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Biomedical subjects

Simin Liu

Publications and source records attributed to Simin Liu.

At least 37 records · Page 2Linked to original sources
PubMed2005

Cucurbit[10]uril.

Melamine diamine 1 is able to displace CB[5] from the CB[10].CB[5] complex resulting in CB[10].12 and precipitated CB[5].1. We were able to isolate free CB[10] by treatment of CB[10].1 with acetic anhydride followed by washing with MeOH, DMSO, and water. The spacious cavity of CB[10] is able to complex large guests, including a cationic calix[4]arene derivative in its 1,3-alternate form (CB[10].1,3-alt-3). The addition of adamantane carboxylic acid (4) to CB[10].3 triggers a conformational change during the formation of termolecular complex CB[10].cone-3.4.

Bridged-Ring Compounds↗
PubMed2005

The cucurbit[n]uril family: prime components for self-sorting systems.

We determined the values of Ka for a wide range of host-guest complexes of cucurbit[n]uril (CB[n]), where n = 6-8, using 1H NMR competition experiments referenced to absolute binding constants measured by UV/vis titration. We find that the larger homologues--CB[7] and CB[8]--individually maintain the size, shape, and functional group selectivity that typifies the recognition behavior of CB[6]. The cavity of CB[7] is found to effectively host trimethylsilyl groups. Remarkably, the values of Ka for the interaction of CB[7] with adamantane derivatives 22-24 exceeds 10(12) M(-1)! The high levels of selectivity observed for each CB[n] individually is also observed for the CB[n] family collectively. That is, the selectivities of CB[6], CB[7], and CB[8] toward a common guest can be remarkably large. For example, guests 1, 3, and 11 prefer CB[8] relative to CB[7] by factors greater than 10(7), 10(6), and 3000, respectively. Conversely, guests 23 and 24 prefer CB[7] relative to CB[8] by factors greater than 5100 and 990, respectively. The high levels of selectivity observed individually and collectively for the CB[n] family renders them prime components for the preparation of functional biomimetic self-sorting systems.

Biomimetic Materials↗
PubMed2005

Transmission of digital images consisting of white-light dark solitons.

A distortion-free digital image is transmitted through parallel propagation of white-light photovoltaic dark solitons. The waveguide channels induced by white-light dark solitons can guide both the laser beam and the white-light beam well. We determine experimentally the critical separations of the dark solitons in the directions parallel and perpendicular to the crystalline c axis for the given crystal thickness.

Journal Article↗
PubMed2005

Dietary magnesium intake and risk of cardiovascular disease among women.

This study assessed the hypothesis that greater magnesium intake is associated with reduced risk for cardiovascular disease (CVD), including myocardial infarction (MI) and stroke, in a large prospective cohort of women. In 1993, a semi-quantitative food frequency questionnaire was used to assess magnesium intake in 39,876 female health professionals aged 39 to 89 years who had no history of CVD or cancer. During a median of 10 years of follow-up, 1,037 incident cases of CVD were identified, including 280 nonfatal MIs and 368 strokes. After adjustment for age and randomized treatment status, magnesium intake was not significantly associated with risk for incident CVD. Comparing the highest quintile of magnesium intake (median 433 mg/day) with the lowest quintile (median 255 mg/day), the relative risks were 0.87 (95% confidence interval [CI] 0.72 to 1.05, p for trend = 0.24) for total CVD, 0.88 (95% CI 0.70 to 1.12, p for trend = 0.34) for coronary heart disease (CHD), 1.03 (95% CI 0.72 to 1.49, p for trend = 0.96) for nonfatal MI, 1.11 (95% CI 0.61 to 2.00, p for trend = 0.95) for CVD death, and 0.87 (95% CI 0.64 to 1.18, p for trend = 0.55) for total stroke. Additional adjustment for other CVD risk factors did not materially change the observed null associations. In conclusion, the results do not support the hypothesis that magnesium intake reduces the development of CHD, although a modest inverse association with stroke cannot be ruled out.

Adult↗
PubMed2005

Association between consumption of beer, wine, and liquor and plasma concentration of high-sensitivity C-reactive protein in women aged 39 to 89 years.

Although cross-sectional studies have shown an inverse or U-shaped relation between alcohol consumption and plasma concentration of high-sensitivity C-reactive protein (hs-CRP), the associations between specific types of alcoholic beverages--beer, wine, and liquor--and hs-CRP concentrations are less clear. Plasma concentrations of hs-CRP were measured in 11,815 participants in the Women's Health Study who had never used postmenopausal hormones. Alcohol intake was measured using a semiquantitative food-frequency questionnaire. Alcohol consumption had an inverse association with geometric mean hs-CRP concentrations (nondrinkers 1.43 mg/L, 0.1 to 6 g alcohol/day 1.37 mg/L, 6.1 to 12 g alcohol/day 1.29 mg/L, >12 g alcohol/day 1.28 mg/L, p for trend = 0.003). In age-adjusted analyses, beverage preference was a significant predictor of geometric mean hs-CRP concentration. However, after adjustment for body mass index (BMI), beer drinkers who consumed 6.1 to 12 g alcohol/day had a geometric mean hs-CRP concentration of 1.03 mg/L, wine drinkers 1.09 mg/L, liquor drinkers 1.28 mg/L, and combination drinkers 1.09 mg/L (p = 0.43). The association between alcohol and hs-CRP concentration appears to be mediated primarily by ethanol and was independent of the type of alcoholic beverage consumed once BMI was taken into account.

Adult↗
PubMed2005

White-light photorefractive phase mask.

A volume photorefractive phase mask has been fabricated with incoherent white light from an incandescent source in LiNbO3:Fe self-defocusing photorefractive crystal for the first time, to our knowledge. It can guide and modulate a probe white light or a laser beam and can be used to transmit an incoherent dark image as the guided modes of the waveguides induced by white-light dark spatial solitons. This also proves the existence of photorefractive nonlinearity of white light.

Journal Article↗
PubMed2005

SNPHunter: a bioinformatic software for single nucleotide polymorphism data acquisition and management.

BACKGROUND: Single nucleotide polymorphisms (SNPs) provide an important tool in pinpointing susceptibility genes for complex diseases and in unveiling human molecular evolution. Selection and retrieval of an optimal SNP set from publicly available databases have emerged as the foremost bottlenecks in designing large-scale linkage disequilibrium studies, particularly in case-control settings. RESULTS: We describe the architectural structure and implementations of a novel software program, SNPHunter, which allows for both ad hoc-mode and batch-mode SNP search, automatic SNP filtering, and retrieval of SNP data, including physical position, function class, flanking sequences at user-defined lengths, and heterozygosity from NCBI dbSNP. The SNP data extracted from dbSNP via SNPHunter can be exported and saved in plain text format for further down-stream analyses. As an illustration, we applied SNPHunter for selecting SNPs for 10 major candidate genes for type 2 diabetes, including CAPN10, FABP4, IL6, NOS3, PPARG, TNF, UCP2, CRP, ESR1, and AR. CONCLUSION: SNPHunter constitutes an efficient and user-friendly tool for SNP screening, selection, and acquisition. The executable and user's manual are available at http://www.hsph.harvard.edu/ppg/software.htm

Algorithms↗
PubMed2005

Carbohydrate intake, glycemic index, glycemic load, and dietary fiber in relation to risk of stroke in women.

The associations of dietary carbohydrate, glycemic index, and glycemic load with stroke risk were examined among 78,779 US women who were free of cardiovascular disease and diabetes in 1980 and completed a food frequency questionnaire. During an 18-year follow-up, 1,020 stroke cases were documented (including 515 ischemic and 279 hemorrhagic). In analyses adjusting for nondietary risk factors and cereal fiber, carbohydrate intake was associated with elevated risk of hemorrhagic stroke when the extreme quintiles were compared (relative risk = 2.05, 95% confidence interval: 1.10, 3.83; p(trend) = 0.02), but not with ischemic stroke. The positive association between carbohydrate intake and stroke risk was most evident among women with a body mass index of > or =25 kg/m(2). Likewise, dietary glycemic load was positively associated with total stroke among only those women whose body mass index was > or =25 kg/m(2). Cereal fiber intake was inversely associated with total and hemorrhagic stroke risk; for total stroke, relative risk = 0.66 (95% confidence interval: 0.52, 0.83; p(trend) = 0.001) and for hemorrhagic stroke, relative risk = 0.51 (95% confidence interval: 0.33, 0.78; p(trend) = 0.01). Findings suggest that high intake of refined carbohydrate is associated with hemorrhagic stroke risk, particularly among overweight or obese women. In addition, high consumption of cereal fiber was associated with lower risk of total and hemorrhagic stroke.

Adult↗
PubMed2005

Intake of purine-rich foods, protein, and dairy products and relationship to serum levels of uric acid: the Third National Health and Nutrition Examination Survey.

OBJECTIVE: Various commonly consumed foods have long been suspected of affecting the serum uric acid level, but few data are available to support or refute this impression. Our objective was to evaluate the relationship between dietary factors and serum uric acid levels in a nationally representative sample of men and women in the US. METHODS: Using data from 14,809 participants (6,932 men and 7,877 women) ages 20 years and older in the Third National Health and Nutrition Examination Survey (for the years 1988-1994), we examined the relationship between the intake of purine-rich foods, protein, and dairy products and serum levels of uric acid. Diet was assessed with a food-frequency questionnaire. We used multivariate linear regression to adjust for age, sex, total energy intake, body mass index, use of diuretics, beta-blockers, allopurinol, and uricosuric agents, self-reported hypertension and gout, serum creatinine level, and intake of alcohol. RESULTS: The serum uric acid level increased with increasing total meat or seafood intake and decreased with increasing dairy intake. After adjusting for age, the differences in uric acid levels between the extreme quintiles of intake were 0.48 mg/dl for total meat (95% confidence interval [95% CI] 0.34, 0.61; P < 0.001 for trend), 0.16 mg/dl for seafood (95% CI 0.06, 0.27; P = 0.005 for trend), and -0.21 mg/dl for total dairy intake (95% CI -0.37, -0.04; P = 0.02 for trend). After adjusting for other covariates, the differences between the extreme quintiles were attenuated but remained significant (P < 0.05 for all comparisons). The total protein intake was not associated with the serum uric acid level in multivariate analyses (P = 0.74 for trend). Those who consumed milk 1 or more times per day had a lower serum uric acid level than did those who did not drink milk (multivariate difference -0.25 [95% CI -0.40, -0.09]; P < 0.001 for trend). Similarly, those who consumed yogurt at least once every other day had a lower serum uric acid level than did those who did not consume yogurt (multivariate difference -0.26 [95% CI -0.41, -0.12]; P < 0.001 for trend). CONCLUSION: These findings from a nationally representative sample of adults in the US suggest that higher levels of meat and seafood consumption are associated with higher serum levels of uric acid but that total protein intake is not. Dairy consumption was inversely associated with the serum uric acid level.

Adult↗
PubMed2005

A sparse marker extension tree algorithm for selecting the best set of haplotype tagging single nucleotide polymorphisms.

Single nucleotide polymorphisms (SNPs) play a central role in the identification of susceptibility genes for common diseases. Recent empirical studies on human genome have revealed block-like structures, and each block contains a set of haplotype tagging SNPs (htSNPs) that capture a large fraction of the haplotype diversity. Herein, we present an innovative sparse marker extension tree (SMET) algorithm to select optimal htSNP set(s). SMET reduces the search space considerably (compared to full enumeration strategy), and therefore improves computing efficiency. We tested this algorithm on several datasets at three different genomic scales: (1) gene-wide (NOS3, CRP, IL6 PPARA, and TNF), (2) region-wide (a Whitehead Institute inflammatory bowel disease dataset and a UK Graves' disease dataset), and (3) chromosome-wide (chromosome 22) levels. SMET offers geneticists with greater flexibilities in SNP tagging than lossless methods with adjustable haplotype diversity coverage (phi). In simulation studies, we found that (1) an initial sample size of 50 individuals (100 chromosomes) or more is needed for htSNP selection; (2) the SNP tagging strategy is considerably more efficient when the underlying block structure is taken into account; and (3) htSNP sets at 80-90% phi are more cost-effective than the lossless sets in term of relative power, relative risk ratio estimation, and genotyping efforts. Our study suggests that the novel SMET algorithm is a valuable tool for association tests.

Algorithms↗
PubMed2005

Dietary intakes of fruit, vegetables, and fiber, and risk of colorectal cancer in a prospective cohort of women (United States).

OBJECTIVE: Although animal studies suggest an inverse association between consumption of plant foods and risk of colorectal cancer, many observational data have failed to support such an association. We prospectively examined the association between dietary intakes of fruit, vegetables, and fiber and colorectal cancer risk in a large female cohort from the Women's Health Study. METHODS: Among 39,876 healthy women aged >/=45 years at baseline, 36,976 with baseline self-reported information on dietary intakes and other risk factors for colorectal cancer were included in the analyses. During an average follow-up of 10 years, 223 women were diagnosed with colorectal cancer. Intakes of fruit, vegetables, and fiber were assessed by a baseline food-frequency questionnaire. The analyses were carried out using the Cox proportional hazards regression and all tests were two-sided. RESULTS: Intakes of fruit, vegetables, and the specific subgroups were not found to be associated with colorectal cancer risk. Multivariate relative risks (RRs) comparing the highest with lowest quintile were 0.79 (95% CI=0.49-1.27,p for trend =0.30) for fruit intake, and 0.88 (95% CI=0.56-1.38,p for trend=0.30) for vegetables intake. Similarly, intake of total fiber was not associated with colorectal cancer risk; the RR for the highest relative to lowest quintile was 0.75 (95% CI=0.48-1.17,p for trend=0.12). However, higher intake of legume fiber was associated with a lower risk of colorectal cancer; the RR for the highest versus slowest quintile was 0.60 (95% CI=0.40-0.91,p for trend=0.02). CONCLUSIONS: Our data offer little support for associations between intakes of fruit, vegetables, and fiber, and colorectal cancer risk. However, our data suggest that legume fiber and/or other related sources may reduce risk of colorectal cancer.

Colorectal Neoplasms↗
PubMed2005

Dietary intake of whole and refined grain breakfast cereals and weight gain in men.

OBJECTIVE: Prospective studies have suggested that substituting whole grain for refined grain products may lower the risk of overweight and obesity. Breakfast cereal intake is a major source of whole and refined grains and has also been associated with having a lower BMI. The aim of this study was to prospectively assess the association between whole and refined grain breakfast cereal intakes and risk of overweight (BMI >or= 25 kg/m(2)) and weight gain. RESEARCH METHODS AND PROCEDURES: We examined 17,881 U.S. male physicians 40 to 84 years of age in 1982 who were free of cardiovascular disease, diabetes mellitus, and cancer at baseline and reported measures of breakfast cereal intake, weight, and height. RESULTS: Over 8 and 13 years of follow-up, respectively, men who consumed breakfast cereal, regardless of type, consistently weighed less than those who consumed breakfast cereals less often (p value for trend = 0.01). Whole and refined grain breakfast cereal intake was inversely associated with body weight gain over 8 years, after adjustment for age, smoking, baseline BMI, alcohol intake, physical activity, hypertension, high cholesterol, and use of multivitamins. Compared with men who rarely or never consumed breakfast cereals, those who consumed >or=1 serving/d of breakfast cereals were 22% and 12% less likely to become overweight during follow-up periods of 8 and 13 years (relative risk, 0.78 and 0.88; 95% confidence interval, 0.67 to 0.91 and 0.76 to 1.00, respectively). DISCUSSION: BMI and weight gain were inversely associated with intake of breakfast cereals, independently of other risk factors.

Adult↗
PubMed2005

Prevention of type 2 diabetes by diet and lifestyle modification.

Diabetes mellitus is an epidemic of our time. This disease affects nearly 150 million adults worldwide and nearly 11 million in the United States in 2000. Because of the prevalence of obesity and diabetes and associated vascular complications, preventing even a small proportion of cases would save thousands of lives and billions of dollars in healthcare costs and lost productivity. Researchers have made great strides in identifying many lifestyle and dietary factors associated with diabetes, but solidifying the scientific basis for prevention and control of this disease as well as implementation at a national level remains a difficult challenge. The literature on the influence of diet and lifestyle in the development of diabetes is reviewed here, with emphasis on epidemiologic data. We outline a systematic approach to primary and secondary prevention of this disease by evaluating and prioritizing risk factors for which intervention is effective and developing a framework for application of intervention strategies. Effective interventions must target not only the affected individuals but also families, workplaces, schools and communities. Prevention of this devastating disease calls for the identification of culture-sensitive measures that can be applied to the population in general and some high-risk minority groups in particular.

Alcohol Drinking↗
PubMed2005

Associations of dietary flavonoids with risk of type 2 diabetes, and markers of insulin resistance and systemic inflammation in women: a prospective study and cross-sectional analysis.

OBJECTIVE: Flavonoids, as antioxidants, may prevent the progressive impairment of pancreatic beta-cell function due to oxidative stress and may thus reduce the occurrence of type 2 diabetes. The aim of the present study was to examine the association of dietary flavonol and flavone intake with type 2 diabetes, and biomarkers of insulin resistance and systemic inflammation. METHODS: In 38,018 women aged > or =45 y and free of cardiovascular disease, cancer and diabetes with an average 8.8 y of follow-up, we calculated relative risks (RRs) of incident type 2 diabetes (1,614 events) according to dietary intake of total or individual flavonols and flavones and flavonoid-rich foods. We also measured and examined plasma concentrations of insulin, HbA(1C), CRP, and IL-6 in relation to total flavonol and flavone intake among 344 nondiabetic women. RESULTS: During 332,905 person-years of follow-up, none of total flavonols and flavones, quercetin, kaempferol, myricetin, apigenin, and luteolin was significantly associated with risk of type 2 diabetes. Among flavonoid-rich foods, apple and tea consumption was associated with diabetes risk. Women consuming > or =1 apple/d showed a significant 28% reduced risk of type 2 diabetes compared with those who consumed no apples (the multivariate-adjusted RR = 0.72, 95% CI: 0.56, 0.92; p = 0.006 for trend). Tea consumption was also inversely associated with diabetes risk but with a borderline significant trend (> or =4 cups/d vs. none: RR 0.73, 95% CI: 0.52-1.01; p for trend = 0.06). In 344 nondiabetic women, total intake of flavonols and flavones was not significantly related to plasma concentrations of fasting insulin, HbA(1C), CRP, or IL-6. CONCLUSIONS: These results do not support the hypothesis that high intake of flavonols and flavones reduces the development of type 2 diabetes, although we cannot rule out a modest inverse association with intake of apples and tea.

Biomarkers↗
PubMed2005

Fruit and vegetable intake and the risk of cataract in women.

BACKGROUND: Prospective data on cataract in relation to total fruit and vegetable intake are limited. OBJECTIVE: We aimed to examine whether higher fruit and vegetable intake reduces the risk of cataract and cataract extraction in a large, prospective cohort of women. DESIGN: Fruit and vegetable intake was assessed at baseline in 1993 among 39 876 female health professionals with the use of a validated, semiquantitative food-frequency questionnaire. A total of 35 724 of these women were free of a diagnosis of cataract at baseline and were followed for incident cataract and cataract extraction. Cataract was defined as an incident, age-related lens opacity responsible for a reduction in best-corrected visual acuity to 20/30 or worse, based on self-report confirmed by medical record review. Individuals, rather than eyes, were the unit of analysis. RESULTS: During an average of 10 y of follow-up, 2067 cataracts and 1315 cataract extractions were confirmed. Compared with women in the lowest quintile of fruit and vegetable intake, women with higher intakes had modest 10-15% reduced risks of cataract (P for trend < 0.05). For cataract extraction, no significant inverse trend was observed (P for trend = 0.12). CONCLUSION: These prospective data suggest that high intake of fruit and vegetables may have a modest protective effect on cataract.

Aged↗
PubMed2005

Dietary calcium, vitamin D, and the prevalence of metabolic syndrome in middle-aged and older U.S. women.

OBJECTIVE: To examine whether and to what extent intakes of calcium and vitamin D are related to the metabolic syndrome in middle-aged or older women. RESEARCH DESIGN AND METHODS: We analyzed data from 10,066 women aged > or =45 years participating in the Women's Health Study who were free of cardiovascular disease, cancer, or diabetes and who never used postmenopausal hormones. We used multiple logistic regression models to estimate multivariable odds ratios (ORs) and 95% CIs comparing different dietary intake levels of calcium and vitamin D. RESULTS: In age- and calorie-adjusted analyses, higher intakes of total, dietary, and supplemental calcium were significantly and inversely associated with the prevalence of metabolic syndrome. After further adjusting for smoking status, exercise, alcohol intake, multivitamin use, and parental history of myocardial infarction before age 60 years, the ORs of having the metabolic syndrome for increasing quintiles of total calcium intake were 1.00 (reference), 0.82 (95% CI 0.70-0.97), 0.84 (0.71-0.99), 0.70 (0.59-0.83), and 0.64 (0.54-0.77) (P for trend <0.0001). This association was not appreciably altered by additional adjustment for other dietary factors or total vitamin D intake. In contrast, neither total (P for trend = 0.13) nor supplemental (P for trend = 0.45) vitamin D was significantly associated with metabolic syndrome. Dietary vitamin D was inversely associated with prevalence of metabolic syndrome but was not independent of total calcium intake. Similar strong relations between intakes of dairy products and metabolic syndrome were also observed. After adjustment for lifestyle and dietary factors, the multivariable ORs comparing highest with lowest intake categories were 0.66 (0.55-0.80) (P for trend <0.0001) for total dairy products and 0.85 (0.71-1.02) (P for trend = 0.05) for total milk intake. CONCLUSIONS: Our results indicate that intakes of calcium and dairy products may be associated with lower prevalence of the metabolic syndrome in middle-aged and older women.

Aged↗
PubMed2005

Dietary glycemic index, glycemic load, cereal fiber, and plasma adiponectin concentration in diabetic men.

OBJECTIVE: Adiponectin may improve insulin sensitivity, reduce inflammation, and ameliorate glycemic control. However, few studies have evaluated dietary predictors of plasma adiponectin levels, especially among subjects with type 2 diabetes. RESEARCH DESIGN AND METHODS: To examine the associations of dietary glycemic load, glycemic index, and fibers with plasma adiponectin levels, we conducted a cross-sectional analysis in 780 diabetic men from the Health Professionals' Follow-up Study. Dietary information was obtained in 1986, 1990, and 1994 using semiquantitative food-frequency questionnaires. RESULTS: After adjustment for age, BMI, smoking, alcohol consumption, physical activity, aspirin use, HbA(1c), history of hypertension or hypercholesterolemia, and fiber intake, dietary glycemic index and glycemic load were inversely associated with plasma adiponectin in a dose-dependent fashion (P for trend = 0.005 for glycemic index and 0.004 for glycemic load). Adiponectin levels were 13% lower in the highest quintile of dietary glycemic index than in the lowest quintile. For dietary glycemic load, adiponectin levels were 18% lower in the highest quintile than in the lowest. In contrast, high intake of cereal fiber was associated with increased plasma adiponectin levels, adjusting for lifestyle factors and dietary glycemic load (P for trend = 0.003). Adiponectin levels were 19% higher in the highest quintile than in the lowest quintile. Higher magnesium intake was also associated with increased plasma adiponectin. CONCLUSIONS: Diets low in glycemic load and high in fiber may increase plasma adiponectin concentrations in diabetic patients.

Adiponectin↗