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Biomedical subjects

Chen Xu

Publications and source records attributed to Chen Xu.

At least 37 records · Page 2Linked to original sources
PubMed2006

The three-dimensional structure of the flagellar rotor from a clockwise-locked mutant of Salmonella enterica serovar Typhimurium.

Three-dimensional reconstructions from electron cryomicrographs of the rotor of the flagellar motor reveal that the symmetry of individual M rings varies from 24-fold to 26-fold while that of the C rings, containing the two motor/switch proteins FliM and FliN, varies from 32-fold to 36-fold, with no apparent correlation between the symmetries of the two rings. Results from other studies provided evidence that, in addition to the transmembrane protein FliF, at least some part of the third motor/switch protein, FliG, contributes to a thickening on the face of the M ring, but there was no evidence as to whether or not any portion of FliG also contributes to the C ring. Of the four morphological features in the cross section of the C ring, the feature closest to the M ring is not present with the rotational symmetry of the rest of the C ring, but instead it has the symmetry of the M ring. We suggest that this inner feature arises from a domain of FliG. We present a hypothetical docking in which the C-terminal motor domain of FliG lies in the C ring, where it can interact intimately with FliM.

Bacterial Proteins↗
PubMed2006

Optimal probing of optical contrast of breast lesions of different size located at different depths by US localization.

We report a frequency domain optical tomography system utilizing three RF modulation frequencies, which are optimized for probing breast lesions of different size located at different depths. A real-time co-registered ultrasound scanner is used to provide on-site estimation of lesion size and location. Based on the lesion information, an optimal light modulation frequency can be selected, which may yield more accurate estimates of lesion angiogenesis and hypoxia. Phantom experiments have demonstrated that a high modulation frequency, such as 350Mhz, is preferable for probing small lesions closer to the surface while a low modulation frequency, such as 50Mhz, is desirable for imaging deeper and larger lesions. A clinical example of a large invasive carcinoma is presented to demonstrate the application of this novel technique.

Algorithms↗
PubMed2006

[Specialized gene expression and regulation in the epididymis].

The epididymis is a single and highly convoluted tubule system in mammals. The epithelium is the major compartment for epididymal function. Proteins synthesized and secreted by epididymal epithelium provide a special and ever-changing luminal fluid environment for sperm as they progress through the epididymis, which makes sperm achieve motility and ultimately results in sperm functional maturation. Specialized genes expressed in the epididymis have regional-specific characteristics. They are regulated by androgen and/or testicular factors and present spatial and tempel-specialized expression pattern in postnatal development, all these hint that they play important and unique roles in epididymis.

Animals↗
PubMed2006

[Progress in the study of immunocontraceptive antigens].

Fertility management is a global issue of medical, economic, and social consequence. Although many methods have been devised to inhibit reproduction, more acceptable alternatives are still needed. Regulation by immune intervention is a promising technology as applied to human beings. The objective of this review is to indicate several immunocontraceptive antigens.

Acrosin↗
PubMed2006

[Laser capture microdissection and its application in andrology].

Laser capture microdissection (LCM) is a novel technique developed in the recent years. Under direct microscopic visualization, LCM permits rapid one-step procurement of the selected pure target cell subgroup, even a single cell from a section of the complex, heterogeneous tissue. This technique has rapidly been introduced in the researches for the cellular and molecular mechanisms of diseases. It helps improve diagnosis, therapy and prognosis. This article reviews the progress in the application of LCM in andrology.

Andrology↗
PubMed2006

[Cloning, expression and purification of human nuclear autoantigenic sperm protein (hNASP) and preparation of its polyclonal antibody].

OBJECTIVE: To acquire the purified human nuclear autoantigenic sperm protein (hNASP) and its polyclonal antibody for investigating the possible functions of hNASP involved in fertilization. METHODS: The coding sequence of hNASP gene was amplified from human testis RNA with specific primers, and the PCR product was cloned first into pMD-18T and then into pET-28a ( + ) after restriction digestion with BamH I and Hind III. The fusion protein was expressed in E. coli BL21 (DE3) after induction with IPTG. The recombinant protein NASP was purified from the supernatant with Ni2 -NTA His-bind resin under native conditions. RESULTS: The results of DNA sequencing and SDS-PAGE analysis showed the protein to be what we had hoped to acquire. ELISA showed that we had acquired rabbit anti-hNASP serum with high titer. CONCLUSION: High purity recombinant hNASP protein could be obtained with the above-mentioned prokaryotic expression method, and so could the rabbit anti-hNASP serum with high titer and high specificity.

Adult↗
PubMed2005

Antioxidant properties and PC12 cell protective effects of APS-1, a polysaccharide from Aloe vera var. chinensis.

Through a combination of anion-exchange and repeated gel chromatographies, APS-1 was isolated from fresh leaves of Aloe vera L. var. chinensis (Haw.) Berger (an edible and medicinal plant widely cultivated and consumed in China) as a principal polysaccharide composed of mannose and glucose (ca. 18:5) with its molecular weight around 2.1 x 10(5). In a dose-dependent manner, APS-1 was demonstrated to be free radical scavenging in superoxide and hydroxyl radical assays, inhibitory to the copper-mediated oxidation of human low density lipoprotein (LDL), and protective against hydrogen peroxide (H(2)O(2))-induced lesion to rat PC12 cell (pheochromocytoma cell line). The result suggested that APS-1 could be of considerable preventive and therapeutic significance to some free radical associated health problems such as coronary heart ailments, Parkinson's and Alzheimer's diseases. Furthermore, the finding shed as well fresh light helpful for a better understanding of the health-benefiting potential of the edible plant consumed by the Chinese people for a couple of centuries.

Aloe↗
PubMed2005

Estimation of chest-wall-induced diffused wave distortion with the assistance of ultrasound.

The chest-wall layer underneath breast tissue consists of muscles and bones, which induce distortion in near-infrared diffused waves measured at distant source--detector pairs when reflection geometry is used. A priori information on chest-wall depth obtained from coregistered real-time ultrasound can be used to assist in the removal of distant measurements. We applied Monte Carlo simulation to a simple two-layer model consisting of breast tissue and a chest wall to investigate chest-wall-induced distortion. The Monte Carlo method indicates that, when more than 50% of the received photons travel through the breast tissue layer before being detected, the detected signal may be useful for image reconstruction. The results of phantom experiments obtained from the two-layer model further validate the distortion problem and demonstrate imaging improvement after distant measurements have been filtered out. Clinical examples have shown similar imaging improvements on reconstructed absorption maps. Clinical data obtained from 20 patients with the chest-wall depths of less than 2 cm from the skin surface suggest that the cutoff distances of distorted measurements are largely related to the chest-wall depth and are relatively independent of the optical properties of tissue.

Algorithms↗
PubMed2005

In vitro anti-Helicobacter pylori action of 30 Chinese herbal medicines used to treat ulcer diseases.

Infection by Helicobacter pylori has been ascertained to be an important etiologic impetus leading usually to chronic active gastritis and gastric ulcer with growing incidences worldwide. Utilizing as the test pathogen a standard and five clinic strains of Helicobacter pylori, the antibacterial action was assessed in vitro with ethanol extracts of 30 Chinese herbal medicines which have been frequently prescribed since ancient times for treating gastritis-like disorders. Among the 30 tested materials, the ethanol extracts of Abrus cantoniensis (Fabaceae), Saussurea lappa (Asteraceae) and Eugenia caryophyllata (Myrtaceae) were strongly inhibitory to all test strains (MICs: approximately 40 microg/ml), and Hippophae rhamnoides (Elaeagnaceae), Fritillaria thunbergii (Liliaceae), Magnolia officinalis and Schisandra chinensis (Magnoliaceae), Corydalis yanhusuo (Papaveraceae), Citrus reticulata (Rutaceae), Bupleurum chinense and Ligusticum chuanxiong (Apiaceae) substantially active with MICs close to 60.0 microg/ml. As to antibacterial actions of the aqueous extracts of the same drugs, those derived from Cassia obtusifolia (Fabaceae), Fritillaria thunbergii and Eugenia caryophyllata were remarkably inhibitory against all the six Helicobacter pylori strains (MICs: approximately 60 microg/ml). The work compared almost quantitatively the magnitude of the anti-Helicobacter pylori actions of the 30 most prescribed gastritis-treating Chinese herbal drugs, and located as well some source plants where potent anti-Helicobacter pylori phytochemicals could be characterized.

Anti-Bacterial Agents↗
PubMed2005

Single particle analysis of relaxed and activated muscle thin filaments.

The movement of tropomyosin from actin's outer to its inner domain plays a key role in sterically regulating muscle contraction. This movement, from a low Ca2+ to a Ca2+-induced position has been directly demonstrated by electron microscopy and helical reconstruction. Solution studies, however, suggest that tropomyosin oscillates dynamically between these positions at all Ca2+ levels, and that it is the position of this equilibrium that is controlled by Ca2+. Helical reconstruction reveals only the average position of tropomyosin on the filament, and not information on the local dynamics of tropomyosin in any one Ca2+ state. We have therefore used single particle analysis to analyze short filament segments to reveal local variations in tropomyosin behavior. Segments of Ca2+-free and Ca2+ treated thin filaments were sorted by cross-correlation to low and high Ca2+ models of the thin filament. Most segments from each data set produced reconstructions matching those previously obtained by helical reconstruction, showing low and high Ca2+ tropomyosin positions for low and high Ca2+ filaments. However, approximately 20% of segments from Ca2+-free filaments fitted best to the high Ca2+ model, yielding a corresponding high Ca2+ reconstruction. Conversely, approximately 20% of segments from Ca2+-treated filaments fitted best to the low Ca2+ model and produced a low Ca2+ reconstruction. Hence, tropomyosin position on actin is not fixed in either Ca2+ state. These findings provide direct structural evidence for the equilibration of tropomyosin position in both high and low Ca2+ states, and for the concept that Ca2+ controls the position of this equilibrium. This flexibility in the localization of tropomyosin may provide a means of sterically regulating contraction at low energy cost.

Actins↗
PubMed2005

Calcium pectinate capsules for colon-specific drug delivery.

The calcium pectinate (CaP) capsule, a novel, colon-specific delivery system, was designed and developed using 5-fluorouracil (5-FU) as a model drug. Technically, CaP capsules were prepared by dipping a glass or stainless steel rod successively into pectin and calcium chloride solutions, followed by subsequent air-drying and coating. In vitro studies showed that the release of 5-FU from CaP capsules markedly increased in the presence of rat cecal contents, and the release characteristic was mainly associated with some capsule parameters such as calcium content, shell thickness, and coat amount. Gamma scintigraphic studies demonstrated that CaP capsules could pass through the stomach and small intestine intact and could release drug in colon. The 5-FU releasing characteristics acquired both from in vitro biomimic dissolution experiments and from healthy volunteers indicated that the newly developed CaP capsule possessed the ideal colon-specific drug delivery characteristic.

Administration, Oral↗
PubMed2005

Benign versus malignant breast masses: optical differentiation with US-guided optical imaging reconstruction.

PURPOSE: To investigate prospectively the feasibility of using optical tomography with ultrasonographic (US) localization to differentiate malignant from benign breast masses and to compare optical tomography with color Doppler US. MATERIALS AND METHODS: The study was approved by the local internal review board committee and by the Human Subjects Research Review Board of Army Medical Research and Materiel Command. Signed informed consent was obtained, and the study was HIPAA compliant. Between May 2003 and March 2004, 65 consecutive women (mean age, 51 years; age range, 24-80 years) with 81 breast lesions underwent US-guided biopsy and were scanned with a combined imager. The hand-held probe, which consisted of a centrally located US transducer surrounded by near-infrared sensors, was used to simultaneously acquire coregistered US images and optical data. The lesion location obtained at US was used to guide optical imaging reconstruction. Light absorption was measured at two wavelengths. From these measurements, tumor angiogenesis was assessed on the basis of calculated total hemoglobin concentration. A Student t distribution was used to calculate the statistical significance of mean maximum and mean average hemoglobin concentrations obtained in malignant and benign lesion groups, and P < .001 was considered to indicate a statistically significant difference. RESULTS: Biopsy results revealed eight early stage invasive carcinomas (malignant group) and 73 benign lesions (benign group). The mean maximum and mean average hemoglobin concentrations in the malignant group were 122 micromol/L +/- 26.8 (+/- standard deviation) and 88 micromol/L +/- 24.5, respectively. The mean maximum and mean average hemoglobin concentrations in the benign group were 55 micromol/L +/- 24.8 and 38 micromol/L +/- 17.4, respectively. Both the maximum and average total hemoglobin concentrations were significantly higher in the malignant group compared with the benign group (P < .001). When a maximum hemoglobin concentration of 95 micromol/L was used as the threshold value, the sensitivity, specificity, positive predictive value, and negative predictive value of optical tomography were 100%, 96%, 73%, and 100%, respectively, and the sensitivity, specificity, positive predictive value, and negative predictive value of color Doppler US were 63%, 69%, 19%, and 94%, respectively. CONCLUSION: Findings indicate that optical tomography with US localization is feasible for differentiating benign and early stage malignant breast lesions.

Adult↗
PubMed2005

Acceptability of HIV/AIDS counseling and testing among premarital couples in China.

Premarital counseling is required for couples wishing to be married in China. The counseling primarily provides information about contraception. We evaluated adding premarital HIV/AIDS counseling and voluntary HIV testing to the standard counseling. The test was offered free to one group and at the standard cost to the other. The proportion of those accepting HIV testing among all participants receiving premarital counseling was used as a measure of acceptability. Sixteen percent of participants not charged chose to accept testing versus 1.4% of those charged ( p < .001). Lack of HIV/AIDS knowledge and charging for the test were correlated with refusal. Over 5% of participants admitted to premarital sex, most with their fianceé, and a significantly higher portion was female. Only 22% used condoms. Study participants were randomized for 1-year follow-up. Only four participants reported extramarital sexual activity during that year. Acceptance of HIV testing was disappointingly low. Implementing strategies to reduce stigmatization and increase knowledge of HIV/AIDS, in addition to not charging for testing, may increase the acceptance of HIV testing.

AIDS Serodiagnosis↗
PubMed2005

[Establishment and application of the approach to detecting two biovars of Ureaplasma urealyticum in human semen].

OBJECTIVE: To establish the approach to detecting two biovars of Ureaplasma urealyticum (Uu) in human semen and to investigate the relationship between the two biovars of Uu infection and the quality of human semen. METHODS: Based on the 16S-23S rRNA intergenic spacer region, three pairs of primers were designed, the species specific primer and two biovars primers (Parvo primer and T960 primer). The two biovars of Uu were detected in the semen from 949 men by semen culture and PCR assay. Meanwhile, semen routine analyses were performed. RESULTS: In the 949 subjects, 199 were Uu positive both in Uu liquid culture and PCR assay (199/949, 21.1%), of which 136 (136/199, 68.3%) were Parvo biovar, 54 (54/199, 27.1%) T960 biovar, and 9 (9/199, 4.5%) both Parvo and T960 biovars. Compared with the Parvo and the negative groups, human sperm viability was significantly decreased (P < 0.05 ) in the Uu T960 infection group. The difference of sperm motility and density had no statistic significance. CONCLUSION: A significant correlation has been found between Uu T960 biovar infection and human sperm viability

Adult↗
PubMed2005

[Clinical study on anti-leukemia effect mediated by dentritic cells].

Immunotherapy of tumor is extensively attentioned as an important part of combined therapy of tumor in recent years. Dendritic cell (DC) is the most powerful antigen presenting cell (APC) by now which not only activates auto-immunity to attack tumor cells, but also does help to enhance antitumor effect for allogenic bodies. To explore the feasibility and safety of clinical therapy application of peripheral blood derived DC cultured ex vivo, and analyze the influence of DC-inducing-immunotherapy upon long-term survival of ANLL patients accepted autologous bone marrow transplantation, peripheral blood mononuclear cells (PBMNC) of 13 ANLL patients after autologous bone marrow transplantation were collected by using CS3000Plus. DC immunotherapy was administered after cultivation of PBMNC ex vivo for 2 weeks, desease-free survival time was observed after therapy for long time follow-up. The results showed that no any severe adverse event associated with DC therapy was observed, the survival analysis of Kaplan-Meier suggested that five year survival rate was 75.52% in DC group while 45.71% in non-DC group. DC group surpassed non-DC group in accumulative survival rate. It is concluded that the ex vivo cultivation and clinical therapy application of DC derived from peripheral blood are feasible and safe, DC immunotherapy in patients with acute non-lymphocytic leukemia after autologous bone marrow transplantation prolongs desease-free survival time and enhances long-term survival rate.

Adolescent↗
PubMed2005

[Role of estrogen in male reproduction].

Estrogen plays an essential role in male reproduction. In human and other mammalians, a number of tissues express aromatase and hence synthesize estrogen. ERs and aromatase are present at all developmental stages of the male reproductive organs in many mammalian species. Estrogen is important in different aspects in male reproductive physiology, including its effects on germ cells, Sertoli cells, Leydig cells and epididymal functions.

Animals↗
PubMed2005

[Experimental study of T lymphocyte reactivity inhibited by allogeneic bone marrow mesenchymal stem cells].

OBJECTIVE: To address the question whether bone marrow mesenchymal stem cells (MSCs) could lower responsiveness of allogeneic T lymphocytes against alloantigens, and explore a feasible strategy for prevention of graft versus host disease (GVHD) occurred in allogeneic bone marrow transplantation. METHODS: T cells were co-cultured with (60)Co-irradiated bone marrow MSCs from different individuals. The proliferative activity of T cells and their reactivity to allogeneic cells and ConA were evaluated with (3)H-TdR incorporation assay. RESULTS: T cells could not be activated upon primary or even secondary exposure to allogeneic MSCs (compared the CPM value of 27,529 +/- 969 of T cell alone with that of primary and secondary exposures to allogeneic MSCs were 9,126 +/- 654 and 13,260 +/- 874, respectively). When MSCs were induced to express HLA-DR, they still could not elicit T cell activation. The proliferation rate of allogenous T cells exposed to MSCs was dramatically declined when T cells from the same donor's MSCs were used as stimulator (CPM value decreased from 45,876 +/- 5285 before coculture to 9850 +/- 1618 after coculture). Furthermore, the results remained unchanged even ConA was added into the culture system. CONCLUSIONS: Heterogenetic MSCs could suppress T cell activation. MSCs pretreatment might be useful in the prevention of GVHD in HLA-mismatched bone marrow transplantation.

Bone Marrow Cells↗