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Biomedical subjects

D T Yew

Publications and source records attributed to D T Yew.

At least 19 recordsLinked to original sources
PubMed1992

Acetylcholinesterase-containing neurons, substance P and enkephalin fibers in the ventral horns of developing human embryos and fetuses.

The presence of the acetylcholinesterase neurons and substance P-like and enkephalin-like fibers in the various nuclear columns of the ventral horns of the spinal cords was studied in the developing human by acetylcholinesterase histochemistry and substance P and enkephalin immunohistochemistry. Acetylcholinesterase-positive neurons initially appeared in the lateral neuronal columns and eventually were also observed in the medial columns as well as the median columns at various levels of the spinal cord by 10 weeks' gestation. Acetylcholinesterase-positive neurons in the lower sacral levels were not detected until 11-12 weeks' gestation. Diffused substance P- and enkephalin-like fibers were demonstrated as early as 10 weeks' gestation but did not align with any particular nuclear column until after 15 weeks' gestation. These fibers further increased in length and adopted reticular branching patterns and many of these tended to surround the cell bodies of the nuclear columns. Possible interaction of acetylcholinesterase neurons and substance P and enkephalin fibers would commence by 15 weeks' gestation.

Acetylcholinesterase↗
PubMed1992

Immunohistochemical localization of enkephalin and substance P in the nucleus caudalis of the spinal trigeminal V in the medulla oblongata of the human fetus.

The distribution of enkephalin-positive neurons, substance P-positive and enkephalin-positive fibers was studied in the nucleus caudalis of the trigeminal spinal V in the medulla oblongata regions of developing humans (12 weeks gestation to 40 weeks gestation). Enkephalin-positive neurons were identified in all the subnuclei of the nucleus caudalis as early as 12 weeks of gestation and increased in number as the fetus aged. Substance P-positive neurons were absent in this area throughout development. On the other hand, substance P-positive and enkephalin-positive fibers were present in all the subnuclei, again commencing as early as 12 weeks of gestation. These fibers tended to be linked to each other in the different subnuclei and to the reticular formation in this area and to increase significantly in quantity by the latter quarter of pregnancy. These results show the early presence of these neurons and fibers in the first trimester of development.

Abortion, Spontaneous↗
PubMed1979

Cell kinetic in retinal cell morphogenesis.

The nuclear volumes and the percentage of pycnosis were studied in the various forms of retinal cells as related to the critical stages of morphogenesis. Each cell type was found to have a different mode of nuclear volume increase. The percentage of pycnosis was found to be highest at the stages when the inner and outer segments were established, i.e., a stage when the retinal circuitry was completed.

Animals↗
PubMed1979

Aging in retinas and optic nerves of 2.5- to 9-month-old mice.

Aging of the retina and optic nerve was studied in 2.5- to 9-month-old albino mice. A change was found in the number of visual cells and in the distribution of large versus small optic nerve fibers. No significant change was found in the number of retinal phagosomes and in the total number of optic nerve fibers.

Age Factors↗
PubMed1979

Comparative ultrastructural study of the optic nerves and visual cortices of young (2.5 months) and old (17 months) mice.

The aging optic nerves and visual cortices were studied in mice. Changes in the morphology of neuroglia were evident in the optic nerve but no difference in the numbers of neurotubules or myelin sheaths optic nerve fibers in the aged were observed. Large myelinated fibers, however, begun to degenerate. In the aging visual cortices, a higher proportion of dendrodendritic contacts were present and microglia cells were found to be active.

Aging↗
PubMed1979

Ratio of rods and different cones in fishes of shallow sea.

The retinas of 4 fishes (Periophthalmus chrysopilos, Scorpaenoides marmoratus, Nemipterus bathybins, Taius tumifrons) were analysed. Rods were found to increase with depth but twin cones were not found to descrease with depth. A regional difference was also observed in the distribution of these elements in the retinas.

Animals↗
PubMed1979

The sequential development of the higher visual centers in the C.N.S. of the quail.

The development of the optic tectum and the main nuclei of the visual pathways were studied in the quail and correlated with retinal development. The lateral geniculate nuclei began to establish by the 8th day of ineubation and the optic fibre reached the optic tectum by the 10th day, a time when the retina acquired its inner segments. By the 14th day when the retina became fully development, the cytological architecture in the tectum and the appearing of the other visual nuclei were completed.

Animals↗
PubMed1979

The various forms of outer segment disk shedding in the albino rats.

The forms of shedding of outer segment disks were observed in the retinas of albino rats. Different forms included those coming from the tips and sides of the outer segments and many other variations. All these detached disks began to undergo morphological changes before being taken into the pigment epithelium.

Animals↗
PubMed1978

Further studies on the effect of red and far red light on rat retinal development.

The influence on the development of the outer segments of the rat retina of far red and red light in different sequences was investigated. The far red treatment appeared to be dominating, and for animals treated with far red light first, further treatment of red light could not bring the outer segment growth back to normal. The treatments also initiated different dopamine uptakes in the retinas.

Animals↗
PubMed1978

The origin and initial development of the pecten oculi.

The development of the pecten oculi was studied in the chick (Gallus gallus). The initial development commenced on the 9th day of incubation. The pigment cells in the pecten were derived from the pigment epithelium of the retina and the connective tissue and blood vessels were continuous with those of the choroid.

Animals↗