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PubMed1996

Neural cell pattern formation on glass and oxidized silicon surfaces modified with poly(N-isopropylacrylamide).

Control over the adsorption of proteins and over the adsorption and spatial orientation of mammalian cells onto surfaces has been achieved by modification of glass and other silicon oxide substrates with poly(N-isopropylacrylamide) (PNIPAM). The functionalization of the substrates was achieved either by a polymer-analogous reaction of aminosilanes with reactive N-(isopropylacrylamide) (NIPAM)-copolymers and by copolymerization of NIPAM with surface-bound methacrylsilane. The obtained coatings were characterized by FT-1R, ellipsometry, and surface plasmon resonance measurements. The adsorption of two proteins-fibrinogen and ribonuclease A-on these surfaces was studied in situ by real time surface plasmon resonance measurements. The PNIPAM-grafted surfaces prepared by either chemical procedure inhibited the adsorption of both proteins. More importantly they prevented the adhesion of neuroblastomaXglioma hybrid cells cultured either in serum-free medium or in a medium containing serum proteins. Deep-UV irradiation was used to perform ablation processes and to create patterns permitting the examination of spatially controlled adhesion and growth of cells. This study showed that patterned ultrathin polymer films on glass are suitable substrates for controlling the interactions of cells with surfaces and are capable of directing the attachment and spreading of cells.

Acrylamides↗
PubMed1998

Novel expression pattern of interphotoreceptor retinoid-binding protein (IRBP) in the adult and developing zebrafish retina and RPE.

PURPOSE: Interactions between the neural retina and retinal pigment epithelium (RPE) are mediated by the interphotoreceptor matrix (IPM). The transport of retinoids across the IPM is mediated by interphotoreceptor retinoid-binding protein (IRBP). To explore the possibility that IRBP is important during retinal development, we examined its spatiotemporal expression pattern in embryonic zebrafish. METHODS: IRBP mRNA expression was examined using RT-PCR and in situ hybridization. IRBP was localized using antiserum against recombinant zebrafish IRBP. IRBP synthesis and secretion were studied by in vitro metabolic labeling of retinas and RPE-eyecups. RESULTS: IRBP mRNA was first observed in the pineal at 24 hours post-fertilization (hpf) and in the ventral retina at 50 hpf. Immunoreactive IRBP was first observed at 72 hpf. Remarkably, IRBP was expressed not only by photoreceptors but also by the adult and embryonic RPE. In embryos, expression in both retina and RPE began in a ventronasal patch and spread to involve the entire eye. In general, early IRBP expression was dominated by photoreceptors, but then RPE expression spread beyond the limit of photoreceptor expression. Double in situ hybridizations suggests that cones express IRBP mRNA before they express a specific opsin, while rods may express rod opsin prior to IRBP. CONCLUSIONS: The temporal and spatial patterns of IRBP expression by the RPE and retina are consistent with a role in retinal development and suggest coordination of RPE and photoreceptor differentiation.

Animals↗
PubMed1997

Spreading of vasogenic edema and cytotoxic edema assessed by quantitative diffusion and T2 magnetic resonance imaging.

BACKGROUND AND PURPOSE: The apparent diffusion coefficient (ADC) of water should be sensitive to the cytotoxic edema triggered by energy failure during ischemia. Elevated values of T2. the nuclear MR transverse relaxation time of water, seen on T2 nuclear MR images detect vasogenic edema and infarcted areas. The temporal and spatial changes in ADC and T2 abnormalities after occlusion of the middle cerebral artery (MCAO) were therefore estimated by these two quantitative techniques. METHODS: Permanent MCAO was performed on rats. Quantitative ADC and T2 maps of brain water were obtained, from which the ischemic volumes were calculated at various times up to 48 hours after MCAO. RESULTS: The areas of decreased ADC represented 36 +/- 7% of the final infarct volume (24 hours) at 0.5 hours and 64 +/- 4% at 5 hours after MCAO, suggesting that there is recruitment of peripheral areas with disturbed energy metabolism and cytotoxic edema. The ADC and T2 contours closely matched at 3.5, 24, and 48 hours after MCAO. CONCLUSIONS: T2 imaging can assess ischemic insults as well as ADC imaging, but only 3.5 hours after the onset of ischemia. Assessment of edematous swelling (approximately 24.5% of total infarcted volume) demonstrates that ADC and therefore T2 imaging detect all the tissue that will become infarcted approximately 7 hours after occlusion. The spread of ADC and T2 abnormalities would therefore stop at approximately 7 hours, and any further increase in volume observed on the images would be mainly due to edematous swelling.

Animals↗
PubMedDate not supplied

Correction of PET data for partial volume effects in human cerebral cortex by MR imaging.

Due to the limited spatial resolution of positron emission tomography (PET), the accuracy of quantitative measurements of regional metabolism or neuroreceptor concentration is influenced by partial volume averaging of brain with CSF, bone, and scalp. This effect is increased in the presence of cortical atrophy, as in patients with Alzheimer disease (AD). Correction for this underestimation in PET measurements is necessary for the comparison of AD patients and normal controls. We have developed a method for three-dimensional correction of human PET data using magnetic resonance (MR) imaging. A composite brain tissue image is created by summing the binary representation of nine MR images, weighted to the PET z-axis line-spread function. This composite tissue image is convolved to the resolution of the PET image. The original PET image is divided by the convolved tissue image on a pixel-by-pixel basis, resulting in an atrophy-corrected PET image in which count density represents activity per volume of brain tissue rather than spatial volume. This has been performed in [11C]carfentanil mu-opiate receptor PET studies of the temporal cortex in two AD patients and one normal volunteer. After correction, average regional increases in count density were 11% (range = 4-21%) in the normal and 46% (range = 28-99%) and 48% (range = 14-109%) in the patient studies. The accuracy of this method of partial volume correction was estimated using a spherical phantom.

Aged↗
PubMed1999

Spatial and temporal summation of sensory and affective dimensions of deep somatic pain.

There is considerable evidence in support of differential information processing of the sensory-discriminative and motivational-affective meanings of pain. The purpose of this work was to examine whether temporal (acute, tonic, persistent) and spatial (local, regional, widespread) aspects of deep somatic pain influence the sensory and affective dimensions of pain. Acute pain consisted of a short bout of pain, lasting about 100 s. Tonic pain was the experience of experimentally maintained pain for 18 min. Both acute and tonic pain were induced by infusion of an algesic or control substance into muscle with the subject blinded with respect to the type of infusion and randomization of the application sequence. Comparing the response of experimental subjects to a group of matched cases with persistent masticatory myalgia alone or in combination with widespread musculoskeletal pain, we examine whether the experimental state is different from the matched clinical condition, and whether there is a difference between the condition being restricted to the face or not. The McGill pain questionnaire was used to assess the sensory and affective correlates of pain. The normalized sensory score for acute/unilateral face pain was different from that established for tonic/unilateral face pain (P = 0.055, borderline s.), and so was the normalized affective score (P = 0.009, s.). When comparing tonic/unilateral versus tonic/bilateral face pain, the affective scores increased with increased pain involvement (P = 0.009, s.) while the sensory sores were unaffected by the additional pain induced in the contralateral masseter muscle (P = 0.357, n.s). Notably, sensory and affective scores for tonic/bilateral and persistent/bilateral face pain were not statistically different (sensory: P = 0.169, n.s.; affective: P = 0.643, n.s). On the other hand, when contrasting persistent/bilateral face pain with persistent/ widespread musculoskeletal pain, both scores were significantly different (sensory: P < 0.001, s.; affective: P = 0.041, s.). Time in and spread of pain influenced the perceptual correlates of pain to a significant degree. The major increase in the sensory dimension occurred from 'no pain' to 'acute pain'. Affective scores showed the most significant increases from acute to tonic pain, particularly with greater spatial involvement. The significant increases in sensory scores observed when contrasting persistent facial pain alone and in combination with widespread musculoskeletal pain was attributed to the broader body experience. Because the perceptual correlates of tonic and matched persistent (chronic) pain states were similar, we concluded that it does not require months for the development of the sensory and affective meaning of persistent pain as assumed.

Acute Disease↗
PubMed2003

Ephrin signaling: One raft to rule them all? One raft to sort them? One raft to spread their call and in signaling bind them?

The Eph receptor tyrosine kinases (RTK) and their membrane-bound ligands, the ephrins, mediate cell-contact-dependent signaling events that control multiple aspects of metazoan embryonic development. The ephrins and their receptors regulate cell movement that is essential for forming and stabilizing the spatial organization of tissues and cell types. This includes the guidance of migrating cells or neuronal growth cones to specific targets. Although the biological responses mediated by the ephrin-Eph system were thought to be imparted by the Eph receptor via 'classical' RTK signaling pathways, there is now accumulating evidence that the ephrins are not merely ligands but have biological activity independent of the kinase activity of their cognate Eph receptor. This activity is commonly referred to as 'reverse' or 'bi-directional' signaling. Furthermore, ephrin-mediated signaling is restricted to specific membrane microdomains known as 'lipid rafts', which we believe imparts specificity to the extracellular signal. This review highlights the current data to support a role for lipid rafts in regulating aspects of ephrin-mediated signaling.

Animals↗
PubMed1998

Characterization of middle cerebral artery occlusion infarct development in the rat using fast nuclear magnetic resonance proton spectroscopic imaging and diffusion-weighted imaging.

A nuclear magnetic resonance study of the middle cerebral artery occlusion in the rat is presented. Experiments were performed on seven animals before and after occlusion, which occurred in situ. The emphasis in this study was on evaluating rapid proton spectroscopic imaging. Data were acquired with experimental durations of between 4 and 15 minutes for a 32 by 32 spatial matrix, with 64 spectroscopic data points per spatial element. The spectroscopic data were interleaved with diffusion-weighted nuclear magnetic resonance water images of the same slice. The study was terminated at about 6 hours after occlusion. The brains were then frozen in liquid nitrogen for biochemical imaging. The results showed that the signal from N-acetyl aspartate decreased and that of lactate increased within the infarcted region. The temporal course of these intensity changes varied between animals. Nineteen cortical spreading depressions (CSD) were observed by electrophysiologic monitoring during the experiments. Of these, 11 could be unambiguously detected in the lactate images, and a further 3 were on the threshold of detectability. As only a single slice could be examined, it is possible that the centers of depression for the remaining 6 CSD were outside the slice. To the authors' knowledge, this is the first report of the measurement of CSD using proton spectroscopic imaging. Thus, it is shown that this method is valuable not only in following the continuous evolution of proton metabolites with a good spatial and temporal resolution, but also in observing transient phenomena which are believed to play an important role in the expansion of the infarcted territory.

Animals↗
PubMed1982

Metabolic mapping of functional activity in the rat olfactory system after a bilateral transection of the lateral olfactory tract.

The effects of the bilateral transection of the LOT on the patterns of 2-deoxyglucose uptake within the olfactory bulb and the olfactory projections were studied in adult rats. Animals were exposed to a pure neutral odor, ethyl acetoacetate (EAA) or to a biological alarming odor, fox odor. In intact animals, the patterns of glomerular activity elicited by EAA and fox odor appeared complex. An average number of 30-40 foci of 2-DG uptake was noted in each bulb and the optical density of the foci spread out according to a continuous gradient. These patterns were largely overlapping on the lateral aspect and the third-to-posterior part of the medial aspect of the bulb. Nevertheless, they were somewhat different and the spatial distribution of the darkest foci seemed particularly relevant for the pattern recognition. In lesioned animals, the same spatial distribution of the foci as in intact rats, was observed in the lateral and the medial aspects of the bulb. Nevertheless, lesioned animals presented some quantitative changes in their patterns of glomerular labeling. Moreover, these patterns appeared different according to the biological meaning of the odor tested. The bilateral transection of the LOT brought about a very strong decrease of the optical density in the direct olfactory projections. No evident change of 2-DG uptake was noted in the different tertiary olfactory projections. These 2-DG results confirm the anatomical data relating to the LOT projections.

Amygdala↗
PubMed1982

Contrast sensitivity function and visual acuity of the opossum.

The Modulation Transfer Function (MTF) of the visual system of the opossum, D. marsupialis aurita, was determined using the amplitude of Visually Evoked Cortical Potentials (VECP) as response indicator. Stimuli consisted of a 180 degrees phase reversal of sinusoidally modulated gratings with an average luminance of 2.4 cd/m2. Contrast sensitivity was determined for various spatial frequencies and the MTF was calculated by the least square fit of an exponential function. The average acuity value obtained was 1.25 c/deg. The Fourier transform of the MTF was considered an approximation of the Line Spread Function of the visual system. The lowest value observed was 14 min of arc. The visual acuity observed in the mesopic range was not altered when stimulus intensity was raised to photopic levels.

Animals↗
PubMed2006

Origin, structure, and role of background EEG activity. Part 4: Neural frame simulation.

OBJECTIVE: To develop a method for simulating background EEG based on the premise that the self-organized activity from synaptic interaction among populations of neurons creates sustained fluctuations that can be modeled with the filtered output of a random number generator. METHODS: The logarithm of the amplitude of activity was weighted in accordance with 1/f, the log frequency in both temporal (PSD(T)) and spatial (PSD(X)) power spectral densities. The activity was spatially smoothed by volume conduction. Further deviation from full randomness was by sustained spatial coherence averaging 25% of total power. The departure from the background state to an active state, as seen in the awake EEG, was simulated by adding segments that were 90% correlated while attenuating by 50% the uncorrelated background activity in those segments. Spatial amplitude modulation was imposed on the correlated noise to create signals that simulated AM patterns. RESULTS: The statistical properties of the EEG that were replicated (Freeman, 2004a,b, 2005) included the PSD(T), PSD(X), point spread function (PSF), partitioning of the variance with PCA, and the percentages of correct classification of AM patterns. CONCLUSIONS: The origin of background EEG was traced to self-sustaining mutual excitation among pyramidal cells creating stable noise that was filtered by self-organized criticality to give 1/f(2) PSD, by inhibitory feedback to give oscillations in the classic clinical bands, and by volume conduction to give smoothing. The essential change that identified a frame in EEG was transient synchrony by phase transition among cortical populations in beta and gamma bands of the PSD(T). SIGNIFICANCE: This simulation can provide test data with which to optimize techniques for noninvasively extracting information from the EEG for diagnosis and treatment evaluation of neuropsychiatric disorders and for operation by paraplegics of prosthetic devices.

Brain↗
PubMed2004

Dynamics of DNA replication: an ultrastructural study.

DNA replication in cells takes place in domains scattered throughout the nucleoplasm. We have characterized the dynamics of DNA synthesis in synchronized mid-S-phase HeLa cells. Saponin-permeabilized cells were allowed to elongate nascent DNA chains in presence of biotin-dUTP for 5, 15, and 30 min (a pulse experiment), or for 5 min followed by an incubation with unlabeled precursors for 10 or 25 min (a pulse-and-chase experiment). The replication foci were then identified in ultrathin sections using immunogold labeling of the incorporated biotin. Total number of particles per nucleus, total scanned area of the nucleus, size, shape, and gold particle number of each labeled cluster, and the density of clusters per nucleus were evaluated. We have demonstrated that as replication proceeds, the labeled sites increase in size up to 240 nm (30 min incorporation) while maintaining a broadly round shape. In pulse-and-chase experiments the labeled DNA was shown to spread to occupy DNA foci of approximately 400 nm in diameter. These results demonstrate that DNA replication is compartmentalized within cell nuclei at the level of DNA foci and support the view that the synthetic centers are spatially constrained while the chromatin loops are dynamic during DNA synthesis.

Binding Sites↗
PubMed1998

Hydrological studies of schistosomiasis transport in Sichuan Province, China.

Schistosomiasis is a water-bourne parasitic disease endemic to Sichuan Province of China. Long-term studies of infection and disease ecology in catchments in Sichuan have been supplemented by detailed hydrometric measurements to produce a model of water velocity and flow in an irrigation system. The model provides a means of estimating travel times of two infectious stages of the parasite from source sites to water contact exposure sites for individuals of both the human population and the intermediate vector snail populations. The hydrological transport model will be part of an overall model of schistosomiasis transmission in the catchments. A GIS system is used to manage spatial data of the drainage network, land use, infection sources and population centres. The development of the Three Gorges Dam in China will increase marshlands and irrigation in areas currently free of schistosomiasis. The potential for the spread of schistosomiasis into these new areas is a major concern. Hydrological models can be of particular importance in assessing future environmental risk.

Animals↗
PubMed2003

Connectivity analysis with structural equation modelling: an example of the effects of voxel selection.

Structural equation modelling (SEM) of neuroimaging data is commonly applied to a network of distributed brain regions. We applied SEM to an fMRI dataset to identify condition-specific effects in a simple experiment composed of visual stimulation and baseline conditions. The visual network was composed of three well-defined anatomical regions (V1, V2, and V5) and three path connections (V1 --> V2, V1 --> V5, and V2 --> V5). This network was used to test four hypotheses: (1) whether the condition-specific effects for all three connections vary according to the data selected for modelling; (2) whether the "summary" measures that are often used are indeed appropriate; (3) whether measures taken from the voxel timecourse can reliably predict the condition-specific effects for each one of the three path connections, and (4) whether all voxels within an anatomical region yield equivalent SEM outcomes. There was some variability in the significance of the condition-specific effects across randomly selected voxels within regions. However, the SEM outcome from the "summary" measures was comparable to the most frequent pattern of condition-specific effects. Magnitude, delay, spread, and goodness-of-fit measures taken from a gamma fit to the voxel time courses predicted reliably the significance of the SEM condition-specific effects for each connection. This result enabled us to identify spatially coherent regions at the boundaries of V2 that displayed different condition-specific effects from those seen in the majority of the voxels. Although the generality of these results awaits further investigation, this example highlights a number of important issues for SEM. We have provided further evidence that the SEM outcome does vary somewhat according to the voxels selected and that, although the use of summary measures can give a generalised view of the connectivity pattern, they could fail to capture functional differences within specialised areas.

Adult↗
PubMed2001

Assessment of effective orifice area of prosthetic aortic valves with Doppler echocardiography: an in vivo and in vitro study.

OBJECTIVES: We sought to evaluate the Doppler assessment of effective orifice area in aortic prosthetic valves. The effective orifice area is a less flow-dependent parameter than Doppler gradients that is used to assess prosthetic valve function. However, in vivo reference values show a pronounced spread of effective orifice area and smaller orifices than expected compared with the geometric area. METHODS: Using Doppler echocardiography, we studied patients who received a bileaflet St Jude Medical valve (n = 75; St Jude Medical, Inc, St Paul, Minn) or a tilting disc Omnicarbon valve (n = 46; MedicalCV, Incorporated, Inver Grove Heights, Minn). The prosthetic valves were also investigated in vitro in a steady-flow model with Doppler and catheter measurements in the different orifices. The effective orifice area was calculated according to the continuity equation. RESULTS: In vivo, there was a wide distribution with the coefficient of variation (SD/mean x 100%) for different valve sizes ranging from 21% to 39% in the St Jude Medical valve and from 25% to 33% in the Omnicarbon valve. The differences between geometric orifice area and effective orifice area in vitro were 1.26 +/- 0.41 cm(2) for St Jude Medical and 1.17 +/- 0.38 cm(2) for Omnicarbon valves. The overall effective orifice areas and peak catheter gradients were similar: 1.35 +/- 0.37 cm(2) and 25.9 +/- 16.1 mm Hg for St Jude Medical and 1.46 +/- 0.49 cm(2) and 24.6 +/- 17.7 mm Hg for Omnicarbon. However, in St Jude Medical valves, more pressure was recovered downstream, 11.6 +/- 6.3 mm Hg versus 3.4 +/- 1.6 mm Hg in Omnicarbon valves (P =.0001). CONCLUSIONS: In the patients, we found a pronounced spread of effective orifice areas, which can be explained by measurement errors or true biologic variations. The in vitro effective orifice area was small compared with the geometric orifice area, and we suspect that nonuniformity in the spatial velocity profile causes underestimation. The St Jude Medical and Omnicarbon valves showed similar peak catheter gradients and effective orifice areas in vitro, but more pressure was recovered in the St Jude Medical valve. The effective orifice area can therefore be misleading in the assessment of prosthetic valve performance when bileaflet and tilting disc valves are compared.

Aortic Valve↗
PubMed2006

Spatial variation of mortality for common and rare cancers in Piedmont, Italy, from 1980 to 2000: a Bayesian approach.

A Bayesian hierarchical model was used to study the spatial variation in mortality risk from lung and pleural cancer in both sexes, and breast and soft tissue sarcoma (STS) in women in Piedmont (north-west Italy, average population 4 349 411) from 1980 to 2000. Of these four neoplasms, two are common (lung and breast) and two rare (pleura and STS); two have well recognized risk factors (lung and pleura) while the other two (breast and STS) have no single strong risk factor. Data were analysed at a small-area level (1206 municipalities, population 39 to 989 663), using both standardized mortality ratios and Bayesian-estimated mortality risks. The Bayesian model allowed for both heterogeneity (through spatially independent random effects) and clustering (through spatially correlated random effects) and, by borrowing information from neighbouring areas, provided stable estimates for areas with sparse data. The aim was to reduce the noise in the disease maps to highlight the true underlying mortality distribution. Lung cancer in men showed strong spatial structure with a marked east-west gradient, but no appreciable urban-rural differences. In contrast, high mortality areas for female lung cancer were observed around conurbations. Female breast cancer and STS appeared to be spread uniformly across the region. Pleural cancer mortality clusters were evident around areas with major asbestos manufacturers, or natural asbestiform fibre pollution. Maps of Bayesian-estimated mortality risk provided appreciably clearer pictures of risk distribution than did maps of the standardized mortality ratio.

Bayes Theorem↗
PubMed1997

Decidual cell regulation of hemostasis during implantation and menstruation.

Progesterone stimulation of the estradiol (E2)-primed human endometrium initiates DZ of the stromal cells around the spiral arterioles. Under continued steroid stimulation, DZ spreads wave-like to establish the decidual cell as a major cell type of the luteal phase and pregnant endometrium. Because of their widespread distribution throughout the endometrium and concentration at perivascular sites, decidual cells are spatially and temporally positioned to mediate the opposing requirements of maintaining hemostasis during endovascular trophoblast invasion, yet promoting menstrual hemorrhage in the absence of implantation. The experimental results summarized in this review indicate that the paradoxical properties manifested by endometrial stromal/decidual cells are controlled by several proteins with either hemostatic or ECM-degrading or vasoactive activity, and that their expression is altered in response to changes in levels of circulating ovarian steroids during the menstrual cycle. These conclusions are drawn primarily from studies with a well-characterized in vitro model of DZ using monolayers of stromal cells derived from specimens of predecidualized endometrium. Thus, progestins modify the expression of several DZ-related markers in the cultured stromal cells, and E2 enhances these effects despite the lack of response to E2 alone. These responses are consistent with the differential actions displayed by E2 and progesterone in vivo, by which E2 primes the endometrium for the decidualizing effects of progesterone by elevating progesterone receptor levels. Accordingly, during steroid-induced in vitro DZ, a marked increase in the expression of stromal cell TF and PAI-1 and reciprocal inhibition of tPA activity suggest mechanisms to account for the absence of hemorrhage during invasion of the endometrial vasculature by implanting trophoblasts. In contrast to steroid-induced DZ, the events of menstruation are initiated in response to a decline in circulating levels of ovarian steroids. Accordingly, subjecting in vitro decidualized stromal cells to steroid withdrawal results in pronounced reversal in the expression of all of the end points listed above. Consequently, the local hemostatic environment is transformed into a hemorrhage-promoting milieu. Taken together with vascular injury resulting from ischemia induced by spiral artery vasoconstriction, the net effect is attainment of two prerequisites for menstrual hemorrhage, vascular injury and inadequate hemostasis.

Decidua↗
PubMedDate not supplied

A high-resolution digital dosimetric system for spatial characterization of radiation fields using a thermoluminescent CaF2:Dy crystal.

A high-resolution digital dosimetric system has been developed for the spatial characterization of radiation fields. The system comprises the following: 0.5-mm-thick, 25-mm-diam CaF2:Dy thermoluminescent crystal; intensified charge coupled device video camera; video cassette recorder; and a computerized image processing subsystem. The optically flat single crystal is used as a radiation imaging device and the subsequent thermally stimulated phosphorescence is viewed by the intensified camera for further processing and analysis. Parameters governing the performance characteristics of the system were measured. A spatial resolution limit of 31 +/- 2 microns (1 sigma) corresponding to 16 +/- 1 line pairs/mm measured at the 4% level of the modulation transfer function has been achieved. The full width at half maximum of the line spread function measured independently by the slit method or derived from the edge response function was found to be 69 +/- 4 microns (1 sigma). The high resolving power, speed of readout, good precision, wide dynamic range, and the large image storage capacity make the system suitable for the digital mapping of the relative distribution of absorbed doses for various small radiation fields and the edges of larger fields.

Health Physics↗