928 resultados para Life cycle stages


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The variations in the activities of the alkaline and acid phosphatases of the silkworm, Bombyx mori, were studied in all stages of the life cycle. From hatching until the spinning stage a steady increase was recorded in the activity of both the enzymes followed with a conspicuous decrease at each moult. During the pupal stage the alkaline phosphatase was almost absent, whereas the acid phosphatase maintained a high and constant value. Increase or decrease of the activity of the enzymes during larval development was reflected in a decrease or increase in the acid-soluble phosphorus content. Acid phosphatase activity slowly increased from laying of the eggs to hatching of the larvae with a concomitant decrease in the acid-soluble phosphorus. Tissue analysis showed a high concentration of the alkaline enzyme in the intestines, but the haemolymph was almost free of both enzymes. Feeding of inorganic phosphate increased the alkaline enzyme in the intestines, whereas glucose had no effect on either of the enzymes in the intestines.

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The modern subject is what we can call a self-subjecting individual. This is someone in whose inner reality has been implanted a more permanent governability, a governability that works inside the agent. Michel Foucault s genealogy of the modern subject is the history of its constitution by power practices. By a flight of imagination, suppose that this history is not an evolving social structure or cultural phenomenon, but one of those insects (moth) whose life cycle consists of three stages or moments: crawling larva, encapsulated pupa, and flying adult. Foucault s history of power-practices presents the same kind of miracle of total metamorphosis. The main forces in the general field of power can be apprehended through a generalisation of three rationalities functioning side-by-side in the plurality of different practices of power: domination, normalisation and the law. Domination is a force functioning by the rationality of reason of state: the state s essence is power, power is firm domination over people, and people are the state s resource by which the state s strength is measured. Normalisation is a force that takes hold on people from the inside of society: it imposes society s own reality its empirical verity as a norm on people through silently working jurisdictional operations that exclude pathological individuals too far from the average of the population as a whole. The law is a counterforce to both domination and normalisation. Accounting for elements of legal practice as omnihistorical is not possible without a view of the general field of power. Without this view, and only in terms of the operations and tactical manoeuvres of the practice of law, nothing of the kind can be seen: the only thing that practice manifests is constant change itself. However, the backdrop of law s tacit dimension that is, the power-relations between law, domination and normalisation allows one to see more. In the general field of power, the function of law is exactly to maintain the constant possibility of change. Whereas domination and normalisation would stabilise society, the law makes it move. The European individual has a reality as a problem. What is a problem? A problem is something that allows entry into the field of thought, said Foucault. To be a problem, it is necessary for certain number of factors to have made it uncertain, to have made it lose familiarity, or to have provoked a certain number of difficulties around it . Entering the field of thought through problematisations of the European individual human forms, power and knowledge one is able to glimpse the historical backgrounds of our present being. These were produced, and then again buried, in intersections between practices of power and games of truth. In the problem of the European individual one has suitable circumstances that bring to light forces that have passed through the individual through centuries.

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Plant organs are initiated as primordial outgrowths, and require controlled cell division and differentiation to achieve their final size and shape. Superimposed on this is another developmental program that orchestrates the switch from vegetative to reproductive to senescence stages in the life cycle. These require sequential function of heterochronic regulators. Little is known regarding the coordination between organ and organismal growth in plants. The TCP gene family encodes transcription factors that control diverse developmental traits, and a subgroup of class II TCP genes regulate leaf morphogenesis. Absence of these genes results in large, crinkly leaves due to excess division, mainly at margins. It has been suggested that these class II TCPs modulate the spatio-temporal control of differentiation in a growing leaf, rather than regulating cell proliferation per se. However, the link between class II TCP action and cell growth has not been established. As loss-of-function mutants of individual TCP genes in Arabidopsis are not very informative due to gene redundancy, we generated a transgenic line that expressed a hyper-activated form of TCP4 in its endogenous expression domain. This resulted in premature onset of maturation and decreased cell proliferation, leading to much smaller leaves, with cup-shaped lamina in extreme cases. Further, the transgenic line initiated leaves faster than wild-type and underwent precocious reproductive maturation due to a shortened adult vegetative phase. Early senescence and severe fertility defects were also observed. Thus, hyper-activation of TCP4 revealed its role in determining the timing of crucial developmental events, both at the organ and organism level.

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The malaria parasite experiences a significant amount of redox stress during its growth in human erythrocytes and heavily relies on secretory functions for pathogenesis. Most certainly, the parasite is equipped with machinery to tackle perturbations in the secretory pathway, like the unfolded protein response pathway in higher eukaryotes. Our bioinformatics analysis revealed the complete absence of genes involved in the canonical unfolded protein response pathway in Plasmodium falciparum. Accordingly, the parasite was unable to up-regulate endoplasmic reticulum (ER) chaperones or ER-associated degradation in response to DTT-mediated ER stress. Global profiling of gene expression upon DTT treatment revealed a network of AP2 transcription factors and their targets being activated. The overall outcome was up-regulation of genes involved in protein export and the sexual stage of the parasite life cycle culminating in gametocytogenesis. Our results suggest that the malaria parasite uses ER stress as a cue to switch to the transmissible sexual stages.

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T-protein, an aminomethyltransferase, represents one of the four components of glycine cleavage system (GCS) and catalyzes the transfer of methylene group from H-protein intermediate to tetrahydrofolate (THF) forming N-5, N-10-methylene THF (CH2-THF) with the release of ammonia. The malaria parasite genome encodes T-, H- and L-proteins, but not P-protein which is a glycine decarboxylase generating the aminomethylene group. A putative GCS has been considered to be functional in the parasite mitochondrion despite the absence of a detectable P-protein homologue. In the present study, the mitochondrial localization of T-protein in the malaria parasite was confirmed by immunofluorescence and its essentiality in the entire parasite life cycle was studied by targeting the T-protein locus in Plasmodium berghei (Pb). PbT knock out parasites did not show any growth defect in asexual, sexual and liver stages indicating that the T-protein is dispensable for parasite survival in vertebrate and invertebrate hosts. The absence of P-protein homologue and the non-essentiality of T protein suggest the possible redundancy of GCS activity in the malaria parasite. Nevertheless, the H- and L-proteins of GCS could be essential for malaria parasite because of their involvement in alpha-lcetoacid dehydrogenase reactions. (C) 2014 Elsevier B.V. All rights reserved.

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Enteric protozoan Entamoeba histolytica is a major cause of debilitating diarrheal infection worldwide with high morbidity and mortality. Even though the clinical burden of this parasite is very high, this infection is categorized as a neglected disease. Parasite is transmitted through feco-oral route and exhibit two distinct stages namely - trophozoites and cysts. Mechanism and regulation of encystation is not clearly understood. Previous studies have established the role of Heat shock protein 90 (Hsp90) in regulating stage transition in various protozoan parasites like Giardia, Plasmodium, Leishmania, and Toxoplasma. Our study for the first time reports that Hsp90 plays a crucial role in life cycle of Entamoeba as well. We identify Hsp90 to be a negative regulator of encystation in Entamoeba. We also show that Hsp90 inhibition interferes with the process of phagocytosis in Entamoeba. Overall, we show that Hsp90 plays an important role in virulence and transmission of Entamoeba.

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The proteins of Plasmodium, the malaria parasite, are strikingly rich in asparagine. Plasmodium depends primarily on host haemoglobin degradation for amino acids and has a rudimentary pathway for amino acid biosynthesis, but retains a gene encoding asparagine synthetase (AS). Here we show that deletion of AS in Plasmodium berghei (Pb) delays the asexual-and liver-stage development with substantial reduction in the formation of ookinetes, oocysts and sporozoites in mosquitoes. In the absence of asparagine synthesis, extracellular asparagine supports suboptimal survival of PbAS knockout (KO) parasites. Depletion of blood asparagine levels by treating PbASKO-infected mice with asparaginase completely prevents the development of liver stages, exflagellation of male gametocytes and the subsequent formation of sexual stages. In vivo supplementation of asparagine in mice restores the exflagellation of PbASKO parasites. Thus, the parasite life cycle has an absolute requirement for asparagine, which we propose could be targeted to prevent malaria transmission and liver infections.

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In this study, the fine-scale structure of the diurnal variability of ground-based lightning is systematically compared with satellite-based rain. At the outset, it is shown that tropical variability of lightning exhibits a prominent diurnal mode, much like rain. A comparison of the geographical distribution of the timing of the diurnal maximum shows that there is very good agreement between the two observables over continental and coastal regions throughout the tropics. Following this global tropical comparison, we focus on two regions, Borneo and equatorial South America, both of which show the interplay between oceanward and landward propagations of the phase of the diurnal maximum. Over Borneo, both rain and lightning clearly show a climatological cycle of ``breathing in'' (afternoon to early morning) and ``breathing out'' (morning to early afternoon). Over the equatorial east coast of South America, landward propagation is noticed in rain and lightning from early afternoon to early morning. Along the Pacific coast of South America, both rain and lightning show oceanward propagation. Though qualitatively consistent, over both regions the propagation is seen to extend further in rainfall. Additionally, given that lightning highlights vigorous convection, the timing of its diurnal maximum often precedes that of rainfall in the convective life cycle. (C) 2015 Elsevier B.V. All rights reserved.

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This profile covers life history and environmental requirements of both alewife (Alosa pseudoharengus) and blueback herring (Alosa aestivalis), since their distribution is overlapping and their morphology, ecological role, and environmental requirements are similar. The alewife is an anadromous species found in riverine, estuarine, and Atlantic coastal habitats, depending on life cycle stage, from Newfoundland (Winters et al. 1973) to Soutn Carolina (Berry 1964). Landlocked populations are i n the Great Lakes, Finger Lakes, and many other freshwater lakes (Bigelow and Sch roeder 1953; Scott and Crossman 1973). The blueback herring is an anadromous species found in riverine, estuarine, and Atlantic coastal habitats, depending on life stage cycle, from Nova Scotia to the St. Johns River, Florida (Hildebrand 1963)

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Changes in sustainability of aquatic ecosystems are likely to be brought about by the global warming that has been widely predicted. In this article, the effects of water temperature on water-bodies (lakes, oceans and rivers) are reviewed followed by the effects of temperature on aquatic organisms. Almost all aquatic organisms require exogenous heat before they can metabolise efficiently. An organism that is adapted to warm temperatures will have a higher rate of metabolism of food organisms and this increases feeding rate. In addition, an increase in temperature raises the metabolism of food organisms, so food quality can be altered. Where populations have a different tolerance to temperature the result is habitat partitioning. One effect of prolonged high temperature is that it causes water to evaporate readily. In the marine littoral this is not an important problem as tides will replenish water in pools. Small rain pools are found in many tropical countries during the rainy season and these become incompletely dried at intervals. The biota of such pools must have resistant stages within the life cycle that enable them to cope with periods of drying. The most important potential effects of global warming include (i) the alteration of existing coastlines, (ii) the development of more deserts on some land masses, (iii) higher productivity producing higher crop production but a greater threat of algal blooms and (iv) the processing of organic matter at surface microlayers.

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The authors present the findings of a restoration project in Loch Enoch in Scotland. There are historical references that brown trout was present in Loch Enoch up to the 1920s but it is believed the acidity of loch triggered the disappearance of Salmo trutta. The recent observed reduction in the acidity of L. Enoch to a level close to that found in nearby lochs with trout populations, suggested that trout might now survive in L. Enoch. For a population to survive, all stages in the life-cycle of a species must be able to develop. Accordingly, tests were undertaken, first with eggs and fry. The availability of food was also studied. In October 1994, 3,000 yearling trout of L. Grannoch origin which had been reared in a local hatchery were distributed throughout the loch. The fish population was studied from 1995-98. The authors conclude that survival of the trout population is possible if the acidity of the loch water remains low.

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Reconhecida como uma das maiores empresas do Brasil, controlada pelo governo, a Petrobras apresenta um processo de internacionalização dividido em duas fases: (i) busca de melhores condições contratuais para o abastecimento do mercado interno e (ii) posicionamento mundial, segurança financeira e internacionalização da marca. Ambas as perspectivas de atuação internacional promoveram o aproveitamento de vantagem competitiva, ainda que sob comportamentos distintos. Diante disso, o objetivo do presente estudo é mensurar o impacto do processo de internacionalização no sistema de controle gerencial da unidade de estudo: Petrobras Uruguay Distribución, subsidiária no segmento de downstream1 e constituída em 2006 por meio de um processo de reorganização societária decorrente da aquisição dos ativos da Shell. Para atender a este propósito, analisam-se as possíveis alterações dos sistemas de controle gerencial e a relação existente, em termos de proximidade e afastamento da literatura presente e o caso estudado. Para tanto, o capítulo de revisão de literatura representa o embasamento teórico responsável pelas abordagens das características dos sistemas de controles, identificação dos contextos influenciadores de seu desenho e destaque para os tipos de internacionalização, nas tangentes comportamentais e motivacionais, além de abordar as teorias de ciclo de vida organizacional. O método aplicado no teste do referencial teórico foi o estudo exploratório com caso único, mediante a aplicação de um questionário padronizado. As variáveis de pesquisa consubstanciaram-se no relacionamento da literatura abordada e as questões de pesquisa e foram classificadas, segundo a natureza, em contingentes e identificadoras. Os resultados obtidos possibilitaram avaliar o nível do impacto do processo de internacionalização e a capacidade de adaptabilidade da organização aos novos contextos, comprovando que o empreendimento de novas estratégias, sejam elas internacionais ou em novos negócios, influencia o desenho do sistema de controle gerencial que refletirá, na proporção do interesse dos gestores, num processo de controle mais adequado à organização.

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The Argentine sandperch Pseudopercis semifasciata (Pinguipedidae) sustains an important commercial and recreational fishery in the northern Patagonian gulfs of Argentina. We describe the morphological features of larvae and posttransition juveniles of P. semifasciata and analyze the abundance and distribution of early life-history stages obtained from 19 research cruises conducted on the Argentine shelf between 1978 and 2001. Pseudopercis semifasciata larvae were distinguished from other larvae by the modal number of myomeres (between 36 and 38), their elongated body, the size of their gut, and by osteological features of the neuro- and branchiocranium. Pseudopercis semifasciata and Pinguipes brasilianus (the other sympatric species of pinguipedid fishes) posttransition juveniles were distinguished by their head shape, pigmentation pattern, and by the number of spines of the dorsal fin (five in P. semifasciata and seven in P. brasilianus). The abundance and distribution of P. semifasciata at early stages indicate the existence of at least three offshore reproductive grounds between 42−43°S, 43−44°S, and 44−45°S, and a delayed spawning pulse in the southern stocks.

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This is the River Bovey (main Teign tributary) fisheries survey 1978 report produced by South West Water Authority in 1978. The aim of this report is to confirm or disprove the presence of alien coarse fish species thought present in the Bovey system. A chosen site was electro fished using D.C. methods wading upstream. All fish taken were measured and identified. Since it was not possible to distinguish between the young parr stages of migratory and non migratory trout, all parr taken have been included under the heading of Brown trout whereas in fact some of these parr may become migratory later in their life cycle.