Biomedical subjects

Jun Cai

Publications and source records attributed to Jun Cai.

At least 37 records · Page 2Linked to original sources

PubMed2005

Density and chain conformation profiles of square-well chains confined in a slit by density-functional theory.

Density and chain conformation profiles of square-well chains between two parallel walls were studied by using density-functional theory. The free energy of square-well chains is separated into two contributions: the hard-sphere repulsion and the attraction. The Heaviside function is used as the weighting function for both of the two parts. The equation of state of Hu et al. is used to calculate the excess free energy of the repulsive part. The equation of state of statistical associating fluid theory for chain molecules with attractive potentials of variable range [A. Gil-Villegas et al. J. Chem. Phys. 106, 4168 (1997)] is used to calculate the excess free energy of the attractive part. Because the wall is inaccessible to a mass center of a longer chain, there exists a sharp fall in the distribution of end-to-end distance near the wall as the chain length increases. When the average density of the system is not too low, the prediction of this work is in good agreement with computer simulation results for the density profiles and the chain conformation over a wide range of chain length, temperature, and attraction strength of the walls. However, when the average density and the temperature are very low, the prediction deviates to a certain degree from the computer simulation results for molecules with long chain length. A more accurate functional approximation is needed.

Journal Article↗

PubMed2005

Placenta growth factor is over-expressed and has prognostic value in human breast cancer.

Placenta growth factor (PlGF) belongs to the vascular endothelial growth factor (VEGF) family, a group of angiogenic factors that are crucial for tumour angiogenesis. Very little is known about the significance of PlGF in human cancer. We hypothesise that PlGF may have a potent influence in breast cancer. This study examined PlGF levels in human breast cancer in relation to patient's clinical parameters. PlGF expression and distribution was examined quantitatively using real-time quantitative polymerase chain reaction (Q-PCR) on a cohort of human breast cancer tissue (n = 119) and background breast tissue (n = 33), qualitatively using reverse transcriptase polymerase chain reaction (RT-PCR) on a range of cell lines, and immunohistochemically on patient samples. All these techniques revealed that PlGF expression was dramatically increased (P = 0.028) in breast cancer tissues compared with normal breast tissue. We demonstrate that PlGF displays prognostic value through analysis of patient survival status (6-year follow-up), as elevated levels of PlGF were significantly associated (P = 0.017) with recurrence, metastasis and patient mortality. Our study has shown that PlGF is over-expressed in breast cancer tissues and correlates with patient prognosis, and is likely to play a major role in the pathogenesis of tumours.

Breast Neoplasms↗

PubMed2005

Molecular cloning and characterization of bovine P-selectin glycoprotein ligand-1.

Human P-selectin glycoprotein ligand-1 (PSGL-1) is a dimeric membrane mucin expressed on leukocytes that binds selectins. Here, we report that the open reading frame (ORF) of bovine PSGL-1 (bPSGL-1) cDNA is 1284 base pairs in length, predicting a protein of 427 amino acids including an 18-amino-acid signal peptide, an extracellular region with a mucin-like domain, and transmembrane and cytoplasmic domains. The amino acid sequence of bPSGL-1 demonstrated 52, 49 and 40% overall homology to equine, human and mouse, respectively. A single extracellular cysteine, at the transmembrane and extracellular domain junction, suggests a disulfide-bonding pattern. Alignment of bovine with equine, human and mouse PSGL-1 demonstrates high conservation of transmembrane and cytoplasmic domains, but diversity of the extracellular domain, especially in the anionic NH(2)-terminal of PSGL-1, the putative P-selectin binding domain. In the NH(2)-terminal of bPSGL-1, there are three potential tyrosine sulfation sites and three potential threonine O-glycosylation sites, all of which are required for P-selectin binding in human PSGL-1 (hPSGL-1). bPSGL-1 shares only 57% homology in amino acid sequence with the corresponding epitope region which binds the monoclonal antibody PL1 for hPSGL-1, and no cross-reactivity was found in bovine leukocytes. In summary, bPSGL-1 shares homology with hPSGl-1, but has differences in the putative extracellular P-selectin binding domain.

Amino Acid Sequence↗

PubMed2005

Fatty acid transport and metabolism in HepG2 cells.

The mechanism(s) of fatty acid uptake by liver cells is not fully understood. We applied new approaches to address long-standing controversies of fatty acid uptake and to distinguish diffusion and protein-based mechanisms. Using HepG2 cells containing an entrapped pH-sensing fluorescence dye, we showed that the addition of oleate (unbound or bound to cyclodextrin) to the external buffer caused a rapid (seconds) and dose-dependent decrease in intracellular pH (pH(in)), indicating diffusion of fatty acids across the plasma membrane. pH(in) returned to its initial value with a time course (in min) that paralleled the metabolism of radiolabeled oleate. Preincubation of cells with the inhibitors phloretin or triacsin C had no effect on the rapid pH(in) drop after the addition of oleate but greatly suppressed pH(in) recovery. Using radiolabeled oleate, we showed that its esterification was almost completely inhibited by phloretin or triacsin C, supporting the correlation between pH(in) recovery and metabolism. We then used a dual-fluorescence assay to study the interaction between HepG2 cells and cis-parinaric acid (PA), a naturally fluorescent but slowly metabolized fatty acid. The fluorescence of PA increased rapidly upon its addition to cells, indicating rapid binding to the plasma membrane; pH(in) decreased rapidly and simultaneously but did not recover within 5 min. Phloretin had no effect on the PA-mediated pH(in) drop or its slow recovery but decreased the absolute fluorescence of membrane-bound PA. Our results show that natural fatty acids rapidly bind to, and diffuse through, the plasma membrane without hindrance by metabolic inhibitors or by an inhibitor of putative membrane-bound fatty acid transporters.

Biological Transport, Active↗

PubMed2005

ATID: a web-oriented database for collection of publicly available alternative translational initiation events.

SUMMARY: Alternative translational initiation is an important cellular mechanism contributing to the diversity of protein products and functions. We develop a database that provides a comprehensive collection of alternative translational initiation events. The purpose of this alternative translational initiation database (ATID) is to facilitate the systematic study of alternative translational initiation of genes. The current version of database contains 300 genes from Homo sapiens, Mus musculus and other species. Each of the genes has two or more isoforms due to alternative translational initiation. Resources in ATID, including gene information, alternative products of genes and domain structures of isoforms, are provided through a user-friendly web interface. AVAILABILITY: The ATID database is available for public use at http://bioinfo.au.tsinghua.edu.cn/atie/.

Amino Acid Sequence↗

PubMed2005

Endothelium-dependent and direct relaxation induced by ethyl acetate extract from Flos Chrysanthemi in rat thoracic aorta.

The aims of the present study were to investigate the vasoactive effects of ethyl acetate extract from Flos Chrysanthemi (FCE) and its mechanisms on the rat thoracic aorta. FCE (9.4-150 mg/L) caused a concentration-dependent relaxation on endothelium-intact rings precontracted with phenylephrine (PE, 10(-6)M) or a high level of K+ (6x10(-2)M). By removal of endothelium, the effect was not abolished but reduced significantly. N(G)-nitro-l-arginine methyl ester (l-NAME) (10(-4) M), methylene blue (10(-5) M) significantly inhibited the effect of FCE. Meanwhile, NO synthase of aorta in FCE group was markedly elevated versus the control. However, indomethacin did not influence FCE effect. SKF-525A combined with l-NAME had the same effect as l-NAME. Tetraethylammonium, BaCl2, 4-aminopyridine, 5-HD and propranolol also did not influence the vascular effect of FCE, but glibenclamide significantly attenuated its vasodilation. FCE did not reduce PE-induced transient contraction in Ca(2+)-free medium, but inhibited PE-induced contraction in K(+)-free solution or Ca2+ caused contraction after PE induced a stable contraction in Ca(2+)-free solution. It is concluded that FCE induced both endothelium-dependent and -independent relaxation. NO and cGMP-mediated pathway are likely involved in the endothelium-dependent relaxation, whereas inhibition of voltage-dependent Ca2+ channel, receptor-operate Ca2+ channel and activation of K(ATP) contribute in part to the endothelium-independent relaxation.

Animals↗

PubMed2005

Comparative venom toxicity between Pteromalus puparum and Nasonia vitripennis (Hymenoptera: Pteromalidae) toward the hemocytes of their natural hosts, non-target insects and cultured insect cells.

Crude venoms from two parasitoid species, Pteromalus puparum and Nasonia vitripennis (Hymenoptera: Pteromalidae) were assayed for biological activities toward hemocytes from two species of their natural hosts and eight species of their non-natural hosts as well as two lines of cultured Lepidoptera cells, respectively. By inhibiting the spreading and viability of insect hemocytes, the venom from P. puparum displayed significantly higher activities toward plasmatocytes and granular cells from both larvae and pupae of two natural hosts, Pieris rapae and Papilio xuthus, and lower activity toward those from Spodoptera litura, Musca domestica and Sarcophaga peregrina. However, no effect was found towards any type of hemocytes from other five insects tested, namely, Ectropis oblique, Galleria mellonella, Sesamia inferens, Bombyx mori and Parnara guttata. In contrast, the venom from N. vitripennis showed a narrower range of targeted insects. It appeared to have highly adverse effects on the spreading and viability of plasmatocytes and granular cells only from the natural hosts, M. domestica and S. peregrina, little toxicity to cells from P. rapae and P. xuthus, and no effect on any of the other insects tested. Pteromalus puparum venom also apparently presented a high ability to block the spreading of Tn-5B1-4 cells derived from Trichoplusia ni, and high cytotoxicity to the cells and Ha cells derived from Helicoverpa armigera. Nasonia vitripennis venom, however, only had a marked lethal effect to Ha cells. In addition, the possibility that the host range of a defined parasitoid could be assessed using our method of treating hemocytes from candidate insects with venom in vitro, and the potential of our venoms tested in the development of bio-insecticides, insect-resistant transgenic plants, are discussed.

Animals↗

PubMed2005

Role of transcription factors in motoneuron differentiation of adult human olfactory neuroepithelial-derived progenitors.

Neurosphereforming cell (NSFC) lines have been established from cultures of human adult olfactory neuroepithelium. Few of these cells ever express mature neuronal or glial markers in minimal essential medium supplemented with 10% fetal bovine serum or defined medium. However, these neural progenitors have the potential to differentiate along glial or neuronal lineages. To evaluate the potential of NSFCs to form motoneurons, transcription factors Olig2, Ngn2, and HB9 were introduced into NSFCs to determine if their expression is sufficient for motoneuron specification and differentiation, as has been shown in the early development of the avian and murine central nervous systems in vivo. NSFCs transfected with Olig2, Ngn2, and HB9 alone exhibited no phenotypic lineage restriction. In contrast, simultaneous transfection of Ngn2 and HB9 cDNA increased the expression of Isl1/2, a motoneuron marker, when the cells were maintained in medium supplemented with retinoic acid, forskolin, and sonic hedgehog. Furthermore, a population of Olig2-expressing NSFCs also expressed Ngn2. Cotransfection of NSFCs with Olig2 and HB9, but not Olig2 and Ngn2, increased Isl1/2 expression. Coculture of NSFCs trans-fected with Ngn2-HB92 or Olig2 and HB9 with purified chicken skeletal muscle demonstrated frequent contacts that resembled neuromuscular junctions. These studies demonstrate that transcription factors governing the early development of chick and mouse motoneuron formation are able to drive human adult olfactory neuroepithelial progenitors to differentiate into motoneurons in vitro. Our long-term goal is to develop cell populations for future studies of the therapeutic utility of these olfactory-derived NSFCs for autologous cell replacement strategies for central nervous system trauma and neurodegenerative diseases.

Adult↗

PubMed2005

Maleimido-terminated self-assembled monolayers.

Four approaches have been explored for the preparation of maleimido-functionalized self-assembled monolayers (SAMs) on silicon. SAMs prepared by self-assembly of maleimido-functionalized alkyltrichlorosilanes (11-maleimido-undecyl-trichlorosilane) on oxide-covered silicon yield higher signals from maleimido functionalities in ATR-IR (attenuated total reflection IR) spectroscopy and XPS (X-ray photoelectron spectroscopy) than the other three methods. The surface composition of maleimido groups was tailored further by the formation of mixed monolayers with nonfunctionalized alkyltrichlorosilanes (decyltrichlorosilane). The order of the alkyl chains within the monolayers only slightly depends on the composition of the mixed monolayers. We utilized the maleimido-terminated SAMs to bind various nucleophilic compounds, alkylamines, alkylthiols, and thiol-tagged DNA oligonucleotides by means of conjugate addition.

Journal Article↗

PubMed2005

Noggin and bFGF cooperate to maintain the pluripotency of human embryonic stem cells in the absence of feeder layers.

Human embryonic stem (hES) cells are typically maintained on mouse embryonic fibroblast (MEF) feeders or with MEF-conditioned medium. However, these xenosupport systems greatly limit the therapeutic applications of hES cells because of the risk of cross-transfer of animal pathogens. Here we showed that the bone morphogenetic protein antagonist noggin is critical in preventing differentiation of hES cells in culture. Furthermore, we found that the combination of noggin and basic fibroblast growth factor (bFGF) was sufficient to maintain the prolonged growth of hES cells while retaining all hES cell features. Since both noggin and bFGF are expressed in MEF, our findings suggest that they may be important factors secreted by MEF for maintaining undifferentiated pluripotent hES cells. Our data provide new insight into the mechanism how hES cell self-renewal is regulated. The newly developed feeder-free culture system will provide a more reliable alternative for future therapeutic applications of hES cells.

Animals↗

PubMed2005

Generation of oligodendrocyte precursor cells from mouse dorsal spinal cord independent of Nkx6 regulation and Shh signaling.

In the developing spinal cord, early progenitor cells of the oligodendrocyte lineage are induced in the motor neuron progenitor (pMN) domain of the ventral neuroepithelium by the ventral midline signal Sonic hedgehog (Shh). The ventral generation of oligodendrocytes requires Nkx6-regulated expression of the bHLH gene Olig2 in this domain. In the absence of Nkx6 genes or Shh signaling, the initial expression of Olig2 in the pMN domain is completely abolished. In this study, we provide the in vivo evidence for a late phase of Olig gene expression independent of Nkx6 and Shh gene activities and reveal a brief second wave of oligodendrogenesis in the dorsal spinal cord. In addition, we provide genetic evidence that oligodendrogenesis can occur in the absence of hedgehog receptor Smoothened, which is essential for all hedgehog signaling.

Animals↗

PubMed2005

Biological pacemaker created by fetal cardiomyocyte transplantation.

BACKGROUND: The aim of this study was to investigate the feasibility of an alternative approach to electronic pacemaker by using spontaneously excitable cell grafts as a biological pacemaker in a large animal model of complete atrioventricular block. METHODS AND RESULTS: Dissociated male human atrial cardiomyocytes including sinus nodal cells were grafted into the free wall of the left ventricle in five female pigs. Three weeks after the injection of cell-grafted solution/control medium the pigs underwent catheter ablation of the atrioventricular node (AV-node). After complete AV block was created, the idioventricular beat rate was more rapid in cell-grafted pigs than that in control pigs (86+/-21 vs. 30+/-10 bpm; P<0.001). Administering of isoprenalin significantly increased idioventricular rate from 86+/-21 to 117+/-18 bpm in the cell-grafted animals (P<0.01). Electrophysiological mapping studies demonstrated that the idioventricular rhythm originated from the cell-injection site. Polymerase chain reaction verifying the existence of SRY DNA in the cell injection site indicated that the grafted male cells were survived. Furthermore, the connexin-43 and N-cadherin positive junctions between donor cardiomyocytes and host cells were identified. CONCLUSION: Xenografted fetal human atrial cardiomyocytes are able to survive and integrate into the host myocardium, and show a pacing function that can be modulated by autonomic agents.

Animals↗

PubMed2005

Induction of oligodendrocytes from adult human olfactory epithelial-derived progenitors by transcription factors.

Neurosphere-forming cell (NSFC) lines have been derived from cultures of adult olfactory neuroepithelium obtained from patients and cadavers. These progenitors remain undifferentiated when maintained in minimal essential medium with 10% fetal bovine serum, but have the potential to differentiate along glial or neuronal lineages. However, few of these cells ever express mature neuronal or glial markers in defined medium. To evaluate the potential of NSFCs to form oligodendrocytes, two transcription factors, Olig2 and Nkx2.2, were introduced into NSFCs to determine whether their expression is sufficient for oligodendrocyte differentiation, as has been shown in the embryonic avian and murine central nervous systems in vivo. NSFCs transfected with Olig2 or Nkx2.2 alone exhibited no phenotypic lineage restriction. In contrast, simultaneous transfection of Olig2 and Nkx2.2 cDNA produced characteristic oligodendrocyte morphology and antigenicity, including myelin basic protein (MBP). Furthermore, a population of Olig2-expressing NSFCs also expressed Sox10. Cotransfection of NSFCs with Nkx2.2 and Sox10, but not Olig2 and Sox10, produced a MBP(+) oligodendrocytic phenotype. Coculture of NSFCs transfected with Olig2 and Nkx2.2 or Nkx2.2 and Sox10 with purified sensory neurons, demonstrated frequent contacts between NSFC processes and axons, including the early stages of ensheathment. These studies demonstrate transcription factors governing early development of chick and mouse oligodendrocyte formation, also apply to human progenitors isolated from adult olfactory neuroepithelium. Our long-term goal is to develop cell populations for future studies used to determine the therapeutic utility of these olfactory-derived NSFCs for autologous transplantation into donors with central nervous system trauma or neurodegenerative diseases.

Adult↗

PubMed2005

[Effects of perioperative administration of Rhubarb on acute inflammatory response in patients with gastric cancer].

OBJECTIVE: To observe the effect of perioperative administration of rhubarb on the acute inflammatory response in patients with gastric cancer. METHODS: In this prospective, single-blinded, controlled clinical trial, thirty-one patients with gastric cancer operatively treated were randomly divided into two groups, with 14 patients in control group and 17 in study group. Patients in both groups were given an isocaloric and isonitrogenous enteral diet. The enteral diet was started 36 hours after operation, and continued for 6 days. Patients in the study group were fed with rhubarb before operation, and at 1 day and 2 days after operation. Indexes of acute inflammatory response such as serum C-reactive protein (CRP), interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-alpha), and indexes of nutritional status such as serum albumin (ALB), prealbumin (PA) and transferrin (TRF) were measured before operation, and at 1 day, 3 and 7 days after operation. RESULTS: Patients in both groups had acute inflammatory response, and the indexes of nutritional status decreased after operation.IL-6, CRP and TNF-alpha tested at 3 and 7 days after operation were lower in the study group as compared with those in the control group, and the recovery time of gastrointestinal motility such as borborygmus, gas elimination and defecation was shorter in the study group as compared with that in the control group. The indexes of nutritional status showed no significant differences between two groups after operation. CONCLUSION: Rhubarb can positively modulate the acute inflammatory response, promote the recovery of postoperative gastrointestinal motility, and benefit enteral nutrition support in patients who have undergone major operations for gastric cancer.

Adult↗

PubMed2005

Long-term curative effects of combined hepatocholangioplasty with choledochostomy through an isolated jejunum passage on hepatolithiasis complicated by stricture.

BACKGROUND: Hepatocholangioplasty combined with choledochostomy was designed through an isolated jejunum passage in 1988. This study was undertaken to evaluate its long-term curative effects in 163 patients. METHODS: The 163 patients with hepatolithiasis complicated by stricture were treated with this procedure from 1988 to 2003. RESULTS: Among these patients, 19 patients with postoperative hepatolithiasis complicated by acute cholangitis were treated successfully with percutaneous paracentesis drainage through the isolated jejunum passage and without operation, 36 patients had postoperative residual or recurrent stones (35 patients had stones removed through the stoma and one underwent relaparotomy because of stenosis of the common bile duct along with stone in canceration). The clearance rate of stones after the isolated jejunum passage was 97%; 35 patients (21%) complicated with stricture due to hepatolith were treated with combined hepatocholangioplasty and choledochostomy. Follow-up for 1 to 15 years showed no recurrent stricture of the biliary tract. The operation also successfully prevented reflux cholangitis and other serious complications after Roux-en-Y cholangio-jejunostomy. CONCLUSION: Hepatocholangioplasty combined with choledochostomy through an isolated jejunum passage may significantly improve the long-term curative effects of hepatolithiasis with stricture.

Anastomosis, Surgical↗

PubMed2004

Classifying G-protein coupled receptors with bagging classification tree.

G-protein coupled receptors (GPCRs) play a key role in different biological processes, such as regulation of growth, death and metabolism of cells. They are major therapeutic targets of numerous prescribed drugs. However, the ligand specificity of many receptors is unknown and there is little structural information available. Bioinformatics may offer one approach to bridge the gap between sequence data and functional knowledge of a receptor. In this paper, we use a bagging classification tree algorithm to predict the type of the receptor based on its amino acid composition. The prediction is performed for GPCR at the sub-family and sub-sub-family level. In a cross-validation test, we achieved an overall predictive accuracy of 91.1% for GPCR sub-family classification, and 82.4% for sub-sub-family classification. These results demonstrate the applicability of this relative simple method and its potential for improving prediction accuracy.

Algorithms↗

PubMed2004

Parasitism of Pieris rapae (Lepidoptera: Pieridae) by a pupal endoparasitoid, Pteromalus puparum (Hymenoptera: Pteromalidae): effects of parasitization and venom on host hemocytes.

In contrast to the situation with egg-larval and larval endoparasitic wasps, little is known about the effects of pupal endoparasitoids and their secretions on the hemocytes of their insect hosts. This study focuses on the pupal endoparasitoid, Pteromalus puparum, and its host, the small white butterfly, Pieris rapae. Parasitism by P. puparum, resulted in a significant increase in the total number of host hemocytes up to day five after parasitization. From day one to day four after parasitization, the percentage of plasmatocytes significantly decreased, and the proportion of granular cells increased. Moreover, from 12 h to day three after parasitization, hemocyte mortality in parasitized pupae was noticeably higher. When P. rapae pupae were parasitized by adult females of P. puparum irradiated by gamma-ray (pseudoparasitization), it was clear that the treated wasps could induce similar hemocyte changes. However, such phenomena did not occur in punctured host pupae (mimic-parasitization). After treatment with P. puparum venom, both the percentages of spreading plasmatocytes and encapsulated Sephadex G-25 beads were lessened significantly in vitro. Electron microscopy analysis and visualization of hemocyte F-actin with phalloidin-FITC showed that hemocytes treated with venom had a rounded configuration and neither spread nor extended pseudopods, while there was no marked alteration of hemocyte cytoskeletons after venom treatment. The results suggested that venom of P. puparum could actively suppress the hemocyte immune response of its host, but not by destroying the host hemocyte cytoskeleton.

Animals↗

PubMed2004

Expression of placenta growth factor is regulated by both VEGF and hyperglycaemia via VEGFR-2.

Placenta growth factor (PlGF) has been implicated in both physiological and pathological angiogenesis; however, little is known about what regulates its expression. In this study, retinal microvascular endothelial cells and pericytes were exposed to varying concentrations of VEGF and glucose and PlGF expression measured by RT-PCR and Western blotting. Both PlGF mRNA and protein were observed in unstimulated microvascular endothelial cells with only weak expression in pericytes. In endothelial cells, VEGF (100 ng/ml) and glucose (15 mM) induced an increase in expression of PlGF at both the mRNA and protein level while no effect was observed for pericytes. The increase in PlGF expression could be totally abolished by blocking VEGFR-2, and in the case of glucose by neutralising VEGF. VEGF-stimulated PlGF expression was largely inhibited by PD 98059, an inhibitor of mitogen-activated protein kinase (MAPK) and partially by GF 109203X, an inhibitor of protein kinase C (PKC), indicating that VEGF up-regulates PlGF expression via the MAPK signalling pathway and partially through PKC. Taken together, our findings suggest that VEGF orchestrates the contribution of PlGF in angiogenesis via more than one intracellular pathway and that hyperglycaemia, as occurs in diabetes, is an important regulator of PlGF expression via VEGF up-regulation.

Animals↗