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J K Critser

Publications and source records attributed to J K Critser.

At least 37 records · Page 2Linked to original sources
PubMed2000

Cryobiology of rat embryos I: determination of zygote membrane permeability coefficients for water and cryoprotectants, their activation energies, and the development of improved cryopreservation methods.

New rat models are being developed at an exponential rate, making improved methods to cryopreserve rat embryos extremely important. However, cryopreservation of rat embryos has proven to be difficult and expensive. In this study, a series of experiments was performed to characterize the fundamental cryobiology of rat fertilized 1-cell embryos (zygotes) and to investigate the effects of different cryoprotective agents (CPAs) and two different plunging temperatures (T(p)) on post-thaw survival of embryos from three genetic backgrounds. In the initial experiments, information on the fundamental cryobiology of rat zygotes was determined, including 1) the hydraulic conductivity in the presence of CPAs (L(p)), 2) the cryoprotectant permeability (P(CPA)), 3) the reflection coefficient (sigma), and 4) the activation energies for these parameters. P(CPA) values were determined for the CPAs, ethylene glycol (EG), dimethyl sulfoxide (DMSO), and propylene glycol (PG). Using this information, a cryopreservation method was developed and the cryosurvival and fetal development of Sprague-Dawley zygotes cryopreserved in either EG, DMSO, or PG and plunged at either -30 or -80 degrees C, were assessed. The highest fetal developmental rates were obtained using a T(p) of -30 degrees C and EG (61.2% +/- 2.4%), which was not different (P > 0.05) from nonfrozen control zygotes (54.6% +/- 3.0%).

Algorithms↗
PubMed2000

Cryobiology of rat embryos II: A theoretical model for the development of interrupted slow freezing procedures.

Current mammalian embryo cryopreservation protocols typically employ an interrupted slow freezing (ISF) procedure. In general, ISF consists of initial slow cooling, which raises the extracellular solute concentration, and results in cell dehydration. Permeating cryoprotective agents (CPAs), such as dimethyl sulfoxide (DMSO), are typically included in the medium to protect the cells against high solute concentrations. As this ISF procedure continues, slow cooling is terminated at an intermediate temperature (T(p)), followed by plunging into liquid nitrogen (LN(2)). If the slow cooling step allowed a critical concentration ([CPA](c)) of CPA to be reached within the cell, the CPA will interact with the remaining intracellular water during rapid cooling, resulting in the majority of the intracellular solution becoming vitrified and preventing damaging intracellular ice formation (IIF). This study presents a theoretical model to develop efficient ISF procedures, on the basis of previously developed data for the rat zygote. The model was used to select values of initial CPA concentrations and slow cooling rates (from initial estimated ranges of 0 to 4 molal DMSO and 0 to 2.5 degrees C/min cooling rates) that would allow the intracellular solute concentration to exceed the critical concentration. The optimal combination was then determined from this range based on minimizing the duration of slow cooling.

Algorithms↗
PubMed1999

Temperature-dependent osmotic behavior of germinal vesicle and metaphase II stage bovine oocytes in the presence of Me2SO in relationship to cryobiology.

Plasma membrane permeability coefficients and their activation energies (Ea) for water (Lp) and dimethyl sulfoxide (PMe2SO) as well as the reflection coefficient (sigma) were determined for germinal vesicle (GV) and metaphase II (MII) bovine oocytes. A micropipette perfusion technique was used with a temperature controlled circulation chamber, which was adapted to a micromanipulator. Experiments were performed at five different temperatures (30, 20, 10, 4 and -3 degrees C). The Kedem and Katchalsky model was assumed and L(p), P(Me2SO) and sigma were estimated. Estimated permeability values from the experimental temperatures were then applied to Arrhenius plots In(Lp) or In(PMe2SO) vs 1/Temperature (K) to estimate the activation energies (Ea) for L(p)Me2SO and P(Me2SO). The estimated E(a) for L(p)Me2SO for GV and MII oocytes were 23.84 Kcal/mol and 8.46 Kcal/mol, respectively. The E(a) for P(Me2SO) were 21.0 Kcal/mol and 23.20 Kcal/mol, respectively. The correlation (r2) for these linear regression plots for GV oocytes were 0.83 and 0.95 for L(p)Me2SO and P(Me2SO), respectively. For MII oocytes, r2 values were 0.95 and 0.99 for L(p)Me2SO and P(Me2SO), respectively. There was a possible discontinuity detected in the Arrhenius plot for L(p)Me2SO for GV oocytes. A significant decrease of the reflection coefficient was observed at 10 degrees C compared to other experimental temperatures. These data provide a fundamental basis that should be taken into account for low temperature preservation of bovine oocytes in the presence of Me2SO.

Animals↗
PubMed1999

Determination of human platelet membrane permeability coefficients using the Kedem-Katchalsky formalism: estimates from two- vs three-parameter fits.

Attempts to cryopreserve human blood platelets have resulted in poor postthaw survival rates and have been inadequate for routine clinical application. As a result, most blood banks maintain platelets in nonfrozen solutions. Using this approach, platelets can be stored for only about 5 days and are then discarded. This situation greatly limits the use of platelet transfusion in clinical practice. Information regarding fundamental cryobiological characteristics can be applied to predict platelet response to cryoprotective agent (CPA) addition/removal and to cooling/warming. Methods can then be engineered to optimize cryopreservation procedures, thereby minimizing platelet damage and maximizing postthaw recovery. It was therefore the purpose of this study to determine some of the necessary biophysical parameters required for this process: (i) plasma membrane hydraulic conductivity (Lp), (ii) cryoprotectant solute permeability coefficient (Ps), (iii) the associated reflection coefficient (sigma), and (iv) their activation energies. The CPAs studied included dimethyl sulfoxide (Me2SO) and propylene glycol at 1.5 M concentration. Permeability was measured at 22, 10, and 4 degrees C using a modified Coulter counter in conjunction with a water-jacketed beaker system for temperature regulation. The Kedem-Katchalsky formalism was used to estimate the parameters using: (1) a three-parameter fit and (2) a two-parameter fit in which a noninteracting value of sigma was calculated. Two-parameter estimates were in closer agreement with previously published values, and these were used in a model to simulate addition and removal of 0.64 M (5%) and 1.0 M (7.8%) Me2SO, the most common CPA currently used in empirically determined platelet cryopreservation protocols.

Blood Platelets↗
PubMed1999

Equations for obtaining melting points for the ternary system ethylene glycol/sodium chloride/water and their application to cryopreservation.

The present study describes the H(2)O-NaCl-ethylene glycol ternary system by using a differential scanning calorimeter to measure melting points (T(m)) of four different ratios (R) of ethylene glycol to NaCl and then devising equations to fit the experimental measurements. Ultimately an equation is derived which characterizes the liquidus surface above the eutectic for any R value in the system. This study focuses on ethylene glycol in part because of recent evidence indicating it may be less toxic to pancreatic islets than Me(2)SO, which is currently used routinely for islet cryopreservation. The resulting physical data and previously determined information regarding the osmotic characteristics of canine pancreatic islets are combined in a mathematical model to describe the volumetric response to equilibrium-rate freezing in varying initial concentrations of ethylene glycol.

Animals↗
PubMed1999

Effects of Percoll separation, cryoprotective agents, and temperature on plasma membrane permeability characteristics of murine spermatozoa and their relevance to cryopreservation.

Cryopreservation of murine spermatozoa would provide an efficient method for preserving important genotypes. However, to date such methods have resulted in low survivals with significant variability. To address this issue, a series of five experiments was performed to determine the cryobiological characteristics of murine spermatozoa. Experiments 1 and 2 investigated the effect of Percoll separation on the hydraulic conductivity (L(p)) of murine spermatozoa. Both Percoll separation and cryoprotective agents (CPAs) decreased the L(p). However, these effects were not additive. Experiment 3 was performed to determine the effect of temperature on L(p) in the presence of cryoprotectants (L(p)(CPA)), cryoprotectant permeability (P(CPA)), and the reflection coefficient (sigma) in spermatozoa from both ICR and B6C3F1 mice. Permeability parameters decreased as temperature decreased, and permeability characteristics differed between strains. In experiments 4 and 5, theoretical simulations for CPA addition and removal were developed and empirically tested. Strain-specific methods for CPA addition and removal based upon the fundamental cryobiological characteristics of murine spermatozoa resulted in higher survivals than current methods or procedures, which were used as controls.

Animals↗
PubMed1998

Effect of developmental stage on bovine oocyte plasma membrane water and cryoprotectant permeability characteristics.

Knowledge of bovine oocyte plasma membrane permeability characteristics at different developmental stages in the presence of cryoprotective agents (CPAs) is limited. The objective of this study was to determine the oolema hydraulic conductivity (Lp), cryoprotectant permeability (P[CPA]), and reflection coefficient (sigma) for immature (germinal vesicle stage, GV) and in vitro-matured (metaphase II, MII) bovine oocytes. Two commonly used cryoprotective agents, dimethyl sulfoxide (DMSO) and ethylene glycol (EG), were studied. Osmometric studies were performed using a micromanipulator connected to an inverted microscope at 22 +/- 2 degrees C. Each oocyte was immobilized via a holding pipette, and osmotically induced volume changes over time (dv/dt) were recorded. The Lp values for GV and MII oocytes in DMSO (L(p)DMSO) were 0.70 +/- 0.06 and 1.14 +/- 0.07 microm/min/atm (mean +/- SEM) and in EG (L(p)EG) were 0.50 +/- 0.06 and 0.83 +/- 0.07 microm/min/atm, respectively. Estimates of P(DMSO) for GV and MII oocytes were 0.36 +/- 0.03 and 0.48 +/- 0.03 microm/sec, and PEG values for GV and MII oocytes were 0.22 +/- 0.03, 0.37 +/- 0.03 microm/sec, respectively. The values for GV and MII oocytes in DMSO (sigma[DMSO]) were 0.86 +/- 0.03 and 0.90 +/- 0.04 and in EG (sigma[EG]) were 0.94 +/- 0.03 and 0.76 +/- 0.04, respectively. These data demonstrate that bovine oolema permeability coefficients to water and cryoprotectants change after in vitro maturation. Furthermore, the bovine oocyte P(DMSO) is higher than the P(EG). These results may provide a biophysical basis for developing criteria for choosing optimal CPAs and for minimizing damage during addition and removal of the CPAs. Additionally, these data support the hypothesis that different procedures may be required for optimal cryopreservation of different oocyte developmental stages.

Animals↗
PubMed1998

Fundamental cryobiology of human hematopoietic progenitor cells. I: Osmotic characteristics and volume distribution.

While methods for the cryopreservation of hematopoietic stem cells are well established, new sources of progenitor cells, such as umbilical cord blood, fetal tissue, and ex vivo expanded progenitor cells, may require refined protocols to achieve optimal recovery after freezing. To predict optimal protocols for cryopreservation of human hematopoietic progenitors, knowledge of fundamental cryobiological characteristics including cell osmotic characteristics, water and cryoprotectant permeability coefficients of cell membrane, and activation energies of these coefficients is required. In this study, we used CD34+CD33- cells isolated from human bone marrow as hematopoietic progenitor cell models/representatives to study the osmotic characteristics of the progenitor cells. Volume distribution and osmotic behavior of the CD34+CD33- cells were determined using two different methods: (a) a shape-independent electronic sizing technique and (b) a shape-dependent optical image analysis. The cell diameter was measured to be 8.2 +/- 1.1 microns (mean +/- SD, n = 1,091,475, the number of donors = 8) using the electronic sizing technique or 8.7 +/- 1.2 microns (mean +/- SD, n = 1508, the number of donors = 6) by image analysis at initial (isotonic) osmolality, 325 mosm/kg. The cell volume change was measured after the cells were exposed and equilibrated to different anisosmotic conditions. The cell volume was found to be a linear function of the reciprocal of the extracellular osmolality (Boyle van't Hoff plot) ranging from 163 to 1505 mosm/kg. The volume fraction of intracellular water which is osmotically active was determined to be 79.5% of the cell volume. It was concluded that human CD34+CD33- cells osmotically behave as ideal osmometers. This information coupled with cell water and cryoprotectant permeability coefficients as well as their activation energies (to be determined in the ongoing research projects) will be used to design optimum conditions for cryopreservation of human hematopoietic progenitor cells.

Antigens, CD↗
PubMed1998

Membrane permeability characteristics of metaphase II mouse oocytes at various temperatures in the presence of Me2SO.

In this study, the hydraulic conductivity (Lp), Me2SO permeability (PMe2SO), and the reflection coefficients (sigma) and their activation energies were determined for Metaphase II (MII) mouse oocytes by exposing them to 1.5 M Me2SO at temperatures of 30, 20, 10, 3, 0, and -3 degrees C. These data were then used to calculate the intracellular concentration of Me2SO at given temperatures. Individual oocytes were immobilized using a holding pipette in 5 microliters of an isosmotic PBS solution and perfused with precooled or prewarmed 1.5 M Me2SO solutions. Oocyte images were video recorded. The cell volume changes were calculated from the measurement of the diameter of the oocytes, assuming a spherical shape. The initial volume of the oocytes in the isoosmotic solution was considered 100%, and relative changes in the volume of the oocytes after exposure to the Me2SO were plotted against time. Mean (means +/- SEM) Lp values in the presence of Me2SO were (LpMe2SO) at 30, 20, 10, 3, 0 and -3 degrees C were determined to be 1.07 +/- 0.03, 0.40 +/- 0.02, 0.18 +/- 0.01, 7.60 x 10(-2) +/- 0.60 x 10(-2), 5.29 x 10(-2) +/- 0.40 x 10(-2), and 3.69 x 10(-2) +/- 0.30 x 10(-2) microns/min/atm, respectively. The PMe2SO values were 3.69 x 10(-3) +/- 0.3 x 10(-3), 1.07 x 10(-3) +/- 0.1 x 10(-3), 2.75 x 10(-4), +/- 0.15 x 10(-4), 7.83 x 10(-5) +/- 0.50 x 10(-5), 5.24 x 10(-5) +/- 0.50 x 10(-5), and 3.69 x 10(-5) +/- 0.40 x 10(-5) cm/min, respectively. The sigma values were 0.70 +/- 0.03, 0.77 +/- 0.04, 0.81 +/- 0.06, 0.91 +/- 0.05, 0.97 +/- 0.03, and 1 +/- 0.04, respectively. The estimated activation energies (Ea) for LpMe2SO, and PMe2SO, and sigma were 16.39, 23.24, and -1.75 Kcal/mol, respectively. These data may provide the fundamental basis for the development of more optimal cryopreservation protocols for MII mouse oocytes.

Animals↗
PubMed1998

Hydraulic conductivity (Lp) and its activation energy (Ea), cryoprotectant agent permeability (Ps) and its Ea, and reflection coefficients (sigma) for golden hamster individual pancreatic islet cell membranes.

Long-term cryopreservation of islets of Langerhans would be advantageous to a clinical islet transplantation program. Fundamental cryobiology utilizes knowledge of basic biophysical characteristics to increase the understanding of the preservation process and possibly increase survival rate. In this study several of these previously unreported characteristics have been determined for individual islet cells isolated from Golden hamster islets. Using an electronic particle counting device and a temperature control apparatus, dynamic volumetric response of individual islet cells to anisosmotic challenges of 1.5 M dimethyl sulfoxide (DMSO) and 1.5 M ethylene glycol (EG) were recorded at four temperatures (8, 22, 28, and 37 degreesC). The resulting curves were fitted using Kedem and Katchalsky equations which describe water flux and cryoprotectant agent (CPA) flux based on hydraulic conductivity (Lp), CPA permeability (Ps), and reflection coefficient (final sigma) for the membrane. For Golden hamster islet cells, Lp, Ps, and final sigma for DMSO at 22 degreesC were found to be 0.23 +/- 0.06 microm/min/atm, 0.79 +/- 0.32 x 10(-3) cm/min, and 0.55 +/- 0.37 (n = 11) (mean +/- SD), respectively. For EG at 22 degreesC, Lp equaled 0.23 +/- 0.06 microm/min/atm, Ps equaled 0.63 +/- 0.20 x 10(-3) cm/min, and final sigma was 0.75 +/- 0.17 (n = 9). Arrhenius plots (ln Lp or ln Ps versus 1/temperature (K)) were created by adding the data from the other three temperatures and the resulting linear regression yielded correlation coefficients (r) of 0.99 for all four plots (Lp and Ps for both CPAs). Activation energies (Ea) of Lp and Ps were calculated from the slopes of the regressions. The values for DMSO were found to be 12.43 and 18.34 kcal/mol for Lp and Ps (four temperatures, total n = 52), respectively. For EG, Ea of Lp was 11.69 kcal/mol and Ea of Ps was 20.35 kcal/mol (four temperatures, total n = 58).

Animals↗
PubMed1998

Mouse spermatozoa in high concentrations of glycerol: chemical toxicity vs osmotic shock at normal and reduced oxygen concentrations.

The cryobiological preservation of mouse spermatozoa has presented difficulties in the form of poor motilities or irreproducibility. We have identified several likely underlying problems. One is that published studies have used concentrations of the cryoprotectant glycerol that are substantially lower (0.3 M) than the approximately 1 M concentrations that are optimal for most cells. Another may arise from the known high susceptibility of mouse sperm to free radical damage. We have identified two contributors to damage from higher concentrations of glycerol, namely, chemical toxicity proportional to concentration and exposure time and osmotic damage arising from too rapid an addition and removal of the glycerol. When toxicity is minimized by restricting the exposure time to 1 or 5 min and osmotic shock is minimized by adding and removing the glycerol stepwise, relatively high percentages of the sperm survive contact with 0.8 M glycerol. Free-radical damage in mouse sperm is known to be proportional to the oxygen concentration. We have determined the consequences of reducing the oxygen to <3% of atmospheric by the use of a bacterial membrane preparation, Oxyrase. Oxyrase reduced damage from centrifugation and substantially reduced damage from osmotic shock; however, it did not significantly reduce glycerol toxicity.

Animals↗
PubMed1998

Fundamental cryobiology of selected African mammalian spermatozoa and its role in biodiversity preservation through the development of genome resource banking.

Fundamental cryobiological characteristics of spermatozoa from threatened or endangered species must be determined for successful cryopreservation techniques to be established. In this study, spermatozoa from four diverse species, impala (Aepyceros melampus), wart hog (Phacochoerus aethiopicus), elephant (Loxodonta africana), and lion (Panthera leo), were collected by electroejaculation or epididymal aspiration. Spermatozoal plasma membrane permeability to water (hydraulic conductivity, Lp) and the osmotically inactive fraction of the sperm cell (Vb) were determined from each species. Changes in cell volume were measured over time using an electronic particle counter. A Kedem-Katchalsky membrane transport model was used to theoretically characterize the data to determine Lp and Vb for each species. In addition to determining plasma membrane characteristics, spermatozoa were also studied to determine their sensitivity to low temperatures and to permeating cryoprotectant solutes. Cells maintained at room temperature (20-22 degrees C) were slowly or rapidly exposed to cold temperatures (1-4 degrees C), and percent motility was estimated to determine the sensitivity of the cells to cooling. Spermatozoa were also in media containing 1 M glycerol, dimethyl sulfoxide or ethylene glycol, and percent motility was measured at 15, 30 and 60 min intervals to determine the sensitivity of the cells to the cryoprotectant agent over time. Results indicate that sperm motility is significantly effected by decreased temperatures and the presence of cryoprotectant agents.

Animals↗
PubMed1998

Antral follicles develop in xenografted cryopreserved African elephant (Loxodonta africana) ovarian tissue.

The preservation of germ plasm from endangered species could augment captive breeding programs aimed at maintaining genetic diversity. Mammalian female germ plasm (oocytes) is extremely difficult to collect and cryopreserve; however, a promising alternative is the cryopreservation of ovarian tissue. In the present study, athymic nude (nu/nu) Balb/C mice were used to evaluate in vivo viability of cryopreserved ovarian tissue from Institute of Cancer Research genotype (ICR) mice or elephants. Female mice were ovariectomized prior to transplant of cryopreserved-thawed ovarian tissue from ICR mice (n=4) or elephants (n=6). Control mice were sham operated (n=4) or ovariectomized (n=5). Transplants were in the ovarian bursa, enabling in vivo ovulation and pregnancies from allografts. Vaginal cytology was monitored daily, and the intervals between and duration of epithelial cells present in smears were evaluated. Appearance of epithelial cells in sham-operated and allografted mice were at intervals of 4.3+/-0.6 and 3.3+/-0.5 days, lasting for 1.4+/-0.1 and 1.6+/-0.2 days, respectively. Sporadic incidence of epithelial cells in ovariectomized animals occurred at longer intervals (8.6+/-3.8 days). Females with xenografted elephant ovarian tissue demonstrated epithelial cells in vaginal smears at intervals of 4.5+/-1.0 days, for 2.5+/-0.5 days duration, which was significantly longer than the other groups (P < 0.05). Histological evaluation of tissues at the time of epithelial cells in smears demonstrated well-developed antral follicles, although oocytes were of poor morphological appearance or only cumulus-like complexes were seen. The nude mouse model is effective for assessing cryopreserved ovarian tissue xenograft function which can support the development of antral follicles.

Animals↗
PubMed1998

Current status of semen banking in the USA.

Anonymous donor sperm banking has been a fundamental aspect of reproductive medicine for several decades. In 1987, >170,000 women in the USA were treated for infertility using artificial insemination. Current estimates suggest that the number of women seeking treatment for infertility has increased markedly since that time; however, there are no accurate, updated data to indicate the magnitude of that increase. Most anonymous donor sperm banks in the USA can be categorized as one of three types based upon administrative structure: (i) physician practice based; (ii) hospital/clinic based; or (iii) commercial corporations. Of these it is estimated that the most common structures are the physician office and hospital/clinic based banks. However, the largest (i.e. those processing the most units) are the for-profit corporate banks. A survey conducted in 1989 found that there were at least 135 sperm banks operating in the USA. More recent information indicates the number of banks to be somewhere between 50 and 150. Guidelines for anonymous donor sperm banking practices have been established by the American Society for Reproductive Medicine and standards have been established by the American Association of Tissue Banks (AATB). The AATB has recently established an inspection and accreditation programme and six anonymous donor banks have been accredited in the last few years. It is anticipated that mandatory registration of all donor banks will be required by the FDA in the near future with mandatory inspection and accreditation to follow shortly thereafter.

Federal Government↗