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Biomedical subjects

D Chen

Publications and source records attributed to D Chen.

At least 829 records · Page 46Linked to original sources
PubMed1991

Chromosome aberration, cancer mortality and hormetic phenomena among inhabitants in areas of high background radiation in China.

The respective average annual doses are about 330 and 110 mR/yr, in the high background radiation areas (HBRA) in Yangjiang County and the control areas (CA) in Enping and Taishan Counties. Both the HBRA and CA are in Guangdong Province which borders the South China Sea. The frequencies of chromosome aberration in circulating lymphocytes were examined for persons residing in the HBRA and CA. Those in the HBRA had increased frequencies of detectable abnormalities in stable aberrations (translocations and inversions) and unstable aberrations (dicentrics and rings). Previous reports have shown that when samples of circulating lymphocytes taken from inhabitants were tested in vitro for mitotic responses to phytohemagglutinin (PHA) and for the degree of unscheduled DNA synthesis (UDS) induced by UV-irradiation, there were higher responsiveness and UDS rates for those in the HBRA than in the CA. In contrast, mortality from all cancers and those from leukemia, breast and lung cancers that are inducible by radiation was not higher in the HBRA. Although the differences in the cancer mortality rates for the HBRA and CA are not significant, the findings are compatible with the assumption that the lower mortality from cancer in the HBRA is the result of the hormetic effects of the three-fold higher dose rate of background radiation in that areas. This assumption requires further study.

Adolescent↗
PubMed1991

A population-based study of Stevens-Johnson syndrome. Incidence and antecedent drug exposures.

To determine the incidence of Stevens-Johnson syndrome, a descriptive epidemiology study was performed using computerized Medicaid billing data from 1980 to 1984 from the states of Michigan, Minnesota, and Florida. The ratio of persons hospitalized with a discharge diagnosis of erythema multiforme (ICD-9-CM code 695.1) to persons with any claim for medical service was first used as an estimate of the incidence rate of the disease. Then, since the ICD-9-CM code for erythema multiforme includes other illnesses in addition to Stevens-Johnson syndrome and because these illnesses are frequently misdiagnosed, the information provided by a review of medical records for a subset of cases of erythema multiforme was used to determine the proportion of patients with true Stevens-Johnson syndrome. The incidence rates of Stevens-Johnson syndrome were 7.1 (6.1 to 8.2), 2.6 (1.6 to 4.0), and 6.8 (4.3 to 10.3) per million per year in each state, respectively. Penicillins, especially aminopenicillins, were frequently used in the 19 patients judged to be true cases of Stevens-Johnson syndrome. In conclusion, Stevens-Johnson syndrome is a uncommon condition. The excess risk of Stevens-Johnson syndrome due to any drug must, therefore, be very low.

Adolescent↗
PubMed1990

Prevention of thromboembolism after spinal cord injury using low-molecular-weight heparin.

OBJECTIVE: To examine the safety and effectiveness of a low-molecular-weight heparin in the prevention of thromboembolism in patients with recent spinal cord injury and complete motor paralysis. DESIGN: Randomized evaluation of two heparin regimens in 41 consecutive patients meeting eligibility requirements for anticoagulant prophylaxis. Daily bedside examinations were supplemented by serial venous flow studies; suspicious or positive tests were confirmed by venography. INTERVENTION: Standard heparin, 5000 units subcutaneously three times a day; low-molecular-weight heparin 3500 anti-Xa units subcutaneously once daily. MEASUREMENTS AND MAIN RESULTS: Five patients in the standard heparin group had thrombotic events, including two patients with fatal pulmonary embolism; two other patients had bleeding severe enough to necessitate withdrawing the heparin. The cumulative event rate was 34.7% (95% CI, 13.7% to 55.2%). None of the patients treated with low-molecular-weight heparin had thrombosis or bleeding (CI, 0% to 14%). The difference between the two groups was significant (P = 0.006, log-rank test). CONCLUSIONS: Low-molecular-weight heparin is safe and effective in the prevention of thromboembolism in selected patients with spinal cord injury and complete motor paralysis, and is superior to standard heparin in fixed doses of 5000 units three times a day.

Administration, Cutaneous↗
PubMed1990

Trans-acting factors in chromosomal instability.

The hypothesis that trans-acting factors affect chromosome stability was explored using human X Chinese hamster somatic cell hybrids. Two types of hybrids were examined. In either case, the human parent consisted of human diploid fibroblasts, the chromosomes of which tended to be lost from the hybrid cell. Comparisons were made between hybrid clones in which the hamster parent had a very stable karyotype (line CHO) and clones from a hamster parent with an unusual ongoing unstable karyotype (line CHX). Chinese hamster-human hybrid cell clones were expanded, and metaphase spreads were analyzed with an in situ hybridization procedure that uses biotin-labeled human genomic DNA as probe. Analyses of chromosome numbers and interspecies translocations were made after 20, 60, and 100 population doublings. Throughout the experiments, the generation of human-hamster-translocated chromosomes was more frequent in the hybrid cells with the CHX background. In addition, these cells also generated human acentric fragments, which were rare in cells with the CHO background. These results favor explanations for the instability of the CHX line that involve ongoing production of a diffusible clastogenic factor.

Animals↗
PubMed1990

Intracellular RNA synthesis directed by temperature-sensitive mutants of simian rotavirus SA11.

The kinetics of intracellular synthesis of single-stranded (ss) RNA and double-stranded (ds) RNA directed by prototype temperature-sensitive (ts) mutants representing the 10 mutant groups of rotavirus SA11 were examined. Cells were infected with individual mutants or wild type under one-step growth conditions and maintained at permissive temperature (31 degrees) or nonpermissive temperature (39 degrees). At various times postinfection, infected cells were pulse-labeled, ssRNA and dsRNA were purified, RNA species were resolved by electrophoresis and autoradiography, and RNA synthesis was quantitated by computer-assisted densitometry. The mutants representing all groups synthesized significantly less ssRNA and dsRNA at both 31 degrees and 39 degrees, when compared to wild type. When the ratio of synthesis at 39 degrees/31 degrees was determined for ssRNA and dsRNA of each mutant, three RNA synthesis phenotypes were evident. The tsB(339), tsC(606), and tsE(1400) mutants synthesized both ssRNA and dsRNA in a temperature-dependent manner. The group G mutant, tsG(2130), synthesized ssRNA in temperature-independent fashion but was temperature-dependent for the synthesis of dsRNA. The remaining mutants, tsA(778), tsD(975), tsF(2124), tsH(2384), tsI(2403), and tsJ(2131), synthesized both ssRNA and dsRNA in a temperature-independent fashion. The RNA synthesis phenotypes of the ts mutants are discussed in terms of what is known of the function(s) of the protein species to which ts lesions have been assigned.

Animals↗
PubMed1990

Interleukin-1 synergy with phosphoinositide pathway agonists for induction of interleukin-2 gene expression: molecular basis of costimulation.

The macrophage-derived cytokine interleukin-1 (IL-1) can provide a second signal with antigen to elicit production of interleukin-2 (IL-2) by helper T cells. The pathway(s) involved remains controversial, with protein kinase C and cyclic AMP (cAMP) invoked as possible second messengers. In the murine thymoma EL4.E1, IL-1 could synergize with the phosphoinositide pathway, because the cells made higher levels of IL-2 in the presence of IL-1 than could be induced by phorbol ester plus calcium ionophore alone. IL-1 is unlikely to act through a sustained increase in cAMP in these cells because it did not raise cAMP levels detectably and because IL-1 and forskolin had opposite effects on IL-2 gene expression. Inducible expression of a transfected reporter gene linked to a cloned fragment of the murine IL-2 gene promoter was initially increased by IL-1 costimulation, implying that IL-1 can increase the rate of transcription of IL-2. The minimal promoter elements required for iL-1 responsiveness were located within 321 bp of the IL-2 RNA cap site, and further upstream sequences to -2800 did not modify this response. IL-1 costimulation resulted in enhanced activity of both an inducible NF-kappa B-like factor and one of two distinct AP-1-like factors that bind to IL-2 regulatory sequences. Neither was induced, however, by IL-1 alone. Another AP-1-like factor and NFAT-1, while inducible in other cell types, were expressed constitutively in the EL4.E1 cells and were unaffected by IL-1. These results are discussed in terms of the combinatorial logic of IL-2 gene expression.

Animals↗
PubMed1990

The importance of surgery as the first step in multimodality treatment of small cell bronchial carcinoma. The ISC Lung Cancer Study Group.

For patients with small cell lung cancer (SCLC) in their early stages (TNM I, II), surgery for cure was used to eliminate the primary tumour and its regional lymph-nodes followed by intermittent chemotherapy and radiotherapy within the first six postoperative months. After the pathohistological examination of the operation-specimen a two-arm-randomization was performed: standard chemotherapy (1000 mg/m2 cyclophosphamide, 50 mg/m2 doxorubicin, 1.4 mg/m2 vincristine) compared with sequential chemotherapy using three different drug-combinations (A: 1500 mg/m2 cyclophosphamide, 100 mg/m2 lomustine, 15 mg/m2 methotrexate; B: 1000 mg/m2 cyclophosphamide, 40 mg/m2 doxorubicin, 1 mg/m2 vincristine; C: 5 x 1.6 g/m2 ifosfamide plus mesna, 5 x 120 mg/m2 etopside). Thereafter disease-free patients only received prophylactic cranial irradiation (PCI: administering 3600 TD Gy/18 fractions) according to the protocols of the International Society of Chemotherapy Studies I and II. Preliminary evaluations in March 1990 of 170 patients from 24 cooperating departments for thoracic surgery showed that the projected life-table four-year-survival rate of 63 patients with SCLC at pTNM-stage I was 61%, of 54 patients at pTNM-stage II was 35%, of 13 patients at stage pT3, 4 NO, 1 MO was 59% and of 40 patients at stage pT N2 MO was 35%. The indication for surgery is emphasized for pTNM-stages I + II. For N2-lesions surgery would not be recommended in general, but the survival rate seems to indicate that this treatment was not detrimental, being rather more favourable compared with chemotherapy or radiotherapy alone. The continuation and enlargement of these studies seem not only justified, but emphatically indicated.(ABSTRACT TRUNCATED AT 250 WORDS)

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1990

[Study on several systems used for chemiluminescent determination of horseradish peroxidase].

Four systems were studied used for chemiluminescent determination of HRP and the determination conditions optimized. In luminol-H2O2 (NaOH) system, HRP was determined conveniently in the range of 0.05-4 pmol, with a correlation coefficient of 0.998 for the linear log-log equation and a limit of detection of 16 fmol HRP. In pyrogallol-H2O2 (pH 6.5) system, 0.1-100 pmol of HRP were determined, based on three log-log regression equations with correlation coefficients of 0.997, 0.994 and 0.999, respectively, and limits of detection of 3-17 fmol HRP. Luminol-H2O2-para iodophenol system was used to determine HRP in the range to 10-50 fmol, based on the chemiluminescence intensity at 1 min and the correlation coefficient of the log-log equation being 0.996 with a limit of detection of 10 fmol HRP. When p-hydroxybiphenyl was used to take the place of p-iodophenol and the chemiluminescence intensity at 1 min or 3 min measured, 6-40 fmol HRP were determined with a correlation coefficient of 0.994 or 0.995 for the log-log equation and a limit of detection of 6.5 or 3.3 fmol HRP.

Horseradish Peroxidase↗
PubMed1990

Cardiac pacemaker inhibition by transcutaneous electrical nerve stimulation.

The use of transcutaneous electrical nerve stimulation (TENS) has increased in recent years for the management of chronic pain. One of its few contraindications is the presence of a cardiac pacemaker. Clinicians have recommended that cardiac monitoring be performed for a short interrupted period during the first application of TENS to ensure safety. We present two patients who were given trials of TENS for different chronic pain complaints. In both cases, electrocardiograms during the TENS trial did not reveal cardiac pacemaker dysfunction, but extended cardiac monitoring with the Holter monitor showed interference with pacemaker function. The abnormalities did not recur after reprogramming the sensitivity of the pacemakers. We suggest the use of extended cardiac monitoring for patients with cardiac pacemakers during the prolonged use of TENS to ensure safety and to determine any need for reprogramming of the pacemakers. Patients with cardiac pacemakers should not be excluded from the use of TENS, but careful evaluation and extended cardiac monitoring should be performed.

Aged↗
PubMed1990

[Determination of indapamide in human serum by high performance liquid chromatography].

A HPLC method for determination of indapamide in human serum with Sulfisoxazole as internal standard has been established. This method was carried out ODS column (5 microns). We used a mobile phase of acetonitrile: 0.05 mol/L sodium acetate buffer at pH 3.72 (45:55 V/V) and a flow rate of 1.2 ml/min. The procedure was as follows: Transfer 0.5 ml of patient serum add 10 microliters of the internal standard (0.2 mg/ml) and 9 ml ethyl acetate into 12 ml of glass centrifuge tube. Shake for 10 minutes and centrifuge at 3000 r/min for 10 minutes. Transfer the ethyl acetate phase into another tube and evaporate to dryness at 70 c under a nitrogen steam. Reconstitute the residue with methanol 50 microliters and inject 15 microliters into the chromatograph. This method is simple, rapid, sensitive and has a good linearity. The average recoveries of indapamide and internal standard were 99.5% and 98.5% respectively. The method was linear from 0.04 micrograms/ml to 0.5 micrograms/ml with correlation coefficient of 0.9998. The coefficient of variation was less than 4.6% within a day (n = 8) and less than 4.3% between days (n = 8) respectively.

Chromatography, High Pressure Liquid↗
PubMed1990

Drug performance sensitivity: a pilot study.

Thirty noninsomniac healthy adult men were enrolled in a multicenter pilot study to evaluate the sensitivity of psychomotor and cognitive tasks and subjective evaluation of performance and mood after treatment with flurazepam (Dalmane) 45 mg (larger than the recommended prescribing dose of 15-30 mg). This pilot study was also used to standardize testing procedures. The subjects were given either flurazepam or placebo at 72-hour intervals in a double-blind Latin square crossover design. Choice reaction time, but not simple reaction time, was drug sensitive. Divided attention and vigilance tasks were also sensitive to drug effects. Of the two cognitive tasks tested, addition was impaired by drug, but reading comprehension was not. Subjective evaluations of performance and mood states indicate that these are useful measures, but responses on the Hopkins Symptom Checklist were not influenced.

Adult↗