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PubMed1997

[Cancer-associated retinopathy].

A variety of paraneoplastic syndromes affect the central nervous system including eye. So far, two types of retinopathy are known to be associated with patients with malignancies, cancer-associated retinopathy (CAR), and melanoma-associated retinopathy (MAR). CAR is associated with epithelial cancers, mostly lung small cell carcinoma, and is characterized by retinitis pigmentosa-like retinal degeneration. Usually CAR can be found before an underlying primary cancer is diagnosed. MAR is associated with cutaneous malignant melanoma and is characterized by the relatively sudden onset of photophobia and nyctalopsia. The flash electroretinogram (ERG) of MAR patients shows a negative waveform, reduced b-wave amplitude, and reservation of a-wave amplitude, suggesting that bipolar cells may be affected. CAR and MAR are believed to result from an autoimmune response. In CAR, a calcium binding protein called recoverin, a 70 kDa protein, and neurofilaments are the retinal antigens recognized by the patient's serum. In contrast, the retinal antigens in MAR have not yet been identified, although patient sera specifically recognized retinal bipolar cells in immunocytochemistry.

Animals↗
PubMed1996

Expression of glial markers in a retinal precursor cell line.

PURPOSE: To determine glial characteristics of the retinal precursor cell line R28, which has previously been shown to express proteins immunoreactive with photoreceptor markers IRBP, S-Ag, recoverin, the ganglion cell marker 2G12, as well as the Muller cell marker RetG1. METHODS: R28, an immortalized retinal precursor cell line derived from P6 rat retinal tissue, was analyzed to determine expression of glial cell markers. R28 cells were analyzed both immunocytochemically and by western immunoblot for GFAP, S-100, and vimentin. These results were compared with the primary postnatal day 6 retina. Double fluorescence immunolabelling was used to identify R28 cells which simultaneously expressed vimentin and the photoreceptor marker IRBP (interphotoreceptor retinoid-binding protein). RESULTS: GFAP, S-100 and vimentin immunoreactive proteins were detected in R28 cells. Western blot analysis showed the GFAP immunoreactive band to migrate at a slightly higher apparent molecular weight for R28 than for P6 retina, and demonstrated a less fibrillary staining pattern than P6 retina, but appeared to be present to some degree in all R28 cells. Variations in molecular weight were seen for S-100, although the nuclear staining pattern was the same for both the R28 cell line and P6 retina. S-100 immunoreactivity was seen in approximately 50% of the R28 cell population. Vimentin was expressed by virtually all R28 cells, and to a greater degree than that seen in P6 retina (both in cell number and intensity). Double labelling studies revealed R28 cells which expressed both vimentin and IRBP simultaneously. CONCLUSIONS: There is a very strong glial component to the R28 retinal precursor cell line, as evidenced by the expression of proteins immunoreactive to GFAP, S-100 and vimentin. However, even the most strongly immunoreactive marker vimentin was compatible with co-expression of the photoreceptor marker IRBP as evidence of the "multi-phenotypic" nature of the precursor-like R28 cells. Ongoing studies will assess the differentiation potential of R28 cells and applicability in future studies of retinal cell differentiation and gene expression.

Animals↗
PubMed1998

Rhodopsin transgenic pigs as a model for human retinitis pigmentosa.

PURPOSE: To further characterize the retinas of Pro3471Leu rhodopsin transgenic pigs, a model for human retinitis pigmentosa. METHODS: Retinas from normal and transgenic pigs, newborn to 20 months old, were processed for light and electron microscopic immunocytochemical examination. RESULTS: At birth, rod numbers were normal in the transgenic retinas, but their outer segments were short and disorganized and their inner segments contained stacks of rhodopsin-positive membranes. The newborn rod synapses lacked synaptic vesicles and ribbons and had numerous rhodopsin-positive, filopodia-like processes that extended past the cone synapses into the outer plexiform layer. Rod cell death was apparent by 2 weeks and was pronounced in the mid periphery and central regions by 6 weeks. Far peripheral rods were initially better preserved, but by 9 months virtually all rods had degenerated. Cones degenerated more slowly than rods, but by 4 weeks the cone synapses were shrunken and some mid peripheral cones had lost their immunoreactivity for phosphodiesterase-gamma, arrestin, and recoverin. From 9 months to 20 months, the cone outer segments shortened progressively, and more cones lost immunoreactivity for these proteins. CONCLUSIONS: The rhodopsin transgenic pig retina shares many cytologic features with human retinas with retinitis pigmentosa and provides an opportunity to examine the earliest stages in photoreceptor degeneration, about which little is known in humans. The finding of abnormal rhodopsin localization in newborn rods is consistent with misrouting of mutant rhodopsin as an early process leading to rod cell death. Novel changes in the photoreceptor synapses may correlate with early electrophysiological abnormalities in these retinas.

Animals↗
PubMed1987

Cancer-associated retinopathy.

Antiretina antibodies have been found in the serum samples of four patients with cancer experiencing concomitant loss of vision (cancer-associated retinopathy [CAR] syndrome). These immunoglobulins bound an antigen from normal pooled retina having a molecular weight of 23,000 daltons, which we describe as the CAR antigen. No corresponding antibodies could be found in serum samples obtained from patients with cancer not experiencing vision loss, from patients having retinitis pigmentosa, or from normally sighted individuals who did not have cancer. The early detection of rising antibody titers against the CAR antigen could prove important in the identification of patients likely to suffer from CARs.

Aged↗
PubMed1992

Management and monitoring of cancer-associated retinopathy.

Cancer-associated retinopathy is a rare paraneoplastic event that can involve allergic reactions and result in retinal degradation. A patient, who had a 35-year smoking history, complained of visual loss and was found to have serum antibodies that reacted with an extract of retina, including the previously described retinal cancer-associated retinopathy antigen. Prednisone treatment appeared to reduce the patient's antibody titers to normal levels. Visual fields stabilized, and the patient was able to maintain useful vision throughout the course of treatment until his death 1 year following initial diagnosis. To our knowledge, this is the first reported case in which monitoring of antibody responses to retinal antigens appeared to be useful in the decision whether to initiate prednisone therapy. Rising antibody titers to the cancer-associated retinopathy antigen probably occurs before progressive visual field loss and may be considered an indication for prompt steroid therapy.

Aged↗
PubMed1993

Antibody reactions with retina and cancer-associated antigens in 10 patients with cancer-associated retinopathy.

OBJECTIVE: Our objectives were to determine what clinical characteristics are common to the form of cancer-associated retinopathy (CAR) encountered in patients with small-cell carcinoma of the lung (SCCL). Is the 23-kd retinal CAR antigen/antibody reaction present in other forms of retinopathy? Can an antigen identical or similar to the 23-kd retinal CAR antigen be identified in an established culture of SCCL? METHODS: Ten patients with CAR who had SCCL were identified by their antibody reactivity with the 23-kd retinal CAR antigen. We inquired into common clinical characteristics by means of questionnaires to the referring physicians. We looked for antigen/antibody reactions with the 23-kd retinal CAR antigen in patients with diabetic and age-related macular degenerations and in a continuous, in vitro propagated culture of SCCL (HTB 119) obtained from the American Type Culture Collection. RESULTS: We encountered many similar signs and symptoms in our patient population. These included rapid vision loss, night blindness, color loss, vitreous cells, and either flat or greatly reduced electroretinograms. No corollary to the 23-kd CAR antigen/antibody could be identified in unrelated retinopathies or cultured SCCL. CONCLUSIONS: We conclude that patients with SCCL-related CAR consistently produce antibodies against the 23-kd retinal CAR antigen. This immunologic reaction was not found in patients with unrelated retinopathies and may possibly represent a cancer marker for SCCL.

Aged↗
PubMed1993

Intraperitoneal cultivation of small-cell carcinoma induces expression of the retinal cancer-associated retinopathy antigen.

OBJECTIVE: We have inquired into the reason why patients with cancer-associated retinopathy (CAR) produce antibody reactions with the 23-kd retinal CAR antigen. Possible reasons include the expression of this antigen in the related carcinoma. Previous studies have failed to identify any antigenic counterpart expressed by in vitro cultivated small-cell carcinoma of the lung. We, therefore, inquired into the effects of in vivo cultivation of the cancer cells and its influence on protein expression, with specific reference to the appearance of the 23-kd retinal CAR antigen. DESIGN: A complementary DNA library was prepared from small-cell carcinoma of the lung cells propagated intraperitoneally in Lewis rats and probed with antibodies reactive with the 23-kd retinal CAR antigen. RESULTS: We found evidence of the expression of a cancer-associated gene in ascites-propagated small-cell carcinoma of the lung that encodes for a protein antigenically similar to the 23-kd retinal CAR antigen. A complementary DNA encoding this protein revealed complete DNA sequence homology with the retinal CAR antigen showing the cancer cells are expressing this photoreceptor protein. CONCLUSIONS: We hypothesize that the carcinoma-retina immunologic cross-reaction is responsible for the induction of the unique antibody response encountered in patients with CAR with vision loss developing as a cancer-evoked autoimmune retinopathy.

Animals↗
PubMed2005

Localization of glycine receptor alpha subunits on bipolar and amacrine cells in primate retina.

The major inhibitory neurotransmitter glycine is used by about half of the amacrine cells in the retina. Amacrine cells provide synaptic output to bipolar, ganglion, and other amacrine cells. The present study investigated whether different bipolar and amacrine cell types in the primate retina differ with respect to the expression of glycine receptor (GlyR) subtypes. Antibodies specific for the alpha1, alpha2, and alpha3 subunits of the GlyR were combined with immunohistochemical markers for bipolar and amacrine cells and applied to vertical sections of macaque (Macaca fascicularis) and marmoset (Callithrix jacchus) retinae. For all subunits, punctate immunoreactivity was expressed in the inner plexiform layer. The GlyRalpha2 immunoreactive (IR) puncta occur at the highest density, followed by GlyR(alpha)3 and GlyR(alpha)1 IR puncta. Postembedding electron microscopy showed the postsynaptic location of all subunits. Double immunofluorescence demonstrated that the three alpha subunits are clustered at different postsynaptic sites. Two OFF cone bipolar cell types (flat midget and diffuse bipolar DB3), are predominantly associated with the alpha1 subunit. Two ON bipolar cell types, the DB6 and the rod bipolar cell, are predominantly associated with the alpha2 subunit. The glycinergic AII amacrine cell is presynaptic to the alpha1 subunit in the OFF-sublamina, and postsynaptic to the alpha2 subunit in the ON-sublamina. Another putative glycinergic cell, the vesicular glutamate transporter 3 cell, is predominantly presynaptic to the alpha2 subunit. The dopaminergic amacrine cell expresses the alpha3 subunit at a low density.

Amino Acid Transport Systems, Acidic↗
PubMed2004

Retargeting of adenoviral infection to melanoma: combining genetic ablation of native tropism with a recombinant bispecific single-chain diabody (scDb) adapter that binds to fiber knob and HMWMAA.

Gene therapy is an emerging and promising modality for the treatment of malignant melanoma and other neoplasms for which conventional therapies are inadequate. Various therapeutic genes have shown promise for tumor cell killing. However, successful gene therapy depends on the development of efficient and targeted gene transfer vectors. Here we describe a novel strategy for targeting of adenovirus-mediated gene transfer to melanoma cells. This strategy combines genetic ablation of native adenoviral tropism with redirected viral binding to melanoma cells via a bispecific adapter molecule, a bacterially expressed single-chain diabody, scDb MelAd, that binds to both the adenoviral fiber protein and to the high molecular weight melanoma-associated antigen (HMWMAA). This antigen is widely and specifically expressed on the surface of melanoma cells and its expression is associated with tumor development and progression. Our results showed specific and strong binding of the anti-HMWMAA scFv RAFT3 and the bispecific adapter scDb MelAd to melanoma cells. In adenoviral infection experiments, we demonstrated i) substantially (>50-fold) reduced infectivity of capsid mutant adenoviruses, ii) restored (up to 367-fold increase), CAR-independent and HMWMAA-mediated infectivity of these mutant viruses by scDb MelAd specifically in melanoma cells, and iii) higher levels of transgene expression in melanoma cells by fiber mutant virus complexed with scDbMelAd, relative to a vector with wild-type fibers. We confirmed the utility of this targeting strategy with human primary melanoma cells that represent clinically relevant substrates. These experiments established that the retargeting strategy mediates up to 54-fold increased adenoviral gene transfer to CAR-negative melanoma cells compared to the vector with native tropism. Hence, the HMWMAA-targeted adenoviral vector lacking native tropism exhibits both enhanced specificity and augmented infectivity of gene transfer to melanoma cells, suggesting that it is feasible to use this vector to improve gene therapy for malignant melanoma.

Adenoviridae↗
PubMed1997

Functional expression and characterization of frog photoreceptor-specific calcium-binding proteins.

S-modulin (sensitivity-modulating protein) is a photoreceptor-specific calcium-binding protein which plays an important role in the light adaptation process by controlling rhodopsin phosphorylation in rods. S-modulin and its cone homologue, s26, were expressed at high level (more than 30% of total protein) in Escherichia coli and then purified. They both inhibited rhodopsin phosphorylation in a calcium dependent manner. Myristoylated recombinants of S-modulin and s26 showed calcium-dependent changes in tryptophan emission spectra with half-maxima at about 0.7 microM free calcium concentration. However, the spectral changes are distinctive from each other, suggesting that there is some difference in the structural change between S-modulin and s26.

Adenosine Triphosphate↗
PubMed1996

Structural diversity in a family of homologous proteins.

An interesting example of a structurally diverse group of sequentially homologous proteins is analyzed at the level of molecular interactions. In this family, the EF-hand calcium-binding proteins, there are examples of at least three distinct mutual positions of the N and C-terminal domains, despite significant sequence homology between all members of this family. Why does a particular protein choose one arrangement over another? To answer this question, detailed models of all proteins in their native structures as well as all alternative sequence/structure combinations are built by comparative modeling. By studying and comparing interactions stabilizing native structures and destabilizing alternative conformations, it is possible to gain insight into how such conformational diversity is achieved. It is shown that some mechanisms used to achieve it are: correlated mutations on the surface of two units and the presence of additional domains/chain fragments stabilizing desired topologies. The implications of these findings, both for structure predictions for other members of this family as well as the general problem of quaternary structure formation, are discussed.

Amino Acid Sequence↗
PubMed2005

In vivo and in vitro proliferative and differentiation activity of human embryonic retinal cells.

Differentiation of human embryonic retinal cells (20-22 weeks gestation) was studied using morphological, immunohistochemical, and biomolecular approaches. The retina included several regions differing by the degree of cell differentiation. Mitoses were rarely found in the marginal zone. This zone contained low differentiated cells. The central retinal area consisted of typical layers with differentiated cells. Culturing was accompanied by the formation of aggregates and neurospheres, where mitoses and progenitor or differentiated cells expressing markers of photoreceptors, neurons, and glia were found.

Cell Differentiation↗
PubMed1991

P26-calcium binding protein from bovine retinal photoreceptor cells.

The primary structure of bovine retinal calcium binding protein P26 has been determined by parallel analysis of protein and corresponding cDNA. This protein is identical to recovering and shares 59% homology with visinin, a cone specific calcium binding protein from chicken retina. Preliminary data are presented on expression of P26 as a fusion protein in E. coli.

Amino Acid Sequence↗
PubMed1993

On the activation of phosphodiesterase by a 26 kDa protein.

The effects of a 26 kDa protein isolated from vertebrate retina rod outer segments (ROS) and its reconstituted analog on the phosphodiesterase (PDE) activity and cGMP-dependent conductance have been studied [Nature 313 (1985) 310-313]. Using the patch-clamp technique it was shown that the 26 kDa protein in concentrations up to 1 microM accelerates hydrolysis of cGMP by near-membrane PDE by 1-2 orders of magnitude. This process is suggested to be mediated by some intracellular agent. At the same concentrations the 26 kDa protein was shown to inhibit cGMP-dependent conductance of the photoreceptor membrane. A possible role of these effects in the processes of phototransduction and adaptation is discussed.

Animals↗