Aplicação do método de mineralização de nitrogênio com lixiviação para solo tratado com lodo de esgoto e composto orgânico

A determinação da taxa de mineralização de nitrogênio (N) em solos tratados com resíduos é fundamental para definir as doses a serem aplicadas, fornecendo N às plantas na época adequada, sem perdas do elemento por lixiviação. Inúmeros estudos em solos tratados com resíduos utilizam o teste de mineralização de N sem lixiviação e a caracterização das formas mineralizadas pelo método volumétrico. Em razão da deficiente repetibilidade do teste e da baixa sensibilidade do método de determinação observada em estudos com lodo de esgoto e composto orgânico, adotaram-se o método pouco difundido de mineralização de N com lixiviação e a especificação das formas minerais de N, por meio de métodos espectrofotométricos. O teste foi realizado em colunas de PVC, com 30 mm de diâmetro, preenchidas com terra retirada da camada 0,20 m de um solo classificado como Nitossolo Háplico, álico, argiloso, misturada às seguintes doses de resíduos, em Mg ha-1 (base úmida): lodo de esgoto - L1: 3,6; L2: 7,2; e L3: 14,4; e composto de lodo de esgoto e material vegetal triturado proveniente da poda de árvores urbanas - C1: 7,2; C2: 14,4; e C3: 28,8. As colunas foram incubadas e lixiviadas periodicamente com solução 0,01 mol L-1 KCl e as formas minerais de N determinadas colorimetricamente. Maiores taxas de mineralização ocorreram nas menores doses aplicadas de lodo e composto, evidenciando efeito priming, indesejado à fertilidade de solos sob condições tropicais. Menores taxas ocorreram nas doses L2 e C2, com valores próximos àqueles sugeridos pela legislação, não suprindo a demanda de N almejada, indicando possível necessidade de revisão na norma vigente. De modo geral, as taxas de mineralização foram maiores para o composto orgânico, enquanto a velocidade de degradação do composto orgânico foi menor que para o lodo, revelando maior distribuição da disponibilidade de N para a cultura ao longo do tempo. O método de mineralização com lixiviação e a determinação das formas de N-minerais por colorimetria evidenciaram-se rápidos e eficientes; estudos com solos e resíduos diversos podem validá-los para seu uso em rotina.

Matriconditioning integrated with gibberellic acid to hasten seed germination and improve stand establishment of pepper and tomato

Emergence and stand establishment of tomato (Lycopersicon lycopersicum (L.) (Karsten ex Farw) and pepper (Capsicum annus L.) seeds are often slow and erratic, particularly under stress conditions. Field emergence trials sometimes have not responded to priming in pepper. This study examined the combined effects of matriconditioning and gibberellin application on the germination and stand establishment of pepper and tomato seeds. Pepper and tomato seeds were conditioned with a solid carrier, Micro Cel E, in the presence of gibberellic acid (GA) for 1, 2 , 3 and 4 days at 15 and 25ºC. The results showed that, in all cases, even under stress conditions, the combination of matriconditioning with GA was effective in improving germination and emergence of pepper and tomato. The germination time was, in average, reduced by 2 to 3 days by primed seeds. Thus, matriconditioning, during which germination is suspended, provides an unique means to rapidly and efficiently digest the endosperm by GA-induced enzymes and reduce the mechanical restraints of endosperm thus providing energy to start and sustain embryo growth.

Biochar effect on the mineralization of soil organic matter

The objective of this work was to verify whether the addition of biochar to the soil affects the degradation of litter and of soil organic matter (SOM). In order to investigate the effect of biochar on the mineralization of barley straw, soil was incubated with 14C-labelled barley straw with or without unlabelled biochar. To investigate the effect of straw on the mineralization of biochar, soil was incubated with 14C-labelled biochar with or without straw. In addition, to investigate the effect of biochar on old SOM, a soil labelled by applying labelled straw 40 years ago was incubated with different levels of biochar. All experiments had a control treatment, without any soil amendment. The effect of biochar on the straw mineralization was small and nonsignificant. Without biochar, 48±0.2% of the straw carbon was mineralized within the 451 days of the experiment. In comparison, 45±1.6% of C was mineralized after biochar addition of 1.5 g kg-1. In the SOM-labelled soil, the organic matter mineralized more slowly with the increasing doses of biochar. Biochar addition at 7.7 g kg-1 reduced SOM mineralization from 6.6 to 6.3%, during the experimental period. The addition of 15.5 g kg-1 of biochar reduced the mineralized SOM to 5.7%. There is no evidence of increased degradation of either litter or SOM due to biochar addition; consequently, there is no evidence of decreased stability of SOM.

Potasssium chloride as a nutrient seed primer to enhance salt‑tolerance in maize

The objective of this work was to determine if KCl could be a useful nutrient primer for safe seed germination in maize crop under salt stress conditions. Seed priming was done using 50 mmol L‑1 of muriate of potash, and germination and seedling growth were evaluated after salt stress with NaCl up to 50 mmol L‑1. Another set of seeds was tested under the same salt stress conditions without priming. Under salinity stress, germination percentage, germination rate index, germination coefficient, and seedling vigor indexes were higher in primed seeds. In unprimed seeds, mean germination time increased, while the germination rate index and the fresh and dry matter mass decreased more sharply with salinity stress. The Na/K ratio was higher in unprimed seeds.

Qualidade sanitária e fisiológica de sementes de milho submetidas a termoterapia e condicionamento fisiológico

A termoterapia é uma medida de controle tradicionalmente utilizada com sucesso para eliminação de patógenos em sementes de espécies hospedeiras. Trata-se, no entanto, de uma medida que provoca alterações fisiológicas e bioquímicas nas sementes em diferentes intensidades, podendo comprometer o desempenho das mesmas nas condições de cultivo. Objetivou-se com este trabalho avaliar a eficácia da termoterapia no controle de alguns fungos associados a sementes de milho e do condicionamento osmótico, após o tratamento térmico, no sentido de reparar danos nas sementes provocados nestas circunstâncias. Os fungos associados às sementes foram avaliados por meio do método de incubação em substrato de papel com congelamento, e a qualidade fisiológica das sementes pelos testes de germinação, primeira contagem, condutividade elétrica, e padrões eletroforéticos das enzimas esterase (EST), malato desidrogenase (MDH) e álcool desidrogenase (ADH). O tratamento térmico utilizado foi por imersão em água aquecida a 60°C por 5, 10 e 20 minutos. Após o tratamento, uma fração das sementes foi submetida ao condicionamento fisiológico em rolo de papel embebido em solução de PEG 6000 a -1,2 MPa. Todos os tratamentos térmicos reduziram ou eliminaram Acremonium strictum das sementes. A incidência de Fusarium verticillioides foi reduzida significativamente pelo tratamento térmico nos períodos de 10 e 20 minutos. À medida que se aumentou o tempo de exposição ao tratamento térmico, houve aumento dos valores de condutividade elétrica e redução significativa da primeira contagem e germinação das sementes. O tratamento térmico durante 20 minutos alterou os padrões eletroforéticos das enzimas esterase e malato desidrogenase. O condicionamento fisiológico das sementes não foi capaz de reverter os danos causados pela termoterapia.

Evaluation of the physiological quality of anadenenthera peregrina (L.) Speg. seeds during storage

The aim of this experiment was to evaluate the effect of storage temperature on the viability and vigour of A. peregrina seeds. Seeds of A. peregrina harvested in Viçosa-MG, in September 2005 were used. The seeds were stored in the Laboratory of Forest Seeds Analysis (LASF) of the Universidade Federal de Viçosa (UFV), in a cold chamber, under approximately 5ºC over150 days. The seeds were stored under 20ºC for 150 days more. Seed moisture was determined after oven-drying at 105 ± 3ºC for 24 hours. The seeds were analyzed monthly using germination, tetrazolium and electrical conductivity tests and Osmopriming during 300 days, with four repetitions of 25 seeds. A. peregrina seeds kept a constant percentage of germination and viable seeds under the tetrazolium test for five months of storage, under either 5ºC and 20ºC. The electrical conductivity test showed significant differences in relation to the storage period, proving to be more sensitive than the standard germination test. Seed priming in PEG -0,4 MPa solution was not efficient in recovering the viability and vigor of the stored seeds at 5ºC and 20ºC.

Restrição hídrica em sementes de Jenipapo (Genipa americana L.)

O jenipapo, originário da América Latina, pertence à família Rubiaceae e apresenta valor madeireiro e alimentício, sendo explorado sem estratégias de conservação. O objetivo deste trabalho foi avaliar o efeito da restrição hídrica, por meio de duas metodologias, na germinação de sementes de Genipa americana L. A primeira foi realizada com sementes imersas em soluções de polietilenoglicol (PEG 6000) por 18 dias a 0,0; -0,1; -0,3 e -0,4 MPa à 20ºC, simulando condições de alagamento, e após este período as sementes foram colocadas para germinar em placas de Petri com folhas de papel tipo mata-borrão umedecidas em água. A segunda utilizou os mesmos potenciais osmóticos umedecendo-se os papéis tipo mata-borrão, para simular a restrição hídrica. O delineamento utilizado foi o inteiramente casualizado com 4 repetições de 25 sementes. Para as sementes imersas em soluções de PEG, o potencial -0,3MPa permite condicionamento osmótico, enquanto à -0,4MPa interfere no vigor. Para as sementes embebidas em papel, ocorre redução da germinação em função do tempo, até não se observar eventos para potenciais a partir de -0,3 MPa.

The role of T cell subsets and cytokines in the regulation of intracellular bacterial infection

Cellular immune responses are a critical part of the host's defense against intracellular bacterial infections. Immunity to Brucella abortus crucially depends on antigen-specific T cell-mediated activation of macrophages, which are the major effectors of cell-mediated killing of this organism. T lymphocytes that proliferate in response to B. abortus were characterized for phenotype and cytokine activity. Human, murine, and bovine T lymphocytes exhibited a type 1 cytokine profile, suggesting an analogous immune response in these different hosts. In vivo protection afforded by a particular cell type is dependent on the antigen presented and the mechanism of antigen presentation. Studies using MHC class I and class II knockout mice infected with B. abortus have demonstrated that protective immunity to brucellosis is especially dependent on CD8+ T cells. To target MHC class I presentation we transfected ex vivo a murine macrophage cell line with B. abortus genes and adoptively transferred them to BALB/c mice. These transgenic macrophage clones induced partial protection in mice against experimental brucellosis. Knowing the cells required for protection, vaccines can be designed to activate the protective T cell subset. Lastly, as a new strategy for priming a specific class I-restricted T cell response in vivo, we used genetic immunization by particle bombardment-mediated gene transfer

The early facilitatory effect of a peripheral spatially noninformative prime stimulus depends on target stimulus features

We investigated the dependency of the early facilitatory effect of a prime stimulus (S1) on the physical characteristics of the target stimulus (S2). A go-no go reaction time paradigm was used. The S1 was a gray ring and the S2s were a white vertical line, a white horizontal line, a white cross and a white small ring, all inside a white ring with the same dimensions as the S1. S1 onset-S2 onset asynchrony was 100 ms. The stimuli appeared randomly in any one of the quadrants of a monitor screen. The S2 could occur at the same position as the S1 or at a different one. We observed a strong facilitatory effect when the vertical line or the horizontal line was the go stimulus and no effect when the cross was the go stimulus. These results show that the features of the target stimulus can be decisive for the appearance of the facilitatory effect of a peripheral spatially noninformative prime stimulus.

Butyrate induces apoptosis in murine macrophages via caspase-3, but independent of autocrine synthesis of tumor necrosis factor and nitric oxide

We demonstrated that 4 mM butyrate induces apoptosis in murine peritoneal macrophages in a dose- and time-dependent manner as indicated by studies of cell viability, flow cytometric analysis of annexin-V binding, DNA ladder pattern and the determination of hypodiploid DNA content. The activity of caspase-3 was enhanced during macrophage apoptosis induced by butyrate and the caspase inhibitor z-VAD-FMK (100 µM) inhibited the butyrate effect, indicating the major role of the caspase cascade in the process. The levels of butyrate-induced apoptosis in macrophages were enhanced by co-treatment with 1 µg/ml bacterial lipopolysaccharide (LPS). However, our data indicate that apoptosis induced by butyrate and LPS involves different mechanisms. Thus, LPS-induced apoptosis was only observed when macrophages were primed with IFN-gamma and was partially dependent on iNOS, TNFR1 and IRF-1 functions as determined in experiments employing macrophages from various knockout mice. In contrast, butyrate-induced macrophage apoptosis was highly independent of IFN-gamma priming and of iNOS, TNFR1 and IRF-1 functions.

The modulation of simple reaction time by the spatial probability of a visual stimulus

Simple reaction time (SRT) in response to visual stimuli can be influenced by many stimulus features. The speed and accuracy with which observers respond to a visual stimulus may be improved by prior knowledge about the stimulus location, which can be obtained by manipulating the spatial probability of the stimulus. However, when higher spatial probability is achieved by holding constant the stimulus location throughout successive trials, the resulting improvement in performance can also be due to local sensory facilitation caused by the recurrent spatial location of a visual target (position priming). The main objective of the present investigation was to quantitatively evaluate the modulation of SRT by the spatial probability structure of a visual stimulus. In two experiments the volunteers had to respond as quickly as possible to the visual target presented on a computer screen by pressing an optic key with the index finger of the dominant hand. Experiment 1 (N = 14) investigated how SRT changed as a function of both the different levels of spatial probability and the subject's explicit knowledge about the precise probability structure of visual stimulation. We found a gradual decrease in SRT with increasing spatial probability of a visual target regardless of the observer's previous knowledge concerning the spatial probability of the stimulus. Error rates, below 2%, were independent of the spatial probability structure of the visual stimulus, suggesting the absence of a speed-accuracy trade-off. Experiment 2 (N = 12) examined whether changes in SRT in response to a spatially recurrent visual target might be accounted for simply by sensory and temporally local facilitation. The findings indicated that the decrease in SRT brought about by a spatially recurrent target was associated with its spatial predictability, and could not be accounted for solely in terms of sensory priming.

Relative contribution of expectancy and immediate arousal to the facilitatory effect of an auditory accessory stimulus

An auditory stimulus speeds up a digital response to a subsequent visual stimulus. This facilitatory effect has been related to the expectancy and the immediate arousal that would be caused by the accessory stimulus. The present study examined the relative contribution of these two influences. In a first and a third experiment a simple reaction time task was used. In a second and fourth experiment a go/no-go reaction time task was used. In each of these experiments, the accessory stimulus preceded the target stimulus by 200 ms for one group of male and female volunteers (G Fix). For another group of similar volunteers (G Var) the accessory stimulus preceded the target stimulus by 200 ms in 25% of the trials, by 1000 ms in 25% of the trials and was not followed by the target stimulus in 50% of the trials (Experiments 1a and 1b) or preceded the target stimulus by 200 ms in 6% of the trials and by 1000 ms in 94% of the trials (Experiments 2a and 2b). There was a facilitatory effect of the accessory stimulus for G Fix in the four experiments. There was also a facilitatory effect of the accessory stimulus at the 200-ms stimulus onset asynchrony for G Var in Experiments 1a and 1b but not in Experiments 2a and 2b. The facilitatory effects observed were larger in the go/no-go task than in the simple task. Taken together, these results suggest that expectancy is much more important than immediate arousal for the improvement of performance caused by an accessory stimulus.

Linking immunity and hematopoiesis by bone marrow T cell activity

Two different levels of control for bone marrow hematopoiesis are believed to exist. On the one hand, normal blood cell distribution is believed to be maintained in healthy subjects by an "innate" hematopoietic activity, i.e., a basal intrinsic bone marrow activity. On the other hand, an "adaptive" hematopoietic state develops in response to stress-induced stimulation. This adaptive hematopoiesis targets specific lineage amplification depending on the nature of the stimuli. Unexpectedly, recent data have shown that what we call "normal hematopoiesis" is a stress-induced state maintained by activated bone marrow CD4+ T cells. This T cell population includes a large number of recently stimulated cells in normal mice whose priming requires the presence of the cognate antigens. In the absence of CD4+ T cells or their cognate antigens, hematopoiesis is maintained at low levels. In this review, we summarize current knowledge on T cell biology, which could explain how CD4+ T cells can help hematopoiesis, how they are primed in mice that were not intentionally immunized, and what maintains them activated in the bone marrow.

Connections: can the 20th century coronary heart disease epidemic reveal something about the 1918 influenza lethality?

This essay proposes that the ecologic association shown between the 20th century coronary heart disease epidemic and the 1918 influenza pandemic could shed light on the mechanism associated with the high lethality of the latter. It suggests that an autoimmune interference at the apoB-LDL interface could explain both hypercholesterolemia and inflammation (through interference with the cellular metabolism of arachidonic acid). Autoimmune inflammation, then, would explain the 1950s-60s acute coronary events (coronary thrombosis upon influenza re-infection) and the respiratory failure seen among young adults in 1918. This hypothesis also argues that the lethality of the 1918 pandemic may have not depended so much on the 1918 virus as on an immune vulnerability to it, possibly resulting from an earlier priming of cohorts born around 1890 by the 1890 influenza pandemic virus.

Evidence for divided automatic attention

A long-standing debate in the literature is whether attention can form two or more independent spatial foci in addition to the well-known unique spatial focus. There is evidence that voluntary visual attention divides in space. The possibility that this also occurs for automatic visual attention was investigated here. Thirty-six female volunteers were tested. In each trial, a prime stimulus was presented in the left or right visual hemifield. This stimulus was characterized by the blinking of a superior, middle or inferior ring, the blinking of all these rings, or the blinking of the superior and inferior rings. A target stimulus to which the volunteer should respond with the same side hand or a target stimulus to which she should not respond was presented 100 ms later in a primed location, a location between two primed locations or a location in the contralateral hemifield. Reaction time to the positive target stimulus in a primed location was consistently shorter than reaction time in the horizontally corresponding contralateral location. This attentional effect was significantly smaller or absent when the positive target stimulus appeared in the middle location after the double prime stimulus. These results suggest that automatic visual attention can focus on two separate locations simultaneously, to some extent sparing the region in between.