Seasonal variations in a population of the monogenean Ancyrocephalus mogurndae Gussev, 1955 were investigated on gills of cage-cultured mandarin fish, Siniperca chuatsi (Basilewsky), during the period from April 1994 to April 1995. The abundance of A. mogurndae peaked in late spring and summer. Prevalence was high (75-100 %) throughout the study period, and did not vary significantly between months. More than 50 % of all monogeneans were found on the first and second gill arches, except one occasion when the fourth gill arch had the majority in April 1995. The niche breadths were significantly correlated with the population abundance. A coexistent parasitic myxosporean, Henneguya weishanensis Hu, 1965, on the gills of the fish was found to have little influence on the gill-arch preference of the monogenean, although the monogenean abundance was higher in those fish infected with the myxosporean.
In herbivorous insects, differences in the degree of specialization to host plants emerge when the distribution of an herbivore differs from that of its host plants, which results in a mosaic of populations differing in performance on the different host plants. Using a specialized butterfly, Battus polydamas archidamas Boisduval, 1936, which feeds exclusively on the genus Aristolochia, we test whether host plant co-occurrence and associated differences in host quality modify local adaptation in terms of larval preference and performance. We compared individuals from a monospecific host stand of Aristolochia chilensis with those from a mixed host stand of A. chilensis and A. bridgesii. Individuals were reared in a reciprocal transfer experiment in which source population and the host species fed to larvae were fully crossed in a two-by-two factorial experiment in order to quantify their preference, performance (development time, size and growth rate) and survival. Individuals from both populations preferred the species they ate during their larval development over the other host, which indicates host plant-induced preference with non-adaptive implications. Larvae from mixed and monospecific stands grew faster and survived better when reared on A. bridgesii than A. chilensis. Larvae from a monospecific host stand grew slower and fewer individuals survived under the same local conditions, which is contrary to expectations. Therefore, rearing the butterfly on A. bridgesii consistently resulted in better performance, which indicates that the monospecific population is less well adapted to its host than the mixed population. Variation in the occurrence of the two host plants in the two populations can result in divergent selection due to the variation in plant quality, which in this case could result in opposing adaptive processes., Rodrigo S. Rios, Cristian Salgado-Luarte, Gisela C. Stotz, Ernesto Gianoli., and Obsahuje bibliografii
For a finitely generated group, we study the relations between its rank, the maximal rank of its free quotient, called co-rank (inner rank, cut number), and the maximal rank of its free abelian quotient, called the Betti number. We show that any combination of the group’s rank, co-rank, and Betti number within obvious constraints is realized for some finitely presented group (for Betti number equal to rank, the group can be chosen torsion-free). In addition, we show that the Betti number is additive with respect to the free product and the direct product of groups. Our results are important for the theory of foliations and for manifold topology, where the corresponding notions are related with the cut-number (or genus) and the isotropy index of the manifold, as well as with the operations of connected sum and direct product of manifolds., Irina Gelbukh., and Obsahuje seznam literatury
The nullity of a graph G is the multiplicity of zero as an eigenvalue in the spectrum of its adjacency matrix. From the interlacing theorem, derived from Cauchy’s inequalities for matrices, a vertex of a graph can be a core vertex if, on deleting the vertex, the nullity decreases, or a Fiedler vertex, otherwise. We adopt a graph theoretical approach to determine conditions required for the identification of a pair of prescribed types of root vertices of two graphs to form a cut-vertex of unique type in the coalescence. Moreover, the nullity of subgraphs obtained by perturbations of the coalescence G is determined relative to the nullity of G. This has direct applications in spectral graph theory as well as in the construction of certain ipso-connected nano-molecular insulators., Didar A. Ali, John Baptist Gauci, Irene Sciriha, Khidir R. Sharaf., and Obsahuje seznam literatury
Faecal examination of the long nosed vine snake Ahaetulla nasuta Lacépède, 1789 revealed two species of caryosporan coccidia. The morphology of one species fits well with a description of Caryospora ahaetullae Modrý et Koudela, 1994, the second is a previously undescribed species. Oocysts of Caryospora veselyi sp. n. were spherical, 18.9 (16.5-21.5) pm in diameter, with pitted and brownish oocyst wall about 1.5 pm thick. An irregular polar granule about 2,0 x 1.0 pm was observed in 35% of the oocysts examined. Sporocysts were octozoic, ovoidal to ellipsoidal, 13.7 (13.0-15.5) x 10.3 (9.0-11.0) pm with a shape index 1.3 (1.2-1.4). Stieda and substieda bodies were present. Sporocyst residuum was present as small granules of irregular size scattered among sporozoiles. Both species sporulated within 72 hours. The infected snake did not show clinical signs of disease.
The processing of species-specific communication signals in the auditory system represents an important aspect of animal behavior and is crucial for its social interactions, reproduction, and survival. In this article the neuronal mechanisms underlying the processing of communication signals in the higher centers of the auditory system - inferior colliculus (IC), medial geniculate body (MGB) and auditory cortex (AC) - are reviewed, with particular attention to the guinea pig. The selectivity of neuronal responses for individual calls in these auditory centers in the guinea pig is usually low - most neurons respond to calls as well as to artificial sounds; the coding of complex sounds in the central auditory nuclei is apparently based on the representation of temporal and spectral features of acoustical stimuli in neural networks. Neuronal response patterns in the IC reliably match the sound envelope for calls characterized by one or more short impulses, but do not exactly fit the envelope for long calls. Also, the main spectral peaks are represented by neuronal firing rates in the IC. In comparison to the IC, response patterns in the MGB and AC demonstrate a less precise representation of the sound envelope, especially in the case of longer calls. The spectral representation is worse in the case of low-frequency calls, but not in the case of broad-band ca lls. The emotional content of the call may influence neuronal responses in the auditory pathway, which can be demonstrated by stimulation with time-reversed calls or by measurements performed under different levels of anesthesia. The investigation of the principles of the neural coding of species-specific vocalizations offers some keys for understanding the neural mechanisms underlying human speech perception., D. Šuta, J. Popelář, J. Syka., and Obsahuje bibliografii a bibliografické odkazy
Let $(R,\mathfrak m)$ be a commutative Noetherian regular local ring of dimension $d$ and $I$ be a proper ideal of $R$ such that ${\rm mAss}_R(R/I)={\rm Assh}_R(I)$. It is shown that the $R$-module $H^{{\rm ht}(I)}_I(R)$ is $I$-cofinite if and only if
${\rm cd}(I,R)={\rm ht}(I)$. Also we present a sufficient condition under which this condition the $R$-module $H^i_I(R)$ is finitely generated if and only if it vanishes., Jafar A'zami, Naser Pourreza., and Obsahuje bibliografické odkazy
We recently reported that in vitro Cognac polyphenolic compounds (CPC) induce NO-dependent vasorelaxant effects and stimulate cardiac function. In the present study, we aim to investigate the effect of CPC on both nitric oxide (NO) and superoxide anions (O2-) production in cultured human endothelial cells. In addition, its effect on the bradykinin (BK)-induced NO production was also tested. The role and sources of O2- in the concomitant effect of BK plus CPC were pharmacologically determined. NO and O2- signals were measured using electron paramagnetic resonance technique using specific spin trappings. Both, CPC and BK induced an in crease in NO production in human endothelial cells. The combination of both further enhanced NO release. The capacity of CPC plus BK to increase NO signal was blunted by the NO synthase inhibitor, NG-nitro-L-arginine methyl ester, and was enhanced in the presence either of superoxide dismutase or catalase. Moreover, CPC plus BK response was greater after inhibition of either NADPH oxidase by apocynin or xanthine oxidase by allopurinol but it was not affected by rotenone. CPC did not affect O2- level either alone or after its increase upon lipopolysaccharide treatment. Finally, the capacity of BK alone to increase NO was enhanced either by apocynin or allopurinol. Altogether, these data demonstrate that CPC is able to directly increase NO production without affecting O2- and enhances the BK-induced NO production in human endothelial cells. The data highlight the ability of BK to stimulate not only NADPH oxidase- but also xanthine oxidase-inhibitor sensitive mechanisms that reduce its efficiency in increasing NO either alone or in the presence of CPC. These results bring pharmacological evidence for vascular protection by CPC via its potentiating effect of BK response in terms of endothelial NO release., A. Sall Diallo, M. Sarr, H. A. Mostefai, N. Carusio, M. Pricci, R. Andriantsitohaina., and Obsahuje bibliografii a bibliografické odkazy
Spatiotemporal dynamics of event-related potentials (ERP) evoked by non-target stimuli in a visual oddball experiment and the presence of coherent oscillations in beta 2 frequency band of decomposed EEG records from peristimulus period were investigated by means of intracranial electrodes in humans. Twenty-one patients with medically intractable epilepsy participated in the study. The EEG signal was recorded using platinum electrodes implanted in several cortical and subcortical sites. Averaged 2 s EEG records were analyzed. Task-specific EEG changes were found in each patient, ERPs were derived from 92 electrodes used (96 % of possible cases). In the majority of analysed cases, ERPs were composed of several distinct components, and their duration was mostly longer than 1 s. The mean onset of the first ERP component was 158±132 ms after the stimulus (median 112 ms, minimum value 42 ms, maximum value 755 ms), and large variability of these onset times was found in all the investigated structures. Possible coherence between neural activities of remote brain sites was investigated by calculating running correlations between pairs of decomposed EEG records (alpha, beta 1, beta 2 frequency bands were used, total number of correlated pairs was 662 in each frequency band). The record pairs exhibiting highly correlated time segments represented 23 % of all the investigated pairs in alpha band, 7 % in beta 1 band, and 59 % in beta 2 band. In investigated 2 s record windows, such segments were distributed evenly, i.e. they were also found before the stimulus onset. In conclusion, the results have implicated the idea that a lot of recorded ERPs was more or less by-products of chance in spreading a signal within the neuronal network, and that their functional relevance was somewhat linked with the phenomenon of activity synchronization., M. Kukleta ... [et al.]., and Obsahuje seznam literatury
Celestial pole offsets are the displacements between the observed position of the Earth’s spin axis in space and its position predicted by the adopted models of precession and nutation. At present, the models are IAU2006 and IAU 2000, respectively. The celestial pole offsets are regularly measured by Very Long-Baseline Interferometry (VLBI), the observations being coordinated and published by the International VLBI Service for Geodesy and Astrometry (IVS). These offsets contain a mixture of several effects: the unpredictable free term, Free Core Nutation (FCN) that is due to the presence of the outer fluid core of the Earth, forced motions excited by the motions in the atmosphere and oceans, and also imperfections of the adopted precession-nutation models. The geophysical excitations are also available, as determined by several atmospheric and oceanographic services. The aim of this paper is to compare the time series of these integrated excitations with the observed celestial pole offsets and estimate the level of coherence between them., Cyril Ron and Jan Vondrák., and Obsahuje bibliografii