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PubMed1997

Origin and differentiation of supernumerary midline glia in Drosophila embryos deficient for apoptosis.

Drosophila embryos deficient for programmed cell death produce 9 midline glia (MG) in addition to the wild-type complement of 3.2 MG/segment. More than 3 of the supernumerary MG derive from the MGP (MG posterior) lineage and the remainder from the MGA/MGM (MG anterior and middle) lineage. There is one unidentified additional neuron in the mesectoderm of embryos deficient for apoptosis. The supernumerary MG are not diverted from other lineages nor do they arise from an altered pattern of mitosis. Instead, these MG appear to arise from a normally existing pool of 12 precursor cells, larger than anticipated by earlier studies. During normal development, MG survival is dependent upon signaling to the Drosophila EGF receptor. The persistence of supernumerary MG in embryos deficient for apoptosis does not alter the spatial pattern of Drosophila EGF receptor signaling. The number and position of MG which express genes dependent upon EGF receptor function, such as pointed or argos, are indistinguishable from wild type. Genes of the spitz group are required for Drosophila EGF receptor function. Surviving MG in spitz group/H99 double mutants continue to express genes characteristic of the MG, but the cells fail to differentiate into ensheathing glia and are displaced from the nerve cord.

Animals↗
PubMed1990

Developmental regulation of expression of the malate synthase gene in transgenic plants.

The cucumber malate synthase (MS) gene, including 1856 bp of 5' non-transcribed sequence, has been transferred into Petunia (Mitchell) and Nicotiana plumbaginifolia plants using an Agrobacterium binary vector. The transferred gene is found in variable copy number in different transformants, and is stably transmitted in each case as a single Mendelian character. Transgene mRNA accumulates in the seedling during the first three days of germination, then declines in amount as the cotyledons emerge from the seed. The decline is more pronounced in light-grown seedlings than in dark-grown seedlings. Expression of the MS transgene is also detected at a low level in petals of transformed Petunia plants. In these respects the pattern of MS gene expression is similar in cucumber and in transformed plants, showing that the transferred DNA fragment contains a functional MS gene. A 1076 bp fragment of 5' sequence was linked to the beta-glucuronidase reporter gene and transferred into Nicotiana, where it was shown to direct temporal and spatial patterns of expression similar to that of the complete MS gene. However, histochemical localisation of beta-glucuronidase activity demonstrated that the chimaeric gene is expressed not only in cotyledons of transgenic plants, but also in endosperm and some hypocotyl cells during early germination. The relevance of these findings to the control of malate synthase gene expression is discussed.

Base Sequence↗
PubMed1990

Mediation of Drosophila head development by gap-like segmentation genes.

The first phase of embryonic development in Drosophila consists of the elaboration and interpretation of maternally encoded information that specifies spatial pattern in the embryo. The product of the maternal gene bicoid (bcd) is thought to organize the anterior pattern of the embryo. Although the bcd transcript is localized at the anterior pole of the egg the bcd protein forms a stable concentration gradient through the anterior two thirds of the embryo. The graded distribution of bcd protein defines position along the anterior-posterior axis of the embryo through the spatially restricted activation of subordinate targets such as the gap gene hunchback (hb). In vitro manipulation of specific bcd protein binding sites has shown that the gradient of bcd protein can in principle define more than one discrete domain of spatially restricted gene activation in the head of the embryo, depending on the affinity of the available binding sites for the bcd protein. Genetic analysis has indicated the need for at least one additional zygotic segmentation gene to mediate bcd function in portions of the head that lie anterior to the hb domain. The missing gene activity is expected to be activated in response to higher levels of bcd protein than are required for hb activation. We report here that three previously identified zygotic genes buttonhead (btd), empty spiracles (ems) and orthodenticle (otd) may behave like gap genes that mediate bcd function in the embryonic head.

Animals↗
PubMed2002

Density and distribution of white matter neurons in schizophrenia, bipolar disorder and major depressive disorder: no evidence for abnormalities of neuronal migration.

The neurodevelopmental hypothesis of schizophrenia suggests that this disorder may result from a disruption of normal brain development. While widely cited, neuropathological evidence for this is far from conclusive. Alterations in the density and position of white matter neurons have been previously described in the frontal and temporal lobes and have led to suggestions that abnormal neuronal migration may play a role in the aetiology of schizophrenia. However, these findings have not been replicated. Furthermore, developmental abnormalities may not be specific to schizophrenia. The aim of this study was to examine the density and spatial pattern distribution of white matter neurons in psychiatric and control subjects using sophisticated computerised image analysis techniques. White matter neurons immunoreactive for microtubule associated protein-2 were quantified in the frontal lobe in schizophrenia, bipolar disorder, major depressive disorder and matched controls (each group n = 15). Analysis showed that the density and spatial distribution of white matter neurons did not differ significantly between the control and psychiatric groups. This study cannot replicate the earlier findings of white matter abnormalities in schizophrenia and finds no evidence for abnormal brain development in any of the disorders studied.

Adult↗
PubMed2004

Bioconvective pattern formation of Tetrahymena under altered gravity.

Bioconvection is a result of the negative gravitactic behavior of microorganisms. When the top-heavy density gradient generated by gravitaxis grows sufficiently large, an overturning convection occurs leading to a formation of characteristic patterns, which involve highly concentrated aggregation of cells into extended two-dimensional structures. Although gravity is a crucial factor, few experiments have been done with reference to gravity as an experimental variable. In order to gain an insight into the hydrodynamic as well as biological dependence of the convective motion on gravity, we investigated changes in bioconvective patterns of Tetrahymena under altered gravity acceleration generated by a long-arm centrifuge. Bioconvective patterns recorded of three different cell strains (T. pyriformis, T. thermophila and its behavioral mutant, TNR) were analyzed quantitatively using space-time plot and Fourier analysis. For example, under subcritical conditions, when T. pyriformis (1.0 x 10(6) cells ml(-1)) was placed in a 2 mm-deep chamber, no spatial pattern was observed at 1 g. When the suspension was centrifuged, however, patterns began to appear as acceleration increased over a critical value (1.5 g), and then remained steady. The formation was reversible, i.e. the patterns disappeared again as acceleration decreased. Under supracritical conditions, i.e. when a suspension of the same density was placed in a 4 mm-deep chamber, a steady state pattern was formed at 1 g. The pattern spacing in the steady state was observed to decrease stepwise in response to step increases in acceleration. Fourier analysis demonstrated that for TNR the mean wave number changed almost simultaneously with step changes in acceleration, whereas the responses were less sharp in the wild-type strains. This may suggest that the locomotor phenotype of the cell, such as its avoiding response ability, has a crucial role in bioconvective pattern formation. These findings are discussed in relation to former theoretical studies.

Animals↗
PubMed1999

Multidimensional chemotopic responses to n-aliphatic acid odorants in the rat olfactory bulb.

In an effort to understand the means by which similar chemical odorants are encoded in the mammalian brain, we exposed rats to a homologous series of n-aliphatic acids and mapped the response of the entire olfactory bulb glomerular layer by using a high-resolution [14C]-2-deoxyglucose uptake technique. We found that these similar odorants evoked spatially clustered but distinct responses in the bulb that changed systematically with carbon chain length. In addition to these chemotopic responses, different odorants within the series evoked systematic differences along two other dimensions: amount of deoxyglucose uptake and extent of the glomerular layer showing high activity. Increases along these two dimensions also were correlated with increasing carbon number. The focal glomerular responses were mirrored by responses in deeper bulb layers. Decreasing the odorant concentration decreased the deoxyglucose uptake within focal regions. The focal regions of activity occurred in pairs involving both medial and lateral representations in the bulb, perhaps reflecting the paired medial and lateral projections of olfactory sensory neurons expressing specific types of odorant feature receptor proteins. The observed spatial pattern of response also may explain both the failure of some bulb lesions to interfere with behavioral olfactory responses and the success of other lesions in blocking olfactory responses. These data support a model of parallel, distributed processing of odorants along multiple dimensions. They also support the notion that analyses of the spatial relationships among odorant responses in the olfactory bulb can demonstrate aspects of the mechanism for odor chemical coding.

Animals↗
PubMed1988

Multisite hippocampal slice recording and stimulation using a 32 element microelectrode array.

A technique has been developed in which a planar array of 32 microelectrodes, arranged in a 4 by 8 pattern with 200 micron separation, is used to record from and stimulate the hippocampal slice preparation at multiple sites. Control of media flow past the tissue is critical to observe signals and preserve viability. Active suppression circuitry is used to prevent device saturation due to large stimulation artifacts. The field potentials recorded are spatially unique and provide a 2-dimensional description of the underlying population activity in the various pyramidal strata and subpopulations. Multisite stimulation is also possible with the array, permitting the experimenter to quickly stimulate and record from brain slices in many spatial patterns.

Animals↗
PubMed2006

An auxin-driven polarized transport model for phyllotaxis.

Recent studies show that plant organ positioning may be mediated by localized concentrations of the plant hormone auxin. Auxin patterning in the shoot apical meristem is in turn brought about by the subcellular polar distribution of the putative auxin efflux mediator, PIN1. However, the question of what signals determine PIN1 polarization and how this gives rise to regular patterns of auxin concentration remains unknown. Here we address these questions by using mathematical modeling combined with confocal imaging. We propose a model that is based on the assumption that auxin influences the polarization of its own efflux within the meristem epidermis. We show that such a model is sufficient to create regular spatial patterns of auxin concentration on systems with static and dynamic cellular connectivities, the latter governed by a mechanical model. We also optimize parameter values for the PIN1 dynamics by using a detailed auxin transport model, for which parameter values are taken from experimental estimates, together with a template consisting of cell and wall compartments as well as PIN1 concentrations quantitatively extracted from confocal data. The model shows how polarized transport can drive the formation of regular patterns.

Arabidopsis↗
PubMed2005

Density dependence, spatial scale and patterning in sessile biota.

Sessile biota can compete with or facilitate each other, and the interaction of facilitation and competition at different spatial scales is key to developing spatial patchiness and patterning. We examined density and scale dependence in a patterned, soft sediment mussel bed. We followed mussel growth and density at two spatial scales separated by four orders of magnitude. In summer, competition was important at both scales. In winter, there was net facilitation at the small scale with no evidence of density dependence at the large scale. The mechanism for facilitation is probably density dependent protection from wave dislodgement. Intraspecific interactions in soft sediment mussel beds thus vary both temporally and spatially. Our data support the idea that pattern formation in ecological systems arises from competition at large scales and facilitation at smaller scales, so far only shown in vegetation systems. The data, and a simple, heuristic model, also suggest that facilitative interactions in sessile biota are mediated by physical stress, and that interactions change in strength and sign along a spatial or temporal gradient of physical stress.

Analysis of Variance↗
PubMed1993

A unified functional/anatomic substrate for circus movement atrial flutter: activation and refractory patterns in the canine right atrial enlargement model.

OBJECTIVES: This study was designed to test the concept of a functional/anatomic interaction in a canine model of reentry based on right atrial enlargement and to elucidate the electrophysiologic basis for functional conduction block. BACKGROUND: The monotonic feature of atrial flutter suggests a uniform substrate for the arrhythmia. Atrial flutter in the sterile pericarditis model is due to single-loop circus movement around a functional or a functional/anatomic obstacle near the atrioventricular (AV) ring. Sustained circus movement requires a critical interaction of a functional arc of block, a natural obstacle, the AV ring and a zone of slow conduction. The location of the inferior vena cava predisposes the lower right atrium to single-loop reentry. METHODS: In 11 dogs with right atrial enlargement, 127 bipolar epicardial electrograms were obtained during atrial flutter. For correlation of activation and refractory maps, the effective refractory period under each electrode was determined using the extrastimulus technique. RESULTS: Atrial flutter was due to single-loop reentry around functional arcs of block near the AV ring (n = 2) or around functional/anatomic obstacles (n = 8) involving the inferior vena cava. A slow zone was located between the arc and the AV ring and between the inferior vena cava and AV ring, respectively. During initiation, the arc joined the AV ring, forcing activation to proceed around the free end of the arc before breaking through the arc near the AV ring. Arrhythmia termination required the arc of block to rejoin the AV ring. Inducibility of sustained atrial flutter was associated with a marked spatial dispersion of refractoriness. The configuration of the functional arc of block was critically dependent on the spatial pattern of refractoriness. CONCLUSIONS: Atrial flutter requires a similar functional or functional/anatomic substrate independent of the underlying etiology. The spatial distribution of refractoriness in enlarged canine atria provides an adequate substrate for the development of functional conduction block.

Animals↗
PubMed1994

Detecting climate-induced patterns using wavelet analysis.

One of the difficulties encountered in the detection of ecosystem responses to climate change is distinguishing climate-induced patterns from those created by other sources. For example, changes in the trend of stream discharge records over time may reflect a composite response of changes in the climate (i.e. precipitation and temperature), land-use (e.g. timber harvesting and grazing), and local basin characteristics. Methods which quantify and relate information of temporal and spatial patterns across scales are critical to assess climatically induced changes in the forest and stream ecosystems. A methodology utilizing wavelet analysis is introduced for the purpose of identifying and isolating inferred climatic components of the hydrologic record. Trends observed in stream discharge records from eastern Oregon, USA are identified and used to illustrate the utility of a new time series technique, wavelet analysis, as a complementary approach for discerning pattern. This methodology affords an informed procedure for choosing filter dimensions for the purpose of signal decomposition. The wavelet cross-covariance is applied to precipitation and discharge records to identify the climatic component in the discharge record. Reconstruction of these dominant frequencies is effected to isolate the climatic components. The discharge pattern shows two dominant scales of pattern coincident with the precipitation record. A 3-year half-period pattern is found to be correlated with the Southern Oscillation Index at the same frequency.

Journal Article↗
PubMed2006

Nanoparticle-assisted surface immobilization of phospholipid liposomes.

Phospholipid liposomes (100-200 nm diameter) are deposited onto solid substrates after stabilizing them against fusion with the solid by allowing charged nanoparticles to adsorb at approximately 25% surface coverage. The immobilized vesicles remain stable over a period of days. Epifluorescence imaging shows that they diffuse freely over surfaces with the same charge but adsorb tightly onto surfaces with opposite charge. Nanoparticle adsorption to surface patterns of opposite charge provides a facile method to create large-scale surface-supported arrays of intact liposomes. This surface attachment method is simple chemically and applies generally for solid surfaces that can be hydrophobic or hydrophilic. Offering routes to localize proteins and other vesicle-contained objects at surfaces in tailored spatial patterns, these immobilized liposome arrays may find diverse applications in the emerging field of nanobiotechnology.

Adsorption↗
PubMed1995

Contrast-dependent responses in the human visual system: childhood through adulthood.

Visual evoked potentials (VEPs) to temporal modulation of spatial patterns, recorded from humans ranging in age from 4-42 years, demonstrated that contrast-dependent responses exist in early childhood and change dramatically throughout childhood. Bright or dark isolated-check stimuli were used to emphasize contributions from ON or OFF pathways to the VEP. (ON and OFF pathways constitute one major pair of parallel subsystems, which process brightness [positive-contrast] and darkness [negative-contrast] information, respectively.) The developmental effects observed for each pathway were similar in magnitude and time course, suggesting maturation of a common physiological mechanism dependent on spatial contrast. Children's responses were more variable and larger than those of adults, and exhibited a relative phase lag. In addition, we recorded transient VEPs to a conventional contrast-reversing checkerboard pattern. The latency of the major positive wave (P100) was found to decrease, while the latency of the initial positive wave (P60) was found to increase, with increasing age. We propose a vector-summation model, which posits a relative decrease in cortical excitation with increasing age, to explain our major findings.

Adolescent↗
PubMed1996

Differential pattern in tissue-specific somatic mosaicism of expanded CAG trinucleotide repeats in dentatorubral-pallidoluysian atrophy, Machado-Joseph disease, and X-linked recessive spinal and bulbar muscular atrophy.

We investigated the somatic mosaicism of trinucleotide repeat expansion in the neural and nonneural tissues of a dentatorubral-pallidoluysian atrophy (DRPLA), Machado-Joseph disease (MJD), and spinal and bulbar muscular atrophy (SBMA) patient and their correlation to the topographical distribution of the pathological involvement. The spatial pattern of tissue-specific somatic mosaicism in the CAG repeat size was significantly different among the DRPLA, MJD and SBMA patients. The size of the major bands of the mutant CAG repeat allele was significantly smaller in the cerebellar cortex in both DRPLA and MJD patients by 6 and 2 repeat units respectively and larger in the colon and liver of DRPLA by 5 repeats or more. There were also 1-2 repeat-sized small variations of major band size among the neural tissues in DRPLA. In contrast, there was no tissue-specific variation of major bands of CAG repeats and diversity of extra bands among the examined tissues including the cerebellum in the SBMA patient. There was no parallel occurrence of tissue-specific CAG instability and severity of neuropathological involvement in the neural and nonneural tissues of DRPLA, MJD and SBMA patients. Lack of significant tissue-specific somatic mosaicism in SBMA including the cerebellar cortex may suggest that CAG repeat expansion in the mutant androgen receptor gene is far more stable compared with that in DRPLA and MJD as well as those reported in Huntington's disease.

Adult↗
PubMed1993

Serotonin1B receptor activation mimics behavioral effects of presynaptic serotonin release.

The locomotor hyperactivity induced by 3,4-methylene-dioxymethamphetamine (MDMA) and related drugs in rats appears to be due to the drug-induced release of presynaptic serotonin (5-HT). Thus, these drugs increase locomotor activity by acting as indirect 5-HT agonists. The subtype of 5-HT receptor upon which this released 5-HT acts postsynaptically to produce the activating effect of MDMA-like drugs is not known. When tested under conditions in which MDMA increases locomotion, direct agonists at both 5-HT1A and 5-HT1C/2 receptors consistently decrease locomotion. Hence, the present experiments tested the hypothesis that the hyperactivity produced by the release of endogenous 5-HT is due to the activation of 5-HT1B receptors. Using the Behavioral Pattern Monitor (BPM), the profile of behavioral effects of a 5-HT1B agonist, 5-methoxy-3(1,2,3,6)tetrahydropyridin-4yl)-1H-indole (RU 24969), was compared to that previously described for MDMA and related indirect 5-HT agonists. The BPM provided detailed information regarding the amount and qualitative patterning of locomotor activity and investigatory responses in rats. Various doses of RU 24969 (1.25 to 5 mg/kg) were administered to naive male rats 10 minutes prior to placement in the test chambers. As previously reported for MDMA, locomotor activity increased with dose, and investigatory rearings and holepokes decreased. The hyperactivity was characterized by repetitive spatial patterns of locomotion that were qualitatively similar to those produced by indirect 5-HT agonists such as MDMA and dissimilar to those produced by indirect dopamine (DA) agonists such as amphetamine. Pretreatment with racemic propranolol but not (+)propranolol antagonized the hyperactivity induced by RU 24959. Fluoxetine, a 5-HT reuptake inhibitor, failed to block the locomotor activating effects of RU 24969. These findings confirm the similarity between the behavioral effects of RU 24969 and indirect 5-HT agonists and suggest that the locomotor hyperactivity produced by both RU 24969 and MDMA is mediated by the activation of 5-HT1B receptors. Although the effects of MDMA on 5-HT1B receptors are secondary to its ability to release presynaptic 5-HT, the activation produced by RU 24969 appears to be a consequence of its direct agonist effects.

3,4-Methylenedioxyamphetamine↗
PubMed2001

Integrating genetic and environmental forces that shape the evolution of geographic variation in a marine snail.

Temporal and spatial patterns of phenotypic variation have traditionally been thought to reflect genetic differentiation produced by natural selection. Recently, however, there has been growing interest in how natural selection may shape the genetics of phenotypic plasticity to produce patterns of geographic variation and phenotypic evolution. Because the covariance between genetic and environmental influences can modulate the expression of phenotypic variation, a complete understanding of geographic variation requires determining whether these influences covary in the same (cogradient variation) or in opposing (countergradient variation) directions. We focus on marine snails from rocky intertidal shores as an ideal system to explore how genetic and plastic influences contribute to geographic and historical patterns of phenotypic variation. Phenotypic plasticity in response to predator cues, wave action, and water temperature appear to exert a strong influence on small and large-scale morphological variation in marine snails. In particular, plasticity in snail shell thickness: (i) may contribute to phenotypic evolution, (ii) appears to have evolved across small and large spatial scales, and (iii) may be driven by life history trade-offs tied to architectural constraints imposed by the shell. The plasticity exhibited by these snails represents an important adaptive strategy to the pronounced heterogeneity of the intertidal zone and undoubtedly has played a key role in their evolution.

Animals↗
PubMed1998

Physiologic aspects of event related paradigms in magnetic resonance functional neuroimaging.

In order to substantiate event related paradigms in magnetic resonance functional neuroimaging, we assessed the temporal and spatial characteristics of oxygenation-sensitive MRI responses to 1 s periods of visual activation in repetitive protocols. A main finding is a reduction of the functional contrast between conditions (reversing checkerboard vs. darkness) for decreasing interstimulus intervals yielding 4.5% signal change for 89 s, 4% for 9 s, 3% for 6 s, and 1% for 3 s, respectively. Although rapid repetitions of identical stimuli preclude the development of the full positive and negative MRI signal deflections, pertinent responses leave the spatial pattern of activated brain regions unaffected and result in identical maps. These findings suggest the use of interstimulus intervals of the order of the response time from stimulus onset to maximum signal strength (5-6 s in the visual system). The resulting distinction in time will allow for separate mapping of stimulus-related responses with spatially overlapping cortical representations.

Adult↗
PubMed2004

Extracellular matrices as elastic scaffold and mechanical interaction.

Development of spatial pattern and form is one of the central issues in embryology and is included under the general name of morphogenesis. Recently, many investigations have revealed how does development occurs by each embryonic stem cell or which Genes play a crucial role for morphogenesis. However, still fundamental question is unclear; such as how does each cell recognize spatial information or which kind of information guides each cell to the suitable place. Approximately, we have 6x10(13) cells in our body. If each frame of reference of each cell is included in the gene, gene must have included more than 6x10(13) of information to inform each cell where they are. We could simply suggest this kind of the idea is quite wrong because we know genes are few enough to include such informations. Recently, it has been suggested that interaction between intracellular and extracellular fiber play crucial roll for morphogenesis. The fibers inside cell are quite complicated but well organized the system, and fibers outside of the cell are comparatively very simple fiber. Each of the fibers is well studied, but quantitative investigation of their interaction is lacking although importance is suggested by many researchers. A major problem is lacking of new method or technique. In our topics, we would like to introduce how intracellular and extracellular fiber generate morphogenesis and how we could investigate them using new technique for tissue engineering, one of the promising field of applied cell biology.

Cell Adhesion↗