Biomedical subjects

T Cheng

Publications and source records attributed to T Cheng.

At least 55 records · Page 3Linked to original sources

PubMed1997

Structural and developmental analysis of the mouse peripherin/rds gene.

Mutations in the peripherin/rds gene have been reported to be associated with different forms of human autosomal dominant retinitis pigmentosa (ADRP) and macular degeneration (MD). To better understand the disruptive role of these mutations, knowledge of the structure-function relationship of the peripherin/rds gene is needed. To facilitate that, genomic clones encoding the mouse gene were isolated using bovine cDNA sequences as probes. Sequence analysis of clone lambda 6-1-1, that contained the entire coding sequence for the mouse peripherin/rds, yielded the exon-intron organization of the gene. The gene is composed of three exons (581, 247, and 213 bp) and two introns with the first and second introns 8.6 kb and 3.7 kb in size, respectively. Two major (1.6 and 2.7 kb) and three minor (4.0, 5.5, 6.5 kb) transcripts were detected on RNA blots. The major transcripts first appeared in the brain at embryonic day 13 and in the retina at postnatal day 1. Transcripts were missing in brain and eye of mice at embryonic day 15. Several transcription start sites were mapped within 26 nucleotides approximately 200 bp upstream from the translation initiation site. However, transcripts varied in the lengths of their 3' untranslated portion as a result of the utilization of different polyadenylation signals.

Amino Acid Sequence↗

PubMed1997

Nucleotide sequence of a gene encoding an organophosphorus nerve agent degrading enzyme from Alteromonas haloplanktis.

Organophosphorus acid anhydrolases (OPAA) catalyzing the hydrolysis of a variety of toxic organophosphorus cholinesterase inhibitors offer potential for decontamination of G-type nerve agents and pesticides. The gene (opa) encoding an OPAA was cloned from the chromosomal DNA of Alteromonas haloplanktis ATCC 23821. The nucleotide sequence of the 1.7 -kb DNA fragment contained the opa gene (1.3 kb) and its flanking region. We report structural and functional similarity of OPAAs from A. haloplanktis and Alteromonas sp JD6.5 with the enzyme prolidase that hydrolyzes dipeptides with a prolyl residue in the carboxyl-terminal position. These results corroborate the earlier conclusion that the OPAA is a type of X-Pro dipeptidase, and that X-Pro could be the native substrate for such an enzyme in Alteromonas cells.

Amino Acid Sequence↗

PubMed1997

[Effects of different components of serum from radiation, burn and combined radiation-burn injury on L-type calcium channel of cultured myocardial cells].

The effects of different components of serum from radiation, burn and combined radiation-burn injury on the activity of L-type calcium channel in cultured myocardial cells were investigated in this study. The results revealed that the serum from different injury groups could all activate the L-type calcium channel of cultured myocardial cells. These changes altered the calcium level in cells, which might be an important cause of dysfunction in cardiovascular system. Among the components of postinjury serum, the effect of high molecular components (> 8-10 kD) was not significant, whereas low molecule (< 8-10kD) and lipid components were the major effective components. The low molecule of postinjury serum affected not only on the opening activity of L-type channel, but also on the state of molecular movement in the membrane. The effect of serum lipids from injury groups could be depressed by SOD, which suggests that there may be free radical reactions during the serum lipids effect on calcium channel. The effects of serum and its components from combined radiation-burn group were the most intensive, and those from radiation injury were the weakest. The nature of the toxic material in serum remains to be further investigated.

Animals↗

PubMed1997

Induction of basic fibroblast growth factor mRNA by basic fibroblast growth factor in Müller cells.

PURPOSE: To investigate the induction of basic fibroblast growth factor (bFGF) gene expression in cultured rat Müller cells by bFGF and to study the mechanism of induction. METHODS: Müller cells from 1- to 3-day-old Sprague-Dawley rats were isolated and cultured with Dulbecco's modified Eagle's medium with 10% fetal calf serum. Cultured cells were identified by immunocytochemistry using antibodies against vimentin, carbonic anhydrase II, and glutamine synthetase. Cells of passages 1 through 4 were treated with bFGF, the protein kinase C (PKC) inhibitor, H-7; calphostin C, or the PKC activator, PMA; and protein kinase A (PKA) inhibitor, H-89; as well as the adenylate cylase activator, forskolin; or the adenylate cyclase inhibitor, SQ22536. Northern blot analysis was performed to determine the mRNA expression of bFGF, ciliary neurotrophic factor (CNTF) and brain-derived neurotrophic factor (BDNF). RESULTS: Addition of bFGF to culture medium induced bFGF gene expression in a dose- and time-dependent manner. Induction of bFCF mRNA started at a bFGF concentration of 0.1 ng/ml. The bFGF mRNA level was elevated by 2-fold at 1 ng/ml of bFGF, 2.8-fold at 5 ng/ml, and reached a peak of 4-fold at 10 ng/ml and 3.7-fold at 50 ng/ml. At 10 ng/ml of bFGF, induction of bFGF mRNA was observed as early as 2 hours (2-fold) after treatment. The bFGF mRNA level continued to increase to 3.7-fold by 4 hours, and reached a maximum of 4.4-fold by 8 hours. A slow decline of the bFGF mRNA level was observed after 8 hours of bFGF treatment (3.5-fold by 12 hours, and 3-fold by 24 hours). This induction of bFGF gene expression was blocked by PKC inhibitors H-7 (30 microM). The PKC activator PMA (0.1 microM) also upregulated bFGF gene expression, but the effects of bFGF and PMA were not additive. An adenylate cyclase inhibitor, SQ22536 (100 microM), did not inhibit bFGF-induced bFGF gene expression. Although forskolin (5 microM), an adenylate cyclase activator, also upregulated the level of bFGF mRNA, the effects of forskolin and bFGF were additive. In addition, no inhibitory effect on bFGF-induced expression of bFGF mRNA was found using H-89 (1 microM). Exogenous bFGF did not alter the mRNA levels of CNTF and BDNF. CONCLUSIONS: These results indicate that bFGF induces bFGF gene expression in cultured rat Müller cells through PKC activation. The authors' findings raise the possibility that Müller cells in vivo also respond to available bFGF (for example, that released from the endogenous reservoirs in the case of injury) or to exogenous bFGF by producing more bFGF, which could in turn promote photoreceptor survival.

Animals↗

PubMed1997

[The effect of systemic and local irradiation on wound macrophages and the repair promoting action of phenytoin sodium].

OBJECTIVE: To study the effect of systemic and local irradiation on wound macrophages (M phi) and the pair promoting action of phenytoin sodium on irradiation-impaired wound healing. METHODS: Wound M phi was collected by polyvinyl alcohol sponges which were implanted in a rat dorsum incision. The number of M phi, phagocytic function of wound M phi, and the release of tumor necrosis factor (TNT alpha) and interleukin-1 (IL-1) from wound M phi, and wound breaking strength (WBS) were respectively investigated. RESULTS: WBS was deceased after 6Gy systemic irradiation and 20Gy local irradiation, and phenytoin sodium improved WBS in normal wound and radiation-impaired wound. After 6Gy systemic irradiation the phagocytic function of wound M phi, the release of TNF alpha and IL-1 from wound M phi, as well as the number of M phi in wound, were significantly decreased on days 3, 5, 8 after wounding. After 20Gy local irradiation, the ratio of M phi in wound cells was significantly decreased on days 3, 5, 8, 13 after wounding, but the function of macrophage was not significantly decreased. Phenytoin sodium significantly increased the number of wound M phi, improved the phagocytic function of M phi, and the release of TNF alpha and IL-I from wound M phi on days 3, 5, 8 days after wounding despite the rats were radiated or not. CONCLUSION: The results indicated that the decrease of number and function of wound M phi play an important role in the impairment of early wound healing by systemic irradiation. Phenytoin sodium accelerated normal and irradiation-impaired wound healing by increasing the number of wound M phi and improving the M phi function.

Animals↗

PubMed1996

Temporal mapping of gene expression levels during the differentiation of individual primary hematopoietic cells.

A hierarchical order of gene expression has been proposed to control developmental events in hematopoiesis, but direct demonstration of the temporal relationships between regulatory gene expression and differentiation has been difficult to achieve. We modified a single-cell PCR method to detect 2-fold changes in mRNA copies per cell (dynamic range, 250-250,000 copies/cell) and used it to sequentially quantitate gene expression levels as single primitive (CD34+,CD38-) progenitor cells underwent differentiation to become erythrocytes, granulocytes, or monocyte/macrophages. Markers of differentiation such as CD34 or cytokine receptor mRNAs and transcription factors associated with their regulation were assessed. All transcription factors tested were expressed in multipotent progenitors. During lineage-specific differentiation, however, distinct patterns of expression emerged. SCL, GATA-2, and GATA-1 expression sequentially extinguished during erythroid differentiation. PU.1, AML1B, and C/EBP alpha expression profiles and their relationship to cytokine receptor expression in maturing granulocytes could be distinguished from similar profiles in monocytic cells. These data characterize the dynamics of gene expression accompanying blood cell development and define a signature gene expression pattern for specific stages of hematopoietic differentiation.

Adult↗

PubMed1996

Alpha 2-adrenergic agonists induce basic fibroblast growth factor expression in photoreceptors in vivo and ameliorate light damage.

We observed an induction of basic fibroblast growth factor (bFGF) mRNA in the rat retina after systemic administration of the alpha 2-adrenergic agonists xylazine and clonidine. A single injection of xylazine or clonidine transiently increased bFGF mRNA. Preinjection of yohimbine, an alpha 2-adrenergic antagonist, completely inhibited this increase. Higher dosage of yohimbine inhibited the baseline expression of bFGF. Of particular interest is the finding that the induced bFGF expression occurred almost exclusively in the inner segment region of photoreceptors. No increase in bFGF mRNA was found in the brain after either xylazine or clonidine injection. Xylazine or clonidine given systemically before and during constant light exposure also reduces photoreceptor degeneration in albino rats. These results indicate that regulation of bFGF expression in photoreceptors is unique in the CNS and suggest that endogenous bFGF promotes photoreceptor survival.

Adrenergic alpha-Agonists↗

PubMed1996

1,25(OH)2 vitamin D3, and retinoic acid antagonize endothelin-stimulated hypertrophy of neonatal rat cardiac myocytes.

1,25(OH)2 Vitamin D3 (VD3) and retinoic acid (RA) function as ligands for nuclear receptors which regulate transcription. Though the cardiovascular system is not thought to represent a classical target for these ligands, it is clear that both cardiac myocytes and vascular smooth muscle cells respond to these agents with changes in growth characteristics and gene expression. In this study we demonstrate that each of these ligands suppresses many of the phenotypic correlates of endothelin-induced hypertrophy in a cultured neonatal rat cardiac ventriculocyte model. Each of these agents reduced endothelin-stimulated ANP secretion in a dose-dependent fashion and the two in combination proved to be more effective than either agent used alone (VD3: 49%; RA:52%; VD3 + RA:80% inhibition). RA, at concentrations known to activate the retinoid X receptor, and, to a lesser extent, VD3 effected a reduction in atrial natriuretic peptide, brain natriuretic peptide, and alpha-skeletal actin mRNA levels. Similar inhibition (VD3:30%; RA:33%; VD3 + RA:59% inhibition) was demonstrated when cells transfected with reporter constructs harboring the relevant promoter sequences were treated with VD3 and/or RA for 48 h. These effects were not accompanied by alterations in endothelin-induced c-fos, c-jun, or c-myc gene expression, suggesting either that the inhibitory locus responsible for the reduction in the mRNA levels lies distal to the activation of the immediate early gene response or that the two are not mechanistically coupled. Both VD3 and RA also reduced [3H]leucine incorporation (VD3:30%; RA:33%; VD3 + RA:45% inhibition) in endothelin-stimulated ventriculocytes and, once again, the combination of the two was more effective than either agent used in isolation. Finally, 1,25(OH)2 vitamin D3 abrogated the increase in cell size seen after endothelin treatment. These findings suggest that the liganded vitamin D and retinoid receptors are capable of modulating the hypertrophic process in vitro and that agents acting through these or similar signaling pathways may be of value in probing the molecular mechanisms underlying hypertrophy.

Animals↗

PubMed1995

Apoptosis induced by c-myc overexpression is dependent on growth conditions.

Recent reports have suggested a causal link between the expression of the c-myc gene and ensuing cell death by apoptosis, particularly in cells prevented from dividing or after withdrawal of growth factors. In contrast, other studies have suggested that cells constitutively expressing c-myc are actually more resistant to cell death induced by some chemotherapeutic drugs that block cell division. We have examined the frequency of cell death in several Chinese hamster ovary cell lines that contain 20 to 30 copies of the human c-myc gene and that express high levels of human c-myc mRNA and protein. We found that constitutive c-myc expression in cells incubated at low density in medium containing 0.1% serum correlates with increased cell death due to apoptosis, as indicated by oligonucleosomal DNA fragmentation and a requirement for ongoing protein synthesis. However, apoptosis was not enhanced in these cells when they were blocked in cell division in the presence of serum, nor when grown at moderate to high density under low-serum conditions, despite their continued accumulation of high levels of c-Myc protein. Our results show that overexpression of c-Myc protein can promote cell death under some but not all conditions that block cell division and further suggest that c-Myc may accelerate but does not necessarily initiate apoptosis.

Animals↗

PubMed1995

Love-styles among Latino community college students in Los Angeles.

145 Latino community college students enrolled in Chicano Studies classes in Los Angeles, California were administered a love-attitudes scale. Analysis showed that the mean scores and endorsement patterns were similar to those in earlier research on white-Latino and white-non-Latino students in the United States. Significant gender differences were found. Latino men scored more Ludic and Agapic than women. Researchers might examine the love-styles and ethnic identity in and out of marriage among Latinos, whites, and Asians in southern California.

Adolescent↗

PubMed1995

Injury-induced upregulation of bFGF and CNTF mRNAS in the rat retina.

Focal mechanical injury to the retina has been shown to slow or prevent photoreceptor degeneration near the lesion site in two animal models of retinal degeneration, inherited retinal dystrophy in the Royal College of Surgeons (RCS) and light damage in albino rats. Thus, when injured, the rat retina activates a self-protective mechanism to minimize damage. To identify injury responsive factors and cells, we examined the mRNAs for the following factors and some of their receptors: basic and acidic fibroblast growth factors (bFGF, aFGF) and FGF receptor-1 (FGFR1); ciliary neurotrophic factor (CNTF) and CNTF receptor alpha (CNTFR alpha); brain-derived neurotrophic factor (BDNF) and its receptor trkB; and insulin-like growth factor-1 (IGF-1) and IGFR-1 receptor (IGF-1R). After a single mechanical lesion to the subretinal space and retina, there was a substantial increase in bFGF and CNTF expression that persisted for the entire 10 d period of study. The increase in bFGF mRNA after injury was prompt and great in amplitude, while the elevation of CNTF mRNA was relatively slower. In addition, there was a transient increase in FGFR1 mRNA. In situ hybridizations showed that the elevation of bFGF and CNTF was localized to the vicinity of the lesion. The expression of GFAP (glial fibrillary acidic protein) mRNA also increased in response to injury. These findings strongly suggest that increases in endogenous bFGF and/or CNTF play key roles in injury-induced photoreceptor rescue.

Animals↗

PubMed1995

HIMeg-1, a cell line derived from a CML patient, is capable of monocytic and megakaryocytic differentiation.

We have characterized HIMeg-1, a subclone of the promegakaryoblastic cell line HIMeg, in terms of its capability of proliferation and differentiation when it is exposed to various agents. We observed that phorbol 12-myristate 13-acetate (PMA) arrested HIMeg-1 growth and induced expression of monocytic surface antigens CD11c and CD14, but not the megakaryocytic surface antigen CD14a. In addition, PMA treatment of HIMeg-1 led to rapid activation of mRNA expression of egr-1, a transcription factor involved in regulating differentiation of hematopoietic progenitor cells. On the other hand, treatment of HIMeg-1 with the activated peripheral blood lymphocyte-conditioned medium (PBL-CM) resulted in greatly enhanced incorporation of 3H-thymidine into newly synthesized DNA. This enhanced 3H-thymidine incorporation appears to be specific to HIMeg-1 since the same concentrations of PBL-CM had little effect on the growth of the megakaryoblastic leukemia cell line SAM-1. The PBL-CM-induced DNA synthesis in HIMeg-1 was associated with activation of CD41a and CD41b surface antigen expression and down-regulation of expression of the erythroid marker glycophorin A and the early myeloid surface antigen CD33. HIMeg-1 capable of responding differentially to PMA and PBL-CM by changing its growth rate as well as its differentiation patterns will provide an ideal model to study the underlying mechanism regulating lineage restriction of hematopoietic progenitor cells.

Antigens, CD↗

PubMed1995

[Antitumor effect in vitro and immuno-response in vivo of fructus Mume].

The antitumor action of extracts from Fructus Mume and the main triterpenoid component ursolic acid on HIMeg and HL-60 cells in vitro was tested. The immuno-response in rats was also studied. The result showed that Fructus Mume had inhibiting effect on proliferation of HIMeg and HL-60 cells.

Animals↗

PubMed1995

[Ultrastructural changes in pulmonary microvascular damage in rats inflicted with burn, blast and combined burn-blast injury].

The pathological changes in pulmonary microvasculature in rats inflicted with overpressure blast, 15% third degree burns and combined burn-blast injury, respectively, were studied with electron microscopy and ultrastructural morphometry. Results indicated that the pathological changes in pulmonary microvasculature in 15% third degree burns were slight, and mainly restricted to ultrastructural level. While in severe blast and burn-blast injuries, the damage of pulmonary microvasculature including endothelial swelling and regeneration and dispersal of arteriole wall structure, was prominent. These changes form the basis of pulmonary hemorrhage and edema. Apart from vessel structural damages, arteriole constriction and capillary closure were also observed during 2 to 4 h postinjury. The vessel damage and dysfunction were more severe in combined injury than in blast injury alone. The mechanisms needed to be studied further.

Animals↗

PubMed1994

Transcription factor egr-1 is involved in phorbol 12-myristate 13-acetate-induced megakaryocytic differentiation of K562 cells.

Transcription factors play important roles in regulating cell growth and differentiation. egr-1, a transcription factor of the zinc finger family, is rapidly activated in many types of cells after mitogen treatment. In this report, we demonstrate that egr-1 mRNA expression, detected by Northern blotting, is activated within 30 min of treatment of the erythroleukemia cell line K562 with phorbol 12-myristate 13-acetate (PMA), and the increased egr-1 mRNA level is associated with an elevated egr-1 antigen expression detected by Western blotting and with its DNA binding activity shown by the gel mobility shift assay. In addition, PMA-mediated activation of egr-1 mRNA expression involves no new protein synthesis and is followed by sequential down-regulation of the mRNA level of GATA-1 and glycophorin A. On the other hand, CD41a surface antigen expression is dramatically up-regulated. Furthermore, enforced expression of egr-1, through transfection of K562 cells with the egr-1 expression plasmid construct, results in expression of the egr-1 transcript that accompanies a significant accumulation on the cell surface of CD41a but not CD14 nor glycophorin A. These observations suggest that egr-1 is involved in regulating PMA-induced megakaryocytic differentiation of K562 cell line.

Base Sequence↗

PubMed1994

Monitoring mRNA expression by polymerase chain reaction: the "primer-dropping" method.

We have developed a method to monitor mRNA expression that is based upon the reverse transcriptase-polymerase chain reaction (RT-PCR) and includes multiple sets of primer pairs in coamplification reactions. To observe relative changes in mRNA steady-state levels, each target in a multiplex reaction was amplified to within a predetermined range by using PCR cycle numbers specific for each target. Optimal PCR cycle numbers for target templates were determined by preliminary titration experiments performed using the "primer-dropping" method. By employing this method, the overall amplification reaction was limited, permitting the PCR products to remain within the exponential range of the amplification curve and yet be detectable on ethidium bromide-stained gels. We demonstrated the utility of this method by monitoring the expression kinetics of cyclins A, B1, D1, and E, and of the immediate-early genes c-fos, c-myc, and beta-actin. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was included in the multiplex reactions as an endogenous internal standard to control for variations in product abundances due to differences in individual RT and PCR reaction efficiencies. Changes in gene expression of less than twofold to greater than 75-fold were readily distinguished.

Actins↗

PubMed1994

Enzyme-linked immunosorbent assay and enzyme-linked coagulation assay for detection of Clostridium botulinum neurotoxins A, B, and E and solution-phase complexes with dual-label antibodies.

The measurement of toxins A, B, and E from Clostridium botulinum was accomplished by use of a modified sandwich enzyme-linked immunosorbent assay (ELISA) employing labeled horse antibody and either chicken antibody or biotinylated horse antibody. The complexes formed in solution phase were captured onto solid phases coated with rabbit anti-chicken immunoglobulin G (chicken antibody) or avidin (biotinylated antibody). The assay was brought to the sensitivity of the mouse bioassay (5 to 10 pg/ml, or 0.03 to 0.07 pM) by employing as labeling enzyme the factor X activator of Russell's viper venom (RVV-XA) and a sensitive coagulation-based assay amplification system known as enzyme-linked coagulation assay. Complex formation was found to be a slower reaction than binding to the capture plate, and so the assay used a preincubation step to produce the solution-phase complexes before they were bound to the solid phase. Keeping the concentrations of Russell's viper venom factor X activator antibody and capture antibody constant for diluted samples and diluting complexes into buffer without keeping labeled antibody concentrations constant were equivalent in allowing the detection of low neurotoxin concentrations. This ELISA-enzyme-linked coagulation assay procedure is a convenient alternative to the mouse bioassay, which shows complete resolution of the neurotoxins in addition to the requisite sensitivity.

Antibodies, Bacterial↗

PubMed1993

Expression and localization of tissue factor-based procoagulant activity (PCA) in pigeon monocyte-derived macrophages.

Monocyte-derived macrophages, focal to initiation and progression of atherosclerosis, have been implicated in thrombotic complication of this disease. In the present study we demonstrated tissue factor based procoagulant activity in cultured macrophages from the White Carneau pigeon following endotoxin (1-2 micrograms/ml) stimulation. This macrophage procoagulant activity paralleled activity obtained with pigeon brain homogenate. We used Enzyme-Linked Coagulation Assay (ELCA), an ultrasensitive microtiter plate assay, to measure procoagulant activity in these cells. Through the use of clotting factors purified from pigeon plasma, procoagulant activity could be detected with as few as 1-3 cells. Tissue factor antigen, detected through the use of immunogold labelling in conjunction with a polyclonal antibody which was highly specific to human tissue factor, was distributed uniformly over the plasma membrane of the endotoxin-stimulated cells. These studies suggest that this procoagulant activity might play an important role in the pathobiology of atherosclerosis in White Carneau pigeons by initiating fibrin polymerization and thus leading to thrombotic complications of the disease.

Animals↗