A functional analysis of cell cycle events in developing and germinating tomato seeds

Seeds are complex biological structures and the primary dispersal units of higher plants. They consist of nutrient reserve storage tissue(s), an embryo and encapsulating structures designated for protection and that may also regulate germination. Seeds have developed mechanisms of withstanding desiccation without losing the ability of immediate reactivation of embryo growth upon rehydration.The arrest and reactivation of cell cycle related events appear to be intimately linked to the arrest of growth during seed development and reactivation of growth during germination. In this thesis, DNA synthesis,β-tubulin accumulation and appearance of microtubular cytoskeleton are studied in relation to morphological and physiological events that are involved in seed development and germination. Biochemical techniques are used to study the relation between DNA replication andβ-tubulin accumulation in embryonic cells of germinating seeds (Chapters 2 and 3). Then, immunocytochemical techniques are applied for the detection and visualisation of DNA synthesis activity and appearance of microtubular cytoskeleton in seed tissues during development and in embryos during germination (Chapters 4, 5 and 6).The results obtained in this study show a general pattern of tomato seed development and germination based on the quantitation and distribution of nuclear DNA synthesis activity,β-tubulin accumulation and microtubular cytoskeleton appearance in cells of the seed tissues. The pattern in embryos during seed germination appeared as a "mirror image"of that during development (Chapters 4 and 5). Cell cycle activities are intense during early stages of seed development and then arrest as seeds become mature. Embryonic DNA synthesis activity, together with the presence of mitotic microtubular cytoskeleton arrays and cell divisions define the period of embryo histodifferentiation. Therafter, the presence of cortical microtubular cytoskeleton and absence of DNA synthesis acitvity defines the phase of embryo growth and completion of morphogenesis. Finally, the microtubular cytoskeleton is degraded as seeds become quiescent, defining the maturation phase. The roles of GA and ABA in seed development are evaluated in the differing developmental patterns observed for the GA-deficient ( gib1 ) and ABA-deficient ( sit w) mutants. Upon imbibition in water, the cell cycle is reactivated and becomes intense as germination is completed. Initially, the cortical microtubular cytoskeleton appears and DNA synthesis is initiated in meristematic cells of embryonic radicle tip region. Thereafter, replicated nuclear DNA is detected together with mitotic microtubular cytoskeleton arrays and cell divisions, prior to radicle protrusion through the seed coat. Both primary and secondary dormancy are characterised by a very low cell cycle activity. The depth of dormancy appears to be related to the progression of the cell cycle prior to the induction of dormancy (Chapter 6).Finally, in the form of a descriptive model, it is proposed to modify the current notion of the different phases in tomato seed development and germination.</p

Depth of dormancy in tomato (Lycopersicon esculentum Mill.) seeds is related to the progression of the cell cycle prior to the induction of dormancy

Cell cycle activities are initiated following imbibition of non-dormant seeds. However, it is not known whether cell cycle related events other than DNA replication also remain suppressed in imbibed dormant seeds. The objective of this study was to demonstrate that the transitions between the non-dormant and dormant (both primary and secondary) states are reflected in cell cycle events, such as DNA replication and the changing patterns of the microtubular cytoskeleton involved in the processes of growth and development. The present studies were conducted on seeds from tomato (Lycopersicon esculentum cv. Moneymaker) that possessed primary dormancy or were manipulated to attain secondary dormancy. In addition, a non-dormant abscisic acid (ABA)-deficient mutant, sitw, was used. DNA replication, as measured by flow cytometry, and -tubulin accumulation, analysed by immunoblotting, were compared with immunocytological studies of active DNA synthesis and microtubular cytoskeleton formation. It is shown that the depth of dormancy, which distinguishes primary and secondary dormancy, may depend on the progression of the cell cycle prior to the induction of dormancy

Guidelines On The Treatment Of Anemia Of Chronic Renal Failure Using Recombinant Human Erythropoietin: Associação Brasileira De Hematologia, Hemoterapia E Terapia Celular Guidelines Project: Associação Médica Brasileira - 2014

[No abstract available

Low-mass pre--main-sequence stars in the Magellanic Clouds

[Abridged] The stellar Initial Mass Function (IMF) suggests that sub-solar stars form in very large numbers. Most attractive places for catching low-mass star formation in the act are young stellar clusters and associations, still (half-)embedded in star-forming regions. The low-mass stars in such regions are still in their pre--main-sequence (PMS) evolutionary phase. The peculiar nature of these objects and the contamination of their samples by the evolved populations of the Galactic disk impose demanding observational techniques for the detection of complete numbers of PMS stars in the Milky Way. The Magellanic Clouds, the companion galaxies to our own, demonstrate an exceptional star formation activity. The low extinction and stellar field contamination in star-forming regions of these galaxies imply a more efficient detection of low-mass PMS stars than in the Milky Way, but their distance from us make the application of special detection techniques unfeasible. Nonetheless, imaging with the Hubble Space Telescope yield the discovery of solar and sub-solar PMS stars in the Magellanic Clouds from photometry alone. Unprecedented numbers of such objects are identified as the low-mass stellar content of their star-forming regions, changing completely our picture of young stellar systems outside the Milky Way, and extending the extragalactic stellar IMF below the persisting threshold of a few solar masses. This review presents the recent developments in the investigation of PMS stars in the Magellanic Clouds, with special focus on the limitations by single-epoch photometry that can only be circumvented by the detailed study of the observable behavior of these stars in the color-magnitude diagram. The achieved characterization of the low-mass PMS stars in the Magellanic Clouds allowed thus a more comprehensive understanding of the star formation process in our neighboring galaxies.Comment: Review paper, 26 pages (in LaTeX style for Springer journals), 4 figures. Accepted for publication in Space Science Review

Rhesus macaques self-curing from a schistosome infection can display complete immunity to challenge

To date there is only one single drug with modest efficacy and no vaccine available to protect from schistosomiasis. Here, Amaral et al. characterize the self-cure process of rhesus macaques following primary infection and secondary challenge with Schistosoma mansoni to inform future vaccine development studies.The rhesus macaque provides a unique model of acquired immunity against schistosomes, which afflict >200 million people worldwide. By monitoring bloodstream levels of parasite-gut-derived antigen, we show that from week 10 onwards an established infection with Schistosoma mansoni is cleared in an exponential manner, eliciting resistance to reinfection. Secondary challenge at week 42 demonstrates that protection is strong in all animals and complete in some. Antibody profiles suggest that antigens mediating protection are the released products of developing schistosomula. In culture they are killed by addition of rhesus plasma, collected from week 8 post-infection onwards, and even more efficiently with post-challenge plasma. Furthermore, cultured schistosomula lose chromatin activating marks at the transcription start site of genes related to worm development and show decreased expression of genes related to lysosomes and lytic vacuoles involved with autophagy. Overall, our results indicate that enhanced antibody responses against the challenge migrating larvae mediate the naturally acquired protective immunity and will inform the route to an effective vaccine.Cancer Signaling networks and Molecular Therapeutic

Land management shapes drought responses of dominant soil microbial taxa across grasslands

Soil microbial communities are dominated by a relatively small number of taxa that may play outsized roles in ecosystem functioning, yet little is known about their capacities to resist and recover from climate extremes such as drought, or how environmental context mediates those responses. Here, we imposed an in situ experimental drought across 30 diverse UK grassland sites with contrasting management intensities and found that: (1) the majority of dominant bacterial (85%) and fungal (89%) taxa exhibit resistant or opportunistic drought strategies, possibly contributing to their ubiquity and dominance across sites; and (2) intensive grassland management decreases the proportion of drought-sensitive and non-resilient dominant bacteria—likely via alleviation of nutrient limitation and pH-related stress under fertilisation and liming—but has the opposite impact on dominant fungi. Our results suggest a potential mechanism by which intensive management promotes bacteria over fungi under drought with implications for soil functioning

Efeito do uso do traje de neoprene sobre variáveis técnicas, fisiológicas e perceptivas de nadadores

Ao contrário do que ocorre em provas de piscina, competições em águas abertas estão sujeitas as condições ambientais, sendo uma delas as baixas temperaturas. Em determinadas circunstâncias é permitido o uso de roupas especiais para evitar hipotermia. O objetivo do estudo foi verificar os efeitos do uso da roupa de neoprene em um grupo composto por triatletas e nadadores, comparado ao uso de vestimentas convencionais (sunga) sobre variáveis cinemáticas e psicofisiológicas do nado. Participaram 20 homens (12 triatletas e oito nadadores) de idade 22,0 ± 6,6 anos com desempenhos que correspondem a 75 ± 7,7% do melhor tempo brasileiro na prova de 400 m. Os atletas realizaram duas repetições máximas e duas submáximas de 400 m em nado "crawl", com e sem o uso da roupa de neoprene. Foram comparadas a velocidade média (VM), comprimento de braçada (CB), frequência de braçada (FB), índice de nado (IN), percepção subjetiva de esforço (PSE), frequência cardíaca (FC), e concentração de lactato sanguíneo (LAC). Um conjunto de ANOVAs com medidas repetidas do tipo "two-way" foi aplicado. Quando diferenças foram encontradas o teste de Tukey foi empregado. Com o traje de neoprene, em máxima intensidade, o tempo para nadar a distância foi 6,4% menor, com manutenção da FB e aumento da CB, as variáveis psicofisiológicas não diferiram estatisticamente. Em esforço submáximo, o uso do traje de neoprene resultou em menor FB, maior CB, maior IN e em menores valores de FC, LAC e PSE (p In open water swimming competitions, athletes are prone to environmental conditions and are frequently exposed to low temperatures, in contrast to what occurs in indoor competitions. In some circumstances the use of special swimming suits is allowed to avoid hypothermia. The aim of this study was to verify the effects of the use of a neoprene swimming suit in comparison to a conventional swimming suit on a number of cinematic and psychophysiological variables. Twenty athletes experienced in swimming competitions (12 triathletes and 8 swimmers; 22.0± 6.6 yearsold), whose the performance was 75 ± 7.7% of the National record. Athletes performed two maximal and two submaximal 400m crawl simulated competition with a whole body neoprene swimming suit and with a conventional swimming suit. Mean speed (VM) stroke length (CB), stroke frequency (FB), swimming index (IN), rate of perceived effort (PSE), heart rate, and blood lactate concentration (LAC) were compared between conditions. The time to perform maximal trials with the use of the neoprene swimming suit was 6.4% shorter than when wearing the traditional swimming suit. FB and the psychophysiological variables remained unchanged, while CB increased in response to the use of the neoprene swimming suit. The use of the neoprene swimming suit in submaximal trials provided smaller FB, FC, LAC and PSE and larger CB and IN in comparison to the use of the traditional swimming suit. The results indicated that the neoprene swimming suit increases performance in biomechanical, physiological and perceptive aspects. The VM increase in maximal efforts does not depend exclusively on changes in FB and CB. Possibly, increments of the parameters related to the swimming may have improved the mechanical efficiency of the movement, which may have provided a movement economy that resulted in a better performance