In-vitro antibacterial properties of tilmicosin against Australian isolates of Pasteurella multocida and Pasteurella haemolytica from cattle   总被引：2，自引：0，他引：2  

CP STEPHENS  PJ BLACKALL  LK WADE  LB LOWE 《Australian veterinary journal》1993,70(10):391-392

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Effects of frequency of irrigation and gypsum treatment on leaf water potential and leaf stomatal conductance of lucerne (Medicago sativa L.) grown on a heavy clay soil     

G. C. Wright  D. M. Whitfield  O. A. Gyles  A. J. Taylor 《Irrigation Science》1986,7(2):73-82

Summary Concurrent diurnal measurements of water potential, osmotic potential and conductance were made on leaves of lucerne grown under weekly (W) and fortnightly (F) irrigation on gypsum-treated (G) and untreated soil (C). Measurements were made throughout the period of vegetative growth.Leaf water potentials were lower both at dawn and in the afternoon under fortnightly as compared to weekly irrigation. Gypsum application led to a slower decline in water potential under fortnightly irrigation, although the effect was small compared with more frequent irrigation. Stomatal conductance was reduced under treatments F_G and F_C during the later stages of vegetative growth, coinciding with leaf water potentials of less than c. –1.6 MPa.The relationship between leaf water potential and turgor potential changed with time such that positive turgor was maintained as leaf water potential declined. Turgor maintenance was achieved through a decrease in leaf osmotic potential. These data suggest that lucerne is capable of osmotic adjustment.Stomatal conductance declined rapidly below a leaf turgor potential of c. 0.1 MPa. It is hypothesised that osmotic adjustment enabled stomatal adjustment, which contributed to continued assimilation despite increasing soil moisture deficits.  相似文献   

Use of two spatially explicit models to determine the effect of injury geometry on natural resource recovery     

Mark S. Fonseca  Paula E. Whitfield  W. Judson Kenworthy  David R. Colby  Brian E. Julius 《水产资源保护:海洋与淡水生态系统》2004,14(3):281-298

• 1. Disturbance to sessile communities has been evaluated in a wide variety of terrestrial and marine settings, but, to our knowledge, recovery has not explicitly considered the effects of injury shape, except in an exploratory fashion. Therefore, we have developed a simple, but spatially explicit relationship between the geometry of a disturbance and the recovery rate in the context of natural resource damage assessment.
• 2. Here, grounding of motor vessels in shoalgrass (Halodule wrightii), manatee grass (Syringodium filiforme), and turtlegrass (Thalassia testudinum) habitats results in a variety of injury shapes whose recovery must be evaluated to assign penalties and restoration costs to the party responsible.
• 3. We developed two spatially explicit, cellular automata modelling techniques to evaluate injury recovery trajectory. Techniques in both SAS^® and ArcINFO^® were developed and applied to injuries of varying perimeter but fixed area.
• 4. The SAS method utilized either a simple Boolean or probabalistic interrogation of the status of adjacent pixels using the matrix language component of the software. ArcINFO utilized a cost/distance module to evaluate proximity of unfilled to filled (colonized) pixels and then applied a decision rule that governed conversion from unfilled to a filled state. As expected, the greater the perimeter/area ratio, the faster the recovery; and modelling approaches yielded almost identical results.
• 5. A case study involving ～1200 m² of almost monotypic T. testudinum revealed that both models predicted that 100% recovery of above‐ground components of the injury would not occur for approximately 60 years. This model is now being used routinely in the assessment of vessel groundings in seagrass beds within the Florida Keys National Marine Sanctuary and has been used successfully by the Government to prevail in US Federal Court challenges. Both methods have substantial, untapped capabilities to explore the effect of numerous ecological effects on the processes influencing recovery from disturbance.

Published in 2004 by John Wiley & Sons, Ltd.  相似文献   

Distribution of bromophenols in species of marine algae from eastern Australia   总被引：6，自引：0，他引：6  

Whitfield FB  Helidoniotis F  Shaw KJ  Svoronos D 《Journal of agricultural and food chemistry》1999,47(6):2367-2373

Forty-nine species (87 samples) of marine macroalgae from eastern Australia were analyzed by GC/MS for the key seafood flavor components 2- and 4-bromophenol, 2,4- and 2,6-dibromophenol, and 2,4, 6-tribromophenol. All five bromophenols were found in 62% of samples, four in 32% of samples, and three in the remaining 6% of samples. 2, 4,6-Tribromophenol was found in all samples and, with few exceptions, was present in the highest concentrations. The total bromophenol content determined on a wet-weight basis varied widely across species from 0.9 ng/g in the green alga Codium fragile to 2590 ng/g in the red alga Pterocladiella capillacea. Species with the highest concentrations of bromophenols were all collected from sites exposed at low tide. The study demonstrates the wide occurrence of bromophenols in marine algae and provides a possible source of such compounds in fish that feed predominantly on ocean plants. The possible effect that dietary marine algae has on the flavor of omnivorous ocean fish is discussed.  相似文献   

Spatial association as an indicator of the potential for future interactions between wind energy developments and golden eagles Aquila chrysaetos in Scotland     

Alan H. Fielding  D. Philip Whitfield 《Biological conservation》2006,131(3):359-369

Despite their environmental benefits in generating electricity without emission of ‘greenhouse’ gases, wind farms have attracted controversy with regard to their impacts on birds, especially golden eagles Aquila chrysaetos. Evidence from USA studies suggest eagle fatalities through collision with turbines may be the main potential impact whereas for breeding eagles in Scotland, displacement from wind farm areas (indirect habitat loss) may be the primary impact. In this study, we examined the co-occurrence potential for golden eagles and wind farms in Scotland by documenting the spatial association between wind farm proposals and breeding eagle territories and areas potentially suitable for non-breeding eagles. Although there were records for over 500 wind farm proposals at various stages of development, relatively few coincided with eagle territories (ca. 4% of territories had a proposal within 3 km of territory centre). Similarly, only 2% of habitat predicted to be suitable for non-breeding eagles overlapped with proposed or installed wind farm areas. Moreover, estimates of the potential for electricity generation from all wind farm proposals, with respect to government targets for renewable energy supplies, suggested most proposals were unlikely to be constructed. We conclude that in comparison with other constraints on Scotland’s golden eagles, notably persecution, wind farms should not represent a serious concern if best practice in planning their location and minimising their impact are maintained. Potential future regional pressures on breeding eagles from wind farms are highlighted, however, and uncertainty of impact with respect to displacement or collision fatalities requires continued scrutiny.  相似文献   

Bilateral distal radial epiphysectomy and pancarpal arthrodesis for correction of complex carpal deformities in an American Miniature horse     

C. Whitfield‐Cargile  J. P. Watkins 《Equine Veterinary Education》2011,23(8):381-385

A 9‐day‐old American Miniature horse was referred for evaluation and treatment of congenital bilateral carpal deformities. Clinical examination revealed a combination of flexural, angular and rotational deformities affecting both carpi. Radiographic evaluation of both forelimbs revealed malformation of the distal radial epiphysis accompanied by flexural contracture and external rotation of the limb distal to the antebrachial carpal joint. Conservative therapy was attempted with splints and bandages and failed to result in improvement. Surgical intervention was elected and a bilateral distal radial epiphysectomy and pancarpal arthrodesis performed. Fourteen months later the mare was turned out to pasture and ambulating well.  相似文献   

High-frequency jet ventilation during bronchoscopy in a dog     

D E Bjorling  M R Lappin  J B Whitfield 《Journal of the American Veterinary Medical Association》1985,187(12):1373-1375

A dog with severe pulmonary disease caused by Filaroides osleri (Oslerus osleri) infection was anesthetized with thiopental sodium IV for diagnostic bronchoscopy. The dog was ventilated continuously during bronchoscopy with a high-frequency jet ventilator (using a rate of 100 breaths/min, drive pressure of 20 psi, and inspiratory fraction of 0.30). High-frequency jet ventilation provided satisfactory ventilatory support during bronchoscopy despite the dog's pulmonary disease.  相似文献   

Effect of humidification on the airways of cats during high-frequency ventilation     

J B Whitfield  D E Bjorling  J F Munnell 《American journal of veterinary research》1991,52(9):1474-1478

The effect of humidity on the histologic lesions induced by high-frequency jet ventilation was investigated in 12 healthy cats. After 16 hours of ventilation, the appearance of the tracheal epithelium ranged from normal to necrotic. The damage was considerably more severe in the trachea of cats of the group ventilated without added humidity. Increasing the relative humidity to 63% at 24 C had a protective effect, but further increasing the relative humidity to 92% at 35 C did not appear to provide significantly more protection. The bronchi and distal airways had minimal, if any, damage in all groups.  相似文献   

Effects of irrigation and nitrogen on growth, light interception and efficiency of light conversion in wheat   总被引：2，自引：0，他引：2  

D. M. Whitfield  C. J. Smith 《Field Crops Research》1989,20(4):279-295

Effects of three irrigation treatments (rainfed, and irrigation at 7-day and 14-day frequencies beginning in spring) and two rates of nitrogen (0 and 150 kg N ha⁻¹) on growth, light absorption, and conversion efficiency in wheat were studied. Growth was considered in four phases extending from 95 days after sowing ( 95) to the beginning of rapid stem growth ( 120), the stem growth-phase lasting to the onset of rapid grain-filling ( 148), the grain-filling phase between 148 and 170, and the final period to harvest. The first irrigation treatments were applied at 120.Radiation interception was the major determinant of growth. Rainfed treatments captured ca. 1100 MJ m⁻² between 95 and 148, by which time they had achieved maximum above-ground biomass. Irrigated treatments continued to grow until 170. They captured ca. 1300 MJ m⁻² to 170 where no nitrogen was applied, and ca. 1500 MJ m⁻² where N was applied.In addition to effects on leaf-area duration and radiation absorption, treatments also affected conversion efficiency, ε. In the first phase, ε increased from 0.85 g MJ⁻¹ to 1.15 g MJ⁻¹ where N was applied. After 120, irrigation increased ε from a mean of 0.8 g MJ⁻¹ in rainfed treatments to 1.2 g MJ⁻¹. In the periods of rapid stem-growth and grain-filling, ε was a maximum of 1.45 g MJ⁻¹ in the frequently irrigated treatment which received N, resulting in a maximum above-ground biomass of 2100 g m⁻². Mean maximum biomass was 1670 g m⁻² in the other irrigated treatments, as compared with a mean of 1100 g m⁻² in rainfed treatments.Growth rates were compared with predicted potential rates. After accounting for differences in light absorption between treatments, rates of growth ranged between 0.4 and 0.65 of potential rates in treatments other than I_wN₁₅₀, in which the growth rate between 120 and 170 was almost 0.8 of the potential rate. These proportions were strongly correlated with estimates of ε, although the relationship varied between phases as a result of differences in global radiation. Collectively, the data suggest that physiological constraints, associated with both N and water, contributed to differences in rates of growth in addition to those imposed by leaf-area duration and radiation absorption.The yield potential of the frequently irrigated treatment which received N was, however, not realised in the field. Lodging after 162 was estimated to decrease yield from a potential of ca. 900 g m⁻² to 650 g m⁻².  相似文献   

Echocardiographic evaluation of dogs receiving 1:1 thiopental/propofol in a clinical setting     

AT  Evans  LK Anderson  J Hauptman 《Veterinary anaesthesia and analgesia》2003,30(2):102-102

The purpose of this study was to compare the echocardiographic Doppler blood pressure and heart rate effects of 1:1 thiopental/propofol with thiopental and propofol, when used as anesthesia‐induction agents. Seven healthy dogs (six Beagles and one Pembroke Welsh Corgi), ranging in age from 1 to 9 years and weighing 14.2 ± 2.4 kg (mean ± SD), were used during the study. In a cross‐over study design with a minimum drug interval of 3 days, each dog received propofol, thiopental, or a mixture of propofol–thiopental IV until each dog received all the three anesthetic agents. An initial dose (propofol 4.9 ± 0.8 mg kg^?1; thiopental 12.9 ± 2.4 mg kg^?1; propofol–thiopental 2.3 ± 0.3 mg kg^?1 (P)?5.7 ± 0.8 mg kg^?1 (T)) of each anesthetic agent was titrated IV until intubation was accomplished. Echocardiographic Doppler blood pressure and heart rate variables were recorded prior to anesthesia and at 1, 5, and 10 minutes after induction of anesthesia. anova and the Bonferroni's t‐test were used to evaluate the groups for differences. Alpha was <0.05. There was no significant effect of treatment on systolic or diastolic ventricular wall thickness, septal thickness, left atrial diameter, or systolic left ventricular diameter. There was a tendency for diastolic left ventricular diameter to decrease over time. There was a tendency for heart rate to increase with a significant difference at the 10‐minute time period between propofol (109 ± 26 beats minute^?1) and thiopental (129 ± 23 beats minute^?1). At the 10‐minute recording period, heart rate following the propofol/thiopental mixture (110 ± 34 beats minute^?1) was closer to that following propofol than to that following thiopental. With all induction agents, indirect blood pressure tended to decrease over time (p = 0.005); however, there was no difference between the groups. The changes observed were not considered to be of clinical significance. The propofol/thiopental mixture produces similar changes in echocardiographic variables when compared to propofol or thiopental, and could be substituted for propofol for induction of anesthesia in dogs.  相似文献