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L Xiao

Publications and source records attributed to L Xiao.

At least 55 records · Page 3Linked to original sources
PubMed2001

A multilocus genotypic analysis of Cryptosporidium meleagridis.

Cryptosporidium meleagridis is a common cause of cryptosporidiosis in birds. In addition, recent reports have described the parasite as an etiologic agent of cryptosporidiosis in both immunocompetent and immunocompromised humans. Therefore, it is important to genetically characterize isolates of C. meleagridis from different hosts and geographic areas, and to develop molecular tools to differentiate isolates from various hosts or areas. In this study, a total of 11 isolates of Cryptosporidium meleagridis from both human and avian hosts were examined at three genetic loci: the small-subunit rRNA, 60-kDa glycoprotein precursor, and 70-kDa heat shock protein genes. Two genotypes of C. meleagridis were seen at the small-subunit rRNA locus. These differed from each other by the presence or lack of a heterogeneous copy of the gene and an ATT repeat. The 60-kDa glycoprotein precursor gene divided these eleven isolates of C. meleagridis into six genotypes with high sequence diversity between groups. The highest genetic heterogeneity, however, was seen at the 70-kDa heat shock protein locus, and was primarily present at the 3' end of the gene. This heterogeneity separated eight isolates of C. meleagridis into six genotypes. These data could be useful in the development of molecular tools to promote understanding of the transmission of C. meleagridis in humans.

AIDS-Related Opportunistic Infections↗
PubMed2001

Molecular characterization of cryptosporidium oocysts in samples of raw surface water and wastewater.

Recent molecular characterizations of Cryptosporidium parasites make it possible to differentiate the human-pathogenic Cryptosporidium parasites from those that do not infect humans and to track the source of Cryptosporidium oocyst contamination in the environment. In this study, we used a small-subunit rRNA-based PCR-restriction fragment length polymorphism (RFLP) technique to detect and characterize Cryptosporidium oocysts in 55 samples of raw surface water collected from several areas in the United States and 49 samples of raw wastewater collected from Milwaukee, Wis. Cryptosporidium parasites were detected in 25 surface water samples and 12 raw wastewater samples. C. parvum human and bovine genotypes were the dominant Cryptosporidium parasites in the surface water samples from sites where there was potential contamination by humans and cattle, whereas C. andersoni was the most common parasite in wastewater. There may be geographic differences in the distribution of Cryptosporidium genotypes in surface water. The PCR-RFLP technique can be a useful alternative method for detection and differentiation of Cryptosporidium parasites in water.

Animals↗
PubMed2001

In vitro culture, ultrastructure, antigenic, and molecular characterization of Encephalitozoon cuniculi isolated from urine and sputum samples from a Spanish patient with AIDS.

In this report we describe the cultivation of two isolates of microsporidia, one from urine and the other from sputum samples from a Spanish AIDS patient. We identified them as Encephalitozoon cuniculi, type strain III (the dog genotype), based on ultrastructure, antigenic characteristics, PCR, and the sequence of the ribosomal DNA internal transcribed spacer region.

AIDS-Related Opportunistic Infections↗
PubMed2001

Genotyping Encephalitozoon hellem isolates by analysis of the polar tube protein gene.

To develop an alternative genotyping tool, the genetic diversity of Encephalitozoon hellem was examined at the polar tube protein (PTP) locus. Nucleotide sequence analysis of the PTP gene divided 24 E. hellem isolates into four genotypes, compared to two genotypes identified by analysis of the internal transcribed spacer of the rRNA gene. The four PTP genotypes differed from each other by the copy number of the 60-bp central repeat as well as by point mutations. A simple PCR test was developed to differentiate E. hellem genotypes based on the difference in the size of PTP PCR products, which should facilitate the genotyping of E. hellem in clinical samples.

Animals↗
PubMed2001

Genotyping Encephalitozoon cuniculi by multilocus analyses of genes with repetitive sequences.

Encephalitozoon cuniculi infects a wide range of mammalian hosts. Three genotypes based on the number of GTTT repeats in the internal transcribed spacer (ITS) of the rRNA have been described, of which genotypes I and III have been identified in humans. In this study, the genetic diversity of E. cuniculi was examined at the polar tube protein (PTP) and spore wall protein I (SWP-1) loci. Nucleotide sequence analysis of the PTP gene divided 11 E. cuniculi isolates into three genotypes in congruence with the result of analysis of the ITS of the rRNA gene. The three PTP genotypes differed from one another by the copy number of the 78-bp central repeat as well as point mutations. These E. cuniculi isolates also differed from one another in the number of 15- and 36-bp repeats in the SWP-1 gene. In addition, some E. cuniculi isolates had heterogeneous copies of the SWP-1 gene with various numbers of repeats. Intragenotypic variation was also observed at the SWP-1 locus. Based on the length polymorphism and sequence diversities of the PTP and SWP-1 genes, two simple PCR tests were developed to differentiate E. cuniculi in clinical samples.

Animals↗
PubMed2001

Cryptosporidium canis n. sp. from domestic dogs.

Oocysts of Cryptosporidium, from the feces of a naturally infected dog and from an HIV-infected human, were identified as the previously reported canine genotype of Cryptosporidium parvum, hereafter referred to as Cryptosporidium canis n. sp. Also among the oocysts from the dog, a trace amount of C. parvum bovine genotype was detected. Cryptosporidium canis oocysts from both the dog and human were infectious for calves. Oocysts excreted by calf 1 (dog source) were approximately 90% C. canis and 10% C. parvum, whereas those excreted by calf 3 (human source) were 100% C. canis. Oocysts from calf 1 infected calf 2 resulting in excretion by calf 2 of oocysts approximately 90% C. parvum and 10% C. canis. Oocysts of C. canis were not infectious for BALB/c neonatal mice or immunosuppressed C57 juvenile mice, although all control mice became infected with the C. parvum Beltsville isolate. Oocysts of C. canis from calf 1 and the human were structurally indistinguishable from oocysts of the C. parvum Beltsville isolate (bovine). However, C. canis oocysts differed markedly at the molecular level from all known species of Cryptosporidium based on sequence data for the 18S rDNA and the HSP 70 gene. The differences in genetics and host specificity clearly differentiate C. canis as a new species.

Animals↗
PubMed2001

Immune privilege induced by cotransplantation of islet and allogeneic testicular cells.

OBJECTIVE: To induce islet allograft long-term survival through cotransplantation of islet cells with sertoli cells. METHODS: Testicular sertoli cells were prepared by digestion with collagenase, trypsin and DNase, and were cultured for 48 hours. Collagenase digested and Ficoll purified donor (Wistar rat) islets were cotransplanted with allogeneic sertoli cells in the absence of systemic immunosuppression. Terminal deoxynucleotidyl transferase-mediated X-dUTP nick-end labeling (TUNEL) was used to label apoptosis of lymphocytes surrounding the islet graft. RESULTS: Cotransplantation of islets and 1 x 10(7) sertoli cells reversed the diabetic state for more than 60 days in 100% (6/6) of the chemically diabetic Sprague Dawley rats. Grafts consisting of islets alone or islets plus 1 x 10(5) sertoli cells survived only for 5-6 days. Apoptosis of lymphocytes surrounding the islets was quite clear. CONCLUSION: Cotransplantation of islets with FasL+ sertoli cells induces local immune privilege and allows long-term graft survival without systemic immunosuppression.

Animals↗
PubMed2001

[Analysis of short tandem repeats with fluorescence labeling polymerase chain reaction to document engraftment following allogeneic bone marrow transplantation].

OBJECTIVE: In order to determine the status of engraftment following allogeneic bone marrow transplantation (allo-BMT) and predict the outcome, short tandem repeats (STR) were analysed by fluorescence labeling polymerase chain reaction (PCR). METHOD: Fluorescence labeling PCR detecting STR 9 loci was established. DNA was extracted by monoclonal magnetic beads from recipients peripheral blood nucleated cells and labeled with four color fluorescences before and from 7 days to six months after allogeneic bone marrow transplantation. RESULTS: 1. STR and clinical feature of 12 patients after allogeneic bone marrow transplantation were analysed. In the ten patients with full donor chimeras, 8 received marrow grafts from HLA identical sibling donors, 1 from HLA identical unrelated donor and 1 from HLA haploidentical mother. All of the 10 patients had durable engraftment and survived disease-freely for 3-25 months of follow-up. 2. One patient received a HLA-AB loci mismatched graft and his STR showed mixed chimeras at day 30, and converted into full donor chimeras at day 60 after transplantation. 3. One patient received HLA haploidentical sibling donor stem cells failed to be engrafted and died 4 months later. CONCLUSION: Analysis of multi-loci of STR after allo-BMT provided a real indication of engraftment. Mixed chimeras after transplantation suggested that donor lymphocytes or bone marrow cells be re-infused to enhance the conversion from mixed chimeras to full donor chimeras. For the documentation of engraftment, analysis of STR was better than any other available methods.

Adolescent↗
PubMed2001

[Effect of rheumatoid arthritis associated HLA-DRbeta1 subtypes on protein kinase A signaling].

OBJECTIVE: To investigate the impact of rheumatoid arthritis (RA)-associated HLA-DRbeta(1) (*)0401, (*)0402, (*)0403 and (*)0404 subtypes on protein kinase A (PKA) signaling. METHODS: To detect the activities of adenylate cyclase (AC), cAMP and PKA in transfectants expressing rheumatoid arthritis-associated HLA-DRbeta(1) subtypes and their mutants. RESULTS: The levels of AC, cAMP and PKA of HLA-DRbeta(1) (*)0401 and (*)0404 transfectants were significant lower than that of HLA-DRbeta(1) (*)0402 and (*)0403 transfectants (P < 0.01). The mutant HLA-DRbeta(1) (*)0403 transfectants expressing DRRAE or QRRAA secreted lower levels of PKA, cAMP and AC (P < 0.01). CONCLUSION: RA-associated HLA-DRbeta(1) (*)0401 and (*)0404 expression suppressed intracellular PKA signaling pathway, and may mediate abnormal intracellular signaling in rheumatoid arthritis.

Adenylyl Cyclases↗
PubMed2001

[Microsatellite instability and loss of heterozygosity in squamous cell carcinoma of the head and neck].

OBJECTIVE: To identify the frequency of loss of heterozygosity (LOH) and microsatellite instability (MI) in Chinese sample of squamous cell carcinoma of the head and neck (SCCHN). METHODS: 18 microsatellite markers were selected and used in the analysis of 30 paired SCCHN for LOH and MI by polymerase chain reaction. RESULTS: In 30 cases of SCCHN, LOH was identified in 12 cases (40%) with at least 1 marker. The prevalence rate of LOH was 0 to 21%, much lower than those reported for most markers. 7 out of the 18 markers (D7S480, D7S522, D9S162, D9S168, D9S304, D9S171 and D17S520) were identified as significant (P < 0.05). However there was no statistically significant correlation between the LOH at these loci and the clinical parameters such as pathological types, tumor size and lymph-node metastasis. MI occurred in only 4 patients, but no MI could be observed using the common criteria for defining MI in two or more markers. CONCLUSION: The most common LOH at D7S480, D7S522, D9S162, D9S168, D9S304, D9S171 and D17S520 might imply the existence of potential tumor suppressor gene of a subset of SCCHN, while MI might not be a crucial event.

Adolescent↗
PubMed2001

[Allele-specific chromosome 9p deletion in oral cancer].

OBJECTIVE: The aim of this study was to investigate the relationship between loss of heterozygosity (LOH) on chromosome 9p and the pathogenesis of oral squamous cell carcinoma (OSCC). METHODS: A total of 24 human OSCC specimens were analyzed for LOH on chromosome 9p using 8 microsatellite markers by means of polymerase chain reaction. RESULTS: In 24 cases of OSCC, LOH on chromosome 9p was identified in 10 of 24 cases (41.67%) with at least one marker. The main LOH were found on 9p21 at locus D9S171 (21.05%) and D9S304 (10.00%). There were also a deletion on 9p22-23 at locus D9S168 (22.22%) and D9S162 (15.38%). However, there was no statistically significant correlation between LOH at these loci with such clinical parameters as pathological types, tumor size and lymph-node metastasis. Microsatellite instability (MSI) is rare for any of the 8 markers in 24 OSCC. No MSI could observed using the common criteria for defining MSI-its detection in two or more markers. CONCLUSION: We found that high frequency of LOH occurred at 9p21-23 band. Their results indicate that more than one tumor suppressor genes at chromosome 9p21-23 region related to a subset of OSCC, while MSI might not be a crucial event.

Carcinoma, Squamous Cell↗
PubMed2001

[Treatment of nuclein 32P colloid perfusion with chronic suppurative maxillary sinusitis].

OBJECTIVE: To determine the effect of nuclein 32P colloid in treatment of chronic maxillary sinusitis (CMS). METHOD: 22 patients (31 sides) with CMS after washing of sinucavity were perfused with nuclein 32P in sinucavity. 20 patients (31 sides) with routine conservative treatment were served as a control group. Two groups were followed up for one year. RESULT: In nuclein group, 27 sides were cured, 4 sides were recurred and the rate of cure was 87%. In routine group, 19 sides were cured, 12 sides were recurred and the rate of cure is 61%. There is significant difference between the two groups (P < 0.01). The treatment active of nuclein group is better than that of routine group. CONCLUSION: Nuclein 32P colloid with the function of ionizing radiation can increase the pathogenic tissue immunocompetence and metabolic course, obstruct the microvascular and promote the absorption of inflammatory exudation and edema subsidence. It can also make the proliferous tissue atrophy thence accelerate the rate of cure of CMS.

Adult↗
PubMed2001

[Effects of estrogen in the central nervous system].

Estrogen exerts a variety of effects (including electrophysiological, neutrophic and metabolic effects) on neurons in the adult central nervous system. With the many progresses made in the study of estrogen signaling through both genomic and nongenomic pathways, awareness of estrogen's effects on neural function is broadening rapidly. And it also helped people to understand more about the mechanisms by which estrogen regulating GnRH neurons, inducing or maintaining dendritic spine in hippocampus and protecting neurons from a variety of insults. Recently, epidemiological studies have suggested that estrogen, as a hormone replacement therapy in postmenopausal women, may protect against Alzheimer's disease (AD). Findings in these areas demonstrate a role for estrogen that is beyond direct control of reproductive function.

Alzheimer Disease↗
PubMed2000

Identification of 5 types of Cryptosporidium parasites in children in Lima, Peru.

Cryptosporidium parvum is usually considered to be the pathogen responsible for human cryptosporidiosis. We genotyped Cryptosporidium in 132 stool specimens from 80 Peruvian children, representing 85 infection episodes, using techniques that differentiate Cryptosporidium species and C. parvum genotypes. Five types of Cryptosporidium were identified: C. parvum human (67), bovine (8), and dog (2) genotypes, C. meleagridis (7), and C. felis (1). Twenty-five (29%) of the 85 infection episodes were associated with diarrhea. There was no significant difference in age, antecedent stunting, percentage with diarrhea, or duration of diarrhea for episodes with human genotype, compared with those of zoonotic Cryptosporidium. Duration of oocyst shedding was longer for human genotype than for zoonotic Cryptosporidium (mean, 13.9 days and 6.4 days, respectively; P=.004). Serum samples from 8 children with C. meleagridis, C. felis, or C. parvum dog genotype were tested for anti-human immunodeficiency virus (HIV) type 1 antibodies; all were found to be negative. Contrary to common belief, novel Cryptosporidium species and C. parvum genotypes can infect HIV-negative children.

Animals↗
PubMed2000

Cloning, heterologous expression, and distinct substrate specificity of protein farnesyltransferase from Trypanosoma brucei.

Protein prenylation occurs in the protozoan that causes African sleeping sickness (Trypanosoma brucei), and the protein farnesyltransferase appears to be a good target for developing drugs. We have cloned the alpha- and beta-subunits of T. brucei protein farnesyltransferase (TB-PFT) using nucleic acid probes designed from partial amino acid sequences obtained from the enzyme purified from insect stage parasites. TB-PFT is expressed in both bloodstream and insect stage parasites. Enzymatically active TB-PFT was produced by heterologous expression in Escherichia coli. Compared with mammalian protein farnesyltransferases, TB-PFT contains a number of inserts of >25 residues in both subunits that reside on the surface of the enzyme in turns linking adjacent alpha-helices. Substrate specificity studies with a series of 20 peptides SSCALX (where X indicates a naturally occurring amino acid) show that the recombinant enzyme behaves identically to the native enzyme and displays distinct specificity compared with mammalian protein farnesyltransferase. TB-PFT prefers Gln and Met at the X position but not Ser, Thr, or Cys, which are good substrates for mammalian protein farnesyltransferase. A structural homology model of the active site of TB-PFT provides a basis for understanding structure-activity relations among substrates and CAAX mimetic inhibitors.

Alkyl and Aryl Transferases↗