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 631 records · Page 35Linked to original sources
PubMed1978

Isolation and characterization of epithelial cells from bovine pancreatic duct.

Epithelial cells derived from bovine pancreatic duct have been grown continuously in culture for 30 weeks (approximately 90 doublings of the cell population). The cells were grown in Eagle's minimal essential medium supplemented with 10% heat-inactivated fetal bovine serum, 2 mM glutamine, 0.1 mM nonessential amino acids, and antibiotics. In confluent cultures, the cells are multilayered and form circular structures. When tested at various passages, the cells neither formed colonies in soft agar nor produced tumors after inoculation into athymic, nude mice. Hydrocortisone (1 and 5 microgram per ml) and insulin (1,5 and 10 microgram per ml) had no effect on the growth of the cells. beta-Retinyl acetate inhibited growth rate and cell yield at a concentration of 5 microgram per ml but was not growth-inhibitory at lower concentrations. By electron microscopy the cells have numerous mitochondria, Golgi and microvilli. Mucous droplets were observed in a small proportion of the cells. Desmosome-like structures and occluding junctions were observed more frequently between cells that had been transferred as aggregates than between cells transferred as single cells. Cytochemical studies indicated that some cells produce PAS positive granules that were not removed after treatment of the cultures with diastase. Eleven cell clones were isolated from the mass culture. The growth rates of the clones are different as well as the period of time in which the clones can be propagated in vitro.

Animals↗
PubMed1987

Structure of a protein catalyzing the formation of 11 cis-retinal in the visual cycle of invertebrate eyes.

A pigment made up of a protein able to bind retinal as well as retinol is described. The molecule consists of a dimer with a molecular weight of 50,000 which binds one molecule of retinal. The binding site for retinal is a Schiff base buried in the interior of the protein. Retinol is probably bound to the protein in the same site as for retinal, although not covalently, as suggested by the absorbance spectra. The protein, extracted from honeybee retina, is involved in visual pigment metabolism, and its structure may elucidate the mechanism of the stereospecific photoisomerization of all trans-retinal to 11-cis-retinal.

Amino Acids↗
PubMed2003

Specific isomerization of rhodopsin-bound 11-cis-retinal to all-trans-retinal under thermal denaturation.

The natural ligand of the retinal photoreceptor rhodopsin, 11-cis-retinal, is isomerized to its all-trans configuration as a consequence of light absorption in the first step of the visual phototransduction process. Here we show, by means of difference spectroscopy and high-performance liquid chromatography analysis, that thermal denaturation of rhodopsin induces the same type of isomerization. This effect is likely due to thermally induced conformational rearrangements of amino acid residues in the retinal-binding pocket--possibly implying helical movements--and highlights the tight coupling between 11-cis-retinal and opsin. This effect could have implications in the instability and functional changes seen for certain mutations in rhodopsin associated with retinal disease, and in the stability of the different conformers induced by mutations in other G protein-coupled receptors.

Animals↗
PubMed2001

The role of retinal in the long-range protein-lipid interactions in bacteriorhodopsin-phosphatidylcholine vesicles.

The effects of bacteriorhodopsin analogues and the analogues of a bacteriorhodopsin mutant (D96N) on the lateral organization of lipids have been investigated with lipid species with a variety of acyl chain lengths. The analogues, obtained by regeneration of bacterioopsin or mutant opsin with 14-, 12-, 10-, or 8-fluororetinal, were reconstituted with 1,2-didodecanoyl-sn-glycero-3-phosphocholine, 1,2-ditetradecanoyl-sn-glycero-3-phosphocholine, 1,2-dihexadecanoyl-sn-glycero-3-phosphocholine, and 1,2-dioctadecanoyl-sn-glycero-3-phosphocholine. The phase behavior of the protein-lipid systems was investigated at different temperatures and different protein/lipid molar ratios by analyzing the fluorescence and phase properties of the 1-acyl-2-[8-(2-anthroyl)octanol]-sn-glycero-3-phosphocholine probe. The (8,10,12)-bacteriorhodopsins had a similar effect on the lipid phase transition to that induced by native bacteriorhodopsin: a rigidifying effect on the three shorter lipid species and a fluidifying effect on the longest-chain lipids used. The substitution of retinal with 14-fluororetinal resulted in much stronger effects of the protein on the lipids: a more pronounced up-shift of the lipid phase transition temperature, a rigidifying effect on all the lipids used, and an elongation of the distance over which the hydrophobic thickness of the lipid bilayer was perturbed by the protein. Evidence was provided that retinal contributed to the long-range protein-lipid interactions in bacteriorhodopsin-phosphatidylcholine vesicles. The extent of this contribution was dependent on the retinal structure in close vicinity to the Shiff base and on the compactness of the protein structure.

Bacteriorhodopsins↗
PubMed2005

[Function of bestrophin].

Clarification of the function of bestrophin, the gene product of VMD2, establishes a basis for the understanding of the pathomechanisms leading to Best's vitelliform macular degeneration. Studies of heterologously expressed bestrophin showed that bestrophin can function as a Cl(-) channel. All four known bestrophins were found to display Cl(-) channel activity. A loss in Cl(-) channel function would elegantly explain the development of the leading symptom for Best's disease, the reduction of the light peak amplitude in the patient's electro-oculogram. However, there are still gaps in the chain of evidence demonstrating that bestrophin is a Cl(-) channel, and this hypothesis is inconsistent with newly published follow-up observations. In an alternative hypothesis bestrophin appears as a regulator of voltage-dependent Ca(2+) channels assuming an indirect involvement of bestrophin in the generation of the light peak. Further studies on either bestrophin-deficient mice or transgenic mice will show that either one of the hypotheses is right or maybe both will be proven correct, showing bestrophin as a Cl(-) channel and Ca(2+) channel regulator.

Bestrophins↗
PubMed2000

[Inhibition of proliferation of retinal pigment epithelium in vitro: vitamin A pharmacodynamics I].

BACKGROUND: In proliferative vitreoretinopathy and choroidal neovascularization, retinal pigment epithelial (RPE) cells proliferate among other cell types. Cell proliferation is controlled by many factors. One such factor is the "superfamily" of nuclear receptors. Ligands of these receptors are vitamin A and D, triiodothyronine and dexamethasone. All-trans-retinal (atR) inhibits human RPE-cell proliferation. AtR binds to the nuclear ligand-dependent transcription factors RAR (retinoic acid receptor) and RXR (retinoid X receptor). Pharmacodynamics of atR were investigated with respect to inhibition of RPE cell proliferation. MATERIALS AND METHODS: Primary human RPE cell lines were used up to passage 5. RPE cells were incubated with atR ranging from 1 pM up to 1 microM. AtR was added every other day for 7 days. Cell proliferation was determined by cell counting. RESULTS: AtR inhibited RPE cell proliferation in a biphasic manner. Two IC50 values were calculated, one in the picomolar range, 10 pM (5-24, 95% confidence interval) and one in the nanomolar range, 17 nM (8-37). Furthermore, inhibition of cell proliferation was examined using specific RAR agonists. Agonists of the RAR-b subgroup inhibited cell proliferation at the lowest concentrations. CONCLUSIONS: RPE cell proliferation in vitro is inhibited by agonists of RAR. Agonists of the RAR-b subgroup inhibit RPE cell proliferation at the lowest concentrations.

Cell Count↗
PubMed1996

Corticofugal feedback can reduce the visual latency of responses to antagonistic stimuli.

A biophysically realistical model of the primary visual pathway is designed, including feedback connections from the visual cortex to the lateral geniculate nucleus (LGN) - the so-called corticofugal pathway. The model comprises up to 10,000 retina and LGN cells divided into the ON and the OFF pathway according to their contrast response characteristics. An additional 6000 cortical simple cells are modeled Apart from the direct excitatory afferent pathway we include strong mutual inhibition between the ON and the OFF subsystems. In addition, we propose a novel type of paradoxical corticofugal connection pattern which links ON dominated cortical simple cells to OFF-center LGN cells and vice versa. In accordance with physiological findings these connections are weakly excitatory and do not interfere with the steady-state responses to constant illumination, because during the steady-state inhibition arising from the active pathway effectively silences the non-stimulated pathway. At the moment of a contrast reversal the effect of the paradoxical connection pattern comes into play and the depolarization of the previously silent channel is accelerated, leading to a latency reduction of up to 4 ms using moderate synaptic weights. With increased weights reductions of more than 10 ms can be achieved. We introduce different synaptic characteristics for the feedback (AMPA, NMDA, AMPA + NMDA) and show that the strongest latency reduction is obtained for a combination of the membrane channels (i.e., AMPA + NMDA). The effect of the proposed paradoxical connection pattern is self-regulating; because the levels of inhibition and paradoxical excitation are always driven by the same inputs (strong inhibition is counter-balanced by a stronger paradoxical excitation and vice versa). In addition, the latency reduction for a contrast inversion which ends at a small absolute contrast level (small contrast step) is stronger than the reduction for an inversion with large final contrast (large contrast step). This leads to a more pronounced reduction in the reaction times for weak stimuli. Thus, reaction time differences for different contrast steps are smoothed out.

Contrast Sensitivity↗
PubMed2006

Computational photochemistry of retinal proteins.

High spectral tunability and quantum yield are the striking features of rhodopsin photochemistry. They rely on a strong and complex interaction of their chromophore, the protonated Schiff base of retinal, with its protein environment. In this article, we review the progress in the computational modeling of these systems, focusing on the optical properties and the excited state dynamics. While the earlier success of atomistic theoretical models was based on the breakthrough in X-ray crystallography and combined quantum mechanical molecular mechanical (QM/MM) methodology, recent advances point out the importance of high-level QM methods and the incorporation of effects that are neglected in conventional QM/MM or ONIOM schemes, like polarization and charge transfer.

Computational Biology↗
PubMed2005

Vitamin a deficiency in patients with common variable immunodeficiency.

Vitamin A, a naturally occuring antioxidant micronutrient, has immunomodulating effect in patients with immunodeficiency, including an influence on cytokine production and lymphocyte growth and functions. Vitamin A deficiency is associated with a shift from type 2 cytokines to predominantly type 1 cytokines. The aims of this study were to determine Vitamin A status in Common variable immunodeficiency (CVID) patients and the relationship between Vitamin A status and cytokines production. Serum Vitamin A, neopterin, TNF-alpha, IL-2, IL-4, and IL-10 levels were determined in 19 CVID patients and 15 healthy children. Effects of 9-cis retinal, Vitamin A derivative, on cytokines (TNF-alpha, IL-2, IL-4 and IL-10) production in lymphocytes were tested in vitro condition using lymphocyte cultures obtained from CVID patients and healthy children.Serum Vitamin A level in CVDI patients was, 21.1+/- 1.5 microg/dL, significantly (p < 0.001) lower than the value, 35.7+/- 1.8 microg/dL, observed in healthy children. Serum neopterin level in the patients was, 9.8+/- 2.9 nmol/L, higher (p < 0.05) than the value, 3.9+/- 0.7 nmol/L, observed in control group. Common variable immunodeficiency patients, serum IL-4 level was significantly (p < 0.05) lower than the value observed for healthy children. Serum TNF-alpha, IL-2 and IL-10 levels were similar in the patients and healthy children. Vitamin A derivative, 9-cis retinal, increased TNF-alpha and IL-4 production in cultured mononuclear cells obtained from control and CVID patients. Vitamin A derivative, also, increased IL-2 and Il-4 production in cultured mononuclear cells obtained from CVID patients. These results show that CVID patients have low serum Vitamin A levels and high serum neopterin levels. A supplementation with Vitamin A may have role in downregulation of inflammatory responses in CVID patients.

Adolescent↗
PubMed1983

Analysis of retinal and 3-dehydroretinal in the retina by high-pressure liquid chromatography.

A sensitive analytical method was developed in order to study the rhodopsin-porphyropsin system in the eye. Oximes of 11-cis-retinal, all-trans-retinal, 11-cis-3-dehydroretinal, and all-trans-3-dehydroretinal were determined quantitatively by high-pressure liquid chromatography. This method was applied to the analysis of retinal and 3-dehydroretinal in the retinas of bullfrog and goldfish. The results agreed with those obtained from the bleaching kinetics of visual pigment extracted with detergent. A reliable result is obtained if the tissue contains more than 5 pmol of retinal (or 3-dehydroretinal). The chromophore composition could be determined in the eye of a small freshwater prawn, Palaemon pancidence, using 50 pmol of 11-cis-retinal and no 3-dehydroretinal.

Animals↗
PubMed1986

Aggregation and proton release of purple and white membranes following cleavage of the carboxyl-terminal tail of bacteriorhodopsin.

Our results indicate that the previously reported decrease in proton release by proteolyzed purple membrane sheets was due merely to the aggregation state of these preparations and not to the loss of the carboxyl-terminal tail. Changes in H+/M412 ratios obtained for purple and white membrane preparations correlate with the measured aggregation. White membrane preparations consistently exhibit H+/M412 ratios more than twice those measured for native purple membranes under the same conditions. Quasi-elastic light scattering was used to characterize the size of isolated purple and white membrane sheets before and after proteolysis. The results clearly show that native purple membrane preparations are larger in size than would be expected and that, following trypsin treatment, they are on average more than an order of magnitude larger. Negative staining electron microscopy showed that the purple membrane became aggregated in stacked arrays. Bleaching and reconstitution with retinal also affect aggregation, but iodination or nitration of purple membrane does not affect the measured size. The average size of white membranes is smaller; this is consistent with results of electron microscopy and the size increase is much less than that of purple membranes following trypsin treatment. No size change occurs with retinal reconstitution. In aggregated purple membrane preparations, protons and other cations are unable to exchange freely with the aqueous medium, explaining why proteolysis lowers the proton release from purple membrane sheets in suspension.

Bacteriorhodopsins↗
PubMed1987

NAD+-dependent retinol dehydrogenase in liver microsomes.

A microsomal NAD+-dependent retinol dehydrogenase is being described with optimal activity at physiological pH. The enzyme was present in liver microsomes of rats and also in a strain of deermice which lacks the cytosolic retinol dehydrogenase. Unlike the latter enzyme, the microsomal retinol dehydrogenase was not inhibited by either ethanol or 4-methylpyrazole; its activity was insensitive to CO and not oxygen dependent, in contradistinction with that of the microsomal cytochrome P-450 and NADPH-dependent retinol oxidase. Chronic ethanol consumption resulted in an increased activity of the microsomal retinol dehydrogenase which may contribute to hepatic retinol depletion, especially in view of the insensitivity of the enzyme to ethanol inhibition.

Alcohol Oxidoreductases↗
PubMed1989

An investigation of the electrochemical cycle of bacteriorhodopsin analogs with the modified ring.

5,6-Epoxy-, 4-methoxy-, 4-hydroxy-, and 3,4-dehydrobacteriorhodopsins can generate delta psi coupled to a photochemical cycle with intermediate M. The kinetics of delta psi comprises three main electrogenic phases: the fast small negative, the microsecond, and the millisecond positive phases. The photocycle efficiency is lower in all the analogs. The photocycle is modified insignificantly only in 3,4-dehydrobacteriorhodopsin. In the other pigments the decay of the flash-induced bleaching in the chromophore main absorption band is slower than the decay of M or long-wave intermediates, especially in the 4-hydroxy analog. In the latter analog, such distinctions, according to delta pH measurements, are partly due to deceleration of the decay of the novel intermediate (P). In 5,6-epoxybacteriorhodopsin, at all wavelengths, the decay of the intermediates takes seconds upon M formation. According to our and literature data, no bacteriorhodopsin analogs are known to have a cycle which preserves the M-intermediate and does not transport a proton.

Bacteriorhodopsins↗
PubMed1989

The chromophore retinal hinders passive proton/hydroxide ion translocation through bacteriorhodopsin.

Experiments have been performed to examine any influence of the chromophore retinal in bacteriorhodopsin (BR) on the passive proton/hydroxide ion flux through this integral membrane protein. BR was reconstituted into dimyristoylphosphatidylcholine (DMPC)-phosphatidylserine or DMPC-dimyristoylphosphatidylglycerol unilamellar vesicles with molar lipid to protein ratios ranging from 30 to 150. The entrapped fluorescence dye pyranine served as a reliable indicator of the internal proton concentration. Transmembrane pH-gradients were quickly established across the vesicular membrane and the kinetics of the induced fluorescence changes were compared for vesicles with incorporated native BR, BR bleached to the chromophore-free protein bacterioopsin, and BR regenerated from bacterioopsin with all-trans-retinal, respectively. For aggregated protein molecules, the H+/OH- diffusion across bacterioopsin was always considerably faster than that through the protein containing covalently bound retinal. The decay rate of the imposed pH-gradient was 4.4-9.1 and 2.0-5.1 times slower for native and regenerated BR, respectively, as compared to bacterioopsin. Stepwise regeneration of bacterioopsin with all-trans-retinal revealed a linear dependence of the predominant delta pH-decay time on the degree of regeneration. Essentially the same observations were made with monomeric protein molecules in vesicular lipid membranes. The results demonstrate that the chromophore retinal itself blocks the H+/OH- conducting pathway across the transmembrane protein BR or indirectly controls this path by inducing conformational changes in the protein upon binding.

Bacteriorhodopsins↗
PubMed1990

C(13)-substituted bacteriorhodopsin analogs.

13-Ethyl-, 13-isopropyl-, 13-tert-butyl-, 13-phenyl-, 13-alpha-naphthyl-, and 13-demethyl-retinals were synthesized and incubated with bacterioopsin (bO) to give the corresponding bacteriorhodopsin (bR) analogs. The capability of the 13-tert-butyl- and 13-alpha-naphthyl-bRs to exist and to photocycle shows that apparently around C(13) of the chromophore there lies a large enough cavity. A study of the light-induced conversions of the artificial pigments prepared has shown that the introduction at position 13 of the chromophore of the hydrocarbon substituents bulkier than that of the natural bR diminished the amplitudes of the electric photoresponses. Bulky C(13)-substituents or absence of substitution at that position decelerated the relaxation of the M-intermediates and disturbed the 13-cis-in equilibrium all-trans-isomerization.

Bacteriorhodopsins↗