Effect of increased rearing temperature on digestive function in cobia early juvenile.

The present study is focused to elucidate the main characteristics of the digestive function of this carnivorous fast-growing fish living at high temperatures. With this aim, we have examined the effects of an increased temperature from 30 to 34 °C on the daily pattern of gastrointestinal pH, enzymatic proteolytic digestive activity and the feed transit time in early juveniles of cobia (Rachycentron canadum), a species living in tropical and subtropical waters with an increasing aquaculture production. Fish were fed two meals a day. Gastric luminal pH was permanently acidic (mean pH values: 2.76-4.74) while the intestinal pH increased from neutral/slightly acidic to slightly alkaline when the digesta was present, with an increasing alkalinity from proximal to distal intestine (mean pH values: 6.05 to 7.69). The temperature did not affect the gastric pH but a slightly higher acidity was induced in the intestine at 34 °C. Pepsin activity showed a daily rhythm at 30 °C with maximum in the middle of the light period, while at 34 °C some hourly changes coinciding with feed adding without a clear daily trend during the 24-h period were observed. The trypsin activity exhibited a daily rhythm at both temperatures with an increase after morning feeding to reach a maximum several hours later. Average pepsin activity during the daily cycle was slightly higher at 34 °C (6.1 and 7.3 U mg-1 BW at 30 and 34 °C respectively), but values were significantly different only at 8 and 24 h after the morning meal. Similarly, the trypsin activity was significantly affected by the temperature only at 8 and 16 h after the morning meal, but daily activity averages were similar (1.20 and 1.29 U g-1 BW at 30 and 34 °C respectively). The partial transit rates of the first meal in the stomach for each period inter-samplings were higher during the first 4-h period and decreased progressively along the rest of the 24-h cycle at both temperatures, but no significant differences were detected at 30 °C. In addition, the transit was notably faster at 34 °C particularly during the first 8 h after feeding, with rates between 100 and 65% of total volume displaced (intake or released) during each 4-h period. In the intestine the transit rate was relatively constant and similar at both temperatures during 12 h after feeding. Then the rates remained very low during the following 12 h. Residence time of the first meal was longer at 30 than at 34 °C, particularly in the stomach (12 h:02 min vs 4 h:54 min respectively). In the intestine the difference was not so large (8 h:18 min vs 6 h:24 min respectively). In a parallel study under same conditions, cobia reared at 30 °C grew faster and showed a more favorable feed conversion ratio than those at elevated temperature (34 °C). The present results indicate that at 34 °C, a subtle increase of proteolytic activity cannot compensate for the faster gut transit rate. Therefore, 30 °C is more appropriate temperature for the early on-growing of cobia because at higher temperatures the digestion efficiency decrease being one of the causes for a lower growth.

Influence of lipid content and packaging methods on the quality of dried capelin (Mallotus villosus) during storage.

Capelin annual catch exceeds half a million tons in Iceland, with only a small quantity (<20%) of female with roe used for human food. There is a potential to use dried male capelin as a new product for human consumption, but its lipid content varies considerably (4-20% body weight). Earlier studies were more concentrated on the influence of drying conditions than the influence of storage conditions on the quality of dried fish, as dried fish are usually considered to be stable and safe during storage. Three batches of dried male capelin differing in lipid content were packaged and studied during 5 months storage at 22 ± 2 °C to establish appropriate lipid content at harvesting and product packaging method. Lipid composition, lipid hydrolysis and oxidation, sensory attributes and microbial activity were evaluated. Batches differed in composition and stability, with low lipid capelin constituting higher proportion of polyunsaturated fatty acids (22% lipid) than high lipid (18% lipid) capelin. Lipid oxidation was influenced by lipid content and packaging method, as accelerated oxidation occurred in high lipid and open packed capelin. Lipid hydrolysis was less influenced by packaging and was greater in low lipid capelin. High lipid capelin in open bags scored the highest for rancid odor. All batches were micro-biologically stable with colony-forming unit counts increasing less than log 1 (log 5-6) during 5 months storage.

IL-1beta mediates MMP secretion and IL-1beta neosynthesis via upregulation of p22(phox) and NOX4 activity in human articular chondrocytes.

OBJECTIVES: Osteoarthritis (OA) is characterized by a progressive alteration of the biochemical properties of the articular cartilage. Inflammation plays a major role in OA, particularly through the cytokine Interleukine-1ß, promoting reactive oxygen species (ROS) generation and matrix metalloproteinases (MMP) synthesis by the chondrocytes, orchestrating matrix proteolysis. NADPH oxidases (NOX) are membrane enzymes dedicated to the production of ROS. Role of oxidative stress is well established in OA; however, contribution of NOX in this process is still poorly documented. In this study, we addressed the role of NOX in primary human articular chondrocytes (HAC) upon inflammatory conditions--namely IL-1ß and OA. DESIGN: HAC were collected from patients undergoing hip surgery. Chondrocytes were treated with IL-1ß and NOX inhibitors Diphenylene Iodonium, GKT136901, Tiron and Heme oxygenase-1 before MMP expression and NOX activity assessment. Finally, NOX4 expression was compared between OA and non OA parts of hip cartilage (n = 14). RESULTS: This study establishes for the first time in human that NOX4 is the main NOX isoform expressed in chondrocytes. We found a significant upregulation of NOX4 mRNA in OA chondrocytes. Expression of NOX4/p22(phox) as well as ROS production is enhanced by IL-1ß. On the other hand, the use of NOX4 inhibitors decreased IL-1ß-induced collagenase synthesis by chondrocytes. Moreover, our study support the existence of a redox dependant loop sustaining pro-catabolic pathways induced by IL-1ß. CONCLUSIONS: This study points out NOX4 as a new putative target in OA and suggests that NOX-targeted therapies could be of interest for the causal treatment of the pathology.

Desferrioxamine enhances hypoxic ventilatory response and induces tyrosine hydroxylase gene expression in the rat brainstem in vivo.

The iron chelator desferrioxamine (DFO) induces accumulation of the hypoxia-inducible factor (HIF-1), a transcription factor that up-regulates genes involved in adaptative responses to hypoxia. This property makes DFO a potential neuroprotector against hypoxic stress. We investigated in rats the effects of DFO on the ventilatory response to mild hypoxic tests and the expression of tyrosine hydroxylase (TH), a target gene of HIF-1. Two protocols were used, the first with repeated injections of 50 mg/kg DFO every 2 days during a 2-week period. This was aimed at define the time course of the ventilatory responses to a hypoxic test. In the second protocol, rats were given a single injection of 300 mg/kg DFO. Every day over 4 days, the hypoxic ventilatory response was recorded before the animal was sacrificed, and Western blot analysis of TH in the dorsal brainstem cardiorespiratory area was performed. DFO produced a delayed increase in the hypoxic ventilatory response, which appeared in the same time window as TH up-regulation (2-3 days after the bolus injection of DFO). This delay suggests a genic effect of the drug that improves the ventilatory response to hypoxia.

Synthesis and ESR study of new dihydroxamic acid siderophores S as scavengers of hydroxyl radicals.

Five new dihydroxamic acid ligands (L) (8, 10a, 10b, 10c and 13) have been synthesised and characterised as potential chelating agents for iron (Fe3+). The log stability constants of Fe2L3 and FeL+ from Fe3+ and L2- have been estimated to be log beta = 61.96 and log beta 1 = 22.8 respectively. The ability of these compounds to scavenge hydroxyl radicals (oOH) responsible for cell damage have been studied by esr spectroscopy.