Multiple roles of the replication initiation protein Cdtl during helicase loading in S. cerevisiae

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Biology, 2011.Cataloged from PDF version of thesis.Includes bibliographical references.The faithful transmission of genetic information is critical for the events of cell division and propagation. In eukaryotic cells, chromosomal replication is carefully coordinated with the cell cycle to ensure that the entire genome is replicated exactly once prior to cell division. Underpinning this coordination is the tightly regulated loading and activation of the eukaryotic replicative DNA helicase, the hetero-hexameric Mcm2-7 complex. As cells enter G1 phase of the cell cycle, all potential sites of replication initiation are selected by the loading of inactive Mcm2-7 double hexamers. The anti-parallel orientation of the Mcm2-7 hexamers within the double hexamer is proposed to be critical to establish bidirectional sister replisomes upon helicase activation in S phase. Although the proteins involved in helicase loading are known, the mechanism that drives Mcm2-7 double-hexamer formation and loading is unclear. The replication initiation protein Cdtl is essential for loading Mcm2-7 onto origin DNA, but its functions during the loading event are unclear. Through analysis of Cdtl mutations, I identified regions of Cdtl that are essential for Mcm2-7 helicase binding, origin recruitment, and activation. I found that multiple Cdtl molecules are recruited to the origin during the helicase-loading process, and disrupting of the assembly of the multi-Cdtl intermediate prevents Mcm2-7 loading. Finally, I demonstrated that the Nterminal domain of Cdtl, although dispensable for stable helicase loading, is required for subsequent helicase activation and replication initiation. These findings reveal that Cdtl performs multiple functions during helicase loading and influences the competence of loaded Mcm2-7 to subsequently become activated. This work provides insight into the process of Mcm2-7 double-hexamer loading and supports a model in which Cdtl initiates Mcm2-7 double-hexamer formation early in the helicase-loading process.by Thomas J. Takara.Ph.D

Interval valued multi criteria decision making methods for the selection of flexible manufacturing system

In real world multi criteria decision making (MCDM) problem, it is tough to solve a decision matrix with vague and imprecise data. The degree of impreciseness depends on the kind of data avail-able. For interval valued data this impreciseness is less and interval-valued MCDM methods can be effectively used to solve the problem. A flexible manufacturing system (FMS) selection prob-lem was taken into consideration to find the best FMS among available alternatives. An interval extension of CODAS method is proposed in this paper which was used to solve the problem along with two other interval-valued decision-making methods i.e. interval-valued TOPSIS, interval-valued EDAS. All the three methods are distance-based approaches and it was found that the interval-valued CODAS method gave the exact same ranking with that of interval-valued TOPSIS and interval-valued EDAS

Changes in Home Versus Clinic Blood Pressure With Antihypertensive Treatments: A Meta-Analysis

Home blood pressure (HBP) monitoring is recommended for assessing the effects of antihypertensive treatment, but it is not clear how the treatment-induced changes in HBP compare with the changes in clinic blood pressure (CBP). We searched PubMed using the terms “home or self-measured blood pressure,” and selected articles in which the changes in CBP and HBP (using the upper arm oscillometric method) induced by antihypertensive drugs were presented. We performed a systematic review of 30 articles published before March 2008 that included a total of 6794 subjects. As there was significant heterogeneity in most of the outcomes, a random effects model was used for the meta-analyses. The mean changes (±SE) in CBP and HBP (systolic/diastolic) were −15.2±0.03/−10.3±0.03 mm Hg and −12.2±0.04/−8.0±0.04 mm Hg respectively, although there were wide varieties of differences in the reduction between HBP and CBP. The reductions in CBP were correlated with those of HBP (systolic BP; r=0.66, B=0.48, diastolic BP; r=0.71, B=0.52, P<0.001). In 7 studies that also included 24-hour BP monitoring, the reduction of HBP was greater than that of 24-hour BP in systolic (HBP; −12.6±0.06 mm Hg, 24-hour BP; −11.9±0.04 mm Hg, P<0.001). In 5 studies that included daytime and nighttime systolic BP separately, HBP decreased 15% more than daytime ambulatory BP and 30% more than nighttime ambulatory BP. In conclusion, HBP falls ≈20% less than CBP with antihypertensive treatments. Daytime systolic BP falls 15% less and nighttime systolic BP falls 30% less than home systolic BP

Nocturnal nondipping of heart rate predicts cardiovascular events in hypertensive patients

Objective: It has not been established whether nocturnal nondipping of heart rate (HR) predicts future cardiovascular disease (CVD). We performed this study to test the hypothesis that nocturnal nondipping of HR predicts the risk of incident CVD independent of nocturnal blood pressure dipping pattern. Methods: Ambulatory blood pressure monitoring was performed in 457 uncomplicated patients, who were being treated or evaluated for hypertension. They were followed for an average of 72 ± 26 months. Nondipping HR was defined as a night/day HR ratio greater than 0.90. We chose two outcomes for this analysis: CVD events (defined as stroke, myocardial infarction, or sudden cardiac death) and all-cause mortality. Cox regression analyses (stepwise method) were used to estimate hazard ratios and their 95% confidence interval after adjusting for covariates. Results: In univariate analysis, increased sleep HR and nondipping of HR were associated with increased risk of CVD and all-cause mortality, but awake HR was not. In multivariable analyses, HR nondipping status significantly predicted an increased risk of CVD events (hazard ratio, 2.37; 95% confidence interval, 1.22–4.62; P = 0.01), but not for all-cause mortality. Increased 24-h HR was significantly associated with increased risk of all-cause mortality (hazard ratio, 1.67; 95% confidence interval, 1.11–2.51; P = 0.01). Conclusion: The risk of future CVD was shown to be 2.4 times higher in those whose HR does not exhibit the typical nocturnal decline. The relationship was independent of nondipping of SBP and was not dependent on diabetes status or blood pressure level

Night Time Blood Pressure Variability Is a Strong Predictor for Cardiovascular Events in Patients With Type 2 Diabetes

Background: We aimed this study to test the hypothesis that short-term blood pressure (BP) variability and abnormal patterns of diurnal BP variation, evaluated by ambulatory BP (ABP), predicts risk of incident cardiovascular disease (CVD) in patients with type 2 diabetes (T2DM). Methods: ABP monitoring (ABPM) was performed in 300 patients with uncomplicated T2DM without known CVD and without BP medications, who were followed for 54 ± 20 months. The relationships of different measures of BP variability, the presence of abnormal patterns of diurnal BP variation (nondipper, riser, or morning BP surge) and the standard deviations of awake and asleep ABP were determined. Cox proportional hazards models were used to estimate hazard ratios (HRs) and their 95% confidence intervals (CIs) before and after controlling for various covariates. Results: The mean age was 67.8 ± 9.6 years, 48% were male, 253 (84%) had a diagnosis of hypertension, and the mean of the standard deviations of awake systolic BP/diastolic BP (SBP/DBP) were 18 ± 6/11 ± 4 mm Hg, and those of sleep SBP/DBP were 13 ± 5/9 ± 3 mm Hg. During follow-up, there were 29 cardiovascular events. In multivariable analyses, the standard deviations of sleep SBP (HR = 1.08; 95% CI, 1.01–1.16, P < 0.05) and sleep DBP (HR = 1.13; 1.04–1.23, P < 0.01) were independently associated with incident CVD. Neither the nondipper and riser patterns nor the morning BP surge were associated with incident CVD events independently of clinic and 24-h BP levels. Conclusions: Abnormal diurnal BP variation was not a predictor of CVD in patients with T2DM. Night time BP variability was an independent predictor of future incidence of CVD, suggesting that this measure could reflect pathophysiology of T2DM

Ambulatory Blood Pressure Is a Better Marker Than Clinic Blood Pressure in Predicting Cardiovascular Events in Patients With/Without Type 2 Diabetes

Background - The prognostic significance of ambulatory blood pressure (ABP) has not been established in patients with type 2 diabetes (T2DM). Methods - In order to clarify the impact of ABP on cardiovascular prognosis in patients with or without T2DM, we performed ABP monitoring (ABPM) in 1,268 subjects recruited from nine sites in Japan, who were being evaluated for hypertension. The mean age of the patients was 70.4 ± 9.9 years, and 301 of them had diabetes. The patients were followed up for 50 ± 23 months. We investigated the relation between incidence of cardiovascular diseases (CVDs) and different measures of ABP, including three categories of awake systolic blood pressure (SBP 150 mm Hg), sleep SBP (135 mm Hg), and dipping trends in nocturnal blood pressure (BP) (dippers, nondippers, and risers). Cox regression models were used in order to control for classic risk factors. Results - Higher awake and sleep SBPs predicted higher incidence of CVD in patients with and without diabetes. In multivariable analyses, elevated SBPs while awake and asleep predicted increased risk of CVD more accurately than clinic BP did, in both groups of patients. The relationships between ABP level and CVD were similar in both groups. In Kaplan–Meier analyses, the incidence of CVD in nondippers was similar to that in dippers, but risers experienced the highest risk of CVD in both groups (P < 0.01). The riser pattern was associated with a ∼150% increase in risk of CVD, in both groups. Conclusions - These findings suggest that ABPM is a better predictor of cardiovascular risk than clinic BP, and that this holds true for patients with or without T2DM

Tuning the structure, stability and responsivity of polymeric arsenical nanoparticles using polythiol cross-linkers

The use of organic arsenicals in polymer chemistry and biomaterials science is limited despite the distinctive and versatile chemistry of arsenic. The interchangeable oxidation states of arsenic and the subsequent changes in chemical properties make it a promising candidate for redox-responsive materials. Thus, reversible addition–fragmentation chain transfer (RAFT) polymerization has been employed for the first time to synthesize thermoresponsive organic arsenical containing block copolymers. The polymers undergo simultaneous self-assembly and cross-linking, via the organic arsenical pendant groups, under reductive conditions (to reduce As(V) to As(III)) in the presence of polythiol reagents as cross-linkers. The formation of As–S bonds stabilizes the nanoparticles formed (Dh = 19–29 nm) and enables the stability and responsivity to oxidative stress of the particles, in aqueous and model biological solutions, to be tuned as a function of the number of thiols in the cross-linker or the [SH]/[As] stoichiometric ratio. The parent block copolymers and nanoparticles are nontoxic in vitro, and the tunable responsivity of these nanoparticles and the (bio)chemical activity of organic arsenical reagents could be advantageous for targeted drug delivery and the other bio(nano)medical applications. To the best our knowledge, this is the first time that arsenic–thiolate (As–S) bonding has been employed for stimuli-responsive cross-linking of polymeric nanoparticles

Age and the difference between awake ambulatory blood pressure and office blood pressure: a meta-analysis

Background: Ambulatory blood pressure (BP) (ABP) is a better predictor of adverse cardiovascular events than office BP (OBP). Owing to the extensive literature on the ‘white coat effect’, it is widely believed that ABP tends to be lower than OBP, with statements to this effect in Joint National Committee VII. However, recent evidence suggests that the difference varies systematically with age. Methods: We searched PubMed to identify population studies, published before April 2009, which assessed OBP and either ABP or home BP (HBP). On account of significant heterogeneity in the outcomes, random effect models were used for the meta-analyses. Results: OBP increased with age more steeply than awake ABP. OBP became higher than awake systolic/diastolic ABP at the age of 51.3/42.7 years in men (13 studies, N=3562) and 51.9/42.3 years in women (11 studies, N=2585). In the data in which OBP and HBP were measured (eight studies, N=4916), OBP was higher than HBP at all ages. In the data in which OBP, awake ABP, and HBP were all measured (two studies, N=895), awake ABP was higher than HBP at younger ages, becoming similar at the older age. Conclusion: OBP tends to be higher than awake ABP only after the age of 50 years for systolic and after the age of 45 years for diastolic BP, but is lower than ABP at younger ages; in contrast OBP tends to exceed HBP at all ages

Analysis of a Cashew Shell and Fly Ash Rich Brake Liner Composite Material

Hybrid materials collected from organic and inorganic sources, which are traditionally used as brake lining mate- rials, generally include fly ash, cashew shell powder, phenolic resins, aluminium wool, barites, lime powder, car- bon powder and copper powder. The present research focuses on the specific effects produced by fly ash and aims to provide useful indications for the replacement of asbestos due to the health hazards caused by the related fibers. Furthermore, the financial implications related to the use of large-volume use of fly ash, lime stone and cashew shell powder, readily available in most countries in the world, are also discussed. It is shown that many manu- facturing and automotive industries, which are currently experiencing difficulties in meeting the increasing demand for brake lining material, may take advantage from the proposed solution