Light-dark Adaptation Research Articles

Usefulness of red light profile and dark adaptation in diagnosis of chloroquine damage

Usefulness of red light profile and dark adaptation in diagnosis of chloroquine damage

Movement on dark–light adaptation in beetle eyes of the neuropteran type

Beetles of several species belonging to the families Carabidae, Dytiscidae, Gyrinidae and Hydrophilidae have an eye of the neuropteran type which is characterized as follows. In the dark-adapted state a long column formed by retinula cells (in these families numbering seven) stretches from the cone tip to the rhabdom layer. In the light a crystalline tract, formed from the outer layer of the cone, extends about 100 µ m from the cone and is surrounded by pigment cells. Scarabaeid beetles examined are similar but lack the distal rhabdomere always found in the above groups. All have a basal retinula cell with rhabdomere. In the scarabaeids the retinula cell columns have a content of solids greater than the surrounding cells, suggesting that they act as light guides across the clear zone.

Ultrastructure of amphibian melanophores after light-dark adaptation and hormonal treatment

Melanophores in dark-adapted or melatonin-treated tadpoles of Xenopus laevis and Hyla regilla are punctate with the melanosomes aggregated in the perikaryon. The processes of these melanophores are devoid of melanosomes and markedly reduced in diameter. Upon exposure to light or MSH, the evacuated processes imbibe fluid by macropinocytosis, distending the evacuated processes and allowing the melanosomes to migrate distally. When light-adapted melanophores are placed in the dark, the melanosomes migrate toward the perikaryon and the processes then collapse, the melanosomes being forced proximally. It is proposed that fluid uptake is involved in melanosome dispersion and fluid loss in melanosome aggregation. Microtubules do not appear to aid in the movement of melanosomes or to function as a cytoskeleton.

LIGHT-DARK ADAPTATION, AND 'GLOW', IN ABNORMAL MOTH EYES WITHOUT PIGMENT.

THE role of pigment migration in light–dark adaptation of the eyes of nocturnal moths has long interested investigators1,2. Efforts have been made to find out what part pigment migration plays in the behavioural changes associated with light–dark adaptation3, and in the phenomenon called ‘glow’4. Recently, it has been reported that adaptation in nocturnal moths occurs in two stages, the first of which is not accompanied by pigment migration5. The discovery that variations can occur in the light-threshold of a dark-adapted compound eye with practically no change in the glow area6 is further evidence of the independence of adaptation and pigment position.

Binocular vision in light adaptation and dark adaptation in normal subjects and coal-miners.

Binocular vision in light adaptation and dark adaptation in normal subjects and coal-miners.

Binocular vision in light adaptation and dark adaptation in normal subjects and coal-miners.

Binocular vision in light adaptation and dark adaptation in normal subjects and coal-miners.

The Relationship Between Light Adaptation and Dark Adaptation and its Significance for Appraisal of the Glare Effect of Different Illuminants

The Relationship Between Light Adaptation and Dark Adaptation and its Significance for Appraisal of the Glare Effect of Different Illuminants

INSTRUMENTS AND TECHNICS FOR THE CLINICAL TESTING OF LIGHT SENSE

The instrument described in this paper was devised for the especial purpose of making comparative studies of light sensitivity from the center to the periphery throughout the entire retina. A review of the recent literature on instruments and technics for measuring light sense and dark adaptation 1 indicated that none of them were suitable for this particular type of investigation. In the first paper of this series I outlined what I believed to be the requirements of an ideal clinical instrument for testing light sense. These requirements were as follows: ( a ) a preexposure field of constant brightness; ( b ) illumination of the test field with light of known composition, variable in intensity by known amounts over a wide range ; ( c ) standardization of the size of the pupil; ( d ) control of fixation, and ( e ) norms for distinguishing between pathologic and normal light thresholds. This instrument was devised to fulfil these five requirements

CRITICAL ILLUMINATION AND CRITICAL FREQUENCY FOR RESPONSE TO FLICKERED LIGHT, IN DRAGONFLY LARVAE

Curves relating flicker frequency (F) to mean critical illumination (I(m)) for threshold response to flickered light, with equal durations of light and no light intervals, and relating illumination (I) to mean critical flicker frequency (F(m)) for the same response, have been obtained from homogeneous data based upon the reactions of dragonfly larvae (Anax junius). These curves exhibit the properties already described in the case of the fish Lepomis. The curve for F(m) lies above the curve of I(m) by an amount which, as a function of I, can be predicted from a knowledge either of the variation of I(m) or of F(m). The law of the observable connection between F and I is properly expressed as a band, not as a simple curve. The variation of I(m) (and of F(m)) is not due to "experimental error," but is an expression of the variable character of the organism's capacity to exhibit the reaction which is the basis of the measurements. As in other series of measurements, P.E.(I) is a rectilinear function of I(m); P.E.(F) passes through a maximum as F (or I) increases. The form of P.E.(F) as a function of I can be predicted from the measurements of P.E.(I). It is pointed out that the equations which have been proposed for the interpretation of curves of critical flicker frequency as a function of intensity, based upon the balance of light adaptation and dark adaptation, have in fact the character of "population curves;" and that their contained constants do not have the properties requisite for the consistent application of the view that the shape of the F - I curve is governed by the steady state condition of adaptation. These curves can, however, be understood as resulting from the achievement of a certain level of difference between the average effect of a light flash and its average after effect during the dark interval.

DARK ADAPTATION AND THE LIGHT-GROWTH RESPONSE OF PHYCOMYCES

1. A single-celled, elongating sporangiophore of Phycomyces responds to a sufficient increase in intensity of illumination by a brief increase in growth rate. This is the "light-growth response" of Blaauw. 2. The reaction time is compound, consisting of an exposure period and a latent period (this comprising both the true latent period resulting from photochemical action and any "action time" necessary for the response). During the latter period the plant may be in darkness, responding nevertheless at the end of the latent period. 3. Both light adaptation and dark adaptation occur in the sporangiophore. The kinetics of dark adaptation can be accounted for on the basis of a bimolecular reaction, perhaps modified by autocatalysis. Attention is called to the bimolecular nature of the "dark" reaction in all other photosensory systems that have been studied, in spite of the diversity of the photosensitive substances themselves and of the different forms of the responses to light.

A Clinical Method to Determine the Rate of Macular Elimination of After-Images (Eikonoscopy ): A preliminary report

By means of special apparatus which is described and illustrated, adaptation time relations were studied as to light adaptation, dark adaptation, and recovery adaptation (eradication of residual after images). Results are tabulated in regard to twenty eyes of ten individuals between the ages of twenty-two and thirty-seven years. By means of special apparatus which is described and illustrated, adaptation time relations were studied as to light adaptation, dark adaptation, and recovery adaptation (eradication of residual after images). Results are tabulated in regard to twenty eyes of ten individuals between the ages of twenty-two and thirty-seven years.