Effects of midazolam before or after alfaxalone for co-induction of anaesthesia in healthy dogs

Objective

To study the effect of alternating the order of midazolam and alfaxalone administration on the incidence of behavioural changes, alfaxalone induction dose and some cardiorespiratory variables in healthy dogs.

Elevation and infiltration in a level basin. II. Impact on soil water and corn yield

The spatial variability of irrigation water recharge and crop yield is affected by a number of factors. Soil surface elevation, infiltration and soil water MAD are the most relevant related to level-basin irrigation. Measurements of soil water recharge (using a neutron probe) were compared to estimates based on ring infiltrometers and observations of the opportunity time. Estimates of cumulative infiltration (ECI) were obtained, separating the variability of infiltration and opportunity time (largely determined by elevation). Soil surface elevation was correlated with measured recharge, grain yield and total dry matter. A correlation was found between infiltration and the measurements of water recharge. While soil surface elevation can be regarded as a management variable, little can be done to reduce the variability of infiltration. Distribution uniformities from ECI were about 20% higher than those obtained from measurements of water recharge. Seasonal uniformity was only marginally higher than average uniformity, confirming the low random component of water recharge in level-basin irrigation. Deep percolation was more intense in areas with low MAD. This finding emphasizes the relevance of characterizing the variability of soil physical properties in surface irrigation. Extrapolation of the results of this research to field-scale irrigation basins should take into account the methodology used: in particular, the reduced scale of the experimental level basin. Received: 24 February 1998     

Field test of an automatic controller for solid-set sprinkler irrigation

The application of new technologies to the control and automation of irrigation processes is becoming very important, and the automatic generation and execution of irrigation schedules is receiving growing attention. In this paper, a prototype automatic irrigation controller for solid-set systems is presented. The device is composed by software and hardware developments. The software was named Ador-Control and it integrates five modules: the first four modules simulate drop trajectories, water distribution, crop growth and yield, and the last module ensures bidirectional communication between software and hardware. Decision variables based on soil, crop, and irrigation performance indexes were used to make real-time irrigation decisions. A randomized experimental design was designed to validate the automatic controller over a corn crop during two seasons. Three treatments were analyzed: T0) manual programmer or advanced farmer; T1) automatic scheduling controlled by indexes based on soil simulated water content and irrigation performance; and T2) advanced automatic scheduling controlled by simulated thresholds of crop and irrigation indexes. Experimental results in 2009 and 2010 indicated that automatic irrigation treatments resulted in similar maize yield but using less water than manual irrigation (10 % between T0 and T1, and 18 % between T0 and T2).     

Effects of Land Use Conversion from Native Forests to Exotic Plantations on Nitrogen and Phosphorus Retention in Catchments of Southern Chile

In six small catchments located at the Cordillera de la Costa in southern Chile (40° S), concentrations and fluxes of NO₃-N, NH₄-N, organic-N, total-N and total-P in bulk precipitation and runoff water were measured. The main objective of this study was to compare nitrogen and phosphorus retention of catchments with varying land cover of native forest and exotic plantations, in order to evaluate possible effects of land use change. Nitrate-N was the dominant fraction (>50%) of nitrogen loss, especially in the catchments dominated by exotic plantations. In the catchment with native forests, NO₃ ^? only contributed with 34% of the nitrogen loss and DON was the main output with 55%. Annual NO₃ ^? export was lower in the catchment with native forest compared to the catchments with exotic plantations where the streamflow output exceed the precipitation input. Average inputs of total-N were 2.6 kg ha^?1 year^?1 (DIN?=?1.4 kg ha^?1 year^?1, DON?=?1.2 kg ha^?1 year^?1) and outputs were 1.7 kg ha^?1 year^?1 (DIN?=?1.2 kg ha^?1 year^?1, DON?=?0.5 kg ha^?1 year^?1). Annual retention of total nitrogen fluctuated between 61% in a catchment dominated by native forests to 15% in catchments dominated by exotic plantations of Eucalyptus sp. Nitrogen retention was positively related with native forest coverage. The N retention capacity of the catchments could be both attributed to consequences of clear cutting practices and differences in vegetation cover.     

Integration of two simple models in a geographical information system to evaluate salinization risk in irrigated land of the Valencian Community, Spain

Abstract. Salt affected soil is one of the main problems decreasing the productivity of irrigated agriculture in the Mediterranean area. Simulation models in combination with geographical information systems (GISs) could be used to evaluate the risk of salinization at a regional scale. In this study, two logical models (Pla and Riverside) were combined in a GIS to evaluate the risk of soil salinity and sodicity in the irrigated agriculture of the Valencian Community, Spain. Simple models were chosen so that they could be used at a regional scale. Before running them in a GIS framework, a soil and irrigation water survey was conducted to validate the models with observed data. The Pla model fitted observed data better than Riverside guidelines, probably because parameters of water quality, soil and climate were considered by the Pla model. The resulting maps indicated that the soils most affected by salts are those located in the south of study area, owing to the arid climate, and those areas near the coast due to saline intrusion. Close to 42% of the irrigated area was predicted to be somewhat affected by salinization. The regional-scale soil salinity assessment presented here for the Valencian Community is the first to be made for this region and will be useful in targeting critical areas that may require special management.     

Phytochemical induction by herbivores could affect quality of essential oils from aromatic plants

Plant tissues may show chemical changes following herbivory. In aromatic plants such changes could affect the specific compounds on which commercial exploitation is based. This possibility was analyzed for Mintosthachys mollis, a member of the Lamiaceae native to Central Argentina with medicinal and aromatic uses in the region, and two types of insect herbivores: a leaf miner and a gall insect. Analysis of the essential oils of mined/undamaged leaves, as well as leaves from stems with and without galls, revealed changes in concentrations of the two main monoterpenes. A decrease in pulegone concentration was associated with both types of insect damage, whereas menthone increased significantly only in mined leaves. Inducible chemical changes in aromatic and medicinal plants may be common and widespread; their economic implications deserve investigation.     

Litter decomposition of Acacia auriculiformis Cunn. Ex Benth. and Acacia mangium Willd. under coconut trees on quaternary sandy soils in Ivory Coast

Litter decomposition of Acacia auriculiformis and Acacia mangium on sandy soil under coconut trees was studied in a field trial using the litterbag technique. The study was conducted during 2001 and 2002 in Ivory Coast. Litterbags containing 450 g of dried leaves and 450 g of dried small stems were set up in two coconut plantations of different ages, 3 and 20 years old. Dry matter weight and concentrations of total nitrogen (N), phosphorus (P), potassium (K), magnesium (Mg), and C/N ratio were determined at 90, 180, 270, and 360 days. The decomposition rate constant (k) and the half-life time decomposition of dry matter (T ¹/₂) were calculated. The study showed that A. auriculiformis and A. mangium have the same rate of decomposition on each coconut plantation. The k value varied from −1.592 day⁻¹ to −1.492 day⁻¹. The half-life time decomposition value of dry matter (T ¹/₂) ranged from 283 to 301 days. Nitrogen was released between 0 and 180 days with an N concentration for A. auriculiformis and A. mangium varying from 2.03 to 1.80% and 1.97 to 1.79%, respectively. After 180 days, the litters immobilized N. Phosphorus and Mg were released faster from A. mangium than from A. auriculiformis. A positive correlation was found between the N concentration of each Acacia species and the litter dry weight at 90 and 180 days. Likewise, C/N ratio was positively correlated with litter dry weight at 90 days.     

Ghrelin antagonist D-Lys3-GHRP-6 counteract ghrelin effects in bovine cumulus-oocytes complexes matured in vitro

Ghrelin is a gut hormone related to energy balance and reproductive functions. The aim of this study was to evaluate the effect of ghrelin antagonist D-Lys3-GHRP-6 (GA) as a potential agent that prevents ghrelin effects during bovine oocyte maturation on progesterone production, cumulus cell (CC) viability, CC DNA damage and embryo development and hatching rates. Ghrelin's potential to induce oxidative stress in cumulus-oocyte complexes (COC) was also evaluated. COCs were cultured for 24 hr in medium without supplementation (C) or supplemented with 60 pM ghrelin (Ghrelin60), Ghrelin60 + 20 pM GA (GA20), Ghrelin60 + 60 pM GA (GA60) or Ghrelin60 + 100 pM GA (GA100) for experiment I. For experiment II, C and Ghrelin60 treatments were used. Differences between C and Ghrelin60 and the linear or quadratic association between GAs on Ghrelin60 were evaluated. Results demonstrated that Ghrelin60 increased progesterone concentration, reduced CC viability, induced CC DNA damage and decreased blastocyst and hatching rate compared with C (p < .05). GA20, GA60 and GA100 had a linear effect on CC genetic damage index (p ≤ .05) and a quadratic effect on CC viability (p < .01). GA20 counteracted the low hatching rate produced by Ghrelin60. However, GAs did not counteract progesterone concentration and blastocyst rate (p ≥ .21). GRH60 did not differ from C in the oxidative status (p ≥ .19). Our study highlights that GA could prevent the negative effects of ghrelin during bovine IVM.     

Spawning aggregation behaviour in the Creole perch,Percichthys trucha (Percichthyidae): A target species for conservation

1. Habitat fragmentation and loss threaten freshwater biodiversity worldwide. Habitats that are essential as fish spawning and nursery sites are critical, and must be identified for conservation purposes. Littoral zones within Patagonian lakes, especially shallow vegetated areas, represent important areas for the Creole perch, Percichthys trucha.
2. Spawning behaviour has been little studied, so it is not known whether these movements are performed in groups. A particular area of a deep lake in northern Patagonia was studied to identify the environmental conditions under which spawning occurs, and to analyse spawning aggregation behaviour in relation to the lunar cycle.
3. To identify spawning sites, spawning occurrence time, and the environmental parameters that determine it, fish capture data were analysed. Underwater cameras were also set up at three depth strata in the shallow zone to detect spawning aggregation behaviour. Aggregation was scored as the greatest number of individuals present in a single frame, and the number present per depth stratum. The relationship between the lunar cycle and Creole perch abundance by depth was then determined.
4. This is the first visual record of a spawning bed and the spawning aggregation behaviour of Creole perch in Patagonian lakes. The abundance of mature Creole perch in the shallow strata during the austral spring suggests that vegetated areas constitute spawning sites. Spawning aggregation takes place at a shallow depth 2 days before the full moon.
5. As the reproductive behaviours of Creole perch are important phenomena in the life history of the species, the results of this study have important implications for conservation and management.

     

Bioactivity of essential oils from leaves and bark of Laurelia sempervirens and Drimys winteri against Acyrthosiphon pisum

BACKGROUND: The pea aphid, Acyrthosiphon pisum (Harris), is a cosmopolitan pest that attacks a wide range of legume crops and vectors important plant virus diseases. In this project, essential oils from the leaf (L) and bark (B) of Laurelia sempervirens (Ruiz & Pavón) Tul. (L) and Drimys winteri JR Forster & G Forster (D) were extracted, and their deterrent and insecticidal activities were tested under laboratory conditions. RESULTS: By use of GC‐MS, safrole was found as the main constituent in LL and LB oils, while the main constituents were more diverse in DL and DB oils. In the deterrent bioassays with A. pisum under choice conditions, the four oils were active, with LL being the most active, followed by LB, DB and DL. The respective deterrence indices were 1.0, 0.89, 0.87 and 0.46 when aphids were exposed for 24 h to 4 µL mL^?1. Although there was no aphid mortality when oils were sprayed on faba bean leaves before aphid infestation, there was 58 and 42% mortality when settled aphids were directly sprayed with 4.0 µL mL^?1 of LL and LB respectively; DB and DL oils caused ≤18% mortality. In a third series, the essential oils of LL and LB caused 100% mortality when applied at a dose of 64 µL L^?1 air by fumigation to faba bean plants infested with A. pisum; at the same dose, DB and DL oils caused 68 and 63% mortality respectively. When fumigation was limited to 2 h, the respective LC₅₀ values for LL and LB oils were 10.6–14.3 µL L^?1 air and 9.8–13.2 µL L^?1 air. CONCLUSION: Because of their high deterrent and insecticidal activities, the essential oils from leaf and bark of L. sempervirens may be explored as potential natural aphicides. Copyright © 2010 Society of Chemical Industry