Visible light is able to regulate neurite outgrowth

The pheochromocytoma cell line PC12 displays neuronal characteristics. PC12 cells differentiate their phenotype from a proliferating cell to a neurite-bearing neuron upon treatment with nerve growth factor (NGF). The neurite outgrowth of PC12 cells on polystyrene tissue culture flasks and extracellular matrix protein-adsorbed glass plates was reversibly controlled using visible light. The percentage of cells with neurites decreased with increasing light intensity. Furthermore, neurite outgrowth was dramatically suppressed with light intensities over 300 Lux (approximately 130 microW). Neurite outgrowth occurred in the absence of irradiation by visible light, but did not occur or was limited with irradiation, depending on the membranes on which PC12 cells were cultured. These results hold promise for the creation of patterned neuronal networks corresponding to patterned irradiation of visible light on nerve cells.     

Visible light is able to regulate neurite outgrowth

The pheochromocytoma cell line PC12 displays neuronal characteristics. PC12 cells differentiate their phenotype from a proliferating cell to a neurite-bearing neuron upon treatment with nerve growth factor (NGF). The neurite outgrowth of PC12 cells on polystyrene tissue culture flasks and extracellular matrix protein-adsorbed glass plates was reversibly controlled using visible light. The percentage of cells with neurites decreased with increasing light intensity. Furthermore, neurite outgrowth was dramatically suppressed with light intensities over 300 Lux (approximately 130 μW). Neurite outgrowth occurred in the absence of irradiation by visible light, but did not occur or was limited with irradiation, depending on the membranes on which PC12 cells were cultured. These results hold promise for the creation of patterned neuronal networks corresponding to patterned irradiation of visible light on nerve cells.     

Growth of the blue-green algae virus LPP-1 under conditions which impair photosynthesis

The growth of blue-green algae virus LPP-1 has been studied under conditions that impair photosynthesis in the host, Plectonema boryanum. Virus replication occurs in the dark, but the burst size is decreased to 15% of that observed in the light. The inhibitor of photosystem II, DCMU, lengthens the latent period by several hours and reduces the burst size to 60–70% of uninhibited controls. An inhibitor of electron transport, CCCP, abolishes viral growth completely. These results are interpreted to mean that (a) cyclic phosphorylation can supply most of the energy requirements for viral reproduction and (b) P. boryanum has a low level of energy production in the dark which, although insufficient for cellular growth and division, can fuel a small burst of virus.     

Production of pollution-tolerant strains of unicellular algae through mutagenic treatment. I. Ethyl methane sulphonate

The unicellular algae Anacystis nidulans and Chlorella vulgaris were collected from effluents of the Indian Oil Refinery Barauni and the Sindri Fertilizer Factory (India), respectively, and isolated in unialgal and bacteria-free culture. The algae were treated with the mutagen ethyl methane sulphonate and such mutagenically treated algae were compared with untreated controls with respect to growth characteristics and the capacity to absorb the two important components of polluted habitats, viz., phosphate and nitrate. Treated A. nidulans grew faster and showed a consistently higher uptake of phosphate than untreated. Treated C. vulgaris cells grew more slowly than untreated cells and showed lesser phosphate uptake during early phases of growth but greater uptake during the later phases. Nitrate uptake capacity was increased in both algae following treatment.     

Development of remineralizing, antibacterial dental materials

Light curable methacrylate dental monomers containing reactive calcium phosphate filler (monocalcium phosphate monohydrate (MCPM) with particle diameter of 29 or 90 μm) and β-tricalcium phosphate (β-TCP) at 1:1 weight ratio in a powder:liquid ratio (PLR) of 1:1 or 3:1 and chlorhexidine diacetate (0 or 5 wt.%), were investigated. Upon light exposure, approximately 90% monomer conversion was gained irrespective of the formulation. Increasing the PLR promoted water sorption by the set material, induced expansion and enhanced calcium, phosphate and chlorhexidine release. Concomitantly, a decline in compressive and biaxial flexural strengths occurred. With a reduction in MCPM particle diameter, however, calcium and phosphate release was reduced and less deterioration in strength observed. After 24 h, the remaining MCPM had reacted with water and β-TCP, forming, within the set materials, brushite of lower solubility. This provided a novel means to control water sorption, component release and strength properties. Measurable chlorhexidine release was observed for 6 weeks. Both diffusion rate and total percentage of chlorhexidine release decreased with lowering PLR or by adding buffer to the storage solutions. Higher chlorhexidine release was associated with reduced bacterial growth on agar plates and in a biofilm fermenter. In cell growth media, brushite and hydroxyapatite crystals precipitated on the composite material surfaces. Cells spread on both these crystals and the exposed polymer composite surfaces, indicating their cell compatibility. These formulations could be suitable antibacterial, biocompatible and remineralizing dental adhesives/liners.     

Effects of amphetamine and illumination on activity following frontal ablation

Hyperactivity in the rat resulting from the removal of the frontal lobe, including the head of the caudate-putamen nucleus, in combination with d-amphetamine administration was studied in the light and dark over a 30 day postsurgical recovery period. Both d-amphetamine administration and frontal ablation increased activity level. In addition, d-amphetamine administration reversed the normal relationship of illumination with activity level. The postoperative hyperactivity following frontal ablation was dependent on the illumination level during testing. Potentiation of frontal induced hyperactivity by d-amphetamine was observed but the potentiation was not independent of the ambient illumination.     

The in situ synthesis of biphasic calcium phosphate scaffolds with controllable compositions, structures, and adjustable properties

In this study, biphasic calcium phosphate (BCP) porous scaffolds with controllable phase compositions, controllable macropore percentages, and thus adjustable properties were in situ prepared by sintering a series of composites consisted of calcium phosphate cement (CPC) and porous resin negative mold made from rapid prototyping (RP) technique. The CPC pastes were formed by mixing a powder mixture of tetracalcium phosphate and anhydrous dicalcium phosphate with liquid phase of diluted phosphate acid solution. Results show that the phase composition was easily adjustable by controlling both weight ratio of the powder mixture to the liquid phase (P/L) and concentration of the liquid phase. The macropore structure of the BCP scaffold can be regulated by using different RP negative molds. Through in vitro compressive strength (CS) and immersion tests, it was demonstrated that both macropore percentage and phase composition played important roles in the CS and also the dissolving rates of the scaffolds. As the macropore percentage of the scaffold increased, its CS decreased but the dissolving rate increased; also, as the weight ratio of hydroxyapatite to tricalcium (HA/TCP) in the scaffold increased, the CS first increased and then decreased but the dissolving rate uniformly decreased. The CS values of the BCP scaffolds with a HA/TCP weight ratio of 59:41 were 5.84 +/- 1.16 MPa for a total porosity of approximately 67.67% containing a macropore percentage of 30%, and 3.34 +/- 0.79 MPa for a total porosity of approximately 70.90% containing a macropore percentage of 50%, respectively, comparable to the corresponding levels of human cancellous bone (2-12 MPa).     

Optimizing conditions for the use of chlorophyll derivatives for photodynamic control of parasites in aquatic ecosystems

Recently, it was demonstrated that mosquito larvae can be killed by means of photodynamic processes after the larvae have incorporated the photosensitizer chlorophyllin or pheophorbid, and were treated with light. The water-soluble substances were applied to and incorporated by the larvae in darkness. With Chaoborus sp. a dark incubation of about 3 h is sufficient to yield mortality of about 90% and ≥6 h resulted in almost 100% mortality during subsequent illumination. Temperature did not influence mortality of the larvae significantly in a treatment of 6 h dark incubation and subsequent 3 h illumination. At 10°C, 20°C, or 30°C, between 80% and 100% of the treated larvae died when the light intensity from a solar simulator was above 30 W/m². Lower irradiances were less effective. The LD₅₀ value of magnesium chlorophyllin was about 22.25 mg/l and for Zn chlorophyll 17.53 mg/l, while Cu chlorophyll (LD₅₀ 0.1 mg/l) was shown to be toxic also without light. Chlorophyllin, which was lyophilized immediately after extraction, was far more lethal to the larvae (LD₅₀ 14.88 mg/l) than air-dried Mg chlorophyllin.     

The effect of composition of poly(acrylic acid)-gelatin hydrogel on gentamicin sulphate release: in vitro

Hydrogels based on poly(acrylic acid) and gelatin crosslinked with N,N'-methylene bisacrylamide (0.5mol%) and glutaraldehyde (4%), respectively, forming an interpenetrating network were employed as matrices, for studying the loading and release of gentamicin sulphate. The release kinetics of gentamicin sulphate was evaluated in water (pH approximately 5.8), phosphate buffer (pH 7.4) and citrate buffer (pH 4) at 37+/-0.1 degrees C. The drug release in phosphate buffer was faster as compared to water or citrate buffer. Fitting the data of release studies in Peppas model indicated that the release of drug from full IPNs in phosphate buffer (pH 7.4), water (pH approximately 5.8) and citrate buffer (pH 4) were diffusion controlled. However, semi-IPNs showed both anomalous and Fickian diffusion mechanisms. With increasing gelatin percentage in the polymer, rate of drug release was faster and almost 85% of the loaded drug was released within 7 days in phosphate buffer (pH 7.4).     

Control of the rat's circadian self-stimulation rhythm by light-dark cycles.

Rats with hypothalamic and septal electrodes were maintained in continuous test environments where bar-press responses produced brief reinforcing electrical stimulations. Long-term trends in response emission were measured under continuous exposure to light, dark and 12 hr light-dark alternations. In addition, transient behavioral adjustment to sudden 180 degrees phase shifts in the light-dark schedule was studied. The ambient light condition was found to control the period and phase of the circadian rhythm of brain self-stimulation behavior, as quantified by Fourier analysis. The circadian period was greatest under constant light (up to 24.90 hr under dim illumination), and approximated 24.00 hr under constant dark. Successful nocturnal entrainment to 12 hr light-dark alternations was obtained, with the peak of the 24 hr Fourier fundamental occurring in the middle-to-late dark segments. Three to 11 days were required for re-entrainment to 180 degrees light-dark phase shifts, during which the behavioral oscillation period increased to values comparable to periods under constant light. The rate of re-entrainment appeared to be proportional to illumination intensity during light segments.     

Different effects of unexpected changes in environmental conditions on prepulse inhibition in rats and humans

The reduction of the startle response to an auditory stimulus caused by the presentation of another stimulus of lower intensity closely preceding it, a phenomenon known as prepulse inhibition (PPI), can be modulated by changes in dopaminergic activity. Schmajuk, Larrauri, De la Casa, and Levin (2009) demonstrated that this dopaminergic modulation of PPI in rats can be influenced by manipulating the experimental context, specifically by introducing changes in the ambient lighting condition that include novel elements. In this paper we analyze the effects of introducing changes in context illumination on PPI in male rats (Experiment 1) and humans (Experiment 2). The results with rats showed a reduction of PPI when the illumination condition switched from dark to light, but not from light to dark. In the experiment with human participants the reduction of PPI occurred for both changes in illumination conditions. The animal experiment results are interpreted in terms of competing exploratory behavior that appear when the context is illuminated after the dark-light transition; while in the case of human participants a perceptual and/or attentional mechanism after both illumination transitions is proposed, which may result in a reduced processing of the prepulse and subsequent lower PPI.     

Near-infrared imaging of fast intrinsic optical responses in visible light-activated amphibian retina

High performance functional imaging is needed for dynamic measurements of neural processing in retina. Emerging techniques for visual prosthesis also require advanced methodology for reliable validation of electromagnetic stimulation of the retina. Imaging of fast intrinsic optical responses associated with neural activation promises a variety of technical advantages over traditional single and multichannel electrophysiological techniques for these purposes, but the application of fast optical signals for neural imaging has been limited by low signal-to-noise ratio and high background light intensity. However, by using an optimized near-infrared probe light and improved optical system, we improve the optical signals substantially, allowing single pass measurements with approximately micron resolution. We image fast intrinsic optical responses with different optical modalities, i.e., bright field, dark field, and cross-polarization, from isolated retina activated by visible light stimulation. At single cell resolution, bright-field imaging discloses the maxima of optical responses approximately 5% dI/I, where dI is the dynamic optical change and I is the baseline light intensity. Dark-field imaging techniques further enhance the sensitivity of optical measurements, and show the maxima of optical responses exceeding 10% dI/I. Cross-polarized imaging provides optical sensitivity similar to dark-field imaging, but different patterns of neural activation are observed.     

A method for evaluating behavioral activity in Rana pipiens induced by changes in illumination

The method involved: (a) using the change in level of illumination to determine the start of the time base; (b) recycling the illumination conditions with sessions; and, (c) averaging activity scores within corresponding minutes across cycles. Frogs were generally more active in the light than in the dark when subjected to sufficiently long light and dark periods; several minutes were required to stabilize the activity levels after illumination changes. The lateral eyes had to be functional for the animals to respond relatively rapidly to illumination changes while the lateral eyes were not essential for general activation in the presence of a changing illuminated environment.     

Fluid intake of rats in constant light and during feeding restricted to the light or dark portion of the illumination cycle

Rats restricted to eating and drinking during the light phase of a 12:12 light-dark (L-D) cycle (L-drinkers) consumed much smaller volumes of saccharin and NaCl than did rats whose feeding and drinking was restricted to the dark phase (D-drinkers). The patterns of fluid intake within the respective 12-hr feeding periods were markedly different for L- and D-drinkers and the food/fluid ratios were significantly lower for D- than for L-drinkers. It was concluded that illumination affects fluid intake independently of changes in food intake and that light limits the rat's capacity for fluid ingestion. L- and D-drinkers did not differ in their preference for saccharin over water in two bottle preference tests; this suggests that light does not interfere with the rat's ability to detect and determine the quality of the taste stimulus. Differences in ingestive behavior between L- and D-drinkers may in part reflect constraints imposed by changes in the sleep-wakefulness cycle. Intake of a wide concentration range of saccharin solutions was decreased in ad lib fed rats housed in constant light (L-L); differences in fluid intake between the L-L and L-D groups varied directly with the hedonic value of the saccharin solutions. Only 44% of rats housed in constant light as compared to 100% of rats maintained in a L-D cycle decreased their intake of a saccharin solution whose ingestion was followed by injection of lithium chloride. This finding is relevant to studies of illness-induced aversions and was related to circadian rhythms in drug susceptibility and their alteration in constant light. The necessity for controlling and specifying environmental illumination in studies of ingestive behavior was emphasized and various methodological considerations related to illumination cycles were discussed.     

Responses of single rods in the retina of the turtle

1. The responses of rods in the retina of the turtle, Chelydra serpentina, have been studied by intracellular recording.2. The identification of rods as the origin of the recorded responses has been confirmed by marking with Procion Yellow.3. The response to a small spot of light was a hyperpolarization which increased with increasing light intensity. For dim, small diameter stimuli, the shape of the rod response was similar to that of cones but 2x slower and 2x larger in amplitude. The time integral of the rod response to a dim, small diameter flash is, therefore, approximately 4x greater than the integral of the cone response.4. The shape of the rod response depended on the pattern of retinal illumination as well as stimulus intensity. Enlarging the area of illumination increased the peak amplitude and delayed repolarization following a light step. The area of retina which influenced the response was approximately 200 mum in radius.5. It is concluded that for dim light the responses of rods are larger than those of cones because of (i) a greater response to direct illumination and (ii) an enhancement of response by interaction from a large retinal area.     

Phase dependent response of vasoactive intestinal polypeptide to light and darkness in the suprachiasmatic nucleus

Responsiveness of the vasoactive intestinal polypeptide (VIP) content to light and darkness in the rat suprachiasmatic nucleus (SCN) was examined by enzyme immunoassay of micropunched tissues. VIP content in the SCN has been shown to decrease monotonically in animals maintained in illumination. Decreases in VIP content in the SCN in response to both 6-h light and dark pulses depended on the phase of the circadian cycle when the pulses were applied. Light imposed at circadian time (CT) 18 or CT 22 was more effective in suppressing VIP levels than light exposure of the same intensity imposed at CT 0 or CT 6. Darkness interrupting continuous light was more effective at around CT 0 and less effective at around CT 12. These results suggest that VIP responsiveness to light and darkness in the SCN is regulated by the circadian clock in different ways and are correlated with phase-dependent phase shifts in the activity rhythm after light and dark pulses.     

Adaptation and dynamics of cat retinal ganglion cells

1. The impulse/quantum (I/Q) ratio was measured as a function of background illumination for rod-dominated, pure central, linear square-wave responses of retinal ganglion cells in the cat.2. The I/Q ratio was constant at low backgrounds (dark adapted state) and inversely proportional to the 0.9 power of the background at high backgrounds (the light adapted state). There was an abrupt transition from the dark-adapted state to the light-adapted state.3. It was possible to define the adaptation level at a particular background as the ratio (I/Q ratio at that background)/(dark adapted I/Q ratio).4. The time course of the square-wave response was correlated with the adaptation level. The response was sustained in the dark-adapted state, partially transient at the transition level, and progressively more transient the lower the impulse/quantum ratio of the ganglion cell became. This was true both for on-centre and off-centre cells.5. The frequency response of the central response mechanism at different adaptation levels was measured. It was a low-pass characteristic in the dark-adapted state and became progressively more of a bandpass characteristic as the cell became more light-adapted.6. The rapidity of onset of adaptation was measured with a time-varying adapting light. The impulse/quantum ratio is reset within 100 msec of the onset of the conditioning light, and is kept at the new value throughout the time the conditioning light is on.7. These results can be explained by a nonlinear feedback model. In the model, it is postulated that the exponential function of the horizontal cell potential controls transmission from rods to bipolars. This model has an abrupt transition from dark- to light-adapted states, and its response dynamics are correlated with adaptation level.     

Dark threshold and steady-state reactions of the pupillary light reflex in the pigmented rabbit

Summary The light reflex of the pupil was used as an indicator of retinal activity in the awake, unanesthetized pigmented rabbit.The change of the area of the pupil in response to light flashes subtending a circular field of 22° and of 0.1 sec duration was measured continuously by reflecting infrared light from the iris to a photocell (dynamic response). The photopupillar contraction showed latencies between 0.136 sec (at 700 cd/m²) and 0.290 sec (at 0.12 cd/m²) and was maximal within 0.7 sec. The least stimulus luminance producing a just perceptible contraction of the iris muscle in the most sensitive animal was 4×10^–2 cd/m² which is nearly 10⁴ times the intensity threshold in the human eye. It is concluded that some interaction takes place in the rod-dominated rabbit's retina which results in a masking effect of the rod-mediated pupillomotor response to flashes. Evidence for this effect is the large change of threshold of the rabbit's pupillomotor response during illumination to steady lights of threshold luminance.The actual size of the pupil was measured photographically on infrared film first in the dark, then at increasingly higher levels of illumination. With illumination of white light the size of apparent pupillary diameter decreases from 6,0 mm (after dark adaptation) to 4,5 mm (during illumination with 500 cd/m²). Evidence is given that the steady state reactions of the rabbit's pupil are governed by the activity of the photopic system.     

Self-sterilization using silicone catheters coated with Ag and TiO2 nanocomposite thin film

Ag/titanium dioxide (TiO(2))-coated silicon catheters were easily fabricated with Ag nanoparticles deposition on both the inside wall and the outside wall of TiO(2)-coated catheters by TiO(2) photocatalysis. This is an application of the silicon catheters coated with TiO(2), which possess a self-sterilizing and self-cleaning property combining with UV light illumination (Ohko et al., J Biomed Mater Res: Appl Biomater 2001;58:97). Ag/TiO(2)-coated silicon catheters exhibited a strong bactericidal effect even in the dark. When the 2-5 x 10(5) of colony-forming units of Escherichia coli, Pseudomonas aeruginosa, or Staphylococcus aureus were respectively applied to the surface of the Ag/TiO(2) catheters, which were loaded with approximately 15 nmol cm(-2) of Ag, 99% effective sterilization occurred in a very short time: 20 min for E. coli, 60 min for P. aeruginosa, and 90 min for S. aureus. Additionally, the Ag/TiO(2)-coated catheters possessed a strong self-cleaning property. Using UV illumination, the photocatalytic decomposition rate of methylene blue dye representing the self-cleaning capability, on an Ag/TiO(2) catheter which was loaded with 2 nmol cm(-2) of Ag, was approximately 1.2 times higher (at maximum) than that on TiO(2) coating alone. Furthermore, the Ag nanoparticles can be pre-eminently and uniformly deposited onto the TiO(2) coating, and the amount of Ag was easily controllable from a few nanomoles per square centimeter to approximately 70 nmol cm(-2) by changing the UV illumination time for TiO(2) photocatalysis. This type of catheter shows a great promise in lowering the incidence of catheter-related bacterial infections.     

Temperature and pH effect on lindane removal by Streptomyces sp. M7 in soil extract

This work was conducted to study the removal of gamma-hexachlorocyclohexane (lindane) in a soil extract liquid medium (SE) by Streptomyces sp. M7 and to determine the influence of pH and temperature on bacterial growth and pesticide removal in this medium. When Streptomyces sp. M7 was cultured in SE supplemented with lindane 100 microg l(-1 )at different initial pH, the maximum growth was observed at pH 7 and the microorganism was not able to grow at pH 5 and 9; the highest pesticide removal (70.4%) by Streptomyces sp. M7 was noted at an initial pH of 7 at 4 weeks of incubation. The maximum removal (70% approximately) was observed when the microorganism was incubated in SE at 30 degrees C; although the optimal temperature for Streptomyces sp. M7 growth, with and without lindane, was 25 degrees C, and for the pesticide removal was 30 degrees C. The results of this study suggest that this actinomycete strain appears as an effective alternative in the remediation of lindane polluted sites.