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Biomedical subjects

B Chen

Publications and source records attributed to B Chen.

At least 541 records · Page 30Linked to original sources
PubMed1985

Hereditary persistence of fetal hemoglobin or (delta beta)o-thalassemia: three types observed in South-Chinese families.

Hematological and hemoglobin composition data, and results from extensive gene mapping, using a battery of restriction enzymes and probes, have been used to distinguish different types of hereditary persistence of fetal hemoglobin (HPFH) (or delta beta-thal) among three Chinese families from the southern part of China. The first (Family Z) is an A gamma-(delta beta)+-HPFH without a detectable deletion and may be the same as, or similar to, that described by Farquhar et al (Am J Hum Genet 35:611, 1983). The second (Family C) resembles a G gamma(A gamma delta beta)o-thalassemia and is characterized by a large deletion of DNA originating 3' to the G gamma globin gene and extending beyond sequences recognized by the pRK28 probe. Data from various digests indicate possible differences in the 3' end of the deletion when compared with data for some other types of G gamma(A gamma delta beta)o-thalassemia, described by Trent et al (Br J Haematol 57:279, 1984). The third (Family Zh) concerns a G gamma A gamma(delta beta)+-HPFH, which is characterized in heterozygotes by a fetal hemoglobin level of 20% to 25% with a G gamma value averaging 60% and by the absence of any DNA deletion detectable by extensive gene mapping analyses. The C----G mutation at position 202 5' to the G gamma globin gene [characteristic for the high G gamma-(delta beta)+-HPFH (Proc Natl Acad Sci USA 81:4894, 1984; Blood 64:1292, 1984)] was absent, but the Xmn I site at position 158 5' to the G gamma globin gene [characteristic for a modest increase in G gamma values and thus and increased G gamma to A gamma ratio (Blood)] was present. No indication has yet been obtained explaining the elevation in both G gamma and A gamma chains; haplotyping showed that the chromosome carrying this G gamma A gamma(delta beta)+ determinant is unusual among the Chinese population.

China↗
PubMed1985

Effects of interferon and radiation dose on the suppressive activity of human lymphocytes primed with allogeneic cells in mixed lymphocyte cultures.

Peripheral blood lymphocytes (PBL) primed in vitro with irradiated allogeneic PBL can suppress alloactivated proliferation of fresh autologous PBL in a primary mixed lymphocyte culture (MLC). Proliferation of fresh PBL was measured by tritiated thymidine uptake after 6 days of coculture with irradiated fresh allogeneic stimulator PBL; irradiated autologous primed PBL were added to assess suppression. These primed cells had been cultured for 6 to 10 days prior to their irradiation and addition to a primary MLC. Suppression in this assay by PBL primed for 6 days was inversely correlated with radiation dose. The addition of highly purified recombinant interferon-alpha (IFN) during the 6-day priming of these lymphocytes did not alter their suppressive ability, nor did it alter the radiation sensitivity of their suppression. In contrast, PBL primed for 10 days were highly suppressive even if irradiated before their addition to the assay. However, when PBL were primed for 10 days in the presence of IFN, their ability to suppress was again radiation sensitive. These data suggest that between days 6 and 10 of primary MLC, IFN inhibits either proliferation or differentiation of a lymphocyte population involved in the generation of radioresistant suppressive activity.

Cells, Cultured↗
PubMed1985

Ascorbic acid-induced regression of amyloidosis in experimental animals.

Ascorbic acid was found to accelerate amyloid degradation in an experimental animal model. Based on experiments in vitro which demonstrated the ability of ascorbic acid to restore the amyloid-degrading activity of amyloidotic human serum, the effect of orally administered ascorbic acid was tested in casein-induced murine amyloidosis. Histopathological examination of splenic tissue of mice killed at different times after the termination of the amyloidogenic stimulus showed a markedly decreased amyloid deposition in ascorbic acid-treated animals as compared to the controls. The effect of ascorbic acid was to a certain degree dose-dependent. Colchicine blocked amyloid synthesis when administered during amyloid induction. In animals which were given the drug during the post-induction period it had no effect. The amyloid-degrading activity of mouse serum was reduced in amyloidotic mice. Administration of ascorbic acid partially restored the amyloid-degrading activity of these animals.

Amyloidosis↗
PubMed1983

Recurrent agranulocytosis induced by two different antithyroid agents.

A 45-year-old woman with thyrotoxicosis developed agranulocytosis after treatment with propylthiouracil. When the thyrotoxicosis recurred, accompanied by a severe psychotic reaction, administration of antithyroid medication was recommenced. The patient was given methimazole instead of propylthiouracil but, 10 weeks later, agranulocytosis again occurred. This is, to the best of our knowledge, the first report of a case in which agranulocytosis followed treatment with both propylthiouracil and methimazole in the same patient.

Agranulocytosis↗
PubMed1979

Estimation of polymerization efficiency in the formation of polyacrylamide gel, using continuous optical scanning during polymerization.

The Ferguson plot and 'quantitative' gel electrophoresis (based on the Ferguson plot) depend on a knowledge of accurate gel concentrations. The easiest way to estimate accuracy of gel concentrations, in terms of the degree of completion of the polymerization reaction which gives rise to a gel, is by spectrophometry. Making use of the apparatus for continuous optical scanning of polyacrylamide gels, the extent and rate of polymerization of cross-linked polyacrylamide were estimated by measuring the absorbance at 275 nm of the reaction mixture subsequent to free radical initiation of polymerization. Under appropriate conditions of monomer concentration, initiator levels and temperature, absorbance decreased monotonically after a lag period of 10 min, and after 20--30 min of reaction the absorbance reached a plateau value which provided a measure of polymerization efficiency. Application of a standard curve of absorbance vs. monomer concentration allowed one to quantitate concentrations of residual monomer throughout the course of polymerization. Under a set of arbitrary polymerization conditions (e.g. 6--20% total gel concentration), the reaction went to 63--96% completion. The rate of polymerization was approximately proportional to the square of the monomer concentration (2nd-order reaction kinetics). Absorbance decrease subsequent to the initiation of the polymerization reaction appeared suitable as a measure of efficiency of polymerization since: (a) absorbance spectra of monomers at 0.5 %T and residual monomers in a 10 %T gel, at a time when polymerization seemed terminated, coincided; (b) values of residual monomer obtained were reasonable (10--30%); (c) bimolecular reaction kinetics were found, in agreement with expectation; and (d) absorbance of incomplete polymerization mixtures, deficient in either initiators or monomers, was constant with time.

Acrylamides↗
PubMed1979

Studies on duck nutrition. III. Arginine and lysine requirements of mule ducklings.

Growth assays were conducted to determine the dietary arginine and lysine requirements of mule ducklings. The metabolizable energy content of the basal diets used for the arginine and lysine requirement studies was 2810 and 2828 kcal/kg, respectively. Two-day-old ducklings of mixed sexes were fed on a starter diet for one week, fasted for 8 to 12 hr and then were fed on experimental diets for 12 or 14 days. Weight gain and feed consumption were recorded at the end of each experiment. The minimum requirements for arginine and lysine were obtained by regression analysis of weight gain or feed efficiency against arginine or lysine content in the diet. The minimum arginine requirements for maximum growth and efficiency of feed utilization were 1.08% of the diet or 6.0% of the dietary crude protein. The minimum requirements of the total lysine and available lysine were 1.06% and .97%, respectively, of the diet or 5.9% and 5.4%, respectively, of the dietary crude protein for both maximum growth and feed efficiency.

Animal Feed↗