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31.
Robert L. Metcalf 《Agriculture and Human Values》1987,4(4):15-25
The use of pesticides is one of the more controversial of public issues. This is so because their very widespread use produces immediate benefits to a small section of society, the agricultural industry, while the long term risks are shared by society as a whole. This discussion focuses on the contrast between benefits and risks and outlines some of the long term ecological problems that have resulted from the overuse, misuse, and injudicious use of pesticides. Detailed discussion is provided for such ecological disasters as insect pest resistance to pesticides, pest resurgences and the development of secondary pests; together with contamination of food webs and general ecotoxicity. It is concluded that implementation of integrated pest management (IPM) tactics provides the only practical answer to the manifold problems arising from the sole reliance on pesticides for pest control. IPM provides an ecological oriented strategy for pest control that can maximize the benefits of pesticide use and minimize the risks. 相似文献
32.
Accelerator mass spectrometer dating of an assemblage of fibrous and leather footwear from Arnold Research Cave in central Missouri documents a long sequence of shoe construction by prehistoric Midwestern peoples, beginning perhaps as early as 8300 calendar years before the present (cal years B.P.). An earlier fibrous sandal form dates from 8325 to 7675 cal years B.P., and later fibrous or leather slip-ons span the period from 5575 to 1070 cal years B.P. The assemblage adds to a growing picture of the highly varied nature of prehistoric footwear production in the United States throughout the Holocene. 相似文献
33.
34.
Jan Hendrik Reinders Larry G. Hansen Robert L. Metcalf Robert A. Metcalf 《Pesticide biochemistry and physiology》1983,20(1):67-75
Inhibition of chicken brain neurotoxic esterase (NTE) by a series of O-halogenated-phenyl-O-alkyl phenylphosphonates was studied in vitro. The “apparent” activity was found to consist of “true” NTE (sensitive to mipafox) plus a minor mipafox-resistant component. The pI50 of O-(2,6-dichlorophenyl) O-methyl phenylphosphonate for “true” NTE was 6.65, whereas it was about 3 for mipafox-resistant hydrolysis of phenyl valerate. This compound is suitable as an alternative to mipafox in the assay of “true” NTE, whereas the use of leptophos oxon gives a less accurate measure. The ethoxy analogs are about as potent in vitro as the corresponding methoxy compounds. Leptophosoxon and ethoxyleptophosoxon are more potent in vitro inhibitors than desbromoleptophosoxon. Within a like group of chlorinated phenylphosphonates, a reasonable correlation between in vitro neurotoxic esterase inhibition of the oxon and in vivo delayed neurotoxic potential by the corresponding phosphonothionate exists. In vivo inhibition of “apparent” NTE from chicken brain, studied 24 hr after an oral dose, is dose dependent for leptophos, ethoxyleptophos, and desbromoleptophos, the latter one being a very potent in vivo inhibitor. Ethoxyleptophos and leptophos have about equal in vivo esterase inhibitory properties. For desbromoleptophos and leptophos there is good agreement between the minimum dose causing delayed neurotoxicity and the dose leading to substantial inhibition of “apparent” NTE; ethoxyleptophos, on the other hand, inhibits the esterase at a dose much lower than the one which is neurotoxic. Several possible explanations for this discrepancy are considered. 相似文献
35.
Joel R. Coats Robert L. Metcalf Inder P. Kapoor 《Pesticide biochemistry and physiology》1974,4(2):201-211
Dianisylneopentane or 1,1-bis(p-methoxyphenyl)-2,2-dimethylpropane was metabolized largely by O-demethylation to form mono- and diphenol derivatives. Only a small percentage was degraded by α-hydroxylation and rearrangement. In the model ecosystem, dianisylneopentane reacted very similarly to methoxychlor, accumulating in fish to about the same extent and yielding a slightly higher ratio of polar to nonpolar metabolites. The neopentyl group proved to be approximately as stable in biological systems as the isosterically equivalent trichloromethyl group. 相似文献
36.
K. L. Hepworth‐Warren B. L. Hay Kraus D. M. Wong A. C. Krull G. L. Metcalf 《Equine Veterinary Education》2017,29(11):603-608
This report describes an 11‐year‐old Percheron mare that presented with signs of colic and was ultimately diagnosed with bacterial peritonitis of unknown origin. Bacterial culture of a peritoneal fluid sample isolated 2 Clostridial species, one of which was strongly suspected to be Clostridium haemolyticum. The horse was markedly hypoalbuminaemic at presentation, leading to the development of low oncotic pressure and ventral oedema. The mare was administered a low molecular weight/low molar substitution hydroxyethyl starch solution in conjunction with other therapies that resulted in marked improvement of clinical signs. The purpose of this report is to describe the clinical findings associated with equine peritonitis associated with C. haemolyticum, a rarely identified pathogen in the horse. Secondly, this report serves to describe the beneficial effects of tetrastarch administration in a clinical case with severe hypoalbuminaemia and ventral oedema. 相似文献
37.
K. J. Evans A. K. Palmer D. A. Metcalf 《European journal of plant pathology / European Foundation for Plant Pathology》2013,135(4):661-673
Aerated compost tea (ACT), prepared from immature compost, was applied to foliage and fruit of grapevines (Vitis vinifera) to assess its potential for suppressing two important diseases: botrytis bunch rot, caused by Botrytis cinerea, and powdery mildew, caused by Erysiphe necator. An ACT applied to leaves of Cabernet Sauvignon vines in pots 7 days before inoculation with E. necator conidia reduced mean powdery mildew severity on the three youngest expanded leaves (at inoculation) to less than 1 %; mean severity on non-treated, inoculated leaves was 15 %. Multiple applications of ACTs at two vineyards in different growing seasons suppressed powdery mildew to <1 % mean severity on Chardonnay leaves (non-treated 79 % severity) and bunches (non-treated 77 % severity), and on Riesling leaves (non-treated 24 % severity). The same treatments reduced the incidence of Chardonnay bunches with latent B. cinerea and Riesling bunches with sporulating B. cinerea, although the level of botrytis bunch rot in both experiments was not economically damaging. The numbers of culturable bacteria, fungi and yeasts on Chardonnay leaves were higher than pre-treatment levels 10 days after ACT application, as were fungal numbers on Riesling leaves 21 days after treatment. Suppression by ACTs of two fruit and foliar pathogens of grapevine with different biology and epidemiology indicated potential for their use as a tactic in integrated disease management. Further testing of ACTs in a range of viticultural environments and application regimes will contribute to a better understanding of the impact of this tactic on disease, grape and wine quality. 相似文献
38.
Robert L. Metcalf 《Pest management science》1989,26(4):333-358
The past 40 years have seen insect resistance to insecticides develop from a scientific curiosity to an immense practical problem that threatens man's ability to control not only the insect pests of agriculture but also the insect vectors that transmit major human and animal diseases. The spread of genes for cross and multiple resistance among insect pests has rendered most of our present insecticides obsolescent and very few novel insecticides are under development as substitutes. The most feasible strategy to maintain adequate control of insect pests is integrated pest management or I P M, in which insecticide management is a useful component. However, much of our present planning for the future of insect control is carried out in ignorance of past failures. We must learn from the past if we are to retain the use of chemical insecticides as a viable component of IPM. 相似文献
39.
Michael R. Metcalf DVM MS Lloyd P. Tate DVM Loouis C. Sellett MS 《Veterinary radiology & ultrasound》1989,30(2):80-87
40.
Robert L. Metcalf B.Magnus Francis Robert A. Metcalf Larry G. Hansen 《Pesticide biochemistry and physiology》1983,20(1):57-66
Nineteen O-halogenated-phenyl O-methyl phenylphosphonothionates were evaluated for acute toxicity (LD50) to the female house fly Musca domestica L. and to the male Swiss white mouse, and for delayed neurotoxicity to the White Leghorn hen. The electron-withdrawing power of the phenyl substituents (Σσ? values) correlate with the LD50 values to house fly and mouse, with departures from linearity attributable to the steric hindrance of di-ortho-Cl substitution and by variations in the accessibility of the anionic site of acetylcholinesterase in the two species. The relationship with delayed neurotoxicity is less predictable although it clearly depends on suitable electron-withdrawing capacity. Delayed neurotoxicity also relates to a high degree of lipophilicity and prolonged residence time of the inhibitor in the nerve axon. 相似文献