High Level of Pre-Treatment HIV-1 Drug Resistance and Its Association with HLA Class I-Mediated Restriction in the Pumwani Sex Worker Cohort

Background: We analyzed the prevalence of pre-antiretroviral therapy (ART) drug resistance mutations (DRMs) in a Kenyan population. We also examined whether host HLA class I genes influence the development of pre-ART DRMs. Methods: The HIV-1 proviral DNAs were amplified from blood samples of 266 ART-naïve women from the Pumwani Sex Worker cohort of Nairobi, Kenya using a nested PCR method. The amplified HIV genomes were sequenced using next-generation sequencing technology. The prevalence of pre-ART DRMs was investigated. Correlation studies were performed between HLA class I alleles and HIV-1 DRMs. Results: Ninety-eight percent of participants had at least one DRM, while 38% had at least one WHO surveillance DRM. M184I was the most prevalent clinically important variant, seen in 37% of participants. The DRMs conferring resistance to one or more integrase strand transfer inhibitors were also found in up to 10% of participants. Eighteen potentially relevant (p < 0.05) positive correlations were found between HLA class 1 alleles and HIV drug-resistant variants. Conclusions: High levels of HIV drug resistance were found in all classes of antiretroviral drugs included in the current first-line ART regimens in Africa. The development of DRMs may be influenced by host HLA class I-restricted immunity.     

Isothermal Vulcanization and Non-Isothermal Degradation Kinetics of XNBR/Epoxy/XNBR-g-Halloysite Nanotubes (HNT) Nanocomposites

The effect of several concentrations of carboxylated nitrile butadiene rubber (XNBR) functionalized halloysite nanotubes (XHNTs) on the vulcanization and degradation kinetics of XNBR/epoxy compounds were evaluated using experimental and theoretical methods. The isothermal vulcanization kinetics were studied at various temperatures by rheometry and differential scanning calorimetry (DSC). The results obtained indicated that the n^th order model could not accurately predict the curing performance. However, the autocatalytic approach can be used to estimate the vulcanization reaction mechanism of XNBR/epoxy/XHNTs nanocomposites. The kinetic parameters related to the degradation of XNBR/epoxy/XHNTs nanocomposites were also assessed using thermogravimetric analysis (TGA). TGA measurements suggested that the grafted nanotubes strongly enhanced the thermal stability of the nanocomposite.     

Dietary Total Antioxidant Capacity and Cardiovascular Disease Risk Factors: A Systematic Review of Observational Studies

Objective: Measurement of dietary total antioxidant capacity (DTAC) is considered a new holistic dietary approach and assesses total antioxidants present in the overall diet. Our aim was to perform a comprehensive review of the literature on the association between DTAC and cardiovascular disease (CVD) risk factors.

Methods: PubMed, Web of Science, and Scopus were used to conduct a comprehensive search for articles published on this topic through September 2017. There was no limit on earliest year of publication. The search was based on the following keywords: dietary total antioxidant capacity, nonenzymatic antioxidant capacity, total radical-trapping antioxidant parameter, ferric reducing ability of plasma, oxygen radical absorbance capacity, Trolox equivalent antioxidant capacity, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), triglycerides (TG), total cholesterol (TC), waist circumference (WC), insulin resistance, homeostatic model assessment of insulin resistance (HOMA-IR), insulin, obesity, glucose, C-reactive protein (CRP), blood pressure (BP), and body mass index. In total, 16 papers were identified for inclusion in the present systematic review.

Results: Most well-designed studies that evaluated associations between DTAC and CVD risk factors showed inverse associations for fasting blood glucose, CRP, BP, and WC and positive associations for HDL-C. However, there was no association between DTAC and LDL-C or TC in any of the studies. Results regarding the association of DTAC with insulin, HOMA-IR, high-sensitivity CRP, and TG in the published literature were inconsistent.

Conclusions: Findings indicated a substantial association between high DTAC and most CVD-related risk factors.     

UiO-66-based metal–organic framework for dispersive solid-phase extraction of vanillylmandelic acid from urine before analysis by capillary electrophoresis

Dispersive solid-phase extraction (DSPE) was developed for the extraction of vanillylmandelic acid (VMA) in urine samples prior to capillary electrophoresis with diode array detection (CE-DAD). Extraction of VMA by DSPE was carried out by direct addition of 7.5 mg of synthesized amino-functionalized UiO-66 (Zr) metal–organic framework adsorbent into the 5 mL sample solution (pH 4.0), followed by sonication and centrifugation. The supernatant layer was discarded, then the sedimented adsorbent was eluted using borate buffer (75 mM, pH 10). Effective extraction parameters including the amount of adsorbent, sample pH, adsorption and desorption time, type, volume and pH of eluent, and type of adsorbent dispersion method were systematically investigated. Under the optimized conditions, linearity of the method was from 40 to 2000 μg L⁻¹ with a correlation coefficient over 0.9948. The method detection and quantification limits were 12 and 40 μg L⁻¹, respectively. The relative standard deviations for intra-and inter-day precision were 2.4 and 2.8% (n = 5), respectively. The extraction recovery and enrichment factor values were 90% and 9.0 respectively.

Dispersive solid-phase extraction (DSPE) was developed for the extraction of vanillylmandelic acid (VMA) in urine samples prior to capillary electrophoresis with diode array detection (CE-DAD).     

Regulation of enamel hardness by its crystallographic dimensions

Enamel is a composite biomaterial comprising a minor organic matrix (~2%) and a hierarchically organized inorganic ultrastructure (~96-98%). Surprisingly, to date there is no available information in the literature regarding the possible role of the enamel ultrastructure on the nanoscale level in tooth macroscopic properties. Understanding this relationship is of special interest for restorative purposes in dentistry. Accordingly, this study was designed to investigate how enamel nanocrystals regulate its hardness. We performed microindentation analysis on 100 extracted human teeth. The tooth enamel hardness was quantified and correlated with changes in enamel chemical composition and crystallographic dimensions obtained from Fourier transform infrared spectroscopy and X-ray diffraction, respectively. Enamel hardness was not related to the variability in organic content, but was associated with the size of apatite crystals along the c-axis. This association followed the Hall-Petch model for polycrystalline materials, indicating that the optimal size of apatite nanocrystals (larger than the critical size) provides enamel with the greatest hardness, which enables teeth to survive the heavy wear over a human lifetime.