Can Antarctic lichens acclimatize to changes in temperature?

The Antarctic Peninsula, a tundra biome dominated by lichens and bryophytes, is an ecozone undergoing rapid temperature shifts. Such changes may demand a high physiological plasticity of the local lichen species to maintain their role as key drivers in this pristine habitat. This study examines the response of net photosynthesis and respiration to increasing temperatures for three Antarctic lichen species with different ecological response amplitudes. We hypothesize that negative effects caused by increased temperatures can be mitigated by thermal acclimation of respiration and/or photosynthesis. The fully controlled growth chamber experiment simulated intermediate and extreme temperature increases over the time course of 6 weeks. Results showed that, in contrast to our hypothesis, none of the species was able to down‐regulate temperature‐driven respiratory losses through thermal acclimation of respiration. Instead, severe effects on photobiont vitality demonstrated that temperatures around 15°C mark the upper limit for the two species restricted to the Antarctic, and when mycobiont demands exceeded the photobiont capacity they could not survive within the lichen thallus. In contrast, the widespread lichen species was able to recover its homoeostasis by rapidly increasing net photosynthesis. We conclude that to understand the complete lichen response, acclimation processes of both symbionts, the photo‐ and the mycobiont, have to be evaluated separately. As a result, we postulate that any acclimation processes in lichen are species‐specific. This, together with the high degree of response variability and sensitivity to temperature in different species that co‐occur spatially close, complicates any predictions regarding future community composition in the Antarctic. Nevertheless, our results suggest that species with a broad ecological amplitude may be favoured with on‐going changes in temperature.     

Relationship between sleep stages and short‐term changes in rectal temperature in humans

Abstract

Sixteen volunteers have been studied during 3–4 control nights and eight of these subjects again during four successive sleeps on 30‐h “days”;. The experiments took place in a comfortable environment provided by an isolation chamber. Rectal temperature and the sleep EEG were measured throughout. The relationship between sleep stages, particularly SWS and REM sleep, and short‐term changes in rectal temperature has been investigated during both protocols. Care was taken to correct for or remove those temperature changes that could be attributed to circadian rhythmicity or the effects of loss of masking due to being awake. Results showed that there was a small but significant effect of sleep stages, with SWS producing a fall and REM sleep a rise in rectal temperature after a delay of about 30–48 minutes. It is concluded that such spontaneous changes in sleeping subjects accord with the results of other studies which indicate that thermoregulatory reflexes to hot or cold stimuli alter in different sleep stages.     

How do changes in temperature during growth affect leaf pigment composition and photosynthesis in Zea mays genotypes differing in sensitivity to low temperature?

The changes in photosynthetic activity and composition of pigments induced by changes in temperature were examined in the third leaf of three chilling-tolerant and three chilling-sensitive genotypes of maize (Zea mays L.). The plants were grown under a controlled environment at a photon flux density of 550 mol m^-2 s^-1, a 12 h photoperiod and at a suboptimal temperature of 14/12 C (day/night) until the full expansion of the third leaf. After this treatment, the chilling-tolerant genotypes, when compared with the sensitive ones, displayed a higher photosynthetic activity, a higher content of chlorophyll (Chl) a+b, a higher Chl a/b ratio, a larger total carotenoid pool size as well as a different carotenoid composition. When temperature was subsequently increased to 24/22 C for 3 d the composition of the pigments changed, but the chilling-sensitive genotypes, while adjusting their lower Chl a/b ratio and their different carotenoid composition, were unable to adjust their lower content of chlorophyll, their smaller total carotenoid pool size or their lower photosynthetic performance. Moreover, while the chilling-tolerant genotypes converted the most part of zeaxanthin to violaxanthin in the xanthophyll cycle, the chilling-sensitive genotypes retained high amounts of zeaxanthin. The changes in pigment composition that occurred over the 3 d at 24/22 °C were largely conserved when the plants were returned to 14/12 °C, but photosynthetic activity decreased and zeaxanthin accumulated again. The results suggest that the capability of the chilling-tolerant genotypes, when compared with the sensitive ones, to retain high amounts of pigments and to form a competent photosynthetic apparatus at low temperature is the basis for their more vigorous growth in cool climates.     

High temperature — induced changes in germination,seedling vigour and the metabolic activities in rice seeds

The effects of temperature treatments on rice seeds in the early imbibitional phase were studied with respect to changes in germination percentage, seedling growth in terms of root and shoot lengths, water uptake, respiration and hydrolytic enzymes,viz. α-amylase, adenosine triphosphatase (ATPase) and phytase. As compared with the control, the treatment for 30 min at 50 °C caused a variable degree of increase in all these characters and a positive correlation existed between seedling vigour and hydrolase activities. The treatment for 30 min at 60 °C, on the other hand, elicited a retarding influence on these characters. As regards the enzyme activities, the damaging effect of 60 °C could, however, be visualized only after 72 h of germination which was preceded by an enhancement during the early hours.     

Long-term changes in Krill biomass and distribution in the Barents Sea: are the changes mainly related to capelin stock size and temperature conditions?

Krill plays a significant role in the Barents Sea ecosystem, providing energy transport between different trophic levels. The current paper presents the results of a long-term study (1980–2009) based on pelagic trawl catches from August to September. Our investigations show that the krill species were distributed widely in the Barents Sea and that the largest krill concentrations were restricted to the west-central and eastern parts of the Barents Sea. The current paper presents the relative biomass indices, and the estimates must be interpreted as minimum biomass. The mean annual krill biomass was estimated to be 22 million tonnes in wet weight, with the highest values being as much as 48 million tonnes. Capelin is the largest pelagic stock, and in some years, their biomass can amount to 4–7 million tonnes, which can impose high predation pressure on krill. When their biomass is high, capelin may consume close to 26 million tonnes annually. The predation from pelagic (herring and blue whiting) and bottom (cod and haddock) fish species was much lower, being 9 and 1 million tonnes, respectively. A negative relationship between krill biomass and capelin stock size above 74°N was observed during the study period. However, during the last decade, the krill biomass has increased despite heavy predation from capelin in some years. A positive significant linear relationship between the mean annual Kola temperature and the krill biomass seems to indicate that the recent warming conditions have favourable impacts on the krill populations in the Barents Sea.     

Do peptide-induced changes in feeding occur because of changes in motivation to eat?

The usual paradigm in which peptides are tested for their effect on food intake involves measuring intake of readily available food. In the lever press apparatus, the subjects must "work" to get food. Such work has traditionally been used as a means of measuring motivation. Mice were trained to press a lever for milk reinforcement. After achieving a stable level of performance, we tested the effects of gastrin-related peptide (GRP), bombesin (BBS) and cholecystokinin octapeptide (CCK-8) on lever pressing. All three peptides suppressed lever pressing for milk reinforcement. Prefeeding mice with milk increased the suppression of lever pressing to a greater extent in peptide-treated mice than in saline-treated mice. As the duration of prefeeding increased, lever pressing decreased. When mice were required to make more lever presses to obtain milk, both saline- and CCK-8-treated mice increased their lever pressing. However, saline-treated mice pressed at a higher rate than CCK-8-treated mice. Unlike the results obtained with saline and CCK-8, administration of a known gustatory adversant, lithium chloride, suppressed lever pressing to the same degree in mice fed or not fed prior to training. The results are consistent with the hypothesis that these peptides act as satiety agents.     

Are changes in maximal squat strength during preseason training reflected in changes in sprint performance in rugby league players?

Because previous research has shown a relationship between maximal squat strength and sprint performance, this study aimed to determine if changes in maximal squat strength were reflected in sprint performance. Nineteen professional rugby league players (height = 1.84 ± 0.06 m, body mass [BM] = 96.2 ± 11.11 kg, 1 repetition maximum [1RM] = 170.6 ± 21.4 kg, 1RM/BM = 1.78 ± 0.27) conducted 1RM squat and sprint tests (5, 10, and 20 m) before and immediately after 8 weeks of preseason strength (4-week Mesocycle) and power (4-week Mesocycle) training. Both absolute and relative squat strength values showed significant increases after the training period (pre: 170.6 ± 21.4 kg, post: 200.8 ± 19.0 kg, p < 0.001; 1RM/BM pre: 1.78 ± 0.27 kg·kg(-1), post: 2.05 ± 0.21 kg·kg(-1), p < 0.001; respectively), which was reflected in the significantly faster sprint performances over 5 m (pre: 1.05 ± 0.06 seconds, post: 0.97 ± 0.05 seconds, p < 0.001), 10 m (pre: 1.78 ± 0.07 seconds, post: 1.65 ± 0.08 seconds, p < 0.001), and 20 m (pre: 3.03 ± 0.09 seconds, post: 2.85 ± 0.11 seconds, p < 0.001) posttraining. Whether the improvements in sprint performance came as a direct consequence of increased strength or whether both are a function of the strength and power mesocycles incorporated into the players' preseason training is unclear. It is likely that the increased force production, noted via the increased squat performance, contributed to the improved sprint performances. To increase short sprint performance, athletes should, therefore, consider increasing maximal strength via the back squat.     

Postural impairments in Parkinson’s disease are not associated with changes in circadian rhythms changes

ABSTRACT

Parkinson’s disease (PD) is a progressive neurodegenerative disease, with a worldwide incidence of 1% in individuals >60 years of age. Its primary characteristics include postural impairments and changes in circadian rhythms. The authors investigated the association between postural impairment and changes in circadian rhythms in 24 PD subjects diagnosed with stages 1 to 3 on the Hoehn-Yard (HY) scale and regularly used dopaminergic medication for at least 1 year (experimental group – EG) and 24 healthy elderly individuals without a history of neurological impairment as the control group (CG). Static balance tests using a force plate were performed, and activity/rest rhythm, according to the relative amplitude of L5 and M10 values, was monitored for seven consecutive days using actimetry. The results indicated differences in posturographic indicators of mediolateral displacement (ML) [EG, 4.71 ± 0.85 mm; CG, 2.79 ± 0.53 mm (p < .0001)] and anteroposterior displacement of the center of pressure (COP) [EG, 5.61 ± 2.43 mm; CG, 8.23 ± 1.72 mm (< 0.0001)], ML velocity of the COP [EG, 2.39 ± 0.83 mm/s; CG, 1.40 ± 0.18 mm/s (p < .0001)], and total distance of the COP in the tandem stance condition [EG, 227.6 ± 75 mm; CG, 53.4 ± 6.1 mm (p < .0001)] between the EG and CG. There was no correlation between relative amplitude and posturographic data for the EG. Postural impairments were verified in comparing the EG and CG; however, there was no association between posturographic indicators and activity/rest rhythm.     

Seasonal changes in the germination responses of Hordeum maritimum and H. murinum seeds in relation to salinity,temperature and after‐ripening time

Abstract

The effects of temperature and salinity (NaCl) on germination of Hordeum maritimum With, (halophyte) and H. murinum L. (glycophyte) seeds were investigated. Dehulled caryopses were used for monthly germination trials, starting from November (120 days of after‐ripening in darkness at 20±1°C). Trials were continued for one year. Differences in germination response between the two species were observed, confirming that H. Maritimum is better adapted to high salinity levels and to variations in external temperature than H. murinum. H. maritimum showed a germination control mechanism related to after‐ripening time and based on seed dormancy break/resumption. At higher temperature (30°C), thermodormancy was also recorded. No germination strategies were observed in H. murinum that is relatively insensitive to the combined effects of temperature and salinity. Thus, in virtually all treatments, H. murinum exhibited a higher germination rate compared with H. maritimum, as early as 72 h after imbibition, suggesting that dormancy, both in the presence or absence of salt, is totally abolished by early fall or at the latest in winter.     

Effects of temperature changes on thymidine kinase in heat- and cold-sensitive cell-cycle mutants and ‘wild-type’ murine P-815 cells

Two heat-sensitive (arrested in G1 at 39.5°C) and two cold-sensitive (arrested in G1 at 33°C) clonal cell-cycle mutants that had been isolated from the same clone (K 21), of the murine mastocytoma P-815 cell line, were tested for thymidine kinase (EC 2.7.1.21) activity. After shift of mutant cells to the nonpermissive temperature, thymidine kinase activity decreased, and minimal levels (i.e., less than 3% of those observed for ‘wild-type’ K 21 cells at the respective temperature) were attained within 16 h in heat-sensitive and after 3–4 days in cold-sensitive mutants, which is in good agreement with kinetics of accumulation of heat-sensitive and cold-sensitive cells in G1 phase. After return of arrested mutant cells to the permissive temperature, thymidine kinase of heat-sensitive cells increased rapidly and in parallel with entry of cells into the S phase. In cultures of cold-sensitive cells, however, initiation of DNA synthesis preceded the increase of thymidine kinase activity by approx. one cell-cycle time. Thymidine kinase activities in revertants of the heat-sensitive and cold-sensitive mutants were similar to those of ‘wild-type’ cells. In ‘wild-type’ K 21 cells incubated at 39.5°C, thymidine kinase activity was approx. 30% of that at 33°C. This difference is attributable, at least in part, to a higher rate of inactivation of the enzyme at 39.5°C, as determined in cultures incubated with cycloheximide. The rapid increase of thymidine kinase activity that occurred after shift of K 21 cells and of arrested heat-sensitive mutant cells from 39.5°C to 33°C was inhibited by actinomycin D and cycloheximide.     

Thermal variability in body temperature in an ectotherm: Are cloacal temperatures good indicators of tortoise body temperature?

Historically, studies of reptilian thermal biology have compared ambient temperatures (T_a) to body temperatures (T_b) from the animal under study, with T_b usually taken from the cloaca and various instruments being used to measure T_b. The advent of surgically implanted miniature temperature loggers has offered the opportunity to test the efficacy of cloacal T_b as a measurement in thermoregulatory studies. We expected that there was a difference between skin, cloacal, and core T_b's. Temperatures were measured from various positions on leopard tortoises (Stigmochelys pardalis) using thermocouples and miniature temperature loggers, including surgically implanted temperature loggers. Measurements of temperature from various positions on and in the tortoise were significantly different from T_a. Cloacal T_b's were significantly lower than all other body temperatures measured, and core T_b's were significantly different from cloacal T_b, skin and carapace temperatures. In addition, significant differences were found between measures of temperature from other parts of the body. The variations between core T_b, cloacal T_b and other measures of T_b indicated that there are large thermal gradients within the body of a relatively large tortoise at any given time with cloacal T_b not an accurate measure of core T_b.     

Hormonal changes in spontaneous and aglépristone-induced parturition in dogs

To increase our understanding of the endocrine changes associated with parturition in dogs, plasma concentrations of progesterone (P4), 15-ketodihydroprostaglandin F(2alpha) (PGFM), estradiol-17-beta (E2beta), cortisol, ACTH, prolactin (PRL), LH, and FSH were measured in six spontaneously whelping bitches and in six bitches in which parturition was induced with the progesterone-receptor blocker aglépristone on day 58 of pregnancy. Expulsion of pups in the induced group took place in the presence of P4 concentrations that were still elevated. PGFM concentrations increased before parturition in both groups, but levels were lower in the induced bitches. PGFM levels reached a maximum in both groups during parturition and quickly decreased in the spontaneously whelping group after parturition, but remained elevated in the induced group. In both groups, cortisol concentrations reached similar maximum levels during the last 30 h before the onset of expulsion. During the 3 days postpartum, cortisol concentrations were higher in the induced group. The highly variable ACTH concentrations did not differ significantly throughout the study within or between groups. In both groups, E2beta concentrations decreased and PRL concentrations increased between the late gestational period and the 30-h period before parturition. Concentrations of both LH (spontaneously whelping group) and FSH (both groups) decreased between late gestation and the postpartum period. The results of this study illustrate the hormonal changes around parturition in the bitch, and reveal that aglépristone-induced parturition is associated with still incomplete luteolysis, an altered PGFM profile, and elevated postpartum cortisol concentrations as compared with spontaneously whelping dogs.     

Microbiological changes in mawè during natural fermentation

Lactic acid bacteria increased from 3.2 × 10⁶ and 1.6 × 10⁷ c.f.u./g (wet wt) to 2 × 10⁹ and 1.6 × 10⁹ c.f.u./g after 12 to 24 h of fermentation of home-produced mawè (a dough produced from dehulled maize) and commercial mawè, respectively. In commercial mawè, the yeast count increased from 1.3 × 10⁵ to 2.5 × 10⁷ c.f.u./g after 48 h of fermentation before decreasing, whereas in the home-produced mawè it increased from 2.5 × 10⁴ to 3.2 × 10⁷ c.f.u./g after 72 h of fermentation; the dominant yeasts were mainly Candida krusei, although C. kefyr, C. glabrata and Saccharomyces cerevisiae were also present. Enterobacteriaceae counts increased slightly during the initial stage ofthe fermentation, but decreased below the detection level after 24 to 48 h. Enterobacter cloacae was mostly found in commercial mawè and Escherichia coli mostly in homeproduced mawè.D.J. Hounhouigan and C.M. Nago are with the Université Nationale du Bénin, Faculté des Sciences Agronomiques, Département de Nutrition et de Sciences Alimentaires, BP 526, Cotonou, Benin; M.J.R. Nout and F.M. Rombouts are with the Agricultural University, Department of Food Science, Bomenweg 2, 6703 HD Wageningen, The Netherlands. J.H. Houben is with Utrecht University, Department of the Science of Foods of Animal Origin, Yalelaan 2, 3508 TD Utrecht, The Netherlands.     

Are adhesion molecules involved in stress-induced changes in lymphocyte distribution?

Acute psychological stress is associated with important changes in circulating cell populations and reductions in cell-mediated immune responses. However, the mechanisms underlying these phenomena are poorly understood. In this study, we investigated (i) acute and chronic restraint stress effects in Sprague-Dawley rats on peripheral lymphocyte subsets and (ii) adhesion molecule (beta2 integrins) expression and (iii) also determined whether glucocorticoids could underlie stress-related changes in cellular redistribution. We observed time-dependent changes in lymphocyte distribution including decreased (-21%) percentages of peripheral T helper cells and increased (88%) NK cell numbers following acute brief restraint. Acute stress was also found to overall upregulate beta2-integrin (CD11a and CD11b) expression on T cells and to raise (1049%) plasma corticosterone levels. However, this stress response was found habituated (-75% vs. acute) in the animals previously exposed to chronic restraint stress. Stress effects on circulating lymphocytes were not observed in animals previously exposed to chronic intermittent restraint stress or chronically stressed animals re-exposed to the same stressor. Our results indicate that 1) stress alters lymphocyte distribution, 2) that adhesion molecules may be involved in stress-induced alterations of T-cell distribution and 3) that these changes may be related to circulating glucocorticoids and subjected to adaptation with repeated stress exposure.     

Are changes in remotely sensed canopy cover associated to changes in vegetation structure,diversity, and composition in recovered tropical shrublands?

The recovery of vegetation cover is a process that has important implications for the conservation of biodiversity and ecosystem services. Generally, the recovery of vegetation cover is documented over large areas using remote sensing, and it is often assumed that ecosystem properties and processes recover along with remotely sensed canopy cover. Here we analyze and compare the structure, composition, and diversity of trees and shrubs among plots established in a stratified random sampling design over four remotely sensed canopy cover change (CCC) categories defined according to a gradient in the percent of canopy cover. Plots were located in the Lake Cuitzeo basin (Mexico), where canopy recovery associated with agricultural abandonment has occurred in recent decades (1975–2000). We found that diversity measures, basal area, tree and shrub density, ground-truthed canopy cover, and mean plant height increased with increasing CCC category. However, Shannon index (H′) was lower in the CCC category with the most closed canopy cover category than in plots apparently not affected by agriculture. Furthermore, ordination analyses showed that composition of dominant species were not associated with CCC categories. Our results suggest that canopy closure in our study area is not associated with the recovery of species diversity, and does not result in similar species dominance as in sites not affected by agriculture.     

Are changes in breeding habitat responsible for recent population changes of long-distance migrant birds?

Capsule: The direction and magnitude of changes in structure of UK woodlands since the 1980s, are inconsistent with them playing a causative role in the declines of four migrant bird species in upland oak woods.

Aims: To investigate whether changes in woodland structure were a possible cause of population changes of four Afro-Palearctic migrants (Wood Warbler Phylloscopus sibilatrix, Tree Pipit Anthus trivialis, Pied Flycatcher Ficedula hypoleuca and Common Redstart Phoenicurus phoenicurus) in the upland oakwoods of western and northern Britain.

Methods: Bird population estimates and measures of woodland structure were recorded in two time periods 1982–85 and 2003–04 across six regions of the UK. We modelled the effect of habitat change and initial habitat state on population changes between the two time periods. The predicted effects of habitat change on populations were then compared with observed population changes across the different regions.

Results: All four species underwent population declines; there were also significant increases in ground cover and understorey cover. The number of birds in 2003–04 was influenced by habitat structure at this time in addition to showing regional differences. Change in bird numbers varied between regions and was affected by both the initial habitat state and change in habitat structure, with regional variation in the effect of habitat change. There was however no relationship between the predicted effect of change in habitat structure on population size and observed regional population changes.

Conclusions: Changes in woodland structure are unlikely to be the main driver of population change in these four migrant bird species, and large-scale factors affecting demographics in other parts of their breeding range or in their wintering areas are likely reasons for local population declines.