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At least 325 records · Page 18Linked to original sources
PubMed2002

Unravelling a biogeographical knot: origin of the 'leapfrog' distribution pattern of Australo-Papuan sooty owls (Strigiformes) and logrunners (Passeriformes).

Molecular analysis of two Australo-Papuan rainforest birds exhibiting correlated 'leapfrog' patterns were used to elucidate the evolutionary origin of this unusual pattern of geographical differentiation. In both sooty owls (Tyto) and logrunners (Orthonyx), phenotypically similar populations occupy widely disjunct areas (central-eastern Australia and upland New Guinea) with a third, highly distinctive population, occurring between them in northeastern Queensland. Two mechanisms have been proposed to explain the origin of leapfrog patterns in avian distributions: recent shared ancestry of terminal populations and unequal rates or phenotypic change among populations. As the former should generate correlated patterns of phenotypic and genetic differentiation, we tested for a sister relationship between populations from New Guinea and central-eastern Australia using nuclear and mitochondrial DNA sequences. The resulting phylogenies not only refute recent ancestry as an explanation for the leapfrog pattern, but provide evidence of vastly different spatio-temporal histories for sooty owls and logrunners within the Australo-Papuan rainforests. This incongruence indicates that the evolutionary processes responsible for generating leapfrog patterns in these co-distributed taxa are complex, possibly involving a combination of selection and drift in sooty owls and convergence or retention of ancestral characteristics in logrunners.

Adenosine Triphosphatases↗
PubMed1980

Pattern regulation and the origin of extra parts following axial misalignments in the urodele limb bud.

Pattern regulation following axial misalignments in the stage-38+to stage-40 urodele limb bud was studied on one newt and two salamander species. Grafts of the distal tip of the limb bud were made to the stump of a host limb bud from which a similar piece had been removed. The grafts were positioned with either their anteroposterior, dorsoventral, or both of these axes reversed with respect to the host axes. Mirror-imaged duplications, positioned posteriorly or both anteriorly and posteriorly, occurred nearly all (96%) of the time when the anteroposterior axis was reversed. Dorsoventral axial misalignment rarely promoted the generation of mirror-imaged duplication (8%) but did affect the organization along the anteroposterior axis by causing a serial repetition of either digit 2 or digit 3. Regulation, therefore, does not always occur along each axis independently of the others. Consistent with the data derived from reversing individual axes, most of the duplications which occurred when both axes were reversed were in the anteroposterior plane. Some were in the dorsoventral plane, and a few had intermediate positions. Of these duplications a few were neither right not left hands, rather they were of mixed handedness with a change in the dorsoventral polarity from the anterior border to the posterior border. Whether extra parts which result from axial misalignments arise from the graft, the host, or both the graft and the host was investigated using heteroplastic grafts and grafts exchanged between triploid and diploid axolotls. Duplications were found to have cellular contributions from both the graft and the host. In some cases on source would dominate but usually both made a substantial contribution. The diploid-triploid material suggests that a considerable mixing of host and graft cells may occur in duplications. Additionally, some digits of the graft sequence of digits can be derived from host tissue. The extra digit in those hands displaying a serial repetition was derived from host tissue in some cases and graft tissue in other cases.

Ambystoma↗
PubMed1998

Emergence of multicellular organisms with dynamic differentiation and spatial pattern.

The origin of multicellular organisms and the mechanism of development in cell societies are studied by choosing a model with intracellular biochemical dynamics allowing for oscillations, cell-cell interaction through diffusive chemicals on a two-dimensional grid, and state-dependent cell adhesion. Cells differentiate due to a dynamical instability, as described by our "isologous diversification" theory. A fixed spatial pattern of differentiated cells emerges, where spatial information is sustained by cell-cell interactions. This pattern is robust against perturbations. With an adequate cell adhesion force, active cells are release that form the seed of a new generation of multicellular organisms, accompanied by death of the original multicellular unit as a halting state. It is shown that the emergence of multicellular organisms with differentiation, regulation, and life cycle is not an accidental event, but a natural consequence in a system of replicating cells with growth.

Animals↗
PubMed1996

Monophyletic origin and unique dispersal patterns of domestic fowls.

With the aim of elucidating in greater detail the genealogical origin of the present domestic fowls of the world, we have determined mtDNA sequences of the D-loop regions for a total of 21 birds, of which 12 samples belong to red junglefowl (Gallus gallus) comprising three subspecies (six Gallus gallus gallus, three Gallus gallus spadiceus, and three Gallus gallus bankiva) and nine represent diverse domestic breeds (Gallus gallus domesticus). We also sequenced four green junglefowl (Gallus varius), two Lafayette's junglefowl (Gallus lafayettei), and one grey junglefowl (Gallus sonneratii). We then constructed a phylogenetic tree for these birds by the use of nucleotide sequences, choosing the Japanese quail (Coturnix coturnix japonica) as an outgroup. We found that a continental population of G. g. gallus was the real matriarchic origin of all the domestic poultries examined in this study. It is also of particular interest that there were no discernible differences among G. gallus subspecies; G. g. bankiva was a notable exception. This was because G. g. spadiceus and a continental population of G. g. gallus formed a single cluster in the phylogenetic tree. G. g. bankiva, on the other hand, was a distinct entity, thus deserving its subspecies status. It implies that a continental population of G. g. gallus sufficed as the monophyletic ancestor of all domestic breeds. We also discussed a possible significance of the initial dispersal pattern of the present domestic fowls, using the phylogenetic tree.

Animals↗
PubMed1994

Origin of the foveal granular pattern in entoptic viewing.

PURPOSE: To investigate the controversial origin of the foveal granular pattern at the center of the entoptic Purkinje vessel shadows. Both phenomena may be vividly elicited by oscillating a focused spot of light across the scleral surface of the eye in a circumferential direction. METHODS: The site and pattern of oscillation of the light spot were varied and were correlated with the appearance of the foveal granular pattern. Movement of the granular pattern relative to a foveal afterimage was also observed. RESULTS: Oscillation of the light in a meridional direction abolishes the granular pattern. Oscillating illumination through the central pupil can elicit Purkinje vessel shadows but not the characteristic foveal granular pattern. With transscleral illumination, the granular pattern oscillates with an "against" motion with respect to the motion of the Purkinje vessel shadows and with a "with" motion with respect to apparent motion of an afterimage serving as a fixed anatomic reference, and it is displaced from the center of the foveal avascular zone in the visual direction away from the source of illumination. CONCLUSIONS: These observations strongly suggest that the foveal granular pattern is a random moire pattern produced by spatial aliasing as the striated light pattern cast by the parafoveal nerve fiber elements sweeps over the photoreceptors in the form of a faint, high-spatial-frequency, irregular grating. An anatomic section of the fovea reveals the necessary geometry for production of such striated patterns, and the Nyquist frequency for the foveal photoreceptor mosaic supports the spatial aliasing effect. Also, a grating moving over a stationary random dot background demonstrates the origin of the "against" motion that is characteristic of the foveal granular pattern.

Fovea Centralis↗
PubMed1992

[Studies on marginal castability of cast crown].

The castability of the crown margins was studied. The smoothness and quantitative measurement of the margins were compared with the original wax patterns and their casted products. Wax patterns of the plate and crown forms were fabricated with sharp, straight and even margins. Margin angles of the wax patterns were prepared at both 20 and 40 degrees for the plate type and 20 degrees for the crown type samples. Each wax pattern was casted with Type IV gold alloy and gold-silver-palladium alloy. The casted margins were evaluated by comparing them with their original wax patterns. The results were as follows: 1. Compared to the current procedure, more precise evaluation of the marginal castability is now possible with this new method. 2. The shortness of the margins was observed in all of the casted samples. Casted samples with 20-degree margins resulted in twice as much deficiency as compared to those with 40-degree margins. 3. The smoothness and evenness of the margins were inferior in all of the casted samples when compared to their original wax patterns. 4. The margin thickness was between 50 and 70 microns when the wax patterns with sharp margins were casted. 5. A certain thickness is required at the margins of the wax patterns in order to achieve precise casted margins. In this study, it was found to be 79.1 microns.

Crowns↗
PubMed1987

Independent temporal and pitch structures in determination of musical phrases.

In two experiments we addressed the roles of temporal and pitch structures in judgments of melodic phrases. Musical excerpts were rated on how good or complete a phrase they made. In Experiment 1, trials in the temporal condition retained the original temporal pattern but were equitonal; trials in the pitch condition retained the original pitch pattern but were equitemporal; and trials in the melody condition contained both temporal and pitch patterns. In Experiment 2, one pattern (pitch or temporal) was shifted in phase and recombined with the other pattern to create the pitch and temporal conditions. In the melody condition, both patterns were shifted together. In both experiments, ratings in the temporal and pitch conditions were uncorrelated, and the melody condition ratings were accurately predicted by a linear combination of the pitch and temporal condition ratings. These results were consistent across musicians with varying levels of experience.

Adolescent↗
PubMedDate not supplied

Origins of differentiation via phenotypic plasticity.

How cell types of multicellular organisms came to be differentiated is still an open issue. Here I offer a model that posits that the origins of some cell differentiation patterns were originally passive outcomes of environmental effects. As cells' contact with the external environment was diminished, their patterns of gene expression were altered, due to changes in concentrations of externally supplied substances. Later, as multicellular growth continued, the relationships of cell layers to each other shifted, producing concentration gradients of signaling molecules. These gradients emanated both from the external cell layer toward the inside and from internal cell layers to adjacent layers. In this scenario then, differentiation arose initially as a by-product of the changing patterns of gene expression and of the complex mixtures and changing concentrations of substances passing among layers. Subsequent selection would operate to stabilize the expression patterns in those cell layers whose phenotypes provide a fitness advantage to the organism.

Animals↗
PubMed2002

Variations in angiotensin-converting enzyme gene insertion/deletion polymorphism in Indian populations of different ethnic origins.

The pattern of angiotensin-converting enzyme (ACE) gene insertion/deletion (I/D) polymorphism in the Indian population is poorly known. In order to determine the status of the polymorphism, young unrelated male army recruits were screened. The population had cultural and linguistic differences and lived in an environment that varied significantly from one region to another. Analysis of the genotype, showed higher frequency of the insertion allele in four of the five groups i.e. I allele frequency was significantly higher (P < 0.05) in Dogras, Assamese and Kumaonese. The deletion allele frequency was comparatively higher in the fifth group that belonged to Punjab. A correlation was observed between the genotype and enzyme activity. Involvement of a single D allele in the genotype enhanced the activity up to 37.56 3.13%. The results suggested ethnic heterogeneity with a significant gene cline with higher insertion allele frequency. Such population-based data on various polymorphisms can ultimately be exploited in pharmacogenomics.

Ethnicity↗
PubMed1980

Urinary purines and pyrimidines in patients with hyperammonemia of various origins.

Excretion patterns of pyrimidines and purines in patients with various types of hyperammonemia have been investigated by 2-dimensional thin-layer chromatography and high pressure liquid chromatography (HPLC). For the quantitative analysis of pseudouridine, uracil and uridine a new procedure has been developed, consisting of pre-fractionation with Dowex 1 X 8, followed by dual column HPLC on a strong anion-exchanger and a reverse phase column. Thymine has also been analyzed in the pre-fractionated urine by a new HPLC method using the reverse phase column in combination with a strong cation-exchange column. Quantitative data for urinary pyrimidines and uric acid in hyperammonemia are given. In patients with a defect in one of the urea cycle enzymes, the level of pyrimidine excretion was found to depend on plasma ammonia concentrations. In other hyperammonemic patients, an increased excretion of orotic acid, uracil and uridine has only been found in one of the two patients with lysinuric protein intolerance, all other patients showing normal excretion patterns. Elevated uric acid excretions have been found frequently in our patients with hyperammonemia, but they did not always coincide with high plasma ammonia levels. A possible explanation for the difference in the excretion levels of the various pyrimidines is discussed.

Amino Acid Metabolism, Inborn Errors↗
PubMed2006

Lipopolysaccharide heterogeneity among Burkholderia pseudomallei from different geographic and clinical origins.

Heterogeneous patterns were obtained for lipopolysaccharide (LPS) from 1,327 Burkholderia pseudomallei isolates by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, silver staining, and immunoblot analysis. Two LPS serotypes (A and B) possessing different ladder profiles and a rough LPS without ladder appearances were identified. All three LPS types were antigenically distinct by immunoblotting. The predominant type A (97%) produced the lowest amount of biofilm. The two less common types (smooth type B and rough type) were found more in clinical than environmental isolates and more in Australian isolates than Thai isolates. These isolates were more often associated with relapse than with primary infection.

Animals↗
PubMed2004

An evaluation of the origin of trabecular bone patterns using visual and digital image analysis.

OBJECTIVE: The purpose of this research project was to investigate the origin of the anatomical structures interpreted as trabecula bone on dental radiographic images. STUDY DESIGN: Mandible sections were cut sagitally into halves. Trabecular bone was removed from each section in 4 stages. Following each stage, standardized radiographs were made, using CDR direct digital equipment. Trabecular bone in the resulting digital images was measured with 4 methods: (1) mean gray level; (2) the fractal dimension of the basic images; and, following morphological image processing, (3) counting the number of trabecular ends, intercepts, and segments (EIS) and (4) performing fractal analyses of the skeletonized images. Additionally, human visual interpretation of the collected images was conducted through a written examination. Repeated measures analysis of variance (ANOVA) was used to test for changes in measurements attributable to bone removal. RESULTS: Repeated measures ANOVA indicated that the use of gray levels, fractal dimension, and morphologic operations quantifying using EIS or fractal analysis had similar performance and resulted in significant changes in measurements following bone removal ( P < .05). Visual differences were not always apparent between each stage of bone reduction. Radiometric and morphologic analysis showed measurable differences between stages. CONCLUSIONS: These results imply that the inner trabecula, the junctional trabecula, and the actual cortical housing all contribute to some extent to the radiograph, although changes in the radiographic architecture are not always clinically detectible.

Absorptiometry, Photon↗
PubMed2003

[Negative selection and computer models of the joint evolution of the patterns of polygenes, transposable elements, and origin identity labels].

Computer simulation of the population dynamics of the genomic patterns of polygenes, transposable elements (TEs), and origin identity labels (OILs) in the course of negative selection for an additive quantitative trait has been performed. It was demonstrated that active polygene alleles disappear very rapidly, whereas the patterns of TEs and OILs continue their evolution determined by strict selective inbreeding and gene drift. Dendrograms of the patterns of polygenes, TEs, and OILs were constructed for all generations. It was demonstrated that the final consensus pattern of OILs consists of the fragments of the original patterns, which contain neither active polygene alleles nor modifier or marker TEs. Neutral TE copies were present in the final pattern, as should be expected in the case of gene drift. Inbreeding coefficient increased steadily but by generation 100 reached values higher than 0.9. All other parameters and initial conditions being the same, the responses to negative and positive selections were asymmetric.

Animals↗
PubMed1986

Pattern in the laminar origin of corticocortical connections.

The laminar origin of cortical projections to the frontal cortex was studied in 17 adult rhesus monkeys with the use of the retrograde transport of horseradish peroxidase (HRP). The frontal regions injected with HRP extended from the posterior periarcuate region to the frontal pole. The architectonic boundaries of areas containing HRP-labeled neurons were determined from matched sections stained for the visualization of cell bodies, myelin, or acetylcholinesterase. The results showed that the laminar origin of both nearby and distant corticocortical projections was correlated with the architectonic differentiation of the regions giving rise to the projecting afferent fibers. Frontally directed projections from limbic cortices, which show a rudimentary laminar organization, emanated mainly from deep layers. On the other hand, projections from increasingly more differentiated cortices arose progressively from the upper (or supragranular) layers. This pattern was observed for projections originating along the axis of architectonic differentiation of the visual, somatosensory, auditory, motor, and prefrontal cortical systems. Thus, as the cortical architecture within each system changes from limbic areas toward the primary cortices, the origin of frontally directed projections shifts from predominantly infragranular to predominantly supragranular layers.

Animals↗
PubMed2001

Hypoxia-induced respiratory patterned activity in Lymnaea originates at the periphery.

Respiration in Lymnaea is a hypoxia-driven rhythmic behavior, which is controlled by an identified network of central pattern generating (CPG) neurons. However, the precise site(s) (i.e., central or peripheral) at which hypoxia acts and the cellular mechanisms by which the respiratory chemosensory drive is conveyed to the CPG were previously unknown. Using semi-intact and isolated ganglionic preparations, we provide the first direct evidence that the hypoxia-induced respiratory drive originates at the periphery (not within the central ring ganglia) and that it is conveyed to the CPG neurons via the right pedal dorsal neuron 1 (RPeD1). The respiratory discharge frequency increased when the periphery, but not the CNS, was made hypoxic. We found that in the semi-intact preparations, the frequency of spontaneously occurring respiratory bursts was significantly lower than in isolated ganglionic preparations. Thus the periphery exerts a suppressive regulatory control on respiratory discharges in the intact animal. Moreover, both anoxia (0% O(2)) and hypercapnia (10% CO(2)) produce a reduction in respiratory discharges in semi-intact, but not isolated preparations. However, the effects of CO(2) may be mediated through pH changes of the perfusate. Finally, we demonstrate that chronic exposure of the animals to hypoxia (90% N(2)), prior to intracellular recordings, significantly enhanced the rate of spontaneously occurring respiratory discharges in semi-intact preparations, even if they were maintained in normoxic saline for several hours. Moreover, we demonstrate that the peripherally originated hypoxia signal is likely conveyed to the CPG neurons via RPeD1. In summary, the data presented in this study demonstrate the important role played by the periphery and the RPeD1 neuron in regulating respiration in response to hypoxia in Lymnaea.

Animals↗
PubMed2002

Clinical and molecular features of congenital disorder of glycosylation in patients with type 1 sialotransferrin pattern and diverse ethnic origins.

OBJECTIVE: To increase awareness of congenital disorders of glycosylation (CDG), we report the features of patients with a variety of clinical presentations ranging from mild hypotonia and strabismus to severe neurologic impairment. STUDY DESIGN: Nine North American patients with CDG type I and different ethnic origins were studied. RESULTS: All patients had transferrin isoelectric focusing studies with a type 1 sialotransferrin pattern. Molecular analysis showed the previously described R141H, V231M, and T237M PMM2 mutations in four patients as well as 3 rare mutations (DeltaC389, L104V, and IVS1 -1 G-->A) in the PMM2 gene in two Asian patients. CONCLUSIONS: The clinical features of these patients with diverse ethnic backgrounds confirm the variable course of CDG type I. Screening for CDG should be considered in children with relatively mild neurologic impairment, especially if they have suggestive findings such as cerebellar hypoplasia and abnormal fat distribution.

Congenital Disorders of Glycosylation↗
PubMed2000

Allozyme variation patterns and multiple hybridization origins: clonal variation among four sibling parthenogenetic Caucasian rock lizards.

Allozyme electrophoresis of four sibling parthenogenetic Caucasian rock lizards Darevskia unisexualis, D. uzzelli, D. sapphirina, and D. bendimahiensis found seven clones and five variable loci. The data supported the hypothesis that D. raddei and D. valentini are the parental species of all four parthenogens. Variation patterns in Darevskia were summarized. Species that originated from a single F1 typically consisted of one widespread clone with a few rare clones. Species with multiple origins displayed variation only slightly higher than species with a single origin. This is contrary to other genera of parthenogenetic lizards, in which cases massive clonal variations were observed.

Animals↗
PubMed1998

Asylum applications in the European Union: patterns and trends and the effects of policy measures.

"Statistics on asylum applications have been used in a highly selective way in the debates on refugees and asylum policies in Western Europe, to justify restrictive measures. This paper provides a more systematic analysis of these statistics. It focuses on the pattern of origins and destinations for asylum seekers in the European Union in the period 1985-1994.... When the patterns of origin and destinations are compared for separate years, it becomes clear that the destinations of asylum movements have been constantly changing. Though some of the more remarkable shifts were clearly related to policy measures in the relevant countries, many measures produced only limited effects or failed to have any effect at all."

Demography↗