Mathematical model formulation and validation of water and solute transport in whole hamster pancreatic islets.

Optimization of cryopreservation protocols for cells and tissues requires accurate models of heat and mass transport. Model selection often depends on the configuration of the tissue. Here, a mathematical and conceptual model of water and solute transport for whole hamster pancreatic islets has been developed and experimentally validated incorporating fundamental biophysical data from previous studies on individual hamster islet cells while retaining whole-islet structural information.

Rationally optimized cryopreservation of multiple mouse embryonic stem cell lines: II--Mathematical prediction and experimental validation of optimal cryopreservation protocols.

In Part I, we documented differences in cryopreservation success measured by membrane integrity in four mouse embryonic stem cell (mESC) lines from different genetic backgrounds (BALB/c, CBA, FVB, and 129R1), and we demonstrated a potential biophysical basis for these differences through a comparative study characterizing the membrane permeability characteristics and osmotic tolerance limits of each cell line. Here we use these values to predict optimal cryoprotectants, cooling rates, warming rates, and plunge temperatures. We subsequently verified these predictions experimentally for their effects on post-thaw recovery.

Rationally optimized cryopreservation of multiple mouse embryonic stem cell lines: I--Comparative fundamental cryobiology of multiple mouse embryonic stem cell lines and the implications for embryonic stem cell cryopreservation protocols.

The post-thaw recovery of mouse embryonic stem cells (mESCs) is often assumed to be adequate with current methods. However as this publication will show, this recovery of viable cells actually varies significantly by genetic background. Therefore there is a need to improve the efficiency and reduce the variability of current mESC cryopreservation methods.

Completion of the swine genome will simplify the production of swine as a large animal biomedical model.

Background: Anatomic and physiological similarities to the human make swine an excellent large animal model for human health and disease.

Methods: Cloning from a modified somatic cell, which can be determined in cells prior to making the animal, is the only method available for the production of targeted modifications in swine.

Results: Since some strains of swine are similar in size to humans, technologies that have been developed for swine can be readily adapted to humans and vice versa.

Analytical optimal controls for the state constrained addition and removal of cryoprotective agents.

Cryobiology is a field with enormous scientific, financial, and even cultural impact. Successful cryopreservation of cells and tissues depends on the equilibration of these materials with high concentrations of permeating chemicals (CPAs) such as glycerol or 1,2 propylene glycol. Because cells and tissues are exposed to highly anisosmotic conditions, the resulting gradients cause large volume fluctuations that have been shown to damage cells and tissues.

A general model for the dynamics of cell volume, global stability, and optimal control.

Cell volume and concentration regulation in the presence of changing extracellular environments has been studied for centuries, and recently a general nondimensional model was introduced that encompassed solute and solvent transmembrane flux for a wide variety of solutes and flux mechanisms. Moreover, in many biological applications it is of considerable interest to understand optimal controls for both volume and solute concentrations. Here we examine a natural extension of this general model to an arbitrary number of solutes or solute pathways, show that this system is globally asymptotically stable and controllable, define necessary conditions for time-optimal controls in the arbitrary-solute case, and using a theorem of Boltyanski prove sufficient conditions for these controls in the commonly encountered two-solute case.

Melting point equations for the ternary system water/sodium chloride/ethylene glycol revisited.

Partial phase diagrams are of considerable utility in the development of optimized cryobiological procedures. Recent theoretical predictions of the melting points of ternary solutions of interest to cryobiology have caused us to re-examine measurements that our group made for the ethylene-glycol-sodium chloride-water phase diagram. Here we revisit our previous experiments by measuring melting points at five ethylene-glycol to sodium chloride ratios (R values; R=5, 10, 15, 30, and 45) and five levels of concentration for each ratio.

Note: Microelectromechanical systems Coulter counter for cell monitoring and counting.

This note describes the design, fabrication, and testing of a novel microelectromechanical systems Coulter counter. The Coulter counter will be used to detect and monitor impedance changes of cells as a function of time in response to different experimental extracellular environments. The device consists of SU-8 (negative photoresist) microchannels, vertical electroplated electrodes, polydimethylsiloxane cover, and is divided into a passive mixing region, a focusing region using negative dielectrophoretic forces, and a measuring region defined by multiple electroplated electrode pairs.

Determination of the quaternary phase diagram of the water-ethylene glycol-sucrose-NaCl system and a comparison between two theoretical methods for synthetic phase diagrams.

Characterization of the thermodynamic properties of multi-solute aqueous solutions is of critical importance for biological and biochemical research. For example, the phase diagrams of aqueous systems, containing salts, saccharides, and plasma membrane permeating solutes, are indispensible in the field of cryobiology and pharmacology. However, only a few ternary phase diagrams are currently available for these systems.

Mutational insertion of a ROSA26-EGFP transgene leads to defects in spermiogenesis and male infertility in mice.

Pronuclear injection has been a successful strategy for generating genetically engineered mouse models to better understand the functionality of genes. A characteristic of pronuclear injection is that random integration of the transgene into the genome can disturb a functional gene and result in a phenotype unrelated to the transgene itself. In this study, we have characterized a mouse model containing an insertional mutation that, in the homozygous state, severely affects spermatogenesis as characterized by lack of sperm motility and acrosomal aplasia.

Measurement of the size of intracellular ice crystals in mouse oocytes using a melting point depression method and the influence of intracellular solute concentrations.

Characterization of intracellular ice formed during the cooling procedures of cells significantly benefits the development and optimization design of cryopreservation or cryosurgery techniques. In this study, we investigated the influence of the concentration of extracellular non-permeable and permeable solutes on the melting points of the intracellular ice in mouse oocytes using cryomicroscopy. The results showed that the melting points of the intracellular ice are always lower than the extracellular ice.

Osmotic tolerance limits and membrane permeability characteristics of stallion spermatozoa treated with cholesterol.

Stallion spermatozoa exhibit osmotic damage during the cryopreservation process. Recent studies have shown that the addition of cholesterol to spermatozoal membranes increases the cryosurvival of bull, ram and stallion spermatozoa, but the exact mechanism by which added cholesterol improves cryosurvival is not understood. The objectives of this study were to determine if adding cholesterol to stallion sperm membranes alters the osmotic tolerance limits and membrane permeability characteristics of the spermatozoa.

Measurement of the apparent diffusivity of ethylene glycol in mouse ovaries through rapid MRI and theoretical investigation of cryoprotectant perfusion procedures.

Successful organ cryopreservation will significantly benefit human health and biomedical research. One of the major challenges to this accomplishment is the need for optimization of cryoprotectant agent (CPA) perfusion procedures that involve highly complicated mass transfer processes in organs. The diffusivity of CPA is of critical importance for designing perfusion procedures to minimize the associated toxicity and osmotic damage.

Proceedings of the Conference on Swine in Biomedical Research.

The Conference on Swine in Biomedical Research was held April 2-3, 2008, in San Diego, California. The goal of the conference was to bring together individuals who are using swine as models, creating new swine models, or studying human health and disease. This is the only conference that focuses exclusively on swine models and as such is the premier meeting for investigators who use or develop swine as models for biomedical research.

Osmotic characteristics and fertility of murine spermatozoa collected in different solutions.

Osmotic stress is an important factor that can result in cell damage during cryopreservation. Before ejaculation or collection for cryopreservation, murine spermatozoa are stored in epididymal fluid, a physiologically hyperosmotic environment (approximately 415 mmol/kg). The objectives of this study were to determine the osmotic tolerance limits of sperm motion parameters of ICR and C57BL/6 mouse spermatozoa collected in isosmotic (290 mmol/kg) and hyperosmotic (415 mmol/kg) media, and the effect of the osmolality of sperm collection media on sperm fertility after cryopreservation.

Towards cryopreservation of Greenshell mussel (Perna canaliculus) oocytes.

Cryopreservation is a powerful tool for selective breeding in aquaculture as it enables genetic material from selected stock to be stored and crossed at will. The aim of this study was to develop a method for cryopreserving oocytes of the Greenshelltrade mark mussel (Perna canaliculus), New Zealand's main aquaculture species. The ability of oocytes to be fertilized post-thawing was used as the criterion for success in initial experiments and then subsequently, the ability of frozen oocytes to develop further to D-stage larvae was assessed.

Reversible disassembly of the actin cytoskeleton improves the survival rate and developmental competence of cryopreserved mouse oocytes.

Effective cryopreservation of oocytes is critically needed in many areas of human reproductive medicine and basic science, such as stem cell research. Currently, oocyte cryopreservation has a low success rate. The goal of this study was to understand the mechanisms associated with oocyte cryopreservation through biophysical means using a mouse model.

Cryopreservation and vitrification: recent advances in fertility preservation technologies.

Over the last half the 20th Century, reproductive medicine has become a critically important branch of modern medical science. Fertility preservation is a vital branch of reproductive medicine and involves the preservation of gametes (sperm and oocytes), embryos, and reproductive tissues (ovarian and testicular tissues) for use in artificial reproduction. This technology gives millions of people suffering from reproductive ailments, cancer patients who have their reproductive functions destroyed by therapy (chemotherapy and radiation) and people undergoing sterilization, a chance to conceive.

Progress and prospects in rat genetics: a community view.

The rat is an important system for modeling human disease. Four years ago, the rich 150-year history of rat research was transformed by the sequencing of the rat genome, ushering in an era of exceptional opportunity for identifying genes and pathways underlying disease phenotypes. Genome-wide association studies in human populations have recently provided a direct approach for finding robust genetic associations in common diseases, but identifying the precise genes and their mechanisms of action remains problematic.

Investigations on the heat transport capability of a cryogenic oscillating heat pipe and its application in achieving ultra-fast cooling rates for cell vitrification cryopreservation.

Theoretically, direct vitrification of cell suspensions with relatively low concentrations ( approximately 1 M) of permeating cryoprotective agents (CPA) is suitable for cryopreservation of almost all cell types and can be accomplished by ultra-fast cooling rates that are on the order of 10(6-7) K/min. However, the methods and devices currently available for cell cryopreservation cannot achieve such high cooling rates. In this study, we constructed a novel cryogenic oscillating heat pipe (COHP) using liquid nitrogen as its working fluid and investigated its heat transport capability to assess its application for achieving ultra-fast cooling rates for cell cryopreservation.

An improved cryopreservation method for a mouse embryonic stem cell line.

Embryonic stem (ES) cell lines including the C57BL/6 genetic background are central to projects such as the Knock-Out Mouse Project, North American Conditional Mouse Mutagenesis Program, and European Conditional Mouse Mutagenesis Program, which seek to create thousands of mutant mouse strains using ES cells for the production of human disease models in biomedical research. Crucial to the success of these programs is the ability to efficiently cryopreserve these mutant cell lines for storage and transport. Although the ability to successfully cryopreserve mouse ES cells is often assumed to be adequate, the percent post-thaw recovery of viable cells varies greatly among genetic backgrounds and individual cell lines within a genetic background.

Human oocyte vitrification: the permeability of metaphase II oocytes to water and ethylene glycol and the appliance toward vitrification.

Objective: To determine the permeability of human metaphase II oocytes to ethylene glycol and water in the presence of ethylene glycol, and to use this information to develop a method to vitrify human oocytes.

Design: An incomplete randomized block design.

Setting: A university-affiliated assisted reproductive center.

Osmotic responses and tolerance limits to changes in external osmolalities, and oolemma permeability characteristics, of human in vitro matured MII oocytes.

Background: Oocyte cryopreservation remains a realistic objective, provided that more systematic approaches are applied, such as thorough analysis of the oocyte oolemma permeability to water and diverse cryoprotectants.

Methods: We prospectively investigated volume changes over time at different temperatures (30 degrees C, 22 degrees C and 8 degrees C) of human metaphase II (MII) oocytes (obtained in stimulated ICSI cycles and matured in vitro from the germinal vesicle stage) when exposed to changes in external osmolality. We also investigated human in vitro matured (IVM) oocytes membrane permeability characteristics at 22 degrees C to 1,2-propanediol (PG) and dimethylsulphoxide (DMSO) and at 30 degrees C, 22 degrees C and 8 degrees C to ethylene glycol (EG), and calculated corresponding oocyte oolemma permeability coefficients (Lp and Pcpa).

Detection of mouse parvovirus in Mus musculus gametes, embryos, and ovarian tissues by polymerase chain reaction assay.

We used primary and nested polymerase chain reaction (PCR) assays to determine the presence of mouse parvovirus (MPV) in mouse sperm, oocytes, preimplantation embryos, and ovarian tissues collected from MPV-infected mice. The primary PCR assay detected MPV in 56% of the sperm samples. MPV was not eliminated by passing sperm samples through a Percoll gradient.