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PubMed1999

Melanotic pigmentation in excision scars of melanocytic and non-melanocytic skin tumors.

The appearance of pigmented lesions in melanoma surgical scars is a frequent finding that in some instances may cause confusion with a melanoma persistence. Nevertheless, only a few papers have dealt with this subject in the dermatologic literature. The melanoma surgical scars of 60 consecutive patients were reviewed with special attention to the presence of pigmentation and its clinical characteristics. Simultaneously, the scars of 60 consecutive patients who had been subjected to excision of a non-melanoma skin tumor were also studied. Biopsies were performed in representative clinical cases of pigmented lesions arising on the scars of both groups, as well as in non-pigmented scars, and processed for hematoxylin-eosin and immunohistochemistry. Pigmented lesions were present in a similar percentage in both groups (30% in melanoma scars (18/60) and 25% in non-melanoma scars (15/60)). Clinically, three types of clinical pigmentation were observed: lentigine-like lesions; pigmented streaks in scars after direct closure; and diffuse pigmentation in grafts. Histologically, two patterns emerged: one with lentiginous epidermal hyperplasia, hyperpigmentation, and a normal or moderately increased number of melanocytes; and a second one characterized by melanocytic hyperplasia of a variable degree. The scar process itself, irrespective of the tumor excised, seems to be responsible for the pigmentation. We suggest the existence of an induction process of scar tissue acting on melanocytes of the overlying epidermis.

Adult↗
PubMed1984

Thyroid gland pigmentation and minocycline therapy.

Thyroid pigments in black thyroid glands from minocycline-treated patients were compared by light and electron microscopy, histochemistry, and energy-dispersive x-ray analysis with minocycline-induced pigment in thyroid glands of laboratory animals, and with naturally occurring lipofuscins in untreated laboratory animals and humans. All thyroid samples examined contained nonbirefringent, Schmorl-positive pigment. However, the pigments in black thyroids from minocycline-treated patients resembled lipofuscins of untreated humans since both fluoresced and were Ziehl-Neelsen- and Sudan IV-positive. Minocycline induced pigment in rats was nonfluorescent and Ziehl-Neelsen- and Sudan IV-negative. Ultrastructurally, pigments in black thyroid glands of minocycline-treated humans resembled lipofuscins in untreated humans, and initial elemental analyses yielded similar spectra. Repeated analyses of the most electron-dense pigment deposits yielded spectra that resembled those of minocycline-induced pigment in laboratory animals-ie, both contained calcium. Black thyroid glands associated with minocycline administration contained predominantly lipofuscins with a small amount of another, possibly minocycline-related pigment. The absence of functional changes in patients and animals given minocycline suggests that discoloration of the thyroid gland associated with minocycline administration is innocuous. This is further supported by the lack of documented changes in thyroid physiology in patients that have received tetracyclines for a variety of indications in the last 30-odd years since their introduction to therapy.

Adult↗
PubMedDate not supplied

[Is the pigmentation a characteristic sign for chronic venous insufficiency?].

In epidemiological studies pigmentations were declared a decisive criterium of stadium II of chronic venous insufficiency. It is discussed in this work if it is possible as the pigmentation is sometimes absent in advanced stages of chronic venous insufficiency. On the other hand it has got to be considered that there are many other possibilities of pigment building on the legs without chronic venous insufficiency. Pigmentation may be of actinic, endocrine, atrophic or especially of inflammatory origin. These pigmentations cannot be differentiated from those caused by chronic venous insufficiency macroscopically, and therefore, in our opinion, the question if pigmentation is a specific sign for chronic venous insufficiency has to be negated. Further, it is examined if the histomorphology of the pigmentation caused by chronic venous insufficiency offers a different aspect from that caused by other diseases. Special attention is given to the pigments containing melanin and iron. Melanin, as an example, is increased in skin inflammation whether there is chronic venous insufficiency or independent of any edematous changes, In subfascial chronic venous insufficiency without any inflammatory component, only the pigment containing iron increased.

Chronic Disease↗
PubMed1988

Histopathologic features of adult-onset foveomacular pigment epithelial dystrophy.

We studied the clinical and histopathologic characteristics of the eyes obtained after death from a patient with adult-onset foveomacular pigment epithelial dystrophy. The pigmentation seen in the central fovea corresponded histologically to a hyperplastic clump of retinal pigment epithelium. The pale yellow rim surrounding the central pigmentation corresponded histologically to dense periodic acid-Schiff-positive material underlying thinned, atrophic retinal pigment epithelium. Fluorescence microscopy demonstrated homogeneous autofluorescence in the retinal pigment epithelium that was similar in intensity to that of an age-matched control. The results of this clinicopathologic study suggest that in adult-onset foveomacular pigment epithelial dystrophy, an alteration of macular retinal pigment epithelium causes an accumulation of abnormal subretinal pigment epithelial material, photoreceptor degeneration, and serous retinal detachment.

Aged↗
PubMed1995

Retinal pigment epithelial repopulation in monkeys after submacular surgery.

BACKGROUND: Transplantation of retinal pigment epithelium may be a treatment for retinal diseases, such as age-related macular degeneration and hereditary macular degeneration. Before transplantation studies are undertaken, questions concerning repopulation of retinal pigment epithelial cells in situ and photoreceptor repair after submacular surgery need to be addressed. METHODS: We removed the retinal pigment epithelium from Bruch's membrane in the macaque monkey in the macula and outside the vascular arcades. This model allowed the study of in situ retinal pigment epithelium regrowth and photoreceptor repair for 9 months following débridement. RESULTS: Fluorescein angiography revealed a window defect in the area of denuded retinal pigment epithelium. Histologic studies revealed repopulated nonpigmented retinal pigment epithelial cells in the denuded areas in both the early and late periods. At 9 months, the repopulated retinal pigment epithelium was associated with repaired, normal-appearing photoreceptor outer segments. Retinal pigment epithelium regrowth was observed only if Bruch's membrane was intact. CONCLUSIONS: Repopulation of retinal pigment epithelium in the adult primate can occur rapidly and can support the repair of damaged photoreceptors following submacular surgery.

Animals↗
PubMed1999

A clinical study on the removal of gingival melanin pigmentation with the CO(2) laser.

BACKGROUND AND OBJECTIVE: In a previous study, the possibility of removal of dog gingival melanin pigmentation with CO(2) laser therapy was reported. The present study was designed to investigate the effect of the CO(2) laser on human gingival pigmentation and evaluate the clinical outcome. STUDY DESIGN/MATERIALS AND METHODS: A CO(2) laser (output: 6-8 W, pulse duration: 0.2 seconds) was irradiated on the melanin pigmented gingival surface of 10 patients, aged 20-49 years. Follow-up clinical and histopathological evaluations were performed. RESULTS: The CO(2) laser was effective in removing melanin pigmentation in all patients. In the histopathological study, no pigmented-laden cells nor any inflammatory cell infiltration was observed following laser irradiation. No re-pigmentation was seen in any case in the first year. However, four of seven cases showed re-pigmentation at 24 months. The re-pigmentation was almost equal to the preoperative state. CONCLUSIONS: The CO(2) laser has proved to be another effective, safe, and easily applicable therapy for the removal of gingival melanin pigmentation.

Adult↗
PubMed1982

Pigmented olfactory neuroblastoma: a new example of melanotic neuroepithelial neoplasm.

The light and electron microscopic features of a pigmented olfactory neuroblastoma are described. The neuroblastic nature of the tumor was confirmed by the demonstration of axons, some of which originated from the neoplastic cells, and by the presence of dense-core vesicles in the perikarya and processes of the tumor cells. The tumor contained a large amount of pigment, most of which had the histochemical reactions of melanin, but some of which had that of lipofuscin. Electron microscopy failed to demonstrate the presence of melanosomes or premelanosomes: the pigment showed some of the features of neuromelanin, although the fine structural appearances were not typical. The pigment was interpreted in this case as presumably representing a modified catecholamine degradation product, perhaps related to lipofuscin. The presence of melanotic pigment in an example of olfactory neuroblastoma, unreported until now, augments the list of neurogenic neoplasms in which an association with melanin formation has been described. The significance of this association in tumors originating from the nervous system or its coverings needs further investigation, as the nature of pigment appears to be heterogeneous. These tumors may contain either melanosomal pigment or pigment identified as neuromelanin (or a related substance), seemingly regardless of the derivation of the pigment-bearing cells.

Adult↗
PubMed1995

One-step extraction and concentration of pigments and acyl lipids by sec-butanol from in vitro and in vivo samples.

Photosynthetic pigments and acyl lipids were simultaneously extracted and concentrated by sec-butanol. Pigments extracted with sec-butanol were indistinguishable from those extracted using acetone as determined by quantitative and qualitative HPLC. Use of sec-butanol has several advantages over conventional extraction solvents: (1) pigments are extracted directly from polyacrylamide gel slices without an elution step; (2) pigments in dilute, isolated pigment-protein complexes are extracted and concentrated without first concentrating the sample; (3) when necessary, the concentration factor is readily increased by addition of water; (4) sec-butanol extracts acyl lipids and vitamin K1 as effectively, but much quicker, than chloroform:methanol; (5) sec-butanol rapidly extracts and concentrates pigments from thylakoids of all plant species tested and even directly from many algal/higher plant cells, facilitating analysis of pigment biosynthetic pathways using radioactive substrates; and (6) pigments are stable in sec-butanol for several days at room temperature in the dark or for many weeks if stored at -20 degrees C in darkness. Finally, sec-butanol is preferable to ether for concentrating pigments extracted with acetone.

Butanols↗
PubMed1994

Cytokine regulation of nitric oxide synthase in mouse retinal pigment epithelial cells in culture.

Nitric oxide is an intercellular signaling molecule whose numerous functions include regulation of vascular tone, mediation of the cytotoxic effects of macrophages and potentiation of synaptic transmission. For some cellular functions, nitric oxide synthesis is mediated by the inducible form of nitric oxide synthase. We now show that cultured mouse retinal pigment epithelial cells exposed to interferon-gamma and lipopolysaccharide, express inducible nitric oxide synthase. The latter was detected immuno-cytochemically in interferon-gamma-lipopolysaccharide-treated retinal pigment epithelium using rabbit antiserum to a synthetic peptide of mouse nitric oxide synthase. Untreated cultures of retinal pigment epithelium or cultures treated with either interferon-gamma or or lipopolysaccharide alone were not immunoreactive. Induction of iNOS in gamma-interferon-lipopolysaccharide-stimulated retinal pigment epithelial cells was also evidenced by the presence of nitric oxide synthase enzyme activity in lysates of stimulated but not unstimulated retinal pigment epithelial cells. On immunoblots of lysates of stimulated murine retinal pigment epithelial cells, rabbit antiserum to iNOS recognized a 130-kDa protein which comigrated with the inducible nitric oxide synthase of macrophages and which was not detectable in lysates of unstimulated retinal pigment epithelial cells nor in lysates of cells treated with only interferon-gamma or lipopolysaccharide alone. Nitrite, a stable endproduct of NO formation by cells, was detectable in the culture supernatants after 18-24 hr of exposure to interferon-gamma and lipopolysaccharide, and continued to accumulate in a linear fashion for at least 96 hr. Treatment of cultured retinal pigment epithelium with interferon-gamma, lipopolysaccharide and either basic fibroblast growth factor or epidermal growth factor as third signals augmented inducible nitric oxide synthase expression as evidenced by intensified signals on immunoblots, enhanced accumulation of nitrite and increased iNOS enzyme activity. Conversely, when transforming growth factor-beta was present in the culture medium, gamma-interferon-LPS-induced expression of nitric oxide synthase and NO release were reduced. We conclude that interferon-gamma synergizes with lipopolysaccharide to induce synthesis of inducible nitric oxide synthase and production of nitric oxide by murine retinal pigment epithelium and that this induction can be modulated by basic fibroblast growth factor, epidermal growth factor or transforming growth factor-beta.

Amino Acid Oxidoreductases↗
PubMed1996

Interleukin-1 beta increases prostaglandin E2-stimulated adenosine 3',5'-cyclic monophosphate production in rabbit pigmented ciliary epithelium.

This study was designed to determine the effects of interleukin-1 on basal and prostaglandin E2-stimulated adenosine 3',5'-cyclic monophosphate production by primary and first passage cultures of non-transformed rabbit pigmented and non-pigmented ciliary epithelial cells. Confluent cultures of rabbit pigmented and non-pigmented ciliary epithelial cells were incubated for varying periods of time in serum-free medium with or without interleukin-1 beta, tumor necrosis factor-alpha, bacterial lipopolysaccharide, transforming growth factor-beta 2, cycloheximide, indomethacin and combinations of these agents. Cells were then preincubated for 10 min with serum-free medium plus the phosphodiesterase inhibitor, 3-isobutyl-1-methylxanthine (for basal adenosine 3',5'-cyclic monophosphate production) or serum-free medium containing several concentrations of prostaglandin E2 and 3-isobutyl-1-methylxanthine. In certain experiments isoproterenol, vasoactive intestinal peptide, or forskolin was substituted for prostaglandin E2. Adenosine 3',5'-cyclic monophosphate was then extracted into ice-cold absolute ethanol and measured by radioimmunoassay. Prostaglandin E2 stimulated adenosine 3',5'-cyclic monophosphate production in pigmented and non-pigmented ciliary epithelial cells in a dose-dependent manner. Incubation with interleukin-1 beta (150 U ml-1) increased prostaglandin E2-stimulated, but not basal adenosine 3',5'-cyclic monophosphate production in pigmented ciliary epithelial cells. This interleukin-1 beta-induced enhancement of prostaglandin E2-stimulated adenosine 3',5'-cyclic monophosphate production, called the interleukin-1 effect, was not seen with non-pigmented ciliary epithelial cells. The interleukin-1 effect was dependent upon interleukin-1 beta concentration, time and de novo protein synthesis. The interleukin 1 effect could not be reproduced by replacing interleukin-1 beta with tumor necrosis factor-alpha or bacterial lipopolysaccharide and was specific for prostaglandin E2, since interleukin-1 beta did not enhance isoproterenol-, vasoactive intestinal peptide-, or forskolin-induced adenosine 3',5'-cyclic monophosphate production. Chronic exposure to prostaglandin E2 (during the 3 hr incubation period), with or without interleukin-1 beta in the incubation medium, reduced subsequent prostaglandin E2-stimulated adenosine 3',5'-cyclic monophosphate production. Inhibition of de novo prostaglandin synthesis with indomethacin increased the interleukin-1 effect. The interleukin-1 effect was inhibited by the immunosuppressive cytokine, transforming growth factor-beta 2, in a dose-dependent manner. This is the first report of prostaglandin E2-induced stimulation of adenosine 3',5'-cyclic monophosphate production by pigmented ciliary epithelial cells and of the unique ability of interleukin-1 to increase this effect. The results are consistent with interleukin-1-induced upregulation of prostaglandin E receptors. Since transforming growth factor-beta 2 inhibited this interleukin-1 effect, this immunosuppressive cytokine may exert negative feedback and thus regulate the physiological consequences of the interleukin-1 effect.

Animals↗
PubMed1997

Tissue culture of retinal pigment epithelium following isolation with a gelatin matrix technique.

Prior to transplantation of the retinal pigment epithelium, it is necessary to develop techniques to harvest viable retinal pigment epithelium as an organized monolayer. Unfortunately, current techniques result in contraction of the harvested monolayer and coiling of the cell sheets, which hinders successful transplantation. The purpose of this study was to develop a method for harvesting retinal pigment epithelium from eye cups and from tissue culture prior to transplantation. Passage 1 porcine retinal pigment epithelium and native retinal pigment epithelium from fresh porcine eye cups were pretreated with 0.25% edetic acid for 12 minutes and coated with a 100 micron layer of 12% gelatin. Patches of the retinal pigment epithelial cell monolayer were harvested and transferred to culture plates, and cell viability and the ability of the transferred cells to proliferate in culture was determined. Our results demonstrated that retinal pigment epithelium can be harvested from tissue culture and eye cups as an organized monolayer with high efficiency (94.7 +/- 3.5% and 99.7 +/- 0.3% harvesting rates, respectively) and high cell viability (91.3 +/- 2.9% and 89.4 +/- 4.3%, respectively). Cells harvested from tissue culture plates divided and became confluent within 10 to 14 days. Cells harvested from eye cups maintained a differentiated phenotype and migrated outward from the margin of the exoplant. There was no contraction of the retinal pigment epithelial monolayer isolated from either substrate. Thus, we were able to harvest retinal pigment epithelium as an organized monolayer from tissue culture plates and freshly enucleated eyes with edetic acid and gelatin. The harvested cells were viable and proliferated without contraction of the monolayer in vitro.

Animals↗
PubMed1998

In vitro transplantation of fetal human retinal pigment epithelial cells onto human cadaver Bruch's membrane.

Retinal pigment epithelium transplantation has been proposed as adjunctive treatment for age-related macular degeneration following surgical excision of choroidal neovascular membranes. The goal of this study was to develop a model to evaluate retinal pigment epithelium transplantation onto human Bruch's membrane in vitro. We investigated the ability of cultured fetal human retinal pigment epithelium to colonize human cadaver Bruch's membrane, determined the incubation time needed to form a monolayer and to exhibit apical microvilli and tight junctions, and assessed the production of basement membrane. Freshly enucleated (less than 48 hours old) human eyes were cut through the pars plana, and the anterior segment, vitreous, and retina were removed. The native retinal pigment epithelium was debrided with a surgical sponge. Bruch's membrane and choroid at the macula were trephined with a 7.0 mm diameter trephine and then incubated with 1/2 ml of Dulbecco's modified Eagle's medium +15% fetal calf serum+basic fibroblast growth factor (1 ng ml-1), and fetal human retinal pigment epithelium at a concentration of 242,000 cells ml-1. Specimens were incubated for 1, 4, 6, 8, 12, or 24 hours. The specimens were fixed in half strength Karnovsky's fixative, processed, and analysed with scanning and transmission electron microscopy. The retinal pigment epithelium covered the debrided macular specimens to different degrees at different incubation times. After 1 hour, the cells started to attach and flatten (median percent coverage: 78%). The extent of Bruch's membrane coverage by fetal retinal pigment epithelium varied greatly between specimens. After 4-6 hours, the cells covered the entire debrided surface in a monolayer (median percent coverage: 97.2% at 4 hours, 99.8% at 6 hours). Tight junctions were observed, and the cells had few apical microvilli. The lateral cell borders were obliquely oriented with respect to Bruch's membrane, and the nuclei were elongated, exhibited prominent nucleoli, and were oriented parallel to Bruch's membrane. After 6-8 hours, cells started to become hexagonal (median percent coverage at 8 hours: 99.97%). Cells attached to the inner collagenous layer tended to be flatter than cells attached to residual native basement membrane. At 12 and 24 hours, expression of hexagonal shape, tight junctions, and apical microvilli were observed more frequently (median percent coverage: 99.87% at 12 and 100% at 24 hours). No newly formed basement membrane was observed at these time points. In separate experiments comparing attachment in the presence and absence of native RPE basement membrane, the presence of native retinal pigment epithelial basement membrane promoted the early attachment of the cells and more rapid expression of normal morphology. This in vitro system provides a reproducible way to study the adherence of retinal pigment epithelium to normal and diseased human Bruch's membrane.

Aged↗
PubMed1991

Labelling of regenerating retinal pigment epithelium by colloidal iron oxide and ferritin conjugated to wheat germ agglutinin.

In order to determine if there are biochemical changes in plasma-membrane oligosaccharides of regenerating retinal pigment epithelium, the binding of colloidal iron oxide at low pH and ferritin-conjugated wheat germ agglutinin--probes of sialic acid and N-acetylglucosamine on the cell surface--was examined electron-microscopically. An animal model of retinal pigment epithelium regeneration--rabbits with sodium iodate induced retinopathy--was used. In this model, large expanses of regenerating pigment epithelium are present for comparison with zones of spared pigment epithelium in the same animals. In thin sections examined by transmission electron microscopy, ferritin-conjugated wheat germ agglutinin appeared to bind more intensely to the exposed plasma membrane of regenerating retinal pigment epithelium than to spared pigment epithelium, or that of normal rabbits. Morphometry verified this. Colloidal iron oxide intensely labelled the plasma membranes of regenerating, spared, and normal pigment epithelium, and was visibly reduced after exposure of tissue to neuraminidase. The observations indicate that the plasma membrane of regenerating retinal pigment epithelium bears sialic acid and N-acetylglucosamine residues as in normal retinal pigment epithelium. However, the amount of plasma membrane bearing exposed N-acetylglucosamine increases during regeneration.

Animals↗
PubMed1989

Interspecific variation in the visual pigments of deep-sea fishes.

Visual pigments in the rods of 38 species of deep-sea fish were examined by microspectrophotometry. 33 species were found to have a single rhodopsin with a wavelength of maximum absorbance (lambda max) in the range 470-495 nm. Such visual pigments have absorbance maxima close to the wavelengths of maximum spectral transmission of oceanic water. 5 species, however, did not conform to this pattern and visual pigments were found with lambda max values ranging from 451 nm to 539 nm. In 4 of these species two visual pigments were found located in two types of rod. Some 2-pigment species which have unusual red sensitivity, also have red-emitting photophores. These species have both rhodopsin and porphyropsin pigments in their retinae, which was confirmed by HPLC, and the two pigments are apparently located in separate rods in the same retinal area. In deep-sea fishes the occurrence of 'unusual' visual pigments seems to be correlated with aspects of the species' depth ranges. In addition to ecological influences we present evidence, in the form of lambda max spectral clustering, that indicates the degree of molecular constraint imposed on the evolution of visual pigments in the deep-sea.

Animals↗
PubMed1982

Studies on the development of extra-endothelial and intra-endothelial pigment deposits by means of direct and indirect contact specular microscopy of the cornea.

Retro-corneal pigmentation as a result of primary (degenerative) or secondary (inflammatory, traumatic) pigment dispersion represents one of the most frequent findings in specular microscopy. The analysis of the pigment distribution patterns of dense deposits like those in Krukenberg spindle (KS) permits the postulation of a hypothesis concerning the development of such typical corneal pigmentations and the pigmentation of the posterior surface of the cornea in general, such as diffuse pigment dispersion (Vogt 1930), which is seen frequently. In a particular case of double KS with extreme myopia and cataract, endothelial morphological findings were documented over a period of 1 year, both before and after cataract extraction. This was done by means of contact and non-contact specular microscopy in various spindle areas. The morpho-metric studies (cell density/mm2; cell perimeter; largest smallest and average cell diameter; specific surface; horizontal and vertical cell orientation) were carried out automatically using a computerised video image analyser. The changes in the area of densest pigmentation in the KS centre confirm the histologically proven capacity of pigment phagocytosis by human corneal endothelium. These findings indicate that in specular microscopy, both endothelial cellular surface modifications and intra-cellular changes are documentable. The extracellular pigment deposits can also be shown by means of 'indirect' specular microscopy, the optical principle of which is described.

Aged↗
PubMed1982

Induction of pigmentation by continuous X-irradiation of amelanotic tumors of B16-XI mouse melanoma and induced change in chromosomes of amelanotic cells.

Non-pigmented tumor cells of B16-XI mouse melanoma were found to contain a diploid number of chromosomes similarly to those of melanotic tumors and the parental cells in tissue culture. A major difference between pigmented and non-pigmented cells was in the number of biarmed chromosomes per cell. There was no difference in growth rate between non-pigmented and pigmented tumors, but growth usually begins about 2 days earlier in the former. Pigmentation lost in the course of serial transplantation was restored by irradiating the non-pigmented tumor continuously with 2,500-3,000 rads/passage of X-rays during six transfer generations. In the course of repeated irradiations, the chromosomes changed structurally and numerically as the pigmentation of the tumor was gradually restored. The observations of tumor growth and chromosomal changes are discussed in relation to the pigmentation of B16-XI melanoma cells.

Animals↗
PubMed2002

Temporal variation in community composition, pigmentation, and F(v)/F(m) of desert cyanobacterial soil crusts.

Summers on the Colorado Plateau (USA) are typified by harsh conditions such as high temperatures, brief soil hydration periods, and high UV and visible radiation. We investigated whether community composition, physiological status, and pigmentation might vary in biological soil crusts as a result of such conditions. Representative surface cores were sampled at the ENE, WSW, and top microaspects of 20 individual soil crust pedicels at a single site in Canyonlands National Park, Utah, in spring and fall of 1999. Frequency of cyanobacterial taxa, pigment concentrations, and dark adapted quantum yield [F(v)/F(m)] were measured for each core. The frequency of major cyanobacterial taxa was lower in the fall compared to spring. The less-pigmented cyanobacterium Microcoleus vaginatus showed significant mortality when not in the presence of Nostoc spp. and Scytonema myochrous (Dillw.) Agardh. (both synthesizers of UV radiation-linked pigments) but had little or no mortality when these species were abundant. We hypothesize that the sunscreen pigments produced by Nostoc and Scytonema in the surface of crusts protect other, less-pigmented taxa. When fall and spring samples were compared, overall cyanobacterial frequency was lower in fall, while sunscreen pigment concentrations, chlorophyll a concentration, and F(v)/F(m) were higher in fall. The ratio of cyanobacterial frequency/chlorophyll a concentrations was 2-3 times lower in fall than spring. Because chlorophyll a is commonly used as a surrogate measure of soil cyanobacterial biomass, these results indicate that seasonality needs to be taken into consideration. In the fall sample, most pigments associated with UV radiation protection or repair were at their highest concentrations on pedicel tops and WSW microaspects, and at their lowest concentrations on ENE microaspects. We suggest that differential pigment concentrations between microaspects are induced by varying UV radiation dosage at the soil surface on these different microaspects.

Climate↗
PubMed2002

Macular pigment and visual acuity in Stargardt macular dystrophy.

PURPOSE: To test the hypothesis that macular pigment reflects foveal cone function and possibly the presence of foveal cones in recessive Stargardt macular dystrophy. METHODS: Sixteen patients (32 eyes) diagnosed to have Stargardt macular dystrophy by clinical criteria were studied with a scanning laser ophthalmoscope (SLO) comparing argon laser blue (488 nm), green (514), helium-neon laser red (633 nm) and infrared diode laser (780 nm) images for the presence or absence of macular pigment in the fovea. Fifteen of the patients were screened for mutations in the ABCR gene. Eyes were graded into three categories: those without foveal macular pigment, those with partial pigment and those with normal amounts of macular pigment. These categories were compared with visual acuity determined by the Snellen chart. RESULTS: All patients with a visual acuity of 20/200 or worse had no macular pigment in the fovea. All patients with visual acuity of 20/40 or better had a normal amount of macular pigment in the fovea. Patients with partial macular pigment had intermediary acuity values except for two eyes, one with 20/20 and another with 20/200 acuity. Infrared light revealed more retinal abnormalities than blue light at early stages of the disease. CONCLUSION: Foveal macular pigment is related to foveal cone acuity in Stargardt macular dystrophy and may be a marker for the presence of foveal cones. Infrared light is a sensitive monitor of early Stargardt macular dystrophy.

Adolescent↗