Search PubMed⌕ Search

Biomedical subjects

D T Yew

Publications and source records attributed to D T Yew.

At least 91 records · Page 5Linked to original sources
PubMed1985

Acute responses of rat retina after optic nerve ligation: a biochemical and histochemical study.

The response of rat retina after optic nerve ligation was studied by biochemical and light microscope autoradiographic methods. The uptake of labelled leucine, dopamine and GABA in operated retinas were all decreased as early as 1 day after ligation. Autoradiographic morphometry revealed variations in the time course as well as in the degree of reduction of substrate uptake ability in different retinal cell layers after ligation. Findings indicate the ganglion cells and the dopaminergic cells in the outer plexiform layer are more sensitive to interruption of neuronal flow. Moreover, there may be interactions between the photoreceptors, the GABAergic and the dopaminergic cells in rat retina.

Animals↗
PubMed1985

Photic responses of the retina at different ages: a comparative study using histochemical and biochemical methods.

The alkaline phosphatase and DNA-RNA activities in the retinas of young and old albino mice were determined histochemically after photic exposure. Different patterns between the two age groups were obtained for the alkaline phosphatase reaction before and after photic exposure. In the young animals, more retinal layers showed increased activity after exposure whereas in the old animals, the converse was true. DNA-RNA reaction also revealed decreased DNA activities in the old animals 30 h after exposure. The results were also correlated with biochemical studies on 2-deoxyglucose, dopamine and leucine uptakes.

Aging↗
PubMed1985

Photic responses of the retina at different ages. A comparative study using histochemical and biochemical methods.

The alkaline phosphatase and DNA-RNA activities in the retinas of young and old albino mice were determined histochemically after photic exposure. Different patterns between the two age groups were obtained for the alkaline phosphatase reaction before and after photic exposure. In the young animals, more retinal layers showed increased activity after exposure whereas in the old animals, the converse was true. DNA-RNA reaction revealed decreased DNA activities in the old animals 30 h after exposure. The results were also correlated with biochemical studies on the uptake of 2-deoxyglucose, dopamine and leucine.

Aging↗
PubMed1985

Eye enucleation and regeneration of neural retina in axolotl larvae (Ambystoma mexicanum).

The eyes of Axolotl larvae were enucleated at stages 30 and 37. Animals with single dorsomedian eyes resulted in the first case (i.e. stage 30). When a piece of pigment epithelium was re-implanted into stage 37 animals at the site of the lesion, limited regeneration was observed when the implant formed a vesicle, but, when the pigment epithelium remained "open" regeneration of the neural retina was extensive. The possible resons for this difference was discussed.

Ambystoma↗
PubMed1984

Labelled leucine uptake in the visual cells and pigment epithelium of young albino rats in response to different light-dark cycles.

The leucine uptake in the visual cells and pigment epithelium were studied in the young albino rats after exposing to different light-dark cycles. Some form a cycle pattern was found in the visual cell layer and two peaks were recorded. The pattern on the uptake in the pigment epithelium was less distinct but at least a peak in the morning was recognized. The peaks could be shifted by manipulating the light-dark environment.

Age Factors↗
PubMed1984

A multiple approach to the study of high dose laser lesions on the retina.

The retinae after high dose laser treatment were followed for a period of 60 d. Histochemical evaluation (cytochrome oxidase and succinic dehydrogenase reactions), neurochemical evaluation (labelled DOPAmine uptake) as well as ERG recordings of the lesioned eyes were performed in this period. It was found that the results of different evaluations agreed well with each other and with our previous E.M. studies.

Animals↗
PubMed1984

Studies of the maturation of the visual system of the albino mouse.

The maturation of the albino mouse visual system was studied using mainly the retinae and visual cortices. Increased proportion of ganglion cells was detected in the central region of the retinae of 4 month old animals. The relative thickness of layer 4 of the visual cortex also reached a high in the 4 month old mouse. These results were further strengthened by detection of an increase in the spicules on the dendrites of stellate cells in layer 4 of the cortex concomitant with an increase in GABA and Noradrenaline uptake in the visual cortex. All that appeared to point to that the visual system of the albino mouse reached maturation when they were 4 months old.

Aging↗
PubMed1984

Observations on the "dorsal eyes" of fishes.

The positioning of the eyes in 14 species of flat fishes and 8 species of non-flat fishes were studied by morphometrical means. All of these had dorsally located eyes and the eye positioning of the flatfish was related to the positioning of the mouth and significant shifting in the position was evident in this group during growth.

Aging↗
PubMed1984

A biophysical, morphological and morphometrical survey of the eye of the small shark (Hemiscyllium plagiosum).

The biophysical and morphological characteristics of the small shark's ( Hemiscyllium plagiosum ) eye were studied. The focal lengths of the lens were found to be very short. A small proportion of cones were present in the retina and this proportion varied with the weights of the sharks. The topographic distribution of cones in different segments of the retina was also presented.

Animals↗
PubMed1983

An autoradiographic study of the retinofugal projections in the shark, Hemiscyllium plagiosum.

The retinofugal projections in the shark, Hemiscyllium plagiosum were studied after unilateral eye injection of tritiated proline. The results showed that each eye in this animal projects not only to the contralateral side of the brain but also to several ipsilateral visual centers including the nucleus suprachiasmaticus, ventrolateral nucleus of the optic tract and the optic tectum. These results suggest that some of the visual centers in this animal receive direct retinal inputs from both eyes as is the case in many other animals and most notably in mammals.

Animals↗
PubMed1983

Microscopic evaluation of the sequential degeneration and repair of the retinae of albino mice after high-dose laser irradiation.

After irradiation of the retinae of albino mice with a dose of 13 J, using a ruby pulse laser, the lesions were followed for a period of 60 days. Severe degenerations were observed in the outer layer 2-9 days after irradiation. By the 21st day after irradiation, the pigment epithelium started to regenerate and outer segments began to reform. Progressive recovery and repair were by and large completed by the 60th day after irradiation.

Animals↗
PubMed1983

The morphology and maturation of the optic tectum of the small shark (Hemiscyllium plagiosum): a morphometrical, ultrastructural and histochemical study.

The morphometrical, ultrastructural and histochemical aspects of the optic tectums of the sharks (Hemiscyllium plagiosum) of different sizes were studied. The 1,000 g animals revealed 2 areas of heavy neuronal concentration. Ultrastructural studies showed an increase in the sizes of tectal neurons and in the sizes of myelinated fibers as well as an increase in the branching system of neurons as the animal matured. A change in the ratio of the types of synaptic contacts was evident in the larger animals. 3 types of glia cells were also observed in these animals. Histochemical studies indicated very little difference between the animals of different sizes except a possible increase of cytochrome oxidase activity.

Animals↗
PubMed1982

Stimulating effect of the low dose laser - a new hypothesis.

Increase in the amount of secretary material (interreceptor matrix) surrounding the visual cells was observed after laser treatment. At the same time, an increase in labelled uridine uptake by the pigment epithelium was detected. The increase uptake was highest 4 h after laser treatment.

Animals↗