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PubMed1994

Postictal behavior. A clinical and subdural electroencephalographic study.

OBJECTIVE: To examine postictal behaviors after temporal lobe complex partial seizures (CPSs) and to correlate these behavioral phenomena with side of origin and ictal spread pattern. DESIGN: Review language and other behavioral phenomena after seizures defined by subdural electroencephalography. SETTINGS: A surgical epilepsy center. PATIENTS: We studied postictal behavior following 65 CPSs in 18 patients with left hemisphere language dominance using subdural electrode recordings. INTERVENTION: Subdural electrodes. MAIN OUTCOME MEASURES: Language function, affect, orientation, and postictal automatisms. RESULTS: Following the CPS ictal discharge, the mean interval for initial nonreflexive response to an environmental stimulus was 43 seconds (left foci, 57 seconds; right foci, 29 seconds; not significantly) and for first correct verbal response was 219 seconds (left foci, 275 seconds; right foci, 167 seconds; not significant). Impaired comprehension with fluent but unintelligible speech, as well as anomia, occurred after seizures arising from either temporal lobe. All nine seizures followed by global or nonfluent aphasia originated on the left side. Paraphasic errors were significantly more common after left temporal CPSs. Prolonged disorientation for place and flat affect were significantly more common after right temporal CPS. Postictal automatisms were frequent and included rubbing of the face, fumbling and picking hand movements, and repetitive oral movements. CONCLUSIONS: Postictal paraphasias, disorientation for place, and flat affect most likely reflect the functions of the area from which seizures arise but not the areas involved by spread.

Adolescent↗
PubMed1990

Somatodendritic morphology of on- and off-cells in the rostral ventromedial medulla.

The rostral ventromedial medulla (RVM) contains two classes of physiologically defined neurons, on-cells and off-cells, that are implicated in nociceptive modulation. In a continuing effort to detail the neural circuitry that underlies the activity of these two distinct neuronal types, the somatodendritic morphology of on- and off-cells was studied in the cat, rat, and ferret. In lightly anesthetized animals, on-cells increased and off-cells decreased their discharge rate during a withdrawal reflex evoked by noxious stimuli. Following their physiological characterization by using intracellular recording, on- and off-cells were injected with either horseradish peroxidase or biocytin and their somatodendritic arborizations were examined. Labeled on- and off-cells included fusiform and stellate cells of all sizes as well as large multipolar neurons. Although the somatic shape of both on- and off-cells in RVM was heterogeneous, off-cells tended to be fusiform neurons whose long axis was oriented mediolaterally. The dendritic domains of both on- and off-cells extended bilaterally past the lateral edge of the trapezoid body or pyramid and ventrally to, and sometimes including, the trapezoid body or pyramid. In contrast to their extensive mediolateral spread, the dendritic domains of both cell types were limited to the ventral half of the reticular formation and were compressed along the rostrocaudal axis. The dendritic arbor of individual on- and off-cells extended well beyond the cytoarchitectonic boundaries of any single nuclear region, within the domain delineated as the RVM. The spatial domains of the dendritic arbors of on- and off-cells are further evidence that the on- and off-cells throughout the RVM constitute an integrated unit in the modulation of nociceptive transmission.

Animals↗
PubMed2002

Hierarchical statistical modelling of influenza epidemic dynamics in space and time.

An infectious disease typically spreads via contact between infected and susceptible individuals. Since the small-scale movements and contacts between people are generally not recorded, available data regarding infectious disease are often aggregations in space and time, yielding small-area counts of the number infected during successive, regular time intervals. In this paper, we develop a spatially descriptive, temporally dynamic hierarchical model to be fitted to such data. Disease counts are viewed as a realization from an underlying multivariate autoregressive process, where the relative risk of infection incorporates the space-time dynamic. We take a Bayesian approach, using Markov chain Monte Carlo to compute posterior estimates of all parameters of interest. We apply the methodology to an influenza epidemic in Scotland during the years 1989-1990.

Bayes Theorem↗
PubMed1988

Temporal and spatial control of silk gene transcription analyzed by nuclear run-on assays.

In vivo transcriptional activity of the Bombyx mori fibroin and sericin genes was estimated by nuclear run-on assay. Tissue-specific and developmental stage-specific expression of the fibroin and sericin genes through larval development was shown to be primarily regulated at the level of transcription. The expression patterns of these two genes are quite different in their developmental profile, suggesting that they are probably regulated by different underlying mechanisms. A finer spatial control of transcription could be found. The sericin gene transcription is mostly restricted to the posterior region of the middle silk gland throughout the fifth larval instar. Interestingly, the fibroin gene transcription is observed only in the anterior region of the posterior silk gland on the first day of the fifth instar, and spreads toward the posterior region as the fifth instar stage proceeds.

Age Factors↗
PubMed1996

Filling-in percepts produced by luminance modulation.

We report that when the luminance of a homogeneous spot of light is gradually increased or decreased, there are conditions in which the brightness of the spot is spatially nonuniform. When the spot luminance is increased, brightness changes in the spot's center lag behind changes at the edge and brightness appears to sweep inward. Conversely, if the luminance of the spot is decreased, there is a relative lag in the darkening toward the center of the spot and darkness seems to spread inward. In Experiment 1 we found that with both increasing and decreasing luminance sweeps, the strength of the brightness filling effects was strongest with luminance sweep durations of 0.25-0.5 sec. In Experiment 2, the sweep duration was held constant at 0.5 sec; the filling effect was seen when the dwell time spent at each luminance step was less than about 100 msec, but nonuniformities were not observed at longer dwell times. In Experiment 3, a spot of light was positioned to surround the optic disk in one eye. Surprisingly, when the spot was luminance modulated from bright to dark, darkness appeared to sweep from the edge to the center of the modulated disk, even though most of the disk's interior was imaged on a portion of the retina devoid of photoreceptors. These findings are consistent with the hypothesis that a neural filling-in mechanism in visual cortex plays a key role in brightness perception.

Darkness↗
PubMed2004

Molecular evolution of epididymal lipocalin genes localized on mouse chromosome 2.

We previously identified two murine secretory proteins, mE-RABP(Lcn5) and mEP17(Lcn8), belonging to the lipocalin family and specifically expressed in the epididymis. The genes are contiguous and localized on mouse chromosome 2. We now show that five other related lipocalin genes, Lcn9, Lcn10, Lcn11, Lcn12, and Lcn13, that evolved by in situ tandem duplication are present on the same locus. Lcn9, Lcn10, Lcn12, and Lcn13 genes, like Lcn5 and Lcn8 genes, are specifically expressed in the mouse epididymis. However, each gene has a distinct spatial expression within the epididymis and different regulation. Analysis of the human genome sequence shows the presence of genes encoding lipocalins with genomic organization, chromosomal arrangement, and orientation similar to that of the corresponding murine genes, indicating that the epididymal cluster is evolutionary conserved. A phylogenetic analysis of the new epididymal proteins reveals their spread position in the lipocalin protein family tree. This suggests the preservation of the regulatory sequences, while protein sequences have greatly diverged, reflecting functional diversity and possibly multifunctionality. In terms of the cluster ancestry, epididymal expression possibly appeared in a PGDS-like lipocalin in amniotes, and the duplications generating the cluster occurred at least in the common ancestor of rodents and primates. The presence and conservation of a cluster of five genes encoding epididymal lipocalins, differently regulated and regionalized in the epididymis, strongly suggests that these proteins may play an important role for male fertility.

Acute-Phase Proteins↗
PubMed2004

Intra-household clustering of hepatitis C virus infection in Karachi, Pakistan.

Transmission rates of hepatitis C virus (HCV) infection through non-sexual household contacts have been considered to be very low. This study evaluated intra-household clustering of cases of HCV infection in a low socio-economic community in Karachi, Pakistan. Serum samples from 341 household contacts of 86 thalassaemic HCV-seropositive children were evaluated for antibodies to HCV using an ELISA. Spatial analysis of data was carried out to test for intra-household clustering. Seventy of 341 (20.5%) household contacts were HCV-seropositive. Of the households studied, 44.2% (38/86) had one or more contacts who tested HCV-seropositive. Ecological analysis of variables at household level showed that in households where HCV-seropositive index thalassaemic children were male HCV tended to be transmitted to one or more familial contacts. Spatial analysis with an asymptotic score test of the null hypothesis of no extra within-family infectivity revealed that there was a significant tendency of HCV infection to cluster within a household (score statistic = 19.44, P=0.032). The results showed that non-sexual household exposure may play a role in efficient HCV spread to household contacts of HCV-infected persons and needs further evaluation.

Adolescent↗
PubMed2003

Air distribution in the Borden aquifer during in situ air sparging.

A field experiment was conducted at Canadian Forces Base Borden (CFB Borden) to assess the air distribution from a single in situ air sparging injection point. This aquifer consists of fine to medium sand deposited in horizontal layers. The permeability at the study location varied from 10(-10) to 10(-14) m2 and distinct low permeability horizons were present at approximately 1.2, 2.0, and 2.9 m below the water table. Prior to air injection, a 15x15-m portion of the vadose zone was excavated to the water table (approximately 1 m below ground surface) in order to visually observe air release distribution at the water table. The water table was actively maintained 5 cm above the excavated surface. The sparging system operated for a period of 7 days with an injection flow rate of 200 m3/days (5 scfm). The resulting subsurface air distribution was assessed using a variety of techniques including neutron logging, borehole and surface ground penetrating radar, piezometric head measurements, surface visualization, and hydraulic testing. Through this combination of tests, it was demonstrated that variations in permeability and, hence, capillary pressure at the site were sufficient to cause the injected air to spread laterally, forming stratigraphically trapped air pockets beneath the low permeability horizons. The formation of these air pockets eventually resulted in a buildup of capillary pressure that exceeded the air entry pressure and allowed some air to migrate up through the lower permeability layers. Each of the assessment techniques employed generated information at different spatial scales that prevented a direct comparison of the results from the various techniques; however, the results from all techniques proved to be critical in the interpretation of the experimental data. As a consequence, the different assessment techniques should not be viewed as alternatives, but rather as complimentary techniques.

Air↗
PubMed1995

Bovine tuberculosis in badger (Meles meles) populations in southwest England: the use of a spatial stochastic simulation model to understand the dynamics of the disease.

A spatial stochastic simulation model was developed to describe the dynamics of bovine tuberculosis in badger populations in southwest England, based on data from the literature and from unpublished sources. As there are no data on intra- and intergroup infection probabilities, estimates of these were obtained through repeated simulations based on field observations of the spread and prevalence of the disease. The model works on a grid-cell basis, with each grid cell potentially occupied by one badger social group; immigration to and emigration from the main grid are incorporated. Population regulation is assumed to occur at the group level through density-dependent fecundity and cub mortality, and the model can be run for various disease-free equilibrium group sizes (which are determined by the carrying capacity of the environment). The model works on a quarterly (three-monthly) basis and processes are stochastic at the individual level. Three classes of individual (adults, yearlings and cubs) and three classes of infection (susceptible, infected-but-not-infectious and infectious) are recognized. Bovine tuberculosis wa shown to persist in badger populations for long periods of time, even in populations with a disease-free equilibrium group size of only four adults and yearlings. However, with standard rates of intergroup infection and movement, the disease only became endemic in populations with a disease-free equilibrium group size greater than six adults and yearlings. In the endemic situation, the prevalence of the disease ranged between 11-22 degrees depending on the combination of inter- and intragroup infection probabilities used. Endemic infection within the homogeneous environment of the grid was characterized by a high degree of heterogeneity. Patches of infection were spatio-temporally unstable, but shifted in location relatively slowly. Spread of the disease from a point source of infection with standard rates of intergroup movement and infection only occurred to any marked extent in populations with disease-free equilibrium group sizes of eight or more adults and yearlings. Increasing the intergroup infection probability had a significant effect on increasing the probability and rate of spread, and considerably lowered the threshold group size for spread from a point source to around four adults and yearlings. However, increasing the rates of intergroup movement reduced the probability of spread of the disease except at the largest groups sizes. When both intergroup infection and movements were increased, the effects of increased infection in enhancing spread were offset to some degree by the increased movements. Perturbation to the badger population, as may be caused by control operations, could therefore increase the probability of persistence or spread of an infection.

Animals↗
PubMed2002

Synthetic aperture imaging with arrays of arbitrary shape--part I: General case.

The problem of synthesizing full-aperture resolution with linear transmitting and receiving arrays of arbitrary shape is considered. The arrays are assumed to lie in the same plane and can be open (e.g., curved or straight line segments) or closed (e.g., circles). It is shown that a full (area) aperture can be synthesized by suitably weighting the transmitted and received signals. This weighting turns out to be the Jacobian of a transformation that yields uniform coverage in the spatial-frequency domain. If the Jacobian is factorable, then full-aperture resolution can be achieved in a single transmission. The theory is illustrated with two annular arrays of different diameter: one that transmits and one that receives. If the radii of the annular arrays are a and b, then the synthesized point-spread function (PSF) is shown to be equivalent to that of a filled circular aperture of radius a + b.

Journal Article↗
PubMed1990

Volume-dependent spatial distribution of microinjected thyrotropin-releasing hormone (TRH) into the medial preoptic nucleus of the rat: an autoradiographic study.

The present study was performed to quantify the distribution of a peptide neurotransmitter after microinjection into the medial preoptic area (POM), using a technique suitable for conscious animal preparations. The results indicate that only 50-nl volumes of injected tracer were sufficiently localized with 77 +/- 9% recovery in the POM. Injections of higher volumes resulted in an increasing spread of tracer into distant anatomical regions and structures, including the needle tract and cerebral ventricles. The amount of tracer localized in the POM decreased to 38 +/- 4% (200 nl) (P less than 0.05) and 14 +/- 8% (500 nl) (P less than 0.05), respectively. The data suggest that the volume of injection is critical for intraparenchymal injections into structures of a diameter of 1mm or less, such as the POM and should not exceed 50 nl in conscious animal preparations.

Animals↗
PubMed1998

On rugged shape of skin tumor (basal cell carcinoma).

Basal cell carcinoma (BCC) is the most common cancer of the skin that is made of transformed basal cells of the human epidermis, and spreads along the epidermis--dermis junction. It often forms tumor cell mass that protrudes towards the dermal connective tissue with many branches. Histopathological examination of the cancer demonstrates the cell mass of a rugged shape appearing as many regular spaced islands in a two-dimensional section. We study the process of cell proliferation and spatial pattern formation of the skin tumor by a pair of partial differential equations of tumor cells and nutrients. The assumptions are: (1) proliferation rate of tumor cells depends on the availability of nutrients, which simply diffuse out of capillaries through connective tissue; (2) nutrients are consumed by active tumor cells; (3) cell diffusion coefficient expressing tumor cell movements increase with the cell density and the nutrient availability. Starting from the initial condition with a single layer of tumor cells. the model develops a smooth colony if n'0 is large, but a characteristic rugged spatial pattern of tumor cell mass if n'0 is small, in which n'0 is nutrient concentration multiplied by square root of growth efficiency divided by diffusion coefficient of nutrients. The proportion of the area occupied by tumor cells increases with n'0. The coefficient of variation in the width of "islands" of tumor cell mass is rather small (0.2 reverse similar0.6), implying the regularity of the spatial pattern. We also analyses the photographs of a two-dimensional section of tumor cell mass and compare the spatial patterns generated by the model.

Aged↗
PubMed1993

Segmentation versus integration in visual motion processing.

Reliable motion perception requires processes that integrate visual motion signals from neighbouring locations in the visual field, which should have the effect of smoothing out spatial variations in velocity. However, we also require motion processing to be very sensitive to local velocity differences, so that moving objects appear sharply distinct from their background and specific differential properties of optic flow associated with the observer's motion can be detected. Perceptual experiments give evidence both for integrative processes, which lead to spreading of perceived motion, and for differential processes, which lead to motion contrast and segmentation. Current and future experiments might allow tests of theoretical schemes that employ adaptive networks and/or multiple representations in order to reconcile the conflicting demands of integration and segmentation.

Animals↗
PubMed1998

Multiple modes of cellular activation and virus transmission in HIV infection: a role for chronically and latently infected cells in sustaining viral replication.

CD4(+) T cell activation, required for virus replication in these cells, occurs in local microenvironmental domains in transient bursts. Thus, although most HIV originates from short-lived virus-producing cells, it is unlikely that chronic infection is generally sustained in rapid continuous cycles of productive infection as has been proposed. Such continuity of productive infection cycles would depend on efficient long-range transmission of HIV from one set of domains to another, in turn requiring the maintenance of sufficiently high concentrations of cell-free virus across lymphoid tissues at all times. By contrast, long-lived cellular sources of HIV maintain the capacity to infect newly activated cells at close range despite the temporal and spatial discontinuities of activation events. Such proximal activation and transmission (PAT) involving chronically and latently infected cells may be responsible for sustained infection, particularly when viral loads are low. Once CD4 cells are productively infected through PAT, they can infect other activated cells in their immediate vicinity. Such events propagate locally but generally do not spread systemically, unlike in the acute phase of the infection, because of the early establishment of protective anergy. Importantly, antiretroviral drug treatment is likely to differentially impact long-range transmission and PAT.

CD4-Positive T-Lymphocytes↗
PubMed2005

Reconstruction of optical properties of phantom and breast lesion in vivo from paraxial scanning data.

We report on the reconstruction of absorption and reduced scattering coefficients of breast tissue in vivo of a patient with mastopathic disease. Distributions of times of flight of photons through the compressed breast were recorded by paraxial scanning. From data measured at four different source-detector offsets optical properties were reconstructed within the linear Rytov approximation by a fast inverse Fourier space method. Low-pass filtering in Fourier space was employed to remove excessive noise from high spatial frequency components and to reduce the computational efforts by a factor of 3, typically. The mammograms displaying reconstructed absorption and reduced scattering coefficients were compared with projection mammograms either obtained by time-window analysis of experimental data or based on average absorption and reduced scattering coefficients which were derived from measured temporal point spread functions within a simple homogeneous model. All inhomogeneities which were visible in the projection mammograms and which could be associated with specific breast tissue compartments could be correlated with inhomogeneities in the reconstructed absorption coefficient. In particular, the mastopathic disease was detected in the reconstructed absorption mammogram. In order to assess reliability of optical properties reconstructed from data obtained by paraxial scanning, corresponding phantom experiments and reconstructions of phantom optical properties were carried out. Because of the limited angular range sampled by the in vivo and phantom measurements, considerable blurring of the absorption coefficient occurs along the compression direction, compromising longitudinal resolution.

Algorithms↗
PubMed2004

Model for spreading of liquid monolayers.

Manipulating fluids at the nanoscale within networks of channels or chemical lanes is a crucial challenge in developing small scale devices to be used in microreactors or chemical sensors. In this context, ultrathin (i.e., monolayer) films, experimentally observed in spreading of nanodroplets or upon extraction from reservoirs in capillary rise geometries, represent an extreme limit which is of physical and technological relevance since the dynamics is governed solely by capillary forces. In this work we use kinetic Monte Carlo (KMC) simulations to analyze in detail a simple, but realistic model proposed by Phys. Rev. Lett. 76, 86 (1996)]] for the two-dimensional spreading on homogeneous substrates of a fluid monolayer which is extracted from a reservoir. Our simulations confirm the previously predicted time dependence of the spreading, X ( t--> infinity ) =A square root of t, with X (t) as the average position of the advancing edge at time t, and they reveal a nontrivial dependence of the prefactor A on the strength U0 of interparticle attraction and on the fluid density C0 at the reservoir as well as an U0 -dependent spatial structure of the density profile of the monolayer. The asymptotic density profile at long time and large spatial scale is carefully analyzed within the continuum limit. We show that including the effect of correlations in an effective manner into the standard mean-field description leads to predictions both for the value of the threshold interaction above which phase segregation occurs and for the density profiles in excellent agreement with KMC simulation results.

Computer Simulation↗
PubMed1997

Linear synthetic aperture modes for ultrasonic pulse-echo imaging.

A unified approach is developed to characterize and compare the most widely used two-dimensional ultrasound pulse-echo imaging procedures. The methods of monostatic, bistatic and multistatic time-domain holography are theoretically investigated with regard to line spread functions, resolution capabilities, and the effects of multiple scattering and object inhomogeneities. Analytical derivations and computer simulations show the superiority of monostatic holography in applications such as nondestructive testing, where in most cases the assumptions generally made in the calculation of the inverse scattering formulae are justified. However, if higher order scattering and/or the spatial variations of the sound speed play a significant role, then multistatic imaging is more advantageous. A modification of this latter mode, with fixed focus on transmission, is commonly used in medical imaging B-scan systems, but implementation of the full algorithm would offer improved resolving power and reduced side lobe levels throughout the image plane.

Artifacts↗
PubMed2006

Spatial and temporal dynamics of overwintering Homalodisca coagulata (Hemiptera: Cicadellidae).

A 4-yr landscape-scale study was conducted to investigate spatial and temporal dynamics of overwintering Homalodisca coagulata (Say) (Hemiptera: Cicadellidae) in the lower San Joaquin Valley, California. Spatial structures of H. coagulata distributions were characterized with Moran's I index, and spatial associations between H. coagulata and the surrounding environment were investigated with a geographic information system. H. coagulata was caught consistently with sticky traps throughout the winter, and trap catches formed a distinctive peak in December or January, indicating active flight of H. coagulata during the winter. In 2000-2001, the mean +/-SE trap count was 4.8 +/- 1.21 per trap per wk, and H. coagulata trap catches were spatially autocorrelated within approximately 1.3 km. Approximately 49% of H. coagulata were caught in citrus, 23% in stone fruit, and 11% in grape. After a control program began in spring 2001, the mean trap count was considerably lower (0.041 +/- 0.0004 per trap per wk), and no spatial autocorrelations were detected in 2001-2004. H. coagulata trap catch-crop associations also changed after initiation of the control program. Between 25 and 38% of H. coagulata trap catches were from citrus, between 8 and 20% were from stone fruit, and between 11 and 25% were from grape. Potential for winter-season spread and management of Xylella fastidiosa Wells et al., a pathogen causing Pierce's disease, are discussed.

Animals↗