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A X Li

Publications and source records attributed to A X Li.

11 recordsLinked to original sources
PubMed2006

Practical PCR tools for the delineation of Contracaecum rudolphii A and Contracaecum rudolphii B (Ascaridoidea: Anisakidae) using genetic markers in nuclear ribosomal DNA.

Using genetic markers defined previously in the internal transcribed spacers (ITS-1 and ITS-2) of nuclear ribosomal DNA (rDNA), PCR-coupled restriction fragment length polymorphism (PCR-RFLP) and specific PCR assays were established for the specific detection of each of two morphologically indistinguishable operational taxonomic units (Contracaecum rudolphii A and Contracaecum rudolphii B) within Contracaecum rudolphii (s.l.) and their differentiation from Contracaecum septentrionale, a closely related congener. Application of these tools to C. rudolphii (s.l.) adults from Phalacrocorax carbo sinensis (the Eurasian subspecies of the great cormorant) from Qinghai Lake in China, revealed C. rudolphii B to infect this host. This is the first report of C. rudolphii B in P. carbo sinensis outside of Europe (where it was originally detected), supporting the proposal that this species has a broad geographical distribution. Together with other methods, each of these molecular tools will be useful for investigating the ecology of C. rudolphii A and C. rudolphii B as well as C. septentrionale.

Animals↗
PubMed2006

Characterization of Cryptocaryon irritans isolates from marine fishes in Mainland China by ITS ribosomal DNA sequences.

Seven isolates of Cryptocaryon irritans from different host species and geographical locations in Mainland China were characterized by the first (ITS-1) and second (ITS-2) internal transcribed spacers (ITS) of nuclear ribosomal DNA (rDNA) using two isolates of Ichthyophthirius multifiliis for comparative purposes. The rDNA region including the ITS-1, 5.8S, ITS-2, and flanking 18S and 28S sequences were amplified by polymerase chain reaction and the amplicons were sequenced directly. The ITS-1, 5.8S, and ITS-2 sequences were 129, 160, and 190 bp in length, respectively, for all seven C. irritans isolates, whereas the corresponding sequences for the two I. multifiliis isolates were 142, 153, and 194 bp, respectively. While sequence variation among the seven C. irritans isolates ranged from 0 to 1.6% in both the ITS-1 and ITS-2, and the two I. multifiliis isolates differed by 1.4% in the ITS-1 and 1.0% in the ITS-2; C. irritans differed from I. multifiliis by 57.1-60.9% in the ITS-1 and 79.4-83.0% in the ITS-2, indicating that ITS sequences provide reliable genetic markers for the identification and differentiation of the two species. Phylogenetic analysis using the sequence pairwise-distance data using the neighbor-joining method inferred that the seven C. irritans isolates from Mainland China and two other isolates (T.A and Aus.C) from other countries clustered together to show monophyly, which could be readily distinguished from the other monophyletic group all from other regions. Therefore, ITS sequence data and phylogenetic analysis provided strong support that C. irritans isolates from Mainland China represent a single species. The definition of genetic markers in the ITS rDNA provide opportunities for studying the ecology and population genetic structures of the C. irritans from Mainland China and elsewhere and is also relevant to the diagnosis and control of fish diseases they cause.

Animals↗
PubMed2006

The radiation of Haliotrema (Monogenea: Dactylogyridae: Ancyrocephalinae): molecular evidence and explanation inferred from LSU rDNA sequences.

The D1-D2 domains of LSU rDNA were used to reconstruct the phylogenetic relationships within the Ancyrocephalinae (Monogenea: Dactylogyridae) utilizing maximum-parsimony (MP), maximum-likelihood (ML), minimum evolution (ME) and neighbour-joining (NJ) methods. A total of 32 monogenean taxa were examined in the present study, including 9 Haliotrema species and 13 other species representing the Ancyrocephalinae, 4 Thaparocleidus species representing the Ancylodiscoididae, and 6 species representing the Diplectanidae which were used as multiple outgroups. All 4 analyses (i.e. MP, ML, ME and NJ) inferred the same interrelationship pattern: (Diplectanidae, (Ancylodiscoididae, Dactylogyridae)) with high bootstrap support. However, 9 Haliotrema species were dispersed to form 4 clades together with species from other genera, indicating the apparent non-monophyly of Haliotrema. Three major groups were defined based on reconstructed phylogenetic trees to explain the radiation of Haliotrema species. The morphology of the reproductive organ, particularly the male copulatory organ (MCO), was discussed to further understand the formation of each group. (1) Results of the present study indicated an intimate relationship among Metahaliotrema (2 species), Protogyrodactylus (4 species) and Haliotrema (2 of 9 species), and notably, all these species share vagina-absence. (2) Based on the present molecular analyses and the morphological characters of the MCO, we propose to transfer H. spirotubiforum and the undetermined Haliotrema sp. ZHDDb to Euryhaliotrema as new combinations. (3) We propose to erect a new genus to accommodate the Haliotrema species with horn-like shaped MCO. Taxonomic implications of the present molecular phylogenetic analyses are discussed. A wider range of taxa and more DNA markers displaying various evolutionary rates should be used to estimate phylogenetic relationships among species within the Ancyrocephalinae and Ancylodiscoididae in further studies.

Animals↗
PubMed2006

[Production and identification of the monoclonal antibodies specific for MHC class I complexes bound with HPV16E7 CTL epitopic peptide.].

BACKGROUND: To produce specific monoclonal-antibodies (MAbs) for MHC class I complexes bound with HPV16E7 CTL epitopic peptide (49-57), and provide a foundation for the investigation of the present pathway of viral antigen protein after in vitro viral infection. METHODS: Highly purified HPV16E7CTL epitope (49-57) (RAHYNIVTF) was produced, and then TAP deficient RMA-S cells incubated with RAHYNIVTF were used to immunize the BALB/c mouse. The spleen cells of the mice were regularly harvested and fused with the SP2/0 cells. The growing fusion wells were screened and the abstracted Mabs were identified in terms of sensitivity, specificity and affinity. RESULTS: The screened hybriroma cells could steadily secrete the MAbs specific for MHC class I complexes bound with HPV16E7CTL epitopic peptide. The MAbs showed high reactivity with TAP-deficient RMA-S cells loaded with RAHYNIVTF and RMA-S cells which have the ability to process the endogenous MHC class I complexes, while minimally bound to class I molecules bearing other peptides, the results indicated excellent sensitivity, specificity and affinity of the MAbs. CONCLUSION: The experiments provide a method for producing MAbs for epitopic peptide bound MHC class I complexes.

Amino Acid Sequence↗
PubMed2005

Molecular and morphological evidence indicates that Pseudorhabdosynochus lantauensis (Monogenea: Diplectanidae) represents two species.

Sequences of the first internal transcribed spacer (ITS-1) and the D1-D3 domains of the large subunit (LSU) of the ribosomal DNA (rDNA) were determined for multiple specimens of 4 operational taxonomic units (OTUs) of the monogenean, Pseudorhabdosynochus lantauensis. OTUs were defined based on their collecting localities, host and/or morphological characteristics. All P. lantauensis specimens of one group (OTUs 1 and 3) differed in their sequences of the ITS-1 and partial LSU rDNA when compared with specimens of a second group (OTUs 2 and 4) by 12% and 2%, respectively. Results of the phylogenetic analyses of the LSU rDNA sequence data showed total (100%) bootstrap support for the separation of P. lantauensis into 2 distinct clades. At least 11 of the 18 nucleotide differences in the LSU sequence between the two P. lantauensis clades were derived (i.e. autapomorphic) characters when the morphologically distinct species, P. epinepheli and P. coioidesis, were used as outgroups. Furthermore, there were several autapomorphic character states for each P. lantauensis clade. This provides sufficient evidence to reject the null hypothesis that P. lantauensis represents a single species. Morphological and morphometric differences between these two clades provided additional strong support for the separation of P. lantauensis into two species. These two parasite species were found to co-exist on one of the two species of serranid fish (i.e. Epinephelus coioides) examined in the South China Sea (Guangdong Province, China).

Animals↗
PubMed2004

Multiplexed analysis of polymorphisms in the HLA gene complex using bead array chips.

A novel custom bead array technology is introduced, and it is applied to multiplexed analysis of highly polymorphic human leukocyte antigen (HLA) genetic loci. Our technology combines the construction of probe libraries on color-encoded microparticles (beads) with semiconductor chip processing to produce custom-designed high-density bead array chips in large quantities. Using this novel assay format, two modes of parallel molecular typing of the HLA complex were implemented, namely direct hybridization, illustrated here for class II HLA-DR, and a novel format of on-chip polymerase-mediated primer elongation, illustrated here for class I HLA-A, HLA-B, and HLA-DR using patient and reference cell-line DNA samples. Hybridization-mediated multiplexed analysis of polymorphism method was validated with 142 samples, resulting in 100% concordance with sequence-specific oligonucleotide typing results and a concomitant average of 40% less allele ambiguity. In addition, elongation and hybridization reactions were combined to identify multiple polymorphisms on the same phase of DNA for allele identification.

HLA Antigens↗
PubMed2000

An acyltransferase catalyzing the formation of diacylglucose is a serine carboxypeptidase-like protein.

1-O-beta-acyl acetals serve as activated donors in group transfer reactions involved in plant natural product biosynthesis and hormone metabolism. However, the acyltransferases that mediate transacylation from 1-O-beta-acyl acetals have not been identified. We report the identification of a cDNA encoding a 1-O-beta-acylglucose-dependent acyltransferase functioning in glucose polyester biosynthesis by Lycopersicon pennellii. The acyltransferase cDNA encodes a serine carboxypeptidase-like protein, with a conserved Ser-His-Asp catalytic triad. Expression of the acyltransferase cDNA in Saccharomyces cerevisiae conferred the ability to disproportionate 1-O-beta-acylglucose to diacylglucose. The disproportionation reaction is regiospecific, catalyzing the conversion of two equivalents of 1-O-beta-acylglucose to 1, 2-di-O-acylglucose and glucose. Diisopropyl fluorophosphate, a transition-state analog inhibitor of serine carboxypeptidases, inhibited acyltransferase activity and covalently labeled the purified acyltransferase, suggesting the involvement of an active serine in the mechanism of the transacylation. The acyltransferase exhibits no carboxypeptidase activity; conversely, the serine carboxypeptidases we have tested show no ability to transacylate using 1-O-acyl-beta-glucoses. This acyltransferase may represent one member of a broader class of enzymes recruited from proteases that have adapted a common catalytic mechanism of catabolism and modified it to accommodate a wide range of group transfer reactions used in biosynthetic reactions of secondary metabolism. The abundance of serine carboxypeptidase-like proteins in plants suggests that this motif has been used widely for metabolic functions.

Acyltransferases↗
PubMed1999

Glucose polyester biosynthesis. Purification and characterization of a glucose acyltransferase.

Glandular trichomes of the wild tomato species Lycopersicon pennellii secrete 2,3,4-O-tri-acyl-glucose (-Glc), which contributes to insect resistance. A Glc acyltransferase catalyzes the formation of diacyl-Glc by disproportionating two equivalents of 1-O-acyl-beta-Glc, a high-energy molecule formed by a UDP-Glc dependent reaction. The acyltransferase was purified 4,900-fold from L. pennellii leaves by polyethylene glycol fractionation, diethylaminoethyl chromatography, concanavalin A affinity chromatography, and chromatofocusing. The acyltransferase possesses an isoelectric point of 4.8, a relative molecular mass around 110 kD, and is composed of 34- and 24-kD polypeptides as a heterotetramer. The 34- and 24-kD proteins were partially sequenced. The purified enzyme catalyzes both the disproportionation of 1-O-acyl-beta-Glcs to generate 1,2-di-O-acyl-beta-Glc and anomeric acyl exchange between 1-O-acyl-beta-Glc and Glc.

Acetates↗
PubMed1992

Immunohistochemical study of HER-2/neu, epidermal growth factor receptor, and steroid receptor expression in normal and malignant endometrium.

HER-2/neu oncogene protein, epidermal growth factor receptor, progesterone receptor, and estrogen receptor were examined immunohistochemically in specimens of normal and neoplastic endometrium. Tissues obtained at the time of hysterectomy were snap-frozen at liquid nitrogen temperature and serially sectioned at 4 microns. Normal endometrial epithelial cells stained with anti-epidermal growth factor receptor and anti-HER-2/neu with intensities graded from 0 to 3+. Of the 49 endometrial malignancies studied, seven (14%) contained tissue exhibiting HER-2/neu staining in excess (4+) of any of the normal tissues or the other 42 cancer specimens. Expression of both HER-2/neu and steroid receptors was heterogeneous within these seven tumors. To examine this heterogeneity more closely, sections of these and other tumors were double-stained for HER-2/neu and progesterone receptor. It was found that the cells exhibiting 4+ HER-2/neu staining were progesterone receptor-negative. Conversely, cells that were progesterone receptor-positive within the same specimen exhibited HER-2/neu immunostaining equal to or less than 3+. All specimens containing 4+ HER-2/neu tissue were graded 1 or 2 adenocarcinomas, stage I. Thus, there is an inverse relationship between overexpression of HER-2/neu and progesterone receptor in endometrial cancer. On the other hand, overexpression of HER-2/neu in endometrial cancer does not seem to be related to loss of other differentiated characteristics. The prognostic value of these observations awaits continued study.

Biomarkers, Tumor↗
PubMed1990

Strain differences in the ontogeny of estrogen receptors in murine uterine epithelium.

The expression of estrogen receptor (ER) in the reproductive tracts of neonatal mice was examined using immunocytochemical and autoradiographic methods. Two strains of mice used in previous studies that reported contradictory results showed different rates of uterine epithelial development. In the inbred strain, BALB/c, the epithelium was devoid of receptor from birth through 5 days of age, while uterine epithelial cells of the outbred strain, CD-1, expressed ER as early as 3 days of age. Oviductal epithelium and cervical epithelium expressed ER on the day of birth in CD-1 mice. Glandular ontogeny in the uteri of CD-1 animals was also advanced by 3 days compared to that of BALB/c mice. These observations reconcile the conflicting reports of ER ontogeny in the neonatal mouse. More importantly, these results confirm our earlier observations, indicating that the cells lining uteri of 2- and 4-day-old BALB/c mice lack ER at a time when estrogen induces their proliferation.

Aging↗