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PubMed2006

Acclimation to chronic constant-rate peripheral stimulation provided by a vestibular prosthesis.

We are developing two types of vestibular prosthetics that electrically stimulate afferent neurons. One type replaces absent sensory function by providing stimulation that modulates above and below a baseline established with the head stationary. The other type provides constant stimulation and is turned on only when necessary, for example, to override unnatural variations like those experienced by patients suffering from Ménère's syndrome; this prosthesis does not provide motion information. Both prostheses require neural plasticity, which we investigated by providing chronic constant-rate stimulation to semicircular canal neurons in three guinea pigs. The stimulation was alternately switched on or off for eight consecutive weeks before being switched daily. A brisk horizontal nystagmus was measured when the stimulation was first turned on and then dissipated over the course of a day. The nystagmus demonstrated an after-effect in the opposite direction when the stimulation was turned off. The nystagmus that we measured after just a few (2 to 5) off-to-on transitions returned to baseline more rapidly than when first turned on. In fact, after many such off-to-on or on-to-off transitions, little nystagmus was evoked by turning the stimulation on or off. These findings show that the brain acclimates to constant-rate stimulation.

Acclimatization↗
PubMed2006

Methionine-rich storage protein gene in the rice stem borer, Chilo suppressalis, is expressed during diapause in response to cold acclimation.

Gene expressions of acclimatized and non-acclimatized diapausing larvae were examined in Chilo suppressalis using a subtraction technique. A gene encoding a methionine-rich storage protein, CsSP1, was cloned and its complete cDNA sequence was determined. Potentially, CsSP1 encoded a 758-amino acid protein, with a calculated molecular weight of 88.8 kDa. The expression level of CsSP1 was higher in nondiapausing larvae than in diapausing ones. The CsSP1 expression was up-regulated in diapausing larvae when the temperature of cold acclimation was shifted to 5 degrees C. The up-regulated level was maintained at 40 days after incubation at 5 degrees C. In nondiapausing larvae, CsSP1 expression was down-regulated when the temperature was below developmental zero. Involvement of CsSP1 in diapause, cold tolerance acquisition and postdiapause development in C. suppressalis is discussed.

Acclimatization↗
PubMed2004

Roles of CmpR, a LysR family transcriptional regulator, in acclimation of the cyanobacterium Synechococcus sp. strain PCC 7942 to low-CO(2) and high-light conditions.

The cmp operon of Synechococcus sp. strain PCC 7942, encoding a high-affinity bicarbonate transporter, is induced under low CO(2) conditions by a LysR family protein CmpR. CmpR was found to be required also for induction of the operon by transfer of the cells from low-light to high-light conditions, indicating involvement of a common mechanism in the high-light- and low-CO(2)-responsive regulation. Expression of the high-light inducible genes psbAII and psbAIII, on the other hand, was found to be induced also by low-CO(2) conditions. A single promoter was responsible for the high-light and low-CO(2) induction of each of psbAII and psbAIII, suggesting involvement of a common regulatory mechanism in the light and CO(2) responses of the psbA genes. CmpR was, however, not required for the induction of psbAII and psbAIII, indicating the presence of multiple mechanisms for induction of genes under high-light and low-CO(2) conditions. The CmpR-deficient mutant nevertheless showed lower levels of the psbAII and psbAIII transcripts than the wild-type strain under all the light and CO(2) conditions examined. Gel shift assays showed that CmpR binds to the enhancer elements of psbAII and psbAIII, through specific interaction with a sequence signature conforming to the binding motif of similar LysR family proteins. These findings showed that CmpR acts as a trans-acting factor that enhances transcription of the photosystem II genes involved in acclimation to high light, revealing a complex network of gene regulation in the cyanobacterium.

Bacterial Proteins↗
PubMed1974

Inhibition of thermoregulatory non-shivering thermogenesis by trauma in cold-acclimated rats.

1. Heat production and blood flow in the interscapular brown adipose tissue of 3 degrees C acclimated rats have been measured by the heated thermo-couple technique.2. When the environmental temperature (T(a)) was reduced from 30 to 3 degrees C heat production by the brown adipose tissue began to increase at the lower limit of the thermoneutral zone and then increased linearly.3. Blood flow also increased when T(a) was reduced but was not so well correlated with T(a). There was however a good positive correlation between blood flow and heat production.4. During the first hour after a 4 hr period of bilateral hind-limb ischaemia in a 20 degrees C environment the percentage of rats not producing heat in the interscapular brown adipose tissue increased and the tissue blood flow fell.5. By varying the T(a) of the injured rat it was found that the T(a) at which heat transfer from the interscapular brown adipose tissue commenced was significantly lower than in the controls although the slope of the regression lines relating heat production and T(a) was unaltered.6. Blood flow also increased in the injured rat when T(a) was lowered but the increase in the tissue blood flow per unit increase in heat production was less than in the controls.7. In a 5 degrees C environment heat production in the interscapular brown adipose tissue of the injured rat was further increased by the S. C. injection of L-isoprenaline or L-noradrenaline.8. It is concluded that the central control of thermoregulatory non-shivering thermogenesis is inhibited after injury in the rat.

Adipose Tissue, Brown↗
PubMed1979

Cold acclimation in the secretory responses of the isolated exocrine pancreas of the rat.

1. The secretory function of the isolated and perfused exocrine pancreas has been studied in the course of cold acclimation in rats that were fed at an ambient temperature of 1 degrees C in an artificial climatic room.2. A series of experiments was carried out in early autumn (autumn series). The sums of the outputs of protein, amylase, zymogen protease, lipase, and juice flow in samples collected for a total of 30 min during and after 5 min stimulation with different concentrations of cholecystokinin-pancreozymin (CCK-PZ; 5-50 m-u./ml.) were simultaneously measured in the autumn series of experiments, and they were plotted against the logarithmic scale of concentration of CCK-PZ to obtain a dose-response relation.3. The sums of protein output, lipase output, and juice flow evoked by different concentrations of CCK-PZ in the group of rats fed at 1 degrees C for 3 weeks were almost identical to the corresponding value in the group fed at about 21 degrees C for 3 weeks.4. The sum of output of zymogen protease in the former group was almost identical to the corresponding value in the latter group except that the sum induced by 20 m-u. CCK-PZ/ml. was significantly larger in the former.5. The sum of output of amylase induced by various concentrations of CCK-PZ in the former group was significantly smaller than the corresponding value in the latter group.6. It was thus concluded that the CCK-PZ-induced outputs of protein, lipase, and zymogen protease were little affected if any by 3 weeks of cold exposure, whereas the CCK-PZ-induced amylase output was significantly suppressed.7. Another similar series of experiments was performed in the summer of the same year. The results obtained suggest that the secretory function of exocrine pancreas is directly inhibited by prolonged cold exposure in summer but it is not in autumn.

Acclimatization↗
PubMed1987

Exercise during intermittent cold exposure prevents acclimation to cold rats.

1. Energy balance and brown adipose tissue growth were examined in four groups of male Wistar rats: (i) sedentary, living at 24 degrees C (warm), (ii) exercise-trained, 2 h daily, living at 24 degrees C, (iii) living at 24 degrees C but exposed to -5 degrees C, 2 h daily and (iv) living at 24 degrees C but exercise-trained while being exposed to -5 degrees C, 2 h daily. 2. Cold exposure during exercise training appeared to have little additional influence on body composition following 28 days of treatment; body mass gain, in addition to protein and fat gains, of exercised cold-exposed rats were similar to the gains observed in exercised warm-exposed control animals. However, in sedentary cold-exposed rats protein, fat and body mass gains were significantly lower than the gains measured in sedentary rats not exposed to cold. 3. Metabolizable energy intake, expressed mass-independently, was similar in sedentary warm-exposed rats and both groups of animals that were exercise-trained. Metabolizable energy intake was increased almost 15% in sedentary cold-exposed rats. 4. Energy expenditure (mass independent), excluding the net cost of exercise training, was not different in sedentary warm-exposed and exercised rats; energy expenditure was almost 20% higher in sedentary cold-exposed rats. 5. Total protein and deoxyribonucleic acid (DNA) contents of brown adipose tissue were more than doubled in sedentary rats exposed to cold; protein and DNA levels were similar among the other three groups of rats. 6. Treadmill running during daily, 2 h exposure at -5 degrees C appears to prevent the cold acclimation responses that occur in sedentary rats receiving similar cold exposure.

Acclimatization↗
PubMed1991

Effect of heat acclimation on diurnal changes in body temperature and locomotor activity in rats.

1. The present study was performed to examine the effects of heat exposure hours hours at a fixed time once a day on diurnal variations of deep body temperature, heat balance and locomotor activity in rats. 2. The heat-exposed group (HE) was subjected to an ambient temperature of 33.5 degrees C for about 5 h in the last half of the dark phase daily for at least 10 consecutive days, while the control rats were constantly kept at 24 degrees C. 3. After the completion of the heat exposure schedule, hypothalamic temperature (Thy), heat loss, heat production and locomotor activity of HE rats significantly decreased for 3-4 h during the period of previous heat exposure time and formed a characteristic trough in the dark phase, which was never observed in the control rats or in the HE rats before the start of the heat exposure schedule. 4. The troughs of Thy, heat loss and heat production in the dark phase were persistent for at least 2 days after the end of the heat exposure schedule. The reductions of locomotor activity in this period were, however, observed only on the first day after stopping the heat exposure schedule. 5. These results suggest that the time memory for heat exposure was formed in heat-acclimated rats and was persistent for at least 2 days after the removal of heat exposure. It is also concluded that the reduction in metabolic heat production contributed to the fall of Thy during the period of heat exposure.

Acclimatization↗
PubMed1993

Responses to moderate and low sodium diets during exercise-heat acclimation.

This investigation examined whether low sodium (Na+) (LNA; 68 mEq Na+.d-1) or moderate Na+ (MNA; 137 mEq Na+.d-1) intake allowed humans to maintain health, exercise, and physiologic function during 10 days of prolonged exercise-heat acclimation (HA). Seventeen volunteers, ages 19 to 21, consumed either LNA (n = 8) or MNA (n = 9) during HA (41 degrees C, 21% RH; treadmill walking for 30 min.h-1, 8 h.d-1 at 5.6 km.h-1, 5% grade), which resulted in significantly reduced heart rate, rectal temperature, and urine Na+ for both groups. There were few between-diet differences in any variables measured. Mean plasma volume in LNA expanded significantly less than in MNA by Days 11 and 15, but reached the MNA level on Day 17 (+12.3 vs. +12.4%). The absence of heat illness, the presence of normal physiologic responses, and the total distance walked indicated successful and similar HA with both levels of dietary Na+.

Acclimatization↗
PubMed2026

The OsUVR8-OsNAC3-OsERF117 signaling module mediates metabolic acclimation and climate adaptation in rice.

Ultraviolet-B (UV-B; 280 to 315 nanometers) radiation increasingly threatens crop productivity, yet the genetic basis of plant adaptation remains poorly understood. We delineate a UV-B signaling module in rice that links photoreceptor activation to transcriptional reprogramming and metabolic acclimation. The AP2/ERF transcription factor OsERF117 acts as a central regulator, directly activating flavonoid and melatonin biosynthetic genes to drive photoprotective metabolite accumulation and enhance UV-B stress tolerance. Promoter variation in OsERF117 defines 10 haplotypes across 4093 rice accessions, with high-expression haplotypes enriched in high-UV-B regions and correlated with adaptive divergence. OsERF117 is transcriptionally activated by OsNAC3, with a cis-regulatory SNP at an OsNAC3-binding site modulating responsiveness and contributing to subspecies diversification. Genetic and biochemical evidence supports a model in which UV-B-activated OsUVR8 promotes OsNAC3 activity and antagonizes OsCOP1-mediated ubiquitination and degradation in rice. This OsUVR8-OsCOP1-OsNAC3-OsERF117 module reveals how UV-B perception drives regulatory and metabolic diversification, offering targets for breeding UV-B-resilient crops.

Oryza↗
PubMed1992

Reductive dechlorination of chlorophenols by a pentachlorophenol- acclimated methanogenic consortium.

Anaerobic digester sludge fed 5,300 mg of acetate per liter, 3.4 microM pentachlorophenol, and nutrients for 10 days biotransformed pentachlorophenol by sequential ortho dechlorinations to produce 2,3,4,5-tetrachlorophenol and 3,4,5-trichlorophenol. Upon acclimation to 3.4 microM pentachlorophenol for 6 months, the methanogenic consortium removed chlorines from the ortho, meta, and para positions of pentachlorophenol and its reductive dechlorination products. Pentachlorophenol was degraded to produce 2,3,4,5-tetrachlorophenol, 2,3,4,6-tetrachlorophenol, and 2,3,5,6-tetrachlorophenol. Dechlorination of 2,3,4,5-tetrachlorophenol produced 3,4,5-trichlorophenol, which was subsequently degraded to produce 3,4-dichlorophenol and 3,5-dichlorophenol. 2,3,4,6-Tetrachlorophenol was dechlorinated at the ortho and meta positions to produce 2,4,6-trichlorophenol and 2,4,5-trichlorophenol. 2,3,5,6-Tetrachlorophenol yielded 2,3,5-trichlorophenol, followed by production of 3,5-dichlorophenol. 2,4,6-Trichlorophenol was degraded to form 2,4-dichlorophenol, and 2,4,5-trichlorophenol was dechlorinated at two positions to form 2,4-dichlorophenol and 3,4-dichlorophenol. Of the three dichlorophenols produced (2,4-dichlorophenol, 3,4-dichlorophenol, and 3,5-dichlorophenol), only 2,4-dichlorophenol was degraded significantly within 3 weeks, to produce 4-chlorophenol.

Adaptation, Physiological↗
PubMed1997

Differentiation between cold shock proteins and cold acclimation proteins in a mesophilic gram-positive bacterium, Enterococcus faecalis JH2-2.

Transfer of Enterococcus faecalis to a cold temperature (8 degrees C for 4 to 30 h) led to increased expression of 11 cold shock proteins (CSPs). Furthermore, this mesophilic prokaryote synthesized 10 cold acclimation proteins, five of them distinct from CSPs, during continuous growth (4 days) at the same temperature (8 degrees C).

Bacterial Proteins↗
PubMed2005

The periplasmic alpha-carbonic anhydrase activity of Helicobacter pylori is essential for acid acclimation.

The role of the periplasmic alpha-carbonic anhydrase (alpha-CA) (HP1186) in acid acclimation of Helicobacter pylori was investigated. Urease and urea influx through UreI have been shown to be essential for gastric colonization and for acid survival in vitro. Intrabacterial urease generation of NH3 has a major role in regulation of periplasmic pH and inner membrane potential under acidic conditions, allowing adequate bioenergetics for survival and growth. Since alpha-CA catalyzes the conversion of CO2 to HCO3-, the role of CO2 in periplasmic buffering was studied using an alpha-CA deletion mutant and the CA inhibitor acetazolamide. Western analysis confirmed that alpha-CA was bound to the inner membrane. Immunoblots and PCR confirmed the absence of the enzyme and the gene in the alpha-CA knockout. In the mutant or in the presence of acetazolamide, there was an approximately 3 log10 decrease in acid survival. In acid, absence of alpha-CA activity decreased membrane integrity, as observed using membrane-permeant and -impermeant fluorescent DNA dyes. The increase in membrane potential and cytoplasmic buffering following urea addition to wild-type organisms in acid was absent in the alpha-CA knockout mutant and in the presence of acetazolamide, although UreI and urease remained fully functional. At low pH, the elevation of cytoplasmic and periplasmic pH with urea was abolished in the absence of alpha-CA activity. Hence, buffering of the periplasm to a pH consistent with viability depends not only on NH3 efflux from the cytoplasm but also on the conversion of CO2, produced by urease, to HCO3- by the periplasmic alpha-CA.

Acetazolamide↗
PubMed1996

Cold shock proteins and cold acclimation proteins in the psychrotrophic bacterium Pseudomonas putida Q5 and its transconjugant.

The production of cold shock proteins (csps) and cold acclimation proteins (caps) was characterized in the psychrotrophic bacterium Pseudomonas putida Q5 and its transconjugant P. putida Q5T which contains the toluene-degradative TOL (pWWO) plasmid, using two-dimensional gel electrophoresis and computing scanning laser densitometry. Similar growth rates for the psychrotrophic bacterium P. putida Q5 and the transconjugant were found at temperatures ranging from 30 to 0 degree C. Sixteen proteins were quantified and compared in P. putida Q5 and P. putida Q5T following a 25 to 5 degrees C cold shock or constant growth at 5 degrees C. During constant growth at 25 degrees C, a decrease in the synthesis of various proteins occurred in the transconjugant. Following cold shock to 5 degrees C or constant growth at 5 degrees C, csps and caps were produced with a greater number occurring in the transconjugant. This may suggest an additional stress response in the transconjugant owing to metabolic load exerted by the TOL plasmid. Growth of P. putida Q5T with toluate produced seven proteins that appeared to be TOL-plasmid mediated and of which some were also designated as caps.

Acclimatization↗
PubMed1986

Selective loss of uncoupling protein from mitochondria of surgically denervated brown adipose tissue of cold-acclimated mice.

The effects of unilateral surgical denervation on brown adipose tissue (BAT) composition were evaluated to assess the importance of the sympathetic innervation in the maintenance of a high concentration of the uncoupling protein thermogenin in cold-acclimated (CA) mice and to assess whether suppression of neural activity could account for BAT atrophy observed during fasting or when CA mice are returned to a thermoneutral environment (33 degrees C). Denervation-induced BAT atrophy was characterized by protein and thermogenin losses in absence of changes in the tissue cellularity (DNA content). There was a marked reduction in the concentration of thermogenin in mitochondria isolated from denervated BAT, but the concentration of the adenine nucleotide translocator was unchanged. Fasting or exposure of CA mice to 33 degrees C induced a rapid and extensive loss of tissue protein from both innervated and denervated BAT. In CA mice exposed to 33 degrees C, there was also reduction in tissue cellularity and loss of thermogenin from BAT mitochondria. Since surgical denervation suppressed BAT hyperplasia and the increase in the mitochondrial concentration of thermogenin observed during cold exposure, these results indicate that an intact innervation is required for both synthesis and maintenance of a high mitochondrial content of thermogenin in CA mice. In addition, the lesser changes in tissue composition caused by denervation compared with those caused by fasting or exposure of CA mice to 33 degrees C question the importance of the suppression of neural activity as the exclusive cause of rapid BAT atrophy in mice.

Acclimatization↗
PubMed1987

Selective loss of uncoupling protein mRNA in brown adipose tissue on deacclimation of cold-acclimated mice.

The time course of changes in the level of uncoupling protein mRNA when cold-acclimated mice were returned to a thermoneutral environment (33 degrees C) was examined using a cDNA probe. Upon deacclimation, there was a marked loss of uncoupling protein mRNA within 24 h, which precedes the loss of uncoupling protein from mitochondria. This loss of uncoupling protein mRNA was selective, since there was no change in the relative proportion of cytochrome c oxidase subunit IV mRNA or poly(A)+ RNA in total RNA. The results suggest that the decrease in the mitochondrial content of uncoupling protein during deacclimation is likely the result of turnover of existing protein, with very little replacement due to a lower level of its mRNA.

Acclimatization↗
PubMed1987

Effects of diet and thermal acclimation on oxygen consumption in rats.

The relationship between food intake and oxygen consumption was studied in a group of 60 rats acclimated at environmental temperatures of either 30 or 10 degrees C. Three separate experiments were performed. In the first, 28 rats were divided into two groups: control, which received 20 and 32 g of food/day at 30 and 10 degrees C, respectively, from 0800 to 1700 and experimental, which received 10 and 25 g of food/day at 30, and 10 degrees C, respectively. The experimental period lasted 6 weeks. Oxygen consumption was measured weekly at environmental temperatures of 5, 15, 25, 30, and 35 degrees C. In the second experiment, 16 rats were subjected to the same food intake as the animals in the first experiment. After 1 week, their oxygen consumption was measured at 25 degrees C over a period of 24 h. The third experiment was carried out with 16 other rats in which the control groups received the same amount of food as in the first experiment, and the experimental groups were fed 6 and 11 g/day at 30 and 10 degrees C, respectively, during 1 week. In the first experiment, no changes in oxygen consumption (per kilogram 0.67) were apparent in the experimental rats during 6 weeks. However, after 1 week on severe food restriction a significant decrease in oxygen consumption (per kilogram 0.67) was observed. A long-lasting thermic effect of food was observed in control rats from the second experiment and a rapid effect was apparent in restricted rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Acclimatization↗
PubMed1993

Shivering and nonshivering thermogenic responses of rats subjected to different patterns of heat acclimation.

Male Wistar rats were divided into five groups: a control group kept at an ambient temperature of 24 degrees C for 14 days, and four heat-acclimated groups (two groups subjected to a constant ambient temperature of 33 degrees C for 4 days or 14 days (HC-14) immediately preceding the measurement; and another two groups subjected to an ambient temperature of 33 degrees C for about 5 h once a day for 4 days, or 14 days (HI-14) just prior to the measurement). After the completion of the schedule, the rats were placed in a temperature-controlled chamber. Hypothalamic (Thy) and interscapular brown adipose tissue (TBAT) temperatures, oxygen consumption (VO2), and shivering activity were measured during a gradual fall in temperature of a water jacket surrounding the chamber (TW) from 30 to 10 degrees C at a constant rate of 0.18 degree C/min. During the fall in TW, VO2 and TBAT increased significantly and shivering was induced without associate changes in Thy in all groups. TW at the onset of a rise in metabolic heat production (onset of cold-induced thermogenesis) coincided with that at the onset of a rise in TBAT (onset of BAT thermogenesis), but was significantly higher than that at the onset of shivering. In HC-14 and HI-14 rats, TWS at the onset of cold-induced thermogenesis and BAT thermogenesis were significantly higher than those in control rats, whereas TWS at the onset of shivering were not different from those in control rats. The onset of cold-induced thermogenesis did not change after the 4-day heat exposure.(ABSTRACT TRUNCATED AT 250 WORDS)

Acclimatization↗