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Results for “spatial patterning”

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PubMed1984

Spatial pattern of nerve fiber abnormality indicative of pathologic mechanism.

Estimates of the number, density, and size distribution of myelinated fibers at selected levels of roots, spinal tracts, and sampled levels of peripheral nerves may be used in the detection and characterization of alterations of motor, sensory, and autonomic neurons and their axons with development, aging and disease. Use of imaging techniques, now available, increases the reliability, versatility, and speed of such analysis. In this study, the authors evaluated the spatial pattern of fibers in sampled frames and contour areas of transverse sections of nerve fascicles, utilizing, the coefficient of variation and index of dispersion (ID), the latter extensively employed by plant ecologists. The ID was used for recognization of increased, normal, or decreased variability of density within fascicles, between fascicles, and between nerves in health and in various experimental neuropathies. In addition, various morphometric measurements were made in transverse sections at defined levels along the hind limb nerves of rats in acute and chronic ischemia, after rhizotomy and in galactose neuropathy. These stereomorphometric studies, emphasizing the number, size, shape, and spatial pattern of fibers, revealed differences among experimental neuropathies and may be found to be helpful in the characterization and prediction of pathologic mechanisms in neuropathies of unknown cause. Specifically, these approaches could be used for study of whether fiber loss in human diabetic neuropathy is multifocal and determination of the levels of such losses.

Acute Disease↗

PubMed1982

The spatial pattern of RNA in fully grown oocytes of an amphibian, Xenopus laevis.

The possibility that maternal RNA may be localized in specific oocyte regions was examined in fully grown oocytes of Xenopus laevis. These oocytes were subdivided into six regions perpendicular to their animal-vegetal axis. Each region was analyzed to determine the amount of total cellular RNA, poly(A)+RNA, and newly synthesized ribosomal RNA. As would be expected from current evidence, total cellular RNA was found to exist in a gradient-like fashion, highest at the animal pole and lowest at the vegetal pole. However, poly(A)+RNA and newly synthesized ribosomal RNA had significantly different spatial patterns from each other and from total cellular RNA. In addition, evidence suggests that newly synthesized ribosomal RNA requires two to three days before it is uniformly distributed within the oocyte. These results suggest that a mechanism may exist to create different spatial patterns for different classes of RNA.

Animals↗

PubMed1992

Temporal and spatial patterns of expression of laminin, chondroitin sulphate proteoglycan and HNK-1 immunoreactivity during regeneration in the goldfish optic nerve.

Current views suggest that the extracellular environment is critically important for successful axonal regeneration in the CNS. The goldfish optic nerve readily regenerates, indicating the presence of an environment that supports regeneration. An analysis of changes that occur during regeneration in this model may help identify those molecules that contribute to a favourable environment for axonal regrowth. We examined the distribution and expression of two extracellular matrix molecules, laminin and chondroitin sulphate proteoglycan, and a carbohydrate epitope shared by a family of adhesion molecules (HNK-1), using immunocytochemical detection in sections from the normal adult goldfish optic nerve and in nerves from one hour to five months following optic nerve crush. We also used in vitro preparations to determine if neurites in retinal explants could express these same molecules. The linear distributions of laminin and chondroitin sulphate proteoglycan immunoreactivity in control optic nerves are co-extensive with the glia limitans, suggesting both are expressed by non-neuronal components surrounding the axon fascicles. Between one and three weeks postoperatively when axons elongate and reach their target, laminin and chondroitin sulphate proteoglycan immunoreactivity increases around the crush site and distally. At six weeks postoperatively the pattern of immunoreactivity has returned to normal. While the temporal pattern of changes in immunoreactivity is similar, the spatial pattern of these two extracellular proteins in the regenerating nerve differs. Chondroitin sulphate proteoglycan immunoreactivity is organized in discrete columns associated with regenerating axons while laminin immunoreactivity is more diffusely distributed. Examination of retinal explants reveals growing neurites express chondroitin sulphate proteoglycan but not laminin. Our results suggest that laminin is only associated with non-neuronal cells, while chondroitin sulphate proteoglycan is associated with axons as well as non-neuronal cells. HNK-1 immunoreactivity is co-extensive with both the glia limitans and axon fascicles and is more extensively distributed in the intact nerve than either laminin or chondroitin sulphate proteoglycan immunoreactivity. In contrast to laminin and chondroitin sulphate proteoglycan, HNK-1 immunoreactivity is substantially decreased at the crush site within one week following optic nerve crush. HNK-1 immunoreactivity reappears through the crush site during the next several weeks, although non-immunoreactive regions, co-extensive with areas predominantly containing non-neuronal cells, persist both proximal and distal to the crush, up to six weeks postoperatively. The pattern suggests that HNK-1 epitope expression by these non-neuronal cells is decreased during axonal regeneration.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1989

Spatial patterns and ESS's.

The classical idea of an evolutionarily stable strategy (ESS) does not involve any spatial dependence. An evolution equation for analyzing games in a region is suggested and the possibility of spatial patterns is investigated. It is shown that an ESS is so stable that it forbids any spatial dependence but that other equilibria may have patterns associated with them if the dispersion rates are suitably chosen.

Biological Evolution↗

PubMed1988

Spatial pattern representation and transformation in monkey somatosensory cortex.

Embossed letters, used previously in pattern recognition experiments in humans, were used to study the spatial patterns of neural activity evoked in peripheral fibers and cortical neurons in areas 3b and 1 of the primary somatosensory cortex of alert rhesus (Macaca mulatta) monkeys. The object was to investigate the representation and transformation of spatial information during the early stages of peripheral and cortical neural processing. Our method consisted of sweeping each letter of the alphabet across the skin repeatedly and constructing a two-dimensional plot (called a spatial event plot) of the action potentials evoked in afferent fibers and cortical neurons. By using this method, slowly and rapidly adapting primary afferents were shown to transmit isomorphic neural images of the letters. Although the slowly adapting images were more spatially acute, both populations conveyed images of sufficient quality to account for human psychophysical performance. In the cortical areas studied, the slowly adapting neurons of area 3b stood out for the acuity, complexity, and variety of their responses. Some of the spatial event plots for these neurons were isomorphic and at least as acute as those obtained from any primary afferent. Others were highly structured but nonisomorphic. The quality and variety of responses in area 3b slowly adapting neurons suggest that they play an important role in the processing of information underlying tactual pattern recognition. The rapidly adapting neurons of area 3b and all types of neurons in area 1 yield much less structured and differentiated responses.

Animals↗

PubMed1992

Spatial patterns of spinal cord [14C]-2-deoxyglucose metabolic activity in a rat model of painful peripheral mononeuropathy.

Spatial patterns of spinal cord glucose metabolic activity were examined in unanesthetized rats with painful peripheral mononeuropathy produced by sciatic nerve ligation (chronic constrictive injury, CCI). Spinal cord metabolic activity was assessed 10 days after nerve ligation by using the fully quantitative [14C]2-deoxyglucose technique. This technique allows simultaneous examination of both neural activity inferred from local glucose utilization and its spatial distribution in multiple spinal regions previously implicated in nociceptive processing. Rats used in the experiment exhibited thermal hyperalgesia to radiant heat applied to the hind paw ipsilateral to nerve ligation and behaviors indicative of spontaneous pain. Sciatic nerve ligation produced a significant increase in spinal cord metabolic activity in four sampling regions (laminae I-IV, V-VI, VII and VIII-IX) of lumbar segments compared to sham-operated rats. The pattern of altered metabolic activity in CCI rats presented 3 distinct features. (1) The spinal cord grey matter both ipsilateral and contralateral to nerve ligation exhibited substantial increases in metabolic activity compared to sham-operated rats. (2) This increase in metabolic activity was somatotopically specific, i.e., higher metabolic rates were observed on the side ipsilateral to nerve ligation than on the contralateral side, and higher metabolic rates were seen in the medial portion of the ipsilateral spinal cord dorsal horn than in the lateral portion. The peak metabolic activity occurred in laminae V-VI of CCI rats, a region involved in nociceptive processing. (3) The increase in spinal cord metabolic activity of CCI rats extended from lumbar segment L1 to L5 in all 4 sampling regions. The substantial increase in metabolic activity in both the ipsilateral and contralateral spinal cord that occurs over an extensive rostro-caudal area in CCI rats may represent a unique pattern of spinal cord metabolic activity distinct from that observed in rats exposed to acute thermal pain. This pattern of spinal cord neural activity in CCI rats may reflect possible radiation of neuropathic pain. In addition, the procedure of curare-induced paralysis in a separate group of CCI rats did not change the extent and patterns of metabolic activity seen in non-paralyzed CCI rats, reflecting a minimal influence of the afferent feedback from flexor motor reflexes on spinal cord metabolic activity following sciatic nerve ligation. This chronic increase in spinal cord neural activity in the absence of overt peripheral stimulation suggests a spinal cord hyperactive state and may account for behaviors suggestive of spontaneous pain in CCI rats.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMedDate not supplied

[Spatial pattern and consequences of demographic aging processes for regional planning].

The spatial dimension of man-environment interactions in old age is analyzed within urban, suburban, and rural residential environments of the German Rhine-Main-Agglomeration. By comparing the three levels of organization, utilization, and interpretation, housing conditions as well as geographical distribution and redistribution (migrations) our outside-home-activities and environmental perception show a fundamental influence on the everyday lives of the 750 elderly who were interviewed. The majority of the target population and, especially, the rural elderly is characterized by traditional patterns of spatial organization and distribution, mobility, regional attachment, and a concern about preserving the stability of their current residential environment from changes. The suburban and urban seniors, however, exhibit a greater amount of locational flexibility and utility-oriented behavior patterns. These spatial variations are induced by specific regional values and intensity of local and regional identification. They might be interpreted as different stages in the process of modernization within postindustrial societies. Reflecting, however, the paradigms of planning for the elderly, these different patterns are not systematically considered to the necessary and sufficient extent. Instead of promoting regional or local networks that are favored by senior citizens, agencies usually prefer comprehensive approaches on a macrolevel. First steps to improve this situation and to combine life- and system-world demands have been taken by the federal government, which implemented a neighborhood-related research program on housing for the elderly. As a result of this, further research on environmental aspects on aging should pay more methodological attention to the hitherto neglected regional and local level, and also for the transfer of its findings into planning policy.

Aged↗

PubMed1976

Spatial patterning of response to odors in the peripheral olfactory system.

The low odor specificities of the olfactory receptors suggest that odor recognition depends on the simultaneous activity in an ensemble of receptor neurons. This ensemble could conceivably code quality without reference to the point of origin of each input on the receptor sheet. However, the nose-to-bulb projection appears sufficiently precise to provide the bulb with a topographical map of the receptor sheet although it is poorly delineated in the anteroposterior plane. (It is also known that the morphological changes that follow prolonged exposure to odors are more differentiated in the coronal than in the anteroposterior plane.) Furthermore, it is clear from work at both epithelial and bulbar levels that a spatiotemporal pattern of excitation is generated by odor stimulation of the receptor sheet and that this pattern differs for different odors. This evidence, then, supports the view that there is a spatial component to odor quality coding. This spatial pattern has two elements. One is imposed and depends (at least in part) on differences in the retentivity of different odorants by the mucous sheet, which has powerful sorptive properties. It effectiveness seems particularly weak for odorants with relatively long retention times. The second component is inherent and depends on the tendency of receptors with similar peak odor specificities to aggregate in the same region (or regions) of the epithelium. Different odors or groups of odors maximally excite different regions, which may overlap. The imposed component could not, in itself, provide an adequate mechanism for odor recognition, partly because many compounds have comparable or even identical mean retention times (e.g., enantiomeric isomers). The inherent component, on the other hand, possesses this potential. However, either or both forms of patterning may cooperate with a third nonspatial mechanism (based on differential responsiveness of receptors to different odors) in coding odor quality.

Animals↗

PubMed1983

Relationships between speed, accuracy of performance and hemispheric superiorities for visuo-spatial pattern processing in the two sexes.

The aim of this study was to investigate the relationship between visual field differences in tachistoscopic recognition of visuo-spatial patterns and overall proficiency in the two sexes. The results demonstrated a left visual field advantage in males but not in females. A female subgroup showed opposite rather than lacking visual field superiorities without affecting speed and accuracy of performance. These data warn against explaining differences in performance in the two sexes in terms of different hemispheric asymmetries.

Achievement↗

PubMed1991

Capillary spatial pattern and muscle fiber geometry in three hamster striated muscles.

Since most oxygen exchange in muscle is thought to occur by diffusion across the walls of capillaries, it is important to determine the spatial relationship between capillaries and muscle fibers. We have extended the work of Kayar et al. (Microvasc. Res 24: 326-341, 1982) to include other statistical tests that allow one to make stronger statements regarding the spatial pattern. Data for hamsters were obtained from two sartorius, three retractor, and five soleus muscle sections. Distances between all pairs of capillaries, distances between a capillary and its first nearest neighbor for all capillaries, and distances between random tissue sample points and the closest capillary were used to test the spatial arrangement of capillaries. The null hypothesis tested of complete spatial randomness of capillary locations was rejected in favor of a regular alternative in one each of the sartorius and retractor fields and in all five soleus fields. We formulated a geometric model, composed of a space-filling array of identical hexagonal muscle fibers with capillaries placed randomly at the juncture of three fibers or between two fibers, according to the observed relative probability of those occurrences. The model simulations of muscle fibers and capillaries were then analyzed by the same statistical tests used on the histological sections. The findings were similar in both cases, providing confidence that the assumptions of the model were sufficient approximations. The results of this study provide a basis for the placement of capillaries around muscle fibers in mathematical models of oxygen transport in capillary networks.

Animals↗

PubMed1986

Spatial patterning in Polysphondylium: monoclonal antibodies specific for whorl prepatterns.

In this report we describe three monoclonal antibodies which detect prepatterning events preceding the appearance of visible tips in Polysphondylium pallidum whorls. A spatial and temporal analysis of the antigens against which these antibodies are directed reveals that the radial distribution of arms within whorls has its origins in an initial global amplification of tip-specific antigens over the surface of very early whorl masses. This two-dimensional distribution becomes restricted with time to a single dimension, a smooth distribution of antigen in a band about the equator of the whorl mass. This equatorial distribution breaks up into patches which eventually become visible tips. These results reveal that a spatial pattern can arise from a smooth prepattern, and grow through a series of intermediates characteristic of the symmetry breaking model first described by A. Turing (1952).

Antibodies, Monoclonal↗

PubMed1987

Spatial patterns of visual cortical fast EEG during conditioned reflex in a rhesus monkey.

A preliminary assay was made of the existence of time-space coherence patterns of fast EEG activity in the visual cortex of a Rhesus monkey. The primary intent of the present study was to evaluate the similarities and differences in relation to the olfactory bulb, where such coherences have been described and have been demonstrated to be associated with behaviour. Segments 1.5 s in duration were recorded simultaneously without averaging from 16 to 35 subdural electrodes fixed over the left occipital lobe in an array 3.6 cm X 2.8 cm. Each segment was taken during the delivery of a visual conditioned stimulus (CS) and the performance of a conditioned response (CR) by a well-trained Rhesus monkey. The EEGs appeared chaotic with irregular bursts lasting 75-200 ms, resembling those in the olfactory EEG but with lower peak frequencies. Fourier spectra showed broad distributions of power resembling '1/f noise' with multiple peaks in the range of 20-40 Hz. Time intervals were selected where coherent activity seemed to be present at a number of electrodes. A dominant component waveform that was common to all channels was extracted by principal components analysis (PCA) of each segment. The distribution of the power of this component across the electrodes (the factor loadings) was used to describe the spatial pattern of the coherent cortical activity. Statistical analyses suggested that different patterns could be associated to the CS and the CR, as has been found in the olfactory system. These patterns remained stable over a 6 week recording interval. The patterns can be better discriminated, when the factor loadings of each channel are normalized to zero mean and unit variance, to discard a basic pattern of power distribution, which may reflect anatomical and electrode positioning factors that are related to behavioral information processing by the cortex. The wide spatial distribution of the common patterns found suggests that EEG patterns that manifest differing states of the visual cortex may also be accessible with scalp electrodes.

Animals↗

PubMed1976

High reliability rates of spatial pattern analysis by vectorcardiogram in assessing the severity of eccentric left ventricular hypertrophy.

In 33 patients, including 12 control subjects and 21 with eccentric LVH, LV mass determined by angiocardiogram was correlated to 26 VCG measurements (Frank system) calculated from the scalar X, Y, and Z leads. The results demonstrated that the most reliable indices of VCG in assessing the severity of eccentric LVH determined by angiocardiogram were the magnitude of the spatial mean QRS vector and the time of the spatial maximal QRS vector ("spatial VAT"), of which correlation coefficients were 0.93 and 0.93, respectively. Such high correlation coefficients have never been obtained with the usual ECG analysis. These findings strongly suggest that (1) increased QRS voltage and usual prolonged QRS duration in eccentric LVH are due to an increase in LV mass, and (2) prolonged VAT observed in eccentric LVH is closely related to an anatomic alteration, namely, the greater distance of intra-ventricular conducting pathways as the result of LV dilatation, as an increase in LV mass is usually paralleled by the grade of the chamber enlargement in this type of LVH. Regarding the T loop, correlations between the LV mass and the VCG measurements were less as compared to those of the QRS loop. In general, T changes in moderate or severe LVH may be also related to a certain altered cardiac muscle state, in addition to an increase in LV mass. Angiocardiographic and light microscopic findings of a patient with eccentric LVH in whom a widened QRS-T angle was demonstrated to an extent much more than that expected with an increase in LV mass are presented and discussed. The spatial pattern analysis by VCG is very useful and reliable in assessing the severity of eccentric LVH.

Adolescent↗

PubMed1991

The spatial pattern of the synaptic vesicular apparatus as a correlate of transmitter storage models.

A statistical stereological approach which allows one to derive a three-dimensional pattern of synaptic vesicle accumulation in relation to the active zone from an analysis of electron micrograms (random sections) of synapses is described. This approach is illustrated with a study of presynaptic terminals from the dorsal horn of the cat spinal cord, based on the morphometrical treatment of 105 micrographs containing 5190 synaptic vesicles. The spatial pattern obtained was found to have a bimodal shape, which can be considered a possible structural correlate of the two-pool model of transmitter storage. The connection of similar quantitative estimates with physiological data is discussed.

Animals↗

PubMed1990

Spatial patterns of use of health services in the Kingston metropolitan area, Jamaica.

This study focuses on the influence of distance, transport and accessibility on the use of health services in Kingston, Jamaica. It reviews various factors affecting the use of health care with particular reference to Third World cities and presents results from a case study of utilization in the Kingston Metropolitan Area. Three pairs of sites of contrasting social status were selected and 50 respondents questioned in each about spatial patterns of primary health care (PHC) attendance. Types of facility attended, mode of transport, travel times, distance and frequency of utilization were discussed. Some distinctive differences appeared between low and high status site respondents with regard to distances to facilities and travel times, which were almost always higher for the low status respondents. Most respondents were not using their nearest facilities, for varying reasons which included, for poorer respondents, need to attend frequently distant public facilities and, for wealthier respondents, loyalty to old family doctors and use of company-related doctors. The mobility of the higher status respondents afforded them considerable choice of locations used for health care and their attendance was much more convenient than that of lower status respondents. Utilization rates were somewhat higher in the high status sites although not to the extent found by some earlier studies in similar settings.

Developing Countries↗

PubMed1986

Chemical dependencies of learning in the rabbit olfactory bulb: acquisition of the transient spatial pattern change depends on norepinephrine.

Intracerebral cannulas were implanted in both olfactory bulbs of 6 rabbits. A surface electrode-array (8 X 8) was implanted epidurally on the lateral surface of the left bulb. Each rabbit was conditioned to respond to sniffing to an odor paired with cutaneous shock while receiving continuous intrabulbar infusion of either vehicle or propranolol (100 microM at 1 microliter/hr) in vehicle. After two training sessions to the original odor, a response to a new odor was conditioned under the influence of the alternate infusate. Electroencephalographic (EEG) activity was sampled on inspirations before and during odor presentations. During vehicle infusion a transient alteration in the pattern of activity was acquired that occurred during the second and third inspirations following presentation of the reinforced odor. The acquisition did not occur when propranolol was infused. No significant pattern changes occurred with unreinforced odors in either condition. There was no local anesthetic effect of the racemic mixture of propranolol found for any type of electric activity, including antidromic spike activity observed in an independent control group. Intrabulbar norepinephrine injection (100 microM, 10 microL) resulted in an amplitude increase of the bulbar 40-80-Hz EEG and a potentiation of the transient spatial pattern change to a novel odor, when compared with those observed during vehicle infusion. It is concluded that norepinephrine released under centrifugal control may act to prevent or delay habituation that otherwise occurs rapidly to unreinforced odors.

Animals↗

PubMed1987

Changing spatial patterns of DNA replication in the developing wing of Drosophila.

Using an antibody against bromodeoxyuridine we have analyzed the distribution of S-phase nuclei in the wing disc of Drosophila as the larval disc transforms into the adult wing during metamorphosis. On the basis of the timing of replication three cell populations can be distinguished: the cells of the presumptive wing margin, the precursor cells of the longitudinal veins, and those of the intervein regions. In each of these populations the cell cycle is first arrested and later resumes at a specific time, so that at each developmental time point a characteristic spatial pattern of S-phase nuclei is seen. An interpretation of these changing patterns in terms of vein formation, compartments, and neural development is offered.

Animals↗

PubMed1986

Spatial pattern of catalase (Cat2) gene activation in scutella during postgerminative development in maize.

The scutellum of maize is a fully differentiated, nondividing, diploid embryonic tissue. Two distinct structural genes (Cat1 and Cat2) encoding the enzyme catalase (CAT) are differentially expressed in this tissue during postgerminative development. As development proceeds, the expression of Cat1 diminishes, while that of Cat2 is enhanced, leading to the disappearance of the CAT-1 protein and the gradual accumulation of the CAT-2 protein. The present investigation was undertaken to determine whether all scutellar cells may be genetically programmed to activate expression of Cat2 synchronously or whether there is an asynchronous spatial gradient of Cat2 activation. By using immunofluorescence microscopy and anti-CAT-2 IgG, we have found that a gradient of Cat2 activation occurs within the scutellar cell mass during postgerminative development. The gradient of Cat2 activation occurs from the outer perimeter of the tissue inward toward the embryonic axis. To determine a potential site of origin for any putative "triggering signal" for Cat2 activation, we demonstrated that Cat2 is expressed in the single layer of aleurone cells prior to its expression in any other tissue during kernel development. To our knowledge, this is the first observation of a gradient-type spatial pattern of a eukaryote gene activation occurring in a stable, virtually nondividing tissue such as the maize scutellum. The significance of these results with respect to developmental gene regulation is discussed.

Catalase↗