Effects of Tributyltin(IV) Chloride Exposure on Larvae of Ciona intestinalis (Urochordata): An Ultrastructural Study

The effects of tributyltin(IV) chloride (TBT chloride) have been tested on embryos of the ascidian Ciona intestinalis , at two different stages of development: (1) before hatching (coiled larval stage) and (2) 2 h after hatching (swimming larval stage). In vivo observations carried out with a light microscope showed that embryos at the coiled larval stage did not hatch following exposure to TBT chloride. Severe anomalies in the swimming larva, mainly concerning the morphology of the tail, which appeared twisted and squatter than in the controls, were observed. Such anomalies were also found at a functional level, i.e. contractile movements were poor so that the larvae appeared motionless. Ultrastructural investigations carried out using a transmission electron microscope (TEM) evidenced that the muscle cells were damaged. Modifications mainly occurred in mitochondria and myofibrils, i.e. the energetic and enzymic centres. This fact is probably the main cause of the loss of mobility of the larvae.     

Stentor coeruleus SHOWS POSITIVE PHOTOKINESIS

Abstract— Stentor coeruleus responds to a sudden increase in light intensity with a step-up photophobic response (avoiding reaction), and to collimated light with negative phototaxis. The peaks of the action spectra for the photophobic response and for the phototaxis are in common, 610 nm.
5. coeruleus showed changes in its steady-state swimming velocity induced with varying intensities of light (photokinesis). The cells swam fast in light regions but slowly in dark ones (positive photokinesis); the mean velocity of swimming was about 0.6 mm/s at 100 lx but reached about 1.0 mm/s at 50000 lx. The peak of the action spectrum for this photokinesis was about 680 nm.
The organism is the first protozoan cell reported to show three types of photoresponse: photophobic response, phototaxis and photokinesis.     

PHOTOTACTIC RESPONSE OF CHLAMYDOMONAS TO FLASHES OF LIGHT –II. RESPONSE OF INDIVIDUAL CELLS

Abstract— –Video-microscope studies provide further evidence that Chlamydomonas can become oriented in response to a single short flash of light. Following a flash, 50% of the cells in a negatively phototactic population undergo a transient deflection in swimming path ('turn response'), 10% show a 'stop response', and 40% continue to swim straight ahead. The direction of turning is related to the direction of the stimulus; a majority of cells turn away from the flash source. Repetitive flashing at 60 per s elicits oriented swimming, indistinguishable from that observed with continuous light. Responses at the onset of repetitive flashing resemble single-flash responses, reinforcing the idea that response to a single flash corresponds to the initial stages of orientation to continuous light. A stop response sometimes occurs at the onset of orientation to repetitive flashing, but it is apparently not an essential component of orientation. The fact that only 60% of the cells turn or stop in response to a flash is consistent with the hypothesis that light direction is perceived by comparing light absorbed in one photoreceptive region at two instants in time (before and during the flash). The only cells to turn or to stop would be those in which the photoreceptor organelle is appropriately oriented at the instant of the flash.     

PHOTOTACTIC BEHAVIOR OF INDIVIDUAL CELLS OF CRYPTOMONAS SP. IN RESPONSE TO CONTINUOUS AND INTERMITTENT LIGHT STIMULI

Abstract— The phototactic response of cells of Cryptomonas sp. to stimulation with continuous or intermittent lateral light was determined by an individual cell method using photomicrography and videomicrography. The cells showed positive phototaxis under the conditions studied. The phototactic orientation of individual cells was induced most effectively by irradiation with light of 570 nm; blue light was less effective, and no orientation was found in red light. An intermittent stimulus regime with a long dark interval (250 ms) elicited a weaker phototactic orientation than did a regime with a short dark interval (63 ms) irrespective of the duration of light pulses (16, 250 and 1000 ms). The swimming rate was ca. 240 ums ^-1 and the rotation period ca. 450 ms in the dark, neither of which was greatly affected by stimulation with continuous or intermittent light. Neither step-up nor step-down photophobic responses were observed at the time of onset or removal of the light stimulus under the experimental conditions. The swimming direction of individual cells became gradually oriented toward the light source. Phototactic response was detectable within 4 s after the onset of light stimulation, reaching a saturation level after more than 30 s.     

Behaviors producing photodispersal in Stentor coeruleus

The ciliate Stentor coeruleus exhibits photodispersal, that is, these cells swim away from light sources and collect in dimly lighted areas. We imaged and reconstructed the tracks of 48 Stentor to determine which swimming behaviors produced their photodispersal. We observed that their photodispersal is not due to a change in their swimming speed but rather to a change in the frequency with which they reorient their swimming direction. Therefore, their photodispersal must be due to either (1) a gradual reorientation of the organism's swimming direction determined by the direction of the light beam (phototaxis) or (2) multiple randomly directed reorientations in swimming direction that occur less frequently when the cell is swimming away from the light source (biased random walk). Sixteen (19%) of the 83 observed forward swimming tracks lasting three or more seconds exhibited a gradual bending away from the light source consistent with a phototaxis. However, most tracks were interrupted repeatedly by abrupt reorientations resulting from ciliary reversals and "smooth turns" that caused cells to reorient through 5.4 times as many degrees as were needed to direct them away from the light source. When cells were swimming away from the light source, their probability of reorienting was reduced and photodispersal resulted.     

DOUBLET Stentor DO NOT DISPLAY PHOTODISPERSAL

Normal Stentor, called singlets since they have a single membranellar band and oral groove surrounding their frontal field, swim away from light sources and collect in the darker areas of an unevenly illuminated container (photodispersal). Phenotypic variants, called doublets since they have 2 membranellar bands and 2 oral grooves, do not exhibit this behavior. Doublets produce photophobic responses and contractions when illuminated at the same fluence rates which produce those responses in singlets, hence their sensitivity to light is normal. Illumination of the frontal field of doublets produces a photophobic response at lower fluence rates than does illumination of their side or posterior. This directional sensitivity is quantitatively similar to that observed in singlets. However, doublets do not reorient their swimming direction after a phobic response as extensively as do singlets. This failure in reorientation is the probable reason that doublets fail to show photodispersal. These results imply that the mechanism producing photodispersal in singlets depends on photophobic responses or some other, presently undescribed, response which requires an asymmetric frontal field.     

Vertical migration and motility responses in three marine phytoplankton species exposed to solar radiation

Diurnal vertical migration in the water column and the impact of solar radiation on motility were investigated in three marine phytoplankton species: Tetraselmis suecica, Dunaliella salina and Gymnodinium chlorophorum. Cells were exposed to solar radiation either in ultraviolet radiation (UVR, 280-400 nm) transparent Plexiglas tubes (45 cm length, 10 cm diameter) or in quartz tubes under three radiation treatments: PAB (280-700 nm), PA (320-700 nm) and P (400-700 nm). The three species displayed different behavior after exposure to solar radiation. Tetraselmis suecica was insensitive to UVR and under high solar radiation levels, cells accumulated preferentially near the surface. Exposure experiments did not indicate any significant changes in swimming speed nor in the percentage of motile cells after 5 h of exposure. On the other hand, D. salina was sensitive to UV-B displaying a significant decrease in swimming speed and percentage of motile cells after 2-3 h of exposure. Moreover, D. salina cells migrated deep in the water column when irradiance was high. The response of G. chlorophorum was in between that of the other two species tested, with a slight (but significant) decrease in swimming speed and percentage of motile cells in all radiation treatments after 5 h of exposure. While G. chlorophorum cells were more or less homogenously distributed in the water column, a slight (but significant) avoidance response to high radiation was observed at local noon, with cells migrating deep in the water column. Our data clearly indicate that these sub-lethal effects of solar radiation are species-specific and they might have important implications for the aquatic ecosystem.     

THE ACTION SPECTRUM OF DAPHNIA MAGNA (CRUSTACEA) PHOTOTAXIS IN A SIMULATED NATURAL ENVIRONMENT

Abstract— The action spectrum of phototaxis in Daphnia magna (Crustacea) was measured in a chamber which simulated a natural angular distribution of underwater light. A 17% step-down in irradiance was used to stimulate the phototactic response at all wavelengths and irradiances tested. Peaks in the spectral response curves depended on the fluence rate to which the zooplankton were acclimated. The wavelength of maximum response (Z_max) shifted from yellow-green at the highest acclimation fluence rate (5.1 × 10⁻² Wm⁻²) to blue-violet at moderate rates. At low acclimation fluence rates, the blue-violet maximum was retained and another maximum developed in the red. At the lowest fluence rate (1.6 × 10⁻⁵ Wm⁻²), the blue-violet and red maxima were lost and another maximum developed in the near ultraviolet. The action spectrum indicates the presence of three, and possibly four, photopigments with Z_max, at ∼405, 440, 570 and 690nm. The 440 and 690nm maxima may belong to the same photopigment; however, this was not tested. Changes in zooplankton swimming speed, caused either by large changes in irradiance or by mechanical stimuli, were accompanied by changes in the strength of the phototactic response to the −17% stimulus at any irradiance level for white and monochromatic light, and indicated the presence of a mechanism connecting swimming speed and photosensitivity.     

MODE OF COACTION BETWEEN UV-A AND LIGHT ABSORBED BY PHYTOCHROME IN CONTROL OF APPEARANCE OF RIBULOSE-1.5-BISPHOSPHATE CARBOXYLASE IN THE SHOOT OF MILO (Sorghum vulgare Pers.)

Abstract— In shoots of milo ( Sorghum vulgare Pers.) appearance of ribulosebisphosphate carboxylase (RuBPCase) and of translatable mRNA for its small subunit is stimulated strongly by red light (R, operating through phytochrome) and UV-A light (UV-A). Ultraviolet-A is more effective than R.
The mode of coaction between phytochrome and light absorbed by the blue/UV-A light photoreceptor ('cryptochrome') was analyzed in detail in case of enzyme appearance. Fluence rate dependencies, lagphases and the time course of the response are compatible with the view that UV-A intensifies a process which is occurring in R alone albeit at a lower rate.
With both light qualities the light effect is fully reversible by far-red light up to 1 h. This means that during this period only phytochrome (P_fr) controls the terminal response, i.e. the actual appearance of RuBPCase. During this 1 h period after the onset of light UV-A or R have no effect on the level of translatable mRNA for the small subunit of RuBPCase indicating that it requires more than 1 h for the light signal to affect gene expression.
When R and UV-A are given longer onset of escape from full reversibility is observed at the same time for both light qualities in the case of RuBPCase appearance. The extent of the reversible response is greater after UV-A pretreatment than after a R pretreatment.
It is argued that the data are consistent with the concept that phytochrome (P_fr) controls the terminal photoresponse, in the present case appearance of RuBPCase, while light absorbed via cryptochrome leads to an increase in responsiveness of the RuBPCase producing machinery towards P_fr.     

In vivo 31P-NMR SPECTROSCOPY OF MAMMARY CARCINOMA SUBJECTED TO SUB CURATIVE PHOTODYNAMIC THERAPY

Abstract In vivo ³¹P-NMR spectroscopy was applied to the investigation of the time course of metabolic response of MCA mammary carcinoma in the C,H mouse subjected to a subcurative treatment with photodynamic therapy. Eleven animals were injected with 12.5 mg kg^_1 Photofrin II and after 24 h were photoactivated with 25 J cm⁻² of light between 630 ± 5 nm. In vivo NMR spectroscopy was performed 1-4, 24 and 72 h after treatment. The ratio of (J-ATP intensity to inorganic phosphate (Pi) intensity changed over the time course of the study. At the 1-4 and 24 h time points the ratio of fi-ATP to Pi decreased from control values. At 72 h there was a significant increase in the ratio above the post treatment values to levels equal to or exceeding that of control pretreatment ratios.     

PAR and UV effects on vertical migration and photosynthesis in Euglena gracilis

Recently it was shown that the unicellular flagellate Euglena gracilis changes the sign of gravitaxis from negative to positive upon excessive radiation. This sign change persists in a cell culture for hours even if subsequently transferred to dim light. To test the ecological relevance of this behavior, a vertical column experiment was performed (max. depth 65 cm) to test distribution, photosynthetic efficiency and motility in different horizons of the column (surface, 20, 40 and 65 cm). One column was covered with a UV cut-off filter, which transmits photosynthetically active radiation (PAR) only, the other with a filter which transmits PAR and UV. The columns were irradiated with a solar simulator (PAR 162 W m(-2), UV-A 32.6 W m(-2), UV-B 1.9 W m(-2)). The experiment was conducted for 10 days, normally with a light/dim light cycle of 12 h:12 h, but in some cases the light regime was changed (dim light instead of full radiation). Under irradiation the largest fraction of cells was found at the bottom of the column. The cell density decreased toward the surface. Photosynthetic efficiency, determined with a pulse amplitude modulated fluorometer, was negligible at the surface and increased toward the bottom. While the cell suspension showed a positive gravitaxis at the bottom, the cells in the 40 cm horizon were bimodally oriented (about the same percentage of cells swimming upward and downward, respectively). At 20 cm and at the surface the cells showed negative gravitaxis. Positive gravitaxis was more pronounced in the UV + PAR samples. At the surface and in the 20 and 40 cm horizons photosynthetic efficiency was better in the PAR-only samples than in the PAR + UV samples. At the bottom photosynthetic efficiency was similar in both light treatments. The data suggest that high light reverses gravitaxis of the cells, so that they move downward in the water column. At the bottom the light intensity is lower (attenuation of the water column and self shading of the cells) and the cells recover. After recovery the cells swim upward again until the negative gravitaxis is reversed again.     

CALCIUM CONTROL OF PHOTOTACTIC ORIENTATION IN Chlamydomonas reinhardtii: SIGN AND STRENGTH OF RESPONSE

Abstract— Chlamydomonas reinhardtii responds to a blue light stimulus by an oriented swimming (phototaxis) toward or away from the stimulus source. In this study it is established that the sign and strength of the phototactic response are a complex function of extracellular [Ca²⁺], stimulus fluence rate, time of analysis after onset of stimulation and light pretreatment. At very low extracellular [Ca²⁺] the response is weak and usually negative. At [Ca²⁺] close to the preconditioning level, phototactic response becomes stronger and positive. As [Ca²⁺] is raised further, the initial (2 s) response remains positive but the long term (20 s) becomes negative and very strong. At extremely high [Ca²⁺] the cells become immobile. This bimodal behavior suggests that two different mechanisms determine the direction of the turn. Data cannot be explained in terms of a simple model. The model which accounts for most of the details of the behavior is that of Kamiya and Witman (1984), which proposes that positive response is triggered by a transient increase in intracellular [Ca²⁺] and negative response by a decrease below unstimulated level of Ca²⁺, at least in the range of 10^-9-10^-6 M [Ca²⁺]. The strong negative orientation which follows an initial positive response above this level of [Ca²⁺], in these experiments, is best explained by an adaptation of the cells due to an increased (on average) intracellular [Ca²⁺].     

THE SENSORY PHOTORECEPTORS OF Halobacterium halobium REVISITED: ACTION SPECTRA and INFLUENCE OF BACKGROUND LIGHT*

Abstract– Action spectra of the light-dependent behavior of Halobacterium and the effect of background light have been measured with regard to the current hypothesis of Spudich and Bogomolni [Nature 312 ,509–513 (1984)], which proposes sensory rhodopsin I (sRI₅₈₇) to be the receptor for long-wavelength light, and its photoproduct S₃₇₃ to be the receptor for UV light. The action spectrum shows three maxima for attractant responses (prolonged swimming intervals) at 565, 590, and 610 nm, and two maxima for repellent responses (shortened intervals) at 370 and 480 nm. The latter is assigned to sensory rhodopsin II (P-480). All peaks are red-shifted after substitution of the endogeneous retinal by 3, 4-dehydroretinal. The peaks at 590 and 610 nm are suppressed by long-wavelength background light. Ultraviolet background light converts all attractant peaks into repellent peaks. The response at 370 nm is strongly activated by visible background light, the maximal effect occurring with 510 nm. The activated state declines with a half-life of about 1.2 s. In a growing culture, full sensitivity to UV and blue light is restored about 10 h earlier than sensitivity to long-wavelength light. Some of the results cannot easily be explained by the sRI₅₈₇/S₃₇₃ hypothesis. Explanations for the three maxima in the long-wavelength range and for the maximal activation of the UV response by 510 nm light are discussed.     

Light-induced Damage in the Retina: Differential Effects of Dimethylthiourea on Photoreceptor Survival, Apoptosis and DNA Oxidation

In the rat, photoreceptor cell death from exposure to intense visible light can be prevented by prior treatment with antioxidants. In this study we subjected albino rats raised in dim cyclic light and rats made more susceptible to light damage by rearing in darkness to exposures of green light that led to similar losses of photoreceptor cells. Rhodopsin and photoreceptor DNA, indicators of the number of surviving photoreceptor cells, were determined at various times over a period of 14 days after light exposure. Fragmentation of DNA was determined over a similar time course by neutral and alkaline agarose gel electrophoresis. Apoptosis in retinal DNA was measured by quantitating the appearance of 180 base pair (bp) nucleosomal fragments. Oxidation of DNA was measured by electrochemical detection of the nucleoside 8-hydroxydeoxyguanosine (8-OHdG) after separation by high-performance chromatography. For albino rats reared in dim cyclic light, 24 h of intense light exposure resulted in the loss of 50% rhodopsin and photoreceptor cell DNA. In dark-reared rats, the losses were 40%, respectively, after only 3 h of intense light treatment. In both cases pretreatment with the antioxidant dimethylthiourea (DMTU) prevented rhodopsin and photoreceptor cell DNA loss. The kinetics of the light-induced apoptosis depended markedly on the rearing environment of the rats. The DNA ladders appeared within 12 h of the onset of intense light in the rats reared in dim cyclic light. In these rats the 180 bp fragment was at two-thirds of its maximum intensity immediately after 24 h of light exposure and reached the maximum 12 h later. Dimethylthiourea partially inhibited ladder formation in rats reared in dim cyclic light and delayed the time of appearance of the 180 bp maximum by 6 h. By contrast, in rats reared in darkness the 180 bp fragment was undetected immediately after 3 h of light exposure and reached its maximum 2 days later. Pretreatment with DMTU completely eliminated DNA ladders in these rats. Alkaline gel electrophoresis revealed a pattern of single-strand DNA breaks, with relatively high molecular weight fragments, 6 h after light exposure of dark-reared rats. Single-strand DNA breaks in cyclic light rats corresponded with the onset of apoptotic ladders, but peak values preceded by 12 h the peak of DNA ladder formation. The quantity of 8-OHdG in retinal DNA remained close to control values in all samples with the exception of a peak of twice the control value 18 h after light exposure in the dark-reared rats and a value 60% higher 16 days after exposure in cyclic light animals. Dimethylthiourea had no effect on the amount of oxidized purine in any of the samples. The differences between dark-reared rats and rats reared in dim cyclic light in the kinetics of DNA fragmentation and in their response to treatment with DMTU is consistent with previous observations of fundamental differences in retinal cell physiology in these animals. In dim light-reared rats, the pathway to apoptosis may be qualitatively different from the pathway to net photoreceptor loss in rats reared in darkness. The lack of effect of DMTU on 8-OHdG formation suggests that the oxidation of DNA bases is not a causal factor in light-mediated photoreceptor cell death.     

ARE THERE SEVERAL PHOTORECEPTORS INVOLVED IN PHOTOTROPISM OF Phycomyces blakesleeunus? KINETIC STUDIES OF DICHROMATIC IRRADIATION*

Abstract— Photogeotropic equilibrium angles were measured for Phycomyces blakesleeanus wild type firstly by means of dichromatic fluence rate response curves using simultaneous irradiation with near threshold 450 nm reference light (constant at 1.2 × 10^?8 W m^?2) and variable fluence rates of test light (498–630 nm) from the same side. These curves showed minima for test light fluence rates that were close to the photogeotropic threshold for these wavelengths. Secondly, the time course of this inhibitory effect was studied with both the inductive reference 450 nm light (2 × 10^?-⁷ W m^?2) and the test light (606 or 450 nm) given as light pulses of 2 s duration (2 s light/48 s dark periods for 6 h). The dark period between the onset of the inductive reference light and test light pulses was varied between 0 and 48 s. No inhibitory effects were observed for simultaneous pulses; however, inhibitory effects were demonstrated for delay times of 2 s and 20 s for 606 nm as well as 450 nm test light. If the test light pulses were given immediately before the inductive reference light, only 606 nm test light was effective in producing a significant inhibitory effect. The results are discussed with regard to a multichromophoric photoreceptor system and to the wavelength dependence of the effects observed. The data and conclusions favor a photoreceptor system with at least two separate chromophoric absorptions of the blue light receptor type, one acting positively, the other acting inhibitorily, and at least one other photoreceptor of presumably minor influence.     

Pharmacokinetics and pharmacodynamics of tetra(m-hydroxyphenyl)chlorin in the hamster cheek pouch tumor model: comparison with clinical measurements

The pharmacokinetics (PK) of the photosensitizer tetra(m-hydroxyphenyl)chlorin (mTHPC) was measured by optical fiber-based light-induced fluorescence spectroscopy (LIFS) in the normal and tumoral cheek pouch mucosa of 29 Golden Syrian hamsters with chemically induced squamous cell carcinoma. Similar measurements were carried out on the normal oral cavity mucosa of five patients up to 30 days after injection. The drug doses were between 0.15 and 0.3 mg per kg of body weight (mg/kg), and the mTHPC fluorescence in the tissue was excited at 420 nm. The PK in both human and hamster exhibited similar behavior although the PK in the hamster mucosa was slightly delayed in comparison with that of its human counterpart. The mTHPC fluorescence signal of the hamster mucosa was smaller than that of the human mucosa by a factor of about 3 for the same injected drug dose. A linear correlation was found between the fluorescence signal and the mTHPC dose in the range from 0.075 to 0.5 mg/kg at times between 8 and 96 h after injection. No significant selectivity in mTHPC fluorescence between the tumoral and normal mucosa of the hamsters was found at any of the applied conditions. The sensitivity of the normal and tumoral hamster cheek pouch mucosa to mTHPC photodynamic therapy as a function of the light dose was determined by light irradiation at 650 nm and 150 mW/cm2, 4 days after the injection of a drug dose of 0.15 mg/kg. These results were compared with irradiations of the normal oral and normal and tumoral bronchial mucosa of 37 patients under the same conditions. The reaction to PDT of both types of human mucosae was considerably stronger than that of the hamster cheek pouch mucosa. The sensitivity to PDT became comparable between hamster and human mucosa when the drug dose for the hamster was increased to 0.5 mg/kg. A significant therapeutic selectivity between the normal and neoplastic hamster cheek pouch was observed. Less selectivity was found following irradiations of normal mucosa and early carcinomas in the human bronchi. The pharmacodynamic behavior of mTHPC was determined by test irradiations of the normal mucosa of hamsters and patients between 6 h and 8 days after injection of 0.5 and 0.15 mg/kg in the hamsters and the patients, respectively. The normal hamster cheek pouch showed a maximum response to irradiation 6 h after injection and then decreased continuously to no observable reaction at 8 days after injection. The reaction of the normal human oral mucosa, however, showed an increasing sensitivity to the applied light between 6 h and 4 days after mTHPC injection and then decreased again at 8 days. The hamster model with the chemically induced early squamous cell cancer in the cheek pouch thus showed some similarity to the early squamous cell cancer of the human oral mucosa considering the PK. However, a quantitative difference in fluorescence signal for identical mTHPC doses as well as a significant difference in pharmacodynamic behavior were also observed. The suitability of this animal model for the optimization of PDT parameters in the clinic is therefore limited. Hence great care must be taken in screening new dyes for PDT of early squamous cell cancer of the upper aerodigestive tract based upon observables in the hamster cheek pouch model.     

New-chitosan characterization and its bioassay in different salinity solutions using <Emphasis Type="Italic">Artemia salina</Emphasis> as bio tester

New chitosan powder extracted from eggs capsules of Rapana venosa and commercial chitosan powder were analyzed by spectral (UV–Vis) and color methods. The novelty of this study consists in the first time toxicity evaluation of the chitosan extracted from the walls of Rapana venosa eggs capsules. The evaluation was focused on the cytological behaviour of the new-chitosan particles in two different salinity conditions (3 and 35‰), at different concentrations, on bio tester organisms. The aim of this study was to determine the biological effect of the chitosan easily extracted from new marine sources and with a low financial effort. The experimental studies were performed by exposure of Artemia salina larvae, naupliar stage in saline chitosan solutions. The larvae were picked-up in 24 h time, after hatching and they were placed in the experimental recipients of 1 mL volume capacities, three repetitions were made for each test. The bioassay effects were recorded at 24 and 48 h after experiment started. The toxicity was indicated by the registration of larvae mortality, probably, induced by the cell growth inhibitions. The obtained results showed that the high toxicity effects could be observed at low concentrations of chitosan, in law salinity solutions. Due to this cytotoxicity variability, chitosan solutions could be useful in a wide range of applications (antifouling, biomedical or sewage cleaning).     

A Comparison of Functional Bladder Damage after Intravesical Photodynamic Therapy with Three Different Photosensitizers

Abstract— The influence of type of photosensitizer, drug and light dose, and time interval between photosensitizer and illumination on the extent of photodynamic therapy (PDT)-induced bladder damage and recovery was investigated using a mouse model. The three photosensitizers studied were Photofrin, meso-tetrahydroxyphenylchlorin (m-THPC) and bacteriochlorin a (BCA). Functional bladder damage was quantitatively assessed from increases in urination frequency index (FI) at 1-35 weeks after illumination and histological damage was qualitatively assessed at 1 day, 1, 2 and 12 weeks. Photofrin-mediated PDT caused an acute increase in FI at 1 week, with recovery within 2-8 weeks after light doses of 2.7-8.2 J/cm². After higher light doses there was only partial recovery. Previous results indicated that the acute response and rate of recovery was the same whether Photofrin was given at 1 day or up to 7 days before illumination. The m-THPC-mediated PDT at drug doses of 0.3 mg/kg also resulted in a marked acute response with good recovery, even after 10.8 J/cm². Lower drug doses in combination with 5.4 J/cm² did not result in acute or late damage. There was no significant difference in acute response when m-THPC was given 1, 3 or 7 days before illumination, although recovery was faster for the longer illumination intervals (3 or 7 days). Illumination at 1 h after 20 mg/kg BCA induced an acute response within 2 days after illumination, with recovery within 4-8 weeks. Lower drug doses did not result in damage. The most prominent histological changes during the acute period with all three photosensitizers were submucosal edema and vessel dilation, with epithelial denudation (depending on drug/light dose). We conclude that BCA and m-THPC are both potent new photosensitizers. They can induce a moderate to severe acute bladder response with complete healing over a period of a few weeks. The photosensitizer m-THPC is very effective with low doses of photosensitizer and light, whereas relatively high doses of BCA and light are required to obtain equivalent functional bladder damage in our mouse model.     

Ultraviolet-B radiation effects on antioxidant status and survival in the zebrafish, Brachydanio rerio

Direct impact of ambient (1.95 W/m2) and subambient doses of UV-B radiation on muscle/skin tissue antioxidant status was assessed in mature zebrafish (Brachydanio rerio). The influence of these doses on hatching success and survival in earlier life stages was also examined. Subambient doses of UV-B radiation in the presence (1.28 W/m2) and absence (1.72 W/m2) of a cellulose acetate filter significantly depressed muscle/skin total glutathione (TGSH) levels compared with controls (0.15 W/m2) and low (0.19 W/m2) UV-B-treated fish after 6 and 12 h cumulative exposure. Ambient UV-B exposure significantly decreased muscle/skin glutathione peroxidase (GPx) activity after a 6 h exposure; activities of glutathione reductase (GR) were unchanged over this exposure period. Superoxide dismutase (SOD) and catalase activities peaked after 6 and 12 h cumulative exposure, respectively, but fell back to control levels by the end of the exposure period. The changes in tissue antioxidant status suggested UV-B-mediated increases in cytosolic superoxide anion radicals (O2-) and hydrogen peroxide (H2O2). This apparent UV-B-mediated increase in oxidative stress is further supported by a significant increase in muscle/skin thiobarbituric acid reactive substances (TBARS). Hatching success of newly fertilized eggs continuously exposed to ambient UV-B was only 2% of the control value. Even at 30 and 50% of ambient UV-B, hatching success was only 80 and 20%, respectively, of the control. Newly hatched larvae exposed to an ambient dose of UV-B, experienced 100% mortality after a 12 h cumulative exposure period. This study supports a major impact of UV-B on both the mature and embryonic zebrafish.     

Enhancement of cutaneous immune response to bacterial infection after low-level light therapy with 1072 nm infrared light: a preliminary study

We investigated the photobiomodulation effects of 1072 nm infrared light on the natural immune response involved in anti-bacterial and wound healing processes. Thirty mice infected with MRSA on the skin were divided into two groups. The experimental group was treated with 1072 nm infrared light (irradiance: 20 mW/cm(2), fluence: 12 J/cm(2) for 10 min) at 2, 4, 8, 12, 24 h, 3 and 5 days after inoculation and the control group with sham light. Serial changes of the mRNA levels of TLR2, IL-1β, TNF-α, IL-6, iNOS, MCP-1, TGF-β, bFGF and VEGF were studied by real time RT-PCR and those of the expression level of VEGF, bFGF, TGF-β and NF-κB by immunohistochemistry. The mRNA levels of the cytokines involved in the early phase of anti-bacterial immune response (IL-1β, TNF-α, IL-6, MCP-1) increased significantly in the 1072 nm group, peaking between 12 and 24 h post-inoculation. These levels normalized after 3-5 days. Immunohistochemistry revealed a notably stronger expression of VEGF in the 1072 nm group from 8-h post-inoculation to 5-day post-inoculation. We concluded that 1072 nm infrared light had a photobiomodulation effect which resulted in an enhanced biological immune response to the bacterial infection by MRSA and also increased the expression of VEGF to a significant level.