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At least 307 records · Page 17Linked to original sources
PubMed2006

Analysis of segregation distortion of molecular markers in F2 population of rice.

A genetic linkage map comprising 148 SSR markers loci was constructed using an F2 population consisting of 90 lines derived from a sub-specific cross between a japonica variety Nipponbare and an indica variety Guangluai-4. The F2 population showed high significantly distorted segregations. Among these SSR markers, 49 markers(33.11%) showed the genetics distortion(P<0.05). Of them, 36 markers deviated toward male parent indica GuangLuAi-4 and 13 markers toward heterozygote, but none toward the female parent Nipponbare. It was found that the segregation distortion might be caused by gametophyte and zygote. Since most gametophyte loci and sterility loci were mapped in segregation distortion regions, it indicated that the segregation distortion may be caused by these gametophyte loci and sterility loci. Finally, this research also analyzed the skewed segregation of some markers, which had not been mapped on chromosome.

Biomarkers↗
PubMedDate not supplied

The segregation of ON- and OFF-center responses in the lateral geniculate nucleus of normal and monocularly enucleated ferrets.

We have investigated the distribution of ON- and OFF-center responses in the lateral geniculate nucleus of ferrets with normal and abnormal retinal projections. Electrophysiological recordings in normal pigmented animals confirm previous studies on mustelids showing that ON-center responses are found in the anterior, inner parts of laminae A and A1 and OFF-center responses in posterior, outer leaflets. In albino animals, lamina A displays normal patterns of ON/OFF segregation but in lamina A1', which receives an abnormal crossed retinal projection, no consistent patterns of segregation are found. Following monocular enucleation on the day of birth, the uncrossed projection in pigmented ferrets remains expanded across the LGN. Anatomically and physiologically, this projection is segregated into two leaflets: an anterior, inner ON-center leaflet and a posterior outer OFF-center leaflet. We conclude that the persistence of ON/OFF segregation, independent of geniculate location, suggests that self-sorting of retinal input is an important factor in generating the segregation.

Afferent Pathways↗
PubMed2002

Sexual segregation in ungulates: a comparative test of three hypotheses.

In most social ungulate species, males are larger than females and the sexes live in separate groups outside the breeding season. It is important for our understanding of the evolution of sociality to find out why sexual segregation is so widespread not only in ungulates but also in other mammals. Sexual body size dimorphism was proposed as a central factor in the evolution of sexual segregation in ungulates. We tested three hypotheses put forward to explain sexual segregation: the predation-risk, the forage-selection, and the activity budget hypothesis. We included in our analyses ungulate species ranging from non-dimorphic to extremely dimorphic in body size. We observed oryx, zebra, bighorn sheep and ibex in the field and relied on literature data for 31 additional species. The predation-risk hypothesis predicts that females will use relatively predator-safe habitats, while males are predicted to use habitats with higher predation risk but better food quality. Out of 24 studies on different species of ungulates, females and their offspring chose poorer quality but safer habitat in only eight cases. The forage-selection hypothesis predicts that females would select habitat based on food quality, while males should prefer high forage biomass. In fact, females selected higher quality food in only six out of 18 studies where males and females segregated, in eight studies there was no difference in forage quality and in four studies males were in better quality habitat. The activity budget hypothesis predicts that with increasing dimorphism in body size males and females will increasingly differ in the time spent in different activities. Differences in activity budgets would make it difficult for males and females to stay in mixed-sex groups due to increased costs of synchrony to maintain group cohesion. The predictions of the activity budget hypothesis were confirmed in most cases (22 out of 23 studies). The heavier males were compared to females, the more time females spent foraging compared to males. The bigger the dimorphism in body mass, the more males spent time walking compared to females. Lactating females spent more time foraging than did non-lactating females or males. Whether species were mainly bulk or intermediate feeders did not affect sexual differences in time spent foraging. We conclude that sexual differences in activity budgets are most likely driving sexual segregation and that sexual differences in predation risk or forage selection are additive factors.

Animals↗
PubMed1995

Auditory stream segregation by musical timbre: effects of static and dynamic acoustic attributes.

Two experiments examined the influence of timbre on auditory stream segregation. In experiment 1, listeners heard sequences of orchestral tones equated for pitch and loudness, and they rated how strongly the instruments segregated. Multidimensional scaling analyses of these ratings revealed that segregation was based on the static and dynamic acoustic attributes that influenced similarity judgements in a previous experiment (P Iverson & CL Krumhansl, 1993). In Experiment 2, listeners heard interleaved melodies and tried to recognize the melodies played by a target timbre. The results extended the findings of Experiment 1 to tones varying pitch. Auditory stream segregation appears to be influenced by gross differences in static spectra and by dynamic attributes, including attack duration and spectral flux. These findings support a gestalt explanation of stream segregation and provide evidence against peripheral channel model.

Acoustics↗
PubMed2000

Auditory motion segregation: a limited analogy with vision.

Interaural time delay (ITD) is the dominant cue to sound-source location. When one component of a complex sound changes rapidly but smoothly in ITD, it perceptually segregates from the complex. When different components were changed in ITD in succession, a recognizable melody was heard. Each note was more detectable from the transition than from a distinct ITD with respect to the complex. However, a transition relative to a coherently changing complex produced no segregation, whereas cyclic modulation of ITD, too rapid to be perceived as movement, did produce segregation. These two results suggest that the relevant cue is not movement per se but rather the lack of a well-defined ITD during the transition. Segregation largely disappeared when the transition in ITD was replaced by a temporal gap in the complex of the order of 100 ms. The effect seems similar to visual motion segregation but is best explained by the mechanism of binaural unmasking.

Auditory Perception↗
PubMedDate not supplied

Mismatch-specific post-meiotic segregation frequency in yeast suggests a heteroduplex recombination intermediate.

Post-meiotic segregation of alleles, which is seen, for example, in the 5:3 distribution of alleles in the products of a single meiosis in fungi, has been thought to be due to the non-repair of heteroduplex regions formed during genetic recombination. In current models of genetic recombination, heteroduplex DNA is formed either as the primary intermediate generated by two interacting non-sister chromatids or as a short region flanking a double-stranded gap. The frequency of post-meiotic segregation differs for different alleles, and this is presumed to reflect the varying efficiencies with which different types of mismatches in the heteroduplex are repaired. To gain some insight into this process, we have now determined the nucleotide sequences of various yeast alleles with different post-meiotic segregation frequencies and compared the mismatches predicted to occur in heteroduplexes of these alleles with wild-type DNA with those repaired with varying efficiency in bacterial systems. A striking correlation is observed, with the mismatches predicted for high post-meiotic segregation frequency alleles being similar to mismatches repaired with low efficiency in bacteria. These results support the view that postmeiotic segregation frequency reflects heteroduplex repair efficiency and the contention that meiotic gene conversion is the result of the successful repair of heteroduplex mismatches.

DNA Repair↗
PubMed2002

Segregation analysis of HDL cholesterol in the NHLBI Family Heart Study and in Utah pedigrees.

We investigated the genetic determination of high-density-lipoprotein cholesterol (HDL-C) levels in the NHLBI Family Heart Study by segregation analysis. Included was a total of 3755 subjects from 560 randomly selected nuclear families and 522 families selected due to a high family risk of coronary heart disease (CHD). In the whole dataset, there was no evidence for an allele at a major gene locus responsible for HDL-C levels lower than the population mean or even for significant bimodality for low levels of HDL-C. However, we observed evidence for a recessive allele that was associated with higher HDL-C levels than average. This evidence for a recessive major gene was independent of triglyceride concentrations and was most strongly observed in families recruited for CHD. The environmental model was rejected (P=0.0027) while the codominant and recessive models were not rejected (P=0.085 and P=0.133, respectively). The dominant model was also rejected (P<0.0001). In the recessive segregation model, the means of those inferred to be homozygous for the high HDL-C allele and those without the high HDL-C allele were separated by about 25 mg/dl HDL-C (73.9+/-1.99 vs 48.2+/-0.36 mg/dl). Because these results were unexpected, segregation was tested in a separate sample of 2013 individuals in 85 large pedigrees ascertained for early heart disease deaths, early stroke deaths, and early hypertension in Utah. Similar evidence for an allele at a major gene locus for high HDL-C was found. In summary, we did not find evidence for an allele at a major gene locus associated with low HDL-C levels segregating in pedigrees recruited for the NHLBI Family Heart Study, or in pedigrees ascertained in Utah for early CHD or related phenotypes. Instead we found some evidence for the segregation of an allele associated with high HDL-C. d

Alleles↗
PubMed2006

Genetic segregation of microsatellite markers in Saccharum officinarum and S. spontaneum.

Genetic mapping techniques can be used to study the interaction between two different genomes after hybridization. This study investigated a Saccharum officinarum (Green German or GG, 2n approximately 11x approximately 110) x S. spontaneum (IND 81-146 or IND, 2n approximately 7x approximately 56) interspecific cross. Segregation of 193 microsatellite (SSR) loci was evaluated in the F(1) progeny of 169 full-sibs of the cross. Following the two-way pseudo-testcross strategy and 'cross pollination' population type, linkage groups (LG) and phases were established for each parent map, using the criteria of LOD score > or = 3.0 and a maximum recombination frequency of 0.35. Of the 193 markers analyzed, 61 were IND-specific, 106 were GG-specific, and 26 were heterozygous in both parents. About 78% of the markers segregated in a Mendelian fashion and 22% were distorted (as evaluated by chi(2)-tests, P < or = 0.01). The GG map included 91 marker loci arranged into 25 LG covering 1180 cM of the officinarum genome. The IND map consisted of 46 marker loci assembled into 10 LG, which spanned 614 cM of the spontaneum genome. A specific chromosome associated with segregation distortion was detected in the female (GG) genome only, probably as a result of double reduction. The segregation patterns of the marker loci indicated a centromere-driven distortion process with the shared allelic markers (as putative centromeres) regulating the placement and association of markers with opposite phase (coupling vs repulsion) and dosage on either side. Although incomplete, the framework maps were informative with respect to segregation distortion, chromosome fusion, rearrangements, and translocations, observed in both parental genomes as a result of their merger.

Chromosome Mapping↗
PubMed1991

Differential segregation of human and hamster cathepsin D in transfected baby-hamster kidney cells.

The segregation of human cathepsin D, studied in baby-hamster kidney cells (BHK) transfected with human cathepsin D cDNA and compared with that of hamster cathepsin D in the same cells, showed that, in cells that expressed human cathepsin D at a low rate, most of the enzyme remained intracellular. In contrast, when the enzyme was expressed at a high rate, most was secreted. The segregation was examined with an anti-(human cathepsin D) antibody that reacted with the human enzyme exclusively and an anti-(rat cathepsin D) antibody that reacted with both enzymes. In one protocol the cells were metabolically labelled and the two antibodies were used in sequence to precipitate the enzymes from extracts of cells and medium. High expression of the human enzyme did not interfere with the segregation of hamster cathepsin D. In another protocol the activity of cathepsin D in cells and medium was measured before and after titration with anti-(human cathepsin D) antiserum. Human cathepsin D was found predominantly in the medium, and hamster cathepsin D mainly in the cells. In the presence of 10 mM-NH4Cl the intracellular segregation of hamster cathepsin D was strongly inhibited, while the segregation of human cathepsin D was only slightly diminished. In BHK cells, at least two systems participate in the sorting of the two cathepsins, one of them being rather insensitive to NH4Cl.

Ammonium Chloride↗
PubMed2002

Self-concept and adaptive behaviour of people with intellectual disability in integrated and segregated recreation activities.

BACKGROUND: Leisure and recreation are areas in which the inclusion of people with intellectual disability (ID) in the community is required. In Israel, leisure activities have been developed over the past decade as part of the services provided to individuals with ID in the regular programmes of the community. However, even within those frameworks, people with ID are typically segregated from the whole population. METHODS: The purpose of the present study was to examine whether individuals with ID who participate in recreation activities with normal people as equals are different in their self-concept and adaptive behaviour from their counterparts who participate in segregated recreation programmes. Two hypotheses were examined: (1) whether people with ID who participate in integrated recreation programmes have a higher self-concept than those who participate in segregate programmes; and (2) whether individuals with ID who have better adaptive behaviour have a higher self-concept than people with ID who have lower adaptive behaviour. RESULTS: The hypotheses were partially confirmed. Differences were found in two subscales of self-concept. First, the physical self-concept of individuals with ID who participated in integrated programmes was found to be higher than that of their counterparts who participated in segregated programmes. Secondly, satisfaction with the whole self-concept of people with ID who participated in integrated programmes was found to be higher than of those who participated in segregated programmes. CONCLUSIONS: The implications of the research findings are discussed and future planning is recommended.

Adaptation, Psychological↗
PubMed1998

A fixed distance for separation of newly replicated copies of oriC in Bacillus subtilis: implications for co-ordination of chromosome segregation and cell division.

The Spo0J protein of Bacillus subtilis is required for normal chromosome segregation and forms discrete subcellular assemblies closely associated with the oriC region of the chromosome. Here we show that duplication of Spo0J foci occurs early in the DNA replication cycle and that this requires the initiation of DNA replication at oriC but not elongation beyond the nearby STer sites. Soon after duplication, sister oriC/Spo0J foci move rapidly apart to achieve a fixed separation of about 0.7 microm, reminiscent of the segregation of eukaryotic chromosomes on the mitotic spindle. The magnitude of the fixed separation distance may explain how chromosome segregation is kept in close register with cell growth and the initiation mass for DNA replication. It could also explain how segregation can proceed accurately in the absence of cell division. The kinetics of focal separation suggest that one role of Spo0J protein may be to facilitate formation of separate sister oriC complexes that can be segregated.

Bacillus subtilis↗
PubMed2005

Charge induced pattern formation on surfaces: segregation in cylindrical micelles of cationic-anionic peptide-amphiphiles.

Micelles, vesicles, and films composed of two species of incompatible heterogeneous molecules exhibit full internal segregation of the component species. This macroscopic segregation can be inhibited by oppositely charging the two different molecular species. The degree of compatibility achieved by the charges leads to either fully homogenous mixtures or to local segregation and the possible formation of regular patterns. We investigate the induction of periodic surface patterns by the presence of opposite charges in flat films and cylindrical micelles. In the strong segregation limit the incompatibility between species can be described by a line tension parameter gamma. The size of the patterns formed is of the order of a characteristic size L approximately (gamma/sigma(2))(1/2), where sigma is the surface charge density. The pattern symmetry on flat surfaces is function only of the fraction of area covered by the components, f: lamellar for 0.34<f<0.66 and hexagonal otherwise. In cationic and anionic mixtures aggregated into cylindrical micelles the symmetry and size of the surface charged domains depends also on the radius R of the cylinder. For large radii the patterns are similar to those in the plane, but for small radii only lamellar patterns are formed. At high salt concentration the surface domain size jumps discontinuously to an infinite value, resulting in macroscopic phase segregation.

Anions↗
PubMed2006

Visual saliency and texture segregation without feature gradient.

A central notion in the study of texture segregation is that of feature gradient (or feature contrast). In orientation-based texture segregation, orientation gradients have indeed played a fundamental role in explaining behavioral results. Here, however, we show that general, smoothly varying, orientation-defined textures (ODTs) exhibit striking perceptual singularities that are completely unpredictable from orientation gradients. These singularities defy not only popular texture segregation theories but also virtually all computational segmentation methods, and they confound previous behavioral studies with smoothly varying ODTs. We provide psychophysical evidence that perceptual singularities in smooth ODTs are salient visual features consistent across observers and with significant effect on the perception and segregation of oriented textures. We further show that, although orientation gradients cannot predict them, perceptual singularities in smooth ODTs emerge directly from, and can be spatially localized by, two ODT curvatures. Given the traditional role of feature gradients in early vision, the significance of these findings extends well beyond orientation-based texture segregation to issues ranging from curve integration and fragment grouping, through the perception of 3D shape, to the functional organization of the primary visual cortex.

Depth Perception↗
PubMed1999

Segregation-driven organization in chaotic granular flows.

An important industrial problem that provides fascinating puzzles in pattern formation is the tendency for granular mixtures to de-mix or segregate. Small differences in either size or density lead to flow-induced segregation. Similar to fluids, noncohesive granular materials can display chaotic advection; when this happens chaos and segregation compete with each other, giving rise to a wealth of experimental outcomes. Segregated structures, obtained experimentally, display organization in the presence of disorder and are captured by a continuum flow model incorporating collisional diffusion and density-driven segregation. Under certain conditions, structures never settle into a steady shape. This may be the simplest experimental example of a system displaying competition between chaos and order.

Journal Article↗
PubMed2004

Sickness absence due to musculoskeletal diagnoses: association with occupational gender segregation.

BACKGROUND: Musculoskeletal disorders represent a considerable public health problem and the most common diagnoses behind sickness absence and disability pensions. However, little is known about how sickness absence with these diagnoses varies with the strong gender segregation of the labour market. AIMS: A study was undertaken to investigate the association between musculoskeletal-related sickness absence and occupational gender segregation. METHODS: The study was population based, and included all new sick-leave spells exceeding seven days due to musculoskeletal diagnoses, comprising neckl shoulder pain, low back pain, and osteoarthritis in Ostergötland county, Sweden, which has 393,000 inhabitants (5%, of the national population). The participants were all sick-leave insured employed persons in Ostergötland (n = 182,663) in 1985. RESULTS: Cumulative incidence of musculoskeletal-related sickness absence (>7 days) was higher for women (7.5%, 95% confidence interval [C.I.] 7.3-7.7) than for men, (5.8%, C.I. 5.6-5.9), and the same was true for the mean number of sick-leave days (women 81, C.I. 78-83; men 65, C.I. 63-68). Grouping occupations according to degree of numerical gender segregation revealed the highest incidence and duration of sickness absence for women in male-dominated occupations. For both genders, the lowest cumulative incidence and duration occurred in gender-integrated occupations. CONCLUSIONS: Our results indicate a strong association between occupational gender segregation and musculoskeletal-related sickness absence. Further studies are needed to elucidate gender segregation of the labour market in relation to health and rehabilitation measures.

Absenteeism↗
PubMed1990

An instructive role for the interstitial matrix in tissue patterning: tissue segregation and intercellular invasion.

Intercellular invasion is the intrusion of the cells of one tissue into space occupied by a second tissue. The alternative situation to invasion, one characteristic of most coherent tissues, is segregation, with identifiable boundaries existing between contiguous tissues. The interfaces between mesenchymal and myocardial tissues in the developing avian heart show a profoundly different character in different regions of the heart: the interface between epicardial mesenchyme and heart wall myocardium is planar, without intermingling of the two cell types, whereas the interface between endocardial cushion mesenchyme and myocardium is diffuse, with extensive invasion of both tissue types across the border to produce intermingling of the two tissues. Thus, invasion and tissue segregation coexist in different regions of the mesenchyme-myocardium contact zone. Investigation of the involvement of the interstitial matrix in invasion and segregation has been conducted by maintaining the two tissues in mutual contact in organ culture. Investigation of the mechanisms by which the two cell types sort out in randomized chimeric tissue reaggregates has provided insight into the conditions for tissue segregation. We have modeled invasion in organ culture by fusing aggregates of myocardial cells with aggregates of cardiac mesenchymal cells. Cells of both tissues invaded the partner aggregate during a period of 1-3 d of coculture. Both invasion and segregation in the aggregates appear to depend on the presence or absence of a fibronectin-rich interstitial matrix elaborated by the cardiac mesenchyme. During sorting, the matrix appears selectively in regions occupied by the mesenchyme. Under conditions of culture that are nonpermissive for matrix deposition, sorting fails to occur. Stimulation of matrix deposition by addition of serum, transforming growth factor beta, or isolated matrix itself is accompanied by sorting out of the two tissues. Sorting out is blocked reversibly by inclusion of the fibronectin adhesion site peptide, GRGDSP. Invasion of fused aggregates is preceded by a redistribution of the fibronectin-containing matrix of the mesenchymal aggregate such that matrix-poor regions come to occupy the interface with the myocardial partner aggregate. The invasion that ensues involves mesenchymal cells emigrating from, and myocardial cells intruding into, matrix-poor regions of the mesenchymal aggregate.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗
PubMed1995

Microtubule polarity and dynamics in the control of organelle positioning, segregation, and cytokinesis in the trypanosome cell cycle.

Trypanosoma brucei has a precisely ordered microtubule cytoskeleton whose morphogenesis is central to cell cycle events such as organelle positioning, segregation, mitosis, and cytokinesis. We have defined microtubule polarity and show the + ends of the cortical microtubules to be at the posterior end of the cell. Measurements of organelle positions through the cell cycle reveal a high degree of coordinate movement and a relationship with overall cell extension. Quantitative analysis of the segregation of the replicated mitochondrial genome (the kinetoplast) by the flagellar basal bodies identifies a new G2 cell cycle event marker. The subsequent mitosis then positions one "daughter" nucleus into the gap between the segregated basal bodies/kinetoplasts. The anterior daughter nucleus maintains its position relative to the anterior of the cell, suggesting an effective yet cryptic nuclear positioning mechanism. Inhibition of microtubule dynamics by rhizoxin results in a phenomenon whereby cells, which have segregated their kinetoplasts yet are compromised in mitosis, cleave into a nucleated portion and a flagellated, anucleate, cytoplast. We term these cytoplasts "zoids" and show that they contain the posterior (new) flagellum and associated basal-body/kinetoplast complex. Examination of zoids suggests a role for the flagellum attachment zone (FAZ) in defining the position for the axis of cleavage in trypanosomes. Progression through cytokinesis, (zoid formation) while mitosis is compromised, suggests that the dependency relationships leading to the classical cell cycle check points may be altered in trypanosomes, to take account of the need to segregate two unit genomes (nuclear and mitochondrial) in this cell.

Animals↗
PubMed1982

Evidence for a polymorphism in gametic segregation using a malate dehydrogenase locus in the tetraploid treefrog Hyla versicolor.

Artificial cross combinations of tetraploid Hyla versicolor were analyzed electrophoretically using a polymorphic malate dehydrogenase locus (MDH-1) to determine the mechanism of chromosome segregation. Models for differentiating between disomic and tetrasomic inheritance are presented and tested. In some crosses progeny genotypes fit a disomic mode of segregation. In other crosses there is only evidence for a tetrasomic mode of segregation. Additional crosses produced genotypic ratios which conformed to either a disomic or tetrasomic mode of segregation. The same type of inheritance was demonstrated for any individual when used in multiple cross combinations. These results suggest that there exists in H. versicolor a polymorphism with respect to segregation of gametes, resulting from differences in chromosome pairings during meiosis I.

Animals↗