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1.
Dario L. Ringach 《Biological cybernetics》1995,73(6):561-568
A new model of smooth pursuit eye movements is presented. We begin
by formally analyzing the stability of the proportional-derivative
(PD) model of smooth pursuit eye movements using Pontryagin's
theory. The PD model is the linearized version of the nonlinear
Krauzlis-Lisberger (KL) model. We show that the PD model fails to
account for the experimentally observed dependence of the eye
velocity damping ratio and the oscillation period on the total delay
in the feedback loop. To explain the data, a new `tachometer'
feedback model, based on an efference copy signal of eye
acceleration, is proposed and analyzed by computer simulation. The
model predicts some salient features of monkey pursuit data and
suggests a functional role for the extraretinal input to the medial
superior temporal area (MST).
Received:
9 February 1995 / Accepted in revised form: 13 June
1995 相似文献
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Dario Cova Leonardo DE Angelis Elena Monti Francesco Piccinini 《Free radical research》1992,15(6):353-360
Previous investigations, performed on isolated rat atria, showed that the lipophylic spin-trapping agent N-tert-butyl-alpha-phenylnitrone (PBN) is able to prevent the acute cardiotoxic effects produced by doxorubicin (DXR), whereas the hydrophylic compound 5,5-dimethyl-pyrroline-N-oxide (DMPO) is inactive. The present study was designed to ascertain whether differences in the pharmacological effects of the two spin traps are related to their different subcellular distribution. Langendorff rat hearts were perfused for 60 minutes with [I4C]-DXR and either PBN or DMPO. The subcellular mapping of the three compounds was performed by measuring DXR by liquid scintillation counting, PBN by GC/MS, and DMPO by HPLC in the following isolated fractions: nuclei, mitochondria, sarcoplasmic reticulum, sarcolemma, cytosol. DMPO was shown to accumulate in the cytosolic compartment; both PBM and DXR are taken up by nuclei and mitochondria, while only trace amounts of DXR were detected in the sarcoplasmic reticulum. These results suggest that mitochondrial (and not sarcoplasmic) enzymes are mainly involved in DXR-induced free radical production, which is thought to cause the acute cardiotoxic effects of DXR. An involvement of DXR-induced free radical generation in the nuclear compartment seems unlikely in the short-term “in vitro” effects observed with the experimental model adopted for these studies, although it may play a role in the delayed pathology. 相似文献
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Evolutionary algorithms are widespread heuristic methods inspired by natural evolution to solve difficult problems for which analytical approaches are not suitable. In many domains experimenters are not only interested in discovering optimal solutions, but also in finding the largest number of different solutions satisfying minimal requirements. However, the formulation of an effective performance measure describing these requirements, also known as fitness function, represents a major challenge. The difficulty of combining and weighting multiple problem objectives and constraints of possibly varying nature and scale into a single fitness function often leads to unsatisfactory solutions. Furthermore, selective reproduction of the fittest solutions, which is inspired by competition-based selection in nature, leads to loss of diversity within the evolving population and premature convergence of the algorithm, hindering the discovery of many different solutions.Here we present an alternative abstraction of artificial evolution, which does not require the formulation of a composite fitness function. Inspired from viability theory in dynamical systems, natural evolution and ethology, the proposed method puts emphasis on the elimination of individuals that do not meet a set of changing criteria, which are defined on the problem objectives and constraints.Experimental results show that the proposed method maintains higher diversity in the evolving population and generates more unique solutions when compared to classical competition-based evolutionary algorithms. Our findings suggest that incorporating viability principles into evolutionary algorithms can significantly improve the applicability and effectiveness of evolutionary methods to numerous complex problems of science and engineering, ranging from protein structure prediction to aircraft wing design. 相似文献
6.
Riccardo Danielli Roberto Patuzzo Anna Maria Di Giacomo Gianfranco Gallino Andrea Maurichi Annabella Di Florio Ornella Cutaia Andrea Lazzeri Carolina Fazio Clelia Miracco Leonardo Giovannoni Giuliano Elia Dario Neri Michele Maio Mario Santinami 《Cancer immunology, immunotherapy : CII》2015,64(8):999-1009
7.
Luca Luiselli Thomas Madsen Dario Capizzi Lorenzo Rugiero Nic Pacini Massimo Capula 《Ecological Research》2011,26(4):745-753
A review of several long-term studies has recently suggested that snakes might be declining in large parts of the world. Additional
data from other long-term studies are therefore urgently needed in order to assess the generalities of such suggested declines.
Based on a 20-year study, we analyzed demographic data on adult dice snakes (Natrix tessellata) studied in central Italy between 1985 and 2004. Both male and female dice snakes were relatively long-lived, with no significant
differences in longevity between the sexes. Individual males and females were observed over a maximum of 10 and 14 years,
respectively. However, the among-year recapture rates between the year the snakes were initially captured and the subsequent
year (i.e., year 1 to year 2) was significantly lower (45%) than the among-year recapture rates during subsequent years (74%;
i.e., year 2 to year 3), suggesting that a large proportion of the snakes at first capture were in fact not resident within
our study area, and hence many snakes were migrating in and out of our 2-km stream study site, with no inter-sexual difference
in dispersal rates. Sex ratio was virtually equal if we consider the study period as a whole. Significant annual fluctuations
were, however, observed through the study. In 1985–1990, 1993–1995, 1998 and 1999 the sex ratio was male-biased, whereas in
2000–2004 female-biased. In terms of both survival and recapture probabilities, model selection showed that Akaike’s information
criterion favored the model incorporating body size, with the model incorporating year having an intermediate likelihood,
and the model with sex included being the most disfavored. Total population number estimates suggest an average 86 adult individuals
along the 2 km of stream with only minor annual variations. However, a significant decrease in the number of males occurred
during the last 6 years of our study. Thus, further monitoring of this population is warranted in light of the decline of
snake populations reported recently. 相似文献
8.
G Scannapieco P Pauletto A Semplicini C Dario G Vescovo A Mazzucato A Angelini A C Pessina 《Bollettino della Società italiana di biologia sperimentale》1983,59(9):1265-1271
Male Broad Breasted White Turkeys (BBWT) represent an experimental model of arterial hypertension characterized by high levels of circulating and tissue catecholamines. We thought interesting to evaluate the efficacy of the long term treatment with different antihypertensive drugs. 59 male BBWT were studied, divided in five groups. The first group (13 animals) was treated with placebo; the second (14 animals) with oxprenolol 4 mg/Kg/q.d.; the third (10 animals) with labetalol 25 mg/Kg/q.d.; the fourth (11 animals) with verapamil 15 mg/Kg/ q.d.; the fifth (11 animals) with captopril 8 mg/Kg/ q.d. and furosemide 2,5 mg/Kg/q.d. All drugs were given p.o, from the 8th to the 33rd week of age. Weekly or every two weeks Blood Pressure (BP) and Heart Rate (HR) were measured by an indirect method. In all animals BP progressively increased and HR progressively decreased with age. Only the labetalol-treated animals showed a significant reduction of BP and HR through the study period as compared with the placebo-treated animals. These results confirm the preminent role played by the high levels of circulating catecholamines in determining and maintaining the arterial hypertension. 相似文献
9.
Anil K. Ghosh Martin Devenport Deepa Jethwaney Dario E. Kalume Akhilesh Pandey Vernon E. Anderson Ali A. Sultan Nirbhay Kumar Marcelo Jacobs-Lorena 《PLoS pathogens》2009,5(1)
SM1 is a twelve-amino-acid peptide that binds tightly to the Anopheles salivary gland and inhibits its invasion by Plasmodium sporozoites. By use of UV-crosslinking experiments between the peptide and its salivary gland target protein, we have identified the Anopheles salivary protein, saglin, as the receptor for SM1. Furthermore, by use of an anti-SM1 antibody, we have determined that the peptide is a mimotope of the Plasmodium sporozoite Thrombospondin Related Anonymous Protein (TRAP). TRAP binds to saglin with high specificity. Point mutations in TRAP''s binding domain A abrogate binding, and binding is competed for by the SM1 peptide. Importantly, in vivo down-regulation of saglin expression results in strong inhibition of salivary gland invasion. Together, the results suggest that saglin/TRAP interaction is crucial for salivary gland invasion by Plasmodium sporozoites. 相似文献
10.