Digestive enzyme activities and their distribution in the alimentary canal of larvae of the three extant lamprey families     

Max H. Cake  Ian C. Potter  Glen W. Power  Mayamin Tajbakhsh 《Fish physiology and biochemistry》1992,10(1):1-10

The activities of trypsin (EC 3.4.21.4), chymotrypsin (EC 3.4.21.1), lipase (EC 3.1.1.3) and amylase (EC 3.2.1.1) were measured in different regions of the alimentary tract of ammocoetes from each of the three extant lamprey families. In the southern hemisphere speciesGeotria australis (Geotriidae), and even more particularlyMordacia mordax (Mordaciidae), enzymatic activity was almost entirely confined to prominent diverticular extensions which arise at the oesophageal-intestinal junction. However, in the holarcticLampetra richardsoni (Petromyzontidae), which does not possess a diverticulum, the enzymatic activity was highest in the upper anterior intestine. It is not clear whether the presence of significantly higher amylolytic and lower lipolytic activities in the diverticulum ofG. australis than in the exocrine tissue of the other two species reflects interspecific differences in the composition of their diets. The capacity of exocrine tissue extracts for chymotryptic and tryptic digestion was assayed before and afterin vitro exposure to trypsin and enteropeptidase, their respective catalytic activators. Prior to exposure to these exogenous activators, both proteolytic enzymes were fully active inL. richardsoni, partially active inG. australis and totally inactive inM. mordax. Maximal chymotryptic activity was greater inM. mordax than inL. richardsoni andG. australis. In contrast, maximal tryptic activity was greater inL. richardsoni than inG. australis and was very low inM. mordax. Since trypsin is the only known activator of chymotrypsinogen, the negligible activity of trypsin inM. mordax would appear anomalous unless a trypsin inhibitor is present in the protopancreas of this species. Differences in the distribution of enzymatic activity within the alimentary tract of the three species is discussed in relation to proposed phylogenetic relationships amongst the extant lamprey families.  相似文献   

Inherited chondrodysplasia in Texel sheep     

KG Thompson  HT Blair  LE Linney  DM West  T Byrne 《New Zealand veterinary journal》2013,61(3):208-212

CASE HISTORY: A skeletal disease characterised by dwarfism, limb deformity and sometimes sudden death occurred over a period of 5 years in lambs born on a commercial sheep farm in Southland. The disease showed variable expression and occurred in crossbred sheep. A genetic aetiology was supported by the birth of affected lambs over two seasons in a flock of putative carrier and affected sheep transported to Massey University.

CLINICAL FINDINGS: Affected lambs appeared normal at birth but showed evidence of dwarfism, wide-based stance and exercise intolerance as early as 1 week of age. Most died within the first 3 months of life, often after developing bilateral varus deformity of the forelimbs. Some severely-affected lambs died suddenly of respiratory embarrassment, probably due to tracheal collapse. Mildly-affected individuals had a short, blocky stature and some survived to breeding age.

PATHOLOGICAL FINDINGS: Gross and microscopic lesions of variable severity were present in the tracheal, articular, epiphyseal and physeal cartilages. In severe cases, articular cartilage in major joints was eroded from weight-bearing surfaces. The trachea was flaccid, abnormally kinked, and had thickened cartilaginous rings and a narrow lumen. Affected sheep that survived to breeding age eventually developed severe degenerative joint disease. Histologically, chondrocytes were disorganised, surrounded by concentric rings of abnormal fibrillar material, and the matrix often contained focal to coalescing areas of chondrolysis.

DIAGNOSIS: Inherited chondrodysplasia of Texel sheep.

CLINICAL RELEVANCE AND CONCLUSIONS: This chondrodysplasia differs from those previously described in sheep and is considered to be a newly-recognised, recessively-inherited genetic disease of the Texel breed. A defect in the synthesis of glycosaminoglycans in cartilage matrix is suspected. This disease of sheep may provide a suitable model for studying various forms of therapy for human chondrodysplasias.  相似文献   

Finding the mutation responsible for inherited rickets in Corriedale sheep     

KE Dittmer  KG Thompson  X Zhao  L Howe  S Onteru  HT Blair 《New Zealand veterinary journal》2013,61(3)

Inherited rickets of Corriedale sheep is of simple autosomal recessive inheritance. The gross and histological lesions include segmental thickening of physes, persistence of hypertrophic chondrocytes at sites of endochondral ossification, excessive osteoclastic resorption, microfractures and wide unmineralised osteoid seams lining trabeculae and filling secondary osteons. Initial testing revealed concentrations of 25-hydroxyvitamin D₃ were normal, but those of 1,25-dihydroxyvitamin D₃ were increased in serum of affected sheep, suggesting a defect in the vitamin D receptor. However, in vitro studies on cultured skin fibroblasts revealed normal binding and function of the vitamin D receptor.

A genome-wide association study was conducted using the Illumina OvineSNP50 BeadChip. A homozygous region of 199 consecutive single-nucleotide polymorphism loci was identified in affected sheep, covering a region of 10 megabase pairs on ovine chromosome 6. Of the 91 candidate genes in this region, dentin matrix protein 1 gene (dmp1) was considered the most likely as it is known to play critical roles in osteocyte maturation and mineral metabolism. Sequencing of DNA from carriers showed a nonsense mutation 253T/C in dmp1. This T/C transition introduced a stop codon (R145X) that could truncate C-terminal amino acids. Using PCR restriction fragment length polymorphism for this mutation, genotyping showed that all affected sheep were “TT” genotypes, and phenotypically normal sheep were either “CT” or “CC”. These findings suggest that a mutation in dmp1 is responsible for inherited rickets of Corriedale sheep. A simple diagnostic test is currently being designed to identify carriers with the defective “T” alleles.  相似文献   

Familial episodic ataxia in lambs     

IG Mayhew  D Burnham  AL Ridler  GJ Poff  HT Blair 《New Zealand veterinary journal》2013,61(2):107-110

Abstract

HISTORY: A similar episodic neurological disorder occurred in new born lambs on two unrelated properties involving disparate breeds of sheep. Because of the number of lambs born, cross-breeding and the fact it occurred in some mating groups and not others, a dominant mode of inheritance was, initially and separately, suspected in each case. The sires of affected lambs were apparently normal. Whereas one was New Zealand Romney, the other was a composite breed with East Friesian genetics, but both rams originated from the same source property. To investigate the pathogenesis of the disorder these two rams were acquired and mated with unrelated sheep, under experimental conditions in a more controlled environment.

CLINICAL FINDINGS: A proportion of lambs born to both sires exhibited a similar neurological disorder. Some lambs were noted to be abnormal at birth, both on home properties and in the experimental flock. They tended to adopt a head and neck extended posture and were slow to get to their feet and suckle when they then became more or less normal. When forced to move, they and other more robust lambs elicited an asymmetric gait, base-wide extensor hypertonia (hypometria) of thoracic limbs and flexor hypertonia (hypermetria) of pelvic limbs. In some there was nystagmus. After several metres of asymmetric ataxic gait they would fall to one side, sometimes adopting a sitting position. Recovery usually occurred in one to several minutes. As lambs aged, it became more difficult to elicit the episodes of dysfunction and by 6 months of age they appeared normal.

DIAGNOSIS: The disorder was diagnosed as a dominant familial episodic cerebellovestibular ataxia inherited as a dominant trait, with incomplete penetration of observed clinical signs and variable expressivity.

CLINICAL RELEVANCE: A proportion of affected lambs are likely to die in the neonatal period so the specific nature of the disorder may go unrecognised. Because of incomplete penetrance and varying expressivity, many of the lambs carrying this mutation will survive without showing clinical signs and may enter breeding flocks, where the disorder may be perpetuated and contribute to neonatal deaths.  相似文献   

High frequency direct plant regeneration from leaf and petals of Cape Primrose (<Emphasis Type="Italic">Streptocarpus</Emphasis>)     

A. Chaudhury  J. B. Power  M. R. Davey 《Journal of Crop Science and Biotechnology》2010,13(2):107-112

High frequency direct plant regeneration from leaf and petal explants was accomplished for the first time in Streptocarpus varieties. The shoot induction frequency varied with respect to the benzylaminopurine (BAP) concentration added to the Murashige and Skoog (MS) medium. MS medium with 0.5 mg l⁻¹ BAP exhibited the highest (69.9%) plant regeneration frequency with an average of 186 shoots per explant. A higher concentration of BAP inhibited shoot bud induction and plant regeneration along with necrosis of explants. Petal explants derived from the varieties ‘Branwen’ (pink and white) and ‘Chorus Line’ (violet and white) displayed plant regeneration frequency of 22.2–47.4% (within a total of 12 weeks) on MS medium containing 2.0 mg l⁻¹ α-naphthaleneacetic acid and 0.5 mg l⁻¹ BAP for 8 weeks followed by 4 weeks on MS medium with 1.0 mg l⁻¹ BAP. Scanning electron microscopy confirmed direct plant regeneration without callus. Regenerated plants from leaf explants with well-developed leaves and roots were hardened and successfully transferred to pots in glasshouse exhibiting 86% survival at the end of 4–6 weeks. Whereas, regenerated plants from flower petal explants upon transfer to pots in glasshouse exhibited 75–82% survival at the end of 4–6 weeks.  相似文献   

Breed and site predispositions of dogs with atopic dermatitis: a comparison of five locations in three continents     

K. Jaeger  M. Linek  H.T. Power  S.V. Bettenay  S. Zabel  R.A.W. Rosychuk  Ralf S. Mueller 《Veterinary dermatology》2010,21(1):119-123

The objectives of this multicentre study were to analyse and compare breed predispositions and lesion distributions of 552 dogs diagnosed with atopic dermatitis from five different dermatologic referral centres located in Australia, Germany (2) and the United States (2). Breeds were compared with the canine population in the respective locations. Breed predispositions varied from geographical site, although golden retrievers and German shepherd dogs were predisposed in three of five practices. Lesions were present most commonly on the paws (62%), ventrum (51%), ears (48%) and face (39%). Various breeds had specific site predilections. Based on this study, breed predispositions can vary greatly both between continents and also between different locations on the same continent. In addition, some breeds showed predispositions for certain body sites which also varied in some instances with the geographical location.  相似文献   

用径向扩散法定量分析对饲料中的酶     

G.Walsh  R A.Mushy  G-F.Kilken  R. F.Power  程时军 《国外畜牧学(猪与禽)》2010,30(3)

本文介绍的方法能够使按饲料行业常规的推荐水平加入饲料中的纤维素酶、蛋白酶及α-淀粉酶更容易进行定量测定。这些方法必需借助缓冲液通过搅动提取饲料中的酶,随后利用径向扩散技术对提取物活性进行定量分析。在一个很大的活性范围内,可观察到水解底物圈的直径和所测定酶活性的对数值之间呈线性关系。对按1kg/t的浓度添加纤维素酶、蛋白酶和α-淀粉酶的饲料进行酶活性分析后,分别获得了(104±11.7)%、(91.3±6.74)%和(126±29.5)%的净添加酶活性回收率。在常规的添加水平下,相似的方法并不能充分证明对木聚糖酶的敏感性。在未添加酶的饲料中,测得的内源性纤维素酶、蛋白酶和α-淀粉酶活性分别相当于按1kg/t水平添加酶后所添加酶活性的(6.4±0.47)%、(6.6±0.82)%和(29.0±14.1)%。这些方法在技术上易懂,并且将使得测定饲料加工过程(如饲料的高温制粒)酶稳定性变得更容易,同时能够对添加酶的动物饲料进行更严格的质量控制。  相似文献   

The intrinsic plasticity of farm businesses and their resilience to change. An Australian example     

D. Rodriguez  P. deVoilB. Power  H. CoxS. Crimp  H. Meinke 《Field Crops Research》2011,124(2):157-170

This paper examines the idea that plasticity in farm management introduces resilience to change and allows farm businesses to perform when operating in highly variable environments. We also argue for the need to develop and apply more integrative assessments of farm performance that combine the use of modelling tools with deliberative processes involving farmers and researchers in a co-learning process, to more effectively identify and implement more productive and resilient farm businesses.In a plastic farming system, farm management is highly contingent on environmental conditions. In plastic farming systems farm managers constantly vary crops and inputs based on the availability of limited and variable resources (e.g. land, water, finances, labour, machinery, etc.), and signals from its operating environment (e.g. climate, markets), with the objective of maximising a number of, often competing, objectives (e.g. maximise profits, minimise risks, etc.). In contrast in more rigid farming systems farm management is more calendar driven and relatively fixed sequences of crops are regularly followed over time and across the farm. Here we describe the application of a whole farm simulation model to (i) compare, in silico, the sensitivity of two farming systems designs of contrasting levels of plasticity, operating in two contrasting environments, when exposed to a stressor in the form of climate change scenarios;(ii) investigate the presence of interactions and feedbacks at the field and farm levels capable of modifying the intensity and direction of the responses to climate signals; and (iii) discuss the need for the development and application of more integrative assessments in the analysis of impacts and adaptation options to climate change.In both environments, the more plastic farm management strategy had higher median profits and was less risky for the baseline and less intensive climate change scenarios (2030). However, for the more severe climate change scenarios (2070), the benefit of plastic strategies tended to disappear. These results suggest that, to a point, farming systems having higher levels of plasticity would enable farmers to more effectively respond to climate shifts, thus ensuring the economic viability of the farm business. Though, as the intensity of the stress increases (e.g. 2070 climate change scenario) more significant changes in the farming system might be required to adapt. We also found that in the case studies analysed here, most of the impacts from the climate change scenarios on farm profit and economic risk originated from important reductions in cropping intensity and changes in crop mix rather than from changes in the yields of individual crops. Changes in cropping intensity and crop mix were explained by the combination of reductions in the number of sowing opportunities around critical times in the cropping calendar, and to operational constraints at the whole farm level i.e. limited work capacity in an environment having fewer and more concentrated sowing opportunities. This indicates that indirect impacts from shifts in climate on farm operations can be more important than direct impacts from climate on the yield of individual crops. The results suggest that due to the complexity of farm businesses, impact assessments and opportunities for adaptation to climate change might also need to be pursued at higher integration levels than the crop or the field. We conclude that plasticity can be a desirable characteristic in farming systems operating in highly variable environments, and that integrated whole farm systems analyses of impacts and adaptation to climate change are required to identify important interactions between farm management decision rules, availability of resources, and farmer's preference.  相似文献   

模拟技术在水库防洪预案中的应用(英文)     

王学超 《（《农业科学与技术》）编辑部》2011,(7)

[目的]探讨模拟技术在水库防洪预案中的应用。[方法]在研究河流系统模拟相关理论的基础上,采用InfoWorks RS系统建立了河流系统洪水演进模拟数字化模型,并对校核标准洪水下泄进行了仿真模拟分析。[结果]利用基于InfoWorks RS软件的洪灾信息系统对校核标准下洪水下泄对下游的淹没情况进行模拟,得出了各断面最大流量时的各水力参数、各控制断面流量与流速度随时间的变化图、各断面水力要素随时间的变化图以及下游水库控制流域最大淹没面积风险分析图。[结论]为减少洪涝灾害造成的严重损失、制定防洪预案提供了参考。  相似文献   

Dynamics of scale regeneration in seawater- and brackish water-acclimated sea bass, Dicentrarchus labrax     

Pedro M. Guerreiro  Rita Costa  Deborah M. Power 《Fish physiology and biochemistry》2013,39(4):917-930

Scale loss is a common occurrence in both wild fish and those in aquaculture production systems, and regeneration of scales has been described in several freshwater species. Relatively little information exists about this process in marine fish, and in the present study, the chronology of scale regeneration was characterized in juvenile sea bass Dicentrarchus labrax, maintained in full seawater (SW; 36 ‰, 11.2 mM Ca²⁺) or brackish water (BW; 3.5 ‰, 1.1 mM Ca²⁺). Despite the significant differences in plasma osmolality, plasma calcium (Ca) and phosphorus (P) were similar between SW and BW. Removal of scales (2.25 cm²) did not modify plasma osmolality but a significant reduction in plasma Ca occurred in sea bass in BW during early phases of scale regeneration. Scale Ca and P contents changed during regeneration in SW and BW fish, and in fully regenerated scales, their concentration was comparable to ontogenic scales which had a Ca/P ratio around 1.0. Regenerating scales were first visible at 3 days after removal, and by 6 days, the descaled area was covered with new scales in both SW and BW fish. From this stage onwards, while scale area and mass rose gradually, a rapid accretion of calcium crystals was observed over the basal plate, especially in SW, and Ca and P content per scale increased at a very high rate, decreasing only at the later stages, and between 21 and 30 days the newly formed scales had already ontogenic-like morphometric features. Scale tartrate-resistant acid phosphatase (TRAP) or alkaline phosphatase (ALP) activity was initially similar in SW and BW. However, during regeneration, TRAP was significantly higher in scales of sea bass in SW compared to those in BW where ALP predominated; these differences persisted at 30 days.  相似文献