Comparison of Docosahexaenoic Acid (22:6n-3) Levels in Various Artemis Strains during Enrichment and Subsequent Starvation

Abstract.— The aim of this study was to compare the levels of docosahexaenoic acid (DHA, 22:6n-3) in three different bisexual and one parthenogenetic strains of Artemia after enrichment. Freshly-hatched nauplii from A. franciscana (Great Salt Lake, USA), A. sinica (Yimeng, P. R. China), A. persimilis (Argentina), and A. parthenogenetica (Tanggu, P. R. China) were enriched with a purified lipid emulsion containing 95% DHA ethyl esters (% total fatty acids) and subsequently starved. All strains had very low initial DHA levels (< 0.3 mg/g dry weight). Initial eicosapentaenoic acid, 20:5n-3 (EPA) levels were high in A. parthenogenetica (18.2 mg/g dry weight) as compared to those in the other strains (4.6-8.5 mg/g dry weight). After 24-h enrichment, A. sinica contained the highest DHA level (37.0 mg/g dry weight) as well as the highest DHA/ EPA ratio (3.7). The lowest DHA enrichment levels were found in A. franciscana and A. parthenogenetica (26.3 and 22.7 mg/g dry weight, respectively). During the subsequent 24-h starvation period, the contents of DHA decreased rapidly in all strains, whereas EPA levels remained relatively stable. This indicates the high catabolism of DHA for energy production, the relative conservation of EPA, and possibly a partial bioconversion of DHA to EPA during the starvation period in each species.     

Particle Size Distribution in Two Lipid Emulsions Used for the Enrichment of Artemia nauplii as a Function of Their Preparation Method and Storage Time

The present study examined the distribution of particle sizes in two experimental standardized lipid emulsions (distributed by ICES, International Council for the Exploration of the Sea) as a function of the preparation method (hand shaking or ultrasonic blending) and as a function of storage time. A 24-h enrichment trial compared the incorporated HUFA levels in the nauplii of Artemia franciscana .
The emulsion droplets in the 50% HUFA emulsion (ICES 50, ethyl ester based) were much smaller than in the 30% HUFA emulsion (ICES 30, triacylglycerol-based) in which 90% of the droplets had a diameter below 12.3 μm as compared to 1.3 pn in ICES 50. The blending method highly affected particle sizes. High-shear blending instead of the classical hand shaking of the emulsion of both ICES 30 and 50 reduced the mean particle size from 5.06 to 1.07 μm and from 0.38 to 0.11 μm, respectively. The particle size distributions remained stable during the 1-wk storage, suggesting the absence of agglomeration or bacterial development. The fatty acid composition of 24-h enriched Artemia reflected differences in the HUFA profile of the emulsions, but was independent of observed differences in the size of the particles.     

Preliminary Study of the Optimum Dietary Ascorbic Acid Level in Sea Cucumber,Apostichopus japonicus (Selenka)

A 14‐wk feeding trial was carried out to evaluate the optimum dietary ascorbic acid (AA) level in juvenile sea cucumber, Apostichopus japonicus. Sea cucumbers averaging 1.49 ± 0.07 g (mean ± SD) were randomly distributed into 18 rectangular plastic tanks of 20 L capacity in a recirculating system (20 animals per tank). Six semipurified experimental diets were formulated to contain 0 (l ‐ascorbyl‐2‐monophosphate [AMP]; AMP0), 30 (AMP24), 60 (AMP48), 120 (AMP100), 240 (AMP206), and 1200 (AMP1045) mg AA/kg diet in the form of AMP using casein as the main protein source. Sea cucumbers were fed each of the six experimental diets in triplicate groups. At the end of 14 wk of feeding trial, weight gain (WG), specific growth rate (SGR), and feed efficiency (FE) of sea cucumbers fed AMP100, AMP206, and AMP1045 were significantly (P < 0.05) higher than those of animals fed AMP0, AMP24, and AMP48. However, there were no significant differences in WG, SGR, and FE among sea cucumbers fed AMP100, AMP206, and AMP1045 and among animals fed AMP0, AMP24, and AMP48. Whole‐body vitamin C concentration increased with AA content of the diets. Broken‐line analysis of WG showed an optimum dietary AA level of 105.3 mg AA/kg diet in sea cucumber. These results indicated that the optimum dietary vitamin C level in sea cucumber in the form of AMP could be greater than 100 mg AA/kg diet but less than 105.3 mg AA/kg diet.     

Reevaluation of the Dietary Protein Requirements and Optimum Dietary Protein to Energy Ratios in Japanese Eel, Anguilla japonica

A 2 × 3 factorial design was used to reevaluate the dietary protein requirements and to determine the optimum dietary protein to energy (P/E) ratios in Japanese eel, Anguilla japonica, reared in the recirculating system. For each of two experiments, six experimental diets (₄₅P₁₆, ₄₅P₁₇, ₄₅P₁₉, ₅₀P₁₆, ₅₀P₁₇, and ₅₀P₁₉) were formulated and prepared to contain two protein levels (45 and 50%) and three energy levels (16, 17, and 19 kJ/g diet) at each protein level. In the first experiment, glass eel of initial weight 0.1 ± 0.02 g (mean ± SD) were used, while the second experiment was conducted with juvenile eel of initial weight 15.0 ± 3 g (mean ± SD). The first and second experimental periods were 6 and 16 wk for the glass and juvenile eel, respectively. At the end of the first experiment, there were no protein, energy, and their interaction effects. Also, there were no significant differences in weight gain (WG), specific growth rate (SGR), feed efficiency (FE), and protein efficiency ratio (PER) for glass Japanese eel fed all diets. Although there were no significant differences in growth parameters of glass eel fed all experimental diets, these parameters were higher for fish fed ₅₀P₁₆ than for fish fed the other diets. For the second experiment, there were significant protein effects on WG, SGR, and PER (P < 0.05). However, there were neither significant energy effects nor protein and energy interaction effects on WG, SGR, FE, and PER. Fish fed ₄₅P₁₉ had a higher WG, SGR, and PER than did fish fed ₄₅P₁₆, ₅₀P₁₆, and ₅₀P₁₉ (P < 0.05). However, there were no significant differences in growth parameters among fish fed ₄₅P₁₆, ₄₅P₁₇, ₅₀P₁₆, ₅₀P₁₇, and ₅₀P₁₉ and among those fed ₄₅P₁₇, ₄₅P₁₉, and ₅₀P₁₇. These results may indicate that the optimum dietary protein requirement and the P/E ratio could be 44.3% and 24.1 mg protein/kJ (₄₅P₁₉), respectively, in juvenile Japanese eel, based on WG, SGR, and PER.     

Optimum Dietary Protein Level and Protein-to-Energy Ratio for Growth of Juvenile Korean Rockfish Sebastes schlegeli

An 8-wk feeding trial was conducted to estimate the optimum dietary protein level and protein-to-energy (P/E) ratio in juvenile Korean rockfish Sebastes schlegeli. Twenty experimental diets were formulated with four energy levels and five protein levels at each energy level. Four gross energy levels of 14.2, 16.5, 18.6, and 20.9 kJ/g diet were included at various crude protein (CP) levels. Diets containing CP at 30, 40, 45, 50, and 55% had either 14.2 or 16.5 kJ/g energy; those with CP levels of 35, 40, 45, 50, and 60% had either 18.6 or 20.9 kJ/ g energy. After 2 wk of conditioning, fish initially averaging 7.3 ± 0.04 g (means ± SD) were randomly distributed into net cages as groups of 20 fish. Each diet was fed to fish in three randomly selected net cages for 8 wk. After 8 wk of the feeding trial, weight gain (WG) of fish fed 50% and 55% CP with 14.2 kJ/g diet was significantly higher than those of fish fed 30% and 40% CP diets (P 0.05). WG of fish fed 45, 50, and 55% CP with 16.5 kJ/g diet was significantly higher than those of fish fed 30% and 40% CP diets (P < 0.05). WG of fish fed 60% CP with 18.6 kJ/g diet was significantly higher than those of fish fed 35, 40, and 45% CP diets. WG of fish fed 45% CP with 20.9 kJ/g diet was significantly higher than those of fish fed 35, 40, and 60% CP diets. Generally, feed efficiency (FE) and specific growth rate (SGR) showed a similar trend as WG. However, protein efficiency ratio (PER) was negatively related to dietary protein levels. WG of fish did not always increase with increasing dietary protein and energy levels. Comprehensive comparison among diets containing 40, 45, and 50% CP with different energy levels indicated that the increase in protein from 40 to 45% significantly increased WG (P < 0.05), but such effect was not significant when protein increased from 45 to 50% at all energy levels. Increasing dietary energy significantly increased WG of fish fed 40% and 45% CP at each energy level; however, there was no difference in WG of fish fed 50% CP with energy levels of 18.6 and 2.9 kJ/g diet. There was no significant difference in WG of fish fed 50% CP with 18.6 kJ/g or 45 and 50% CP with 20.9 kJ/g diet. Broken-line analysis of weight gain indicated that the optimum dietary protein level was 50.9 ± 1.1% and PIE ratio was 35.4 ± 0.8 mg/kJ with 14.2 kJ/g diet; the optimum dietary protein level was 49.3 ± 5.0% and P/E ratio was 30.2 ± 1.0 mg/kJ with 16.5 kJ/g diet; the optimum dietary protein level was 46.2 ± 9.2% and P/E ratio was 24.7 ± 4.9 mg/kJ with 18.6 kJ/g diet; and the optimum dietary protein level was 45.1 ± 1.8% and P/E ratio was 21.5 ±0.7 with 20.9 kJ/g diet. Therefore, these data indicated that the concept of P/E ratio must be restricted to diets containing adequate protein and energy levels. Based on WG, the optimum P/E ratio was between 21.5 and 35.4 mg protein/kJ gross energy in juvenile Korean rockfish when gross energy ranged from 14.2 to 20.9 kJ/g diet.     

Alleviating neuropathic pain hypersensitivity by inhibiting PKMzeta in the anterior cingulate cortex

Synaptic plasticity is a key mechanism for chronic pain. It occurs at different levels of the central nervous system, including spinal cord and cortex. Studies have mainly focused on signaling proteins that trigger these plastic changes, whereas few have addressed the maintenance of plastic changes related to chronic pain. We found that protein kinase M zeta (PKMζ) maintains pain-induced persistent changes in the mouse anterior cingulate cortex (ACC). Peripheral nerve injury caused activation of PKMζ in the ACC, and inhibiting PKMζ by a selective inhibitor, ζ-pseudosubstrate inhibitory peptide (ZIP), erased synaptic potentiation. Microinjection of ZIP into the ACC blocked behavioral sensitization. These results suggest that PKMζ in the ACC acts to maintain neuropathic pain. PKMζ could thus be a new therapeutic target for treating chronic pain.