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PubMed1987

An antioxidative role of ocular screening pigments.

The action of ocular screening pigments of vertebrates (melanins) as well as those of invertebrates (ommochromes) on lipid peroxidation has been studied. Lipid peroxidation has been induced by one of the following systems: Fe2+ + ascorbic acid; Fe2+ + NADPH + liver microsomes; xanthine + xanthine oxidase; u.v. illumination; intense visible light, high concentration of O2. Measurements of the lipid peroxidation rate, as estimated from the accumulation of malonic dialdehyde, showed a sharp decrease of the lipid peroxidation rate in the presence of either melanosomes or ommochromes. Synthetic DOPA melanin was also found to exert a strong inhibiting effect on lipid peroxidation. A comparative study of lipid peroxidation in retinal pigment epithelium (RPE) of pigmented and albino rabbits demonstrated that the latter tissue is more sensitive to the effect of the above mentioned prooxidant systems. Apparently this finding is related to the presence of melanin-containing granules in the pigmented tissue rather than to differences in efficiency of other endogenous antioxidant systems. The activities of superoxide dismutase and glutathione peroxidase are practically equal in the RPE of pigmented and albino rabbits whereas the alpha-tocopherol content is higher in albinos. Possible mechanisms of inhibition of lipid peroxidation by melanosomes and ommochromes are discussed. It is proposed that their antioxidant function is one of the most important physiological features of melanins (vertebrate eye) and ommochromes (invertebrate eye).

Albinism↗
PubMed1987

Aging and human macular pigment density. Appended with translations from the work of Max Schultze and Ewald Hering.

The optical density of human macular pigment was measured for 50 observers ranging in age from 10 to 90 years. The psychophysical method required adjusting the radiance of a 1 degree, monochromatic light (400-550 nm) to minimize flicker (15 Hz) when presented in counterphase with a 460 nm standard. This test stimulus was presented superimposed on a broad-band, short-wave background. Macular pigment density was determined by comparing sensitivity under these conditions for the fovea, where macular pigment is maximal, and 5 degrees temporally. This difference spectrum, measured for 12 observers, matched Wyszecki and Stiles's standard density spectrum for macular pigment. To study variation in macular pigment density for a larger group of observers, measurements were made at only selected spectral points (460, 500 and 550 nm). The mean optical density at 460 nm for the complete sample of 50 subjects was 0.39. Substantial individual differences in density were found (ca. 0.10-0.80), but this variation was not systematically related to age.

Accommodation, Ocular↗
PubMed1991

A new template for rhodopsin (vitamin A1 based) visual pigments.

A new template curve for rhodopsin visual pigments is presented. The template was constructed from absorbance spectra of purified bovine rhodopsin with an abscissa transform of lambda max/lambda. Absorbance curves generated from the template are compared with absorbance spectra of visual pigments measured in situ in single cells by microspectrophotometry (msp). The template was found to agree well with msp data which included visual pigments with lambda max values ranging from 450 to 570 nm. A cubic polynomial is given by which the new template may be fitted to the long wavelength limb of visual pigment data. A Chebyshev polynomial is also given which models the new template with a high degree of accuracy. This polynomial provides a convenient method for the computer generation of visual pigment absorbance curves.

Animals↗
PubMed1993

Spectral transmission and short-wave absorbing pigments in the fish lens--II. Effects of age.

Examination of the spectral transmission and pigments present in lenses of sixteen species of fish revealed that changes in lens pigment type and/or concentration often occur with age. Age-related changes in lens transmission for all species could be fitted to a common framework composed of three stages: an initial rapid accumulation of lens pigments producing a large increase in the wavelength of 50% transmission, followed by a reduction in the rate of pigment deposition which results in a levelling of the 50% transmission and a final stage after pigment accumulation ceases producing a drop in the wavelength of 50% transmission.

Aging↗
PubMedDate not supplied

Visual pigments and oil droplets in genetically manipulated and carotenoid deprived quail: a microspectrophotometric study.

The spectral absorbances of visual pigments and retinal oil droplets were studied in three groups of Japanese quail (Coturnix coturnix japonica): an unselected control population and two artificially selected strains that exhibited different early approach preferences between blue and red stimuli. The oil droplets were examined with and without prior carotenoid deprivation. Four cone pigments and five oil droplet types were identified, resembling those in other avian species. Carotenoid deprivation eliminated all pigmentation detectable in oil droplets by microspectrophotometry. Placement of chicks on normal diet gradually reintroduced normal pigmentation within the span of about a week. No statistically significant differences were found between normal and genetically selected birds in either visual pigments or oil droplet types, or in their relative proportions. It is concluded that differences in the early colour preferences of quail are unlikely to be a result of variation in the spectral properties of their photoreceptors.

Animals↗
PubMed1994

Visual pigments and the photic environment: the cottoid fish of Lake Baikal.

The endemic cottoid fish of Lake Baikal in Eastern Siberia offer a singular opportunity for examining within a number of closely related species, the relationships of visual pigments, photoreceptor complements and depth within a deep freshwater environment. The lake, the deepest (1600 m) and one of the largest and most ancient in the world, is unique in that the oxygen levels at the bottom are only reduced to about 80% of the surface levels. We have studied, by light microscopy, microspectrophotometry and visual pigment extraction, the retinas from 17 species of Baikal cottoids that live at different depths within the lake. Generally the retinas contain, in addition to rods, large green-sensitive double cones and small blue-sensitive single cones: surprisingly for freshwater fish, the visual pigments are based on Vitamin A1. The lambda max of both rods and cones are displaced to shorter wavelengths with increasing depth. Surface species have cones with lambda max at about 546, 525 and 450 nm and rods at 523 nm, deeper living species retain cones, but with lambda max shifting towards 500 and 425 nm and with rods at 480 nm, whereas the deepest living fish possess only rods (lambda max 480-500 nm). These data clearly show a correlation between photoreceptor complement, visual pigment lambda max and depth, but question the hypothesis that there is a correlation of pigment lambda max with water colour since, in contrast to oceanic waters, the maximum transmission of Baikal water is between 550 and 600 nm.

Animals↗
PubMed1986

Enhancement of expression of lens phenotype in cultures of pigmented epithelial cells by hyaluronidase in the presence of phenylthiourea.

Pigmented epithelial cells isolated from 8-9-day-old chick embryos can transdifferentiate into lens-like cells at the terminal period of the third generation of culture. However, efficiency of this transdifferentiation is usually rather low. Phenylthiourea, a potent inhibitor of melanin synthesis, effectively enhances transdifferentiation of pigmented epithelial cells into lens-like cells in vitro. Lentoid bodies began to appear in the multilayered region of primary cultures of pigmented epithelial cells maintained in medium containing phenylthiourea at concentrations between 0.5 and 1.0 mM. Furthermore, the enhancing effect of phenylthiourea can be amplified with testicular hyaluronidase. Under these conditions, pigmented epithelial cells grow vigorously and lose their differentiative properties, efficiently switching their phenotype into lens-like cells some 20 days after initiation of culture in the presence of both substances. Semiquantitative analysis revealed that testicular hyaluronidase amplified the effect of phenylthiourea more than 100-fold. It has been suggested that phenotypic expression of pigmented epithelial cells during transdifferentiation can be regulated by manipulating the microenvironment in which these cells reside.

Animals↗
PubMed1978

Accumulation and identification of lipofuscin-like pigment in the neurons of Bulla gouldiana (Gastropoda: Opisthobranchia).

A few reports suggest that pigmented granules found in molluscan neurons accumulate with age as do lipofuscin granules in vertebrate cells; however, no reports on molluscan neurons include detailed descriptions of granule accumulation or histochemical tests to identify the pigment as lipofuscin-like. In this study light microscope observations of living ganglia from 1.7, 2.7, and 3.0 cm and larger (shell length) sized Bulla gouldiana showed an increasing accumulation of orange-red pigment in the perikaryon corresponding to increasing shell size (i.e. age). With the electron microscope similar results were obtained, and lipofuscin-like granules were seen in the nerve cell cytoplasm of veliger larvae and in all adult sized Bulla. Staining with Sudan black B, Nile blue, chrome alum hematoxylin, PAS reagents, and exposure of the neurons to u.v. light to observe subsequent autofluorescence, yielded positive results in the areas of pigmented granule accumulation. Thus, the brillant orange-red granules that accumulate with age in the peripheral cytoplasm of adult Bulla neurons, and which are probably also present in larval stages, chemically resemble the lipofuscin granules of vertebrates. Similarities and differences between molluscan pigmented granules and vertebrate lipofuscin granules, in relation to structure and mechanisms of development and accumulation, are discussed.

Animals↗
PubMed1980

Accumulation of lipofuscin pigment in human hepatic cells from different races and in different environmental conditions.

The changing pattern with age of lipofuscin pigment deposition in the hepatic cells of native and Hawaii Japanese and caucasians in the U.S.A. was micrometrically examined. The amount of pigment was generally largest in the Hawaii Japanese, and smallest in the native Japanese; the age-related increase of the pigment was most marked in the latter. The accumulation of pigment in human hepatic cells is considered to be an age-related change in the hepatic cells, but not necessarily of the individual, and seems to be influenced by a relationship between nutritional conditions and constitution of the individual. Though a possible relationship between age and lipofuscin deposition may be noticed, the accumulation of pigment in the hepatic cells is not necessarily an inherent part of the aging process of the individual.

Adult↗
PubMed1991

Are the differential effects of chloral hydrate on hooded rats vs. albino rats due to pigmentation or strain differences?

Effects of chloral hydrate anesthesia on EEG power spectra and VEP components were examined as a function of both pigmentation and strain differences in rats. Ten albino Westenberg Long Evans rats (WLE A) were compared to ten pigmented Westenberg Long Evans rats (WLE P), and to ten Wistar albino (Wis A) rats. Albino rats required less chloral hydrate to reach a deep level of anesthesia than pigmented rats. Wistar rats remained anesthetized longer than WLE rats. During deep levels of anesthesia, the lowest EEG frequency band contained more power in Wistar rats than in WLE rats. During moderate levels of anesthesia, frequencies less than 4 Hz lost power while frequencies greater than 13 Hz gained across all rats. Wistar rats had more power in the frequencies less than 8 Hz than did WLE rats; pigmented rats had more power in the frequencies greater than 13 Hz than did albinos. VEP component latencies of pigmented rats were shorter than albinos. Component amplitudes were not significantly different between groups.

Anesthesia↗
PubMed1986

Bidirectional pigment granule movements of melanophores are regulated by protein phosphorylation and dephosphorylation.

Studies were conducted to investigate the molecular basis for bidirectional pigment granule transport in digitonin-lysed melanophores. Pigment granule dispersion, but not aggregation, required cAMP and resulted in the phosphorylation of a 57 kd polypeptide. cAMP-dependent protein kinase inhibitor prevented this phosphorylation as well as pigment dispersal. In contrast, both pigment aggregation and the concomitant dephosphorylation of the 57 kd polypeptide were blocked by phosphatase inhibitors. These data support a model in which pigment dispersion and aggregation require protein phosphorylation and dephosphorylation, respectively. Furthermore, studies using the ATP analog, ATP gamma S, suggest either that protein phosphorylation alone is sufficient for dispersion or that transport is mediated by a unique force-generating ATPase that can use ATP gamma S for hydrolyzable energy.

Adenosine Triphosphate↗
PubMed1996

A possible involvement of melanocortin 1-receptor in regulating feather color pigmentation in the chicken.

The Extended black (E) locus on chromosome 1 acts within the melanocyte to regulate feather color pigmentation in the chicken. Several alleles exhibiting different pigmentation have been described and their phenotypes are similar to those of the murine extension locus which encodes melanocortin 1-receptor (MC1-R), the receptor for alpha-melanocyte-stimulating hormone (alpha-MSH). To investigate whether the MC1-R gene is responsible for E-locus function, we examined the structure of MC1-R in E-locus mutants by RFLP analysis and genomic DNA sequencing. In the most recessive allele (ey), which exhibits a uniformly red-yellow pigmentation, MC1-R was found to contain amino acid substitutions possibly causing functional deficiency. On the other hand, in the most dominant allele (E), which confers a uniformly black pigmentation, MC1-R possessed mutation responsible for a constitutively active MC1-R and resultant black coat color in mice. Our finding that the structure of MC1-R was affected by individual E-locus alleles strongly suggests that MC1-R is associated with the E-locus. Furthermore, since the same mutation of MC1-R was found in mice and chickens that exhibit the same pigmentation, it is possible that the regulatory mechanism of MC1-R function is shared in chickens and mammals.

Alleles↗
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↗
PubMedDate not supplied

Effect of melanin concentrating hormone on pigment and adrenal cells in vitro.

Highly purified synthetic salmonid melanin concentrating hormone (MCH) and some analogs were investigated for their ability to concentrate the pigment in scale melanophores of the Chinese grass carp, Ctenopharyngodon idellus, to produce melanin dispersion in frog or lizard melanophores and to inhibit alpha-MSH in its action on mouse melanoma and rat adrenal glomerulosa cells in vitro. In the grass carp, MCH produced half-maximal pigment aggregation at 6 X 10(-11) M and its oxidized form at 7 X 10(-11) M. Replacement of the two methionines at position 3 and 6 with norvaline lowered the potency by a factor of 2.7 and with propargylglycine by a factor of about 7. Linear, Cys5,14-Acm-protected MCH was a full agonist of MCH but with a 345-fold lower potency. Iodinated MCH showed similar, low activity. In tetrapods, salmonid MCH and its analogs displayed only marginal pigment dispersion at concentrations greater than 10(-5) M. Alkali-treatment of MCH increased the pigment-dispersing potency by a factor of about 30 whereas the activity for pigment aggregation in the grass carp was destroyed. At high concentrations (10(-6), 10(-5) M) MCH also stimulated tyrosinase activity in B-16 mouse melanoma cells but did not modify the effects of alpha-MSH in this system. By contrast, when tested on rat adrenal glomerulosa cells, salmonid MCH had no effect alone but at a concentration of greater than 10(-10) M it slightly reduced corticosterone production by an alpha-MSH concentration of 10(-7) M. Aldosterone production was not affected and MCH did not influence the response to ACTH.

Adrenal Cortex↗
PubMed1990

Development and degeneration of retina in rds mutant mice: immunoassay of the rod visual pigment rhodopsin.

Development and loss of photoreceptor cells in mice, afflicted by the rds (retinal degeneration slow) gene, was analyzed by measuring the ocular visual pigment content as rhodopsin (spectroscopy) and opsin (immunoassay). With regard to the postnatal age, where opsin was just detectable, and to the initial rate of opsin synthesis, the mutants did not strongly deviate from the normal animals. The final maximal visual pigment level was, however, about half of normal for the heterozygous mutants and about 3% of normal for the homozygous mutants, both in the pigmented and in the albino strain. In the pigmented normal or heterozygous mutant the (rhod)opsin levels remain stable up to at least 1 year of age. For the corresponding albino animals this was only observed up to 9 months of age. Thereafter the level declines. In the homozygous mutants, maximal opsin levels were observed at about 3 weeks postnatal. Subsequently, this level gradually declined to about 40% in the pigmented and about 15% in the albino mutant. The results indicate that the rds gene does not directly affect the biosynthetic pathways of opsin. The physiological effect of the rds gene is aggravated by photodamage for which the albino animal is particularly susceptible.

Aging↗
PubMed1988

Quantification of age pigments (lipofuscin).

1. Three methods have hitherto been applied for age pigment quantification: (a) numerically from micrographs; (b) fluorimetrically from histological sections; (c) spectrofluorimetrically from dissolved age pigments. 2. The spectrofluorimetric method is at present the most commonly used technique for quantification of age pigments. 3. By comparing the related publications since introduction of the spectrofluorimetric method, it has become apparent that few authors specify fluorimetrically significant factors, such as temperature and pH which influence the sample fluorescence during measurement. 4. Recent developments in fluorimetrical age pigment quantification using chloroform/methanol as solvent have additionally revealed the necessity to measure and present the age pigments dissolved in both phases: the polar and non-polar solvents.

Aging↗
PubMed1994

Pigmentation dependent, short time skin reactions to copper vapour laser and argon laser treatment.

Thirteen human volunteers selected to have a varying degree of epidermal skin pigmentation were laser treated on the inside of the brachium in six hexagonal areas; three areas with an argon laser (AL, 488, 514.5 nm) and three corresponding areas with a copper vapour laser (CVL, 578 nm). The lasers were connected to a Hexascan device and the physical settings were identical for the two laser types, except for the wavelengths. Beam diameter was 1 mm, pulse duration 200 ms, intensities 0.7, 1.0 and 1.3 W/spot, corresponding to 14.1, 20.2 and 26.2J/cm2 per treated skin area. The skin pigmentation was objectified by skin reflectance. A correlation was demonstrated between skin pigmentation and wound healing time, maximum wound area, and the acute clinical response at days 0, 1, 4, 7, 11 and 17 after laser treatment. An increased skin pigmentation resulted in increased acute and subacute skin reactions. Comparison of the AL and the CVL demonstrated that the CVL on day 0 (0.7 and 1.0 W/spot) and on day 1 (0.7 W/spot) induced a significantly higher degree of skin reactions as compared with the AL. At 0.7 W/spot the CVL induced a significantly higher maximum wound area and a significantly prolonged wound healing time as compared with the AL. An inverse reaction existed between pigmentation and the threshold intensity required to induce wound formation.

Adult↗
PubMed1996

Centripetal transport of herpes simplex virus in human retinal pigment epithelial cells in vitro.

Herpes simplex virus displays tropism for neurons and other polarized epithelial cells. We have grown human retinal pigment epithelial cells in culture to study potential mechanisms whereby herpes simplex virus (type I) is transported from the plasma membrane of the cell to the nucleus. The cells were highly polarized as determined by a variety of criteria. They were tightly coupled by junctional complexes, as determined by electron microscopy, immunofluorescent staining of tight junctions and measurements of transepithelial electrical resistances > 200 omega cm2. Immunofluorescence and confocal microscopy were used to visualize microtubule orientation. The microtubules were arranged (i) in a single apical cilium, (ii) in a meshwork beneath the apical membrane and (iii) in longitudinally arranged bundles near the lateral membranes and nucleus. The latter microtubules were primarily oriented with their plus ends directed toward the basal surface of the cells. We infected retinal pigment epithelial cells at the apical surface with virus and assayed the uptake and transport of virus to the nucleus by quantitative immunoblot and immunocytochemical staining for the viral immediate early gene product, infected cell protein 4. The antigen first appeared in retinal pigment epithelial cells 2 h after infection. Treatment of the cells with 33 microM nocodazole, a microtubule-destabilizing drug, delayed the appearance of the viral antigen by 1 h. The effect of nocodazole treatment on microtubule integrity was confirmed by immunofluorescent staining and immunoblots of tubulin. Both cytoplasmic dynein and the ubiquitous form of kinesin were identified in the cells using immunoblots. These novel data indicate that human retinal pigment epithelial cells, like neurons, are susceptible to infection by herpes simplex virus and that the centripetal transport of virus to the nucleus in both cell types is facilitated by microtubules. The orientation of microtubules in retinal pigment epithelial cells suggests that the transport of herpes simplex virus from the apical surface is mediated by a microtubule-activated motor enzyme, possibly kinesin.

Biological Transport↗