Water-use efficiency of a poplar plantation in Northern China

The water-use efficiency (WUE) of an ecosystem—defined as the gross ecosystem production (GEP) divided by the evapotranspiration (ET)—is an important index for understanding the coupling of water and carbon and quantifying water–carbon trade-offs in forests. An open-path eddy covariance technique and a microclimate measurement system were deployed to investigate the WUE of a poplar plantation ecosystem in the Daxing District of Beijing, China, during the growing seasons in 2006, 2007, and 2008. We found that WUE values changed diurnally, peaking in early morning and showing a minimum between 2 pm and 3 pm. This pattern was regulated by photosynthetically active radiation, saturated vapor pressure deficit, and stomatal opening and closure. WUE had inter-daily variations but no substantial seasonal variation. The WUE decreased with increasing soil water content due to the higher sensitivity of ET than GEP to increased soil moisture. Under moist soil conditions (i.e., relative extractable water content >0.4), GEP was stable and WUE was generally low. These results suggest that the poplar plantation does not effectively use the available soil water for carbon uptake, and that soil moisture is lost to the atmosphere through ET.     

Ionic composition and osmolality of paddlefish (Polyodon spathula, Acipenseriformes) seminal fluid

Changes in ionic composition as Na⁺,K⁺, Ca²⁺ and Mg²⁺, osmolality inseminal fluid, percentage of motile spermatozoaand velocity were investigated in response toCPP and different dosage of LHRHa. The lowestvelocity of sperm was observed after use CPPtreatment. The velocity of spermatozoa,significant main effect of the treatment(P < 0.0001) and the time of sperm collection(P < 0.0104) were evaluated. The osmolality ofseminal fluid was different betweenexperimental groups of LHRHa (48.0–62.7mOsmol.kg^–1) and CPP (33.0–46.3mOsmol.kg^–1) treatments. The osmolalitywas significantly higher on the first day andone-half, then declined on day three, rangingfrom 33.0 to 62.7 mOsmol.kg^–1. Analysisof variance showed significant main effects ofthe treatment (P < 0.0001) and the time ofsperm collection (P < 0.0002) on the osmolalityof seminal fluid. The level of Na⁺ andK⁺ ion was different between experimentalgroups of LHRHa and CPP treatment. The highestconcentration of 11.11 mmol.l^–1 wasobserved at Na⁺ ion. Then theconcentrations declined on the level 1.56, 0.52and 0.36 mmol.l^–1 for K⁺, Ca²⁺and Mg²⁺ ions, respectively. There werehighly positive correlations between osmolalityof seminal fluid and dosage of LHRHa treatment(r = 0.84), velocity of spermatozoa andosmolality of seminal fluid (r = 0.57) andosmolality of seminal fluid and Na⁺concentration at seminal fluid (r = 0.70).Injection with LHRHa increased quality of spermas velocity of sperm, level of Na⁺,K⁺ and osmolality at seminal fluidcompared to CPP treatments.     

The effects of hypoxia,in vivo,on red blood cell β-adrenoceptors in the rainbow trout,Oncorhynchus mykiss

Rainbow trout, Oncorhynchus mykiss, were exposed to 48h of environmental hypoxia (water partial pressure of oxygen = 8.0 kPa) at either 5 or 15°C. Blood was sampled during hypoxia via a dorsal aorta cannula to measure arterial blood partial pressure of oxygen and plasma catecholamine concentrations. After 48h, the number (B_max) and dissociation constant (K_d) of red blood cell surface -adrenoceptors were determined using a radioligand-displacement binding assay. At 5°C, plasma catecholamine levels were elevated at 24h whereas at 15°C, levels were elevated at 48h. At either temperature, following 48h of hypoxia, there was no change in B_max or K_d of red blood cell surface -adrenoceptors, compared to normoxic control fish. This study demonstrates that chronic exposure to moderate hypoxia does not affect the number or affinity of cell surface -adrenoceptors on trout red blood cells.     

Practical starter pig amino acid requirements in relation to immunity,gut health and growth performance

Immune system activation begins a host of physiological responses. Infectious agents are recognized by monocytes and macrophages which in turn stimulate cytokine production. It is the hormone-like factors called cytokines that orchestrate the immune response. The classic responses observed with immune system activation and cytokine production include： anorexia, fever, lethargy, recruitment of other immune cells, and phagocytosis. While production of immune system components is known to require some amino acids, increases in amino acid requirements are more than offset by the associated decrease in protein accretion and increased muscle protein degradation that also accompanies immune system activation. However, the biggest impact of cytokine production is a decrease in feed intake. Therefore, as feed intake decreases, the energy needed to drive protein synthesis is also decreased. This suggests that diets should still be formulated on a similar calorie：lysine ratio as those formulated for non-immune challenged pigs. The evidence is sparse or equivocal for increasing nutrient requirements during an immune challenge. Nutritionists and swine producers should resist the pressure to alter the diet, limit feed, or add expensive feed additives during an immune challenge. While immune stimulation does not necessitate changes in diet formulation, when pigs are challenged with non-pathogenic diarrhea there are potential advantages on gut health with the increased use of crystalline amino acids rather than intact protein sources （i.e., soybean meal）. This is because reducing crude protein decreases the quantity of fermentable protein entering the large intestine, which lowers post weaning diarrhea. It also lowers the requirement for expensive specialty protein sources or other protein sources such as soybean meal that present immunological challenges to the gut. The objective of this review is two-fold. The first is to discuss immunity by nutrition interactions, or lack thereof, and secondly, to review amino acid re     

Practical starter pig amino acid requirements in relation to immunity,gut health and growth performance

Immune system activation begins a host of physiological responses. Infectious agents are recognized by monocytes and macrophages which in turn stimulate cytokine production. It is the hormone-like factors called cytokines that orchestrate the immune response. The classic responses observed with immune system activation and cytokine production include: anorexia, fever, lethargy, recruitment of other immune cells, and phagocytosis. While production of immune system components is known to require some amino acids, increases in amino acid requirements are more than offset by the associated decrease in protein accretion and increased muscle protein degradation that also accompanies immune system activation. However, the biggest impact of cytokine production is a decrease in feed intake. Therefore, as feed intake decreases, the energy needed to drive protein synthesis is also decreased. This suggests that diets should still be formulated on a similar calorie:lysine ratio as those formulated for non-immune challenged pigs. The evidence is sparse or equivocal for increasing nutrient requirements during an immune challenge. Nutritionists and swine producers should resist the pressure to alter the diet, limit feed, or add expensive feed additives during an immune challenge. While immune stimulation does not necessitate changes in diet formulation, when pigs are challenged with non-pathogenic diarrhea there are potential advantages on gut health with the increased use of crystalline amino acids rather than intact protein sources (i.e., soybean meal). This is because reducing crude protein decreases the quantity of fermentable protein entering the large intestine, which lowers post weaning diarrhea. It also lowers the requirement for expensive specialty protein sources or other protein sources such as soybean meal that present immunological challenges to the gut. The objective of this review is two-fold. The first is to discuss immunity by nutrition interactions, or lack thereof, and secondly, to review amino acid requirement estimates for nursery pigs.     

Assessment of the physiological effect of altered salinity on greenlip (Haliotis laevigata) and blacklip (Haliotis rubra) abalone using respirometry

The early physiological response (3 days) of greenlip (Haliotis laevigata Leach) and blacklip (H. rubra Leach) abalone to a single abrupt change in salinity was monitored using a multi‐channel open‐circuit respirometer. The range of salinity tolerance for both species in this trial was 25–40 ppt. Indications from other trials were that a margin of 2 ppt outside this range will cause mortality. Serum volume was increased by reduced salinity as much as 25% in the short term, with equilibration of the concomitant whole body weight increase (9.2±0.5%) occurring within 1 h. The serum volume appeared to be decreased at high salinity. There was little underlying change in basal oxygen usage levels, but significant behavioural changes that affected overall oxygen consumption. Both high and low salinity appeared to reduce activity. Animals in low salinity exhibit partial recovery of activity levels after 1 day in a manner similar to other stress responses. Animals at high salinity (40 ppt) did not show recovery of activity levels over 3 days. Overall, these results suggest that greenlip and blacklip abalone will have little trouble tolerating moderately low‐salinity environments.     

Growth of cultured mussels (Perna canaliculus Gmelin 1791) at a deep-water chlorophyll maximum layer

We tested the hypothesis that yield of the mussel Perna canaliculus (Gmelin 1791) could be increased by placing culture ropes deep into the water column to take advantage of deep‐water chlorophyll a maxima. The study site, in Pelorus Sound, New Zealand, showed periods of thermal stratification of the water column, causing a high concentration of phytoplankton in deeper water, at the thermocline. Mussels were grown simultaneously at 5 and 17 m, for up to 96 days. Mussel growth and condition index data showed no significant differences between the two depth treatments, indicating that in this system there may not be substantial mussel productivity benefits from lowering mussel farms to the deep‐water chlorophyll maximum layer.     

Quantification of presumptive Na+/H+ antiporters of the erythrocytes of trout and eel

The presumptive Na⁺/H⁺ exchange sites of trout and eel erythrocytes were quantified using amiloride-displaceable 5-(N-methyl-N-[³H]isobutyl)-amiloride (³H-MIA) equilibrium binding to further evaluate the mechanisms of i) hypoxia-mediated modifications in the trout erythrocyte -adrenergic signal transduction system and ii) the marked differences in the catecholamine responsiveness of this system between the trout and eel. MIA was a more potent inhibitor of both trout apparent erythrocyte proton extrusion (IC₅₀ = 20.1 ± 1.1 mol l^–1, N = 6) activity (as evaluated by measuring plasma pH changes after addition of catecholamine in vitro) and specific ³H-MIA binding (IC₅₀ = 257 ± 8.2 nmol l^–1, N = 3) than amiloride, which possessed a proton extrusion IC₅₀ of 26.1 ± 1.6 mol l^–1 (N = 6) and a binding IC₅₀ of 891 ± 113 nmol l^–1 (N = 3). The specific Na⁺ channel blocker phenamil was without effect on adrenergic proton extrusion activity or specific ³H-MIA binding. Trout erythrocytes suspended in Na⁺-free saline and maintained under normoxic conditions possessed 37,675 ± 6,678 (N = 6) amiloride-displaceable ³H-MIA binding sites per cell (B_max, presumptive Na⁺/H⁺ antiporters) with an apparent dissociation constant (K_D) of 244 ± 29 nmol l^–1 (N = 6). Acute hypoxia (PO₂ = 1.2 kPa; 30 min) did not affect the K_D, yet resulted in a 65% increase in the number of presumptive Na⁺/H⁺ antiporters. Normoxic eel erythrocytes, similarly suspended in Na⁺-free saline, possessed only 17,133 ± 3,716 presumptive Na⁺/H⁺ antiporters (N = 6), 45% of that of trout erythrocytes, with a similar K_D (246 ± 41 nmol l^–1, N = 6). These findings suggest that inter- and intra-specific differences in the responsiveness of the teleost erythrocyte -adrenergic signal transduction system can be explained, in part, by differences in the numbers of Na⁺/H⁺ exchange sites.     

Action of Clathrodin and Analogues on Voltage-Gated Sodium Channels

Clathrodin is a marine alkaloid and believed to be a modulator of voltage-gated sodium (Na_V ) channels. Since there is an urgent need for small molecule Na_V channel ligands as novel therapeutics, clathrodin could represent an interesting lead compound. Therefore, clathrodin was reinvestigated for its potency and Na_V channel subtype selectivity. Clathrodin and its synthetic analogues were subjected to screening on a broad range of Na_V channel isoforms, both in voltage clamp and patch clamp conditions. Even though clathrodin was not found to exert any activity, some analogues were capable of modulating the Na_V channels, hereby validating the pyrrole-2-aminoimidazole alkaloid structure as a core structure for future small molecule-based Na_V channel modulators.