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PubMed1997

Immunoelectron-microscopic investigation of the subcellular localization of pinopsin in the pineal organ of the chicken.

Pinopsin is a photoreceptive molecule cloned from the chicken pineal organ. An antibody highly specific for pinopsin was applied in light- and electron-microscopic immunocytochemical studies of the pineal organ of 1 to 2-month-old chickens. Intense immunoreactivity was found in the follicular lumen at the light-microscopic level. In addition, small immunoreactive spherical or fibrous structures were diffusely distributed at the parafollicular aspect of the pineal organ. To identify immunoreactive elements precisely, we used pre-embedding immunoelectron microscopy. These studies revealed immunoreactive outer segments of pinealocytes arranged closely side by side in the follicular lumina. The thin initial portion of the outer segment arose from a basal body located in the inner segment. Immunoreactive pear-shaped outer segments occupied small lumina. Follicular lumina displayed immunonegative arrays of whorl-like lamellar membranes. Occasionally, these immunonegative structures were surrounded by immunoreactive concentric lamellar complexes. In the parafollicular pineal parenchyma, long slender cilium-like structures or enlarged cilia and concentric lamellar arrays showed intense immunoreactivity. All immunoreactive structures observed in this study were considered to represent outer segments of pinealocytes of the chicken pineal organ.

Animals↗
PubMed1999

Differentiation of pinopsin-immunoreactive cells in the developing quail pineal organ: an in-vivo and in-vitro immunohistochemical study.

The avian pineal organ contains several types of photoreceptors with different photopigments: rhodopsin, iodopsin, and pinopsin. We have previously examined the differentiation of both rhodopsin-like and iodopsin-like immunoreactive cells during pineal development in quail embryos to determine the onset of synthesis of specific proteins and their cellular localization. In the present study, we have performed pinopsin immunohistochemistry on in-vivo developing and in-vitro cultured pineal organs of quail embryos. The results were compared with those obtained with rhodopsin and iodopsin immunohistochemistry. In the developing pineal organs, pinopsin immunoreactivity was detected at embryonic day 8, i.e. five days earlier than rhodopsin-like and iodopsin-like immunoreactivities. It was localized exclusively in the protrusions extending into the lumen throughout development, whereas rhodopsin-like and iodopsin-like immunoreactivities were usually found both in cell bodies and processes. These differences were also observed under two different types of culture conditions (dissociated cell culture and organ culture) indicating that, in the avian pineal organ, the expression pattern of the pinopsin gene is basically different from those of the other two pineal photopigments. The present study suggests that pineal cells have a mechanism for the polarized transport of pinopsin molecules.

Animals↗
PubMed2000

Colocalization of pinopsin with two types of G-protein alpha-subunits in the chicken pineal gland.

Pinopsin is a photoreceptive molecule present in the outer segments of chicken pinealocytes. In this paper, the localization of alpha-subunits of G-proteins, rod transducin (Gt1) and Gq/11, was examined by immunoelectron microscopy to investigate whether these G-proteins colocalize with pinopsin in the outer segments. Ultrathin sections of the chicken pineal gland were double-immunolabeled with antibodies to pinopsin and either Gt1alpha or Gq/11alpha. As shown previously, the outer segments around the follicular lumen exhibited divergent morphology with ciliary, bulbous, or lamellate shapes, and most of them displayed pinopsin immunoreactivity. The majority (>90%) of pinopsin-immunopositive outer segments were labeled by anti-Gt1alpha and/or anti-Gq/11alpha antibodies. Application of double-immunolabeling to serial sections demonstrated that a large number of the pinopsin-immunopositive outer segments contained both Gt1alpha and Gq/11alpha immunoreactivities. These results suggest that Gt1alpha and Gq/11alpha are functionally coupled with light-activated pinopsin within a single outer segment.

Animals↗
PubMedDate not supplied

Evaluation of S-cone sensitivity in reattached macula following macula-off retinal detachment surgery.

PURPOSE: To investigate the recovery of short-wavelength sensitivity in patients who had undergone successful reattachment of a rhegmatogenous retinal detachment with macular involvement. METHODS: Postoperative assessment of the visual acuity and the visual fields by standard achromatic automated perimetry (SAP), and short-wavelength automated perimetry (SWAP, Humphrey visual field analyzer; macula test pattern) was performed on 12 patients after the macula was reattached. The follow-up period was up to 12 months. RESULTS: The visual acuity and SAP sensitivity recovered rapidly after reattachment, with further moderate improvements up to 6 months after reattachment. The improvements stabilized by 9 to 12 months. The SWAP sensitivities improved more slowly than the visual acuity or SAP sensitivities, but they continued to improve even when visual acuity or SAP sensitivities had stabilized. CONCLUSION: We conclude that measurement of the sensitivities of the short-wavelength-sensitive cones (S-cones) with SWAP may be a sensitive method to evaluate the visual recovery of the reattached macula following macula-off retinal detachment.

Adult↗
PubMed1983

The enzymatic cleavage of rhodopsin by the retinal pigment epithelium. I. Enzyme preparation, properties and kinetics: characterization of the glycopeptide product.

An enzyme system has been detected in the bovine retinal pigmented epithelium (RPE) which carries out the degradation of rhodopsin. The substrate for these studies was bovine rhodopsin labeled by in vitro techniques with [3H]-glucosamine or [3H]-mannose, the former being the derivative most extensively examined. Labeled rhodopsin was purified by adsorption and affinity chromatography followed by preparative isoelectric focusing. Cell-free preparations from bovine RPE cleaved rhodopsin to a single glycopeptide. The pH optimum for the reaction was about 3.5. The apparent Km for rhodopsin was about 5 microns. Rhodopsin was cleaved about 55% under saturating conditions, the limited extent of reaction due primarily to its partial inactivation for use as a substrate during the course of the reaction. Inhibition by cleavage products was not observed. Among several tissues which were examined, the RPE was the most active in rhodopsin-cleaving activity. Although stable as a crude extract, the activity of the rhodopsin-cleaving enzyme, as well as the bovine serum albumin (BSA)-cleaving enzyme (cathepsin-D) were rapidly lost upon purification by DEAE-Sephacel and pepstatin-Sepharose. Differences in relative specific activity among tissues as well as differential patterns of purification suggest that the rhodopsin-cleaving enzyme and the BSA-cleaving enzyme of the RPE may not be the same. Using N-retinylopsin as a substrate for the rhodopsin-cleaving enzyme, it was shown that the regions of the cleavage products containing vitamin A were not associated with the glycopeptide. Some of the properties of the product were examined. Its response to ion exchange resins, susceptibility to further cleavage by pronase, amino acid analysis, solubility properties, isoelectric point, and binding by concanavalin A (conA)-Sepharose, were consistent with the product being described as an acidic glycopeptide. The glycopeptide was reactive with the antibody prepared against bovine rhodopsin, and retained the full antigenicity of the intact molecule. This enzyme system may be one of the means whereby the RPE participates in maintaining the physiological concentration of rhodopsin which is synthesized in the retina and catabolized in the RPE.

Amino Acids↗
PubMed1982

Activation of phosphodiesterase by chicken iodopsin.

Activation of guanosine 3',5'-cyclic monophosphate phosphodiesterase in outer-segment membrane of chicken retina was investigated. Irradiation of dark-adapted chicken outer segment membrane for bleaching of iodopsin increased the enzyme activity twice as much as that in the dark in the presence of GTP. Further irradiation of the sample for bleaching of rhodopsin in the membrane induced some additional activation of the enzyme. However, chicken iodopsin activated the enzyme in frog rod outer segment membrane without irradiation, while chicken rhodopsin did not. Irradiation of chicken iodopsin increased the enzyme activity twice as much as that in the dark.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1985

Localization of light-induced conformational changes in bovine rhodopsin.

Conformational changes in the extradiscal regions of rhodopsin induced by illumination were investigated by modifying the visual pigment by mild treatment with cyanogen bromide prior to and after light exposure. Light induced an increased yield of cleavage of the Met bond 253-254 and a new cleavage at the Met bond 155-156 of the rhodopsin polypeptide chain. These residues, located at the beginnings of the membrane-buried helices 6 and 4, respectively, were concluded to become extradiscally exposed upon illumination.

Animals↗
PubMed1989

Chicken red-sensitive cone visual pigment retains a binding domain for transducin.

Iodopsin (a red-sensitive cone visual pigment) and rhodopsin (a rod pigment) were isolated from chicken retina. They were separately reconstituted into phosphatidylcholine liposomes and then mixed with rod transducin (T alpha and T beta gamma) purified from bovine retina. Iodopsin enhanced, only when irradiated, the binding of GppNHp to T alpha to a similar extent to irradiated rhodopsin. Furthermore, the binding of GppNHp to T alpha in the presence of a photobleaching intermediate of iodopsin preferably required T beta gamma-2 rather than T beta gamma-1, which is very similar in profile to that in the presence of the intermediate of rhodopsin (J. Biol. Chem., in press). These results indicate that the binding domain for transducin in iodopsin should closely resemble that in rhodopsin.

Animals↗
PubMed1990

The primary structure of iodopsin, a chicken red-sensitive cone pigment.

A purified iodopsin was digested by CNBr or several proteolytic enzymes into fragments, the amino acid sequences of which were determined. A partial sequence of the C-terminal fragment was utilized for synthesizing an oligonucleotide probe which identified the iodopsin cDNA (1339 bases). The deduced amino acid sequence (362 residues) had 80%, 42%, or 43% homology to that of human red-sensitive cone pigment, cattle or chicken rhodospin, respectively. Although the hydropathy profile implies that iodopsin, like rhodopsin, has 7 transmembrane alpha-helical segments, iodopsin may have a hydrophilic pocket near the seventh segment on the basis of the unexpected cleavages in the middle of the segment VII by chymotrypsin under nondenaturing conditions.

Amino Acid Sequence↗
PubMed1994

Thermal recovery of iodopsin from its meta I-intermediate.

The thermal reaction of meta I-intermediate of iodopsin (metaiodopsin I), a chicken red-sensitive cone pigment, was studied by low-temperature spectrophotometry at -20 degrees C. Irradiation of iodopsin at -20 degrees C produced metaiodopsin I, whose absorption maximum was at about 470 nm. An incubation of metaiodopsin I at -20 degrees C resulted in a conversion to metaiodopsin II having absorption maximum at about 380 nm, as well as a concurrent formation of a red-shifted product stable at room temperature. Since the absorption spectrum and photo-reactivity of the red-shifted product were identical with those of iodopsin, the red-shifted product should be iodopsin. Thus a part of metaiodopsin I can revert to iodopsin by the thermal reaction unlike metarhodopsin I.

Animals↗
PubMed1995

Cultured peripheral blood mononuclear leukocytes from anorexia nervosa patients are refractory to visible light.

Cultured human peripheral blood mononuclear leukocytes [PBML] from patients with anorexia nervosa [AN] did not respond to light stimulation as PBML of normal controls [NC] did. During winter, visible light increased [3H]thymidine incorporation into DNA of NC-PBML stimulated with phytohemagglutinin [PHA]. This effect was enhanced by 10(-7) M melatonin. PHA-stimulated DNA synthesis of PBML from AN patients failed to respond to photic stimulation during winter, and their proliferative response to melatonin was significantly blunted. In vitro photic stimulation of NC-PBML reduced melatonin while increasing both serotonin and 5-hydroxyindole 3-acetic acid [HIAA] production in both basal and PHA-stimulated conditions. In contrast AN-PBML, that in darkness enhanced the oxidative deamination of serotonin into HIAA more than NC-PBML, did not switch their indole metabolism in response to light. Light did not inhibit the binding of both melatonin and serotonin to AN-PBML as occurred in NC-PBML. The present data suggest that AN-PBML do not respond to light in vitro, because of a failure in the regulation of serotonin and melatonin metabolism.

Adolescent↗
PubMed1995

Sensitivity of human peripheral blood mononuclear leukocytes to visible light.

Overnight light exposure of cultured human peripheral blood mononuclear leukocytes [PBML], significantly increased basal [3H]thymidine incorporation and upon stimulation with phytohemagglutinin [PHA]. Melatonin (10(-9) to 10(-5) M) enhanced the light-induced increase of [3H]thymidine incorporation, while serotonin (10(-9) to 10(-7) M) stimulated [3H]thymidine incorporation in the dark. The wavelengths responsible of this effect were restricted to the blue-green zone of the spectrum. The stimulatory effect of visible light on PHA-induced DNA replication had a circannual rhythm, being maximal during winter. In winter, white light also reduced melatonin and serotonin binding to PBML membranes and switched the PBML indole metabolism towards serotonin and 5-hydroxy-indole-acetic acid [HIAA] synthesis, with a concomitant decrease of melatonin production.

Base Sequence↗
PubMed1989

Monoclonal antibodies specific to chicken iodopsin.

Monoclonal antibodies (mABs) from hybridoma cells were raised and screened with a purified cone pigment, iodopsin, from the chicken retina. Four different methods were used to test these antibodies: (1) dot-immunobinding assay; (2) enzyme-linked immunoabsorbent assay (ELISA); (3) one dimensional immunoblotting and (4) two dimensional immunoblotting. Three classes of antibody producing cell lines were identified. One class produces a mAB specific to iodopsin. The mAB from the second class crossreacts with iodopsin and probably one of the other three cone pigments. The mAB from the third class probably crossreacts with all the four cone pigments in the chicken retina. The mABs from all these classes of hybridoma cell lines were selected so that they do not crossreact with rhodopsin. Two dimensional immunoblotting indicated that iodopsin has a much higher isoelectric point than rhodopsin, as suggested from the known amino acid sequences of human rod and cone pigments.

Animals↗
PubMed1993

Light-induced binding of proteins to rhabdomeric membranes in the retina of crayfish (Procambarus clarkii).

Light-induced protein interaction as part of the process of visual transduction in arthropods with rhabdomeric photoreceptors was investigated biochemically by using crayfish retina. Two kinds of retinal buffer soluble proteins (one of 40 kDa and the other of 46 kDa) were found to bind to the irradiated rhabdomeric membranes both in vitro and in vivo. The proteins bound to the membranes in the presence of metarhodopsin. An antibody against mouse arrestin (S-antigen) cross-reacted with the 40 kDa protein. These results suggest that the binding of the proteins to the membranes is caused by the formation of metarhodopsin, and that the 40 kDa protein has a similar structure to arrestin.

Animals↗
PubMed1990

Rapid and sensitive sequence comparison with FASTP and FASTA.

The FASTA program can search the NBRF protein sequence library (2.5 million residues) in less than 20 min on an IBM-PC microcomputer and unambiguously detect proteins that shared a common ancestor billions of years in the past. FASTA is both fast and selective because it initially considers only amino acid identities. Its sensitivity is increased not only by using the PAM250 matrix to score and rescore regions with large numbers of identities but also by joining initial regions. The results of searches with FASTA compare favorably with results using NWS-based programs that are 100 times slower. FASTA is slightly less sensitive but considerably more selective. It is not clear that NWS-based programs would be more successful in finding distantly related members of the G-protein-coupled receptor family. The joining step by FASTA to calculate the initn score is especially useful for sequences that share regions of sequence similarity that are separated by variable-length loops. FASTP and FASTA were designed to identify protein sequences that have descended from a common ancestor, and they have proved very useful for this task. In many cases, a FASTA sequence search will result in a list of high scoring library sequences that are homologous to the query sequence, or the search will result in a list of sequences with similarity scores that cannot be distinguished from the bulk of the library. In either case, the question of whether there are sequences in the library that are clearly related to the query sequence has been answered unambiguously. Unfortunately, the results often will not be so clear-cut, and careful analysis of similarity scores, statistical significance, the actual aligned residues, and the biological context are required. In the course of analyzing the G-protein-coupled receptor family, several proteins were found that, because of a high initn score and a low init1 score that increased almost 2-fold with optimization, appeared to be members of this family which were not previously recognized. RDF2 analysis showed borderline z values, and only a careful examination of the sequence alignments that focused on the conserved residues provided convincing evidence that the high scores were fortuitous. As sequence comparison methods become more powerful by becoming more sensitive, they become more likely to mislead, and even greater care is required.

Algorithms↗