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Biomedical subjects

B Tan

Publications and source records attributed to B Tan.

At least 55 records · Page 3Linked to original sources
PubMed1998

[A new approach to correction method for matrix effect in X-ray fluorescence spectroscopy analysis].

With the help of fundamental parameter program developed by the authors, the matrix effect of multicomponent complex sample and the composition of each element's X-ray fluorescence intensity are calculated. A new mathematical model for correcting multicomponent matrix effect is deduced theoretically. This model provides a new method to calculate influence coefficients alpha and beta. The correction model and the influence coefficients introduced by this paper have clear and definite physical meaning, which give satisfactory result when utilized in analyzing stainless steel sample. The paper also indicates that the effect of tertiary fluorescence can not be neglected in some cases. From the result of comparison experiments, we draw a conclusion that the tertiary fluorescence effect must be considered while analyzing Cr in a steel sample with high concentration of Ni.

English Abstract↗
PubMed1998

[Chemical state analysis of chromium by the conventional X-ray fluorescence spectrometer].

X-Ray Kbeta emission spectra of chromium and some of their compounds were studied by conventional XRF spectrometer Rigaku 3080 E1 and PEAKFIT spectrum analyzing programs. Some qualitative and quantitative relations were obtained between the true spectrum profile and its parameters (peak position, peak top intensity, FWHM and asymmetry indices) and chemical state by data processing technique. And making use of these relationship, the chemical state distribution were analyzed of chemical chromate treatment film, stainless steel. Satisfactory results were obtained.

English Abstract↗
PubMed1998

[Determination of the valence of iron by the conventional XRF spectrometer].

FeKbeta emission spectra and parameters of mixtures are studied by conventional XRF spectrometer and PEAKFIT programs. The true spectra profile and it's parameters are obtained by profile resolving method. Integral area ratios are also calculated. The relations of these parameters and the valences of the iron are found. Fe3O4 sample and the iron ore which has different valences are quantified.

English Abstract↗
PubMed1997

Involvement of nuclear factor kappa B in the regulation of cyclooxygenase-2 expression by interleukin-1 in rheumatoid synoviocytes.

OBJECTIVE: To evaluate involvement of the transcription factor nuclear factor kappa B (NF-kappa B) in the increased expression of cyclooxygenase-2 (COX-2) stimulated by interleukin-1 beta (IL-1 beta) in primary rheumatoid synoviocytes. METHODS: We treated early-passage rheumatoid synoviocytes with IL-1 beta and examined the time course of NF-kappa B translocation to the nucleus by Western blot analysis, as well as NF-kappa B binding to the COX-2 promoter/enhancer by electrophoretic mobility shift assay. We correlated the time course of NF-kappa B binding with expression of COX-2 messenger RNA (mRNA) and protein. Synoviocytes were then treated with either sense or antisense phosphorothioate-modified oligonucleotides derived from the transcription start site of the human NF-kappa B p65 RNA. We analyzed NF-kappa B binding to the COX-2 promoter and COX-2 protein levels after these treatments. RESULTS: IL-1 beta rapidly stimulated the translocation of the p65, p50, and c-rel NF-kappa B subunits from the cytoplasm to the nucleus. Electrophoretic mobility shift assay demonstrated binding to 2 NF-kappa B sites within the COX-2 promoter/enhancer, with a time course identical to that of nuclear localization of NF-kappa B. Supershift analysis revealed that binding activity was due primarily to the p65-p50 heterodimer and the p50 homodimer. With appropriate lag time after NF-kappa B binding, COX-2 mRNA and protein were increased. Pretreatment of RA synoviocytes with NF-kappa B p65 antisense oligonucleotides resulted in decreased binding to the COX-2 promoter and decreased COX-2 protein expression. CONCLUSION: These data demonstrate that signaling via the NF-kappa B pathway is involved in regulation of COX-2 expression induced by IL-1 beta in RA synoviocytes.

Arthritis, Rheumatoid↗
PubMed1997

The use of new antiretroviral therapy in combination with chemotherapy.

With rapid scientific advances in HIV pathogenesis and antiretroviral therapy, the oncologist is faced with new challenges in the treatment of patients with HIV infection and malignancy. HIV infection, by causing immune dysregulation and cytokine production, may alter the natural history of certain neoplasms. Treatment of cancer with chemotherapy can also affect the course of HIV disease. The use of combination antiretroviral agents, particularly the protease inhibitors, can maximally suppress replication of HIV. Improved clinical outcome is associated with more profound decreases in plasma HIV RNA, although development of resistant strains may hinder sustained antiretroviral activity. Antiretroviral therapy should be continued during chemotherapy with the goal of achieving plasma HIV-RNA levels below 500 copies/mL. Modifications in the regimen should be done when intolerable toxicity occurs or if viral load is increased. Although information regarding the use of newer antiretroviral agents with chemotherapy is limited, the use of several reverse transcriptase inhibitors has been well tolerated in patients with AIDS-related malignancies such as Kaposi's sarcoma and lymphoma.

Anti-HIV Agents↗
PubMed1997

The Lie/Bet Questionnaire for screening pathological gamblers.

A 2-item questionnaire was derived from 10 DSM-IV criteria for pathological gambling. Subjects were 362 men, 191 classified as pathological gamblers and 171 as nonproblem-gambling controls. The two items were significant in sensitivity and negative predictive value and significant in specificity and positive predictive value.

Adolescent↗
PubMed1996

Cyclosporine in severe childhood atopic dermatitis: a multicenter study.

BACKGROUND: Severe atopic dermatitis (AD) remains difficult to treat. Cyclosporine is effective in adults but has not previously been investigated in children with AD. OBJECTIVE: The aims were to investigate the efficacy, safety, and tolerability of cyclosporine in severe refractory childhood AD. METHODS: Subjects 2 to 16 years of age were treated for 6 weeks with cyclosporine, 5 mg/kg per day, in an open study. Disease activity was monitored every 2 weeks by means of sign scores, visual analogue scales for symptoms, and quality-of-life questionnaires. Adverse events were monitored. Efficacy and tolerability were assessed with five-point scales. RESULTS: Twenty-seven children were treated. Significant improvements were seen in all measures of disease activity. Twenty-two showed marked improvement or total clearing. Quality of life improved for both the children and their families. Tolerability was considered good or very good in 25 subjects. CONCLUSION: Cyclosporine may offer an effective, safe, and well-tolerated short-term treatment option for children with severe AD.

Administration, Oral↗
PubMed1996

Degradation of Perennial Ryegrass Leaf and Stem Cell Walls by the Anaerobic Fungus Neocallimastix sp. Strain CS3b.

The degradation of cell walls isolated from stems and leaves of perennial ryegrass by the anaerobic fungus Neocallimastix sp. strain CS3b was studied in a defined medium. The combined cellulose and hemicellulose fraction represented 53.1 (wt/wt) and 63.3% (wt/wt) of the dry weight of control grass leaf and stem cell walls, respectively. In both leaf and stem cell walls, glucose was the major neutral monosaccharide, followed by xylose, arabinose, and galactose. After 2 days of fermentation with Neocallimastix sp. strain CS3b, treated cell walls contained smaller amounts of neutral sugars compared with those of undigested cell walls. These results were more evident for glucose, xylose, and arabinose than for galactose. Furthermore, the sugar content of leaf cell walls decreased before a decline in the sugar content of stem cell walls was observed. Data from formate and hydrogen production indicated that the growth of Neocallimastix sp. strain CS3b was completed in 4 days in the culture system used. During this period, the fungus liberated about 95% of the fermentable sugars in untreated material. On a percentage basis, no significant differences were found in final extent of degradation of glucose, xylose, and arabinose. Galactose, however, was degraded to a lesser extent.

Journal Article↗
PubMed1996

[Toxicity of cadmium and its mechanism on renal tubular epithelial cells in vitro].

The direct effects of cadmium on the functions and metabolism of renal tubular epithelial cells were observed with radio-immune assay, cytochemical and biochemical methods to study further the mechanism of nephrotoxicity of cadmium. Results revealed uptake of alpha-methyl-D-glucoside (alpha-MG) in renal tubular epithelial cells obviously reduced, outflow of potassium ions increased, c-AMP content reduced and activity of Na+-K+-ATPase was inhibited significantly after exposure to cadmium. Electrochemical gradient of tubular cells maintained by Na+-K+-ATPase played an important role in transference of sodium and glucose, and damage in energy resource system within tubular epithelial cells may be one of the pathogenic mechanisms of kidney injury caused by cadmium. In addition, changes in a group of biological markers and functional enzymes (alkaline phosphatase, AKP; gamma-glutamyltransferase, gamma-GT; lactate dehydrogenase, LDH; glucose-6-phosphate dehydrogenase, G-6-PD; N-acetylglucoside, NAG) were determined in the study, and it was found that they all could reflect better the degree of injury in tubular epithelial cells and their metabolic status and could be used in clinical practice.

Animals↗
PubMed1995

[Effects of cadmium on calcium homeostasis of isolated epithelial cells of proximal renal tubules].

Changes of intracellular calcium homeostasis in epithelial cell damage of renal tubules caused by cadmium and its relationship with the damage were studied in isolated tubular cells of rabbits. Results showed levels of free calcium (Ca++) in tubular cytoplasm increased significantly with the treatment of cadmium, and a series of cellular ultrastructure were damaged. A calcium channel blocker, phenothiazine, showed blocking and protecting effects on it. This suggested calcium overload played a very important role in kidney damage caused by cadmium.

Animals↗
PubMed1995

Serological survey of nasopharyngeal carcinoma in 21 cities of south China.

This paper reports the results of serological survey of 318,912 persons for nasopharyngeal carcinoma (NPC) in 21 cities and counties of south China. There were 8,441 persons with positive VCA-IgA antibody (single item positive) of EB virus (EBV), with a rate of 2.65%. In these VCA-IgA positive persons, 287 persons also had positive EA-IgA (double items positive) of EBV. The overall positive rate was 0.09%. 100 cases of NPC were found and 87 of them (87.0%) were in early stage. NPC found in the group with single item positive accounts for 1.19%, but the rate in the group with double items positive was 19.16% (55 cases). In NPC patients with double items positive, 49 cases were in early stage (89.1%). In 100 cases of NPC found, 45 cases appeared with negative EA-IgA, only with positive VCA-IgA, which indicated that for diagnosis of NPC, sensitivity of EA-IgA was lower than that of VCA-IgA, but its specificity was higher. Therefore, both can increase the detecting rate and early diagnosis rate of NPC. The age of people checked varied with different antibody positive rate and NPC detecting rate. The three items showed a positive correlation. The results are compatible with those of the prospective study for NPC in Wuzhou City, Guangxi, China. The method for NPC serological diagnosis can be extended and applied to raise the NPC detecting rate and early diagnosis rate at secondary prevention. And, it is further proved that there is a close relationship between NPC and EBV.

Adult↗
PubMed1995

[Experimental study on immediate endosseous implantation].

Screw type implants (ITI series) were implanted into the socket of extracted teeth of adult dogs to investigate the histologic recovery process of implantation. Two groups of immediate implantation. (with or without filling of cancellous bone chips) were performed, with a follow-up period of one month and three months. Results showed that marked immature new bone formation was found one month later after implantation. The amount of new bone in the group with cancellous bone implantation was much more than that in the group without bone chips. Mature new bone was observed three month later after operation, no marked difference was found in the amount of new bone between the two groups.

Animals↗
PubMed1994

An outbreak of diarrhea due to verotoxin-producing Escherichia coli in the Canadian Northwest Territories.

In the summer of 1991 a large outbreak of Escherichia coli O157:H7 associated diarrhea occurred in 6 Inuit communities in the Canadian Northwest Territories. The total population of these communities is 5,292. Of the 521 individuals who developed diarrhea, 152 (29%) were positive for E. coli O157:H7 on stool culture or positive by verotoxin analysis. Median age was 6 years. The attack rate for children < 1 year was 43% in the major affected community of Arviat. Hemolytic-uremic syndrome (HUS) developed in 22 cases, and 2 patients died. Asymptomatic stool carriage of verotoxin-producing E. coli (VTEC) 2-5 weeks after diarrheal illness was noted in 4/28 persons followed prospectively. Epidemic curves, case-control studies and phage type testing suggested person-to-person transmission. The original source of infection was not identified, though a food source was suspected. VTEC were detected in 6 food samples (minced beef and caribou) taken from retail outlets and homes. Primary prevention of infection through health education and promotion activities, as well as long-term follow-up of HUS survivors, are indicated in this population.

Adolescent↗
PubMed1993

Acanthamoeba infection presenting as skin lesions in patients with the acquired immunodeficiency syndrome.

Acanthamoeba organisms are a well-known, although rare, cause of central nervous system infection in immunodeficient hosts, including those with the acquired immunodeficiency syndrome. Extracerebral acanthamebiasis, with the exception of contact lens-associated keratitis, is reported but little emphasized in the literature. We describe two patients with the acquired immunodeficiency syndrome in whom skin lesions were the primary manifestations of Acanthamoeba infection. Central nervous system disease was proved in one patient and suspected, but unproved, in the other. The skin lesions exhibited an intact epidermis with suppurative inflammation of the subcutis, associated with numerous amebic cysts and trophozoites. The amebic cyst walls stained with periodic acid-Schiff and Gomori's methenamine-silver stains, creating confusion with Blastomyces dermatitidis yeast in one instance. Immunofluorescence studies and culture identified the organisms as an Acanthamoeba species. Preliminary studies in one of the cases suggested a previously undescribed Acanthamoeba species as the etiologic agent. Our experience emphasizes that skin lesions may be the presenting sign of disseminated Acanthamoeba infection in patients with the acquired immunodeficiency syndrome.

Acanthamoeba↗
PubMed1991

Effects of palm carotenoids in rat hepatic cytochrome P450-mediated benzo(a)pyrene metabolism.

Using benzo(a)pyrene (BaP) metabolism as a probe for chemical carcinogenesis, in vitro and in vivo effects of palm-oil carotenoid [beta-carotene (BC), alpha-carotene (AC), or canthaxanthin (CTX)] on BaP metabolism in the rat hepatic cytochrome P450-mediated monooxygenase system were studied. Apparent Michaelis-Menten constants (Km) for formation of the precursor carcinogen, 7,8-dihydrodiol BaP, were found to be 14.4 (BC), 1.74 (AC), and 0.7 (CTX) mumol/L. The order of anticarcinogenic strength established in this study was BC much greater than AC greater than CTX. Increased formation of the detoxification intermediate, 3-hydroxy BaP, with increased carotenoid concentration was observed. The order of detoxification strength was BC greater than AC = CTX. The presence of carotenoids in vivo inhibited BaP metabolism. Using 9,10-dihydrodiol BaP as an indicator for inhibition, the order of the antioxidative activity was palm oil (with carotenoids) greater than BC greater than CTX greater than palm oil (without carotenoids). BC and AC may selectively modify the rat-liver microsomal enzymes, thus providing a biochemical mechanism for the inhibitory effect of palm carotenoids on chemical carcinogenesis.

Animals↗