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Biomedical subjects

A M Karow

Publications and source records attributed to A M Karow.

At least 19 recordsLinked to original sources
PubMed1992

Effects of temperature, potassium concentration, and sugar on human spermatozoa motility: a cell preservation model from reproductive medicine.

Two experiments were performed in vitro with human sperm from a panel of 11 donors. In both experiments, washed sperm from each donor were divided into four equivolume samples, three of which were resuspended in various formulations of Tyrode's solution and the fourth was resuspended in its own seminal plasma. Each of the four samples was then stored at 37 or 3 degrees C for fixed intervals of 0, 2, 6, 12, and 24 h. Motility was assessed at 37 degrees C for all samples at the end of each interval. The results indicate that sperm survival in vitro at 3 degrees C was significantly enhanced by 20 mM K+ in Tyrode's solution relative to Tyrode's with less K+. A metabolizable sugar such as glucose was essential to maintaining sperm viability in K(+)-free media. The addition of raffinose to media containing glucose improved motility of sperm stored at 3 degrees C for 6 h.

Adolescent↗
PubMed1987

A model for thermal gradients during renal vascular anastomoses.

Quantitative knowledge of warm ischemic intervals is of special importance in organ transplantation. Warm ischemia as a function of time is deleterious to tissue survival. In a laboratory model of a preserved transplantable organ, we determined thermal gradients in pig kidneys similar in size to human kidneys. Sixteen nonviable porcine kidneys cooled to 0 degrees C were placed in an artificial "iliac fossa." The posterior renal wall was in contact with the normothermic fossa. The anterior renal wall was exposed to the ambient temperature of the "operating room." The temperature of both walls was monitored for a minimum of 2 hr. Temperature changes relative to time and kidney weight were studied. The temperature of the posterior wall rises above 20 degrees C within 5 to 10 min; the anterior wall attains this temperature within 30 to 40 min. The thermal gradient between the two walls is significantly greater for larger kidneys (200 g) than for smaller kidneys (100 g). Implications for biochemical pathology are discussed.

Animals↗
PubMed1986

Functional preservation of the mammalian kidney. VII. Autologous transplantation of dog kidneys after treatment with dimethylsulfoxide (2.8 and 4.2 M).

This research demonstrates that dog kidneys perfused with dimethylsulfoxide (Me2SO) in likely cryoprotective concentrations (2.8 M) can survive as the sole source of renal support when autologously transplanted. Kidneys were perfused in vitro with Me2SO in one of two vehicles: solution A (K+-Mg2+-rich) or RPS-2 (K+-glucose-rich). Me2SO concentration in the vehicle was gradually increased to maximum (2.8 or 4.2 M) over a period of 28 to 35 min, held for 5-10 min, then decreased over 55-65 min. All groups except one consisted of 5 kidneys perfused at 25 degrees C. Survivors were dogs living 21 days postoperatively. The first group received kidneys perfused with solution A; 5 dogs survived, serum creatinine on day 21 [Cr], [mean +/- SE] = 1.3 +/- 0.1. The second group received RPS-2 kidneys; 4 survived, Cr=1.4 +/- 0.1. The third group received solution A kidneys with 2.8 M Me2SO; 3 survived, Cr=2.7 +/- 1.3. The fourth group received RPS-2 kidneys with 2.8 M Me2SO; 5 survived, Cr=1.2 +/- 0.2. The fifth group received RPS-2 kidneys with 4.2 M Me2SO; 2 survived, Cr=1.7 +/- 0.3. One group of 6 dogs received kidneys perfused at 10 degrees C with 4.2 M Me2SO in RPS-2; one survived, Cr=1.4. Results demonstrate beneficial interaction of vehicle with Me2SO and the efficacy of 25 degrees C perfusion.

Animals↗
PubMed1985

The influence of temperature on the function of renal cortical slices frozen in various cryoprotectants.

Renal cortical slices were frozen to various subzero temperatures after treatment with 2.1 M of one of three cryoprotectants, dimethyl sulfoxide (Me2SO), ethylene glycol, or glycerol. The effects on tissue [K+]/[Na+] of cooling to these temperatures were tested (using identical procedure times, cooling rates, and warming rates) by holding the slices at each experimental temperature for appropriate periods of time prior to rewarming. The effects of the holding time were assessed by comparison with slices which were cooled and rewarmed with no intermediate holding time. Slices treated with ethylene glycol or glycerol were found to exhibit a continuous decrease in [K+]/[Na+] with lowered temperatures, in contrast to those treated with Me2SO. Slices treated with Me2SO actually experienced a continuous increase in [K+]/[Na+] with lowered temperature (-12 to -33 degrees C). Me2SO does exhibit toxic effects at subzero temperatures. Adverse effects of holding time on viability are seen for Me2SO-treated slices at higher subzero temperatures. These effects were alleviated as the temperature is reduced, suggesting that temperature has a greater effect on survival of renal cortical tissue than Me2SO concentration. However, the toxicity observed at higher subzero temperatures is expected to be of importance, particularly for slowly cooled tissues which are exposed to these temperatures for relatively long periods of time.

Animals↗
PubMed1985

The influence of cooling rate and warming rate on the response of renal cortical slices frozen to -40 degrees C in the presence of 2.1 M cryoprotectant (ethylene glycol, glycerol, or dimethyl sulfoxide).

Renal cortical slices were treated with 2.1 M cryoprotectant in RPS-2 vehicle solution, cooled at one of four rates to -40 degrees C, then immediately warmed at one of four rates to 25 degrees C for determination of the [K+]/[Na+] after a standard incubation period. Results are presented in the form of survival "topographical maps" or surfaces with the x axis representing [K+]/[Na+]; the y axis, cooling rate; and the z axis, warming rate. The rate of temperature change fell in the range of 0.5 to 10 degrees C/min. The results suggest that when RPS-2 vehicle solution is used for 2.1 M cryoprotectants, Me2SO offers the prospect for greatest post-thaw recovery. With this vehicle-cryoprotective agent combination, the greatest post-thaw recovery is attained with cooling-warming combinations of -3, +4, and -0.5, +10 degrees C/min.

Animals↗
PubMed1985

Functional preservation of the mammalian kidney. VI. Viability assessment of rabbit kidneys perfused at 25 degrees C with dimethyl sulfoxide in RPS-2.

The study utilizes an ex vivo perfusion model to evaluate the effects of warm perfusion (25 degrees C) with two K+-rich vehicle solutions (RPS-2 and solution A) on whole rabbit kidneys. The suitability of the solutions as vehicles for introducing cryoprotectant concentrations (2.8 and 3.5 M) of dimethyl sulfoxide (Me2SO) and the effects of the addition of albumin to RPS-2 are also tested. Albumin (5 g/dl) does not appreciably improve the renal perfusion dynamics of RPS-2. Results indicate that both RPS-2 and solution A serve as effective vehicles for the introduction of 2.8 M Me2SO, and the continued investigation of the RPS-2/Me2SO protocol is advocated.

Absorption↗
PubMed1984

Factors influencing renal cryopreservation. I. Effects of three vehicle solutions and the permeation kinetics of three cryoprotectants assessed with rabbit cortical slices.

A renal cortical slice model was used to assess the effects on viability of three vehicle solutions-Krebs-Henseleit (K-H), solution A, and RPS-2--at 25 degrees C. After 120 min incubation no differences in [K+]/[Na+] ratios were found. Tracer techniques were used to study the osmotic effects and permeation kinetics at 25 degrees C of three cryoprotectants (dimethyl sulfoxide (Me2SO), ethylene glycol, and glycerol) and the effect of the vehicle solution (K-H or RPS-2) on Me2SO kinetics. It was found that Me2SO was most permeable and ethylene glycol least, and that ethylene glycol had unusual effects which suggest that it may not act as a simple solute. Differences were found when Me2SO was introduced in K-H and RPS-2 that are believed to be related to the binding properties of Me2SO to cell constituents.

Animals↗
PubMed1984

Factors influencing renal cryopreservation. II. Toxic effects of three cryoprotectants in combination with three vehicle solutions in nonfrozen rabbit cortical slices.

The [K+]/[Na+] ratio of rabbit renal cortical slices was used to examine, at 25 degrees C, the effects on viability of three cryoprotectant agents (CPA) (dimethyl sulfoxide (Me2SO), ethylene glycol, and glycerol) in combination with three vehicle solutions (Krebs-Henseleit (K-H), solution A, and RPS-2). Viability assessment by [K+]/[Na+] for all test solutions was made after incubating the slices in modified Cross-Taggart solution (C-T). With K-H and solution A, all concentrations of ethylene glycol and glycerol resulted in lowered ratios, whereas with Me2SO, concentrations greater than 1.4 M are required to reduce [K+]/[Na+]. With RPS-2 no decrease in the ratios was found until concentrations greater than 2.8 M were reached for all three CPAs. Binding of Me2SO to albumin, studied using [14C]Me2SO, was inhibited by RPS-2 when compared to K-H. Introduction and removal of Me2SO at 10 degrees C allowed an improvement in viability, at higher Me2SO concentrations, as compared to 25 degrees C.

Animals↗
PubMed1983

Factors to consider in the assessment of viability of cryopreserved islets of Langerhans.

With the development of techniques for the isolation and transplantation of pancreatic islets of Langerhans, research has been directed toward low-temperature storage of islets as a means of preservation. For successful islet cryopreservation several factors must be considered. In these studies we have investigated the effects of the cryoprotectant dimethyl sulfoxide (Me2SO) on islet function in the absence of freezing. We have found that Me2SO pretreatment can inhibit subsequent glucose-induced insulin release, but this effect can be minimized by hypothermic exposure to the cryoprotectant using a stepwise addition and dilution protocol for treatment. By studying islet function after freezing and thawing, we have found also that a slow cooling rate (0.3 degrees C/min) results in optimal survival and that islet function can be significantly improved by increasing the duration of post-thaw culture. The results of these studies address only a few of the many questions that need to be answered before clinical application of cryopreserved islet transplantation occurs.

Animals↗
PubMed1983

A functional analysis on isolated rat islets of Langerhans: effects of dimethylsulfoxide and low-temperature preservation.

Cryopreservation of pancreatic islets of Langerhans offers the possibility of storage of sufficient quantities of this tissue for transplantation in the treatment of certain forms of diabetes, as well as providing a means of precise histocompatibility matching. In these studies, the effects of dimethylsulfoxide and various cooling rates on islet function are examined. These studies demonstrate that islets treated with 1.4 M dimethylsulfoxide and slowly cooled at a rate of 0.3 degrees C/min release insulin biphasically upon glucose challenge. In addition, this stimulated release is significantly improved (P less than 0.05) by increasing the duration of post-thaw culture. After thawing, these cryopreserved islets also retain the capacity to synthesize insulin. Islets frozen at faster cooling rates (3, 14, and 48 degrees C/min) exhibit varying degrees of glucose-induced insulin release, indicative of freeze-induced damage. These manifestations of freeze-induced damage include high basal (nonstimulatory) insulin release rates, little or no increase in the stimulated rate versus the nonstimulated rate, and failure of the stimulated release to return to basal levels when the glucose concentration is reduced.

Animals↗