SOIL LAYERS ON HILLSLOPES: A STUDY AT NOWRA, N.S.W., AUSTRALIA     

P. H. WALKER 《European Journal of Soil Science》1962,13(2):167-177

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Pathology in the ovine foetus caused by an ovine pestivirus     

J. W. PLANT  K. H. WALKER  H. M. ACLAND  G. P. GARD † 《Australian veterinary journal》1983,60(5):137-140

Homogenised tissues or tissue culture supernatant fluid containing a noncytopathic pestivirus obtained from a lamb with a neurologic form of border disease, were inoculated into ewes at different stages of pregnancy. Foetal death occurred in 9 ewes of those inoculated between 19 and 47 days of pregnancy while 3 ewes did not lamb. Eight of the foetuses were aborted between 77 and 132 days of pregnancy; of these 6 were autolysed or mummified and one had arthrogryposis. The one full-term dead lamb had a hairy birth coat and lissencephalic micrencephaly. Foetal death occurred in only 7 of 14 ewes inoculated between 57 and 72 days of pregnancy. Four of these ewes aborted between 77 and 108 days of pregnancy and 3 gave birth to full-term, dead, hairy lambs. The remaining 7 ewes gave birth to live hairy lambs with severe inco-ordination. All lambs carried to term and aborted foetuses or lambs that could be examined had a range of intracranial malformations including focal leucomalacia, micrencephaly, hydranencephaly, porencephaly, lissencephaly and cerebellar hypoplasia. Some lambs also had skeletal abnormalities including arthrogryposis, scoliosis and brachygnathia inferior. The pestivirus isolate used in these trials produced more severe effects on the ovine foetus than previously observed in similar inoculation trials using pestivirus isolates from border disease lambs without nervous signs.  相似文献   

VERTICAL DISTRIBUTION OF HERBICIDES IN SOIL AND THEIR AVAILABILITY TO PLANTS: TREATMENT OF DIFFERENT PROPORTIONS OF THE TOTAL ROOT SYSTEM     

A. WALKER 《Weed Research》1973,13(4):416-421

Summary. Uptake of atrazine and linuron by wheat seedlings was measured from different initial distributions of herbicide in the soil. Uptake of both compounds was proportional to the fraction of the total root system exposed to herbicide-treated soil. It was calculated that under the conditions of the experiments, this factor would offset the reduction in concentration of herbicide in the soil following incorporation of 1 kg/ha to 3, 6 or 9 cm, so that after the same time, the concentrations of herbicide in the plants in the different treatments would be similar.
La distribution verticale des herbicides dans le sol et leur disponibilité pour tes plantes: traitement de différentes fractions de l'ensemble du système racinaire total  相似文献   

The neuropathological effects of cardiac arrest in animals: a study of five cases   总被引：1，自引：0，他引：1  

A. C. PALMER  R. G. WALKER 《The Journal of small animal practice》1970,11(12):779-791

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Use of Isobutyl-Cyanoacrylate Adhesive in Osteosynthesis A Preliminary Study     

A. M. WALKER BVSc  J. L. TOMLINSON DVM  MVetSci 《Veterinary surgery : VS》1984,13(4):257-262

Isobutyl 2-cyanoacrylate was used to reattach partial-thickness cortical bone fragments from the femur in rabbits. Stability, apposition, callus formation, and inflammation around the fragments were evaluated at 2, 4, 8, and 12 weeks.
All glued bone fragments were stable, compared with 85% of controls. Good apposition was achieved in 95% of the glued bone fragments, compared with 19% of the controls. Analysis of the mean scores for callus formation revealed a significant difference only in the 8 week survival group.
Bony union was noted in 20 of 21 of the glued fragments. No evidence of inflammation was seen around the glue, and viable bone was seen adjacent to the adhesive in many sections. In control legs, 13 fragments had healed by osseous union, two by fibrous union, and in six the chip had resorbed.  相似文献   

Autologous point‐of‐care cellular therapies variably induce equine mesenchymal stem cell migration,proliferation and cytokine expression     

A. KOL  N. J. WALKER  L. D. GALUPPO  K. C. CLARK  S. BUERCHLER  A. BERNANKE  D. L. BORJESSON 《Equine veterinary journal》2013,45(2):193-198

Reasons for performing study: Autologous cellular therapy products including adipose‐derived stromal vascular fraction (SVF), bone marrow mononuclear cells (BMMNs), cord blood mononuclear cells (CBMNs) and platelet rich plasma are options for treatment of acute orthopaedic lesions while mesenchymal stem cells (MSCs) are culture expanded. These products may contribute to healing by secreting matrix proteins or growth factors, but they may also act on endogenous MSCs to facilitate healing. Objectives: To determine the effects of cell therapy products on MSCs function in vitro. The hypothesis was that cell therapy products promote MSCs functions including proliferation, migration and mediator release. Methods: Fat, bone marrow (BM), cord blood and platelets were obtained from 6 Quarter Horses. The BM‐MSCs and their autologous cell therapy products were co‐incubated in transwells. Mesenchymal stem cells proliferation, migration, gene expression and cytokine concentrations were determined. Results: All cell therapy products increased MSCs proliferation, but SVF induced significantly more proliferation than any other product. Also SVF elicited more MSCs chemotaxis and, along with BMMNs, significantly more MSCs chemoinvasion. Cord blood mononuclear cells stimulated MSCs to produce high concentrations of interleukin‐6 (IL‐6), transforming growth factor‐β1 (TGF‐β1), and prostaglandin E₂ (PGE₂). Stromal vascular fraction and platelet lysate did not stimulate MSCs but SVF and platelet lysate themselves contained high concentrations of PGE₂ and IL‐6 (SVF) and TGF‐β1 (platelet lysate). Conclusions: Autologous cell products variably stimulate MSCs functions with 2 primary patterns apparent. Products either contained preformed mediators that may have intrinsic healing function, or products stimulated MSCs to secrete mediators. Potential relevance: The specific clinical indications for these products may differ to include administration as a sole treatment modality prior to MSCs injection for intrinsic cell and cytokine activity (i.e. SVF) or administration concurrently with MSCs to activate MSCs for treatment of chronic lesions (i.e. CBMNs).  相似文献   

策勒黑羊选育现状及其对策   总被引：2，自引：1，他引：1  

高志英  杨权有  哈迪夏  马合木提  米日尼沙汗  袁军  许椿善  日介甫  於建国  古丽格娜 《中国畜牧兽医》2008,35(7):155-156

策勒黑羊是以生产羔皮为主的多胎优良地方品种,深受当地群众的喜爱。作者从育种的角度阐述了策勒黑羊选育现状及存在的问题,提出了今后的选育方向和对策。  相似文献   

Irrigation development on Cooper Creek,central Australia—prospects for a regulated economy in a boom-and-bust ecology     

KEITH F. WALKER  JIM T. PUCKRIDGE  STUART J. BLANCH 《水产资源保护:海洋与淡水生态系统》1997,7(1):63-73

1. We take issue with a proposal to irrigate cotton crops from Cooper Creek, as the development would be in sharp contrast to the ‘boom-and-bust’ character of the local environment. In dryland rivers the flow regime is influenced by aseasonal climatic phenomena like the Southern Oscillation, so that patterns are highly variable and averages are virtually meaningless. Some irrigation developments on dryland rivers have been planned during periods that were unusually wet and, as a result, present levels of water use are not sustainable. 2. Long, dry periods are the norm in dryland rivers. The biota tolerate drought and respond to occasional floods that may have long-enduring effects (riparian trees, for example, may live for centuries). All are sensitive to the rates of rise and fall and the amplitude, duration and frequency of floods. Where the flood pulse is erratic, as in Cooper Creek, species with opportunistic traits are likely to dominate. Base flows and seasonal variations imposed by irrigation use present a very different physical environment for these species. The plan to tap the Cooper headwaters would amplify the impacts because this region is a refuge for flora and fauna. 3. In general, we contend that the Cooper Creek ecosystem could not accommodate a competitor for water that is vital for its own maintenance, and that the irrigation proposal could be rationalized only in the sophistry of short-term economics. © 1997 John Wiley & Sons, Ltd.  相似文献   

Germination,emergence, and persistence of Sonchus oleraceus,a major crop weed in subtropical Australia     

MICHAEL J. WIDDERICK  STEVEN R. WALKER  BRIAN M. SINDEL  KERRY L. BELL 《Weed Biology and Management》2010,10(2):102-112

Sonchus oleraceus (common sowthistle) is a dominant weed and has increased in prevalence in conservation cropping systems of the subtropical grain region of Australia. Four experiments were undertaken to define the environmental factors that favor its germination, emergence, and seed persistence. Seeds were germinated at constant temperatures between 5 and 35°C and water potentials between 0 and ?1.4 MPa. The maximum germination rate of 86–100% occurred at 0 and ?0.2 MPa, irrespective of the temperature when exposed to light (12 h photoperiod light/dark), but the germination rate was reduced by 72% without light. At water potentials of ?0.6 to ?0.8 MPa, the germination rate was reduced substantially by higher temperatures; no seed germinated at a water potential >?1.0 MPa. Emergence and seed persistence were measured over 30 months following seed burial at 0 (surface), 1, 2, 5, and 10 cm depths in large pots that were buried in a south‐eastern Queensland field. Seedlings emerged readily from the surface and 1 cm depth, with no emergence from below the 2 cm depth. The seedlings emerged during any season following rain but, predominantly, within 6 months of planting. Seed persistence was short‐term on the soil surface, with 2% of seeds remaining after 6 months, but it increased with the burial depth, with 12% remaining after 30 months at 10 cm. Thus, a minimal seed burial depth with reduced tillage and increased surface soil water with stubble retention has favored the proliferation of this weed in any season in a subtropical environment. However, diligent management without seed replenishment will greatly reduce this weed problem within a short period.  相似文献   

Aetiology and pathogenesis of mucosal disease of cattle: current concepts, observations and speculation   总被引：2，自引：0，他引：2  

I. R. LITTLEJOHNS  K. H. WALKER 《Australian veterinary journal》1985,62(3):101-103

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