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1.
Glover Hilary E.; Garside Christopher; Trees Charles C. 《Journal of plankton research》2007,29(3):263-274
A study was conducted in July 1989 at three stations in thenorthern Sargasso Sea, where picoplankton (<1 µm)provided approximately half of the standing crop of chlorophyll.Temporal changes in the position of the nitracline at a singlelocation indicated that the vertical supply of nitrate was notat steady-state and phytoplankton distributionstracked the nitracline. Our main experimental objective wasto examine the short-term effects of ecologically significantnitrate perturbations (+20 and +100 nM) on the physiologyof <1 µm communities growing at low (nanomolar)ambient nitrate concentrations. A chemiluminescent nitrate methodwas used to measure the time course (up to 4 h) of nitratedisappearance at in situ irradiance, in parallel with measurementsof photosynthetic 14CO2 assimilation. Picoplankton growing at<60 nM nitrate rapidly responded to nanomolar nitratesupplements with luxury consumption and enhanced photosynthesisin proportion to their ambient nitrate environment. Light-saturatedSynechococcus populations from the most nitrate-depleted waters(13 nM) had doubled their cellular rate of photosynthesisafter 4 h, in response to a 20 nM nitrate pulse. 相似文献
2.
Onchocerca gutturosa and O. lienalis infections in British cattle were studied by examination of cattle post-mortem originating from North Wales and Cheshire (north west England). In 463 adult animals, the microfilarial (mf) prevalence was 28.5%. In 95.3% of the mf infected animals, gravid worms could not be found at either the ligamentum nuchae or the gastro-splenic omentum. Dermal mf at the head were identified as O. gutturosa on the basis of their highly significant association with the presence of gravid O. gutturosa at the ligamentum nuchae, which were found in only 3.2% of cattle. Mfs were isolated from different skin sites and from adult worms and a minimum of 10 mfs from each isolate were examined for width and acid phosphatase (AP) staining pattern. The width of O. gutturosa dermal mf was less than 4 micron (4 isolations), narrower than that of putative O. lienalis mf isolated from umbilical skin of cattle without evidence of O. gutturosa, which were in 20/22 isolations greater than 4 micron wide. The dermal mf were also distinguished on the basis of different AP staining patterns which, for each species, correlated closely with that of hatched intrauterine mf from their respective adult female worms. Based on the criteria of morphology and AP staining patterns the mf species prevalences in the survey population were estimated as O. lienalis 24.1% and O. gutturosa 2.2%, with a further 2.2% of cattle infected with both species. The results indicate that the predilection site of adult O. lienalis is not the gastro-splenic omentum. In North Wales, the distribution of the two species was different; O. lienalis was widely distributed in all cattle rearing areas both lowland and upland, whereas O. gutturosa was largely restricted to valleys close to major rivers. 相似文献
3.
Rachel B. Slayton George Turabelidze Sarah D. Bennett Colin A. Schwensohn Anna Q. Yaffee Faisal Khan Cindy Butler Eija Trees Tracy L. Ayers Marjorie L. Davis Alison S. Laufer Stephen Gladbach Ian Williams Laura B. Gieraltowski 《PloS one》2013,8(2)
Background
Shiga toxin-producing Escherichia coli (STEC) O157:H7 is the causal agent for more than 96,000 cases of diarrheal illness and 3,200 infection-attributable hospitalizations annually in the United States.Materials and Methods
We defined a confirmed case as a compatible illness in a person with the outbreak strain during 10/07/2011-11/30/2011. Investigation included hypothesis generation, a case-control study utilizing geographically-matched controls, and a case series investigation. Environmental inspections and tracebacks were conducted.Results
We identified 58 cases in 10 states; 67% were hospitalized and 6.4% developed hemolytic uremic syndrome. Any romaine consumption was significantly associated with illness (matched Odds Ratio (mOR) = 10.0, 95% Confidence Interval (CI) = 2.1–97.0). Grocery Store Chain A salad bar was significantly associated with illness (mOR = 18.9, 95% CI = 4.5–176.8). Two separate traceback investigations for romaine lettuce converged on Farm A. Case series results indicate that cases (64.9%) were more likely than the FoodNet population (47%) to eat romaine lettuce (p-value = 0.013); 61.3% of cases reported consuming romaine lettuce from the Grocery Store Chain A salad bar.Conclusions
This multistate outbreak of STEC O157:H7 infections was associated with consumption of romaine lettuce. Traceback analysis determined that a single common lot of romaine lettuce harvested from Farm A was used to supply Grocery Store Chain A and a university campus linked to a case with the outbreak strain. An investigation at Farm A did not identify the source of contamination. Improved ability to trace produce from the growing fields to the point of consumption will allow more timely prevention and control measures to be implemented. 相似文献4.
Jonas De Vylder Jan Aelterman Trees Lepez Mado Vandewoestyne Koen Douterloigne Dieter Deforce Wilfried Philips 《PloS one》2013,8(1)
Cell nuclei detection in fluorescent microscopic images is an important and time consuming task in a wide range of biological applications. Blur, clutter, bleed through and partial occlusion of nuclei make individual nuclei detection a challenging task for automated image analysis. This paper proposes a novel and robust detection method based on the active contour framework. Improvement over conventional approaches is achieved by exploiting prior knowledge of the nucleus shape in order to better detect individual nuclei. This prior knowledge is defined using a dictionary based approach which can be formulated as the optimization of a convex energy function. The proposed method shows accurate detection results for dense clusters of nuclei, for example, an F-measure (a measure for detection accuracy) of 0.96 for the detection of cell nuclei in peripheral blood mononuclear cells, compared to an F-measure of 0.90 achieved by state-of-the-art nuclei detection methods. 相似文献
5.
Genotypes of Toxoplasma gondii in naturally infected tissues from 13 ovine abortions from 10 farms in the United Kingdom, from 2 wild rodents captured on 1 farm, and from 2 isolates in laboratory mouse brains (made from the hearts of healthy, infected lambs) all conformed to the type II lineage determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis of the SAG2 gene. PCR was applied directly to tissue extracts without parasite isolation or DNA extraction. These results demonstrate the feasibility of direct analysis of T. gondii lineages from samples derived either from clinical cases or asymptomatic infections. 相似文献
6.
Feces from 15 dogs at 2 different foxhound kennels in the U.K. were examined microscopically for the presence of oocysts of Neospora caninum. One sample containing approximately 400 candidate oocysts per gram was positive in a polymerase chain reaction (PCR) using N. caninum-specific primers. In a sample taken 4 mo later from the same hound. N. caninum oocysts were again detected visually and by PCR. This is the third reported case of a dog naturally excreting oocysts of N. caninum and suggests that oocyst excretion can occur over a relatively long period of time in some circumstances or that reshedding may occur. 相似文献
7.
Williams DJ Guy CS Smith RF Guy F McGarry JW McKay JS Trees AJ 《International journal for parasitology》2003,33(10):1059-1065
The parasite Neospora caninum is an important cause of abortion in cattle world-wide. Chronically infected dams transmit the parasite transplacentally and infected foetuses may be aborted or born chronically infected but clinically normal. Chronically infected cows repeatedly transmit the parasite to foetuses in several pregnancies and some may abort more than once suggesting that the immune response in these cattle is compromised during pregnancy. To investigate the nature of the immune response in chronically infected cattle, five naturally, chronically infected cows were challenged with N. caninum tachyzoites at 10 weeks of gestation. No foetopathy occurred and all five delivered live calves at full-term. In four naive pregnant cows challenged at the same time, all four foetuses died within 3-5 weeks of challenge. Of the five live calves born to the chronically infected challenged cows, three were transplacentally infected with N. caninum. The kinetics of the maternal anti-N. caninum antibody responses during gestation suggested that these transplacental infections were not the result of the superimposed challenge, but the result of the recrudescence of the maternal chronic infection-which occurred concurrently in non-challenged, chronically infected pregnant controls. These data provide the first experimental evidence that protective immunity occurs in neosporosis. They also suggest that whilst immunity to a pre-existing infection will protect against an exogenous challenge, this protective immunity will not prevent transplacental infection. This implies that a subtle form of concomitant immunity exists in chronically infected cattle and has important implications for vaccine development. 相似文献
8.
Differential kinetics of antigen-specific CD4+ and CD8+ T cell responses in the regression of retrovirus-induced sarcomas 总被引:3,自引:0,他引:3
Schepers K Toebes M Sotthewes G Vyth-Dreese FA Dellemijn TA Melief CJ Ossendorp F Schumacher TN 《Journal of immunology (Baltimore, Md. : 1950)》2002,169(6):3191-3199
Despite the accepted role for CD4+ T cells in immune control, little is known about the development of Ag-specific CD4+ T cell immunity upon primary infection. Here we use MHC class II tetramer technology to directly visualize the Ag-specific CD4+ T cell response upon infection of mice with Moloney murine sarcoma and leukemia virus complex (MoMSV). Significant numbers of Ag-specific CD4+ T cells are detected both in lymphoid organs and in retrovirus-induced lesions early during infection, and they express the 1B11-reactive activation-induced isoform of CD43 that was recently shown to define effector CD8+ T cell populations. Comparison of the kinetics of the MoMSV-specific CD4+ and CD8+ T cell responses reveals a pronounced shift toward CD8+ T cell immunity at the site of MoMSV infection during progression of the immune response. Consistent with an important early role of Ag-specific CD4+ T cell immunity during MoMSV infection, CD4+ T cells contribute to the generation of virus-specific CD8+ T cell immunity within the lymphoid organs and are required to promote an inflammatory environment within the virus-infected tissue. 相似文献
9.
Ubbink-Kok T Boekema EJ van Breemen JF Brisson A Konings WN Lolkema JS 《Journal of molecular biology》2000,296(1):311-321
The V-type Na(+)-ATPase of the thermophilic, anaerobic bacterium Caloramator fervidus was purified to homogeneity. The subunit compositions of the catalytic V(1) and membrane-embedded V(0) parts were determined and the structure of the enzyme complex was studied by electron microscopy. The V(1) headpiece consists of seven subunits present in one to three copies, and the V(0) part of two subunits in a ratio of 5:2. An analysis of over 7500 single particle images obtained by electron microscopy of the purified V(1)V(0) enzyme complex revealed that the stalk region, connecting the V(1) and V(0) parts, contains two peripheral stalks in addition to a central stalk. One of the two is connected to the V(0) part, while the other is connected to the first via a bar-like structure that is positioned just above V(0), parallel with the plane of the membrane. In projection, this bar seems to contact the central stalk. The data show that the stator structure that prevents rotation of the static part of V(0) relative to V(1) in the rotary catalysis mechanism of energy coupling in ATPases/ATPsynthases is more complex than previously thought. 相似文献
10.
Barend M deC Bronsvoort Alfons Renz Virginia Tchakouté Vincent N Tanya David Ekale Alexander J Trees 《Filaria journal》2005,4(1):1-8