PubMed Health⌕ Search

Biomedical subjects

D D Chen

Publications and source records attributed to D D Chen.

28 records · Page 2Linked to original sources
PubMed1996

Development and application of a nonaqueous capillary electrophoresis system for the analysis of porphyrins and their oligomers (PHOTOFRIN).

PHOTOFRIN is a complex porphyrin mixture used in the photodynamic therapy of cancer. A nonaqueous buffer with a polyether additive is used in the development of a capillary electrophoresis method for the analysis of this type of compound. This method achieves partial separation of 60 peaks for PHOTOFRIN in 30 min. A methanol-based buffer is used to improve the efficiency of the separation by decreasing the aggregation of porphyrin, and the resolution is improved by using the electroosmotic flow (EOF) to counterbalance the electrophoretic migration of the analytes. This counter-balancing EOF holds the analytes in the electric field longer, thereby improving the resolution. Brij 35 is used as a complexation reagent to adjust the selectivity and improve the efficiency of the separation. The effects that Brij 35 concentration has on the separation of both monomeric and oligomeric porphyrins are discussed. The polarity of the solvent is adjusted through the addition of water and its effect is rationalized. A qualitative fingerprinting method for characterizing PHOTOFRIN is developed, and different batches and stressed samples are studied.

Biopolymers↗
PubMed1996

Propranolol and bepridil attenuating levothyroxine-induced rat cardiac hypertrophy and mitochondrial Ca2+ Mg(2+)-ATPase activity elevation.

AIM: To study the effects of propranolol and bepridil on levothyroxine-induced rat cardiac hypertrophy and mitochondrial Ca2+ Mg(2+)-ATPase activity elevation. METHODS: Rat heart hypertrophy was induced by i.p., levothyroxine 1 mg.kg-1.d-1 x 10 d. Then rats were treated by ig propranolol (Pro) or bepridil (Bep) 10 mg.kg-1 daily. Ca2+ Mg(2+)-ATPase activity and enzyme kinetic parameters were assayed. RESULTS: The activity and Vmax of mitochondrial Ca2+ Mg(2+)-ATPase isolated from hypertrophic left ventricle were 25 +/- 4 and 35.1 +/- 0.8 mumol Pi.h-1/mg protein, respectively, those of normal were 6.7 +/- 1.8 and 10 +/- 4 mumol Pi.h-1/mg protein, respectively. Apparent K(m) of the hypertrophic group Ca2+ Mg(2+)-ATPase was 0.4 +/- 0.12 mmol.L-1 ATP, and that of normal was 0.59 +/- 0.22 mmol.L-1 ATP. The total protein quantity of hypertrophic left ventricle was 80 +/- 30 mg, and that of normal was 47 +/- 9 mg. After treated with Pro or Bep (both 10 mg.kg-1 ig), the cardiac hypertrophy was attenuated, the enzyme activity and Vmax as well as total protein quantity of hypertrophic left ventricle were reduced to normal level, but apparent K(m) was not affected. CONCLUSION: Both Pro and Bep prevented the myocardium and its mitochondria from ischemia and overload calcium injury.

Adrenergic beta-Antagonists↗
PubMed1996

Bepridil reducing levothyroxine-induced enhancement of mitochondria Ca2+ Mg(2+)-ATPase activity in rat cerebrum.

AIM: To study if bepridil (Bep) could affect the enhancement of activity of cerebral mitochondria Ca2+ Mg(2+)-ATPase caused by levothyroxine (Lev) in relation to ischemic overload calcium cerebrum injury. METHODS: The experimental hyperthyroidism model with ischemic cerebrum was developed in rats by ig Lev 1 mg.kg-1.d-1 for 7 d. Ca2+ Mg(2+)-ATPase activity and its kinetic parameters were assayed. RESULTS: The activity, Vmax and Km of cerebral mitochondria Ca2+ Mg(2+)-ATPase in control rats were 3.1 +/- 0.8, 5.1 +/- 2.3 mmol.P(i).h-1/g protein and 0.81 +/- 0.08 mmol.L-1 (ATP) respectively, whereas those of hyperthyroid rats were significantly altered to 4.6 +/- 0.5, 8.5 +/- 1.9 mmol.P(i).h-1/g protein and 0.49 +/- 0.11 mmol.L-1 (ATP) respectively. After treated with Bep 10 or 20 mg.kg-1.d-1 ig for 3 d, allabove 3 parameters of the enzyme were very significantly reduced vs those of either control or hyperthyroid. CONCLUSION: Bep, via decreasing Ca2+ Mg(2+)-ATPase activity and increasing the affinity of Ca2+ Mg(2+)-ATPase to ATP, could prevent rat cerebrum from ATP depletion and ischemic overload calcium injury.

Animals↗
PubMed1995

Separation and expansion of tumor infiltrating lymphocytes of digestive system in vitro and their cytotoxicity.

Primary tumor tissues in the digestive system were harvested from 15 patients. By mincing, enzymatic digestion and gradient density separation, sufficient TILs (> x 10(6)) were obtained from 13 of 15 (88.7%) patients in vitro in the presence of 500 mu/ml of recombinant interleukin-2 and 5% fetal calf serum after one month culture. 92.3% (12/13) of TILs proliferated well in vitro (92.3%). TILs expanded from 10(/)-folds to 10(3)-folds after being cultured for one month. CD25+ cell of the most fresh TILs was more than that of peripheral blood lymphocytes. CD25+ cells of TILs during 4th week of the culture was significantly greater (P < 0.01) than that of fresh TILs. CD4+/CD8+ ratio was decreased during four culture weeks because of increase of CD8 cells. By using modified colorimetric MTT assay for measuring activity of TILs against various tumor cells the results showed that cytotoxicity of gastro-intestinal TILs in autologous tumor cells is greater than on the other tumor cells.

Adult↗
PubMed1994

Evidence for structural conservation of Lon and RcsA.

DNA probes specific to the Escherichia coli genes encoding Lon protease and RcsA hybridized to specific DNA sequences in a number of different microorganisms. Antiserum to either E. coli protein Lon or RcsA reacted with specific proteins in these organisms. These results provide structural evidence of the presence of Lon and RcsA in organisms other than E. coli.

ATP-Dependent Proteases↗
PubMed1993

[Assay of negative inotropism of bepridil on isolated guinea pig left atrial myocardium by simulating constant rate of absorption and elimination].

The pharmacodynamic characteristic of negative inotropic effect of bepridil on isolated guinea pig cardiac atrium was conducted by gradient perfusion with constant rate of bepridil ranging from 0-20 mumol.L-1 and inverse, simulating a fixed pharmacokinetic parameters of K(a) and K(e), respectively. A counter-clockwise hysteresis loop of negative inotropism of bepridil was presented. Fixing Cp, T, and E by pharmacokinetics/pharmacodynamics (PK/PD) non-parameter model, the hysteresis loop was collapsed in figure plotting C(e) against E. The estimated K(eo) = 0.03 +/- 0.023 h-1, an apparent T1/2 of pharmacological effect was measured, and about 80-fold as long as the pharmacokinetic T1/2. It was suggested that the long-lasting effect of bepridil was partly due to the slow elimination rate from the effect compartment.

Absorption↗
PubMed1990

[Histochemical and electron microscopic observation of the gastric wall after vagotomy].

Eight dogs underwent gastric total truncal vagotomy and another 8 had gastric superselective vagotomy. Specimens were take from anterior wall of gastric corpus and antrum at weeks after operation for histochemical and electron microscopic observation. The results showed: (1) the sympathetic postganglionic fibers in gastric wall were completely damaged. (2) response of gastric antrum mucosa to CCK-8 and gastric G-17 lowered markedly. (3) the amount of parietal cells increased, the structure of follicular atrophied, the number of mitochondrion in cytoplasm, and the stroma and micrailli on folilculi wall increased. (4) The Campylobacter-like organism (CLO) were found in mucosa of gastric antrum and corpus after operation. The authors discussed the role of gastric sympathetic nerve on gastric secretion and movement, and the relationship between CLO and ulcer recurrence after gastric superselective vagotomy.

Animals↗
PubMed1988

The genome of the multicapsid baculovirus of Orgyia pseudotsugata: restriction map and analysis of two sets of GC-rich repeated sequences.

Five cosmids containing inserts that comprise the complete genome of the multicapsid nuclear polyhedrosis virus of Orgyia pseudotsugata were mapped with four restriction enzymes (Bg/II, ClaI, SstI, XhoI). From these cosmid maps, composite maps of the complete genome were constructed for each restriction enzyme. A region containing repeats of the sequence GGC downstream of the polyhedrin gene was used to probe the genome. It cross-hybridized with a region which, upon sequence analysis, was found to be a highly repetitive GC-rich region of nearly 500 nucleotides. The two GC-rich regions appeared to be evolutionarily unrelated.

Animals↗