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High temperatures alter the physiological condition of Octopus maya embryos, juveniles, and adults, and the time of exposure could have a key role in their thermal tolerance. The present study evaluates the effects of temperature and exposure time on octopus juveniles obtained from a thermally stressed female and a control female when exposed to optimal (25 °C) and high temperatures (30 °C) for 20 and 30 days, respectively. The results showed a transgenerational temperature effect that was expressed with low survival, depressed routine resting and high metabolic rates. Moreover, a collapse of antioxidant defense enzymes and high levels of oxidative damage products were detected in juveniles from thermally stressed females. Stress was lethal for animals acclimated at 30 °C, while the performance of juveniles acclimated at optimal temperature (25 °C) was conditioned by high oxidative stress levels and a reduction of the high metabolic rate (HMR) even after 30 days of experiment. In contrast, juveniles from the non-thermally stressed female had an optimal performance when acclimated at 25 °C but at 30 °C, they had a comparatively higher HMR during the first 8 days. These results suggest energy surplus in those animals to escape from warming scenarios before experiencing oxidative damage accumulation. Further studies should confirm if epigenetic alterations could be involved., Author(s): Jorge Arturo Vargas-Abúndez [sup.1] , Alejandra Plata-Díaz [sup.2] , Maite Mascaró [sup.1] , Claudia Caamal-Monsreal [sup.1] , Gabriela Rodríguez-Fuentes [sup.3] , Alejandro Jiménez-Be [sup.1] , Carlos Rosas [sup.1] Author [...]

For marine animals with biphasic life stages, different environmental conditions are experienced during ontogeny so that physiological constraints on early stages could explain adult distributions and life history traits. The invasive and cool-temperate adapted Mytilus galloprovincialis intertidal mussel approaches the eastern limit of its biogeographic distribution on the south coast of South Africa, where it shares a habitat with the warm-temperate adapted and indigenous Perna perna mussel. As adults, the two species exhibit different metabolic regulation capacities in response to temperature. We compared the acute metabolic response to temperature between species during the post-settlement recruit stage. Aerobic respiration rates of recently settled recruits were measured monthly for 5 months for temperatures 5 °C above or below the ambient field seawater temperature at the time of collection. Unlike adults, the capacity for aerobic metabolic regulation in response to temperature differed little between species under the conditions tested, indicating a similar degree of phenotypic or developmental plasticity in response to the thermal environment. In addition, monthly variations in metabolic patterns indicate unexpectedly high plasticity in response to recent seasonal thermal history for both species., Author(s): Aldi Nel [sup.1] [sup.2] , Christopher D. McQuaid [sup.2] , Olwethu O. Duna [sup.1] [sup.2] , Luis Giménez [sup.3] [sup.4] , Francesca Porri [sup.1] [sup.2] Author Affiliations: (1) grid.507756.6, [...]

As climate change continues, anticipating species' responses to rising temperatures requires an understanding of the drivers of thermal sensitivity, which itself may vary over space and time. We measured metabolic rates of three representative marine invertebrate species (hermit crabs Pagurus hirsutiusculus, periwinkle snails Littorina sitkana, and mussels Mytilus trossulus) and evaluated the relationship between thermal sensitivity (Q.sub.10) and thermal history. We tested the hypothesis that thermal history drives thermal sensitivity and quantified how this relationship differs over time (short-term to seasonal time scales) and between species. Organisms were collected from tide pools in Sitka, Alaska where we also recorded temperatures to characterize thermal history prior to metabolic rate assays. Using respirometry, we estimated mass-specific oxygen consumption (MO.sub.2) at ambient and increased temperatures for one individual per species per tide pool across three seasons. We evaluated relationships between thermal sensitivity and pool temperatures for time periods ranging from 1 day to 1 month prior to collection. For all species, thermal sensitivity was related to thermal history for the shorter time periods (1 day to 1 week). However, the direction of the relationships and most important thermal parameters (i.e., maximum, mean, or range) differed between species and seasons. We found that on average, P. hirsutiusculus and L. sitkana were more thermally sensitive than M. trossulus. These findings show that variability in thermal history over small spatial scales influences individuals' metabolic response to warming and may be indicative of these species' ability to acclimate to future climate change., Author(s): Racine E. Rangel [sup.1] , Cascade J. B. Sorte [sup.1] Author Affiliations: (1) grid.266093.8, 0000 0001 0668 7243, Department of Ecology and Evolutionary Biology, University of California - Irvine, [...]

Standard metabolic rates (SMR) were measured in brown bullheads (Ameiurus nebulosus) collected from two locations of the Detroit River, North America, representative of highly contaminated and uncontaminated areas. Measurements of SMR were completed within 10 days of fish collections (acute trials), for fish held in a common pond environment for 1 year (clearance trials) and for F1 generation fish raised in the pond environment ([F.sub.1] study). SMRs were significantly higher (26%) in fish from the contaminated area during acute trials. Both populations showed large decreases in SMR (49% to 52%) following clearance; however, differences between populations were still evident. There were no significant differences in SMRs between populations for [F.sub.1] fish. This study demonstrates that Detroit River brown bullheads from contaminated areas have higher metabolic rates than fish from clean locations, and this metabolic effect is retained for long durations after fish are placed in a common environment. The loss of metabolic differences in [F.sub.1] offspring indicates that the observed differences in SMR were acclimation-based and not adaptive or related to maternal effects. Le metabolisme standard (MS) a ete mesure sur des barbottes (Ameiurus nebulosus) prelevees de deux emplacements le long de la riviere Detroit (Amerique du Nord) representatifs de zones tres contaminees et non contaminees, respectivement. Des mesures du MS ont ete realisees dans les 10 jours suivant le prelevement des poissons (essais aigus), pour des poissons maintenus dans un milieu d'etang commun pendant un an (essais de clairance) et pour des poissons de la generation [F.sub.1] eleves dans le milieu d'etang (etude de la FJ. Le MS etait significativement plus eleve (26 %) chez les poissons issus de la zone contaminee durant les essais aigus. Les deux populations presentaient d'importantes diminutions du MS (de 49 % a 52 %) apres la periode de clairance, bien que des differences entre les populations fussent encore presentes. Aucune difference significative n'etait presente sur le plan du MS entre les deux populations pour les poissons Ft. L'etude demontre que les barbottes de la riviere Detroit issues de zones contaminees ont un metabolisme plus eleve que les poissons de zones non contaminees, et que cet effet metabolique est maintenu longtemps apres que les poissons aient ete places dans un milieu commun. La disparition des differences metaboliques chez la progeniture [F.sub.1] indique que les differences de MS observees sont le fait d'une acclimatation, non de l'adaptation ou reliees a des effets maternels. [Traduit par la Redaction], Introduction Standard metabolic rate (SMR) is an important component of the energy budget and represents the minimal energy required to sustain physiological function excluding consumption, digestion, and activity (Enders et [...]

Ocean acidification, a process caused by the continuous rise of atmospheric C[O.sub.2] levels, is expected to have a profound impact on marine invertebrates. Findings of the numerous studies conducted in this field indicate high variability in species responses to future ocean conditions. This study aimed at understanding the effects of long-term exposure to elevated pC[O.sub.2] conditions on the performance of adult Echinometra sp. EE from the Gulf of Aqaba (Red Sea). During an 11-month incubation under high pC[O.sub.2] (1,433 µatm, p[H.sub.NBS] 7.7) and control (435 µatm, p[H.sub.NBS] 8.1) conditions, we examined the urchins' somatic and gonadal growth, gametogenesis and skeletal microstructure. Somatic and gonadal growths were exhibited with no significant differences between the treatments. In addition, all urchins in the experiment completed a full reproductive cycle, typical of natural populations, with no detectable impact of increased pC[O.sub.2] on the timing, duration or progression of the cycle. Furthermore, scanning electron microscopy imaging of urchin tests and spines revealed no signs of the usual observed effects of acidosis, such as skeletal dissolution, widened stereom pores or non-smoothed structures. Our results, which yielded no significant impact of the high pC[O.sub.2] treatment on any of the examined processes in the urchins studied, suggest high resistance of adult Echinometra sp. EE to near future ocean acidification conditions. With respect to other findings in this area, the outcome of this study provides an example of the complicated and diverse responses of echinoids to the predicted environmental changes., Introduction Anthropogenic increase of atmospheric carbon dioxide (C[O.sub.2]) is acidifying the world's oceans, subsequently leading to a reduction in seawater saturation state with respect to calcium carbonate (CaC[O.sub.3], Caldeira and [...]

With coral reefs impacted by climate change, attention is turning to the extent to which scleractinian corals can acclimatize to new physical conditions. The implicit assumption that acclimatization is beneficial has not been tested for scleractinians, although it has been investigated in other systems and has been referred to as the beneficial acclimation hypothesis (Bah). This study tests this hypothesis for scleractinians in experiments on massive Porites spp. from Moorea, French Polynesia (17° 28.564S, 149° 49.018 W). Corals were acclimated for 15-21 days to three temperatures within the range experienced in the collection habitat and then transferred to each of the same temperatures for a treatment period of 14-15 days. The response of the holobiont was measured as growth, the response of the Symbiodinium populations as maximum photochemical efficiency of open reaction centers II ([F.sub.v]/[F.sub.m]). An ANOVA with polynomial contrasts was used to distinguish among the BAH, three alternative hypotheses and a null hypothesis describing the consequences of acclimation. In the first experiment (2009), massive Porites spp. were unresponsive to temperature. In the second experiment (2013), the BAH was not supported, but growth of the holobiont conformed to the 'hotter is better' (HIB) hypothesis; the response of Symbiodinium populations conformed to developmental buffering. These results suggest that acclimation by massive Porites spp. to temperatures experienced routinely in the natural environment does not have clear beneficial value for growth or photochemical efficiency (i.e., BAH was not supported), but they reveal that acclimation to increased temperature can have value in responding to a variety of subsequent temperatures (i.e., support for HIB)., Introduction The extent to which communities are biologically accommodated or physically controlled has long interested ecologists (Sanders 1968), but now the roles of physical processes in shaping ecosystem structure are [...]

Anthropogenic effects on marine ecosystems (e.g. hypoxia, warming) at and beyond continental margins are assumed to affect physiological and biochemical boundaries to species' distributions, potentially leading to habitat contraction across depth. Whether or not shallow-water benthic invertebrates are capable of undergoing depth-related migrations in response to such perturbations remains largely unknown. The few studies available have focused solely on whether colonisation of deep waters may be ongoing and on the ability of shallow-water species to tolerate low temperatures and high hydrostatic pressures: two physical parameters, which are thought to limit the depth range of a species. Those studies did not consider the effects of acclimation to low temperature and, especially, acclimation to high hydrostatic pressure on pressure tolerance. We demonstrate that acclimation to both low temperature (5°C) and to high hydrostatic pressure (10 MPa) increases the pressure tolerance within the shallow-water shrimp Palaemonetes varians. Previous studies have demonstrated the impressive temperature and pressure tolerance of this shallow-water shrimp. Here, we provide evidence that a shallow-water species may acclimate to low temperature and high pressure and show greater pressure tolerance, suggesting that shallow-water organisms may be able to rapidly--and potentially stepwise--acclimate to the low temperature and high pressure conditions typical of the deep sea. These findings are of importance for understanding phylogenetic development from shallow- to deep-water species and the processes behind past, present and future bathymetric range shifts in species., Introduction The deep sea (below 200 m) is the largest environment on earth, covering > 90% of the surface area of the oceans (see Fig. 1 in Brown and Thatje [...]

The thermal envelope of development to the larval stage of two echinoids from eastern Australia was characterized to determine whether they fill their potential latitudinal ranges as indicated by tolerance limits. The tropical sand dollar, Arachnoides placenta, a species that is not known to have shifted its range, was investigated in Townsville, northern Australia (19°20'S, 146°77'E), during its autumn spawning season (May 2012). The subtropical/temperate sea urchin, Centrostephanus rodgersii, a species that has undergone poleward range expansion, was investigated in Sydney, southern Australia (33°58'S, 151°14'E), during its winter spawning season (August 2012). The thermal tolerance of development was determined in embryos and larvae reared at twelve temperatures. For A. placenta, the ambient water temperature near Townsville and experimental control were 24°C and treatments ranged from 14 to 37°C. For C. rodgersii, ambient Sydney water temperature and experimental control were 17°C, and the treatment range was 9-31°C. A. placenta had a broader developmental thermal envelope (14°C range 17-31°C) than C. rodgersii (9°C range 13-22°C). Both species developed successfully at temperatures well below ambient, suggesting that cooler water is not a barrier to poleward migration for either species. Both species presently live near the upper thermal limits for larval development, and future ocean warming could lead to contractions of their northern range limits. This study provides insights into the factors influencing the realized and potential distribution of planktonic life stages and changes to adult distribution in response to global change., Introduction The latitudinal distribution of many marine ectotherms is closely related to thermal tolerance limits of the adult and planktonic stages (Andronikov 1975; Jones et al. 2009; Sunday et al. [...]

For the antitropical gooseneck barnacle Pollicipes elegans, population-specific physiological temperature tolerance of larvae may serve as a barrier to larval dispersal across the warmest regions of the tropical Pacific Ocean. Thermal tolerance ranges of larvae of three different populations of P. elegans sampled in 2011 and 2012 (Mexico [MX], El Salvador [ES], and Peru [PE]) were investigated by measuring three indicators of physiological performance: swimming activity, oxygen consumption, and lethality or [LT.sub.50]. The thermal tolerance profiles, which include measurable optimum (maximum aerobic performance), pejus ('getting worse') and pessimum (worst aerobic performance) ranges, of larvae from the three populations were consistent with their characteristic environmental temperatures. In MX, larvae live close to the upper border of their optimum during warm months and so have a limited capacity to tolerate higher-than-normal temperatures. Larvae from the ES population likewise appear to live within their optimum temperature range, but these larvae lack a detectable pessimum range, suggesting they would be unable to cope with temperatures above their pejus range. Larvae from PE have a broad optimum but no pejus range. Different thermal tolerance ranges provide strong evidence for population-dependent physiological adaptations in P. elegans. For the southern (PE) and northern (MX) P. elegans populations, high tropical temperatures are likely to be a strong direct physiological barrier to larval survival and dispersal, which is in contrast to the more thermally tolerant ES population., Introduction For marine communities from temperate populations in the northern and southern hemisphere, the warm temperatures and strong currents in shallow tropical oceans function as one of Earth's oldest and [...]

High temperatures are associated with reduced crop yields (1,2), and predictions for future warming (3) have raised concerns regarding future productivity and food security (4-8). However, the extent to which adaptation can mitigate such heat-related losses remains unclear (9-13). Here we empirically demonstrate how maize is locally adapted to hot temperatures across US counties. Using this spatial adaptation as a surrogate for future adaptation, we find that losses to average US maize yields from a 2°C warming would be reduced from 14% to only 6% and that loss in net production is wholly averted. This result does not account for possible changes in temperature variability or water resources, nor does it account for all possible forms of adaptation (14-18), but it does show that adaptation is of first-order importance for predicting future changes in yield. Further research should be undertaken regarding the ability to adapt to a changing climate, including analysis of other crops and regions, the application of more sophisticated models of crop development, and field trials employing artificially increased temperature., Global maize yields are forecast to decline in response to increasing temperature, particularly as the upper range of growing season temperatures become hotter (1,2,4-7,19). The sensitivity of crop yields to [...]

Effects of acclimation to projected near-future ocean acidification (OA) conditions on physiology, reproduction and development were investigated in the tropical sea urchin Echinometra mathaei. Following 6 weeks in control or one of the three elevated pC[O.sub.2] ([pH.sub.NIST] 7.5-8.1; pC[O.sub.2] ~ 485-1,770 µatm) conditions, adult urchins exhibited a slight decline of growth in low pH treatments and moderately reduced respiration at intermediate levels. At 7 weeks, gametes from adults were used to produce larvae that were reared in their respective parental treatments. To assess whether larvae from acclimated parents are more resilient to elevated pC[O.sub.2] than those not acclimated, larvae from control animals were also reared in the elevated pC[O.sub.2] treatments. There was no difference in female 'spawnability' and oocyte size between treatments, but male spawning ability was reduced in increased pC[O.sub.2] conditions. In elevated pC[O.sub.2] treatments, the percentage of normal larvae and larval size decreased in the progeny of control- and elevated pC[O.sub.2]-acclimated parents, and arm asymmetry increased. Thus, acclimation of the parents did not make the progeny more resilient or sensitive to OA effects. Negative effects of increased pC[O.sub.2] on reproduction and development may impact on recruitment and population maintenance of this species., Introduction Present-day atmospheric C[O.sub.2] concentrations are over 30% higher than the maximum observed in the previous 2 Mil years (Honisch et al. 2009). A large percentage of C[O.sub.2] is absorbed [...]

Cardiovascular adaptations that permit successful exploitation of polar marine waters by fish requires a capacity to negate or compensate for the depressive effects of low temperatures on physiological processes. Here, we examined the effects of acute and chronic temperature change on the maximum cardiac performance of shorthorn sculpin (Myoxocephalus scorpius (L., 1758)) captured above the Arctic Circle. Our aim was to establish if the sculpin's success at low temperatures was achieved through thermal independence of cardiac function or via thermal compensation as a result of acclimation. Maximum cardiac performance was assessed at both 1 and 6°C with a working perfused heart preparation that was obtained after fish had been acclimated to either 1 or 6°C. Thus, tests were performed at the fish's acclimation temperature and with an acute temperature change. Maximum cardiac output, which was relatively large (>50 mL x [min.sup.-1] x [kg.sup.-1] body mass) for abenthic fish at a frigid temperature, was found to be independent of both acclimation temperature and test temperature. While maximum β-adrenergic stimulation produced positive chronotropy at both acclimation temperatures, inotropic effects were weak or absent. We conclude that thermal independence of cardiac performance at low temperature likely facilitated the exploitation of polar waters by the shorthorn sculpin. Key words: Myoxocephalus scorpius, perfused heart, cardiac output, adrenaline, power generation, pressure. Les adaptations cardiovasculaires qui permettent aux poissons d'exploiter efficacement les eaux marines polaires necessitent une capacite de contrer les effets depressifs des temperatures faibles sur les processus physiologiques ou de compenser ces effets. Nous avons examine les effets de changements de temperature aigus et chroniques sur la fonction cardiaque maximum de chaboisseaux a epines courtes (Myoxocephalus scorpius (L., 1758)) captures au nord du cercle arctique dans le but de determiner si le succes des chaboisseaux a faible temperature decoulait du fait que la fonction cardiaque etait independante de la temperature ou d'une compensation thermique resultant d'une acclimatation. La fonction cardiaque maximum a ete evaluee a 1 et 6[grados]C sur des cceurs perfuses fonctionnels apres acclimatation prealable des poissons a 1 ou 6[grados]C. Ainsi, les essais ont ete effectues a la temperature d'acclimatation des poissons et apres un changement de temperature aigu. Le debit cardiaque maximum, qui etait relativement eleve (>50 mL x [min.sup.-1] x [kg.sup.-1] de masse corporelle) pour un poisson benthique a temperature tres froide, s'est avere independant de la temperature d'acclimatation et de la temperature d'essai. Si la stimulation beta-adrenergique maximum a produit une chronotropie positive aux deux temperatures d'acclimatation, il n'y avait peu ou pas d'effets inotropes. Nous concluons que l'absence de dependance a la temperature de la fonction cardiaque a faible temperature facilite vraisemblablement l'exploitation des eaux polaires par les chaboisseaux a epines courtes. [Traduit par la Redaction] Mots-cles: Myoxocephalus scorpius, cceur perfuse, debit cardiaque, adrenaline, production de puissance, pressure., Introduction Temperature, termed the 'ecological master factor' for fish (Brett 1971), has a profound influence on all physiological processes, and especially cardiac life support. In general, physiological rate functions are [...]

Purpose: In this study, the authors evaluated the effect of frequency compression hearing aids on speech perception ability and the time course and magnitude of acclimatization-related changes. Method: Participants included children ages 11-18 years. Speech perception ability was evaluated over well-controlled baseline, treatment, and withdrawal study phases. Study-worn hearing aids were individually fitted to all participants. The authors evaluated speech perception ability using outcomes of speech detection (/s/ and /∫/ sounds), /s-∫/ discrimination, and plural and consonant recognition. Results: Indices of change were discussed on a case-by-case basis across all study phases. Significant treatment effects were measured for all cases, on at least one measure, with some listeners displaying significant acclimatization trends following a trial of frequency compression. Conclusion: Findings suggest that frequency compression provided varying outcomes, both in benefit and acclimatization, across listeners. For some, a period of acclimatization was necessary before change could be measured. For others, performance remained stable over the time course under evaluation, suggesting that some but not all children will experience improved speech recognition ability after a period of frequency compression hearing aid use. Key Words: hearing aids, hearing device evaluation, children, single-subject design, Rehabilitation for listeners with hearing impairment (HI) often includes the provision of amplification via hearing aids. When conventional hearing aids are not able to provide audibility of high-frequency speech sounds, [...]

Sustaining forest ecosystem functions and services under climate change is a major challenge for forest management. While conceptual advances of adapting coupled social-ecological systems to environmental changes have been made recently, good practice examples at the operational level still remain rare. The current study presents the development of adaptation options for 164 550 ha of commercial forests under the stewardship of the Austrian Federal Forests (AFF). We used a comprehensive vulnerability assessment as analysis framework, employing ecosystem modeling and multicriteria decision analysis in a participatory approach with forest planers of the AFF. An assessment of the vulnerability of multiple ecosystem goods and services under current management served as the starting point for the development of adaptation options. Measures found to successfully reduce vulnerability include the promotion of mixed stands of species well adapted to emerging environmental conditions, silvicultural techniques fostering complexity, and increased management intensity. Assessment results for a wide range of site and stand conditions, stand treatment programs, and future climate scenarios were used to condense robust recommendations for adapting the management guidelines currently used by AFF practitioners. Overall, our results highlight the importance of timely adaptation to sustain forest goods and services and document the respective potential of silvicultural measures. Resume: Le maintien des fonctions et services de l'ecosysteme forestier malgre le changement climatique represente un defi majeur pour l'amenagement forestier. Bien que des progres conceptuels pour adapter les systemes socio-ecologiques combines aux changements environnementaux aient ete accomplis recemment, les exemples de bonnes pratiques a l'echelle operationnelle sont encore rares. Cette etude presente le developpement d'options d'adaptation pour 164 550 ha de forets commerciales gerees par l'entreprise ≪ Austrian Federal Forests ≫ (AFF). Nous avons utilise une evaluation poussee de vulnerabilite comme cadre d'analyse en ayant recours a la modelisation ecosystemique et a l'analyse de decision multicritere dans une approche participative avec les gestionnaires forestiers de l'AFF. Une evaluation de la vulnerabilite des multiples biens et services de l'ecosysteme dans le cadre de l'amenagement actuel a servi de point de depart pour le developpement d'options d'adaptation. Les mesures capables de reduire la vulnerabilite incluent la promotion des peuplements melanges avec des essences bien adaptees aux conditions environnementales emergentes, les techniques sylvicoles qui favorisent la complexite et un amenagement plus intensif. Les resultats de l'evaluation pour une large gamme de stations et de conditions de peuplement, de programmes de traitement des peuplements et de scenarios climatiques futurs ont servi a formuler des re-commandations robustes pour adapter les lignes directrices d'amenagement actuellement utilisees par les praticiens de l'AFF. Dans l'ensemble, nos resultats font ressortir l'importance d'une adaptation opportune pour maintenir les biens et ser-vices de la foret et documenter le potentiel des differentes interventions sylvicoles. [Traduit par la Redaction], Introduction Climate change is one of the biggest challenges of the coming decades, threatening to exceed the planetary boundaries of a save operating space for humanity (Rockstrom et al. 2009). [...]

ABSTRACT Clinical biochemistry is the measurement of body fluid constituents, and is considered an integral component of disease diagnosis in human and veterinary medicine. Biochemical reference intervals are the ranges [...]

We sought to determine the molecular basis of elevations in aerobic metabolic capacity in the oxidative muscle and liver of Gasterosteus aculeatus in response to cold acclimation. Fishes were cold- or warm-acclimated for 9 wk and harvested on days 1, 2, and 3 and weeks 1, 4, and 9 of cold acclimation at 8[degrees]C, and on day 1 and week 9 of warm acclimation at 20[degrees]C. Mitochondrial volume density was quantified using transmission electron microscopy and stereological techniques in warm- and cold-acclimated fishes harvested after 9 wk at 20 or 8[degrees]C. Changes in aerobic metabolic capacity were assessed by measuring the maximal activity of citrate synthase (CS) and cytochrome-c oxidase (COX) in fishes harvested throughout the acclimation period. Transcript levels of the aerobic metabolic genes CS, COXIII, and COXIV, and known regulators of mitochondrial biogenesis, including peroxisome proliferator-activated receptor-[gamma] coactivators-1[alpha] and - 1[beta] (PGC- l[alpha] and PGC-1[beta]), nuclear respiratory factor-1 (NRF-1), and mitochondrial transcription factor-A were measured in fishes harvested throughout the acclimation period using quantitative real-time PCR. The maximal activities of CS and COX increased in response to cold acclimation in both tissues, but mitochondrial volume density only increased in oxidative muscle (P < 0.05). The time course for changes in aerobic metabolic capacity differed between liver and muscle. The expression of CS increased within 1 wk of cold acclimation in liver and was correlated with an increase in mRNA levels of NRF-1 and PGC-1[beta]. Transcript levels of aerobic metabolic genes increased later in oxidative muscle, between weeks 4 and 9 of cold acclimation and were correlated with an increase in mRNA levels of NRF-1 and PGC-l[alpha]. These results show that aerobic metabolic remodeling differs between liver and muscle in response to cold acclimation and may be triggered by different stimuli. temperature; mitochondrial biogenesis; metabolism doi: 10.1152/ajpregu.00189.2010.

Most studies on coral reefs have focused on shallow reef ( Key words: corals; fluorescence; mesophotic zone; Montastraea cavernosa; productivity: stable isotopes.

Inactivation of the sigC gene (sll0184), encoding the group 2 sigma factor SigC, leads to a heat-sensitive phenotype of Synechocystis sp. PCC 6803. Cells of the [DELTA]sigC strain grew poorly at 43[degrees]C at pH 7.5 under ambient C[O.sub.2] conditions. Addition of inorganic carbon in the form of 3% C[O.sub.2] or use of an alkaline growth medium (pH 8.3) restored the growth of the [DELTA]sigC strain at 43[degrees]C. These treatments compensate for the low concentration of inorganic carbon at high temperature. However, addition of organic carbon as glucose, pyruvate, succinate or 2-oxoglutarate did not restore growth of the [DELTA]sigC strain at 43[degrees]C. In the control strain, the amount of the SigC factor diminished after prolonged incubation at 43[degrees]C if the pH of the growth medium was 7.5 or 6.7. Under alkaline conditions, the amount of the SigC factor remained constant at 43[degrees]C and cells of the control strain grew better than at pH 7.5 or pH 6.7. The pH dependence of high-temperature growth was associated with changes in photosynthetic activity, indicating that the SigC factor is involved in adjustment of photosynthesis according to the amount of available inorganic carbon. Our results indicate that acclimation to low inorganic carbon is a part of acclimation to prolonged high temperature and that the SigC factor has a central role in this acclimation. DOI 10.1099/mic.0.032565-0

We investigated whether the eccrine sweat glands must actively produce sweat during heat acclimation if they are to adapt and increase their capacity to sweat. Eight volunteers received intradermal injections of BOTOX, to prevent neural stimulation and sweat production of the sweat glands during heat acclimation, and saline injections as a control in the contralateral forearm. Subjects performed 90 min of moderate-intensity exercise in the heat (35[degrees]C, 40% relative humidity) on 10 consecutive days. Heat acclimation decreased end-exercise heart rate (156 [+ or -] 22 vs. 138 [+ or -] 17 beats/rain; P = 0.0001) and rectal temperature (38.2 [+ or -] 0.3 vs. 37.9 [+ or -] 0.3[degrees]C; P = 0.0003) and increased whole body sweat rate (0.70 [+ or -] 0.29 vs. 1.06 [+ or -] 0.50 l/h; P = 0.030). During heat acclimation, there was no measurable sweating in the BOTOX-treated forearm, but the control forearm sweat rate during exercise increased 40% over the 10 days (P = 0.040). Peripheral sweat gland function was assessed using pilocarpine iontophoresis before and after heat acclimation. Before heat acclimation, the pilocarpine-induced sweat rate of the control and BOTOX-injected forearms did not differ (0.65 [+ or -] 0.20 vs. 0.66 [+ or -] 0.22 mg x [cm.sup.-2] x [min.sup.-1]). However, following heat acclimation, the pilocarpine-induced sweat rate in the control arm increased 18% to 0.77 [+ or -] 0.21 mg x [cm.sup.-2] x [min.sup.-1] (P = 0.021) but decreased 52% to 0.32 [+ or -] 0.18 mg x [cm.sup.-2] x [min.sup.-1] (p < 0.001) in the BOTOX-treated arm. Using complete chemodenervation of the sweat glands, coupled with direct cholinergic stimulation via pilocarpine iontophoresis, we demonstrated that sweat glands must be active during heat acclimation if they are to adapt and increase their capacity to sweat. eccrine sweat gland; cholinergic sensitivity; pilocarpine; sweat rate doi: 10.1152/ajpregu.00253.2009

The objective of this study was to evaluate the effects of acclimation to handling on growth, plasma concentrations of progesterone (P4) and cortisol, temperament, and reproductive performance of Brahman-crossbred heifers. Over 2 consecutive years, 37 Braford and 43 Brahman x Angus heifers were initially evaluated, within 30 d after weaning, for BW and puberty status via transrectal ultrasonography and plasma P4 concentrations (d 0 and 10), and for temperament by measurements of chute score, pen score, and exit velocity (d 10 only). On d 11, heifers were stratified by breed, puberty status, temperament score, BW, and age and randomly assigned to receive or not (control) the acclimation treatment. Acclimated heirers were exposed to a handling process 3 times weekly (Mondays, Wednesdays, and Fridays) for 4 wk (d 11 to 39 of the experiment). The acclimation treatment was applied individually to heifers by processing them through a handling facility, whereas control heifers remained undisturbed on pasture. Heifer puberty status, evaluated via plasma P4 concentrations and transrectal ultrasonography, and BW were assessed again on d 40 and 50, d 80 and 90, and d 120 and 130. Blood samples collected before (d 10) and at the end of the acclimation period (d 40) were also analyzed for plasma concentrations of cortisol. Heifer temperament was assessed again on d 40 of the study. No interactions containing the effects of treatment, breed, and year were detected. Acclimated heifers had reduced (P < 0.01) ADG compared with control heifers (0.50 vs. 0.58 kg/d, respectively). Attainment of puberty and pregnancy, however, was hastened (P = 0.02 and 0.04, respectively) in acclimated heifers compared with control. Acclimated heifers had reduced chute score (P < 0.01) and concentrations of cortisol (P < 021) and P4 (P = 0.03; prepubertal heifers only) compared with control heifers after the acclimation period (1.37 vs. 1.84 for chute score; 37.8 vs. 50.5 ng/mL of cortisol; 0.52 vs. 0.78 ng/mL of P4). Results from this study indicated that, although acclimation to handling decreased ADG, it resulted in decreased chute score, reduced plasma concentrations of cortisol and prepubertal P4, and enhanced reproductive performance of Brahman-crossbred heifers. Key words: acclimation, Brahman, development, handling, heifer, temperament

Hyperthermia-induced hyperventilation has been proposed to be a human thermolytic thermoregulatory response and to contribute to the disproportionate increase in exercise ventilation (VE) relative to metabolic needs during high-intensity exercise. In this study it was hypothesized that VE would adapt similar to human eccrine sweating (Esw) following a passive heat acclimation (HA). All participants performed an incremental exercise test on a cycle ergometer from rest to exhaustion before and after a 10-day passive exposure for 2 h/day to either 50[degrees]C and 20% relative humidity (RH) (n = 8, Acclimation group) or 24[degrees]C and 32% RH (n = 4, Control group). Attainment of HA was confirmed by a significant decrease (P = 0.025) of the esophageal temperature ([T.sub.es]) threshold for the onset of [E.sub.sw] and a significantly elevated [E.sub.sw] (P [less than or equal to] 0.040) during the post-HA exercise tests. HA also gave a significant decrease in resting [T.sub.es] (P = 0.006) and a significant increase in plasma volume (P = 0.005). Ventilatory adaptations during exercise tests following HA included significantly decreased [T.sub.es] thresholds (P [less than or equal to] 0.005) for the onset of increases in the ventilatory equivalents for [O.sub.2] (VE/V[O.sub.2]) and C[O.sub.2] (VE/Vc[o.sub.2]) and a significantly increased VE (P [less than or equal to] 0.017) at all levels of [T.sub.es]. Elevated VE was a function of a significantly greater tidal volume (P = 0.003) at lower [T.sub.es] and of breathing frequency (P [less than or equal to] 0.005) at higher [T.sub.es]. Following HA, the ventilatory threshold was uninfluenced and the relationships between V[o.sub.2] and either VE/V[o.sub.2] or VE/Vc[o.sub.2] did not explain the resulting hyperventilation. In conclusion, the results support that exercise VE following passive HA responds similarly to [E.sub.sw], and the mechanism accounting for this adaptation is independent of changes of the ventilatory threshold or relationships between V[o.sub.2] with each of VE/V[o.sub.2] and VE/Vc[o.sub.2]. eccrine sweating; skin temperatures; plasma volume; ventilatory equivalents

Short days induce winter-like adaptations in small mammals such as Siberian hamsters (Phodopus sungorus (Pallas, 1773)). Specifically, hamsters adjust food consumption, metabolic processes, and immune function to optimize energetic needs and promote winter survival. One potentially inexpensive behavioral adaptation to increase survival is avoidance of infection. We tested the hypothesis that photoperiod affects avoidance of potentially infected food. In experiment 1, hamsters were weaned into either short or long days with ad libitum food. Three weeks later, hamsters were presented with either skim milk treated with butyric acid (2%), a bacterial product that serves as a potent cue of spoilage, or unadulterated skim milk; consumption was measured. After milk presentation, blood samples were obtained to assess cortisol. In experiment 2, skim-milk consumption was again assessed after 3 weeks in either short or long days. In experiment 3, we tested the hypothesis that food avoidance was due to photoperiod-induced differential neophobia. Short-day hamsters increased milk consumption, which was blocked by butyric acid. Short days increased cortisol concentrations; neither food restriction nor butyric acid affected cortisol concentrations. Photoperiod did not alter neophobic responses. These experiments suggest that short-day hamsters avoid food treated with butyric acid possibly as an adaptive trait to avoid costly winter infections. Les jours courts induisent des adaptations de type hivernal chez les petits mammiferes, tels que les hamsters nains de Dzoungarie (Phodopus sungorus (Pallas, 1773)). En particulier, les hamsters ajustent leur consommation de nourriture, leurs processus metaboliques et leur fonction immunitaire de maniere a optimiser leurs besoins energetiques et de favoriser leur survie durant l'hiver. Une adaptation comportementale potentielle a faible cout pour augmenter la survie est l'evitement des infections. Nous verifions l'hypothese selon laquelle la photoperiode affecte l'evitement de nourriture potentiellement contaminee. Dans l'experience 1, nous avons sevre des hamsters dans des conditions de jours courts ou longs et les avons nourris a volonte. Trois semaines plus tard, nous avons fourni aux hamsters ou bien du lait ecreme traite a l'acide butyrique (2 %), un produit bacterien qui est un puissant indicateur d'avarie, ou alors du lait ecreme sans additif et nous avons mesure leur consommation. Apres la presentation du lait, des prelevements sanguins ont permis de doser le cortisol. Dans l'experience 2, nous avons de nouveau evalue la consommation de lait ecreme apres 3 semaines en conditions de jours courts ou longs. Dans l'experience 3, nous avons teste l'hypothese selon laquelle l'evitement de la nourriture est du a une neophobie differentielle sous l'action de la photoperiode. En conditions de jours courts, les hamsters augmentent leur consommation de lait, qui est cependant enrayee par l'acide butyrique. Les jours courts font augmenter les concentrations de cortisol, mais ni les restrictions alimentaires, ni l'acide butyrique n'affectent les concentrations de cortisol. La photoperiode ne modifie pas les reactions de neophobie. Ces experiences indiquent que les hamsters en conditions de jours courts evitent la nourriture traitee a l'acide butyrique, possiblement comme un trait adaptatif pour ecarter les infections couteuses en hiver. [Traduit par la Redaction], Introduction Small mammals that live in temperate or boreal habitats, including Siberian hamsters (Phodopus sungorus (Pallas, 1773)), have evolved strategies to cope with temporal variations in food availability. Siberian hamsters [...]

We tested the hypothesis that neonatal exposure to hypoxia alters acclimatization to chronic hypoxia later in life. Rat pups were exposed to normobaric hypoxia (12% [O.sub.2]; nHx group) in a sealed chamber, or to normoxia (21% [O.sub.2]; nNx group) from the day before birth to postnatal day 10. The animals were then raised in normal conditions until reaching 12 wk of age. At this age, we assessed ventilatory and hematological acclimatization to chronic hypoxia by exposing male and female nHx and nNx rats for 2 wk to 10% [O.sub.2]. Minute ventilation, metabolic rate, hypoxic ventilatory response, hematocrit, and hemoglobin levels were measured both before and after acclimatization. We also quantified right ventricular hypertrophy as an index of pulmonary hypertension both before and after acclimatization. There was a significant effect of neonatal hypoxia that decreases ventilatory response (relative to metabolic rate, VE/V[CO.sub.2]) to acute hypoxia before acclimatization in males but not in females, nHx rats had an impaired acclimatization to chronic hypoxia characterized by altered respiratory pattern and elevated hematocrit and hemoglobin levels after acclimatization, in both males and females. Right ventricular hypertrophy was present before and after acclimatization in nHx rats, indicating that neonatal hypoxia results in pulmonary hypertension in adults. We conclude that neonatal hypoxia impairs acclimatization to chronic hypoxia in adults and may be a factor contributing to the establishment of chronic mountain sickness in humans living at high altitude. hypoxic ventilatory acclimatization; neonatal hypoxia; chronic mountain sickness

In fewer than two decades after invading the Americas, the European fly Drosophila subobscura evolved latitudinal clines in several traits. Moreover, its chromosomal inversion frequencies at given localities have shifted with climate warming. Temperature may have driven the evolution of both geographic clines and within-site shifts. Nevertheless, whether body temperature ([T.sub.b]) of active flies actually varies geographically and temporally is unknown: if these flies are effective behavioral thermoregulators, they might maintain relatively constant [T.sub.b] when active, independent of season and latitude. To evaluate these possibilities, we monitored activity and estimated [T.sub.b] of active flies in all seasons and at five sites (3[gamma]-49[degrees] N) in western North America. Latitudinal and seasonal shifts in activity are conspicuous. Flies have longer activity seasons (and are much more active) at higher latitudes. Flies are generally active only at midday in cool seasons, and only early and late in the day (if active at all) in warm seasons. Despite these behavioral shifts active flies have much lower [T.sub.b] in cooler seasons and at higher latitudes. The observed pattern is consistent with the hypothesis that geographic shifts in [T.sub.b] may be an evolutionary driver of latitudinal clines in this invading species. Key words: body temperature; Drosophila subobscura; European fruit fly; invasive species; latitudinal clines; North America; thermoregulation.

It is important to maintain internal pH homeostasis in biological systems. In our previous studies, [H.sup.+]-ATPase-rich (HR) cells were found to be responsible for proton secretion in the skin of zebrafish embryos during development. In this study, zebrafish embryos were exposed to acidic and basic waters to investigate the regulation of HR cell acid secretion during pH disturbances. Our results showed that the function of HR cells on the skin of zebrafish embryos can be upregulated in pH 4 water not only by increasing the cell number but also by enlarging the acid-secreting function of single cells. We also identified an 'alveolar-type' apical opening under scanning electron microscopy observations of the apical membrane of HR cells, and the density and size of the alveolar type of apical openings were also increased in pH 4 water, p63 and PCNA immunostaining results also showed that additional HR cells in pH 4 water may be differentiated not only from ionocyte precursor cells but also newly proliferating epithelial stem cells. ionocytes; acid-base regulation; ion regulation; proliferation; differentiation

IncP-9 plasmids are important vehicles for degradation and resistance genes that contribute to the adaptability of Pseudomonas species in a variety of natural habitats. The three completely sequenced IncP-9 plasmids, pWWO, pDTG1 and NAH7, show extensive homology in replication, partitioning and transfer loci (an ~25 kb region) and to a lesser extent in the remaining backbone segments. We used PCR, DNA sequencing, hybridization and phylogenetic analyses to investigate the genetic diversity of 30 IncP-9 plasmids as well as the possibility of recombination between plasmids belonging to this family. Phylogenetic analysis of rep and oriV sequences revealed nine plasmid subgroups with 7-35 % divergence between them. Only one phenotypic character was normally associated with each subgroup, except for the IncP-9[beta] cluster, which included naphthalene- and toluene-degradation plasmids. The PCR and hybridization analysis using pWWO- and pDTG1-specific primers and probes targeting selected backbone loci showed that members of different IncP-9 subgroups have considerable similarity in their overall organization, supporting the existence of a conserved ancestral IncP-9 sequence. The results suggested that some IncP-9 plasmids are the product of recombination between plasmids of different IncP-9 subgroups but demonstrated clearly that insertion of degradative transposons has occurred on multiple occasions, indicating that association of this phenotype with these plasmids is not simply the result of divergent evolution from a single successful ancestral degradative plasmid.

Previous studies suggest that eastern chipmunks (Tamias striatus) avoid roads, but it is unclear whether vehicle traffic plays a role in this avoidance. The purpose of this study was to determine whether road avoidance in chipmunks increases with traffic. We tracked the movements of 68 chipmunks released near roads with widely varying volumes of traffic. Our results suggest that chipmunks responded to changes in traffic volume only in the preliminary stages of their movement pathways. Apart from this initial response, we found that road avoidance was independent of traffic, with evidence that chipmunks avoided both the roadside verge and the road surface. Because avoidance of roads was independent of traffic, effects of roads on populations of chipmunks may be manifest more as population subdivision than as direct mortality. Key words: acclimatization, barrier, edge, fragmentation, highway, pathway, traffic, translocation, vehicle

Abstract: The role that climate plays in determining the temporal dynamics of freshwater zooplankton is poorly understood, despite its potential to synchronize population dynamics on a regional basis. We quantify [...]

A diverse array of fire-adapted plant communities once covered the eastern United States. European settlement greatly altered fire regimes, often increasing fire occurrence (e.g., in northern hardwoods) or substantially decreasing [...]

One way animals can counter the effects of climatic extremes is via physiological acclimation, but acclimating to one extreme might decrease performance under different conditions. Here, we use field releases of Drosophila melanogaster on two continents across a range of temperatures to test for costs and benefits of developmental or adult cold acclimation. Both types of cold acclimation had enormous benefits at low temperatures in the field; in the coldest releases only cold-acclimated flies were able to find a resource. However, this advantage came at a huge cost; flies that had not been cold-acclimated were up to 36 times more likely to find food than the cold-acclimated flies when temperatures were warm. Such costs and strong benefits were not evident in laboratory tests where we found no reduction in heat survival of the cold-acclimated flies. Field release studies, therefore, reveal costs of cold acclimation that standard laboratory assays do not detect. Thus, although physiological acclimation may dramatically improve fitness over a narrow set of thermal conditions, it may have the opposite effect once conditions extend outside this range, an increasingly likely scenario as temperature variability increases under global climate change. field performance | plasticity | thermal stress | climate change | thermal adaptation

Abrupt transfer of rainbow trout from freshwater to 65% seawater caused transient disturbances in extracellular fluid ionic composition, but homeostasis was reestablished 48 h posttransfer. Intestinal fluid chemistry revealed early onset of drinking and slightly delayed intestinal water absorption that coincided with initiation of NaC1 absorption and HC[O.sup.-.sub.3] secretion. Suggestive of involvement in osmoregulation, relative mRNA levels for vacuolar [H.sup.+]-ATPase (V-ATPase), [Na.sup.+]-[K.sup.+]-ATPase, [Na.sup.+]/[H.sup.+] exchanger 3 (NHE3), [Na.sup.+]-HC[O.sup.-.sub.3] cotransporter 1, and two carbonic anhydrase (CA) isoforms [a general cytosolic isoform trout cytoplasmic CA (tCAc) and an extracellular isoform trout membrane-bound CA type IV (tCAIV)], were increased transiently in the intestine following exposure to 65% seawater. Both tCAc and tCAIV proteins were localized to apical regions of the intestinal epithelium and exhibited elevated enzymatic activity after acclimation to 65% seawater. The V-ATPase was localized to both basolateral and apical regions and exhibited a 10-fold increase in enzymatic activity in fish acclimated to 65% seawater, suggesting a role in marine osmoregulation. The intestinal epithelium of rainbow trout acclimated to 65% seawater appears to be capable of both basolateral and apical [H.sup.+] extrusion, likely depending on osmoregulatory status and intestinal fluid chemistry. water absorption; HC[O.sup.-.sub.3] secretion; intestinal [H.sup.+] transport; tCAIV; tCAc

Cardiac activity of the turtle (Trachemys scripta) is greatly depressed with cold acclimation and anoxia. We examined what electrophysiological modifications accompany and perhaps facilitate this depression of cardiac activity. Turtles were first acclimated to 21[degrees]C or 5[degrees]C and held under either normoxic or anoxic (6 h at 21[degrees]C; 14 days at 5[degrees]C) conditions. We then measured cardiac action potentials (APs) using spontaneously contracting whole heart preparations and whole cell current densities of sarcolemmal ion channels using isolated ventricular myocytes under appropriate normoxic and anoxic conditions. Compared with 21[degrees]C-acclimated turtles, 5[degrees]C-acclimated turtles exhibited a less negative resting membrane potential (by 18-29 mV), a 4.7- to 6.8-fold slower AP upstroke rate, and a 4.2- to 4.9-fold greater AP duration. Correspondingly, peak densities of ventricular voltage-gated [Na.sup.+] ([I.sub.Na]) and L-type [Ca.sup.2+] currents and inward slope conductances of inward rectifier [K.sup.+] ([I.sub.KI]) channel current were ~1/7th ([Q.sub.10] = 3.4), 1/13th ([Q.sub.10] = 5.0), and one-half ([Q.sub.10] = 1.4) of those of 21[degrees]C-acclimated ventricular myocytes, respectively. With anoxia at 21[degrees]C, peak [I.sub.Na] density doubled and ventricular AP duration increased by 47%, a change proportional to the reported ~30% reduction of intrinsic heart rate. In contrast, with anoxia at 5[degrees]C, ventricular AP characteristics were unaffected; of the ion currents investigated, only the inward conductance via [I.sub.KI] changed significantly (reduced by 46%). The present findings indicate that cold temperature, more so than prolonged anoxia, results in substantial modifications of cardiac APs and reduction of ventricular ion current densities. These changes likely prepare cardiac muscle for winter anoxia conditions. action potential; delayed-rectifier potassium channel current; voltage-gated sodium channel current; L-type calcium channel current; inward-rectifier potassium channel current; red-eared slider turtle; thermal acclimation doi: 10.1152/ajpregu.00096.2007

The effect of breed [Creole (CR) vs. Large White (LW)] on performance and physiological responses during acclimation to high ambient temperature was studied in 2 experiments involving 24 (12/ breed) growing pigs each. Pigs were exposed to 24 [degrees]C for 10 d (d -10 to -1) and thereafter to a constant temperature of 31 [degrees]C for 16 d (d 1 to d 16) in Exp. 1 and for 20 d (d 1 to d 20) in Exp. 2. For both experiments, the temperature change was achieved over 4 h on d 0. The first experiment began at 105 d of age, and the average BW of CR and LW pigs was 36.6 [+ or -] 2.5 kg and 51.7 [+ or -] 3.0 kg, respectively. The second experiment was designed to compare both breeds at a similar BW (about 52 kg on d 0). Pigs were individually housed and given ad libitum access to feed. At 24 [degrees]C, ADG was lower (P < 0.01) in CR than in LW (602 vs. 913 g/d and 605 vs. 862 g/d in Exp. 1 and 2, respectively), but the ADFI was not affected by breed (190 and 221 g*[d.sup.-1] * [kg.sup.-0.60] in Exp. 1 and 2, respectively). Short-term thermoregulatory responses during the 4-h transition from 24 to 31 [degrees]C (d 0) were analyzed according to a linear plateau model to determine the break point temperature, above which rectal temperature (RT), cutaneous temperature (CT), and respiratory rate (RR) began to change. The CT increased linearly with temperature increase (0.22 [degrees]C/ [degrees]C) and was less (P < 0.05) in CR than in LW (by -0.3 [degrees]C on average). In both experiments, the break point temperature for RT was not affected by breed (27.6 [degrees]C on average), whereas for RR it was greater (P < 0.05) in CR than in LW (27.5 vs. 25.5 [degrees]C, P < 0.01). On average, ADFI declined by about 50 g*[d.sup.-1] * [kg.sup.-0.60] from d -1 to d 1 (P < 0.01), and thereafter at 31 [degrees]C, it gradually increased (23 g * [d.sup.-1] * [kg.sup.-0.60]; P < 0.05), suggesting an acclimation to high exposure. This response was not influenced by breed. After the day that marked the beginning of the acclimation response (i.e., the threshold day), RR, CT, and RT declined over the duration of exposure to 31 [degrees]C (P < 0.05) in both experiments. During this period, RT and CT were less in CR than in LW pigs (39.6 vs. 39.9 [degrees]C and 37.9 vs. 38.2 [degrees]C, respectively; P < 0.05), whereas RR was not affected by breed. The threshold day at which RT began to decline was less in CR than in LW pigs (0.18 vs. 1.17 d and 0.39 vs. 0.93 d in Exp. 1 and 2, respectively; P < 0.05). In conclusion, this study suggests that short- and long-term physiological reactions during heat acclimation differed when CR and LW pigs were compared at the same age or BW. Key words: acclimation, breed, heat stress, pig, thermoregulation

This study was conducted to examine the changes in the levels of carbohydrates and N-rich defense compounds during cold acclimation associated with freezing tolerance. Two bermudagrass [Cynodon dactylon (L.) Pets. var. dactylon] cultivars, Riviera (cold tolerant) and Princess-77 (cold sensitive), were selected and either subjected to cold acclimation at 8/4[degrees]C (day/night) with a light intensity of 200 [micro]mol [m.sup.-2] [s.sup.-1] over a 10-h photoperiod for 21 d or maintained at 25/23[degrees]C (day/night) with natural sunlight in a glasshouse. Cold acclimation induced accumulation of sugars and proline in both cultivars and also an increase in total nonstructural carbohydrates (TNC) and protein in Riviera, but not in Princess-77. Superoxide dismutase (SOD) increased during the first 7 d and then declined, while catalase (CAT) and ascotbate peroxidase (APX) activity decreased in response to cold acclimation in both cultivars. Electrolyte leakage (EL) was reduced in both cultivars following cold acclimation. The LT50 was reduced by 2.2[degrees]C (from -6.1[degrees]C to -8.3[degrees]C) in Riviera and 1.7[degrees]C (from -4.6[degrees]C to 6.3[degrees]C) for Princess-77 following cold acclimation. Riviera had more carbohydrates and N-rich compounds and less EL than Princess-77 at the end of cold acclimation. Significant correlations of LT50 with sugars, proline, protein, CAT, and APX were obtained in Riviera, but only with proline and the antioxidant enzymes in Princess-77. The results suggest selection and use of cultivars with rapid accumulation of C- and N-rich compounds during cold acclimation could improve bermudagrass persistence in transition zone climates.

Systemic hemodynamics, including forearm blood flow and ventilatory parameters, were evaluated in 21 subjects before and after exposure to 8 h of poikilocapnic hypoxia. To evaluate the role of sympathetic nervous system activation in the changes, in 10 of these subjects, we measured muscle sympathetic nerve activity (MSNA) before and after exposure, and the remaining 11 subjects received intra-arterial phentolamine infusion in the brachial artery to define vascular tone in the absence of sympathetically mediated vasoconstriction. Short-term ventilatory acclimatization occurred as evidenced by a decrease in resting [PCO.sub.2] (from 42 [+ or -] 1.4 to 37 [+ or -] 0.96 mmHg) and by an increase in the slope of the ventilatory response to acute hypoxia [from 0.7 [+ or -] 0.1 to 1.2 [+ or -] 0.2 1 x [min.sup.-1] x %[Sp.sub.o.sub.2] (blood [O.sub.2] saturation from pulse oximetry)] after exposure. Subjects demonstrated a significant increase in resting heart rate (from 61 [+ or -] 2 to 65 [+ or -] 2 beats/min) and diastolic blood pressure (from 64.8 [+ or -] 2.7 to 70.4 [+ or -] 2.0 mmHg). MSNA did not change significantly after exposure, although there was a trend toward a decrease in burst frequency (from 19.8 [+ or -] 4.1 to 14.3 [+ o r-] 1.2 bursts/min). Forearm vascular resistance showed a significant decrease after termination of exposure (from 37.7 [+ o r-] 3.6 to 27.6 [+ or -] 2.7 mmHg x [ml.sup.-1] x min x 100 g tissue, P < 0.05). Initially, progressive isocapnic hypoxia elicited significant vasodilation, but after 8 h of poikilocapnic hypoxic exposure, the acute challenge failed to change forearm vascular resistance. Local [alpha]-blockade with phentolamine restored the vasodilatory response to acute hypoxia in the postexposure setting. acclimatization; muscle sympathetic nerve activity; vascular resistance

This investigation evaluated the new National Collegiate Athletic Association model of heat acclimatization for football players using physiological, psychological, fluid balance, anthropometric, and nutritional variables. Eleven football players (20 [+ or -] 1 year, 1.88 [+ or -] 0.05 m, and 115.36 [+ or -] 18.85 kg) from a Division I football team were observed for the first 8 days of preseason practices. Measurements such as heart rate and gastrointestinal temperature ([T.sub.GI]) via telemetric sensor were taken before, 3 times during, and after practice daily. An average 1.39-kg (1.2%) decrease of body mass occurred from prepractice to postpractice (p < 0.01). Consistent with mild body mass losses, urinary indices of hydration status (i.e., color, specific gravity, and osmolality) indicated mild fluid deficits. A significant increase (p < 0.05) from pre- to postpractice was observed in urine color and urine specific gravity, but chronic hypohydration over the 8 days was not noted. The Environmental Symptoms Questionnaire (ESQ) postpractice score was significantly higher (p < 0.05) than the prepractice score was, but averages did not differ across practice days. There was no difference in postpractice [T.sub.GI] measurements across days (p < 0.05). Heart rate, [T.sub.GI], and ESQ measurements indicated that football players experienced gradual heat acclimatization and enhanced heat tolerance, despite progressive increases of exercise variables, clothing, and environmental stressors. Key Words. core body temperature, hydration, football uniform, surface area-to-mass ratio