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PubMed1986

Effect of acclimation to caging on nephrotoxic response of rats to uranium.

Animal studies of the toxicity and metabolism of radionuclides and chemicals often require housing of rats in metabolism cages for excreta collection. Response of rats to toxic substances may be affected by environmental factors such as the type of cage used. Dose-response studies were conducted to assess the effects of two types of cages on the nephrotoxic response of rats to uranium from implanted refined uranium ore (yellowcake). The LD50/21 days was 6 mg of uranium ore per kilogram body weight (6 mg U/kg). The 95% confidence limit (C.L.) was 3-8 mg U/kg for rats housed in metabolism cages beginning on the day of implantation (naive rats). However, for rats housed in metabolism cages for 21 days before implantation (acclimated rats) the LD50/21 days was 360 mg U/kg (95% C.L. = 220-650 mg U/kg), which was the same value obtained for rats housed continuously in polycarbonate cages. This significant difference (P less than 0.01) in response of naive rats compared to response of acclimated rats appeared related to a significantly lower water consumption by the naive rats.

Acclimatization↗
PubMed1979

Effect of vasopressin on vascular smooth muscle from cold- and warm-acclimated rabbits.

Contractile properties of helical auricular arterial strips from warm- and cold-acclimated (WA and CA) rabbits were studied to determine whether vascular smooth muscle shows a cold-induced alteration in response to vasopressen (Vp), similar to the effect seen with catecholamines. The CA response was decreased at all Vp concentrations tested and the decreases were significant at doses between 0.4--100.0 mUnits Vp/ml. Results are discussed in relation to the altered renal tubular response to Vp which has previously been reported to occur in cold-acclimated animals.

Acclimatization↗
PubMed1981

Reactivity of helical strips of carotid arteries from cold- and warm-acclimated rabbits: effects of adrenergic agents, angiotensin II, and KCI.

Increased quantities of catecholamines are found in the adrenals of animals exposed to cold and thus, many studies have focused on determining the effects of catecholamines on metabolism (calorigenesis) and thermoregulation (vasomotor control of superficial blood vessels) during severe cld stress. Many of those studies have shown that the vasoconstriction which occurs in rabbit ears subsequent to an infusion of norepinephrine is diminished in cold-acclimated animals. The present in vitro study investigates the effects of 3 adrenergic agents (phenylephrine, norepinephrine, epinephrine) and 2 non-adrenergic agents (angiotensin II and KC1) on vascular smooth muscle which is though not to participate in the thermoregulatory processes. The sensitivity of helical strips of carotid arteries from cold-acclimated (CA) rabbits to phenylephrine, norepinephrine and angiotensin was decreased from control level (WA), as was the maximum developed tension. Epinephrine showed no statistically relevant decrease in sensitivity, and KC1, showed changes in neither sensitivity nor maximal tension. Histological examination of cross-sections of carotid arteries did not reveal any decrease in wall thickness which might account for the decrease in sensitivity and maximal tension. It is suggested that arterial smooth muscle throughout the body is affected by prolonged cold exposure in its responses to a wide range of constrictor agents.

Acclimatization↗
PubMed1995

Physical performance and heat tolerance after chronic water loading and heat acclimation.

Heat acclimation (HA) and forced water intake (FWI) have both been found to improve the endurance of human subjects working in hot environments. Therefore, we studied the interaction between HA and FWI. Prior to any treatment (control, AI and BI) the subjects (n = 9) underwent a heat tolerance (HT) test. Thereafter, they were divided into two groups. The first (n = 5) were heat-acclimated (AII), underwent a second HT test, doubled their normal daily water intake for 1 week (AIII), and underwent a third HT test; the second group (n = 4) were subjected to the same protocol, except that the FWI came before and during HA (BII). It was found that both regimens (phases AII and BII) significantly increased work duration. Although the results of the two methods were similar, their combination somewhat lengthened work tolerance time (phases AIII, BIII). Maximal oxygen uptake did not change after HA (BII) or FWI (AII), but the maximal values were attained at significantly lower heart rates, both after BII alone or combined with HA (BIII). In an additional experiment, the time needed to "ride" 15 km on a bicycle ergometer was reduced by 10% after FWI as compared to control time.

Acclimatization↗
PubMed1994

Is heat acclimation able to increase whole-body sensitivity to insulin?

The aim of the present study was to determine whether heat acclimation increases whole-body sensitivity to insulin. Male Wistar rats were kept at 34 degrees C for 2 weeks (HA group). Warm-acclimated rats (WA group) at 25 degrees C served as controls. The glucose infusion rate (GIR) was assessed as an index of in vivo insulin sensitivity, using a hyperinsulinemic euglycemic clamp technique. Moreover, the 125I-insulin binding capacity to purified insulin receptor preparations from m. gastrocnemius of rats after 1, 7, or 14 days of heat exposure was examined. Mean GIR values of HA group were slightly higher than those of WA group, but not significant. The great deviation of the HA group, however, appeared to exist. About half of HA rats showed markedly high GIR values (p < 0.01 vs. WA group). Mean GIR value of the remaining HA rats were significantly (p < 0.05) lower than those of the WA group. Likewise, the binding capacity to 125I-insulin was not significantly different among the periods of time of heat exposure, and the deviation went on increasing from 1 to 14 days. These results suggest that there is a wide individual difference between the changes in glucose metabolism under heat exposure. In view of such results, there appears to be a great need for further studies on the factors affecting the variation of insulin action.

Acclimatization↗
PubMed1993

Purification, characterization and cDNA cloning of the 200 kDa protein induced by cold acclimation in wheat.

We have purified to homogeneity the 200 kDa protein induced specifically by low temperature in wheat (Triticum aestivum L.). The boiling solubility of the protein has been used as a main step in the purification procedure. Amino acid composition indicates that the 200 kDa has a compositional bias for glycine (11.4%), threonine (13.3%), and alanine (22.0%). Using oligonucleotide probes, we have isolated a clone (p Wcs200) from a cold-acclimated winter wheat cDNA library. Northern analysis demonstrated that the expression of the corresponding gene was specifically upregulated by low temperature. Southern analysis showed that the gene organization and the relative copy number were identical in two cultivars differing in their capacity to develop freezing tolerance. Protein sequence and immunological analyses indicate that this protein shares similar features with the 50 kDa protein induced during cold acclimation of wheat. The two proteins are boiling-soluble, and possess similar repeated elements. These elements may be important for the development of freezing tolerance. We have shown that the 200 kDa protein is the largest member of a family of immunologically-related cold-induced proteins in wheat. Expression of pWcs200 in E. coli yielded a product of around 200 kDa, indicating that the clone contains most of the coding region for this protein.

Acclimatization↗
PubMed1977

Exercise and heat orthostatism and the effect of heat acclimation and physical fitness.

Twelve trained and 16 untrained young men were administered five orthostatic tests while leaning upright against a wall, for 20 min--before exercise; after 60 min of exercise at a load of 40 W; after 15 min of exercise at a load of 80 W; after a Vo2 max test, and after 3 h of exercise at a load of 40 W in heat (39.4 degrees C DB, 30.3 degrees C WB). Eight of the untrained subjects were retested in the five orthostatic tests after 8 d of heat acclimation. The number of fainters in the orthostatic tests administered before exercise, after exercise at 40 W and 80 W, and after exercise in heat, were 3, 4, 6, and 13, respectively. There were no fainting episodes after the Vo2 max tests. Orthostatic responses in the different conditions were partially related. The trained subjects showed substantially better responses than the untrained ones (10% vs. 25% of fainting episodes), and heat acclimation resulted in marked improvement in orthostatism (decrease to 5% faintings). The results show that Vo2 max and heat tolerance account for most of the variability which determines orthostatic tolerance.

Acclimatization↗
PubMedDate not supplied

[Changes in glycolipid level in the brain of rats with different resistance to hypoxia during acclimation to cold].

Acclimation of rats to cooling (+3 C for 30 days) is accompanied by changes in the content of gangliozides, cerebrozides and sulfatides of brain during 6 hours, returned to the control level in next periods of acclimation. Changes in the content of sulfatides, and in smaller degree of cerebrozides and gangliozides depend from hypoxic stability of rats.

Acclimatization↗
PubMed1998

Two types of mRNA encoding myosin regulatory light chain in carp fast skeletal muscle differ in their 3' non-coding regions and expression patterns following temperature acclimation.

cDNA clones encoding the myosin regulatory light chain (RLC) were isolated from a cDNA library prepared from fast skeletal muscle of the carp Cyprinus carpio L. Two types of cDNA clone encoding carp RLC were found with identical deduced amino acid sequences. The two mRNAs differed in the number of polyadenylation signals prior to the poly(A) tail in the 3' non-coding region. The two mRNA species, with approximate sizes of 1.4 and 0.8 kilobases, were also observed in northern blot analysis. Carp were acclimated for a minimum of 5 weeks to either 10 degreesC or 30 degreesC (14 h:10 h light:dark photoperiod). The total levels of mRNA transcripts coding for the RLC and myosin heavy chain were, respectively, 3.3 and 3.9 times higher in cold- than in warm-acclimated fish. Differences in the levels of RLC in mRNA transcripts were largely due to the concentration of the 1.4 kilobase mRNA species.

Journal Article↗
PubMed1998

Two types of mRNA encoding myosin regulatory light chain in carp fast skeletal muscle differ in their 3' non-coding regions and expression patterns following temperature acclimation.

cDNA clones encoding the myosin regulatory light chain (RLC) were isolated from a cDNA library prepared from fast skeletal muscle of the carp Cyprinus carpio L. Two types of cDNA clone encoding carp RLC were found with identical deduced amino acid sequences. The two mRNAs differed in the number of polyadenylation signals prior to the poly(A) tail in the 3' non-coding region. The two mRNA species, with approximate sizes of 1.4 and 0.8 kilobases, were also observed in northern blot analysis. Carp were acclimated for a minimum of 5 weeks to either 10 degrees C or 30 degrees C (14h:10h light:dark photoperiod). The total levels of mRNA transcripts coding for the RLC and myosin heavy chain were, respectively, 3.3 and 3.9 times higher in cold-than in warm-acclimated fish. Differences in the levels of RLC in mRNA transcripts were largely due to the concentration of the 1.4 kilobase mRNA species.

Adaptation, Physiological↗
PubMed2001

Increasing rice photosynthesis by manipulation of the acclimation and adaptation to light.

There are three important considerations in assessing the interaction of crop plants with light: (a) how does the plant respond to the light environment both in the short-term (regulation) and in the long-term (acclimation), (b) under what conditions are these responses inadequate, leading to photoinhibition, and (c) are the responses optimally adapted for maximum agricultural yield? Despite a wealth of knowledge about these processes in model plant species, it is impossible to predict how significant they are in influencing the yield of rice. Therefore, in collaboration with IRRI, we have undertaken a study of photoinhibition and photoacclimation of rice under field conditions. The results of this study are presented, along with an assessment of the implications for improvement of rice yield.

Adaptation, Physiological↗
PubMed2004

Time-course changes in the expression of Na, K-ATPase and the morphometry of mitochondrion-rich cells in gills of euryhaline tilapia (Oreochromis mossambicus) during freshwater acclimation.

Changes in expression of Na, K-ATPase (NKA) and morphometry of mitochondrion-rich (MR) cells in gills of tilapia were investigated on a 96-hr time course following transfer from seawater (SW) to fresh water (FW). A transient decline in plasma osmolality and Na+, Cl- concentrations occurred from 3 hrs onward. Gills responded to FW transfer by decreasing NKA activity as early as 3 hrs from transfer. This response was followed by a significant decrease in the NKA isoform alpha1-mRNA abundance, which was detected by real-time PCR at 6 hrs post transfer. Next, a decrease of alpha1-protein amounts were observed from 6 hrs until 24 hrs post transfer. Additionally, during the time course of FW transfer, modifications in number and size of subtypes of gill MR cells were observed although no significant difference was found in densities of all subtypes of MR cells. These modifications were found as early as 3 hrs, evident at 6 hrs (exhibition of 3 subtypes of MR cells), and mostly completed by 24 hrs post transfer. Such rapid responses (in 3 hrs) as concurrent changes in branchial NKA expression and modifications of MR cell subtypes are thought to improve the osmoregulatory capacity of tilapia in acclimation from hypertonic SW to hypotonic FW.

Acclimatization↗
PubMed2007

Banana (Musa spp.) as a model to study the meristem proteome: acclimation to osmotic stress.

Banana (Musa spp.) multiple shoot meristems are an excellent model to study the meristem proteome. Using a 2-DE protocol developed for small amounts of tissue and MS-based cross species polypeptide identification, we have revealed the meristem proteome and investigated the influence of sucrose-mediated osmotic stress in a dehydration-tolerant variety. Proteins that were significantly up- or down-regulated due to the high-sucrose treatment were classified using non-parametric univariate statistics. Our results suggest that the maintenance of an osmoprotective intracellular sucrose concentration, the enhanced expression of particular genes of the energy-conserving glycolysis and the conservation of the cell wall integrity are essential to maintain homeostasis, to acclimate and to survive dehydration. By comparing the dehydration-tolerant variety with a dehydration-sensitive variety, we were able to distinguish several genotype-specific proteins (isoforms), and could associate the dehydration-tolerant variety with proteins involved in energy metabolism (e.g., phosphoglycerate kinase, phosphoglucomutase, UDP-glucose pyrophosphorylase) and proteins that are associated with stress adaptation (e.g., OSR40-like protein, abscisic stress ripening protein-like protein). This work shows that proteome analysis can be used successfully to perform quantitative difference analysis and to characterize genetic variations in a recalcitrant crop.

Electrophoresis, Gel, Two-Dimensional↗
PubMed2000

Effect of abscisic acid and cold acclimation on the cytoskeletal and phosphorylated proteins in different cultivars of Triticum aestivum L.

In winter wheat, the tubulin and 60 kDa-phosphorylated proteins/actin ratio is considerably higher in the roots than in the leaves. Differences in the content of the main cytoskeletal proteins were also found in the leaves of the different cultivars. It is suggested that the lower amount of the tubulin and 60 kDa-phosphorylated proteins and higher content of actin determine the greater tubulin cytoskeletal stability in the leaves and their higher frost resistance, as compared with the roots. Also, it is possible that the higher content of the tubulin and 60 kDa-phosphorylated proteins defines the lower microtubule (MT) stability in the leaves of the low frost resistant cultivar than in the leaves of the more frost resistant ones. In the roots and leaves of the low frost resistant cultivar, the low stability of the numerous tubulin structures is apparently one reason for the abscisic acid (ABA)-induced reduction of the cytoskeletal and 60 kDa-phosphorylated proteins in the cells. The cold acclimation compensated the ABA effect in the roots of the very frost resistant cultivar in the most extent. This suggests the existence of the different pathways in the increased plant cell frost resistance through the action of ABA and low temperature.

Abscisic Acid↗
PubMed1998

Post pupariation cold storage of three species of flies: increasing chilling tolerance by acclimation and recurrent recovery periods.

Three species of flies were examined for chilling tolerance from the end of the pupariation to the onset of adult eclosion for the purpose of determining applicability for cold storage. For the housefly, Musca domestica (Diptera, Muscidae), survival to eclosion was affected by developmental stage/age, length of storage, and storage temperature. Houseflies that were closest to having experienced pupariation or the onset of eclosion were the least cold tolerant. For flies stored at 7 or 10 degrees C, age groups placed directly into storage at 36-72 and 36-48 h postpupariation, respectively, had significantly higher poststorage eclosion than younger or older age groups. Death was observed after only 2 or 3 days with the chilling intolerant groups while mid-aged groups survived 10-12 days under cold storage conditions. Damage could be reduced by giving the mid-aged groups chilled at 7 or 10 degrees C recurrent 2- or 3-h recovery periods every 4 days at 28 degrees C. Examination of O2 consumption throughout the housefly pupal and pharate adult stages showed that the most chilling tolerant groups also had the lowest metabolic activity. Combining a prestorage 17-h slow cooling acclimation interval with the recurrent recovery periods increased eclosion of adults 20% for the 12- to 24-h group after 21 days storage at 7 degrees C. Two blowfly species, Lucilia cuprina and Lucilia sericata (Diptera, Calliphoridae), survived 10 degrees C storage best when given a weekly 4-h recovery period. Survival at 90 days poststorage was nearly 50% for L. cuprina and 80% for L. sericata. Increasing survival under subambient temperatures for all three species appears to relate to whether there is a stage of development which allows cold-induced lowering of metabolism that results in a dormant status best characterized as hibernal quiescence. This study indicates that periodic warming during cold storage increases survival by allowing a chilling intolerant stage to develop to a more tolerant stage and/or by eliminating accumulated toxic metabolites.

Adaptation, Biological↗
PubMed1996

Changes in blood cell numbers and formation of eicosanoids during clotting in warm- and cold-acclimated bullfrogs (Rana catesbeiana).

Amphibian blood cells play an important role in eicosanoid synthesis. Formation of eicosanoids during clotting of whole human blood but not frog blood has been reported. Amphibian blood cell numbers are affected by cold exposure; therefore eicosanoid production may reflect these changes. Blood cell changes during warm, and short- and long-term-cold exposure periods were recorded and the formation of leukotriene B4 (LTB4), LTC4, thromboxane (TXB2), and prostaglandin E2 (PGE2) was measured during blood clotting by using radioimmunoassay. Short-term (1 day) cold exposure (5 degrees) did not significantly decrease blood cell number or eicosanoid production during clotting. However, following exposure to cold (5 degrees) for 10 or 30 days, blood cell number and production of LTB4, TXB2, and PGE2 during clotting decreased when compared with warm acclimated controls (22 degrees). LTC4 levels during blood clotting decreased significantly only after 30 days of cold exposure. The results demonstrate that eicosanoid synthesis can be correlated with blood cell number in warm- and cold-exposed bullfrogs.

Acclimatization↗
PubMed1997

Eicosanoid synthesis by purified thrombocytes and erythrocytes from warm- and cold-acclimated American bullfrogs (Rana catesbeiana).

Amphibian blood plays an important role in eicosanoid synthesis. Although clotting frog blood produces eicosanoids, the cellular source of prostaglandins and thromboxanes in bullfrog blood is unknown. Thromboxane (TX)B2 synthesis from purified thrombocytes was affected by 30-day cold-acclimation at 5 degrees, but not PGE2 or leukotriene (LT) synthesis. Although no cyclooxygenase activity has been found in human erythrocytes, frog erythrocytes were capable of forming cyclooxygenase products, but the amounts were lower than those produced by thrombocytes. Additionally, there was no effect of cold exposure on eicosanoid production by isolated erythrocytes. Similar to some mammalian nucleated white blood cells, nucleated bullfrog thrombocytes and erythrocytes produced leukotrienes. The production of eicosanoids by thrombocytes was stimulated by A23187 and thrombin. Erythrocytes were stimulated by A23187. Control synthesis by erythrocytes and thrombocytes was inhibited by 5 microM indomethacin (cyclooxygenase pathway) or nordihydroguaiaretic acid (5-lipoxygenase pathway) and cyclooxygenase products were increased in the presence of nordihydroguaiaretic acid. Thrombin stimulation of eicosanoid production by thrombocytes was inhibited when the inhibitors were present prior to the final centrifugation of the cell isolation. The results suggest that cold exposure can affect eicosanoid synthesis in thrombocytes, but not erythrocytes, and that thrombocytes are a major source of eicosanoids in bullfrogs. The production of cyclooxygenase and lipoxygenase products by nucleated erythrocytes and thrombocytes suggests a role for these compounds in hemostasis and inflammatory responses in these animals.

Acclimatization↗
PubMed1992

Changes in tissue histology associated with adaptation and acclimation to hypoxia.

Newborn kittens are adapted to hypoxia by having an oxygen department respiration rate. In part, this is due to the structure of the liver which results in a great reduction of oxygen consumption in this organ in response to hypoxia. Older animals possess an oxygen independent respiration rate which is not lost when they acclimate to hypoxia. Instead, there are histological changes which permit the liver to consume oxygen at the same rate as before by facilitating intracellular oxygen transport.

Acclimatization↗