Soil microstructure alterations induced by land use change for sugarcane expansion in Brazil

Land use change (LUC) alters soil structure and, consequently, the functions and services provided by these soils. Conversion from extensive pasture to sugarcane is one of the largest land transitions in Brazil as a result of the growth of the domestic and global demands of bioenergy. However, the impacts of sugarcane expansion on the soil structure under extensive pasture remains unclear, especially when considering changes at the microscale. We investigated whether LUC for sugarcane cultivation impacted soil microstructure quality. Undisturbed soil samples were taken from two soil layers (0–10 and 10–20 cm) under three contrasting land uses (native vegetation—NV, pasture—PA and sugarcane—SC) in three different locations in the central-southern Brazil. Oriented thin sections (30 μm) were used for micromorphological analysis. The total area of pores decreased following the LUC in the following order: NV > PA > SC in both soil layers. The area of large complex packing pores (>0.01 mm²) also decreased with the LUC sequence: NV>PA>SC. Qualitative and semi-quantitative micromorphological analysis confirmed porosity reduction was driven by the decrease in complex packing pores and that biological features decreased in the same LUC sequence as the quantitative parameters. Therefore, LUC for sugarcane expansion reduced microscale soil porosity, irrespectively of soil type and site-specific conditions, indicating that the adoption of more sustainable management practices is imperative to preserve soil structure and sustain soil functions in Brazilian sugarcane fields.     

PCR-based diagnosis for detection of Leishmania in skin and blood of rodents from an endemic area of cutaneous and visceral leishmaniasis in Brazil

The technique of polymerase chain reaction (PCR) associated to hybridization was used to screen 123 samples collected from wild and synanthropic rodents captured in a cutaneous and visceral leishmaniasis endemic area in the State of Minas Gerais, Brazil. The detection of Leishmania spp in naturally infected rodents is of fundamental importance for incriminating them as possible reservoir hosts of the diseases in Minas Gerais. A total of 62 specimens belonging to wild (Thrichomys apereoides, Oryzomys subflavus, Galea spixii, Bolomys lasiurus and Wiedomys pyrrhorhinos) and synanthropic (R. rattus) rodent species were captured in different ecotopes. Blood and skin samples were submitted for PCR analyses followed by molecular hybridization with specific probes for the three Leishmania-species complexes. Fifteen samples were found positive after PCR-hybridization and identified as follows: nine belonging to the L. mexicana complex, three to the L. braziliensis complex and three to the L. donovani complex. Positive PCR results were found in 11 out of the 61 (18%) blood samples and in four out of the 62 (6.4%) skin fragments screened. R. rattus and T. apereoides were the most abundant species in the area also presenting high prevalence of natural infection. The presence of parasite DNA belonging to L. braziliensis, L. mexicana and L. donovani complexes was confirmed in several individuals of a rodent species, R. rattus. This work is the first report of the detection of L. (L.) chagasi in a naturally infected T. apereoides. The utility of filter paper as a substrate for PCR analyses and the efficacy of the procedure associated to the hybridization is emphasized.     

Evaluation of immune response and performance of silver catfish fed functional linseed fibres in response to hypoxia stress

This study was conducted to evaluate the immunostimulating activity and growth promoting of diets supplemented with different rations of soluble and insoluble linseed fibre to Rhamdia quelen under hypoxia‐induced acute stress. For this reason, soluble and insoluble fractions of linseed fibre were concentrated separately and combined into four ratios (1:0.5; 1:1; 1:2 and 1:4), which were added to the diets of silver catfish (6.43 ± 0.12 g) and evaluated in a biological assay, along with a control diet (without addition of linseed fibre). After being fed the experimental diets for 45 days, specimens of silver catfish were submitted to hypoxia‐induced acute stress. They were kept out of water for 60 s. Immediately afterwards, blood and cutaneous mucus were collected for subsequent determination of immunological indicators and stress. After stress, the fish were weighed and measured for performance parameter calculation. The experimental design was completely randomized with five treatments and four replications. The data underwent analysis of variance and the means were compared by Tukey's test (p < .05). The fish fed diets containing the 1:2 and 1:4 soluble:insoluble fibre ratios, showed higher total protein content, globulin, plasma alkaline phosphatase activity, and performance in addition to higher mucoprotein content in the cutaneous mucus of the fish. Regardless of their ratio in the diet, linseed fibre provided higher plasma levels of total immunoglobulins and reduction in cortisol levels. The 1:1, 1:2 and 1:4 diets led to higher levels of total immunoglobulins and alkaline phosphatase activity in cutaneous mucus. The results indicate that linseed fibre has a stress‐ reduction, immunostimulant and a growth promoter effect on silver catfish. The 1:2 or 1:4 soluble: insoluble fibre ratios provided greater stimulation of the target immunological indicators and performance.     

Managing threats and restoring wetlands within catchments of the Great Barrier Reef,Australia

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Development of a Suitable Maintenance Diet for Anodonta cygnea

Selenastrum, Chlorella and the Cyanophyta groups, important components of the phytoplankton in the natural habitat of Anodonta cygnea in Mira Lagoon, were used separately as experimental diet for Anodonta cygnea. To assess the effects of the different diets, several organic and inorganic compounds of the haemolymph and extrapallial fluid were measured. Protein content was significantly reduced with experimental Non Feed, and carbohydrate content with Non Feed, Selenastrum, Chlorella , and Cyanophyta diets compared to the control in the lagoon. Lipid contents in body fluids were similar among the different diet groups, with the exception of the Chlorella diet, which showed a higher value. In all diets, the inorganic elements, magnesium and chloride, presented a non-significant variation profile. The concentration of sodium and potassium was significantly affected in Selenastrum and Chlorella diets, observing in the Non Feed diet a minimum value for potassium. The non-significant variation of osmolality suggests the presence of a specific osmotic regulatory mechanism independent of the diet. A particular regulation mechanism seems to exist for both calcium and manganese ion inducing similar profiles for all experimental diets with higher contents in Selenastrum and Cyanophyta diets, respectively. The higher calcium ion concentration appears associated with lower protein-carbohydrate contents, probably due to weak calcium aggregation and deposition mechanism, except for the control and Mixture diets. In general, the concentrations of organic and inorganic compounds in the body fluids of Mixture-fed A. cygnea , were more similar to those found in the control diet group. This suggests that an equal mixture of the three algae, Selenastrum, Chlorella , and Cyanophyta, is more appropriate diet to provide the necessary nutrients for a normal maintenance of A. cygnea in the wild.     

The aspartate aminotransferase family in conifers: biochemical analysis of a prokaryotic-type enzyme from maritime pine

Plant aspartate aminotransferase (AAT, EC 2.6.1.1) plays a key role in primary nitrogen assimilation, the transfer of reducing equivalents and the interchanges of carbon and nitrogen pools between subcellular compartments. We investigated the AAT family in conifers using maritime pine as the experimental model. Genes for cytosolic, mitochondrial and two plastidic isoenzymes (eukaryotic- and prokaryotic-types) were identified and their deduced amino acid sequences compared. The primary structure of the eukaryotic-type enzymes is quite well conserved, whereas the prokaryotic-type AAT is highly divergent (15% of identity). These molecular data were confirmed by the absence of immunological cross-reactivity between the two types of native AATs. The mature prokaryotic-type polypeptide was overexpressed in Escherichia coli, and the native enzyme was purified to apparent homogeneity and its molecular properties determined. The fully active recombinant holoenzyme showed highest catalytic activity at 50-60 degrees C and was moderately thermostable, retaining about 50% of its activity after incubation at 70 degrees C for 5-10 min. The presence of pyridoxal 5'-phosphate significantly increased the thermostability of the enzyme. These molecular characteristics were exploited to develop a rapid protocol for the purification of this prokaryotic-type enzyme from pine cotyledons. The results will be useful for studying aspartate and amino acid metabolism in trees.     

Pilot Study Investigating Fecal Shedding of Salmonella spp. by Horses Used in Competition

This pilot study was performed to determine the need for future investigation of the effect of transportation, environmental changes, and athletic competition on fecal shedding of Salmonella spp. in sport horses. Fecal samples were collected once daily from 20 healthy horses that were competing in National Collegiate Athletic Association equestrian event that occurred over a 3-day period. The horses were divided into four groups with five horses per group. The groups were divided based on travel distance. Fresh fecal samples were collected daily and cultured for Salmonella spp., through bacterial culture, for a minimum of 3 days for three groups that traveled to compete and for 15 days for a group that was housed at the competition location. All fecal samples were negative for Salmonella spp. Although this was a pilot study with a small sample size and limited collection days, the results of this study question the effects of the stress of transportation, new environment, and athletic activity on fecal shedding of Salmonella spp. in horses. A larger study, however, is needed to further investigate these findings.     

Descriptive morphometry and stereology in accessing the testis structure and function of the marsupial Philander frenatus (Olfers, 1818) (Didelphimorphia: Didelphidae)

Philander frenatus is an important marsupial for the maintenance and conservation of the Atlantic Rainforest, however, it has biological characteristics that are still little explored. The study of the reproductive biology is an important key to understand the species reproductive strategies and to improve the development of conservation and management activities. The present study aimed to conduct a histological and morphometric investigation of the testis structure and function of P. frenatus. The average body and testicular weight were 445 g and 0.74 g, respectively, with a gonadosomatic index of 0.17%. The seminiferous tubules occupying 64.95% of the organ, totalising 9.26 m per gram of testis. The tubulesomatic and epitheliumsomatic indexes were 0.10% and 0.07%, respectively. Philander frenatus showed cell loss of approximately 98% during the proliferative phase and the spermatogenic yield was 10.3 cells. The high loss during the mitotic phase contributed to the low spermatogenic yield. The testicular parenchyma was composed of 35% of intertubular components, one of the highest proportions observed in mammals. Leydig cells were responsible for approximately 25% of the testes, followed by lymphatic space (6.44%), blood vessels and connective tissue (4% together). The organisation of the intertubular components resembles the Fawcett III category. The volume and number of Leydig cell per gram of testis were 2,627.12 µm³ and 91.28 × 10⁶ cells, respectively. High investment in the intertubular compartment, specifically number and volume of Leydig cells in P. frenatus is consistent with territorial behaviour and polygynic mating system, which have greater androgenic capacity.     

Cryopreservation of llama semen using a combination of permeable cryoprotectants

Semen cryopreservation is not available for massive use in South American Camelids (SACs) due to the lack of an efficient protocol and the low pregnancy rates obtained with artificial insemination (AI). The use of a single cryoprotectant (CP) is commonly used in SACs frozen semen. The objective of the study was to evaluate the combined cryoprotective capacity of two permeable CPs at different stages of the cryopreservation protocol in llama semen. Sixteen ejaculates from 4 llama males were analysed, and sperm quality was assayed in raw semen, at 5°C, after equilibration of samples with the CPs and when samples were thawed. The following CPs and combination were used: 6% glycerol (GL), 6% dimethylformamide (DMF) and the combination of both CPs: 3% GL and 3% DMF. A Kruskal–Wallis test and an experimental factorial design, considering one factor with four levels (raw semen, 6% GL, 6% DMF and GL/DMF), were used. Total sperm motility and live sperm with intact acrosomes remained unchanged after equilibration of samples (p > .05). A significant decrease in the percentage of functional membrane, motile and live sperm with intact acrosomes was observed when samples were thawed (GL, DMF and GL/DMF). Nevertheless, the cryopreservation protocols used preserved sperm DNA quality; thus, sperm chromatin condensation and DNA fragmentation were unaffected (p > .05) when GL, DMF and GL/DMF were used. To conclude, no superiority was found between the use of a single or a combination of permeable cryoprotectants to freeze llama semen.