Enhancement of gel properties of Scomberomorus niphonius myofibrillar protein using phlorotannin extracts under UVA irradiation.

The effect of phlorotannin extracts (PTE) (from sporophyll of Undaria pinnatifida) added at different levels (0, 25, 125, 625 µmol/g protein) on the gel properties of mackerel (Scomberomorus niphonius) myofibrillar protein (MP) was studied with and without ultraviolet A (UVA) irradiation. The results showed that the gel strength and cooking yield increased in a PTE dose-dependent manner, and at the level of 625 µmol/g protein PTE, the highest gel strength of 308.43 ± 8.12 (mN·cm) and cooking yield of 76.16 ± 1.40% were obtained in the samples treated with UVA irradiation. The same samples also showed increased carbonyl content, decreased total sulfhydryl, unwinding of α-helix, and quenching of fluorescence intensity of endogenous tryptophan, all of which indicated that elevated protein oxidation in these samples led to enhanced protein cross-linking. Results of sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) indicated aggregation of myosin heavy chains (MHCs) in the UVA-treated gels with PTE, also evidenced by the dense three-dimensional network structure in these samples visualized by scanning electron microscopy (SEM). Electron spin resonance (ESR) and spin trapping results indicated that free radicals were produced during the gelation process, possibly originated from UVA-treated PTE, which played a critical role of oxidizing fish MPs, and eventually led to the improvement of the textural properties of the mackerel MP gel. PRACTICAL APPLICATION: Brown algae are a family of high-yield marine algae. Phlorotannin extracts are highly active natural substances extracted from brown algae that can have many applications. Ultraviolet A (UVA) as a green and environmentally friendly physical processing method has been widely used in food processing in recent years. The method proposed in this study could be utilized to improve properties of fish protein gel made from poorly performing low-priced fishes, and provide workable guidance for industry to expand the application of brown algae in food processing to better meet consumer's demand for high-quality marine foods.

Proteomic responses in the gills of fathead minnows (Pimephales promelas, Rafinesque, 1820) after 6 months and 2 years of continuous exposure to environmentally relevant dietary 226Ra.

PURPOSE: To investigate changes in the gill proteome of fathead minnows continually fed an environmentally relevant dietary dose of (226)Ra for 2 years. METHODS: The fish were fed a commercial diet containing 10 mBq-10 Bq (226)Ra g(-1). After 6 months and 2 years the gill proteome was analyzed by two-dimensional electrophoresis (2-DE). Protein spots which exhibited a significant change were identified using mass spectrometry. RESULTS: Six proteins were found to be increased: Glyceraldehyde-3-phosphate dehydrogenase (GAPDH), enolase, protein disulphide isomerase precursor, ATP synthase, glial cell fibrillary protein (GFAP), apolipoprotein A1 (ApoA1). One protein was found to be decreased; malate dehydrogenase. The majority of these changes occurred predominantly at the lowest (226)Ra doses, within 6 months and were maintained for 2 years. CONCLUSIONS: These proteomic changes suggested an adaptive or protective response to radiation induced reactive oxygen species (ROS). Increased GFAP indicated the induction of oxidative stress. Increased GAPDH and enolase indicated enhanced ROS scavenging from glycolytic metabolites. Increased protein disulphide isomerase precursor indicated an enhanced source of radioprotective thiols. Decreased malate dehydrogenase indicated enhanced ROS scavenging within the mitochondria. Increased ATP synthase indicated enhanced protection of healthy cells and increased ApoA1 indicated enhanced protection of the gill lamellae.

Proteomic changes in the gills of wild-type and transgenic radiosensitive medaka following exposure to direct irradiation and to X-ray induced bystander signals.

The directly irradiated and bystander gill proteome was examined in wild-type and radiosensitive transgenic medaka. Direct irradiation increased the expression of annexin max 3, creatine kinase (CK), and lactate dehydrogenase (LDH) in both strains and reduced annexin A4 in wild-type medaka only. In bystander fish, same strain pairings increased CK and LDH in both strains and increased annexin max 3 and annexin A4 in radiosensitive medaka. Mixed strain pairings revealed that, in bystander fish, annexin max 3 was only increased by a bystander signal originating from a radiosensitive source, annexin A4 was increased in radiosensitive bystanders irrespective of the signal source, and CK and LDH were increased if either the bystander signal origin or the recipient bystander fish was radiosensitive. Warm-temperature acclimation related 65-kDa protein (Wap65) was increased in all bystander medaka, whether they were paired with the same or opposite strain and chromosome 5 SR-like CTD-associated factor (SR=serine-argenine-rich, CTD=C-terminal domain) (SCAF) protein was increased in radiosensitive bystander medaka only. Annexin A4, CK and LDH are associated with apoptosis and mirror the increase in apoptotic bodies previously reported in irradiated and bystander medaka, whereas increased Wap65 and LDH suggest a protective response. Thus the proteomic changes reported here could indicate both immediate protection and longer term adaptation to subsequent radiation exposure. In addition this investigation provides further evidence to show that the bystander signal can override the intrinsic genetically determined response and also that signal production and response can be modulated independently.

Functional development of the zebrafish pineal gland: light-induced expression of period2 is required for onset of the circadian clock.

In zebrafish, the pineal gland is a photoreceptive organ that contains an intrinsic circadian oscillator and exhibits rhythmic arylalkylamine-N-acetyltransferase (zfaanat2) mRNA expression. In the present study, we investigated the role of light and of a clock gene, zperiod2 (zper2), in the development of this rhythm. Analysis of zfaanat2 mRNA expression in the pineal gland of 3-day-old zebrafish embryos after exposure to different photoperiodic regimes indicated that light is required for proper development of the circadian clock-controlled rhythmic expression of zfaanat2, and that a 1-h light pulse is sufficient to initiate this rhythm. Analysis of zper2 mRNA expression in zebrafish embryos exposed to different photoperiodic regimes indicated that zper2 expression is transiently up-regulated by light but is not regulated by the circadian oscillator. To establish the association between light-induced zper2 expression and light-induced clock-controlled zfaanat2 rhythm, zPer2 knock-down experiments were performed. The zfaanat2 mRNA rhythm, induced by a 1-h light pulse, was abolished in zPer2 knock-down embryos. These experiments indicated that light-induced zper2 expression is crucial for establishment of the clock-controlled zfaanat2 rhythm in the zebrafish pineal gland.