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PubMed2000

Effects of time intervals and tone durations on auditory stream segregation.

Adult listeners rated the difficulty of hearing a single coherent stream in a sequence of high (H) and low (L) tones that alternated in a repetitive galloping pattern (HLH-HLH-HLH...). They could hear the gallop when the sequence was perceived as a single stream, but when it segregated into two substreams, they heard H-H- ... in one stream and L-L- ... in the other. The onset-to-onset time of the tones, their duration, the interstimulus interval (ISI) between tones of the same frequency, and the frequency separation between H and L tones were varied. Subjects' ratings on a 7-point scale showed that the well-known effect of speed's increasing stream segregation is primarily due to its effect on the ISI between tones in the same frequency region. This has implications for several theories of streaming.

Adult↗
PubMed1997

Antiphase flicker induces depth segregation.

We examined the influence of the temporal phase of flickering stimuli on perceptual organization. When two regions of a uniform random-dot field are flickered in temporal alternation with the same flicker rate, one of the regions appears to lie in front of the other. Within the range of temporal frequencies used in the present experiments, depth perception was maximal between 5 and 31.3 Hz. Which region of the two is perceived as lying in front is different from person to person and sometimes fluctuates within the same subject, but when two regions are of different sizes, the smaller region tends to be perceived in front for longer than the larger region. The depth segregation was not due to a luminance difference, because the average temporal luminance of the regions was kept equal. Strikingly, the illusory depth segregation is perceived even between two adjacent regions whose densities of dots, sizes, shapes, and flicker rates are identical. This result suggests that a difference of temporal phase between two flickering regions is crucial for this new depth perception.

Adult↗
PubMed2004

Cdc14p/FEAR pathway controls segregation of nucleolus in S. cerevisiae by facilitating condensin targeting to rDNA chromatin in anaphase.

The condensin complex is the chief molecular machine of mitotic chromosome condensation. Nucleolar concentration of condensin in mitosis was previously shown to correlate with proficiency of rDNA condensation and segregation. To uncover the mechanisms facilitating this targeting we conducted a screen for mutants that impair mitotic condensin congression to the nucleolus. Mutants in the cdc14, esp1 and cdc5 genes, which encode FEAR-network components, showed the most prominent defects in mitotic condensin localization. We established that Cdc14p activity released by the FEAR pathway was required for proper condensin-to-rDNA targeting in anaphase. The MEN pathway was dispensable for condensin-to-rDNA targeting, however MEN-mediated release of Cdc14p later in anaphase allowed for proper, albeit delayed, condensin targeting to rDNA and successful segregation of nucleolus in the slk19 FEAR mutant. Although condensin was physically dislodged from rDNA in the cdc14 mutant, it was properly assembled, phosphorylated and chromatin-bound, suggesting that condensin was mis-targeted but active. This study identifies a novel pathway promoting condensin targeting to a specific chromosomal address, the rDNA locus.

Adenosine Triphosphatases↗
PubMed1995

[Texture segregation in large visual field].

Using large texture stimuli (72 degrees x 72 degrees or 20 degrees x 20 degrees), we investigated spatial properties of texture segregation. In Experiment 1, we used L-like forms, T-like forms, or tilted T-like forms to create a large background texture field, in which a small target region of the odd forms was embedded. The texture display was presented for 255 ms, and subjects were asked to detect the target and to recall its position. The target upright Ts in the tilted Ts and the target tilted Ts in the upright Ts segregated easily. In contrast to our expectation, however, the target upright Ts in the Ls and the target Ls in the upright Ts were detected better in the periphery than in the central area. In Experiment 2, subjects were asked to detect a single target element embedded in the background. The size of the elements was enlarged to that of the target texture region in Experiment 1. The target Ts and Ls were detected better in the central area than in the periphery. These results can be explained by the differential grouping processing and distribution of attention in the visual field.

Adult↗
PubMed1998

[Effect of presentation time and background size on texture segregation].

We investigated the effect of presentation time and background size on texture segregation in a large visual field. In Experiment 1, participants were asked to detect a target texture embedded in a large background texture. Texture displays were presented for 68 ms, 119 ms or 221 ms. In Experiment 2, background texture size was made smaller than that in Experiment 1, and the presentation time was 119 ms. The detection rate for the target increased as the presentation time increased. Upright Ts in tilted Ts and tilted Ts in upright Ts were segregated easily in central area, but the detection rate decreased in the periphery area for all the presentation times studied. Upright Ts in Ls and Ls in upright Ts were detected better in the periphery than in the central area on 119 ms condition of Experiment 1. On the other hand, there was no difference in detection rate between the central area and the periphery with smaller backgrounds on Experiment 2. Discriminability for Ts and Ls was not determined only by the retinal position, but it was also affected by distribution of participants' attention in their visual fields.

Adult↗
PubMed1999

Segregation analysis of attention deficit hyperactivity disorder.

We performed segregation analysis on 495 nuclear families, ascertained for the father's substance abuse diagnosis, in an attempt to determine the role of genetic and other influences in determining the variability of DSM-III-R-defined attention deficit hyperactivity disorder (ADHD). For our analyses, ADHD was treated as a quantitative variable, utilizing the semicontinuous scale provided by the 15-item symptom count within DSM-III-R. Analyses consisted of both class A and class D regressive models for which covariate effects (socioeconomic status) and sex dependence were estimated. Segregation analysis of the quantitative trait (ADHD symptom count) in the entire data set supported a transmissible non-Mendelian major effect. Models which were sex-dependent and included covariate effects provided the best fit to the data. In addition, similar analyses were performed on a 130-nuclear family subgroup of the data set in which at least one of the members of the nuclear family met DSM-III-R diagnostic criteria for ADHD. The sex-dependent Mendelian codominant model was best supported by the data, while other models could be rejected. Incorporating covariate effects did not provide a better fit for the data. Thus, this study is consistent with Mendelian transmission of ADHD symptom count in a clinically relevant population. Overall, our results support the presence of a heritable continuous trait of which ADHD represents an extreme.

Analysis of Variance↗
PubMed1976

HLA antigen segregation analysis in multiple sclerosis (MS) families.

HLA antigen segregation analysis was performed in 38 families with a total of 52 multiple sclerosis (MS) patients including 14 families with 2 affected sibs. HLA-A3 and especially B7 occurred more frequently in familial MS cases (propositi) (A3: 42.9%, B7: 64.3%) than in non-familial cases (A3: 35.8%, B7: 35.3%). As could be expected from the increased phenotype frequencies of A3 and B7, the haplotype A3-B7 showed a disturbed segregation among the MS patients but not among their healthy sibs. A second haplotype, A1-B8, was found more frequently than expected among the MS patients but also among their unaffected sibs. These data may suggest increased MS susceptibility associated with the haplotype A3-B7 and, conversely autoimmune or protective properties associated with A1-B8 in MS patients and their healthy sibs, respectively.

Female↗
PubMed1999

Identification and characterization of maternally expressed genes with mRNAs that are segregated with the endoplasm of early ascidian embryos.

Endoderm cells of the ascidian embryo are specified autonomously dependent on maternal cytoplasmic information or determinants that are localized in the endoplasm. In the present study, we identified three maternally expressed genes (CsEndo-1, CsEndo-2 and CsEndo-3) by screening a cDNA library of Ciona savignyi fertilized egg mRNAs subtracted with gastrula mRNAs. CsEndo-1 encoded a protein with nuclear localization signals, CsEndo-3 predicted a protein containing both a potential transmembrane domain and the PDZ domain, and CsEndo-2 suggested a protein with no similarity to known proteins. The maternal transcripts of all of these genes were not concentrated during early stages of embryogenesis up to the 8-cell stage, but were concentrated at the endoplasmic region by the 16-cell stage and then segregated later with the endoplasm. At the 110-cell stage, the maternal transcript of CsEndo-1 was evident only in the primordial endoderm cells, while those of CsEndo-2 and CsEndo-3 were found in the primordial endoderm cells as well as the primordial notochord cells. All of the transcripts became barely detectable during gastrulation and neurulation. Later, zygotic expression of the three genes became evident again in the endoderm and notochord cells, suggesting developmental roles in the formation of these types of cell. Although we were not able to deduce their functions, this is the first report of maternal genes with mRNAs that are segregated with the endoplasm of ascidian embryos.

Amino Acid Sequence↗
PubMed1999

Nitric oxide in the retinotectal system: a signal but not a retrograde messenger during map refinement and segregation.

The role of nitric oxide (NO) as a mediator of synaptic plasticity is controversial in both the adult and developing brain. NO generation appears to be necessary for some types of NMDA receptor-dependent synaptic plasticity during development but not for others. Our previous work using several NO donors revealed that Xenopus laevis retinal ganglion cell axons stop growing in response to NO exposure. We demonstrate here that the same response occurs in tectal neuron processes bathed in the NO donor S-nitrosocysteine (SNOC) and in RGC growth cones to which SNOC is very locally applied. We show that NO synthase (NOS) activity is present in the Rana pipiens optic tectum throughout development in a dispersed subpopulation of tectal neurons, although effects of NO on synaptic function in a Rana pipiens tectal slice were varied. We chronically inhibited NOS in doubly innervated Rana tadpole optic tecta using L-N(G)-nitroarginine methyl ester in Elvax. Despite significant NOS inhibition as measured biochemically, eye-specific stripes remained normally segregated. This suggests that NOS activity is not downstream of NMDA receptor activation during retinotectal synaptic competition because NMDA receptor activation is necessary for segregation of retinal afferents into ocular dominance stripes in the doubly innervated tadpole optic tectum. We conclude that NO has some signaling function in the retinotectal pathway, but this function is not critical to the mechanism that refines the projection and causes eye-specific stripes.

Animals↗
PubMed1999

Restricted receptor segregation into membrane microdomains occurs on human T cells during apoptosis induced by galectin-1.

Galectin-1 induces apoptosis of human thymocytes and activated T cells by an unknown mechanism. Apoptosis is a novel function for a mammalian lectin; moreover, given the ubiquitous distribution of the oligosaccharide ligand recognized by galectin-1, it is not clear how susceptibility to and signaling by galectin-1 is regulated. We have determined that galectin-1 binds to a restricted set of T cell surface glycoproteins, and that only CD45, CD43, and CD7 appear to directly participate in galectin-1-induced apoptosis. To determine whether these specific glycoproteins interact cooperatively or independently to deliver the galectin-1 death signal, we examined the cell surface localization of CD45, CD43, CD7, and CD3 after galectin-1 binding to human T cell lines and human thymocytes. We found that galectin-1 binding resulted in a dramatic redistribution of these glycoproteins into segregated membrane microdomains on the cell surface. CD45 and CD3 colocalized on large islands on apoptotic blebs protruding from the cell surface. These islands also included externalized phosphatidylserine. In addition, the exposure of phosphatidylserine on the surface of galectin-1-treated cells occurred very rapidly. CD7 and CD43 colocalized in small patches away from the membrane blebs, which excluded externalized phosphatidylserine. Receptor segregation was not seen on cells that did not die in response to galectin-1, including mature thymocytes, suggesting that spatial redistribution of receptors into specific microdomains is required for triggering apoptosis.

Antigens, CD↗
PubMed1999

[New models of inheritance of complex characteristics and their use in segregation analysis of idiopathic scoliosis].

New methods of segregation analysis of alternative traits have been developed. These methods make it possible to take into account the sex and age specificity of the disease manifestation. Hence, they extend the range of genetic hypotheses to be tested and ensure the correct analysis of inheritance of complex pathologies in humans. Segregation analysis of idiopathic scoliosis performed in this study demonstrates the possibilities of the new methods. Based on pedigrees of 93 probands, it has been demonstrated for the first time that the inheritance of severe (degrees II to IV) forms of this disease can be described by a model that assumes a dominant major gene with incomplete, sex- and age-dependent penetrances of all genotypes. According to this model, severe forms of idiopathic scoliosis do not develop if the mutant allele is absent (the penetrance of genotype A1A1 is zero). The probabilities of the disease for subjects with genotypes A1A2 and A2A2 are similar and approximately equal to 0.3 and 0.5 for males and females, respectively. Mild (degree I) forms of idiopathic scoliosis are heterogeneous. A progressive disease may be expected only in the patients that carry the mutant allele.

Adolescent↗
PubMed2000

A new physiologically based, segregated-flow model to explain route-dependent intestinal metabolism.

Processes of intestinal absorption, metabolism, and secretion must be considered simultaneously in viewing oral drug bioavailability. Existing models often fail to predict route-dependent intestinal metabolism, namely, little metabolism occurs after systemic dosing but notable metabolism exists after oral dosing. A physiologically based, Segregated-Flow Model (SFM) was developed to examine the influence of intestinal transport (absorption and exsorption), metabolism, flow, tissue-partitioning characteristics, and elimination in other organs on intestinal clearance, intestinal availability, and systemic bioavailability. For the SFM, blood flow to intestine was effectively segregated for the perfusion of two regions, with 10% reaching an absorptive layer-the enterocytes at the villus tips of the mucosa where metabolic enzymes and the P-glycoprotein reside, and the remaining 90% supplying the rest of the intestine (serosa and submucosa), a nonabsorptive layer. The traditional, physiologically-based model, which regards the intestine as a single, homogeneous compartment with all of the intestinal blood flow perfusing the tissue, was also examined for comparison. The analytical solutions under first order conditions were essentially identical for the SFM and traditional model, differing only in the flow rate to the absorptive/removal region. The presence of other elimination organs did not affect the intestinal clearance and bioavailability estimates, but reduced the percentage of dose metabolized by the intestine. For both models, intestinal availability was inversely related to the intrinsic clearances for intestinal metabolism and exsorption, and was additionally affected by both the rate constant for absorption and that denoting luminal loss when drug was exsorbed. However, the effect of secretion by P-glycoprotein became attenuated with rapid absorption. The difference in flow between models imparted a substantial influence on the intestinal clearance of flow-limited substrates, and the SFM predicted markedly higher extents of intestinal metabolism for oral over i.v. dosing. Thus, the SFM provides a physiological view of the intestine and explains the observation of route-dependent, intestinal metabolism.

Administration, Oral↗
PubMed2000

Major gene segregation of actinic prurigo among North American Indians in Saskatchewan.

Actinic prurigo is an idiopathic, familial photodermatosis seen especially in American Indians. Segregation analysis was performed on 12 Saskatchewan pedigrees with American Indian ancestry, comprising a total of 1,148 individuals, ascertained via probands diagnosed with actinic prurigo. Although a high degree of familial aggregation has been noted in the past and dominant inheritance has been suggested, no formal segregation analysis has been attempted. Actinic prurigo has a variable age of onset and, therefore, age at the time of censoring must be taken into account in the analysis. However, as these ages of 57% of the unaffected individuals were missing, an algorithm was devised to impute the missing ages from known birth years in the family based on the age differences among relatives and spouses. Using these imputed ages, simple dominant inheritance with incomplete penetrance and a single age of onset distribution was found. The method for imputing the ages at examination was evaluated, as was the correction for ascertainment, by using alternative methods and comparing the results. Regardless of the method used, a dominant mode of inheritance without any multifactorial component remained the best hypothesis.

Adolescent↗
PubMed1999

Mutations of the retinal specific ATP binding transporter gene (ABCR) in a single family segregating both autosomal recessive retinitis pigmentosa RP19 and Stargardt disease: evidence of clinical heterogeneity at this locus.

Stargardt disease (STGD) is an autosomal recessive macular dystrophy of childhood characterised by bilateral loss of central vision over a period of several months. STGD has been mapped to chromosome 1p22.1 and recently ascribed to mutations in the retinal specific ATP binding transporter gene (ABCR). The fundus flavimaculatus with macular dystrophy (FFM), an autosomal recessive condition responsible for gradual loss of visual acuity in adulthood (second to third decade) has also been mapped to the same locus. However, a gene for autosomal recessive retinitis pigmentosa with distinctive features of choriocapillaris atrophy at an advanced stage (RP19) has been mapped to the genetic interval encompassing the STGD gene on chromosome 1p (D1S435-D1S236), raising the question of whether, despite striking differences in clinical course and presentation, RP19 and STGD might be allelic disorders at the ABCR locus. In a family segregating RP and STGD in two first cousins, we found that heterozygosity for a splicing mutation in the ABCR gene (1938-1 G-->A) resulted in STGD while hemizygosity for this splice mutation resulted in RP, and when studying the RP patient's parents, we found a maternal non-contribution with apparent segregation of a null allele ascribed to a partial deletion of the ABCR gene. The present study shows that, despite striking clinical differences, RP19 and STGD are allelic disorders at the ABCR locus.

ATP-Binding Cassette Transporters↗
PubMed2000

Segregation analysis of asthma: recessive major gene component for asthma in relation to history of atopic diseases.

Although asthma has a significant heritable component, the mode of inheritance remains controversial because of the complexity of the disease and the influence of environmental factors. Segregation analysis for asthma are performed with and without a history of atopic diseases (dermatitis and rhinitis) after adjusting for environmental factors. To investigate whether asthma may be inherited through a major gene with two alleles, the REGD program of the Statistical Analysis for Genetic Epidemiology (SAGE) package was conducted in 1,990 individuals from 227 families with at least one asthmatic child in a cross-sectional study of respiratory diseases in Southern Taiwan. Other covariates adjusted for included age, sex, current smoking, and environmental tobacco smoking. The hypothesis of Mendelian model and no parent-offspring transmission was rejected. However, when the variables of atopic disease and environmental factors were included in the model as covariates, the models for a two-allele gene with a recessive or codominant inheritance could not be rejected, and Akaike's Information Criterion was smaller (1,377. 13) for the recessive model than all of the other models tested, assuming a major gene with a population frequency of 0.56 +/- 0.04. However, Mendelian model without family effect was rejected. In conclusion, a history of asthma in parents is a strong risk factor for asthma in offspring. Under the assumptions of the applied segregation, at least one major gene exists that could be a gene involved also in allergy. However, the data suggest that a single locus gene explains a portion of asthma that is related to the history of atopic diseases. In addition, a polygenic/multifactorial (genetic and environmental factors) influence with a recessive component inheritance may be involved in the pathogenesis of asthma.

Adolescent↗
PubMed2001

[Complex segregation analysis of systemic lupus erythematosus].

OBJECTIVE: To explore the genetic model of systemic lupus erythematosus(SLE). METHODS: Complex segregation analysis was performed by using statistical analysis for genetic epidemiology-REGTL(SAGE-REGTL). The genetic model and gene frequency were estimated. 300 pedigrees with SLE were collected from 300 patients as probands. RESULTS: The complex segregation analysis found the genetic model of SLE to be additive,the gene frequency 0.336. The authors believe the possibility of some different modes coexisting under different circumstances. The genetic effect on young man is stronger than that on old one. CONCLUSION: This study suggests that the genetic mode of SLE could be the major gene trait, and additive mode is the best fitted one.

Adolescent↗
PubMed1975

General models for segregation analysis.

Theoretical details are given of various oligogenic models for segregation analysis that are available as a general segregation analysis ("GENSEG") package, programmed in FORTRAN iv. The models allow for up to two autosomal loci and one X-linked locus, normally distributed or dichotomous phenotypes, variable age of onset, and various ascertainment functions (including one that allows the probability of becoming a proband to be dependent on the age of onset). Current programs are limited to the analysis of 2-generational data, using the joint likelihood of the sibship and parental phenotypes, unless it can be assumed that the pedigrees being analyzed are a random sample from the population; half-sibships and twins, however, are explicitly allowed.

Age Factors↗