Thyroidal compensation in rainbow trout (Salmo gairdneri) fed canola meal     

J. F. Leatherland  J. W. Hilton 《Fish physiology and biochemistry》1988,5(4):199-207

Rainbow trout (Salmo gairdneri Richardson) were fed either a soybean mealbased (SM) or canola meal-based (CM) diet for up to 20 weeks. Plasma thyroxine (T₄) and triiodothryonine (T₃) levels were significantly lower in the CM-fed fish sampled after 12 weeks. However, there appeared to be some compensation after 12 and 20 weeks in that the thyroid hormone levels in trout fed the CM were not significantly different from those of the SM-fed fish. Nevertheless, there was marked thyroid hyperplasia and hypertrophy in the CM-fed fish sampled at 12, 16 and 20 weeks after commencement of the experiment. Moreover, the growth rate was significantly lower in the CM-fed fish in comparison to the SM-fed fish throughout the 20 week study period.Plasma T₄ levels were similar in SM-fed fish sampled 12, 16 and 20 weeks after commencement of the experiment, but plasma T₃ levels progressively increased over this period, as did the apparent activity of the thyroid tissue based on histological criteria.Fasting for up to 8 weeks resulted in the arrested growth of the SM-fed fish, and a loss in body weight of the CM-fed animals over the 8 week period of the fast. In addition, the plasma thyroid hormone levels in the fasted fish tended to be lower than in fish fed both the SM and CM diets prior to fasting, and there was histological evidence indicating a reduced activity of the pituitary-thyroid axis. However, thyroid hyperplasia and hypertrophy were still evident in the fasted fish previously fed the CM diet indicating that the adverse affects of CM diets are not completely reversible after 8 weeks.In fish fed the CM diet for 12 weeks and then the SM diet for up to a further 8 weeks (diet C-S) there was a compensatory increase in plasma thyroid hormone levels evident within 4 weeks after the change in diet, but no apparent decrease in thyroid hyperplasia or hypertrophy. In addition, in the fish fed the C-S diet there was a marked compensatory growth rate, and an increased feed: gain ratio; body weights of this group of fish were not significantly different from those of the SM-fed animals after 20 weeks of study, indicating a considerably higher growth rate over the last 8 week period.  相似文献   

Leaf physiology and morphology of Castanea dentata (Marsh.) Borkh., Castanea mollissima Blume,and three backcross breeding generations planted in the southern Appalachians,USA     

Benjamin O. Knapp  G. Geoff Wang  Stacy L. Clark  Lauren S. Pile  Scott E. Schlarbaum 《New Forests》2014,45(2):283-293

Backcross breeding programs have been used to transfer disease resistance and other traits from one forest tree species to another in order to meet restoration objectives. Evaluating the field performance of such material is critical for determining the success of breeding programs. In eastern North America, The American Chestnut Foundation has a backcross breeding program that uses Chinese chestnut (Castanea mollissima Blume) to introduce resistance of the fungal pathogen chestnut blight [Cryphonectria parasitica (Murr.) Barr.] to the native American chestnut [Castanea dentata (Marsh.) Borkh.]. We compared physiological and morphological characteristics among seedlings of American chestnut, Chinese chestnut, and BC₁F₃, BC₂F₃, and BC₃F₃ hybrid chestnuts during their fourth growing season after field-planting. American chestnut and the BC₃F₃ breeding generation displayed photosynthetic light-response curves that were similar to each other but different from Chinese chestnut. Rates of photosynthesis were higher for American chestnut and the BC₃F₃ breeding generation when compared to Chinese chestnut for light levels ≥800 μmol m^?2 s^?1 photosynthetic photon flux density and for maximum photosynthetic capacity. Leaf morphology variables were not different between American chestnut and any of the breeding generations, but leaf area (on a per leaf basis) of Chinese chestnut was lower than that of any other chestnut type. Our results suggest that backcross breeding can be used to transfer desirable traits for restoration of native species threatened by non-native pathogens.  相似文献   

Investigation of the nutritional requirements of Australian snapper Pagrus auratus (Bloch & Schneider 1801): digestibility of gelatinized wheat starch and clearance of an intra-peritoneal injection of d-glucose     

Mark A. Booth  Alex J. Anderson  & Geoff L. Allan 《Aquaculture Research》2006,37(10):975-985

Two experiments were performed to investigate the digestibility and utilization of carbohydrate sources by Australian snapper Pagrus auratus. In the first experiment, snapper of two different size classes (110 and 375 g) were fed a reference diet containing no starch (REF) or diets containing 150 (PN15), 250 (PN25), 350 (PN35) or 450 g kg^?1 (PN45) of 100% gelatinized wheat starch to investigate the interactive effects of fish size and starch inclusion level on apparent organic matter (OM) or gross energy (GE) digestibility (ADC), post‐prandial plasma glucose concentration, hepatosomatic index (HSI) and liver or tissue glycogen content. A second experiment used a 72 h time course study to investigate the ability of larger snapper (300–481 g) to clear an intra‐peritoneal injection of 1 g d ‐glucose kg^?1 body weight (BW). Organic matter and GE ADCs declined significantly in both fish sizes as the level of starch increased (PN45energy small fishenergy large fish). There was no interaction between fish size and inclusion level with respect to GE or OM ADCs. Gross energy ADC for both sized fish was described by the linear function GE ADC=104.97 (±3.39)–0.109 (±0.010) × inclusion level (R²=0.86). Hepatosomatic index, liver and muscle glycogen concentrations were significantly elevated in both small and large snapper‐fed diets containing gelatinized starch compared with snapper fed the REF diet. Three‐hour post‐prandial plasma glucose concentrations were not significantly affected by fish size, inclusion level or the interaction of these factors (REF=PN15=PN25=PN35=PN45), and ranged between 1.60 and 2.5 mM. The mean±SD resting level of plasma glucose (0 h) was 2.4±1.1 mM. Circulating levels of plasma glucose in snapper peaked at 18.9 mM approximately 3 h after intra‐peritoneal injection and fish exhibited hyperglycaemia for at least 12–18 h. There were no significant differences between the plasma glucose concentrations of snapper sampled 0, 18, 24, 48 or 72 h after injection (0=18=24=48=72<12< 1<3=6 h), indicating snapper required almost 18 h to regulate their circulating levels of glucose to near‐basal concentrations. Australian snapper are capable of digesting moderate levels of gelatinized wheat starch; however, increasing the dietary content of starch resulted in a reduction in OM and GE digestibility. Smaller snapper appear to be less capable of digesting gelatinized starch than larger fish, and levels above 250 and 350 g kg^?1 of diet are not recommended for small and large fish respectively. Snapper subjected to an intra‐peritoneal injection of d ‐glucose have prolonged hyperglycaemia; however, the post‐prandial response to the uptake of glucose from normally digested gelatinized starch appears to be more regulated.  相似文献   

Murdoch seeks AVMA accreditation     

Dr Geoff 《Australian veterinary journal》2002,80(11):669-669

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Genetic variability and inheritance of aluminium tolerance as indicated by long root regrowth in lucerne (Medicago sativa L.)     

Xianguang Zhang  Alan Humphries  Geoff Auricht 《Euphytica》2007,157(1-2):177-184

The objective of this study was to quantify the genetic variability and determine the inheritance of Al tolerance in lucerne (or alfalfa) using a 4-parent diallel mating design. Regrowth root length (RRL), along with root length (RL) and total root length (TRL), was measured to indicate relative Al stress response using a hydroponic system in a 3 μM Al solution at pH 4.5. A diallel analysis indicated the significance of general combining ability (gca) variance for RRL but not the specific combining ability (sca) variance; the same result was obtained for TRL but not for RL. For both RRL and TRL, genetic variance appeared to be more important than the environmental variance. For RRL, a strong but non-significant correlation was indicated between parental performance and their gca effects; while mid-parent heterosis and/or over-dominance were detected, as associated with the expressed sca effects in several combinations. These results suggest the complex genetic nature and expression of Al tolerance in the 4-parent diallel crossing system tested. Al-tolerant parent, GAAT‘S’, was the most promising parent, conferring the highest gca effects for RRL as well as for other two characters. The existence of significant gca variance in RRL may also suggest the feasibility of improving Al tolerance through enhanced root regrowth using phenotypic recurrent mass selection to pyramid desirable Al-tolerant genes, focussing on parental lines and/or elite individual plants expressing long regrowth roots.  相似文献   

Susceptibility of oat cultivars to groat discoloration: causes and remedies     

A. C. Newton    A. K. Lees    A. J. Hilton  W. T. B. Thomas 《Plant Breeding》2003,122(2):125-130

Fungal isolations and fungicide efficacy trials were carried out to determine the possible causes of discoloration in oat groats and potential control measures. Alternaria species and Microdochium nivale were isolated from field samples, and Fusarium poae was found in glasshouse tests. Symptoms could be induced reliably in the field through the use of a mist irrigation system. The cultivar ‘Gerald’ was most resistant followed by ‘Jalna’. Cultivar ‘Image’ was most severely affected by discoloration and ‘Millennium’ was of intermediate susceptibility. None of the 28 fungicide‐timing combinations used in the field trials affected the occurrence of discoloured groats. It was concluded that the best strategy for minimizing risk of discoloured groats would be screening new cultivars or breeding material in mist‐irrigated field trials for genetically based resistance.  相似文献   

Germination and hyphal growth of Glomus caledonicum on water agar containing benomyl     

Geoff R. Carr  Mary A. Hinkley 《Soil biology & biochemistry》1985,17(3):313-316

Concentrations of benomyl greater than 10 ng ml^?1 inhibited germination and hyphal growth of the vesicular-arbuscular mycorrhizal fungus Glomus caledonicum on water agar. This effect was attributable to only the activity of methyl-2-benzimidazole carbamate, one of the two hydrolysis products of benomyl. Hyphal growth but not germination was affected by the pH of water agar buffered with 10 mm 2-(N-morpholino)ethane sulphonic acid.  相似文献   

Introduced house mice Mus musculus: a significant predator of threatened and endemic birds on Gough Island, South Atlantic Ocean?     

Richard Cuthbert  Geoff Hilton 《Biological conservation》2004,117(5):483-489

House mice Mus musculus have successfully colonized many temperate and sub-Antarctic islands that are the location for breeding colonies of millions of seabirds. Unlike other introduced mammals, the impact of house mice on seabirds and endemic birds is believed to have been negligible. The breeding ecology of seabirds breeding on Gough Island, central South Atlantic Ocean, was studied for the first time during September 2000 to September 2001. Breeding success of the endangered Tristan albatross Diomedea (exulans) dabbenena and endangered Atlantic Petrel Pterodroma incerta were 27.3 and 19.9% respectively. Mortality of large Tristan albatross and Atlantic petrel chicks was observed, and the pattern of wounds and observations of feeding indicate that introduced mice were responsible for this predation. Breeding numbers of the endemic Gough bunting Rowettia goughensis are mostly found in upland areas of Gough Island where mice are scarce and are restricted to inaccessible cliffs in the lowlands where mice are abundant. This pattern, together with the high predation rates of artificial-eggs in lowland habitats in comparison to the uplands, strongly suggests that mice constrain the distribution of Gough buntings. The results of this study provide the first evidence for the role of house mice as a significant predator of endangered and endemic birds. Further research is required to determine if the observed levels of mice predation are a regular occurrence.  相似文献   

THE HUMAN FACE     

Hilton WA 《Science (New York, N.Y.)》1911,34(864):91-94

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Effect of Synthetic Lysine Vasopressin on Adrenocortical Secretion     

Hilton JG  Scian LF  Westermann CD  Kruesi OR 《Science (New York, N.Y.)》1959,129(3354):970-971

By means of direct arterial perfusion of the adrenal glands in the dog it has been shown that synthetic lysine vasopressin stimulates the secretion of hydrocortisone. This effect is not mediated via the adenohypophysis or any other organ but is rather the result of direct stimulation of the adrenal cortex by vasopressin itself.  相似文献