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Biomedical subjects

G S Chen

Publications and source records attributed to G S Chen.

At least 37 records · Page 2Linked to original sources
PubMed1995

Estimation of PCNA mRNA stability in cell cycle by a serum-deprivation method.

A simple scheme was developed to study the mRNA stability of the proliferating cell nuclear antigen (PCNA) gene during cellular transition from the G1/S boundary to a quiescent state. By this scheme, CHO.K1 cells were grown to about 80% confluence and then serum-starved for 40 h for synchronization in a quiescent state. The quiescent cells were serum-stimulated for a period of time (between 8 h and 12 h) and then grown in serum-free medium until being harvested for further analyses. The cellular PCNA mRNA level was analyzed by Northern blotting. As compared with that in cells which were continuously incubated in serum-containing medium, the decline of the mRNA level, after reaching the peak, in these serum-deprived cells was virtually devoid of mRNA synthesis. Thus, this mRNA decay was taken for the measurement of mRNA stability. The advantage of the scheme is that, unlike the treatment of transcription inhibitors, it does not prevent the cells from completing the rest of the cell cycle before returning to the resting state, and so the mRNA stability observed is cell cycle dependent. In contrast with the previous report that the stability of PCNA mRNA in quiescent cells is less by severalfold than that in S phase cells, our study shows that the mRNA stability of PCNA remained constant during the cellular transition from G1/S boundary to quiescent state.

Animals↗
PubMed1995

[A statistical analysis of oral squamous cell carcinoma].

Oral squamous cell carcinoma is the most common malignant tumor of the oral cavity, and it accounts for about 90% of malignant oral tumors. We have retrospectively reviewed 211 patients with oral squamous cell carcinoma which were confirmed by histopathological examination at Kaohsiung Medical College Hospital in the period between 1987 and 1991. There were 194 males and 17 females, with a male to female ratio of 11.4 to 1. The age of the patients ranged from 23 to 95 years, mean 51.96 years, with the greatest incidence of disease in the ages between 40 and 59 years (63.3%). Squamous cell carcinoma occurred most often on the buccal mucosa. There were 40.8% of cases which occurred on the buccal mucosa, 25.6% on the tongue, 17.1% on the gingiva of mandible, 9.5% on the maxilla, 5.2% on the lower lip and 1.9% on the floor of mouth. 195 cases with a recorded history of habits in the patient's medical records were evaluated for the relationships between habits, patient's age and the location of the tumor involved. We have used a general factorial ANOVA to examine the relationship of habits and patients' age. A Hierarchical Loglinear Analysis was used to determine whether there was an association between habits and the location of tumor involved. Of the 195 cases, 144 (73.85%) chewed betel nut regularly. The mean age of the patients with betel nut chewing habits (49.04 years) was significantly younger than that of the patients without betel nut chewing habits (59.27 years) (p = 0.006).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Pharmacokinetics of tablet huperzine A in six volunteers.

AIM: To study pharmacokinetics of tablet huperzine A (Hup-A) in Chinese volunteers to help establishing its drug administration schedule. METHODS: For 6 volunteers after a single oral dose of 0.99 mg, drug concentrations in plasma were assayed by reverse phase high pressure liquid chromatography (HPLC) at 0.5, 0.75, 1.0, 1.25, 1.5, 2, 4, 6, 8, and 10 h. The pharmacokinetic parameters were calculated with a 3P87 program by computer. RESULTS: The time course of plasma concentrations conformed to a one-compartment open model with a first order absorption. The pharmacokinetic parameters were as follows: T 1/2ka = 12.6 min, T 1/2ke = 288.5 min, Tmax = 79.6 min, Cmax = 8.4 micrograms L-1, AUC = 4.1 mg L-1 min. CONCLUSION: Hup-A was absorbed rapidly, distributed widely in the body, and eliminated at a moderate rate.

Adult↗
PubMed1994

Arsenic-related Bowen's disease and paraquat-related skin cancerous lesions show no detectable ras and p53 gene alterations.

We have investigated point mutations of codons 12, 13, and 61 in H-, K-, and N-ras oncogenes as well as p53 tumour suppressor gene exon 5 through exon 9 by PCR-SSCP analysis in 26 skin biopsy tissues from 16 arsenic-related Bowen's disease patients and 6 skin samples from 4 paraquat manufacturing workers. No mutation was found. These results are different from findings with UV associated skin cancers. Interestingly, a silent change at codon 27 of H-ras in one allele was detected in all 4 paraquat manufacturing workers and in 2 of 16 arsenic-related Bowen's disease patients. It is likely that the molecular mechanisms involved in arsenic and paraquat induced skin cancers differ from sunlight-related skin malignancies.

Arsenic↗
PubMed1994

Responses of cutaneous microcirculation to cold exposure and neuropathy in vibration-induced white finger.

In order to clarify the mechanisms of cold temperature on vibration-induced white finger (VWF), three groups of forestry chain saw operators served as the subjects of this study. Groups I and II worked in a cold high-altitude area, and group III worked in a warm low mountain climate. Group I workers had VWF sign [VWF(+)] but groups II and III did not [VWF(-)]. In the present study, finger nailfold microcirculation before and after cold exposure, finger skin sympathetic alpha receptor response, and sympathetic skin response were measured. The results showed that there was no significantly different neuropathy in any of the groups. However, vibration-induced microcirculatory disturbances including blood stasis and red blood cell aggregation were more prominent in VWF(+) group, whereas both of the VWF(-) groups (groups II and III) had no significant difference in microcirculatory disturbances. This suggests that the severity of the microcirculatory disturbances is dose-effect correlated and is aggravated by cold in vibration syndrome. Thus it can be realized that a cold working environment is an important contributing factor in causing microcirculatory disturbances of VWF.

Altitude↗
PubMed1993

Progressive alterations of cytokeratin expressions in the process of chronic arsenism.

Recent studies of an endemic occurrence of chronic arsenism in a limited area on the southwest coast of Taiwan are focusing on its cytokeratin analysis in hopes of tracing the disease's biochemical expression. Specimens were obtained from uninvolved skin and arsenical cancers including Bowen's disease, basal cell carcinoma, and squamous cell carcinoma. In this study, we used two-dimensional polyacrylamide gel electrophoresis to analyse cytokeratin expression. Progressive alterations in cytokeratin expression were found in various skin lesions. These include an expression of K16 in the uninvolved skin; K16 and K6 in Bowen's disease; and K16, K6 and K17 in squamous cell carcinoma and basal cell carcinoma. In addition, we found that the K1 isoelectric variants shifted to more acidic forms with the complete absence of K1 in basal cell carcinoma. K16 expression in uninvolved skin indicates that it is nevertheless in a hyperproliferative status. K17 was expressed in squamous cell carcinoma and basal cell carcinoma, but not in Bowen's disease. The progressive impairment of phosphorylation of K1 and K2 in the process of chronic arsenism provides us with a suitable model for studying the biological significance of phosphorylation in intermediate filaments during chemical carcinogenesis.

Arsenic Poisoning↗
PubMed1993

Study on blackfoot disease: with special reference to evaluating its cutaneous microcirculatory status.

We evaluated the microcirculatory status of blackfoot disease by skin temperature measurement, laser Doppler flowmetry and capillary microscopy. The results of these assessments revealed a good correlation between the disease stage and the microcirculatory status. No effective therapy other than surgical amputation was recommended before. In this study, we treated this endemic disease with prostaglandin E1 (PGE1) infusion therapy. PGE1 was most effective in the erythematous stage and some minor ulcer with an improvement of microcirculatory status. However, PGE1 had no effect in severe ulcerative (ulcer > 0.5 cm) and gangrenous stages. These microcirculatory improvements foreshadowed the improvement of clinical manifestations. The microcirculatory status after PGE1 treatment demonstrated the effectiveness of the therapy.

Aged↗
PubMed1992

[Clinical and scanning electron microscopic studies on Norwegian scabies infection].

Two typical cases of Norwegian scabies were studied clinically, scanning electron microscopically and histopathologically. Case 1 was a boy with Down's syndrome and case 2 was a man with adult T cell leukemia/lymphoma. Their clinical pictures showed hyperkeratotic plaques and warty crusts on hands, feet, ears, elbows and buttocks. Direct examination of the KOH preparation revealed many embryonated sarcoptic eggs, postpartum egg-shells, fecal pellets, larvae and male and female adult mites. Histopathologic examination showed several burrows inside the thick horny layer. Many sarcoptic egg-shells, mites and fecal pellets were found in the burrows. Psoriasiform hyperplasia and parakeratosis were noted, too. The size and shape of the sarcoptic eggs and the detailed structure of mites and molt were observed by using a scanning electron microscope. Besides, hook-like structures were noted at the tarsi of both forelegs and hindlegs. We suggest that the larvae crawl out from longitudinal openings in the egg-shell by the use of hook-like structures. The mites also used these hook-like structures to make the burrows. Scanning electron microscopy provides a good method to understand the dynamics of these burrowing parasites. It is helpful in illustrating the behavior of the scabies mites in their burrows in Norwegian scabies patients.

Adolescent↗
PubMed1992

Alterations of skin-associated lymphoid tissue in the carcinogenesis of arsenical skin cancer.

We investigated the skin-associated lymphoid tissue in arsenical skin cancers, including 14 Bowen's disease, 6 basal cell carcinoma and 6 squamous cell carcinoma patients from an endemic area by immunohistochemical and morphometric methods. There was a progressive decrease of Langerhans cells in the order of normal skin, normal appearing edge and arsenical cancers. A disruption of the uniform Langerhans cell dendrites was also noticed. The Langerhans cell density in arsenical tumors did not correlate with the peritumoral infiltrates. The prominent infiltrated cells in the peritumoral area had T cell markers. The number of peritumoral T lymphocytes in squamous cell carcinoma was significantly less than that of Bowen's disease and basal cell carcinoma. Peritumoral mononuclear infiltrates in Bowen's disease and squamous cell carcinoma showed a higher helper/suppressor T cell ratio than that in basal cell carcinoma. This may be accounted for by a selective increased recruitment of helper T cells to the tumor infiltrates in Bowen's disease and squamous cell carcinoma.

Arsenic Poisoning↗
PubMed1991

Effects of temperature on cutaneous microcirculation in vibration syndrome.

In order to clarify the role of cold on the cutaneous microcirculation in vibration syndrome, groups of rabbits vibrated at 4 degrees and room temperature served as the subjects of this study. A cold provocation test, capillary microscopy, and laser-Doppler flowmetry were used to evaluate the microcirculations of the test rabbits. The results indicated that vibration-induced impairment of the microcirculation was more prominent in the 4 degrees vibration group than in the room temperature group. The severities of the microcirculatory disturbances were dose-effect correlated. Vibration induced not only functional disturbances but also structural destruction of the capillaries. Furthermore cold temperatures enhanced these abnormalities of the blood vessels.

Animals↗
PubMed1991

[Effect of enhancers on cutaneous permeation of piroxicam in vitro].

Enhancing effects on the permeation of piroxicam (Pir) through excised hairless mouse (inbred HRS mice) skin were investigated by measuring flux. Azone 1% was found to be the most effective enhancer studied, increasing the flux about 21 times. The effect of Azone was enhanced by the presence of propylene glycol. Oleic acid, ethylacetate, and ethanol promoted the diffusion of Pir. Other enhancers, such as DMSO, PEG 400, acetone, urea and salicylic acid, showed little or no effect. Pir-beta-cyclodextrin inclusion compound increased the flux about 3 times. The results revealed that lipophilic enhancers were more effective than lipophobic ones.

Animals↗
PubMed1991

[Transdermal permeability of l- and dl-norgestrel through human skin in vitro].

Transdermal permeability of l-norgestrel (l-NG) and dl-norgestrel (dl-NG) at 6 skin regions with and without stratum corneum was investigated by using Valia-Chien double-compartment permeation cells. The permeation rates and accumulative amounts within 72 h in vitro were measured by HPLC. The results showed that the permeation rates of dl-NG through intact skin were significantly higher than those of l-NG (P less than 0.01). For the skins without stratum corneum, the permeation rates and permeation amounts of l-NG and dl-NG were higher than those for the intact skin (P less than 0.01), but no significant difference was seen between l-NG and dl-NG. Hence the stratum corneum played an important role of rate-limiting barrier in the skin permeation of l-NG and dl-NG. It is possible that the difference in permeability between l-NG and dl-NG is related to their partition coefficients.

Humans↗
PubMed1991

[Influence of vehicles on human skin permeation of norgestrel and levonorgestrel in vitro].

In the experiment Valia-Chien skin permeation cell and methods were constructed for investigating the influence of various vehicles on the transdermal absorption of norgestrel (NG) and levonorgestrel (LNG). All of the vehicles were saturated with NG or LNG at 37 degrees C, so variations in permeation were mainly attributable to the vehicle effects. The results showed that the transdermal fluxes of NG and LNG were increased about 5-6 fold using an optimal concentration range of aqueous ethanol as a vehicle relative to that when normal saline was used as a vehicle. The NG permeation rate was about 1-2 fold greater than that of LNG in the above--mentioned saline aqueous ethanol and neat ethanol. Oleic acid (OA) and aqueous ethanol both enhanced synergistically the permeation of LNG through the human cadaver skin. When OA--80% ethanol (0.75:9.25 v/v) was used as a co--vehicle, the flux of LNG was 0.53 micrograms/cm2.h, which was 3 fold and 29 fold respectively greater than that when 80% ethanol and neat OA were used as the vehicle.

Adult↗
PubMed1990

A possible pathogenesis for Blackfoot disease--effects of trivalent arsenic (As2O3) on cultured human umbilical vein endothelial cells.

Blackfoot disease (BFD) is an endemic peripheral vascular occlusive disease found among the inhabitants of the southwest coast of Taiwan. The clinical features of BFD are similar to those of Buerger's disease. Pathology shows arteriosclerosis obliterans and thromboangiitis obliterans. The high arsenic content of artesian well water in the area is regarded as the main causal factor of this disease. Therefore, the purpose of this study was to observe the toxic effects of various arsenic concentrations on cultured human umbilical vein endothelial cells (HUV-EC). The methods of this study included cell growth assay, 51Cr-release assay, and staining of Factor VIII related antigen (FVIII-RAg) and Ulex europaeus agglutinin I (UEA-I) binding sites of HUV-EC. The following data were obtained: 1) no obvious cytotoxicity in 51Cr-release assay; 2) inhibition of the synthesis of both FVIII-RAg and UEA-I binding sites when the arsenic concentration was above 100 ng/ml; 3) dose-dependent inhibition of growth of HUV-EC by any concentration of arsenic. At a higher concentration of more than 100 ng/ml, arsenic inhibited endothelial cell proliferation and glycoprotein synthesis, whereas it only inhibited the proliferation at a lower concentration of less than 50 ng/ml. It is suggested that arsenic, at both higher and lower concentrations, may damage endothelial cells. Such damage may play an important role in the pathogenesis of BFD.

Arsenic↗
PubMed1990

[Transdermal permeability of estradiol through human skin of different body regions in vitro].

Transdermal permeability of estradiol was carried out by using Valia-Chien double-compartment permeation cell for the following 6 skin regions with intact and without stratum corneum: chest, abdomen, hip, upper arm, thigh and back. The estradiol permeation rates and accumulative amounts within 72 h in vitro were examined by HPLC. The results showed that the permeation rates of intact skin from different regions of the body were significantly different (P less than 0.01), and for the skins without stratum corneum over different regions, the permeation rates or the permeation amounts were about 18-55 times higher than that for the intact skin. The results demonstrated that the stratum corneum acts as the rate-limiting barrier in the skin permeation of estradiol, and that the difference in estradiol permeation rates for different skin regions was mainly caused by the different extents of the barrier.

Adult↗