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Biomedical subjects

C Guo

Publications and source records attributed to C Guo.

At least 19 recordsLinked to original sources
PubMed2003

Hyaluronate for temporomandibular joint disorders.

BACKGROUND: Temporomandibular joint disorders (TMD) refer to a group of heterogeneous pain and dysfunction conditions involving the masticatory system, reducing life quality of the sufferers. Intra-articular injection of hyaluronate for TMD has been used for nearly two decades but the clinical effectiveness of the agent has not been summarized in the form of a systematic review. OBJECTIVES: To assess the effectiveness of intra-articular injection of hyaluronate both alone and in combination with other remedies on temporomandibular joint disorders. SEARCH STRATEGY: Intensive electronic and handsearches were carried out. The Oral Health Group's Trials Register (September 2001), The Cochrane Library CENTRAL database (Issue 3, 2001), MEDLINE (1966- May 2001), PubMed ( up to March 2002), EMBASE (1974 - August 2001), SIGLE (1980 - December 2001), CBMdisc (1983 - July 2001, in Chinese) and Chinese Medical Library were searched. All the Chinese professional journals in the oral health field were handsearched and conference proceedings consulted. There was no language restriction. SELECTION CRITERIA: Randomized or quasi-randomized controlled trials (RCTs), with single or double blind, design testing the effectiveness of hyaluronate for patients with temporomandibular joint disorders. DATA COLLECTION AND ANALYSIS: Two reviewers independently extracted data, and three reviewers independently assessed the quality of included studies. The first authors of the selected articles were contacted for additional information. MAIN RESULTS: Seven studies were included in the review. Three studies, including 109 patients with temporomandibular disorders, compared hyaluronate with placebo. Long term effects (three months or longer) are in favour of hyaluronate for the improvement of clinical signs/overall improvement of TMD (RR=1.71, 95%CI: 1.05, 2.77) from two of the studies (n=71). However, this conclusion was not stable enough at sensitivity analysis. Three studies provided data from 124 patients for the comparison of hyaluronate with glucocorticoids (one study also included a placebo group). Hyaluronate had the same short term and long term effects on the improvement of symptoms, clinical signs or overall conditions of the disorders as glucocorticoids. When comparing the effect of arthroscopy or arthrocentesis with and without hyaluronate, results were inconsistent. Hyaluronate had a potential in improving arthroscopic evaluation scores. Mild and transient adverse reactions such as discomfort or pain at the injection site were reported in the hyaluronate groups. No quality of life data were reported REVIEWER'S CONCLUSIONS: There is insufficient, consistent evidence to either support or refute the use of hyaluronate for treating patients with TMD. Further high quality RCTs of hyaluronate need to be conducted before firm conclusions with regard to its effectiveness can be drawn.

Glucocorticoids↗
PubMed2003

Influence of preapheresis clinical factors on the efficiency of CD34+ cell collection by large-volume apheresis.

We evaluated 120 leukapheresis procedures (93 patients), in order to detect clinical factors that influence the efficiency of CD34+ collection using Cobe Spectra trade mark cell separators. Hematocrit was >27% and platelet count >30 000/microl in >95% of patients. Platelet transfusions were given if the postprocedure count was &<20 000/microl. Multiple regression analysis was used to analyze putative factors, and a predictive equation defined by stepwise regression modeling. The mean efficiency was 0.59 (s.d. 0.27). Sex (M>F; P=0.01), the volume processed (inversely; P=0.01) and CD34+ cell count (inversely; P=0.04) were associated with efficiency, whereas hematocrit, platelet or leukocyte count, catheter type and patient weight were not. The effect size for predictive factors was small (R(2)=0.21). Adverse events were limited to hypocalcemia. We conclude that female sex, volume processed and CD34+ cell count adversely influence the efficiency of CD34+ cell leukapheresis. However, the impact of volume and CD34+ cell count is small, and likely to be offset by the influence of these same factors on overall yield. Leukapheresis appears to be safe and efficient for autologous blood and marrow transplantation patients with hematocrit >27% and platelet count >30 000/microl.

Antigens, CD34↗
PubMed2002

Cleanup of gloves contaminated with granular terbufos and tefluthrin.

Chemical-resistant gloves are used for protection from pesticides in farming operations. Cleanup of gloves after pesticide contamination was the focus of this research. Nitrile, neoprene, and barrier laminate glove specimens were exposed to 300 mg terbufos or tefluthrin granules for 3 or 30 min in petri dishes in a laboratory. Specimens were cleaned by flush with running water or LaunderOmeter washing with detergent. Following the cleanup treatments, specimens were dried and placed in test tubes with solvents to extract pesticide residue. Levels of contamination remaining were determined by gas chromatography. The residue remaining varied with exposure time, material type, cleanup method, and pesticide. Flush was more effective with the shorter exposure time. Tefluthrin was more effectively removed than terbufos. Barrier laminate was confirmed as a single-use material. Cleanup procedures reduced contamination in nitrile and neoprene, but findings show that these materials retained residue after cleanup.

Agriculture↗
PubMed2001

A genetically tractable model of human glioma formation.

Gliomas remain one of the deadliest forms of cancer. Improved therapeutics will require a better understanding of the molecular nature of these tumors. We, therefore, mimicked the most common genetic changes found in grade III-IV gliomas, disruption of the p53 and RB pathways and activation of telomere maintenance and independence from growth factors, through the ectopic expression of the SV40 T/t-Ag oncogene, an oncogenic form of H-ras (H-ras(V12G)), and the human telomerase catalytic subunit hTERT in normal human astrocytes. The resulting cells displayed many of the hallmarks of grade III-IV gliomas, including greatly expanded life span and growth in soft agar and, most importantly, were tumorigenic with pathology consistent with grade III-IV neuroectodermal tumors in mice. This model system will, for the first time, allow the biological significance of selected genetic alterations to be studied in human gliomas.

Animals↗
PubMed2001

[Expression of Epstein-Barr virus membrane antigen induces lymphoma in transgenic mice].

OBJECTIVE: To study the relation between the expression of Epstein-Barr virus (EBV) membrane antigen (MA) and lymphoma and to explore the potentiality of EBV BLLF1 as an oncogene for lymphoma. METHODS: Four transgenic founder mice with EBV MA BLLF1 were created. The development of lymphoma, confirmed by pathology, among them was observed. Flow cytometry was used to analyze the expression of MA in lymphoma cells, and con-focal microscopy was used to localize the expression and observe the nuclei after propidium iodide staining. The immunophenotype of lymphoma cells was analyzed by immunofluorescent technique. RESULTS: Two of the transgenic mice succumbed to lymphoma, confirmed as T cell lymphoma by histopathology and immunophenotypic analysis, at the ages of 4 and 8 months respectively, which were confirmed as MA expression positive. The other 2 MA negative mice remained healthy without lymphoma at the same periods. MA was expressed in the cytoplasm and cytomembrane of the lymphoma cells. Lobulated modification was found in the nuclei of the tumor cells. CONCLUSION: The expression of MA induces lymphoma in transgenic mice. BLLF1 gene is likely an oncogene for lymphoma.

Animals↗
PubMed2001

Ultrafast dynamics of electron thermalization in gold.

Time-resolved surface second-harmonic generation (SHG) is used to probe electron relaxation processes in gold following intense laser excitation at 1.55 eV. For the first time, an electron temperature ( T(e)) dependent enhancement in the SHG signal is clearly observed at T(e) above 0.7 eV, which is shown to relate to the thermalization of nonequilibrium hot electrons. Therefore, the relaxation dynamics of the transient nonequilibrium electrons in the high T(e) regime is directly resolved by monitoring the time evolution of the SHG signal.

Journal Article↗
PubMed2001

Aggrecan domains expected to traffic through the exocytic pathway are misdirected to the nucleus.

In this article, we report the misdirected targeting of expressed aggrecan domains. Aggrecan, the chondroitin sulfate (CS) proteoglycan of cartilage, normally progresses through the exocytic pathway. Proteins expressed from constructs containing the putative aggrecan signal sequence (i.e., the first 23 N-terminal amino acids), specified globular (G) domains G1 and/or G3, and a segment of the CS domain were detected in the endoplasmic reticulum (ER) and Golgi complex. Although proteins expressed from constructs containing the putative signal and G3, but lacking G1, were detected to a limited extent in the secretory pathway, they primarily accumulated in nuclei. Discrete nuclear inclusions were seen when G3 was expressed. Immunoelectron microscopic characterization of the inclusions suggested the association of nuclear G3 with other proteins. When signal-free G3 constructs and those with G3 immediately following the N-terminal signal were expressed, abundant dispersed accumulations filled the nucleoplasm. The data suggest first, that signal-free and signal-containing G3 proteins enter the nucleus from the cytosol, and second, that the entry of signal-containing G3 proteins into the ER lumen is inefficient. Hsp25, Hsp70, and ubiquitin were colocalized with nuclear G3, indicating the involvement of chaperones and the degradative machinery in the formation and/or attempted disposal of the abnormal nuclear inclusions. Overall, the results focus attention on (1) intracellular protein trafficking at the ER membrane and the nuclear envelope and (2) chaperone interactions and mechanisms leading to abnormal protein deposition in the nucleus.

Aggrecans↗
PubMed2001

Allelic deletion at chromosome bands 11q14-23 is common in neuroblastoma.

BACKGROUND: Neuroblastoma tumorigenesis may involve the differential inactivation of multiple tumor suppressor genes. Recent data have suggested that a neuroblastoma suppressor gene may be located on the long arm of chromosome 11 (11q). PROCEDURE: We therefore analyzed 295 primary neuroblastomas from a representative group of patients for loss of heterozygosity (LOH) at 25 polymorphic markers spanning 11q. RESULTS: LOH was observed in 129 primary neuroblastomas (44%), and a common region of LOH mapped to 11q14-23. No correlation was found between 11q LOH and adverse prognostic variables, but a strong inverse relationship between 11q LOH and MYCN amplification (P < 0.001) was observed. There was no difference in overall survival when patients were stratified by 11q LOH status. However, 11q LOH was associated with a decreased overall survival probability when patients whose tumors had a single copy of MYCN were analyzed separately (P = 0.008). CONCLUSION: These data support the hypothesis that a tumor suppressor gene mapping within 11q14-23 is frequently inactivated during the malignant evolution of neuroblastoma.

Alleles↗
PubMed2001

Loss of heterozygosity for chromosome 14q in neuroblastoma.

BACKGROUND: Neuroblastoma is a genetically heterogeneous disease, with subsets of tumors demonstrating rearrangements of several genomic regions. Preliminary studies from several groups have identified loss of heterozygosity (LOH) for the long arm of chromosome 14 (14q) in 20-25% of primary neuroblastomas. PROCEDURE: To determine precisely the frequency and extent of 14q deletions, we performed LOH analysis for a large series of primary neuroblastomas using a panel of 11 highly polymorphic markers. RESULTS: LOH was detected in 83 of 372 tumors (22%). Although the majority of tumors with allelic loss demonstrated allelic loss for all informative markers, 13 cases showed LOH for only a portion of 14q. A single consensus region of deletion, which was shared by all tumors with 14q LOH, was defined within 14q23-q32 between D14S588 and the 14q telomere. Allelic loss for 14q was strongly correlated with the presence of 11q LOH (P < 0.001 ) and inversely correlated with MYCN amplification (P= 0.04). CONCLUSIONS: LOH for 14q was evident in all clinical risk groups, indicating that this abnormality may be a universal feature of neuroblastoma tumor development. These findings suggest that a tumor suppressor gene involved in the initiation or progression of neuroblastoma is located within distal 14q.

Child↗
PubMed2001

Comprehensive analysis of chromosome 1p deletions in neuroblastoma.

BACKGROUND: Chromosome 1p deletions are common in advanced neuroblastomas, but the biological and clinical implications of this clonal rearrangement remain controversial. Previous studies of chromosome 1p loss of heterozygosity (LOH) have been limited by analyses of relatively small number of tumors derived from heterogeneously assessed and treated patient populations. Therefore, a strictly representative cohort of 288 Children's Cancer Group neuroblastoma patients treated on the most recent phase III therapeutic trials was identified. PROCEDURE: Primary tumors from these patients were analyzed for LOH at precisely mapped and highly informative 1p polymorphic loci located from 1p32 to 1p36.3 by multiplex PCR. RESULTS: Ninety-three primary tumor specimens (32%) had LOH at multiple 1p36 marker loci. All 1p deletions overlapped the previously determined smallest region of overlap (SRO). One tumor had a small terminal deletion completely within 1p36.3, allowing for further refinement of the 1p36 SRO. We found no evidence to support an additional, nonoverlapping region of LOH within 1p32-36. We confirmed the strong correlation of 1p36 LOH with MYCN amplification (P < 0.001), advanced disease stage (P < 0.001), and decreased both 3-year event-free survival and overall survival probabilities (P< 0.001). When stratified for MYCN amplification status or entered into a multivariate analysis, 1p36 LOH remained predictive for decreased event-free survival, but not overall survival probability. CONCLUSIONS: These data support the hypothesis that inactivation of a tumor suppressor gene within 1p36.3 is associated with an increased risk for disease relapse.

Alleles↗
PubMed2001

Detailed molecular analysis of 1p36 in neuroblastoma.

BACKGROUND: Several lines of evidence es tablish that chromosome band 1p36 is frequently deleted in neuroblastoma primary tumors and cell lines, suggesting that a tumor suppressor gene within this region is involved in the development of this tumor. PROCEDURE: We analyzed the status of 1p36 in primary neuroblastomas and cell lines to define the region of consistent rearrangement. RESULTS: Loss of heterozygosity (LOH) studies of primary neuro blastomas identified allelic loss in 135 of 503 tumors (27%), with the smallest region of overlap (SRO) defined distal to D15214 (1p36.3). No homozygous deletions were detected at 120 loci mapping to 1p36.1-p36.3 in a panel of 46 neuroblastoma cell lines. A recently identified patient with neuroblastoma was found to have a constitutional deletion within 1p36.2-p36.3, and this deletion, when combined with the LOH results, defined a smaller SRO of one megabase within 1p36.3. We constructed a comprehensive integrated map of chromosome 1 containing 11,000 markers and large-insert clones, a high-resolution radiation hybrid (RH) map of 1p36, and a P1-artificial chromosome (PAC) contig spanning the SRO, to further characterize the region of interest. Over 768 kb (75%) of the SRO has been sequenced to completion. Further analysis of distal 1p identified 113 transcripts localizing to 1p36, 21 of which were mapped within the SRO. CONCLUSION: This analysis will identify suitable positional candidate transcripts for mutational screening and subsequent identification of the 1p36.3 neuroblastoma suppressor gene.

Alleles↗
PubMed2001

Analysis of genomic imprinting at 1p35-36 in neuroblastoma.

BACKGROUND: Deletion of the distal short arm of chromosome 1 occurs in 25-35% of primary neuroblastomas, and a putative tumor suppressor gene has been mapped to a consensus region of deletion at 1p36.2-36.3. Indirect evidence suggests the presence of an imprinted neuroblastoma suppressor gene within this region, as well as an additional nonimprinted, proximal suppressor gene, inactivation of which correlates with MYCN amplification. PROCEDURE: To test this hypothesis, we performed 1p loss of heterozygosity (LOH) studies on a series of neuroblastomas for which parental DNA had been collected. PCR-formatted polymorphic markers were used to determine the size of the 1p deletion and the parental origin of the deleted 1p homologue. RESULTS: Twenty-six neuroblastomas with 1p LOH were evaluated. Twenty-four had MYCN amplification, and of these, 15 demonstrated loss of the paternally inherited 1p. Two neuroblastomas with a single copy of MYCN were evaluated and both had deletion of the paternally inherited 1p, with one case exhibiting a small terminal deletion. In addition, we have reviewed 49 previously reported neuroblastomas where 1p LOH data and the parental origin of the deleted lp homologue were available. CONCLUSIONS: Analyzed together, these 75 neuroblastomas demonstrate random deletion of parental 1p homologues (P = 0.30). Further, tumors with smaller deletions (breakpoints distal to D1S201 or D1S7) showed a random loss of the parental 1p homologues (P = 0.59), contrary to the expected preferential maternal 1p deletion if an imprinted suppressor gene mapped to this region. However, 19 tumors with 1p LOH and single copy MYCN had deletion of the maternal 1p homologue preferentially (P = 0.02), which does not exclude the possibility that loss of an imprinted suppressor gene plays a role in this subset.

Adult↗
PubMed2001

CYP1A1, GSTM1, and GSTT1 polymorphisms and the risk of cervical squamous intraepithelial lesions in a multiethnic population.

OBJECTIVE: In this investigation, we explored the hypothesis that genetic polymorphisms in the cytochrome P4501A1 (T3801C) and glutathione S-transferase classes mu and theta (GSTM1 and GSTT1) gene deletions promote the development of cervical dysplasia by moderating the activation and detoxification of polycyclic hydrocarbons and other compounds that influence oxidative stress and DNA adduct formation. METHODS: A multiethnic, case-control study of 131 women with biopsy-confirmed cervical squamous intraepithelial lesions (SIL) and 180 controls with cytologically normal cervical (Pap) smears was conducted between 1992 and 1996 in Honolulu, Hawaii. We collected in-person interviews, a blood sample to extract genomic DNA, and an exfoliated cervical cell sample to determine the presence and type of human papillomavirus (HPV) using PCR dot-blot hybridization. Genotyping for the CYP1A1 MspI allelic variant and deletion of the GSTM1 and GSTT1 gene loci followed a PCR method. RESULTS: Women who were homozygous, but not heterozygous, for the CYP1A1 MspI variant allele were at significantly increased risk of cervical SIL (odds ratio (OR) = 3.4; 95% confidence interval (CI) = 1.1-10.7) compared to women who were homozygous for the wild-type allele. Subjects with the GSTM1 null genotype had a nonsignificant elevated risk of cervical SIL (OR = 1.6; 95% CI = 0.8-3.0) compared to women with the gene present. No difference in the risk of cervical disease was associated with the GSTT1 null genotype. The combination of the CYP1A1 homozygous variant and the GSTM1 null genotypes increased the odds ratio for cervical SIL to 5.1 (95% CI = 1.3-20.7). There was no evidence for an interaction between genotype and exposure to tobacco smoke, alcohol drinking, or HPV DNA positivity. CONCLUSIONS: These findings, although based on a small number of subjects, suggest that the CYP1A1 MspI polymorphism may be a susceptibility factor for early, premalignant changes in the cervical epithelium.

Adult↗
PubMed2001

Effects of exposure time, material type, and granular pesticide on glove contamination.

Chemical-resistant gloves are recommended for pesticide applicators to reduce their exposure to agricultural chemicals. In this research, three chemical-resistant glove materials-nitrile, neoprene, and barrier laminate-were studied in relation to contamination with granular terbufos and tefluthrin. Surfaces of specimens backed with alpha cellulose were contaminated with 300 mg of either granular terbufos or tefluthrin for 1-, 2-, 4-, 8-, 16-, and 24-h time periods in petri dishes in the laboratory. Residues were extracted using ethyl acetate for terbufos and iso-octane for tefluthrin in test tubes for 24 h. Analysis of extracts by gas chromatograph and statistical analysis of the data showed that contamination levels varied with the time of exposure, material type, and pesticide used. Pesticide was not detected in the alpha cellulose even after 24 h contamination time. A linear relationship was found between contamination level and exposure time for terbufos in the three materials, with longer exposure times causing higher contamination levels. Contamination of nitrile was significantly less than neoprene or barrier laminate. Exposed glove materials contained higher levels of contamination of terbufos than tefluthrin.

Chromatography, Gas↗
PubMed2001

Angular measurement of the cobalt-60 emitted radiation spectrum from a radiosurgery irradiator.

The photon energy spectrum emanating from a Leksell Gamma Knife, Model 23004B, was measured between 0.250 and 3.5 MeV with the sources exposed. Measurements were made using a 2x2 inch NaI detector enclosed in a lead-shielded apparatus having a 1/4 inch diameter measurement aperture, which reduced the amount of radiation received by the crystal. All measurements were made one meter above the floor within a quadrant toward one side of the Gamma Knife couch. The measured spectra displayed the expected 60Co doublet of photon peaks at energies of 1.17 and 1.33 MeV. These peaks appeared in spectra beginning at approximately 50 degrees, as one proceeds from a point directly lateral to the source enclosure (0 degrees) toward the foot of the couch (90 degrees). The average photon energy of the spectrum shifts to lower values as the doublet decreases in magnitude with increasing angle until almost vanishing at an angle equal to 90 degrees. Inserting a 16 cm diameter plastic sphere phantom, provided with the Gamma Knife, into the radiation beams increases the low energy photon emissions appearing in the spectrum, especially for measurements at the foot of the couch. Implications for the design of shielding a treatment room containing the Gamma Knife, Model B, and estimation of the radiation exposure to personnel during an emergency procedure in the treatment room with the sources exposed are discussed.

Cobalt Radioisotopes↗
PubMed2001

N-terminal domains of the human telomerase catalytic subunit required for enzyme activity in vivo.

Most tumor cells depend upon activation of the ribonucleoprotein enzyme telomerase for telomere maintenance and continual proliferation. The catalytic activity of this enzyme can be reconstituted in vitro with the RNA (hTR) and catalytic (hTERT) subunits. However, catalytic activity alone is insufficient for the full in vivo function of the enzyme. In addition, the enzyme must localize to the nucleus, recognize chromosome ends, and orchestrate telomere elongation in a highly regulated fashion. To identify domains of hTERT involved in these biological functions, we introduced a panel of 90 N-terminal hTERT substitution mutants into telomerase-negative cells and assayed the resulting cells for catalytic activity and, as a marker of in vivo function, for cellular proliferation. We found four domains to be essential for in vitro and in vivo enzyme activity, two of which were required for hTR binding. These domains map to regions defined by sequence alignments and mutational analysis in yeast, indicating that the N terminus has also been functionally conserved throughout evolution. Additionally, we discovered a novel domain, DAT, that "dissociates activities of telomerase," where mutations left the enzyme catalytically active, but was unable to function in vivo. Since mutations in this domain had no measurable effect on hTERT homomultimerization, hTR binding, or nuclear targeting, we propose that this domain is involved in other aspects of in vivo telomere elongation. The discovery of these domains provides the first step in dissecting the biological functions of human telomerase, with the ultimate goal of targeting this enzyme for the treatment of human cancers.

Catalytic Domain↗
PubMed2001

A novel vascular smooth muscle chymase is upregulated in hypertensive rats.

While greater than 80% of angiotensin II (Ang II) formation in the human heart and greater than 60% in arteries appears to result from chymase activity, no cardiovascular cell-expressed chymase has been previously reported. We now describe the cloning of a full-length cDNA encoding a novel chymase from rat vascular smooth muscle cells. The cDNA encompasses 953 nucleotides, encodes 247 amino acids, and exhibits 74% and 80% homology in amino acid sequence to rat mast cell chymase I and II, respectively. Southern blot analysis indicates that the rat vascular chymase is encoded by a separate gene. This chymase was induced in hypertrophied rat pulmonary arteries, with 11-fold and 8-fold higher chymase mRNA levels in aortic and pulmonary artery smooth muscle cells from spontaneously hypertensive than in corresponding tissues from normotensive rats. We assayed the activity of the endogenous enzyme and of a recombinant, epitope-tagged chymase in transfected smooth muscle cells and showed that Ang II production from Ang I can be inhibited with chymostatin, but not EDTA or captopril. Spontaneously hypertensive rats show elevated chymase expression and increased chymostatin-inhibitable angiotensin-converting activity, suggesting a possible role for this novel enzyme in the pathophysiology of hypertension.

Amino Acid Sequence↗