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PubMed2006

Embryological ontogeny of aromatase gene expression in Chrysemys picta and Apalone mutica turtles: comparative patterns within and across temperature-dependent and genotypic sex-determining mechanisms.

Although the role of aromatase in many estrogen-dependent reproductive and metabolic functions is well documented in vertebrates, its involvement in the ovarian development of species exhibiting temperature-dependent sex determination (TSD) is incompletely understood. This is partly due to the conflicting temporal and spatial pattern of aromatase expression and activity across taxa. To help resolve this ongoing debate, we compared for the first time the embryological ontogeny of aromatase expression in turtles possessing genotypic sex determination (GSD) (Apalone mutica) and TSD (Chrysemys picta) incubated under identical conditions. As anticipated, we found no significant thermal differences in aromatase expression at any stage examined (prior to until the end of the thermosensitive period) in A. mutica. Surprisingly, the same was true for C. picta. When placed in a phylogenetic context, our results suggest that aromatase expression is evolutionarily plastic with respect to sex determination in reptiles, and that differences between reptilian TSD and GSD are not aromatase-driven. Further research across TSD and GSD species is warranted to fully decipher the evolution of functional differences among sex-determining mechanisms.

Animals↗
PubMed1997

In situ polymerase chain reaction-based localization studies support role of human herpesvirus-8 as the cause of two AIDS-related neoplasms: Kaposi's sarcoma and body cavity lymphoma.

Several lines of investigation point to a new herpesvirus, human herpesvirus-8 (HHV-8), as the cause of two different neoplasms seen in AIDS patients-Kaposi's sarcoma (KS) and body cavity B cell lymphoma. If this virus is the etiological agent, rather than another opportunistic infectious agent, it should be present in the earliest detectable clinical lesions on a temporal basis, and localize to specific target cells in a spatial pattern consistent with tumorigenic pathways. In this study, we take advantage of the clinical accessibility to biopsy early (patch stage) skin lesions of KS to address the temporal issue, combined with in situ PCR and dual immunostaining using a marker identifying malignant cells, to address the spatial localization issue. 21 different tissue samples were subjected to PCR analysis and in situ PCR with and without simultaneous immunostaining. In normal skin from healthy individuals, no HHV-8 DNA was detected by PCR or in situ PCR. However, in all PCR-positive tissues, distinct and specific in situ PCR staining was observed. In four different patch stage KS lesions, in situ PCR staining localized to nuclei of endothelial cells and perivascular spindle-shaped tumor cells. Later stage KS lesions (plaques and nodules) revealed additional positive cells, including epidermal keratinocytes (four of five), and eccrine epithelia (two of four). These patterns were nonrestricted to skin, as pulmonary KS also revealed HHV-8-specific infection of endothelial cells and KS tumor cells, as well as epithelioid pneumocytes (two of two). In body cavity B cell lymphoma by dual staining, HHV-8 was present in malignant tumor cells (EMA immunostained positive) and not in reactive lymphocytes. These results reveal an early temporal onset and nonrandom tissue and cellular distribution pattern for HHV-8 infection that is consistent with a causal link between this DNA virus and two AIDS-related neoplasms.

DNA, Viral↗
PubMed2006

Generation of cell diversity and segmental pattern in the embryonic central nervous system of Drosophila.

Development of the central nervous system (CNS) involves the transformation of a two-dimensional epithelial sheet of uniform ectodermal cells, the neuroectoderm, into a highly complex three-dimensional structure consisting of a huge variety of different neural cell types. Characteristic numbers of each cell type become arranged in reproducible spatial patterns, which is a prerequisite for the establishment of specific functional contacts. The fruitfly Drosophila is a suitable model to approach the mechanisms controlling the generation of cell diversity and pattern in the developing CNS, as it allows linking of gene function to individually identifiable cells. This review addresses aspects of the formation and specification of neural stem cells (neuroblasts) in Drosophila in the light of recent studies on their segmental diversification.

Animals↗
PubMed2003

A GIS model of subsurface water potential for aquatic resource inventory, assessment, and environmental management.

Biological, chemical, and physical attributes of aquatic ecosystems are often strongly influenced by groundwater sources. Nonetheless, widespread access to predictions of subsurface contributions to rivers, lakes, and wetlands at a scale useful to environmental managers is generally lacking. In this paper, we describe a "neighborhood analysis" approach for estimating topographic constraints on spatial patterns of recharge and discharge and discuss how this index has proven useful in research, management, and conservation contexts. The Michigan Rivers Inventory subsurface flux model (MRI-DARCY) used digital elevation and hydraulic conductivity inferred from mapped surficial geology to estimate spatial pattems of hydraulic potential. Model predictions were calculated in units of specific discharge (meters per day) for a 30-m-cell raster map and interpreted as an index of potential subsurface water flux (shallow groundwater and event through-flow). The model was evaluated by comparison with measurements of groundwater-related attributes at watershed, stream segment, and local spatial scales throughout Lower Michigan (USA). Map-based predictions using MRI-DARCY accounted for 85% of the observed variation in base flow from 128 USGS gauges, 69% of the observed variation in discharge accrual from 48 river segments, and 29% of the residual variation in local groundwater flux from 33 locations as measured by hyporheic temperature profiles after factoring out the effects of climate. Although it does not incorporate any information about the actual water table surface, by quantifying spatial variation of key constraints on groundwater-related attributes, the model provides strata for more intensive study, as well as a useful spatial tool for regional and local conservation planning, fisheries management, wetland characterization, and stream assessment.

Conservation of Natural Resources↗
PubMed1985

Simple and B-cells in cat striate cortex. Complementarity of responses to moving light and dark bars.

This report is based on the quantitatively recorded responses of 72 striate cells in the simple (S and SH) and B-cell (B and BH) families to narrow (0.14 degrees) moving light and dark bars. Cells were regarded as hypercomplex (SH and BH) if the end-zone inhibition reduced the response to 50% of its peak value. The contrast of the bars was relatively low and matched to be equal but opposite for the two kinds of bar. Average response histograms to the two kinds of bar were recorded separately and only subsequently combined. The response histogram from a given S- or SH-cell shows separate response peaks to the light and dark bars. The number of peaks varies from two to five in different cells. Cells with two response peaks were encountered most commonly (54%), and rather less common were cells with three (31%), four (7.5%), and five (7.5%) peaks. By defining the sequence of the response peaks according to the direction preferred by a moving light bar, the number of distinct spatial patterns of responses to the moving bars increases from four to eight since the first response in the sequence can be either to a light bar or to a dark bar. Examples of all eight responses have been recorded. For cells in the simple family with two response peaks, as well as for B-cells, the width of the light-bar peak was the same as, or closely similar to, that of the dark-bar peak. For S- and SH-cells with more than two response peaks this was also true for the two principal peaks, namely the largest and the next-largest immediately adjacent peak. In the simple family, the mean widths of the two principal response peaks remained closely similar despite the progressive decrease in their respective widths as the number of peaks in the pattern increased from two to five. The mean width of the two principal response peaks from S- and SH-cells (0.6 degrees) was significantly less than the mean width for B-cells (1.4 degrees). For simple-family cells the spatial overlap between the two principal peaks (mean 14%) was always less than 50% of the overall width of the two peaks, whereas for B-cells the overlap (mean 79%) was always greater than 50%. For cells in both the simple and B-cell families the length of the receptive field as given by a moving light bar is the same as that given by a moving dark bar.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed2004

Spacing patterns on tongue surface-gustatory papilla.

The dorsal surface of the mammalian tongue is covered with four kinds of papillae, fungiform, circumvallate, foliate and filiform papillae. With the exception of the filiform papillae, these types of papillae contain taste buds and are known as the gustatory papillae. The gustatory papillae are distributed over the tongue surface in a distinct spatial pattern. The circumvallate and foliate papillae are positioned in the central and lateral regions respectively and the fungiform papillae are distributed on the anterior part of the tongue in a stereotyped array. The patterned distribution and developmental processes of the fungiform papillae indicate some similarity between the fungiform papillae and the other epithelial appendages, including the teeth, feathers and hair. This is because 1) prior to the morphological changes, the signaling molecules are expressed in the fungiform papillae forming area with a stereotyped pattern; 2) the morphogenesis of the fungiform papillae showed specific structures in early development, such as epithelial thickening and mesenchymal condensation and 3) the fungiform papillae develop through reciprocal interactions between the epithelium and mesenchymal tissue. These results led us to examine whether or not the early organogenesis of the fungiform papillae is a good model system for understanding both the spacing pattern and the epithelial-mesenchymal interaction during embryogenesis.

Animals↗
PubMed2005

Temporal patterns of fos expression in the dentate gyrus after spontaneous seizures in a mouse model of temporal lobe epilepsy.

Identifying the brain regions and neuronal cell types that become active at the time of spontaneous seizures remains an important challenge for epilepsy research, and the involvement of dentate granule cells in early seizure events continues to be debated. Although Fos expression is commonly used to evaluate patterns of neuronal activation, there have been few studies of Fos localization after spontaneous seizures. Thus, in a pilocarpine model of recurrent seizures in C57BL/6 mice, Fos expression was examined at multiple time points after spontaneous seizures to follow the temporal and spatial patterns of Fos activation. By 15 min after the beginning of a spontaneous behavioral seizure, Fos labeling was evident in dentate granule cells. This labeling was particularly striking because of its wide extent and relatively uniform appearance in the granule cell layer. At later time points, from 30 min to 4 h after a spontaneous seizure, Fos labeling was also detected in interneurons within the dentate gyrus and in widespread regions of the temporal lobe. Interestingly, the timing of Fos activation appeared to differ among different types of GABAergic interneurons in the dentate gyrus, with labeling of parvalbumin neurons along the base of the granule cell layer preceding that of GABA neurons in the molecular layer. The findings in this mouse model are consistent with previous suggestions that spontaneous seizures in temporal lobe epilepsy may result from a periodic breakdown of the normal filter functions of the dentate gyrus and a resulting increase in hypersynchronous activity of dentate granule cells.

Animals↗
PubMed2006

Effects of sensing behavior on a latency code.

Sensory information is often acquired through active exploration, yet relatively little is known about how neurons encode sensory stimuli in the context of natural patterns of sensing behavior. We examined the effects of sensing behavior on a spike latency code in the active electrosensory system of mormyrid fish. These fish actively probe their environment by emitting brief electric organ discharge (EOD) pulses. Nearby objects alter the spatial pattern of current flowing through the skin. These changes are encoded by small shifts in the latency of individual electroreceptor afferent spikes after the EOD. In nature, the temporal pattern of EOD intervals is highly structured and varies depending on the behavioral context. We performed experiments in which we varied both the EOD amplitude and the intervals between EODs to understand how sensing behavior affects afferent latency coding. We use white-noise stimuli and linear filter estimation methods to develop simple models characterizing the dependence of afferent spike latency on the preceding sequence of EOD intervals and amplitudes. Comparing the predictions of these models with actual afferent responses for natural patterns of EOD intervals and amplitudes reveals an unexpectedly rich interplay between sensing behavior and stimulus encoding. Implications of our results for how afferent spike latency is decoded at central stages of electrosensory processing are discussed.

Action Potentials↗
PubMed1995

Signal transduction by cAMP-dependent protein kinase A in Drosophila limb patterning.

Interaction between distinctly specified cells in adjacent compartments establishes organizing centres that control growth and specify cell fate in the developing limbs of Drosophila. Localized expression of the secreted Hedgehog protein (Hh) by cells in the posterior compartment induces expression of the secreted signalling molecules decapentaplegic (dpp) or wingless (wg) in nearby anterior cells. wg and dpp in turn organize spatial pattern in the wing and leg imaginal discs. The Hh signal is thought to act by antagonizing the ability of the patched (ptc) gene product to repress wg and dpp expression. Here we present evidence that removing activity of the gene encoding cyclic AMP-dependent protein kinase A (pka) is functionally equivalent to removing ptc activity or to providing cells with the Hh signal. These findings suggest that cyclic AMP-dependent protein kinase A is a component of the signal transduction pathway through which Hh and Ptc direct localized expression of dpp (or wg) and establish the compartment boundary organizer.

Alleles↗
PubMed2004

Stripe patterns in two-dimensional systems with core-corona molecular architecture.

The behavior of a two-dimensional system of particles interacting through a potential consisting of a hard core surrounded by a soft repulsive corona is investigated at several densities and temperatures. We find that the competition between hard and soft repulsions gives origin to the spontaneous formation of spatial patterns resembling stripe textures. The effect of varying the hard and soft core radii ratio as well as that of adding an attractive component to the interparticle interaction is studied. The model investigated is relevant for macromolecular topologies possessing two intrinsic length scales.

Journal Article↗
PubMedDate not supplied

Patterns of excitotoxin-induced brain lesions in the newborn rabbit: a neuropathological and MRI correlation.

There is pressing need to employ new advances in structural MR brain imaging to better diagnose brain damage in newborn infants. Timely application of such technology will enable improved therapeutic interventions. Diffusion-weighted sequences are a sensitive marker of very early neuronal injury, the spatial pattern of which provides critical information regarding the underlying pathophysiology. We have modified our murine model of excitotoxic neonatal brain injury to the rabbit, an animal whose brain is larger and where the neuroanatomic organization of the subcortical white matter more closely resembles that of the human. Utilizing this rabbit model, we undertook an MRI/histopathologic correlation. We found that as with the mouse, there is a spatiotemporal selectivity to the pattern of brain injury, and that the period from postnatal day (P) 7 to P9 in rabbits corresponds to the time of maximum vulnerability of the brain to excitotoxic white matter damage, which neuropathologically simulates periventricular leukomalacia (PVL). We additionally noted that diffusion-weighted imaging provided the most sensitive means of detecting such lesions and that this method was sensitive to structural maturational changes accompanying the normal cortical ontogeny. Taken together, our findings suggest that this rabbit model of perinatal excitotoxic brain injury will be a valuable addition to experimental approaches to further our understanding of perinatal brain damage, that diffusion-weighted imaging will be an invaluable adjunct to the diagnosis of such injury, and that therapeutic strategies aimed at interrupting the evolution of PVL should include targeting the pathophysiologic cascade induced by excitotoxic neonatal brain injury.

Animals↗
PubMed2000

Ecological symmetry breaking can favour the evolution of altruism in an action-response game.

The evolution of altruistic behaviour is studied in a simple action-response game with a tunable degree of conflict of interest. It is shown that for the continuous, mixed-medium approach no stable polymorphism favours altruism. Ecological dynamics are explored with the addition of a spatial dimension and a local energy variable. A continuous spatial model with finite local range does not introduce any substantial difference in the results with respect to the level of altruism. However, the model illustrates how ecological coupling may lead to the formation of stable spatial patterns in the form of discrete and isolated clusters of players as a consequence of inverse density dependence. A discrete, individual-based model is built in which local interactions are also modelled as occurring within a finite neighbourhood of each individual and spatial positions are not restricted as in lattice models. This model shows substantially different results. A high level of altruism is observed for low (but positive) degrees of conflict and this level decreases linearly for higher degrees of conflict. The evolution of altruism is explained by studying the broken symmetries introduced by the spatial clusters themselves, mainly between their central and peripheral regions which, in combination with the discrete and the stochastic nature of the model, result in the stabilization of strategies in which players behave altruistically towards the same type. As a consequence of the activity of the players, energy resources at the centre of an altruistic cluster are very depleted; so much so that, for low conflict, fitter non-altruistic mutants may initially invade only to become locally extinct due to their less efficient use of energy as their numbers increase. In peripheral regions invader may subsist; however, for geometrical reasons long-lasting genealogies tend to originate only at the centre of a cluster.

Altruism↗
PubMed1985

Behavioral effects of xylamine-induced depletions of brain norepinephrine: interaction with LSD.

Male rats were treated with a combination of systemic fluoxetine and intraventricular xylamine (under ether anesthesia) to deplete brain norepinephrine (NE) in the projection areas of the locus coeruleus. Four days later, control and lesioned rats were tested following injections of either saline or 80 micrograms/kg LSD in a Behavioral Pattern Monitor which recorded the sequential patterns of their locomotor and investigatory (holepokes) responses. Liquid chromatographic measures of brain monoamines confirmed that xylamine reduced hippocampal NE by 80.8% and hypothalamic NE by 26% without affecting levels of serotonin or dopamine. Relative to controls, NE-depleted rats exhibited repetitive spatial patterns of locomotion with no alteration in the amount or rate of habituation of locomotor activity. Lesioned animals made fewer rearings and holepokes, particularly early in the hour test session. When given 80 micrograms/kg LSD, sham-lesioned rats exhibited the expected decreases in entries into and time spent in the center of the chamber, an increase in time spent in the corners, and fewer holepokes and rearings early in the session. With the exception of the effect on rearings and holepokes, the effects of LSD were diminished in rats depleted of brain NE. These results indicate that this profile of behavioral effects of LSD, which has been interpreted as a potentiation of neophobia, may be dependent upon the noradrenergic projections of the locus coeruleus.

Animals↗
PubMed2005

Spontaneous neural tube defects in splotch mice supplemented with selected micronutrients.

Splotch (Sp/Sp) mice homozygous for a mutation in the Pax3 gene inevitably present with neural tube defects (NTDs), along with other associated congenital anomalies. The affected mutant embryos usually die by gestation days (E) 12-13. In the present study, the effect of modifier genes from a new genetic background (CXL-Sp) and periconceptional supplementation with selected micronutrients (folic acid, 5-formyltetrahydrofolate, 5-methyltetrahydrofolate, methionine, myoinositol, thiamine, thymidine, and alpha-tocopherol) was determined with respect to the incidence of NTDs. In order to explore how different exposure parameters (time, dose, and route of compound administration) modulate the beneficial effects of micronutrient supplementation, female mice received either short- or long-term nutrient supplements via enteral or parenteral routes. Embryos were collected on E12.5 and examined for the presence of anterior or posterior NTDs. Additionally, whole mount in situ hybridization studies were conducted in order to reveal/confirm normal expression patterns of the Pax3 gene during neurulation in the wild-type and Sp/Sp homozygous mutant mouse embryos utilized in this study. A strong Pax3 signal was demonstrated in CXL-Sp embryos during neural tube closure (E9.5 to E10.5). The intensity and spatial pattern of expression were similar to other Splotch mutant mice. Of all the micronutrients tested, only supplementation with folic acid or 5-methyltetrahydrofolate rescued the normal phenotype in Sp/Sp embryos. When the folate supplementation dose was increased to 200 mg/kg in the diet, the incidence of rescued splotch homozygotes reached 30%; however, this was accompanied by six-fold increased resorption rate.

Animals↗
PubMed1985

A proposed animal model for hallucinogens based on LSD's effects on patterns of exploration in rats.

The utility of various measures of exploratory activity in rats was studied in order to develop an animal model of hallucinogens. A hole board chamber, connected by a door to a home cage, provided two test situations. Rats either were placed directly into the hole board with the door closed (forced exploration) or were placed in the home cage and, following adaptation, the door was opened (free exploration). The monitoring system provided both quantitative measures (crossovers, rearings, and hole pokes) and qualitative measures of locomotor patterns. A series of four experiments, with doses of 2-160 micrograms/kg LSD, revealed three major categories of effects, distinguishable on the basis of dose dependency, time course, or response to environmental manipulation: increased avoidance of novel and central areas, disruption of the spatial patterning of locomotion, and suppression of rearing. All three effects exhibited partial tolerance 24 hr after one injection of 30 micrograms/kg LSD and complete tolerance after five daily injections. The possibility that LSD's enhancement of neophobia in rats may be a valid analogue model of its intensification of affective reactions in humans is discussed.

Animals↗
PubMed2004

Spatiotemporal brain activation pattern during word/picture perception by native Koreans.

The purpose of this study is to explore spatiotemporal brain activation patterns during perception of words from three different languages (Korean, English, Chinese) and pictures. Using 64 channel event-related potential (ERP) recording and source localization using distributed source model, we investigated, with high temporal resolution, whether similar or different spatiotemporal patterns of brain activation are involved in the perception of words of different languages and/or pictures. Experimental results seem to corroborate left hemispheric dominance in language processing, and temporal/spatial characteristics in word perception revealed by previous ERP and neuroimaging studies. Observed differences in spatial pattern of activation at specific time periods between English and Korean, and Korean and Chinese, could be explained in terms of required visual pattern analysis due to the orthographic characteristics of each language.

Adult↗
PubMed2004

Regionalisation of early head ectoderm is regulated by endoderm and prepatterns the orofacial epithelium.

The oral epithelium becomes regionalised proximodistally early in development, and this is reflected by the spatial expression of signalling molecules such as Fgf8 and Bmp4. This regionalisation is responsible for regulating the spatial expression of genes in the underlying mesenchyme. These genes are required for the spatial patterning of bone, cartilage orofacial development and, in mammals, teeth. The mechanism and timing of this important regionalisation during head epithelium development are not known. Using lipophilic dyes to fate map the oral epithelium in chick embryos, we show that the cells that will occupy the epithelium of the distal and the proximal mandible primordium already occupy different spatial locations in the developing head ectoderm prior to the formation of the first pharyngeal arch and neural crest migration. Moreover, the ectoderm cells fated to become proximal oral epithelium express Fgf8 and this expression requires the presence of endoderm. Thus, the first fundamental patterning process in jaw morphogenesis is controlled by the early separation of specific areas of ectoderm that are regulated by ectoderm-endoderm interactions, and does not involve neural crest cells.

Animals↗
PubMed1988

Patterns of visual-spatial performance and 'spatial ability': dissociation of ethnic and sex differences.

Is there a common basis for the ethnic and sex differences that are characteristically obtained on psychometric tests of spatial ability? Three experiments approached this question by observing subject differences in the recognition and reconstruction of visual-spatial displays. The pattern of performance on these experimental tasks was compared with that on a traditional spatial ability test. In the first experiment, two samples of 40 students, balanced for sex, from Zimbabwe and Scotland respectively, attempted a forced-choice recognition task for meaningful scenes. Both ethnic groups and both sexes showed equivalent performance. The same subjects then undertook a task involving the reproduction of an arrangement of blocks into two-dimensional plan and elevation views. On this task, involving spatial reorientation, the Zimbabweans made over three times as many errors as the Scots. In a third experiment the requirement for spatial reorientation was added to the original recognition task and this was performed by a further 40 subjects. A significant difference between ethnic groups now emerged and this effect covaried with spatial ability. Again, however, no sex difference was observed. The overall pattern of results points to spatial reorientation as a major factor in the cross-ethnic differences. The absence of a sex difference on the experimental tasks contrasts with its appearance in both samples on the spatial ability test and represents a puzzling obstacle to our current understanding. This dissociation of sex and ethnic differences provides evidence against the hypothesis that they stem from the same source.

Adult↗