Effects of socking [sic] density on ammonia excretion and the growth of Nile tilapia (Oreochromis niloticus L.)

The effects of stocking density (10, 15, 50 & 75 fish in 65L tank) and ammonia excretion on the growth of Nile tilapia, Oreochromis niloticus (12.19 ± 1.21 g) were investigated. Increasing stocking density of Nile tilapia from 15 fish/tank (2.81 g fish/L) to 75 fish/tank (14.07 g fish/L) resulted in associated increase in ammonia level (1.48 ± 0.87 mg/L to 26.44 ± 11.4 mg/L) and significantly lower growth rates. Significantly better feed conversion ratios were found for fish reared at lower (15 fish/tank) stocking densities compared to higher (75 fish/tank) stocking densities. Individual growth rates were significantly better for fish reared at a lower stocking density 15 fish/tank compared to higher stocking density 75 fish/tank and size variation (coefficient of variation in weight) were positively correlated with stocking density. Although water exchange did not have a significant effect on the growth of Nile tilapia for fish stocked at 10 fish/tank (1.88 g fish/L) and 50 fish/tank (9.38 g fish/L), however, the fish in the higher stocking density (9.38 g fish/L) groups and without water exchange, significantly changed the coloration of their bodies (silver to black) which may be due to the lower oxygen levels combined with higher ammonia levels. Ammonia level increased with increasing stocking density and without water exchange. In this study, it may be suggested that when fish reared at higher stocking densities then water exchange must be taken in to consideration so as to help avoid environmental and physiological stress to the fish.

NR2B-containing N-methyl-D-aspartate subtype glutamate receptors regulate the acute stress effect on hippocampal long-term potentiation/long-term depression in vivo

Behavioral stress facilitates long-term depression but impairs long-term potentiation in the hippocampus. Recent evidence in vitro demonstrates that the NIR2B-containing N-methyl-D-aspartate subtype glutamate receptor antagonist Ro25-6981 prevents the beh

N-methyl-D-aspartate receptor-dependent long-term potentiation in CA1 region affects synaptic expression of glutamate receptor subunits and associated proteins in the whole hippocampus

Long term potentiation in hippocampus, evoked by high-frequency stimulation, is mediated by two major glutamate receptor subtypes, alpha-amino-3-hydroxyl-5-methyl-4-isoxazole propionate receptors and N-methyl-D-aspartate receptors. Receptor subunit compos

PCB-integrated optical waveguide sensors: An ammonia gas sensor

This paper presents a novel platform for the formation of cost-effective PCB-integrated optical waveguide sensors. The sensor design relies on the use of multimode polymer waveguides that can be formed directly on standard PCBs and commercially-available chemical dyes, enabling the integration of all essential sensor components (electronic, photonic, chemical) on low-cost substrates. Moreover, it enables the detection of multiple analytes from a single device by employing waveguide arrays functionalised with different chemical dyes. The devices can be manufactured with conventional methods of the PCB industry, such as solder-reflow processes and pick-and-place assembly techniques. As a proof of principle, a PCB-integrated ammonia gas sensor is fabricated on a FR4 substrate. The sensor operation relies on the change of the optical transmission characteristics of chemically functionalised optical waveguides in the presence of ammonia molecules. The fabrication and assembly of the sensor unit, as well as fundamental simulation and characterisation studies, are presented. The device achieves a sensitivity of approximately 30 ppm and a linear response up to 600 ppm at room temperature. Finally, the potential to detect multiple analytes from a single device is demonstrated using principal-component analysis. © 1983-2012 IEEE.

Diversity and abundance of ammonia-oxidizing bacteria in eutrophic and oligotrophic basins of a shallow Chinese lake (Lake Donghu)

Classical cultivation and molecular methods based on the ammonia monooxygenase gene (amoA) were used to study the abundance and diversity of beta-proteobacterial ammonia-oxidizing bacteria (AOB) in lake sediments. The eutrophic and oligotrophic basins of a Chinese shallow lake (Lake Donghu), in terms of ammonium (NH4+) concentrations, were sampled. The AOB number was significantly lower in the oligotrophic basin, but significantly higher in the eutrophic basin. In addition, using restriction fragment length polymorphism targeting the amoA, ten restriction patterns including six unique ones were found in the eutrophic basin, while five patterns were observed in the oligotrophic basin with only one unique restriction group. Phylogenetic analysis for AOB revealed that Nitrosomonas oligotropha- and Nitrosomonas ureae-related AOB and Nitrosospira-affiliated AOB were ubiquitous; the former dominated in the eutrophic basin (87.2%), while the latter dominated in the oligotrophic basin (65.5%). Furthermore, Nitrosomonas communis-related AOB was only detected in the eutrophic basin, at a small proportion (3.2%). These results indicate significant selection and adaptation of sediment AOB in lakes with differing trophic status. (C) 2009 Elsevier Masson SAS. All rights reserved.

Effects of dietary ascorbic acid supplementation on the growth performance, immune and stress response in juvenile Leiocassis longirostris Gunther exposed to ammonia

This experiment was designed to investigate the effect of dietary supplemental ascorbic acid (AA) on the feed intake, growth, serum lysozyme, hepatic superoxide dismutase (SOD) and handling stress response in Chinese longsnout catfish (Leiocassis longirostris Gunther) exposed to three levels of unionized ammonia nitrogen (UIA-N). Juvenile Chinese longsnout catfish were reared in 54 fibreglass tanks with a 3 x 3 factorial design treatment consisting of three supplemental AA levels in ascorbyl 2-monophosphate (38, 364 and 630 mg AA equivalent kg(-1) diet) and three UIA-N concentrations [0.004 (the control), 0.037 and 0.292 mg L-1]. The fish were sampled on the 11th, 32nd and 60th day. On the 62nd day, the remaining fish were subjected to an acute stress by being held in a dipnet out of water for 60 s, and sampled at 30 min post handling. The results showed that the specific growth rate (SGR) in 32 days significantly decreased with increased water UIA-N (P=0.0476) but was not affected by dietary supplemental AA (P > 0.05). After 60 days, SGR, feeding rate (FR) and feed conversion efficiency (FCE) significantly increased with increased dietary supplemental AA (P < 0.001) while remaining unaffected by water UIA-N (P > 0.05). There was no significant interaction between dietary AA and UIA-N for growth responses (P > 0.05). The serum lysozyme activity on the 11th day and the hepatic SOD activity on the 32nd day were significantly affected at high (0.292 mg L-1) water UIA-N. On the 62nd day, the increase in cortisol resulting from acute stress significantly decreased by higher UIA-N (P=0.038). It is suggested that Chinese longsnout catfish displayed an adaptive response after long-term UIA-N exposure, and AA had beneficial effects on the growth and feed intake of catfish and alleviated the negative effects of chronic ammonia stress. A chronically higher ammonia level shows a tendency to inhibit the cortisol response to another acute stressor.

Influence of AlN Buffer Thickness on GaN Grown on Si(111) by Gas Source Molecular Beam Epitaxy with Ammonia

Hexagonal GaN is grown on a Si(111) substrate with AlN as a buffer layer by gas source molecular beam epitaxy (GSMBE) with ammonia. The thickness of AlN buffer is changed from 9 to 72 nm. When the thickness of AlN buffer is 36 nm, the surface morphology and crystal quality of GaN is optimal. The in-situ reflection high energy electron diffraction (RHEED) reveals that the transition to a two-dimensional growth mode of AlN is the key to the quality of GaN. However, the thickness of AlN buffer is not so critical to the residual in-plane tensile stress in GaN grown on Si(111) by GSMBE for AlN thickness between 9 to 72 nm.

Epitaxial growth and characterization of SiC on C-plane sapphire substrates by ammonia nitridation

The growth of SiC epilayers on C-face (0 0 0 1) sapphire (alpha-Al2O3) has been performed using CVD method. We found that the quality of SiC epilayers has been improved through the nitridation of substrates by exposing them to ammonia ambient, as compared to growth on bare sapphire substrates. The single crystallinity of these layers was verified by XRD and double crystal XRD measurements. Atomic force microscopy was used to evaluate the surface morphology. Infrared reflectivity and Raman scattering measurement were carried out to investigate the phonon modes in the grown SiC. Detailed Raman analysis identified the 6H nature of the as-grown SiC films. (C) 2002 Elsevier Science B.V. All rights reserved.

Low potential detection of glutamate based on the electrocatalytic oxidation of NADH at thionine/single-walled carbon nanotubes composite modified electrode

A glutamate biosensor based on the electrocatalytic oxidation of reduced nicotinamide adenine dinucleotide (NADH), which was generated by the enzymatic reaction, was developed via employing a single-walled carbon nanotubes/thionine (Th-SWNTs) nanocomposite as a mediator and an enzyme immobilization matrix. The biosensor, which was fabricated by immobilizing glutamate dehydrogenase (GIDH) on the surface of Th-SWNTs, exhibited a rapid response (ca. 5 s), a low detection limit (0.1 mu M), a wide and useful linear range (0.5-400 mu M), high sensitivity (137.3 +/- 15.7) mu A mM(-1) cm(-2), higher biological affinity, as well as good stability and repeatability. In addition, the common interfering species, such as ascorbic acid, uric acid, and 4-acetamidophenol, did not cause any interference due to the use of a low operating potential (190 mV vs. NHE). The biosensor can be used to quantify the concentration of glutamate in the physiological level. The Th-SWNTs system represents a simple and effective approach to the integration of dehydrogenase and electrodes, which can provide analytical access to a large group of enzymes for wide range of bioelectrochemical applications including biosensors and biofuel cells.