Variação sazonal do metabolismo energético no primeiro ciclo anual de lagartos teiú Tupinambis merianae: correlatos com atividades diárias, adiposidade e proteção antioxidante

Lagartos teiú eclodem no verão e enfrentam o desafio de crescer e armazenar substratos em um curto período de tempo, antes do início do período de jejum e depressão metabólica (≈80%) a temperaturas amenas durante o inverno (≈17 °C). No despertar, o aumento do metabolismo e a reperfusão de órgãos favoreceriam a ocorrência de estresse oxidativo. Na primeira parte do presente estudo investigou−se os ajustes que compatibilizam as demandas em teiús neonatos, especialmente na pré-hibernação, por meio da gravação do comportamento em vídeo e da análise da massa dos corpos gordurosos abdominais e do nível plasmático de corticosterona (CORT) durante o primeiro ciclo anual. No início do outono a massa corpórea dos teiús foi 27 g e o comprimento rostro−cloacal 9,3 cm e aumentaram 40% e 20%, respectivamente, ao longo do outono, enquanto que as taxas diminuíram progressivamente até atingirem o valor zero no início do inverno. Na primavera, a massa corpórea dos teiús aumentou 80% em relação ao despertar e dobrou em relação ao final do verão; o comprimento acumulou um aumento de 27% em relação ao final do verão. A massa relativa dos corpos gordurosos foi 3,7% no início do outono e diminuiu nos meses subsequentes; no despertar, este estoque acumulou uma perda de 63% da sua massa. No início do outono 74% dos teiús estavam ativos por 4,7 h e permaneceram 2 h assoalhando diariamente; ao longo do outono o número de animais ativos e o tempo em atividade diminuíram até que todos se tornaram inativos. Na primavera 83% dos teiús estavam ativos por 7 h e permaneceram 4 h assoalhando. Um padrão sazonal similar foi observado na atividade locomotora e na alimentação. No outono, a alimentação cessou antes da atividade diária e os teiús tornaram−se afágicos algumas semanas antes da entrada em hibernação. Os maiores níveis de CORT foram observados no início do outono, reduzindo progressivamente até valores 75 e 86% menores na dormência e despertar, respectivamente; na primavera os níveis de CORT foram 32% menores em comparação com o início do outono. Este padrão sugere um papel da CORT nos ajustes que promovem a ingestão de alimento e a deposição de substratos energéticos no outono. A redução da atividade geral no final do outono contribuiria para a economia energética e manutenção da massa corpórea, apesar da redução da ingestão de alimento. O curso temporal das alterações fisiológicas e comportamentais em neonatos reforça a ideia de que a dormência sazonal nos teiús é o resultado da expressão de um ritmo endógeno. Na segunda parte do estudo foi investigada a hipótese de que ocorreriam ajustes das defesas antioxidantes durante a hibernação, em antecipação ao despertar. Foram analisados marcadores de estresse oxidativo e antioxidantes em vários órgãos de teiús em diferentes fases do primeiro ciclo anual. A CS, um indicador do potencial oxidante, não variou no fígado e foi menor no rim e no pulmão na hibernação. As enzimas antioxidantes revelaram (1) um efeito abrangente de redução das taxas na hibernação e despertar; por exemplo, GR e CAT foram menores em todos órgãos analisados e a GST tendeu a diminuir no fígado e no rim, embora constante no coração e no pulmão. A G6PDH no fígado e no rim não variou. (2) No fígado, a GST, a Se−GPX e o teor de TBARS foram maiores na atividade de outono em relação à primavera e a Se−GPX permaneceu elevada na hibernação. (3) No fígado, a SOD foi maior na hibernação e despertar em relação ao outono e a Mn−SOD seguiu este padrão. Em contraste, no rim, coração e pulmão a SOD foi menor na hibernação e as taxas se recuperaram no coração e pulmão no despertar. A Mn−SOD seguiu este padrão no pulmão. A concentração e o estado redox da glutationa não variaram no fígado, rim e coração; no pulmão o teor de Eq−GSH e GSH foi menor na hibernação, com tendência à recuperação no despertar. O teor de PC no rim foi maior na hibernação e diminuiu no despertar. No fígado, as alterações no jejum se assemelham às sazonais, como sugerem a inibição da CAT e GR e aumento da Se−GPX. Os efeitos do jejum na primavera no rim diferem dos efeitos sazonais, como sugerem a redução do teor de Eq−GSH e GSH e o aumento da razão GSSG:GSH, a redução da G6PDH e o aumento de PC. No conjunto, houve um efeito predominante de redução das taxas enzimáticas na hibernação e no despertar, exceto pelas taxas aumentadas da SOD e Se−GPX no fígado e pela recuperação da SOD no coração e da GR, SOD e Mn−SOD no pulmão no despertar. As elevadas taxas das enzimas antioxidantes no teiú em comparação a outros ectotermos e a ausência de evidências de estresse oxidativo no despertar sugerem que a atividade enzimática remanescente é suficiente para prevenir danos aos tecidos face às flutuações do metabolismo

An experimental study of the rest period in plants.

"Second report"--T.p.

An experimental study of the rest period in plants : physiological changes accompanying breaking of the rest period /

"Fifth report"--T.p.

An experimental study of the rest period in plants : the winter rest /

"First report"--T.p.

Current concepts of tumour metastasis

Background: Tumour metastasis remains the principal cause of treatment failure and poor prognosis in patients with cancer. Recent advances in our understanding of the biology of metastasis are providing novel potential targets for anti-cancer therapies. Aim: This paper reviews the current concepts in tumour metastasis. Methods: A review of Medline publications relating to the molecular biology and therapy of human tumour metastasis was conducted. Results and Discussion: Early metastasis models were based upon the premise of uninterrupted tumour growth, with the inevitable formation of distant metastases and eventual death of the patient. However, current research suggests that metastasis is an inefficient process governed by several rate-limiting steps, and that failure to negotiate these steps can lead to tumour dormancy. Successful metastatic tumour growth depends upon appropriate tumour-host microenvironment interactions and, ultimately, the development of vascularised metastases post-extravasation in the target organ. An understanding of the molecular mechanisms involved in this dynamic process will aid in the identification of therapeutic targets that may allow earlier diagnosis and more specific therapies for patients with metastasis.

Germination response of Phalaris paradoxa L. seed to different light qualities

The influence of different light regimes on the germination of Australian and English populations of Phalaris paradoxa L. (awned canary-grass) seed was investigated to determine the impact of changing tillage practices on weed infestation. Seeds of all biotypes were highly viable, but differed in levels of innate dormancy (26-99%). In one experiment seed from a single Australian biotype, either enclosed in the spikelet glumes or having the spikelet glumes removed, were exposed to nine light treatments. Germination was stimulated by red and white light, but was inhibited by far-red light. Time to 50%, germination was less for seed enclosed in the spikelet glumes than for naked caryopses, although the final percentage of seed germinating when still enclosed in the spikelet glumes was significantly lower than for naked caryopses. In another experiment, six Australian and English biotypes with varying dormancy characteristics were exposed to eight light treatments. Red light did not stimulate germination in the deeply dormant biotype, however stimulated all other biotypes. Germination in darkness was below 20% in all biotypes except for one where germination was 51%. To overcome dormancy seeds were imbibed and placed in darkness at 16degreesC for either 7 or 14 days prior to exposure to red or white light for a single 15-min period. Dormancy in all biotypes was overcome indicating that a period of burial may decrease the dormancy level and increase seed sensitivity to light. This increased light sensitivity suggests that exposure to light during tillage may stimulate germination in P. paradoxa seed.

Improved germination of the Australian natives: Hibbertia commutata, Hibbertia amplexicaulis (Dilleniaceae), Chameascilla corymbosa (Liliaceae) and Leucopogon nutans (Epacridaceae)

Hibbertia commutata (Steudel), H. amplexicaulis (Steudel), Chameascilla corymbosa [(R.Br.) F.Muell. Ex Benth.] and Leucopogon nutans (E. Pritzel) are four Australian species that are difficult to germinate during mine-site rehabilitation. Laboratory germination trails were conducted to identify dormancy mechanisms and to improve germination response. Treatments applied to all species included scarification and scarification followed by soaking seeds in smoke water (1, 5 or 10%) or gibberellic-acid solution (50, 200 or 1000 muM). Additional treatments with kinetin solution (50, 200 or 1000 muM) and smoke water (50 or 100%) were applied to scarified or unscarified seeds of C. corymbosa. Thermal-shock treatment was applied to L. nutans fruit, some of which were subsequently scarified and subjected to both smoke water (10%) and gibberellic-acid solution (1000 muM). Significant germination increases were obtained by using dormancy-breaking treatments on H. commutata ( from 12.8 to 76.0%), H. amplexicaulis (from 6.8 to 55.1%) and C. corymbosa (from 48.5 to 86.4%). Scarification alone increased germination of both Hibbertia species, suggesting that these species display a physical seed coat-imposed dormancy mechanism. Germination of H. amplexicaulis was further increased by the application of gibberellic-acid solution, indicating a possible embryo-imposed dormancy mechanism. Scarification followed by the application of smoke water produced the highest germination response for C. corymbosa seeds. Scarification alone did not significantly increase germination, inferring the existence of a smoke-responsive embryo dormancy mechanism. Seeds of L. nutans, although viable, failed to germinate and are thought to display complex seed coat- and embryo-imposed dormancy mechanisms.

Potential to increase yield in lucerne (Medicago sativa subsp sativa) through introgression of Medicago sativa subsp falcata into Australian adapted material

The effect of interspecific heterosis in crosses between Medicago sativa subsp. sativa and M. sativa subsp. falcata was assessed. Three sativa and 3 falcata plants were crossed in a diallel design. Progeny dry matter yield and natural plant height were assessed in a replicated field experiment at Gatton, Queensland. Yield data were analysed using the method of residual maximum likelihood (REML) and Griffing's model 1. There were significant differences between the reciprocal, general combining ability (GCA), and specific combining ability (SCA) effects. As expected, S-1 populations were lower yielding than their respective intraspecific cross and falcata x falcata crosses were significantly lower yielding than sativa x sativa crosses. Some of the interspecific crosses indicated substantial SCA effects, yielding at least as well as the best sativa x sativa crosses. We have demonstrated the potential usefulness of unselected M. sativa subsp. falcata as a heterotic group in the improvement of yield in northern Australian adapted lucerne material, and discuss how it could be incorporated into future breeding to overcome the yield stagnation currently being experienced in Australian programs.

Short- and long-term consequences of thermal variation in the larval environment of anurans

To survive adverse or unpredictable conditions in the ontogenetic environment, many organisms retain a level of phenotypic plasticity that allows them to meet the challenges of rapidly changing conditions. Larval anurans are widely known for their ability to modify behaviour, morphology and physiological processes during development, making them an ideal model system for studies of environmental effects on phenotypic traits. Although temperature is one of the most important factors influencing the growth, development and metamorphic condition of larval anurans, many studies have failed to include ecologically relevant thermal fluctuations among their treatments. We compared the growth and age at metamorphosis of striped marsh frogs Limnodynastes peronii raised in a diurnally fluctuating thermal regime and a stable regime of the same mean temperature. We then assessed the long-term effects of the larval environment on the morphology and performance of post-metamorphic frogs. Larval L. peronii from the fluctuating treatment were significantly longer throughout development and metamorphosed about 5 days earlier. Frogs from the fluctuating group metamorphosed at a smaller mass and in poorer condition compared with the stable group, and had proportionally shorter legs. Frogs from the fluctuating group showed greater jumping performance at metamorphosis and less degradation in performance during a 10-week dormancy. Treatment differences in performance could not be explained by whole-animal morphological variation, suggesting improved contractile properties of the muscles in the fluctuating group.

Can we learn more from fewer seeds?

The vital role that 'design of experiment' (DOE) plays when investigating dormancy, germination and potentially influential factors is discussed. The Taguchi analysis, developed by Dr. Genichi Taguchi, is a special application and analysis of the fractional factorial aimed at achieving maximum information from minimum effort and resources.

The effects of temperature and salinity on Acacia harpophylla (brigalow) (Mimosaceae) germination

Acacia harpophylla F. Muell. (brigalow) used to naturally occur over a range of about 50 000 km(2) in Queensland and New South Wales, Australia. Large scale clearing for agriculture has reduced the area to less than 20 000 km(2) and it is estimated that 20-25% of vertebrate fauna living in brigalow communities will become locally extinct as a result of the current clearing induced loss of habitat. Some coal mining companies in central Queensland have become interested in providing habitat for the endangered bridle nail-tailed wallaby that lives in brigalow vegetation. However, there is little known about establishment techniques for brigalow on mine sites and other disturbed ground; an understanding of brigalow biology and ecology is required to assist in the conservation of this threatened vegetation community and for re-creation of bridled nail-tail wallaby habitat in the post mining landscape. Brigalow is an unusual species of Acacia because it is not hard-seeded and germinates readily without the need to break seed-coat imposed dormancy. Germination trials were undertaken to test the ability of brigalow seed to germinate with a range of temperatures and salinity levels similar to those experienced in coal mine spoil. Optimum germination was found to occur at temperatures from 15 to 38 degrees C and no germination was recorded at 45 degrees C. Brigalow was very tolerant of high salt levels and germinated at percentages greater than 50% up to the highest salinity tested, 30 dS/m. Germination of greater than 90% occurred up to an electrical conductivity of 20 dS/m. The results indicate brigalow seed can be sown in summer when rains are most likely to occur, however, shading of the seed with extra soil or mulch may ensure the ground surface does not become too hot for germination. Because of its ability to germinate at high salinity levels, brigalow may be suitable for use in saline mine wastes which are common on sites to be rehabilitated after mining.

An evolutionary framework for studies of hibernation and short-term torpor

Data from diverse studies endorse ideas that short term torpor and hibernation are expressions of ancient characters. In evolutionary terms, their basic mechanisms are probably plesiomorphic (= ancestral/primitive) and physiologically similar. This contrasts with the alternate view that they are apomorphic (= derived, specialized), arising independently in many taxa from homeothermic ancestry by numerous apparent convergences. This paper explores some of the implications of accepting the plesiomorphic interpretation. Hibernation is, of course, a complex phenomenon that has undergone variations and refinements in different mammalian lineages. The argument is not that hibernation in total is a plesiomorphic character, but that it is built upon fundamental processes that are. Taking this view provides a framework for research that emphasizes the value of comparative studies, particularly of reptiles and birds. Studies of reptiles, for example, might unravel the mystery about periodic arousals. A plesiomorphic framework also explains the most extreme examples of hibernation as derived specializations from ancestry in which heterothermy is more about energy management than escape from cold. It cautions against using low body temperature (Tb) alone to diagnose torpor, emphasizes the need to distinguish between constitutional eurythermy (plesiomorphic) and constitutional stenothermy (apomorphic), and leads to a parsimonious theory about the evolution of endothermy. The paper proposes that brown adipose tissue (BAT) is apomorphic within eutheria and highlights the conundrum posed by the occurrence of both nonshivering thermogenesis (NST) and rapid arousal from hibernation in noneutherian mammals that lack BAT and uncoupling protein 1 (UCP1). It endorses the likely existence of a different, ancient and widespread mechanism for regulatory NST in mammals.

Study of the effects of climate warming on seed germination and seed longevity of snowbed species

Understanding how climate change will affect the distribution and the phenology of plants is becoming an increasingly important topic in ecological studies. In response to climate warming, there are documented upward shift and alterations of phenology and physiology of several plant species. Despite this, the effects of climate change on plant regeneration from seeds have largely been neglected. However, regeneration from seeds, a key event in the plant life cycle, could be significantly affected by climate warming. In this regard, we investigated how climatic changes will affect the seasonal dynamics of seed germination and seedling survival in two different alpine context. The first part refers to five species inhabiting a snowbed located at the Gavia pass (Parco Naturale dello Stelvio). Here, plants were exposed, in the field, to natural conditions and to artificial warming using Open Top Chambers proposed by the ITEX (International Tundra Experiment). The germination curves of seeds produced were compared in order to highlight differences in seed germination ecology and in seed physiology induced by the climate warming. In the second part, we considered two tree species that form the treeline in Davos (Switzerland). As a surrogate of climate warming we used the natural thermal gradient driven by the altitude and we compared the germination behavior of the species studied in three sites at three different elevations in order to evaluate the likelihood of treeline shift under the predicted climate warming.

Embodying and embedding children's sleep: some sociological comments and observations

This paper, drawing on our own research findings data, explores the embodiment and embedment of sleeping in children's everyday/night lives. Key themes here include children's attitudes and feelings toward the dormant body, the processes, routines and rituals associated with going to bed and going to sleep, issues associated with bedrooms and privacy, and finally the relationship between dormancy and domicile. This in turn provides the basis, in the remainder of the paper, for a further series of reflections on the mutually informing relations between the sociology of sleep and the sociology of childhood. Remaining questions and challenges involved in researching children's sleep are also considered. Sleep, it is concluded, is not simply a rich and fascinating sociological topic in its own right it also has the potential to shed valuable new light on a significant yet hitherto under-researched part of children's lives, contributing important new insights in doing so.

Growth, sporulation and spore properties of bacillus stearothemophilus produced in chemically defined media

The nutritional requirements for the vegetative growth of B. stearothermophilus strains NCIB 8919, NCTC lO,OO3 (wild) were found to be DL-methionine, biotin, nicotinic acid, thiamin, glucose and mineral salts. Strains NCIB 8920 required in addition L-tryptophan. B. stearothermophilus NCTC lO,OO3 (mutant) grew in a medium containing only glucose and mineral salts. Separate chemically defined media for the growth of Bacillus stearothermophilus strains NCIB 8919, 8920, NCTC lO,OO3 (wild) and NCTC lO,OO3 (mutant) were developed. Optimally aerated culture of B. stearothermonhilus NCTC lO,OO3(mutant) required 1.0 x 10-4 M. Mn2+ and 2.4 x 10-3 M. glutamic acid for optimal sporulation. Specific nutrient depletion of growth affected percentage sporulation. Spore suspensions of B. stearothermophilus NCTC 10,003 (mutant) were prepared from media in which sulphate (SO4-), nitrogen (N-),phosphate (Po4-), carbon (C-), magnesium-carbon simultaneously (Ng-C-) depleted growth. The heat resistance, dormancy and chemistry of these spores varied considerably. B. stearothermophilus NCTC 10,003 10,00310,00(mutant) spores prepared from carbon depleted cultures containing high and low concentrations of calcium, iron or manganese showed variations in heat resistance,dormancy and chemical composition. Progressive increase in the concentration of medium calciumfrom 1.0 X 10-5  M to 1.4 X 10-4 M. progressively increased theheat resistance of B. stearothermophilus NCTC 10,003 (mutant) spores prepared from nitrogen depleted cultures (N-). The thermodynamic functions for germination rate, magnesium and manganese release of N- and SO4- spores were within the range expected of enzymic reactions. The thermodynamic functions for the breaking of dormancy in SO4- spores and that for the release of D.P.A. were identical. Sublethal heating of SO4- spores (96.5°C and below) induced dormancy in these spores, whereas heating above 96.5°C gave rise to heat activation. Pooled results of the chemical analyses of all spore types studied showed that the concentration of D.P.A. and calcium were positively related to heat resistance whereas magnesium concentration and Mg/Ca molar ratio were inversely proportional to heat resistance.