[The existence range of electric and magnetic induction stimulated subjective light patterns (phosphenes) in dependence of external stimulus parameters].
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Accommodation, Ocular↗
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[The region of existence of electrically and magnetically inductively induced subjective light phenomena (phosphenes) as a function of external excitation parameters].
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Electric Stimulation↗
The induction of allophanate lyase during the vegetative cell cycle in light-synchronized cultures of Chlamydomonas reinhardi.
Allophanate lyase can be induced by urea or acetamide 20-40-fold within 4 h in NH4 + -deprived cultures of Chlamydomonas reinhardi. In light-synchronized cultures, allophanate lyase induction appeared to be limited to the light phase of the cell cycle, provided that culture samples were induced under ongoing illumination conditions (i.e. light induction of light phase cells and dark induction of dark phase cells). However, when culture samples were induced under constant light conditions this cell cycle pattern was abolished. Light was found to be required for allophanate lyase induction and this was shown to be due, in part, to the light requirement for inducer uptake. The relationship between allophanate lyase induction and gametogenesis is discussed.
Acetamides↗
Characterization of the immunogenetic basis of ultraviolet-B light effects on contact hypersensitivity induction.
Ultraviolet-B (UVB) light has proven to be deleterious to the skin immune system in mice, and one major consequence is impairment of the induction of contact hypersensitivity (CH) to haptens applied to UVB-exposed skin. It has been shown recently that the damaging effects of UVB on CH are mediated primarily by tumour necrosis factor-alpha (TNF-alpha). Moreover, not all strains of mice are equally susceptible to the deleterious effects of UVB. Mice that develop CH when hapten is applied to UVB-exposed skin are termed UVB-resistant (UVB-R), whereas mice that fail to acquire CH under these circumstances are termed UVB-susceptible (UVB-S). In the present experiments, we have characterized the UVB-susceptibility of numerous, genetically disparate inbred strains of mice by applying dinitrofluorobenzene (DNFB) epicutaneously to normal and to UVB-exposed body wall skin. The results indicate that the intensities of CH responses of these different strains were distributed in a bimodal fashion, with means at 92% and 28.5% of positive control responses. Among the strains with CH values distributed around the higher mean (i.e. UVB-R mice), the intensity of CH responses after UVB irradiation was uniformly greater than 75% of the intensity found among their positive controls. By contrast, among the strains with CH values distributed around the lower mean (i.e. UVB-S mice), the intensity of CH responses after UVB exposure was uniformly less than 60% of the intensity displayed by their positive controls. The phenotypic traits of UVB-S and UVB-R appear, therefore, to be genetically determined. To that end, we provide in this report additional evidence that UVB-S is a polygenically determined trait that is dictated by polymorphisms at a locus within H-2, and at the Lps locus. Resistance to UVB radiation is a recessive trait, and requires homozygosity of resistance alleles at one or both of the two participating loci, whereas UVB-S acts as a dominant trait. Among H-2 congenic strains of mice that are lipopolysaccharide (LPS)-sensitive (Lpsn), UVB radiation impaired the induction of CH to DNFB in all mice except those of the H-2d and H-2a haplotypes. Thus, UVB-susceptibility is dictated by alleles at two, independent genetic loci that can influence transcriptional and translational activity of the Tnf-alpha gene. The potential biological and medical meaning of regulatory polymorphisms governing TNF-alpha production in the skin may be revealed by the recent demonstration that UVB-susceptibility and UVB-resistance are phenotypic traits in humans.(ABSTRACT TRUNCATED AT 400 WORDS)
Alleles↗
vvd is required for light adaptation of conidiation-specific genes of Neurospora crassa, but not circadian conidiation.
con-10 and con-6 are two of the conidiation (con) genes of Neurospora crassa that were identified based on their preferential expression during macroconidiophore development. They are also regulated by several other environmental stimuli independent of development, including a transient induction by light. We identified an allele of vivid (vvd) in a mutant screen designed to obtain strains with altered expression of con-10. vvd mutants display enhanced carotenoid pigmentation in response to light. In addition, con-10 and con-6 show a heightened response to photoinduction. We tested the function of the light-responsive circadian clock in the vvd mutant and found no major defect in the circadian rhythm of conidiation or light regulation of a key clock component, frequency (frq). We conclude that vvd is primarily involved in a process of light-dependent gene repression, called light adaptation. Although a number of gene products are known to control light induction in fungi, vvd is the first gene shown to have a role in adaptation to constant light.
Carotenoids↗
Light and circadian regulation in the expression of LHY and Lhcb genes in Phaseolus vulgaris.
In order to understand some aspects of the circadian clock function in Phaseolus vulgaris, we analyzed the temporal transcript profile of Lhcb genes, typical clock reporters in plants, and that of PvLHY, an orthologue of Arabidopsis thaliana LHY which is a putative transcription factor of Lhcb genes. Under different light regimes, Lhcb and PvLHY exhibit a clear circadian pattern of expression. Moreover, the rhythm of Lhcb genes appears to be tightly coupled to that of PvLHY with the latter having a slightly earlier phase. This supports the idea that the oscillating capacity of PvLHY may be one of the causes of the rhythmic expression of Lhcb genes in bean. In addition to their circadian regulation, Lhcb and PvLHY are induced by light with similar and relatively slow induction kinetics. Moreover, this light induction is gated by the circadian oscillator: minimal responses occur at times around peaks of the pre-existing rhythm, while maximal ones occur at troughs of the pre-existing rhythm. This pattern of gating is opposite to that observed in Arabidopsis. The failure to block the light induction pathways at pre-existing troughs appears to have a detrimental effect to the subsequent circadian rhythmicity. Briefly, the overall regulation of PvLHY and Lhcb genes by light and the circadian clock reveals different strategies between Phaseolus and Arabidopsis in the adaptation to photoperiodic conditions.
Amino Acid Sequence↗
Light augments FOS protein induction in brain of short-term enucleated hamsters.
FOS protein is synthesized in neuronal nuclei in response to a variety of environmental stimuli and has been used as a marker of stimulus-specific brain function. The present studies were initiated to examine the effects of ultraviolet light on the induction of FOS protein immunoreactivity (FOS-IR) in several brain regions of adult male hamsters. Experiment 1 confirmed previous observations of FOS-IR induced in visual cortex in response to ultraviolet light. However, protein was also induced by ultraviolet or white light in a variety of other areas and induction occurred in both sighted and enucleated animals. Therefore, experiments were conducted to evaluate the effects of a 514 nm light on FOS-IR induction in blind or sighted animals. Experiments 2 and 3 were performed during the early subjective night and mid-subjective day, respectively, using animals about 4 days after bilateral enucleation or sham surgery. In Experiment 2, light and enucleation independently and interactively resulted in increased FOS-IR neuronal nuclei counts. In Experiment 3, there was a main effect of enucleation and an interaction between enucleation and light condition, but no main effect of light. In Experiment 4, conducted during the early subjective night using animals enucleated 60 days earlier, there were neither effects of light or enucleation. The results support the view that, under certain conditions related to subjective time of day and time since enucleation, light can act through unknown extraocular mechanisms to modify brain activity. Further, short term enucleation itself induces widespread alteration in brain function as indicated by increased FOS-IR expression. The results specifically do not support a role for extraretinal photoreception with respect to direct circadian rhythm regulation.
Animals↗
Mutation induction by 365-nm radiation and far-ultraviolet light in Escherichia coli strains differing in near- and far-ultraviolet light sensitivity.
The his-4 locus derived from Escherichia coli strain AB1157 has been transduced into 4 E. coli strains that exhibit all 4 possible combinations of genes controlling sensitivity to near-ultraviolet light (nur versus nur+) and far-ultraviolet light (uvrA6 versus uvrA+). The 4 strains exhibited the predicted sensitivity to 254-nm radiation based on the sensitivity of the parent strains from which they were derived and the frequency of his+ mutations predicted from experiments with AB1157 from which the his-4 locus was derived. When the 4 strains were treated with 365-nm radiation, they exhibited the predicted sensitivity based on the near-ultraviolet light sensitivity of the strains from which they were derived while his+ mutations were undetectable with the 4 strains as well as with strain AB1157. When treated with 365-nm radiation, cells of a WP2s strain (a derivative of B/r transduced to his-4) plated on semi-enriched medium prepared with casamino acids did not yield induced mutations, whereas plating on semi-enriched medium prepared with nutrient broth did yield mutants at both the his-4 and trp loci at frequencies at least an order of magnitude lower than that observed with far-ultraviolet light. The induction of nutritionally independent mutants by 365-nm radiation is strongly dependent on the supplement used for semi-enrichment. When compared at equivalent survival levels, mutant frequencies are significantly less following 365-nm radiation when compared with far-ultraviolet radiation.
Cell Survival↗
Inactivation of phage repressor in a permeable cell system: role of recBC DNase in induction.
UV light causes inactivation of phage (phi80) repressor molecules in a plasmolyzed, permeable cell preparation of Escherichia coli. Induction without UV irradiation occurs when the permeable cells are incubated in the presence of four deoxyribonucleoside triphosphates and ATP. The induction triggered by dNTP's requires a functional recBC gene product and is associated with degradation of the DNA replication fork. The role of recBC DNase in the induction of prophage and SOS functions in general is discussed.
Adenosine Triphosphate↗
Expression of the psbDII gene in Synechococcus sp. strain PCC 7942 requires sequences downstream of the transcription start site.
The psbDI and psbDII genes in Synechococcus sp. strain PCC 7942 encode the D2 polypeptide, an essential component of the photosystem II reaction center. Previous studies have demonstrated that transcripts from psbDII, but not psbDI, increase in response to high light intensity. Soluble proteins from Synechococcus cells shifted to high light were found to have affinity for DNA sequences upstream from the psbDII coding region. DNA mobility-shift and copper-phenanthroline footprinting assays of a 258-bp fragment revealed three distinct DNA-protein complexes that mapped to the untranslated leader region between +11 and +84. Deletion of the upstream flanking region to -42 had no effect on the expression of a psbDII-lacZ reporter gene or its induction by light, whereas a promoterless construct supported only minimal background levels of beta-galactosidase. A 4-bp deletion within the first protected region of the footprint decreased the beta-galactosidase activity to approximately 2% of that of the undeleted control, but gene expression remained responsive to light. Deletion of the three protected regions completely abolished both gene expression and light induction. These results suggest that the psbDII gene requires elements within the untranslated leader region for efficient gene expression, one of which may be involved in regulation by light.
Base Sequence↗
The early and late effect of ultraviolet light exposure on the induction and repair of electron-induced DNA damage in rat epidermis.
Experiments were performed to determine the early and late effects of ultraviolet light (UVL) on induction and repair of DNA damage in rat epidermis by electron radiation. The dorsal skin of 28-day-old rats was irradiated with 8.0 X 10(5) or 13.6 X 10(5) ergs/mm2 UVL or weekly exposures of 0.4 X 10(5) ergs/mm2 UVL for 23 or 48 weeks. At 1, 48, 100, 200, or 400 days after single UVL doses or 28 days after last weekly UVL dose, the animals were irradiated with 1200 rads of electrons and the resultant alkaline labile DNA damage and repair quantitated by the S1 nuclease assay. The cytotoxic effect of UVL on basal epidermal cells was assessed by the labeled doublets technique. Single UV doses were capable of inhibiting repair of electron induced DNA damage for up to 5 h, but did not have any measurable late effect (greater than 20 days) on the rate or extent of DNA repair. The rate of DNA repair in epidermal cells from animals exposed to weekly doses of UVL was more rapid than in age-matched controls. The UV doses used on these experiments were shown to be cytotoxic to a large proportion of the basal epidermal cells. The results indicate that exposure of the rat skin to single cytotoxic or multiple exposures of UVL did not accelerate the age related loss of DNA repair capacity.
Age Factors↗
The 5' upstream region of mPer1 gene contains two promoters and is responsible for circadian oscillation.
The mPer1 gene is assumed to be a key molecule in the regulation and functioning of the mammalian circadian clock, which is based on the oscillation generated by a transcription-(post)translation feedback loop of a set of clock genes [1]. Robust circadian oscillation and acute light-elicited induction of mPer1 mRNA expression have been observed in the suprachiasmatic nucleus (SCN), the mammalian circadian center [2] [3]. To investigate the mechanism underlying the complex regulation of mPer1 expression, we isolated and characterized the 5' upstream region of the mPer1 gene. Unexpectedly, we identified two promoters, each followed by alternative first exons of mPer1. Consistent with the presence of multiple E-boxes in the promoters, exon-specific in situ hybridization of the SCN established that both promoters function in circadian oscillation and in light-induction of mPer1 expression. Transgenic mice carrying the 5' upstream region of the mPer1 gene fused to the luciferase gene demonstrated that a DNA fragment carrying both promoter regions is sufficient to elicit striking circadian oscillation in the SCN and responsiveness to light. Moreover, luminescence in the SCN accurately mirrored the mPer1 transcriptional activity. These transgenic mice will be very useful for monitoring clock-specific mPer1 expression in intact organisms and to follow the circadian clock in real time.
Animals↗
Different apoptotic pathways are induced from various intracellular sites by tetraphenylporphyrins and light.
The induction of apoptosis from different intracellular sites was studied by exposing V79 Chinese hamster fibroblasts to photodynamic therapy (PDT) with various porphyrins and light. The effects of two lipophilic, intracellular membrane-localized porphyrins, tetra(3-hydroxyphenyl)porphyrin (3THPP) and Photofrin, were compared with that of two sulphonated meso-tetraphenylporphines (TPPS2a and TPPS4), which are taken up into lysosomes by endocytosis. Apoptotic fractions induced by the various dyes and light were quantified by flow cytometry using the terminal deoxynucleotidyl transferase (TdT) assay. Cell fragmentation was measured in parallel, while the nuclear morphology of apoptotic cells was studied by fluorescence microscopy. Different kinetics were found for the induction of DNA strand breaks characteristic of apoptotic cells. PDT-induced damage to membranes resulted in an increasing number of apoptotic cells for about 12 h after PDT After damage to lysosomes, apoptotic cells were not detected until more than 12 h after PDT. Furthermore, apoptotic bodies were not observed after PDT-induced damage to intracellular membranes, whereas apoptosis induced from lysosomal sites was characterized by extensive cell fragmentation. Cell fragmentation occurred in combination with or in the absence of nuclear fragmentation. The results support the idea that the degradation phase of apoptosis can consist of a sequence of independent steps rather than a common final pathway.
Animals↗
Synthesis of wheat leaf nitrite reductase de novo following induction with nitrate and light.
Nitrite reductase has been purified almost 3000-fold, in 35% yield, to a specific activity of 77 units (mg protein)-1 from wheat leaves using a multi-step procedure with affinity chromatography on ferredoxin-Sepharose as the final step. The purified enzyme, although not homogeneous, exhibited absorption maxima at 278, 390, 568 and 687 nm. Minor contaminants were removed by gel filtration in the presence of sodium dodecyl sulphate to yield a single polypeptide of Mr 60 500 as judged by polyacrylamide gel electrophoresis. Antibodies raised against this polypeptide were shown to cross-react with native nitrite reductase and were used to study the synthesis of nitrite reductase in vivo and in vitro. The increase in nitrite reductase activity following exposure of dark-grown plants to nitrate and light was shown by immunodecoration of Western blots to be due to synthesis de novo. Poly(A)-rich RNA isolated from plants actively synthesising nitrite reductase was shown to direct the synthesis in a rabbit reticulocyte lysate of a polypeptide of Mr 64000 which was immunoprecipitated by antibodies to nitrite reductase.
Cell-Free System↗
Induction of gentamicin resistance by visible light.
Recent studies have demonstrated the ability of visible light or phototherapy to modify the intracellular DNA of prokaryotic and eukaryotic cells. The present study was undertaken to determine the effect of light used in phototherapy on antibiotic resistance in prokaryotic cells using tester strains of gentamicin-sensitive Escherichia coli and Staphylococcus aureus. A growing population of the tester microorganisms was inoculated on plates containing nutrient medium and gentamicin. Experiments were performed to determine the effect of blue light on the induction of gentamicin-resistant mutants. The plates were divided into two populations, one of which was illuminated, while the other was kept in the dark to serve as a control. During photoirradiation, the plates were protected from direct sunlight and air coded to maintain a temperature of 27 degrees C. The sample distance from the light source was adjusted to maintain a fluence rate (450 nm) of 141 uW/cm2. Control experiments were performed to investigate the effect of photoirradiation on the media and gentamicin. An increased frequency of mutation to gentamicin resistance was seen in the irradiated population of bacteria. The mutagenic effect was observed over a wide range of gentamicin concentrations and correlated in a linear fashion with increasing duration of photoirradiation. There was an inverse correlation between the size of the bacterial inoculum and the recovery of mutant bacteria.
Bacteria↗
Photosynthetic induction responses to variable light under field conditions in three species grown in the gap and understory of a Fagus crenata forest.
Photosynthetic induction responses to abrupt increases in photon flux density (PFD) to 800 and 1500 &mgr;mol m(-2) s(-1) from either darkness or 100 &mgr;mol m(-2) s(-1) were examined in situ in leaves of Fagus crenata Blume, Daphniphyllum humile Maxim., and Acer rufinerve Siebold & Zucc. growing in a gap and the understory of an F. crenata forest. Among the species studied, F. crenata exhibited the highest assimilation rate (A(100)), stomatal conductance (g(s100)) at the background PFD of 100 &mgr;mol m(-2) s(-1), and A(100)/A(max) (A(max) = maximum assimilation rate), in both the gap and the understory. Time required for full induction depended on both background PFD and maximum PFD. The induction period was 2-4-fold shorter at a background PFD of 100 &mgr;mol m(-2) s(-1) than in darkness. For the three understory species, time required to full induction was 2-3-fold longer when irradiance was increased from darkness to 800 &mgr;mol m(-2) s(-1) than when irradiance was increased from darkness to 1500 &mgr;mol m(-2) s(-1). Acer rufinerve showed higher initial stomatal conductance (g(s0)) and a shorter induction period in the understory than in the gap. Fagus crenata exhibited a similar g(s0) and induction period in both habitats. Daphniphyllum humile demonstrated lower g(s0) and a longer induction period in the understory than in the gap. These findings indicate that initial stomatal conductance is closely correlated with the photosynthetic induction response. We conclude that the photosynthetic induction response is affected by the light conditions experienced by plants before the sudden increase in irradiance and by the extent of the increase in irradiance.
Journal Article↗
Focus formation and neoplastic transformation by herpes simplex virus type 2 inactivated intracellularly by 5-bromo-2'-deoxyuridine and near UV light.
The induction of focus formation in low serum and of neoplastic transformation of Syrian hamster embryo cells was examined after the expression of herpes simplex virus type 2 functions. Syrian hamster embryo cells infected at a high multiplicity (5 PFU/cell) with 5-bromo-2'-deoxyuridine-labeled herpes simplex virus type 2 (11% substitution of thymidine residues) were exposed to near UV light irradiation at various times postinfection. This procedure specifically inactivated the viral genome, while having little, if any, effect on the unlabeled cellular DNA. Focus formation in 1% serum and neoplastic transformation were observed in cells exposed to virus inactivated before infection, but the frequency was enhanced (15- to 27-fold) in cells in which the virus was inactivated at 4 to 8 h postinfection. Only 2 to 45 independently isolated foci were capable of establishing tumorigenic lines. The established lines exhibited phenotypic alterations characteristic of a transformed state, including reduced serum requirement, anchorage-independent growth, and tumorigenicity. They retained viral DNA sequences and, even at relatively late passage, expressed viral antigens, including ICP 10.
Animals↗
Interleukin 1-mediated induction of kappa-light chain synthesis and surface immunoglobulin expression on pre-B cells.
In this study we have examined the effect of interleukin 1 (IL 1) on the maturation of normal and neoplastic pre-B cells. We have found that IL 1 can enhance the in vitro functional maturation of surface immunoglobulin negative (sIg-) pre-B cells from normal bone marrow. In addition, IL 1 specifically induced sIg expression on an established pre-B cell line, 70Z/3. These effects of IL 1 were obtained with the same concentrations of IL 1 that are effective in assays for T cell proliferation and functional activation. Previous studies by other investigators have demonstrated that LPS can also induce the expression of sIg on 70Z/3 cells. The stimulatory effect of LPS was dependent on the stimulation of kappa-light chain synthesis, the synthesis of mu-chains being constitutive. Our results indicate that IL 1 may also enhance sIg expression via the induction of kappa-light chain synthesis. The stimulatory effect of IL 1 was not due to contaminating LPS in the IL 1 preparations, because removal of the IL 1 by using specific antibodies against IL 1 and fixed Staphylococcus aureus cells resulted in the disappearance of kappa-chain inducing activity. In addition to IL 1, a pH 2-sensitive mediator(s) present in concanavalin A (Con A)-stimulated spleen cell supernatants was also shown to induce kappa-chain synthesis and the appearance of sIg on 70Z/3 cells. Removal of IL 1 or the inhibition of any contaminating LPS activity with polymyxin B did not diminish the activity of the pH 2-sensitive Con A supernatant factor(s). On the basis of our findings, we have concluded that IL 1 may enhance antibody responses by not only increasing the number of helper T cells but also by stimulating the maturation of B cell precursors.
Animals↗