SOME OBSERVATIONS ON THE LETHAL EFFECTS OF NEAR-ULTRAVIOLET LIGHT ON ESCHERICHIA COLI, COMPARED WITH THE LETHAL EFFECTS OF FAR-ULTRAVIOLET LIGHT

Abstract— Near-ultraviolet light (365.5 nm) reduces the ability of Escherichia coli B/r and B_8-1, to form colonies on nutrient agar after irradiation. This lethal effect is distinct from that obtained after far-u.v. irradiation (253.7 nm) because the far-u.v. sensitive and resistant strains are equally susceptible to near-u.v. Variation in susceptibility to ultraviolet light during growth is more marked for near-u.v. than for far-u.v. The number of survivors after near-u.v. irradiation of log phase cells is affected by several post-irradiation treatments; more cells survive if growth immediately after irradiation occurs at higher temperatures (unlike far-u.v.). Also, the presence of acriflavine and caffeine in the nutrient agar decreases the number of survivors (in common with far-u.v.).     

EFFECTS OF HEMATOPORPHYRIN DERIVATIVE ON THE CELLULAR ENERGY METABOLISM IN THE ABSENCE AND PRESENCE OF LIGHT

Effects of Photofrin II on energy metabolism and metabolic viability were studied in a mammalian transformed cell line (BHK-21) in dark and after photo-irradiation with visible light. Cells were allowed to accumulate Photofrin by incubating for 4 h in buffer containing Photofrin (5-60 micrograms/ml). The results show that Photofrin significantly affects the cellular energy metabolism even in the absence of light; activity of cytochrome c oxidase is decreased and glucose utilization and lactate production (glycolysis) are increased. Irradiation with light resulted in a significant decrease in the activity of cytochrome c oxidase, glycolysis, ATP content, energy charge, ratios of adenine nucleotides like ATP/ADP, ATP/AMP and cell viability (dye exclusion test). Presence of inhibitors of energy metabolism, potassium cyanide (respiration) and 2-deoxyglucose (glycolysis), further enhanced the cytotoxic effects induced by hematoporphyrin derivative and light.     

ACUTE EFFECTS OF NEAR ULTRAVIOLET AND VISIBLE LIGHT ON THE CUTANEOUS ANTIOXIDANT DEFENSE SYSTEM

Reactive oxygen species are considered to play an important role in cutaneous pathology. Enzymic and non-enzymic antioxidants can prevent oxidative damage but may be overcome by strong pro-oxidative stimuli. The acute effect of a single exposure to near ultraviolet (UVA)/visible radiation (greater than 320 nm) on various skin antioxidants was examined in hairless mice immediately after irradiation. Impairment of cutaneous catalase and glutathione reductase activity was observed. Superoxide dismutase and glutathione peroxidase were not significantly influenced. Inhibition of catalase may render skin more susceptible to the damaging effects of hydrogen peroxide and its reaction products such as the hydroxyl radical. Partially diminished glutathione reductase activity is not accompanied by a change in reduced/oxidized glutathione level immediately after irradiation. There was a tendential (not statistically significant) decrease in cutaneous tocopherol, ubiquinol + ubiquinone 9 and ascorbic acid levels, either indicating direct photodestruction or consumption by reaction products of photooxidative stress. This partial impairment of the cutaneous antioxidant defense system by near ultraviolet/visible light, showing that the most susceptible component in skin is catalase, suggests possible pharmacological interventions.     

EFFECTS OF 8-METHOXYPSORALEN PLUS NEAR-ULTRAVIOLET LIGHT ON THE NEMATODE

Abstract— Effects of 8-methoxypsoralen plus near-UV light on the nematode Caenorhabditis elegans were studied as a novel example of photosensitized actions at the individual level. Either the eggs or the worms were illuminated with near-UV light in the presence of 8-methoxypsoralen. The treatment decreased hatchability of the eggs depending on light fluence and concentration of the sensitizer. Inhibition of growth and premature death were observed when the larvae in the second stage were illuminated in the presence of 8-methoxypsoralen. When young adults were treated before the beginning of egg-laying, they grew to lay eggs, but the total number of eggs deposited per hermaphrodite was decreased and the life span was shortened.     

EFFECTS OF PHOTODYNAMIC PROCESSES AND ULTRAVIOLET LIGHT ON DUCK AND HEN EGG-WHITE LYSOZYMES

Abstract— The photochemical yields for inactivation and amino acid destruction in hen and duck egg-white lysozyme are presented. Duck lysozyme II is devoid of histidine but it has two more tyrosine residues than does hen lysozyme. The data indicate that sensitized oxidation of the single histidine residue of hen lysozyme is of no significance for the inactivation of this lysozyme. The ultraviolet destruction of tryptophan and cystine residues appears to be equally related with the loss in enzymatic activity of hen lysozyme. In the case of duck lysozyme, however, the ultraviolet inactivation appears to be predominantly governed by the destruction of cystine residues.     

EFFECTS OF ACRIDINE PLUS NEAR-ULTRAVIOLET LIGHT ON THE OUTER MEMBRANE OF ESCHERICHIA COLI

Abstract The hydrophobic photosensitizer acridine plus near-ultraviolet light damages both plasma membranes and outer membranes in Escherichia coli. Two lines of evidence are presented that outer membrane proteins are affected by acridine plus near-ultraviolet light treatment and that the effect is selective for certain proteins. First, analysis of outer membrane proteins on sodium dodecylsulfate polyacrylamide gels revealed that some protein bands are diminished upon treatment while others remain unaltered. New bands also appear, suggesting degradation or crosslinking reactions. Second, bacteriophage adsorption studies showed that treatment of E. coli F cells with acridine plus near-ultraviolet light causes a loss in functionality of the receptor for phage T5. Treatment of E. coli ABU57 cells under comparable conditions has no discernable effect on the functionality of the receptor for phage BF23.     

EFFECTS OF INORGANIC NITROGEN ON THE RESPONSE OF LEMNA CARBON DIOXIDE OUTPUT TO LIGHT QUALITY AND TIMING*

Abstract —The effects of various light/dark schedules on the time course of CO₂ output by axenic cultures of the short-day plant Lemna perpusilla 6746 differ substantially depending on whether the medium is N-less or contains NH₄ or NO₃ as the sole N source. The steady-state pattern achieved with a daily 1/4 h light pulse in N-less medium is essentially the same whether the light is red or far-red; on NO₃ or NH₄, however, the red and far-red patterns differ in form and suggest the action of a ‘Pfr-hourglass’ timer. In darkness, following either continuous light or entrainment to kh red light daily, CO₂ output oscillates for three or more circadian cycles on NH₄ medium and for at least two on N-less, but damps after a single cycle on NO₃. A schedule of 1/4 h red light every 12 h elicits a 24 h periodicity on NO₃ or NH₄ media and a 12 h periodicity on N-less medium, while a similar far-red schedule elicits a 12 h periodicity on all three. CO₂ output patterns on each of the media respond differently to varying the daily span of light from 1/4 to 6 to 12 h. These results are probably due to differential effects of changing N status on the proportion of total C O₂ arising from various metabolic reactions. They suggest that, rather than being a simple, unitary indicator, CO₂ output can be made to reflect different processes on different media, increasing its value as a real-time indicator of events underlying photoperiodism.     

STUDY OF THE EFFECTS OF ULTRAVIOLET LIGHT ON BIOMEMBRANES—IV. THE EFFECT OF OXYGEN ON UV-INDUCED HEMOLYSIS AND LIPID PHOTOPEROXIDATION IN RAT ERYTHROCYTES AND LIPOSOMES

Abstract— Hemolysis induced by irradiation with ultraviolet (UV) light at 254 nm showed a pronounced oxygen effect: under irradiation in vacuum, the rate of hemolysis was decreased by an order of magnitude. Irradiation at 254 nm in air but not under vacuum caused the peroxidation of erythrocyte membrane lipids. These results suggest that membrane lipid photoperoxidation is one of the causative factors of UV hemolysis. Irradiation at different wavelengths showed that UV-induced lipid photoperoxidation in erythrocyte membranes developed while the antioxidant α-tocopherol was directly photooxidized. It is shown that the process of lipid photolysis in erythrocyte membranes involves sensitization, possibly by protoporphyrin, whose presence in liposomes accelerates the photoperoxidation at 254 and 365 nm of unsaturated fatty acid residues in lecithin. Possible mechanisms of photochemical damage to erythrocyte membranes are discussed.     

INFLUENCE OF THE POOL SIZE OF THE XANTHOPHYLL CYCLE ON THE EFFECTS OF LIGHT STRESS IN A DIATOM: COMPETITION BETWEEN PHOTOPROTECI'ION AND PHOTOINHIBITION

Abstract In a study of the relationship between nonphotochemical quenching of fluorescence and the xanthophyll cycle, we show that the diatom Phaeodactylum tricornutum exhibits several interesting characteristics. This xanthophyll cycle consists of only one reversible epoxidating/deepoxidating step (diadinoxanthiddiatoxanthin). Diadinoxan-thin, which increases from 8 to 17 molecules/100 chlorophyll a (Chl a ) during the ageing of the culture, was present as two separate pools, with a portion (of about 5 molecules/100 Chl a) which was never deepoxidated. Under a defined irradiance, the time necessary to abolish net photosynthesis increases with the pool size of diadinoxanthin available for deepoxidation. A close correlation is found between nonphotochemical quenching and the relative ratio of diatoxanthin until the photosytem II center is inactivated. The photoprotective effect of diadinoxanthin deepoxidation is limited to the phase during which quenching of the minimum fluorescence (F₀) develops.     

EFFECTS OF DIETARY VITAMIN E AND SELENIUM ON LIGHT DAMAGE TO THE RAT RETINA*,†

Abstract—In this study we have investigated effects of dietary supplementation or deficiency in α-tocopherol (vitamin E) and selenium on acute light stress to albino rats. Selenium, which is an essential component of the enzyme glutathione peroxidase, and α-tocopherol are thought to be important in preventing in vivo lipid peroxidation. Before light stress, sections of paraffin embedded eyes show an intense yellow autofluorescent pigment localized in the retinal pigment epithelium (RPE) of the deficient rats which is barely visible in tissue sections from the supplemented rats. The fluorescent pigment is thought to be the result of damaging lipid peroxidation reactions. In addition the dcficient rats show increased electroretinogram (ERG) thresholds and decreased ERG-amplitudes compared to the supplemented rats. Acute 12 h light stress did not produce an increase in autofluorescent pigment in the RPE of the supplemented or deficient rats. The supplemented rats. however. showed marked light damage effects as measured by ERG-parameters. Contrary to our expectations, the deficient rats showed a lesser amount of light damage to the ERG than the supplemented rats. Our ERG results to date fail to implicate r-tocopherol levels or glutathione peroxidase activity as major factors in protecting the retina and pigment epithelium from damage after acute light stress.     

BLUE LIGHT PHOTORECEPTION IN Neurospora ORCADIAN RHYTHM: EVIDENCE FOR INVOLVEMENT OF THE FLAVIN TRIPLET STATE

The mechanism of the photoreceptor acting on the circadian conidiation rhythm of Neurospora crassa was studied, with the following results: (1) the efficiency of 8-haloflavins as sensitizers increased with their triplet yields. (2) Phase shifts were not abolished by removal of oxygen prior to illumination. (3) Oxygen inhibited phase shifts when introduced into the cultures after light treatment. It is proposed that the blue light photoreceptor for the circadian clock of Neurospora crassa acts (1) from its triplet state, but (2) not via singlet oxygen; (3) signal transduction involves (an) oxygen-sensitive intermediate(s).     

SOME EFFECTS OF LIGHT ON LEAF GROWTH IN PISUM SATIVUM AND TROPAEOLUM MAJUS

Abstract— The effect of wave-length of light on leaf expansion in Tropaeolum majus 'Double Orange Gleam' and Pisurn sativum 'Meteor' has been studied. In both species leaf growth is strongly promoted by light.
Increasing the daily duration of exposure to light increased leaf expansion in Tropueolum in both blue and red wave-bands over a range of light intensities. In Pisum a similar effect of ail increase in duration of irradiation was found over the whole range of intensities used for blue light but only at the highest intensity for red light: at the two lower intensities in red an increase in duration of the light treatment beyond 1 hr did not increase leaf expansion.
In both species a period of 4 hr of blue followed by 4 hr of red promoted leaf growth more than 4 hr of red followed by 4 hr of blue. The effect of a 4 hr period of red light was largely prevented when it was followed by far-red; the effect of 4 hr of blue light, on the other hand, was not affected by subsequent exposure to far-red.
It is concluded that leaf growth in Pisum and Tropaeolum is dependent not only on the 'low-energy' red/far-red reversible reaction but also on one or more 'high-enerFy' photo-reactions.     

酸度和光照对草酸盐-高锰酸钾法测定软锰矿有效氧的影响

测定软锰矿中的有效氧,常遇到:(1)两化验室对同一矿样的分析结果差异较大,(2)用同一操作规程复验同批样品测定结果波动.总之,重现性很差.在各种测定方法中,一般常用的是草酸盐法、亚铁盐法和亚砷酸盐法.按照通常规定,亚铁盐法必须采用隔绝空气操作;草酸盐和亚砷酸盐法则否.但依据Katz等的实验,草酸盐法也需在惰性气氛中操作,才能得与亚铁盐法一致的结果.由我们以往的经验,亚砷酸盐法的测定结果也不稳定.目前最通用的是草酸盐法.这种经典方法由于所需仪器、药品和操作都很简便,所以大家仍乐于采用;只是经过衍变,在操作上各有不同而已.     

THE INFLUENCE OF LIGHT ON THE NON-DIAPAUSE RELATED ASPECTS OF DEVELOPMENT AND REPRODUCTION IN INSECTS

A literature review was undertaken to evaluate the effects of light on larval development and adult reproduction excluding diapause. Shortening or lengthening of larval developmental time, adult emergence, gametogenesis, fecundity and oviposition are all affected by both photoperiod and light quality.