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Biomedical subjects

F Chen

Publications and source records attributed to F Chen.

At least 19 recordsLinked to original sources
PubMed2007

Biocompatibility of electrophoretical deposition of nanostructured hydroxyapatite coating on roughen titanium surface: in vitro evaluation using mesenchymal stem cells.

A nano hydroxyapatite (HAp) layer was coated on a roughen titanium surface by means of electrophoretic deposition with an acetic anhydride solvent system. The objectives of this current study are to investigate whether nano-HAp can improve mechanical strength at a lower sintering temperature and biocompatibility. Densification temperature was lowered from usual 1000 to 800 degrees C. The coating interfacial bonding strength, phase purity, microstructure, and biocompatibility were investigated. Degradation of HA phase was not detected in XRD. A porous TiO2 layer acts as a gradient coating layer with an intermediate thermal expansion coefficient between hydroxyapatite and titanium that reduces the thermal stress. From SEM image, the coating does not contain any crack. Mesenchymal stem cell (MSC) is the progenitor cell for various tissues in mature animals, which can improve integration of bone tissue into implant. In this in vitro study, rabbit MSCs culture indicated that the HAp/Ti nanocomposite biomaterial had good biocompatibility and bioactivity. Around materials and on its surface cell grew well with good morphology. Proliferation of the MSCs on the nano-HAp coating was higher than its micron counterpart in XTT assay. These properties show potential for the orthopaedic and dental applications.

Animals↗
PubMed2007

Preliminary investigations on the standardisation and quality control for the determination of gamma-glutamyltranspeptidase activity in seminal plasma.

The present study was designed to assess the effects of centrifugation velocity, standing time after dilution, freezing-thawing and chymotrypsin on the determination of gamma-glutamyltranspeptidase (gamma-GT) activities in seminal plasma, and to establish an instruction for the standardisation and quality control for the determination of gamma-GT within the same laboratory and among different laboratories. The gamma-GT level and sperm concentration of each of 72 samples of seminal plasma obtained by centrifugation at 1000 g for 10 min or 3000 g for 15 min were assayed. In addition, gamma-GT activities in diluted seminal plasma with different standing time and in samples with or without chymotrypsin were measured. The results showed that there was a significant difference of gamma-GT levels in seminal plasma obtained by centrifugation at different velocities (P < 0.001), and that gamma-GT activities in seminal plasma measured after standing for 30 min after dilution were notably lower than those measured immediately after dilution (P < 0.001). However, the data indicated that both chymotrypsin and freezing-thawing had no apparent effect on the determination of seminal gamma-GT. In conclusion, standing time after dilution and centrifugation velocity should be standardised, and frozen seminal plasma could serve as quality control products for the determination of gamma-GT activity among different laboratories.

Centrifugation↗
PubMed2006

Demonstration of the difference in the Casimir force for samples with different charge-carrier densities.

A measurement of the Casimir force between a gold coated sphere and two Si plates of different carrier densities is performed using a high vacuum based atomic force microscope. The results are compared with the Lifshitz theory and good agreement is found. Our experiment demonstrates that by changing the carrier density of the semiconductor plate by several orders of magnitude it is possible to modify the Casimir interaction. This result may find applications in nanotechnology.

Journal Article↗
PubMed2006

CDX2 has tumorigenic potential in the human colon cancer cell lines LOVO and SW48.

CDX2 is a Drosophila caudal-related homeobox transcription factor that is important for the establishment and maintenance of intestinal epithelial cells. CDX2 is a marker of colon cancer, with strong staining in up to 90% of colonic adenocarcinomas. CDX2 heterozygous-null mice develop colonic neoplasms, which have suggested that CDX2 is a tumor suppressor. However, CDX2 has not been reported to affect xenograft growth. Furthermore, CDX2 is rarely mutated in colon cancer, which has led to suggestions that it may play only a minor role as a tumor suppressor in colon cancer. To understand the functional contributions of CDX2 to colon cancer, we disrupted CDX2 in LOVO and SW48 human colon cancer cell lines by targeted homologous recombination. Consistent with the literature, disruption of CDX2 enhanced anchorage-dependent cell proliferation. However, homozygous loss of CDX2 led to significant inhibition of anchorage-independent growth in LOVO cells, and cell lethality in SW48 cells. Further analyses revealed that disruption of CDX2 led to anchorage-independent G1 to S growth arrest and anoikis. In vivo xenograft studies confirmed that disruption of CDX2 inhibited LOVO tumor growth. These data demonstrate that CDX2 mediates anchorage-independent growth and survival. Thus, CDX2 has tumorigenic potential in the human colon cancer cell lines LOVO and SW48.

Animals↗
PubMed2006

CDX2 does not suppress tumorigenicity in the human gastric cancer cell line MKN45.

CDX2 is a Drosophila caudal-related homeobox transcription factor that is expressed specifically in the intestine. In mice, ectopic expression of CDX2 in the gastric mucosa gives rise to intestinal metaplasia and in one model, gastric carcinoma. In humans, increased CDX2 expression is associated with gastric intestinal metaplasia and tubular adenocarcinomas. These patterns of expression have shown that CDX2 is important for the initiation of intestinal metaplasia in the gastric mucosa, but the role of CDX2 in established gastric cancer remains unclear. We sought to determine whether CDX2 contributes to tumorigenic potential in established gastric cancer. The CDX2 gene in MKN45 gastric carcinoma cells was disrupted using targeted homologous recombination. The resulting CDX2-/- cells are essentially identical to their parental cells, with the exception of CDX2 ablation. We found no significant differences in the proliferation of CDX2-/- cells compared to CDX2+/+ cells, in vitro or in vivo. Molecular analyses show that loss of CDX2 predominantly altered the expression of genes involved in intestinal glandular differentiation and adhesion. However, there were no microscopic differences in tumor differentiation. We conclude that disruption of CDX2 in MKN45 cells does not significantly affect their tumorigenic potential.

Adenocarcinoma↗
PubMed2006

Laparoscopic appendectomy significantly reduces length of stay for perforated appendicitis.

INTRODUCTION: Though ruptured appendicitis is not a contraindication to laparoscopic appendectomy (LA), most surgeons have not embraced LA as the first-line approach to ruptured appendicitis. In fact, in 2002, the Cochrane Database Review concluded: 1) the clinical effects of LA are "small and of limited clinical relevance," and 2) the effects of LA in perforated appendicitis require further study. OBJECTIVE: To study the effects of LA vs open appendectomy (OA) among adults with appendicitis. METHODS: In 2003, 272 adults underwent appendectomy at a large County hospital, and were enrolled in a prospective clinical pathway that detailed their hospital course from time of diagnosis to discharge. Data included patient demographics, time elapse from diagnosis to surgery, surgical technique (LA vs. OA), operative diagnosis (acute vs perforated appendicitis) and post-operative length of stay (LOS). RESULTS: Complete data was obtained for 264 (97%) patients. Patient demographics were similar in the LA and OA groups (p > 0.05). Patients with LA had a significantly shorter LOS than OA by 1.6 days (p < 0.05). This LOS was significantly shorter among those with ruptured appendicitis vs. non-ruptured appendicitis (2.0 days vs. 0.3 day reduction, p = 0.0357). Rank-order multiple regression analysis, controlling for all other factors, showed laparoscopy to have a significant effect on postoperative LOS in all appendicitis cases, especially ruptured appendicitis. CONCLUSIONS: The two-day reduction in LOS among those with ruptured appendicitis who underwent LA was significant enough to overcome the smaller benefit of LA in acute appendicitis. From a hospital utilization point of view, LA should be considered as the first-line approach for all patients with appendicitis.

Adult↗
PubMed2006

The effect of thrombin on ACL fibroblast interactions with collagen hydrogels.

Premature loss of provisional scaffold formation has been identified as one of the factors responsible for poor healing of intraarticular tissues. To address this deficiency, substitute provisional scaffolds are being developed. The function of these scaffolds can be enhanced by the addition of specific extracellular matrix proteins. In this study, it was hypothesized that the addition of thrombin to a provisional scaffold material would result in increases in cell proliferation, collagen production, and cell migration within the scaffold. These three parameters are thought to be critical components of wound healing. Gels containing fibrin and collagen supplemented with either 0, 10.5, 21, or 42 U/mL of thrombin were placed in contact with explants of tissue from the anterior cruciate ligament. The addition of thrombin stimulated cell migration at low concentrations and impaired migration at higher concentrations, and had no significant effect on cell proliferation or collagen production. The use of all concentrations of thrombin resulted in mechanically weaker gels. Thus, the use of thrombin to optimize a collagen-platelet rich plasma (PRP) provisional scaffold must be done with caution, and use of high concentrations of thrombin (>42 IU/mL) should be avoided specifically in situations where gel strength or cell ingrowth is important. Use of low concentrations of thrombin (10.5 IU/mL) may be beneficial in applications where a faster set time and enhanced cell migration are desirable and the gel mechanical strength is of secondary importance.

Animals↗
PubMed2006

Steroid withdrawal increases risk of acute rejection but reduces infection: a meta-analysis of 1681 cases in renal transplantation.

OBJECTIVE: To evaluate the safety of steroid withdrawal in renal transplantation recipients. METHODS: These following databases were searched: Medline (1966 to September 2005), OVID (1966 to 2004), Embase (1984 to 2004), Cochrane library (issue 4, 2005), Highwire (1849 to September 2005), American Transplant Congress (2005), Chinese Biomedicine database (CBM 1994 to 2005). The safety was measured by the following factors: patient and graft survival, acute rejection, chronic rejection, infection, serum creatinine. We performed meta-analysis by using Revman 4.2.7. RESULTS: Nine randomized clinical trials were identified to have a steroid withdrawal and a steroid continuing group. They included 1681 patients: 845 with steroid withdrawal and 836 with continuing steroid. The risk of acute rejection after steroid withdrawal was two times higher than steroid-continuing group (RR 2.05; 95% confidence interval [CI]: 1.54, 2.72; P < .00001), while the incidence of opportunistic infection and urinary tract infection of steroid withdrawal group were lower than the control group (RR 0.80; 95%CI 0.64, 1.00; P = .05 vs RR 0.74; 95%CI, 0.60, 0.92; P = .004, respectively). The graft and patient survivals, chronic rejection, and serum creatinine were similar to the steroid continuing group. CONCLUSION: Steroid withdrawal can significantly increase the risk of acute rejection episodes, but reduces the incidence of infection to a certain extent. To prophylaxis against serious infection, steroid withdrawal is worth considering using a sufficient immunosuppressive regimen. The key point is to balance the benefit and harm for the individual recipient.

Adrenal Cortex Hormones↗
PubMed2006

Recurrent lymphangioleiomyomatosis after living-donor lobar lung transplantation.

Living-donor lobar lung transplantation (LDLLT) has been applied to patients with various end-stage lung diseases. The recurrence of pulmonary lymphangioleiomyomatosis (LAM) after lung transplantation has been rarely reported. Herein, we report a case of recurrent pulmonary LAM after LDLLT. A 24-year-old woman presented with pneumothorax and infiltrates in the left lung 1 year after bilateral LDLLT for LAM. These symptoms and radiologic findings occurred repeatedly and then improved quickly. Thereafter, computed tomography of the chest revealed a tiny emphysematous change of the subpleural region in the left lung, which was exacerbated gradually and was finally diagnosed as LAM recurrence by transbronchial lung biopsy. In previous reports of LAM recurrence, the diagnosis was made at the time of autopsy. This is also the first reported case diagnosed early, that is, when the patient was alive and her allograft had not deteriorated badly.

Adult↗
PubMed2006

Studies on a kinetic model for butyric acid bioproduction by Clostridium butyricum.

AIMS: This paper discusses the establishment of a kinetic model for cell growth, butyric acid production and substrate consumption of Clostridium butyricum ZJUCB in batch cultivation. METHODS AND RESULTS: Mathematic simulations were proposed by the logistic equation for the cell growth, the Luedeking-Piret equation for butyric acid production and the Luedeking-Piret-like equation for glucose consumption. CONCLUSION: We compared the performance of our model against that obtained by the empirically experimental design. The experiment-validated model was found suitable for studying butyric acid fermentation kinetics in a complex dynamic behaviour of C. butyricum, especially for its singular growth phenomenon. SIGNIFICANCE AND IMPACT OF THE STUDY: The model parameters are estimated from the data fitting and evaluated for simulation of the time courses of the concentrations of cell biomass, butyric acid and glucose and the model appears to fit the experimental data well. The results may be useful for butyric acid production by microbial fermentation.

Biomass↗
PubMed2006

CCR2 allele polymorphisms in 15 Chinese ethnic populations.

Chemokine receptor-2 (CCR2) is a co-receptor for the entry of human immunodeficiency virus-1 (HIV-1) into the target cells. A mutation in CCR2 (CCR2-64I) exhibited a protective effect to delay the progression of acquired immunodeficiency syndrome (AIDS). To study the mutant frequency and polymorphism of CCR2 in Chinese populations, 1082 individuals from 15 Chinese populations distributing widely from north to south were collected. The genotypes of CCR2-64I were determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) with the digestion of restriction endonuclease FokI. Of the 1082 individuals, 352 (32.53%) were carriers of CCR2-64I allele, 257 of whom (23.75%) were heterozygotes (CCR2-64V/I), whereas 95 (8.78%) were homozygotes (CCR2-64V/V). The frequency of the CCR2-64I allele in those tested individuals was 20.66%. This prevalence of CCR2-64I was higher than what was known for American and European populations. Moreover, the frequencies of CCR2-64I were generally higher in northern China than they were in southern China, and the frequencies had significant variance in 15 populations of China (chi2 = 27.135, P = 0.018).

Alleles↗
PubMed2006

Fertile sporophore production of Typhula phacorrhiza in the field is related to temperatures near freezing.

Two field tests and one lab test were conducted to examine the environmental factors affecting sporophore production in Typhula phacorrhiza and to compare these results with those documented for T. ishikariensis and T. incarnata. In the 2001 lab test where lighting, soil moisture, and soil-sand media were tested in 50 mL screw-cap tubes incubated at 4 degrees C, the limiting factor for Typhula sporophore production was found to be moisture. In the fall 2001 field test, 100 sclerotia of six isolates from three Typhula spp. were placed into pots filled with a sand and soil mixture. The pots were monitored weekly, and maximum sporophore production for all six isolates and for watered and unwatered pots was observed at 11 weeks, which was soon after mean daily temperatures fell below 0 degrees C. In the second field test in fall 2003, five isolates of the three species were tested with similar procedures, but peak sporophore production was observed after 6 weeks, and again only after mean daily temperatures fell below 0 degrees C. In the field, sporophore production of T. phacorrhiza seems to require the same environmental cues as those of T. ishikariensis or T. incarnata, namely high moisture and temperatures near freezing.

Basidiomycota↗
PubMed2005

Molecular and biochemical characterization of puroindoline a and b alleles in Chinese landraces and historical cultivars.

Kernel hardness that is conditioned by puroindoline genes has a profound effect on milling, baking and end-use quality of bread wheat. In this study, 219 landraces and 166 historical cultivars from China and 12 introduced wheats were investigated for their kernel hardness and puroindoline alleles, using molecular and biochemical markers. The results indicated that frequencies of soft, mixed and hard genotypes were 42.7, 24.3, and 33.0%, respectively, in Chinese landraces and 45.2, 13.9, and 40.9% in historical cultivars. The frequencies of PINA null, Pinb-D1b and Pinb-D1p genotypes were 43.8, 12.3, and 39.7%, respectively, in hard wheat of landraces, while 48.5, 36.8, and 14.7%, respectively, in historical hard wheats. A new Pinb-D1 allele, designated Pinb-D1t, was identified in two landraces, Guangtouxianmai and Hongmai from the Guizhou province, with the characterization of a glycine to arginine substitution at position 47 in the coding region of Pinb gene. Surprisingly, a new Pina-D1 allele, designated Pina-D1m, was detected in the landrace Hongheshang, from the Jiangsu province, with the characterization of a proline to serine substitution at position 35 in the coding region of Pina gene; it was the first novel mutation found in bread wheat, resulting in a hard endosperm with PINA expression. Among the PINA null genotypes, an allele designed as Pina-D1l, was detected in five landraces with a cytosine deletion at position 265 in Pina locus; while another novel Pina-D1 allele, designed as Pina-D1n, was identified in six landraces, with the characterization of an amino acid change from tryptophan-43 to a 'stop' codon in the coding region of Pina gene. The study of puroindoline polymorphism in Chinese wheat germplasm could provide useful information for the further understanding of the molecular basis of kernel hardness in bread wheat.

Alleles↗
PubMed2005

Chronic corticotropin-releasing factor type 1 receptor antagonism with antalarmin regulates the dopaminergic system of Fawn-Hooded rats.

Corticotropin-releasing factor is a neuropeptide associated with the integration of physiological and behavioural responses to stress and also in the modulation of affective state and drug reward. The selective, centrally acting corticotropin-releasing factor type 1 receptor antagonist, antalarmin, is a potent anxiolytic and reduces volitional ethanol consumption in Fawn-Hooded rats. The efficacy of antalarmin to reduce ethanol consumption increased with time, suggestive of adaptation to reinforcement processes and goal-directed behaviour. The aim of the present study was to examine the effects of chronic antalarmin treatment on reward-related regions of Fawn-Hooded rat brain. Bi-daily antalarmin treatment (20 mg/kg, i.p.) for 10 days increased tyrosine hydroxylase messenger RNA expression throughout the ventral mesencephalon. Following chronic antalarmin the density of dopaminergic terminals within the basal ganglia and amygdaloid complex were reduced, as was dopamine transporter binding within the striatum. Receptor autoradiography indicated an up-regulation of dopamine D2, but no change in D1, binding in striatum, and Golgi-Cox analysis of striatal medium spiny neurones indicated that chronic antalarmin treatment increased spine density. Thus, chronic antalarmin treatment modulates dopaminergic pathways and implies that chronic treatment with drugs of this class may ultimately alter postsynaptic signaling mechanisms within the basal ganglia.

Amygdala↗
PubMed2005

Expression of survivin and bax/bcl-2 in peroxisome proliferator activated receptor-gamma ligands induces apoptosis on human myeloid leukemia cells in vitro.

The present study was undertaken to investigate the mechanisms of peroxisome proliferator activated receptor-gamma (PPAR-gamma) ligand-induced apoptosis on human myeloid leukemia K562 and HL-60 cell lines. The results revealed that both 15-deoxy-delta(12,14)-prostaglandin J2 (15d-PGJ2) and troglitazone (TGZ) have significant anti-proliferation- and apoptosis-inducing effects on these two kinds of leukemia cells. Marked morphological changes of cell apoptosis including condensation of chromatin and nuclear fragmentation were observed clearly using Wright's and Hoechst 33258 staining. Reverse transcription-PCR and western blot analyses demonstrated that both survivin and bcl-2 expression were downregulated markedly, while bax expression was upregulated concurrently when apoptosis occurred. We therefore conclude that 15d-PGJ2 and TGZ have significant apoptosis effects on K562 and HL-60 cells in vitro, and that upregulation of bax as well as downregulation of survivin and bcl-2 expression may be the important apoptosis-inducing mechanisms. The results suggest that PPAR-gamma ligands may serve as potential therapeutic agents for both acute and chronic myeloid leukemia.

Antineoplastic Agents↗
PubMed2005

Antiproliferative effect of beta-elemene in chemoresistant ovarian carcinoma cells is mediated through arrest of the cell cycle at the G2-M phase.

Elemene is a natural antitumor plant drug. However, the effect of elemene on cell growth in ovarian cancer is unknown. In this study, we show that beta-elemene inhibited the proliferation of cisplatin-resistant human ovarian cancer cells and their parental cells, but had only a marginal effect in human ovary cells, indicating differential inhibitory effects on cell growth between ovarian cancer cells and normal ovary cells. We also demonstrated for the first time that beta-elemene markedly enhanced cisplatin-induced growth inhibition in resistant cells compared to sensitive cells. In addition, cell cycle analysis revealed a synergistic effect of beta-elemene and cisplatin on the induction of cell cycle G2-M arrest in our resistant ovarian carcinoma cells. Furthermore, we showed that treatment of these cells with both drugs downregulated cyclin B1 and Cdc2 expression, but elevated the levels of p53, p21waf1/cip1, p27kip1 and Gadd45. Finally, the combination of beta-elemene and cisplatin was found to increase the phosphorylation of Cdc2 and Cdc25C, which leads to a reduction in Cdc2-cyclin B1 activity. These novel findings suggest that beta-elemene sensitizes chemoresistant ovarian carcinoma cells to cisplatin-induced growth suppression partly through modulating the cell cycle G2 checkpoint and inducing cell cycle G2-M arrest, which lead to blockade of cell cycle progression.

Antineoplastic Combined Chemotherapy Protocols↗