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991.
This paper explores the plasticity of sexually dimorphic characters in subadult female Brevimyrus niger, an African weakly electric mormyrid species. Thirty-five fish were exposed in a staggered fashion (five fish a week) to aromatizable 17α-methyltestosterone over a period of 7 weeks; 18 fish served as untreated controls. 17α-MT induced precocious vitellogenesis that mirrored the natural maturational process during seasonal ovarian recrudescence. At the same time, 17α-MT exposure resulted in complete masculinization of the females’ anal fin support structure normally observed during rainy season in adult males. We discuss possible hormonal mechanisms acting along the brain-pituitary-gonad axis that would explain the occurrence of precocious vitellogenesis and the male-typical transformation of the female’s anal fin ray bases. Our findings are relevant to commercial aquaculture as the use of 17α-MT in fish hatcheries can pose serious environmental issues. 相似文献
992.
Kazuhiro Shiozaki Momo Shiozaki Junko Masuda Akiko Yamauchi Shuichi Ohwada Toshiki Nakano Toshiyasu Yamaguchi Tadao Saito Koji Muramoto Minoru Sato 《Fisheries Science》2010,76(5):865-872
Angiotensin-I-converting enzyme (ACE) plays a crucial role in the crisis of hypertension. Some peptides that originate from
protease hydrolysates are known to suppress ACE activity in vitro and in vivo. Here, we investigated whether trypsin hydrolysate
of oyster Crassostrea gigas showed hypotensive activity and ACE inhibition. The hydrolysate significantly suppressed systolic blood pressure and ACE
activity in spontaneously hypertensive rats following a one-shot oral administration and a long-term feeding experiment lasting
9 weeks. Each hydrolysate from oyster tissue showed ACE inhibitory activity, indicating the hypotensive effect was due to
synergism. One potent ACE inhibitory peptide, Asp-Leu-Thr-Asp-Tyr, was identified from the hydrolysate of the striate muscle,
and the peptide exhibited hypotensive activity in vivo. Protease digestion analysis suggested that Asp-Tyr could be the real
effector of this penta-peptide in vivo. 相似文献
993.
994.
Some Limiting Factors in Superintensive Production of Juvenile Pacific White Shrimp,Litopenaeus vannamei,in No‐water‐exchange,Biofloc‐dominated Systems
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David I. Prangnell Leandro F. Castro Abdulmehdi S. Ali Craig L. Browdy Paul V. Zimba Susan E. Laramore Tzachi M. Samocha 《Journal of the World Aquaculture Society》2016,47(3):396-413
Superintensive shrimp culture in zero‐exchange, biofloc‐dominated production systems is more biosecure and sustainable than traditional shrimp farming practices. However, successful application of this technology depends upon optimizing dietary formulations, controlling Vibrio outbreaks, and managing accumulative changes in water quality and composition. A 49‐d study investigated the effect of two commercial feeds of differing protein content and an indoor limited‐exchange, biofloc‐dominated culture environment on Litopenaeus vannamei performance and tissue composition, water quality and ionic composition, and Vibrio dynamics. Juveniles (5.3 g) were stocked at 457/m3 into four 40 m3 shallow raceways containing biofloc‐dominated water and fed one of two commercial feeds with differing protein content, 35 or 40%. Shrimp performance, Vibrio populations, and changes in shrimp and culture water composition were monitored. There were no significant differences (P > 0.05) in shrimp performance (survival, weight, growth, specific growth rate, total biomass, yield, feed conversion ratio, and protein efficiency ratio) or proximate composition between feed types. The 40% protein feed resulted in higher culture water nitrate and phosphate concentrations, alkalinity consumption and bicarbonate use, and higher phytoplankton density. The presence of Vibrio, specifically Vibrio parahaemolyticus, reduced shrimp survival. This survival decrease corresponded with increased culture water Vibrio concentrations. Culture water K+ and Mg2+ increased significantly (P < 0.05), and Sr2+, Br?, and Cl? decreased significantly (P < 0.05) over time. While Cu2+ and Zn2+ did increase in shrimp tissue, no heavy metals accumulated to problematic levels in culture water or shrimp tissue. These results demonstrate the importance of monitoring Vibrio populations and ionic composition in limited‐exchange shrimp culture systems. 相似文献
995.
Charlie M. Culpepper III Peter J. Allen 《Journal of the World Aquaculture Society》2016,47(3):314-326
Extensive crappie, Pomoxis spp., culture has been practiced for decades, however, knowledge of crappie aquaculture methods is limited. The following review synthesizes existing research on crappie aquaculture and identifies knowledge gaps where further research is needed. Topics such as life history, tank culture, feeding, reproduction and spawning, larval rearing, transport and harvest, triploidy, hybridization, and out‐of‐season spawning were reviewed. The outcome is a better understanding of hindrances preventing crappie aquaculture development in the past, particularly tank culture and induced spawning techniques, and specific research objectives with potential to enhance recreational and commercial production. 相似文献
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998.
Purpose
Carbon nanomaterials (CNMs) have attracted a great deal of research interest for their potential environmental applications because of their unique properties. Adsorption of organic chemicals on CNMs was reported to be important in controlling their environmental risks. However, the kinetics of the adsorption is hardly investigated in literature. The objective of this work was, therefore, to quantitatively describe the sorption kinetics of 17 α-ethinyl estradiol (EE2) and bisphenol A (BPA) on CNMs as compared to activated carbon (AC). 相似文献999.
Ruijuan Li Jinfeng Zhao Chuanfan Sun Wenjing Lu Chengjin Guo Kai Xiao 《Frontiers of Agriculture in China》2010,4(2):195-209
As a kind of enzyme widely existing in eukaryotic species, especially in grains and oil seeds, phytases play an important
role in the degradation of some phosphates containing organic molecules. So far, phytases derived from various species have
been successfully used as animal feed additives. It has also been experimentally verified that phytases have a potential use
in generating crop germplasm with high phosphorus use efficiency, based on their biochemical role in releasing Pi from the
phytate and its derivatives. In this paper, the biochemical properties, molecular characterizations, functions and the potential
application perspective of phytases are reviewed and commented on, aiming at the further exploration of the biochemical and
molecular characterizations, and promotion of the application of phytases, a kind of important enzyme possessing potential
use in animal feeding and creation of high P use crop cultivars, in the future. 相似文献
1000.
It has been found that mechanical activation of amorphous carbon obtained from Katerina SV corn waste encourages formation of carbon nanotubes. At the same time, carbon tube output after 7 and 42 hours of mechanical activation is 11 and 42% by weight, respectively. 相似文献