Stress in veterinary science students: a study at the University of Queensland     

McLennan MW  Sutton RH 《Journal of veterinary medical education》2005,32(2):213-218

This paper reports on the results of a survey of selected University of Queensland (UQ) veterinary students aimed at elucidating factors causing stress during the five undergraduate years of the program. Students from each of the five years were asked to form six- or seven-member focus groups. Each focus group was then interviewed and their opinions sought on causes of ongoing stress and the ranking of those causes into predetermined categories. They were also asked to give their opinions on counseling services available within the university and what, if any, services they would like to see in place to help students with stress-related problems. Students in the first, third, and fourth years of the program rated academic issues as the most likely causes of ongoing stress, while students in the second and fifth years of the program ranked lifestyle and financial issues as more likely to cause ongoing stress. In most cases, students coped well with these causes of stress and tended not to use counseling services available to all UQ students. When faced with stressful issues, students looked to their classmates or family members for help and not to university counseling services. Students were also happy to approach staff members in the Veterinary School when faced with a problem. The authors nevertheless conclude that mechanisms set in place at the undergraduate level to help veterinary students cope with stress should particularly benefit those students when they become new graduates and are faced with the stresses of veterinary practice.  相似文献   

Rapid, non-destructive selection of peanuts for high aflatoxin content by soaking and tandem mass spectrometry     

Schatzki TF  Haddon WF 《Journal of agricultural and food chemistry》2002,50(10):3062-3069

Peanut lots are subject to aflatoxin levels high enough to cause concern to health agencies and trade channels. A possible solution would be to mechanically sort out high aflatoxin nuts from the process stream. Only highly contaminated nuts would need to be removed. However, there exists at present no sorting mechanism which meets commercial needs of adequate reduction and product preservation. To build such a sorter requires knowledge of the properties that can be used for sorting. The first step in the design is to select on the order of one hundred undamaged contaminated nuts which can be compared with noncontaminated ones. Because contaminated nuts are rare, a very large number of nuts needs to be examined nondestructively. We present a method to rapidly carry out such a selection. The method is based on dipping nuts into extraction fluid and examining the resulting fluid by tandem MS without preliminary cleanup. This method has been applied to examine over 65,000 nuts, yielding approximately 120 nuts, each containing more than 250-43000 ng/g aflatoxin (depending on process stream).  相似文献   

Magneto-opto-electronic bistability in a phenalenyl-based neutral radical     

Itkis ME  Chi X  Cordes AW  Haddon RC 《Science (New York, N.Y.)》2002,296(5572):1443-1445

A new organic molecular conductor, based on a spiro-biphenalenyl neutral radical, simultaneously exhibits bistability in three physical channels: electrical, optical, and magnetic. In the paramagnetic state, the unpaired electrons are located in the exterior phenalenyl units of the dimer, whereas in the diamagnetic state the electrons migrate to the interior phenalenyl units and spin pair as a pi-dimer. Against all expectations, the conductivity increases by two orders of magnitude in the diamagnetic state, and the band gap decreases. This type of multifunctional material has the potential to be used as the basis for new types of electronic devices, where multiple physical channels are used for writing, reading, and transferring information.  相似文献   

Chemistry of the fullerenes: the manifestation of strain in a class of continuous aromatic molecules     

Haddon RC 《Science (New York, N.Y.)》1993,261(5128):1545-1550

Within the wr-orbital axis vector theory, the total rehybridization required for closure of the fullerenes is approximately conserved. This result allows the development of a structure-based index of strain in the fullerenes, and it is estimated that about 80 percent of the heat of formation of the carbon atoms in C60 may be attributed to a combination of v strain and steric inhibition of resonance. Application of this analysis to the geometries of structurally characterized organometallic derivatives of C60 and C70 shows that the reactivity exhibited by the fullerenes may be attributed to the relief of a combination of local and global strain energy. C60 is of ambiguous aromatic character with anomalous magnetic properties but with the reactivity of a continuous aromatic molecule, moderated only by the tremendous strain inherent in the spheroidal structure.  相似文献   

E.J. Branson (ed): Fish welfare     

Malcolm Jobling 《Aquaculture International》2008,16(4):375-376

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M. Fingerman & R. Nagabhushanam (eds): Biomaterials from Aquatic and Terrestrial Organisms     

Malcolm Jobling 《Aquaculture International》2007,15(6):497-498

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Prostaglandin E2 and reactive oxygen metabolite damage in the cecum in a pony model of acute colitis   总被引：1，自引：0，他引：1       下载免费PDF全文

Rebecca S. McConnico  Robert A. Argenzio    Malcolm C. Roberts 《Canadian journal of veterinary research》2002,66(1):50-54

The objective of this project was to determine early tissue biochemical events associated with increased colonic secretion during the acute stage of castor-oil-induced colitis by measuring cecal mucosal and submucosal malondialdehyde (MDA) and prostaglandin E₂ (PGE₂), levels in ponies. Intestinal tissue (inflamed or healthy) samples were obtained from 4 age- and sex-matched Shetland ponies. Biochemical methods were used to determine MDA and PGE₂ levels in intestinal tissue samples from inflamed and healthy equine intestine. Inflamed tissue MDA and PGE₂ levels increased with time after castor oil challenge and correlated with granulocyte infiltration, as determined by myeloperoxidase levels in a companion study. Elevated intestinal tissue MDA levels suggest that lipid peroxidation could be attributed to reactive oxygen metabolites (ROM) released from stimulated, recruited, and resident granulocytes. Tissue levels of MDA and PGE₂ suggest a role for granulocyte-derived mediators of intestinal inflammation in the massive secretory response in cases of acute equine colitis. Tissue MDA and PGE₂ levels may be useful laboratory tools to quantify and characterize intestinal secretory inflammatory responses in acute inflammatory conditions in the equine colon.  相似文献   

Growth and its partitioning in Prunus rootstocks in response to root zone temperature     

Peter Malcolm  Paul Holford  Barry McGlasson  Jann Conroy  Idris Barchia 《Scientia Horticulturae》2007

Rootstocks for stone fruit varieties differentially influence tree physiology and one possible explanation for these differences is that varieties vary in their response to root zone temperature (RZT). To examine the effects of RZT, two trials using actively growing plants of five different Prunus rootstocks with chill requirements between 100 and 1100 h were undertaken. Plants were grown at RZTs of 5, 13 and 19 °C for 6 weeks after which total dry matter accumulation and its partitioning amongst roots, stems and leaves was determined. In general, the magnitude of total dry matter and its component parts positively correlated with RZT and significant differences were found among varieties in the magnitude of total dry matter accumulation. Individual varieties ranked differently at the three RZTs with respect to total dry matter: in general, the same ranking was also seen in the ranking of each growth component. RZT significantly influenced partitioning causing differences in leaf, stem and root mass ratios. These differences were greatest at low RZTs and became less as RZT increased. Several patterns of partitioning were found. Firstly, the low chill varieties (Okinawa and Flordagold) were little affected by RZT with similar partitioning occurring at each RZT. Secondly, the higher chill varieties, Green Leaf Nemaguard (GL), Golden Queen (GQ) and Fay Elberta (FE), reacted more strongly to RZT and were particularly affected by the lowest RZT. For these varieties, the root mass ratio rose and stem mass ratio fell as RZT increased. However, with respect to leaf mass ratio, two different trends were found: the leaf mass ratio for FE and GQ positively correlated with RZT whilst the relationship for GL was negative. These findings suggest that the response to RZT is related to a variety's chill requirement; offer an explanation for differences in performance of rootstock–scion combinations at different locations; and will aid the development of more accurate tree performance models by taking RZT into account.  相似文献   

Why are there not more herbicide-tolerant crops?     

Devine MD 《Pest management science》2005,61(3):312-317

Herbicide-tolerant (HT) varieties of corn, soybean, canola (oilseed rape) and cotton have been grown since the mid-1990s, and have been widely adopted by farmers in several countries. HT genes have been inserted into or selected for in many other species, including almost all major crop species in the world and many minor crops and ornamental species. In some cases this has been done specifically to introduce the HT trait, whereas in others the HT gene has been used as a selectable marker (eg the bar gene, conferring glufosinate-ammonium tolerance). However, in very few cases have the HT crops generated been commercialized, despite the weed-control advantages that many such crops would offer. There are several reasons for this, including the high research and development costs associated with developing the new HT crop cultivars, the high cost of obtaining regulatory clearance for the HT crops or products derived from them, international trade issues relating to genetically modified crops, and issues surrounding the expanded herbicide registration for the new use and the potential impact of this on the existing registration status of the herbicide. New HT crops are unlikely to be developed unless they offer a sufficiently large advantage to farmers and a substantial assured market to justify the associated development and regulatory costs.  相似文献   

Mechanism of action and fate of the fungicide chlorothalonil (2,4,5,6-tetrachloroisophthalonitrile) in biological systems: I. Reactions with cells and subcellular components of Saccharomyces pastorianus     

Ronald W. Tillman  Malcolm R. Siegel  John W. Long 《Pesticide biochemistry and physiology》1973,3(2):160-167

The mechanism and sequence of reaction of chlorothalonil in cells of Saccharomyces pastorianus was investigated by the use of either ¹⁴C-labeled fungicide or Na₂³⁵SO₄-labeled cells. The initial uptake of fungicide resulted in rapid formation of substituted chlorothalonil-reduced glutathione (GSH) derivatives. Chlorothalonil reacted with proteins during derivative formation but decreased cell viability did not occur until all the GSH was reacted and inhibition of specific NAD thiol-dependent glycolytic and respiratory enzymes occurred. It is postulated that enzyme activity and cell viability are controlled either directly or indirectly by the concentration of GSH. The loss of GSH through derivative formation with chlorothalonil and the lack of regeneration of the reduced thiol could be an important feature in the sequence of toxicity of the fungicide. The general mechanism of action of chlorothalonil resembles the trichloromethyl sulfenyl fungicides in that treated cells accumulate large concentrations of fungicide; reactions involve both low and high molecular-weight thiols, with the formation of glutathione-fungicide derivatives; and toxicity resides ultimately with the inhibition of thiol-dependent enzymes.  相似文献