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91.
Giroux MA Berteaux D Lecomte N Gauthier G Szor G Bêty J 《The Journal of animal ecology》2012,81(3):533-542
1.?Flows of nutrients and energy across ecosystem boundaries have the potential to subsidize consumer populations and modify the dynamics of food webs, but how spatio-temporal variations in autochthonous and allochthonous resources affect consumers' subsidization remains largely unexplored. 2.?We studied spatio-temporal patterns in the allochthonous subsidization of a predator living in a relatively simple ecosystem. We worked on Bylot Island (Nunavut, Canada), where arctic foxes (Vulpes lagopus L.) feed preferentially on lemmings (Lemmus trimucronatus and Dicrostonyx groenlandicus Traill), and alternatively on colonial greater snow geese (Anser caerulescens atlanticus L.). Geese migrate annually from their wintering grounds (where they feed on farmlands and marshes) to the Canadian Arctic, thus generating a strong flow of nutrients and energy across ecosystem boundaries. 3.?We examined the influence of spatial variations in availability of geese on the diet of fox cubs (2003-2005) and on fox reproductive output (1996-2005) during different phases of the lemming cycle. 4.?Using stable isotope analysis and a simple statistical routine developed to analyse the outputs of a multisource mixing model (SIAR), we showed that the contribution of geese to the diet of arctic fox cubs decreased with distance from the goose colony. 5.?The probability that a den was used for reproduction by foxes decreased with distance from the subsidized goose colony and increased with lemming abundance. When lemmings were highly abundant, the effect of distance from the colony disappeared. The goose colony thus generated a spatial patterning of reproduction probability of foxes, while the lemming cycle generated a strong temporal variation of reproduction probability of foxes. 6.?This study shows how the input of energy owing to the large-scale migration of prey affects the functional and reproductive responses of an opportunistic consumer, and how this input is spatially and temporally modulated through the foraging behaviour of the consumer. Thus, perspectives of both landscape and foraging ecology are needed to fully resolve the effects of subsidies on animal demographic processes and population dynamics. 相似文献
92.
BACKGROUND: The CD8 co-receptor is an important marker used to identify various lymphocyte subsets. A significant decrease in CD8alpha staining intensity was observed in the presence of divalent cation chelators. METHODS: Peripheral blood mononuclear cells (PBMC) obtained from healthy volunteers were treated with calcium chelators, stained with different anti-human CD8 mAbs, and analyzed by flow cytometry. RESULTS: Calcium chelators caused a dose-dependent decrease in fluorescence intensity, using specific anti-human CD8alpha mAbs. This phenomenon was not due to CD8 internalization and could be reversed by the addition of calcium ions. In contrast, calcium depletion increased staining intensity with one anti-CD8beta mAb. CONCLUSIONS: Divalent cation chelators are used as cell anti-clumping agents in MACS or FACS applications. Researchers should be aware that such treatment could lead to the almost complete loss of fluorescence with selected anti-human CD8alpha mAbs. Since CD8 staining is used in conjunction with tetramer staining to identify antigen-specific cytotoxic human T cells, the effect of calcium depletion should be taken into account in experimental design. 相似文献
93.
94.
Olivier?OutteryckEmail author Guillaume?Baille Jér?me?Hodel Marianne?Giroux Arnaud?Lacour Jér?me?Honnorat Hélène?Zéphir Patrick?Vermersch 《BMC neurology》2013,13(1):211
Background
Encephalitis with anti-N-methyl-D-aspartate receptor antibodies (anti-NMDAR-Ab) is a rapid-onset encephalitis including psychosis, seizures, various movement disorders and autonomic system disturbances.Case presentation
We report a very unusual case of extensive myelitis associated with anti-NMDAR-Ab. MRI also revealed a hyperintense T2 lesion, non-suggestive of MS, which progressively extended, associated with periventricular gadolinium enhancement visualized on brain MRI. Ophthalmological evaluation showed subclinical right optic neuritis. The absence of anti-AQP4 antibody argued against neuromyelitis optica spectrum disorder. A slight psychomotor slowing prompted us to search for various causes of autoimmune encephalitis. Anti-NMDAR-Ab was found in cerebrospinal fluid.Conclusion
In patients with extensive myelitis who are seronegative for anti-AQP4 antibodies, and after other classical causes have been excluded, the hypothesis of atypical anti-NMDAR-Ab encephalitis should also be considered.95.
96.
Kristina M. Obom Patrick J. Cummings Janelle A. Ciafardoni Yasunori Hashimura Daniel Giroux 《Journal of visualized experiments : JoVE》2014,(92)
Recent advances in mammalian, insect, and stem cell cultivation and scale-up have created tremendous opportunities for new therapeutics and personalized medicine innovations. However, translating these advances into therapeutic applications will require in vitro systems that allow for robust, flexible, and cost effective bioreactor systems. There are several bioreactor systems currently utilized in research and commercial settings; however, many of these systems are not optimal for establishing, expanding, and monitoring the growth of different cell types. The culture parameters most challenging to control in these systems include, minimizing hydrodynamic shear, preventing nutrient gradient formation, establishing uniform culture medium aeration, preventing microbial contamination, and monitoring and adjusting culture conditions in real-time. Using a pneumatic single-use bioreactor system, we demonstrate the assembly and operation of this novel bioreactor for mammalian cells grown on micro-carriers. This bioreactor system eliminates many of the challenges associated with currently available systems by minimizing hydrodynamic shear and nutrient gradient formation, and allowing for uniform culture medium aeration. Moreover, the bioreactor’s software allows for remote real-time monitoring and adjusting of the bioreactor run parameters. This bioreactor system also has tremendous potential for scale-up of adherent and suspension mammalian cells for production of a variety therapeutic proteins, monoclonal antibodies, stem cells, biosimilars, and vaccines. 相似文献
97.
Neuronal expression of human immunodeficiency virus type 1 env proteins in transgenic mice: distribution in the central nervous system and pathological alterations. 总被引:1,自引:0,他引:1
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F Berrada D Ma J Michaud G Doucet L Giroux A Kessous-Elbaz 《Journal of virology》1995,69(11):6770-6778
It is now well documented that human immunodeficiency virus type 1 (HIV-1) induces encephalopathy in patients with AIDS. In vitro studies have implicated the envelope protein (gp120) as a factor which causes neuronal death. To better evaluate the role and elucidate the mechanisms of gp120 neurotoxicity, we have developed transgenic mice carrying a segment of the HIV-1 genome that expresses the viral gp160 protein under the control of the human neurofilament light gene promoter. In two separate lines of transgenic mice, the Env protein was found to be expressed in several nuclei of the brain stem and in the anterior horns of the spinal cord. The two lines showed identical patterns of Env expression. Neuropathological evaluation revealed numerous abnormal dendritic swellings in the immunostained motor neuron structures. Large and numerous neuritic swellings were also prominent in the nucleus gracilis and in the gracilis and cuneate fascicles. In addition, reactive astrocytosis was observed in several immunoreactive areas of the central nervous system. These transgenic mice offer a unique model to further investigate the role of HIV-1 Env protein in neuronal toxicity and to help elucidate the mechanisms that are involved. 相似文献
98.
99.
Marie-Chantal Giroux Raphael Santamaria Pierre Hélie Patrick Burns Francis Beaudry Pascal Vachon 《Experimental Animals》2016,65(1):63-75
The main objective of this study was to compare the physiological changes (withdrawal and
corneal reflexes, respiratory and cardiac frequency, blood oxygen saturation, and rectal
temperature) following intraperitoneal administration of ketamine (80 mg/kg) and xylazine
(10 mg/kg) to 3-, 6-, 12- and 18-month-old male Sprague Dawley rats (n=6/age group).
Plasma pharmacokinetics, liver metabolism, and blood biochemistry were examined for a
limited number of animals to better explain anesthetic drug effects. Selected organs were
collected for histopathology. The results for the withdrawal and corneal reflexes suggest
a shorter duration and decreased depth of anesthesia with aging. Significant cardiac and
respiratory depression, as well as decreased blood oxygen saturation, occurred in all age
groups however, cardiac frequency was the most affected parameter with aging, since the
6-, 12-, and 18-month-old animals did not recuperate to normal values during recovery from
anesthesia. Pharmacokinetic parameters (T1/2 and AUC) increased and drug
clearance decreased with aging, which strongly suggests that drug exposure is associated
with the physiological results. The findings for liver S9 fractions of 18-month-old rats
compared with the other age groups suggest that following a normal ketamine anesthetic
dose (80 mg/kg), drug metabolism is impaired, leading to a significant increase of drug
exposure. In conclusion, age and related factors have a substantial effect on ketamine and
xylazine availability, which is reflected by significant changes in pharmacokinetics and
liver metabolism of these drugs, and this translates into shorter and less effective
anesthesia with increasing age. 相似文献
100.
Blais ME Brochu S Giroux M Bélanger MP Dulude G Sékaly RP Perreault C 《Journal of immunology (Baltimore, Md. : 1950)》2008,180(4):2299-2312
Age-related thymic involution severely impairs immune responsiveness. Strategies to generate T cells extrathymically are therefore being explored with intense interest. We have demonstrated that T cells produced extrathymically were functionally deficient relative to thymus-derived T cells. The main limitation of extrathymic T cells is their undue susceptibility to apoptosis; they thus do not expand properly when confronted with pathogens. Using oncostatin M-transgenic mice, we found that in the absence of lymphopenia, T cells of extrathymic origin constitutively undergo excessive homeostatic proliferation that leads to overproduction of IL-2 and IFN-gamma. IFN-gamma up-regulates Fas and FasL on extrathymic CD8 T cells, thereby leading to their demise by Fas-mediated apoptosis. Moreover, IFN-gamma and probably IL-2 curtail survival of extrathymic CD4 T cells by down-regulating IL-7Ralpha and Bcl-2, and they support a dramatic accumulation of FoxP3(+) T regulatory cells. Additionally, we show that wild-type thymus-derived T cells undergoing homeostatic proliferation in a lymphopenic host shared key features of extrathymic T cells. Our work explains how excessive lymphopenia-independent homeostatic proliferation renders extrathymic T cells functionally defective. Based on previous work and data presented herein, we propose that extrathymic T cells undergo constitutive homeostatic proliferation because they are positively selected by lymph node hemopoietic cells rather than by thymic epithelial cells. 相似文献