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1.
Supercooling points, lower lethal temperatures, and the effect of short-term exposures to low temperatures were examined
during both winter and summer in the adults of six weevil species from three different habitats on Marion Island. Upper lethal
limits and the effects of short-term exposure to high temperatures were also examined in summer-acclimatized adult individuals
of these species. Bothrometopus elongatus, B. parvulus, B. randi, Ectemnorhinus marioni, and E. similis were freeze tolerant, but had high lower lethal temperatures (−7 to −10°C). Seasonal variation in these parameters was not
pronounced. Physical conditions of the habitat appeared to have little effect on cold hardiness parameters because the Ectemnorhinus species occur in very wet habitats, whereas the Bothrometopus species inhabit drier areas. The adults of these weevil species are similar to other high southern latitude insects in that
they are freeze tolerant, but with high lower lethal temperatures. In contrast, Palirhoeus eatoni, a supra-littoral species, avoided freezing and had a mean supercooling point of −15.5 ± 0.94°C (SE) in winter and −11.8 ± 0.98°C
in summer. Survival of a constant low temperature of −8°C also increased in this species from 6 h in summer to 27 h in winter.
It is suggested that this strategy may be a consequence of the osmoregulatory requirements imposed on this species by its
supra-littoral habitat. Upper lethal temperatures (31–34°C) corresponded closely with maximum microclimate temperatures in
all of the species. This indicates that the pronounced warming, accompanied by the increased insolation that has been recorded
at Marion Island, may reduce survival of these species. These effects may be compounded as a consequence of predation by feral
house mice on the weevils.
Received: 4 February 1997 / Accepted: 3 May 1997 相似文献
2.
Since some amino acids, polyols and sugars in cells are thought to be osmoprotectants, we expected that several amino acids
might also contribute to enhancing freeze tolerance in yeast cells. In fact, proline and charged amino acids such as glutamate,
arginine and lysine showed a marked cryoprotective activity nearly equivalent to that of glycerol or trehalose, both known
as major cryoprotectants for Saccharomyces cerevisiae. To investigate the cryoprotective effect of proline on the freezing stress of yeast, we isolated proline-analogue-resistant
mutants derived from a proline-non-utilizing strain of S. cerevisiae. When cultured in liquid minimal medium, many mutants showed a prominent increase, two- to approximately tenfold, in cell
viability compared to the parent after freezing in the medium at −20 °C for 1 week. Some of the freeze-tolerant mutants were
found to accumulate a higher amount of proline, as well as of glutamate and arginine which are involved in proline metabolism.
It was also observed that proline-non-utilizer and the freeze-tolerant mutants were able to grow against osmotic stress. These
results suggest that the increased flux in the meta-bolic pathway of specific amino acids such as proline is effective for
breeding novel freeze-tolerant yeasts.
Received: 6 November 1996 / Accepted: 7 December 1996 相似文献
3.
Cryoprotective and osmotic responses to cold acclimation and freezing in freeze-tolerant and freeze-intolerant earthworms 总被引:3,自引:3,他引:0
M. Holmstrup J. P. Costanzo R. E. Lee Jr 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1999,169(3):207-214
In this paper we present the results of physiological responses to winter acclimation and tissue freezing in a freeze-tolerant
Siberian earthworm, Eisenia nordenskioeldi, and two freeze-intolerant, temperate earthworm species, Lumbricus rubellus and Aporrectodea caliginosa. By analysing the physiological responses to freezing of both types we sought to identify some key factors promoting freeze
tolerance in earthworms. Winter acclimation was followed by a significant increase in osmolality of body fluids in E. nordenskioeldi, from 197 mosmol kg−1 in 10 °C-acclimated animals to 365 mosmol kg−1 in animals acclimated to 0 °C. Cold acclimation did not cause any change in body fluid osmolality in the two freeze-intolerant
species. As a response to ice formation in the body, the freeze-intolerant species produced copious amounts of slime and expulsion
of coelomic fluids, and thereby lost 10–30% of their total water content. Contrary to this, the freeze-tolerant species did
not lose water upon freezing. At temperatures down to −6.5 °C, the ice content in the freeze-tolerant E. nordenskioeldi was significantly lower than in L. rubellus. At lower temperatures there were no differences in ice content between the two species. Cold acclimated, but unfrozen, specimens
of all three species had low levels of ammonia, urea, lactate, glycerol and glucose. As a response to ice formation, glucose
levels significantly increased within the first 24 h of freezing. This was most pronounced in E. nordenskioeldi where a 153-fold increase of glucose was seen (94 mmol · l−1). In L. rubellus and A. caliginosa a 19-fold and 17-fold increase in glucose was seen. This is the first study on physiological mechanisms promoting freeze
tolerance in E. nordenskioeldi, or any other oligochaete. Our results suggest that the cryoprotective system of this species more closely resembles that
of freeze-tolerant anurans, which synthesize cryoprotectants only after tissues begin to freeze, than that of cold-hardy invertebrates
which exhibit a preparatory accumulation of cryoprotectants during seasonal exposure to low temperature.
Accepted: 10 February 1999 相似文献
4.
Steinernema feltiae is a moderately freeze-tolerant entomopathogenic nematode which survives intracellular freezing. We have detected by gas chromatography that infective juveniles of S. feltiae produce cryoprotectants in response to cold acclimation and to freezing. Since the survival of this nematode varies with temperature, we analyzed their cryoprotectant profiles under different acclimation and freezing regimes. The principal cryoprotectants detected were trehalose and glycerol with glucose being the minor component. The amount of cryoprotectants varied with the temperature and duration of exposure. Trehalose was accumulated in higher concentrations when nematodes were acclimated at 5°C for two weeks whereas glycerol level decreased from that of the non-acclimated controls. Nematodes were seeded with a small ice crystal and held at -1°C, a regime that does not produce freezing of the nematodes but their bodies lose water to the surrounding ice (cryoprotective dehydration). This increased the levels of both trehalose and glycerol, with glycerol reaching a higher concentration than trehalose. Nematodes frozen at -3°C, a regime that produces freezing of the nematodes and results in intracellular ice formation, had elevated glycerol levels while trehalose levels did not change. Steinernema feltiae thus has two strategies of cryoprotectant accumulation: one is an acclimation response to low temperature when the body fluids are in a cooled or supercooled state and the infective juveniles produce trehalose before freezing. During this process a portion of the glycerol is converted to trehalose. The second strategy is a rapid response to freezing which induces the production of glycerol but trehalose levels do not change. These low molecular weight compounds are surmised to act as cryoprotectants for this species and to play an important role in its freezing tolerance. 相似文献
5.
Strong evidence suggests that cryoprotectant accumulation during pre-cold acclimation protects cells against freezing injuries caused by cellular dehydration. In this study, the concentrations of trehalose and glycerol were measured in Meloidogyne incognita and it was found that both cryoprotectants were significantly accumulated in second-stage juveniles (J2) of M. incognita after acclimation at 4°C. However, compared with non-acclimated samples, only a higher level of trehalose was induced in the egg masses of M. incognita in response to cold treatment. Further characterizations indicated that pre-cold acclimation efficiently accelerated the speed of larvae hatching from egg masses that were subjected to freezing at −1°C. In addition, the survival rate and pathogenicity of M. incognita J2 that had been acclimated prior to freezing were significantly enhanced when compared with non-acclimated J2 individuals. As far as we know, this is the first time that this phenomenon has been reported in M. incognita. 相似文献
6.
Hydromedion sparsutum is a locally abundant herbivorous beetle on the sub-Antarctic island of South Georgia, often living in close association
with the tussock grass Parodiochloa flabellata. Over a 4-day period in mid-summer when the air temperature varied from 0 to 20°C, the temperature in the leaf litter 5–10 cm
deep at the base of tussock plants (the microhabitat of H. sparsutum) was consistently within the range of 5–7.5°C. Experiments were carried out to assess the ability of H. sparsutum larvae collected from this thermally stable environment to acclimate when maintained at lower (0°C) and higher (15°C) temperatures.
The mean supercooling points (freezing temperature) of larvae collected in January and acclimated at 0°C for 3 and 6 weeks
and 15°C for 3 weeks were all within the range of −2.6 to −4.6°C. Larvae in all treatment groups were freeze tolerant. Acclimation
at 0°C significantly increased survival in a 15-min exposure at −8°C (from 27 to 96%) and −10°C (from 0 to 63%) compared with
the field-fresh and 15°C-treated larvae. Similarly, survival of 0°C-acclimated larvae in a 72-h exposure at −6°C increased
from 20 to 83%. Extending the acclimation period at 0°C to 6 weeks did not produce any further increase in cold tolerance.
The concentrations of glucose and trehalose in larval body fluids increased significantly with low temperature acclimation.
Larvae maintained at 15°C for 3 weeks (none survived for 6 weeks) were less able to survive 1-h exposures between 30 and 35°C
than the 0°C-treated samples. Whilst vegetation and snow cover are an effective buffer against low winter temperatures in
many polar insects, the inability of H. sparsutum larvae to acclimate or survive at 15°C suggests that protection against high summer temperatures is equally important for
this species.
Accepted: 2 August 1999 相似文献
7.
Cold tolerance and dehydration in Enchytraeidae from Svalbard 总被引:4,自引:1,他引:3
L. Sømme T. Birkemoe 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(4):264-269
When cooled in contact with moisture, eight species of arctic Enchytraeidae from Svalbard were killed by freezing within
minutes or hours at −3 and −5 °C; an exception was Enchytraeus kincaidi which survived for up to 2 days. When the temperature approached 0 °C the enchytraeids apparently tried to escape from the
moist soil. The supercooling capacity of the enchytraeids was relatively low, with mean supercooling points of −5 to −8 °C.
In contrast, specimens of several species were extracted from soil cores that had been frozen in their intact state at −15 °C
for up to 71 days. Compared to freezing in a moist environment, higher survival rates were obtained during cooling at freezing
temperatures in dry soil. Survival was recorded in species kept at −3 °C for up to 35 days, and in some species kept at −6 °C
for up to 17 days. Slow warming greatly increased survival rates at −6 °C . The results strongly suggest that arctic enchytraeids
avoid freezing by dehydration at subzero temperatures. In agreement with this, weight losses of up to ca. 42% of fresh weight
were recorded in Mesenchytraeus spp. and of up to 55% in Enchytraeus kincaidi at water vapour pressures above ice at −3 to −6 °C. All specimens survived dehydration under these conditions.
Accepted: 12 December 1997 相似文献
8.
M. Holmstrup L. Sømme 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1998,168(3):197-203
Specimens of the Arctic Collembolon Onychiurus arcticus were exposed to desiccation at several subzero temperatures over ice and at 0.5 °C over NaCl solutions. The effects of desiccation
on water content (WC), body fluid melting point (MP), supercooling point (SCP) and survival were studied at several acclimation
temperatures and relative humidities. Exposure to temperatures down to −19.5 °C caused a substantial and increasing dehydration.
At the lowest exposure temperature unfrozen individuals lost 91.6% of the WC at full hydration but more than 80% of the individuals
survived when rehydrated. Exposure at 0.5 °C to decreasing relative humidities (RH) from 100% to 91.3% caused increasing dehydration
and increasing mortality. Survival of equally dehydrated individuals was higher at subzero temperatures than at 0.5 °C. Concurrent
with the decline in WC a lowering of the MP was observed. Animals exposed to −3 °C and −6 °C over ice for 31 days had a MP
of −3.8 and < −7.5 °C, respectively. Specimens from a laboratory culture had a mean SCP of −6.1 °C, and acclimation at 0 or
−3 °C had little effect on SCPs. Exposure at −8.2 °C over ice for 8 days, however, caused the mean SCP to decline to −21.8 °C
due to the severe dehydration of these individuals. Dehydration at 0.5 °C in 95.1 and 93.3% RH also caused a decline in SCPs
to about −18 °C. Individuals that had been acclimated over ice at −12.4 °C or at lower temperatures apparently did not freeze
at all when cooled to −30 °C, probably because all freezeable water had been lost. These results show that O. arcticus will inevitably undergo dehydration when exposed to subzero temperatures in its natural frozen habitat. Consequently, the
MP and SCP of the Collembola are substantially lowered and in this way freezing is avoided. The increased cold hardiness by
dehydration is similar to the protective dehydration mechanism described in earthworm cocoons and Arctic enchytraeids.
Accepted: 5 January 1998 相似文献
9.
Layne JR Stapleton MG 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2009,179(2):215-221
This study documents post-thaw recovery of jump distance and cryoprotectant mobilization in the freeze-tolerant frog Hyla versicolor over two successive years. Cold acclimated frogs had plasma glycerol levels near 1.0 mM in 2004 but it was nearly 70× higher
during 2005. Freezing of frogs induced nearly identical levels of plasma glycerol (ca. 177 mM) during 2004 and 2005. Plasma
glucose was only mobilized upon somatic freezing, with averages ranging between 21 and 36 mM. Control jump distance showed
no difference between the two years of the study. The post-thaw jump response was identical during the first 2 years despite
large differences in glycerol mobilization between these 2 years. Recovery proceeded much faster in 2005 when frogs mobilized
glycerol prior to freeze exposure. Frogs were more impaired in their locomotion performance during the initial stages of recovery
period when they were frozen at a lower temperature (−3 vs. −1.5°C) but they eventually recovered. Moderate lengthening of
the freeze duration (3 vs. 7 days) with the 2004 collection group did not affect recovery of jump distance when frogs were
frozen at −1.5°C. Hence, postfreeze impairment of locomotion is dependent of the intensity of the freeze temperature but it
is a reversible process that is mitigated when glycerol is more freely distributed to body tissues. 相似文献
10.
Cerrutti P Segovia de Huergo M Galvagno M Schebor C del Pilar Buera M 《Applied microbiology and biotechnology》2000,54(4):575-580
The effects of vacuum-drying and freeze- drying on the cell viability of a commercial baker's yeast, Saccharomyces cerevisiae, strain with different endogenous contents of trehalose were analyzed. An osmotolerant Zygosaccharomyces rouxii strain was used for comparative purposes. Higher viability values were observed in cells after vacuum-drying than after freeze-drying.
Internal concentrations of trehalose in the range 10–20% protected cells in both dehydration processes. Endogenous trehalose
concentrations did not affect the water sorption isotherm nor the T
g values. The effect of external matrices of trehalose and maltodextrin was also studied. The addition of external trehalose
improved the survival of S. cerevisiae cells containing 5% internal trehalose during dehydration. Maltodextrin (1.8 kDa) failed to protect vacuum-dried samples
at 40 °C. The major reduction in the viability during the freeze-drying process of the sensitive yeast cells studied was attributed
to the freezing step. The suggested protective mechanisms for each particular system are vitrification and the specific interactions
of trehalose with membranes and/or proteins. The failure of maltodextrins to protect cells was attributed to the fact that
none of the suggested mechanisms of protection could operate in these systems.
Received: 6 December 1999 / Received revision: 8 May 2000 / Accepted: 19 May 2000 相似文献
11.
J. P. Costanzo A. L. Allenspach R. E. Lee Jr. 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1999,169(4-5):351-359
We investigated function and ultrastructure of sciatic nerves isolated from wood frogs (Rana sylvatica) endemic to the Northwest Territories, Canada, following freezing at −2.5 °C, −5.0 °C, or −7.5 °C. All frogs frozen at −2.5 °C,
and most frogs (71%) frozen at −5.0 °C, recovered within 14 h after thawing began; however, frogs did not survive exposure
to −7.5 °C. Sciatic nerves isolated from frogs frozen at −7.5 °C were refractory to electrical stimulation, whereas those
obtained from frogs surviving exposure to −2.5 °C or −5.0 °C generally exhibited normal characteristics of compound action
potentials. Frogs responded to freezing by mobilizing hepatic glycogen reserves to synthesize the cryoprotectant glucose,
which increased 20-fold in the liver and 40-fold in the blood. Ultrastructural analyses of nerves harvested from frogs in
each treatment group revealed that freezing at −2.5 °C or −5.0 °C had little or no effect on tissue and cellular organization,
but that (lethal) exposure to −7.5 °C resulted in marked shrinkage of the axon, degeneration of mitochondria within the axoplasm,
and extensive delamination of myelin sheaths of the surrounding Schwann cells.
Accepted: 28 April 1999 相似文献
12.
《Cryobiology》2018
Sperm vitrification is a low cost and simple technique that does not require special equipment and may represent an attractive alternative to the costly and time consuming conventional dog spermatozoa cryopreservation techniques. The objective of this study was to evaluate different cryoprotectants and warming temperatures on the vitrification of dog spermatozoa. Pooled semen samples from 10 beagle dogs were vitrified with four extenders, based on Tris, citric acid and glucose, 20% egg yolk (TCG-20% EY) and different combinations of sucrose and/or trehalose: 250 mM sucrose; 250 mM trehalose; 125 mM sucrose + 125 mM trehalose; 250 mM sucrose + 250 mM trehalose. Samples were vitrified by dropping 50 μL of sperm suspension directly into liquid nitrogen. After vitrification, warming was done either fast (at 65 °C for 2–5 s) or slow (at 37 °C for one minute). Motility was assayed using a computer-aided sperm analysis (CASA) system; membrane integrity and acrosomal status were analyzed by fluorescence microscopy. For comparison, samples were also conventionally frozen in liquid nitrogen vapor using a TCG-20% egg yolk extender plus 5% glycerol. Frozen straws were thawed in a water bath at 37 °C for 30 s. Poorer motility results (P < 0.05) but similar viability were obtained when vitrification was performed, compared to conventional freezing (P > 0.05). When vitrification was used, cryoprotectants containing either 250 mM sucrose or 250 mM trehalose and warmed at 37 °C returned the best sperm quality variables. 相似文献
13.
Colauto Nelson Barros da Eira Augusto Ferreira Linde Giani Andrea 《World journal of microbiology & biotechnology》2011,27(12):3015-3018
The preservation of Agaricus blazei is generally done by mycelial subculturing, but this technique may cause genetic degenerations. Despite this, there is not
an efficient protocol established to preserve this fungus and cryopreservation could be an alternative. This study aimed to
evaluate two freezing protocols for cryopreservation at −80°C of A. blazei strains. Five fungus strains grown on rice grains with husk and were transferred to glycerol (10%) in cryovials. Next, the
cryovials were submitted to two freezing temperature protocols: (1) cryopreservation starting at 25°C, then at 8°C for 30 min
and kept at −80°C; (2) cryopreservation starting at 25°C, then 8°C for 30 min, −196°C for 15 min and kept at −80°C. After
1 year of cryopreservation, the cryovials were thawed in a water bath at 30°C for 15 min and transferred to malt extract agar
medium. It was concluded that the one-year cryopreservation process of A. blazei, grown on rice grains and cryopreserved at −80°C in glycerol 10%, is viable. The slow freezing, from 8 to −80°C, is effective
whereas the fast freezing, from 8 to −196°C and then to −80°C, is ineffective. The different genetic characteristics among
the strains of this fungus do not interfere in the cryopreservation process. 相似文献
14.
The adaptive fitness of a freeze-tolerant insect may be mediated by both endogenous and exogenous interactions. The aim of
the study presented here was to characterize the freeze tolerance of alpine Tiger moth caterpillars (Metacrias huttoni) and highlight two poorly explored indices of the potential attrition of fitness: (1) downstream development and reproduction;
(2) parasitism. Caterpillars survived temperatures as low as −16°C and demonstrated >90% 72-h survival after exposures to
−10°C. Two-week acclimations at 5, 10, and 20°C had no effect on body water content, haemolymph osmolality or survival of
equilibrium freezing, but there was a significant elevation of the temperature of crystallization (T
c) in those caterpillars acclimated to 5°C. Cell viability of fat body tissue was resilient to freezing (−10 to −16°C), but
midgut and tracheal cells showed significant degradation. Pupation and eclosion were unaffected by freezing at −5 or −10°C.
Likewise, there were no significant differences in egg production or the proportion of eggs that hatched between control and
frozen insects. By contrast, the ability of tachinid larvae to survive freezing within their hosts means that parasitism plays
an important role in regulating population size. Mean parasitism of caterpillars by tachinids was 33.3 ± 7.2%. Pupation and
imago emergence of tachinids after host ‘endo-nucleation’ was >75%. Eclosed adult tachinids showed a non-significant increase
in the incidence of wing abnormalities in relation to low temperature exposure. 相似文献
15.
Cryopreservation of shoot tips from in vitro plants of sweet potato [Ipomoea batatas (L.) Lam.] by vitrification 总被引:8,自引:0,他引:8
Routine cryopreservation of shoot tips from sweet potato [Ipomoea batatas (L.) Lam] has been hampered by their survival variability after cryogenic exposure. We examined the effects of light conditions
on stock plants, sucrose preculture and cryoprotectant loading on survival after vitrification using PVS2 solution. The survival
of vitrified sweet potato shoot tips cooled to approximately –208 °C was increased by preculturing with 0.3 M sucrose for 24 h at 22 °C. Survival was also enhanced by excising shoot tips immediately after the 8-h dark photoperiod.
The best survival after cryogenic exposure was obtained using 2 M glycerol +0.4 M sucrose for 1 h at 22 °C followed by dehydration with PVS2 for 16 min at 22 °C. Rapid cooling was used and achieved by
the immersion of foil strips into partially solidified nitrogen. Successfully vitrified and warmed shoot tips directly developed
shoots on a medium containing 1 μM NAA, 0.5 μM BA and 0.1 μM kinetin with only minimum callus formation. Shoot formation occurred in all surviving shoot tips. This procedure shows promise
for cryopreserving sweet potato shoot tips.
Received: 2 March 1999 / Revision received: 21 September 1999 / Accepted: 29 September 1999 相似文献
16.
Andrey V. Boroda Nina A. Aizdaicher Nelly A. Odintsova 《Journal of applied phycology》2014,26(1):387-397
The development of cryopreservation methods for microalgae opens great prospects for marine biotechnology and aims to establish a bank of cryopreserved cultures. Eight of ten marine microalgae species used in this study (the diatoms, green, red, and golden algae), including five previously untested species, were successfully recovered after freezing to ultra-low temperatures (?196 °C) using penetrating (dimethyl sulfoxide, glycerol, and ethylene glycol) and non-penetrating (trehalose and polyvinylpyrrolidone) cryoprotectants. We found that ethylene glycol in combination with trehalose possessed the most effective cryoprotective activity among the algae cryoprotectants tested. However, the chief factor for the successful preservation of microalgal cells during freeze–thawing was shown to be the cooling rate. Cooling was performed in two ways: step or fast droplet freezing. The droplet freezing described here was effective only for cryopreserving green algae, whereas step freezing was optimal for all other algal species. Three diatoms of the genus Attheya were successfully cryopreserved for the first time, but none of the tested protocols had a positive result for the diatoms belonging to Pseudo-nitzschia. The failure may be explained rather by peculiarities in the cell wall composition (higher content of silica and fewer organic components) than by the specific (long and thin) shape of these cells. The pigment content in all of the studied species tended to decrease after thawing as compared with unfrozen cells and increase significantly during cell recovery. Cryosensitivity of marine algae depended on the differences in natural intrinsic characteristics rather than their taxonomic position. 相似文献
17.
J G Lewis R P Learmonth P V Attfield K Watson 《Journal of industrial microbiology & biotechnology》1997,18(1):30-36
Fourteen wild-type baking strains of Saccharomyces cerevisiae were grown in batch culture to true stationary phase (exogenous carbon source exhausted) and tested for their trehalose
content and their tolerance to heat (52°C for 4.5 min), ethanol (20% v/v for 30 min), H2O2 (0.3 M for 60 min), rapid freezing (−196°C for 20 min, cooling rate 200°C min−1), slow freezing (−20°C for 24 h, cooling rate 3°C min−1), salt (growth in 1.5 M NaCl agar) or acetic acid (growth in 0.4% w/v acetic acid agar) stresses. Stress tolerance among
the strains was highly variable and up to 1000-fold differences existed between strains for some types of stress. Compared
with previously published reports, all strains were tolerant to H2O2 stress. Correlation analysis of stress tolerance results demonstrated relationships between tolerance to H2O2 and tolerance to all stresses except ethanol. This may imply that oxidative processes are associated with a wide variety
of cellular stresses and also indicate that the general robustness associated with industrial yeast may be a result of their
oxidative stress tolerance. In addition, H2O2 tolerance might be a suitable marker for the general assessment of stress tolerance in yeast strains. Trehalose content
failed to correlate with tolerance to any stress except acetic acid. This may indicate that the contribution of trehalose
to tolerance to other stresses is either small or inconsistent and that trehalose may not be used as a general predictor
of stress tolerance in true stationary phase yeast.
Received 10 October 1995/ Accepted in revised form 10 September 1996 相似文献
18.
J. P. Costanzo J. B. Moore R. E. Lee Jr. P. E. Kaufman J. A. Wyman 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(3):169-176
This investigation examined the influence of soil moisture and associated parameters on the cold hardiness of the Colorado
potato beetle (Leptinotarsa decemlineata Say), a temperate-zone species that overwinters in terrestrial burrows. The body mass and water content of adult beetles
kept in sand at 4 °C varied over a 16-week period of diapause according to the substratum's moisture content. Changes in body
water content, in turn, influenced the crystallization temperature (range −3.3 to −18.4 °C; n = 417), indicating that environmental moisture indirectly determined supercooling capacity, a measure of physiological cold
hardiness. Beetles held in dry sand readily tolerated a 24-h exposure to temperatures ranging from 0° to −5 °C, but those
chilled in sand containing as little as 1.7% water (dry mass) had elevated mortality. Thus, burrowing in dry soils not only
promotes supercooling via its effect on water balance, but may also inhibit inoculative freezing. Mortality of beetles exposed
to −5 °C for 24 h was lower in substrates composed of sand, clay and/or peat (36–52%) than in pure silica sand (78%) having
an identical water content (17.0% dry mass). In addition to moisture, the texture, structure, water potential, and other physico-chemical
attributes of soil may strongly influence the cold hardiness and overwintering survival of burrowing insects.
Accepted: 10 September 1996 相似文献
19.
Abstract Diapause larvae of the European corn borer (Ostrinia nubilalis (Hubn.)) and the related Mediterranean noctuid Sesamia cretica Led. possess sufficient supercooling ability to avoid freezing over their normal environmental temperature ranges. In progressive chilling experiments (10 days acclimation at each 5° step in the temperature range from 15 to ?5°C), mean supercooling points (measured at a cooling rate of 0.1°C min?1) were lowered from ?20.4°C at 15°C to ?24.0°C at 5°C (lower lethal temperatures: c.?28°C) in O.nubilalis, compared with ?15.0 to ?17.2°C (lower lethal temperatures: ?15 to ?17°C respectively) in S.cretica. Concentrations of glycerol and trehalose determined by gas chromatography of whole body extracts were consistently higher in the former than in the latter species at both 15 and 5°C, and may be responsible for the deeper supercooling in O.nubilalis larvae. Acclimation to 5°C increased glycerol levels in O. nubilalis extracts compared with 15°C, and this was enhanced in larvae exposed for a further 10 days at each of 0 and ?5°C (glycerol being 438μmol ml?1 body water). Haemolymph glycerol concentrations showed a similar pattern to whole body extracts in this species. Fat body glycogen was reduced during low temperature acclimation in both species. Body water contents did not change with acclimation in O.nubilalis, whilst S.cretica, containing significantly more water, lost c.7% during acclimation from 15 to 5°C. Haemolymph osmolalities increased during acclimation, especially in Ostrinia larvae, probably as a result of the accumulation of cryoprotectants. The majority of O.nubilalis larvae survived freezing under the conditions of the cooling experiments, whilst larvae of S.cretica did not, thereby confirming an element of freezing tolerance in the former. 相似文献
20.
Jekkel Zs. Gyulai G. Kiss J. Kiss E. Heszky L.E. 《Plant Cell, Tissue and Organ Culture》1998,52(3):193-197
Cryopreservation of somatic embryos of Aesculus hippocastanum L. cultured on nutritive media containing abscisic acid (ABA)
at concentrations of 0.75 μM, 7.5 μM and 75.0 μM was evaluated for three cooling methods: (i) slow freezing with cryoprotectants,
(ii) fast freezing with cryoprotectants, and (iii) fast freezing with desiccation techniques. The ‘cryoprotectant’ freezing
techniques included the embryo pretreatment on ABA containing medium for 4 days, followed by cryoprotective treatment in liquid
medium containing 0.5 M dimethylsulfoxide, 0.5 M glycerol, 1.0 M sucrose, and cooled at slow, and rapid rates. Embryos pretreated
on a medium containing 0.75 μM ABA, and cooled to −35 °C at 1°C /min, held for 30 min at this transfer temperature and then
immersed in liquid nitrogen (LN) had the best embryo recovery (43%). The ‘desiccation’ method involved an air drying step
of similar ABA-pretreated, non-cryoprotected embryos followed by rapid cooling. Embryos precultured on 0.75 μM ABA, then subjected
to a 4 h period of air desiccation (water content reduction to 13%) showed about the same level of survival (46%) as found
with the ‘cryoprotectant’ slow freezing technique. The air-dry ‘desiccation’ method is easier to apply than the more complicated
‘cryoprotectant’ method.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献