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Biomedical subjects

S Chen

Publications and source records attributed to S Chen.

At least 991 records · Page 55Linked to original sources
PubMed1996

Influence of human factors on performance of Chinese speech recognition systems.

Human factors affecting the performance of the speaker dependent isolated Chinese speech recognition system (SRS) were studied. The results showed that the training mode and dialect factors had significant influence upon recognition accuracy; speaker's psychological factor, cooperativeness and educational background had certain influence, while factors such as sex, age, and profession of the speaker had less influence on recognition performance. With the results taken into consideration, ways for improving performance of the speech recognition systems were explored from the point of view of man-machine integration.

Adolescent↗
PubMed1996

Matrix-induced liver cell aggregates (MILCA) for bioartificial liver use.

Ex vivo reproduction of liver microstructure using isolated hepatocytes is critical for bioartificial liver use. We have developed a method of producing matrix-induced liver cell aggregates (MILCA) using a small number of collagen-coated beads as a nidus for formation of hepatocyte aggregates. Porcine hepatocytes were obtained by EDTA/collagenase digestion. Cell viability was assessed by trypan blue exclusion and LDH release. Cytochrome P-450 activity was determined at 4 and 24 hours by measuring the formation of 7-hydroxycoumarine (7-HC) from 7-ethoxycoumarine (7-EC). At 4 hours, the viability of MILCA was 92 +/- 2%, LDH release was 100 +/- 22 U/L and 7-HC formation was 140 +/- 34 nM/g cells. At 24 hours, MILCA viability remained greater than 90%, but 7-HC formation was lower than that of parallel control monolayer hepatocyte cultures (194 +/- 43 vs 481 +/- 78 nM/g cells; p < 0.002). On transmission electron microscopy, MILCA ultrastructure resembled that of a normal liver (maintenance of cell polarity, gap junctions, bile canaliculi, intact organellae, glycogen granules). MILCA were subsequently inoculated into hollow-fiber bioreactors which were perfused for 6 hours with plasma recovered from patients with fulminant hepatic failure (n = 6; 5 x 10(9) cells/cartridge, recirculation of 350 ml of plasma at 400 ml/min). In these studies, lidocaine (20 micrograms/ml) was cleared in less than 3 hours and 7-HC production at 6 hours was 71 +/- 8 nM/g cells. Other MILCA effects noted in this system included lowering of plasma lactate, bilirubin and ammonia and increase in the level of several non-essential amino acids.

Alginates↗
PubMed1996

High-level expression of a novel epitope of CD59 identifies a subset of CD34+ bone marrow cells highly enriched for pluripotent stem cells.

To further define the hierarchy of human hematopoietic progenitor cells, we have attempted to identify antibodies to cell-surface molecules expressed on CD34+ progenitor cell subsets. Herein we describe the utility of a new monoclonal antibody, HCC-1, which binds to a novel epitope of CD59 differentially expressed among CD34+ progenitor cells. HCC-1 subdivides the adult marrow CD34+ population into HCC-1high and HCC-1low/- fractions of approximately equal size. Cobblestone area-forming cells (CAFC) in long-term bone marrow culture were enriched 10-30-fold in CD34+HCC-1high cells compared with CD34+HCC1-low/- cells and two-fold compared with CD34+ cells. When injected into fetal human bone fragments implanted in SCID mice, the CD34+HCC-1high population showed potent engrafting activity leading to the production of myeloid, lymphoid, and erythroid elements, as well as the retention of progenitor cell phenotype. These studies demonstrate that the CD34+HCC-1high population contains primitive pluripotent hematopoietic stem cells. No hematopoietic engrafting activity was detected in the CD34+HCC-1low/- population. Consistent with this finding, simultaneous five-color flow cytometric analysis revealed that HCC-1high cells include virtually all CD34+Thy-1+Lin- cells, a cell population previously characterized as highly enriched for primitive pluripotent hematopoietic stem cells. The ability of CD34+ cells divided into subsets by HCC-1 to produce T cells was assessed by transplantation of sorted cells into human fetal thymus implanted into SCID mice. A higher frequency of thymus-engrafting activity was observed in the CD34+HCC-1high than in the CD34+HCC-1low/- population. Consistent with the limited ability to engraft in the SCID-hu thymus model, the CD34+HCC-1low/- population was shown to contain a low frequency of CD34+CD10+ lymphoid progenitor cells. We conclude that the HCC-1 epitope is expressed at high levels on a subset of CD34+ cells that contain virtually all primitive pluripotent hematopoietic stem cells and that the population of CD59 molecules expressed on CD34+ cells is not homogeneous.

Animals↗
PubMed1996

Effect of herba artemisiae scopariae on cytogenetic damage induced by aflatoxin B1.

It was found that the per mill rate of micronucleus of marrow cells in mice induced by AFB1 decreased with the increasing dosage of Herba Artemisiae Scopariae, and that there were dosage-effect relations in the lowering of percentage of chromosomal aberration induced by AFB1 and in the inhibition effect on some sister chromatid exchanges per cell.

Aflatoxin B1↗
PubMed1996

[Regeneration of free nerve endings and sensory corpuscles after implantation of nerve into the denervated skin in the monkey].

Two rhesus monkeys were used. Their fingers were denervated first and then the nerve was implanted into the denervated skin. The results showed that: (1) the process of regeneration of nerve fibers was similar to that of previous experiments in rabbits; (2) regeneration of nervous tissue included 2 kinds of sensory receptors with capsule-Meissner corpuscles and Merkel cell-dendrite complex; (3) the regenerative rate of Meissner corpuscles increased progressively and their morphology and structure became matured with elapse of time; (4) no regeneration of pacinian corpuscle was found in 6 months after nerve implantation; (5) Meissner corpuscles also regenerated in the transplanted glabrous skin.

Animals↗
PubMed1996

Plasma membrane calcium pump-mediated calcium efflux and bulk cytosolic free calcium in cultured aortic smooth muscle cells from spontaneously hypertensive and Wistar-Kyoto normotensives rats.

OBJECTIVE: To compare the efficacy of the calcium pump-mediated calcium efflux pathway in spontaneously hypertensive rats (SHR) with that in Wistar-Kyoto normotensive rats (WKY), at rest and after angiotensin II stimulation. DESIGN: The intracellular free calcium concentration and calcium-45 efflux were measured in parallel, in cultured aortic smooth muscle cells isolated from 10-week-old male SHR and WKY rats. METHODS: The intracellular free calcium concentration and calcium-45 efflux were studied in confluent vascular smooth muscle cells in culture. Experiments were performed in the absence of added extracellular calcium and sodium. Fura-2 was used to measure basal and angiotensin II-stimulated intracellular free calcium concentration. Effluxed calcium-45 was measured over 5s intervals to determine basal and angiotensin II-stimulated calcium efflux rates in SHR and in WKY rats. RESULTS: No significant difference between SHR and WKY rats was observed in basal intracellular free calcium concentration or 100nmol/l angiotensin II-stimulated peak intracellular free calcium concentration. However, significantly elevated basal and 100 nmol/l angiotensin II-stimulated calcium-45 efflux rates were found in SHR. The calcium-45 efflux rates in SHR were elevated when the efflux was normalized with respect to the bulk intracellular free calcium concentration. The time taken to reach the maximum calcium-45 efflux rate after angiotensin II stimulation was reduced in SHR compared with that in WKY rats and was dose-dependent in both rat strains. CONCLUSION: The calcium-pump mediated calcium efflux pathway appears to be more efficient in SHR. This may be the result of post-translational modification, enhanced calcium pump sites in a critical region of the membrane, or the presence of a pool of calcium near the plasma membrane that is not readily detected by cytosolic Fura-2 but is higher in SHR both before and after angiotensin II stimulation.

Animals↗
PubMed1996

[The establishment of a three dimensional PCR screening system and quality evaluation of human YAC library].

In order to screen out YAC clones in the CEPH YAC library related to a definite gene, DNA fragment or locus, we need to establish a screening system. This paper includes the establishment of this system and the evaluation of its feasibility. According to the experiments, we suggest that it is better to screen the Mega YAC part of the library at first and put five culture plates as a group. Meanwhile, FISH experiments to assess the quality of CEPH YAC library and the first generation physical map of human genome, Were conducted FISH experiments on 26 YAC clones were carried out. There were 13 clones that were chimeric (about 50%), 6 clones that were mapped by mistake (about 23%). So, there were only 9 clones that were mapped correctly and were not chimeric (about 35%).

Chromosomes, Artificial, Yeast↗
PubMed1996

[Study of chromosome painting for one rare carrier with complex translocation].

This paper reports that one rare male carrier with complex translocation, being married for eight years, made his wife consecutive seven times abortions, stillbirth and teratogenesis of early death. Using human chromosome 7 and 8-specific probe pools constructed with the technique of chromosome microdissection and PCR, we carried out chromosome painting research of the patients, and identified the karyotype was: 46, XY, -7, -8, -9, +der (7)t(7; 9) (q2200; p24), +der(8)inv ins(8; 7) (q2100; q31.2q2200), +der (9)t(9; 7) (p24; q31.2).ish der(7)t(7; 9) (wcp7+), der(8)inv ins(8; 7)(wcp7+, wcp8+), der(9)t(9; 7) (wcp7+). The technique of chromosome painting provided us an effective technique of molecular cytogenetics for the study of chromosomal abnormalities. The formation mechanism of the complex translocation of the carrier is discussed.

Adult↗
PubMed1996

Effects of head down tilt on hemodynamics, fluid volumes, and plasma Na-K pump inhibitor in rats.

BACKGROUND: Hindquarter suspension in rats has been used as a model of simulated weightlessness (SW) for ground based study of the effects of microgravity on the cardiovascular system (CVS). METHODS: Using this rat model of SW we tested the hypothesis that CVS deconditioning following spaceflight results, in part, from a decrease in the circulating concentration of sodium-potassium pump inhibitor (SPI). Control rats similarly prepared were not suspended. RESULTS: During the first hour of suspension, central venous pressure (CVP), blood pressure (BP), heart rate (HR), cardiac output (CO), plasma volume (PV), extracellular fluid volume (ECFV), urine output (UV), atrial natriuretic peptide (ANP), and the plasma level of SPI increased. Plasma renin activity (PRA) and myocardial Na+, K(+)-ATPase activity (NKA) decreased. By the end of 4 h of SW, the changes in CVP, BP, HR, ECFV, and UV persisted, but PV, plasma ANP and SPI, and myocardial NKA activity returned to control levels. By the end of 1 d of SW, ECFV and plasma SPI levels had decreased but the myocardial NKA had not increased. At day 4, CVP and BP were the same as in control sham treated rats. Plasma SPI levels were decreased at day 4 but the myocardial NKA was not different, whereas renal NKA was increased. At day 7, myocardial NKA and renal NKA were increased and vascular smooth muscle cell (VSMC) membrane potentials were hyperpolarized. CONCLUSIONS: These data indicate that prolonged SW causes a decrease in plasma SPI level which, by hyperpolarizing VSMC, may play a role in the CVS deconditioning seen in astronauts following spaceflight.

Animals↗
PubMed1996

[A preliminary study of the relation between topoisomerase I and translocation (15;17)].

The chromosomal translocation (15;17) which produced the PML-RAR alpha fusion gene had been found in acute promyelocytic leukemia (APL) cells. It was identified that the RAR alpha gene on chromosome 17 and PML gene on chromosome 15 were involved in this translocation. For study the molecular mechnisms of t(15:17) in APL, we cloned and sequenced the junctional region of the chromosomal reciprocal translocation in one APL patient. Furthermore, we compared 21 junctional sequences which had been reported with the consensus sequence of the DNA-topoisomerase I-binding sites. Thus, we proposed a hypothesis that topoisomerase I may play certain role in t(15;17) illegitimate recombination.

Adult↗