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  • 1
    Electronic Resource
    Electronic Resource
    Mammalian Growth Hormone-Releasing Hormone Indirectly Stimulates Sex Steroid Production in Tilapia (2000)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the World Aquaculture Society 31 (2000), S. 0 
    Details
    ISSN: 1749-7345
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract.— Fish possess a growth hormone similar to mammalian growth hormone, and the presence of a growth hormone-releasing hormone-like material in the brain has been demonstrated in several teleost species. We investigated the effect of a mammalian growth hormone-releasing hormone on serum estradiol-17β and testosterone concentrations in tilapia Oreochromis mossambicus and a hybrid O. niloticus×O aureus because growth hormone has been implicated in the regulation of gonadal functions in teleosts. Three hours after injecting the releasing hormone, male and female serum testosterone concentrations significantly increased compared to controls, while serum estradiol-17β concentrations increased significantly only in females. These increases were commensurate with respective serum steroid concentrations in fish injected with gonadotropin releasing-hormone. Studies utilizing hypophysectomized fish resulted in non-detectable levels of serum sex steroids in fish treated with the growth hormone-releasing hormone; however, significant increases occurred in fish treated with human chorionic gonadotropin. Similarly, gonadal tissue incubated with growth hormone releasing hormone had non-detectable levels of sex steroids in the media, whereas gonads incubated with human chorionic gonadotropin had significant increases in sex steroid concentrations. These studies suggest that growth hormone-releasing hormone acts at the level of the pituitary. Although mammalian growth hormones have been shown to increase serum gonadotropic hormone concentrations, this study provides evidence that a mammalian growth hormone-releasing hormone has the ability to indirectly increase sex steroid levels in fish.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-7345.2000.tb00891.x
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  • 2
    Electronic Resource
    Electronic Resource
    A Mammalian Growth Hormone-Releasing Hormone Increases Serum Growth Hormone Levels and Somatic Growth at Suboptimal Temperatures in Tilapia (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the World Aquaculture Society 27 (1996), S. 0 
    Details
    ISSN: 1749-7345
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The effects of a mammalian growth hormone-releasing hormone (GHRH), PrebGRF(1–78)OH (bGHRH), on growth and serum growth hormone (GH) levels were investigated in tilapias Oreochromis mossambicus andO. niloticus × O. aureus. Fish were injected intramuscularly or implanted intramuscularly (Silastic or cholesterol implants) with distilled water, 0.1 μg/kg bGHRH, 1.0 μg/kg bGHRH, 10.0 μg/kg bGHRH, or 100.0 μg/kg bGHRH and compared to untreated controls, fish implanted with 60 mg/kg 17α-methyltestosterone (MT), or a combination of bGHRH concentrations plus either MT, 0.01 μg/kg of a thyroid hormone (T3), or 0.01 μg/kg of a glucocorticoid (DEX). The bGHRH increased serum GH levels in tilapia maintained at suboptimal temperatures (18 C). Serum GH levels were highest (5.3–0.45 ng/mL) for fish injected with 10.0 μg/kg bGHRH. Fish implanted with a Silastic implant containing 10.0 μg/kg bGHRH had significantly higher (4.35–0.35 ng/mL) serum GH levels than those with an equivalent dosage in a cholesterol implant. The addition of MT, thyroid hormones, and glucocorticoids did not increase serum GH levels above those obtained for fish receiving bGHRH alone. Tilapia reared at suboptimal temperatures and implanted with 10.0 μg/kg and 100.0 μg/kg bGHRH had significantly greater increases in weight and length than control fish. Fish implanted with bGHRH, MT or bGHRH plus MT had significantly higher moisture and protein content, while fat and ash contents were significantly lower than controls or sham-implanted fish. Fish implanted with bGHRH or bGHRH plus MT had significantly higher gonadosomatic indices than fish implanted with MT alone, shams or non-treated controls. This study demonstrates that a mammalian GHRH stimulates release of GH, promotes somatic and gonadal growth and may affect reproductive performance in tilapia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-7345.1996.tb00623.x
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  • 3
    Electronic Resource
    Electronic Resource
    Environmental and Ethical Concerns Associated with Transgenic Fishes (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the World Aquaculture Society 23 (1992), S. 0 
    Details
    ISSN: 1749-7345
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-7345.1992.tb00756.x
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  • 4
    Electronic Resource
    Electronic Resource
    Procedural Protocol, Survival to Hatching and Plasmid DNA Fate After Microinjection into Tilapia Zygotes (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the World Aquaculture Society 23 (1992), S. 0 
    Details
    ISSN: 1749-7345
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The plasmid vector, pBRd-AK1-BGH4.6.10 (pBGH), containing the bovine growth hormone sequence driven by an avian retroviral long terminal repeat (LTR) was microinjected at 0.1, 0.5, 1 or 5 ng of pDNA/20 nl of physiological saline into tilapia, Oreochromis mossambicus × O. niloticus embryos. In 24 replicates, normally 60 zygotes were microinjected with either the entire linear 8.5 kb pBGH/ClaI vector or a 3.8 kb pBGH/SalI restriction fragment. Overall mean survival to fry hatching was 7.6% in plasmid DNA-microinjected, 15.6% in sham-microinjected and 48.1% in uninjected control embryos. There were no significant (P 〉 0.05) differences in survival to hatching between those embryos microinjected with the 3.8 or the 8.5 kb restriction fragment, nor was there a trend toward decreasing survival as the plasmid DNA concentration increased from 0.1 to 5 ng. The significant (P 〈 0.05) increase in survival among uninjected control embryos to hatching indicates that microinjection trauma was the major cause of mortality. Large quantities of plasmid DNA were recovered from pooled-embryo samples. Multiple bands (positive signals) were detected usually in the high molecular weight (HMW) genomic DNA regions. Position shifting of these HMW bands upon digesting with various restriction endonucleases provided evidence for plasmid DNA integration into tilapia embryo chromosomal DNA. Otherwise, these positive signah may have been end-twnd ligations of increasingly longer plasmid DNA constructs. Putative transgenic O. mossmbicus × O. niloticus were found among eight of 27 surviving adults.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-7345.1992.tb00757.x
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  • 5
    Electronic Resource
    Electronic Resource
    Effects of Dietary Protein Concentration on Growth, Survival, and Body Composition of Muskellunge Esox musquinongy and Tiger Muskellunge Esox masquinongy × E. luscius Fingerlings (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the World Aquaculture Society 26 (1995), S. 0 
    Details
    ISSN: 1749-7345
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Growth rate, survival and body composition of muskellunge Esox musquinongy (initial mean total length = 125 mm) and tiger muskellunge E. masquinongy × E. lucius (initial mean total length = 115 mm) fed semi-purified diets differing in protein level from 31 to 40% and 34 to 45%, respectively, were evaluated in 8-wk trials. The minimum protein level that yielded satisfactory growth rates for muskellunge was 37%, whereas tiger muskellunge growth rates were highest for fish fed a 45% protein diet. Growth differences were caused by changes in protein quantity, not quality, as amino acid ratios were similar for test diets and showed no imbalances among diets. Condition factors for both fishes increased with dietary protein. Survival of muskellunge (73%) and tiger muskellunge (97%) was not pffected by diet type. Body protein increased and fat content decreased in both fishes when fed higher dietary protein. Results suggest that both fishes respond similarly to dietary changes, but that substantial differences exist in protein requirements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-7345.1995.tb00837.x
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  • 6
    Electronic Resource
    Electronic Resource
    Application of High Hybridization Stringency Technology to the Analysis of Putative Transgenic Fish and Their Progeny (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the World Aquaculture Society 23 (1992), S. 0 
    Details
    ISSN: 1749-7345
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Eight putative transgenic hybrid tilapia (Oreochromis mossambicus × O. niloticus) and their F, progeny were screened by Southern blot analysis for the presence of the bovine growth hormone transgene (bGH). Transgenic mice known to contain one copy of the bGH gene per genome were used as positive controls allowing for the determination of detection levels under high hybridization stringency conditions. At a sensitivity level of one copy per genome, the bovine growth hormone transgene was not detected in any of the experimental animals. The apparent lack of bGH transgene in the fish DNA at one copy per genome, coupled with no detectable levels of bovine growth hormone being found in either serum or whole blood of the original adults, indicates these fish are either not transgenic, or that they are mosaics and do not express the transgene. Results demonstrate the need for positive controls when conducting Southern blot analysis of potentially transgenic organisms. Mammalian models appear to be suitable positive controls and should be employed until transgenic piscine models are readily available. It is suggested that high hybridization stringency is necessary when analyzing for evolutionarily conserved transgenes such as those controlling growth hormones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-7345.1992.tb00758.x
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  • 7
    Electronic Resource
    Electronic Resource
    Inability to Detect a Choline Requirement for the Blue Tilapia Oreochromis aureus (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the World Aquaculture Society 21 (1990), S. 0 
    Details
    ISSN: 1749-7345
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-7345.1990.tb01029.x
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  • 8
    Electronic Resource
    Electronic Resource
    Establishment of Tilapia Spawning Families Providing a Continuous Supply of Eggs for in vitro Fertilization (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the World Aquaculture Society 22 (1991), S. 0 
    Details
    ISSN: 1749-7345
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Three hybrid tilapia (Oreochromis mossambicus ± O. niloticus) spawning families were established in three separate culture tanks to provide a continuous supply of fresh gametes. An ovulation event, resulting in a natural spawn, an artificial spawn or oocyte resorption, occurred with a mean of every 1.4 days among 19 females, though only a few females demonstrated periods of evenly spaced 10 to 20 day maturation-ovulation cycles. Ovulation events/female/year were similar among the three spawning families: 13.1, 17.5 and 13.4/female, as were mean interovulation intervals (23.6, 21.9, and 23.9 days). Estimated fertilization rates, both natural and as a result of strip-spawning, were highly variable. Rates from natural spawns ranged from a mean per female of 25.7 to 57.3%, and from artificial spawns from 47.8 to 58.8%. Establishment and active management of spawning families of tilapias proved to be an effective procedure for obtaining a continuous supply of gametes for manipulative genetic research.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-7345.1991.tb00737.x
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  • 9
    Electronic Resource
    Electronic Resource
    Influence of 17-α-Methyltestosterone on Red Tilapia Under Two Thermal Regimes (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the World Aquaculture Society 22 (1991), S. 0 
    Details
    ISSN: 1749-7345
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Fingerling red tilapia (Oreochromis mossambicus±O. niloticus) were orally administered 17-α-methyltestosterone (MT) under a warmwater (27.0 ± 0.5 C) and coolwater (21.5 ± 0.5 C) thermal regime. In the warmwater experiment, fish received either 0, 1, 5, 10, 30, 60, or 100 mg MT/kg feed for 75 days. In the coolwater experiment, fish received 0, 10, or 60 mg MT/kg feed for 75 days followed by a 34 day withdrawal period. After 75 days, fish receiving 60 mg MT/kg feed (best treatment) in the warmwater and coolwater experiments exhibited significantly higher growth rates than controls by 35.3 and 45.8%, respectively. Likewise, feed conversion among groups receiving 60 mg MT/kg feed in the warmwater and coolwater experiments were significantly better than the controls (1.14 versus 1.30 and 1.44 versus 1.77, respectively). During the withdrawal period, no significant differences in growth rates or feed conversion were observed between the control and treatment groups. MT treatment significantly affected the body composition (whole body and empty carcass) of the red tilapia in both experiments, elevating percent moisture and protein values, but depressing percent fat values. Results demonstrated that incorporation of MT into fingerling diets offers potential for extending the period when tilapias actively feed and grow in temperate climates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-7345.1991.tb00720.x
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  • 10
    Electronic Resource
    Electronic Resource
    Effect of Oxygen Saturation in Water on Reproductive Performances of Pacu Piaractus brachypomus (2003)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the World Aquaculture Society 34 (2003), S. 0 
    Details
    ISSN: 1749-7345
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Broodstock pacu Piaractus brachypomus as well as their eggs during their embryonic development were exposed to either normoxia (5.5–7.5 mg O2/L) or hypoxia (2.0–4.5 mg O2/L) conditions. The plasma concentrations of 11-ketotestosterone in males and estradiol-17β in females, as well as that of their precursor testosterone (T) were significantly (P 〈 0.01) higher in fish maintained under normoxic conditions than in fish exposed to hypoxia. After ovulation and spermiation induced by hormonal treatments, the plasma concentrations of T and 17,20β-dihydroxy-4-pregnen-3-one (17,20βP) significantly (P 0.05) increased in both sexes under both normoxic and hypoxic conditions. The plasma levels of T and 17,20βP achieved under normoxic conditions were higher than the ones recorded under hypoxia, except for those of 17,20βP in males. Males responded positively to the hormonal treatments, and the concentration of spermatozoa was 10.5 ± 0.8 109/mL under both oxygen conditions. Hypoxia resulted in significantly lower survival of embryos (17.3 ± 28%) in comparison to normoxic conditions (68.5 ± 25%). Moreover, larval deformities were found when exposed to hypoxia (91.6 ± 6%). During embryonic development of this species 4 mg/L of oxygen is tolerated at 26–27 C without negative impact. We conclude that despite the highly adaptable nature of adult pacu to environmental hypoxia, oxygen concentrations below 4 mg/L severely impacted survival of embryos.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-7345.2003.tb00083.x
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