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Biomedical subjects

D B Tang

Publications and source records attributed to D B Tang.

30 records · Page 2Linked to original sources
PubMed1989

An in vitro micromethod for drug sensitivity testing of Leishmania.

We describe an in vitro microtest which is quantitative, rapid, and readily applicable to parasites isolated from all major forms of human leishmaniasis. It is based on drug-mediated inhibition of promastigote catabolism of a battery of simple 14C-substrates to 14CO2. Each test requires less than 1 microCi. The test is conducted in a serum-free, chemically defined medium containing 120 micrograms protein/ml, minimizing the possible interference of drug: serum protein interaction. Prior adaptation is not necessary to cultivate "difficult-to-grow" species. Leishmania sensitivity to pentavalent antimonials is detectable at micrograms levels below concentrations achievable in patients' sera.

Animals↗
PubMed1988

Plasminogen activator and plasminogen activator inhibitor activities in a reference population.

The influence of age, gender, and aspirin ingestion on plasma levels of tissue plasminogen activator (t-PA) and plasminogen activator inhibitor-1 (PAI-1) activities was studied in a reference population of 35 men and 35 women between the ages of 20 and 65 years. The t-PA values (mean +/- SD) in the women before and after 5 minutes of venous occlusion were 3.8 +/- 1.4 and 7.8 +/- 4.4 micrograms/L, respectively; in men these values were 3.3 +/- 1.2 and 8.8 +/- 8.9 micrograms/L. Men had higher mean PAI levels than did women (5.0 vs. 2.5 kU/L). T-PA showed an inverse relationship to PAI in both sexes. There was a negative correlation of t-PA levels with age, whereas PAI levels were positively correlated. The ingestion of a single dose of aspirin (650 mg) did not alter PAI or t-PA activities. This study indicates that factors such as age and sex may need to be considered when reference populations are developed for clinical studies of fibrinolysis.

Adult↗
PubMed1986

Decreased growth of Plasmodium falciparum in red cells containing haemoglobin E, a role for oxidative stress, and a sero-epidemiological correlation.

The in vitro growth of Plasmodium falciparum in red cells containing haemoglobin E (HbE) was studied at oxygen concentration of 5 to 20%, with and without antioxidants. Under all conditions, parasite growth decreased as the concentration of HbE increased as compared with growth in red cells containing only HbA. The decreases were proportionately greatest at the highest oxygen concentration. The antioxidant vitamin C partially reversed the decreases in growth observed in HbE-containing cells at 20% oxygen. South-east Asian refugees with HbAE or HbEE had high antimalarial IFA titres, indicative of exposure to malaria more frequently than did refugees with HbAA. The decreased growth of P. falciparum in HbE-containing red cells may reduce the severity of malaria infections, conferring a survival advantage and thus increasing the numbers of individuals with HbE in local areas of South-east Asia with high incidences of malaria.

Antibodies↗
PubMed1985

Reduced false positive reactions in the Dot-enzyme-linked immunosorbent assay for human visceral leishmaniasis.

Specificity of the Dot-enzyme-linked immunosorbent assay (Dot-ELISA) for visceral leishmaniasis was significantly improved through the use of enzyme-conjugated antisera specific for IgG heavy chains. Of sera from Kenyans with visceral leishmaniasis, 97% (29/30) were positive using horseradish peroxidase (HRP)-conjugated anti-IgG (heavy and light chain specific) which detected bound IgG and IgM. False positive reactions occurred in 80% of sera from both trypanosomiasis-infected patients (8/10) and apparently healthy Africans (24/30). HRP-conjugated anti-IgG (heavy chain specific), which detected only bound IgG, significantly reduced false positive reactions among trypanosomiasis-infected (2/10, P less than 0.02) and healthy Africans (6/30, P less than 0.001), without reducing test sensitivity in leishmaniasis patients. No false positives occurred when either HRP-conjugated antiserum was used to assay sera from 30 North Americans. Application of enzyme-conjugated antisera specific for IgG improves the serodiagnostic value of the Dot-ELISA for individual patient evaluation and epidemiologic investigations.

Adolescent↗
PubMed1984

L-asparaginase: acute effects on protein synthesis in rabbits with normal and increased fibrinogen production.

The acute effects of a single intravenous dose of L-asparaginase on protein synthesis were studied in normal rabbits and in animals that had received turpentine to stimulate fibrinogen production. Male New Zealand rabbits received L-asparaginase (500 U/kg) 16 hr before the injection of the radiolabeled amino acid [75Se]selenomethionine (75SeM). Incorporation of 75SeM into fibrinogen and serum proteins in the L-asparaginase-treated rabbits was the same as for saline-treated controls, with fibrinogen representing approximately 5% of the labeled plasma proteins. In turpentine-treated rabbits, the maximal incorporation of 75SeM into serum proteins remained unchanged, whereas 75SeM-fibrinogen increased sixfold and accounted for 25% of the labeled proteins. Animals that received L-asparaginase at the same time as turpentine or 14 hr later showed significant decreases in synthesis of both serum proteins and fibrinogen. 75SeM-fibrinogen that was purified from L-asparaginase-treated rabbits underwent normal catabolism when injected into normal recipient rabbits. These data indicate that L-asparaginase can acutely cause partial inhibition of both serum protein and fibrinogen synthesis when administered to rabbits shortly before or during a period of increased fibrinogen production. Fibrinogen that is synthesized in the presence of L-asparaginase does not have an abnormal rate of catabolism.

Animals↗
PubMed1978

Diagnostic tests and Hodgkin's disease: a standardized approach to their evaluation.

We have analyzed a series of 124 young men with Hodgkin's Disease in an attempt to clarify the role of non-invasive tests in the staging evaluation. Data are presented in a way which permits comparison between series and application of the data to decision-making models. Analysis of the data shows our patients to have had primarily limited (stage I and II) disease. In our hands certain tests were quite accurate in predicting the absence of abdominal disease (lymphangiography, hepatic scintigraphy) as determined by laparotomy, but no study appeared to eliminate the need for laparotomy in this group. Data from several other large series are also presented in the same format. The data demonstrate a large variability between institutions in the predictive value of a positive lymphangiogram. Other studies, such as splenic scintigrams, appear to have more consistent predictive values. We encourage further use of this type of data presentation.

Adolescent↗