Grigorios Krey

• Ph.D.
• Researcher at National Agricultural Research Foundation

The aquaculture industry is a rapidly developing and economically important sector for many countries, thus it requires effective solutions to overcome the key challenges that could impede its growth and sustainability. Among the most serious concerns are fish diseases caused by bacterial infections. This study introduces the development of novel r...

Despite significant progress, certain inflammation related to chronic disorders, including cardiovascular diseases (CVD) and cancer, still present high mortality rates. Thus, further study is needed to address such pathologies more appropriately. Apart from classic therapeutics, natural bioactives with less toxic side effects have gained attention,...

The Actinopterygian and specifically the Teleostean peroxisome proliferator-activated receptors (PPARs) present an impressive variability and complexity in their structures, both at the gene and protein levels. These structural differences may also reflect functional divergence from their mammalian homologs, or even between fish species. This revie...

Bacterial infections are one of the most important challenges that fish aquaculture industry faces. One of these bacteria is Tenacibaculum maritimum causing tenacibaculosis, a disease with very important consequences on farmed fish. The early detection and quantification of this bacterial infection could improve the management strategies and the su...

Coastal aquaculture systems are complex environments with multiple microbial interactions that affect fish health and productivity. High-throughput amplicon sequencing is a valuable tool for identifying such bacterial communities and investigating the relationship between bacterial diversity and sustainability in these systems. In the present study...

Marketing of fresh anchovy in Greece is of great importance. In the present study, the effect of ozone on some basic chemical (moisture, ash, protein, fat, fatty acids, biogenic amines), microbial (total viable count, Enterobacteriaceae and pseudomonads) and sensorial (general appearance, color and shape of eyes, color of gills, muscle and abdomen...

The fatty acid profiles of the lipid classes in the polar and neutral fractions of the filet fat of day-fresh European anchovy (Engraulis encrasicolus, Lineus 1758) were determined by a combination of Thin Layer Chromatography and Gas Chromatography. The results show the polar fraction of the fat is rich in polyunsaturated fatty acids with docosahe...

The outbreak of fish diseases is considered a major threat to the development of the growing industry of fish farming. Therefore, the investigation and early detection of common fish pathogens is considered crucial in order to develop effective preventing measures in any aquaculture setting. This study aimed to develop new rapid molecular methods u...

In this study, molecular taxonomy associated with Spicara flexuosa, Spicara maena, and Spicara smaris was examined with a geographical focus along the coasts of the Turkey and the Mediterranean. In addition, the effects of the Turkish Straits System on the evolutionary history and phylogeography of Spicara flexuosa were investigated. The mitochondr...

Anguillicola (Anguillicoides) crassus is a swimbladder nematode parasite of Anguilla anguilla (Linnaeus, 1758). The present study investigates the morphology and pathogenicity of A. crassus in European eel, as well as, the effects of different aquatic environments on the infection of A. crassus, in Greece. A total of 268 nematodes were collected fr...

Rays (Batoidea) are among the most threatened groups of vertebrates. Slow growth and low fecundity make many species vulnerable to overfishing, but increased demand for gill rakers in traditional Chinese medicine and elasmobranch meat means exploitation continues. In response, protection has increased, with manta and devilrays (Mobulidae) and sawfi...

In this study, the taxonomic resolution and phylogenetic relationship of two presumed subspecies of Merlangius merlangus, namely M. m. euxinus and M. m. merlangus, were investigated. In addition, the effect of the Turkish Straits System on the evolutionary history and genetic structure of M. merlangus, was explored. The mitochondrial cytochrome c o...

The cDNAs encoding the hemocyanin subunits from the blue crab (Callinectes sapidus, Rathbun, 1896) were studied. The complementary DNA (cDNA) from the hepatopancreas was amplified, using specific primers, yielding a PCR product of about 700 bases which was cloned into a plasmid vector and used to transform E. coli bacteria. Restriction enzyme diges...

Chondrichthyans, particularly batoids, are under high pressure due to human impacts and unregulated fishing. Ray and skate species are favoured for human consumption in Greece, however, most of the batoids are poorly managed due to the lack of species-specific catch and trade data. In the market, they are usually beforehand processed, whereas ray f...

Bacterial diversity of whole gilt-head sea bream (Sparus aurata L. 1758) originating from Ionian and Aegean Sea aquaculture farms and stored at 0 (ice), 4 and 8 °C was determined by 16S rRNA gene amplicon sequencing method using the Illumina's MiSeq platform. The composition of Aerobic Plate Counts (APC) was also monitored by 16S rRNA gene sequenci...

Overlapping external morphometric characters easily confound the flatfishes Solea aegyptiaca and Solea solea (Soleidae) in areas of the Mediterranean Sea where both species live in sympatry. This leads to uncertainties in the fisheries and marketing of the species, in addition to misinterpretations in biogeography and conservation studies. This pap...

The group of small poor cods and pouts from the genus Trisopterus, belonging to the Gadidae family, comprises four described benthopelagic species that occur across the North-eastern Atlantic, from the Baltic Sea to the coast of Morocco, and the Mediterranean. Here, we combined molecular data from mitochondrial (cytochrome b) and nuclear (rhodopsin...

Understanding the control of piscine fatty acid metabolism is important for determining the nutritional requirements of fish, and hence for the production of optimal aquaculture diets. The regulation and expression of carnitine palmitoyltransferase 1 (CPT1; EC No 2.3.1.21) are critical processes in the control of fatty acid metabolism, and here we...

We report the novel use of proteomics to investigate protein variation among populations of the European hake (Merluccius merluccius). The liver and brain extracts of 18 hake (N = 36) captured in the Mediterranean Sea, Cantabrian Sea, and Atlantic Ocean were examined by 2D/DIGE and mass spectrometry. Significant differences in protein expression am...

Cumulative record of brain tissue samples examined. A, BSE-challenged and bovine control fish samples. B, Srapie-challenged and ovine control fish samples. (0.14 MB DOC)

Temporal observation of the brains from control fish challenged with normal bovine brain homogenate. Sagittal brain sections taken at the indicated timepoints p.i. from fish challenged with normal bovine brain homogenate were stained with H&E (A, D, G), or immunolabeled with SaurPrP1 (1∶2000) without PK-digestion (B, E, H) and with PK-digestion (C,...

Statistical analysis of data derived from the scrapie - challenged group. (0.02 MB DOC)

Percentage amino acid sequence homology between prion proteins of different species. Full sequences were aligned. The NCBI accession numbers of sequence data are: Homo sapien (human), AAC78725; Bos Taurus (cow), AAD19998; Ovis aries (sheep), CAE00188; Mus musculus (mouse), AAH06703; Mesocricetus auratus (hamster), AAA37092; Takifugu rubripes (fugu)...

Comparison of antibody specificities for the PrPs of gilthead sea bream, cow and sheep by western blot analysis. A, Five 0.4 mg brain equivalent-aliquots of gilthead sea bream brain homogenate were loaded onto a 12% SDS-PAGE gel. B, Alternating lanes of a 12% SDS-PAGE gel were loaded with 3 mg tissue equivalents of PrPSc-enriched (see Materials and...

Antibody specificity in IHC. Sagittal, 4 µm-thick serial brain sections from control gilthead sea bream were treated immunohistochemically with four different primary antibodies, without proteinase K digestion. A, SaurPrP1 (1∶2000); B, ZebPrP2 (1∶2000); C, Pre-immune serum from the rabbit in which SaurPrP1 was raised (1∶2000); D, PrP-specific immun...

Cumulative record of the number of fish maintained post challenge. A, Fish inoculated with either scrapie- or normal ovine brain homogenate. B, Fish inoculated with either BSE- or normal bovine brain homogenate. (0.04 MB DOC)

Cytoanatomical analysis of brains from BSE-challenged fish sacrificed 24 months post challenge. The deposits have been classified into 2 morphological categories. F, fibrillary, >10 µm in diameter; NF, non fibrillary, circular<10 µm in diameter. Plus and minus symbols indicate the abundance of deposits: −, 0; +, 1–5; ++, 6–15; +++, 16–50, ++++, >50...

Temporal observation of the brains from control fish challenged with normal ovine brain homogenate. Sagittal brain sections taken at 12 and 24 months p.i. from fish challenged with normal ovine brain homogenate were stained with H&E (A, D), or immunolabeled with SaurPrP1 (1∶2000) without PK-digestion (B, E) and with PK-digestion (C, F). Images show...

Sensitivity to proteinase K treatment of TSE-challenged sea bream brain tissues 24 months p.i.. After a short purification treatment, 0.4 mg brain equivalents from brain homogenates of either scrapie- (lanes 1, 3, 5 & 7) or BSE-challenged (lanes 2, 4, 6 & 8) fish, were digested with increasing proteinase K concentrations (0 µg/ml, lanes 1 & 2; 0.1...

In transmissible spongiform encephalopathies (TSEs), a group of fatal neurodegenerative disorders affecting many species, the key event in disease pathogenesis is the accumulation of an abnormal conformational isoform (PrP(Sc)) of the host-encoded cellular prion protein (PrP(C)). While the precise mechanism of the PrP(C) to PrP(Sc) conversion is no...

Lipids are the predominant source of energy for fish. The mechanisms by which fish allocate energy from lipids, for metabolism, development, growth and reproduction are critical for understanding key life history strategies and transitions. Currently, the major lipid component in aquaculture diets is fish oil (FO), derived from wild capture fisheri...

This report describes a set of 21 polymerase chain reaction primers and amplification conditions developed to barcode practically any teleost fish species according to their mitochondrial cytochrome b and nuclear rhodopsin gene sequences. The method was successfully tested in more than 200 marine fish species comprising the main Actinopterygii fami...

We have identified and characterized a cDNA from the brain tissue of the highly commercial marine fish species, the gilthead sea bream (Sparus aurata), which encodes a 496 amino acid residue protein sharing the organizational and structural features of the mammalian prion proteins. Tissue mRNA expression analyses revealed the presence of this trans...

To maximize growth, farmed fish are fed high-fat diets, which can lead to high tissue lipid concentrations that have an impact on quality. The intake of conjugated linoleic acid (CLA) reduces body fat in mammals and this study was undertaken to determine the effects of dietary CLA on growth, composition, and postprandial metabolic variables in sea...

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors belonging to the nuclear hormone receptor superfamily that functions as critical regulators of lipid and energy homeostasis. Although intensively studied in mammals, their basic biological functions are still poorly understood. The objective of this work...

The dynamic properties of helix 12 in the ligand binding domain of nuclear receptors are a major determinant of AF-2 domain activity. We investigated the molecular and structural basis of helix 12 mobility, as well as the involvement of individual residues with regard to peroxisome proliferator-activated receptor alpha (PPARalpha) constitutive and...

Dietary conjugated linoleic acid (CLA) affects fat deposition and lipid metabolism in mammals, including livestock. To determine CLA effects in Atlantic salmon (Salmo salar), a major farmed fish species, fish were fed for 12 weeks on diets containing fish oil or fish oil with 2% and 4% CLA supplementation. Fatty acid composition of the tissues show...

On or before Apr 5, 2016 this sequence version replaced gi:78172872, gi:78172873, gi:78172871.

On or before Apr 5, 2016 this sequence version replaced gi:78172863, gi:78172864, gi:78172862.

On Nov 1, 2005 this sequence version replaced gi:78172880.

The cloning and characterization of cDNAs and genes encoding three peroxisome proliferator-activated receptor (PPAR) isotypes from two species of marine fish, the plaice (Pleuronectes platessa) and the gilthead sea bream (Sparus aurata), are reported for the first time. Although differences in the genomic organization of the fish PPAR genes compare...

Peroxisome proliferator-activated receptors (PPAR) are nuclear hormone receptors that control the expression of genes involved in lipid homeostasis in mammals. We searched for PPAR in sea bass, a marine fish of particular interest to aquaculture, after hypothesizing that the physiological and molecular processes that regulate lipid metabolism in fi...

Population genetic structures of the mackerel (Scomber scombrus) and chub mackerel (Scomber japonicus) were studied in the Mediterranean Sea. Fragments of 272 bp (S. scomber) and 387 bp (S. japonicus) of the 5'-end of the mitochondrial control region were sequenced from spawning individuals collected off the coasts of Greece, Italy, Spain, and Port...

Two distinct, TATA box-containing promoters regulate the transcriptional activity of the Xenopusvitellogenin A1 gene. These two promoters are of different strength and are separated by 1.8 kilobase pairs of untranslated sequence. Estrogen receptor (ER) and its ligand, 17β-estradiol, induce the activity of both promoters. The estrogen response eleme...

Peroxisome proliferator-activated receptors (PPARs) are nuclear hormone receptors controlling the expression of genes involved in lipid homeostasis. PPARs activate gene transcription in response to a variety of compounds including hypolipidemic drugs as well as natural fatty acids. From the plethora of PPAR activators, Scatchard analysis of recepto...

The nuclear factor I (NFI) family consists of sequence-specific DNA-binding proteins that activate both transcription and adenovirus DNA replication. We have characterized three new members of the NFI family that belong to the Xenopus laevis NFI-X subtype and differ in their C-termini. We show that these polypeptides can activate transcription in H...

The long-chain acyl-coenzyme A synthetase (ACS) gene gives rise to three transcripts containing different first exons preceded by specific regulatory regions A, B, and C. Exon-specific oligonucleotide hybridization indicated that only A-ACS mRNA is expressed in rat liver. Fibrate administration induced liver C-ACS strongly and A-ACS mRNA to a lesse...

Peroxisome proliferator-activated receptor (PPARs) are members of the nuclear receptor superfamily. For transcriptional activation of their target genes, PPARs heterodimerize with the retinoid-X receptor (RXR). The convergence of the PPAR and RXR signaling pathways has been shown to have an important function in lipid metabolism. The promoter of th...