Biomedical subjects

Y Ma

Publications and source records attributed to Y Ma.

At least 109 records · Page 6Linked to original sources

PubMed2001

Metabolic changes following subthalamotomy for advanced Parkinson's disease.

We studied 6 advanced-stage Parkinson's disease patients with [18F] fluorodeoxyglucose/positron emission tomography before and 3 months after unilateral ablation of the subthalamic nucleus performed with microelectrode mapping. Operative changes in glucose metabolism were assessed by comparing baseline and postoperative scans. We also quantified operative changes in the activity of an abnormal Parkinson's disease-related metabolic network that we had identified in previous [18F] fluorodeoxyglucose/positron emission tomography studies. Following unilateral subthalamic nucleus ablation, a highly significant reduction in glucose utilization was present in the midbrain ipsilateral to the lesion site, most pronounced in the vicinity of the substantia nigra pars reticularis. Significant metabolic reductions were also present in the ipsilateral internal globus pallidus, ventral thalamus, and pons. Operative changes in Parkinson's disease network activity differed significantly for the lesioned and unlesioned hemispheres. In the lesioned hemisphere, network activity declined significantly following surgery, but was unaltered in the contralateral, unlesioned hemisphere. These results suggest that subthalamotomy reduces basal ganglia output through internal globus pallidus/substantia nigra pars reticularis and also influences downstream neural activity in the pons and ventral thalamus. This procedure also reduces the activity of abnormal Parkinson's disease-related metabolic brain networks, suggesting a widespread modulation of motor circuitry.

Adult↗

PubMed2001

Characterization of phosphopeptides from protein digests using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and nanoelectrospray quadrupole time-of-flight mass spectrometry.

A two-step mass spectrometric method for characterization of phosphopeptides from peptide mixtures is presented. In the first step, phosphopeptide candidates were identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) based on their higher relative intensities in negative ion MALDI spectra than in positive ion MALDI spectra. The detection limit for this step was found to be 18 femtomoles or lower in the case of unfractionated in-solution digests of a model phosphoprotein, beta-casein. In the second step, nanoelectrospray tandem mass (nES-MS/MS) spectra of doubly or triply charged precursor ions of these candidate phosphopeptides were obtained using a quadrupole time-of-flight (Q-TOF) mass spectrometer. This step provided information about the phosphorylated residues, and ruled out nonphosphorylated candidates, for these peptides. After [(32)P] labeling and reverse-phase high-performance liquid chromatography (RP-HPLC) to simplify the mixtures and to monitor the efficiency of phosphopeptide identification, we used this method to identify multiple autophosphorylation sites on the PKR-like endoplasmic reticulum kinase (PERK), a recently discovered mammalian stress-response protein.

Amino Acid Sequence↗

PubMed2001

Behavioral risk factors among members of a health maintenance organization.

BACKGROUND: Co-occurrence of risk behaviors (RBs) substantially increases the risk of disease. This study examines the co-occurrence of four health risk behaviors (i.e., smoking, high-fat diet, sedentariness, and high-risk drinking) and demographic and psychosocial variables associated with number of RBs in a sample of members of a health maintenance organization who participated in the Seasonal Variation in Cholesterol (Seasons) study. METHODS: Seasons study baseline data were used. Subjects completed a self-administered questionnaire packet containing questions on demographics, smoking history, and leisure-time physical activity, a 7-day dietary recall instrument, and various psychosocial measures. Results presented here are based on 496 subjects with complete data on all RBs. RESULTS: Forty-three percent of participants had > or = two RBs. The most prevalent RB combination was high-fat diet/sedentariness, with 30% of subjects reporting both RBs. Associations between RBs were observed. A greater number of RBs were observed among younger and less-educated subjects, those with higher depression scores, and subjects who perceived their health as poor. CONCLUSIONS: Findings highlight the importance of designing and evaluating primary care-based screening programs and interventions for multiple RBs.

Adult↗

PubMed2001

ATP citrate lyase in the glaucocystophyte alga Cyanophora paradoxa is a cytosolic enzyme: characterisation of the gene for the large subunit at the cDNA and genomic levels.

The single-copy gene for the large subunit of ATP citrate lyase (ACL) from the alga Cyanophora paradoxa was characterized at the cDNA and genome levels. The gene product showed high sequence similarity to its mammalian counterparts, but is smaller in size, as is also found for the fungal subunit Acl1 and, most probably, for the corresponding subunit from Arabidopsis thaliana. The C. paradoxa gene is interrupted by at least 12 introns of 53-65 bp with conserved border and branchpoint sequences, and the product lacks a stroma-targeting peptide. Enzyme activity was found in the cytosol of C. paradoxa but not in the plastid (cyanelle) fraction. This is in contrast to the subcellular distribution of ATP citrate lyases in higher plants, where both chloroplast and cytosolic enzymes have been reported.

ATP Citrate (pro-S)-Lyase↗

PubMed2001

Hsal 1 is related to kidney and gonad development and is expressed in Wilms tumor.

Townes-Brocks syndrome (TBS) is a human genetic disorder with features including urogenital, limb, anal and cardiac malformations associated with mutations of the TBS gene, Hsal 1. To begin to understand the role of the Hsal 1 protein (p140) in both normal development and disease pathogenesis, both message and protein expression were evaluated in specific tissues associated with TBS. DNA sequence information for Hsal 1 predicts that this homeotic, Drosophila homologue (Sal) encodes a zinc-finger protein consistent with a transcription factor. mRNA for Hsal 1 was highly expressed in fetal kidney and brain, with detectable production in thymus and heart. p140 was found in fetal ureteric bud, fetal and postnatal renal tubular epithelium, and renal blastema. In the 14-week fetal testis, the Hsal 1 protein was specifically expressed in the testosterone producing Leydig cells while in adult gonads Hsal 1 was also found in both Leydig and Sertoli cells, spermatogonia of the testis, and granulosa cells of the ovary. Evaluation of Wilms tumor revealed consistently high expression of the gene product in the epithelial and blastemal components. These spatial and temporal patterns of expression for Hsal 1, and the phenotypic effects associated with TBS, suggest that Hsal 1 plays an important role in the development and functional maintenance of the kidney and gonads. Furthermore, the Hsal 1 gene product may play a part in the pathogenesis of specific neoplasms occurring in these organs in addition to its specific role in Townes-Brocks syndrome.

Abnormalities, Multiple↗

PubMed2001

Change in women's diet and body mass following intensive intervention for early-stage breast cancer.

OBJECTIVE: To determine the effectiveness of an intensive dietary intervention on diet and body mass in women with breast cancer. DESIGN: Randomized clinical trial. SUBJECTS: 172 women aged 20 to 65 years with stage I or II breast cancer. INTERVENTION: A 15-session, mainly group-based and dietitian-led nutrition education program (NEP) was compared to a mindfulness-based stress reduction clinic program (SRC); or usual supportive care (UC). MAIN OUTCOME MEASURES: Dietary fat, complex carbohydrates, fiber, and body mass were measured. STATISTICAL ANALYSIS: In addition to descriptive statistics, analysis of variance was conducted to test for differences according to intervention group. RESULTS: Of the 157 women with complete dietary data at baseline, 149 had complete data immediately postintervention (at 4 months) and 146 had complete data at 1 year. Women randomized to NEP (n = 50) experienced a large reduction in fat consumption (5.8% of energy as fat) at 4 months and much of this reduction was preserved at 1 year (4.1% of energy) (both P < .0002) vs no change in either SRC (n = 51) or UC (n = 56). A 1.3-kg reduction in body mass was evident at 4 months in the NEP group (P = .003) vs no change in the SRC and UC groups. Women who had higher-than-average expectations of a beneficial effect of the intervention experienced larger changes. APPLICATIONS: Dietitians' use of group nutrition interventions appear to be warranted. Increasing their effectiveness and maintaining high levels of adherence may require additional support, including the involvement of significant others, periodic individual meetings, or group booster sessions.

Adult↗

PubMed2001

DDT, PAH and PCB in sediments from the intertidal zone of the Bohai Sea and the Yellow Sea.

Current contents of persistent organic contaminants, polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs) and the congeners (naphthalene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, chrysene, benzo(a)anthracene, benzo(a)pyrene and benzo(e)pyrene), DDTs and metabolites in the intertidal sediments of the Bohai Sea and the Yellow Sea were studied. The mean levels of DDTs, PAHs and PCBs were 177.52, 877.2 and 3.4 ng g-1 dry weight, respectively. The spatial trends of the contaminant residue levels were analysed too.

China↗

PubMed2001

Photocatalytic activity of TiO2 films grown on different substrates.

Titanium dioxide films were prepared on glass, indium-tin oxide (ITO) glass and p-type monocrystalline silicon and studied for the photocatalytic degradation of rhodamine B in an aqueous medium. Raman, AFM, and XPS spectroscopic investigations of these films indicated that microstructure of titanium oxide films were greatly affected by the substrate materials. Rutile was confirmed to be easily formed on the surface of ITO glass, and TiO2 tended to grow as closely packed particles that were elongated strips with an average size of 20 nm, and had lovely contrast with the perfectly round particles grown on p-type monocrystalline silicon. Charge transfer between the film and silicon substrate was verified by surface photovoltage spectra. This may be the real reason why the films grown on ITO glass and silicon substrates exhibit higher photocatalytic reactivity than the film on glass substrate. Moreover, the different surface properties also seem to be responsible for the different activity.

Catalysis↗

PubMed2001

Classes of c-KIT activating mutations: proposed mechanisms of action and implications for disease classification and therapy.

Mutations causing constitutive activation of KIT have been shown to be causative in some forms of mastocytosis, and several types of mutations have been associated with myeloproliferative disorders (MPDs), acute myelogenous leukemia (AML), sinonasal lymphomas, and gastrointestinal stromal tumors (GIST). We divide these activating mutation into two types - 'regulatory type' mutations, which affect regulation of the kinase molecule, and 'enzymatic pocket type' mutations, which alter the amino acid sequence directly forming the enzymatic site. KIT inhibitors have been suggested as therapeutic drugs for these conditions, but different types of activating mutations respond differentially to KIT inhibitors, so classification of individuals on the basis of specific mutations is necessary to guide therapy.

Acute Disease↗

PubMed2001

Quantification of solute entry into cochlear perilymph through the round window membrane.

The administration of drugs to the inner ear via the round window membrane is becoming more widely used for both clinical and experimental purposes. The actual drug levels achieved in different regions of the inner ear by this method have not been established. The present study has made use of simulations of solute movements in the cochlear fluids to describe the distribution of a marker solute in the guinea pig cochlear fluid spaces. Simulation parameters were derived from experimental measurements using a marker ion, trimethylphenylammonium (TMPA). The distribution of this ion in the cochlea was monitored without volume disturbance using TMPA-selective microelectrodes sealed into the first and second turns of scala tympani (ST). TMPA was applied to perilymph by irrigation of the intact round window membrane with 2 mM solution. At the end of a 90 min application period, TMPA in the first turn, 1.4 mm from the base of ST, reached an average concentration of 330 microM (standard deviation (S.D.) 147 microM, n = 8). TMPA in the second turn, 7.5 mm from the base of ST reached a concentration of 15 microM (S.D. 33 microM, n = 5). The measured time courses of TMPA concentration change were interpreted using the Washington University Cochlear Fluids Simulator (V 1.4), a public-domain program available on the internet at http ://oto.wustl.edu/cochlea/. Simulations with parameters producing concentration time courses comparable to those measured were: (1) round window permeability: 1.9 x 10(-80 cm/s; (2) ST clearance half-time: 60 min; (3) longitudinal perilymph flow rate: 4.4 nl/min, directed from base to apex. Solute concentrations in apical regions of the cochlea were found to be determined primarily by the rate at which the solute diffuses, balanced by the rate of clearance of the solute from perilymph. Longitudinal perilymph flow was not an important factor in solute distribution unless the bony otic capsule was perforated, which rapidly caused substantial changes to solute distribution. This study demonstrates the basic processes by which substances are distributed in the cochlea and provides a foundation to understand how other applied substances will be distributed in the ear.

Animals↗

PubMed2001

The fractal nature of Escherichia coli biological flocs.

The fractal structures of Escherichia coli biological flocs were characterised in terms of fractal dimension, which is a measurement of how the bacteria in the flocs occupy space. The dimensional analysis methods, based on power law correlations between floc perimeter, projected area and maximum length, were used to determine the one- and two-dimensional fractal dimensions (D(1) and D(2)) of E. coli flocs formed by flocculation in chitosan solution with a concentration of 10.0 mg chitosan per g dry cell weight (DCW), giving D(1)=1.07+/-0.06 and D(2)=1.70+/-0.08 (+/-S.D.). The three-dimensional fractal dimension (D(3)) of the E. coli flocs was determined by the two-slopes method, using cumulative size distributions of floc length and solid volume, to be 1.99+/-0.08 (+/-S.D.), which is close to the value of D(3)=2.14+/-0.04 (+/-S.D.) measured by the small angle light scattering method. The results demonstrate that E. coli flocs flocculated with chitosan have a fractal nature, as their fractal dimensions D(1), D(2) and D(3) differ from the values of 1, 2 and 3 expected for the spherical Euclidean object, respectively.

Journal Article↗

PubMed2001

The association of perceived health, clinical status, and initiation of HAART (highly active antiretroviral therapy) in adolescents.

PURPOSE: To examine factors associated with the initiation of highly active antiretroviral therapy (HAART) in adolescents to understand better how current National Institutes of Health (NIH) Guidelines are being used in practice. METHODS: HIV infected and HAART-naive adolescents seen at 15 REACH clinical sites were selected. Repeated measures methodology using generalized estimating equations was applied to identify associations between subject demographic characteristics, risk behaviors, perceived health, and clinical status with the outcome measure of HAART initiation during the first 24 study months. RESULTS: A total of 219 subjects were eligible for analysis; HAART was prescribed in 115 (53%). Significant univariate associations with HAART prescription included lower CD4(+) T cell counts (OR = 1.7, 95% CI: 1.1-2.6), higher viral loads (OR = 2.7, 95% CI: 1.5-5.0), and calendar year of HAART prescription (OR as high as 2.4, 95% CI: 1.1-5.2). Multivariate results showed that after controlling for CD4(+) T cell counts below 500 cells/mm(3), higher plasma HIV-1 RNA (<or=10,000 copies per ml), and temporal factors, having a high school diploma/GED but no further education (OR = 2.7, 95% CI: 1.3-5.5) and subject's perception of poor health status (OR = .987; 95% CI: .975- .999) were independently associated with prescription of HAART. HAART was most likely to be prescribed during the first half of 1998 in this cohort (OR = 10.8; 95% CI: 4.0-29.0). CONCLUSIONS: In this first ever study of HAART prescription in adolescents infected with HIV, perception of poor health status and having a high school diploma/GED were independently associated with prescription of HAART suggesting that the personal decision to accept therapy is related to the belief that one's health is deteriorating and that the decision to prescribe therapy may be linked in some fashion to the prescriber's assessment of the patient's ability to master the regimen as well as clinical status.

Adolescent↗

PubMed2001

Incident pregnancy rates in HIV infected and HIV uninfected at-risk adolescents.

PURPOSE: To compare pregnancy incidence between HIV infected and HIV uninfected adolescents over a 3-year period and to characterize factors that differentiate pregnant from nonpregnant HIV infected females. METHODS: Female adolescents enrolled in Reaching for Excellence in Adolescent Care and Health (REACH), a national cohort study, and nonpregnant at baseline comprised the sample (n = 345). Subject information on pregnancy, risk behavior, and psychosocial characteristics was obtained through interview, chart review, physical examination and laboratory data collected every 3 months. Incident pregnancy rate was analyzed using Cox proportional hazards modeling; the predictors of incident pregnancy were evaluated using repeated measures analysis. RESULTS: Ninety-four pregnancies were identified over 3 years. No significant difference in pregnancy incidence was detected between HIV infected and uninfected females (20.6 and 28.4 per 100 person-years, respectively, p = .16). However, for adolescents with living children at entry, HIV infected females were significantly less likely to become pregnant than HIV uninfected (HR = .45; p = .03). Among HIV infected adolescents, significant predictors of incident pregnancy were older age (p = .01) and not using hormonal contraception (p = .00), whereas increased spiritual hope and passive problem-solving capacity were protective against pregnancy (p = .02, and.05, respectively). Multivariate analysis revealed pregnancy prior to study entry to be predictive for (OR = 3.0; 95% CI: 1.2-7.7), and increased spiritual hope to be protective (OR = .4; 95% CI: .2-.9) against incident pregnancy in HIV infected females without the hormonal contraceptive variable in the model. CONCLUSIONS: The pregnancy rate is high in this study population. Further research is needed into its determinants and attenuating factors, particularly the role of spiritual elements, to design better contraceptive services and reproduction-related education targeting high-risk youth.

Adolescent↗

PubMed2001

Correlation between urine and cervical specimens for the detection of cervical Chlamydia trachomatis and Neisseria gonorrhoeae using ligase chain reaction in a cohort of HIV infected and uninfected adolescents.

PURPOSE: (a) To examine the concordance between ligase chain reaction (LCR) results from urine and cervical samples for Chlamydia trachomatis and Neisseria gonorrhoeae in HIV infected and uninfected adolescent women, and (b) to examine factors that may influence the concordance of LCR results in this population. METHODS: Baseline specimens from 269 of 334 female subjects enrolled in a longitudinal study of HIV infection in adolescents were analyzed for C. trachomatis and N. gonorrhoeae using ligase chain reaction (LCR) assays in a central laboratory. Concordance was measured using kappa coefficient with permutation analyses to calculate the difference between HIV status groups. Discordant LCR results were examined for the co-infection with the other microorganism, bacterial vaginosis, or Trichomonas vaginalis. RESULTS: The prevalence of C. trachomatis detected by LCR in the HIV infected and uninfected groups was 19.3% and 12.2%, respectively (p = .16); the prevalence of N. gonorrhoeae was 7.0% and 2.4%, respectively (p = .16). Urine LCR assay sensitivity to detect cervical C. trachomatis infection was 86% (95% CI: 68%-96%) in the HIV infected group and 100% (95% CI: 69%-100%) in the HIV uninfected group. Urine LCR assay sensitivity to detect cervical N. gonorrhoeae infection was 92% (95% CI: 62%-100%) in the HIV infected group. There were only 2 N. gonorrhoeae infections in the HIV uninfected group, and both were urine LCR positive. Differences in sensitivity between HIV infected and HIV uninfected subjects were not statistically significant. Coinfection with N. gonorrhoeae, bacterial vaginosis or Trichomonas vaginalis was not associated with the concordance of urine and cervical LCR results. CONCLUSION: The relatively high sensitivity of urine LCR testing overall suggests that urine screening may be reasonable for sexually active adolescent females with or without HIV infection in situations in which urine screening may be more acceptable than pelvic examinations.

Adolescent↗

PubMed2001

Douching practices among HIV infected and uninfected adolescents in the United States.

PURPOSE: To characterize sexual behaviors and sociodemographic factors that are associated with douching among geographically diverse adolescent women with and without HIV infection. METHODS: HIV infected subjects recruited preferentially and behaviorally comparable high-risk HIV uninfected subjects were enrolled in a prospective HIV study from 15 sites in 13 U.S. cities. Baseline interview data from 1996 to 1999 for females aged 12 to 19 years were analyzed using one-way analysis of variance and multiple logistic regression. RESULTS: Among the 342 females/young women, 74.9% were black (non-Hispanic), 11.1% Hispanic/Latina, and 14.0% white or other race/ethnicity; 63.5% were HIV infected. Young women who had dropped out of high school comprised 23.4% of subjects. In the 3 months before the interview, 179 (52.3%) adolescents had douched at least once. In a multivariable logistic regression model, recent douching was more common among sexually active females (OR = 2.2; 95% CI: 1.2-4.2), Blacks (OR = 2.2; 95% CI: 1.2-4.1 vs. Hispanics/Whites/others), females who dropped out of high school (OR = 2.1; 95% CI: 1.2-3.7), and HIV infected females (OR = 1.7; 95% CI: 1.04-2.7). CONCLUSIONS: In this nationwide study, adolescents who are sexually active, African-American, dropped out of high school, and HIV infected were most likely to douche. Interventions to discourage douching should pay special attention to these populations.

Adolescent↗

PubMed2001

No change in health risk behaviors over time among HIV infected adolescents in care: role of psychological distress.

PURPOSE: To investigate the association of psychological distress and health risk behaviors among HIV infected adolescents. It was hypothesized that higher levels of distress would be associated with increased sexual risk behaviors, and increased use of alcohol and drugs. METHODS: HIV infected adolescents (N = 323) were recruited into an observational study in 15 clinical sites; for the 323 subjects, a total of 1212 visits were used in a repeated measures analysis. Data on depression (using the CES-D), anxiety (manifest anxiety scale), sexual behaviors and alcohol and marijuana use were obtained through computer-assisted self-administered interview. RESULTS: Approximately 65% of the sample was sexually active across all six study visits, with approximately 43% consistently reporting having unprotected sex at last intercourse. Higher levels of depression were associated with frequent alcohol use and with unprotected sex at last intercourse, with depressed adolescents significantly more likely to have had unprotected sex than those who were not depressed. Health anxiety was associated with frequent marijuana use and with recent sexual activity, and physiological anxiety was also associated with recent sexual activity. CONCLUSIONS: Despite the fact that these HIV infected adolescents are all engaged in primary care, overall the sample is maintaining its high-risk sexual behavior. In addition, these adolescents may be self-medicating to deal with health-related anxiety. Health interventions for HIV infected adolescents should examine whether psychological distress is contributing to maintenance health risk behaviors.

Adaptation, Psychological↗

PubMed2001

Recombinant expression of human mannan-binding lectin.

Mannan-binding lectin (MBL) constitutes an important part of the innate immune defence by effecting the deposition of complement on microbial surfaces. MBL deficiency is among the most common primary immunodeficiencies and is associated with recurrent infections and symptoms of poor immune complex clearance. Plasma-derived MBL has been used in reconstitution therapy but concerns over viral contamination and production capacity point to recombinant MBL (rMBL) as a future source of this protein for clinical use. Natural human MBL is an oligomer of up to 18 identical polypeptide chains. The synthesis of rMBL has been accomplished in several mammalian cell lines, however, the recombinant protein differed structurally from natural MBL. In this, study we compare rMBL produced in myeloma cells, Chinese hamster ovary (CHO) cells, human hepatocytes, and human embryonic kidney (HEK) cells. We report that rMBL structurally and functionally similar to natural MBL can be obtained through synthesis in the human embryonic kidney cells followed by selective carbohydrate affinity chromatography.

Carrier Proteins↗

PubMed2001

Transforming growth factor-beta administration modifies cyclosporine A-induced bone loss.

Cyclosporine A (CsA), a potent immunosuppressant used in transplantation, induces increased formation with excess resorption in the rat with resultant osteopenia. These findings are confirmed in the human model. Transforming growth factor-beta (TGF-beta) is reported to be involved in the coupling of bone formation with resorption and in vivo and in vitro stimulates osteoblasts, and in vitro inhibits osteoclasts. CsA stimulates secretion of TGF-beta1 in humans, which, while improving immunosuppression, may also contribute to renal toxicity. This study was performed determine whether exogenously administered TGF-beta would modify the bone effects of CsA. Male Sprague-Dawley rats, 6 months of age, were randomized to receive: TGF-beta and CsA vehicle (group A); TGF-beta 5 microg/kg three times per week and CsA vehicle (group B); TGF-beta vehicle and CsA 10 mg/kg (group C); or TGF-beta 5 microg/kg three times per week and CsA 10 mg/kg (group D). These were compared with control over 28 days. CsA, but not TGF-beta, increased serum 1,25(OH)(2)D levels throughout the study. CsA increased osteocalcin (BGP), but TGF-beta negated this effect. Histomorphometry confirmed the known effects of CsA, whereas TGF-beta alone had no effect. However, in combination, TGF-beta blocked CsA's effect and increased osteoblast recruitment and activity, as reflected by increased percent mineralizing surface, percent osteoid perimeter, bone formation rate (bone volume referent), and activation frequency. Thus, it appears as if TGF-beta administration may have potential in modulating the deleterious bone effects of CsA.

Animals↗