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81.
Gudmundsdottir KB Aalbaek B Sigurdarson S Gunnarsson E 《Journal of applied microbiology》2004,96(5):913-921
AIMS: The purpose of this study was to examine the diversity of Listeria monocytogenes strains from healthy sheep, winter feed and environment of sheep farms in Iceland. METHODS AND RESULTS: A total of 104 L. monocytogenes isolates from animals, winter feed and environment on 10 Icelandic sheep farms were compared by serotyping, ribotyping, and pulsed-field gel electrophoresis with ApaI and AscI. The isolates were divided into 24 genotypes, all identified as serovars 1/2a, 1/2b, or 4b. Nine genotypes were detected on more than one farm. On three of the farms there seemed to be a dominant strain of L. monocytogenes. Isolates from incidents of listeriosis in animals occurring on two of the farms belonged to the genotype most commonly found on the particular farm. Nine of the 24 genotypes found on the sheep farms have been associated with disease in animals and/or humans elsewhere in Iceland. CONCLUSIONS: Certain strains of L. monocytogenes seem to be widely distributed on Icelandic sheep farms. On some farms there appears to be a dominant strain of L. monocytogenes. Incidents of listeriosis in animals may tend to be associated with strains commonly found on the farm. SIGNIFICANCE AND IMPACT OF THE STUDY: This study demonstrates the diversity of L. monocytogenes present in healthy sheep and their environment. 相似文献
82.
AIMS: To investigate the biodegrading ability and cometabolism of synthetic pyrethroid (SP) utilizing bacteria in cultures with various minerals and carbon sources. METHODS AND RESULTS: Previously isolated SP-degrading Pseudomonas sp. and Serratia sp. were used in cultures containing either flumethrin SP or cypermethrin SP formulations. The culture media consisted of either (i) water only, (ii) water and sucrose, (iii) mineral broth or (iv) mineral broth and sucrose. The growth of both organisms was greatest in the mineral broth and sucrose medium, but the growth-limiting factor for Pseudomonas sp. strain Circle was the mineral content whereas for Serratia sp. strain White it was the carbon substrate. CONCLUSION: The greatest extent of degradation of both SP-based compounds occurred with Pseudomonas sp. strain Circle but was dependant on the medium. SIGNIFICANCE AND IMPACT OF THE STUDY: This investigation could lead to the development of a relatively inexpensive medium supplement to enhance the microbial biodegradation of undesirable compounds, either in situ or ex situ. In this particular case, for the biodegradation of SPs used in sheep dip. 相似文献
83.
Uyanik F 《Biological trace element research》2001,84(1-3):93-101
The effects of dietary inorganic chromium on some biochemical parameters were determined in lambs fed either a control diet
or a 200-ppb or 400-ppb chromium-supplemented diet. The live weight of the animals were measured and jugular blood samples
were collected prior to supplementation (d 0) and on d 20, 40, and 55. On d 55, three animals from each group were slaughtered
to measure subcutaneous fat. Sera were analyzed for glucose, triglyceride, total cholesterol, high-density lipoprotein (HDL)
and low-density lipoprotein (LDL) cholesterol, total protein, albumin, ALT, AST, and GGT levels. Chromium supplementation
had no significant effect on live weight, but subcutaneous fat was reduced significantly in both chromium groups. There was
a slight decrease in glucose concentrations in the 200-ppb chromium group, although only the differences on d 55 were significant.
Triglyceride levels in both chromium groups were lower than the control group with marked differences in the 400-ppb chromium
group. HDL cholesterol levels increased in both treatment groups compare to control, although the differences in the 400-ppb
chromium group on d 40 were significant. Serum Cr concentrations slightly but not significantly increased in both chromium
groups. No significant differences were found in total and LDL cholesterol, total protein, albumin, ALT, AST, and GGT levels.
In conclusion, chromium supplementation may affect carbohydrate and lipid metabolisms and lipid deposition in lambs. 相似文献
84.
New in vivo and ex vivo models for the experimental study of sheep scrapie: development and perspectives 总被引:1,自引:0,他引:1
Laude H Vilette D Le Dur A Archer F Soulier S Besnard N Essalmani R Vilotte JL 《Comptes rendus biologies》2002,325(1):49-57
Sheep scrapie is a prototypical transmissible spongiform encephalopathy (TSE), and the most widespread of these diseases. Experimental study of TSE infectious agents from sheep and other species essentially depends on bioassays in rodents. Transmission of natural sheep scrapie to conventional mice commonly requires one or two years. In an effort to develop laboratory models in which investigations on the sheep TSE agent would be facilitated, we have established mice and cell lines that were genetically engineered to express ovine PrP protein and examined their susceptibility to the infection. A series of transgenic mice lines (tgOv) expressing the high susceptibility allele (VRQ) of the ovine PrP gene from different constructs was expanded. Following intracerebral inoculation with natural scrapie isolates, all animals developed typical TSE neurological signs and accumulated abnormal PrP in their brain. The survival time in the highest expressing tgOv lines ranged from 2 to 7 months, depending on the isolate. It was inversely related to the brain PrP content, and essentially unchanged on further passaging. Ovine PrP transgene expression thus enhanced scrapie disease transmission from sheep to mice. Such tgOv mice may bring new opportunities for analysing the natural variation of scrapie strains and measuring infectivity. As no relevant cell culture models for agents of naturally-occurring TSE exist, we have explored various strategies in order to obtain stable cell lines that would propagate the sheep agent ex vivo without prior adaptation to rodent. In one otherwise refractory rabbit epithelial cell line, a regulable expression of ovine PrP was achieved and found to enable an efficient replication of the scrapie agent in inoculated cultures. Cells derived from sheep embryos or from tgOv mice were also used in an attempt to establish permissive cell lines derived from the nervous system. Cells engineered to express PrP proteins of a specified sequence may thus represent a promising strategy to further explore, at the cellular level, various aspects of TSE diseases. 相似文献
85.
Numerically equal groups of between five and ten young Merino and Dorper sheep were artificially infested with sheep scab
mites, Psoroptes ovis. Separate groups of sheep were infested during the early winter of two successive years as well as during the early summer
of the second year. Lesion growth was measured at two-weekly intervals for a period of six weeks during the first winter and
for eight weeks during the second winter and in the summer. The rate of lesion growth and mean lesion size on Merino sheep
was significantly greater than that on Dorper sheep at each two-weekly recording during the winter of both years. The rate
of growth of the lesions did not differ significantly between the two sheep breeds during summer, although, with the exception
of eight weeks post-infestation, the mean lesion size on Merino sheep was significantly larger than that on Dorper sheep at
each assessment.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
86.
We review the findings of a longitudinal study of transmission of the intracellular tick-borne bacterium Anaplasma phagocytophilum from sheep to Ixodes ricinus ticks under natural conditions of tick attachment in the UK. In this study, sheep-to-tick transmission efficiency varied
in a quadratic relationship with the number of adult ticks that were feeding on the sheep. We raise the hypothesis that this
relationship may be due to conflicting effects of the density of ticks on bacterial survival and target cell (neutrophil)
fluxes at the tick-host interface: in the same sheep at the same time, resistance to ticks was progressively inhibited with
increasing number of feeding adult ticks, and investigation of serological responses to tick antigens suggesting loss of resistance
may be associated with polarisation of host Th1 to Th2 type responses to ticks. We also raise the hypothesis that these properties,
with superimposed effects on tick survival, may mean that variation in tick density is an important causal factor of observed
variations in the force of A. phagocytophilum infection amongst different geographic foci.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
87.
Effects of chronic fluorosis on electrocardiogram in sheep 总被引:1,自引:0,他引:1
This study was carried out to evaluate the effects of chronic fluorosis by means of the electrocardiograms in sheep. Ten sheep
with fluorosis living around a volcanic mountain (Tendürek Mount) in East Anatolia in Turkey and 10 healthy sheep were used.
Leads I, II, III, aVR, aVL, aVF, V2, V4, and V10 were recorded in the electrocardiographs of the sheep. All waves were seen in all derivations. The P-Q interval was significantly
(p<0.05) prolonged and sinus bradycardia was observed in the sheep with fluorosis. As a result of this, the number of heart
beats was decreased significantly (p<0.05); that is, the number of heart beats was 110±15 in the control group and 75±10 in sheep with fluorosis. 相似文献
88.
The goal of this study was to determine the in vivo pulmonary arterial buffering function (BF) during acute and moderate pulmonary hypertension achieved by phenylephrine-induced smooth muscle activation.Pulmonary pressure (Konigsberg P7) and diameter (sonomicrometry) were measured in nine anesthetized sheep. Transit pulmonary arterial hypertension was induced by mechanical occlusion of the pulmonary artery (HP) and by phenylephrine infusion (5 g/kg/min) (PHE). A viscoelastic Kelvin-Voigt model was used. By increasing the values of the viscous modulus, the pressure-diameter hysteresis area was reduced to a minimum in order to obtain the purely elastic pressure-diameter relationship. The elastic index (E) was calculated as the first derivative of the exponential model of the purely elastic pressure-diameter relationship at the mean pressure point.Systolic, diastolic, mean and pulse pressures were similar during HP and PHE, but significantly higher with regard to control steady state. In HP, E and arterial diameter (both its minimum and maximum values) increased significantly. In contrast, when pulmonary hypertension was induced by VSM activation, E was maintained concomitantly with pulmonary artery vasoconstriction.Pulmonary hypertension produced by occlusion of the pulmonary artery increases elasticity. Smooth muscle activation may offset the deleterious effect of pulmonary hypertension on arterial wall elasticity by reducing E and impeding arterial dilatation and collagen recruitment, maintaining BF during pulmonary hypertension. 相似文献
89.
Di Berardino MA McKinnell RG Wolf DP 《Differentiation; research in biological diversity》2003,71(7):398-401
May 2002 marked the golden anniversary of the first cloned tadpoles. We celebrate this anniversary, as nuclear transplantation of frog cells into enucleated eggs became the prototype for cloning insects, fish, and mammals. We briefly review the salient results from amphibian cloning. Extension of these studies to mammalian species led to cloning adult cells, important advances in understanding nuclear reprogramming, and the construction of transgenic clones for biomedical applications. In addition, murine cloning clarified two problems unresolved in frog cloning: the unequivocal demonstration that nuclei of fully differentiated cells can direct the formation of fertile adults, and that abnormal expression of genes was responsible for the endoderm and neural syndromes in Rana clones. 相似文献
90.
Selfish mothers: reproductive expenditure and resource availability in bighorn ewes 总被引:13,自引:4,他引:9
We present a marginal value model explaining intraspecific andinterspecific variation of mating systems in nonterritorialungulates. The model takes into account the simultaneous effectsof spatial and temporal distribution of females, female groupsize, male-male competition, female choice, and the operationalsex ratio (i.e., the proportion of estrous females). The modelpredicts that higher numbers of females per group increasesthe average exploitation time of such groups by males. An increasein female group density, operational sex ratio, and age-specificfighting success of males are predicted to reduce the averageexploitation time of female groups, leading to roving of males(i.e., moving between female groups). In contrast, an increasein die female rejection rate of males and in the time spentby males on nonmating activities (i. e., foraging, lying down,ruminating, migrating) are predicted to increase the averageexploitation time of female groups and to favor staying behaviorof males (i.e., defending a female group over a longer periodof time). Consequently, die model predicts that young maleswill tend to be "stayers," whereas middle-aged and old malesare expected to be "rovers." Model predictions were tested widifield data collected on muskoxen Ovibos moschatus in a naturalpopulation in west Greenland. Observed correlations betweenbull exploitation times of cow groups and the six above-mentionedsocial and environmental parameters were all in die predicteddirection and statistically significant in five of die six cases.Overall, 69% of die observed variation in exploitation timeof cow groups by males was explained by die model predictions.Stepwise regression suggested that, of die six parameters, variationin sex ratio (R2 = .56) and time spent on nonmating activities(R2 = .35) had the largest effects on male exploitation time.Also, die observed age-specific variation in bull exploitationtime of cow groups was as predicted. 相似文献