The surgical correction of a deviated anterior maxilla in a horse     

GMW McKELLAR  AP COLLINS 《Australian veterinary journal》1993,70(3):112-114

SUMMARY The surgical correction of facial deformities of the horse have rarely been undertaken. The surgical and medical management of submucous clefting of the anterior maxilla in a young colt is described.  相似文献   

Mitotic instability in Aspergillus nidulans caused by the fungicides iprodione,procymidone and vinclozolin     

Spyros G. Georgopoulos  Michael Sarris  Basil N. Ziogas 《Pest management science》1979,10(5):389-392

The fungicides iprodione, procymidone and vinclozolin were found to increase greatly the frequency of mitotic recombination in diploid colonies of Aspergillus niduluns. Although generally more potent, these fungicides do not appear to differ in their activity from members of a previously suggested ?aromatic hydrocarbon group’? with which they should be classified in this context.  相似文献   

Mitochondrial electron transport in a carboxin-resistant,antimycin A-sensitive mutant of Ustilago maydis     

B.N. Ziogas  S.G. Georgopoulos 《Pesticide biochemistry and physiology》1984,22(1):24-31

Succinoxidase activity of mitochondria from an antimycin A-sensitive (ants) mutant of Ustilago maydis is approximately five times less sensitive to the fungicide carboxin than that of mitochondria from wild-type cells. The antimycin A sensitivity is due to the absence of an alternative electron transport pathway in mitochondria obtained from mutant cells grown in control medium. The same mutant, however, develops high rates of alternative respiration if grown in the presence of chloramphenicol. Substrate and oxygen affinity as well as resistance to hydroxamates indicate that this respiration is mediated by only one mitochondrial electron transport pathway, similar to the inducible system described earlier in wild-type mitochondria. Induction appears to be regulated by the activity of the cytochrome pathway. The absence of the constitutive system from the ants mutant mitochondria which are resistant to carboxin, a selective inhibitor of the succinate dehydrogenase complex, supports the view that this system must be related to succinic dehydrogenase.  相似文献   

Suspected salmonellosis in seven broodmares after transportation     

SA McCLINTOCK  AP BEGG 《Australian veterinary journal》1990,67(7):265-267

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Mental rotation of the neuronal population vector   总被引：19，自引：0，他引：19  

A P Georgopoulos  J T Lurito  M Petrides  A B Schwartz  J T Massey 《Science (New York, N.Y.)》1989,243(4888):234-236

A rhesus monkey was trained to move its arm in a direction that was perpendicular to and counterclockwise from the direction of a target light that changed in position from trial to trial. Solution of this problem was hypothesized to involve the creation and mental rotation of an imagined movement vector from the direction of the light to the direction of the movement. This hypothesis was tested directly by recording the activity of cells in the motor cortex during performance of the task and computing the neuronal population vector in successive time intervals during the reaction time. The population vector rotated gradually counterclockwise from the direction of the light to the direction of the movement at an average rate of 732 degrees per second. These results provide direct, neural evidence for the mental rotation hypothesis and indicate that the neuronal population vector is a useful tool for "reading out" and identifying cognitive operations of neuronal ensembles.  相似文献   

Epigenetic flexibility underlying lineage choices in the adaptive immune system     

Kioussis D  Georgopoulos K 《Science (New York, N.Y.)》2007,317(5838):620-622

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Motor cortical encoding of serial order in a context-recall task     

Carpenter AF  Georgopoulos AP  Pellizzer G 《Science (New York, N.Y.)》1999,283(5408):1752-1757

The neural encoding of serial order was studied in the motor cortex of monkeys performing a context-recall memory scanning task. Up to five visual stimuli were presented successively on a circle (list presentation phase), and then one of them (test stimulus) changed color; the monkeys had to make a single motor response toward the stimulus that immediately followed the test stimulus in the list. Correct performance in this task depends on memorization of the serial order of the stimuli during their presentation. It was found that changes in neural activity during the list presentation phase reflected the serial order of the stimuli; the effect on cell activity of the serial order of stimuli during their presentation was at least as strong as the effect of motor direction on cell activity during the execution of the motor response. This establishes the serial order of stimuli in a motor task as an important determinant of motor cortical activity during stimulus presentation and in the absence of changes in peripheral motor events, in contrast to the commonly held view of the motor cortex as just an "upper motor neuron."  相似文献   

A new class of carboxin-resistant mutants of Ustilago maydis     

S. G. Georgopoulos  B. N. Ziogas 《European journal of plant pathology / European Foundation for Plant Pathology》1977,83(1):235

A small percentage of mutants of Ustilago maydis, selected on medium containing 40 μM carboxin, are distinctly more resistant than the mutants previously described, with an ED₅₀ at least 100 times higher than that of wild type strains. Nine mutants of this category were studied. Crosses involving any one of these mutants gave Mendelian ratios in all cases and no transgressive segregation for level of tolerance was observed. All nine mutants were found to carry a mutation at the locus previously designated as oxr-1. In all cases carboxin resistance in vivo could be related to the resistance of the succinic dehydrogenase system in mitochondrial preparations and no other mechanism of resistance has been recognized. It appears that two allelic mutant genes at the oxr-1 locus code for two altered types of the succinic dehydrogenase complex distinguished by the level of carboxin tolerance.  相似文献   

Sensitivity of Ustilago maydis to pyrazophos and one of its conversion products,and failure to induce resistance with UV-treatment     

S. G. Georgopoulos  J. W. G. Geerligs  J. Dekker 《European journal of plant pathology / European Foundation for Plant Pathology》1975,81(1-2):38-41

2-Hydroxy-5-methyl-6-ethoxycarbonylpyrazolo(1,5-a)pyrimidine (PP), a conversion product of pyrazophos, shows considerable toxicity toUstilago maydis, when administered to this fungus in a solution at pH<5. Evidence was obtained thatU. maydis may convert pyrazophos in to PP, and that the latter compound is the toxic principle responsible for the action of pyrazophos. By UV-irradiation of sporidia no PP-resistant mutants were obtained. This does not support the hypothesis that this toxicant acts by specific inhibition of one enzyme system.  相似文献   

Anthelmintic resistance and management of nematode parasites on beef cattle-rearing farms in the North Island of New Zealand     

R Jackson  AP Rhodes  WE Pomroy  DM Leathwick  DM West  TS Waghorn 《New Zealand veterinary journal》2013,61(6):289-296

AIM: To provide information on current farmers’ opinions and farming practices thought to be related to anthelmintic resistance, and to test for associations between the presence of anthelmintic resistance and management practices on beef cattle- rearing farms in the North Island of New Zealand.

METHODS: A study using an interview-based questionnaire about management of internal parasites was conducted on 62 beef cattle-rearing farms in the North Island of New Zealand, using case-control analyses to test for associations between management practices and the presence or absence of resistance to ivermectin or albendazole. Resistance was inferred from faecal nematode egg count (FEC) reduction (FECR) tests (FECRTs) when there was <90% reduction in FEC 7-10 days after treatment of calves <12 months of age.

RESULTS: Of the 59 farmers who completed the questionnaire, most (n=40) ranked parasites highly, and at about the same level as quality and quantity of feed, as important production-limiting factors for their enterprises. In contrast, anthelmintic resistance was not perceived to be a problem on 13 farms, and its importance was rated low on 24, moderate on 15, and high on only six farms. Despite all farms having planned parasite control programmes, there was heavy reliance on clinical signs of parasitism to determine frequency of treatments. About one in three farmers with beef breeder cows routinely treated their calves at marking, one in five treated mixed-age cows, and almost half treated rising 2-year-old cows before calving. One in four farmers used anthelmintics on calves on 8–12 occasions in their first year of life. Co-grazing with other species was rare, but follow-on grazing within 3 months after older cattle or sheep was common. On most farms, grazing cattle was restricted to part of the farm, a finding with implications for parasite control and persistence of larvae in refugia. Macrocyclic lactone (ML) anthelmintics or their combinations with other action families were currently, and for the past 5 years, used more frequently than benzimidazoles and levamisole, and benzimidazole-levami- sole combinations. The prevalence of resistance to ivermectin was high (82%) and no plausible model of associations could be constructed from the data. The prevalence of resistance to albendazole was 60%, and the risk of resistance increased as the number of rising 1-year-old cattle present mid-winter increased, and decreased as the number of breeding cows >2 years old present mid-winter increased.

CONCLUSION: It is clear that in practice anthelmintic resistance is a secondary consideration to obtaining productivity advantages from the use of anthelmintics in beef cattle. Farmers’ opinions were divided on many issues and the overall impres- sion was of confused and diverse thinking regarding the principles of the use of anthelmintics. The overall outlook regarding anthelmintic resistance in cattle is bleak unless the need for integrated and long-term research activities is acted upon soon.  相似文献