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排序方式: 共有88条查询结果,搜索用时 62 毫秒
71.
Rocha I Gonçalves V Bettencourt MJ Silva-Carvalho L 《Physiological research / Academia Scientiarum Bohemoslovaca》2008,57(5):701-707
Activation of sublobule IX-b of the cerebellar vermis evokes hypotension, bradycardia and decrease of the phrenic nerve activity in the anesthetized animal. Cardiac performance during the isovolumic phases of systole and relaxation can be evaluated by dP/dtmax, Vpm, dP/dt/DP40 and tau, respectively. In the present study, we evaluated the changes on cardiac function evoked by the stimulation of sublobule IX-b. New Zealand white rabbits were anesthetized, paralyzed and artificially ventilated. A posterior craniotomy was made to reveal and stimulate the cerebellar uvula (4 s train; 50 Hz; 1 ms; 20 microA). The femoral artery and veins were cannulated and a Swan-Ganz catheter was advanced in the upper abdominal aorta to control afterload when inflating the balloon. The left ventricle was catheterized with a Millar catheter. Blood pressure, heart rate, left ventricular pressure were monitored. Results showed a significant decrease on sublobule IX-b stimulation of all the indices of systolic function and an increase of tau indicating a decrease in the speed of the relaxation. These data provide the first evidence of the influence of sublobule IX-b on cardiac function. They may contribute to the understanding of the origin the cardiovascular changes that were observed in two patients with vermian and paravermian hemorrhage. 相似文献
72.
Background
The heat shock protein Hsp70 promotes inducible thermotolerance in nearly every organism examined to date. Hsp70 interacts with a network of other stress-response proteins, and dissecting the relative roles of these interactions in causing thermotolerance remains difficult. Here we examine the effect of Hsp70 gene copy number modification on thermotolerance and the expression of multiple stress-response genes in Drosophila melanogaster, to determine which genes may represent mechanisms of stress tolerance independent of Hsp70. 相似文献73.
Real time bayesian estimation of the epidemic potential of emerging infectious diseases 总被引:1,自引:0,他引:1
Background
Fast changes in human demographics worldwide, coupled with increased mobility, and modified land uses make the threat of emerging infectious diseases increasingly important. Currently there is worldwide alert for H5N1 avian influenza becoming as transmissible in humans as seasonal influenza, and potentially causing a pandemic of unprecedented proportions. Here we show how epidemiological surveillance data for emerging infectious diseases can be interpreted in real time to assess changes in transmissibility with quantified uncertainty, and to perform running time predictions of new cases and guide logistics allocations.Methodology/Principal Findings
We develop an extension of standard epidemiological models, appropriate for emerging infectious diseases, that describes the probabilistic progression of case numbers due to the concurrent effects of (incipient) human transmission and multiple introductions from a reservoir. The model is cast in terms of surveillance observables and immediately suggests a simple graphical estimation procedure for the effective reproductive number R (mean number of cases generated by an infectious individual) of standard epidemics. For emerging infectious diseases, which typically show large relative case number fluctuations over time, we develop a Bayesian scheme for real time estimation of the probability distribution of the effective reproduction number and show how to use such inferences to formulate significance tests on future epidemiological observations.Conclusions/Significance
Violations of these significance tests define statistical anomalies that may signal changes in the epidemiology of emerging diseases and should trigger further field investigation. We apply the methodology to case data from World Health Organization reports to place bounds on the current transmissibility of H5N1 influenza in humans and establish a statistical basis for monitoring its evolution in real time. 相似文献74.
Chowell G Bettencourt LM Johnson N Alonso WJ Viboud C 《Proceedings. Biological sciences / The Royal Society》2008,275(1634):501-509
Spatial variations in disease patterns of the 1918-1919 influenza pandemic remain poorly studied. We explored the association between influenza death rates, transmissibility and several geographical and demographic indicators for the autumn and winter waves of the 1918-1919 pandemic in cities, towns and rural areas of England and Wales. Average measures of transmissibility, estimated by the reproduction number, ranged between 1.3 and 1.9, depending on model assumptions and pandemic wave and showed little spatial variation. Death rates varied markedly with urbanization, with 30-40% higher rates in cities and towns compared with rural areas. In addition, death rates varied with population size across rural settings, where low population areas fared worse. By contrast, we found no association between transmissibility, death rates and indicators of population density and residential crowding. Further studies of the geographical mortality patterns associated with the 1918-1919 influenza pandemic may be useful for pandemic planning. 相似文献
75.
Santos C Montiel R Sierra B Bettencourt C Fernandez E Alvarez L Lima M Abade A Aluja MP 《Molecular biology and evolution》2005,22(6):1490-1505
We analyzed the control region of the mitochondrial DNA (mtDNA)from maternally related individuals originating from the AzoresIslands (Portugal) in order to estimate the mutation rate ofmtDNA and to gain insights into the process by which a new mutationarises and segregates into heteroplasmy. Length and/or pointheteroplasmies were found at least in one individual of 72%of the studied families. Eleven new point substitutions werefound, all of them in heteroplasmy, from which five appear tobe somatic mutations and six can be considered germinal, evidencingthe high frequency of somatic mutations in mtDNA in healthyyoung individuals. Different values of the mutation rate accordingto different assumptions were estimated. When considering allthe germinal mutations, the value of the mutation rate obtainedis one of the highest reported so far in family studies. However,when corrected for gender (assuming that the mutations presentin men have the same evolutionary weight of somatic mutationsbecause they will inevitably be lost) and for the probabilityof intraindividual fixation, the value for the mutation rateobtained for HVRI and HVRII (0.2415 mutations/site/Myr) wasin the upper end of the values provided by phylogenetic estimations.These results indicate that the discrepancy, that has been reportedpreviously, between the human mtDNA mutation rates observedalong evolutionary timescales and the estimations obtained usingfamily pedigrees can be minimized when corrections for genderproportions in newborn individuals and for the probability ofintraindividual fixation are introduced. The analyses performedsupport the hypothesis that (1) in a constant, tight bottleneckgenetic drift alone can explain different patterns of heteroplasmysegregation and (2) in neutral conditions, the destiny of anew mutation is strictly related to the initial proportion ofthe new variant. Another important point arising from the dataobtained is that, even in the absence of a paternal contributionof mtDNA, recombination may occur between mtDNA molecules presentin an individual, which is only observable if it occurs betweenmtDNA types that differ at two or more positions. 相似文献
76.
Bettencourt BR Kim I Hoffmann AA Feder ME 《Evolution; international journal of organic evolution》2002,56(9):1796-1801
Abstract.— To determine whether and how laboratory and natural selection act on the hsp70 (70-Kd heat-shock protein) genes of Drosophila melanogaster , we examined hsp70 allele frequencies in two sets of populations. First, five populations reared at different temperatures for more than 20 years differentially fixed both a large insertion/deletion (indel) polymorphism at the 87A7 hsp70 cluster ("56H8"/"122") and a single nucleotide polymorphism at the 87C1 hsp70 cluster. In both cases, the 18°C and 25°C populations fixed one allele and the 28°C populations the other, consistent with previously described evolved differences among these populations in Hsp70 expression and thermo-tolerance. Second, we examined 56H8 and 122 frequencies in a set of 11 populations founded from flies collected along a latitudinal transect of eastern Australia. The 56H8 allele frequencies are positively associated with latitude, consistent with maintenance of the 56H8/122 polymorphism by natural selection. Thermal extremes and average values are negatively correlated with latitude. These results suggest that natural selection imposed by temperature and thermal variability may affect hsp70 allele frequencies. 相似文献
77.
Plant communities and their possible exploitation during Late Prehistory are studied based on charcoal data from four archaeological sites. Settlement location in the area appears to have been chosen on the basis of easy access to rivers and good arable land. Quercus (deciduous) and Fabaceae appear to have been the main source of wood; this is in agreement with previous data from north-western Portugal. The abundance of Fabaceae, which thrive in open well-lit areas, is seen as a direct consequence of woodland clearance. The co-occurrence of Quercus (deciduous) and Fabaceae appears as a distinctive feature in north-western Portugal during Late Prehistory and Protohistory. Fabaceae have remained a familiar component of the vegetation cover ever since. Pinus pinaster is present as isolated individuals, in contrast to its present-day abundance. 相似文献
78.
The effects of inhibition of PGF2α synthesis on luteolysis in mares and on the incidence of prolonged luteal activity were studied in controls and in a group treated with flunixin meglumine (FM), a PGF2α inhibitor (n = 6/group). The FM was given every 8 hours (1.0 mg/kg) on each of Days 14.0 to 16.7. Concentration (pg/mL) of PGF2α metabolite averaged over 8 hours of hourly blood sampling at the beginning of each day, was lower in the FM group than in the controls on Day 14 after ovulation (6.7 ± 1.3 vs. 13.8 ± 2.9, P < 0.05), Day 15 (15.0 ± 3.9 vs. 35.2 ± 10.4, P < 0.10), and Day 16 (21.9 ± 5.7 vs. 54.7 ± 11.4, P < 0.03). Concentration (ng/mL) of progesterone (P4) was greater in the FM group than in the controls on Day 14 (10.1 ± 0.9 vs. 7.7 ± 0.9, P < 0.08), Day 15 (9.2 ± 1.0 vs. 4.3 ± 1.0, P < 0.008), and Day 16 (5.6 ± 1.6 vs. 1.2 ± 0.4, P < 0.02). The interval from ovulation to the beginning of a decrease in P4 and to the end of luteolysis (P4 < 1 ng/mL) was each delayed (P < 0.03) by ∼1 day in the FM group. Intervals involving the luteal phase were long (statistical outliers, P < 0.05) in two mares in the FM group, indicating prolonged luteal activity. Results supported the hypotheses that (1) inhibition of PGF2α synthesis interferes with luteolysis in mares and (2) inhibition of PGF2α at the expected time of luteolysis may lead to prolonged luteal activity. 相似文献
79.
Sabrina Dusi Lorella Valletta Tobias B. Haack Yugo Tsuchiya Paola Venco Sebastiano Pasqualato Paola Goffrini Marco Tigano Nikita Demchenko Thomas Wieland Thomas Schwarzmayr Tim M. Strom Federica Invernizzi Barbara Garavaglia Allison Gregory Lynn Sanford Jeffrey Hamada Conceição Bettencourt Henry Houlden Luisa Chiapparini Giovanna Zorzi Manju A. Kurian Nardo Nardocci Holger Prokisch Susan Hayflick Ivan Gout Valeria Tiranti 《American journal of human genetics》2014
80.
Susana Ferreira Anabela Marinho Marta Patacho Elisabete Santa-Clara Cristina Carrondo João Winck Paulo Bettencourt 《BMC pulmonary medicine》2010,10(1):1-8