Analysis of polarized-light effects in glass-promoting solutions with applications to cryopreservation and organ banking.

This study presents experimental results and an analysis approach for polarized light effects associated with thermomechanical stress during cooling of glass promoting solutions, with applications to cryopreservation and tissue banking in a process known as vitrification. Polarized light means have been previously integrated into the cryomacroscope-a visualization device to detect physical effects associated with cryopreservation success, such as crystallization, fracture formation, and contamination. The experimental study concerns vitrification in a cuvette, which is a rectangular container. Polarized light modeling in the cuvette is based on subdividing the tridimensional (3D) domain into a series of planar (2D) problems, for which a mathematical solution is available in the literature. The current analysis is based on tracking the accumulated changes in light polarization and magnitude, as it passes through the sequence of planar problems. Results of this study show qualitative agreement in light intensity history and distribution between experimental data and simulated results. The simulated results help explaining differences between 2D and 3D effects in photoelasticity, most notably, the counterintuitive observation that high stress areas may correlate with low light intensity regions based on the particular experimental conditions. Finally, it is suggested that polarized-light analysis must always be accompanied by thermomechanical stress modeling in order to explain 3D effects.

Specimen Behavior in the Electron Beam.

It has long been known that cryo-EM specimens are severely damaged by a level of electron exposure that is much lower than what is needed to obtain high-resolution images from single macromolecules. Perhaps less well appreciated in the cryo-EM literature, the vitreous ice in which samples are suspended is equally sensitivity to radiation damage. This chapter provides a review of several fundamental topics such as inelastic scattering of electrons, radiation chemistry, and radiation biology, which-together-can help one to understand why radiation damage occurs so "easily." This chapter also addresses the issue of beam-induced motion that occurs at even lower levels of electron exposure. While specimen charging may be a contributor to this motion, it is argued that both radiation-induced relief of preexisting stress and damage-induced generation of additional stress may be the dominant causes of radiation-induced movement.

Vitrificación de espermatozoides: una alternativa a la inyección intracitoplasmática de espermatozoides en paciente con oligoastenozoospermia severa / Vitrification sperm: An alternative to intracytoplasmic sperm injection in oligoasthenozoospermic patient

El tratamiento de elección para pacientes con oligozoospermia severa es la inyección intracitoplasmática de espermatozoides (ICSI), pero su alto coste limita su aplicación en países cuyos sistemas de salud no cubren este procedimiento médico. La nueva técnica de vitrificación permite almacenar espermatozoides post selección espermática hasta obtener la concentración mínima para realizar ciclos de inseminación intrauterina (IIU). Se presenta este caso clínico de un recién nacido sano, tras dicha técnica, de una pareja (varón 32 años, mujer 31 años) con antecedente de 2ciclos ICSI, uno de los cuales fue exitoso, con un hijo vivo sano. Espermatozoides mótiles fueron obtenidos por swim-up, resuspendidos en medio Vitrisperm®, almacenados en pajuelas a una concentración de 0,5-1,5×106células/ml y vitrificados en contacto directo con nitrógeno líquido. Se realizó estimulación ovárica y la IIU se realizó 36h después de la administración de hCG. La muestra post desvitrificación presentó una concentración de 3,0×106espermatozoides motiles. La evolución de un desarrollo fetal normal fue controlada por ecografía 3D, con el posterior nacimiento por parto cesárea de un recién vivo sano de sexo masculino. Aunque son resultados preliminares, la congelación ultrarrápida, al preservar un alto número de espermatozoides con función conservada, genera una alternativa de tratamiento de bajo coste en pacientes con oligozoospermia severa (AU)

Therapy for patients with severe oligozoospermia is the intracytoplasmic sperm injection (ICSI). However, its high cost limits its application in countries whose health systems do not cover this medical technique. The new vitrification technique makes it possible to store sperm after sperm selection until reaching the minimum concentration for cycles of intrauterine insemination (IUI). A clinical case is reported of a couple (male age 32, female age 31) who underwent 2 ICSI procedures, one of which was successful, resulting in the birth of a healthy, live born son. Motile sperm were obtained by swim-up, resuspended in Vitrisperm® medium, stored in straws at a concentration of 0.5 to 1.5×106cells/mL, and vitrified in direct contact by liquid nitrogen. Ovarian stimulation was induced and IUI was performed 36hours after hCG administration. The post-devitrification sample presented a concentration of 3.0×106 motile sperm. The evolution of normal fetal development was controlled by 3D ultrasound and subsequent birth by cesarean delivery of a healthy male newborn. Although these are preliminary results, ultrarapid freezing preserves the physiological function in a high number of spermatozoa. This generates a low-cost alternative treatment for patients with severe oligozoospermia (AU)

Progress in dimethacrylate-based dental composite technology and curing efficiency.

OBJECTIVES: This work aims to review the key factors affecting the polymerization efficiency of light-activated resin-based composites. The different properties and methods used to evaluate polymerization efficiency will also be critically appraised with focus on the developments in dental photopolymer technology and how recent advances have attempted to improve the shortcomings of contemporary resin composites. METHODS: Apart from the classical literature on the subject, the review focused in particular on papers published since 2009. The literature research was performed in Scopus with the terms "dental resin OR dimethacrylate". The list was screened and all papers relevant to the objectives of this work were included. RESULTS: Though new monomer technologies have been developed and some of them already introduced to the dental market, dimethacrylate-based composites still currently represent the vast majority of commercially available materials for direct restoration. The photopolymerization of resin-based composites has been the subject of numerous publications, which have highlighted the major impact of the setting process on material properties and quality of the final restoration. Many factors affect the polymerization efficiency, be they intrinsic; photoinitiator type and concentration, viscosity (co-monomer composition and ratio, filler content) and optical properties, or extrinsic; light type and spectrum, irradiation parameters (radiant energy, time and irradiance), curing modes, temperature and light guide tip positioning. SIGNIFICANCE: : This review further highlights the apparent need for a more informative approach by manufacturers to relay appropriate information in order for dentists to optimize material properties of resin composites used in daily practice.

[Ca2+ exit from intracellular stores of growing and fully grown native and devitrified porcine oocytes].

The exit of Ca2+ from intracellular stores in growing and fully grown native and devitrified porcine oocytes stimulated by somatotropin and GTP was investigated using fluorescent dye chlortetracycline. In native as well as in the devitrified porcines oocytes, in their fully grown phase, joint action of somatotropin and GTP stimulated additional freeing of Ca2+ from intracellular stores, but during subsequent processing of the cell with nocodazole (a polymerization inhibitor of microtubules), additional exit of calcium did not occur. In the growing phase of native oocytes during the joint acting of somatotropin and GTP additional exit for Ca2+ from the intracellular stores did not occur. Join action of somatotropin and GTP on growing devitrified oocytes lead to the additional freeing of Ca2+ from intracellular stores. Injection of nocodazole inhibited the exit for calcium in growing devitrified oocytes treated with somatotropin and GTP. The data obtained points to the absence of difference of signal transduction mechanisms in growing and fully grown oocytes after devitrification.