Electrically-driven modulation of flow patterns in liquid crystal microfludics.

The flow of liquid crystals in the presence of electric fields is investigated as a possible means of flow control. The Beris-Edwards model is coupled to a free energy incorporating electric field effects. Simulations are conducted in straight channels and in junctions.

Conformational Landscape of α-Halopropiophenones Determined by NMR Reveals Unexpected Patterns and Geometric Constraints.

The conformational features of α-halopropiophenones were investigated to understand the influence of α-halogens on conformation through hyperconjugative interactions, electrostatics, and steric factors. Using NMR, C-H scalar coupling constants were measured in different solvents, revealing a pattern in the conformational equilibria, which we validated by computational means. This behavior arises largely from hyperconjugative effects with the exception of the fluoro-derivatives, which are also influenced by steric and electrostatic interactions.

Next-Generation Tags for Fluorine Nuclear Magnetic Resonance: Designing Amplification of Chemical Shift Sensitivity.

Fluorine NMR is a highly sensitive technique for delineating the conformational states of biomolecules and has shown great utility in drug screening and in understanding protein function. Current fluorinated protein tags leverage the intrinsic chemical shift sensitivity of the F nucleus to detect subtle changes in protein conformation and topology. This chemical shift sensitivity can be amplified by embedding the fluorine or trifluoromethyl reporter within a pyridone.

Insights into the Allosteric Response to Acidity by the NikR Transcription Factor.

NikR (HpNikR) is a nickel-responsive transcription factor that regulates genes involved in nickel homeostasis, which is essential for the survival of this pathogen within the acidic human stomach. HpNikR also responds to drops in pH and regulates genes controlling acid acclimation of the bacteria, independently of nickel. We previously showed that nickel binding biases the conformational ensemble of HpNikR to the more DNA-binding competent states via an allosteric network of residues encompassing the nickel binding sites and the interface between the metal- and DNA-binding domains.

Curvature-mediated programming of liquid crystal microflows.

Despite the recognized role of liquid crystal microfluidics in generating programmable, self-organized and guided flow properties, to date, the flow behavior of LCs within curved channels remains unexplored. Using experiments and numerical simulations, we demonstrate that the curvature of microscale conduits allow programming of liquid crystal (LC) flows. Focusing on a nematic LC flowing through U- and L-shaped channels - two simple yet fundamental curved flow paths - with rectangular cross-section, our results reveal that the curvature of flow path can trigger transverse flow-induced director gradients.

Advances in the study of GPCRs by F NMR.

Crystallography and cryo-electron microscopy have advanced atomic resolution perspectives of inactive and active states of G protein-coupled receptors (GPCRs), alone and in complex with G proteins or arrestin. F NMR can play a role in ascertaining activation mechanisms and understanding the complete energy landscape associated with signal transduction. Fluorinated reporters are introduced biosynthetically via fluorinated amino acid analogs or chemically, via thiol-specific fluorinated reporters.

Allosteric regulation of the nickel-responsive NikR transcription factor from Helicobacter pylori.

Nickel is essential for the survival of the pathogenic bacteria Helicobacter pylori in the fluctuating pH of the human stomach. Due to its inherent toxicity and limited availability, nickel homeostasis is maintained through a network of pathways that are coordinated by the nickel-responsive transcription factor NikR. Nickel binding to H.

Distinct Imprinting Signatures and Biased Differentiation of Human Androgenetic and Parthenogenetic Embryonic Stem Cells.

Genomic imprinting is an epigenetic mechanism that results in parent-of-origin monoallelic expression of specific genes, which precludes uniparental development and underlies various diseases. Here, we explored molecular and developmental aspects of imprinting in humans by generating exclusively paternal human androgenetic embryonic stem cells (aESCs) and comparing them with exclusively maternal parthenogenetic ESCs (pESCs) and bi-parental ESCs, establishing a pluripotent cell system of distinct parental backgrounds. Analyzing the transcriptomes and methylomes of human aESCs, pESCs, and bi-parental ESCs enabled the characterization of regulatory relations at known imprinted regions and uncovered imprinted gene candidates within and outside known imprinted regions.

Detergent- and phospholipid-based reconstitution systems have differential effects on constitutive activity of G-protein-coupled receptors.

A hallmark of G-protein-coupled receptors (GPCRs) is the conversion of external stimuli into specific cellular responses. In this tightly-regulated process, extracellular ligand binding by GPCRs promotes specific conformational changes within the seven transmembrane helices, leading to the coupling and activation of intracellular "transducer" proteins, such as heterotrimeric G proteins. Much of our understanding of the molecular mechanisms that govern GPCR activation is derived from experiments with purified receptors reconstituted in detergent micelles.

Early detection of cryostorage tank failure using a weight-based monitoring system.

Purpose: To study the relationship between liquid nitrogen loss and temperature in cryostorage dewars and develop an early-warning alarm for impending tank failure.

Methods: Cryostorage dewars were placed on custom-engineered scales, and weight and temperature data were continuously monitored in the setting of slow, medium, and fast rate-loss of LN to simulate three scenarios of tank failure.

Results: LN Tank weights and temperatures were continuously monitored and recorded, with a calculated alarm trigger set at 10% weight loss and temperature of - 185 °C.

Understanding Protein Function Through an Ensemble Description: Characterization of Functional States by F NMR.

Protein function is a consequence of a complex and dynamic equilibrium between allosterically coupled functional states. However, it is often difficult to distinguish the representative members of an ensemble by spectroscopic means. F NMR is particularly useful in this regard owing to the sensitivity of its chemical shift to subtle differences in environment.

Genetic Drift Can Compromise Mitochondrial Replacement by Nuclear Transfer in Human Oocytes.

Replacement of mitochondria through nuclear transfer between oocytes of two different women has emerged recently as a strategy for preventing inheritance of mtDNA diseases. Although experiments in human oocytes have shown effective replacement, the consequences of small amounts of mtDNA carryover have not been studied sufficiently. Using human mitochondrial replacement stem cell lines, we show that, even though the low levels of heteroplasmy introduced into human oocytes by mitochondrial carryover during nuclear transfer often vanish, they can sometimes instead result in mtDNA genotypic drift and reversion to the original genotype.

Human embryos commonly form abnormal nuclei during development: a mechanism of DNA damage, embryonic aneuploidy, and developmental arrest.

Study Question: What is the prevalence and developmental significance of morphologic nuclear abnormalities in human preimplantation embryos?

Summary Answer: Nuclear abnormalities are commonly found in human IVF embryos and are associated with DNA damage, aneuploidy, and decreased developmental potential.

What Is Known Already: Early human embryonic development is complicated by genomic errors that occur after fertilization. The appearance of extra-nuclear DNA, which has been observed in IVF, may be a result of such errors.

Site-Specific Labeling of Protein Lysine Residues and N-Terminal Amino Groups with Indoles and Indole-Derivatives.

Indoles and indole-derivatives can be used to site-specifically label proteins on lysine and N-terminal amino groups under mild, nondenaturing reaction conditions. Hen egg white lysozyme (HEWL) and α-lactalbumin were labeled with indole, fluoroindole, or fluoroindole-2-carboxylate via electrophilic aromatic substitutions to lysine side chain Nε- and N-terminal amino imines, formed in situ in the presence of formaldehyde. The reaction is highly site-selective, easily controlled by temperature, and does not eliminate the native charge of the protein, unlike many other common lysine-specific labeling strategies.

Human oocytes reprogram adult somatic nuclei of a type 1 diabetic to diploid pluripotent stem cells.

The transfer of somatic cell nuclei into oocytes can give rise to pluripotent stem cells that are consistently equivalent to embryonic stem cells, holding promise for autologous cell replacement therapy. Although methods to induce pluripotent stem cells from somatic cells by transcription factors are widely used in basic research, numerous differences between induced pluripotent stem cells and embryonic stem cells have been reported, potentially affecting their clinical use. Because of the therapeutic potential of diploid embryonic stem-cell lines derived from adult cells of diseased human subjects, we have systematically investigated the parameters affecting efficiency of blastocyst development and stem-cell derivation.

Behaviour of a premixed flame subjected to acoustic oscillations.

In this paper, a one dimensional premixed laminar methane flame is subjected to acoustic oscillations and studied. The purpose of this analysis is to investigate the effects of acoustic perturbations on the reaction rates of different species, with a view to their respective contribution to thermoacoustic instabilities. Acoustically transparent non reflecting boundary conditions are employed.

Nuclear genome transfer in human oocytes eliminates mitochondrial DNA variants.

Mitochondrial DNA mutations transmitted maternally within the oocyte cytoplasm often cause life-threatening disorders. Here we explore the use of nuclear genome transfer between unfertilized oocytes of two donors to prevent the transmission of mitochondrial mutations. Nuclear genome transfer did not reduce developmental efficiency to the blastocyst stage, and genome integrity was maintained provided that spontaneous oocyte activation was avoided through the transfer of incompletely assembled spindle-chromosome complexes.

Human oocytes reprogram somatic cells to a pluripotent state.

The exchange of the oocyte's genome with the genome of a somatic cell, followed by the derivation of pluripotent stem cells, could enable the generation of specific cells affected in degenerative human diseases. Such cells, carrying the patient's genome, might be useful for cell replacement. Here we report that the development of human oocytes after genome exchange arrests at late cleavage stages in association with transcriptional abnormalities.

Derivation of two new human embryonic stem cell lines from nonviable human embryos.

We report the derivation and characterization of two new human embryonic stem cells (hESC) lines (CU1 and CU2) from embryos with an irreversible loss of integrated organismic function. In addition, we analyzed retrospective data of morphological progression from embryonic day (ED) 5 to ED6 for 2480 embryos not suitable for clinical use to assess grading criteria indicative of loss of viability on ED5. Our analysis indicated that a large proportion of in vitro fertilization (IVF) embryos not suitable for clinical use could be used for hESC derivation.

The added burden of comorbidity in patients with asthma.

Objective: Compare the prevalence of comorbidities in adults with and without asthma in Canada and investigate the association between comorbidities in patients with asthma and the occurrence of asthma symptoms or attacks.

Methods: Survey data from the 2005 Canadian Community Health Survey (CCHS) were analyzed. A total of 132,221 Canadians participated in the national survey; 10,089 adult respondents from 10 Canadian provinces and 3 territories reported having asthma.

Non-viable human embryos as a source of viable cells for embryonic stem cell derivation.

Human embryonic stem cells (hESC) hold great promise for use in regenerative medicine. However, the extraordinary potential of hESC as therapeutic tools is tempered by ethical, moral and political issues surrounding their derivation from human embryos. It has previously been proposed that ethical criteria applied to essential organ donation could be employed for derivation of hESC from irreversibly arrested, and thus organismically dead, human embryos produced during routine IVF procedures.

Optimization of IVF pregnancy outcomes with donor spermatozoa.

Purpose: To identify risk factors for suboptimal IVF outcomes using insemination with donor spermatozoa and to define a lower threshold that may signal a conversion to fertilization by ICSI rather than insemination.

Method: Retrospective, age-matched, case-control study of women undergoing non-donor oocyte IVF cycles using either freshly ejaculated (N=138) or cryopreserved donor spermatozoa (N=69). Associations between method of fertilization, semen sample parameters, and pregnancy rates were analyzed.

Trends in psychostimulant and antidepressant use by children in 2 Canadian provinces.

Objective: We used population-based administrative prescription medication data to examine regional differences in psychostimulant and antidepressant (AD) use among children from 2 Canadian provinces: British Columbia (BC) and Manitoba (MB).

Method: Using 1997 to 2003 prescription data, annual rates of psychostimulant and AD use were determined for children aged 19 years and under in both provinces. Further comparisons of rates were made according to sex, age group, and specific classes of dispensed medications.

Identifying persons with treated asthma using administrative data via latent class modelling.

Objective: To develop a parsimonious model of the respiratory patient population in British Columbia (BC), Canada through latent class modelling (LCM), using administrative data records and to assess conventional case definitions for asthma in relation to model-based case selection.

Data Sources: 1996-2001 data from linked provincial databases containing fee-for-service physician billing records, hospital inpatient separation abstracts, and prescription drug purchase records for 1.9 million BC respiratory patients.