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Biomedical subjects

D T Yew

Publications and source records attributed to D T Yew.

At least 73 records · Page 4Linked to original sources
PubMed1989

Immunohistochemical studies on the development of 5-HT (serotonin) neurons in the nuclei of the reticular formations of human fetuses.

5-HT-positive neurons were detected by the PAP immunohistochemical methods in different nuclei of the reticular formations of human fetuses as early as 10 weeks of gestation. The majority of positive 5-HT cells were located in dorsal raphe and central superior nuclei, and there was a reduction of these neurons per 40-microns section as the fetus aged.

Cell Count↗
PubMed1989

Optic nerve sectioning does not affect the development of the retina.

The development of the retina of the albino rat was studied after sectioning of the optic nerves on the 2nd postnatal day. The 2nd day represents a stage at which the retina shows only the ganglion cell layer clearly delineated from an undifferentiated mass. Section of optic nerves at this stage did not affect the subsequent retinal development. Both control and experimental eyes developed at the same pace. Some minor degrees of 'retardation' e.g. the sizes of outer segments, appeared to deviate in the experimental retinae.

Animals↗
PubMed1989

Stimulation of collagen formation in the intestinal anastomosis by low dose He-Ne laser.

The effect of low dose He-Ne laser on the healing of intestinal anastomosis was studied in the albino rat. A small piece of jejunum was removed from each rat and the ends sutured back with a simple interrupted pattern. In the experimental animal, the anastomosis was irradiated through an optic fiber with a He-Ne laser (1 mW) for 15 minutes whereas in the control animal, the anastomosis was not irradiated. The differences between the two groups were compared by histology, transmission electron microscopy, scanning electron microscopy and autoradiography 3 and 7 days after operation. The laser treated experimental animals demonstrated thicker collagen fibers and an increased quantity of collagen at the junction of the anastomosis compared to control animals. Increased uptake of labelled proline was also evident in the laser treated animals. These observations all point to a possible enhancement of collagen synthesis triggered by laser irradiation.

Anastomosis, Surgical↗
PubMed1989

Histochemical responses in the retina after acute blood loss.

Adult albino mice were bleed through the hearts by cardiac puncture under Nembutal anesthetic. 0.3 ml of blood was withdrawn form every animal. The retinae were then studied on a timed basis with succinic dehydrogenase histochemistry and alkaline phosphatase histochemistry. In control retinae, high SDH activities were localized in the inner segments, outer plexiform, inner plexiform, and ganglion cells layers and high alkaline phosphatase activities were localized in the ganglion cell layers and the vessels of the plexiform layers. Decrease in the enzymatic activities of both SDH and alkaline phosphatase in these layers were most evident 5h after bleeding. 9 to 24 h after bleeding, a compensatory increase was detected. 48 to 72 h after, the enzymatic activities decreased again. Reperfusion of experimental animals with 5% dextrose would increase the retinal enzymatic activities back to normal, even if the reperfusion was carried out as late as 48 h after bleeding.

Alkaline Phosphatase↗
PubMed1988

Localization of substance P and enkephalin by immunohistochemistry in the spinal cord of human fetus.

The peroxidase-antiperoxidase method was used to study the distribution of substance P and enkephalin during development of the spinal cords of human fetuses. Thirty-seven cases were collected, ranging from 5- to 40-weeks-old (fetal ages). Both types of transmitters were present initially around the fifth week in the mantle layer of the base of the dorsal horn, around the tenth week at the anterior gray and the intermediate gray and around the sixth week at the marginal layer at the base of the ventrolateral funiculus. Substance P- and enkephalin-positive sites at the marginal layers at the base of the dorsolateral funiculus were evident in the same area at 5-6 weeks. The positive fibers in the dorsal horn were initially located in the superficial layers. By the eleventh week, the positive sites spread to other surface layers at the lateral sides of the dorsal horns bilaterally at all spinal levels above the sacral. In the sacral levels adjacent to the conus medullaris, the spreading to surface layers was not apparent bilaterally until the seventeenth week. By weeks 18-26 the positive sites penetrated deeper in the dorsal horn and by week 27 assumed the adult path. The enkephalin cell bodies were present in the Rexed layers I and II of the dorsal horn and the substance P-positive sites were apparent in the dorsal ganglia of the 28-40-week-old fetuses.

Enkephalins↗
PubMed1988

Responses of the retinal pigment epithelium of the mouse after acute loss of blood.

Albino mice were bled through the hearts by cardiac puncture and 1/2, 1/3 and 1/4 mls of blood were taken out from 3 groups of animals. respectively. Half of the experimental animals were reinfused with 5% dextrose 1 h after bleeding. All were killed either 2, 5, 9, 24, 48 or 72 h after bleeding, and the phagosome numbers per 5 pigment cells counted and compared with control retinae. A severe decrease was evident after bleeding and the decrease leveled off 48 h afterwards. Reinfusion with dextrose had a positive beneficial effect.

Animals↗
PubMed1988

Morphological studies of the choriocapillaries and pigment epithelium of the eye after acute blood loss.

Albino mice were bled through the hearts and 1/3 ml of blood withdrawn from each animal. The choriocapillaries and the pigment epithelia of the eyes were selected for observations using the electron microscope. Morphological changes were apparent during the first 72 h after bleeding. Increase of vesicles in both the endothelial cells and the basal infoldings of pigment cells were features. Thickening of basal infoldings, thinning out of Bruch's membrane (with decrease content of fibrillary substances) as well as a transient disappearance of the diaphragms of pores of endothelial cells were also observed. Trypan blue dye was also found to have diffused into the retina in the first 24 h after bleeding. These processes appeared to augment the decreased nutrient supply to the retina after blood loss.

Animals↗
PubMed1988

Preliminary observations on the effects in vivo and in vitro of low dose laser on the epithelia of the bladder, trachea and tongue of the mouse.

The effects of low dose CW laser were studied by in vivo and in vitro systems. The experimental tissues that were used included bladders, tracheas and tongues as experimental tissues. Buddings (round surface projections) from the transitional epithelium of bladder were frequently observed 3 days after laser treatment in both in vivo and in vitro systems. The trachea and tongue were less affected. In both the in vivo and in vitro systems, some epithelial cells of the trachea showed decreased microvilli and cilia 3 days after treatment whereas the epithelial cells of the tongue revealed no response to laser treatment in both systems. Low dose laser, however, appeared to promote the rate of healing of experimental tongue ulcer: healing was about 1 day earlier in the laser treated than non-treated animals and vessel infiltration and epithelialization were detected earlier in the treated.

Animals↗
PubMed1988

The anatomic basis of femoral component design.

The shape of the femoral canal is variable, much more variable, in fact, than most contemporary designs of femoral components would suggest or can accommodate. In the face of this variability, line-to-line or surface-to-surface contact is not expected between cementless implants and much of the endosteal surface. It also is apparent that changes in implant design are still needed if the normal biomechanics of the hip joint are to be restored in each patient and if component fixation is to be optimized. Most cementless components aim to achieve proximal load transfer to the femoral canal. However, increasing clinical evidence suggests that distal filling of the femur also is necessary to minimize the incidence of postoperative symptoms, particularly in revision procedures. If this is indeed the case, more accommodating designs of femoral components are needed that will enable proximal and distal fitting at the femoral canal so that stable fixation may be achieved regardless of variations in bone geometry.

Aging↗
PubMed1987

Optic nerve transection and tectal removal affect phagocytic activity of the pigment epithelium in goldfish.

The phagocytic ability of the pigment epithelium after optic nerve sectioning and tectal removal was investigated in the goldfish by the method of ingestion of latex beads. 4 days after sectioning, an increase in latex beads was evident which decreased by the end of the first week. Tectal removal also triggered increase intake of latex beads which was presented after 7 days.

Animals↗
PubMed1987

The eyes and the orbits of 2 species of fishes with "dorsal eyes".

The eyes of 2 species of fishes with dorsal eyes Uranoscopus oligolepis and Paralichthyes olivaceus were studied. In the Uranoscopus, ciliary projections were not conspicuous and in the Paralichthyes, the projections were small. 3 types of photoreceptors were observed in both species--rods, single cones and twin cones. In both species, the number of twin cones increased towards the central retinae and in the Paralichthyes, the single cones also increased in number. The rods were lowest in the central region. In the orbit, both species displayed complex solid bones. For example, the lateral border of the orbit was a complex formed by the lacrimal, suborbital, postorbital and parietal. In the Paralichthyes, the lateral orbital border was actually continuous with the orbital and parietal bones and the border was not distinct. The formation of fused plates would serve to restrict eye movement as well as to resist deep sea pressure acting from above.

Animals↗
PubMed1986

Further studies on the effect of low-dose laser irradiation on cultured retinal pigment cells of the chick.

The effect of low-intensity laser irradiation on pigment cells cultured by chorioallantoic method was studied. Laser irradiation influenced the cell shapes and sizes of the pigment cells. Metabolically, this treatment increased thymidine uptake and incorporation but reduced those of leucine. The phagocytic activity as measured by latex particles uptake was not affected. It was concluded that the biological effect of laser irradiation on cell cultures depends on the dose applied, the individual tissue and other factors.

Animals↗
PubMed1986

The functional activities of the pigment epithelium in aging.

The phagocytic ability of the pigment cells of the retinae of mice of different ages was studied in 2-, 5-, 7-, and 9-month-old animals. A decrease in activity was evident as the animals aged. There was also a difference in the response pattern of enzymes (as demonstrated in the case of alkaline phosphatase) in the first 35 h after latex bead injection.

Aging↗
PubMed1986

Early patterns of neuronal degeneration in the retina of the goldfish after optic nerve sectioning.

The early patterns of retinal degeneration were studied in the goldfish after optic nerve sectioning by l.m. and e.m. Beginning on the 2nd postsurgical day there was an initial degeneration of neurons in the ganglion cell and inner nuclear layers of the central retina. Massive ganglion cell degeneration in the whole retina (60%) as well as degeneration of neurons in inner and outer nuclear layer of the peripheral retina was evident around the 7th postsurgical day. The early degenerating cells appeared to be cones and cone bipolars.

Animals↗