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At least 289 records · Page 16Linked to original sources
PubMed1982

The combined effects of light and acute ischemia on the structure of the rabbit retina: a light and electron microscopic study.

The ultrastructure of the rabbit retina has been investigated to determine the combined effects of light and ischemia. Both eyes of 16 adult Dutch rabbits were exposed to light of an intensity known to be near or below the threshold for ultrastructural changes in the retina. In addition, one eye of each animal was subjected to one of four periods of pressure-induced total acute ischemia. Exposure to light alone resulted in only minor disturbances of the receptor cell outer segments. The remainder of the retina was of normal morphologic appearance. Exposure to the combined insults of light exposure and ischemia produced considerably more damage to the inner and outer retina. Light exposure combined with short periods of ischemia (15 to 30 min) resulted in edema of the pigment epithelium and disturbances of the receptor cell inner and outer segments. Light exposure combined with longer ischemic periods (45 to 60 min) resulted in severe disturbances in the structure of the pigment epithelium, breakdown of the receptor cell outer segments, rupture of the inner segment mitochondria, and severe edema of the neural retina. The implication of this addictive or synergistic action of light and ischemia is discussed.

Animals↗
PubMed1996

Effect of constant light and circadian entrainment of perS flies: evidence for light-mediated delay of the negative feedback loop in Drosophila.

Light is the dominant environmental cue that provides temporal information to circadian pacemakers. In Drosophila melanogaster some period gene mutants have altered free-running circadian periods but entrain to 24 h light-dark cycles. To address the mechanism of light entrainment in Drosophila, we examined the effects of constant light on the period gene (per) and timeless gene (tim) products in wild-type and perS flies. The results indicate that light affects three features of the PER-TIM program: PER and TIM phosphorylation, PER and TIM accumulation, and per and tim RNA cycling. A post-transcriptional effect on the PER-TIM complex is the likely primary clock target, which then delays the subsequent decrease in per and tim RNA levels. This is consistent with a negative feedback loop, in which the PER-TIM complex contributes to the decrease in per and tim RNA levels, presumably at the transcriptional level. There are enhanced constant light effects on the perS mutant, which further support negative feedback as well as support its importance to entrainment of these flies to a 24 h cycle, far from their intrinsic period of 19 h. The perS mutant leads to a truncated protein accumulation phase and a subsequent premature perS RNA increase. A standard 24 h light-dark cycle delays the negative feedback circuit and extends the RNA and protein profiles, compensating for the accelerated RNA increase and restoring the rhythms to wild-type-like periodicity.

Animals↗
PubMed1996

Surface hardness of light-cured composite resin cured directly or through a transparent matrix using three different light guides.

The purpose of this study was to compare the Vickers Hardness (HV) of composite resin which was light-cured by 3 different light guides, either through or without a transparent polyester matrix band. The 3 light guides, standard Demetron (SG), Turbo Tip (TT) and a standard Demetron, with obvious accidental damage (DL) were tested with both Model 100 and Cure Rite radiometers. HV tests were done on all samples both immediately and one hour after light-curing. Results were analysed using the Anova and Student t-test. The light intensity readings in mW/cm2 were SG 600 and TT 850 with both radiometers and DL tested 350 and 380. Composite resin surfaces undergo significant surface hardening in the first hour after light-curing. A 350-380 mW/cm2 intensity gives significantly lower HV than 600 + mW/cm2 but 800 mW/cm2 does not produce significantly greater HV than 600 mW/cm2. Curing through a transparent polyester matrix gives marginally greater HV than curing directly. The output of light guides is a significant factor in the surface hardness of cured composite resin.

Analysis of Variance↗
PubMed1994

Light-evoked arachidonic acid release in the retina: illuminance/duration dependence and the effects of quinacrine, mellitin and lithium. Light-evoked arachidonic acid release.

Arachidonic acid (AA) is the precursor molecule of a variety of cellular lipid mediators that interact with retinal physiology. In this study, we investigated the time- and illuminance-dependence of the release of AA in the rat retina in vitro in control and lithium-pretreated rats. We also studied the effects of the specific phospholipase A2 (PLA2) inhibitor quinacrine and the specific PLA2 stimulator mellitin on the release of AA. Isolated rat retinas were labelled with 3H-AA for 90 min in vitro in darkness and the incorporation of AA into retinal phospholipids was monitored by thin-layer chromatography. The release of 3H-AA in the incubation medium was determined under different illuminance and timing conditions, with the addition of quinacrine and mellitin, and after pretreatment of the animals with lithium. Light exposure of the prelabelled isolated retinas evoked up to a two-fold increase in AA release compared with retinas incubated for the same time in darkness. The AA release was dependent on illuminance time (10,000 1x white fluorescent light for 0.25, 2, 5 and 10 min) and illuminance level (0, 100, 1000, 5000, and 10,000 1x for 10 min). Complete rhodopsin bleaching occurred after 2 min at 10,000 1x. Quinacrine significantly suppressed the light-elicited AA release whereas mellitin increased the release of AA in dark-adapted and light-exposed retinas. Lithium pretreatment, which is known to potentiate light-evoked rod outer segment disruptions, significantly augmented the light-evoked AA release. Our results confirm a light-stimulated release of AA in the retina.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed2000

The family of light-harvesting-related proteins (LHCs, ELIPs, HLIPs): was the harvesting of light their primary function?

Light-harvesting complex proteins (LHCs) and early light-induced proteins (ELIPs) are essential pigment-binding components of the thylakoid membrane and are encoded by one of the largest and most complex higher plant gene families. The functional diversification of these proteins corresponded to the transition from extrinsic (phycobilisome-based) to intrinsic (LHC-based) light-harvesting antenna systems during the evolution of chloroplasts from cyanobacteria, yet the functional basis of this diversification has been elusive. Here, we propose that the original function of LHCs and ELIPs was not to collect light and to transfer its energy content to the reaction centers but to disperse the absorbed energy of light in the form of heat or fluorescence. These energy-dispersing proteins are believed to have originated in cyanobacteria as one-helix, highly light-inducible proteins (HLIPs) that later acquired four helices through two successive gene duplication steps. We suggest that the ELIPs arose first in this succession, with a primary function in energy dispersion for protection of photosynthetic pigments from photo-oxidation. We consider the LHC I and II families as more recent and very successful evolutionary additions to this family that ultimately attained a new function, thereby replacing the ancestral extrinsic light-harvesting system. Our model accounts for the non-photochemical quenching role recently shown for higher plant psbS proteins.

Evolution, Molecular↗
PubMed2004

Emotion perception from dynamic and static body expressions in point-light and full-light displays.

Research on emotion recognition has been dominated by studies of photographs of facial expressions. A full understanding of emotion perception and its neural substrate will require investigations that employ dynamic displays and means of expression other than the face. Our aims were: (i) to develop a set of dynamic and static whole-body expressions of basic emotions for systematic investigations of clinical populations, and for use in functional-imaging studies; (ii) to assess forced-choice emotion-classification performance with these stimuli relative to the results of previous studies; and (iii) to test the hypotheses that more exaggerated whole-body movements would produce (a) more accurate emotion classification and (b) higher ratings of emotional intensity. Ten actors portrayed 5 emotions (anger, disgust, fear, happiness, and sadness) at 3 levels of exaggeration, with their faces covered. Two identical sets of 150 emotion portrayals (full-light and point-light) were created from the same digital footage, along with corresponding static images of the 'peak' of each emotion portrayal. Recognition tasks confirmed previous findings that basic emotions are readily identifiable from body movements, even when static form information is minimised by use of point-light displays, and that full-light and even point-light displays can convey identifiable emotions, though rather less efficiently than dynamic displays. Recognition success differed for individual emotions, corroborating earlier results about the importance of distinguishing differences in movement characteristics for different emotional expressions. The patterns of misclassifications were in keeping with earlier findings on emotional clustering. Exaggeration of body movement (a) enhanced recognition accuracy, especially for the dynamic point-light displays, but notably not for sadness, and (b) produced higher emotional-intensity ratings, regardless of lighting condition, for movies but to a lesser extent for stills, indicating that intensity judgments of body gestures rely more on movement (or form-from-movement) than static form information.

Adolescent↗
PubMed1974

The effect of light on the tricarboxylic Acid cycle in green leaves: I. Relative rates of the cycle in the dark and the light.

Excised green leaves of mung bean (Phaseolus aureus L. var. Mungo) were used to determine the effect of light on the rate of endogenous respiration via the tricarboxylic acid cycle. Illumination with white light at an intensity of 0.043 gram calories cm(-2)min(-1) (approximately 8600 lux) of visible radiation (400-700 nm) gave a rate of apparent photosynthesis, measured as net CO(2) uptake, of 21 mg CO(2) dm(-2)hr(-1) which was about 11-fold greater than the rate of dark respiration. The feeding of (14)CO(2) or (14)C-labeled acids of the tricarboxylic acid cycle in the dark for 2 hours was established as a suitable method for labeling mitochondrial pools of cycle intermediates.At a concentration of 0.1 mm 3-(3,4-dichlorophenyl)-1,1-dimethylurea, apparent photosynthesis was inhibited 82%, and the refixation of (14)CO(2) derived internally from endogenous respiration was largely prevented. In the presence of this inhibitor endogenous respiration, measured as (14)CO(2) evolution, continued in the light at a rate comparable to that in the dark. Consequently, under these conditions light-induced nonphotosynthetic processes have no significant effect on endogenous dark respiration. Inhibitors of the tricarboxylic acid cycle, malonate and fluoroacetate, were used to determine the relative rates of carbon flux through the cycle in the dark and in the light by measuring the rate of accumulation of (14)C in either succinate or citrate. Results were interpreted to indicate that the tricarboxylic acid cycle functions in the light at a rate similar to that in the dark except for a brief initial inhibition on transition from dark to light. Evidence was obtained that succinate dehydrogenase as well as aconitase, was inhibited in the presence of fluoroacetate.

Journal Article↗
PubMed1989

Light Quality and Irradiance Level Interaction in the Control of Expression of Light-Harvesting Complex of Photosystem II: Pigments, Pigment-Proteins, and mRNA Accumulation.

Effects of red and blue light at irradiances from 1.6 to 28.3 micromolar per square meter per second on chloroplast pigments, light-harvesting pigment-proteins associated with photosystem II, and the corresponding mRNA were evaluated in maize (Zea mays L.) plants (OP Golden Bantum) grown for 14 days under 14 hours light/10 hours dark cycles. Accumulation of pigments, pigment-proteins, and mRNA was less in blue than in red light of equal irradiance. The difference between blue and red light, however, varied as a function of irradiance level, and the pattern of this variation suggests irradiance-controlled activation/deactivation (switching) of blue-light receptor. The maximum reduction in blue light of mRNA and proteins associated with light-harvesting complex occurs at lower irradiance levels than the maximum reduction of chlorophylls a and b.

Journal Article↗
PubMed1991

Light Intensity-Induced Changes in cab mRNA and Light Harvesting Complex II Apoprotein Levels in the Unicellular Chlorophyte Dunaliella tertiolecta.

During a transition from high growth irradiance (700 micromoles quanta per square meter per second) to low growth irradiance (70 micromoles quanta per square meter per second), the unicellular marine chlorophyte Dunaliella tertiolecta Butcher increases the cellular pool size of the light-harvesting complex of photosystem II (LHC II). We showed that the increase in LHC II apoproteins and in chlorophyll content per cell is preceded by an approximately fourfold increase in cab mRNA. The increase in cab mRNA is detectable within 1.5 hours following a shift from high to low light intensity. An increase in the relative abundance of cab mRNA was also found following a shift from high light to darkness and from high light to low light in the presence of gabaculine, a chlorophyll synthesis inhibitor. However, the LHC II apoproteins did not accumulate in the latter experiments, suggesting that LHC II apoprotein synthesis is coupled to chlorophyll synthesis at or beyond translation. We propose that changes in energy balance brought about by a change in light intensity may control a regulatory factor acting to repress cab mRNA expression in high light.

Journal Article↗
PubMed1992

Involvement of Calmodulin and Calmodulin-Dependent Myosin Light Chain Kinase in Blue Light-Dependent H Pumping by Guard Cell Protoplasts from Vicia faba L.

Signal transduction processes involved in blue light-dependent proton pumping were investigated using guard cell protoplasts from Vicia faba.N-[2-(Methylamino)ethyl]-5-isoquinolinesulfonamide, an inhibitor of cyclic AMP- and cyclic GMP-dependent protein kinases, had no effect. 1-(5-Isoquinolinesulfonyl)-2-methylpiperazine (H-7) and calphostin C, inhibitors of protein kinase C, produced slight inhibition of the blue light-dependent proton pumping. 1-[N, O-Bis(5-isoquinolinesulfonyl)-N-methyl-l-tyrosyl] -4-phenylpiperazine, a specific inhibitor of Ca(2+)/calmodulin (CaM)-dependent protein kinase II, did not inhibit the proton pumping, but 1-(5-iodonaphthalene-1-sulfonyl)-1H-hexahydro-1,4-diazepine and 1-(5-chloro-naphthalene-1-sulfonyl)-1H-hexahydro-1,4-diazepine (ML-9), inhibitors of Ca(2+)/CaM-dependent myosin light chain kinase, strongly suppressed the proton pumping. A CaM antagonist, N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7), inhibited blue light-dependent proton pumping, whereas its less active structural analog, N-(6-aminohexyl)-1-naphthalenesulfonamide (W-5), had little effect on the response. Other CaM antagonists, trifluoperazine, compound 48/80, prenylamine, and 3-(2-benzothiazolyl)-4,5-dimethoxy-N-[3-(4-phenyl-piperidinyl)- propylbenzenesulfonamide inhibited the proton pumping. In accord with these results, light-induced stomatal opening in the epidermis of Commelina benghalensis ssp. was inhibited by ML-9 and W-7, but not by H-7 and W-5. Thus, it is concluded that CaM and Ca(2+)/CaM-dependent myosin light chain kinase are the components of the signal transduction process in blue light-dependent proton pumping in guard cells.

Journal Article↗
PubMed1996

Measurement of light absorption and determination of the specific rate of light uptake in cultures of phototrophic microorganisms.

This article describes a novel method for the measurement of light absorption by cultures of phototrophic microorganisms. The rate of light absorption is calculated as the difference between the rate of light output from a culture containing cells and the rate of light output from a culture containing only growth medium. The specific rate of light uptake is calculated by dividing the rate of light absorption by the total biomass present in the culture. Application of the method to several case studies shows that light output from a culture varies widely depending on the absorption and scattering characteristics of the suspension.

Journal Article↗
PubMed1997

Transcriptional and translational regulation of nitrogenase in light-dark- and continuous-light-grown cultures of the unicellular cyanobacterium Cyanothece sp. strain ATCC 51142.

Cyanothece sp. strain ATCC 51142 is a unicellular, diazotrophic cyanobacterium which demonstrated extensive metabolic periodicities of photosynthesis, respiration, and nitrogen fixation when grown under N2-fixing conditions. N2 fixation and respiration peaked at 24-h intervals early in the dark or subjective-dark period, whereas photosynthesis was approximately 12 h out of phase and peaked toward the end of the light or subjective-light phase. Gene regulation studies demonstrated that nitrogenase is carefully controlled at the transcriptional and posttranslational levels. Indeed, Cyanothece sp. strain ATCC 51142 has developed an expensive mode of regulation, such that nitrogenase was synthesized and degraded each day. These patterns were seen when cells were grown under either light-dark or continuous-light conditions. Nitrogenase mRNA was synthesized from the nifHDK operon during the first 4 h of the dark period under light-dark conditions or during the first 6 h of the subjective-dark period when grown in continuous light. The nitrogenase NifH and NifDK subunits reached a maximum level at 4 to 10 h in the dark or subjective-dark periods and were shown by Western blotting and electron microscopy immunocytochemistry to be thoroughly degraded toward the end of the dark periods. An exception is the NifDK protein (MoFe-protein), which appeared not to be completely degraded under continuous-light conditions. We hypothesize that cellular O2 levels were kept low by decreasing photosynthesis and by increasing respiration in the early dark or subjective-dark periods to permit nitrogenase activity. The subsequent increase in O2 levels resulted in nitrogenase damage and eventual degradation.

Cyanobacteria↗
PubMed2006

Light-emitting-diode-based light source for calibration of an intensified charge-coupled device detection system intended for galvanoluminescence measurements.

A spectrally tunable light source utilizing three light-emitting diodes (LEDs) for calibration of a highly sensitive intensified charge-coupled device (ICCD) optical detection system intended for time-resolved galvanoluminescence (GL) measurements is described. The source has been conceived as a low-cost substitute for standard tungsten lamps usually used for relative and absolute calibration of optical detection systems. Three LEDs with different spectral characteristics in conjunction with a system of two integrating spheres as light mixers and light reducers are used. This construction provides control over the source spectrum by changing individual LED contributions. The use of integration spheres eliminated angular distribution of light intensities of LEDs as well as angular dependence of their spectral contributions. Moreover, by using the source we have avoided the problem of stray and diffuse light of higher wavelengths, as well as different light intensities for different wavelengths (up to three orders of magnitude in the range from 400 nm to 750 nm), which we have with standard tungsten lamps. A complete calibration procedure for the LED source and ICCD detection system is described. Finally, for the first time, we have performed time-resolved spectral GL measurements during aluminum anodization in porous film-forming electrolyte phosphoric acid in a transient regime. Two peaks at 425 nm and 595 nm are recognized, confirming the same mechanism of GL in both transient and steady-state regimes of anodization.

Journal Article↗
PubMed1992

Bi-directional transmission of molecular information by photon or electron beams passing in the close vicinity of specific molecules, and its clinical and basic research applications: 1) Diagnosis of humans or animal patients without any direct contact; 2) Light microscopic and electron microscopic localization of neuro-transmitters, heavy metals, Oncogen C-fos (AB2), etc. of intracellular fine structures of normal and abnormal single cells using light or electro-microscopic indirect Bi-Digital O-Ring Test.

In 1985, Omura, Y. discovered that, when specific molecules were placed anywhere in the close vicinity of the path of a light beam (laser), their molecular information, as well as information on electrical & magnetic fields, is transmitted bi-directionally along the path of this light beam. Namely, this information is transmitted in the direction the light beam is projected and towards the direction from which the light beam is coming. This finding was applied to the following clinical and basic research: 1) In the past, using indirect Bi-Digital O-Ring Test, human or animal patients were diagnosed through an intermediate third person holding a good electrical conducting probe, the tip of which was touching the part of the patient to be examined. However, in order to diagnose the patient in isolation from a distance, or a dangerous or unmanagable unanesthesized animal, such as a lion or tiger, the author succeeded in making a diagnosis by replacing the metal conducting probe with a soft laser beam which is held by the one hand of the third person whose index finger is placed in close vicinity of the laser beam generated by a battery-powered penlight-type solid state laser generator. Thus, diagnosis within visible distance, without direct patient contact, became a reality. 2) Using a projection light microscope, by giving indirect Bi-Digital O-Ring Test while contacting with a fine electro-conductive probe on the magnified fine structure of normal and abnormal cells, various normal and abnormal intracellular substances were localized through a third person holding a pure reference control substance with the same hand that is holding the probe as an intermediary for the indirect Bi-Digital O-Ring Test. Instead of the photon beam in a light microscope, the author found that, using an electron beam passing through the close vicinity of specific molecules of specimens in an electron microscope, the molecular information is transmitted to the magnified fluorescent screen, and an indirect Bi-Digital O-Ring Test could be performed through a projected penlight-type solid state soft laser beam on the magnified intracellular structure through an observation glass window. Using the magnified fine structure of the cells, by either a light projection microscopic field or electron microscope, in various cancer cells of both humans and animals, Oncogen C-fos (AB2) and mercury were found inside of the nucleus. Integrin alpha 5 beta 1 was found on cell membranes and nuclear cell membranes of cancer cells. Acetylcholine was not found anywhere within cancer cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed2002

High light-induced switch from C(3)-photosynthesis to Crassulacean acid metabolism is mediated by UV-A/blue light.

The high light-induced switch in Clusia minor from C(3)-photosynthesis to Crassulacean acid metabolism (CAM) is fast (within a few days) and reversible. Although this C(3)/CAM transition has been studied intensively, the nature of the photoreceptor at the beginning of the CAM-induction signal chain is still unknown. Using optical filters that only transmit selected wavelengths, the CAM light induction of single leaves was tested. As controls the opposite leaf of the same leaf pair was studied in which CAM was induced by high unfiltered radiation (c. 2100 micromol m(-2) s(-1)). To evaluate the C(3)-photosynthesis/CAM transition, nocturnal CO(2) uptake, daytime stomatal closure and organic acid levels were monitored. Light at wavelengths longer than 530 nm was not effective for the induction of the C(3)/CAM switch in C. minor. In this case CAM was present in the control leaf while the opposite leaf continued performing C(3)-photosynthesis, indicating that CAM induction triggered by high light conditions is wavelength-dependent and a leaf internal process. Leaves subjected to wavelengths in the range of 345-530 nm performed nocturnal CO(2) uptake, (partial) stomatal closure during the day (CAM-phase III), and decarboxylation of citric acid within the first 2 d after the switch to high light conditions. Based on these experiments and evidence from the literature, it is suggested that a UV-A/blue light receptor mediates the light-induced C(3)-photosynthesis/CAM switch in C. minor.

Adaptation, Physiological↗
PubMed2002

Light and life--facts and research perspectives at the Cologne Light Symposium 2002.

The international meeting Light, Endocrine Systems and Cancer--Facts and Research Perspectives was convened because recent research suggests that ubiquitous light may have more serious cancer consequences than expected. Beyond the established causal link between (over) exposure to sunlight and skin cancer, many scientists consider a causal relationship between light, endocrine systems and internal cancers as biologically plausible. To identify options to turn biological plausibility of mechanisms into true understanding and to assess the possible public health relevance we chose to bring together leading specialists from clinical, experimental laboratory and epidemiological studies of these issues to stimulate a critical, multi-disciplinary discussion of published and new results. Presentations at the symposium covered the physics of light and evolutionary aspects and provided intriguing information about chronobiology, physiology and patho-physiology of endocrine systems and carcinogenesis. Experimental and epidemiological findings on light and skin cancer, and of very recent investigations of relationships between light and internal cancers such as breast cancer were presented. The meeting concluded with a lively discussion of future research options. The symposium's essence and constructive atmosphere are captured in these proceedings [Neuroendocrinol Lett 2002 Jul;23 Suppl 2:1-104] which contain: (i) original presentation papers [Vladimir Anisimov, David Blask, Roland Böni, George Brainard, Thomas Erren, Alexander Lerchl, Sidney Perkowitz, Chris Portier, Russel Reiter, Richard Stevens, Günter Vollmer]; (ii) abstracts of oral and poster presentations; (iii) four commentaries [Charles Poole, Chris Portier, Till Roenneberg and Rob Lucas, Vladimir Anisimov and Johnni Hansen] on the presentations at the meeting and possible implications for research and public health. In our view, the biological plausibility of mechanistic links between light and hormones and cancer can serve as a unique basis for syn-disciplinary research and we expect that investigations in this area will become a higher priority research focus.

Congresses as Topic↗
PubMed1992

The early genetic response to light in the green unicellular alga Chlamydomonas eugametos grown under light/dark cycles involves genes that represent direct responses to light and photosynthesis.

In the green unicellular alga Chlamydomonas eugametos, cellular division is readily synchronized by light/dark cycles. Under these conditions, light initiates photosynthetic growth in daughter cells and begins the G1 phase. Genes whose expression is regulated upon illumination are likely to be important mechanisms controlling cell proliferation. To identify some of those genes, two cDNA libraries were prepared with poly(A)+ extracted from cells either stimulated with light for 1 h or held in darkness (quiescent cells) during the same period. To restrict our analysis to those genes that are part of the primary response, cells were incubated in presence of cycloheximide. Differential screening of approximately 40,000 clones in each library revealed 44 clones which hybridize preferentially with a [32P] cDNA probe derived from RNA of light-stimulated cells and 15 clones which react selectively with a [32P] cDNA probe synthesized from poly(A)+ RNA of quiescent cells. Cross-hybridization of these clones identified 4 independent sequences in the light-induced (LI) collection and 2 in the uninduced (LR) library. Four of these cDNAs correspond to mRNAs that are positively or negatively regulated upon activation of photosynthesis. One clone represents a mRNA that accumulates transitorily at both transitions. Finally, LI818 cDNA identifies a new chlorophyll a/b-binding (cab) gene family whose mRNA accumulation is controlled by light and a circadian oscillator. The endogenous timing system controls LI818 mRNA accumulation so that it precedes the onset of illumination by a few hours. On the other hand, light affects LI818 mRNA levels independently of active photosynthesis.

Amino Acid Sequence↗
PubMed1998

Evidence that the TIM light response is relevant to light-induced phase shifts in Drosophila melanogaster.

Light is a major environmental signal for the entrainment of circadian rhythms. In Drosophila melanogaster, recent experiments suggest that photic information is transduced to the clock through the timeless gene product, TIM. We provide genetic and spectral evidence supporting the relevance of TIM light responses to clock resetting. A missense mutant TIM, TIM-SL, exhibits greater sensitivity to light in both TIM protein disappearance and locomotor activity phase shifting assays. We show that the wavelength dependence of light-induced decreases in TIM levels and that of light-mediated phase shifting are virtually identical. Analysis of dose response of TIM disappearance in a variety of mutant genotypes suggests cell-autonomous light responses that are largely independent of the canonical visual transduction pathway.

Animals↗