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PubMed1975

Latency differences to monochromatic stimuli measured by disjunctive reaction time.

Two studies were done in order to assess the effects of wavelength on visual perceptual latency as measured in a disjunctive RT paradigm. The results of the first study, though not statistically significant, suggested a trend toward shorter RT to longer wavelength stimuli. In the second study, using well-practiced subjects, significant differences were found between disjunctive RT to red and green stimuli. The results suggest that latency differences as a function of wavelength are demonstrable in an experimental situation in which the subject must react to chromatic information, as differentiated from brightness information.

Adult↗
PubMed2000

A signal detection model predicts the effects of set size on visual search accuracy for feature, conjunction, triple conjunction, and disjunction displays.

Recently, quantitative models based on signal detection theory have been successfully applied to the prediction of human accuracy in visual search for a target that differs from distractors along a single attribute (feature search). The present paper extends these models for visual search accuracy to multidimensional search displays in which the target differs from the distractors along more than one feature dimension (conjunction, disjunction, and triple conjunction displays). The model assumes that each element in the display elicits a noisy representation for each of the relevant feature dimensions. The observer combines the representations across feature dimensions to obtain a single decision variable, and the stimulus with the maximum value determines the response. The model accurately predicts human experimental data on visual search accuracy in conjunctions and disjunctions of contrast and orientation. The model accounts for performance degradation without resorting to a limited-capacity spatially localized and temporally serial mechanism by which to bind information across feature dimensions.

Adult↗
PubMed1999

Parental origin and meiotic stage of non-disjunction in 139 cases of trisomy 21.

The parental origin and the meiotic stage of non-disjunction have been determined in 139 Down syndrome patients with regular trisomy 21 and in their parents through the analysis of DNA polymorphism. The meiotic error is maternal in 91.60% cases and paternal in 8.39% of cases. Of the maternal cases, 72.41% were due to meiosis I errors (MMI) and 27.58% were due to meiosis II errors (MMII). Of the paternal cases, 45.45% were due to meiosis I (PMI) and 54.54% were due to meiosis II (PMII). The mean maternal ages were 31.6 +/- 5.3 (+/- SD) years in errors from MMI, 32.3 +/- 6.4 years in errors from MMII, 31.4 +/- 4.6 years in errors from PMI and 29.5 +/- 2.7 years in errors from PMII. No significant statistical differences were observed between maternal and paternal errors, further supporting the presence of a constant chromosome 21 non-disjunction error type.

Adolescent↗
PubMed2002

[Induction of non-disjunction of chromosome 8 by Tripterygium hypoglaucum (Lévl.) Hutch in mouse sperm].

Fluorescence in situ hybridization (FISH) was employed to detect non-disjunction of chromosome 8 during meiosis in young adult male mice after treated by Tripterygium hypoglaucum(Lévl.) Hutch(THH). The Kunming male mice were given THH(120 mg/kg, 240 mg/kg, 480 mg/kg) by abdominal cavity injection, and sacrificed 22 days sfter the treatment of THH. Epididymis sperm was used to make smear. FISH using bio-16-dUTP-labelled DNA probes specific for chromosome 8 was performed on epididymal sperm decondensed for 60 min each in 10 mmol/L DTT and 4 mmol/L LIS. The aneuploidy frequencies of chromosome 8 were significantly higher than the solvent control (P < 0.001) in both 240 mg/kg group and 480 mg/kg group. The aneuploidy frequencies were not significantly different between the sperm in 120 mg/kg group and the solvent control (P > 0.05). It is concluded that THH could induce non-disjunction of chromosome 8 in mouse sperm, and THH is a potential germinal aneugen in mammalian during the meiosis.

Aneuploidy↗
PubMed1991

DiGeorge anomaly in an infant with deletion of chromosome 22 and dup(9p) due to adjacent type II disjunction.

A term white girl presented with low birth weight, minor anomalies, and congenital heart defects. The infant had microcephaly, upslanting palpebral fissures, prominent nasal bridge, short philtrum, thin upper lip vermilion, down-turned corners of the mouth, receding mandible, and short broad neck. The hands showed proximal placement of the thumbs, bilateral clinodactyly of the index finger, and bilateral transverse crease. Both hands were clenched, with the index finger overlapping the third finger and the fifth finger overlapping the fourth. There was also talipes calcaneo-valgus, bilateral dorsiflexion of the metatarsophalangeal joints, flexion of the interphalangeal joints, and hypoplasia of all nails. The patient's karyotype was 46,XX,-22, + der(9)t(9;22)(q21.13;q12.1)mat; the mother had the balanced translocation 46,XX,t(9;22)(9pter----9q21.13::22q12.1----22qter++ +;22pter---- 22q12.1::9q21.3----9qter). The infant died at age 10 days, and the autopsy showed absent thyroid isthmus and rudimentary thymus, with one small ectopic parathyroid attached to it. The lungs were hypoplastic, with abnormal lobation. The cardiac anomalies included truncus arteriosus, truncal valve stenosis, single carotid trunk, subclavian arteries arising from the distal part of the aortic arch, atrial and ventricular septal defects, right ventricular hypertrophy, and a hypoplastic left pulmonary artery. Also, multiple small accessory spleens were present in addition to a normal-sized spleen. This case combines features associated with DiGeorge anomaly and dup(9p). The chromosome abnormality in this patient appears to have arisen in a maternal germ cell due to adjacent type II disjunction.

Chromosome Deletion↗
PubMed2000

Ribosomal DNA evidence and disjunctions of western American Portulacaceae.

Phylogenetic analysis of ribosomal DNA internal transcribed spacer sequences from 35 members of western American Portulacaceae plus seven Portulacaceae outgroups generally supports morphologically based interpretations of multiple intercontinental disjunctions. The data neither support nor refute monophyly of the western American group but strongly support a group comprising the western American taxa plus Phemeranthus, the only strictly American genus of the morphology-based eastern American/African group of Portulacaceae, along with the Australian genus Parakeelya. Support is strong for the monophyly of Calandrinia, Montiopsis, Lewisia, Claytonia, and Montia, along with a sister relationship of the last two. The data neither strongly support nor refute the morphologically based diagnosis of Cistanthe, but they strongly support a clade including the North American Cistanthe section Calyptridium and the South American Cistanthe sections Amarantoideae and Philippiamra. The internal transcribed spacer data fail to resolve the phylogenetic relationships among most of the western American lineages, suggesting either rapid radiation or, alternatively, erratic evolution of the internal transcribed spacer. The internal transcribed spacer and morphological evidence together suggest that in this group there have been 8-13 dispersal and colonization events across >2000 km (1 for every 15-26 extant species in this group). The internal transcribed spacer data document complex molecular evolutionary patterns, including strong substitution biases, among-site rate heterogeneity, positional bias for deamination-type substitutions, nonstationarity, and variable rates of insertion/deletion. Our phylogenetic conclusions, however, do not appear to be sensitive to these patterns.

Base Sequence↗
PubMed1990

Analysis of non-disjunction in sex chromosome tetrasomy and pentasomy.

X-linked DNA markers were used to determine the parental origin of the additional sex chromosomes in eight individuals with sex chromosome tetrasomy or pentasomy. In all cases studied, one parent contributed a single sex chromosome while the other parent contributed three or four sex chromosomes. Thus, it seems likely that most, if not all, sex chromosome tetrasomy and pentasomy is attributable to successive non-disjunctional events involving the same parent.

Female↗
PubMed1988

High efficiency in the attribution of parental origin of non-disjunction in trisomy 21 by both cytogenetic and molecular polymorphisms.

The precise origin of the supernumerary chromosome can be defined in the majority of trisomy 21 cases. This is achieved by evaluating the chromosome 21 short arm polymorphism and analysing restriction fragment length polymorphisms (RFLPs) of multiple chromosome 21 loci. We report a study on 37 Italian families with Down's syndrome. In 35 cases (94.6%) both the parental and the meiotic stage of non-disjunction could be established. Knowledge of the origin of the extra chromosome 21 is a pre-requisite for investigations of genetic or environmental factors that may affect the meiotic process.

Down Syndrome↗
PubMed1977

Somatic pairing and meiotic nonrandom disjunction in a pericentric inversion of Hylemya antiqua (Meigen).

An asymmetrical pericentric inversion in the onion fly, Hylemya antiqua was studied. Somatic pairing was studied in young eggs from test-and sibcrossed inversion heterozygous females which gave four and seven distinguishable karyotypes respectively. From these seven, three are balanced: the normal type, the inversion heterozygote and homozygote, and four are unbalanced recombinant karyotypes descending from crossovers in the loop. In all types at all mitotic stages the centromeres are paired. The telomeres only show association during prophase but this decreases from mid to late prophase. Quantitative analysis of the four different crossover products as produced by inversion heterozygous females showed the presence of nonrandom disjunction. A significant disparity was observed, viz. the normal chromosome was taken up preferentially into the functional gamete compared to the inverted chromosome. Dragging of long chromatids in the asymmetric dyad during M I-A I is a possible explanation of this feature.

Animals↗
PubMed1999

Tests of two hypotheses to account for different-sized saccades during disjunctive gaze shifts.

Rapid shifts of the point of visual fixation between objects that lie in different directions and at different depths require disjunctive eye movements. We tested whether the saccadic component of such movements is equal for both eyes (Hering's law) or is unequal. We compared the saccadic pulses of abducting and adducting movements when horizontal gaze was shifted from a distant to a near target aligned on the visual axis of one eye (Müller paradigm) in ten normal subjects. We similarly compared horizontal saccades made between two distant targets lying in the same field of movement as during the Müller paradigm tests, and between targets lying symmetrically on either side of the midline, at near side of the midline, at near or far. We measured the ratio of the amplitude of the movements of each eye in corresponding directions due to the saccadic component, as well as corresponding ratios of peak velocity and peak acceleration. In response to a Müller test paradigm requiring about 17 degrees of vergence, the change in position of the unaligned eye was typically twice the size of the corresponding movement of the aligned eye. The ratio of peak velocities for the unaligned/aligned eyes was about 1.5, which was greater than for saccades made between distant targets. The ratio of peak acceleration for unaligned/aligned eyes was about 1.0 during shifts from near to far and about 1.3 for shifts from far to near, these values being similar to corresponding ratios for saccades between distant targets. These measurements of peak acceleration indicate that the saccadic pulses sent to each eye during the Müller paradigm are more equal than would be deduced by comparing the changes in eye position. We retested five subjects to compare directly the peak acceleration of saccades made during the Müller paradigm with similar-sized "conjugate" saccades made between targets at optical infinity. Saccades made during the Müller paradigm were significant slower (P < 0.005) than similar-sized conjugate saccades; this indicated that the different-sized movements during Müller paradigm are not simply due differences in saccadic pulse size but are also influenced by the concurrent vergence movement. A model for saccade-vergence interactions, which incorporates equal saccadic pulses for each eye, and differing contributions from convergence and divergence, accounts for many of these findings.

Acceleration↗
PubMed2004

The Iml3 protein of the budding yeast is required for the prevention of precocious sister chromatid separation in meiosis I and for sister chromatid disjunction in meiosis II.

The mitotic kinetochore of the budding yeast contains a number of proteins which are required for chromosome transmission but are non-essential for vegetative growth. We show that one such protein, Iml3, is essential for meiosis, in that the absence of this protein results in reduced spore viability, precocious sister chromatid segregation of artificial and natural chromosomes in meiosis I and chromosome non-disjunction in meiosis II.

Chromosome Segregation↗
PubMed2006

A cytological study on Kelloggia (Rubiaceae), an intercontinental disjunct genus between eastern Asia and western North America.

A cytological study was carried out for the first time on four populations of the only two species of Kelloggia (Rubiaceae), which occur disjunctly in eastern Asia (K. chinensis Franch.) and western North America (K. galioides Torr.). The consistent mitotic prophase chromosome condensation pattern and interphase nuclei type were determined for both species. The chromosome base number of the genus is suggested to be x = 11. The karyotype of 2n = 22 = 2x = 16m + 6sm was examined for both species. The karyotypical asymmetry of 1A and 2A was found in K. chinensis and K. galioides, respectively. According to the predominant evolutionary direction of karyotype asymmetry in angiosperms, K. galioides (2A) seems slightly more evolved than K. chinensis (1A). Our finding is consistent with the hypothesis of the Old World origin of Kelloggia based on molecular study.

Biological Evolution↗
PubMed1986

Characterization of O2 evolution by a wheat photosystem II reaction center complex isolated by a simplified method: disjunction of secondary acceptor quinone and enhanced Ca2+ demand.

An O2-evolving photosystem II (PSII) reaction center complex was prepared from wheat by a simple method consisting of octylglucoside solubilization of Triton PSII particles followed by one-step sucrose density gradient centrifugation. The complex contained six species of proteins including the 33-kDa extrinsic protein with the same relative abundance as in the original PSII particles, one cytochrome b559, 4 Mn, and about 40 chlorophyll (Chl) per O2-evolving unit, and evolved O2 at a high rate of 1400-1700 mumol O2/mg Chl/h. O2 evolution by the complex was dependent on acceptor species, showing a hierarchy, ferricyanide greater than dichlorobenzoquinone greater than phenylbenzoquinone greater than dimethylbenzoquinone greater than duroquinone, and insensitive to DCMU, indicative of disjunction of the secondary quinone acceptor of PSII from the electron transport pathway. O2 evolution also showed a marked dependence on Cl- and Ca2+: about 10-fold acceleration by Cl- and an additional 2- to 3-fold by Ca2+. Comparison of the dissociation constants for Cl- and Ca2+ between the complex and NaCl-washed PSII particles revealed that octylglucoside treatment gives rise to a new Ca2+-sensitive site by removal of some unknown factor(s) other than the extrinsic 22- and 16-kDa proteins, while it preserves the Cl(-)-sensitive site as native as in NaCl-washed PSII particles. Analysis of the relationship between Cl- demand and Ca2+ demand revealed that Ca2+ absence noncompetitively inhibits the Cl(-)-supported O2 evolution, indicative of the independence of the binding site of these two factors.

Benzoquinones↗
PubMed1995

ADP release is the rate-limiting step of the MT activated ATPase of non-claret disjunctional and kinesin.

The motor protein non-claret disjunctional (ncd) moves towards the minus ends of microtubules (MTs), whereas its close relative kinesin moves in the opposite direction towards the plus ends of MTs. The mechanisms of movement and directional reversal for these motor proteins are unknown. Here we report the rate constants for MT activated ADP release from a recombinant double-headed ncd protein, GST-MC5, and a recombinant double-headed kinesin protein, K delta 401, measured using the fluorescent nucleotide analogues methylanthranilyol ATP (mantATP) and mantADP. Comparison of the maximal MT activated mantADP release rates for these proteins with their maximal MT activated mantATP turnover rates indicates that ADP release is the rate-limiting step for ATP turnover for both ncd and kinesin. This data supports the view that directional reversal may result from structural rather than chemical kinetic differences in the way the motors interact with MTs.

Adenosine Diphosphate↗
PubMed1979

Stress analysis of disjunct removable partial dentures.

The (1) tooth-supported, (2) ridge-supported, and (3) tooth- and ridge-supported variations of the disjunct removable partial denture were studied. When testing loads were applied to three sites, bilaterally and unilaterally, it was found that the stresses were highest when the removable partial framework was tooth-support. No significant difference was recorded between the ridge-supported partial denture and the tooth- and ridge-supported partial framework. Further refinement of the pinsleeve mechanism may be necessary to effect better control over the distributions of the stresses.

Alveolar Process↗
PubMed1979

A first exploration of a Robertsonian translocation heterozygote in the mouse for its usefulness in cytological evaluation of radiation-induced meiotic autosomal non-disjunction.

In this report some data concerning the male meiotic system of mice heterozygous for Rb(11.13)4Bnr are presented and compared with those of a chromosomally normal Swiss random-bred stock. Change of the genetic background from a C3H/Swiss hybrid situation to the fourth backcross generation (to the Swiss random-bred stock), did not alter the average frequency of aneuploid secondary spermatocytes. This was confirmed by studies on post-implantation loss. Spermatogenic characteristics of Rb4/+ mice, such as testis weight, sperm production and the number of diplotene-metaphase-I figures found in stage XII of the seminiferous epithelium, suggest delay and cell death during this period. These data support our working hypothesis that such an aberrant chromosome system may be more prone to radiation effects and therefore is promising in our cytological studies into the causes of spontaneous and in our cytological studies into the causes of spontaneous and induced autosomal non-disjunction during meiosis in the mouse.

Animals↗