PubMed Health⌕ Search

Biomedical subjects

R Cheng

Publications and source records attributed to R Cheng.

At least 37 records · Page 2Linked to original sources
PubMed2000

[Intestinal parasites in school children at a public institution in Maracaibo municipality, Venezuela].

To determine the prevalence and epidemiological parameters of intestinal parasites in schoolchildren, a faecal analysis was performed in 349 individuals of both sexes, between 5 and 16 years of age. The methodology used included, a fresh test, formol-ether technique and faecal egg counts by the Kato-Katz method. Eighty three per cent of the children presented enteroparasites, with a high prevalence of polyparasitism (71.6%). There was not significative difference between parasitoses, sex and age. However, it was observed an increase of helminthiasis and protozooses in children between 7 and 10 years of age. The principal enteroparasites founded were: Trichuris trichiura (41.8%), Ascaris lumbricoides (35.2%), Blastocystis hominis (48.1%) and Endolimax nana (22.9%). When the intensity of infestation was studied by the faecal egg counts, it was observed that the highest percentage of children with T. trichiura had light infestations (84.3%), while 45.9% of the children with A. lumbricoides had severe infestations. The Abundance, Mean Intensity and Aggregation Coefficient (k) values show an over-dispersed spatial disposition of both helminths, where only few children harbour heavy burdens and eliminate a large quantity of eggs. This aggregation was higher for T. trichiura (k = 0.298) than for A. lumbricoides (k = 1.138).

Adolescent↗
PubMed1999

Two related G protein-coupled receptors: the distribution of GPR7 in rat brain and the absence of GPR8 in rodents.

GPR7 and GPR8, orphan G protein-coupled receptor (GPCR) genes, expressed in the brain and periphery share highest sequence identity to each other and significant similarity with opioid and somatostatin receptors. To further our knowledge of GPR7's physiological function, we performed in situ hybridization analyses of rat brain to reveal specific patterns of expression in the brain. GPR7 mRNA was found to be discretely localized in areas of the amygdala, hippocampus, hypothalamus and cortex. We previously reported that GPR7 was highly conserved in both human and rodent orthologs while GPR8 was not found in the rodent [9]. We speculated that GPR8 originated after the divergence of the human and rodent. Using primers designed from human GPR8, we isolated lemur GPR8 and subsequently aligned human, monkey, and lemur GPR8 orthologs to design primers recognizing highly conserved regions of GPR8. Using these primers, orthologs of GPR7 and GPR8 were isolated by the PCR from rabbit, tree shrew, and flying lemur, as well as GPR7 in the rat. Subsequent analysis of the clones obtained demonstrated that both GPR7 and GPR8 sequences were highly conserved amongst the species studied, but a rodent GPR8 was not isolated. The absence of a GPR8 gene in the rodent suggests that GPR8 originated from gene duplication of GPR7 after the rodent line diverged from the rabbit, tree shrew, flying lemur, lemur, monkey and human lines. In addition, the taxonomic distribution of GPR8 is consistent with molecular studies grouping rabbits with primates, tree shrews and flying lemurs rather than with rodents.

Amino Acid Sequence↗
PubMed1999

Discovery of a receptor related to the galanin receptors.

We report the isolation of a cDNA clone named GPR54, which encodes a novel G protein-coupled receptor (GPCR). A PCR search of rat brain cDNA retrieved a clone partially encoding a GPCR. In a library screening this clone was used to isolate a cDNA with an open reading frame (ORF) encoding a receptor of 396 amino acids long which shared significant identities in the transmembrane regions with rat galanin receptors GalR1 (45%), GalR3 (45%) and GalR2 (44%). Northern blot and in situ hybridization analyses revealed that GPR54 is expressed in brain regions (pons, midbrain, thalamus, hypothalamus, hippocampus, amygdala, cortex, frontal cortex, and striatum) as well as peripheral regions (liver and intestine). In COS cell expression of GPR54 no specific binding was observed for 125I-galanin. A recent BLAST search with the rat GPR54 ORF nucleotide sequence recovered the human orthologue of GPR54 in a 3.5 Mb contig localized to chromosome 19p13.3.

Amino Acid Sequence↗
PubMed1999

Discovery of three novel orphan G-protein-coupled receptors.

We have discovered three novel human genes, GPR34, GPR44, and GPR45, encoding family A G-protein-coupled receptors (GPCRs). The receptor encoded by GPR34 is most similar to the P2Y receptor subfamily, while the receptor encoded by GPR44 is most similar to chemoattractant receptors. The receptor encoded by GPR45 is the mammalian orthologue of a putative lysophosphatidic acid receptor from Xenopus laevis. Partial sequence of GPR34 was discovered during a search of the GenBank database of expressed sequence tags (ESTs). This sequence information was used both to isolate the full-length translational open reading frame from a human genomic library and to assemble a contig from additional GPR34 EST cDNAs. Northern blot and in situ hybridization analyses revealed GPR34 mRNA transcripts in several human and rat brain regions. Also, we used polymerase chain reaction (PCR) to amplify human genomic DNA using degenerate oligonucleotides designed from sequences encoding transmembrane domains 3 and 7 of opioid and somatostatin receptors. Two PCR products partially encoding novel GPCRs, named GPR44 and GPR45, were discovered and used to isolate the full-length translational open reading frames from a human genomic library. Both GPR44 and GPR45 are expressed in the central nervous system and periphery. For chromosomal localization, fluorescence in situ hybridization analysis was performed to assign GPR34 to chromosomes 4p12 and Xp11. 3, GPR44 to chromosome 11q12-q13.3, and GPR45 to chromosome 2q11. 1-q12.

Amino Acid Sequence↗
PubMed1999

Identification and cloning of three novel human G protein-coupled receptor genes GPR52, PsiGPR53 and GPR55: GPR55 is extensively expressed in human brain.

The G protein-coupled receptor (GPCR) family share a structural motif of seven transmembrane segments with large numbers of conserved residues in those regions. Here, we report the identification and cloning of two novel human intronless GPCR genes, GPR52, GPR55 and a pseudogene PsiGPR53. GPR55 was identified from the expressed sequence tags (EST) database whereas GPR52 and pseudogene PsiGPR53 originated from the high throughput genome (HTG) database. A partial cDNA clone obtained from the IMAGE Consortium of GPR55 was used to screen a human genomic library to acquire the full length gene. GPR52 and PsiGPR53 were amplified from human genomic DNA using primers based on the HTG sequences. GPR55 and GPR52 encode receptors of 319 and 361 amino acids, respectively. GPR55 gene was mapped to chromosome 2q37, using fluorescence in situ hybridization (FISH), and its mRNA transcripts have been detected in the caudate nucleus and putamen, but not in five other brain regions. Human receptors showing the highest amino acid identity to GPR55 include P2Y5 (29%), GPR23 (30%), GPR35 (27%) and CCR4 (23%). GPR52 gene localized to chromosome 1q24 shares the highest identity with GPR21 (71%), histamine H2 (27%) and 5-HT4 (26%) human receptors. PsiGPR53 is a pseudogene mapped to chromosome 6p21 that demonstrates the highest similarity to the MRG (35%), MAS (28%) and C5a (24%) human receptor genes.

Amino Acid Sequence↗
PubMed1999

Human papillomavirus may be common within nasopharyngeal carcinoma of Caucasian Americans: investigation of Epstein-Barr virus and human papillomavirus in eastern and western nasopharyngeal carcinoma using ligation-dependent polymerase chain reaction.

BACKGROUND: Nasopharyngeal carcinoma (NPC), particularly those tumors endemic to the Far East, commonly harbor Epstein-Barr virus (EBV), thought to serve as an important oncogenic promoter. Human papillomavirus (HPV) is associated with a proportion of upper aerodigestive tract carcinomas. We hypothesized that HPV might also contribute to the pathogenesis of NPC, and we queried whether geographic and racial distinctions may be identified between NPC of the Far East versus those diagnosed in Caucasian American patients with regard to the interrelationship of histologic subtype and viral infection. MATERIALS AND METHODS: Formalin-fixed paraffin-embedded tissue (FFPET) from 30 patients (6 Caucasian Americans, 1 Chinese American, 14 and 9 patients from Korea and China, respectively) were studied using the ligation-dependent polymerase chain reaction (LD-PCR). These cases were histologically classified according to the World Health Organization (WHO) schema for NPC. Consensus target probes complementary to the L1 region of over 30 HPV types, as well as target probes complementary to EBER-1 (EBV-related nontranslated latency-associated RNA), were used to amplify target sequences. RESULTS: Seven of 30 NPC (23%) contained HPV sequences. There were 6 Caucasian American patients with NPC; 3 cases (50%) were HPV positive (HPV+). Two of these Caucasian Americans had WHO type I tumors: one was HPV+ and EBV negative (EBV-) and the other was HPV-/EBV+. The remaining Caucasian American NPCs were WHO-II/III tumors which tested as follows: two were coinfected with HPV and EBV, the other two contained EBER but not HPV sequences. The single Oriental American patient had a WHO-III NPC which was HPV-/EBV+. Of the Eastern NPC patients, 4 (1 WHO-I, 3 WHO-II/III) of 23 (17%) NPCs contained HPV sequences as well as EBV. Conclusion. Human papillomavirus appears to be uncommonly (17%) associated with NPC in patients from the Far East and was detected more often (50%) in NPC from American Caucasian patients. Some of these tumors conformed to our perceptions and expectations of NPC (eg, WHO-I tumors being EBV-/HPV+ and WHO-III tumors being EBV+/HPV-), but other tumors did not conform to these expectations (eg, WHO-III NPC occasionally harboring both HPV and EBV). There appears to be a broad profile in the relationship between HPV, EBV, and NPC histologic subtype. Unfortunately, the number of American Caucasian cases studied are too small to allow for strong conclusions.

Asian People↗
PubMed1999

New mutations, polymorphisms, and rare variants in the ATM gene detected by a novel SSCP strategy.

The gene for ataxia-telangiectasia, ATM, spans about 150 kb of genomic DNA. ATM mutations are found along the entire gene, with no evidence of a mutational hot spot. Using DNA as the starting material, we screened the ATM gene in 92 A-T patients, using an optimized single-strand conformation polymorphism (SSCP) technique that detected all previously known mutations in the polymerase chain reaction (PCR) segments being analyzed. To expedite screening, we sequentially loaded the SSCP gels with three different sets of PCR products that were pretested to avoid overlapping patterns. Many of the DNA changes we detected were intragenic polymorphisms. Of an expected 177 unknown mutations, we detected approximately 70%, mostly protein truncating mutations (that would have been detectable by protein truncation testing if RNA starting material had been available). Mutations have now been defined for every exon of the ATM gene. Herein, we present 35 new mutations and 34 new intragenic polymorphisms or rare variants within the ATM gene. This is the most comprehensive compilation of ATM polymorphisms assembled to date. Defining polymorphic sites as well as mutations in the ATM gene will be of great importance in designing automated methods for detecting mutations.

Ataxia Telangiectasia↗
PubMed1999

Using case-control designs for genome-wide screening for associations between genetic markers and disease susceptibility loci.

We used a case-control design to scan the genome for any associations between genetic markers and disease susceptibility loci using the first two replicates of the Mycenaean population from the GAW11 (Problem 2) data. Using a case-control approach, we constructed a series of 2-by-3 tables for each allele of every marker on all six chromosomes. Odds ratios (ORs) and 95% confidence intervals (95% CI) were estimated for all alleles of every marker. We selected the one allele for which the estimated OR had the minimum p-value to plot in the graph. Among these selected ORs, we calculated 95% CI for those that had a p-value < or = adjusted alpha level. Significantly high ORs were taken to indicate an association between a marker locus and a suspected disease-susceptibility gene. For the Mycenaean population, the case-control design identified allele number 1 of marker 24 on chromosome 1 to be associated with a disease susceptibility gene, OR = 2.10 (95% CI 1.66-2.62). Our approach failed to show any other significant association between case-control status and genetic markers. Stratified analysis on the environmental risk factor (E1) provided no further evidence of significant association other than allele 1 of marker 24 on chromosome 1. These data indicate the absence of linkage disequilibrium for markers flanking loci A, B, and C. Finally, we examined the effect of gene x environment (G x E) interaction for the identified allele. Our results provided no evidence of G x E interaction, but suggested that the environmental exposure alone was a risk factor for the disease.

Alleles↗
PubMed1999

Whole genome association studies for genes affecting alcohol dependence.

We applied the transmission/disequilibrium test (TDT) for sibs (S-TDT) and for families with one parent (1-TDT), to the Collaborative Study on the Genetics of Alcoholism data set. The combined test is used to screen the whole genome to locate genes responsible for alcohol dependence. This analysis supports the previous finding that the region close to GABRB1 on chromosome 4 might be associated with alcohol dependence. The regions close to D6S474 and D11S1998 are also of particular interest. We found segregation distortion at the GR1K1 locus. The segregation distortion might be due to the binning method used in genotyping at this locus.

Alcoholism↗
PubMed1999

Identification of a third metalloprotease toxin gene in extraintestinal isolates of Bacteroides fragilis.

To further understand the epidemiology of enterotoxigenic Bacteroides fragilis (ETBF), 89 extraintestinal B. fragilis strains from Seoul, Korea, were examined for secretion of B. fragilis toxin (BFT) by the HT29/C1 biologic assay and for the B. fragilis toxin gene (bft) by colony blot hybridization and PCR. Complete agreement between the three techniques was found. Overall, 34 B. fragilis strains (38%) were identified as ETBF. Eleven of the 34 ETBF strains (32%) expressed a new isoform of BFT (Korea-BFT). This new isoform is more related to BFT-2 than to BFT-1. Like BFT-1 and BFT-2, Korea-BFT cleaves E-cadherin, the zonula adherens protein.

Amino Acid Sequence↗
PubMed1999

New approaches to virtual environment surgery.

This research focused on two main problems: 1) low cost, high fidelity stereoscopic imaging of complex tissues and organs; and 2) virtual cutting of tissue. A further objective was to develop these images and virtual tissue cutting methods for use in a telemedicine project that would connect remote sites using the Next Generation Internet. For goal one we used a CT scan of a human heart, a desktop PC with an OpenGL graphics accelerator card, and LCD stereoscopic glasses. Use of multiresolution meshes ranging from approximately 1,000,000 to 20,000 polygons speeded interactive rendering rates enormously while retaining general topography of the dataset. For goal two, we used a CT scan of an infant skull with premature closure of the right coronal suture, a Silicon Graphics Onyx workstation, a Fakespace Immersive WorkBench and CrystalEyes LCD glasses. The high fidelity mesh of the skull was reduced from one million to 50,000 polygons. The cut path was automatically calculated as the shortest distance along the mesh between a small number of hand selected vertices. The region outlined by the cut path was then separated from the skull and translated/rotated to assume a new position. The results indicate that widespread high fidelity imaging in virtual environment is possible using ordinary PC capabilities if appropriate mesh reduction methods are employed. The software cutting tool is applicable to heart and other organs for surgery planning, for training surgeons in a virtual environment, and for telemedicine purposes.

Computer Simulation↗
PubMed1999

[Regulation of p53 and bcl-2 proteins to apoptosis and cell proliferation in liver cirrhosis and hepatocellular carcinoma].

In situ apoptosis labelling was used for detecting apoptotic cells, and immunohistochemistry for p53, bcl-2 proteins and proliferation cell nuclear antigen(PCNA) in hepatocellular carcinoma(HCC) and liver cirrhosis tissues. The results were that in HCC, the number of apoptotic cells was higher, the density of proliferation cells lower, and expressions of p53 and bcl-2 protein were stronger than that in liver cirrhosis, and they were related to differentiation degree of HCC. The data indicate that overexpression of bcl-2 and mutant p53 proteins, which causes imbalance between cell proliferation and apoptosis, may bring about genesis and development of HCC by selecting proliferation of cells.

Adult↗
PubMed1999

[Observation of apoptosis and proliferation in nasopharyngeal carcinoma].

In order to observe the apoptosis and proliferation of cells in nasopharyngeal carcinoma(NPC) and pericarcinomatous tissue(PCT), 49 cases of NPC and partly PCT were detected by in situ end-labelling (ISEL) technique and proliferating cell nuclear antigen(PCNA) immunohistochemical staining. The results showed that: 1. Massive distribution of ISEL positive cells was frequently exhibited in vesicular nucleus cell carcinoma(VNCC) of NPC, in which no apoptotic pattern character was found. 2. The positive rate and the staining intensity index(SII) of ISEL signals in NPC were higher than that in PCT(P < 0.05); the positive correlation between ISEL SII and PCNA SII was found in NPC(r = 0.341, P < 0.05), whereas the positive rate and the SII of ISEL signals were significantly lower than that of PCNA (P < 0.01). 3. The ISEL SII and the PCNA SII in VNCC were obviously higher than that in poorly differentiated squamous cell carcinoma(PDSCC) (P < 0.01, P < 0.05). Patients with VNCC had a high five-year survival rate. The results suggest that there is a relationship between cellular proliferation and cellular apoptosis in NPC.

Apoptosis↗
PubMed1999

[Monitoring and elimination of sulfur dioxide and nitrogen dioxide by passive sampling method].

The concentration of atmospheric pollutants, sulfur dioxide and nitrogen dioxide, were monitored by passive sampler with spectrophotometric determination method. The results were compared with active sampling method. It was found that the two methods got the same results. The adsorption of sulfur dioxide and nitrogen dioxide by sorbent-saturated filter paper was also studied.

Air Pollutants↗
PubMed1998

Cloning genes encoding receptors related to chemoattractant receptors.

We report the cloning of a novel human gene (GPR32) encoding a putative G-protein-coupled receptor (GPCR) of 356 amino acids and a related pseudogene psi GPR32. The deduced amino acid sequence of GPR32 shares 35-39% identity with members of the chemoattractant receptor family. psi GPR32 shares 93% nucleotide identity with GPR32. We identified a mouse EST encoding a putative GPCR (GPR33) of 309 amino acids. The deduced amino acid sequence of GPR33 shares 30-35% identity with members of the chemoattractant receptor family and 36% identity with the receptor encoded by GPR32. The human orthologue of GPR33 contains a single basepair substitution with respect to the mouse, resulting in the presence of an in-frame stop codon within the predicted second intracellular loop, demonstrating that it is a pseudogene. Through fluorescence in situ hybridization and physical mapping of YACs, both GPR32 and psi GPR32 were mapped to chromosomal 19, region q13.3, while psi GPR33 was mapped to chromosome 14q12.

Amino Acid Sequence↗
PubMed1998

Discovery of three novel G-protein-coupled receptor genes.

We report here the molecular cloning, tissue distribution, and chromosomal localization of novel genes encoding G-protein-coupled receptors (GPCRs). A search of a mouse database of expressed sequence tags revealed an EST partially encoding a GPCR, which was used to screen a mouse genomic library to obtain the translational open reading frame (ORF). The resultant clone, GPR27, contained an intronless ORF, encoding a receptor of 379 amino acids. In an alternate strategy, human genomic DNA was subjected to polymerase chain reaction (PCR) amplification, using degenerate oligonucleotides based on GPR1. Two PCR products partially encoding GPCRs were isolated and used to screen a genomic library to obtain the translational ORF. One of the resultant clones, GPR30, contained an intronless ORF encoding a receptor of 375 amino acids. The other clone, GPR35, also contained an intronless ORF encoding a receptor of 309 amino acids. Transcripts corresponding to GPR27 and GPR30 were detected in several areas of human and rat CNS, While GPR35 expression was detected only in the rat intestine. Through fluorescence in situ hybridization analysis the gene encoding GPR30 was localized to chromosome 7p22 and GPR35 to chromosome 2q37.3.

Amino Acid Sequence↗
PubMed1998

A national center for biocomputation: in search of a patient-specific interactive virtual surgery workbench.

This report describes the three-dimensional imaging and virtual environment technologies developed in NASA's Biocomputation Center for scientific purposes that have now led to applications in the field of medicine. A major goal is to develop a virtual environment surgery workbench for planning complex craniofacial and breast reconstructive surgery, and for training surgeons.

Breast Neoplasms↗