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PubMed1993

Isolation of enterohemolysin (Ehly2)-associated sequences encoded on temperate phages of Escherichia coli.

We have cloned and sequenced the enterohemolysin (ehl)-associated region from a temperate bacteriophage isolated from an Escherichia coli O26:H11 strain. Phage phi C3208 was isolated together with other temperate bacteriophages which transduce the enterohemolytic phenotype to non-hemolytic E. coli O26 strains. The nucleotide sequence of the 1245-bp phi C3208 DNA insert in plasmid pEO39, which mediates Ehly2 production in E. coli K-12, was determined and was found to be partially homologous to DNA of bacteriophage lambda but is completely unrelated to DNA sequences encoding the synthesis of Ehly1 [Stroeher et al. Gene 132 (1993), 89-94]. It was shown that part of this region can be used as an Hly2-associated specific DNA probe.

Amino Acid Sequence↗
PubMed2006

Polar cod, Boreogadus saida (Gadidae), show an intermediate stress response between Antarctic and temperate fishes.

To examine whether the attenuated stress response observed in Antarctic notothenioid fishes is a specialism for life in sub-zero waters, the polar cod, Boreogadus saida, and the temperate shorthorned sculpin, Myoxocephalus scorpius, were subjected to various stress treatments. Activity stress in both species had no effect on plasma catecholamine and cortisol levels, splenic mass, and on the haematological variables in B. saida. In contrast, heat stress caused a significant rise in circulating noradrenaline and adrenaline levels in B. saida, accompanied by a significant increase in haematocrit and haemoglobin concentrations, at constant plasma cortisol levels, red blood cell count and splenic mass. A concomitant rise in blood lactate concentrations indicated that heat-stressed B. saida were hypoxaemic. The capacity to synthesise catecholamines in B. saida was 38% of the value in M. scorpius, but similar to the values for Antarctic notothenioids. The lack of any adrenergic response to activity stress suggests that dominance of cholinergic control of the cardiovascular system may not be restricted to Antarctic notothenioids. Rather, the stress response in B. saida appears to be intermediate between Antarctic and temperate teleosts, in keeping with their relatively recent occupation of cold Arctic waters.

Animals↗
PubMed2005

Temperature sensitivity of calcium binding for parvalbumins from Antarctic and temperate zone teleost fishes.

Parvalbumin (PV) is a soluble calcium-binding protein that is especially abundant in fast-twitch muscles of fish and other lower vertebrates. Despite its prevalence in ectothermic taxa, few data address the effects of temperature on PV binding function. In this study, calcium dissociation constants (KD) were measured as a function of temperature (0-25 degrees C) for PV from two Antarctic (Gobionotothen gibberifrons and Chaenocephalus aceratus) and two temperate zone fish species (Cyprinus carpio and Micropterus salmoides). Measurements by fluorometric competitive binding assay show that KD values for PVs from the Antarctic species were significantly higher at all assay temperatures and were less sensitive to temperature relative to carp and bass. However, estimates of KD are fundamentally similar for PVs from the Antarctic and temperate zone species when examined at their native physiological temperature. Variation in pH and ionic strength within a physiologically relevant range had only modest effects on KD. Thermodynamics of calcium binding to PV from G. gibberifrons and C. carpio was measured by isothermal microcalorimetry. When measured at 15 degrees C, the Gibbs free energy change (deltaG) was significantly greater for calcium binding to PV from G. gibberifrons than from carp (-43.4+/-1.5 kJ mol(-1) and -46.6+/-3.0 kJ mol(-1), respectively), and the relative contribution of entropy to deltaG for calcium binding to PV from the Antarctic species was about twice that of carp (deltaS=16.0+/-0.8 J degrees C(-1) mol(-1) for G. gibberifrons; deltaS=7.5+/-0.8 J degrees C(-1) mol(-1) for C. carpio).

Animals↗
PubMed2005

Total lactate dehydrogenase activity of tail muscle is not cold-adapted in nocturnal lizards from cool-temperate habitats.

The dependence of metabolic processes on temperature constrains the behavior, physiology and ecology of many ectothermic animals. The evolution of nocturnality in lizards, especially in temperate regions, requires adaptations for activity at low temperatures when optimal body temperatures are unlikely to be obtained. We examined whether nocturnal lizards have cold-adapted lactate dehydrogenase (LDH). LDH was chosen as a representative metabolic enzyme. We measured LDH activity of tail muscle in six lizard species (n=123: three nocturnal, two diurnal and one crepuscular) between 5 and 35 degrees C and found no differences in LDH-specific activity or thermal sensitivity among the species. Similarly, the specific activity and thermal sensitivity of LDH were similar between skinks and geckos. Similar enzyme activities among nocturnal and diurnal lizards indicate that there is no selection of temperature specific LDH enzyme activity at any temperature. As many nocturnal lizards actively thermoregulate during the day, LDH may be adapted for a broad range of temperatures rather than adapted specifically for the low temperatures encountered when the animals are active. The total activity of LDH in tropical and temperate lizards is not cold-adapted. More data are required on biochemical adaptations and whole animal thermal preferences before trends can be established.

Adaptation, Physiological↗
PubMed2005

Radiocarbon and stable carbon isotope compositions of chemically fractionated soil organic matter in a temperate-zone forest.

To better understand the role of soil organic matter in terrestrial carbon cycle, carbon isotope compositions in soil samples from a temperate-zone forest were measured for bulk, acid-insoluble and base-insoluble organic matter fractions separated by a chemical fractionation method. The measurements also made it possible to estimate indirectly radiocarbon ((14)C) abundances of acid- and base-soluble organic matter fractions, through a mass balance of carbon among the fractions. The depth profiles of (14)C abundances showed that (1) bomb-derived (14)C has penetrated the first 16cm mineral soil at least; (2) Delta(14)C values of acid-soluble organic matter fraction are considerably higher than those of other fractions; and (3) a significant amount of the bomb-derived (14)C has been preserved as the base-soluble organic matter around litter-mineral soil boundary. In contrast, no or little bomb-derived (14)C was observed for the base-insoluble fraction in all sampling depths, indicating that this recalcitrant fraction, accounting for approximately 15% of total carbon in this temperate-zone forest soil, plays a role as a long-term sink in the carbon cycle. These results suggest that bulk soil organic matter cannot provide a representative indicator as a source or a sink of carbon in soil, particularly on annual to decadal timescales.

Carbon Isotopes↗
PubMed2005

The significance of agricultural vs. natural ecosystem pathways in temperate climates in assessments of long-term radiological impact.

Recent developments in performance assessment biosphere models have begun to emphasise the importance of natural accumulation pathways. In contrast to the agricultural pathways, the database for natural ecosystem pathways is less well developed, leading to a mismatch in quality of representations of the two types of system. At issue is the lack of reliable soil-plant and animal ingestion transfer factors for key radionuclides in natural ecosystems. The relative importance of the agricultural vs. natural ecosystem pathways is investigated here, in the context of a temperate site in present day, Eastern France. The BIOMASS Candidate Critical Group (CCG) methodology has been applied to map a set of eight candidate critical groups derived from the present-day societal context onto physical locations within a simple model of a river catchment system. The overall assessment model has been implemented using the Aquabios code. Annual individual dose to each of the CCGs has been calculated for each of the key radionuclides (79Se, 94Nb, 99Tc, 129I, 135Cs and 237Np) released to the valley aquifer and river. In addition to the traditional agricultural pathways, lifestyle groups exploiting natural habitats are explicitly addressed. Results show the susceptibility of different candidate critical groups to different radionuclides. A reference database typical of those employed in long-term performance assessment models is employed. Doses from external exposure (94Nb) and dust inhalation (237Np) are shown to dominate agricultural food consumption by factors of more than six, but, with the reference data set, foodstuffs obtained from natural ecosystems do not contribute significantly to critical group dose and, at most, show similar exposures to the agricultural pathways. This may lead to the conclusion that natural food can be ruled out of consideration in performance assessment models. However, systematic parametric sensitivity studies carried out on soil-plant and animal ingestion transfer factors restrict the validity of this observation and demonstrate the limitations of existing databases. Remaining uncertainties can be reduced by improving structural models for performance assessment and by better characterisation of sources of locally obtained foods. Improved characterisation of radionuclide accumulation in natural ecosystems in temperate as well as alternative future climate states should complement the modelling approach.

Agriculture↗
PubMed2006

Prevalence and seasonality of Ascogregarina culicis (Apicomplexa: Lecudinidae) in natural populations of Aedes aegypti (Diptera: Culicidae) from temperate Argentina.

Ascogregarina infections from South America were recently documented in Brazil and Argentina. The aim of this study was to report our recent findings on the prevalence and seasonality of Ascogregarina culicis in Aedes aegypti adults from temperate Argentina. Between December 2003 and May 2005, 391 females of Ae. aegypti were captured in two areas of Greater Buenos Aires. Overall prevalence of A. culicis was 21.2% (83/391), and a significant difference was observed between both areas (28.4% vs. 8%). Infected Ae. aegypti were found from November to May, with highest values in March (24-37%). Parasite prevalence and host abundance showed similar seasonal patterns. Our observations suggest a widespread infestation of A. culicis among Ae. aegypti populations from temperate Argentina.

Aedes↗
PubMed2005

Chronological and physiological ageing in a polar and a temperate mud clam.

We investigated chronological and physiological ageing of two mud clams with regard to the "rate of living theory" (Pearl, 1928) and the "free radical theory of ageing" (Harman, 1956). The Antarctic Laternula elliptica (Pholadomyoida) and the temperate Mya arenaria (Myoida) represent the same ecotype (benthic infaunal filter feeders), but differ in maximum life span, 36 and 13 years, respectively. L. elliptica has a two-fold lower standard metabolic rate than M. arenaria, but its life long energy turnover at maximal age is three times higher. When comparing the two species within the lifetime window of M. arenaria, antioxidant capacities (glutathione, catalase) are higher and tissue oxidation (ratio of oxidised to reduced glutathione, lipofuscin accumulation) is lower in the polar L. elliptica than in the temperate mud clam. Tissue redox state in L. elliptica remained stable throughout all ages, whereas it increased dramatically in aged M. arenaria. Our results indicate that metabolic rates and maintenance of tissue redox state are major factors determining maximum lifespan in the investigated mud clams.

Aging↗
PubMed2005

Mitochondrial ageing of a polar and a temperate mud clam.

We investigated mitochondrial ageing in a temperate (Mya arenaria) and an Antarctic (Laternula elliptica) mud clam, with similar lifestyle (benthic filter feeders) but different maximum life spans (MLSP), 13 and 36 years, respectively. The short-lived temperate M. arenaria showed a more pronounced decrease in mitochondrial function (respiration, respiratory control ratio, proton leak, membrane potential) with age than the long-lived Antarctic L. elliptica. H2O2 generation rates at habitat temperature were far higher in the short-lived M. arenaria compared to L. elliptica. Reactive oxygen species (ROS) production as proportion of the mitochondrial oxygen consumption rate (%H2O2/O2) increased significantly with age in M. arenaria, whereas in L. elliptica the proportion remained unchanged. Lower rates of mitochondrial H2O2 generation were presumably due to mild uncoupling as L. elliptica mitochondria showed higher proton leak compared to M. arenaria mitochondria. The results are discussed in to the light of the "Free Radical-Rate of Living theory", (Pearl, R., 1928. The Rate of Living. Alfred Knopf, New York; Harman, D., 1956. Aging: a theory based on free radical and radiation biology. J. Gerontol. 11, 298-300) and the "Uncoupling to Survive" hypothesis (Brand, M.D., 2000. Uncoupling to survive? The role of mitochondrial inefficiency in ageing. Exp. Gerontol. 35, 811-820).

Aging↗
PubMed2006

The chaotic nature of temper in humans: a long short-term memory recurrent neural network model.

In mathematics and physics, chaos theory deals with the behavior of certain nonlinear dynamical systems that under certain conditions exhibit a phenomenon known as chaos, which is characterised by a sensitivity to initial conditions. Mathematicians paradoxically call such states of order chaos and distinguish them from randomness. New models for describing and predicting different aspects of behavior are being created which once seemed unpredictable. This is done by focusing on the overall patterns of behavior, showing how stable or unstable they are and identifying the circumstances that make them change. In this paper, we indicate why human temper and mood changes have a chaotic nature. Then, we develop a chaotic model based on a long short-term memory recurrent neural network with irregular embeddings derived by the gamma test to model temper tantrum. We finally use a feedback delay controller to stabilize its chaotic behavior, because it is a plausible method for stabilizing biological neural systems. A lot of aspects of this model are analogous to the human counterpart. The model might suggest, for example, that if a particular person had stronger ego defenses, and attended a little less vigilantly to the external world, he or she might find a stable attractor amidst of a broader landscape of chaotic attractors. A therapist or self-control would be analogous to the delayed feedback controller, by specifically encouraging those changes, he might help the person reach a stable behavior. Finally, some comments are proposed to facilitate the normal behavior.

Computer Simulation↗
PubMed2006

Cell response of Antarctic and temperate strains of Penicillium spp. to different growth temperature.

The effect of growth temperature (10, 15, 20, 25, and 30 degrees C) on the cell response was compared between two Antarctic Penicillium sp. strains (Penicillium sp. p14 and Penicillium sp. m12) and a European temperate strain, Penicillium sp. t35. According to the temperature profiles, Penicillium sp. p14 was identified as psychrophilic, while Penicillium sp. m12 and Penicillium sp. t35 as mesophilic fungi, respectively. The results demonstrated that the growth at low temperature does clearly induce oxidative stress events in all strains tested. Decreases in growth temperature below the optimal coincided with markedly enhanced protein carbonyl content, an indicator of oxidatively damaged proteins. Also, the cellular response to growth temperature in terms of reserve carbohydrate was determined. In the mesophilic strains there was essentially no enhancement of glycogen content. This was in contrast to the psychrophilic Penicillium sp. p14, which gradually accumulated glycogen in response to cold (10 degrees C) during the exponential phase. In addition, elevated endogenous levels of trehalose upon low-temperature stress were exhibited by all model microorganisms. Compared with temperate mesophilic Penicillium sp. t35, Antarctic strains (psychrophilic Penicillium sp. p14 and mesophilic Penicillium sp. m12) demonstrated a marked rise in activities of protective enzymes such as superoxide dismutase and catalase at decreasing temperatures. The results suggested that low-temperature resistance is partially associated with enhanced scavenging systems.

Biomass↗
PubMed2004

Limitation of photosynthetic carbon metabolism by dark chilling in temperate and tropical soybean genotypes.

In the experiments reported in this paper, we characterised the physiological and biochemical factors involved in the chilling-induced inhibition of photosynthetic carbon metabolism in soybean [Glycine max (L.) Merr.] genotypes of temperate and tropical adaptation. Plants of Maple Arrow (temperate genotype) and Java 29 (tropical genotype) were exposed to a single night at 8 degrees C. Dark chilling resulted in the inhibition of diurnal CO2 assimilation rate and decreased stomatal conductance in both genotypes. Further analysis, however, revealed a difference in the response of the two genotypes. Stomatal limitation was largely responsible for the inhibition of CO2 assimilation in Maple Arrow, whereas mesophyll limitation dominated the inhibition in Java 29. The results indicate that inhibition of stromal fructose-1,6-bisphosphatase (sFBPase; EC 3.1.3.11) activity and impaired electron transport capacity were responsible for the decrease in ribulose-1,5-bisphosphate (RuBP) regeneration capacity in Java 29. Sucrose-phosphate synthase (SPS; EC 2.4.1.14) activity was progressively inhibited during the light period in this genotype and might impose an additional constraint on photosynthesis. Maple Arrow appears to possess, at least with respect to photosynthetic carbon metabolism, physiological and biochemical characteristics that contribute towards its superior dark chilling tolerance.

Carbon↗
PubMed2004

Excremental androgen metabolite concentrations and gonad sizes in temperate zone vs. tropical Stonechats (Saxicola torquata ssp.).

Many songbirds in the temperate zones have comparatively short breeding seasons and are migratory. This often implies high breeding synchrony and competition for food, space, and mates. Tropical birds, in contrast, tend to be resident and react more flexibly to a more variable onset of environmental conditions conducive for breeding. Therefore, it can be expected that androgen metabolite concentrations in breeding males vary among birds from different latitudes. Studies on tropical birds, however, have revealed inconsistent results suggesting that additional factors not directly related to latitude, modify hormone levels. Furthermore, there is a potential for a phylogenetic bias when comparing birds of different taxonomic groups. In the present study, we compared androgen metabolite concentrations among closely related taxa of hand-raised male stonechats originating from tropical and temperate-zone populations in Kenya (0 degrees latitude), Kazakhstan (52 degrees N), and Ireland (52 degrees N), which differ partly in latitude of their provenance but also in the length of their breeding season (birds from Kazakhstan vs. Ireland). Hand-raised birds were housed in their natural photoperiod under otherwise identical environmental conditions. Androgen levels were determined from excrements to reduce disturbance. All three groups demonstrated a seasonal cycle of androgen metabolite concentrations concomitant with testis growth. Peak androgen metabolite concentrations were significantly lower in Kenyan stonechats compared to Kazakh stonechats. Irish birds had intermediate concentrations. Differences between Kazakh and Kenyan stonechats correlate with latitude, but data from the Irish population suggest the involvement of factors not directly related to latitude.

Adaptation, Physiological↗
PubMed1998

Temperature dependence and acclimatory response of amylase in the High Arctic springtail Onychiurus arcticus (Tullberg) compared with the temperate species Protaphorura armata (Tullberg).

Amylolytic activity was measured in whole body homogenates of High Arctic (Onychiurus arcticus) and temperate (Protaphorura armata) springtails (Collembola: Onychiuridae) in the temperature range 5-55 degrees C. A pH of ca. 8 was optimum for amylolytic activity in both species. A higher weight-specific amylolytic activity was observed in P. armata. In O. arcticus, amylolytic activity depended on thermal acclimation, which increased during 2 and 9 weeks of cold acclimation (5 degrees C) and decreased over 7 weeks of warming (15 degrees C) of animals that were previously acclimated to cold for 2 weeks. In cold-acclimated O. arcticus, a slower decrease of amylolytic activity occurred with lowering of temperature in the range 5-20 degrees C in comparison with warm-acclimated specimens and P. armata, which resulted in higher activity at 5 degrees C. The activation energy calculated from an Arrhenius plot for P. armata was 68.7 kJ.mol(-1). In O. arcticus it was between 30.2 and 61.5 kJ.mol(-1), being lower in cold-acclimated samples. The temperature optimum for amylolytic activity was higher in the temperate species (40 degrees C), whilst in O. arcticus it depended on the acclimation regime: it rose to 35 degrees C after warm acclimation and decreased to 20 degrees C after cold adaptation. The total soluble protein content of body tissues of O. arcticus also increased during cold acclimation. These differences between the two species suggest that amylolytic activity is an indicator of cold adaptation in the High Arctic O. arcticus.

Journal Article↗
PubMed1998

Heat- and cold-shock responses and temperature adaptations in subtropical and temperate species of Drosophila.

Accumulation of Hsp70 mRNA was investigated with relation to heat and cold tolerance in adult males of three Drosophila species. The subtropical lowland species (D. watanabei) and the cool-temperate species (D. triauraria) were more tolerant to heat than the subtropical highland species (D. trapezifrons), and the cool-temperate species were much more tolerant to cold than the two subtropical species. Thus, heat and cold tolerance was related to temperature conditions in the habitats. The threshold temperatures for the induction of Hsp70 mRNA at heat and cold were higher in D. watanabei than in D. trapezifrons or D. triauraria, but were not different between the latter two species in spite of the difference in their heat and cold tolerance. In D. trapezifrons, exposures to 0 degrees C for 12h and 6 degrees C for 24h killed about 40% of individuals, but the former treatment induced Hsp70 mRNA while the latter one did not. Thus, the relation between the heat- and cold-shock responses and temperature tolerance was not rigid in the species studied. In D. triauraria, the threshold temperatures for the induction of Hsp70 mRNA at heat and cold were lower when reared at a lower temperature.

Journal Article↗
PubMed2004

An examination of seasonality experienced by Australians living in a continental temperate climate zone.

BACKGROUND: To date, there has been only limited information on factors associated with seasonal changes in mood and behaviour experienced by a random sample of Australians living in a continental temperate climate region. This paper identifies socio-demographic, psychological and personality factors associated with reporting higher levels of seasonality. METHOD: Information on seasonal change using the Seasonal Pattern Assessment Questionnaire (SPAQ) was obtained from 7485 persons in three age groups. Age and sex differences in seasonality scores were examined. Those meeting probable caseness for seasonal affective disorder were identified and compared with less-seasonal participants on a range of state and trait measures. RESULTS: Levels of seasonality reported by survey participants were comparable to those reported in northern hemisphere studies of randomly selected community samples. However, these levels were significantly lower than other key studies outside Australia and previous Australian findings. Compared with less-seasonal participants, those reporting seasonal change had more current depressive and anxiety symptoms and higher levels of negative affect, regardless of season of interview. LIMITATIONS: This study is likely to over-estimate the number of participants who meet requirements for caseness for seasonal affective disorder. CONCLUSION: Levels of seasonality experienced by a random sample of Australians living in a temperate climate are comparable to those reported by similar groups in the northern hemisphere. Importantly, this study found that those experiencing higher levels of seasonality had significantly more current depressive symptoms than less-seasonal participants across all seasons. These results raise questions about the usefulness of the SPAQ as a measure of seasonal variation in mood and behaviour.

Adult↗
PubMed2004

How common is seasonal affective disorder in temperate Australia? A comparison of BDI and SPAQ estimates.

BACKGROUND: The frequency of winter Seasonal Affective Disorder (SAD) in temperate Australia is unknown. METHOD: A random community sample in Melbourne completed four waves of data collection (winter and summer across two years). The presence of winter SAD was estimated in three ways: (i) self-reports on the Seasonal Pattern Assessment Questionnaire (SPAQ), (ii) evidence of significant depression as assessed on the Beck Depression Inventory (BDI) in winters and not summers, and (iii) a combined definition based on both SPAQ and BDI estimates. RESULTS: Of 1080 questionnaires originally mailed, complete four-wave BDI data was obtained from 380 respondents, and complete SPAQ data from 297. The frequency of winter SAD as estimated from SPAQ data was 0.7% and from BDI data was 0.5%. One participant (1 of 297, 0.3%) met BDI criteria and approached caseness on SPAQ criteria. LIMITATIONS: A larger sample is necessary to definitively estimate prevalence. CONCLUSIONS: Winter SAD appears to be rare in temperate Australia. The best estimate from the current study (0.3%) is an advance on simple self-report estimates and provides a necessary reference point for clinicians and researchers.

Adult↗
PubMed2001

Species coexistence in temperate, mixed deciduous forests.

The response of tree life-history traits to community profiles (horizontal and vertical heterogeneity, disturbances and biotic interactions) determines community assembly rules, which are currently a hot issue in community ecology. Important mechanisms of coexistence differ throughout the developing stages of tree life history. Many processes of niche partitioning and tradeoffs that potentially enable tree coexistence have been reported to be present in temperate forests, although some of these life-history traits are either correlated with each other or are not independent. Not all of the proposed mechanisms explain coexistence equally well; some could predominate in determining the community organization of forest communities. Population studies need to concentrate more on the component species of a target community to detect the ecological assembly rule. These approaches can also address how chance factors contribute to the composition of temperate tree communities, which might be less dependent on chance than are tropical ones.

Journal Article↗