Aging- and temperature-related activity of spermatogonial stem cells for germ cell transplantation in medaka.

Spermatogonial transplantation can contribute to developing a novel method of producing seedlings for both aquaculture and biotic conservation. This study's purpose was to investigate aging- and temperature-related changes in the numbers and stem cell functions of type-A spermatogonia (ASG) in the model fish medaka (Oryzias latipes). The ASG numbers in medaka of different ages were quantified via histological observation and enzymatic dissociation of vasa-Gfp medaka testes. The ASG numbers were higher in eight-month-old medaka (maturation) than in four-month-old medaka (the onset of maturation). However, ASG numbers decreased in 18-month-old medaka (senescence). Low water temperature appeared to slow down both testis development and aging processes. To study the effects of aging on ASG stem cell activity, testicular cell suspensions containing GFP-expressed ASG were prepared from vasa-Gfp medaka donors at 4 and 18 months of age and transplanted into recipient hybrid larvae of medaka (O. latipes x O. curvinotus), which provided young stem-cell-niches. The findings revealed no significant differences in ASG colonization rates isolated from medaka of different ages. Each group displayed similar rates of germ-line transmission. Furthermore, water temperature had no significant effects on each ASG's stem cell activity. Taken together, these results indicated that aging and temperature affect ASG numbers. However, ASG isolated from medaka with different ages were transplanted into gonads with a young niche microenvironment, and there was no evidence of donor aging on stem cell activity.

Characterization and expression of a vasa homolog in the gonads and primordial germ cells of the striped catfish (Pangasianodon hypophthalmus).

The analysis of early gonadogenesis during larval development requires a molecular marker that is specifically expressed in the germ cell lineage, such as the vasa gene. In this study, we cloned and characterized vasa in the striped catfish (Pangasianodon hypophthalmus), and designated this as Phy-vasa. Phy-vasa contained all of the predicted consensus motifs that are shared among the vasa genes in other fish species, including RG and RGG repeats, ATPase motifs, and a DEAD-box, and phylogenetic analysis using various DEAD-box family proteins demonstrated that the Phy-vasa protein clustered within the Vasa family. Reverse transcription polymerase chain reaction (RT-PCR) indicated that Phy-vasa mRNA only occurred in the testis and ovary, and in situ hybridization showed that the gene was expressed only in the germ cells, with strong expression in the spermatogonia and oogonia. To investigate early gonadogenesis in catfish larvae, we undertook histological characterization and in situ hybridization using a Phy-vasa probe, which showed that migration of the primordial germ cells (PGCs) most commonly occurred in larvae at 2-10 days post-fertilization (dpf), the PGCs started to be surrounded by gonadal somatic cells at around 10-20 dpf, and rapid proliferation of the PGCs had begun by 30 dpf. These findings provide a valuable insight into early gonadal development in the striped catfish.

Effects of dietary lipid sources on hepatic nutritive contents, fatty acid composition and proteome of Nile tilapia (Oreochromis niloticus).

Dietary oils of varying fatty acid composition have been used in tilapia feeds; nevertheless, investigation of their effects on metabolism and physiological processes has been limited. Therefore, in this study, using proteomic technology, the effects of different dietary lipids (DLs) on hepatic lipid metabolism and physiological processes were investigaed in Nile tilapia (Oreochromis niloticus). Fish were fed with different DL, which included palm oil (PO), linseed oil (LO) and soybean oil (SBO) for 90 days. Growth performance appeared to be similar among the dietary group. Hepatic FA contents were reflected by DL. Dietary PO (source of saturated fatty acids; SFA) led to an increase in the hepatosomatic index as well as lipid and protein contents in liver. Dietary SBO (source of n-6 polyunsaturated fatty acids; n-6 PUFAs) increased hepatic carbohydrate contents, but decreased the hepatic protein. The proteomic analysis showed that these nutritive changes in the liver were mediated by several proteins involved in lipid, carbohydrate, and amino acid metabolism. Dietary SBO showed an increased accumulation in proteins related to oxidative stress, immune and inflammatory processes. Dietary LO (source of n-3 PUFAs) increased abundance of cytoskeleton-related proteins. qRT-PCR was performed to provide supportive information for the result of proteomic study. Similar effects of DLs on mRNA levels were observed for atp5b, krt18, and selenbp1. Combined together, dietary SFA could supply as energy reservoir for regular activites. Dietary n-3 and n-6 PUFAs led to induce vital metabolic and physiologic processes which would contribute to maintaining normal health and/or providing health-related benefits. SIGNIFICANCE: Dietary SBO increased hepatic carbohydrate contents, but decreased the hepatic protein. Different dietary lipid led to alter the abundance of several proteins (i.e., DHRS1, ATP5B, PLA2G12B, APO, AMY2A, GRP78, PRSS1, FAH, and PRSS36) involved in lipid, carbohydrate, and amino acid metabolism. Dietary SBO showed an increased accumulation in proteins (i.e., QDPR, CABC1, and PRDX6) that respond to oxidative stress, suggesting that n-6 PUFAs induce oxidative conditions. Dietary SBO led to increase the accumulation of proteins (i.e., NITR26, NCCRP1, and LCN) involved in immune and inflammatory processes. Dietary LO increased the abundant levels of cytoskeleton-related proteins (i.e., ACTB, AHNAK, ERC2, KRT18, and RILP1). Other proteins (i.e., SELENBP1, FAM46C, and ANC1) involved in other physiological processes were also modulated by DL. qRT-PCR was performed to provide supportive information of proteomic study. Similar effects of DLs on mRNA levels were observed for atp5b, krt18, and selenbp1.