Osteological development and deformities in hatchery‐reared longtooth grouper (Epinephelus bruneus): Vertebral column,dorsal‐fin supports and caudal‐fin skeleton

Skeletal deformities are one of the serious problems in hatchery‐reared longtooth grouper (Epinephelus bruneus). In this study, seed production of longtooth grouper was carried out in four large hatchery‐grade tanks. Osteological development of the vertebral column, caudal‐fin skeleton and dorsal‐fin supports in larvae and juveniles was described. The vertebral ontogeny started at 4.8 mm total length (TL) with the formation of neural spines 2 and 3, and the vertebral centra began forming at 5.3 mm TL. By 16 mm TL, all vertebral bony elements were formed except for the dorsal ribs. The onsets of the ontogeny of the caudal‐fin skeleton and dorsal‐fin supports occurred at approximately 5.1 mm and 3.9 mm TL, respectively, and the completion of these bony elements occurred at approximately 20 mm TL. The incidence of deformity was examined; some type of deformity was observed in 57%–68% of the specimens. These deformities mainly occurred as three types: lordosis, around vertebrae 1–5; saddleback‐like syndrome, around vertebrae 7–11; and vertebrae fusion, around vertebrae 22–24. The incidence of prehaemal lordosis was significantly higher among individuals with an uninflated swim bladder than among those with an inflated swim bladder.     

Soluble organic nitrogen pools in greenhouse and open field horticultural soils under organic and conventional management: A case study

The aim of this study was to investigate the influence of four different horticultural management practices in open field and in greenhouse conditions under organic and conventional cultivation on the amount of soluble organic nitrogen (SON) present in the soil. Soils used in greenhouses and open field cultivation were sampled in Shanghai, China, where organic farming has been conducted for 3 years or conventional faming has been continued in the same area. The amounts of SON, nitrate (NO₃^?) and ammonium (NH₄⁺) were greater in the greenhouse soils than those under open field cultivation, which indicated a higher degree of soil management was imposed under greenhouse conditions. Greenhouse cultivation is also known to accelerate the turnover of SON in the soils, which may explain the significantly higher amounts of SON present in these soils. Organic farming, which does not use artificial fertilizers and pesticides, also resulted in significantly higher amounts of SON (average 42.10 mg kg^?1) compared with soils under conventional faming (24.59 mg kg^?1). The reasons for the observed differences in pool sizes of soluble inorganic nitrogen (SIN) and NO₃^? in the greenhouse soils and the open fields include (a) the heavy application of both complex fertilizer and organic fertilizer that exceeded crop requirements and (b) warmer temperatures and moist soils in the greenhouses, which are likely to lead to greater rates of N cycling compared with the open field soils. These results suggest that SON may be an important source of N in all horticultural systems, representing a pool of labile N readily available for plant growth. However, its concentration is less sensitive to different management practices than SIN. In contrast to SON, the total soluble nitrogen and inorganic N (SIN) pools varied widely with the different management practices although they were dominated by NO₃^? in all treatments. Soil organic N was positively related to dissolved organic carbon and NO₃^? contents. This relationship indicates that NO₃^? and dissolved organic matter play a key role in the retention of SON in soil.     

Sequential preovulatory expression of a gonadotropin-releasing hormone-inducible gene,Nr4a3, and its suppressor Anxa5 in the pituitary gland of female rats

Functional relationship between nuclear receptor subfamily 4 group A member 3 (Nr4a3) and annexin A5 (Anxa5), which are two gonadotropin-releasing hormone (GnRH)-inducible genes, has been established while evaluating pituitary gonadotropes in relation to follicle-stimulating hormone beta (Fshb) expression. However, the physiological variations that arise due to the differential expression of these genes in the pituitary gland during rat estrous cycle remain unknown. This study aimed to evaluate the Nr4a3 and Anxa5 mRNA expression during the estrous cycle in rats in comparison with the expression of the gonadotropin subunit genes, luteinizing hormone beta (Lhb) and Fshb. Nr4a3 mRNA expression showed a single peak at 1400 h of proestrus during the 4-d estrous cycle. Anxa5 mRNA level was elevated along with increased Fshb mRNA expression after the decline of Nr4a3 mRNA until 2300 h. Lhb mRNA expression levels were not significantly changed during the estrous cycle. Notably, addition of a GnRH antagonist at 1100 h completely eradicated luteinizing hormone secretion at 1400 h and 1700 h of proestrus, and significantly reduced the Nr4a3 mRNA expression level at both the time points. These results suggest that GnRH is, at least partly, responsible for the increase in pituitary Nr4a3, and that the interaction between NR4A3 and ANXA5 is required to regulate Fshb expression during the preovulatory gonadotropin surge.     

Accumulation of lipofuscin in broiler chicken with wooden breast

Lipofuscin is one of the indicators of oxidative stress. To elucidate the role of oxidative stress in the development of wooden breast, this study investigates lipofuscin accumulation in various parts of wooden breast muscles. Sampling was performed using 46-day-old broiler chickens housed at a commercial Japanese poultry slaughterhouse. Fourteen wooden breast fillets and 13 normal breast fillets were collected in the deboning line. The samples used to measure shear force, 2-thiobarbituric acid reactive substance (TBARS), and for histological analysis were taken from the six portions of breast muscle fillets. In muscles affected by wooden breast, vacuolated muscle fibers were observed, and connective tissues appearing like perimysium were expanded with fibrosis. TBARS value and accumulation of lipofuscin were significantly higher in the wooden breast than in the normal breasts. A lot of lipofuscin granules were localized in the cytoplasm of collapsed muscle fibers of the wooden breast. The cranial portion of the wooden breast showed the highest shear force. The cranial position had a large amount of connective tissue and lipofuscin granules. The results of the present study strongly suggest that high oxidative stress, especially with a significant accumulation of lipofuscin, is associated with the development of wooden breasts.     

Atomic force microscopy of thermally treated myosin filaments

Heat-induced morphological change in myosin filaments was observed using atomic force microscope. The thickness of fixed native myosin filament was estimated to be 95 +/- 5 nm. When myosin filaments in 0.1 M NaCl at pH 6.0 were heated at 40, 55, and 70 degrees C for 10 min, the particulate structure appeared spirally on the surface of the filament at 40 degrees C, and the thickness of the filament was 75 +/- 10 nm. When myosin filaments were treated at 55 degrees C, several filaments were formed associated with side-by-side interaction through projected myosin heads to form a strand. The surface of the strand looked knobby. The thickness of thermally denatured filaments at 55 degrees C was 48 +/- 5 nm, and that of strands was about 80-110 nm, indicating the involvement of several filaments in a strand. The strands became to be rope-like at 70 degrees C, and the individual filaments in a strand were not distinguishable.     

Abnormal functions of Leydig cells in crossbred cattle–yak showing infertility

In Mongolia, yak (Bos grunniens) are able to live in alpine areas and their products greatly influence the lives of the local people. Increased vigour in hybridized yak and cattle can offer benefits for livestock farmers. However, male hybrids show reproductive defects resulting from spermatogenesis arrest, affecting the conservation and maintenance of dominant traits in the next generation. The underlying mechanisms involved in hybrid cattle–yak infertility have recently been investigated; however, the genetic cause is still unclear. Androgens and androgen receptor (AR) signalling are required for spermatogenesis. We, therefore, evaluated the expression of AR, 3β-hydroxysteroid dehydrogenase (3βHSD) and 5α-reductase 2 (SRD5A2) in Leydig cells to investigate their function in cattle–yak spermatogenesis. Testicular tissues from yaks (1–3 years old) and hybrids (F1–F3, 2 years old) were collected and subjected to immunohistochemistry and image analyses to investigate the expression of each parameter in the Leydig cells. After maturation at 2 years, the expression levels of AR increased and the levels of 3βHSD decreased, but the SRD5A2 levels remained constant in yak. However, the cattle–yak hybrid F2 showed immature testicular development and significantly different expression levels of AR and 3βHSD compared with mature yak. These results suggest that the decreased expression of AR and increased expression of 3βHSD in the Leydig cells of cattle–yak hybrid testes may represent one of the causes of infertility. Our study might help in solving the problem of infertility in crossbreeding.