Water relations, gas exchange, and nutrient response to a long term constant water deficit     

Berry WL  Goldstein G  Dreschel TW  Wheeler RM  Sager JC  Knott WM 《Soil Science》1992,153(6):442-451

Wheat plants (Triticum aestivum) were grown for 43 days in a micro-porous tube nutrient delivery system. Roots were unable to penetrate the microporous tube, but grew on the surface and maintained capillary contact with the nutrient solution on the inside of the tube through the 5-micron pores of the porous tube. Water potential in the system was controlled at -0.4, -0.8, and -3.0 kPa by adjusting the applied pressure (hydrostatic head) to the nutrient solution flowing through the microporous tubes. A relatively small decrease in applied water potential from -0.4 to -3.0 kPa resulted in a 34% reduction of shoot growth but only a moderate reduction in the midday leaf water potential from -1.3 to -1.7 MPa. Carbon dioxide assimilation decreased and water use efficiency increased with the more negative applied water potentials, while intercellular CO2 concentration remained constant. This was associated with a decrease in stomatal conductance to water vapor from 1.90 to 0.98 mol m-2 s-1 and a decrease in total apparent hydraulic conductance from 47 to 12 micromoles s-1 MPa-1. Although the applied water potentials were in the -0.4 to -3.0 kPa range, the actual water potential perceived by the plant roots appeared to be in the range of -0.26 to -0.38 MPa as estimated by the leaf water potential of bagged plants. The amount of K, Ca, Mg, Zn, Cu, and B accumulated with each unit of transpired water increased as the applied water potential became less negative. The increase in accumulation ranged from 1.4-fold for K to 2.2-fold for B. The physiological responses observed in this study in response to small constant differences in applied water potentials were much greater than expected from either the applied water potential or the observed plant water potential. Even though the micro-porous tube may not represent natural conditions and could possibly introduce morphological and physiological artifacts, it enables a high degree of control of water potential that facilitates the investigation of many aspects of water relations not practical with other experimental systems.  相似文献   

Histopathologic, immunohistochemical, and cytologic analysis of feline myeloma-related disorders: further evidence for primary extramedullary development in the cat     

Mellor PJ  Haugland S  Smith KC  Powell RM  Archer J  Scase TJ  Villiers EJ  McNeil PE  Nixon C  Knott C  Fournier D  Murphy S  Polton GA  Belford C  Philbey AW  Argyle DJ  Herrtage ME  Day MJ 《Veterinary pathology》2008,45(2):159-173

Feline myeloma-related disorders (MRD) are rare neoplasms of plasma cells. The multistep transformation model of myeloma in humans is based on the premise that plasma cells undergo neoplastic transformation primarily within the intramedullary compartment and that over time they become poorly differentiated and metastasize to extramedullary locations. Historically, diagnostic criteria used for human multiple myeloma have been applied to the cat, with the assumption that feline MRD commonly arises in the intramedullary compartment. Our objectives were to describe the features of feline MRD confirmed by cytology, histopathology, histochemistry, and immunohistochemistry and to categorize these tumors. A priori hypotheses were 1) tumor category predicts survival and 2) cats with well-differentiated tumors commonly have extramedullary involvement in contrast to human myeloma patients. This multicenter, retrospective study identified 26 MRD cases. There was good agreement between histopathologic and cytologic tumor categorization. Histochemistry and immunohistochemistry were shown to be valuable adjunct tests in the diagnosis of MRD. Cats with well-differentiated tumors had increased median survival relative to those with poorly differentiated tumors (254 versus 14 days). We have reported that marked extramedullary involvement at initial clinical presentation is significantly more common in the cat than in human MRD patients. In this study, we demonstrate that cats with well-differentiated tumors more commonly have extramedullary involvement than human myeloma patients with well-differentiated tumors (90% versus 20%, P < 0.0002). These results contrast strongly with the human myeloma model of primary intramedullary neoplastic transformation and suggest that primary extramedullary neoplastic transformation may be more common in feline MRD.  相似文献   

Diagnosis and surgical treatment of thyroid adenoma-induced hyperthyroidism in a green iguana (Iguana iguana).     

S J Hernandez-Divers  C D Knott  J MacDonald 《Journal of zoo and wildlife medicine》2001,32(4):465-475

An adult female green iguana (Iguana iguana) presented with polyphagia, loss of the dorsal spines, hyperactivity, increased aggression, tachycardia, and a bilobate mass palpable anterior to the thoracic inlet. Diagnosis of hyperthyroidism was based on a total T4 (30.0 nmol/L) elevated above that of clinically healthy iguanas (3.81 +/- 0.84 nmol/L), and histopathology confirmed a functional thyroid adenoma. Surgical thyroidectomy safely returned the lizard to a euthyroid state.  相似文献   

VACCINATION WITH BABESIA ARGENTINA IN 5 BEEF HERDS IN SOUTH-EASTERN QUEENSLAND     

F. R. Emmerson>  Q.D.A.H.  S. G. Knott  B.V.Sc.  D.A.E. L. L. Callow  B.V.Sc.  Ph.D.† 《Australian veterinary journal》1976,52(10):451-454

Observations on the use of a vaccine containing Babesia argentina in 5 partly susceptible beef herds in south-eastern Queensland were made on 1,029 female breeding cattle over a period of 4 years. Groups averaging about 20 heifers were given 0, 1, 2 or 3 vaccinations. Incidence derived from groups experiencing clinical attacks were 17.9% for unvaccinated cattle and 1.2% for vaccinates. Increasing the number of vaccinations did not appear to increase protection. The one clinical manifestation of infection with B. bigemina was associated with a concurrent reaction to vaccination with Anaplasma centrale. There were no cases of haemolytic anaemia in new-born calves. No severe reactions followed primary vaccination, but 2 revaccinated animals became sick.  相似文献   

Rams with poor feed efficiency are highly responsive to an exogenous adrenocorticotropin hormone (ACTH) challenge     

Knott SA  Cummins LJ  Dunshea FR  Leury BJ 《Domestic animal endocrinology》2008,34(3):261-268

An animal's response to a stressor is to increase metabolic rate, and thus energy consumption through the activation of the hypothalamic-pituitary-adrenal axis. Changes to energy use by an animal are likely to influence the efficiency with which it is utilised. In this study, we tested the hypothesis that less efficient sheep are more responsive to exogenous administration of adrenocorticotropin hormone. This was done by firstly determining the appropriate dose (0.4, 1.6 or 6.4microg/kg LW) and peak serum cortisol response time (45min) to exogenous administration of adrenocorticotropin hormone in a pilot study (n=3 sheep). Following this, adrenocorticotropin hormone (2.0microg/kg LW) stimulated cortisol levels were measured in a larger group of sheep (n=50) of known feed efficiency (feed conversion ratio and residual feed intake values). Less efficient sheep (more positive residual feed intake values) were found to have a greater (P<0.001) increase in cortisol concentration in comparison to more efficient animals. Those sheep which had higher levels of cortisol also had a greater proportion (P<0.001) of fat tissue. These data clearly demonstrated that efficiency of energy use, when measured as residual feed intake, is significantly related to an animal's stress response. These findings have important implications for understanding the physiological mechanisms underpinning efficiency of energy use, and may be useful in successfully identifying animals which are superior in terms of feed efficiency.  相似文献   

OBITUARY: John McDonald Beames     

Stan Knott 《Australian veterinary journal》1999,77(4):254-254

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Size and age are important factors for marine sanctuaries: evidence from a decade of systematic sampling in a subtropical marine park          下载免费PDF全文

Hamish A. Malcolm  Alan Jordan  Robert G. Creese  Nathan A. Knott 《水产资源保护:海洋与淡水生态系统》2016,26(6):1090-1106

Reduced Acetazolamide Dosing in Countering Altitude Illness: A Comparison of 62.5 vs 125 mg (the RADICAL Trial)     

Scott E. McIntosh  Mika Hemphill  Marion C. McDevitt  Tsering Yangzom Gurung  Mukhiya Ghale  Jonathan R. Knott  Ghan Bahadur Thapa  Buddha Basnyat  Jennifer Dow  David C. Weber  Colin K. Grissom 《The Forestry Chronicle》2019,30(1):12-21

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Mapping of quantitative trait loci affecting organ weights and blood variables in a broiler layer cross     

Navarro P  Visscher PM  Knott SA  Burt DW  Hocking PM  Haley CS 《British poultry science》2005,46(4):430-442

1. A genome scan was performed to locate genomic regions associated with traits that are known to vary in birds (most commonly broilers) suffering from heart, lung or muscular dysfunction and for weight of the dressed carcass and some internal organs. 2. The F2 population studied was derived from a cross between a broiler and a layer line and consisted of over 460 birds that were genotyped for 101 markers. 3. There was strong support for segregation of quantitative trait loci (QTL) for carcass and organ weights and blood variables. We identified 11 genome-wide significant QTL (most of them for dressed carcass weight) and several genome-wide suggestive QTL. 4. The results point to some genome regions that may be associated with health-related traits and merit further study, with the final aim of identifying linked genetic markers that could be used in commercial breeding programmes to decrease the incidence of muscular and metabolic disorders in broiler populations.  相似文献   

AN OUTBREAK OF BOVINE ABORTIONS ASSOCIATED WITH LEPTOSPIROSIS     

S. G. Knott  B.V.Sc. L. P. Dadswell  B.V.Sc. 《Australian veterinary journal》1970,46(8):385-386

A severe abortion storm on a grazing property, in which 50% of Hereford cows aborted in 2 months, is described. Serological evidence suggested that the abortion storm was due to leptospirosis. Epidemiological factors associated with the abortion storm were (a) introduction of infected cows into a susceptible population; (b) the practice of seasonal calving, which resulted in the susceptible population being in the last third of gestation when exposed to infection; and (c) environmental conditions suitable for the propagation of leptospira being coincident with the introduction of infection into the susceptible herd.  相似文献