Computer analysis of photochemical changes in the human retina

Ripps, Harris; Snapper, Arthur G.

doi:10.1016/0010-4825(74)90010-9

Cited by 21 publications

(11 citation statements)

References 15 publications

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“…Absorbance difference spectra were derived from density differences (⌬D ) recorded at 24 wavelengths ranging from 420 to 700 nm; ⌬D represents the change in absorbance between the dark-adapted retina and the retina immediately after a 1 min exposure to an intense yellow (Wratten 16; 460 mW/mm 2 ) light (cf. Ripps and Snapper, 1974). Figure 1 shows representative histological sections of retinas from normal albino mice reared in cyclic-light ( Fig.…”

Section: Methodsmentioning

confidence: 99%

Polygenic Disease and Retinitis Pigmentosa: Albinism Exacerbates Photoreceptor Degeneration Induced by the Expression of a Mutant Opsin in Transgenic Mice

Naash

Ripps

et al. 1996

J. Neurosci.

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Expression of a mouse opsin transgene containing three point mutations (V20G, P23H, and P27L; termed VPP) causes a progressive photoreceptor degeneration that resembles in many important respects that seen in patients with autosomal dominant retinitis pigmentosa caused by a P23H point mutation. We have attempted to determine whether the degree of degeneration induced by expression of the transgene is influenced by albinism, a genetically mediated recessive trait that results in a deficiency in melanin formation in pigmented tissues throughout the body. Litters of albino and pigmented mice (normal as well as transgenic) were reared in either darkness or cyclic light. Retinal structure and function were evaluated by light microscopy, electroretinography (ERG), and retinal densitometry. The data were consistent in demonstrating that at similar ages, the extent of photoreceptor degeneration was greater in transgenic albino animals than in their pigmented counterparts. The albino VPP mice had significantly fewer cell bodies in the outer nuclear layer of the retina, a larger reduction in ERG amplitude, and a lower rhodopsin content in the rod photoreceptors. These structural and functional differences could not be attributed to the greater level of retinal illumination experienced by the albino retina under normal ambient conditions, because they persisted when pigmented and albino mice were reared in darkness from birth. Although the explanation remains unclear, our findings indicate that the rate of photoreceptor degeneration in VPP mice is adversely affected by the existence of the albino phenotype, a factor that may have implications for the counseling of human patients with retinitis pigmentosa and a familial history of other genetic disorders.

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Section: Methodsmentioning

confidence: 99%

Polygenic Disease and Retinitis Pigmentosa: Albinism Exacerbates Photoreceptor Degeneration Induced by the Expression of a Mutant Opsin in Transgenic Mice

Naash

Ripps

et al. 1996

J. Neurosci.

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“…But even more impressive than its structural elegance are the dynamic properties of the visual cells and the mechanisms available for signal generation, intercellular communication, and molecular renewal. The influx of sodium ions constitutes the receptor's dark current [64], the movement of an internal transmitter that is mobilized by light to close the channels of entry [65], the shuttling of vitamin A between the rod and the pigment epithelium to support the rhodopsin cycle [66], the shedding of disk membranes and their incorporation into phagosomes [67], the translocation of proteins and other macromolecules to the outer segment where new disks are assembled and to the receptor terminal for replenishment of its chemical messenger [68], and finally, the Ca-dependent discharge of transmitter by exocytotic release [69]. Each of these activities, as well as many others, is essential to the functional integrity of the cell.…”

Section: Discussionmentioning

confidence: 99%

Evaluation of Essential Trace and Toxic Elements in Biological Samples of Normal and Night Blindness Children of Age Groups 3–7 and 8–12 Years

Afridi

Kazi

et al. 2010

Biol Trace Elem Res

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The most common cause of blindness in developing countries is vitamin A deficiency. The World Health Organization estimates 13.8 million children to have some degree of visual loss related to vitamin A deficiency. The causes of night blindness in children are multifactorial, and particular consideration has been given to childhood nutritional deficiency, which is the most common problem found in underdeveloped countries. Such deficiency can result in physiological and pathological processes that in turn influence biological samples composition. Vitamin and mineral deficiency prevents more than two billion people from achieving their full intellectual and physical potential. This study was designed to compare the levels of Zn, Mg, Ca, K, Na, As, Cd, and Pb in scalp hair, blood, and urine of night blindness children age ranged 3-7 and 8-12 years of both genders, comparing them to sex- and age-matched controls. A microwave-assisted wet acid digestion procedure was developed as a sample pretreatment, for the determination of As, Ca, Cd, K, Pb, Mg, Na, and Zn in biological samples of night blindness children. The proposed method was validated by using conventional wet digestion and certified reference samples of hair, blood, and urine. The concentrations of trace and toxic elements were measured by atomic absorption spectrophotometer prior to microwave-assisted acid digestion. The results of this study showed that the mean values of As, Cd, Na, and Pb were significantly higher in scalp hair, blood, and urine samples of male and female night blindness children than in referents (p < 0.001), whereas the concentrations of Zn, Ca, K, and Mg were lower in the scalp hair and blood but higher in the urine samples of night blindness children. These data present guidance to clinicians and other professional investigating deficiency of essential mineral elements in biological samples (scalp hair and blood) of night blindness children.

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“…); the signals consisted of a series of 29 positive deflections, each corresponding to the wavelength of light derived from one of the interference filters in the spinning wheel. The area under each of the deflections was approximated by converting the analog signals to digital values at brief, regular time intervals, and integrating these values using the trapezoidal rule (Ripps and Snapper, 1974); the sums were held in a temporary buffer, each in its appropriate wavelength bin. This process was repeated for eight complete spectral scans, after which averages and variances of the eight areas corresponding to each test wavelength were calculated, and the means were stored as one time vector.…”

Section: Fundus Reflectomet~7mentioning

confidence: 99%

Flash photolysis of rhodopsin in the cat retina.

Ripps¹,

Mehaffey²,

Siegel³

et al. 1981

The Journal of General Physiology

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A B ST R A C T The bleaching of rhodopsin by short-duration flashes of a xenon discharge lamp was studied in vivo in the cat retina with the aid of a rapid, spectral-scan fundus reflectometer. Difference spectra recorded over a broad range of intensities showed that the bleaching efficacy of high-intensity flashes was less than that of longer duration, steady lights delivering the same amount of energy. Both the empirical results and those derived from a theoretical analysis of flash photolysis indicate that, under the conditions of these experiments, the upper limit of the flash bleaching of rhodopsin in cat is ~90%. Although the fact that a full bleach could not be attained is attributable to photoreversal, i.e., the photic regeneration of rhodopsin from its light-sensitive intermediates, the 90% limit is considerably higher than the 50% (or lower) value obtained under other experimental circumstances. Thus, it appears that the duration (~ 1 ms) and spectral composition of the flash, coupled with the kinetic parameters of the thermal and photic reactions in the cat retina, reduce the light-induced regeneration of rhodopsin to -10%.

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Computer analysis of photochemical changes in the human retina

Cited by 21 publications

References 15 publications

Polygenic Disease and Retinitis Pigmentosa: Albinism Exacerbates Photoreceptor Degeneration Induced by the Expression of a Mutant Opsin in Transgenic Mice

Polygenic Disease and Retinitis Pigmentosa: Albinism Exacerbates Photoreceptor Degeneration Induced by the Expression of a Mutant Opsin in Transgenic Mice

Evaluation of Essential Trace and Toxic Elements in Biological Samples of Normal and Night Blindness Children of Age Groups 3–7 and 8–12 Years

Flash photolysis of rhodopsin in the cat retina.

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