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Biomedical subjects

H S Yu

Publications and source records attributed to H S Yu.

At least 127 records · Page 7Linked to original sources
PubMed1990

Diurnal rhythms of immunoreactive melatonin in the aqueous humor and serum of male pigmented rabbits.

Using specific radioimmunoassays, melatonin was quantified in the aqueous humor and serum of male pigmented rabbits adapted to 12L:12D with lights on at 06.00 h. Melatonin concentrations in the aqueous humor at 08.00 and 16.00 h were similar (mean: 5.23 pg/ml) and significantly lower than those at 22.00 and 01.00 h (mean: 22.06 pg/ml). A parallel rhythm was also demonstrated in the serum with higher melatonin concentrations (daytime mean: 75.26 pg/ml; nighttime mean: 168.94 pg/ml). We propose that the aqueous melatonin rhythm is associated with the rhythmic change in aqueous flow.

Animals↗
PubMed1990

Depletion and repopulation of Langerhans cells in nonsegmental type vitiligo.

The role of Langerhans cells in the pathogenesis of nonsegmental type vitiligo is still unknown. In this study, biopsies were taken from 26 patients at various stages of nonsegmental type vitiligo and morphometrically observed to investigate the kinetics of Langerhans cells in patients at various stages of the disease. A marked depletion of OKT6-positive and ATPase-positive epidermal dendritic cells was noted in patients with active nonsegmental type vitiligo. A repopulation of both OKT6-positive and ATPase-positive epidermal dendritic cells was noted in patients with stable nonsegmental type vitiligo. Profound depletion of epidermal OKT6-positive and ATPase-positive dendritic cells was noted in patients with repigmenting nonsegmental type vitiligo receiving treatments involving topical use of 0.05% Fluocinonide cream or PUVA photochemotherapy. Transmission electron microscopy confirmed the absence of epidermal dendritic cells (Langerhans cells and intermediate cells) in patients with active and repigmenting nonsegmental type vitiligo. In active nonsegmental type vitiligo, two possible explanations are proposed for the depletion of OKT6-positive and ATPase-positive epidermal dendritic cells (presumptive Langerhans cells): 1) the cells are destroyed by cytotoxic factors released during the course of destruction of melanocytes in active vitiligo, and/or 2) they leave the epidermis and migrate to regional lymph nodes to present certain antigens which are released from certain destroyed epidermal cells (keratinocytes or melanocytes) during the course of active vitiligo. The repopulated epidermal Langerhans cells may result from phenotypically transformed dermal dendritic cells in the depigmented lesions of patients with stable vitiligo. Since various therapies which result in repigmentation deplete the density of epidermal Langerhans cells markedly, it is suggested that depletion of epidermal Langerhans cells in stable vitiligo may aid in repigmentation. It is also proposed that the repopulated epidermal Langerhans cells may play a role in inhibiting the proliferation of epidermal melanocytes in depigmented lesions of stable vitiligo, thus various methods of treatment which deplete the Langerhans cells may eventually aid in the repigmentation of nonsegmental type vitiligo.

Adolescent↗
PubMed1990

Ascorbate-enhanced copper toxicity on bovine corneal endothelial cells in vitro.

The present results indicate that 30 micrograms/ml copper was toxic to bovine corneal endothelial cells (BCEC) cultured in a serum-free medium (SFM) when the duration of treatment was 72 hours or more. Copper at 10 micrograms/ml, if mixed with 50 micrograms/ml ascorbate 2 to 3 hours before treatment, caused a transient decrease in the number of nuclei/mm2 at 72 hour, whereas 10 micrograms/ml copper alone was apparently non-toxic. When 10 micrograms/ml copper was added to 50 micrograms/ml ascorbate at the time of treatment, the toxicity was increased. All the treated cells failed to survive beyond 24 hours, and copper at a lower concentration of 1 microgram/ml could inhibit the proliferation of BCEC. We propose that copper toxicity on BCEC is augmented by ascorbate possibly through the increased replenishment of Cu+ and the subsequent enhanced production of free radicals by copper auto-oxidation.

Analysis of Variance↗
PubMed1990

The occurrence of carpal tunnel syndrome in frozen food factory employees.

Two hundred and seven (207) active workers from two frozen food plants were classified according to their daily tasks and placed into three groups. Each classification was evaluated for risk factors which could lead to Carpal Tunnel Syndrome (CTS). The workers were thoroughly studied by structured interviews, neurological screening, and electrophysiological studies. Those workers who experienced little hands' local exposure to cold and low repetitive movements of the wrist (group I) served as the internal standard. In groups II (no local exposure to cold, but a high degree of repetitiveness) and III (a combination of local exposure to cold and a high degree of repetitiveness) 40.54% and 37.19%, of the workers respectively were diagnosed to have CTS by neurological studies. The risk of CTS for group II + III was 14.39 times higher than that of group I, when group I was compared with group II + III (high repetitiveness). After adjusted for sex, age, and/or the length of employment, group III still had a higher risk of CTS than group II. Repetitiveness as well as hands' local exposure to cold were found to be contributing factors in leading to CTS. Recognition, evaluation, and management of CTS in the related industries in Taiwan should be initiated to assure early diagnosis and prevention of this occupationally related syndrome.

Adult↗
PubMed1990

[A study of changes in the ratio of collagen types in skin after long-term treatment with topical glucocorticoids].

The topical glucocorticoids, widely used in the treatment of a variety of skin disorders, usually induce skin atrophy after long-term administration. In this study, the skin from a 30-year-old female patient was used, and the changes in the ratio of collagen types in atrophic skin derived from the treatment with glucocorticoid were investigated in comparison with that of normal human skin. By transmission electron microscopy, the collagen fibrils in the papillary dermis of normal skin were loose and fine, their diameters ranging from 30 to 40 nm; while those in the atrophic skin appeared tightly compact, their diameters increasing to 50-60 nm. The collagen chains, alpha 1 (I), alpha 2 and alpha 2 (III), from peptic digest of skin were separated by interrupted gel electrophoresis. The ratios of collagen type III to type I as calculated from the normal skins of a 21- and a 39-week fetus and a 36-year-old human were 49.45, 45.51 and 43.65%, respectively, while that of the atrophic skin was 12.89%. Therefore, the persistent treatment of skin with topical glucocorticoids results in a decrease in the ratio of collagen type III to type I.

Administration, Topical↗
PubMed1989

Ultrastructural changes of the peripheral nerve induced by vibration: an experimental study.

To investigate the effects of vibration on the peripheral nerves, rabbits were exposed to vibration of 60 cycles/s frequency with 0.35 mm amplitude (acceleration: 51 m/s2) for two hours daily. After 150, 250, 450, and 600 hours vibration, thin sections of the saphenous and median nerves were examined under the electron microscope. Vibration was found to induce the following changes: (1) disruption of the myelin sheath and constriction of the axon, (2) accumulation of vacuoles in the nodal gap and paranodal region, (3) disorganisation of the paranodal end loops and detachment of the paranodal end loops from the axolemma, (4) dilatation of the Schmidt-Lanterman incisures (SLI) and increased density of SLI, and (5) disappearance of neurotubules and neurofilaments in axons. The diameters of myelin sheaths disrupted by vibration varied from 2 to 12 microns. The extent of the myelin disruption is proportional to the vibration dose.

Animals↗
PubMed1989

[Skin eruption and histopathological changes in dengue fever].

Evaluation of histopathological and ultrastructural changes in skin eruptions of three dengue fever patients was performed. The main pathological findings in skin lesions were swelling of the endothelial cells in small vessels of papillary dermis, diapedesis of neutrophils, extravasation of erythrocytes and perivascular mononuclear cells infiltration. Ultrastructural observation revealed degeneration of endothelial cells and neutrophils. The relationships among endothelial cell damage, cell infiltration and hemorrhage were discussed.

Adult↗
PubMed1989

Isolation of Cryptococcus albidus var. albidus in patient with pemphigus foliaceus.

Cryptococcus albidus var. albidus was isolated from the blood of a patient with pemphigus foliaceus after steroid therapy. This organism was found in triple extract peptone medium which is used in our laboratory for blood culture to detect aerobic and anaerobic bacteria. Identification of Cryptococcus was made by the API 20C yeast carbohydrate assimilation test, together with conventional procedures. These include the demonstration of chlamydospore production, germ tube test, urease test, nitrate assimilation test and colony morphology. The patient infected with Cryptococcus albidus var albidus had a good response to oral ketoconazole therapy, then the recovered and was discharged. The isolate obtained from this case may be regarded as an etiologic agent in fungemia.

Cryptococcosis↗
PubMed1988

Interstrand crosslinks due to 4,5',8-trimethylpsoralen and near ultraviolet light in specific sequences of animal DNA. Effect of constitutive chromatin structure and of induced transcription.

We have used low-level photocrosslinkage to study chromatin effects on psoralen intercalation at specific DNA sequences of various complexities in intact, cultured, Drosophila cells. Alkali-denatured DNA connected in both strands to a 4,5',8-trimethylpsoralen (TMP) interstrand crosslink is insensitive to digestion by the single strand-specific nuclease S1 and does not hybridize to complementary DNA. Crosslink number at any ultraviolet light exposure increases in proportion to the concentration [PS] of TMP dark binding sites that are occupied. The crosslinking constant, K, is the increase in crosslink number per length DNA per increment [PS]. Many factors influence K, including sequence composition and ionic strength. We show here that the ratio of K at any specific sequence (Kh, from hybridization measurements) to Kh at any other specific sequence or to K of total DNA (Kf, from fluorimetry measurements) can be calculated from measurements of crosslinkage, the mass fraction of the sequence in question or of total DNA that is connected in both strands to a crosslink. When crosslinked and uncrosslinked DNAs fragmented by mechanical shear were mixed in known proportions, Kf exceeded Kh of a single-copy gene by 15%. We treated cells with TMP plus near ultraviolet light, then tested for crosslinkage and for hybridization. A single-copy, larval gene at 70D, and a 250-copy type 1 ribosomal DNA intervening sequence, neither of which is transcribed in these cells, were as sensitive to crosslinkage as total, cell DNA. However, single-copy, heat shock gene sequences from loci 63BC and 95D, and the 180-copy ribosomal DNA coding sequence were more sensitive to crosslinkage than total DNA in the same preparations. The excess was largest in the shortest fragments, indicating a localized effect. The same sequences were crosslinked less readily than total DNA in vitro; we calculate a 3.4 to 3.8-fold excess crosslink number in these sequences due to chromatin microenvironment. We tested for effect of transcriptional induction on crosslink sensitivity in the heat shock genes. At low [TMP], heat shock stimulated crosslinkage at or very near heat shock genes in cells, but not in other sequences or in naked DNA. However, overall crosslink sensitivity was unaffected by heat shock. This suggests that transcription increased the affinity of some heat shock gene DNA binding sites for TMP without increasing the number of such sites.

Animals↗
PubMed1988

Zinc amelioration of cadmium toxicity on preimplantation mouse zygotes in vitro.

Zinc, at a concentration of 5 or 10 micrograms/ml medium, has been shown to protect mouse preembryos in vitro from the toxicity of cadmium at a concentration of 5 micrograms/ml medium after a simultaneous treatment of the ions from four-cell to morula or from morula to blastocyst for 24 hours. Such an amelioration indicates that cadmium toxicity is a result of the unique property of the cadmium ion and is not due to an alteration in the culture medium after the addition of an extra metallic ion. Zinc probably ameliorates cadmium-treated mouse preembryo by competing with cadmium for uptake or some other metabolic processes. In view of the well-documented competition between cadmium and zinc ions for binding sites in many other cell types, some macromolecules to which similar divalent metallic ions bind competitively may also exist in the mouse preembryo. This suggests that a protective mechanism dependent on the metal-metal interactions begins to operate in the mouse preembryo at a very early stage of differentiation before implantation.

Animals↗
PubMed1988

Cadmium toxicity on mouse pre-implantation zygotes in vitro: interactions of cadmium with manganese, zinc and calcium ions.

Simultaneous treatment with cadmium chloride (5 micrograms/ml medium) and manganese chloride (5 or 10 micrograms/ml medium) was less toxic to mouse pre-implantation zygotes in vitro than cadmium alone. Such a protective effect of manganese, resembling that of zinc, suggests that amelioration of cadmium-treated pre-embryos in vitro is not unique to zinc. The amelioration may require only the presence of another divalent metallic ion, such as zinc or manganese, which is capable of competing with cadmium for binding sites possibly involved in uptake. Under calcium-free conditions cadmium embryotoxicity is enhanced, showing a summation effect of the cadmium toxicity and the lack of calcium. This supports the notion that excessive exogenous calcium may render the effects of cadmium on compaction inconspicuous. The non-compacted pre-embryos treated with 5 micrograms/ml cadmium in a calcium-free medium had fewer blastomeres than those treated at a lower dose of 1 microgram/ml. Cadmium appeared to inhibit the cleavage from 8-cell to 16-cell stage, but not from 4-cell to 8-cell.

Animals↗
PubMed1988

Syndrome of deltoid and/or gluteal fibrotic contracture: an injection myopathy.

One hundred and fifteen cases of injection myopathy with deltoid and/or gluteal fibrotic contracture were studied, almost all of whom had definite histories of repeated intra-gluteal or intra-deltoid injections. One third had siblings affected by the same fibro-muscular disorders manifested by focal muscle atrophy and limitation of adduction and flexion of the shoulder or hip. Electromyography disclosed myopathic changes of the fibrotic muscles. Muscle biopsy showed marked perimysial and endomysial fibrosis with non-specific degeneration, regenerative changes and, in some cases, partial denervation signs. Under the electron microscope, endomysial and perimysial collagen fibrils lost their normal unimodal diameter distribution and showed a rather broad spectral distribution of diameters suggesting a defective control of collagen formation in this disease entity. Repeated injection injuries and myotoxicity resulting in multifocal myositis are the first trigger of this fibrotic syndrome, and abnormal control of collagen formation could be another important pathogenic factor.

Adolescent↗