AN ACCESSORY PHOTOSENSITIVE SUBSTANCE IN VISUAL PURPLE REGENERATION

Science ◽  
1937 ◽  
Vol 85 (2211) ◽  
pp. 484-484 ◽  
Author(s):  
A. M. Chase
Keyword(s):  
Photosensitive Substance

scholarly journals REGENERATION OF VISUAL PURPLE IN SOLUTION

1939 ◽  
Vol 23 (1) ◽  
pp. 21-39 ◽  
Author(s):  
Aurin M. Chase ◽  
Emil L. Smith
Keyword(s):  
Order Process ◽  
First Order ◽  
Color Changes ◽  
Violet Light ◽  
Frog Retina ◽  
Significant Difference ◽  
Kinetics Of ◽  
Photosensitive Substance ◽  
Subsequent Regeneration

1. Measurements of visual purple regeneration in solution have been made by a procedure which minimized distortion of the results by other color changes so that density changes caused by the regenerating substance alone are obtained. 2. Bleaching a visual purple solution with blue and violet light causes a greater subsequent regeneration than does an equivalent bleaching with light which lacks blue and violet. This is due to a photosensitive substance which has a gradually increasing effective absorption toward the shorter wavelengths. It is uncertain whether this substance is a product of visual purple bleaching or is present in the solution before illumination. 3. The regeneration of visual purple measured at 560 mµ is maximal at about pH 6.7 and decreases markedly at more acid and more alkaline pH's. 4. The absorption spectrum of the regenerating material shows only a concentration change during the course of regeneration, but has a higher absorption at the shorter wavelengths than has visual purple before illumination. 5. Visual purple extractions made at various temperatures show no significant difference in per cent of regeneration. 6. The kinetics of regeneration is usually that of a first order process. Successive regenerations in the same solution have the same velocity constant but form smaller total amounts of regenerated substance. 7. In vivo, the frog retina shows no additional oxygen consumption while visual purple is regenerating.

scholarly journals THE PHOTOTROPIC SENSITIVITY OF PHYCOMYCES AS RELATED TO WAVE-LENGTH

1931 ◽  
Vol 14 (6) ◽  
pp. 701-711 ◽  
Author(s):  
E. S. Castle
Keyword(s):  
Absorption Spectrum ◽  
Wave Length ◽  
Ultra Violet ◽  
Photosensitive Substance

Under the circumstances of experimentation described, the sporangiophores of Phycomyces are found to be most sensitive to stimulation by light in the violet between 400 and 430 mµ. Toward the red, sensitivity falls to nearly zero near 580 mµ, while in the near ultra-violet around 370 mµ, sensitivity is still high. The previous experiments of Blaauw had placed the point of greatest sensitivity some 80 mµ nearer the red end of the spectrum. Because of the known presence in the sporangiophores of Phycomyces of "accessory" pigments, care must be taken in identifying such results with the absorption spectrum of the photosensitive substance.

Photodynamic antimicrobial therapy

2010 ◽  
Vol 5 (4) ◽  
pp. 400-406 ◽  
Author(s):  
Lenka Ryskova ◽  
Vladimir Buchta ◽  
Radovan Slezak
Keyword(s):  
Photodynamic Therapy ◽  
Research And Development ◽  
Broad Spectrum ◽  
Antimicrobial Therapy ◽  
Photodynamic Effect ◽  
Invasive Approach ◽  
Antimicrobial Substances ◽  
Non Invasive ◽  
Photodynamic Antimicrobial Therapy ◽  
Photosensitive Substance

AbstractPhotodynamic antimicrobial therapy (PACT) involves the utilisation of photosensitizers activated by exposure to visible light in order to eradicate microbes (this method has already been applied in photodynamic therapy of tumours). Photodynamic effect of the particular photosensitive substance (PS) is attributed to its ability to penetrate susceptible microorganisms, to absorb the light of certain wavelength, and to generate reactive cytotoxic oxygen products. The target microorganisms for photoinactivation are bacteria, fungi, viruses and protozoa. Photodynamic antimicrobial therapy is proposed as a potentially topical, non-invasive approach suitable for treatment of locally occurring infection. The fact that bacteria are becoming increasingly resistant to antibiotics and antiseptics has lead to an increased interest in the development of new alternative eradication methods, such as PACT. Research and development of photosensitive substances are aimed at finding effective antimicrobial substances, which would have a broad-spectrum potency.

scholarly journals SENSORY EQUILIBRIUM AND DARK ADAPTATION IN MYA ARENARIA

1919 ◽  
Vol 1 (5) ◽  
pp. 545-558 ◽  
Author(s):  
Selig Hecht
Keyword(s):  
Reaction Time ◽  
Latent Period ◽  
Dark Adaptation ◽  
Photochemical Reaction ◽  
Short Interval ◽  
Bimolecular Reaction ◽  
Mya Arenaria ◽  
Rational Explanation ◽  
Order Of Magnitude ◽  
Photosensitive Substance

1. The reaction time of Mya to light is composed of two parts. The first, a sensitization period, is an exceedingly short interval of the order of magnitude associated with photographic processes. The second is a latent period of about 1.3 seconds, during which Mya need not remain exposed to the stimulating light. 2. The process of dark adaptation in Mya is orderly. Its progress may be represented by the formation of a photosensitive substance according to the dynamics of a bimolecular reaction. See PDF for Structure 3. Photosensory equilibrium as represented by the light- and dark-adapted conditions finds a rational explanation in terms of the "stationary state" of a reversible photochemical reaction involving a photosensitive substance and its two precursors. 4. There are two corollaries to this hypothesis. The first requires that the reaction time at sensory equilibrium for a given intensity should vary inversely with the temperature; the second, that the rate of dark adaptation should vary directly with the temperature. Experiments verified both of these requirements.

scholarly journals THE PHOTIC SENSITIVITY OF CIONA INTESTINALIS

1918 ◽  
Vol 1 (2) ◽  
pp. 147-166 ◽  
Author(s):  
Selig Hecht
Keyword(s):  
Reaction Time ◽  
Latent Period ◽  
Dark Adaptation ◽  
Local Reaction ◽  
The Body ◽  
Chemical System ◽  
Intensity Analysis ◽  
Constant Ratio ◽  
Neural Mass ◽  
Photosensitive Substance

1. Ciona possesses two means of responding to an increase in the intensity of illumination. One is by means of a local reaction; the other is by a retraction reflex of the body as a whole. 2. The "ocelli" are not photoreceptors. The photosensitive area is in the intersiphonal region containing the neural mass. This area contains no pigment. 3. The reaction time to light is composed of a sensitization period during which Ciona must be exposed to the light, and of a latent period during which it need not be illuminated in order to react to the stimulus received during the sensitization period. 4. The duration of the reaction time varies inversely as the intensity. Analysis shows the latent period to be constant. The relation between the sensitization period and the intensity follows the Bunsen-Roscoe rule. 5. During dark adaptation the reaction time is at first large, then it decreases until a constant minimum is reached. 6. A photochemical system consisting of a reversible reaction is suggested in order to account for the phenomena observed. This system includes a photosensitive substance and its precursor, the dynamics of the reaction following closely the peculiarities of the photosensitivity of Ciona. 7. It is shown that in order to produce a reaction, a constant ratio must be reached between the amount of sensitive substance broken down by the stimulus and the amount previously broken down. 8. From the chemical system suggested certain experimental predictions were made. The actual experiments verified these predictions exactly. 9. The results obtained with regularly repeated stimulation not only fail to show any basis for a learning process or for the presence of a "higher behavior," but follow the requirements of the photochemical system suggested before.

scholarly journals A study of Photodynamic Therapy with Photosensitive Substance, Doxycycline, in Arteriosclerosis Rabits

1992 ◽  
Vol 13 (Supplement) ◽  
pp. 487-490
Author(s):  
K. Senoo ◽  
T. Ohkuma ◽  
A. Sato ◽  
H. Kaneda ◽  
T. Kinefuti ◽  
...  
Keyword(s):  
Photodynamic Therapy ◽  
Photosensitive Substance

The Effect of Light and Darkness on the Fine Structure of the Retinal Clubs of Dendrocoelum Lacteum

1962 ◽  
Vol s3-103 (64) ◽  
pp. 543-548
Author(s):  
P. RÖHLICH ◽  
L. J. TÖRÖK
Keyword(s):  
Fine Structure ◽  
Structural Changes ◽  
Marginal Zone ◽  
Original Structure ◽  
Photosensitive Substance ◽  
Effect Of Light

The number and size of the vacuoles in the retinal clubs of the eye of Dendrocoelum lacteum increase considerably in animals kept in darkness. As a consequence, the volume of the whole retinal club enlarges, the microvilli forming its marginal zone becoming shorter and thicker. When exposed to light, the retinal clubs regain their original structure; the number and size of the vacuoles diminish and the zone of the microvilli widens. These structural changes are interpreted as due to a photosensitive substance which is produced in the axial cytoplasm of the club, stored in vacuoles and disintegrated by light in the zone of the microvilli.

scholarly journals THE DARK ADAPTATION OF THE HUMAN EYE

1920 ◽  
Vol 2 (5) ◽  
pp. 499-517 ◽  
Author(s):  
Selig Hecht
Keyword(s):  
Dark Adaptation ◽  
Photochemical Reaction ◽  
Quantitative Data ◽  
Dark Reaction ◽  
Human Eye ◽  
Visual Threshold ◽  
Bimolecular Chemical Reaction ◽  
Dim Light ◽  
Visual Reception ◽  
Photosensitive Substance

During the dark adaptation of the human eye, its visual threshold decreases to a small fraction of its original value in the light. An analysis of the quantitative data describing this adaptation shows that it follows the course of a bimolecular chemical reaction. On the basis of these findings it is suggested that visual reception in dim light is conditioned by a reversible photochemical reaction involving a photosensitive substance and its two products of decomposition. Accordingly, dark adaptation depends on the course of the "dark" reaction during which the two products of decomposition reunite to synthesize the original photosensitive substance.

scholarly journals THE SENSIBILITY OF THE SUN-FISH, LEPOMIS, TO MONOCHROMATIC RADIATION OF LOW INTENSITIES

1932 ◽  
Vol 15 (3) ◽  
pp. 307-328 ◽  
Author(s):  
Harry Grundfest
Keyword(s):  
Absorption Spectrum ◽  
Orienting Response ◽  
Monochromatic Radiation ◽  
New Method ◽  
The Sun ◽  
Visibility Function ◽  
Visual Orienting ◽  
Photosensitive Substance

1. A test is proposed of the hypothesis that visual purple is the photosensitive substance concerned in dim vision. It is based on the fact that fish visual purple is different from that of other vertebrates. If the hypothesis is correct, the fish dim-visibility function should be different from that of other vertebrates and should be determined by the absorption spectrum of its visual purple. 2. A new method is described for obtaining the visibility function of fish, in quantitative terms. It depends on the measurement of the least amounts of various spectral energies which will produce a visual orienting response to the displacement of a constant background. 3. Data are presented on thirteen animals. It is shown that the maximum of the visibility function is identical with the maximum of the absorption spectrum of fish visual purple. The shapes of the visibility curves obtained are, however, variable and different from that of the absorption spectrum. 4. The possibility that Lepomis visual purple is different from that of other fish is ruled out by a series of measurements which confirm the results of Koettgen and Abelsdorff on other fish. 5. Reasons are given for the conclusion that there are present in Lepomis special conditions which distort the visibility curve out of true agreement with that predictable from the absorption spectrum of its visual purple. The suggestion is made that the presence of light absorbing, but not light sensitive, pigments is responsible for this distortion. One of these pigments may perhaps be carotin while the second is unspecified.

scholarly journals Photodynamic inactivation of in vitro bacterial cultures from pressure ulcers

2006 ◽  
Vol 21 (suppl 4) ◽  
pp. 32-35 ◽  
Author(s):  
Paulo de Tarso Camillo de Carvalho ◽  
Ana Paula da Costa Marques ◽  
Felipe Abdalla dos Reis ◽  
Ana Carulina Guimarães Belchior ◽  
Iandara Schettert Silva ◽  
...  
Keyword(s):  
Gram Negative Bacteria ◽  
Significance Level ◽  
Gram Positive Bacteria ◽  
Skin Ulcers ◽  
Colony Forming Units ◽  
Post Hoc ◽  
Infected Material ◽  
Photosensitive Substance ◽  
Infected Skin

PURPOSE: To evaluate in vitro the antibacterial effect of diode laser light of wavelength 650 nm, in association with the photosensitive substance toluidine blue, on the bacteria in infected skin ulcers. METHODS: Samples were collected by means of swabs containing a medium for transporting infected material from skin ulcers. The material was inoculated into culturing medium containing azide blood agar for the growth of Gram-positive bacteria, and MacConkey agar for Gram-negative bacteria, and incubated for 48 hours. The results obtained from counting the colony-forming units were correlated and subjected to statistical analysis, adopting the significance level of p > or = 0.05. RESULTS: From analysis of variance (ANOVA), the result for the general mean was p = 0.0215. Using the t test with post-hoc test, the result for TBO vs. Control was p = 0.0186, and for TBO + Laser vs. Control it was p = 0.0039. CONCLUSION: There was a significant reduction in colony-forming units when the cultures were subjected to photodynamic therapy.

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