizing neurons can respond to glycine. They also suggest that a neuron containing multiple neuroactive substances can selectively affect postsynaptic elements by means of heterogeneous receptor localization.

Animals↗

PubMed1992

Transplantation of embryonic retina to the subretinal space in rabbits.

Embryonic rabbit retina can be transplanted to the subretinal space of adult rabbit with a new method, which gives a high rate of successful short-term transplants. Embryonic (stage E 15) neural retina cells were injected through an incision just behind the sclerocorneal border with a thin (inner diameter 0.15-0.4 mm, outer diameter 0.3-0.5 mm) plastic tube attached to a specially designed instrument, by which the length of the protruding plastic tip could be controlled. The retina was penetrated from the vitreous side and the donor tissue was injected into the subretinal space. The cells survived in the host for at least 5 months, although the long-term survival rate tended to decrease. The transplanted cells matured and differentiated, forming an approximation of the layered, retinal structure with some anomalies (e.g. rosettes). The subretinal location offers an interesting and convenient way of studying the development of retinal cell transplants in rabbits. Large transplants can be produced, and the risk for failures due to erroneous vitreous placement is small.

Animals↗

PubMed1991

Ultrastructure of human retinal cell transplants with long survival times in rats.

Human fetal retinas (6-12 weeks post-conception) were obtained from elective abortions, transplanted to rat retinas and examined by electron microscopy. The oldest transplants that form the basis of this report were obtained 40 and 41 total weeks post-conception. The host rats were immunosuppressed with cyclosporin A. The transplants developed according to their intrinsic, genetically determined timetable. The development was heterogeneous with some parts showing almost normal differentiation and others, little. Both rods and cones developed with inner and outer segments and synaptic terminals. In regions corresponding to the inner plexiform layer, bipolar cell processes were seen in the typical dyad arrangement. Likewise, amacrine cell processes formed typical conventional synapses. Serial synapses were seen, engaging amacrine cell synapses as well as a few reciprocal synapses at the bipolar cell dyads. Monad-type synaptic complexes, a sign of immaturity, were common in bipolar cell processes. Similarly, incompletely differentiated synapses of both the amacrine and bipolar cell types were often observed. Ganglion cell processes could not be identified with certainty. A structure with morphological characteristics similar to the inner limiting membrane was noted to form inside the transplant. Both epi-retinal and sub-retinal transplants were obtained. Transplant cells touched host photoreceptor cells or pigment epithelium without any obvious specializations. The host pigment epithelium microvilli were absent adjacent to the graft. However, graft cells did appear in the host retina, and nerve cell processes were observed to cross the membrane separating the transplant and host.

Animals↗

PubMed1988

Synaptic organization of dopaminergic interplexiform cells in the goldfish retina.

The synaptic organization of dopaminergic interplexiform cells (DA-IPC) in the goldfish retina was studied by a combined double-label electron-microscopical (EM) immunocytochemical/autoradiographical study. DA-IPCs were labeled with antisera against tyrosine hydroxylase. The possibility of synaptic contact with GABAergic amacrine cells in the proximal inner plexiform layer (IPL) was studied by using 3H-GABA uptake. Most synaptic input and output from DA-IPC processes involved amacrine cell processes. In addition, synaptic interactions were observed between DA-IPC processes and bipolar cell terminals, other DA-IPC processes, very small dendrites in the IPL, ganglion cell and optic fiber layers (OFL), and cell bodies in the ganglion cell layer (GCL). Input and output synapses with GABAergic amacrine processes also were observed. Two-thirds of the DA-IPC boutons in the proximal IPL were involved in "junctional appositions," that is, the junctions appeared to be specialized but they were different than classical chemical synapses. The synaptic organization of DA-IPCs in the goldfish IPL appears to be far more complex than previously thought. Although earlier studies have attempted to explain the action of dopamine in terms of interaction only with amacrine cells, the present study shows that effects involving bipolar cells, other DA-IPCs, unidentified processes and cell bodies in the GCL and OFL must be considered as well.

Animals↗

PubMed1987

Regulation of dopamine release from interplexiform cell processes in the outer plexiform layer of the carp retina.

The gamma-aminobutyric acid (GABA) antagonists bicuculline and picrotoxin stimulate a four- to fivefold increase in endogenous dopamine release from isolated intact carp retina. The release evoked by these agents is Ca2+ dependent, a finding suggesting a vesicular release. Using light microscopic autoradiography, we have localized the sites of dopamine release to the dopaminergic interplexiform cell processes of the outer plexiform layer, which synapse onto horizontal cells. Our findings support previous suggestions that the dopaminergic interplexiform cells receive GABAergic inhibitory input and that the effects of GABA antagonists on horizontal cells are mediated by dopamine release from the interplexiform cells.

Animals↗

PubMed1986

Neurotoxic action of kainic acid in the isolated toad and goldfish retina: I. Description of effects.

The neurotoxic action of kainic acid (KA) was investigated by histological methods in the isolated retina of toads and goldfish. Particular attention was paid to the earliest and most sensitive response to KA in the outer plexiform layer (OPL). KA caused vacuolization of proximal and distal segments of horizontal cell dendrites in the OPL as well as perikaryal vacuolization and/or chromatin clumping in selected classes of neurons in the inner nuclear layer. Further, KA caused vacuolization and swelling in the inner plexiform layer. These effects were very similar in the retinae of goldfish and toad. The extent of vacuolization in the OPL was graded with KA concentration and with length of incubation. For 15-minute incubations, half-maximal vacuolization was found at 10-20 microM KA. At 25 microM KA, OPL vacuolization was evident within 1-2 minutes of application of KA. In goldfish, but not in toad, rod-connecting dendrites were less sensitive to KA than cone-connecting dendrites.

Animals↗

PubMed1986

Neurotoxic action of kainic acid in the isolated toad and goldfish retina: II. Mechanism of action.

The specificity and mechanism of the neurotoxic action of kainic acid (KA) was investigated by histological methods in the isolated retina of toads and goldfish. Particular attention was paid to the earliest and most sensitive response to KA in the outer plexiform layer (OPL). Of 21 compounds tested as potential mimics of KA neurotoxicity in the OPL, only the enantiomers of glutamate and aspartate mimicked KA, inducing a low-level neurotoxic effect at concentrations 5,000-10,000-fold higher than concentrations of KA giving comparable effects. Further, of 22 compounds tested as potential blockers of KA neurotoxicity in the OPL, only D-gamma-glutamylglycine, D,L-alpha-amino pimelic acid, sodium pentobarbital, D,L-alpha-amino adipic acid, L-glutamate, and L-aspartate blocked KA neurotoxicity (IC50 values of 0.1, 0.3, 0.3, 2, 5, and 15 mM, respectively). In ionic substitution experiments, KA-induced vacuolization was found to require sodium and chloride ions but not calcium ions in the extracellular medium. These findings support the hypothesis that KA combines with specific receptors in the membrane of susceptible neurons in the retinal OPL, leading to prolonged opening of membrane channels permeable to sodium and potassium ions. An accompanying equilibrating chloride influx may result in intracellular ion excess, leading to osmotic swelling and vacuolization. The membrane receptors involved in mediating the action of KA in the OPL are likely to be a class of postsynaptic or extrasynaptic glutamate receptor.

Amino Acids↗

PubMed1985

Synaptic organization of substance P-like immunoreactive amacrine cells in goldfish retina.

A class of amacrine cells in the goldfish retina displays substance P-like immunoreactivity (SPIR). We studied the synaptic organization of SPIR amacrine cells by electron microscopical immunocytochemistry. Amacrine cells showing SPIR have processes which ramify in a very narrow band in layer 3 of the inner plexiform layer. SPIR is restricted to large dense-cored vesicles (DCVs), which are distributed throughout the dendrites. Processes labeled with SPIR contain a mixture of DCVs and numerous small agranular vesicles. Of 88 synaptic contracts analyzed, SPIR processes occurred as the presynaptic element 57 times and as the postsynaptic element 31 times. SPIR processes made synapses upon amacrine and ganglion cell dendrites with equal frequency and received synaptic input from both amacrine and bipolar cells. The stratification of SPIR amacrine cells in proximal sublamina a suggests that their synaptic interactions are restricted to "off" and "on-off" neurons. However, this is in contrast to published electrophysiological data. Possible explanations for this discrepancy are discussed in detail.

Animals↗

PubMed1984

Role of taurine in feeding the low-birth-weight infant.

Plasma and urinary taurine concentrations, growth, nitrogen balance, duodenal bile salt concentration and pattern, fecal bile acid excretion, and intestinal fat absorption were determined in appropriate for gestational age low-birth-weight infants fed either a whey-predominant cow milk formula or the same formula supplemented with taurine (45 mumol/kg/day). Mean plasma taurine concentration in the two groups did not differ. Mean urinary taurine concentration in the control and supplemented groups over the entire study period were 2.67 +/- 0.69 and 12.41 +/- 5.20 mumol/dl, respectively (P less than 0.05). Urinary taurine concentration in the supplemented infants, however, decreased significantly during the study period. Neither growth nor nitrogen retention differed between the two groups. Mean duodenal concentrations of taurine as well as glycine conjugates of both cholate and chenodeoxycholate were higher in supplemented infants. Total duodenal bile salt concentration correlated positively with taurine status as reflected by urinary taurine excretion (r = 0.71); this correlation plus the lower duodenal cholesterol concentration in supplemented infants suggests that conversion of cholesterol to bile acids was greater in supplemented infants. Mean intestinal fat absorption in control and supplemented infants, however, did not differ.

Bile Acids and Salts↗

PubMed1982

Use of medium-chain triglycerides in feeding the low-birth-weight infant.

Intestinal fat absorption and anthropometric and clinical variables were monitored weekly in 21 low-birth-weight (LBW) infants fed either a whey-predominant cow's-milk formula (formula 1) or identical formulas with medium-chain triglycerides (MCTs) comprising 40% (formula 2) or 80% (formula 3) of the fat content. Fat absorption of infants fed formula 1 averaged 86.7% of intake, whereas that of infants fed formulas 2 and 3 averaged 93.8% and 95.4%, respectively. However, no differences in weight, length, head circumference, or skin fold thickness were observed. Moreover, intestinal symptoms were encountered more frequently in infants fed formulas 2 and 3. This demonstrated failure of the resulting small increase in fat absorption incident to MCTs either to promote enhanced growth or to confer obvious clinical benefit does not support the increasing use of MCT formulas for routine feeding of LBW infants.

Diet Therapy↗

PubMed1980

Some statistical methods useful in circulation research.

Some statistical techniques for analyzing the kinds of studies typically reported in Circulation Research are described. Particular emphasis is given to the comparison of means from more than two populations, the joint effect of several experimentally controlled variables, and the analysis of studies with repeated measurements on the same experimental units.

Analysis of Variance↗

PubMedDate not supplied

Synaptic connections involving immunoreactive glycine receptors in the turtle retina.

The distribution of glycine receptors in the turtle retina was studied with the aid of a monoclonal antibody that detects the 93-kD protein associated with the strychnine-sensitive glycine receptor. Light microscopically, receptors were found in the inner plexiform layer and, more sparsely, in the innermost parts of the inner nuclear layer. No receptors were seen to be associated with photoreceptor cells, horizontal cells, or any other structures in the distal inner nuclear layer or outer plexiform layer. Ultrastructurally, glycine receptors were found on the inner face of postsynaptic membranes of processes from amacrine and presumed ganglion cells and always involved amacrine cell processes as the presynaptic element. Such glycine receptor immunoreactive synapses onto amacrine cell processes were distributed throughout the inner plexiform layer with a peak density near the middle. On the other hand, output synapses onto ganglion cell processes displaying immunoreactive glycine receptor sites showed a bimodal distribution in the inner plexiform layer. Glycine receptor immunoreactivity was not detected on bipolar cells, but presumed glycine-utilizing processes (i.e. those presynaptic to immunoreactive glycine receptors) were occasionally found to be postsynaptic in bipolar cell dyads. The majority of the synaptic input to the presumed glycine-utilizing amacrine cell processes was from other amacrine processes, some of which were themselves glycine utilizing. The observations suggest that glycinergic synapses in the turtle retina are, to a large extent, engaged in processing interamacrine signals.

Animals↗

PubMedDate not supplied

GABAA receptors in neurons of the nerve fiber layer in rabbit retina.

Two synapse-rich layers are well recognized in the mammalian retina, the inner and outer plexiform layers. However, synapses occur also in other layers, particularly in the innermost nerve fiber layer. These synapses form a tenuous layer at times referred to as the superficial plexiform layer. We have found that staining for GABAA receptors in whole-mounted rabbit retina demonstrates this layer. It is most well developed in the region of the visual streak 2-4 mm below the center of the myelinated streak and is very sparse in other parts. Most or all of the processes in the plexus originate from cells in the ganglion cell layer.

Animals↗

PubMedDate not supplied

Localization of gephyrin and glycine receptor subunit immunoreactivity in the rabbit retina.

Being utilized by over 40% of the amacrine cells, glycine is considered to be a major inhibitory neurotransmitter in the retinas of all vertebrate species examined. Localization of gephyrin, which is a 93-kD peripheral membrane glycine receptor-associated anchoring protein, has been used in several studies to identify the sites of glycinergic interactions in the retina and other regions of the central nervous system. Recent studies have shown that gephyrin colocalizes with GABA(A) receptors which, like those for glycine, are also inhibitory amino acid receptors usually associated with a chloride channel. In the present study, we have used two antibodies which recognize either gephyrin (mAb7a), or the alpha and beta subunits of the glycine receptor (mAb4a) in order to determine to what extent gephyrin is associated with glycine receptors in the mammalian retina. Single-label studies showed extensive punctate staining throughout most of the inner plexiform layer with each antibody. Double labeling showed that nearly 90% of the glycine receptor sites were also immunoreactive for gephyrin. However, nearly 60% of the total punctae immunoreactive for gephyrin were not stained for glycine receptors. This distinction was most pronounced in the most proximal inner plexiform layer where only 24% of the gephyrin-immunoreactive sites were glycine receptor positive. This study suggests that although most glycine receptors in the rabbit retina colocalize with the anchoring protein gephyrin, a significant proportion of the gephyrin-labeled sites are not associated with glycine receptors. In light of studies showing gephyrin association with GABA(A) receptor subunits, the localization of gephyrin may be indicative of chloride-mediated inhibitory amino acid transmission in general and not solely that of glycinergic. Given several studies which show that bipolar cells express glycine receptors and respond to glycine but do not express gephyrin, the 10% of glycine receptors not colocalized with gephyrin shown in the present study may represent a subtype of glycine receptors found on bipolar cells which do not require gephyrin for the functional clustering of receptor subunits.

Animals↗