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PubMed2006

Quasimonoenergetic deuteron bursts produced by ultraintense laser pulses.

We report on the generation and laser acceleration of bunches of energetic deuterons with a small energy spread at about 2 MeV. This quasimonoenergetic peak within the ion energy spectrum was observed when heavy-water microdroplets were irradiated with ultrashort laser pulses of about 40 fs duration and high (10(-8)) temporal contrast, at an intensity of 10(19) W/cm(2). The results can be explained by a simple physical model related to spatial separation of two ion species within a finite-volume target. The production of quasimonoenergetic ions is a long-standing goal in laser-particle acceleration; it could have diverse applications such as in medicine or in the development of future compact ion accelerators.

Journal Article↗
PubMed2004

Transcriptional response to circumscribed cortical brain ischemia: spatiotemporal patterns in ischemic vs. remote non-ischemic cortex.

Focal brain infarcts are surrounded by extended perilesional zones that comprise the partially ischemic penumbra but also completely non-ischemic cortex of the remote ipsilateral hemisphere. To delineate the impact of lesion-associated vs. remote processes on transcriptional programming after focal ischemia, we used cDNA array analysis, quantitative real-time polymerase chain reaction and immunohistochemistry in the photothrombosis model of circumscribed cortical ischemia in rats. At an early stage of 4 h after ischemia, gene induction occurred to a similar extent in the ischemic infarct and remote non-ischemic cortex of the ipsilateral hemisphere. Among the genes induced in non-ischemic cortex we found the NGF-inducible genes PC3, VGF and Arc, the transcriptional regulators I kappa B-alpha and Stat3, and the beta-chemokine MIP-1 alpha (CCL3). At 3 days, the spatial pattern of gene expression had changed dramatically with brain fatty acid-binding protein as the only gene significantly induced in non-ischemic ipsilateral cortex. In contrast, numerous genes were exclusively regulated at the lesion site, comprising genes involved in cell cycle regulation, proteolysis, apoptosis, lipid homeostasis and anti-inflammatory counter-regulation. Cortical spreading depression was identified as the main mechanism underlying gene induction in remote non-ischemic cortex. Our data demonstrate a dynamic spatiotemporal pattern of gene induction, which may contribute to delayed progression of damage or, alternatively, mediate neuroprotection, tissue remodeling and functional compensation.

AIDS-Related Complex↗
PubMed1991

Pulmonary surfactant as a vehicle for intratracheal delivery of technetium sulfur colloid and pentamidine in hamster lungs.

Tracheal instillation of pentamidine in a surfactant vehicle may be an effective direct method of antibiotic delivery to the lungs. In 10 healthy hamsters, we compared the pulmonary distribution of 99mTc sulfur colloid (TcSC) mixed with pentamidine, using as a vehicle either surfactant (n = 5) or saline (n = 5). Each animal was instilled with 0.25 ml/kg of suspension containing 0.0018 mCi TcSC and pentamidine mixed with either surfactant or saline. After 4 h of spontaneous respiration, the lungs were excised, inflated to TLC, dried, and sliced into 3-mm cross sections from apex to base. Autoradiographs were examined to evaluate 99mTc distribution. The surfactant group had detectable radioactivity in 93% of all slices compared with 72% in the saline group (p = 0.02). Six slices per animal (43% of total) and their corresponding autoradiographs were analyzed for distribution of radioactivity. Lung slice area was determined by planimetry, and autoradiograph area was determined by video densitometry. We calculated the fraction of each lung slice with detectable radioactivity. The surfactant group had 41% of the lung slice areas exposed compared with 21% in the saline group (p = 0.02). The coefficient of variation of radioactive intensities within each slice was used as an index of spatial uniformity. There was a trend towards more uniform distribution in the surfactant group, with a narrower range of variation of intensities (1.51 to 2.56) than the saline group (1.95 to 6.47). We conclude that a surfactant vehicle significantly increases airspace deposition of TcSC and pentamidine instilled intratracheally in normal hamster lungs, and may improve uniformity of spread.

Animals↗
PubMed1996

Extracellular matrix organization in various regions of rat brain grey matter.

Previous studies revealed the concentration of extracellular matrix proteoglycans in the so-called perineuronal nets on the one hand and in certain zones of the neuropil on the other. This nonhomogeneous distribution suggested a non-random chemical and spatial heterogeneity of the extracellular space. In the present investigation, regions dominated by one of both distribution patterns, i.e. piriform and parietal cortex, reticular thalamic nucleus, medial septum/diagonal band complex and cerebellar nuclei, were selected for correlative light and electron microscopic analysis. The labelling was performed by the use of the N-acetylgalactosamine-binding plant lectin Wisteria floribunda agglutinin visualized by peroxidase staining and additionally by photoconversion of red carbocyanine fluorescence labelling for electron microscopy. The intense labelling of the neuropil of a superficial piriform region, presumably identical with sublayer Ia, was confined to a fine meshwork spreading over the extracellular space between non-myelinated axons, dendrites and glial profiles. In the reticular thalamic nucleus the neuronal cell bodies were embedded in zones of labelled neuropil. In contrast to these patterns, the labelled extracellular matrix in different cortical layers and in the other subcortical regions was concentrated in perineuronal nets as large accumulations at surface areas of the neuronal perikarya and dendrites and the attached presynaptic boutons. Astrocytic processes usually were separated from the neuronal surface by the interposed extracellular material. Despite a great variability, the width of the extracellular space containing the labelled matrix components in all perineuronal nets appeared to be considerably larger than that in the labelled zones of neuropil and the non-labelled microenvironment of other neurons. Our results support the view that differences expressed in topographical and spatial peculiarities of the extracellular matrix constituents are related to neuron-type and system-specific functional properties.

Acetylgalactosamine↗
PubMed2006

Zinc-rich transient vertical modules in the rat retrosplenial cortex during postnatal development.

The rat retrosplenial cortex is part of a heavily interconnected limbic circuit, considered to have an important role in spatial memory. Interestingly, the granular retrosplenial cortex has an exceptionally distinct system of dendritic bundles, originating from callosally projecting pyramidal neurons in layer II. These can be detected as early as postnatal day 5; and, although their functional significance remains to be elucidated, the existence of these bundles makes the granular retrosplenial cortex an attractive model system for a wide range of development and functional investigations. Here, we report four results concerning the development of modularity in the granular retrosplenial cortex in rats as investigated by neurochemical markers associated to cortico-cortical and thalamo-cortical connections. Emphasis is placed on zinc, an activity-related substance associated with glutamatergic, non-thalamic terminations. 1) Zinc shows a transient strong expression during early postnatal development, but later than the appearance of the upper layer bundles (at postnatal day 5). By postnatal day 11 to postnatal day 15 staining for zinc achieved its most complex pattern; such that layer I had an elaborate organization both in the tangential and radial dimensions. Three sublaminae were distinguished (layers Ia-c): a superficial, thin tier (Ia) with patchy, moderate staining which periodically intruded into the underlying layer Ib ("funnel" modules), a middle band of variable width and light staining (Ib), and a deep, thin band with heavy and patchy staining (Ic) which, at rostral levels, spread upward into layer Ib (as "dome-like" modules). 2) At postnatal day 15, immunohistochemical methods showed that layers Ia, b zinc-funnels were co-localized with glutamate receptor subunits 2/3, GABA receptor type A alpha1 subunit and the thalamo-cortical marker, vesicular glutamate transporter 2. Layer Ic and the zinc dome-like modules were co-labeled for the cortico-cortical marker, vesicular glutamate transporter 1 and calretinin. 3) The spatial coincidence between zinc funnels in layers Ia, b and vesicular glutamate transporter 2 was further investigated by electron microscopy, which demonstrated co-localization of zinc and vesicular glutamate transporter 2 in synaptic boutons. The unusual co-localization of zinc and thalamo-cortical terminations was confirmed by retrograde transport of zinc to neurones in the anterodorsal thalamic nucleus at postnatal day 9 and postnatal day 13, and can thus be considered a transient zinc expression in thalamo-cortical boutons. This was not observed at postnatal day 28 or later. 4) After postnatal day 18, zinc staining started to fade in all layers. Before postnatal day 21, the heavy staining for zinc in the domes had completely disappeared. Zinc staining in layer Ia and the funnels virtually disappeared after postnatal day 28. A transient expression of zinc is reported in at least one other cortical area (layer IV of barrel cortex from postnatal day 5 to postnatal day 14, maximal at postnatal days 9-11). We conclude that the transient expression of zinc can occur in both limbic and sensory areas, and that down-regulation of zinc in cortical modules might be related to synaptic plasticity and remodeling during development.

Aging↗
PubMed2004

A parametric model for estimation of dispersal patterns applied to five passerine spatially structured populations.

Natal dispersal capture-recapture data from five fragmented populations of house sparrows, great tits, and blue tits were analyzed using maximum likelihood methods. A new two-parametric distribution was constructed that includes four distributions previously used as special cases in the literature. Dispersal standard deviations were estimated at 22.9 km for the house sparrows and ranged from 0.66 to 4.4 km for the tits. Female great tits and blue tits dispersed consistently further than males. Estimates of the shape parameter of the dispersal distribution ranged from 0.66 to 2.27, indicating strong to moderately leptokurtic dispersal displacements. There were significant effects of density on local immigration rates and a consistent tendency for immigration rates to depend underproportionally on local densities. Potential implications of the shape of the dispersal distribution for the spread of invading organisms were investigated and compared with previous results. It is shown that the wave speed, for a given dispersal standard deviation, depends only to some extent on leptokurtosis, provided that the intrinsic growth rate of the population is moderate or small. In estimating the dispersal standard deviation, however, incorrect assumptions about the degree of leptokurtosis can lead to a large bias in estimation and predictions.

Animal Migration↗
PubMed1994

Compartmentalization of cellular and viral DNAs in adenovirus type 5 infection as revealed by ultrastructural in situ hybridization.

We describe the respective distributions of cellular DNA and viral genomes in adenovirus type 5 (Ad5)-infected HeLa cells by means of electron microscope in situ hybridization using biotinylated Alu DNA and Ad5 DNA probes in a post-embedding technique. When hybridization was performed on sections of formaldehyde-fixed material, Alu elements were restricted to the cellular chromatin, irrespective of the stage of the infectious cycle, without any interpenetration within the virus-induced regions. Viral DNA was confined entirely to the latter. Similar topological distributions of cellular and viral DNA were obtained when in situ hybridizations were performed at the optical level on methanol-acetone fixed cells. Such separation between cellular and viral DNA persisted under experimental conditions which partially loosened the nucleoproteins. In addition, the viral DNA of the different viral structures spread without interpenetration. On the other hand, the procedure did not dissociate the clusters of viruses which remained, as usual, closely surrounded by innumerable viral genomes. It also preserved the shapes, content (viral ssDNA + viral 72 kD protein) and the topological localization of the pleomorphic viral ssDNA accumulation sites. These data, which suggest that all viral DNAs are spatially linked in the infected nuclei, suggest a prominent role for the internal nuclear matrix in virus replication, assembly and maturation.

Adenoviruses, Human↗
PubMed1988

The onset of decline in ischemic heart disease mortality in the United States.

Temporal and spatial patterns of the onset of the decline in ischemic heart disease mortality in the United States for each of the 48 contiguous US states and the District of Columbia are examined for the years 1955-1978 for age-sex-race-specific mortality. Mortality rates are derived from National Center for Health Statistics mortality data, and a polynomial interpolation is used to estimate intercensal population counts employing 1950, 1960, 1970, and 1980 US Census data. A quadratic regression equation is used to estimate the date of highest rate, which marks the beginning of the decline for each of the US states. The temporal distribution of the onset of the decline among men occurred primarily between 1960 and 1965. Among women, the onset of decline was more variable. Furthermore, strong and regular spatial patterns were seen among the groups examined and these impressions are supported by statistical analysis. California, Maryland, and the District of Columbia were early decliners in most groups studied, whereas states in the southeast were consistently among the last to experience the onset of decline. These patterns suggest the existence of an underlying phenomenon accounting for the spread or diffusion of the onset of decline in ischemic heart disease mortality.

Adult↗
PubMed1994

Resolution limits for optical transillumination of abnormalities deeply embedded in tissues.

Random walk theory is used to calculate the line spread function (LSF) of photons as they cross the midplane of a slab of finite thickness. The relationship between the LSF and the photon transit time in transillumination time-resolved experiments is investigated. It is found that the LSF is approximately Gaussian distributed, with a standard deviation, sigma, which can be used as a criterion of the spatial resolution of the imaging system. Results are substantiated by comparison with actual data in the literature. Any given resolution can be improved by reducing the excess transit time delta t, but heterogeneity of the scattering medium and low levels of detected light enormously complicate the achievement of subcentimeter spatial resolution. The latter point is discussed by using optical parameters of breast tissues for visible and near-infrared radiation (NIR) light.

Breast Diseases↗
PubMed2002

Searching with unilateral neglect.

We address two longstanding conflicts in the visual search and unilateral neglect literature by studying feature and conjunction search performance of neglect patients using laterally presented search arrays. The first issue relates to whether feature search is performed independently of attention, or rather requires "spread attention." If feature search is "preattentive," it should survive neglect. However, we find neglect effects for both feature and conjunction search, suggesting that feature search, too, has an attentional requirement. The second controversy refers to the space- or object-based nature of neglect following unilateral right-hemisphere parietal lobe damage. If neglect were a purely spatial phenomenon, then we would expect no detriment in performance in the right (nonneglect) field, and diminished performance for the whole left (neglect) field. On the other hand, if neglect were purely object-based, we would expect diminished performance on the left side of the search array, irrespective of its location in the visual field. We now demonstrate a combination of strong object-based and space-based neglect effects for conjunction search with laterally placed element arrays, suggesting that these two mechanisms work in tandem.

Adult↗
PubMedDate not supplied

[The migrations of the green oak tortrix Tortrix viridana L. (Lepidoptera, Torticidae): an analytical study].

The author analyses mono-factorial theories of population dynamics of Tortrix viridana and discusses the hypothesis of its distant and attended migrations together with its specialized parasitoid Dirophanes invisor. Data on T. viridana temporal-spatial distribution for the period of 1938-1995 are presented. It was shown that the main factors caused the decrease in population numbers are intra-population mechanisms, providing the initiation long embryonic diapause for some part of population, the decrease in the frequency of its outbreaks. Some data indicate that large scale migrations are not important for spreading of T. viridana outbreaks.

Animals↗
PubMed1998

Temporal modulation of spatial borders in rat barrel cortex.

We examined the effects of varying vibrissa stimulation frequency on intrinsic signal and neuronal responses in rat barrel cortex. Optical imaging of intrinsic signals demonstrated that the region of cortex activated by deflection of a single vibrissa at 1 Hz is more diffuse and more widespread than the territory activated at 5 or 10 Hz. With the use of two different paradigms, constant time of stimulation and constant number of vibrissa deflections, we showed that the optically imaged spread of activity is more discrete at higher stimulation frequencies. We combined optical imaging with multiple electrode recording and confirmed that the neuronal response to individual vibrissa stimulation at the optically imaged center of activity is greater than the response away from the imaged center. Consistent with the imaging data, these recordings also showed no response to a second vibrissa deflection at 5 Hz at a peripheral recording site, though there was a significant response to a second vibrissa deflection at 1 Hz at the same peripheral site. These findings demonstrate that vibrissa stimulation at higher frequencies leads to more focused physiological responses in cortex. Thus the spread of activation in rat barrel cortex is modulated in a dynamic fashion by the frequency of vibrissa stimulation.

Animals↗
PubMed2004

Pulsatile motion effects on 3D magnetic resonance angiography: implications for evaluating carotid artery stenoses.

In-plane carotid artery motion during a 3D MR angiography (MRA) scan can significantly degrade the resulting image resolution. This study characterizes the effect of cardiac pulsatility on 3D contrast-enhanced (CE) MRA with elliptical centric acquisitions using a point-spread function (PSF) analysis. Internal carotid artery (ICA) motion was collected from volunteers and patients using both MR and ultrasound (US) scans. After measuring the carotid artery motion displacement, a simulation was performed which calculated the blurring effects for three different protocols: nongated and two different cardiac gating schemes. The motion sensitivity of each protocol was evaluated for different spatial resolutions. The selection of optimal imaging parameters for a given scan time was investigated. The final results showed that cardiac-gated acquisitions only over a limited region of k-space high spatial frequencies are more time-efficient than cardiac gating for the entire k-space, as it allows for higher resolutions to be achieved and for capturing the arterial phase with low spatial frequencies. Selecting the optimal gating parameters depends directly on the motion characteristics of each individual. Our initial clinical experience is presented, and the need for a real-time tool that characterizes motion behavior for each individual as a prescan protocol is discussed.

Carotid Arteries↗
PubMed1980

Orientation-specific adaptation: effects of checkerboards on the detectability of gratings.

The predictive values of Fourier analysis and local-feature analysis of spatial stimuli were compared in an orientation-specific adaptation experiment. Observers adapted to checkerboard patterns, which have fundamental Fourier components oriented 45 degrees away from the edges. Detection of gratings was found to be maximally impaired when fundamental Fourier components of adaptation and test patterns were in the same orientation and minimal when edges were aligned. The orientation spread and amount of adaptation effect were similar to that found in previous experiments which employed sinusoids as adaptation and test stimuli.

Adaptation, Ocular↗
PubMed1984

The application of EDXS to the biological sciences.

The distribution of chemical elements in soft tissues may be faithfully preserved by very rapid freezing. Most often the material is then cryosectioned and the sections frozen-dried prior to analysis, but direct analysis in the hydrated state is an established alternative. For bulk specimens, the shape of the analysed volume is uncertain. But whichever current model is accepted, analytical spatial resolution must generally be limited to the order of 1 micron. Such specimens can be suitable for the specific analysis of cytoplasm, cell nuclei and large extracellular spaces but not for study on a finer scale. Analytical spatial resolution in the range 200-500 nm is obtainable with sections cut approximately 1 micron thick. In the frozen-hydrated state, small extracellular spaces can be analysed but multiple scattering obscures intracellular detail in the STEM image. The irradiation required for an EDXS analysis, approximately 50 nanoCoulomb (50 nanoAmpere seconds), need not produce intolerable radiation damage when spread over an area 200 nm or more in diameter. Finer structure, for example mitochondria and regions of rough or smooth endoplasmic reticulum, can be identified and analysed in frozen-dried cryosections cut approximately 100 nm thick. Recently such features have been visualized in 100 nm frozen-hydrated sections where the water is vitreous. This opens the prospect of analysing material where elemental distributions have been preserved on a very fine scale, since one might avoid even the ionic shifts from aqueous solution to supramolecular structures which must occur on freeze-drying. But radiation damage may be prohibitive when an irradiation of 50 nanoCoulomb is concentrated into a hydrated area less than 200 nm in diameter.

Animals↗
PubMed1983

Relationship of General Aptitude Test Battery scores to successful employment for epileptics in a rehabilitation setting.

The US Employment Service's (USES) General Aptitude Test Battery (GATB), when used with USES-developed cut-off scores, has been found to be an accurate predictor of successful job performance. In the present study, results of the GATB scores obtained by vocational rehabilitation clients (n = 15) who were successfully placed into permanent employment were evaluated with reference to published GATB norms and cut-off scores. The major finding of this study was that the scores were not accurate predictors of successful employment for this population. Subjects' subtest scores averaged between 1/2 and 2 SD below the published means, with scores on subtests measuring motor speed and dexterity producing the lowest values. Subtests measuring verbal and visual--spatial ability produced relatively higher values. In only 3 instances was successful employment predicted by the cut-off scores. For the entire sample, GATB scores were frequently low enough to indicate poor job performance in nearly all occupations covered by published cut-off scores. Based on the results from the present study, and considering the wide-spread use of the GATB in the United States, a more comprehensive research project is being implemented to adapt GATB material for use with the targeted population.

Adult↗
PubMed2003

Progressive agraphia, acalculia, and anomia: a single case report.

A case of a 50-year-old, right-handed female, mono-lingual native Spanish-speaker with a university-level education and cognitive changes is reported. Over approximately 2 years, she presented with a progressive deterioration of writing abilities associated with acalculia and anomia. An MRI disclosed a left parietal temporal atrophy. Two years later, further significant cognitive decline consistent with a dementia of the Alzheimer's type was observed. Amnesia, executive dysfunction, and ideomotor apraxia were found. Writing was severely impaired, and some difficulties in reading were observed. Copying abilities, however, were relatively well preserved, and the patient could drive and go to different city locations without significant spatial orientation difficulties. A second MRI approximately 2 years later showed that brain atrophy had progressed significantly. Spontaneous writing and writing to dictation were impossible. The ability to read words was preserved, but the ability to read pseudowords was lost. Changes in calligraphy were noted. This case clearly illustrates the progression of focal cognitive defects over time and the spread of abnormalities to other domains.

Agraphia↗
PubMed1999

Three-dimensional morphometry in ultrasound.

The clinical use of three-dimensional (3D) ultrasound has rapidly spread to many specialities over the last ten years. The reason is easy to see, namely that single two-dimensional (2D) scans are often difficult to interpret and the mental correlation of multiple 2D scans to form a 3D image of anatomical morphology is taxing and uncertain. The rapid development of techniques for the realtime tracking of the spatial position and orientation of ultrasound probes and the development of computer graphics techniques for the presentation of anatomical images have made 3D ultrasound a realistic diagnostic tool. The authors describe the range of methods of data acquisition and display and provide illustrations of some current clinical applications.

Adult↗