ALBERT

Notes: Summary Bovine red cells, like other cells, exhibit maximum survival when frozen at certain optimum rates. Cells cooled more slowly are apparently injured by alterations in the cytoplasm or surrounding medium such as the increased concentration of solutes induced by extracellular ice formation. Additives like glycerol protect against this “slow” freezing injury. It has been generally believed that such protection requires permeation by the additive, but we have found that this supposition is not valid for the bovine red cell. Cells were suspended in 1, 2 or 3m glycerol at 20, 15 or 0°C for 0.7 to 30 min or more and then frozen to −196°C at 43 or 1.7°C/min. In nearly all cases, the percentage survival after thawing was as high for cells held in glycerol for 1 min or less prior to freezing as for cells held in glycerol for 30 min, and it was as high for cells held at 0°C as for cells held at 20°C. Survivals were the same for these times and temperatures of exposure in spite of the fact that the osmolal ratio of glycerol to salts in the cell after 30 min at 20°C, for example, was as much as 800 times greater than that in cells held at 0°C for 0.7 min. In addition, the survival after a contact of 1 or 30 min with 2.3 osmolal sucrose was the same as that after exposure to 2.3 osmolal glycerol even though the bovine red cell is impermeable to sucrose. Although exposures of 1 and 30 min to glycerol yielded similar survivals, exposures for intermediate times produced a transitory but dramatic decrease in survival. The dip occurred after longer periods of incubation when the concentration of glycerol was increased and when the incubation temperature was decreased. No dip was evident in cells chilled to 0°C or in cells frozen in sucrose. Thus, the dip seems to be associated in some way with partial permeation of glycerol prior to freezing.

Notes: Summary A central tenet in cryobiology is that low-molecular-weight protective solutes such as glycerol must permeate cells in high concentration in order to protect them from freezing injury. To test this supposition, it is necessary to estimate the amount of solute that has permeated a cell prior to freezing. The amount in bovine red cells was estimated from the flux equation $${{ds} \mathord{\left/ {\vphantom {{ds} {dt}}} \right. \kern-\nulldelimiterspace} {dt}} = P_\gamma A[(activity external solute) - (activity internal solute)].$$ Solving the equation required estimates ofP γ, the permeability constant for the solute. Estimates for glycerol in bovine red cells were made in two ways: (1) by measuring the time to 50% hemolysis of red cells suspended in isosmotic or hyperosmotic (1 to 3m) solutions of glycerol that were hypotonic with respect to NaCl, and (2) by measuring the time required for red cells in hyperosmotic solutions of glycerol in isotonic salinebuffer to become susceptible to osmotic shock upon 10-fold dilution with isotonic saline-buffer. The measurements were made at 0, 10, 15 and 20°C. The values by the second technique ranged from 2.3×10−6 cm/min to 2.7×10−6 cm/min at 20°C, depending on the concentration of glycerol. The values by the first technique were 0 to 30% lower. Both techniques yielded about the same activation energy for permeation between 0 and 20°C, 21 kcal/mole. This is equivalent to a halving of the permeation rate for every 5° drop in temperature. Expressing the flux equation in the formulation of irreversible thermodynamics changed the value ofP by less than 10%, probably because σ, the reflection coefficient, is 0.95 at 25°C. Expressing the driving force as the difference in molality or osmolality of glycerol, rather than as the difference in activity, however, had somewhat greater effects on the numerical values ofP, but had no effect on the activation energy. It is concluded that estimates ofP based on differences in activities and on the osmotic shock technique are the least subject to error. The use of the usual irreversible thermodynamic equations to express the flux may be a misleading refinement, in that the assumptions underlying them become questionable for concentrations of glycerol as high as 1, 2, or 3m.

Notes: Summary The results of the Viking Biology experiments are best explained by non-biological phenomena: The interaction of the reagents with the materials comprising the regolith. Conditions of water activity, temperature, availability of carbon sources and others in most regions of the planet are too extreme for survival and growth of any known Earth microorganisms. Although the possibility persists that some very unusual form of life is somewhere on that planet the evidence is best interpreted as negative. Even though there is no evidence for current life on Mars, whether or not life ever originated there is not known.

Notes: [Auszug] SIRá€"Jared Diamond describes in his News and Views article1, "The recent spectacular discovery of the first reptile to survive natural freezing". He refers to Storey's 1988 report2 that hatchlings of the Canadian painted turtle in the labora-tory can survive the freezing of 52-53 ...

Notes: Abstract A central purpose of Viking was to search for evidence that life exists on Mars or may have existed in the past. The missions carried three biology experiments the prime purpose of which was to seek for existing microbial life. In addition the results of a number of the other experiments have biological implications: (1) The elemental analyses of the atmosphere and the regolith showed or implied that the elements generally considered essential to terrestrial biology are present. (2) But unexpectedly, no organic compounds were detected in Martian samples by an instrument that easily detected organic materials in the most barren of terrestrial soils. (3) Liquid water is believed to be an absolute requisite for life. Viking obtained direct evidence for the presence of water vapor and water ice, and it obtained strong inferential evidence for the existence of large amounts of subsurface permafrost now and in the Martain past. However it obtained no evidence for the current existence of liquid water possessing the high chemical potential required for at least terrestrial life, a result that is consistent with the known pressure-temperature relations on the planet's surface. On the other hand, the mission did obtain strong indications from both atmospheric analyses and orbital photographs that large quantities of liquid water flowed episodically on the Martian surface 0.5 to 2.5 G years ago. The three biology experiments produced clear evidence of chemical reactivity in soil samples, but it is becoming increasingly clear that the chemical reactions were nonbiological in origin. The unexpected release of oxygen by soil moistened with water vapor in the Gas Exchange experiment together with the negative findings of the organic analysis experiment lead to the conclusion that the surface contains powerful oxidants. This conclusion is consistent with models of the atmosphere. The oxidants appear also to have been responsible for the decarboxylation of the organic nutrients that were introduced in the Label Release experiment. The major results of the GEX and LR experiments have been simulated at least qualitatively on Earth. The third, Pyrolytic Release, experiment obtained evidence for organic synthesis by soil samples. Although the mechanism of the synthesis is obscure, the thermal stability of the reaction makes a biological explanation most unlikely. Furthermore, the response of soil samples in all three experiments to the addition of water is not consistent with a biological interpretation. The conditions now known to exist at and below the Martian surface are such that no known terrestrial organism could grow and function. Although the evidence does not absolutely rule out the existence of favourable oases, it renders their existence extremely unlikely. The limiting conditions for the functioning of terrestrial organisms are not the limits for conceivable life elsewhere, and accordingly one cannot exclude the possibility that indigenous life forms may currently exist somewhere on Mars or may have existed sometime in the past. Nevertheless, the available information about the present Martian environment puts severe constraints and presents formidable challenges to any putative Martian organisms. The Martian environment in the past, on the other hand, appears to have been considerably less hostile biologically, and it might possibly have permitted the origin and transient establishment of a biota.

Notes: Abstract The framework of nonequilibrium thermodynamics is used to study the phenomenon of enhanced Rayleigh scattering from the liquid-solid interface of a growing crystal. The scattering is treated as resulting from small “objects” of finite lifetime produced at the interface by the growth process and confined thereafter to one phase or the other. The thermodyanmic analysis leads to the formation, adjacent to the interface, of a boundary layer, various properties of which are studied. The analysis is then used to discuss the data obtained in two different experiments on the anomalous light scattering from the ice-water interface. It is found that the various data presented in these two experiments cannot be reconciled with each other in all respects.

Notes: Abstract Liquid water is generally considered an absolute requisite for functional life; consequently, life is expected to function only over the range of temperatures that permit its existence. These limits, however, do not apply to cell survival. Some cells can survive the closest attainable approach to 0 K, and some can survive the loss of over 99% of their water.