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At least 19 recordsLinked to original sources
PubMed1977

Comparative treatment of psoriasis with UV-light, trioxsalen plus UV-light, and coal tar plus UV-light.

Areas within psoriasis plaques have been treated with UV-light alone, trioxsalen plus UV-light, and coal tar (liquid carbonis detergens) plus UV-light, using the 313, 365 and 405 nm wavelength bands in various doses. With the 313 nm band, the same degree of healing was obtained with all three types of treatment. With the 365 nm band, no healing was achieved with UV-light alone, but healing did occur with UV-light when the skin was sensitized with trioxsalen. Coal tar itself has a certain healing effect on psoriasis but the effect is so markedly enhanced by light of the 365 nm band that the healing is comparable to that obtained with the 313 nm band. No healing was seen with light of the 405 nm band. The patients who were healed with the 313 nm band alone, also healed with trioxsalen or coal tar plus UV-light of the 365 nm band. With each method there is an individual optimal light dose of 1--2 MED that gives healing.

Coal Tar↗
PubMed1976

Measurements on fast light-induced light-scattering and -absorption changes in outer segments of vertebrate light sensitive rod cells.

Flash-induced changes of light-absorption and of light-scattering of vertebrate rod outer segments (ROS) from frog and cattle in suspension were measured at 380 and 800 nm. The photometer used allows the observation of light intensity changes under well defined angles. We studied the successive decrease of the signal amplitude in series of flashes. One flash bleaches about 1% rhodopsin. The following results are discussed: 1. The signal at 380 nm is a superposition of the absorption change caused by formation of metarhodopsin II and of a biphasic additional signal. The latter exists only for the initial range of bleaching (15 to 25% rhodopsin). 2. At 800 nm three scattering signals are observed which are characterized by their successive amplitude decrease and time course: N: A small signal with time course and successive amplitude decrease comparable to the metarhodopsin II absorption change, probably arising from a structural change within the disc membrane. Ni: A slow signal, disappearing with the first flash, which may be understood as an outer membrane effect. P: A biphasic signal with a successive decrease rate, by a factor of 10 to 20 higher than that of the metarhodopsin II signal. The two kinetically different components are separated by variation of the observation angle. Two regions of different extension appear to change structurally with different time course. "P" may reflect an influence of the light-induced transmitter release on disc shape and/or mass.

Absorption↗
PubMed1977

A light-activated GTPase in vertebrate photoreceptors: regulation of light-activated cyclic GMP phosphodiesterase.

We have been studying the mechanism by which light and nucleoside triphosphates activate the discmembrane phosphodiesterase (oligonucleate 5'-nucleotidohydrolase; EC 3.1.4.1) in frog rod outer segments. GTP is orders of magnitude more effective than ATP as a cofactor in the light-dependent activation step. GTP and the analogue guanylyl-imidodiphosphate function equally as allosteric activators of photoreceptor phosphodiesterase rather than participating in the formation of a phosphorylated activator. Moreover, we have found a light-activated (5-fold) GTPase which participates in the modulation of photoreceptor phosphodiesterase. This GTPase activity appears necessary for the reversal of phosphodiesterase activation in vitro and may play a critical role in the in vivo regulation of light-sensitive phosphodiesterase. The K(m) for GTP in the light-activated GTPase reaction is <1 muM. The light sensitivity of this GTPase (number of photons required for half-maximal activation) is identical to that of light-activated phosphodiesterase. The GTPase action spectrum corresponds to the absorption spectrum of rhodopsin. There is, in addition, a light-insensitive GTPase activity with a K(m) for GTP of 90 muM. At GTP concentrations above 5 muM, there is no appreciable activation of GTPase activity by light. The substrate K(m) values for guanylate cyclase, light-activated GTPase, and light-activated phosphodiesterase order an enzyme array that might permit light to simultaneously cause the hydrolysis of both the substrate and product of guanylate cyclase. These findings reveal yet another facet of light regulation of photoreceptor/cyclic GMP levels and also provide a striking analogy to the GTP regulation of nonphotoreceptor, hormone-sensitive adenylate cyclase.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed2026

Blue light therapy delivered through light glasses improves sleep quality and daytime sleepiness in Parkinson's disease: A randomized trial.

BackgroundSleep disturbances, including excessive daytime sleepiness (EDS) and fragmented nocturnal sleep, are common in Parkinson's disease (PD) and significantly reduce quality of life. This pilot study evaluated the efficacy of a novel approach using blue light, delivered via dedicated glasses with integrated LED lights, to improve sleep and non-motor symptoms.MethodsRandomised, placebo-controlled, single-blind pilot study with a 2-week light intervention. Participants were assessed at baseline, two weeks, and five weeks. The study was designed to evaluate between- and within-group changes. Participants were randomly allocated to receive blue light therapy (n&#x2009;=&#x2009;15) or red light placebo (n&#x2009;=&#x2009;15), delivered via LED-integrated glasses for one hour, twice daily, given for a 2-week period. Primary outcome was improvement in sleep quality, assessed via the Pittsburgh Sleep Quality Index. Secondary outcomes included diary-based sleep outcomes, excessive daytime sleepiness, mood, anxiety, and motor symptoms.ResultsThere was a significant group&#x2009;&#xd7;&#x2009;time effect with blue light therapy leading to better Pittsburgh Sleep Quality Index scores (p&#x2009;=&#x2009;0.021). Between-group analyses showed that at two weeks a trend toward significance was observed (p&#x2009;=&#x2009;0.065), while sleep quality significantly improved at five weeks compared to placebo (p&#x2009;=&#x2009;0.029) with a large effect size (0.896). Excessive sleepiness improved in the blue light group (p&#x2009;<&#x2009;0.001), with a reduction in clinically relevant sleepiness from 50.0% to 6.7% (p&#x2009;=&#x2009;0.005).ConclusionsBlue light therapy delivered through dedicated glasses appeared to show an improvement in sleep quality and daytime sleepiness in individuals with PD. Blue light therapy offers a promising alternative to traditional light therapy utilising lower light intensities and eliminating the need for light boxes.

Aged↗
PubMed1992

UV light stress induces the synthesis of the early light-inducible protein and prevents its degradation.

ELIP is a nuclear-encoded protein localized in the thylakoid membranes. The protein is specifically induced by blue light in mature, light-grown plants (Adamska, I., Ohad, I., and Kloppstech, K. (1992) Proc. Natl. Acad. Sci. U. S. A. 89, 2610-2613), as well as in plants developed in the light in which pigment synthesis and plastid development were inhibited by the bleaching herbicide norflurazon. ELIP transcription and protein accumulation are induced also by UVA but not by UVB light. However, UVB light allows ELIP synthesis induced by superimposed white light. The protein is stable under light stress including UVA and UVB light, but it is rapidly degraded upon cessation of the light stress conditions. ELIP synthesis and integration into the chloroplast membranes is related neither to chloroplast translation activity nor to photosynthetic electron flow. Inhibition of carotenoid synthesis by fluridone, a bleaching herbicide which causes extensive damage to the photosynthetic apparatus, does not affect induction of ELIP transcription during light stress but greatly enhances ELIP accumulation. Based on these results it is proposed that ELIP turnover is related to the light stress and recovery process in plants.

Arabidopsis Proteins↗
PubMed1975

Characterization of light chain and light chain constant region fragment mRNAs in MPC 11 mouse myeloma cells and variants.

Cultured MPC 11 mouse myeloma cells synthesize not only gamma2b heavy and kappa light chains but also a carboxyl terminal (constant region) fragment of kappa light chain. In vitro translational analysis of total cytoplasmic and microsomal RNA indicates that these cells contain RNA which directs synthesis of both a light chain precursor and a light chain fragment precursor. Variant clones which do not synthesize either heavy or light chains continue to synthesize the light chain fragment. One such "nonproducing" variant was studied in detail. It does not contain translatable mRNA for the intact light chain but does contain RNA which is translated into the light chain fragment precursor. Nucleic acid hybridization analysis with a cDNA probe specific for the constant region of kappa light chains revealed that microsomal RNA from the wild-type cell contains both 14S and a 10S species of kappa specific RNA, whereas the variant contains only the 10S species. Translational analysis of these same RNAs indicates that the 14S species codes for the light chain precursor, while the 10S RNA codes for the light chain fragment precursor.

Animals↗
PubMed1976

Isolation of a human plasmin-derived, functionally active, light (B) chain capable of forming with streptokinase an equimolar light (B) chain-streptokinase complex with plasminogen activator activity.

A functionally active human plasmin light (B) chain derivative, stabilized by the streptomyces plasmin inhibitor leupeptin, was isolated from a partially reduced and alkylated enzyme preparation by an affinity chromatography method with a L-lysine-substituted Sepharose column. This light (B) chain derivative was found to be relatively homogeneous by electrophoretic analysis in both an acrylamide gel/dodecyl sulfate system and on cellulose acetate. It possessed approximately 3% of the proteolytic activity (casein substrate) of the original enzyme, and it incorporated 0.09 mol of [3H]diisopropyl phosphorofluoridate per mol of protein. It contained 3.1 +/- 0.3 carboxymethylated cysteines per mol of protein and can be designated as a CmCys5-light (B) chain (CmCys)3. When this isolated light (B) chain derivative was mixed in equal molar amounts with streptokinase, the mixture developed both human and bovine plasminogen activator activities; the bovine activator activity was approximately 66% of the bovine activator activity of the equimolar human plasmin-streptokinase complex. Although this complex now incorporated 0.50 mol of [3H]diisopropyl phosphorofluoridate per mol of protein, its proteolytic activity, on a molar basis, was the same as the proteolytic activity of the isolated light (B) chain derivative. It was shown by electrophoretic analysis in both an acrylamide gel/epsilon-aminocaproic acid system and on cellulose acetate that the light (B) chain derivative and streptokinase forms an equimolar light (B) chain-streptokinase complex, indicating that the binding site for streptokinase is located on the light (B) chain of the enzyme. A functionally active equimolar light (B) chain-streptokinase complex was also isolated from a partially reduced and alkylated equimolar human plasmin-streptokinase complex by the affinity chromatography method. The plasminogen activator activities (human and bovine) of this light (B) chain-streptokinase complex were similar to those of the plasmin-streptokinase complex from which it was derived. Although this complex incorporated 0.70 mol of [3H]diisopropyl phosphorofluoridate per mol of protein, its proteolytic activity, on a molar basis, was only 14% of proteolytic activity of the plasmin-streptokinase complex.

Amino Acids↗
PubMed1978

The plastid membranes of barley (Hordeum vulgare). Light-induced appearance of mRNA coding for the apoprotein of the light-harvesting chlorophyll a/b protein.

Illumination of dark-grown barley plants induces a massive insertion of the light-harvesting chlorophyll a/b protein into the developing thylakoid membrane. In addition to the onset of chlorophyll synthesis, light induces specifically the appearance of a prominent mRNA species which codes for a polypeptide of Mr 29500. This component was identified as a precursor of the apoprotein of the light-harvesting chlorophyll a/b protein. The precursor has an Mr larger than the authentic protein by approximately 4000. Studies of the chlorophyll-b-less mutant chlorina f2 of barley offer the first clue to the mechanism which controls the light-dependent mRNA formation. The induction of the mRNA coding for the aproprotein of the light-harvesting chlorophyll a/b protein does not seem to be linked directly to the assembly process of the light-harvesting structure and does not require chlorophyll b. It is proposed that light exerts its influence on the mRNA formation by a reaction which is different from the phototransformation of protochlorophyll(ide) to chlorophyll(ide).

Cell Membrane↗
PubMed2025

Effects of light on chloroplast translation in Marchantia polymorpha are similar to those in angiosperms and are not influenced by light-independent chlorophyll synthesis.

Translation of the chloroplast psbA mRNA in angiosperms is activated by photodamage of its gene product, the D1 subunit of photosystem II (PSII), providing nascent D1 for PSII repair. The involvement of chlorophyll in the regulatory mechanism has been suggested due to the regulatory roles of proteins proposed to mediate chlorophyll/D1 transactions and the fact that chlorophyll is synthesized only in the light in angiosperms. We used ribosome profiling and RNA-seq to address whether the effects of light on chloroplast translation are conserved in the liverwort Marchantia (Marchantia polymorpha), which synthesizes chlorophyll in both the dark and the light. As in angiosperms, ribosome occupancy on psbA mRNA decreased rapidly upon shifting plants to the dark and was rapidly restored upon a transfer back to the light, whereas ribosome occupancy on other chloroplast mRNAs changed very little. The results were similar in a Marchantia mutant unable to synthesize chlorophyll in the dark. Those results, in conjunction with pulse-labeling data, suggest that light elicits a plastome-wide activation of translation elongation and a specific increase in psbA translation initiation in Marchantia, as in angiosperms. These findings show that light regulates chloroplast translation similarly in vascular and non-vascular plants, and that constitutive chlorophyll synthesis does not affect light-regulated psbA translation initiation. Additionally, the translational outputs of chloroplast genes are similar in Marchantia and angiosperms but result from differing contributions of mRNA abundance and translational efficiencies. This adds to the evidence that chloroplast mRNA abundance and translational efficiencies co-evolve under selection to maintain protein outputs.

Chloroplasts↗
PubMed1975

Ultrastructure of the larval firefly light organ as related to control of light emission.

The firefly larva has a pair of light organs consisting of a layer of interdigitating, light emitting cells, covered dorsally with a layer of opaque, white cells. Each light organ is ventilated by one large and several smaller tracheal branches and is innervated by a branch of the segmental nerve containing two axons. These axons branch profusely in the photocyte layer so that several nerve profiles are seen around any photocyte. Nerve terminals contain large dense-core vesicles and small light-core vesicles. Clusters of light-core vesicles surrounding irregularly shaped membrane densifications, presumably the synapses between nerve and photocyte, are common in nerve terminals. Light emitting cells in insects characteristically contain photocyte vesicles. In the larva there are both full and empty photocyte vesicles; the full vesicles contain a matrix with tubular membrane invaginations in contrast to the empty vesicles which contain amorphous membrane invaginations.

Animals↗
PubMed1979

Isolation of cardiac myofibrils and myosin light chains with in vivo levels of light chain phosphorylation.

Conditions are described for the preparation of functional myofibrils and myosin light chains from freeze-clamped beating hearts with the state of light chain phosphorylation chemically 'frozen' during the extraction procedure. Myofibrils were shown to be functionally intact by measurement of Ca2+ binding and ATPase activity. Highly purified cardiac myosin light chains could be routinely isolated from myofibrillar preparations using ethanol fractionation together with ion-exchange chromatography. Analysis of light chains for covalent phosphate indicated that basal levels of phosphorylation of the 18--20 000 dalton light chain of myosin in rabbit hearts beating in situ or in a perfusion apparatus were 0.3--0.4 mol/mol. Covalent phosphate content of the light chain fraction did not change during perfusion of hearts with 10 microM epinephrine.

Animals↗
PubMed1975

Voluntary exposure to light by young and aged albino and pigmented inbred mice as a function of light intensity.

Young (5 month) and old mice (23 and 26 months) of the inbred A/J and C5BL/6J strains (N = 80) were isolated in ventilation chambers with ad lib food and water for 1 week at a time. Each animal was allowed to select its own lighting schedule by pressing one lever to turn on a light of either 10.76 or 166.40 lux illumination and pressing another lever to turn the light off. Three-way analyses of variance for Age, Strain, and Illumination effects on parameters of bar pressing, stimulus change, and light duration patterns per circadian period (24 hr) indicate that old mice are less active than young mice and the A/J mice are less active than C57BL/6J mice. Young mice spent more time in the dark than old mice and the A/J albino mice spent more time in the dark than did the C57BL/6J pigmented mice. Other age and strain differences were noted as well and are discussed with respect to some theories of light exposure by nocturnal animals.

Aging↗
PubMed1979

Predictive value of the analogy between hormone-sensitive adenylate cyclase and light-sensitive photoreceptor cyclic GMP phosphodiesterase: a specific role for a light-sensitive GTPase as a component in the activation sequence.

We report experiments which involve a light sensitive GTPase in the light dependent activation of retinal rod 3'5'-cyclic guanosine monophosphate (cGMP) phosphodiesterase (PDE). The data suggest that the light activated GTPase is intermediate between rhodopsin and PDE in the light-dependent activation sequence. We list the many striking similarities between hormone sensitive adenylate cyclase and light activated PDE in order to emphasize that the findings presented herein may have predictive value for ongoing studies of the hormone sensitive adenylate cyclase specifically regarding the role of the hormone activated GTPase in the activation sequence.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1976

Light-chain nephropathy. Renal tubular dysfunction associated with light-chain proteinuria.

We observed idiopathic light-chain proteinuria in a patient with multiple abnormalities of proximal-tubule transport mechanisms (Fanconi syndrome), nephrogenic diabetes insipidus, and distal renal tubular acidosis. Seventeen of the 19 urinary amino acid levels measured were elevated. Uric acid and phosphate clearances were greater than 60 per cent and 50 per cent, respectively, of the simultaneous inulin clearance. When water deprivation was coupled with vasopressin administration, the maximum urinary concentration observed was 384 mOsm per kilogram of water. During ammonium-chloride loading, the level of hydrogen-ion concentration in the urine remained less than 100 times that in the blood. Kappa light-chain excretion was 149 mg per 24 hours. It appears that the concurrence of proximal tubular dysfunction, distal tubular dysfunction and light-chain proteinuria represents a distinct syndrome, which we call "combined light-chain nephropathy." Available evidence indicates that excessive light-chain production with subsequent filtration, reabsorption and catabolism, causes the complex tubular dysfunctions observed.

Acidosis, Renal Tubular↗
PubMed1979

Interpretation of light diffraction by cross-striated muscle as Bragg reflexion of light by the lattice of contractile proteins.

1. The diffraction spectrum obtained by illuminating a cross-striated muscle fibre with a narrow beam of monochromatic light generally shows asymmetry of light intensity between left and right spectral lines. 2. The asymmetry of light intensity in left and right spectral lines is reversed when the fibre is rotated by 180 degrees. This indicates that intensities of the spectral lines are determined more by Bragg reflexion than by simple diffraction as in a plane grating. Populations of myofibrils with differing tilt of lattice planes must exist in each illuminated fibre segment to account for simultaneous Bragg reflexion to the left- and right-hand sides. 3. The light intensity of spectral lines shows a complicated dependence on the angle at which the incident beam is directed against the fibre. This 'intensity distribution' seems to reflect the specific myofibrillar arrangement at the site of illumination. 4. The intensity distributions of the left and right first order lines show close correlation if the deflexion of the incident beam differs by twice the Bragg angle. 5. The deflexion angle of the incident beam at which maximum intensity in spectral lines is obtained depends on sarcomere length as predicted by Bragg's formula. 6. Intensities of the first and second order lines are little correlated when recorded at the same beam deflexion, but are well correlated when recorded at beam deflexions calculated from Bragg's formula. 7. When a diffraction line is scanned perpendicularly to the meridional plane, the light intensity shows fluctuations resembling those obtained by beam deflexion within the meridional plane.

Animals↗
PubMed1976

Hepatic hydroxylation of 3beta-hydroxy-5-androsten-17-one in orchiectomized or adrenalectomized rats exposed to a reversed light cycle, constant light, or constant darkness.

The oxidative metabolism of 3beta-hydroxy-5-androsten-17-one (DHA)2 by liver microsomes in vitro was studied in sham-operated, castrated, or adrenalectomized rats maintained for 21 days in a normal light cycle, a reverse light cycle, constant light, or constant darkness and killed either at 0600 or 1800 h. Statistical analysis of the data (3-way analysis of variance) indicated the following significant effects: 1) exposure to a reverse light cycle resulted in lower body weights and increased rates of formaation of 7alpha-OH-DHA and 7-oxo-DHA; 2) despite an increase in microsomal protein content, livers from rats in constant light had the lowest rates of formation of all DHA products; 3) rats kept in constant darkness exhibited the highest rates of DHA metabolism; 4) castration decreased the microsomal protein content and the rates of formation of 16alpha-OH-DHA, 7alpha-OH-DHA, and 7-oxo-DHA; 5) adrenalectomized rats exhibited high rates of 7alpha-OH-DHA formation although microsomal protein and liver and body weights decreased; and 6) the formation of 7-oxygenated products of DHA was greater in the rats killed at 1800 than at 0600 h. We conclude that the type of illumination is quantitatively more important in determining the magnitude of DHA metabolism by the adult male rat liver than either the adrenals or the testes.

Adrenalectomy↗