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Biomedical subjects

J G Chen

Publications and source records attributed to J G Chen.

72 records · Page 4Linked to original sources
PubMed1991

[Study on screening for primary liver cancer in high risk population of an endemic area].

Positive HBsAg males aged 30-59 years in Qidong were considered a high risk population for primary liver cancer (PLC). A screening study was conducted among 3,958 high risk population which were assigned randomly to a screening group or to a non-screening group. 2,580 persons were screened by alpha-fetoprotein (AFP) once every six months, the incidence rate of PLC was 1,599.38 per 100,000 person-years (PYs), and that in non-screening group with 1,378 persons was 729.39 per 100,000 PYs. Screening survey was also done among 2,332 males aged 30-59 years with negative HBsAg at one-year interval, and the incidence was 128.76 per 100,000 PYs. 26 (86.67%) of 30 PLC patients found in the screening survey were stage I PLCs, but none in 11 out-patients was found in this stage. This study suggests that periodic AFP screening for high risk population is suitable for the high-incidence area, and is one of the effective ways of secondary prevention for PLC.

Adult↗
PubMed1991

Feasibility of a prospective study of smoking and mortality in Qidong, China.

Qidong is a rural county in eastern China with particularly good facilities for epidemiological research: cigarette use by adult males is widespread (70% now smoke), male lung cancer rates already appear to be rising, the population is stable and well served by a county-wide network of health care facilities, and systematic county-wide registration of all deaths has existed since the mid-1970s, causes currently being assigned according to the 9th International Classification of Diseases.

Adolescent↗
PubMed1990

Immunoglobulin G-dependent classical complement pathway activation in neutrophil-mediated cytotoxicity to infective larvae of Angiostrongylus cantonensis.

The participation of antibody and complement in cell-mediated adherence and cytotoxicity to infected larvae (L3) of Angiostrongylus cantonensis was investigated in vitro. Of the different cell types involved in the reaction, neutrophils were seen to have a predominant role in immune serum--dependent adherence and cytotoxicity to L3. In the presence of immune serum, cytotoxicity to L3 by neutrophils from infected rats was twice that of neutrophils from normal rats. Although mononuclear cells and eosinophils from infected rats significantly increased the adherence to L3, they had little lethal effect on L3. A further study using gel filtration (Sephacryl S-200) and affinity chromatography (protein A) revealed that immunoglobulin G (IgG) alone was responsible for the complement activation in neutrophil-mediated killing of L3. Neither adherence nor cytotoxicity to L3 by neutrophils were affected when immune serum was heated to 50 degrees C or treated with zymosan, but they were markedly decreased when immune serum was treated with Mg2(+)-ethylene glycol-bis-(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid. The results of this study indicate that the neutrophil-mediated adherence and cytotoxicity to L3 of A. cantonensis are mediated through IgG-dependent classical complement pathway activation.

Angiostrongylus↗
PubMed1990

Studies on the relation between bladder cancer and benzidine or its derived dyes in Shanghai.

Shanghai is the largest industrial centre in China and has a history of about 50 years in producing and applying benzidine derived dyes. A series of epidemiological studies on the carcinogenicity of benzidine and its derived dyes have been performed since 1979. This report describes three such studies. A case-control study was carried out on 344 cases of bladder cancer, each matched for age and sex, with a person without bladder cancer. Factors studied were occupational exposure, smoking, drinking, medical histories, and family history of bladder cancer and other carcinomas. The correlation between bladder cancer and occupational exposures (relative risk (RR) 5.71) was greater than that between bladder cancer and smoking (RR 1.53). A retrospective cohort study was conducted in seven dyestuffs factories where benzidine had served as an intermediate in the manufacture of dyes before 1976. The cohort was made up of 550 men and 186 women. The men were divided into two groups according to job; 354 were assigned to a presynthesis group and 196 to a postsynthesis group. Those in the presynthesis group were thought to have been exposed to benzidine and the subjects in the postsynthesis group were exposed mainly to its derived dyes. The 15 cases of bladder cancer diagnosed were all in the presynthesis group, although an excess of bladder cancer was also seen in the whole cohort. The standardised incidence ratio (SIR) of bladder cancer was 1918 in the whole cohort and 3500 in the presynthesis group. Moreover, the SIR of bladder cancer in a subgroup working directly with the assignment, transport, and mixing of benzidine was as high as 7500. A further retrospective cohort study was made on incidence of cancer among 1420 workers who used benzidine derived dyes in 43 textile printing and dyeing factories. No excess carcinoma was found. These results suggest that, in Shanghai, the main cause of bladder cancer is occupational exposure, especially to benzidine. The risk of bladder cancer, however, existed only in the presynthesis stage of dye manufacture.

Benzidines↗
PubMed1990

[A cohort study on the cancer experience among workers exposed to benzidine-derived dyes in Shanghai leather-tanning industry].

901 male workers who have ever been exposed to the benzidine-derived dyes for more than 1 year in Shanghai leather-tanning industry, were investigated about their occupational history, smoking and drinking histories, case history of cancer, and the causes of death. The results showed that there was an excess morbidity of bladder cancer in this population, and the SIR was 273 (P = 0.05) compared with the general population of Shanghai urban. It may be noted that the excess of the bladder cancer was presented mainly in those workers whose ages of the first exposure were under 19 years old, and the bladder cancer incidence seemed to be associated positively with the cumulative duration of exposure. The survey about the smoking history did not show any obvious relationship between smoking and the development of the bladder cancer. Moreover, it was seen that a trend of excessive in incidence of the nasopharyngeal cancer and the lymphosarcoma existed in this population.

Adult↗
PubMed1990

[Lung cancer mortality in Qidong (1958-1989) and its trend prediction].

An epidemiologic study of lung cancer mortality in Qidong in the years 1958-1989 was performed based on the data from retrospective survey and registry on cancer. The mortality of the cancer was found to be increasing since 1958. For instance, the rate was 1.04/100,000 in 1958, 9.00/100,000 in 1972, and 21.38/100,000 in 1989. Grey dynamic model was used and the equation established was written in the form Yt = (X1 + 285.078676) exp [0.040 851 (t-1)]-285. 078 676. The rising trend in lung cancer leads to the prediction that this disease will rank second instead of stomach at the end of this century, and may eventually overtake liver cancer as the number one cancer death cause two decades later. As a research strategy lung cancer studies in the rural area should be equally stressed.

China↗
PubMed1989

Monoclonal antibodies specific to chicken iodopsin.

Monoclonal antibodies (mABs) from hybridoma cells were raised and screened with a purified cone pigment, iodopsin, from the chicken retina. Four different methods were used to test these antibodies: (1) dot-immunobinding assay; (2) enzyme-linked immunoabsorbent assay (ELISA); (3) one dimensional immunoblotting and (4) two dimensional immunoblotting. Three classes of antibody producing cell lines were identified. One class produces a mAB specific to iodopsin. The mAB from the second class crossreacts with iodopsin and probably one of the other three cone pigments. The mAB from the third class probably crossreacts with all the four cone pigments in the chicken retina. The mABs from all these classes of hybridoma cell lines were selected so that they do not crossreact with rhodopsin. Two dimensional immunoblotting indicated that iodopsin has a much higher isoelectric point than rhodopsin, as suggested from the known amino acid sequences of human rod and cone pigments.

Animals↗
PubMed1989

Wavelength regulation in iodopsin, a cone pigment.

The opsin shift, the difference in wavenumber between the absorption peak of a visual pigment and the protonated Schiff base of the chromophore, represents the influence of the opsin binding site on the chromophore. The opsin shift for the chicken cone pigment iodopsin is much larger than that for rhodopsin. To understand the origin of this opsin shift and the mechanism of wavelength regulation in iodopsin, a series of synthetic 9-cis and 11-cis dehydro- and dihydro-retinals was used to regenerate iodopsin-based pigments. The opsin shifts of these pigments are quite similar to those found in bacteriorhodopsin-based artificial pigments. On the basis of these studies, a tentative model of wavelength regulation in iodopsin is proposed.

Animals↗
PubMed1989

Immunoglobulin M-dependent classical complement pathway activation in killing of Pentatrichomonas hominis.

Complement pathway activity in the killing of Pentatrichomonas hominis was investigated in this study. At 10(5) organisms per ml, P. hominis was completely killed by the presence of 1% normal human serum. In contrast, no killing effect on P. hominis was observed when specific antibodies were absorbed or when the complement was destroyed. Moreover, Mg2+-ethylene glycol-bis-(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid-treated serum had no killing effect on P. hominis, while serum heated at 50 degrees C or treated with zymosan killed P. hominis as well as did normal human serum. Further study using gel filtration (Sephacryl S-300) and affinity chromatography (protein A) revealed that immunoglobulin M (IgM; 20 micrograms/ml) alone was responsible for the complement activation in the killing of P. hominis, but both IgA (24 micrograms/ml) and IgG (180 micrograms/ml) had no effect on complement-mediated lysis. On the other hand, IgG at 1,260 micrograms/ml completely inhibited complement-mediated killing by IgM, suggesting that a blocking factor is present in IgG. The results of this study indicate that a mechanism of IgM-dependent classical complement pathway activation contributes to the killing effect of normal human serum on P. hominis.

Animals↗
PubMed1989

[Distribution pattern and risk factors of lung cancer in Qidong rural area].

Distribution pattern, epidemiologic trend and risk factors of lung cancer in rural area were studied and analysed based on the data of Qidong cancer registry (1972-1986), of sampling survey of cigarette smoking rate among rural residents, and of consumption of cigarette and fuel in Qidong. The results showed that: 1. Lung cancer mortality had increased from 9.00/10(5) in 1972 to 20.03/10(5) in 1986 with annual increase rate of 5.88%; 2. Lung cancer mortality in 1980s (1984-1986) was increased by 61.68% as compared with that in 1970s (1974-1976), in which the male incidence was increased by 79.99% and female, 25.73%; 3. Cigarette consumption in rural area increased rapidly, and the mean daily sale of cigarette per Qidong person in 1986 was four times as high as that in 1950, those trends will continue to influence lung cancer mortality of this area in the near future; and 4. The consumption of industrial and civilian fuel in Qidong rural area are also on the increase. However, the relationship between air pollution and lung cancer remains to be studied. In view of the above-mentioned facts, epidemiologic and etiologic research on lung cancer in rural area must be emphasized. An appeal for campaign on abstinence of smoking in rural area, especially for non-smoking education in the youth should be waged urgently.

Adolescent↗
PubMed1989

[Inhibition of renal sympathetic efferent activities induced by stimulation of the paraventricular nucleus of the hypothalamus(PVH) in rabbits].

Experiments were performed on rabbits anesthetized with chloralose-urethane mixture, paralyzed with gallamine triethiodide, and ventilated artificially. Bilateral vagi, aortic and carotid sinus nerves were severed. Renal sympathetic efferent discharge (RSED) and its histogram were recorded, while the blood pressure (BP) of the femoral artery was monitored. When PVH was strongly stimulated, a transient increase of RSED was observed, which was followed by an inhibition of RSED. The inhibition of RSED was divided into two phases: the initial inhibitory phase without change in BP and the late inhibitory phase with an increase of BP. It was found that both the duration of total inhibition and the late, but not initial, inhibitory phase were positively correlated with the alterations of BP. When PVH was weakly stimulated, no change in BP was observed, but the inhibition of RSED still appeared. The inhibition duration was shortened remarkably following cutting of baroreceptor nerves. In some experiments, the RSED inhibition was not accompanied by a definite excitatory response. The present results indicate that 1) an inhibitory mechanism of PVH-renal sympathetic efferent system is present in the central nervous system; 2) the initial inhibitory phase of RSED originates from central mechanisms, while the late inhibitory phase is associated with the baroreceptor reflex and a direct action of the central nervous system; 3) the inhibition of RSED seems not to be a post-excitation depression, but an active inhibition exerted by the PVH on the spinal sympathetic preganglionic neurons.

Animals↗
PubMed1987

A comparison of various methods for the determination of viability of parasitic flagellates.

To find out a simple, rapid, accurate, and reliable viability assay for in vitro anti-protozoa drug testing, a comparison among the various methods for the determination of flagellate viability was made. Micro-colony forming efficiency up to 90% for three different flagellates was obtained by the agar plate method. Macro-colony forming efficiency obtained by the culture tube method was generally lower (20-45%). Viability determined by trypan blue exclusion correlated closely with viability determined by micro-colony count (r = 0.94). The growth of the remaining parasites survived from serum treatment was not inhibited while that from metronidazole pretreatment was inhibited. The standard regrowth assay based on the 48-hr cultivation could be applied only for those survival not inhibited. The inhibitory effect of metronidazole on parasites was further testified by the longer generation time for metronidazole-pretreated flagellates in comparison with that for control (p less than 0.001). If the inhibitory effect of a drug is involved in the mechanisms against parasites, only the trypan blue exclusion and the micro-colony count can give an accurate and reliable viability determination. Moreover, the simple and rapid diagnosis provided by trypan blue exclusion is especially useful for the in vitro anti-protozoa drug susceptibility test.

Animals↗
PubMed1985

Cation binding by bacteriorhodopsin.

We have found that extensively washed purple membrane has about 1 calcium and 3-4 magnesium ions bound per bacteriorhodopsin molecule. When these divalent cations are removed by any of a variety of means, the pigment changes its color from purple to blue (lambda(max) approximately 600 nm). This blue pigment, which can be formed at near neutral pH, is probably very similar to blue species formed when the pH of a purple membrane sample is lowered to approximately 2. When any of a wide variety of cations are added to a blue membrane preparation, the characteristic purple color of bacteriorhodopsin returns. Divalent and trivalent cations are much more efficient than monovalent cations in restoring the purple color and are effective at a ratio approaching one cation per pigment molecule. Besides shifting the absorption spectrum, removal of the divalent cations drastically alters the photochemical cycle of bacteriorhodopsin, including abolishing the unprotonated Schiff base (M-type) intermediate. Finally, lanthanum not only displaces the divalent cations normally bound to the purple membrane but also greatly reduces both the rate of decay of the M412 intermediate and proton uptake.

Journal Article↗
PubMedDate not supplied

Hybrid expert-system approach to nurse scheduling.

The objective of this research was to develop a hybrid expert system entitled NURSE-HELP to achieve flexible and effective scheduling for nurses. NURSE-HELP was developed with the emphasis on following the ergonomics guidelines, which will improve the performance of nurses. Moreover, the combination of linear zero-one goal programming and an expert system program reduces the program run time while maintaining the quality of the schedule. The system was evaluated by comparing 18 sets of 4-week schedules generated by the head nurses manually and by NURSE-HELP. Concerning the amount of time required to generate the schedules, NURSE-HELP averaged less than 20 minutes, whereas head nurses spent from 2 to 4 hours. The quality of the schedules was measured using the following four criteria: 1) minimum staff level not satisfied, 2) day off request not granted, 3) backward rotation, and 4) maximum consecutive work periods on the night shift. NURSE-HELP was superior in all these aspects.

Ergonomics↗