Tillering dynamics in pastures of guinea grass subjected to grazing severities under intermittent stocking

This experiment was carried out to analyze the tillering dynamics of the species Panicum maximum cv. Mombaca subjected to three post-grazing heights: residue of 30 cm (30); residue of 50 cm (50); and residue of 50 cm during spring and summer, lowered to 40 cm in the first fall season grazing and to 30 cm in the following grazing cycle, resuming to 50 cm after the first grazing of the following spring season (50-30). Grazings were initiated whenever the swards intercepted 95% of the incident light. The post-grazing heights were allocated in the experimental units in a completely randomized block design with three replications. The density of basal tillers did not vary between the residual heights evaluated. Swards managed with variable residual height (50-30) presented higher rates of appearance and mortality of basal tillers during the summer of 2007, indicating high tiller renovation. Regardless of the post-grazing height evaluated, lower rates of appearance of basal tillers were found in the spring of 2006. The stability index of guinea grass cv. Mombaca was close to 1.0 throughout the experimental period. Swards managed with variable post-grazing present structural changes able to improve the regrowth vigor, which may be important to maximize the use of the forage species in the production system.

Morphogenesis in guinea grass pastures under rotational grazing strategies

This study was conducted in order to evaluate the morphogenetic and structural characteristics of guinea grass cv. Mombasa under three post-grazing heights (intense - 30 cm, lenient - 50 cm and variable - 50 in spring-summer and 30 cm in autumn-winter) when sward light interception reached 95% during regrowth. Post-grazing heights were allocated to experimental units (0.25 ha) in a completely randomized block design with three replications. Post-grazing heights affected only leaf elongation rate and the number of live leaves. Pastures managed with variable post-grazing height showed higher leaf elongation rate in the summer of 2007. This management strategy also resulted in a higher number of live leaves. During the spring of 2006, plants showed lower leaf elongation rate, leaf appearance rate and number of live leaves, and greater phyllochron and leaf lifespan. In contrast, during the summer of 2007, the leaf appearance rate, leaf elongation rate, number of live leaves, and final leaf length were greater while phyllochron, stem elongation rate, and leaf senescence rate were lower. The management of the guinea grass cv. Mombasa with intense or variable post-grazing height throughout the year seems to represent an interesting management target, in terms of leaf appearance rate and number of live leaves.

Morphogenetic and structural characteristics of guinea grass tillers at different ages under intermittent stocking

The objective of this research was to assess morphogenetic and structural characteristics of tillers of guinea grass cv. Tanzania at different ages. The pastures of guinea grass were managed in six pasture conditions related to the combination of three frequencies (90, 95, and 99% light interception) and two post-grazing heights (25 and 50 cm). In these six pastures conditions, three tiller ages were evaluated (young, mature, and old). The design was of completely randomized block with three replications. Young tillers exhibited higher leaf appearance rate and leaf elongation rate and, consequently, higher final leaf length and number of live leaves than mature and old tillers, regardless of the pasture condition. On pastures managed with 90 or 95% light interception associated with a post-grazing height of 25 cm, old tillers presented longer leaf lifespan than young and mature ones. There is a progressive reduction in the vigor of growth of pastures of guinea grass cv. Tanzania with advancing tiller age.

Deep chlorophyll maximum and upper ocean structure interactions: Case of the Guinea Thermal Dome

Deep Chlorophyll Maximum (DCM) modifies the upper ocean heat capture distribution and thus impacts water column temperature and stratification, as well as biogeochemical processes. This energetical role of the DCM is assessed using a 1 m-resolution 1D physical-biogeochemical model of the upper ocean, using climatological forcing conditions of the Guinea Dome (GD). This zone has been chosen among others because a strong and shallow DCM is present all year round. The results show that the DCM warms the seasonal thermocline by +2 degrees C in September/October and causes an increase of heat transfer from below into the mixed layer (ML) by vertical diffusion and entrainment, leading to a ML warming of about 0.3 degrees C in October. In the permanent thermocline, temperature decreases by up to 2 degrees C. The result is a stratification increase of the water column by 0.3 degrees C m(-1) which improves the thermocline realism when compared with observations. At the same time, the heating associated with the DCM is responsible for an increase of nitrate (+300%, 0.024 mu M), chlorophyll (+50%, 0.02 mu g l(-1)) and primary production (+45%: 10 mg C m(-2) day(-1)) in the ML during the entrainment period of October. The considered concentrations are small but this mechanism could be potentially important to give a better explanation of why there is a significant amount of nitrate in the ML. The mechanisms associated with the DCM presence, no matter which temperature or biogeochemical tracers are concerned, are likely to occur in a wide range of tropical or subpolar regions; in these zones a pronounced DCM is present at least episodically at shallow or moderate depths. These results can be generalized to other thermal dome regions where relatively similar physical and biogeochemical structures are encountered. After testing different vertical resolutions (10 m, 5 m, 2.5 m, 1 m and 0.5 m), we show that using at least a 1 to vertical resolution model is mandatory to assess the energetical importance of the DCM.

Attenuation of foot pressure during running on four different surfaces: asphalt, concrete, rubber, and natural grass

The practice of running has consistently increased worldwide, and with it, related lower limb injuries. The type of running surface has been associated with running injury etiology, in addition other factors, such as the relationship between the amount and intensity of training. There is still controversy in the literature regarding the biomechanical effects of different types of running surfaces on foot-floor interaction. The aim of this study was to investigate the influence of running on asphalt, concrete, natural grass, and rubber on in-shoe pressure patterns in adult recreational runners. Forty-seven adult recreational runners ran twice for 40 m on all four different surfaces at 12 +/- 5% km . h(-1). Peak pressure, pressure-time integral, and contact time were recorded by Pedar X insoles. Asphalt and concrete were similar for all plantar variables and pressure zones. Running on grass produced peak pressures 9.3% to 16.6% lower (P < 0.001) than the other surfaces in the rearfoot and 4.7% to 12.3% (P < 0.05) lower in the forefoot. The contact time on rubber was greater than on concrete for the rearfoot and midfoot. The behaviour of rubber was similar to that obtained for the rigid surfaces - concrete and asphalt - possibly because of its time of usage (five years). Running on natural grass attenuates in-shoe plantar pressures in recreational runners. If a runner controls the amount and intensity of practice, running on grass may reduce the total stress on the musculoskeletal system compared with the total musculoskeletal stress when running on more rigid surfaces, such as asphalt and concrete.

Dry matter production of Tanzania grass as a function of agrometeorological variables

The objective of this work was to develop and validate linear regression models to estimate the production of dry matter by Tanzania grass (Megathyrsus maximus, cultivar Tanzania) as a function of agrometeorological variables. For this purpose, data on the growth of this forage grass from 2000 to 2005, under dry-field conditions in Sao Carlos, SP, Brazil, were correlated to the following climatic parameters: minimum and mean temperatures, degree-days, and potential and actual evapotranspiration. Simple linear regressions were performed between agrometeorological variables (independent) and the dry matter accumulation rate (dependent). The estimates were validated with independent data obtained in Sao Carlos and Piracicaba, SP, Brazil. The best statistical results in the development and validation of the models were obtained with the agrometeorological parameters that consider thermal and water availability effects together, such as actual evapotranspiration, accumulation of degree-days corrected by water availability, and the climatic growth index, based on average temperature, solar radiation, and water availability. These variables can be used in simulations and models to predict the production of Tanzania grass.

Effects of atrazine and picloram on grass carp: acute toxicity and histological assessment

The aim of this study was to evaluate the acute toxicity of atrazine and picloram separately to grass carp (Ctenopharyngodon idella). Firstly, fingerlings were exposed to nominal concentrations of these herbicides to determine the lethal concentration (LC50) (96 h). After this, the animals were treated with sub-acute concentrations of the herbicides to measure the effects on gill histology. The LC50 (96 h) of the atrazine and picloram were, respectively, 37mg L-1 and 4.4 mgL(-1). Four types of alterations were found in gills exposed to atrazine, which were epithelial lifting, partial cell proliferation, lamellar fusion, and aneurysm. Nominal concentrations of picloram caused epithelial lifting, partial cell proliferation, and lamellar fusion.

The SUCEST-FUN regulatory network database: Designing an energy grass

Modern sugarcane cultivars are complex hybrids resulting from crosses among several Saccharum species. Traditional breeding methods have been employed extensively in different countries over the past decades to develop varieties with increased sucrose yield and resistance to pests and diseases. Conventional variety improvement, however, may be limited by the narrow pool of suitable genes. Thus, molecular genetics is seen as a promising tool to assist in the process of developing improved varieties. The SUCEST-FUN Project (http://sucest-fun.org) aims to associate function with sugarcane genes using a variety of tools, in particular those that enable the study of the sugarcane transcriptome. An extensive analysis has been conducted to characterise, phenotypically, sugarcane genotypes with regard to their sucrose content, biomass and drought responses. Through the analysis of different cultivars, genes associated with sucrose content, yield, lignin and drought have been identified. Currently, tools are being developed to determine signalling and regulatory networks in grasses, and to sequence the sugarcane genome, as well as to identify sugarcane promoters. This is being implemented through the SUCEST-FUN (http://sucest-fun.org) and GRASSIUS databases (http://grassius.org), the cloning of sugarcane promoters, the identification of cis-regulatory elements (CRE) using Chromatin Immunoprecipitation-sequencing (ChIP-Seq) and the generation of a comprehensive Signal Transduction and Transcription gene catalogue (SUCAST Catalogue).

Responses of transplanted native tree species to invasive alien grass removals in an abandoned cattle pasture in the Lacandon region, Mexico

We tested the early performance of 16 native early-, mid-, and late-successional tree species in response to four intensities of grass removal in an abandoned cattle pasture dominated by the introduced, invasive African grass, Cynodon plectostachyus, within the Lacandon rainforest region, southeast Mexico. The increase in grass removals significantly improved the performance of many species, especially of early-and mid-successional species, while performance of late-successional species was relatively poor and did not differ significantly among treatments. Good site preparation and at least one additional grass removal four months after seedling transplant were found to be essential; additional grass removals led to improved significantly performance of saplings in most cases. In order to evaluate the potential of transplanting tree seedlings successfully in abandoned tropical pastures, we developed a "planting risk index", combining field performance measurements and plantation cost estimations. Our results showed a great potential for establishing restoration plantings with many early-and mid-successional species. Although planting risk of late-successional species was considered high, certain species showed some possibilities of acclimation after 18 months and should be considered in future plantation arrangements in view of their long-term contributions to biodiversity maintenance and also to human welfare through delivery of ecosystem services. Conducting a planting risk analysis can help avoid failure of restoration strategies involving simultaneous planting of early-, mid-, and late-successional tree species. This in turn will improve cost-effectiveness of initial interventions in large-scale, long-term restoration programs.

Effects of aerobic exercise on chronic allergic airway inflammation and remodeling in guinea pigs

We evaluated the effects of aerobic exercise (AE) on airway inflammation, exhaled nitric oxide levels (ENO), airway remodeling, and the expression of Thl, Th2 and regulatory cytokines in a guinea pig asthma model. Animals were divided into 4 groups: non-trained and non-sensitized (C), non-sensitized and AE (AE), ovalbumin-sensitized and non-trained (OVA), and OVA-sensitized and AE (OVA + AE). OVA inhalation was performed for 8 weeks, and AE was conducted for 6 weeks beginning in the 3rd week of OVA sensitization. Compared to the other groups, the OVA + AE group had a reduced density of eosinophils and lymphocytes, reduced expression of interleukin (IL)-4 and IL-13 and an increase in epithelium thickness (p < 0.05). AE did not modify airway remodeling or ENO in the sensitized groups (p > 0.05). Neither OVA nor AE resulted in differences in the expression of IL-2, IFN-gamma, IL-10 or IL1-ra. Our results show that AE reduces the expression of Th2 cytokines and allergic airway inflammation and induces epithelium remodeling in sensitized guinea pigs. (c) 2012 Elsevier B.V. All rights reserved.

Chemical characterization and in vitro biological activity of four tropical legumes, Styzolobium aterrimum L., Styzolobium deeringianum, Leucaena leucocephala, and Mimosa caesalpiniaefolia, as compared with a tropical grass, Cynodon spp. for the use in ruminant diets

Leucaena leucocephala (LEU) and three under-utilized tanniferous legumes, Styzolobium aterrimum L. (STA), Styzolobium deeringianum (STD), and Mimosa caesalpiniaefolia Benth (MIC) were chemically characterized and the biological activity of tannins was evaluated using in vitro simulated ruminal fermentation through tannin-binding polyethylene glycol (PEG) and compared with a non-tanniferous tropical grass hay, Cynodon spp. (CYN). The Hohenheim gas test was used and gas production (GP) was recorded at 4, 8, 12, 24, 32, 48, 56, 72, 80, and 96 h incubation with and without PEG. Kinetic parameters were estimated by an exponential model. STA, STD, and LEU contained higher (P < 0.05) crude protein than MIC, which had greater neutral detergent fibre and acid detergent fibre. Total phenols, total tannins, and condensed tannins (CT) were consistently the highest in MIC. Gas production was the lowest from MIC (P < 0.05) and the highest in LEU and STA. MIC + PEG largely reduced (P < 0.05) the lag phase and the fractional rate of fermentation and increased potential GP. Kinetic parameters of STA + PEG and LEU + PEG were not affected. LEU + PEG produced greater gas increment (P < 0.05) than STD + PEG, although both legumes had the same CT. All legumes except MIC were more extensively degraded than CYN. However, fermentation of the legumes was differently affected by the presence and proportions of CT, indigestible fibre or both.

Soil sulfur fractions dynamics and distribution in a tropical grass pasture amended with nitrogen and sulfur fertilizers

Soil sulfur (S) partitioning among the various pools and changes in tropical pasture ecosystems remain poorly understood. Our study aimed to investigate the dynamics and distribution of soil S fractions in an 8-year-old signal grass (Brachiaria decumbens Stapf.) pasture fertilized with nitrogen (N) and S. A factorial combination of two N rates (0 and 600?kg N ha1 y1, as NH4NO3) and two S rates (0 and 60?kg S ha1 y1, as gypsum) were applied to signal grass pastures during 2 y. Cattle grazing was controlled during the experimental period. Organic S was the major S pool found in the tropical pasture soil, and represented 97% to 99% of total S content. Among the organic S fractions, residual S was the most abundant (42% to 67% of total S), followed by ester-bonded S (19% to 42%), and C-bonded S (11% to 19%). Plant-available inorganic SO4-S concentrations were very low, even for the treatments receiving S fertilizers. Low inorganic SO4-S stocks suggest that S losses may play a major role in S dynamics of sandy tropical soils. Nitrogen and S additions affected forage yield, S plant uptake, and organic S fractions in the soil. Among the various soil fractions, residual S showed the greatest changes in response to N and S fertilization. Soil organic S increased in plots fertilized with S following the residual S fraction increment (16.6% to 34.8%). Soils cultivated without N and S fertilization showed a decrease in all soil organic S fractions.

Opioidergic, GABAergic and serotonergic neurotransmission in the dorsal raphe nucleus modulates tonic immobility in guinea pigs

Tonic immobility (TI) is an innate defensive behavior that can be elicited by physical restriction and postural inversion and is characterized by a profound and temporary state of akinesis. Our previous studies demonstrated that the stimulation of serotonin receptors in the dorsal raphe nucleus (DRN) appears to be biphasic during TI responses in guinea pigs (Cavia porcellus). Serotonin released by the DRN modulates behavioral responses and its release can occur through the action of different neurotransmitter systems, including the opioidergic and GABAergic systems. This study examines the role of opioidergic, GABAergic and serotonergic signaling in the DRN in TI defensive behavioral responses in guinea pigs. Microinjection of morphine (1.1 nmol) or bicuculline (0.5 nmol) into the DRN increased the duration of TI. The effect of morphine (1.1 nmol) was antagonized by pretreatment with naloxone (0.7 nmol), suggesting that the activation of pi opioid receptors in the DRN facilitates the TI response. By contrast, microinjection of muscimol (0.5 nmol) into the DRN decreased the duration of TI. However, a dose of muscimol (0.26 nmol) that alone did not affect TI, was sufficient to inhibit the effect of morphine (1.1 nmol) on TI, indicating that GABAergic and enkephalinergic neurons interact in the DRN. Microinjection of alpha-methyl-5-HT (1.6 nmol), a 5-HT2 agonist, into the DRN also increased TI. This effect was inhibited by the prior administration of naloxone (0.7 nmol). Microinjection of 8-OH-DPAT (1.3 nmol) also blocked the increase of TI promoted by morphine (1.1 nmol). Our results indicate that the opioidergic, GABAergic and serotonergic systems in the DRN are important for modulation of defensive behavioral responses of TI. Therefore, we suggest that opioid inhibition of GABAergic neurons results in disinhibition of serotonergic neurons and this is the mechanism by which opioids could enhance TI. Conversely, a decrease in TI could occur through the activation of GABAergic interneurons. (C) 2012 Elsevier Inc. All rights reserved.

Comparison of different delivery systems of DNA vaccination for the induction of protection against tuberculosis in mice and guinea pigs

The great challenges for researchers working in the field of vaccinology are optimizing DNA vaccines for use in humans or large animals and creating effective single-dose vaccines using appropriated controlled delivery systems. Plasmid DNA encoding the heat-shock protein 65 (hsp65) (DNAhsp65) has been shown to induce protective and therapeutic immune responses in a murine model of tuberculosis (TB). Despite the success of naked DNAhsp65-based vaccine to protect mice against TB, it requires multiple doses of high amounts of DNA for effective immunization. In order to optimize this DNA vaccine and simplify the vaccination schedule, we coencapsulated DNAhsp65 and the adjuvant trehalose dimycolate (TDM) into biodegradable poly (DL-lactide-co-glycolide) (PLGA) microspheres for a single dose administration. Moreover, a single-shot prime-boost vaccine formulation based on a mixture of two different PLGA microspheres, presenting faster and slower release of, respectively, DNAhsp65 and the recombinant hsp65 protein was also developed. These formulations were tested in mice as well as in guinea pigs by comparison with the efficacy and toxicity induced by the naked DNA preparation or BCG. The single-shot prime-boost formulation clearly presented good efficacy and diminished lung pathology in both mice and guinea pigs.

Tiller population density and tillering dynamics in marandu palisade grass subjected to strategies of rotational stocking management and nitrogen fertilization

The objective of this experiment was to evaluate tiller population density and the dynamics of the tillering process in marandu palisade grass subjected to strategies of rotational stocking management and nitrogen fertilization. Treatments corresponded to combinations between two targets of pre-grazing conditions (sward surface height of 25 and 35 cm) and two rates of nitrogen application (50 and 200 kg ha-1 year-1), and were allocated to experimental units according to a 2 x 2 factorial arrangement in a randomised complete block design, with four replications. The following response variables were studied: initial (TPDi), intermediate (TPDm) and final (TPDf) tiller population density as well as the rates of tiller appearance (TAR) and death (TDR) and the tiller population stability index (SI). TPDi was similar to all treatments, with differences in tiller population density becoming more pronounced as the experiment progressed, resulting in larger TPDf on swards managed at 25 cm pre-grazing height. Tiller death was larger on swards managed at 35 cm, with differences in tiller appearance being recorded only from February 2010 onwards. Stability of tiller population was higher on swards managed at 25 cm pre-grazing height. Overall, there was no effect of nitrogen on the studied variables, and the most adequate grazing strategy corresponded to the pre-grazing height of 25 cm, regardless of the nitrogen application rate used.