Oocyte development and serum profiles of vitellogenin and steroid hormone levels in captive female Pacific herring Clupea pallasii during their first maturational cycle

ABSTRACT:   The present study investigates the relationship between oocyte development and serum steroid hormone levels in captive Pacific herring, Clupea pallasii , during the first reproductive cycle. The process of oocyte development in Pacific herring belongs to the group-synchronous type. Maturity of the ovary was divided into six periods based on histological observation (i.e. immature (April to September), onset of vitellogenesis (August to October), progress of vitellogenesis (October to December), completion of vitellogenesis (December to March), maturation and spawning (March to April) and spent (late April)). The pattern of seasonal change in the gonadosomatic index (GSI) well reflected the ovarian maturity. Serum vitellogenin levels showed good correlation with change in GSI, which increased from September to a peak (4.2 ± 0.3 mg/mL) in March. Serum estradiol-17β (E2) levels elevated from September and reached a peak (15.8 ± 4.2 ng/mL) in December, and remained comparatively high until March, suggesting that the active vitellogenin synthesis during vitellogenesis is controlled by the high E2 level. 17,20β-Dihydroxy-4-pregnen-3-one showed a single sharp peak (2.4 ± 0.28 ng/mL) in early April of the second year, suggesting it was a maturation-inducing steroid in this species.     

Molecular cloning of an elongation factor 1α and its mRNA localization in testis of the Nile tilapia Oreochromis niloticus

During spermatogenesis, many proteins are synthesized in the testis prior to the completion of sperm maturation. Many components are involved in the testicular protein synthesis and one of the components that is implicated in the polypeptide chain elongation is elongation factor 1α. In the present study, the molecular cloning of elongation factor 1α (EF-1α) was conducted from a testis cDNA library of the Nile tilapia. The cDNA for tilapia EF-1α (tEF-1α) contains a complete open reading frame encoding 462 amino acids. The predicted amino acid sequence of EF-1α shows an approximate 90% similarity to those identified in other teleost fish, such as medaka, sea bream and zebrafish. Northern blotting revealed that the gene is expressed in all of the examined tissues and in ovulated eggs. The results of in situ hybridization indicate that the gene is expressed specifically in Leydig cells in testis, suggesting the involvement of EF-1α as an actin-binding protein in the cluster formation of Leydig cells. In the ovary, the gene is expressed in the perinucleolus stage of oocytes, suggesting that EF-1α is also implicated in oocyte growth.     

QUANTITATIVE CONTRAST-ENHANCED ULTRASONOGRAPHY OF CANINE SPLEEN

Contrast-enhanced ultrasonography has an important role in the detection of tumors in humans. The second-generation contrast agent Sonazoid has the ability of real-time contrast imaging along with parenchymal imaging. The purposes of this study were to determine the effect and duration of Sonazoid on the changes in gray-scale enhancement of canine spleen and to establish an appropriate protocol for contrast-enhanced ultrasonography of canine spleen. Six healthy beagles were injected with an intravenous bolus of Sonazoid. In the spleen parenchyma, the enhancement was maintained up to 30 min after injection. Moreover, for 5–22 s after injection, gray-scale enhancement of splenic arteries afforded arterial imaging. Perfusion of the kidney may be investigated from 3.6 s to 3.5 min after injection of Sonazoid. These results suggest that Sonazoid is applicable to canine spleen parenchymal imaging and that the optimal time for the parenchymal imaging is 7–30 min after injection. The findings of this quantitative study should prove useful in the evaluation of diffuse or focal splenic and renal diseases in dogs.     

Herbicide pyrazolate causes cessation of carotenoids synthesis in early watergrass by inhibiting 4-hydroxyphenylpyruvate dioxygenase

In aqueous solution, the herbicide pyrazolate [4‐(2,4‐dichlorobenzoyl)‐1,3‐dimethyl‐5‐pyrazolyl p‐toluenesulfonate] is rapidly hydrolyzed to destosyl pyrazolate (DTP), 4‐(2,4‐dichlorobenzoyl)‐1,3‐dimethyl‐5‐hydroxypyrazole, which is an active form of the herbicide. The objective of this study was to examine the effect of pyrazolate and DTP on carotenoids synthesis in susceptible weed, early watergrass (Echinochloa oryzicola Vasing.). Furthermore, their in vitro effect on 4‐hydroxyphenylpyruvate dioxygenase (HPPD) was determined. Roots of the plants at the two‐leaf stage were soaked for 24 h into pyrazolate (5 × 10^–5 mol L^?1) or norflurazon (10^–6 mol L^?1) solution containing 0.5% volume of acetone. At the first sampling time (3 days after treatment: 3 DAT), the chlorophyll content in the third leaves of pyrazolate‐treated plants were not different compared with the untreated control, but it was decreased between 3 and 6 DAT. The declining pattern of β‐carotene in the third leaf of early watergrass was very similar to that of chlorophyll. Both herbicides induced greater accumulation of phytoene in the third leaves of early watergrass 3 DAT, and the levels were kept until 9 DAT. However, feeding of homogentisate reduced the phytoene accumulation only in pyrazolate‐treated plants, suggesting the site of action of the herbicide located in the pathway of plastoquinone synthesis. In a HPPD assay, DTP revealed to inhibit the enzyme with an IC₅₀ value of 13 nmol L^?1 and that of pyrazolate was 52 nmol L^?1. In the pyrazolate solution used in the assay, some of the herbicide possibly has been hydrolyzed to DTP. From the all results obtained, it is strongly suggested that pyrazolate inhibits carotenoids synthesis and causes bleaching on the developing leaves by the similar mechanism with norflurazon, but its action site is not phytoene desaturase and is HPPD.     

Testicular development and serum profiles of steroid hormone levels in captive male Pacific herring Clupea pallasii during their first maturational cycle

The present study investigates the relationship between testicular development and serum steroid hormone levels in captive Pacific herring Clupea pallasii during the first reproductive cycle. The maturity of the testis was divided into five periods based on histological observation. These are early spermatogenic stage (April to July), mid-spermatogenic stage (August to November), late spermatogenic stage (December to March), functional maturation stage (early April) and spent stage (late April). The pattern of seasonal change in gonadosomatic index (GSI) clearly reflected testicular maturity. 11-Ketotestosterone (11-KT) levels increased from October to a peak level (6.58 ± 1.87 ng/mL) in January, and were maintained at this level until March. In contrast, testosterone levels were consistently low, less than 1 ng/mL, at all times. These results suggest that 11-KT is the predominant androgen that controls spermatogenesis in this species. 17,20β-Dihydroxy-4-pregnen-3-one (DHP) showed a single sharp peak (3.38 ± 0.35 ng/mL) in early April of the second year, suggesting that milt production is induced by DHP as in some other teleost species.