Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Retinaldehyde”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 811 records · Page 45Linked to original sources
PubMed1993

Enzymatic conversion of all-trans-beta-carotene to retinal.

Enzymatic conversion of all-trans-beta-carotene to retinal by a partially purified enzyme from rabbit, rat, and human neonatal intestinal mucosa has been demonstrated. The enzymatic product was characterized based on the following evidence. First, the product gave rise to its O-ethyl oxime by treatment with O-ethylhydroxylamine with an absorption maximum at 363 nm in ethanol characteristic of authentic retinal (O-ethyl) oxime. High-performance liquid chromatography of this derivative yielded a sharp peak with a retention time of 7.99 min, corresponding to the authentic compound. The enzyme blank and boiled enzyme blank failed to show any significant HPLC peaks corresponding to retinal (O-ethyl) oxime or retinal or retinol. Second, the mass spectrum of the O-ethyl oxime of the enzymatic product was identical to that of authentic retinal (O-ethyl) oxime (m/z 327, 45%; m+ and m/z 282, 100%, methoxy). Third, the 14C radioactivity persisted to constant specific activity even after repeated crystallization of the retinal (O-ethyl) oxime isolated from the enzyme reaction with purified beta-[14C]carotene. Fourth, the enzymatic product exhibited an absorption maximum at 370 nm in light petroleum characteristic of authentic retinal. Furthermore, it was reduced by horse liver alcohol dehydrogenase to retinol with an absorption maximum at 326 nm in light petroleum. This retinol was enzymatically esterified to retinyl palmitate by rat pancreatic esterase with a retention time of 10 min on HPLC, corresponding to authentic retinyl palmitate. Thus, the enzymatic product of beta-carotene cleavage by the partially purified intestinal enzyme has been unequivocally confirmed to be retinal. Similarly, enzymatic conversion of all-trans-beta-carotene to retinal by an intestinal mucosal enzyme from autopsy samples of human neonates has also been demonstrated. Based on the observed activities among intestinal samples from 12 premature infants, the BCC enzyme activity ranged from 3.3 to 1210 pmol/mg mucosal protein/hr. However, the observed activities in the human autopsy samples may be markedly underestimated, presumably because of marked loss of enzyme activity from the time of death to the time of assay. Therefore, the true activity of the enzyme can be assessed only after the extent of the loss of its activity on storage of the human samples can be accurately measured. Nonetheless, the demonstration of BCC enzyme activity in human neonates shows that beta-carotene may be an important source of vitamin A nutrition during gestation.

Animals↗
PubMed1995

Effects of season on electro-oculographic ratio in winter seasonal affective disorder.

Low electro-oculographic (EOG) ratios have been reported in patients with seasonal affective disorder (SAD) during the winter. This study evaluated the effects of the changing seasons on EOG ratios in SAD patients. Sixteen outpatients with SAD and 16 age-, sex-, and medication-matched normal volunteers had EOG testing during the winter and again during the summer. There was a significant season x group interaction in EOG ratios, with normal subjects showing higher ratios in winter than in summer--a seasonal variation not observed in SAD patients. SAD patients may have a subsensitivity to environmental light that leads them to experience symptoms during the winter.

Adult↗
PubMed1991

Alterations of visual cortical connections in cats following early removal of retinal input.

The major afferent pathways to the visual cortex were studied in cats enucleated at postnatal days 0, 15, 30 and 60 using the retrograde tracer wheat germ agglutin conjugated horseradish peroxidase (WGA-HRP). Following enucleation at days 0 and 15, the lateral gyrus was shrunken and cortical thickness was decreased, but the thickness of layer I was increased relative to normal adult cats. The laminar portion of the lateral geniculate complex occupied only half its normal volume, but the pathway from the intralaminar nuclei to visual cortex was doubled in volume. The ipsilateral and contralateral claustrum and ipsilateral medial septal nucleus also provided increased input to visual cortex. The changes in these projection patterns were not as dramatic in the cats enucleated at days 30 and 60. The callosal pathway between areas 17 and 18 was also significantly altered in cats enucleated on the day of birth and at day 15. Callosal cells were found in the infragranular layers throughout area 18. The number of supragranular callosal cells in the medial half of area 18 and in area 17 was reduced to approximately one third the normal adult number, but the mediolateral extent of this zone was not reduced. In the infragranular layers, the callosal cell number was approximately twice that in adult cats, and they occupied at least twice their normal mediolateral extent. Following bilateral enucleation at days 30 and 60, the cell numbers and mediolateral extent of the callosal cell zones approximated those in normal adult cats. Taken together, these results indicate that early deafferantiation of a cortical area can alter the thalamic, extrathalamic and callosal connections of that area.

Afferent Pathways↗
PubMed1991

In vitro expression of bovine opsin using recombinant baculovirus: the role of glutamic acid (134) in opsin biosynthesis and glycosylation.

Expression levels of functional bovine opsin in the insect cell line IPLB-Sf9 using recombinant baculovirus were shown not to depend on the use of novel transfer vectors (pAcRP23, pAcDZ1) that were reported to improve biosynthesis levels of other proteins in this system. A production of 5 micrograms opsin per 10(6) cells (approx. 1.5% of total cell protein) was achieved by batch fermentation of infected cells in spinner cultures. Infection of the cells in the presence of the glycosyltransferase inhibitor tunicamycin led to the synthesis of the complete protein, which, however, now migrated with a substantially lower Mr. This demonstrates that opsin in insect cells also undergoes N-linked glycosylation and allowed partial purification (10-fold) of the resulting rhodopsin by affinity chromatography over Concanavalin A-Sepharose. Through site-directed mutagenesis (rhod)opsin mutants have been obtained allowing dissection of functional domains of opsin. Amino acid substitutions that involved Glu-134 and/or Arg-135 affected the normal biosynthetic process leading in part to nonglycosylated, to a small extent even incomplete, protein. A number of mutations, that involve other charged residues within the second and third transmembrane domain of the protein, had no effect on the biosynthetic processing of the protein. We therefore suggest that the charge-pair Glu-134-Arg-135 is part of an important internal signal sequence and that alterations in this region may result in incorrect membrane translocation and/or folding of the protein.

Animals↗
PubMed1988

Amino acid sequence of the retinal binding site of squid visual pigment.

The retinylpeptides of visual pigments of two species of squid were identified in invertebrate visual pigments. Their primary structures were identical: H-Phe-Ala-Lys-Ala-Ser-Ala-Ile-His-Asn-pro-Hse(Met)-OH. The sequence was homologous to those of the corresponding region of other visual pigments, but the eighth amino acid, His, was found in squid visual pigments. In this experiment the retinylpeptides of eleven amino acid residues were isolated by monitoring the absorbance spectrum of the reduced retinal Schiff base without using radio-active [3H]retinal. This method is valid for the isolation and identification of retinylpeptides of other invertebrate visual pigments in which the chromophore is not exchangeable.

Amino Acid Sequence↗
PubMed1992

Microsomal retinal synthesis: retinol vs. holo-CRBP as substrate and evaluation of NADP, NAD and NADPH as cofactors.

Holo-CRBP (cellular retinol binding protein) is recognized specifically by an NADP-dependent microsomal retinol dehydrogenase and protects retinol from conversion into retinal by NAD and NADPH dependent dehydrogenases. The synthesis of retinal from free retinol is catalyzed by both NADP- and NAD-dependent pathways, with the former being the preferred one (Km of 4 vs. 22 microM for retinol, and Vmax/Km of 33 vs. 9, respectively). NADPH does not support quantitatively significant retinal synthesis from physiological concentrations of retinol or holo-CRBP, if an NADPH regenerating system is used to prevent NADP formation.

Animals↗
PubMed1993

Identification and immunohistochemistry of retinol dehydrogenase from bovine retinal pigment epithelium.

We studied the properties of retinol dehydrogenase (11-cis-specific) from bovine retinal pigment epithelium. Detergents caused a loss of retinol dehydrogenase activity; therefore, we added 3 mM NADH as a stabilizer to solubilize this enzyme and partially purified this enzyme using Sepharose CL-6B and hydroxyapatite column chromatography. The partially-purified sample, which contained two major proteins (66 kDa, 33 kDa), had substrate preference to 11-cis and 13-cis-retinal but not to all-trans and 9-cis isomers. Monoclonal anti-33 kDa protein of retinal pigment epithelial crude extract by Western blotting. In addition, we found that monoclonal anti-retinol dehydrogenase antibody bound specifically to retinal pigment epithelium and not to Müller cells or to rod outer segments by immunohistochemical methods.

Alcohol Oxidoreductases↗
PubMed1994

Characteristic properties of retinal oxidase (retinoic acid synthase) from rabbit hepatocytes.

Retinal oxidase (retinoic acid synthase) (EC 1.2.3.11) was purified electrophoretically, as a single protein band, from rabbit liver cytosol. The characteristic properties, enzymatic reaction mechanism, substrate specificity and kinetic parameters for retinals and molecular oxygen of the retinal oxidase were investigated. The Km values for all-trans-retinal of the retinal oxidase was the lowest than those for the other retinal derivatives. The retinal oxidase is a metalloflavoenzyme containing 2 FADs as the coenzyme, and 8 irons, 2 molybdenums, 2 disulfide bonds and 8 inorganic sulfurs. Its relative molecular mass was determined to be 270 kDa by gel filtration HPLC on a TSKgel G3000swXL column. Its minimum molecular mass was estimated to be 135 kDa by SDS-PAGE. The optical spectrum of the retinal oxidase showed absorption peaks at 275, 340 and 450 nm, and shoulders at 420 and 473 nm, in the oxidized form. The molecular extinction coefficients of the oxidase at selected wavelengths were determined. Circular dichroism spectra of the retinal oxidase were measured in the ultraviolet and visible regions. These spectra showed positive absorption in the visible region. The amino-acid composition was determined. The activity of the oxidase was not affected by any cofactors, such as NADP+, NAD+, NADPH and NADH, and it did not occur under anaerobic conditions. The oxidase was not inhibited by BOF-4272, a potent inhibitor of xanthine dehydrogenase, or rat anti-xanthine dehydrogenase IgG. Experiments on retinoic acid formation under 18O2 or H2(18)O demonstrated that the oxygen of water was incorporated into retinoic acid by the retinal oxidase, but not molecular oxygen.

Aldehyde Oxidoreductases↗
PubMed1994

Retinal-protein complexes as optoelectronic components.

Naturally occurring retinal-protein complexes (RPCs) have recently received much attention with regard to their potential use as light-sensitive elements for optical recording. The best-known RPC is bacteriorhodopsin (BR), a photosensitive protein from the membrane of extreme halophilic bacteria, which has been studied in great detail. The remarkably robust nature of BR, coupled with its ability to reversibly change color upon illumination and its high cyclicity of ground-to-photoinduced state transitions, makes BR a promising material for optical information processing.

Animals↗
PubMed1994

Vasoactive intestinal peptide modulation of adherence and mobility in rat peritoneal lymphocytes and macrophages.

In this work, the effects of vasoactive intestinal peptide (VIP) in a concentration range from 10(-13) to 10(-7) M were studied in vitro on two common activities of peritoneal rat lymphocytes and macrophages: adherence and mobility (spontaneous and chemotaxis). The results show that VIP stimulated the adherence of the two cells studied, and increased the macrophage mobility but decreased this activity in lymphocytes. Moreover, a specific protein kinase C (PKC) activator such as phorbol myristate acetate (PMA, 50 ng/ml) also stimulated significantly the adherence and chemotaxis of both macrophages and lymphocytes. By contrast, a PKC inhibitor, retinal (2 x 10(-5) M), decreased significantly these capacities. Macrophages incubated with both VIP and PMA in relation to those incubated with VIP or PMA showed an increase in adherence and chemotaxis, whereas in lymphocytes adherence was also increased but chemotaxis decreased. The incubation with forskolin (10(-5) M), an enhancer of intracellular cAMP levels, produced an inhibitory effect of the chemotaxis activity in both types of cells. VIP prevented this inhibitory effect of forskolin in macrophages but not in lymphocytes. In addition, VIP was chemoattractant for macrophages but not for lymphocytes. The present study proves that VIP proves that VIP has a coronary effect on the two principal and representative types of immune cells in the rat peritoneum: lymphocytes and macrophages, stimulating macrophage chemotaxis through PKC activation and inhibiting lymphocyte chemotaxis through adenylate cyclase activation.

Animals↗
PubMed1992

Involvement of Ca2+ entry and inositol trisphosphate-induced internal Ca2+ mobilization in muscarinic receptor-mediated catecholamine release in dog adrenal chromaffin cells.

Catecholamine (CA) release from adrenal medulla evoked by muscarinic receptor stimulation has been studied using isolated perfused adrenal gland and cultured chromaffin cells from dogs. Muscarine and oxotremorine (1-100 microM), and bethanechol (0.1-1 mM) dose-dependently stimulated CA release. Muscarine-evoked CA release was antagonized with M1-antagonist, pirenzepine and, to a lesser extent, with atropine; and was reduced either by removal of extracellular Ca2+ or treatment with Ca2+ channel blockers. Muscarine caused an increase of 45Ca uptake and 22Na uptake. Tetrodotoxin (TTX) did not affect muscarine-evoked increase of 22Na uptake and CA release. Under the absence of extracellular Ca2+, muscarine stimulated a 45Ca efflux. Muscarine-induced CA release was attenuated by treating the cells with 8-(N,N-diethylamino)-octyl-3,4,5-trimethoxybenzoate-HCl (TMB-8) which blocks Ca2+ release from the intracellular store. A phospholipase C inhibitor, neomycin, markedly reduced muscarine-induced CA release but not nicotine- and high K(+)-evoked release. Cinnarizine, a Ca2+ channel blocker, attenuated muscarine-evoked but not caffeine-induced CA release and 45Ca efflux in the absence of extracellular Ca2+. Muscarine caused an increase in intracellular free Ca2+ concentration ([Ca2+]i) in the presence of extracellular Ca2+. It caused a similar increase, but to a lesser extent, in the absence of extracellular Ca2+. The increase of [Ca2+]i induced by muscarine without extracellular Ca2+ was reduced by neomycin and cinnarizine. Polymixin B and retinal, which reduced 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced CA release, had little effect on muscarine-induced CA release. Muscarine increased cellular Ins(1,4,5)P3 production, and atropine inhibited this increase.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗
PubMedDate not supplied

Bacteriorhodopsin: the mechanism of 2D-array formation and the structure of retinal in the protein.

Bacteriorhodopsin, the light driven proton pump of the extreme halophilic bacterium H. salinarium, is an integral membrane protein (M(r) ca. 26000) which forms 2D arrays in the purple membrane of the bacterium. It is this feature which has permitted the use of electron diffraction methods to resolve the protein structure to some degree of atomic detail, although the prosthetic group has not been fully resolved. However, the features which induce the protein to form these arrays have not been previously clarified. We have now shown that the protein array formation is driven by specific interaction of the protein with the charged phospholipid, phosphatidyl glycerol phosphate (or the sulphate derivative), a major (ca. 60%) lipid of the bacterial host membrane. In addition, in an effort to provide further structural information about the chromophore, retinal, of this protein, the orientation of the individual methyl groups of retinal have been determined from solid state deuterium NMR studies of the deuterated chromophore when in the protein binding site. This approach to structural resolution of the prosthetic group is ab initio, agrees with other studies on the chromophore and resolves new features of the bound retinal to a high degree (+/- 2 degrees) of precision. Here, these two studies on this integral membrane protein will be reviewed.

Bacteriorhodopsins↗
PubMedDate not supplied

High-resolution structural studies of the retinal--Glu113 interaction in rhodopsin.

The key to understanding the reaction mechanism of rhodopsin lies in determining the structure of the retinal binding site and in defining the charge interactions between Glu113 and the retinal protonated Schiff base chromophore. We have been using 13C-NMR chemical shift data to determine the location of the Glu113 carboxyl side chain in relation to the retinal. The NMR data constrain one of the carboxylate oxygens of Glu113 to be ca. 3 A from the C12 position of the retinal with the second oxygen oriented away from the conjugated chain. A water molecule forming a hydrogen bond with the Schiff base is incorporated into the model to account for the high C = N stretching frequency [Han et al., Biophys. J., 65 (1993) 899]. In this study, we have refined the counterion position and have shown that it can reproduce the observed chemical shift data as well as the red-shifted absorption maximum of rhodopsin. Furthermore, the retinal binding site geometry derived from the NMR constraints can be readily incorporated into a recent structural model of the apoprotein.

Amino Acid Sequence↗
PubMedDate not supplied

On modeling the vibrational spectra of 14-s-cis retinal conformers in bacteriorhodopsin.

The vibrational properties of 13-cis, 14-s-trans and 13-cis, 14-s-cis protonated retinal Schiff base model compounds are explored with MNDO calculations. In particular, the effect of isomerization about the C14-C15 single bond on the vibrational properties of the deuterium in-plane rocking vibrations has been examined. Our MNDO calculations, using a variety of lysine models, lysine conformations and Schiff base charge environments, demonstrate that the C14-D and C15-D in-plane rocking vibrations in the 14,15-dideuterio retinal protonated Schiff base are strongly coupled in 13-cis, 14-s-cis molecules producing a splitting of ca. 80 cm-1 between the symmetric and antisymmetric rocking mode combinations but that these modes are only weakly coupled in 14-s-trans molecules. This analysis demonstrates that the 14,15-dideuterio labeling method developed earlier for determining C14-C15 conformation (S.P.A. Fodor, W. T. Pollard, R. Gebhard, E. M. M. van den Berg, J. Lugtenburg and R. A. Mathies, Proc. Natl. Acad. Sci. USA, 85, (1988) 2156-2160) is valid, and hence that the structure of the retinal chromophore in bacteriorhodopsin's L550 intermediate is 13-cis, 14-s-trans. The reasons for the misleading conclusions derived from MNDO calculations performed earlier by Schulten and Tavan are discussed.

Bacteriorhodopsins↗
PubMedDate not supplied

Structure and photobleaching process of chicken iodopsin.

Iodopsin, a dominant cone pigment in a chicken retina, has an absorption spectrum in longer wavelength region than rhodopsin. To account for this red-shift of iodopsin, we had proposed a structural model from retinal analogue experiments, in which iodopsin would have a relatively long distance between the protonated Schiff base nitrogen and the counterion. This was confirmed by a resonance Raman spectroscopy. The photochemical properties of iodopsin were studied and compared with those of rhodopsin, which revealed the following differences. The regeneration rate of iodopsin with 11-cis-retinal was 240 times faster than rhodopsin. Meta-iodopsin II, the signalling state of iodopsin, decayed about 100 times faster than meta-rhodopsin II. The Km value of meta-iodopsin II and rhodopsin kinase was lower than meta-rhodopsin II. These results are in consistent with rapid adaptation and low photosensitivity of cones relative to those of rods.

Amino Acid Sequence↗
PubMedDate not supplied

Computational studies of the early intermediates of the bacteriorhodopsin photocycle.

Starting from a refined model of bacteriorhodopsin's ground state, alternative models of the K and L intermediates with retinal in either 13-cis or 13-14-dicis configuration have been generated by molecular dynamics simulations. All models have been submitted to electrostatic calculations in order to determine the pK1/2 values of particular residues of interest in the active site. Our pK1/2 calculations for the refined ground state can reestablish our former results, this time without adjusting the intrinsic pK of the Schiff base. For the K intermediate the electrostatic calculations show no significant change in the pK1/2 values compared to the ground state for most of the titrating groups in the active site. For the L intermediate where retinal possesses a 13-cis configuration, we found that electrostatic factors decrease the pK1/2 value of the Schiff base by 4-5 pK-units compared to the ground state. The calculations suggest that changes of the electrostatic environment via a pure 13-cis model are sufficient to produce a pK reduction of the Schiff base that will promote subsequent proton transfer steps.

Amino Acid Sequence↗
PubMedDate not supplied

Vibrational spectra of room-temperature rhodopsin: concentration dependence in picosecond resonance coherent anti-Stokes Raman scattering.

The vibrational degrees of freedom of room-temperature rhodopsin (RhRT), the central trans-membrane protein in vision, are measured at room temperature by picosecond resonance coherent anti-Stokes Raman scattering (PR/CARS). High signal-to-noise PR/CARS data for the ethylenic stretching, Schiff base, and hydrogen-out-of-plane modes of the retinal chromophore are quantitatively analyzed via third-order susceptibility relationships. The accurate determination of spectral features permit the PR/CARS bandshapes to be analyzed as a function of RhRT concentration, an essential factor in using picosecond time-resolved CARS techniques to measure the vibrational spectroscopy of picosecond intermediates in the RhRT photosequence. Of particular importance is the recognition that PR/CARS bandshapes are sensitive functions of both the chromophore concentration and the excitation wavelength, as measured relative to the absorption spectra of specific chromophores (static and transient).

Animals↗
PubMed1980

The culture of hormone-dependent epithelial cells from the rat ventral prostate.

This paper describes a method for obtaining cultures of rat ventral prostate epithelial cells. The prostate is first perfused with a collagenase solution before removal from the animal; subsequent mincing and incubation in vitro produces a suspension of alveolar cell clumps. Upon incubation, these clumps attach to the surface of the culture dish and spread into discrete epithelial cell colonies, which both retain differentiated morphology, and secrete a species of plasminogen activator that is characteristic of prostatic tissue. These properties were not observed in cultures prepared from single cell suspensions of the same organ. Maintenance of epithelial colony integrity and secretory activity specifically required the continued presence of stromal cells, glucocorticoids and insulin. Androgenic steroids were much less effective than glucocorticoids in stimulating plasminogen activator secretion and in maintaining colony integrity, in spite of the well-established androgen dependence of prostatic tissue morphology in vivo and in organ culture. Furthermore, no effects of prolactin were observed, either when this hormone was tested alone or in conjunction with steroid hormones. Of 3 retinoids tested, retinal was highly cytotoxic at concentrations in the range of 1 microM, whereas retinol and retinoic acid were without detectable effect.

Animals↗