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Biomedical subjects

B Chen

Publications and source records attributed to B Chen.

At least 397 records · Page 22Linked to original sources
PubMed1995

Enrichment of human hematopoietic stem cell activity in the CD34+Thy-1+Lin- subpopulation from mobilized peripheral blood.

The number of CD34+ cells in the peripheral blood of cancer patients is known to be increased following the administration of high dose chemotherapy and hematopoietic growth factors. These so-called peripheral blood stem cell grafts are now frequently used for autologous transplantation of patients with malignancies. In this report, we address the question of whether true long-term repopulating pluripotent hematopoietic stem cells (PHSC) are mobilized into peripheral blood following chemotherapy plus granulocyte/macrophage colony-stimulating factor (GM-CSF) or granulocyte colony-stimulating factor (G-CSF) mobilization. We have examined the presence of stem cells in mobilized peripheral blood (MPB) by using an antibody to the human Thy-1 molecule to stain the CD34+Lineage- (Lin-) population. The kinetics of mobilization of CD34+Thy-1+ Lin- cells into peripheral blood were studied, and the percentage of cells with this phenotype was found to vary widely depending on the day of leukapheresis. A CD34+Thy-1+Lin- cell population, potentially containing PHSCs, was isolated by fluorescence activated cell sorting (FACS) and analyzed for activity. The multilineage differentiative capacity of this candidate stem cell-containing population in MPB was determined using an in vitro long-term culture system, in which cobblestone area formation was used as a means of detecting PHSCs. We also measured repopulating capacity by using two in vivo models in which severe combined immunodeficiency (SCID)-hu mice were implanted with human fetal bone or thymus grafts. Using these assays, we show that the highest frequency of cobblestone area-forming cells (CAFC) after 7 weeks of culture was observed in a subpopulation of CD34+Lin- cells, which expressed low levels of Thy-1. This cell population was capable of producing both B and myeloid cells, and maintaining CD34+Lin- cells in these long term cultures. Moreover, the CD34+Thy-1+Lin- cell subset possessed a higher ability to engraft and to demonstrate multilineage differentiative potential at 8 weeks in the SCID-hu bone assay. However, in the SCID-hu thymus model, both Thy-1+ and Thy-1- subpopulations were capable of donor T-cell engraftment at 6 weeks, suggesting the presence of cells capable of initiating T lymphopoiesis in both populations.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1995

Virus-mediated or transgenic suppression of a G-protein alpha subunit and attenuation of fungal virulence.

Strains of the chestnut blight fungus Cryphonectria parasitica harboring RNA viruses of the genus Hypovirus exhibit significantly reduced levels of virulence (called hypovirulence). The accumulation of a heterotrimeric GTP-binding protein (G protein) alpha subunit of the Gi class was found to be reduced in hypovirus-containing C. parasitica strains. Transgenic cosuppression, a phenomenon frequently observed in transgenic plants, reduced the accumulation of this alpha subunit in virus-free fungal strains. Significantly, the resulting transgenic fungal strains were also hypovirulent. These results indicate a crucial role for G-protein-linked signal transduction in fungal pathogenesis and suggest a molecular basis for virus-mediated attenuation of fungal virulence.

Amino Acid Sequence↗
PubMed1995

Differential regulation of fyn-associated protein tyrosine kinase activity by macrophage colony-stimulating factor (M-CSF) and granulocyte-macrophage colony-stimulating factor (GM-CSF).

The proliferation and differentiation of macrophages are regulated by, among others, GM-CSF and M-CSF. Treatment of bone marrow nonadherent (NA) cells with M-CSF induced a greater percentage of NA cells into adherent cells, recognized as monocyte/macrophages, than did GM-CSF. The effect of GM-CSF and M-CSF on the activation of fyn kinase, a 59-kDa src family-related protein tyrosine kinase (PTK), was studied. Control cultures of bone marrow NA cells expressed only minimal levels of fyn kinase activity. Treatment of bone marrow NA cells with M-CSF, but not GM-CSF, for 12 to 24 h greatly enhanced the levels of fyn kinase activity. The effect of M-CSF on the activation of fyn kinase was further investigated using bipotential adherent bone marrow-derived macrophages (BMDMs) that coexpress receptors for both GM-CSF and M-CSF. BMDMs can be induced by either growth factor to undergo extensive proliferation in vitro. Compared to bone marrow NA cells, BMDMs displayed higher levels of basal fyn kinase activity, which were similarly elevated by M-CSF but not GM-CSF treatment. The role of fyn kinase in regulating cell adhesion was investigated by growing BMDMs in both tissue culture and Teflon flasks. The growth of BMDMs was anchorage independent; the majority of them continued to proliferate as cell suspension in Teflon flasks. Whereas the levels of fyn kinase activity in adherent BMDMs grown in tissue culture flasks increased steadily, those in BMDMs grown in Teflon flasks diminished. To study the role of fyn kinase in growth regulation, BMDMs were treated with c-fyn sense and antisense s-oligos. In the presence of c-fyn antisense s-oligos, the proliferative response of BMDMs to M-CSF but not GM-CSF was inhibited. In contrast, the proliferation of BMDM in response to either GM-CSF or M-CSF was not influenced by c-fyn sense s-oligos. Collectively, our data suggest that the activation of fyn kinase is closely associated with the acquisition of adherent capacity in maturing macrophages.

Animals↗
PubMed1995

Association of polymorphisms of the apolipoprotein B gene with coronary heart disease in Han Chinese.

Four polymorphic sites of the apolipoprotein B (apo B) gene were investigated by using polymerase chain reaction (PCR) in 103 patients with coronary heart disease (CHD) and 100 age-matched healthy individuals selected from a population of Han Chinese in the Beijing area. The rare X+ allele of the XbaI restriction site was more frequently seen in CHD patients than in controls (0.088 vs. 0.025, P < 0.01). The relative frequency of rare E- allele of the EcoRI restriction site was significantly higher in CHD patients compared with controls (0.11 vs. 0.04, P < 0.01). Similarly, 3'VNTR-L allele (number of repeat units > 39) at the VNTR region was also present at an apparently high frequency in CHD patients in comparison to that in controls (0.602 vs. 0.290, P < 0.001). However, the difference in relative frequency of rare Del allele of the Ins/Del polymorphism at the signal peptide was not significant between the two groups (0.282 vs. 0.235. P > 0.05). In comparison with Caucasians, the relative frequencies of rare alleles (Del, X+ and E-) were found to be statistically lower in Han Chinese. Furthermore, the Del and X+ alleles, in linkage disequilibrium, were associated with significantly lower plasma level of HDL-C in CHD patients. Therefore it is suggested that genetic variation with the apo B gene may exert some impact on lipid metabolism and contribute to the susceptibility to development of CHD in Han Chinese.

Alleles↗
PubMed1995

Acute and chronic effects of marijuana smoking on pulmonary alveolar permeability.

Pulmonary clearance of technetium (99mTc)-labeled diethylene triamine pentaacetate (DTPA), a sensitive test of alveolar epithelial permeability, was measured twice in 34 healthy subjects, including 10 control nonsmokers (NS), 10 habitual smokers of marijuana alone (MS) (> or = 10 joints/wk), 9 regular smokers of tobacco alone (TS) (> or = 15 cigarettes/day) and 4 habitual smokers of both marijuana and tobacco (MTS). In smokers, the first study was performed after > or = 12 hrs of abstinence from smoking to assess chronic effects of marijuana and/or tobacco smoking on alveolar permeability; the second study was performed within 15 min of smoking to assess possible acute effects. TS exhibited abnormally rapid 99mTc-DTPA clearance after > or = 12 hours of abstinence, indicating an increase in pulmonary epithelial permeability, consistent with chronic tobacco-induced lung injury. MS showed a more modest and less consistent chronic effect than TS on 99mTc-DTPA clearance, suggesting a more variable and smaller degree of marijuana-induced lung injury. No acute effect of tobacco or marijuana smoking on 99mTc-DTPA clearance was apparent. Concomitant habitual smoking of marijuana and tobacco had no additive effect on alveolar permeability.

Adult↗
PubMed1995

Mutagenic activity of dopamine after nitrosation.

Dopamine hydrochloride is reported to be a new mutagen precursor in this study. After treatment with nitrite under acidic conditions, dopamine hydrochloride showed direct-acting mutagenicity on Salmonella typhimurium TA100, TA98 and Escherichia coli WP2uvra. The addition of S9 mix did not affect the mutagenicity of nitrosated dopamine significantly in these three strains. Meanwhile, a comparison of the mutagenicity of nitrosated dopamine with nitrosated tyramine was carried out.

Dopamine↗
PubMed1995

Human T, B, natural killer, and dendritic cells arise from a common bone marrow progenitor cell subset.

The early stages of lymphoid cell formation were studied by testing the differentiative potential of phenotypically defined subsets of CD34+ bone marrow cells. A subpopulation of CD34+ Lin- CD45RA+ cells expressing CD10 was isolated by flow cytometry. Such cells are CD38+, HLA-DR+, do not express significant levels of Thy-1 and c-kit, lack erythroid, myeloid, megakaryocytic potential, and give rise only to lymphoid T, B, natural killer (NK), and dendritic cells (DC) in kinetics and titration experiments. Limiting dilution analysis demonstrates the existence of multipotential B/NK/DC progenitor clones in the CD34hi Lin-CD10+ adult bone marrow cell population. Thus, nonprimitive progenitors for lymphoid cells and for DCs can be distinct from those of myeloid, megakaryocytic, and erythroid cells, implying that the DC lineage is developmentally more closely related to the lymphoid lineage than to the myeloid lineage. This study provides new insights into the organization and development of the human lympho-hematopoietic system.

Animals↗
PubMed1995

Intraperitoneal foreign body as a cause of acute abdomen in pregnancy.

Although surgical textbooks commonly include foreign bodies in the differential diagnosis of acute abdomen, this cause of abdominal pain has not been reported in the obstetric literature. A 35-year-old woman presented at 24 weeks' gestation with right lower quadrant pain and peritoneal signs. The only abnormal finding at exploratory laparotomy was a free-floating intraperitoneal foreign body, presumably left inadvertently during prior surgery. The differential diagnosis of acute abdomen in pregnancy should include intraperitoneal foreign body in any woman with a history of previous abdominal surgery.

Abdomen, Acute↗
PubMed1995

Development of a clinically applicable high-speed flow cytometer for the isolation of transplantable human hematopoietic stem cells.

A high-speed cell sorter capable of a throughput speed 4-5-fold greater than commercially available systems was developed and evaluated as a processing tool for isolating purified hematopoietic stem cell grafts. The clinical high-speed sorter (CHSS) serves as a single-pass, multiparameter processing tool that provides the means to isolate a highly purified population of cells from starting cell populations with extremely low frequencies. The sorter incorporates environmental barriers to create a sterile environment for cell processing. Monoclonal antibodies and reagents produced under good manufacturing practices (GMP) are used to isolate hematopoietic stem cells by means of the CHSS. Using this technology, the CD34+Thy-1+Lin- hematopoietic stem cell population has been isolated from normal adult bone marrow and mobilized peripheral blood. The sorted cells have been shown to be sterile and viable and to retain hematopoietic function.

Cell Separation↗
PubMed1995

Antisense oligonucleotide down-regulation of E-cadherin in the yolk sac and cranial neural tube malformations.

The cadherins are a family of calcium-dependent cell adhesion molecules that are regulated both spatially and temporally during development. Epithelial cadherin (E-cadherin) is present in epithelial cells in both the embryo and yolk sac during organogenesis. The consequences of disrupting the expression of E-cadherin at this stage of development are poorly understood. We report here our studies on the effects of antisense oligonucleotides on E-cadherin in the rat whole embryo culture system. Four 18-base single strand phosphorothioate oligodeoxynucleotides (AS-oligos), complementary to various regions of the mouse E-cadherin cDNA sequence, were dissolved in saline and injected into the amniotic cavities of 5-7 somite rat embryos; a sense (S-oligo) to oligo-1, an 18-base random sequence oligo (C-oligo), and PBS were used as controls. Embryos were cultured for up to 45 h; embryo morphology and the relative concentrations of E-cadherin protein were examined. All six oligonucleotides (AS-oligos and control oligos) induced malformations when amounts ranging from 25 to 50 pmol of oligonucleotide were injected per embryo. The malformations induced by all the oligos included craniofacial hypoplasia, an enlarged pericardium, twisted spinal cord, swelling of the rhombencephalon, and underdeveloped forelimb. Injection of AS-oligo-1, a sequence starting at the tenth base downstream from the translation initiation codon (ATG), resulted in malformed embryos with a high incidence of cranial neural tube malformations. The effects of AS-oligo-1 on the relative abundance of E- and neural (N)-cadherin proteins were examined by Western blot analysis. In the AS-oligo-1-exposed malformed embryos, the relative abundance of E- and N-cadherin proteins was not altered up to 24 h after injection; E- and N-cadherin concentrations in the embryo were decreased at 45 h postinjection. In contrast, the relative abundance of the E-cadherin protein in the yolk sac was reduced at 1-2 h after injection of AS oligo-1 and returned to control levels by 4 h. S-oligo-1 did not induce any change in the relative abundance of E- or N-cadherins. Thus, there was a tissue-specific and temporary "knockdown" of E-cadherin expression in the yolk sac of embryos exposed to antisense (AS-oligo-1); the down-regulation of yolk sac E-cadherin appears to lead to the induction of neural tube defects in the embryo. The exposure of whole embryos in culture to antisense oligonucleotides provides a model system in which the roles of developmentally important molecules and their spatial and temporal contributions to embryogenesis can be elucidated.

Animals↗
PubMed1995

Geographic variation in preventable deaths from motor vehicle crashes.

OBJECTIVE: In Michigan, drivers in rural motor vehicle crashes (MVCs) are twice as likely to die as nonrural drivers: this could be due to variation in the quality of acute trauma care. This study tests the hypothesis that the preventable death rate (PDR) is higher and that anatomic injury severity is lower for rural compared to nonrural MVC fatalities. DESIGN: Retrospective cohort study. METHODS: Autopsy results from MVC victims of three rural counties and one nonrural county were reviewed. The time period was 1986-1991. Using the Abbreviated Injury Scale, 1985 version (AIS-85), Injury Severity Scores (ISSs) and Anatomical Profile G scores were calculated. Preventability was determined based on ISSs (< 59) and AIS scores in the head region (< 5). Student's t test and the chi-squared test were used for analysis; a p value of < 0.05 was considered statistically significant. RESULTS: 143 rural and 306 nonrural fatalities were analyzed. The rural PDR was 37.1% and nonrural 48.0% (p < 0.05). ISSs and also G scores were significantly different between rural (54.8; -2.1) and nonrural (50.2; -1.2) areas. CONCLUSION: This study suggests that regional variation in the quality of acute trauma care is not a significant factor in regional variation in MVC mortality.

Accidents, Traffic↗
PubMed1995

Respiratory rate and signs in roentgenographically confirmed pneumonia among children in China.

A clinical study was conducted in three Chinese community hospitals to investigate the reliability of respiratory rate and various clinical signs in the diagnosis of pneumonia among 54 children less than 5 years of age. Anteroposterior chest film was used as the diagnostic standard. The cutoff criterion for rapid breathing was 50 breaths/minute for infants ages 2 to 11 months and 40/minute in children 1 to 5 years old. Rapid breathing was a better predictor of pneumonia than rales (positive predictive values of 74.5 and 66.9%). Nasal flaring, chest indrawing, stridor and cyanosis of the tongue had predictive values of > 86%, but these clinical signs were observed in only a small proportion of patients. We recommend that village health workers use rapid breathing for diagnosis of pneumonia, rather than auscultation which is difficult and has proved unreliable. Sensitivity, specificity and positive and negative predictive values are presented for seven signs and symptoms of pneumonia.

Auscultation↗
PubMed1995

Mixed-subunit capsids can be assembled in vitro with coat protein subunits from two cucumoviruses.

Virus particles were reassembled in vitro from tomato aspermy virus strain V (V-TAV) RNA and a mixture of subunits prepared from V-TAV and 35S-labelled cucumber mosaic virus strain T (T-CMV). Immunodiffusion tests showed that the reassembled particles reacted with polyclonal antisera raised against both V-TAV and T-CMV. Radioactivity was found in the precipitin line formed between the reassembled particles and antiserum raised against T-CMV as well as in the precipitin line formed between the reassembled particles and antiserum raised against V-TAV. This shows that 35S-labelled T-CMV protein subunits were incorporated with V-TAV protein subunits into the same particles. Thus, coat proteins of V-TAV and T-CMV can co-assemble and form mixed-subunit capsids in vitro.

Capsid↗