G.J. Schwartz Research Assistant. K. R. Diller Associate Professor of Mechanical Engineering and Biomedical Engineering Mem. ASME Department of Mechanical Engineering, Biomedical Engineering Center, The University of Texas at Austin, Austin, Tex. 78712 Analysis of the Water Permeability of Human Granulocytes at Subzero Temperatures in the Presence of Extracellular Ice1 The plasma membrane water permeability of human granulocytes in the presence of extracellular ice was determined experimentally on a cryomicroscope. Transient volumes of individual cells were measured at constant subzero temperatures subsequent to ice nucleation. Permeability values were deduced by adjustment of multiple parameters in a model to obtain an optimal fit to the data. The permeability was determined to be a function of both temperature and intracellular solute osmolality, with a reference value at 0°C of 0.407 pmlatm'min and temperature and solute coefficients of 2l8kJ I mol and 1.09 Osm/kg. Introduction Living cells may be exposed to a large osmotic stress during freezing due to a concentrating of extracellular electrolytes resulting from the selective initial formation of ice exterior to the cells. The subsequent response of the cells to the rigors of freezing is determined in large part by the magnitude of water flux which may occur across the plasma membrane as the temperature is lowered. Thus, the membrane water permeability and its thermal coefficient at subzero temperatures are among the most important physiological parameters which govern cell freezing. Measurement of those properties at freezing temperatures present a very challenging task, and is the problem addressed in the present study. The physio-chemical basis of cell freezing can be modeled in simple terms according to the following scenario. Upon nucleation at a subfreezing temperature ice is formed initially in the extracellular solution giving rise to a water activity difference across the plasma membrane. The ice depresses the extracellular water activity in comparison to the liquid intracellular water. In response to this imbalance of activities, water is expressed from the intracellular volume so as to osmotically relax toward a state of thermodynamic equilibrium. As the temperature decreases progressively, the extracellular ice mass continues to grow, resulting in a further reduction of the water activity and a concomitant cell volume diminution. At relatively fast cooling rates the extracellular activity drops more rapidly than can be compensated by cellular dehydration. Consequently the intracellular water activity remains at an elevated level, thereby increasing the likelihood of intracellular ice formation [1, 2] with its associated injury [3]. Conversely, at relatively slow cooling This investigation was sponsored by the National Science Foundation, GrantNo.ECS 8021511. Contributed by the Bioengineering Division for publication in the JOURNAL OF BIOMECHANICAI ENGINEERING. Manuscript received by the Bioengineering Division, February 4, 1983; revised manuscript received July 11, 1983. rates the intracellular and extracellular water activities can be maintained nearly equal via continual adjustment of the intracellular solution concentration by dehydration. Under these conditions intracellular freezing is avoided, although injury may occur by concentrated solution effects [4] or excessive cell shrinkage [5]. In either case, the membrane permeability is a governing factor dictating the cellular response to freezing. Several quantitative models have been published describing the volumetric behavior of cells during freezing [6-10]. Models are useful for explaining observed freezing phenomena, and potentially, for designing optimal cryopreservation protocols. However, quantitative predictions are of questionable validity at this point of time due to a lack of information detailing the magnitude of the membrane permeability to water in frozen cells. Presently, there exist no measured values for the water permeability of human granulocytes at subzero temperatures. For the entire spectrum of research involving freezing cells, there are only a few reports of subzero temperature permeability measurements, with two studies for yeast [11, 12], a report detailing erythrocyte permeability [13], and a study involving a determination of lymphocyte permeability [14]. The current study involves an analysis of the membrane water permeability of human granulocytes at subfreezing temperatures. Permeability values are deduced by matching a cell dehydration model to measured transient cell volumes under osmotic stress induced by extracellular ice formation. The permeability represents an unknown quantity which is adjusted until the model most accurately matches the experimental data. Results indicate that the permeability is a function of both temperature and intracellular solution concentration. Experimental Procedure Human granulocytes were 3 6 0 / V o l . 105, NOVEMBER 1983 harvested by dextran Transactions of the ASME Copyright © 1983 by ASME Downloaded From: http://biomechanical.asmedigitalcollection.asme.org/ on 02/18/2016 Terms of Use: http://www.asme.org/about-asme/terms-of-use GRANULOCYTES IN PLASMA NUCLEATION TEMP(C)--2.00 GRANULOCYTES IN PLASMA NUCLEATION TEMP (C) = -3.00 UJ . LU-. 2: <;' > I Oil UJ <_> to o<> Oc UJl rvi. Mr d CC 2: OZtn CD (M ^ O CM NO. OF TRIALS NO. OF CELLS - 00 0.50 1.00 TIME 1.50 2.00 2.50 NO. OF TRIALS NO. OF CELLS = "bToo" 0.50 1.00 TIME (MIN) 1. 50 2.00 2. 50 (MIN) Fig. 1 Transient cell volumes at a nucleation temperature of - 2 C representing an average of 2 trials with 7 cells Fig. 2 Transient cell volumes at a nucleation temperature of representing an average of 2 trials with 7 cells sedimentation. Venous blood was drawn and mixed with 6 percent T-500 dextran (suspended in citrated, modified Hank's medium). The suspension was maintained at 4 C for 60 min, during which time the various cellular elements differentially settled in the dextran solution. The supernatant containing the granulocytes was pipetted and centrifuged at lOOg for 10 min. The cells were washed once with citrated modified Hank's medium (M.H.M.), followed by centrifugation at lOOg for 10 min. The cell pellet was resuspended with 2 parts autologous plasma and 1 part M.H.M. The cell separation technique reduced the population ratio of erythrocytes to leukocytes from 700:1 to 3:1, with 92 percent of the leukocytes identified as granulocytes. The granulocyte suspension was viable according to diacetyl fluorescien assay for up to 4 hr of liquid storage at near ice-water temperature. The experimental trials were conducted on a cryomicroscope stage [15] equipped with a programmable, microprocessor based temperature regulation system [16]. A l-/xL sample of the granulocyte suspension was positioned on the top surface of the cryostage. Approximately 2 to 6 cells were viewed during each freezing experiment using transmitted bright field illumination. The specimen temperature was monitored via a 25-/xm-dia copper-constantan thermocouple embedded in the cryostage, and was regulated by the microprocessor controller. Specimen cooling was provided by the flow of low temperature nitrogen gas through the cryostage. Complete descriptions of the cryomicroscope and the control system are given by Schwartz and Diller [15] and by Evans and Diller [16], respectively. A series of experiments was conducted in which the temperature of the granulocyte sample was lowered and maintained at a specified constant subzero temperature. The suspension was independently nucleated by briefly spraying a stream of liquid nitrogen onto the surface of the cryostage after which the temperature was continuously maintained at the same constant value. It was possible to freeze the cell •3 C Nomenclature 2 A = area(/xm ) a = water activity B = computational function used in curve-fitting algorithm £,; = intracellular concentration coefficient (Osm-kg - ' ) activation energy (kJ-mol ~') ELP membrane permeability (/xmLn atm "' - min ~') reference permeability (/xmatm "' - min ~') number of moles n ideal gas const (cm3 - atm R mol-'-K-1) T = temperature (K) t = time (s) V = volume (ftm3) v„ = partial molar water volume (/xm3 -mol~') X = osmole fraction Journal of Biomechanical Engineering a = generalized permeability parameters 5a = increment in permeability parameters A = computational function used in curve-fitting algorithm X = interpolating factor for biasing curve-fitting algorithm between gradient search and linearizing techniques 7r = intracellular solution concentration (Osm-kg ~') a = uncertainties in experimentally measured cell volumes 2 X = chi-squared statistic Ax2 = variation in x2 due to increment in permeability parameter values Subscripts b = bound e = electrolyte / = free g = reference value h = hydrated j = iteration parameter for the curve-fitting algorithm k = iteration parameter for the curve-fitting algorithm / = iteration parameter for serial experimentally measured cell volumes s = solute w = water Superscripts ;' = intracellular o = extracellular NOVEMBER 1983, Vol. 105/361 Downloaded From: http://biomechanical.asmedigitalcollection.asme.org/ on 02/18/2016 Terms of Use: http://www.asme.org/about-asme/terms-of-use GRANULOCYTES IN PLASMA NUCLEATION TEMP (C) =-6. 00 GRANULOCYTES IN PLASMA NUCLEATION TEMP (C) = -4. 00 i°4 > >• m IT) UJ (_) O o LU m O CD CM CM NO. NO. ^3. 00 OF TRIALS = 2 OF CELLS = 5 * - 1. 00 1.50 2.00 2. 50 TIME ( M I N ) Fig. 3 Transient cell volumes at a ncleation temperature of -4 C representing an average of 2 trials with 8 cells 0.50 NO. NO. i—i ^Too 1.50 2.50 1.00 2.00 TIME (MIN) Fig. 5 Transient cell volumes at a nucleation temperature of -6 C representing an average of 3 trials with 14 cells GRANULOCYTES IN PLASMA NUCLEATION TEMP (C) = -5. 00 0.50 GRANULOCYTES IN PLASMA NUCLEATION TEMP IC)=-7. 00 „, % o o OF TRIALS = 3 OF CELLS = 10 o (I LU ()<> (_) <> Oo LU I/) O o Mr,' cr 2: D CM O CM NO. OF T R I A L S NO. OF C E L L S = "bTw NO. NO. ^.00 0.50 1.00 1.50 2.00 2.50 TIME (MIN) Fig. 4 Transient cell volumes at a nucleation temperature of -5 C representing an average of 2 trials with 5 cells suspension under these conditions without spontaneously nucleating intracellular ice for temperatures between - 2 and - 10°C. It was possible to effect a continuously isothermal process due in particular to the ability of the cryostagethermal controller apparatus to compensate for the release of latent heat during the phase change process. The sequential images of the freezing granulocytes were recorded on ASA 400 black and white negative film using a motor-driven 35-mm camera. The resultant photomicrographs were analyzed to determine individual cell volumes. The planar area was measured by overlaying a transparent rectangular grid over a projection of the cell 362/Vol. 105, NOVEMBER 1983 OF TRIALS = 3 OF CELLS = 10 0. 50 1.50 2.00 2. 50 (MIN) Fig. 6 Transient cell volumes at a nucleation temperature of - 7 C representing an average of 3 trials with 10 cells 1.00 TIME image. The measured projected area consisted of the number of rectangles enclosed by the cell boundary. The area was converted to volume by assuming a spherical geometry, so that V/V,= (A/Ai)i/2 (1) where the volume and area are normalized relative to the prefreeze values. Figures 1 through 9 present experimental data illustrating the transient nature of the granulocyte volume as a function of extracellular nucleation temperature. Each experimental volume curve represents the average behavior of a minimum of 2 trials, each trial consisting of 2 or more cells. The Transactions of the ASME Downloaded From: http://biomechanical.asmedigitalcollection.asme.org/ on 02/18/2016 Terms of Use: http://www.asme.org/about-asme/terms-of-use GRANULOCYTES IN PLASMA NUCLEflTION TEMP ld = -8. 00 GRANULOCYTES IN.PLASMA NUCLEATION TEMP (C) =-9. 00 <!> Hlli -Jo > in \\ u I ( m M^1 UJ NO. OF TRIALS = 6 NO. OF CELLS = 18 U Q 00 0. 50 l. 00 TIME O CM l. 50 2. 00 2. 50 "b 00 (MIN) Fig. 7 Transient cell volumes at a nucleation temperature of - 8 C representing an average of 6 trials with 18 cells NO. OF TRIALS = 3 NO. OF CELLS = 7 0.50 1.00 TTIME IME 1.50 2.00 2.50 (MIN) (MIN) Fi 9- 8 Transient cell volumes at a nucleation temperature Of - 9 C representing an average of 3 trials with 7 cells GRANULOCYTES IN PLASMA NUCLEATION TEMP (C) = -10. 00 standard deviations of the measured volumes are indicated by the bars associated with each data point. Cell Dehydration Model The dehydration model is designed to consider an idealized biologic cell as an open thermodynamic system having a semipermeable membrane boundary. The system is constrained such that: (a) no pressure gradients exist, (b) temperature differentials are negligible, and (c) no concentration gradients exist except across the plasma membrane. The cell is suspended in a binary solution consisting of water and sodium chloride, whereas the intracellular solution is ternary due to the presence of proteins. The membrane is permeable only to water. Water flux across the semi-permeable membrane can be expressed by dnu ~LpARTln aH (2) dt wherein molar flux is defined in terms of the membrane permeability (Lp), the membrane surface area (A), the ideal gas constant (R), the absolute temperature (7), the partial molar water volume (D"„), and the logarithm of the transmembrane water activity ratio. Chemically, the sodium chloride in solution is assumed to undergo complete ionic dissociation, thus providing two osmoles for every mole of salt. The extracellular solution is assumed ideal, from which the water activity is defined in terms of the osmole water fraction by « l v°=*,/=«,v 0 /(n l v 0 +2V) (3) The extracellular osmole water fraction is determined as a function of temperature from phase data for the watersodium chloride system [17]. The intracellular solution is composed of water, salt, and proteins. The proteins are assumed to exist in a hydrated form, which results in the exclusion of some of the cell water from being available for transport. Levin [18] illustrated that a hydrated water-salt-protein solution, when treated by excluding the bound water from the water activity, could acJournal of Biomechanical Engineering If II, t T o O CN NO. OF TRIALS = 4 NO. OF CELLS = 16 "TJ 00 0.50 1.00 1.50 2.00 2.50 TIME (MIN) Fig. 9 Transient cell volumes at a nucleation temperature of -10 C representing an average of 4 trials with 16 cells curately describe changes in erythrocyte volume. For an ideal, hydrated solution, the water activity is defined as [19] aj =Xv)h> = (nw''--«„&'V(«w' -nwb''+ns') = nv///(nw/ + nj) (4) The free water content is determined from an inactive cell volume of 35 percent of the initial value [20, 21] and the criterion for pre-freezing equality of intracellular and extracellular water activities. The water flux is transformed from a mole to a volume basis by definition nw = V„/vw, or - — =———— A dt Av„ dt (5) NOVEMBER 1983, Vol. 105/363 Downloaded From: http://biomechanical.asmedigitalcollection.asme.org/ on 02/18/2016 Terms of Use: http://www.asme.org/about-asme/terms-of-use Table 1 Measured permeability coefficients for frozen granulocytes. The estimated error is computed from the error matrix of the least squares curve fit of the experimental data. The volume variance is calculated between the experimental and model values. Coefficient L Value pg E LP E ci FROZEN GRANULOCYTES IN PLASMA Estimated Error .407 jjm-atnf -min" .033 218 k j - m o l " 1 14,5 1.09 Osm-kg"1 .174 Overall normalized volume variance = 1.65*10 -3 and the membrane permeability is defined as a function of temperature and intracellular solution concentration by Lp=Lpgexp[(ELp/R)(l/Tg-l/D + Ed(l/T-l/irg)] (6) Substituting equations (3)-(6) into (2) yields the equation used to fit the experimental data. dVw dt _ J ART txV[(ELp/R)(\/Tg-\/T) + £' c / (l/-jr-l/7r„)] In Xw (7) Xw An iterative process was employed to obtain a best fit between experimental transient cell volume data and the cell dehydration model described by equation (7). The applied fitting technique minimized the difference between the simulated and experimental volume curves as judged by the magnitude of the chi-squared statistic, x 2 • An initial estimate for the values of the unknown transport parameters (Lpg, ELP, Eci) was used to solve the model equation, and to calculate the chi-squared statistic, x 2 • Based on these results, a new estimate was then made for the unknown coefficients, generating an updated, lower value of x 2 - Values of the transport coefficients were adjusted by iteration until x2 could no longer be reduced [12]. Practically, the chi-squared statistic, x 2 , can only be made to approach a minimum value as opposed to zero [11, 23, 24]. The iterative solution for the transport coefficients is 3 da. dE,Lp -0, jt dEr, -0 4.00 (KG/0SM) Fig. 10 Membrane permeability of granulocytes to water, calculated as a function of intracellular solution concentration and temperature Permeability Fitting Technique -0, 3.00 1/ 3 0 0 - 1 / T T This nonlinear first-order differential equation is solved by a fourth-order Runge-Kutta algorithm [22]. -o, 2.00 1. 00 0. 00 FROZEN GRANULOCYTES IN PLASMA COOLING RATE (C/MIN) = 5. 00 U J LT> (8) where X 2 («i • < X m ) = X 2 ( £^Pg> p ^Lpi f^ci 0. 00 -10.00 = -20.00 -30.00 TEMPERATURE n Ti\.v„i-vw(tl)}/al2 Saj=A'- B where 364/Vol. 105, NOVEMBER 1983 - 5 0 . 00 Fig. 11 Comparison of model to experimental transient cell volumes for granulocytes cooled at a rate of 5 C/min and with an extracellulai nucleation temperature of - 2 C Determination of the transport coefficients involved two methods for minimizing x 2 • The first technique, referred to as the gradient method, defined convergence in the direction of steepest descent by -dx 2 /do,-. The second approach was to linearize x2 as dx2/d8aj. For the present application the gradient method was applied for conditions far from convergence, and the linearization method for conditions near convergence [23]. This procedure defined a system of equations for the increments, 5a,, l - 4 0 . 00 (C) A',* = Ajk for A'it Jk = A,jk for y* /=1 ^ OUj j*k j*k dak (9) and Transactions of the AS ME Downloaded From: http://biomechanical.asmedigitalcollection.asme.org/ on 02/18/2016 Terms of Use: http://www.asme.org/about-asme/terms-of-use (C) TEMPERATURE FROZEN GRANULOCYTES IN PLRSHfl 1 •w -r 30. ~: - zi.—-^ « IT IN 1 o_ z-E i— r 10. \ : •N, T" . ^.°-. 1_1 - : \ \ " a ' — o_ 0Q-: Q; ; v IE UNFROZEN VALUES 0-0_ U"U oc - :: H . UJ h- \ \ \\ \S v : oc -10. FROZEN VALUES 5 : >t— 0 '0 \ * \ \\ \ <n o_ n r 20. \x *v : ' \ \ \\ \ s \ \ \ ^ _ FROZEN VALUES \\ s \ UNFROZEN VALUES (2 9 1 - \ A "L -: 1. 00 7 " O 1 0.30 0.32 1 0.34 —,— r 0.36 1/TEMPERATURE (1/rO . 0.38 0. 40 • 10" Fig. 12 Comparison of the temperature coefficients of membrane permeability at suprazero and subzero temperatures. Solid lines indicate the temperature range for which permeability values are confirmed by experimental data, whereas broken lines represent extrapolations. 2.00 • 3.00 4.00 5.00 1/. 300-1/tt (KG/0SM) Fig. 13 Comparison of membrane permeability as a function of intracellular solution concentration for coefficients measured at suprazero temperatures with values extrapolated from subzero temperature measurements. Figure 10 illustrates a family of isothermal permeability curves generated from the coefficients given in Table 1 as a -Vw(a, am, ti)} function of intracellular solution concentration. It is apparent that the permeability decreases for higher solute concentrations. In addition, the permeability exhibits the exdv» pected reduction concomitant with decreasing temperature. (ai, . . . ,am, ti). dot: The validity of the deduced permeability coefficients was The computational procedure followed that used by Levin tested by comparing the simulated volumetric behavior of [11, 24]. It began with a determination of x2 using an initial granulocytes with the measured transient volume of cells estimate of the transport coefficients and of X = 0.001. These frozen for a defined thermal protocol. Figure 11 shows the values were used to compare increments defining a new set of results for a cooling rate of 5 C/min in which the simulated coefficients. If the x2 resulting from the new coefficients behavior agreed with the measured values to within the range decreased, then X was decremented; otherwise X remained of experimental uncertainty. constant. This procedure was repeated until the change in x2 between successive iterations converged to a preset minimum Discussion of Permeability Coefficients (in this study Ax2/x2 = 0.05). Prior investigators have characterized the osmotic coefficient of membrane permeability as a function of exPermeability Estimation tracellular solution concentration [14, 25, 26]. In the current The membrane permeability coefficients, Lpg, ELp, and Eci, study the permeability was initially also correlated were determined from the cell volume curves shown in Figs. 1 simultaneously with the temperature and extracellular through 9. The composite set of permeability coefficients, as solution concentration. It was found that, although the described by (6), were deduced by determining the composite derived permeability coefficients simulated granulocyte best fit for the complete set of all experimental data and volume behavior quite well for the constant temperature applying the matching technique described by equations (8) trials, the cell volume response was underpredicted for and (9). Consequently, the coefficients were established over a transient thermal histories of actual preservation protocols spectrum of temperatures from - 2 to -10 C, instead of [27]. Neither was an alternate analysis of the experimental deriving the permeability values at discrete, subzero tem- data based on a permeability dependency on both temperature peratures. In this manner, the permeability was weighted and cooling rate able to provide a satisfactory correlation. towards those experimental trials which included large data The most accurate description of cell water transport for sets and small values of experimental variance. both constant and variable temperature freezing processes Values of the permeability coefficients, Lpg, ELp, and Ech was obtained for permeability defined in terms of the absolute as calculated using the granulocyte solids content and isotonic temperature and the intracellular solution concentration. volume described by Hempling [20], are listed in Table 1. The Intuitively, it may be possible that the intracellular comcoefficients were estimated for temperatures between - 2 and position would directly affect the granulocyte water transport -10 C, with a reference state of Tg = 273.15 K and IT/ = system, due to the presence of extensive intracellular morphology. The granulocyte is a complex cell, containing in.300Osm-kg'. 1 Journal of Biomechanicat Engineering NOVEMBER 1983, Vol. 105/365 Downloaded From: http://biomechanical.asmedigitalcollection.asme.org/ on 02/18/2016 Terms of Use: http://www.asme.org/about-asme/terms-of-use tracellular membranes whhich may contribute to the transport of water [28], and which may be affected by the intracellular solution composition. Hempling [20] determined values for Lpg (at a reference temperature of 298.15 K) and ELp for granulocytes at suprazero temperatures as 0.65 ^m-atm ~' - min ~' and 77 kJmol - ', respectively. Bradley and Diller [29] measured Eci for granulocytes as 1.30 osm-kg"1 at 25°C. Compared to nonfrozen granulocytes, the frozen cells exhibit a significantly higher activation energy, 218 kJ/mol, and a similar magnitude for the intracellular concentration coefficient, 1.09 Osm-kg ~'. Figure 12 illustrates a comparison of permeabilities determined at suprazero and subzero temperatures as a function of temperature. It is clear that the permeability determined from freezing data and extrapolated to suprazero temperatures is significantly greater than that actually measured by Hempling [20] at suprazero temperatures. Furthermore, extrapolation of the nonfrozen permeability values to subzero temperatures indicates a lesser permeability than deduced from the data in this study. It is obvious that application of activation energies obtained at temperatures above freezing is not acceptable for modeling the freezing process. Alternatively, granulocyte membrane permeability can be viewed as a function of intracellular concentration as in Fig. 13, comparing permeabilities deduced from frozen cell data and extrapolated to a temperature of 25 C with values determined at 25 C [29]. As expected, the two curves are parallel, with the values measured at room temperature being smaller than the permeability values deduced from frozen cell data. Conclusions The analysis presented illustrates that constant temperature freezing of cells provides an effective method of measuring the plasma membrane water permeability at subzero states. The technique is readily adapted to any cell type which can be prepared as a thin suspension for the cryomicroscopic stage. Prerequisite to the application of this procedure is the availability of a cryomicroscope for which the degree of extracellular supercooling can be regulated as an independent parameter and which has a temperature control system capable of effecting isothermal processes. The method enables a more direct determination of permeabilities than can be obtained from measurement and correlation of cell volumes from actual transient temperature preservation protocols [11,12]. For this and previous studies, the plasma membrane permeability to solutes was assumed negligible. In situations for which the solute flux is nonzero, the solute permeability and the relation of solute transport to water transport can be ascertained by using an expanded version of the presented fitting technique. The transient cell volume curve would represent a superposition of water and solute volume alterations, which can be modeled by irreversible thermodynamics in terms of conjugate fluxes and forces [30]. The transmembrane transport would be governed not only by the permeability to water, but also the solute permeability and the reflection coefficient representing the membrane selectivity. Quantification of membrane properties at subzero temperatures provides necessary data for modeling the dehydration of freezing cells. The model could be used to design thermal protocols that would avoid freezing states that may cause injury by either excessive cell shrinkage or concentration of electrolytes. 366/Vol. 105, NOVEMBER 1983 References 1 Toscano, W. M., Cravalho, E. G., Silvares, O. M., and Huggins, C. E., "The Thermodynamics of Intracellular Ice Nucleation in the Freezing of Erythrocytes," ASME Journal of Heat Transfer, Vol. 97, 1975, pp. 326-332. 2 Diller, K. R., "Intracellular Freezing: Effect of Extracellular Supercooling," Cryobiology, Vol. 12, 1975, pp. 480-485. 3 Mazur, P., "The Role of Intracellular Freezing in the Death of Cells Cooled at Supraoptimal Rates," Cryobioology, Vol. 14, 1977, pp. 251-272. 4 Mazur, P., "Cryobiology: The Freezing of Biological Systems," Science, Vol. 168, 1970, pp. 939-949. 5 Meryman, H. T., Williams, R. J., and Douglas, M. St. J., "Freezing Injury from Solution Effects and Its Prevention by Natural and Artificial Cryoprotection," Cryobiology, Vol. 14, 1977, pp. 287-302. 6 Mazur, P., "Kinetics of Water Loss from Cells at Subzero Temperatures and the Likelihood of Intracellular Freezing," Journal of General Physiology, Vol. 47, 1963, pp. 347-369. 7 Silvares, O. M., Cravalho, E. G., Toscano, W. M., and Huggins, C. E., "The Thermodynamics of Water Transport from Biological Cells during Freezing," ASME Journal of Heat Transfer, Vol. 97, 1975, pp. 582-588. 8 Mansoori, G. A., "Kinetics of Water Loss from Cells at Subzero Centigrade Temperatures," Cryobiology, Vol. 12,1975, pp. 34-45. 9 Levin, R. L., Cravalho, E. G., and Huggins, C. E., "A Membrane Model Describing the Effect of Temperature on the Water Conductivity of Erythrocyte Membranes at Subzero Temperatures," Cryobiology, Vol. 13, 1976, pp. 415-429. 10 Knox, J. M., Schwartz, G. J., and Diller, K. R., "Volumetric Changes in Cells During Freezing and Thawing," ASME JOURNAL OF BIOMECHANICAL ENGINEERING, Vol. 102, 1980, pp. 91-97. 11 Levin, R. L., "Water Permeability of Yeast Cells at Subzero Temperatures," Journal of Membrane Biology, Vol. 46,1979, pp. 191-214. 12 Schwartz, G. J ., and Diller, K. R., "Osmotic Response of Individual Cells During Freezing. II. Membrane Permeability Analysis," Cryobiology, 1983, in press. 13 Papanek, T. H., The Water Permeability of the Human Erythrocyte in the Temperature Range +25°C to -10°C, Ph.D. thesis, Massachusetts Institute of Technology, 1978. 14 Scheiwe, M. W., Untersuchungen zum Verfahren der Langzeitknonservierung Lebender Blutzellen durch Gefrieren, doctoral dissertation, der Rheinisch-Westflischen Technischen Hoschule Aachen, 1981. 15 Schwartz, G. J., and Diller, K. R., "Design and Fabrication of a Simple Versatile Cryomicroscopy Stage," Cryobiology, Vol. 19, 1982, pp. 529-538. 16 Evans, C. D., and Diller, K. R., " A Microprocessor Based, Programmable, Controlled, Temperature Microscope Stage for Microvascular Studies," Microvascular Research, Vol. 24,1982, pp. 314-325. 17 Handbook of Chemistry and Physics, 54th Edition, The Chemical Rubber Co., Cleveland, Ohio, 1973. 18 Levin, R. L., Cravalho, E. G., and Huggins, C. E., "Effect of Hydration on the Water Content of Human Erythrocytes," Biophysical Journal, Vol. 16, 1976, pp.1411-1426. 19 Prausnitz, J. M., Molecular Thermodynamics of Fluid-Phase Equilibria, Prentice-Hall Inc., Englewood Cliffs, 1969. 20 Hempling, H. G., "Heats of Activation for the Exosmotic Flow of Water Across the Membrane of Leukocytes and Leukemic Cells," Journal of Cellular and Comparative Physiology, Vol. 81, 1973, pp. 1-9. 21 Armitage, W. J., and Mazur, P., "The Response of Granulocytes to Osmotic Shrinkage," Cryobiology, Vol. 19, p. 678. 22 Carnahan, B., Luther, H. A., and Wilkes, J. O., Applied Numerical Methods, Wiley, New York, 1969. 23 Stusnick, E., and Hurst, R. P., "Numerical Determination of Membrane Permeability Parameters," Journal of Theoretical Biology, Vol. 37, 1972, pp. 261-271. 24 Bevington, P. R., Data Reduction and Error Analysis for the Physical Sciences, McGraw-Hill, New York, 1969. 25 Rich, G. T,, Sha'afi, R. I., Romualdez, A., and Solomon, A. K., "Effect of Osmolality on the Hydraulic Permeability Coefficient of Red Cells," Journal of General Physiology, Vol. 52,1968, pp. 941-954. 26 Vieira, F. L., Sha'afi, R. I., and Solomon, A. K., "The State of Water in Human and Dog Red Cell Membranes," Journal of General Physiology, Vol. 54, 1970, pp.451-466. 27 Schwartz, G. J., and Diller, K. R., "Cryomicroscopic Measurement and Interpretation of Transient Granulocyte Volumes During Freezing," Cryobiology, 1983, submitted. 28 Schmid-Schonbein, G. W., Shih, Y. Y., and Chien, S., "Morphometry of Human Leukocytes," Blood, Vol. 56, 1980, pp. 866-875. 29 Bradley, D. A., and Diller, K. R., "Membrane Permeability Measurement in Isolated Cells," 1982 Advances in Bioengineering, ed., L. E. Thibault, ASME, New York, 1982, pp. 115-118. 30 Lynch, M, E., and Diller, K. R., "Analysis of the Kinetics of Cell Freezing with Cryophylactic Additives," 1981 Advances in Bioengineering, ed., D. C. Viano, ASME, New York, 1981, pp. 229-232. Transactions of the ASME Downloaded From: http://biomechanical.asmedigitalcollection.asme.org/ on 02/18/2016 Terms of Use: http://www.asme.org/about-asme/terms-of-use
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