Biomedical subjects

Zhao Chen

Publications and source records attributed to Zhao Chen.

28 records · Page 2Linked to original sources

PubMed2004

[Development of a subtype screening assay for human immunodeficiency virus type 1 by nested multiplex PCR].

OBJECTIVE: The current available assays for HIV subtyping, such as sequence-based phylogenetic analysis or heteroduplex mobility assay (HMA), are labor-intensive and time-consuming. The authors have just developed a simple and rapid subtype-screening assay for subtypes B, C, and CRF01-AE using a single nested multiplex PCR. METHODS: Proviral DNA from HIV-positive samples was extracted and subjected to first round PCR with universal primers for gag region that can detect HIV-1 M group isolates. In the second round PCR, three pairs of subtype-specific primers, respectively detecting subtype B, C and CRF01-AE, were added into one tube. The PCR products of different subtypes could be distinguished in agarose-gel electrophoresis. Another pair of primers exclusively detecting the prevalent recombinant B/C strains CRF07-BC and CRF08-BC were designed and used. Additionally, all of these samples were sequenced and analyzed phylogenetically. RESULTS: Phylogenetic analysis showed that out of 119 samples, there were 43 subtype B samples (Euro-American B 11, Thailand B 32), 54 subtype C, 17 CRF01-AE, 3 subtype A and 2 subtype D samples. The subtype B, C, and CRF01-AE specific primer sets detected 35 (81.4%), 46 (85.2%), and 13(76.5%) samples with accuracy and specificity. Non-specific bands occasionally appeared but did not interfere with interpretation of the results. The primer pairs for CRF07-BC and CRF08-BC amplified target sequences were confirmed by sequencing and phylogenetic analysis. The specificity of all these subtype-specific primers was found to be 100%. CONCLUSION: A simple and rapid assay was developed for screening subtypes B, C, CRF01-AE, CRF07-BC and CRF08-BC in China. This assay may have potential application in HIV laboratories in China and worldwide.

Acquired Immunodeficiency Syndrome↗

PubMed2003

Effects of estrogen plus progestin on risk of fracture and bone mineral density: the Women's Health Initiative randomized trial.

CONTEXT: In the Women's Health Initiative trial of estrogen-plus-progestin therapy, women assigned to active treatment had fewer fractures. OBJECTIVE: To test the hypothesis that the relative risk reduction of estrogen plus progestin on fractures differs according to risk factors for fractures. DESIGN, SETTING, AND PARTICIPANTS: Randomized controlled trial (September 1993-July 2002) in which 16 608 postmenopausal women aged 50 to 79 years with an intact uterus at baseline were recruited at 40 US clinical centers and followed up for an average of 5.6 years. INTERVENTION: Women were randomly assigned to receive conjugated equine estrogen, 0.625 mg/d, plus medroxyprogesterone acetate, 2.5 mg/d, in 1 tablet (n = 8506) or placebo (n = 8102). MAIN OUTCOME MEASURES: All confirmed osteoporotic fracture events that occurred from enrollment to discontinuation of the trial (July 7, 2002); bone mineral density (BMD), measured in a subset of women (n = 1024) at baseline and years 1 and 3; and a global index, developed to summarize the balance of risks and benefits to test whether the risk-benefit profile differed across tertiles of fracture risk. RESULTS: Seven hundred thirty-three women (8.6%) in the estrogen-plus-progestin group and 896 women (11.1%) in the placebo group experienced a fracture (hazard ratio [HR], 0.76; 95% confidence interval [CI], 0.69-0.83). The effect did not differ in women stratified by age, body mass index, smoking status, history of falls, personal and family history of fracture, total calcium intake, past use of hormone therapy, BMD, or summary fracture risk score. Total hip BMD increased 3.7% after 3 years of treatment with estrogen plus progestin compared with 0.14% in the placebo group (P<.001). The HR for the global index was similar across tertiles of the fracture risk scale (lowest fracture risk tertile, HR, 1.20; 95% CI, 0.93-1.58; middle tertile, HR, 1.23; 95% CI, 1.04-1.46; highest tertile, HR, 1.03; 95% CI, 0.88-1.24) (P for interaction =.54). CONCLUSIONS: This study demonstrates that estrogen plus progestin increases BMD and reduces the risk of fracture in healthy postmenopausal women. The decreased risk of fracture attributed to estrogen plus progestin appeared to be present in all subgroups of women examined. When considering the effects of hormone therapy on other important disease outcomes in a global model, there was no net benefit, even in women considered to be at high risk of fracture.

Aged↗

PubMed2003

Statin use, clinical fracture, and bone density in postmenopausal women: results from the Women's Health Initiative Observational Study.

BACKGROUND: 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) have been shown to stimulate bone formation in laboratory studies, both in vitro and in vivo. While early epidemiologic studies showed lower risk for hip fracture among statin users than nonusers, subsequent studies have produced mixed results. OBJECTIVE: To examine the association of statin use with incidence of hip, lower arm or wrist, and other clinical fractures and with baseline levels of bone density. DESIGN: Prospective study. SETTING: Women's Health Initiative Observational Study conducted in 40 clinical centers in the United States. PARTICIPANTS: 93 716 postmenopausal women ages 50 to 79 years. MEASUREMENTS: Rates of hip, lower arm or wrist, and other clinical fractures were compared among 7846 statin users and 85 870 nonusers over a median follow-up of 3.9 years. In 6442 women enrolled at three clinical centers, baseline levels of total hip, posterior-anterior spine, and total-body bone density measured by using dual-energy x-ray absorptiometry were compared according to statin use. RESULTS: Age-adjusted rates of hip, lower arm or wrist, and other clinical fractures were similar between statin users and nonusers regardless of duration of statin use. The multivariate-adjusted hazard ratios for current statin use were 1.22 (95% CI, 0.83 to 1.81) for hip fracture, 1.04 (CI, 0.85 to 1.27) for lower arm or wrist fracture, and 1.11 (CI, 1.00 to 1.22) for other clinical fracture. Bone density levels did not statistically differ between statin users and nonusers at any skeletal site after adjustment for age, ethnicity, body mass index, and other factors. CONCLUSION: Statin use did not improve fracture risk or bone density in the Women's Health Initiative Observational Study. The cumulative evidence does not warrant use of statins to prevent or treat osteoporosis.

Aged↗

PubMed2003

[Sequence variation in the env V3-V4 region of HIV type 1 predominant subtype B and C strains circulating in China].

OBJECTIVE: To identify genetic variation of HIV-1 predominant subtype B and C strains in China during rapid horizontal transmission and to elucidate the potential relationship between genetic variation and selective pressure. METHODS: After the fragments of HIV-1 env gene were amplified by nested-PCR from the whole blood of 258 HIV-1 infected individuals, PCR products were directly sequenced using ABI 377 DNA sequencer. The sequences covering env V3-V4 region of 72 HIV-1 subtype B(n=37) and C(n=35) strains were selected for phylogenetic analysis. In addition, the ratios of synonymous (Ks) substitutions per nonsynonymous (Ka) substitutions were calculated using DIVERGE. RESULTS: The genetic distances of the V3-V4 region of subtype B strains were higher than that of subtype C strains. Furthermore, sequence analysis revealed that the V4 region was more variable than the V3 region for both subtype B and C strains. What's more, the V3 loop was less variable compared with the V3 upstream region and C3 region for subtype C Ks/Ka ratios of the entire aligned sequence of the two subtypes were below 1 0, with the lowest values found in the V3 region of subtype B strain and the V4 region of subtype C strain. CONCLUSIONS: The majority of variation in both subtypes B and C strains occurred in the V4 rather than the V3 region. It is important that our study found for the first time the V3 loop was more conservative than the V3 upstream region and C3 region for subtype C. Calculations of the Ks/Ka ratios throughout the V3-V4 region demonstrate that significant selective pressures experienced during the rapid horizontal spread of the virus in the Chinese HIV-1 infected population may have directed change in the V3 loop for the subtype B strain and the V4 loop for the subtype C strain. These results will contribute to the policy of AIDS prevention and control and the ongoing development vaccine.

Amino Acid Sequence↗

PubMed2003

[Study on the evolutionary pressure on the env gene of the human immunodeficiency virus type 1 CRF01-AE strains circulating in China].

OBJECTIVE: To identify variations in the env gene of human immunodeficiency virus type 1 (HIV-1) subtype CRF01-AE strains circulating in China and to elucidate the potential relationship between genetic variation and evolutionary pressure. METHODS: Fragments of the HIV-1 env gene were amplified by nested-polymerase chain reaction (n-PCR) from the whole blood of HIV-1 infected individuals from four provinces in Southeast China (Guangdong, Hunan, Jiangsu and Jiangxi). The PCR products were then directly sequenced by ABI 377 DNA sequencers. The sequences covering the env V3-V4 region of 34 HIV-1 subtype CRF01-AE strains were selected to analyse phylogenetic trees and amino acid mutations. The accumulation of synonymous (Ks) and antonymous (Ka) substitutions as well as Ks/Ka ratios were calculated using DIVERGE. RESULTS: Phylogenetic trees showed that the 34 HIV-1 subtype CRF01-AE strains from China clustered with the Chinese AE reference strain (AE.97CNGX2F), as well as with the reference strains from Thailand (AE.CM240 and AE.93TH253). The amino acid sequences of the env V4 and C3 regions in the samples were highly variable, compared with those of V3 and V3-downstream regions. The V3 loop central motif in the majority (87.5%) of the strains was GPGQ. The majority of strains did not contain positively charged amino acids at positions 306 and 320 in V3 loop. The N-linked glycosylation sites in the V3-V4 region and flanking regions in these strains were relatively conserved. Analysis of the entire region showed that the mean Ks values were significantly higher than that of the Ka values (P < 0.001), with the Ks/Ka significantly higher than 1.0 (P < 0.001). In contrast, the Ks/Ka ratio in the V4 region was significantly lower than 1.0 (P < 0.01). CONCLUSIONS: Our study indicated that the majority of HIV-1 subtype CRF01-AE strains circulating in China were highly homogeneous. The amino acid sequences of the V4 and C3 regions were significantly more variable than those of the V3 loop. Our analysis also suggested that the phenotype of nearly all strains was likely to be non-syncytium inducing (NSI). Finally, the variation found in the V3-V4 sequence was significantly influenced by functional constraints as opposed to positive selective pressure, while the variability of the lone V4 region was strongly related to positive selective pressure.

Adult↗

PubMed2003

[A molecular epidemiological study on the human immunodeficiency virus infection in Jiangsu province].

OBJECTIVE: To identify subtypes of human immunodeficiency virus 1 (HIV-1) strains and their distribution, infection sources, and the trends of HIV infection in Jiangsu province. METHODS: Anticongulated bloods from 46 infected persons were collected to separate previrus DNA. HIV-1 env genes were then amplified by nested-PCR and sequenced for their C2-V3 region so as to identify subtypes. The analysis of consensus sequence, genetic distance and phylogenetic tree were conducted with GCG software. RESULTS: By the end of 2001, there had been six subtypes of HIV-1 strains identified in Jiangsu province: A, B, B', C, D and E. The predominant subtypes were C (accounting for 40.48%) and B' (accounting for 38.10%). Subtype C accounted for 86.67% among injecting DUs while subtype B' accounted for 91.67% among commercial blood donors and receivers. CONCLUSION: Subtype B'among commercial blood donors was brought to Jiangsu from neighboring provinces. The outbreak of HIV-1 infection among local DUs was caused by subtype C from Xinjiang province. Findings from HIV/AIDS molecular epidemiologic study suggest that it is challenging for Jiangsu to treat patients, apply vaccine, prevent and control AIDS in the future.

China↗

PubMed2002

Low bone density and high percentage of body fat among men who were treated with androgen deprivation therapy for prostate carcinoma.

BACKGROUND: Men with prostate carcinoma who are treated with androgen deprivation therapy (ADT) are reported to be at an increased risk of bone loss and weight changes due to the sudden disruption of hormonal levels. In the current case-control study, the authors examined the prevalence and magnitude of low bone density and obesity among men with prostate carcinoma who were treated with ADT. METHODS: Sixty-two men with prostate carcinoma who had been receiving ADT for 1-5 years were included as cases. Healthy men (n = 47) with a prostate specific antigen level < 4.0 ng/mL were recruited as controls. Body composition and bone mineral density (BMD) were measured using dual-energy X-ray absorptiometry. The average age was 74.3 years for the cases and 72.8 years for the controls. RESULTS: The results of the current study demonstrate that prostate carcinoma cases had significantly higher body weight (86.5 kg vs. 80.6 kg), a higher percentage of body fat (30% vs. 26%), and a lower total body BMD (1.12 mg/cm(2) vs. 1.17mg/ cm(2)) compared with controls (P < 0.05). Cases were more likely to be obese (27.4% vs 43%) and have low BMD at trochanter (32.3% vs. 10.6%), intertrochanter (48.4% vs. 29.8%), and total hip measurements (50.0% vs. 25.3%). CONCLUSIONS: The results of the current study indicate that men with prostate carcinoma who are treated with ADT have a significantly increased risk of low bone density and obesity.

Absorptiometry, Photon↗

PubMed2000

Cloning and Analysis of Intron 3 of Human Telomerase Reverse Transcriptase (hTERT) Gene.

Total RNA was extracted from telomerase-positive cell line SPC-A, and reverse transcribed to cDNA. The long template PCR was performed using this cDNA as template and the hTERT cDNA specific oligonucleotides as primers. A long fragment of about 2.2 kb was produced as well as a short fragment of about 150 bp. The long fragment was purified from the gel, cloned into T-easy vector and sequenced from two directions. The sequencing result and homologous comparison indicated that the fragment contained the intron 3 of hTERT gene. Further assay showed that the precursor of this fragment is premature mRNA (pre-mRNA) of hTERT gene and the copy number varied among different cell lines, as verified in this study. These results suggest the feasibility of cloning the intron of eucaryotic gene by the combination of reverse transcription and long template PCR system. And the different splicing efficiency of the intron 3 from the hTERT pre-mRNA was also implied from this assay.

Journal Article↗

PubMedDate not supplied

Validity of self-report for fractures among a multiethnic cohort of postmenopausal women: results from the Women's Health Initiative observational study and clinical trials.

OBJECTIVE: The purpose of this study is to examine the validity of, and factors associated with, the accuracy of self-report (participant-report and proxy-report) for fractures. DESIGN: Study participants were from the Women's Health Initiative Clinical Trial and Observational Study cohorts. All women were postmenopausal; populations included American Indian, Asian/Pacific Islander, black, Hispanic, and non-Hispanic white. The average length of follow-up was 4.3 years. Self-reported fractures were adjudicated by reviewing medical records. The first adjudicated self-report of fractures for each participant was included in the analysis (n = 6,652). RESULTS: We found substantial variations in validity of self-report by the fracture site. Agreements between self-reports for single-site fractures and medical records were high for hip (78%) and forearm/wrist (81%) but relatively lower for clinical spine fractures (51%). The average confirmation rate for all single-site fractures was 71%. Misidentification of fracture sites by participants or proxy-reporters seemed to be a cause of unconfirmed self-reports. Higher confirmation rates were observed in participant-reports than in proxy-reports. Results of the multivariate analysis indicated that multiple factors, such as ethnicity, a history of osteoporosis or fractures, body mass index, years since menopause, smoking status, and number of falls in the past year were significantly (P < 0.05) related to the validity of self-report. CONCLUSION: The validity of self-reports for fracture varies by fracture sites and many other factors. The assessed validity in this study is likely conservative because some of the unconfirmed self-reports may be due to poor medical record systems. The validity of self-reports for hip and forearm/wrist fractures is high in this study, supporting their use in epidemiological studies among postmenopausal women.

Aged↗

PubMedDate not supplied

Pilot study of dietary influences on mammographic density in pre- and postmenopausal Hispanic and non-Hispanic white women.

OBJECTIVE: The extent to which modifiable dietary factors may account for some of the variability demonstrated in mammographic density across ethnic groups is unknown. The purpose of this study was to provide pilot data describing the relationship between dietary variables and mammographic density in pre- and postmenopausal Hispanic and non-Hispanic white (NHW) women (N=238) ranging in age from 41 to 50 years (premenopausal only) or 56 to 70 years (postmenopausal only). DESIGN: Using a cross-sectional design, computer-assisted density assessments were performed on mammograms of both breasts and averaged for analysis. The Arizona Food Frequency Questionnaire was used to estimate dietary intake. RESULTS: Study participants were well educated and overweight, with mean mammographic densities ranging from 20.25% for postmenopausal Hispanic women to 46.94% for premenopausal NHW women. Hispanic women reported higher energy intake than NHW women, but energy-adjusted intake of other nutrients was generally comparable. There was preliminary evidence of ethnic variability in diet-mammographic density associations. Among premenopausal Hispanic women, density was inversely associated with dairy, calcium, and vitamin D intakes (P<or=0.05 for all). Among premenopausal NHW women, lower mammographic density was associated with greater intake of vegetables (P<or=0.05), and higher density was associated with greater fruit intake (P<or=0.05). Among postmenopausal Hispanic women, for every 4.54 increase in the polyunsaturated-to-saturated fat ratio, there was a 9.0% reduction in mammograph density. CONCLUSIONS: These preliminary results suggest that a differential pattern of dietary nutrient associations with mammographic density could potentially exist among Hispanic and NHW women. These ethnic differences in diet and mammographic density associations need to be further explored in larger studies.

Adult↗