Genetic diversity and sex ratio of naked mole rat, Heterocephalus glaber, zoo populations.

The naked mole rat, Heterocephalus glaber, is a highly unusual mammal that displays a complex social system similar to that found in eusocial insects. Colonies of H. glaber are commonly maintained in zoo collections because they represent fascinating educational exhibits for the public. However, little is known about the genetic structure or sex ratio of captive populations of H. glaber. In this study, we developed a set of microsatellite markers to examine genetic variation in three captive zoo populations of H. glaber. We also studied sex ratio of these captive populations. Our goal was to determine levels of genetic variation within, and genetic differences between, captive populations of H. glaber. Overall, we found modest levels of genetic variation in zoo populations. We also uncovered little evidence for inbreeding within the captive populations. However, zoo populations did differ genetically, which may reflect the isolation of captive naked mole rat colonies. Finally, we found no evidence of biased sex ratios within colonies. Overall, our study documents levels of genetic variation and sex ratios in a captive eusocial mammalian population. Our results may provide insight into how to manage captive populations of H. glaber.

Caliber and fitness of the axillary artery as a conduit for large-bore cardiovascular procedures.

OBJECTIVES: We sought to describe the caliber and vascular health of the subclavian and axillary arteries as related to their potential utilization in complex cardiovascular procedures. BACKGROUND: Patients referred for advanced catheter-based therapies frequently have lower extremity peripheral vascular disease that may prohibit the use of large bore arterial catheters. Utilization of the upper extremity peripheral vasculature is rarely considered as an alternative access strategy. This may be due in part to a lack of familiarity with the thoracic vasculature. METHODS AND RESULTS: 208 consecutive patients undergoing routine CTA prior to transcatheter aortic valve replacement were retrospectively evaluated in a systematic analysis of upper and lower extremity vasculature. Minimal luminal diameters (MLDs) for the axillary arteries and iliofemoral arteries were 6.0 ± 1.1 mm and 6.6 ± 1.8 mm respectively. Compared to the iliofemoral arteries, the axillary arteries demonstrated substantially lower rates of significant stenosis (2% vs. 12%, p < 0.01) and significantly lower rates of moderate to severe calcification disease (9% vs. 64%, p < 0.01). Diabetes and tobacco use were independently associated with smaller axillary artery caliber by MLD (p < 0.01) but not with significant stenotic disease. CONCLUSIONS: The axillary arteries are slightly smaller but less frequently diseased than the corresponding iliofemoral vessels.

Investigations of redox magnetohydrodynamic fluid flow at microelectrode arrays using microbeads.

Microbeads are used to track fluid flow over microband electrode arrays to investigate fundamentals of redox magnetohydrodynamics (redox-MHD) in a confined solution. The results may lead toward the design of micro total analysis systems with microfluidics based on the redox-MHD concept. Ion flux was generated by reduction and oxidation of electroactive potassium ferri- and ferrocyanide at selected individually addressable microelectrodes in the array. An external magnetic field was produced by a small, permanent magnet (0.38 T) placed directly below the array with its field perpendicular to the plane of the array. The cross product of ion flux and magnetic field produces a magnetic force (a portion of the Lorentz force equation) that causes the fluid to rotate around the active electrodes. Velocities up to 1.4 mm/s are demonstrated here. The effects on velocities were obtained for different concentrations of redox species, widths of electrodes, gaps between electrodes, and combinations of anodically- and cathodically polarized electrodes. The microbeads allowed mapping of flow patterns and velocities, both parallel and perpendicular to the array chip. The influence of counteracting shear forces, drag along the walls, and reinforcing flow are discussed. A significant result is the fairly flat flow profile across 650 microm, attained between electrodes that are oppositely biased.

Redox magnetohydrodynamic enhancement of stripping voltammetry: toward portable analysis using disposable electrodes, permanent magnets, and small volumes.

The use of redox magnetohydrodynamics (MHD) to enhance the anodic stripping voltammetry (ASV) response of heavy metals has been investigated, with respect to achieving portability: disposable electrodes consisting of screen-printed carbon (SPC) on a low temperature co-fired ceramic (LTCC) substrate, small volumes, and permanent magnets. The analytes tested (Cd(2+), Cu(2+), and Pb(2+)) were codeposited on SPC with Hg(2+) to form a Hg thin film electrode. High concentrations of Fe(3+) were used to produce a high cathodic current which generates a significant Lorentz force in the presence of a magnetic field. This Lorentz force induces solution convection during the deposition step, enhancing the mass transport of analytes to the electrode and increasing their preconcentrated quantity in the mercury thin film. Therefore, larger ASV peaks and improved sensitivities are obtained, compared to analyses performed without a magnet. The effects on ASV signal of varying Hg(2+) concentration (0.10 and 1.0 mM), deposition time (10-600 s), and electrode surface roughness were investigated. In addition, analyses were performed using a real lake water matrix. By using the disposable LTCC-SPC working electrodes in small volumes (150 microL) and with small permanent magnets (0.78 T), peak areas were increased by 75% when compared to the signal obtained in the absence of a magnetic field. A limit of detection of 25 nM for Cd(2+) was observed with only a 1 min preconcentration time.

Feedback-independent Pt nanoelectrodes for shear force-based constant-distance mode scanning electrochemical microscopy.

A new generation of platinum nanoelectrodes for constant-distance mode scanning electrochemical microscopy (CD-SECM) has been prepared, characterized, and used for high spatial resolution electrochemical measurements and visualization of electrochemically induced concentration gradients in microcavities. The probes have long (1-2 cm), narrow quartz tips that were conically polished and have a Pt nanoelectrode that is slightly offset from center. Because of the size and location of the electrode on the probe, it does not exhibit SECM feedback while approaching the analyzed sample surfaces even to distances within a few hundred nanometers. The probe was positioned near the surface while scanning and performing electrochemical measurements through use of nonoptical shear force control of the tip-to-sample distance. Test structures consisted of cylindrically shaped microcavities that are 50 microm in diameter with three individually addressable electrodes: a gold disk at 8-microm depth, a crescent-shaped gold ring at 4-microm depth along the wall, and a top gold electrode at the rim. Different electrodes within the microcavity were used to reduce and oxidize redox species in 250 microL of a solution of 5 mM hexaamineruthenium(III) chloride and 0.1 M potassium chloride, protected from evaporation by mineral oil, while the SECM tip followed the topography of the structures and monitored the current from the oxidation of [Ru(NH3)6]2+. Electrochemically generated concentration profiles were obtained from these complex test structures that are not possible with any other SECM technology at this time.

Factors influencing redox magnetohydrodynamic-induced convection for enhancement of stripping analysis.

Factors affecting the use of redox magnetohydrodynamics (MHD) to enhance the stripping analysis response to heavy metals have been investigated. The analytes were Pb2+, Cd2+, Cu2+, and Tl+ at concentrations ranging from 5 nM to 2 microM. Co-deposition of analytes with Hg2+ (to form a thin Hg film electrode) occurs along with reduction of a high concentration of Fe3+. The Fe3+ provides the high cathodic current necessary to produce a significant Lorentz force, and therefore enhanced convection and larger stripping signals and sensitivities, when the analysis is performed in the presence of an external magnetic field. The effects of varying Fe3+ concentration (1-100 mM), working electrode size (10 microm-3 mm), and magnetic field strengths (0-1.77 T) generated with electromagnets and NdFeB permanent magnets were investigated. Using 100 mM Fe3+ as the MHD-generating redox species at a 3-mm working electrode and in a magnetic field of 1.77 T, peak areas from linear sweep voltammetry were increased by as much as 159 +/- 5%, compared to the signal obtained in the absence of a magnetic field. Experimental detection limits as low as 5 nM were achieved with only a 1-min preconcentration time. A field strength as low as 0.12 T offers some signal enhancement with 100 mM Fe3+. While linear scan anodic stripping voltammetry was used primarily to obtain the signals after the deposition step, potentiometric stripping analysis was also investigated. Redox MHD is an attractive alternative convection method for applications involving sample volumes too small for mechanical stirring or for in-field applications using portable devices that cannot be complicated by the instrumentation required for mechanical stirring.