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1.
Voituron Y Paaschburg L Holmstrup M Barré H Ramløv H 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2009,179(2):223-230
Freeze tolerance and changes in metabolism during freezing were investigated in the moor frog (Rana arvalis) under laboratory conditions. The data show for the first time a well-developed freeze tolerance in juveniles of a European
frog capable of surviving a freezing exposure of about 72 h with a final body temperature of −3°C. A biochemical analysis
showed an increase in liver and muscle glucose in response to freezing (respectively, 14-fold and 4-fold between 4 and −1°C).
Lactate accumulation was only observed in the liver (4.1 ± 0.8 against 16.6 ± 2.4 μmol g−1 fresh weight (FW) between 4 and −1°C). The quantification of the respiratory metabolism of frozen frogs showed that the aerobic
metabolism persists under freezing conditions (1.4 ± 0.7 μl O2 g−1 FW h−1 at −4°C) and decreases with body temperature. After thawing, the oxygen consumption rose rapidly during the first hour (6-fold
to 16-fold) and continued to increase for 24 h, but at a lower rate. In early winter, juvenile R. arvalis held in an outdoor enclosure were observed to emerge from ponds and hibernate in the upper soil and litter layers. Temperature
recordings in the substratum of the enclosure suggested that the hibernacula of these juvenile frogs provided sheltering from
sub-zero air temperatures and reduced the time spent in a frozen state corresponding well with the observed freeze tolerance
of the juveniles. This study strongly suggests that freeze tolerance of R. arvalis is an adaptive trait necessary for winter survival. 相似文献
2.
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
3.
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
4.
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
5.
Changes in selected aspects of immune function in the leopard frog, Rana pipiens, associated with exposure to cold 总被引:3,自引:0,他引:3
Gregory D. Maniero Cynthia Carey 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(4):256-263
The effect of exposure to low temperatures (5 °C) on lymphocyte proliferation, leukocyte populations, and serum complement
levels was examined in the northern leopard frog, Rana pipiens. Proliferation of T lymphocytes in response to phytohemagglutinin stimulation was significantly decreased in frogs kept for
2, 3, and 5 months at 5 °C compared to that of animals kept at 22 °C. A significant increase in the average percentage of
neutrophils and a decrease in the mean percentage of eosinophils was observed in the blood of frogs held for 5 months in the
cold compared to animals held at 22 °C for the same length of time. Mean serum complement activity after 1 month at 5 °C was
significantly reduced in comparison to animals held at 22 °C and was not detectable after 5 months in the cold. Recovery of
complement levels at room temperature (22 °C) was also examined after cold exposure. Complement levels were significantly
higher than controls (at 22 °C) in frogs returned to 22 °C for 7 and 14 days after 5 months in the cold. After frogs were
held at 5 °C for 1 month, serum complement levels increased significantly within 2 days after returning to 22 °C and continued
to rise 5 and 9 days after warming. Injections with Aeromonas hydrophila following a 5-week exposure to 5 °C failed to cause death or observable symptoms of disease in frogs that were returned to
22 °C.
Accepted: 20 November 1996 相似文献
6.
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
7.
Effects of hypothermic hypoxia on anaerobic energy metabolism in isolated anuran livers 总被引:1,自引:0,他引:1
C. A. Fedorow T. A. Churchill N. M. Kneteman 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1998,168(8):555-561
Many lower vertebrates (reptilian and amphibian species) are capable of surviving natural episodes of hypoxia and hypothermia.
It is by specific metabolic adaptations that anurans are able to tolerate prolonged exposure to harsh environmental stresses.
In this study, it was hypothesized that livers from an aquatic frog would possess an inherent metabolic ability to sustain
high levels of ATP in an isolated organ system, providing insight into a metabolic system that is well-adapted for low temperature
in vitro organ storage. Frogs of the species, R. pipiens were acclimated at 20 °C and at 5 °C. Livers were preserved using a clinical preservation solution after flushing. Livers
from 20 °C-acclimated frogs were stored at 20 °C and 5 °C and livers from 5 °C-acclimated frogs were stored at 5 °C. The results
indicated that hepatic adenylate status was maintained for 96 h during 5 °C storage, but not longer than 4–10 h during 20 °C
storage. In livers from 5 °C-acclimated animals subjected to 5 °C storage, ATP was maintained at 100% throughout the 96-h
period. Warm acclimation (20 °C) and 20 °C storage resulted in poorer maintenance of ATP; energy charge values dropped to
0.50 within 2 h and by 24 h, only 24% of control ATP remained. Lactate levels remained less than 25 μ mol/g dry weight in
all 5 °C-stored livers; 20 °C-stored livers exhibited greater accumulation of this anaerobic end-product (lactate reached
45–50 μ mol/g by 10 h). The data imply that hepatic adenylate status is largely dependent on exposure to hypothermic hypoxia
and although small amounts of ATP were accounted for by anaerobic glycolysis, there must have been either a substantial reduction
in cellular energy-utilization or an efficient use of low oxygen tensions.
Accepted: 24 August 1998 相似文献
8.
Hartley LM Packard MJ Packard GC 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2000,170(1):45-50
Hatchlings of the North American painted turtle (Chrysemys picta) typically spend their first winter of life inside the shallow, subterranean nest where they completed embryogenesis the
preceding summer. Neonates at northern localities consequently may be exposed during winter to subzero temperatures and frozen
soil. Hatchlings apparently survive exposure to such conditions by supercooling, but the physiological consequences of this
adaptive strategy have not been examined. We measured lactate in hatchling painted turtles after exposure to each of three
temperatures (0 °C, −4 °C, and −8 °C) for three time periods (5 days, 15 days, and 25 days) to determine the extent to which
overwintering hatchlings might rely on anaerobic metabolism to regenerate ATP. Whole-body lactate increased with increasing
duration of exposure and decreasing temperature, and the highest levels were associated with the group that experienced the
highest mortality. These results indicate that animals may develop a considerable lactic acidosis during a winter in which
temperatures fall below 0 °C for weeks or months and that accumulation of lactate may contribute to mortality of overwintering
animals.
Accepted: 20 October 1999 相似文献
9.
A heat shock following electroporation induces highly efficient transformation of Corynebacterium glutamicum with xenogeneic plasmid DNA 总被引:10,自引:0,他引:10
An improved method for the electrotransformation of wild-type Corynebacterium glutamicum (ATCC 13032) is described. The two crucial alterations to previously developed methods are: cultivation of cells used for
electrotransformation at 18 °C instead of 30 °C, and application of a heat shock immediately following electrotransformation.
Cells cultivated at sub optimal temperature have a 100-fold improved transformation efficiency (108 cfu μg−1) for syngeneic DNA (DNA isolated from the same species). A heat shock applied to these cells following electroporation improved
the transformation efficiency for xenogeneic DNA (DNA isolated from a different species). In combination, low cultivation
temperature and heat shock act synergistically and increased the transformation efficiency by four orders of magnitude to
2.5 × 106 cfu μg−1 xenogeneic DNA. The method was used to generate gene disruptions in C. glutamicum.
Received: 26 March 1999 / Received revision: 9 June 1999 / Accepted: 11 June 1999 相似文献
10.
The freeze tolerant wood frog Rana sylvatica was studied to determine the impact of the freezing and thawing of this frog on the activity of γ-glutamyltranspeptidase in the liver. On exposure to ?2·5°C, for 1, 12 and 24 h, frogs were found to be cool, covered with ice crystals and frozen, respectively. Thawing for 24 h at 4°C recovered the frogs completely. A 45 per cent decrease in the liver weight: body weight ratio was notable after 1 h at ?2·5°C, suggestive of an early hepatic capacitance response. A glycemic response to freezing was observed: blood glucose levels exhibited a 55 per cent decrease after 1 h at ?2·5°C on cooling; a 10·5-fold increase after 12 h at ?2·5°C on the initiation of freezing; and a 22-fold increase after 24 h at ?2·5°C in the fully frozen state. Blood glucose levels remained elevated four-fold in the thawed state. Plasma insulin levels were increased twofold in the frozen state and 1·8-fold in the thawed state, while plasma ketone levels were increased 1·8-fold in the frozen state and 1·5-fold in the thawed state. Plasma total T3 levels were decreased by 22 per cent in the frozen state and normalized on thawing. In homogenates and plasma membranes isolated from the livers of Rana sylvatica, the activity of γ-glutamyltranspeptidase was found to be elevated at all stages of the freeze–thaw process. After 1, 12 and 24 h at ?2·5°C, activities were increased 2·5-, 2·3-, 2·4-fold respectively in the homogenates and 2·5-, 2·2-, 2·4-fold respectively in the plasma membranes. After thawing, activities were still increased 1·9-fold in both homogenates and plasma membranes. In homogenates prepared from the kidneys of Rana sylvatica, the activity of γ-glutamyltranspeptidase was increased 1·4-fold after 1 h at ?2·5°C after which it returned to normal. The role of thyroid hormone in producing the increase in γ-glutamyltranspeptidase in the liver of Rana sylvatica in response to freezing is discussed as is the significance of the enzyme increase in terms of hepatic cytoprotection and freeze tolerance. 相似文献
11.
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
12.
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
13.
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
14.
TheRhodotorula rubra strain isolated from waste waters of a gold mining plant has demonstrated the ability to grow in the presence of cyanide.
The maintenance of this strain in complex organic media leads to a loss of this ability. To preserve the cyanide resistance
ofR. rubra we tested the following maintenance methods: subculturing in sterile distilled water, freezing at −20, −40, −70°C, liquid
nitrogen freezing and the paper replica method. The ability to grow in the presence of cyanide was preserved and a higher
viability level was observed for cells maintained frozen at −70°C, in liquid nitrogen and by the paper replica method. Preservation
in distilled water resulted in the lowest viability after twelve months of storage. 相似文献
15.
Lynn R. Trusal Albert W. Guzman Carol J. Baker 《In vitro cellular & developmental biology. Plant》1984,20(4):353-364
Summary The pathophysiology of endothelial cells is important to a variety of vascular conditions including coagulation and hemostasis
resulting from clinical frostbite. Use of an in vitro model system demonstrated that when bovine endothelial cells were frozen
at 1°C or 20°C/min and thawed immediately (20°C/min), a variety of ultrastructural alterations occurred. Membraneous structures
were most extensively damaged, with mitochondria the most sensitive organelle. Low amplitude mitochondrial swelling, first
evident at 0°C, progressed to high amplitude swelling by −10°C (frozen). In addition, the rough endoplasmic reticulum was
dilated and formed large vesicles with a homogeneous matrix. Nuclear changes first occurred at −15°C. These included separation
and distortion of the nuclear membrane, changes in chromatin distribution, and disruption of the nucleolus. Scanning electron
microscopy revealed perforated plasma membranes in some cells at −10°C (frozen) and in most cells by −20°C. Cultures frozen
at 20°C/min revealed mostly the same ultrastructural damage noted at 1°C/min except a higher percentage of cells exhibited
alterations. Data from the recovery index and lactic dehydrogenase (LDH) release correlated well with observed ultrastructural
changes. Early swelling of mitochondria and dilation of rough endoplasmic reticulum was not lethal in the absence of freezing.
Increased swelling in cytoplasmic organelles coupled with nuclear alterations at −15°C resulted in a decreased survival rate
and release of significant quantities of LDH by −20°C. No unique morphological changes were temperature specific, but the
total number of cells that displayed alterations increased as temperature decreased.
The views, opinions or findings, or both, contained in this report are those of the authros and should not be construed as
indicative of an official Department of the Army position, policy, or decision unless so designated by other official documentation. 相似文献
16.
M. Jose Comez-L Pilar Lopez Jose V. Castell 《In vitro cellular & developmental biology. Plant》1984,20(11):826-832
Summary The present study was undertaken to define the conditions for optimal cryopreservation of hepatocytes. Two different freezing
procedures were analyzed: a slow freezing rate (SFR) (−2° C/min down to −30°C and then quick freezing to −196° C) and a fast
freezing rate (FFR) (direct freezing of tubes to −196° C: −39° C/min). Cells were frozen in fetal bovine serum containing
10% Dimethyl sulfoxide (DMSO). After rapid thawing at 37° C, followed by dilution and removal of the cryoprotectant, cells
were plated and several parameters were followed as criteria for optimal cryopreservation of cells. The FFR cells showed no
apparent ultrastructural damage after 24 h of culture. Plating efficiency and spreading were similar as controls. Gluconeogenesis
from pyruvate and fructose, tyrosine amino transferase induction by glucagon and dexamethasone, urea production, and plasma
protein synthesis of FFR cells were similar to those found in control cultures. The FFR procedure, in comparison to the SFR
method, seemed to render the best preserved hepatocytes.
The financial support for this work was from Fondo de Investigaciones Sanitarias de la Seguridad Social, Grants 41/82 and
48/82. 相似文献
17.
The effects of light and elevated temperatures on the efficiency of energy conversion in PSII [?PSII = (Fm′−Fs)/Fm′], pigment composition and heat tolerance of shade-acclimated Alocasia macrorrhiza were investigated. Leaf discs were exposed for 3 h to high light (HL; 1600 μmol photons · m−2 · s−1) or low light (LL; 20 μmol photons · m−2 · s−1) and a series of constant temperatures ranging from 30 to 49 °C. All HL treatments led to rapid and severe decreases in ?PSII. During the 2-h recovery period (LL, 25 °C) following the HL treatments, fast and slow recovery phases could be distinguished.
Leaf discs that had experienced HL and 30 °C recovered completely while no recovery of ?PSII was seen after a 3-h exposure to HL and 45 °C. A 3-h exposure to 45 °C at LL led to a less severe decrease in ?PSII and complete recovery was accomplished after less than 1 h. Under LL conditions a temperature of 49 °C was necessary to cause
an irreversible decrease in ?PSII, followed by necrosis the next day. Streptomycin had no effect on the degree of reduction and recovery in ?PSII discs exposed to HL and 35–45 °C, but partially inhibited recovery in discs exposed to HL and 30 °C. Streptomycin led to
a more severe decrease in ?PSII at LL and 49 °C and completely inhibited recovery. Streptomycin had no effect on the conversion of the xanthophyll-cycle
pigments during the treatment or the recovery. The epoxidation state was roughly the same in all leaf discs after a 3-h HL
treatment (0.270–0.346) irrespective of the exposure temperature. The back-conversion of zeaxanthin into violaxanthin after
a 2-h recovery period was only seen in leaf discs that had been exposed to HL and 30 °C. The thermotolerance of shade A. macrorrhiza leaves of 49.0 ± 0.7 °C (determined by fluorescence) coincided with the temperature at which damage occurred in leaf discs
exposed to LL. However, under HL the critical temperature under which necrosis occurred was much lower (42 °C). The thermotolerance
of A. macrorrhiza shade leaves could be increased by a short exposure (<20 min) to slightly elevated temperatures.
Received: 11 June 1997 / Accepted: 9 September 1997 相似文献
18.
Settled zoospores of the green macroalga Enteromorpha intestinalis were subjected to several different freezing and storing
treatments at both cryogenic and non-cryogenic temperatures after which their viability was assessed using a spore germination
bioassay. Three different cooling rates were tested: slow cooling at –1°C min−1 and –0.5°C min−1 to end temperatures in the range –20°C to –40°C, and a two-step procedure whereby the spores were frozen to –30°C at a rate
of –1°C min−1 prior to immersion in liquid nitrogen at –196°C. Spore viability was also investigated using the cryoprotectants glycerol
and dimethyl suphoxide (DMSO), a reduced saline medium and various storage times. In the majority of experiments, the use
of a cryoprotectant during the freezing process significantly increased the viability of the spores, with DMSO affording slightly
greater protection than glycerol. All treatments produced high viabilities (ranging from 75.3–100.0%) after 5-min storage
at the different end temperatures. However, progressively longer storage up to 7 days generally resulted in a marked reduction
in viability. This was with the exception of spores frozen in a reduced saline medium; a medium of 75% seawater and either
5 or 10% DMSO greatly increased spore viability, with values of > 40% recorded for spores stored at –20°C for up to 5 weeks.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
19.
C. E. Crocker J. J. Cech Jr. 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1998,168(1):50-60
The effect of environmental hypercapnia on respiratory and acid-base variables was studied in white sturgeon, Acipenser transmontanus. Blood PCO2, PO2, pH, hemoglobin concentration, and plasma lactate, glucose, catecholamines and cortisol were measured first under normocapnia
(water PCO2 < 0.5 Torr, 1 Torr = 133.32 Pa), then under hypercapnia (25–35 Torr) and a final return to normocapnia at 19 ± 0.5 °C. Acute
(≤ 2h) hypercapnia significantly increased arterial PCO2 (8-fold increase), ventilation frequency (2-fold increase), plasma HCO3
− (2.3-fold) and decreased arterial pH (to 7.15 ± 0.02). After 24 h, norepinephrine, epinephrine and cortisol, were significantly
increased, and arterial pH reached its nadir (7.10 ± 0.03). During the 72- and 96-h-periods, arterial PCO2 (24 ± 4.4 Torr) and ventilatory frequency (105 ± 5 breaths min−1) stabilized, HCO3
− reached its apparent maximum (23.6 ± 0.0 mmol−1), glucose decreased by 32%, and pH increased significantly to 7.31 + 0.03. The return to normocapnia completely restored
arterial PCO2 (2.5 ± 0.14 Torr), HCO3
− (7.4 ± 0.59 mmol · l−1), ventilation frequency (71 ± 7 breaths · min−1), and pH (7.75 ± 0.04). Overall, hypercapnia produced a respiratory acidosis, hyperventilation, a transient norepinephrine
“spike”, and increased plasma catecholamines, cortisol, and arterial PO2. The respiratory acidosis was only partially compensated (35% pH restoration) 96 h after the onset of hypercapnia and resulted
in a significantly decreased blood-O2 affinity (Bohr effect), as determined by construction of in vitro blood O2 equilibrium curves at 15 °C and 20 °C. Prolonged exposure to hypercapnia may lead to acid-base disturbances and negatively
affect growth of white sturgeon.
Accepted: 17 August 1997 相似文献
20.
Josef Elster Peter Degma Ľubomír Kováčik Lucia Valentová Katarína Šramková Antonio Batista Pereira 《Biologia》2008,63(6):843-851
The freezing and desiccation tolerance of 12 Klebsormidium strains, isolated from various habitats (aeroterrestrial, terrestrial, and hydro-terrestrial) from distinct geographical
regions (Antarctic — South Shetlands, King George Island, Arctic — Ellesmere Island, Svalbard, Central Europe — Slovakia)
were studied. Each strain was exposed to several freezing (−4°C, −40°C, −196°C) and desiccation (+4°C and + 20°C) regimes,
simulating both natural and semi-natural freeze-thaw and desiccation cycles. The level of resistance (or the survival capacity)
was evaluated by chlorophyll a content, viability, and chlorophyll fluorescence evaluations. No statistical differences (Kruskal-Wallis tests) between strains
originating from different regions were observed. All strains tested were highly resistant to both freezing and desiccation
injuries. Freezing down to −196°C was the most harmful regime for all studied strains. Freezing at −4°C did not influence
the survival of studied strains. Further, freezing down to −40°C (at a speed of 4°C/min) was not fatal for most of the strains.
RDA analysis showed that certain Antarctic and Arctic strains did not survive desiccation at +4°C; however, freezing at −40°C,
as well as desiccation at +20°C was not fatal to them. On the other hand, other strains from the Antarctic, the Arctic, and
Central Europe (Slovakia) survived desiccation at temperatures of +4°C, and freezing down to −40°C. It appears that species
of Klebsormidium which occupy an environment where both seasonal and diurnal variations of water availability prevail, are well adapted to
freezing and desiccation injuries. Freezing and desiccation tolerance is not species-specific nor is the resilience only found
in polar strains as it is also a feature of temperate strains.
Presented at the International Symposium Biology and Taxonomy of Green Algae V, Smolenice, June 26–29, 2007, Slovakia.
This paper is dedicated to the memory of the late Dr. Bohuslav Fott (1908–1976), Professor of Botany at the Charles University
in Prague, to mark the centenary of his birth. 相似文献