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Biomedical subjects

B Chen

Publications and source records attributed to B Chen.

At least 379 records · Page 21Linked to original sources
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

Transplantation of encapsulated neonatal porcine islet-like cluster cells into diabetic rats.

OBJECTIVE: To evaluate the function of alginate poly-L-ysine membrane in protecting porcine to rat islet xenografts. MATERIAL AND METHODS: Newborn porcine islet-like cluster cells (ICC) were obtained by digesting pancreas with type XI collagenase. After 2-3 days' incubation, encapsulated ICC were formed through instrument. In vitro, insulin release and insulin stimulating test was performed. In vivo, encapsulated ICC were transplanted into streptozotocin-induced diabetic rats. RESULTS: Unlike ICC only (insulin can be tested within 14 days) encapsulated ICC maintained insulin release at certain level for nearly 28 days. High insulin response to 16.7 mM glucose and 10 mM theophylline significantly differed from low insulin response to 5.6 mM or 16.7 mM glucose (P < 0.01). Extended survival of porcine ICC xenografts implanted in diabetic rats had been achieved by encapsulation. After transplantation, rats sustained normal glycemia for average 4 months. The capsules with ICC obtained from experimental group could be stained with neutral red. Insulin release of survival capsules with ICC in response to 16.7 mM glucose and 10 mM theophylline was 3 times more as compared to the insulin response to 5.6 mM glucose. Sections of encapsulated ICC (H&E) showed fairly good cell clusters and the membranes were generally free of fibrosis and host cell adherence. CONCLUSION: Artificial membrane can protect discordant islet xenografts from rejection.

Animals↗
PubMed1996

Effects of verapamil on acute murine Chagas' disease.

Continuous administration of verapamil significantly reduced the mortality rate of acute murine Trypanosoma cruzi infection (P < 0.05). The mechanistic basis for these observations was investigated. Verapamil and other calcium-channel blockers did not inhibit the growth of epimastigotes in culture. Furthermore, verapamil did not inhibit the intracellular growth of amastigotes in endothelial cells as determined by the uptake of 3H-uracil. There were no significant differences in parasitemia between infected mice that were untreated and those treated with verapamil. Twenty days postinfection infected, untreated mice had a parasitemia of 5.8 x 10(6) trypomastigotes/ml (SD +/- 2 x 10(6)), whereas infected, verapamil-treated mice had a parasitemia of 2.2 x 10(6) trypomastigotes/ml (SD +/- 0.5 x 10(6)). There was no significant difference in mortality between mice administered verapamil only for the initial 10 days of murine infection compared to those treated continuously. A 3-day delay in the initiation of verapamil administration reduced the mortality rate, but a 10-day delay did not. Propranolol (beta-adrenergic blocker), prazosin (alpha 1-adrenergic blocker), and diltiazem (another calcium-channel blocker) reduced the mortality but not significantly (P = 0.07). In biochemical studies of the beta- adrenergic signal transduction complex, we determined that verapamil and propranolol reversed the infection-associated decrease in myocardial beta- adrenergic adenylyl cyclase activity. In contrast, complementary western blot analysis revealed no significant changes in the G-proteins of the beta- adrenergic receptor complex 45 days postinfection. Therefore, these results suggest that the basis of verapamil's influence on the early critical period of infection is multifactorial and independent of a direct trypanocidal effect.

Acute Disease↗
PubMed1996

[Protective effect of ATP-MgCl2 on gut mucosa in burn rat].

In order to study the protective effect of ATP-MgCl2 on gut mucosal barrier function in trauma-induced stressed animal, full thickness burn of 30% total body surface area (TBSA) was produced in rats, and ATP-MgCl2 was injected intraperitoneally right after scald-injury. Malondialdehyde (MDA) contents of ileum mucosa were determined and morphological alteration in the ileum was observed under light microscope. The results showed that ileum mucosal MDA content increased significantly, accompanied by obvious morphological change, after the injury, whereas MDA content was maintained at the normal control level and pathological alteration in ileum tissue was abated after the use of ATP-MgCl2. It suggests that ATP-MgCl2 possesses a protective effect on gut mucosal barrier function of scald-injured rat, and the mechanism involved may be related to the inhibition of lipid peroxidation in gut mucosa.

Adenosine Triphosphate↗
PubMed1996

[Observation and analysis of postburn changes in substance P (SP) and SP peptidergic nerve fibers in the intestine of rat].

Substance P (SP) was measured by radioimmunoassay (RIA) and SP peptidergic nerve fibers were identified by Immunohistochemistry (IHC) in the intestinal wall of rats (TBSA 30% and with full-thickness burn) during 72 hours after burn. The results were as follows: (1) SP increased significantly at 1 hr and 4 hr postburn, then decreased markedly 8 hr later, and the low was maintained up to 72 hr. (2) The significant changes in SP peptidergic nerve fibers in the villi after burn were found with immunohistochemical studies including the morphology, distributive densities and SP contents of the SP peptidergic nerve fibers. The results from image analysis showed that the distributive densities of the nerve fibers elevated distinctly in 1 hr group, then dropped at 8 hr and 12 hr and finally elevated again. The results indicated that, the SP release might occur leading to SP consumption in the intestinal wall of rats after burn. It is possible that SP contributes to the postburn intestinal lesion in rats. The SP peptidergic nerve fibers in villus have a direct effect on the damage of intestinal mucosal barrier.

Animals↗
PubMed1996

[IL-2, IL-2R mRNA gene expression and protein production].

OBJECTIVE: To analyse IL-2, IL-2R mRNA gene expression and protein production before, during, and after rejection of heart transplantation in vitro model. METHOD: The in vitro system consists of peripheral PBMC of health donor as response cells and cardiomyocytes of patient suffering from acyanotic congenital heart disease as stimulating cells. Reverse transcription-polymerase chain reaction (RT-PCR) was used. RESULTS: mRNA transcription and protein production of IL-2, IL-2R rose markedly after stimulation of alloantigen, and were different from those of the control (P < 0.05, P < 0.01). The summit of IL-2, IL-2R mRNA transcription was detected 24 hours after initiation of mixed culture, 48 hours earlier than the time (72 hours) at which damage of cardiomyocytes was detected electronmicroscopy and the peak of IL-2, IL-2R protein production detected. CONCLUSION: IL-2/IL-2R system plays an important role in the rejection of heart transplantation. Detection of IL-2, IL-2R mRNA transcription is significant for early diagnosis of rejection. RT-PCR makes analysis of mRNA rapid, and is sensitive and high specific.

Gene Expression↗
PubMed1996

[Prediction of skin flap viability by laser Doppler scanning].

Twelve female pigs were used for the experiment. An island flap (8 cm x 15 cm) pedicled with the superficial circumflex iliac vessels was elevated on the flank of the pig. The blood flow of the flap was measured with laser doppler scanning at different times, i.e. before and after flap elevation; before clipping the feeding artery of the flap and 9 hours after clipping the artery; 5 minutes, 20 minutes, 40 minutes, 1 hour and 40 hours after reperfusion. The flap viability was also examined with naked eye and fluorography. Biopsy examinations were used as gold standard of flap viability. The results showed that predicting accuracy of flap viability by naked eye was 76%; fluorography was 94% and laser doppler scanning was 91.3%. No significant difference was found between the results from fluorography and laser doppler scanning while there was significant difference between naked eye and laser doppler scanning. The authors discussed the clinical applications of predicting skin flap viability.

Animals↗
PubMed1996

[Clinical study and application of 3DCT in oral and maxillofacial regions].

3DCT reconstruction as a new roentgenographic technique has not been used so much in oral and maxillofacial regions in our country. From May 1993 to May 1995, 72 cases of 3DCT reconstruction have been performed by a Siemens Plus-s CT scanner for the maxillofacial injuries and jaw bone diseases. The 3DCT reconstruction of soft tissuses has been used too. It is showed that 3DCT reconstruction is a useful technique for the diagnosis and surgical planning of diseases in oral and maxillofacial regions.

Adolescent↗
PubMed1996

[Clinical diagnostic problems of the female coronary heart disease evaluated by coronary artery angiography].

The clinical data of 100 female cases with suspected coronary heart disease (CHD) undergoing coronary artery angiography (CAA) were analysed. CHD was defined as an estimated diameter stenosis of 75% and more in the main coronary arteries or coronary stenosis of 50%-75% with evidence of cardiac ischemia. Forty-eight case were confirmed as having CHD by CAA. The remaining 52 cases were confirmed as non-CHD and served as the control group, including 49 cases with normal coronary arteries and 3 cases with stenosis of less than 50% in the right coronary artery or left anterior descending artery. The risk factors of CHD and clinical characteristics of chest pain were compared for the two groups. The data demonstrated that menopause was a special risk factor for females and the incidence of CHD was increasing with aging after menopause. However, the clinical characteristics of chest pain in female CHD were usually atypical. When chest pain, whether clinically typical or atypical, were present after menopause and accompanied by evident risk factors, the probability of CHD would be high. If there was only chest pain without any risk factor after menopause, the diagnosis of CHD would be less likely.

Adult↗
PubMed1996

[Consecutive study on alveolar macrophage release of tumor necrosis factor-alpha and platelet-derived growth factor in bleomycin-induced pulmonary fibrosis in rats].

OBJECTIVE: Observe consecutively alveolar macrophage (AM) release of tumor necrosis factor-alpha (TNF-alpha) and platelet-derived growth factor (PDGF in bleomycin-induced pulmonary fibrosis in rats. METHODS: ELISA method for TNF-alpha quantitation; Bioassay method for PDGF assessment. RESULTS: (1) AM TNF-alpha release was elevated on 3rd day, peaked on 7th day and then remained at higher level than that in control. (2) AM PDGF release was elevated on 3rd day, also peaked on 7th day, but then decreased to a near normal level. CONCLUSION: AM might play a role in the pathogenesis of pulmonary fibrosis through release of TNF-alpha and PDGF.

Animals↗
PubMed1995

Molecular and structural characterization of the heat-resistant thyroxine-binding globulin-Chicago.

Thyroxine-binding globulin (TBG) is the main transport protein for thyroxine (T4) in blood. It shares considerable sequence homology with alpha 1-antitrypsin (AT) and other members of the serine proteinase inhibitor (serpin) superfamily of proteins. The crystallographic structure of AT has been determined and was found to represent the archetype of the serpins. This model has been used for structure-function correlations of TBG. Sequence analysis of the heat-resistant variant TBG-Chicago (TBG-CH) revealed a substitution of the normal tyrosine 309 with phenylalanine. For further analysis, vectors containing the coding regions of normal TBG (TBG-N) and TBG-CH were constructed, transcribed in vitro, and expressed in Xenopus oocytes. Both TBGs were secreted into the culture medium and could not be distinguished by gel electrophoresis. Scatchard analysis of T4 binding to TBG-N and -CH revealed no significant differences in binding affinity. The rate of heat denaturation of TBGs was determined by measurement of residual T4 binding capacity after incubation at 60 degrees C for various periods of time. The half-life values of denaturation of TBG-N and -CH were 7 and 132 min, respectively. The tyrosine 309 to phenylalanine substitution of TBG-CH involves a highly conserved phenylalanine residue of the serpins. The respective phenylalanine 312 of AT ties the alpha-helix hI1 to the molecule, thus stabilizing the tertiary structure. A substitution with tyrosine would disrupt this interaction. Accordingly, stabilization of the TBG molecule by replacement of tyrosine with phenylalanine in position 309 causes the increased heat stability of TBG-CH.

Amino Acid Sequence↗
PubMed1995

Morphological diversity and glutamate immunoreactivity of retinal terminals in the suprachiasmatic nucleus of the cat.

Although the cat visual system has been the subject of intensive investigation, little attention has been given to the morphological features of ganglion cell projections to the suprachiasmatic nucleus. The present study has utilized anterograde transport of horseradish peroxidase and wheat germ agglutinin-conjugated horseradish peroxidase to label ganglion cell terminals in the cat suprachiasmatic nucleus. Visualization of the reaction product was facilitated through the use of gold-substituted silver intensification. Ganglion cell terminals were found to be morphologically diverse, making both asymmetric and symmetric contacts with postsynaptic processes. Synaptic vesicles were either scattered or densely packed, sometimes forming paracrystalline arrays. In contrast to other retinorecipient areas in which ganglion cell terminals have been characterized by the presence of lightly staining mitochondria, many of the retinal terminals in the suprachiasmatic nucleus were seen to contain darkly stained mitochondria. Postembedding antiglutamate immunocytochemistry was used to evaluate the level of endogenous glutamate in these ganglion cell terminals. Although morphologically diverse, all of the retinal terminals in the suprachiasmatic nucleus were glutamate positive, consistent with the postulated role of glutamate as the neurotransmitter of retinal ganglion cells.

Animals↗
PubMed1995

Evaluation of secular trends in CD4+ lymphocyte loss among human immunodeficiency virus type 1 (HIV-1)-infected men with known dates of seroconversion.

The rate at which immunodeficiency develops in untreated human immunodeficiency virus type 1(HIV-1)-infected persons might be increasing or decreasing over time because of viral evolution or other factors. Beginning in 1984, Multicenter AIDS Cohort Study investigators recruited HIV-1-seronegative homosexual/bisexual men from four US metropolitan areas and examined them semiannually for HIV-1 seroconversion. To assess possible secular changes in the natural history of HIV-1 infection, the authors examined CD4+ lymphocyte data from 354 men who seroconverted between 1984 and 1991. To control for measurement differences among centers and over time, the authors adjusted CD4+ lymphocyte values to those of persistently seronegative participants. CD4+ lymphocyte percentage measurements at the first seropositive visit formed a U-shaped pattern, with the lowest values observed in 1988 and 1989. The authors observed no consistent secular pattern of CD4+ percentages at later visit dates, except that mean CD4+ percentages were consistently lowest in men who seroconverted in 1988. In a proportional hazards model, the time to the adjusted CD4+ lymphocyte count of < 500 cells/mm3 was not associated with the secular time of seroconversion (relative hazard = 1.05, 95% confidence interval 0.97-1.13). The authors' data do not suggest a major change in the natural history of HIV-1 infection of this population.

Acquired Immunodeficiency Syndrome↗
PubMed1995

Microsomal cytochrome P450-mediated liver and brain anandamide metabolism.

Anandamide (AN) is an arachidonic acid congener, found in the brain, that binds to the cannabinoid receptor and elicits cannabinoid-like pharmacological activity. Cytochromes P450 (P450s) are known to oxidize arachidonic acid to a wide variety of metabolites, yielding many physiologically potent compounds. To determine if AN could be similarly oxidized by P450s, its metabolism by mouse liver and brain microsomes was examined. Mouse hepatic microsomal incubation of AN with NADPH resulted in the generation of at least 20 metabolites, determined after HPLC separation by increased UV-absorbance at 205 nm. Pretreatment of mice with various P450 inducers resulted in increased hepatic microsomal formation of several AN metabolites, with dexamethasone being the most effective inducer. Phenobarbital pretreatment resulted in a metabolic profile similar to that observed after dexamethasone pretreatment, whereas 3-methylcholanthrene pretreatment selectively increased the formation of several other metabolites. Clofibrate pretreatment had no effect on hepatic AN metabolism. Polyclonal antibodies prepared against mouse hepatic P450 3A inhibited the formation of several AN metabolites by hepatic microsomes from untreated mice as well as the formation of those metabolites found to be increased after dexamethasone pretreatment. AN metabolism by brain microsomes resulted in the formation of two NADPH- and protein-dependent metabolites. Hepatic P450 3A antibody partially inhibited the formation of only one of these metabolites. Thus, P450 3A is a major contributor to AN metabolism in the liver but not in the brain. The physiological consequences of P450-mediated AN metabolism remain to be determined.

Animals↗
PubMed1995

Association between Lyn protein tyrosine kinase (p53/56lyn) and the beta subunit of the granulocyte-macrophage colony-stimulating factor (GM-CSF) receptors in a GM-CSF-dependent human megakaryocytic leukemia cell line (M-07e).

The role of the lyn product (p53/p56lyn), a membrane-associated protein tyrosine kinase in the signaling pathway used by granulocyte macrophage-CSFR (GM-CSFR) was investigated by using the GM-CSF-dependent human megakaryoblastic leukemia cell line M-07e. M-07e cells express GM-CSFR and are dependent on GM-CSF for survival and proliferation in vitro. Treatment with anti-lyn Abs coimmunoprecipitated, along with lyn product, the beta subunit of GM-CSFR and a phosphoprotein with a molecular mass of 120 kDa (p120) in the lysates of M-07e cells but not in the lysates of human monocyte-derived macrophages (HMDM) or human lymphoid leukemia cells. That the 120-kDa phosphoprotein coimmunoprecipitated by anti-lyn Abs is the beta subunit of GM-CSFR was confirmed in the immunoprecipitates (IP) of M-07e cells with the use of an agarose-conjugated anti-p-tyr mAb. The formation of GM-CSF/GM-CSFR/lyn signaling complexes was verified in an autoradiographic study with anti-lyn IP of M-07e cells that had been bound with 125I-labeled recombinant human (rh)GM-CSF. The p120 protein (beta subunit) was not detected in the IP of M-07e cells with anti-fyn or anti-PI3 Abs. A direct association of Lyn kinase with the beta subunit of GM-CSFR was illustrated with a reversed approach showing the recovery of Lyn protein in anti-beta (CRS1) but not anti-alpha IP of M-07e cells that had been starved for a prolonged period. Finally, the interaction of Lyn kinase with the GM-CSFR complexes was further corroborated using anti-GM-CSF (G133) mAb, which coimmunoprecipitated both the p120 beta subunit and lyn product in the lysates of M-07e cells that had been bound with rhGM-CSF before cell lysis. Removal of rhGM-CSF from culture medium for 10 to 12 h resulted in a marked decrease in lyn-associated kinase activity but not the beta subunit/lyn kinase complex formation. Taken together, our results showed that, in M-07e cells, Lyn protein tyrosine kinase (p53/p56lyn) is stably associated with a constitutively phosphorylated beta subunit of the GM-CSFR in a manner that seems to be independent of lyn kinase activity.

Animals↗