共查询到20条相似文献，搜索用时 31 毫秒
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P. Thomas D. Breckenridge-Miller C. Detweiler 《Fish physiology and biochemistry》1997,17(1-6):109-116
The binding characteristics of 17,20,21-trihydroxy-4-pregnen-3-one (20-S) to plasma membranes prepared from the testes and sperm of spotted seatrout (Cynoscion nebulosus) were investigated using a filtration method to retain the bound 20-S. A single class of high affinity (Kd = 17.9 nM), low capacity (Bmax = 0.072 nM g-1 testes) binding sites was identified by saturation and Scatchard analyses on testicular membranes of spermiating spotted seatrout. A corresponding receptor (Kd = 22.17 nM, Bmax = 0.00261 nM ml-1 milt) was also detected in spermatozoan membrane preparations. The rates of 20-S association and dissociation were rapid, both had Thalfs of less than 1 min. Competition studies indicated that the receptor was highly specific for 20-S. 17,20-dihydroxy-4-pregnen-3-one, which had the highest affinity of the other steroids tested, had a relative binding affinity (RBA) of 14.3%. Progesterone, 11-deoxycortisol and testosterone competed with an order of magnitude less affinity (RBA's of 7.4, 1.8 and 1.1%, respectively). Estradiol displayed low affinity for the receptor (RBA = 0.4%) and cortisol did not cause any displacement at 1000-fold excess concentration. Specific 20-S receptor binding was detected in plasma membranes from testes of both spermiating and non-spermiating seatrout and on spermatozoa. Prolonged incubation of testicular fragments from a spermiating fish with gonadotropin (15 IU ml-1 human chorionic gonadotropin) or forskolin (10 µM) caused a 2–3 fold increase in membrane receptor binding. Previous studies have shown that gonadotropin-induced upregulation of the 20-S plasma membrane receptor in seatrout ovaries is required for the oocytes to become responsive to 20-S and undergo final maturation. The existence of a 20-S membrane receptor on sperm and its upregulation in the testes by gonadotropin raises the possibility that final maturation of spermatozoa in male seatrout may be regulated by a similar mechanism. 相似文献
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Plasma levels of 17,20-dihydroxy-4-pregnen-3-one (17,20OHP), which is involved in the regulation of spermiation in male salmonid fish, increase dramatically at the time of spermiation. To advance the understanding of the regulation of 17,20OHP production during the spermatogenetic cycle in trout, we have studied the in vitro effect of gonadotropin type II (GtH II) and the precursor 17-hydroxy-4-pregnene-3,20-dione (17OHP) on the production of 17,20OHP. The sensitivity with which testes secreted 17,20OHP following stimulation with GtH II was maximum during spermatogenesis. The addition of 17OHP (10 to 1600 ng ml-1) to the culture medium of testes fragments induced a significant and dose-related increase in 17,20OHP secretion. Although the capacity to produce 17,20OHP was not saturated by the 17OHP concentrations used, the conversion rate was highest for tested at an immature stage. As to the regulation of 17OHP, in vivo, a single injection of partially purified salmon gonadotropin (50 ng g-1 body weight) induced a significant increase in the circulating levels of 17OHP of immature males. In conclusion, the maximum sensitivity to GtH II stimulation and the highest conversion rate of 17OHP to 17,20OHP in vitro, occurred before the dramatic increase in the 17,20OHP secretion observed in rainbow trout at the time of spermiation. 相似文献
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LINDe-fang GUANChang-tao HUANGWen-qiang 《海洋水产研究》2004,25(4):71-77
报道了我国大洋渔业技术现状,评述了技术水平、发展趋势,分析渔业技术存在的问题,提出了大洋渔业可持续发展应当进行的研究课题及建议。 相似文献
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Genome size (C value) is an important index for phylogenetic studies. Haliotidae (abalones) includes many species widely distributed throughout the world??s oceans, which makes this family interesting for phylogenetic studies. To examine Haliotidae phylogeny, we determined the C value and adenine and thymine base pair content (AT?%) of Haliotis discus hannai and H.?diversicolor aquatilis by using flow cytometry. The C values of H.?discus hannai and H.?diversicolor aquatilis were 1.84 and 1.45?pg, with AT?% of 62.3 and 66.3?%, respectively. These data represent the first report of abalones classified as Pacific Northwest (H.?discus hannai) and Indo-Pacific (H.?diversicolor aquatilis) groups, and provides new validation for previous theories related to Haliotidae phylogeny. 相似文献
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Elham Payandan Mahshid Shamloofar Hadi Koohsari 《Journal Of Aquatic Food Product Technology》2017,26(5):593-603
This study has evaluated the effects of different concentrations of the water and ethanolic extracts of Iranian propolis (WEP and EEP) on the microbiological and sensory parameters of minced common carp meat that was stored at 4°C for 9 days. The chemical compounds of the extracts were identified by gas chromatography–mass spectroscopy (GC-MS) analysis. The results revealed that WEP and EEP extracts were efficient against the spoilage microorganisms, including total plate counts (TPCs), psychrotrophic populations (PTCs), lactic acid bacteria (LAB), and even Staphylococcus aureus. There was a significant difference in the bacteria growth between samples treated with WEP or EEP and the control sample during storage. Inhibitory effects were, respectively, 7% EEP > 5% EEP > 3% EEP > 7% WEP > 5% WEP > 3% WEP. In all treatments, PTC counts were higher than 7 log CFU/g after 6 days as well as TPC, LAB, and S. aureus populations after 9 days. Overall, the results show that EEP and WEP have good antimicrobial activity due to high phenolic and flavonoid compounds, including caffeic acid, tectochrysin, aceacetin, chrysin, pinostrobin, pinobanksin-3-acetate, galangin-3-methyl ester, and pinocembrin chalcone. Sensory evaluation shows very slight improvement in sensory properties (color, odor, texture, and overall acceptability) of the treated samples with the different extracts of Iranian propolis. 相似文献
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J. Antonio Martinez J. Carlos Seijo 《Aquaculture Economics & Management (Blackwell Science)》2013,17(3-4):129-145
Abstract Reducing water exchange in shrimp aquaculture to minimize discharge of pollutants is a search for sustainability. In desert regions, like most of northwest Mexico, low water exchange must be complemented with artificial aeration to compensate for low levels of oxygen in warm and highly saline water. The economic yield of a low‐water‐exchange production system is compared against yield from a typical water‐exchange‐without‐aeration system for Penaeus vannamei culture. The difference between two systems is centered on pumping and aeration rates for a 100 ha semi‐intensive farm in northwest Mexico. A bioeconomic model was built to compare the systems. Risk analysis is adopted to account for uncertainty of seed price, shrimp growth rate, survival rate, and shrimp prices. The typical system was slightly more profitable than the low‐water‐exchange, aerated system. The latter used less electricity than the former in all of the three mortality‐rate scenarios. However, the difference in profitability is so small that for practical purposes both production systems provide similar economic yield. For a typical system, the probability of reaching a positive net present value (NPV) is high, therefore under the assumed risks, a 100 ha semi‐intensive shrimp farm in northwest Mexico is a good investment choice. 相似文献
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Fisheries Science - The effects of temperature and prey density on the recent growth rate (RGR) of chub mackerel, Scomber japonicus, were examined. Scomber spp. larvae and juveniles were collected... 相似文献
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LisbethPlassa 《海洋水产研究》2001,22(4):18-20
Activities1994In 1994 Peter Gullestad(Present Director General of Fisheries in Bergen) headed a Norwegian delegationvisiting China.In his presentation of“The N orwegian exp erience in fisheries management and control” - hestressed the fact that overcapacity is“the root of all evil”.He also underlined that it is important not only toset up a legal system for fisheries management but also to establish reliable catch statistics.He further morepointed out that good scientific advice is th… 相似文献
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J.P. Nash B. Davail- Cuisset S. Bhattacharyya H.C. Suter F. Le Menn D.E. Kime 《Fish physiology and biochemistry》2000,22(4):355-363
A simple and rapid Enzyme Linked ImmunoSorbant Assay (ELISA) is described and validated for testosterone, estradiol, and 17,20-dihydroxy-4-pregnen-3-one (17,20P). A general procedure for preparation of the acetylcholinesterase labeled steroid is described which is applicable to any steroid. Use of acetylcholinesterase tracer increased the sensitivity of assay so that reliable measurements of each steroid could be achieved with only 10 l of plasma. The ELISA was applied to measurement of all three steroids every hour for over 24 hours in a female trout using cannulation of the dorsal aorta. This high sampling frequency revealed several short-term (<2 h) episodic pulses of testosterone and estradiol. 相似文献
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Rotary feed spreaders are extensively used in large scale fish aquaculture and are tasked with distributing pelletized feed in a spatially uniform manner over the water surface. Questions have been raised with respect to the performance of classical spreader designs regarding the size and uniformity of the covered area as well as their inability to adapt to changing environmental conditions. This study presents a robotic model of rotary spreaders with experimental validations. Classic rotary spreaders are simulated as well as two alternative designs in the form of a spreader releasing pellets at an optimal initial ballistic angle and a motorized version to increase throw length and provide a more spatially homogeneous surface feed distribution. The alternative designs both yielded improved surface coverage without the need of higher conveying airspeed which may lead to increased pellet attrition. In addition, the motorized design may be used to position pellets at a given location within the sea cage, such as into the wind and current so that pellets can reside inside the sea cage for a prolonged period of time. The presented model may be of interest to researchers and equipment manufacturers who desire to explore performance of a given spreader design. 相似文献
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Anna Hellqvist Monika Schmitz Christina Lindberg Per-Erik Olsson Bertil Borg 《Fish physiology and biochemistry》2001,25(4):311-317
The mRNA expression of the LH- and FSH- subunits were measured in nesting and post-breeding male three-spined sticklebacks, Gasterosteus aculetaus, as well as in castrated and sham-operated nesting males. Furthermore, expression of an androgen induced kidney protein, spiggin, and 11-ketotestosterone (11KT) levels, were measured in the castrated and sham-operated males. Nesting males had significantly higher levels of both LH- and FSH- mRNA expression compared to post-breeding males. Furthermore, sham-operated males had significantly higher levels of LH- mRNA and spiggin mRNA expression than the castrated fish. Expression of FSH-, on the other hand, did not differ between castrated and sham-operated males. There were strong positive individual correlations between circulating levels of 11KT on the one hand and expressions of LH- and spiggin mRNA, whereas the correlation between 11KT levels and FSH- mRNA was weak. The negative effect of castration on -LH mRNA indicates that gonadal hormones stimulate this expression, whereas this was not the case for -FSH. The observed decline in -LH expression after the end of the breeding season may be the result of cessation of the gonadal stimulation of the pituitary. On the other hand, it is not likely that this can explain the decline in FSH- expression. 相似文献
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Domitília Matias Sandra Joaquim Alexandra Leitão Clara Massapina 《Aquaculture International》2009,17(3):257-271
Culture of Ruditapes decussatus is clearly limited by the availability of seed, as this production proceeds almost exclusively from natural recruitment.
Artificial spawning and larval rearing programs could provide an alternative source of spat. This study was designed to evaluate
the effect of different conditioning temperatures on the broodstock maturation, spawning success and larval viability of two
geographically (north and south of the Iberian Peninsula) distinct populations of European clam (R. decussatus) collected at different periods of the year in order to create “optimal” artificial spawning and larval rearing programs.
Two batches of clams from each population were collected in October and February, and conditioned at 18 ± 1°C, 20 ± 1°C and
22 ± 1°C. Of the three variables analysed the timing of broodstock collection was the most determining factor for gametogenic
development, spawning and larval rearing. Geographic origin and conditioning temperature also greatly affected the spawning.
The results also showed that the February conditioning was more effective than October and that the best conditioning temperatures
were 20 ± 1°C and 22 ± 1°C for the northern and southern populations, respectively. These results suggest that the efficient
conditioning temperature for each population of the same species is related to the seasonal temperature regime from their
geographic origin. Larval viability and growth performance seemed to be independent of the broodstock conditioning. 相似文献
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This study was undertaken to determine the influence of orally administered 3,3,5-triiodo-L-thyronine (T3) or 17--methyltestosterone (MT) on growth and body composition of the eel (Anguilla anguilla L.) during the glass stage.Elvers receiving 20 or 40 ppm of T3 in the food weighed significantly more (P < 0.05) than controls. However, after 61 days of treatment a dosage of 60 ppm was not efficacious.Terminal percentages of body protein were significantly lower (P < 0.05) in elvers that received 20 ppm or 40 ppm T3 in their diets, than in the control. Crude body fat content was higher (P < 0.05) in elvers receiving 20 ppm (29% fat) or 40 ppm (28% fat), than in the controls (26% fat). Compared to the control, diets containing T3 at 20 or 40 ppm increased the body glucose concentration.Glass eels fed a diet containing 1 or 10 ppm MT grew significantly more slowly (P < 0.05) than the controls.Total body protein content was higher (P < 0.05), but total body crude fat content was lower (P < 0.05) in elvers fed a diet with 1 or 10 ppm MT compared to the controls. Total body glucose concentration of elvers administered 10 ppm MT was significantly lower (P < 0.05) than that of the control groups. 相似文献
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In this study we examined the endocrine mediation between environmental factors (temperature and photoperiod) and the brain–pituitary–gonadal
axis in females of pejerrey Odontesthes bonariensis. Changes in the expression of brain gonadotropin-releasing hormones (GnRHs) and gonadotropin (GtH) subunit [follicle stimulating-β
(FSH-β), luteinizing hormone-β (LH-β), glycoprotein hormone-α (GPH-α)] genes, plasma gonadal steroids [estradiol (E2) and testosterone (T)], gonadal histology, and gonadosomatic index (GSI) in adult females exposed to combinations of short-day
(8 h) or long-day (16 h) photoperiods and low (12°C) or high (20°C) temperatures after winter conditions (8 h light, 12°C)
were analyzed. Pejerrey females kept under the short photoperiod had low GSIs, and their ovaries contained only previtellogenic
oocytes regardless of the experimental temperature. In contrast, females exposed to the long photoperiod had high GSIs and
ovaries with vitellogenic oocytes at both temperatures. These fish also showed a significantly higher expression of sGnRH,
pjGnRH, cGnRH-II (the three different GnRH variants found to date in the pejerrey brain), FSH-β, LH-β and GPH-α genes and
plasma E2 levels than those at the shorter photoperiod. No significant changes were observed in plasma T levels. Based on these results,
we concluded that the increase in day length but not that of temperature triggers the maturation of pejerrey females after
the winter period of gonadal rest and that this occurs by an integrated stimulation of the various components of the brain–pituitary–gonad
axis. 相似文献
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ABSTRACT: As part of a study to clarify the differences in the temporal change in K -value among fish species, the temporal change in K -value and the 5'-inosine monophosphate (5'-IMP) and p-nitrophenol phosphate (p-NPP) degrading activities in the red, pink, and white muscle fibers in the dorsal muscle of the carp were compared. The temporal change in K -value was fastest in red, followed by pink, and white muscle fibers, at both 0°C and 32°C. Moreover, the 5'-IMP and p-NPP degrading activities were highest in red, followed by pink, and white muscle fibers at near optimum pH concentrations. The 5'-IMP degrading activity at pH 7.0 had a positive correlation with the increasing rate of K -value at 32°C for all types of muscle fibers. These results suggest that differences in increasing rates of K -values between red, pink, and white muscle fibers corresponded to the 5'-IMP degrading activities. 相似文献
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M. Aldegunde J.L. Soengas C. Ruibal M.D. Andrés 《Fish physiology and biochemistry》1999,20(4):325-330
Rainbow trout (Oncorhynchus mykiss) were implanted intraperitoneally with 0.5 ml.100 g–1 body weight of coconut oil alone (controls) or coconut oil contaning 0.05 mg of -HCH (Lindane). After 18 days, changes in brain serotonin and GABA metabolism, as well as in serum cortisol and thyroxine levels, were measured. A lower final body weight was observed in -HCH treated fish when compared with control fish. No significant differences were found for serum thyroxine levels between control and treated fish, but a significantly higher cortisol level was found in the -HCH-implanted trout. Although GABA levels did not differ significantly in any brain region in the two treatment groups, the activity of the serotonergic system was significantly altered by the pesticide in both the hypothalamus and the telencephalon. 相似文献