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Biomedical subjects

X X Chen

Publications and source records attributed to X X Chen.

At least 19 recordsLinked to original sources
PubMed2005

Phylogenetic relationships among the Braconidae (Hymenoptera: Ichneumonoidea) inferred from partial 16S rDNA, 28S rDNA D2, 18S rDNA gene sequences and morphological characters.

Phylogenetic relationships among the Braconidae were examined using homologous 16S rDNA, 28S rDNA D2 region, and 18S rDNA gene sequences and morphological data using both PAUP* 4.0 and MRBAYES 3.0B4 from 88 in-group taxa representing 35 subfamilies. The monophyletic nature of almost all subfamilies, of which multiple representatives are present in this study, is well-supported except for two subfamilies, Cenocoelinae and Neoneurinae that should probably be treated as tribal rank taxa in the subfamily Euphorinae. The topology of the trees generated in the present study supported the existence of three large generally accepted lineage or groupings of subfamilies: two main entirely endoparasitic lineages of this family, referred to as the "helconoid complex" and the "microgastroid complex," and the third "the cyclostome." The Aphidiinae was recovered as a member of the non-cyclostomes, probably a sister group of Euphorinae or Euphorinae-complex. The basal position of the microgastroid complex among the non-cyclostomes has been found in all our analyses. The cyclostomes were resolved as a monophyletic group in all analyses if two putatively misplaced groups (Mesostoa and Aspilodemon) were excluded from them. Certain well-supported relationships evident in this family from the previous analyses were recovered, such as a sister-group relationships of Alysiinae+Opiinae, of Braconinae+Doryctinae, and a close relationship between Macrocentrinae, Xiphozelinae, Homolobinae, and Charmontinae. The relationships of "Ichneutinae + ((Adeliinae + Cheloninae) + (Miracinae + (Cardiochilinae + Microgastrinae)))" was confirmed within the microgastroid complex. The position of Acampsohelconinae, Blacinae, and Trachypetinae is problematic.

Animals↗
PubMed2005

Autoantibody production from a thymoma and a follicular dendritic cell sarcoma associated with paraneoplastic pemphigus.

BACKGROUND: Paraneoplastic pemphigus (PNP) is an autoimmune mucocutaneous disease. We previously reported that B cells in a Castleman tumour associated with PNP produced autoantibodies. However, it is uncertain whether the production of autoantibodies from the associated tumour is a common mechanism in PNP. OBJECTIVES: To investigate autoantibody production in a thymoma and a follicular dendritic cell sarcoma that were excised from two patients with PNP. METHODS: Tumour cells were cultured, and their surface markers were identified. Indirect immunofluorescence, immunoblotting and enzyme-linked immunosorbent assay (ELISA) using culture media from the tumours were used to detect PNP autoantibodies. RESULTS: B cells with markers (CD22+, surface membrane IgG+ and surface membrane IgM+) of mature B lymphocytes constituted a proportion of cultured tumour cells in both tumours. Western blot showed that the medium from both the thymoma and the follicular dendritic cell sarcoma cells recognized 190-kDa periplakin and 210-kDa envoplakin bands of human epithelial proteins as well as recombinant linker regions of periplakin, envoplakin, desmoplakin and bullous pemphigoid antigen 1. ELISA was positive for antidesmoglein 3 antibody. CONCLUSIONS: The presence and localization in tumours of B-lymphocyte clones against proteins of the plakin family and desmoglein 3 in skin may not be confined to PNP with Castleman disease, but is possibly a common mechanism in PNP associated with various tumours.

Adult↗
PubMed2001

Versatile two-phase solvent system for alkaloid separation by high-speed counter-current chromatography.

In order to find a versatile high speed counter-current chromatography solvent system that can be used as a general prefractionation system for most alkaloids, the crude extracts of five Chinese traditional medicinal herbs, Cortex phellodendri, Semen strychni, green tea, Sophora flavescens ait, and Datura mete L. were resolved. All separations were performed only with a two-phase system composed of CHCl3-CH3OH-water (4:3:2). The water had different acidities controlled by adding NaH2PO4 or HCl to each sample. The fractionated components were identified by thin-layer chromatography, which confirmed this solvent system was versatile and very useful for the separation of alkaloids.

Alkaloids↗
PubMed1999

Use of PCR/DNA probes to identify circumsporozoite genotype of Plasmodium vivax in China.

The paper reports the result of identifying cirumsporozoite (CS) genotype of Plasmodium vivax by using PCR/DNA probe labeled with biotin. The sensitivity of this method to detect patient blood samples was 0.2 parasite/microl and also with high specific to P. vivax. CS genes from 52 blood samples collected from patients with P. vivax in Hainan and Yunnan Provinces were amplified by PCR and 49 were positive by gel-e electrophoresis analysis, positive rate was 94%. Then the amplified CS genes further were probed with special oligoprobes (PV210 and PV247) that hybridized with the predominant CS repeat region and the variant CS repeat region. The results showed 46 (88.5%) PV210 positive and 6 (11.5%) PV247 positive; 2 hybridized with both probes. The variant genotype was present only in samples from Yunnan Province. The above results showed that the PCR/DNA probe labeled with biotin was highly sensitive and specific to P. vivax and found a CS variant genotype of P. vivax in Yunnan Province of China.

Animals↗
PubMed1998

Stereoselective metabolism of metoprolol in isolated rat liver.

AIM: To study the stereoselective pharmacokinetics of the enantiomers of metoprolol (Met). METHODS: The enantiomers of Met were metabolized in isolated rat liver with hemoglubin-free medium. The enantiomers of Met were analyzed with HPLC. RESULTS: The linear kinetics were found in 3 doses (0.16, 0.32, and 0.64 mg) of R-(+)- and S-(-)-Met. The time-concentration curve of Met was fitted in first order-kinetics compartment model. There were differences in the pharmacokinetic parameters (K, T1/2, and Cl) between the enantiomers at the same dose (P < 0.01). The ratio of liver clearence of S-(-)-Met/R-(+)-Met was 0.14-0.17. CONCLUSION: Pharmacokinetics of enantiomers of Met in the isolated rat liver were stereoselective, with a preferential clearance of R-(+)-Met, which elimination was not a saturable process.

Adrenergic beta-Antagonists↗
PubMed1997

Reduced p53 dosage associated with mammary tumor metastases in C3(1)/TAG transgenic mice.

Transgenic mice expressing the simian virus 40 large T-antigen (TAG) under the regulatory control of the rat prostatic steroid binding protein C3(1) gene develop mammary carcinomas (in females) and prostate carcinomas (in males). The development of carcinomas occurs several months after the appearance of dysplastic lesions, suggesting that TAG is necessary but insufficient for tumor formation and that other genetic events are involved in this process. TAG is known to bind to p53 and to result in its functional inactivation, which is believed to be a critical step in TAG-induced transformation. We investigated whether the TAG-p53 interaction is rate limiting in the development of phenotypic changes in these transgenic mice by crossing C3(1)/TAG transgenics with mice carrying null mutations of the p53 gene. TAG-expressing animals with a p53+/- genotype developed much more aggressive mammary tumors, as evidenced by increased numbers and size of metastases, than did TAG-expressing animals carrying two wild-type p53 alleles. While p53 was expressed in primary tumors, p53 expression appeared to be reduced or lost in many metastases in mice carrying either the p53+/+ or p53+/- genotypes. The tumorigenic process did not appear to be due to the loss of the second wild-type p53 allele or the gain of dominant oncogenic mutations in p53, as no mutations were detected in either primary or metastatic tumors by polymerase chain reaction--single-strand conformation polymorphism analyses. These findings suggest that despite the presence of TAG, p53 levels influence the characteristics of the late stages of mammary tumor growth and accelerate metastases. Functional loss of p53 and not p53 mutations participates in TAG-induced mammary carcinoma development and progression.

Adenocarcinoma↗
PubMed1997

Pharmacokinetics of bendazac lysine in 10 Chinese young men.

AIM: To compare the pharmacokinetics of domestic and imported tablets of bendazao lysine (BL). METHODS: A single oral dose of 500 mg BL of this 2 kinds of tablets was given to 10 Chinese volunteers of Han nationality in a randomized crossover study. Plasma levels were determined with HPLC-UV method. Data were analyzed automatically by using a CAPP program on microcomputer. RESULTS: The plasma concentration-time curve was fitted to 2-compartment open model, and the major pharmacokinetic parameters of domestic and imported BL tablets were shown respectively as following: Cmax 66 +/- 16 and 65 +/- 8 mg.L-1; Tmax 0.98 +/- 0.22 and 0.98 +/- 0.21 h; T1/2 beta 6.2 +/- 1.8 and 6.2 +/- 1.7 h; AUC 335 +/- 47 and 337 +/- 58 mg.h.L-1. There was no significant difference between domestic and imported tablets. The bioavailability of the domestic vs that of the imported tablet was 99 +/- 12%. The unchanged BL in urine were about 5.4% and 5.6% respectively of the dosage in 24 h after a single oral dose. CONCLUSION: The two kinds of tablets had the same biological effects.

Adult↗
PubMed1995

Identification of malaria-infected dried mosquitoes by biotinylated DNA probe.

Dot-blot hybridization with cloned genomic DNA labeled with photobiotin as a probe is used to detect Plasmodium falciparum sporozoites in dried mosquitoes. The assay is sensitive enough to detect 2 pg Plasmodium parasite DNA, or one infected mosquito in a pool of 40 insects using DNA extraction samples, or one infected mosquito in a pool of 25 insects without DNA extraction. A single mosquito squashed directly on a nitrocellulose filter for the determination of parasites provides a simple method for the detection of sporozoites. The mosquitoes triturated in reduction buffer were efficient for the screening of malaria infection of mosquitoes in a large number of samples. The species specificity, sensitivity, and ease of performance of this assay as well as the stability of the reagents may make it a useful epidemiological tool.

Animals↗
PubMed1994

Changes in anti-filarial antibody after control of filariasis in Shandong Province.

The changes in anti-filarial antibody level at different periods in different population groups of various controlled areas were studied by indirect fluorescent antibody test (IFT) using frozen sections of Brugia malayi adult worms as antigen. The positive rates by IFAT in formerly hyper-, moderate- and low-endemic areas decreased to the level as those in non-endemic areas 15, 10 and 10 years respectively after the control of filariasis. In the children born after the control of filariasis, the IFAT positive rate was less than 1%. An analysis of IFAT positive cases showed that the positive rate was lowest in children under 10 years old and highest in those aged 20-40 and decreased progressively with the increasing of age. In addition, the IFAT positive rates of microfilaremia cases, the residents in currently endemic area and control group from non-endemic area were 91.4%, 33.9% and 4.5% respectively. These data demonstrated the present distribution pattern of anti-filarial antibody.

Adolescent↗
PubMed1994

[Evaluation of fetal well-being by vibro-acoustic stimulation test].

For monitoring of fetal well-being, non-stress test (NST) and vibro-acoustic stimulation test (VAS-T) were tested simultaneously in 295 normal pregnant women with gestational age over 36 weeks. In 130 women who delivered babies within 1 week after testing, the monitoring results were compared with the newborn's condition immediately after birth. The results showed that VAS-T improved the accuracy rate diagnosed by NST and shorten the time period required for examination. The clinical significance of 5 different wave forms of VAS-T were studied. Type I and Ib were typical reactive pattern which represented a good fetal condition. Type II, III and IV suggested that the fetus were in various degree of hypoxia. Specifically, Type III reflected the cord around the neck, and type IV was a sign of severe fetal distress and nervous system defect.

Acoustic Stimulation↗
PubMed1992

[Influence of vacuum mixing on mechanical properties of homemade bone cement].

Porosity, density and rotating bar bending fatigue life of homemade bone cement are analyzed with scanning electron microscopy for two different mixing techniques: manually vacuum mixing and manually non-vacuum mixing. By vacuum mixing the rotating bar bending fatigue life is increased from 0.98 x 10(4) +/- 0.31 x 10(4) to 1.33 x 10(4) +/- 0.17 x 10(4) (P < 0.05), density increased from 1.0638 +/- 0.0005g/cm3 to 1.1024 +/- 0.0068g/cm3 (P < 0.05), porosity reduced from 10.35% +/- 2.33% to 5.83% +/- 1.74% (P < 0.05), and incidence rate of big air inclusion reduced from 5.93% to 0.9%. We believe, vacuum mixing technique of bone cement should be recommended as a routine procedure to prevent aseptic loosening of prosthesis after total joint arthroplasty.

Bone Cements↗
PubMed1991

[A study on motility of sphincter of Oddi in postcholecystectomy syndrome].

Endoscopic manometry of sphincter of Oddi (SO) and serum levels of gastrin, glucagon, and somatostatin were measured in patients with postcholecystectomy syndrome (n = 12), asymptomatic cholecystectomy patients (n = 6), and controlled subjects (n = 14). Pentagastrin-stimulated gastric acid secretion test was also performed in part of patients who had symptoms or no symptoms after the removal of gallbladder. The results showed that the patients of symptomatic group had hypertonic dyskinesia of SO as shown by deep and wide waves superimposed on high basal pressure plateau of SO. The symptomatic group also had a higher serum level of gastrin and a greater BAO than those of other two groups. No difference of serum levels of glucagon and somatostatin was found among these three groups. The hypertonic dyskinesia of SO and hypergastrinemia are possibly important factors in the pathogenesis of postcholecystectomy syndrome.

Adult↗
PubMed1989

The displacement of copper by iron at the specific binding sites of ovotransferrin.

We have examined the kinetics and mechanism by which iron can displace copper at the specific metal-binding sites of ovotransferrin. Fe2+ was added to Cu2+-ovotransferrin-CO3(2-) in the presence of NaHCO3 and ambient O2. The reaction has been followed by standard and stopped-flow spectrophotometry, EPR spectroscopy and analysis of chromogen-reactive Fe2+. The reaction is best described as triphasic. An initial jump in absorbance takes place in the first 2 s. In the next minute there is a further increase in absorbance and shift in the spectral maximum from 440 to 446 nm. The third phase is complex. The bulk of the spectrophotometric change, a decrease in absorbance with a shift to a maximum of 453 nm, lasts approx. 3 min. Minor spectral and EPR changes, however, take place over the next several hours. Chromogenic analysis of Fe2+ indicates that approx. 1 min is required to oxidize the Fe2+. EPR spectra reveal the formation of an Fe3+-ovotransferrin complex within the first 20 s; however, this lacks the characteristic doublet of specific Fe3+-ovotransferrin-CO3(2-). The simultaneous presence of specific Cu2+-ovotransferrin-CO3(2-) and Fe3+-ovotransferrin-CO3(2-) signals suggests a period in which the protein specifically binds both metal ions perhaps resulting from a differential reactivity of the two metal-binding sites. The addition of Cu(NO3)2 to Fe3+-ovotransferrin-CO3(2-) resulted in a complex with specific Fe3+ and non-specific Cu2+. The EPR spectrum of this complex and the final product of our displacement reaction were virtually identical. Distinct parallels in reaction of Cu2+-ovotransferrin-CO3(2-) with Fe(NH4)2(SO4)2, Fe(NO3)3 and Fe3+-nitrilotriacetic acid were observed. A reaction sequence involving the binding and oxidation of non-specific Fe2+ followed by Cu2+ displacement by Fe3+ at the specific sites and binding of non-specific Cu2+ is suggested.

Animals↗
PubMed1985

[Rhabdomyosarcoma in E. N. T--report of 4 cases].

This paper reports 4 cases of rhabdomyosarcoma arising from the middle ear, maxillary sinuses, soft palate and larynx. In 3 patients, tumor resection was performed and the other was only biopsied. 3 patients died 6 months, 40 days and 19 months after diagnosis. One had recurrence 4 months after operation and was then treated with hematoporphyrin derivative (HPD)-laser photoradiation. The result was satisfactory and the patient has been living well for 2 years. Histopathology, treatment and prognosis of this tumor are discussed.

Child↗