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Biomedical subjects

C Jiang

Publications and source records attributed to C Jiang.

At least 163 records · Page 9Linked to original sources
PubMed1997

Modulation of K+ channels by intracellular ATP in human neocortical neurons.

ATP-modulated K+ channels play an important role in regulating membrane excitability during metabolic stress. To characterize such K+ channels from the human brain, single channel currents were studied in excised inside-out patches from freshly dissociated human neocortical neurons. Three currents that were sensitive to physiological concentrations of ATP and selectively permeable to K+ were identified. One of these currents had a unitary conductance of approximately 47 pS and showed a strong inward rectification with symmetric K+ concentrations across the membrane. This K+ current was inhibited by ATP in a concentration-dependent manner with an IC50 (half-inhibition of channel activity) of approximately 130 microM. Channel activity also was suppressed by ADP, non-hydrolyzable ATP analogue AMP-PNP, and sulfonylurea receptor/ channel blocker glibenclamide. The second K+ current had a unitary conductance of approximately 200 pS and showed a weak inward rectification. Similarly, this current was inhibited by ATP (IC50 = 350 microM), AMP-PNP, and glibenclamide. Unlike the small-conductance ATP-inhibitable K+ channel (S-KATP), activation of this large-conductance K+ channel (L-KATP) required the presence of micromolar concentration of Ca2+ in the internal solution, but charybdotoxin did not inhibit this channel. The third K+ current was also Ca2+ dependent and had a large conductance (approximately 280 pS). It was inhibited by external charybdotoxin, iberiotoxin, and tetraethylammonium. In contrast to the other two KATP channels, ATP enhanced channel open-state probability and unitary conductance, and glibenclamide at concentration of 10-20 microM had no inhibitory effect on this current. K+ channels that have single-channel and pharmacological properties similar to these three human ATP-modulated K+ channels also were observed in experiments on rat neocortical neurons. These results therefore indicate that KATP channels are expressed in human neocortical neurons, and two distinct KATP channels (S-KATP and L-KATP) exist in the human and rat neurons. The observation that ATP at different concentrations modulates different K+ channels suggests that metabolic rate may be continuously sensed in neurons with resulting alterations in neuronal membrane excitability.

Adenosine Triphosphate↗
PubMed1997

Steroid regulated programmed cell death during Drosophila metamorphosis.

During insect metamorphosis, pulses of the steroid hormone 20-hydroxyecdysone (ecdysone) direct the destruction of obsolete larval tissues and their replacement by tissues and structures that form the adult fly. We show here that larval midgut and salivary gland histolysis are stage-specific steroid-triggered programmed cell death responses. Dying larval midgut and salivary gland cell nuclei become permeable to the vital dye acridine orange and their DNA undergoes fragmentation, indicative of apoptosis. Furthermore, the histolysis of these tissues can be inhibited by ectopic expression of the baculovirus anti-apoptotic protein p35, implicating a role for caspases in the death response. Coordinate stage-specific induction of the Drosophila death genes reaper (rpr) and head involution defective (hid) immediately precedes the destruction of the larval midgut and salivary gland. In addition, the diap2 anti-cell death gene is repressed in larval salivary glands as rpr and hid are induced, suggesting that the death of this tissue is under both positive and negative regulation. Finally, diap2 is repressed by ecdysone in cultured salivary glands under the same conditions that induce rpr expression and trigger programmed cell death. These studies indicate that ecdysone directs the death of larval tissues via the precise stage- and tissue-specific regulation of key death effector genes.

Acridine Orange↗
PubMed1997

Coordination of larval and prepupal gene expression by the DHR3 orphan receptor during Drosophila metamorphosis.

The DHR3 orphan receptor gene is induced directly by the steroid hormone ecdysone at the onset of Drosophila metamorphosis. DHR3 expression peaks in early prepupae, as the early puff genes are repressed and betaFTZ-F1 is induced. Here we provide evidence that DHR3 directly contributes to both of these regulatory responses. DHR3 protein is bound to many ecdysone-induced puffs in the polytene chromosomes, including the early puffs that encode the BR-C and E74 regulatory genes, as well as the E75, E78 and betaFTZ-F1 orphan receptor loci. Three DHR3 binding sites were identified downstream from the start site of betaFTZ-F1 transcription, further indicating that this gene is a direct target of DHR3 regulation. Ectopic expression of DHR3 revealed that the polytene chromosome binding pattern is of functional significance. DHR3 is sufficient to repress BR-C, E74A, E75A and E78B transcription as well as induce betaFTZ-F1. DHR3 thus appears to function as a switch that defines the larval-prepupal transition by arresting the early regulatory response to ecdysone at puparium formation and facilitating the induction of the betaFTZ-F1 competence factor in mid-prepupae. This study also provides evidence for direct cross-regulation among orphan members of the nuclear receptor superfamily and further implicates these genes as critical transducers of the hormonal signal during the onset of Drosophila metamorphosis.

Animals↗
PubMed1997

Development and characterization of a transformed human periodontal ligament cell line.

Periodontal ligament (PDL) cells are thought to be important for establishing and maintaining a stable interface between bone and teeth. In addition, PDL cells are thought to play critical roles in both the pathogenesis of periodontal disease and the regeneration of periodontal ligament tissues. The purpose of this study was to develop a continuous or stable human PDL cell line as an in vitro model for the investigation of cellular mechanisms involved in periodontal regeneration and destruction. Human PDL cells, derived from a primary cell culture, were transfected with simian virus 40 (SV40) T antigen-containing virus with a neomycin resistance gene. The transformed cells expressed the SV40 T antigen mRNA as assayed by reverse transcription polymerase chain reaction (RT-PCR). This cell line was also characterized for morphological changes and growth characteristics compared to primary PDL cell cultures. The transformed cells were shown to form a multilayer pattern and distinct colonies on tissue culture surfaces. However, no colony formation was found in soft agar. The transformed PDL cell line was found to have a greater rate of proliferation in 10% fetal bovine serum than primary culture, and continued to proliferate in low serum concentrations capable of producing quiescence in primary cells. Interleukin-1 beta (IL-1 beta) was shown to produce a 7-fold elevation in collagenase (MMP-1) mRNA levels, consistent with primary PDL cells. In addition, IL-1 beta was shown to produce a decrease in alkaline phosphatase activity in a concentration-dependent manner. The transformed cell line has been maintained for over 30 generations of cell culture. In conclusion, a stable human PDL cell line has been established to serve as a model for future in vitro investigations into periodontal pathogenic mechanisms and to evaluate therapies directed at the regeneration of periodontal ligament.

Adult↗
PubMed1997

[The effects of hydroxyurea on cell-cycle distribution and the expression of human beta-globin gene in K 562 cells].

Although the hydroxyurea (HU) has been extensively studied, little is known of its molecular mechanism in controlling the expression of human globin gene and in modulating the progression of cell-cycle in K 562 cell. In the present study, the effect of hydroxyurea on proliferative kinetics of K 562 cells was examined by monitoring the number of cells during a period of 8 day's cell culture. Our results showed that there was a dose related decrease in cell growth when K562 cells were incubated with HU. Moreover, cell-cycle analysis demonstrated that HU had profound effect on cell-cycle distribution. In the case of the induced K 562 cells, there was an increased accumulation of cells in S phase and a decreased fraction of cells in G 1 and G 2 + M phase. Furthermore, HU could induce the expression of human beta-globin gene in the induced K 562 cells. Our results indicate that HU has a potential to inhibit the proliferation of K 562 cells and to stimulate the terminal differentiation of this cell.

Cell Cycle↗
PubMed1997

[The role of hydroxyurea in globin gene expression and cell differentiation of human erythroleukemia cell line].

The HEL cells, a human erythroleukemia cell line, express mainly the fetal globin gene and small amount of the embryonic (epsilon) globin gene, but not the adult (beta) globin gene. Hydroxyurea, a small organic compound, has been successfully used to treat sickle cell anemia and beta-thalessaemia. Our data demonstrated that the growth rate of HEL cell proliferation was inhibited by different doses of hydroxyurea (from 50 mumol/L to 200 mumol/L). Using both routine RT-PCR and quantitative PCR analyses, we revealed that the expression of beta-globin gene was sharply activated and alpha-globin gene was almost completely silenced when HEL cells were induced for 3 or 5 days. Meanwhile, gamma-globin gene was expressed with no much difference between induced and uninduced HEL cells. We also demonstrated that the expression of GATA-1 and NF-E 2, which were two of the most important transcription factors in erythrocyte development, was activated about 3 folds in the induced cells. We suggested that the induction of GATA-1 and NF-E 2 expression by hydroxyurea might lead to activation of the adult beta-globin gene through some pathways of signal transduction, therefore, hydroxyurea might play a role to induce HEL cells to terminal differentiation.

Antineoplastic Agents↗
PubMed1997

[Transacting factors binding to the positive control region (PCR) in the 5' flanking sequence of human beta-globin gene].

Using gel mobility shift assay, three protein factors (Pa, Pb, Pc) binding to the positive control region (PCR) in the 5' flanking sequence of human beta-globin gene were detected in the nuclear extracts from mouse fetal liver at d 18 or d 19 of gestation. Competitive experiment showed that Pb and Pc could bind to GATA-1 motif, therefore could be the members of GATA family. While Pa was a new and developmental stage specific trans-acting factor, we suggested that the factor Pa was related to the activation of beta-globin gene.

Animals↗
PubMed1997

[Clinical study on the antithrombotic effects of Holothuria ldeucospilota acidic mucopolysaccharide].

OBJECTIVE: To study the antithrombotic effects of Holothuria Ldeucospilota Acidic Mucopolysaccharide (HLAM). METHODS: A series of variables were observed before and after treatment with HLAM in normal middle-aged subjects and patients recovering from cerebral embolism or suffering from ischemic heart disease, each of which were divided into two groups according to the dosage administered (60 mg/d and 120 mg/d). RESULTS: The fat metabolism was enhanced in addition to the anticoagulant and the blood viscosity reducing effects. No side-effect was found. CONCLUSION: HLAM is a promising drug for antithrombotic therapy.

Adult↗
PubMed1997

[Determination of R- and S-mephenytoin in human urine by gas chromatography].

The levels of R- and S-mephenytoin in human urine were determined by chiral capillary gas chromatography with nitrogen-phosphorus detector. The conditions of the chromatography and detection included a chiral capillary column (Chirasil-Val, 25 m x 0.25 mm i.d., Alltech), column temperature (T) 190 degrees C, injector T 220 degrees C, detector T 240 degrees C, and the flow-rates of 0.85, 3.5 and 120 mL/min for nitrogen, hydrogen and air respectively. Based on the above conditions, the satisfactory separation of R- and S-mephenytoin was gained, and other interference from urine sample was not found. The linear curves for both tested compounds ranged between 12.5 and 2500 microg/L, with a minimum detectable concentration of about 6 microg/L. Because of its simplicity, rapidity, sensitivity and accuracy, this method has been extensively used for testing metabolic ability of S-mephenytoin polymorphic oxidation in the Chinese populations and for the determination of the activity of hepatic drug-metabolizing enzyme CYP2C19 using mephenytoin S/R ratio of the urine samples of subjects as an indicator.

Anticonvulsants↗
PubMed1997

An investigation of attitudes, beliefs and behaviour of leprosy patients, family members and PHC workers towards multidrug therapy in Yangzhou and Dongtai Districts of China.

To improve the operational efficiency of multidrug therapy (MDT) implementation in rural areas, an investigation into the attitudes, beliefs and behaviour of leprosy patients and their family members as well as primary health care (PHC) workers towards MDT was carried out in Yangzhou and Dongtai Districts of China. A sample of 370 leprosy patients, 594 family members and 730 PHC workers was interviewed or investigated individually using questionnaires. The results showed that: 1, the presently used MDT is acceptable to a wide range of patients although a small number of patients have various problems in their treatment; 2, the patients' habit in daily drug administration, their awareness of the risk of default and confidence in MDT have a positive influence in increasing drug compliance; and 3, the supervision and encouragement of family members to patients' treatment which is associated with their knowledge on MDT is also beneficial to patients' drug compliance. However, only half of the PHC workers had a basic knowledge of MDT and a desire to participate in MDT implementation, a finding which clearly calls for urgent attention and improvement. In order to ensure the effective implementation of MDT, there is a need to educate leprosy patients and their family members as well as PHC workers to establish the patients' correct awareness of MDT, obtain the family support and motivate the PHC workers.

Adult↗
PubMed1996

An essential role for p300/CBP in the cellular response to hypoxia.

p300 and CBP are homologous transcription adapters targeted by the E1A oncoprotein. They participate in numerous biological processes, including cell cycle arrest, differentiation, and transcription activation. p300 and/or CBP (p300/CBP) also coactivate CREB. How they participate in these processes is not yet known. In a search for specific p300 binding proteins, we have cloned the intact cDNA for HIF-1 alpha. This transcription factor mediates hypoxic induction of genes encoding certain glycolytic enzymes, erythropoietin (Epo), and vascular endothelial growth factor. Hypoxic conditions lead to the formation of a DNA binding complex containing both HIF-1 alpha and p300/CBP. Hypoxia-induced transcription from the Epo promoter was specifically enhanced by ectopic p300 and inhibited by E1A binding to p300/CBP. Hypoxia-induced VEGF and Epo mRNA synthesis were similarly inhibited by E1A. Hence, p300/CBP-HIF complexes participate in the induction of hypoxia-responsive genes, including one (vascular endothelial growth factor) that plays a major role in tumor angiogenesis. Paradoxically, these data, to our knowledge for the first time, suggest that p300/ CBP are active in both transformation suppression and tumor development.

Adenovirus E1A Proteins↗
PubMed1996

Negative regulation of hypoxia-inducible genes by the von Hippel-Lindau protein.

Inactivation of the von Hippel-Lindau protein (pVHL) has been implicated in the pathogenesis of renal carcinomas and central nervous system hemangioblastomas. These are highly vascular tumors which overproduce angiogenic peptides such as vascular endothelial growth factor/vascular permeability factor (VEGF/VPF). Renal carcinoma cells lacking wild-type pVHL were found to produce mRNAs encoding VEGF/VPF, the glucose transporter GLUT1, and the platelet-derived growth factor B chain under both normoxic and hypoxic conditions. Reintroduction of wild-type, but not mutant, pVHL into these cells specifically inhibited the production of these mRNAs under normoxic conditions, thus restoring their previously described hypoxia-inducible profile. Thus, pVHL appears to play a critical role in the transduction of signals generated by changes in ambient oxygen tension.

Carcinoma, Hepatocellular↗
PubMed1996

Detailed analysis of structures and formulations of cationic lipids for efficient gene transfer to the lung.

Cationic lipid-mediated gene transfer of cystic fibrosis transmembrane conductance regulator (CFTR) cDNA represents a promising approach for treatment of cystic fibrosis (CF). Here, we report on the structures of several novel cationic lipids that are effective for gene delivery to the lungs of mice. An amphiphile (#67) consisting of a cholesterol anchor linked to a spermine headgroup in a "T-shape" configuration was shown to be particularly efficacious. An optimized formulation of #67 and plasmid vector encoding chloramphenicol acetyl-transferase (CAT) was capable of generating up to 1 microgram of CAT enzyme/lung following intranasal instillation into BALB/c mice. This represents a 1,000-fold increase in expression above that obtained in animals instilled with naked pDNA alone and is greater than 100-fold more active than cationic lipids used previously for CFTR gene expression. When directly compared with adenovirus-based vectors containing similar transcription units, the number of molecules of gene product expressed using lipid-mediated transfer was equivalent to vector administration at multiplicities of infection ranging from 1 to 20. The level of transgene expression in the lungs of BALB/c mice peaked between days 1 and 4 post-instillation, followed by a rapid decline to approximately 20% of the maximal value by day 7. Undiminished levels of transgene expression in the lung could be obtained following repeated intranasal administration of #67:DOPE:pCF1-CAT in nude mice. Transfection of cells with formulations of #67:DOPE:pCF1-CFTR generated cAMP-stimulated CFTR chloride channel and fluid transport activities, two well-characterized defects associated with CF cells. Taken together, the data demonstrate that cationic lipid-mediated gene delivery and expression of CFTR in CF lungs is a viable and promising approach for treatment of the disease.

Adenoviruses, Human↗