Gradient sperm selection for reproductive techniques in cattle: Is Isolate a suitable replacement for Percoll?

In assisted reproductive techniques, it is essential to perform a sperm selection to obtain spermatozoa with high motility and membrane integrity for in vitro fertilisation (IVF) and high-DNA integrity for intracytoplasmic sperm injection (ICSI). In this study, we evaluated whether Isolate® was a suitable substitute for Percoll® for assisted reproductive techniques. Commercial cryopreserved bovine semen was used after selection in both gradients, and plasma and acrosome membrane integrity, reactive oxygen species (ROS) levels, DNA integrity and mitochondrial membrane potential (ΔΨm) were assessed by flow cytometry. Motility parameters were also evaluated by CASA system. A similar percentage of spermatozoa with intact plasma membrane, acrosome integrity and high ΔΨm was observed in both sperm selection methods, but only Percoll® showed higher percentage of spermatozoa with intact plasma and acrosome membrane compared to the post-thawing group. No differences were observed in the motility, ROS, DNA fragmentation and on the in vitro embryo production in all experimental groups. In conclusion, the selection of bovine spermatozoa with Isolate® generates spermatozoa with similar quality parameters and embryonic development compared to Percoll® providing a suitable alternative sperm selection method for assisted reproductive techniques in this species.

Antifungal activity of the essential oil obtained from Cryptocarya alba against infection in honey bees by Nosema ceranae.

The honeybee disease nosemosis type C is a serious problem since its causative agent, microsporidium Nosema ceranae, is widespread among adult honey bees. Some of the feasible alternative treatments that are used to control this disease are plant extracts. The aim of the present work was to evaluate the effects of essential oils of Chilean plant species, such as Cryptocarya alba, which is used against N. ceranae, and to identify and quantify the majority active compounds in the EO as well as their potential use for the control of nosemosis. Essential oils were obtained using the stripping steam technique with Clevenger equipment and were subsequently analyzed by Gas chromatography-mass spectrometry. Mortality was recorded daily over at least 8days as worker honeybees were exposed to a range of doses of EO dispersed in a sucrose solution. C. alba oil appears to be nontoxic to A. mellifera adults at the tested concentration (the same concentration inhibits the growth of N. ceranae), showing that this oil can be used for the treatment of nosemosis. EO effectiveness was demonstrated against N. ceranae by calculating the percentage of decrease in infected bees from untreated infected groups vs infected groups treated with EO or the reference drug fumagillin. It was determined that a dose of 4µg EO/bee was most effective in controlling N. ceranae development. We determined innocuous doses of C. alba essential oil for honeybees. We demonstrated the antifungal activity of C. alba EO at 4µg/bee against N. ceranae and compared it to its major monoterpenes, such as ß-phellandrene (20µg/bee), eucalyptol (20µg/bee) and α-terpineol (20µg/bee). The major compounds of C. alba EO, α-terpineol, eucalyptol and ß-phellandrene, had significant effects against Apis mellifera infection by N. ceranae, but the antifungal effect of the complete essential oil on N. ceranae was larger than the effect of α-terpineol, eucalyptol or ß- phellandrene separately, showing that C. alba oil may be a candidate for the treatment or prevention of nosemosis.

Tailored Height Gradients in Vertical Nanowire Arrays via Mechanical and Electronic Modulation of Metal-Assisted Chemical Etching.

In current top-down nanofabrication methodologies the design freedom is generally constrained to the two lateral dimensions, and is only limited by the resolution of the employed nanolithographic technique. However, nanostructure height, which relies on certain mask-dependent material deposition or etching techniques, is usually uniform, and on-chip variation of this parameter is difficult and generally limited to very simple patterns. Herein, a novel nanofabrication methodology is presented, which enables the generation of high aspect-ratio nanostructure arrays with height gradients in arbitrary directions by a single and fast etching process. Based on metal-assisted chemical etching using a catalytic gold layer perforated with nanoholes, it is demonstrated how nanostructure arrays with directional height gradients can be accurately tailored by: (i) the control of the mass transport through the nanohole array, (ii) the mechanical properties of the perforated metal layer, and (iii) the conductive coupling to the surrounding gold film to accelerate the local electrochemical etching process. The proposed technique, enabling 20-fold on-chip variation of nanostructure height in a spatial range of a few micrometers, offers a new tool for the creation of novel types of nano-assemblies and metamaterials with interesting technological applications in fields such as nanophotonics, nanophononics, microfluidics or biomechanics.

Plasmon-induced magneto-optical activity in nanosized gold disks.

In this Letter we show that nanostructures made out of pure noble metals can exhibit measurable magneto-optic activity at low magnetic fields. This phenomenon occurs when the localized surface plasmon resonance of the nanostructure is excited in the presence of a static magnetic field parallel to the propagation of incident light. The large magneto-optical response observed comes from an increase of the magnetic Lorentz force induced by the large collective movement of the conduction electrons in the nanostructures when the resonance is excited.

Shape effects in the localized surface plasmon resonance of single nanoholes in thin metal films.

We report on the polarization-dependent optical response of elongated nanoholes in optically thin gold films. We measured elastic scattering spectra of spatially isolated ellipsoidal nanoholes with varying aspect ratio and compared the results to electrodynamic simulations. Both experiments and theory show that the plasmon mode that is polarized parallel to the short axis of the ellipsoidal hole red-shifts with increasing aspect ratio. This behavior is completely opposite to the case of elongated metal particles. We present a simple analytical model that qualitatively explains the observations in terms of the different orientations of the induced dipole moments in holes and particles.

Nanometric control of the distance between plasmonic nanoparticles using optical forces.

We theoretically analyze the optical forces between two nearby silver nanoparticles for the case when the wavelength of the incoming light is close to the localized surface plasmon resonance (LSPR). It is shown that the optical force between the nanoparticles is enhanced by the LSPR and that it changes from attractive to repulsive for wavelengths slightly shorter than the resonance when the polarization of the incident light is parallel to the axis of the dimer. This behavior can be utilized to generate a stable separation distance between the nanoparticles. In the Rayleigh limit, the equilibrium distance is uniquely determined by the real part of the particle polarizability and the wavelength of the incident light. The results suggest that near-field optical forces can be used to manipulate and organize plasmonic nanoparticles with a tunable spatial resolution in the nanometer regime.

L1 cell adhesion molecule promotes resistance to alcohol-induced silencing of growth cone responses to guidance cues.

Alcohol exposure in utero is a common cause of mental retardation, but the targets and mechanisms of action are poorly understood. Several lines of data point toward alterations in cortical connectivity, suggesting that axon guidance may be vulnerable to alcohol exposure. To test this, we asked whether ethanol directly affects cortical axonal growth cone responses to guidance cues. We find that even low concentrations of ethanol (12.5 mM; 57.2 mg/dl) commonly observed in social drinking prevent growth cone responses to three mechanistically independent guidance cues, Semaphorin3A, Lysophosphatidic Acid, and Netrin-1. However, this effect is highly dependent on substrate; axonal growth cones extending on an L1 cell adhesion molecule (L1CAM) substrate retain responsiveness to cues following exposure to ethanol, while those growing on poly-L-lysine or N-cadherin do not. The effects of ethanol on axon extension are, by contrast, quite modest. Quantitative assessments of the effects of ethanol on the surface distribution of L1CAM in growth cones suggest that L1CAM homophilic interactions may be particularly relevant for retaining growth cone responsiveness following ethanol exposure. Together, our findings indicate that ethanol can directly and generally alter growth cone responses to guidance cues, that a substrate of L1CAM effectively antagonizes this effect, and that cortical axonal growth cone vulnerability to ethanol may be predicted in part based on the environment through which they are extending.