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At least 649 records · Page 36Linked to original sources
PubMed2006

A spatial genetic structure and effects of relatedness on mate choice in a wild bird population.

Inbreeding depression, as commonly found in natural populations, should favour the evolution of inbreeding avoidance mechanisms. If natal dispersal, the first and probably most effective mechanism, does not lead to a complete separation of males and females from a common origin, a small-scale genetic population structure may result and other mechanisms to avoid inbreeding may exist. We studied the genetic population structure and individual mating patterns in blue tits (Parus caeruleus). The population showed a local genetic structure in two out of four years: genetic relatedness between individuals (estimated from microsatellite markers) decreased with distance. This pattern was mainly caused by immigrants to the study area; these, if paired with fellow immigrants, were more related than expected by chance. Since blue tits did not avoid inbreeding with their social partner, we examined if individuals preferred less related partners at later stages of the mate choice process. We found no evidence that females or males avoided inbreeding through extra-pair copulations or through mate desertion and postbreeding dispersal. Although the small-scale genetic population structure suggests that blue tits could use a simple rule of thumb to select less related mates, females did not generally prefer more distantly breeding extra-pair partners. However, the proportion of young fathered by an extra-pair male in mixed paternity broods depended on the genetic relatedness with the female. This suggests that there is a fertilization bias towards less related copulation partners and that blue tits are able to reduce the costs of inbreeding through a postcopulatory process.

Animals↗
PubMed2004

ISSR and AFLP analysis of the temporal and spatial population structure of the post-fire annual, Nicotiana attenuata, in SW Utah.

BACKGROUND: The native annual tobacco, Nicotiana attenuata, is found primarily in large ephemeral populations (typically for less than 3 growing seasons) after fires in sagebrush and pinyon-juniper ecosystems and in small persistent populations (for many growing seasons) in isolated washes typically along roadsides throughout the Great Basin Desert of the SW USA. This distribution pattern is due to its unusual germination behavior. Ephemeral populations are produced by the germination of dormant seeds from long-lived seed banks which are stimulated to germinate by a combination of unidentified positive cues found in wood smoke and the removal of inhibitors leached from the unburned litter of the dominant vegetation. Persistent populations may result where these inhibitors do not exist, as in washes or along disturbed roadsides. To determine if this germination behavior has influenced population structure, we conducted an AFLP (244 individuals), ISSR (175 individuals) and ISSR+ AFLP (175 individuals) analysis on plants originating from seed collected from populations growing in 11 wash and burns over 11 years from the SW USA. RESULTS: Genetic variance as measured by both ISSR and AFLP markers was low among sites and comparatively higher within populations. Cluster analysis of the Utah samples with samples collected from Arizona, California, and Oregon as out-groups also did not reveal patterns. AMOVA analysis of the combined AFLP and ISSR data sets yielded significantly low genetic differentiation among sites (Phict), moderate among populations within sites (Phisc) and higher genetic differentiation within populations (Phist). CONCLUSIONS: We conclude that the seed dormancy of this post-fire annual and its resulting age structure in conjunction with natural selection processes are responsible for significantly low among sites and comparatively high within-population genetic variation observed in this species.

Analysis of Variance↗
PubMed2004

Bodily systems and the spatial-functional structure of the human body.

The human body is a system made of systems. The body is divided into bodily systems proper, such as the endocrine and circulatory systems, which are subdivided into many sub-systems at a variety of levels, whereby all systems and subsystems engage in massive causal interaction with each other and with their surrounding environments. Here we offer an explicit definition of bodily system and provide a framework for understanding their causal interactions. Medical sciences provide at best informal accounts of basic notions such as system, process, and function, and while such informality is acceptable in documentation created for human beings, it falls short of what is needed for computer representations. In our analysis we will accordingly provide the framework for a formal definition of bodily system and of associated notions.

Anatomy↗
PubMed2005

[Three-dimensional atlas of subthalamic nucleus and its adjacent structures].

The deep brain stimulation (DBS) is an effective treatment modality of the functional neurosurgery for disorders such as Parkinson's disease, essential tremor and generalized dystonia. Recently, the targets of DBS for treatment of Parkinson's disease are the thalamus, the Globus pallidus and subthalamic nucleus (STN). The STN-DBS induces improvements in axial motor fluctuation and the on-off phenomenon. The important problem for STN-DBS is that DBS is inserted properly into the STN for good results. The STN is a small body in the deep brain structures. We cannot understand the STN clearly because of its small size and complex shape. The topographical information of deep brain structures has been essential for accurate stereotactic placement of the stimulating electrode of DBS. The target of a deep brain structure is based on the Schaltenbrand and Wahren atlas (S-W atlas). The S-W atlas consists of two-dimensional images such as a coronal section. For this reason, it is difficult to understand localization and the shape of deep brain structures spatially, especially of the subthalamic nucleus on S-W atlas. The three-dimensional image is a useful tool for diagnosis and preoperative planning, because it can easily give neurosurgeons the vivid spatial image of complex structures. We studied a practical use of a three-dimensional atlas of deep brain structures in functional neurosurgery. We devised a three-dimensional atlas to see an image at a free angle on a personal computer. It provided us with more useful information about structures than ones by two-dimentional images. Three-dimensional atlas also helped us make a decision for placement of the deep brain electrode and appropriate electrophysiological recording.

Brain Mapping↗
PubMed1988

[The spatial-temporal structure of fluctuations in tick-borne encephalitis morbidity in the Maritime Territory].

The annual dynamics of the epidemic process in tick-borne encephalitis and its spread in the Maritime Territory, endemic for this infection, have been studied. The study has shown that in the central mountainous regions grown with boreal forest, in contrast to the rest of this focal area, a higher morbidity level and more severe outcomes of this infection are observed. This indicates that in those regions more ancient nuclei of the endemic area of this infection with the main stable elements of the natural focus are preserved.

Disease Outbreaks↗
PubMed1996

The structure of spatial receptive fields of neurons in primary auditory cortex of the cat.

Transient broad-band stimuli that mimic in their spectrum and time waveform sounds arriving from a speaker in free space were delivered to the tympanic membranes of barbiturized cats via sealed and calibrated earphones. The full array of such signals constitutes a virtual acoustic space (VAS). The extra-cellular response to a single stimulus at each VAS direction, consisting of one or a few precisely time-locked spikes, was recorded from neurons in primary auditory cortex. Effective sound directions form a virtual space receptive field (VSRF). Near threshold, most VSRFs were confined to one quadrant of acoustic space and were located on or near the acoustic axis. Generally, VSRFs expanded monotonically with increases in stimulus intensity, with some occupying essentially all of the acoustic space. The VSRF was not homogeneous with respect to spike timing or firing strength. Typically, onset latency varied by as much as 4-5 msec across the VSRF. A substantial proportion of recorded cells exhibited a gradient of first-spike latency within the VSRF. Shortest latencies occupied a core of the VSRF, on or near the acoustic axis, with longer latency being represented progressively at directions more distant from the core. Remaining cells had VSRFs that exhibited no such gradient. The distribution of firing probability was mapped in those experiments in which multiple trials were carried out at each direction. For some cells there was a positive correlation between latency and firing probability.

Acoustic Stimulation↗
PubMed1977

[Spatial-temporal structure of the primary evoked activity of visual cortex neurons].

The unit activity displayed a mosiac position of the activated neuronal ensembles with asymmetrically inhibited adjacent areas development of primary response. The average distance between the centers of these ensembles, the latter's diameter being less than 240 mcm, was not more than 300 mcm. The centers displayed the most intensive activity of the neurons ranged in a column, with the shortest latency, the greatest synchronization, and the diffuse peripheral area which might be asymmetrical in respect to the center.

Animals↗
PubMed2000

Spatial and temporal structure of receptive fields in primate somatosensory area 3b: effects of stimulus scanning direction and orientation.

This is the third in a series of studies of the neural representation of tactile spatial form in somatosensory cortical area 3b of the alert monkey. We previously studied the spatial structure of >350 fingerpad receptive fields (RFs) with random-dot patterns scanned in one direction () and at varying velocities (). Those studies showed that area 3b RFs have a wide range of spatial structures that are virtually unaffected by changes in scanning velocity. In this study, 62 area 3b neurons were studied with three to eight scanning directions (58 with four or more directions). The data from all three studies are described accurately by an RF model with three components: (1) a single, central excitatory region of short duration, (2) one or more inhibitory regions, also of short duration, that are adjacent to and nearly synchronous with the excitation, and (3) a region of inhibition that overlaps the excitation partially or totally and is temporally delayed with respect to the first two components. The mean correlation between the observed RFs and the RFs predicted by this three-component model was 0.81. The three-component RFs also predicted orientation sensitivity and preferred orientation to a scanned bar accurately. The orientation sensitivity was determined most strongly by the intensity of the coincident RF inhibition in relation to the excitation. Both orientation sensitivity and this ratio were stronger in the supragranular and infragranular layers than in layer IV.

Action Potentials↗