A study of the transfer of tetracycline resistance genes between Escherichia coli in the intestinal tract of a mouse and a chicken model     

Hart WS  Heuzenroeder MW  Barton MD 《Journal of veterinary medicine. B, Infectious diseases and veterinary public health》2006,53(7):333-340

Experiments to demonstrate the transfer of genes within a natural environment are technically difficult because of the unknown numbers and strains of bacteria present, as well as difficulties designing adequate control experiments. The results of such studies should be viewed within the limits of the experimental design. Most experiments to date have been based on artificial models, which only give approximations of the real-life situation. The current study uses more natural models and provides information about tetracycline resistance as it occurs in wild-type bacteria within the environment of the normal intestinal tract of an animal. Tetracycline sensitive, nalidixic acid resistant Escherichia coli isolates of human origin were administered to mice and chicken animal models. They were monitored for acquisition of tetracycline resistance from indigenous or administered donor E. coli. Five sets of in vivo experiments demonstrated unequivocal transfer of tetracycline resistance to tetracycline sensitive recipients. The addition of tetracycline in the drinking water of the animals increased the probability of transfer between E. coli strains originating from the same animal species. The co-transfer of unselected antibiotic resistance in animal models was also demonstrated.  相似文献   

Computer science. Creating a science of the Web     

Berners-Lee T  Hall W  Hendler J  Shadbolt N  Weitzner DJ 《Science (New York, N.Y.)》2006,313(5788):769-771

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Global warming. Climate change demands action, says U.K. report     

Clery D 《Science (New York, N.Y.)》2006,311(5761):592

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Treatment for fear of fireworks in dogs     

Mills D  Cracknell N 《The Veterinary record》2006,159(16):536

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Evaluation of a vessel-sealing device for laparoscopic granulosa cell tumor removal in standing mares     

Hubert JD  Burba DJ  Moore RM 《Veterinary surgery : VS》2006,35(4):324-329

OBJECTIVE: To describe a laparoscopic technique for granulosa cell tumor removal using a vessel sealing device (LigaSuretrade mark) in standing mares. STUDY DESIGN: Retrospective study. ANIMALS: Eight mares (8-24 years old; weighing, 406-525 kg). METHODS: Before surgery, ovarian size and adjacent body wall thickness was determined by ultrasonography. Mares were sedated and after local anesthesia (inverted L and local infiltration), laparoscopic cannulation was performed without insufflation. The mesovarium was anesthetized and the LigaSure instrument applied to the mesovarium for hemostasis and resection to remove the affected ovary. Mares were hospitalized for 24 hours before discharge. RESULTS: Median ovarian diameter was 10.5 cm (range, 6-14 cm). Median surgery time was 75 minutes (range, 40-180 minutes). Hemostasis was achieved using the LigaSure device in all mares. Median length of the abdominal wall incision made to remove the ovary was 13 cm (range, 5-17 cm); no incisional complications occurred. CONCLUSIONS: The LigaSure vessel sealing device provided adequate hemostasis for removal of larger neoplastic ovaries in standing mares. CLINICAL RELEVANCE: Concerns of ligature placement can be alleviated by use of the LigaSure device and standing laparoscopic technique provides excellent observation of the surgical field ensuring hemostasis.  相似文献   

Bovine monocytes and a macrophage cell line differ in their ability to phagocytose and support the intracellular survival of Mycobacterium avium subsp. paratuberculosis     

Woo SR  Sotos J  Hart AP  Barletta RG  Czuprynski CJ 《Veterinary immunology and immunopathology》2006,110(1-2):109-120

Bovine monocytes exhibited a greater ability to phagocytose Mycobacterium avium subsp. paratuberculosis (i.e. greater percentage of infected cells, and more bacilli per infected cell), than did a bovine macrophage cell line (BoMac). Phagocytosis of M. paratuberculosis by monocytes, but not the cell line, was significantly enhanced by the addition of autologous serum. Following ingestion, the numbers of viable M. paratuberculosis cells in monocytes increased during the first 4 days and then declined between day 4 and day 8 after infection, as determined by a radiometric method. In contrast, BoMac cells were not permissive for bacillary multiplication; the numbers of M. paratuberculosis remained largely unchanged in the cell line during the 8 day incubation period. The numbers of microscopically visible acid-fast bacilli increased with time in monocytes but not in the macrophage cell line. These observations suggest that replication and inactivation of bacilli may both occur in monocytes. The differing abilities of bovine monocytes and the macrophage cell line to ingest and restrain the intracellular growth of M. paratuberculosis provide contrasting model systems for investigating how M. paratuberculosis enters and persists within its preferred niche, the mononuclear phagocyte.  相似文献   

Black cohosh (Actaea racemosa, Cimicifuga racemosa) behaves as a mixed competitive ligand and partial agonist at the human mu opiate receptor     

Rhyu MR  Lu J  Webster DE  Fabricant DS  Farnsworth NR  Wang ZJ 《Journal of agricultural and food chemistry》2006,54(26):9852-9857

Black cohosh is a commonly used botanical dietary supplement for the treatment of climacteric complaints. Because the opiate system in the brain is intimately associated with mood, temperature, and sex hormonal levels, the activity of black cohosh extracts at the human mu opiate receptor (hMOR) expressed in Chinese hamster ovary cells was investigated. The 100% methanol, 75% ethanol, and 40% 2-propanol extracts of black cohosh effectively displaced the specific binding of [3H]DAMGO to hMOR. Further studies of the clinically used ethanol extract indicated that black cohosh acted as a mixed competitive ligand, displacing 77 +/- 4% [3H]DAMGO to hMOR (Ki = 62.9 microg/mL). Using the [35S]GTPgammaS assay, the action of black cohosh was found to be consistent with an agonist, with an EC50 of 68.8 +/- 7.7 microg/mL. These results demonstrate for the first time that black cohosh contains active principle(s) that activate hMOR, supporting its beneficial role in alleviating menopausal symptoms.  相似文献   

Common Kibra alleles are associated with human memory performance   总被引：1，自引：0，他引：1  

Papassotiropoulos A  Stephan DA  Huentelman MJ  Hoerndli FJ  Craig DW  Pearson JV  Huynh KD  Brunner F  Corneveaux J  Osborne D  Wollmer MA  Aerni A  Coluccia D  Hänggi J  Mondadori CR  Buchmann A  Reiman EM  Caselli RJ  Henke K  de Quervain DJ 《Science (New York, N.Y.)》2006,314(5798):475-478

Human memory is a polygenic trait. We performed a genome-wide screen to identify memory-related gene variants. A genomic locus encoding the brain protein KIBRA was significantly associated with memory performance in three independent, cognitively normal cohorts from Switzerland and the United States. Gene expression studies showed that KIBRA was expressed in memory-related brain structures. Functional magnetic resonance imaging detected KIBRA allele-dependent differences in hippocampal activations during memory retrieval. Evidence from these experiments suggests a role for KIBRA in human memory.  相似文献   

Growth and phenology variation in progeny of Scots pine seed orchards and commercial seed stands     

Daniel J. Chmura  Roman Rożkowski  Władysław Chałupka 《European Journal of Forest Research》2012,131(4):1229-1243

Tree improvement in Poland has been most advanced for Scots pine, but existing seed orchards have not been progeny-tested yet. We examined variation in growth traits—tree height at ages 4 and 8 years, and diameter at age 13 years—in the common garden experiment testing open-pollinated progenies of 31 seed orchards and 5 commercial seed stands (referred to as populations) at 5 locations. We also examined bud burst phenology at two to five sites at three growing seasons. At one experimental site during the 5th growing season, we measured shoot growth rhythm on all populations. Similar measurements of shoot growth were done on a subset of populations during the 6th growing season together with the analysis of needle growth and foliar chemistry. We found significant variation among populations in growth traits, but also significant population × site (G × E) interactions. We used the regression approach and ecovalence analysis to examine populations’ performance stability. Most populations had average responsiveness to environment, and a set of least-responsive poor-growing populations contributed the most to the G × E interaction. Variation in bud burst phenology was associated with geographical distribution of tested progenies. The early bud-bursting populations originated from the north-eastern to north-central Poland, and a group of late bud-bursting populations originated mainly from the south-eastern region. Correlations between bud burst and growth traits were weak to medium and varied by site, but early bud-bursting populations tended to show stronger growth on height and diameter. We found significant differences among populations in final leader length, shoot elongation time and relative growth rate (RGR). However, RGR and shoot elongation time explained less than 30% of variation in leader length and were weakly correlated with tree height. Populations varied in needle length, specific leaf area and foliar nitrogen concentration, but time trends in these traits did not vary among populations or predefined groups of populations. Therefore, the analysis of growth rhythm or needle traits did not help resolve variation in tree growth to support selection decisions. Contrary to our expectation, progeny of seed orchards did not perform significantly better than that of commercial seed stands. This finding, however, should not be extrapolated beyond our set of populations. Nonetheless, the local seed sources were not always the best. From a selection standpoint, our results help culling the worst populations rather than selecting the best ones. Therefore, testing individual family progeny and genetic roguing of existing seed orchards is highly recommended.  相似文献   

Evolution and functional impact of rare coding variation from deep sequencing of human exomes     

Tennessen JA  Bigham AW  O'Connor TD  Fu W  Kenny EE  Gravel S  McGee S  Do R  Liu X  Jun G  Kang HM  Jordan D  Leal SM  Gabriel S  Rieder MJ  Abecasis G  Altshuler D  Nickerson DA  Boerwinkle E  Sunyaev S  Bustamante CD  Bamshad MJ  Akey JM;Broad GO;Seattle GO;NHLBI Exome Sequencing Project 《Science (New York, N.Y.)》2012,337(6090):64-69

As a first step toward understanding how rare variants contribute to risk for complex diseases, we sequenced 15,585 human protein-coding genes to an average median depth of 111× in 2440 individuals of European (n = 1351) and African (n = 1088) ancestry. We identified over 500,000 single-nucleotide variants (SNVs), the majority of which were rare (86% with a minor allele frequency less than 0.5%), previously unknown (82%), and population-specific (82%). On average, 2.3% of the 13,595 SNVs each person carried were predicted to affect protein function of ~313 genes per genome, and ~95.7% of SNVs predicted to be functionally important were rare. This excess of rare functional variants is due to the combined effects of explosive, recent accelerated population growth and weak purifying selection. Furthermore, we show that large sample sizes will be required to associate rare variants with complex traits.  相似文献