Temperature-dependent changes in the swimming behaviour of Tetrahymena pyriformis-NT1 and their interrelationships with electrophysiology and the state of membrane lipids

The swimming velocity and the amplitude of the helical swimming path of T. pyriformis-NT1 cells grown at 20 degrees C (Tg 20 degrees C) and 38 degrees C (Tg 38 degrees C) were monitored between 0 and 40 degrees C in the presence and absence of electric fields. Within physiological limits the swimming velocity increased and the amplitude decreased as temperature was raised. The temperature profiles of these properties were not linear, and showed discontinuities at different temperatures for the different cultures. The break points in Arrhenius plots of the resting potential, regenerative spike magnitude, repolarization time, swimming velocity and swimming amplitude are tabulated and compared. The initial breakpoints upon cooling were clustered about the breakpoints in fluorescence polarization of D.P.H. in extracted phospholipids, and around the transition temperatures estimated from the literature for the pellicular membrane of these cells. The average of the initial breakpoints on cooling was 22.9 degrees C for Tg 38 degrees C cells and 13.7 degrees C for Tg 20 degrees C cells, a shift of 9.2 degrees C. Unlike Paramecium there is no depolarizing receptor potential in Tetrahymena upon warming. It is suggested that this may be the basis of a behavioural difference between Tetrahymena and Paramecium--namely that in Tetrahymena maximum swimming velocity occurs above growth temperature whereas in Paramecium the two points coincide. Swimming velocity and resting potential were correlated with membrane fluidity within physiological limits, but for other parameters the relationship with fluidity was more complex.(ABSTRACT TRUNCATED AT 250 WORDS)     

Loss of secretory response of rat basophilic leukemia (2H3) cells at 40 degrees C is associated with reversible suppression of inositol phospholipid breakdown and calcium signals

Antigen-induced stimulatory signals as well as histamine secretion from the RBL-2H3 cells were found to be highly temperature dependent. There was no hydrolysis of inositol phospholipids, increase in cytosol calcium concentration (calcium signal), or secretion upon antigen stimulation at temperatures below 20 degrees C. At higher temperatures (i.e., 20 to 37 degrees C), all responses increased in extent with increase in temperature. Temperatures of 38 degrees C or higher, however, resulted in a marked decline in all responses, until no responses were observed at 40 to 42 degrees C. As indicated by the decay in calcium signal, the duration of response was also temperature dependent. The response was of long duration at 30 to 32 degrees C, but it became progressively more transient as the temperature was increased from 32 to 40 degrees C. The effects of low or high temperature were fully reversible. For example, in the presence of antigen, stimulatory signals immediately appeared once the temperature was decreased from 40 to 37 degrees C. Although the diminished responses could be explained, in part, by a reduction in rates of IgE receptor aggregation and phospholipase C activity, the reductions were insufficient to account for complete loss of activity at 40 degrees C. We conclude that generation of intracellular signals in 2H3 cells is blocked by quite small elevations in temperature above 37 degrees C, possibly as consequence of changes in membrane fluidity.     

Temperature effects on the Na and Ca currents in rat and hedgehog ventricular muscle

Cardiac transmembrane potentials and Na and Ca currents were recorded at different temperatures in rat and hedgehog ventricular muscle. At 35 degrees C in both species resting potential was about -80 mV and upstroke velocity (Vmax) of the action potential above 100 V/s. The shape of the action potential in hedgehog ventricular cells at 35 degrees C was similar to that in the rat showing a fast repolarization phase. When temperature was decreased, the membrane resting potential depolarized and action potential amplitude and Vmax declined. In rat ventricular cells at 10 degrees C, the resting potential was about -40 to -50 mV and Vmax was reduced to about 5 V/s. In hedgehog ventricular cells, however, the transmembrane potentials and Vmax were better maintained at low temperature. Phase 3 of the action potential was markedly prolonged below 20 degrees C in hedgehog but not in rat ventricular cells. When temperature was decreased to 10 degrees C the availability curve of the Na current shifted toward more negative potentials and ICa.peak declined in rat ventricular cells. In hedgehog cardiac preparations, the Na current was less influenced by the cooling and ICa.peak did not change very much at low temperatures. A transient inward current usually considered to induce cardiac arrhythmias could be recorded in rat ventricular cells below 20 degrees C but not in hedgehog preparations. These features of hedgehog cardiac membranes may contribute to the cold tolerance and the resistance to ventricular fibrillation during the hypothermia in mammalian hibernators.     

Effect of low temperature on the axons of chick embryo in in vitro culture

Hanging drop cultures of rhombencephalon of 6-11 day chick embryos were placed for 15'-24 hours at low temperatures (0 degree, 10 degrees, 15 degrees, 20 degrees, 25 degrees). Phase contrast time-lapse cinemicrography were made of the axons outgrowth from the explants, during recovery of normal temperature (38 degrees). A number of cultures were also filmed during cooling from 38 degrees to 15 degrees or 20 degrees. It was thus possible follow the sequence of the axon changes, especially of its growth cone, and demonstrate the reversible nature of the modifications observed at some subnormal temperatures.     

An assessment of tumor cell viability after in vitro freezing

The identification of the minimum lethal temperature for tumor cells in vivo is difficult because of the secondary factors that are associated with the cryoinjury. This study attempts to identify this temperature by a combination of in vitro and in vivo techniques. Suspensions of Walker carcinoma cells were frozen at a rate of 1 degree C/min without cryoprotection, to either -10, -15, -20, -25, -30, -35 or -40 degrees C and held at that temperature for either 0, 10, 20, or 30 min. After spontaneous rewarming viability was assessed by a combination of vital dye studies and the growth of tumor cells inoculated into the liver and subcutaneous tissue of male, Sprague-Dawley rats. Trypan blue studies indicated that less than 1% of the cells frozen to -35 degrees C were considered viable, yet significant tumor take rates were noted, suggesting that for some cells the cryoinjury is reversible. As expected tumor take rates were reduced by lowering the temperature but were independent of the holding time. The volume doubling time and final tumor volume of the subcutaneous tumors was similar to that of controls, indicating that the growth potential of the cells which survive freezing is normal. The minimum lethal temperature was dependent upon the site of inoculation, subcutaneous tumors developing from cells frozen to -35 degrees C, whereas liver tumors did not develop from cells frozen beyond -25 degrees C, this may have important clinical implications.     

The action of caffeine on X-irradiated HeLa cells. IX. Hypothermic effects

Hypothermic enhancement of the lethal effect of 3.5 Gy of 220-kV X rays in the absence of caffeine as well as in its presence (4 mM) was examined at temperatures between 10 and 34 degrees C in monolayer cultures in the G1 phase of the cell cycle. Correction has been made for the toxicity of low temperatures, and of caffeine at low temperatures, by concomitantly measuring cell killing in unirradiated cells. In the absence of caffeine, incubation of irradiated cells for up to 34 h at temperatures in the range 15 to 30 degrees C (or possibly 34 degrees C) enhances killing compared to that observed at 38 degrees C; the amount of enhancement is about the same throughout this range, but is nil at 10 degrees C. The enhanced killing induced by caffeine at 38 degrees C decreases as the temperature is lowered to 15 degrees C; there is no enhancement at 10 degrees C. Less killing is manifested in the range 15 to 25 degrees C in the presence of caffeine than in its absence. Recovery (loss of sensitivity to caffeine) and fixation of potentially lethal damage were studied in late-S/G2-phase cells at reduced temperatures by delaying treatment with caffeine for increasing times after irradiation. As the temperature is progressively lowered to 20 degrees C, less recovery is manifested after 5 h of incubation; no recovery is detected in the range 10 to 20 degrees C. Despite extensive recovery at 34 degrees C, no fixation is observed at that (or any lower) temperature in G2-phase cells: the cells are able to recover essentially fully when returned to 38 degrees C. In addition, responses of unirradiated control series to incubation at low temperatures appear to differ from those reported by others for longer treatment times of different cell systems.     

Changes in lipid fluidity and fatty acid composition with altered culture temperature in Tetrahymena pyriformis-NT1

Cultures of T. pyriformis-NT1 were grown at 20 degrees C (Tg 20 degrees C) and 38 degrees C (Tg 38 degrees C). G.L.C. analysis and D.P.H. fluorescence polarization measurements in extracted phospholipids indicated that there was increased saturation of fatty acids and relatively reduced fluidity as growth temperature was increased. Breakpoints occurred in the Arrhenius plots of fluorescence polarization at 16 degrees C for Tg 38 degrees C total extracted phospholipids and 9 degrees C for Tg 20 degrees C lipids.     

Temperature-induced changes in metabolism and body weight of cattle (Bos taurus).

The metabolic and body weight changes in two non-pregnant beef cows were studied during prolonged exposure to warm (20 +/- 3 degrees C, relative humidity 50-70%) and cold (-10 +/- 2 or -25 +/- 4 degrees C) temperatures. Other factors including daily food intake were held constant throughout each 8-week exposure. During cold exposures, metabolic rate, blood hematocrit, and plasma concentrations of glucose and free fatty acid were elevated and respiratory frequencies and skin temperatures decreased. Resting metabolic rates measured at 20 degrees C, i.e., without the direct influence of cold, were 83.4-95.3 litres 02 per hour when the cows were cold acclimated, at either -10 or -25 degrees C, and 30-40% greater than when the cows were warm acclimated. The resting metabolic response and the concomitant reduction in intensity of shivering is indicative of metabolic acclimation to cold in these animals of greater than 500 kg body weight. As well as the expected changes in body weight with changes in energy metabolism there were losses in weight (13-24 kg) during the first 3 days of each cold exposure. Weight gains occurred when the cold stress was abruptly removed. These short term weight changes were associated with changes in water intake and apparent shifts in body fluid content.     

Temperature-related duration of aquatic stages of the Afrotropical malaria vector mosquito Anopheles gambiae in the laboratory

Vector abundance is an important factor governing disease risk and is often employed when modelling disease transmission. The longevity of the aquatic stages of mosquitoes (Diptera: Culicidae) dictates the rate of production of adults and hence the intensity of disease transmission. We examined how temperature influences the survival of larval stages (larvae and pupae) of Anopheles gambiae Giles sensu stricto and subsequent adult production of this most efficient malaria vector. Groups of 30 mosquitoes were reared at constant temperatures (from 10 to 40 degrees C) from the first instar and observed until death or metamorphosis of the last individual. Larvae developed into adults at temperatures ranging from 16 to 34 degrees C. Larval survival was shortest (< 7 days) at 10-12 degrees C and 38-40 degrees C, and longest (> 30 days) at 14-20 degrees C. Within the temperature range at which adults were produced, larval mortality was highest at the upper range 30-32 degrees C, with death (rather than adult emergence) representing over 70% of the terminal events. The optimal survival temperatures were lower than the temperatures at which development was quickest, suggesting a critical relationship between temperature and the life cycle of the insect. These data provide fundamental information about An. gambiae s.s. adult productivity at different temperatures, which may facilitate the construction of process-based models of malaria risk in Africa and the development of early warning systems for epidemics.     

Thermal adaptation of Tetrahymena membranes with special reference to mitochondria. II. Preferential interaction of cardiolipin with specific molecular species of phospholipid

A specific effect of cardiolipin on fluidity of mitochondrial membranes was demonstrated in Tetrahymena cells acclimated to a lower temperature in the previous report (Yamauchi, T., Ohki, K., Maruyama, H. and Nozawa, Y. (1981) Biochim. Biophys. Acta 649, 385-392). This study was further confirmed by the experiment using fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene (DPH). Anisotropy of DPH for microsomal and pellicular total lipids from Tetrahymena cells showed that membrane fluidity of these lipids increased gradually as the cells were incubated at 15 degrees C after the shift down of growth temperature from 39 degrees C. However, membrane fluidity of mitochondrial total lipids was kept constant up to 10 h. This finding is compatible with the result obtained using spin probe in the previous report. Additionally, the break-point temperature of DPH anisotropy was not changed in mitochondrial lipids whereas those temperatures in pellicular and microsomal lipids lowered during the incubation at 15 degrees C. Interaction between cardiolipins and various phospholipids, which were isolated from Tetrahymena cells grown at 39 degrees C or 15 degrees C and synthesized chemically, was investigated extensively using a spin labeling technique. The addition of cardiolipins from Tetrahymena cells grown at either 39 degrees C or 15 degrees C did not change the membrane fluidity (measured at 15 degrees C) of phosphatidylcholine from whole cells grown at 39 degrees C. On the other hand, both cardiolipins of 39 degrees C-grown and 15 degrees C-grown cells decreased the membrane fluidity of phosphatidylcholine from Tetrahymena cells grown at 15 degrees C. The same results were obtained for phosphatidylcholines of mitochondria and microsomes. Membrane fluidity of phosphatidylethanolamine, isolated from cells grown at 15 degrees C, was reduced to a small extent by Tetrahymena cardiolipin whereas that of 39 degrees C-grown cells was not changed. Representative molecular species of phosphatidylcholines of cells grown at 39 degrees C and 15 degrees C were synthesized chemically; 1-palmitoyl-2-oleoylphosphatidylcholine for 39 degrees C-grown cells and dipalmitoleoylphosphatidylcholine for 15 degrees C-grown ones. By the addition of Tetrahymena cardiolipin, the membrane fluidity of 1-palmitoyl-2-oleoylphosphatidylcholine was not changed but that of dipalmitoleoylphosphatidylcholine was decreased markedly. These phenomena were caused by Tetrahymena cardiolipin. However, bovine heart cardiolipin, which has a different composition of fatty acyl chains from the Tetrahymena one, exerted only a small effect.     

Assessment of the cell viability of cultured Perkinsus marinus (Perkinsea), a parasitic protozoan of the Eastern oyster, Crassostrea virginica, using SYBRgreen-propidium iodide double staining and flow cytometry

A flow cytometry (FCM) assay using SYBRgreen and propidium iodide double staining was tested to assess viability and morphological parameters of Perkinsus marinus under different cold- and heat-shock treatments and at different growth phases. P. marinus meront cells, cultivated at 28 degrees C, were incubated in triplicate for 30 min at -80 degrees C, -20 degrees C, 5 degrees C, and 20 degrees C for cold-shock treatments and at 32 degrees C, 36 degrees C, 40 degrees C, 44 degrees C, 48 degrees C, 52 degrees C, and 60 degrees C for heat-shock treatments. A slight and significant decrease in percentage of viable cells (PVC), from 93.6% to 92.7%, was observed at -20 degrees C and the lowest PVC was obtained at -80 degrees C (54.0%). After 30 min of heat shocks at 40 degrees C and 44 degrees C, PVC decreased slightly but significantly compared to cells maintained at 28 degrees C. When cells were heat shocked at 48 degrees C, 52 degrees C, and 60 degrees C heavy mortality occurred and PVC decreased to 33.8%, 8.0%, and 3.4%, respectively. No change in cell complexity and size was noted until cells were heat shocked at >or=44 degrees C. High cell mortality was detected at stationary phase of P. marinus cell culture. Cell viability dropped below 40% in 28-day-old cultures and ranged 11-25% in 38 to 47-day-old cultures. Results suggest that FCM could be a useful tool for determining viability of cultured P. marinus cells.     

The sodium current underlying action potentials in guinea pig hippocampal CA1 neurons

Neurons were acutely dissociated from the CA1 region of hippocampal slices from guinea pigs. Whole-cell recording techniques were used to record and control membrane potential. When the electrode contained KF, the average resting potential was about -40 mV and action potentials in cells at -80 mV (current-clamped) had an amplitude greater than 100 mV. Cells were voltage-clamped at 22-24 degrees C with electrodes containing CsF. Inward currents generated with depolarizing voltage pulses reversed close to the sodium equilibrium potential and could be completely blocked with tetrodotoxin (1 microM). The amplitude of these sodium currents was maximal at about -20 mV and the amplitude of the tail currents was linear with potential, which indicates that the channels were ohmic. The sodium conductance increased with depolarization in a range from -60 to 0 mV with an average half-maximum at about -40 mV. The decay of the currents was not exponential at potentials more positive than -20 mV. The time to peak and half-decay time of the currents varied with potential and temperature. Half of the channels were inactivated at a potential of -75 mV and inactivation was essentially complete at -40 to -30 mV. Recovery from inactivation was not exponential and the rate varied with potential. At lower temperatures, the amplitude of sodium currents decreased, their time course became longer, and half-maximal inactivation shifted to more negative potentials. In a small fraction of cells studied, sodium currents were much more rapid but the voltage dependence of activation and inactivation was very similar.     

Factors affecting steroid and prostaglandin secretion by reproductive tissues of cycling and pregnant sows in vitro

Mitochondrial, microsomal and pellicular membranes were isolated from Tetrahymena cells grown at 39 degrees C or 15 degrees C, and phospholipids, in turn, were separated from total lipids extracted from these membranes. The effect of growth temperature on their solid-to-fluid phase transition temperature was examined by wide-angle X-ray diffraction. The transition temperatures of phospholipids from mitochondria, microsomes and pellicles were 21, 19 and 26 degrees C for cells grown at 39 degrees C and -8, -3 and 6 degrees C for cells grown at 15 degrees C, respectively. All phospholipids were found in a completely fluid state at these growth temperatures. From a comparison between the phospholipids and total lipids from pellicles of cells grown at 39 degrees C, a triterpenoid alcohol, tetrahymanol, caused the transition temperature to increase. The alignment of tetrahymanol in membranes was examined with pellicle'a total lipid oriented in a sample holder.     

不同品系萼花臂尾轮虫休眠卵的形态特征

对采自青岛和芜湖两地的萼花臂尾轮虫在3种温度(20 ℃、25 ℃和30 ℃)和2种藻类食物浓度(1.0×10⁶和5.0×10⁶ cells·ml^-1)下所产休眠卵的长径、短径和体积等形态特征进行了显微测量、计算和分析.结果表明,2种食物浓度下,培养温度以及培养温度和品系间的交互作用均对轮虫休眠卵的长径、短径和体积具有显著影响.当食物浓度分别为1.0×10⁶和5.0×10⁶ cells·ml^-1时,轮虫在20 ℃下所产休眠卵的长径、短径和体积均最大;在25 ℃和30 ℃下所产休眠卵的短径和体积均最小.品系对轮虫休眠卵长径、短径和体积的影响也取决于食物浓度.当食物浓度为1.0×10⁶ cells·ml^-1时,芜湖品系轮虫的休眠卵长径、短径和体积(156.00 μm、99.95 μm和12 269.11 μm³)均显著大于青岛品系轮虫的休眠卵(145.13 μm、91.97 μm和10 498.19 μm³);而当食物浓度为5.0×10⁶ cells·ml^-1时,芜湖品系轮虫的休眠卵长径、短径和体积(155.68 μm、100.85 μm和12 348.59 μm³)均与青岛品系轮虫的休眠卵(156.63 μm、98.04 μm和12 054.20 μm³)之间无显著差异.两品系中,仅芜湖品系轮虫休眠卵的长径、短径和体积分别与温度呈曲线相关.同一温度下,两品系轮虫的休眠卵体积均随着食物浓度升高而增大;但30 ℃下芜湖品系轮虫所产休眠卵体积却随着食物浓度的升高而减小.     

Effect of different cryoprotectants and transfer temperatures on the survival rate of hemp (Cannabis sativa L.) cell suspension in deep freezing

Adequate cell dehydration is the precipitating element in the successful cryopreservation of plant cells and organs. This could be achieved by using different cooling rates, transfer temperatures and cryoprotectants. Experiments were performed to determine these critical points in the freeze preservation procedure of Cannabis sativa (L.) suspension cultures. The explants were frozen at a cooling rate of 2 degrees C/min, while the transfer temperatures were -10 degrees C, -20 degrees C, -30 degrees C, -40 degrees C and -50 degrees C. The applied cryoprotectants were the DMSO, glycerol, proline and PEG in different concentration. The highest viability (58%) was obtained by using 10% DMSO and at -10 degrees C transfer temperature. The optimum transfer temperature varied remarkably by different cryoprotectant concentrations indicating the importance of their interactions.     

Characterization of a cycloheximide-resistant Tetrahymena thermophila mutant which also displays altered growth properties.

A cycloheximide-resistant strain of Tetrahymena thermophila, expressing a mutant chx-B gene (Ares and Bruns, Genetics 90:463-474, 1978), displayed very different temperature-dependent growth characteristics than either wild-type cells or another cycloheximide-resistant strain expressing a different mutant gene. Whereas wild-type cells showed an immediate decline in ribosome translocation rates when shifted from 30 to 38 or 40 degrees C, this mutant strain (X-8) showed no such decline. These results directly correlated with the growth rate differences we found for these cells at these temperatures. By genetic analysis, we showed that the phenotype of cycloheximide resistance cosegregated with the ability to grow rapidly at 40 degrees C. Analyses, both direct and indirect, suggested that a number of functional and structural characteristics of the ribosomes from strain X-8 cells are most likely conformationally different from those of wild-type ribosomes.     

Oxygen consumption and body temperature of active and resting honeybees

We measured the energy turnover (oxygen consumption) of honeybees (Apis mellifera carnica), which were free to move within Warburg vessels. Oxygen consumption of active bees varied widely depending on ambient temperature and level of activity, but did not differ between foragers (>18 d) and middle-aged hive bees (7-10 d). In highly active bees, which were in an endothermic state ready for flight, it decreased almost linearly, from a maximum of 131.4 microl O(2) min(-1) at 15 degrees C ambient temperature to 81.1 microl min(-1) at 25 degrees C, and reached a minimum of 29.9 microl min(-1) at 40 degrees C. In bees with low activity, it decreased from 89.3 microl O(2) min(-1) at 15 degrees C to 47.9 microl min(-1) at 25 degrees C and 14.7 microl min(-1) at 40 degrees C. Thermographic measurements of body temperature showed that with increasing activity, the bees invested more energy to regulate the thorax temperature at increasingly higher levels (38.8-41.2 degrees C in highly active bees) and were more accurate. Resting metabolism was determined in young bees of 1-7 h age, which are not yet capable of endothermic heat production with their flight muscles. Their energy turnover increased from 0.21 microl O(2) min(-1) at 10 degrees C to 0.38 microl min(-1) at 15 degrees C, 1.12 microl min(-1) at 25 degrees C, and 3.03 microl min(-1) at 40 degrees C. At 15, 25 and 40 degrees C, this was 343, 73 and 10 times below the values of the highly active bees, respectively. The Q(10) value of the resting bees, however, was not constant but varied in a U-shaped manner with ambient temperature. It decreased from 4.24 in the temperature range 11-21 degrees C to 1.35 in the range 21-31 degrees C, and increased again to 2.49 in the range 30-40 degrees C. We conclude that attempts to describe the temperature dependence of the resting metabolism of honeybees by Q(10) values can lead to considerable errors if the measurements are performed at only two temperatures. An acceptable approximation can be derived by calculation of an interpolated Q(10) according to the exponential function (V(O(2))=0.151 x 1.0784(T(a))) (interpolated Q(10)=2.12).     

Effect of input resistance voltage-dependency on DC estimate of membrane capacitance in cardiac myocytes

The measure of membrane capacitance (C(m)) in cardiac myocytes is of primary importance as an index of their size in physiological and pathological conditions, and for the understanding of their excitability. Although a plethora of very accurate methods has been developed to access C(m) value in single cells, cardiac electrophysiologists still use, in the majority of laboratories, classical direct current techniques as they have been established in the early days of cardiac cellular electrophysiology. These techniques are based on the assumption that cardiac membrane resistance (R(m)) is constant, or changes negligibly, in a narrow potential range around resting potential. Using patch-clamp whole-cell recordings, both in current-clamp and voltage-clamp conditions, and numerical simulations, we document here the voltage-dependency of R(m), up to -45% of its resting value for 10-mV hyperpolarization, in resting rat ventricular myocytes. We show how this dependency makes classical protocols to misestimate C(m) in a voltage-dependent manner (up to 20% errors), which can dramatically affect C(m)-based calculations on cell size and on intracellular ion dynamics. We develop a simple mechanistic model to fit experimental data and obtain voltage-independent estimates of C(m), and we show that accurate estimates can also be extrapolated from the classical approach.     

Some Factors Affecting the Activity of Diethylpyrocarbonate as a Sterilant

Quantitative data indicated logarithmic death in 5 degrees Brix Concord grape juice when concentrations of cells under 10(7)/ml were exposed to diethylpyrocarbonate (DEPC). Species differed considerably in their resistance; e.g., 50 ppm reduced the viable count of Saccharomyces cerevisiae over nine log(10) cycles, whereas 200 ppm reduced the count of Byssochlamys fulva ascospores by only about 1 log. DEPC lethality was enhanced by higher temperatures; destruction at 40 C was 10- to 100-fold greater than at 20 C. Studies on death rates showed that most yeasts and fungal spores were killed during the first hour of exposure, whereas 24 h or longer was needed for maximal destruction of several lactic acid bacteria. Repair of DEPC-induced damage was believed responsible for the slower death rates of the lactics.     

Rapid cold hardening in the predatory mite Euseius (Amblyseius) finlandicus (Acari: Phytoseiidae)

A rapid cold hardening response was studied in diapause and non-diapause females of the predatory mite Euseius finlandicus. When laboratory reared diapause and non-diapause females were transferred and maintained from the rearing temperature of 20 degrees C for 2 h to -11.5 degrees C and -10 degrees C, 10 to 20% survived respectively. However, conditioning of diapause females for 4 h at a range of temperatures from 0 to 10 degrees C before their exposure for 2 h to -11.5 degrees C, increased survival to approximately 90%. Similarly, conditioning of non-diapause females for 4 h at 5 degrees C before their exposure for 2 h to -10 degrees C increased survival to 90%. A similar rapid cold hardening response in both diapause and non-diapause females was also induced through gradual cooling of the mites, at a rate of approximately 0.4 degrees C per min. The rapid increase in cold tolerance after prior conditioning of the mites to low temperatures, was rapidly lost when they returned to a higher temperature of 20 degrees C. Rapid cold hardening extended the survival time of diapause and non-diapause females at sub-zero temperatures. The cost of rapid cold hardening in reproductive potential after diapause termination was negligible. In non-diapause females, however, the increase in cold tolerance gained through gradual cooling could not prevent cold shock injuries, as both fecundity and survival were reduced.