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Biomedical subjects

B Chen

Publications and source records attributed to B Chen.

At least 361 records · Page 20Linked to original sources
PubMed1996

Intravenous somatic gene transfer with antisense tissue factor restores blood flow by reducing tumor necrosis factor-induced tissue factor expression and fibrin deposition in mouse meth-A sarcoma.

Fibrin is deposited on the endothelial cell surface in the vasculature of murine methylcholanthrene A-induced sarcomas after injection of tumor necrosis factor (TNF). Capillary endothelial cells of the tumor vascular bed become positive for tissue factor after TNF injection, based on immunocytochemistry and in situ hybridization. Intravascular clot formation was not dependent on tissue factor derived from tumor cells, since in vessels of tumors not expressing tissue factor, TNF also induced fibrin/fibrinogen deposition. However, the time course of fibrin/fibrinogen deposition after TNF differed in tumors expressing no, little, or greater amounts of tissue factor. Fibrin/fibrinogen deposition was more rapid in tumors in which the neoplastic cells expressed tissue factor than in tumors not expressing tissue factor. In the tumors not expressing tissue factor, activation of coagulation was dependent on TNF-induced synthesis of tissue factor by host cells, i.e., endothelium or monocytes/macrophages. Intravenous somatic gene transfer with tissue factor cDNA in the antisense orientation (but not sense or vector alone) reduced intravascular fibrin/fibrinogen deposition and restored blood flow to the tumor, showing that de novo tissue factor expression is central in TNF-induced activation of the coagulation mechanism.

Animals↗
PubMed1996

Leukemic burden in subpopulations of CD34+ cells isolated from the mobilized peripheral blood of alpha-interferon-resistant or -intolerant patients with chronic myeloid leukemia.

We attempted to determine the frequency of normal hematopoietic stem cells (HSC) and contaminating leukemic cells in mobilized peripheral blood (MPB) collected from chronic myeloid leukemia (CML) patients, intolerant of alpha-interferon or with interferon-resistant disease. A total of 14 MPB samples, six from patients in chronic phase (CP) and eight from patients in accelerated phase or blast crisis (AP/BC) were studied. Cytogenetic analysis of MPB collected from AP/BC patients showed that 100% of the cells were Ph+, whereas cells from four of five CP MPB were Ph-. By contrast, fluorescence in situ hybridization (FISH) analysis of CP MPB showed a mean frequency of 14.7% Ph+ cells, while AP/BC MPB contained 39.2% Ph+ cells. In an attempt to purify normal HSC, subpopulations of the MPB CD34+ cells were isolated based on expression of the Thy-1 antigen (CDw90). The mean Ph+ cell frequency as determined by FISH within the CD34+Thy-1+Lin- and CD34+Thy-1-Lin- populations from CP patients was 19.2% and 33.9%, respectively. In the AP/BC patients, levels of residual leukemic cells were significantly greater with mean Ph+ cell frequencies of 59.2% and 72.7% for the CD34+Thy-1+Lin- and CD34+Thy-1-Lin- fractions, respectively. The frequency of cobblestone area forming cells (CAFC) was used as a means of quantitating the numbers of functional HSC within these cell subpopulations. The mean CAFC frequency was 1 of 19 for the CD34+Thy-1+Lin- cells as compared with 1 of 133 for the Thy-1-fraction indicating a higher frequency of primitive progenitor cells in the Thy-1+ subpopulation. CD34+ cell subsets from two patients were also injected into SCID-hu bone assays to determine the in vivo behavior of these cell populations. After 8 weeks, multilineage donor engraftment was observed in these grafts. FISH analysis of the donor cells within the grafts showed that 55.3% and 60.0% of the cells were Ph+. We conclude that unfractionated MPB from this patient population is not leukemia-free and that the CD34+Thy-1+Lin- cell subpopulation, although predominantly enriched for normal HSC, still contains substantial numbers of residual leukemic cells.

Adolescent↗
PubMed1996

Association of mitogen-activated protein kinases with microtubules in mouse macrophages.

Taxol, a microtubule-binding diterpene, mimics many effects of lipopolysaccharide (LPS) on mouse macrophages. The LPS-mimetic effects of taxol appear to be under the same genetic control as responses to LPS itself. Thus we have postulated a role for microtubule-associated proteins (MAP) in the response of macrophages to LPS. Stimulation of macrophages by LPS quickly induces the activation of mitogen-activated protein kinases (MAPK). MAPK are generally considered cytosolic enzymes. Herein we report that much of the LPS-activatable pool of MAPK in primary mouse peritoneal macrophages is microtubule associated. By immunofluorescence, MAPK were localized to colchicine- and nocodazole-disruptible filaments. From both mouse brain and RAW 264.7 macrophages, MAPK could be coisolated with polymerized tubulin. Fractionation of primary macrophages into cytosol-, microfilament-, microtubule-, and intermediated filament-rich extracts revealed that approximately 10% of MAPK but none of MAPK kinase (MEK1A and MEK2) was microtubule bound. Exposure of macrophages to LPS did not change the proportion of MAPK bound to microtubules, but preferentially activated the microtubule-associated pool. These findings confirm the prediction that LPS activates a kinase bound to microtubules. Together with LPS-mimetic actions of taxol and the shared genetic control of responses to LPS and taxol, these results support the hypothesis that a major LPS-signaling pathway in mouse macrophages may involve activation of one or more microtubule-associated kinases.

Animals↗
PubMed1996

Cloning and characterization of the Neurospora crassa cyt-5 gene. A nuclear-coded mitochondrial RNA polymerase with a polyglutamine repeat.

The Neurospora crassa mutants, cyt-5-1 and cyt-5-4 have a cytochrome b- and aa3-deficient phenotype, suggesting that they result from a deficiency in a nuclear-coded component of the mitochondrial gene expression apparatus (Bertrand, H., Nargang, F. E., Colllins, R. A., and Zagozeski, C. A. (1977) Mol. Gen. Genet. 153,247-257). The complementing wild-type gene has been cloned and and shown to encode a protein with significant sequence similarity to Saccharomyces cerevisiae mitochondrial RNA polymerase and bacteriophage RNA polymerases. There are remarkable differences between the N. crassa protein and its yeast homologue, including a region of very little homology near the N termini of the two gene products. The cyt-5 gene encodes a stretch of polyglutamine in this region of uniquesequence. In addition, an acidic insertion (86 amino acids, of which 24 are Asp or Glu and 10 are Arg or Lys) is present near the C terminus of the cyt-5 gene product. Transcript levels of the cytochrome b and cytochrome oxidase subunit III genes are severely reduced in cyt-5 mutants, suggesting a likely mechanism for the cytochrome-deficient phenotype. In contrast, mitochondrial rRNAs accumulate to nearly normal levels in cyt-5 mutants. However, mitochondrial rRNA levels are not indicative of the rate of transcription of the corresponding genes, since crude lysates of mitochondria from cyt-5 mutants exhibit greatly reduced transcriptional activity with a 19 S rRNA promoter. The cyt-5 gene is flanked by at least one gene whose product also may be involved in mitochondrial function.

Amino Acid Sequence↗
PubMed1996

Loss of heterozygosity on chromosomes 1, 11, 12, and 14 in hybrid mouse lung adenocarcinomas.

An allelotype analysis of lung tumors in mouse hybrids was conducted to identify common regions of allelic loss. By using 50 informative genetic markers, the autosomes of 36 (A/J x C3H/HeJ) F1 adenocarcinomas were examined. Additional adenocarcinomas from as many as 72 (C3H/HeJ x A/J) F1 and 15 (BALB/cJ x DBA/2J) F1 hybrids also were analyzed for DNA loss at some of the loci. Loss of heterozygosity (LOH) was observed at multiple loci and occurred with the most regularity at markers on chromosomes 12 (28%), 14 (28%), 11 (21%), and 1 (20%). The frequency of LOH was not greater than 11% on any of the other chromosomes. Chromosomes 11 and 14 often displayed allelic loss at markers located near the p53 and retinoblastoma tumor suppressor loci, respectively. LOH at markers on chromosomes 12 and 14 was associated with tumors having overall frequencies of allelic loss that exceeded the median value. Losses on chromosomes 1, 11, 12, and 14 also showed a significant association with the adenocarcinoma stage of mouse lung tumorigenesis, suggesting that the inactivation of tumor suppressor loci on these chromosomes may participate in the progression of these tumors.

Adenocarcinoma↗
PubMed1996

Evaluation of plant availability of soil trace metals by chemical fractionation and multiple regression analysis.

Soil samples with a range of chemical and physical properties were collected from 10 different rural regions of China. Trace metals (Ni, Co, Cu, and Pb) in the soils were partitioned by a sequential extraction procedure into Mg(NO(3))(2) extractable (F1), CH(3)COONa extractable (F2), NH(2)OH.HCl extractable (F3), HNO(3)?H(2)O(2) extractable (F4), and residual (F5) fractions. Chemical fractionation showed that F1 fraction of the metals was less than 1% and residue was the dominant form for Cu and Ni in all samples, and for Co in most of the samples. Significant interrelationships of the fractions varied considerably with the different metals. Winter wheat (Triticum aestivum L.) and alfalfa (Medicago sativa L.) had been grown on the soils in a pot-culture experiment under greenhouse conditions for 40 days. Metal availability to the plants was evaluated by simple and multiple regression analysis. The Mg(NO(3))(2) extractable Co (F1) was significantly correlated with Co concentrations in different parts of wheat and in the whole of alfalfa. For the other metals, the independent variables of the multiple regression models, chosen by stepwise selection, were given as: F1 and F2 + F3 + F4 for Ni; F1, F2 + F3 and F4 for Cu; and F3 + F4 for Pb. The results of this study demonstrate that the sequential extraction procedure, in conjunction with multiple regression models using a combination of correlated fractions as an independent variable, may be useful for the prediction of plant absorption of trace metals in soils.

Journal Article↗
PubMed1996

Changes in substance P in the jejuna of rats after burns.

Radioimmunoassay (RIA) was used to determine the dynamic changes of immunoreactive substance P (iSP) in the jejuna of rats (TBSA 30 per cent full skin thickness burn) during the first 72 h postburn. Immunohistochemistry and image analysis techniques were used to observe and quantitate the SP immunoreactivity (SP-IR) of positive nerve fibres in the villi of jejuna postburn. Changes in the amount of iSP in jejuna of burned rats were: (1) iSP increased significantly at 1 h postburn, and the high level of iSP lasted 4 h; it then decreased greatly 8 h later with the low level of iSP persisting for 72 h. (2) Significant changes in SP-IR-positive nerve fibres in the villi after burn were shown by the immunohistochemical studies including the morphoses; the distributive densities and SP-IR-positive products in the SP-IR-positive nerve fibres. The results quantified by image analysis showed similar alterations in the distributive densities and SP-IR-positive products in the nerve fibres in the villi during 72 h postburn; which were distinctly elevated by 1 hr then dropped by 8 h and 12 h and finally elevated again. The results indicated that the irritation-release and consumption of SP occurred in jejuna of rats after burns. It might be that SP contributed to the postburn intestinal lesion in rats by bioactivities, such as enhancing the vascular permeability and regulating the intestinal movement. The SP peptidergic nerve fibres of the villus had a direct effect on the damage to mucosal epithelia.

Animals↗
PubMed1996

Alcohol, central nervous system injury, and time to death in fatal motor vehicle crashes.

OBJECTIVES: Motor vehicle crash (MVC) studies have found that alcohol (ALC) is associated with increased mortality and decreased time to death (TTD). Clinical and experimental data suggest that ALC potentiates central nervous system injury (CNSI). We hypothesize that ALC-intoxicated, MVC fatalities with CNSI are more likely to die in the immediate postinjury period than are sober victims with CNSI. Methods; DESIGN: A retrospective cohort of 401 MVC fatalities from four Michigan counties for the time period 1985 to 1991 was studied. MEASUREMENTS: Medical examiner records were reviewed to determine age, blood alcohol concentration (BAC), and TTD. Injury severity was calculated with the Abbreviated injury Scale (1985 version). Anatomical profile scores and G scores were also calculated and used to identify CNSI subjects. ANALYSIS: chi 2 and Student's t test were used, and odds ratios with 0.95 confidence intervals (CIs) were calculated. RESULTS: ALC(+) cases (BAC > or = 100 mg/dl) (n = 99) were significantly younger and more frequently had TTD < 1 hr than ALC(-) cases (n = 233): odds ratio 1.62[0.95 CI (1.02 to 2.58)]. Overall, CNSI cases (n = 297) were significantly younger and had fewer thoracic injuries, but did not have significantly shorter TTD, compared with non-CNSI cases. However, ALC(+) CNSI cases (n = 77) were over twice as likely to have TTD < 1 hr ¿odds ratio 2.04 [0.95 CI (1.13 to 3.70)]¿. For ALC(+) isolated CNSI cases, the odds ratio for TTD < 1 hr, compared with nonisolated CNSI cases was 8.25 (0.95; CI 0.66 to 102.5). Injury Severity Score, anatomical profile, and G scores were not significantly different for ALC(+) CNSI cases, compared with ALC(-) CNSI cases, whether isolated or nonisolated. CONCLUSIONS: These data suggest that alcohol intoxication is associated with increased frequency of early death in MVC victims with CNSI, despite there being no detectable difference in anatomical injury scoring.

Accidents, Traffic↗
PubMed1996

Nitric oxide production: a mechanism of Chlamydia trachomatis inhibition in interferon-gamma-treated RAW264.7 cells.

IFN-gamma and/or LPS induced nitrite production and inhibition of Chlamydia trachomatis (CT) replication in the murine macrophage cell line, RAW264.7. Linear regression analysis demonstrated a strong correlation between nitrite production and inhibition of CT replication (correlation coefficients: -0.93, P < 0.001). L-NMMA specifically inhibited nitrite production and restored CT replication (55-71%). Inducible nitric oxide synthase (iNOS) mRNA was analyzed by Northern and dot blot hybridization with an iNOS cDNA probe. A strong correlation between iNOS mRNA expression and inhibition of CT replication also was observed (correlation coefficient: -0.97, P < 0.05). Furthermore, anti-TNF-alpha antibody, which completely neutralized biological activity of the secreted TNF-alpha, neither inhibited nitrite production nor restored CT replication in the LPS- and/or IFN-gamma-treated RAW264.7 cells. In mouse peritoneal macrophages treated with IFN-gamma, both L-NMMA and anti-TNF-alpha antibody inhibited nitrite production and restored CT replication. However, L-NMMA and the antibody had no effect upon nitrite production and CT inhibition in LPS-treated peritoneal macrophages. These data indicate that NO production is one mechanism for inhibition of CT replication in IFN-gamma-activated murine macrophages.

Animals↗
PubMed1996

Establishment of a human B-CLL xenograft model: utility as a preclinical therapeutic model.

Chronic lymphocytic leukemia (CLL), a proliferative disease of mature looking B lymphocytes, is the commonest leukemia in western countries. It remains incurable by available treatment modalities. We report on the establishment of a permanent, EBV-negative, B-CLL line (WSU-CLL) from the peripheral blood of a patient with CLL. The cells grow as suspension in liquid culture, express IgG lambda and other B cell markers and show lg heavy and light gene rearrangements. Karyotypic analysis shows 45,X,del(3)(p14;p24),t(4;12;12) (q31;q22;p13), t(5;12) (q31;p13), add(16)(q24)X2, t(18;21) (q12;p12). WSU-CLL forms colonies when grown on soft agar. A xenograft model was established by injecting the WSU-CLL cells subcutaneously (s.c.) in severe combined immune deficient (SCID) mice. When the s.c. tumor was transplanted in vivo to other SCID mice, the success rate was 100% with a doubling time of 7.3 days. The CLL-SCID xenograft model was used to test the efficacy of selected standard chemotherapy drugs and new therapeutic agents against WSU-CLL. The cell line and the xenograft described can be used as a model to facilitate the development of new therapeutic agents against CLL in man.

Aged↗
PubMed1996

Compromised microcirculation in acute murine Trypanosoma cruzi infection.

Microvascular compromise has been 1 of many factors implicated in the etiology of the cardiomyopathy associated with Chagas' disease. To further assess the effect of Trypanosoma cruzi infection on the microcirculation, we examined the cremaster microvascular model in CD-1 male mice infected with the Brazil strain at 20-25 days postinfection. There was a significant decrease in red cell velocity (Vrbc) in first and third-order arterioles and venules, which was reversed by verapamil treatment. Video recordings revealed a marked inflammatory response that was confirmed by transmission electron microscopy. A marked inflammatory response was not seen in verapamil-treated infected mice. Segmental vasospasm and dilatation was evident in the microvascular bed of infected mice. This was not seen in control or verapamil-treated mice. This model provides a readily accessible method to observe directly the effects of T. cruzi infection on the microcirculatory flow in vivo. In addition, it confirms and extends our previous observations regarding T. cruzi-associated microvascular spasm and underscores a role for verapamil, a calcium-channel blocker, in the amelioration of the Chagas' disease.

Acute Disease↗
PubMed1996

Regulation of granulocyte-macrophage colony-stimulating factor (GM-CSF) receptors in a GM-CSF-dependent human myeloid leukemia cell line (AML-193) by interleukin-6.

AML-193 is a cytokine-dependent human leukemia cell line established from the bone marrow of an M5-type acute monocytic leukemia (AML) patient. The effect of recombinant human interleukin-6 (rhIL-6) on the proliferation of AML-193 cells was investigated. Both granulocyte-macrophage colony-stimulating factor (rhGM-CSF) and rhIL-3 promoted the DNA synthesis and growth of AML-193 cells in vitro. rhIL-6 alone did not support the growth of AML-193 cells, yet pretreatment of AML-193 cells with rhIL-6 markedly enhanced their proliferative response to subsequent rhGM-CSF or rhIL-3 stimulation. The growth-promoting effect induced by rhIL-6 was attributable in part to the upregulation of GM-CSF receptors on AML-193 cells; treatment of AML-193 cells with rhIL-6 for 24 to 48 hours greatly increased their GM-CSF binding activity, which occurred in a dose-dependent manner. Both the growth-promoting and receptor-upregulating effects induced by rhIL-6 could be blocked by treating AML-193 cells with neutralizing anti-gp130 antibodies (GPX7). Treatment of AML-193 cells with anti-gp130 antibodies alone also led to a notable decline in GM-CSF binding activity, suggesting a possible role of gpl30 in regulating the expression of GM-CSF receptors. When AML-193 cells were starved in cytokine-free medium and then restimulated with rhGM-CSF, a rapid increase (5 minutes) in lyn kinase activity was observed. A similar upregulation of lyn kinase activity by rhIL-6 treatment also was noted in AML-193 cells, but only after a prolonged incubation of the cells with rhIL-6 (>24 hours). These findings show that the growth-promoting effects of rhIL-6 are mediated through the upregulation of GM-CSF receptors on AML-193 cells by mechanisms that appear to involve the activation of both gp130 and lyn kinase.

Antigens, CD↗