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PubMed1980

Conceptual rule learning in normal and learning disabled children.

Conceptual-rule learning performance of 36 normal and learning-disabled children, matched on CA, MA, and sex was compared with the use of a modified reception paradigm. Four types of rules (affirmation, conjunction, disjunction, conditional) and familiar and nonfamiliar shape attributes were used to test Bourne's stimulus-encoding hypothesis. Main findings indicated that when tested, learning-disabled children were deficient in all conceptual-rule tasks on an experimental paced, continuous-reinforcement schedule. Expected differences in rule complexity were found; however, disabled children's conceptual-rule response difficulties did not compare with normals. Manipulation of the attribute of shape familiarity produced only discernible saliency advantages in normal children. It was hypothesized that learning-diabled children were poor in problem solving because of a deficit in the comprehension of negative instances.

Child↗

PubMed1995

Perception of the combined effect of smoking and alcohol on health.

Because smoking is significantly associated with drinking, the consumption of alcohol can be associated with indirect consumption of tobacco (passive smoking), and alcohol and tobacco can have synergetic effects, the ways people perceive their combined effects were investigated. Information integration theory was applied, and the results showed that rather than representing the combined effects of tobacco consumption and alcohol consumption in a synergetic or summative way, the sample of 40 French adults apparently considered that indulging in only one of these two behaviors results almost unilaterally in maximal alteration of health. The two effects were seen to combine disjunctively, a way of perceiving the combined effects of the two substances that runs counter to current medical data on the subject.

Adult↗

PubMed1995

Termination in child analysis. A child-led process?

The paper begins by drawing attention to the disjunction between the theoretical conceptualizations of termination in child analysis and the process as it actually occurs. The central focus is on the process itself. Material is presented from four child analyses to illustrate the idiosyncratic ways in which the termination phase unfolded. The cases selected make it possible to consider termination in relation to each developmental phase. Our central argument is that, although the analyst should have certain criteria for termination in mind, termination in child analysis is essentially a child-led process.

Child↗

PubMed2004

Mental representation of logical connectives.

Logical connectives, such as "AND", "OR", "IF. THEN", and "IF AND ONLY IF" are ubiquitous in both language and cognition; however, reasoning with logical connectives is error-prone. We argue that some of these errors may stem from people's tendency to minimize the number of possibilities compatible with logical connectives and to construct a "minimalist" one-possibility representation. As a result, connectives denoting a single possibility (e.g., conjunctions) are likely to be represented correctly, whereas connectives denoting multiple possibilities (e.g., disjunctions or conditionals) are likely to be erroneously represented as conjunctions. These predictions were tested and confirmed in three experiments using different paradigms. In Experiment 1, participants were presented with a multiple-choice task and asked to select all and only those possibilities that would indicate that compound verbal propositions were true versus false. In Experiment 2, a somewhat similar task was used, except that participants were asked later to perform a cued recall of verbal propositions. Finally, Experiment 3 used an old/new recognition paradigm to examine participants' ability to accurately recognize different logical connectives. The results of the three experiments are discussed in relation to theories of representation of possibilities and theories of reasoning.

Adult↗

PubMed1998

Spring mediated dynamic craniofacial reshaping. Case report.

A new technique of using implantable springs as an adjunct after corrective surgery for craniofacial malformations is presented. A 6-month-old boy with multiple premature craniosynostoses and extreme turricephaly underwent surgery of limited extensiveness but supplemented with a set of indwelling springs for gradual postoperative skull reshaping. At spring removal three months later the skull was normalised both clinically and on cephalogram. A 5-year-old boy with Apert syndrome, severe midface retrusion, exorbitism, and sleep apnoea underwent a monobloc full face disjunction without repositioning, but was fitted with two springs for postoperative facial advancement. Three months postoperatively cephalometric analysis revealed 14 mm advancement at incisor level and at least 16 mm in the frontal region. There was no more exorbitism or clinically noticeable midface retrusion. Sleep studies revealed that the sleep apnoea was significantly improved, meaning complete cure except when sleeping flat on the back. It was concluded from these first clinical applications of spring assisted craniofacial distraction that springs hold significant promise for the future in many respects.

Acrocephalosyndactylia↗

PubMed1980

Formal aspects of theories of development.

The presentation of theories of adult development and aging in terms of their formal aspects can promote precision and clarity in theory construction, facilitate communication between subdisciplines of gerontology, provide a vehicle for the heuristic impact of theories and models upon each other, and alert older persons, practitioners, and researchers that there is a variety of models available for describing social and psychological changes. Theories may be categorized as simple or cumulative sequences, the latter permitting within-person response variation, and as disjunctive or conjunctive sequences, the latter implying the some characteristics are subordinate to others. These categories are illustrated with familiar examples from social, personality, and cognitive development, with particular attention given to the formal aspects of Erikson's theory.

Aging↗

PubMed1992

Multivariate analysis of craniomandibular disorders.

This article presents the clinical application of a special statistical method, the Multiple Correspondence Analysis (MCA), derived from data analysis and particularly suited to study a restricted population (here, 202 patients with temporomandibular joint [TMJ] disorders) whose characteristics are defined by a large number of modalities (140). Processing of a Burt-type data table, or Complete Disjunctive Table (CDT), provided a geometrical visualization of information, and permitted determination of the prevalent factor axes. Results showed a significant relationship between all the articular disorders, either peripheral or focal (TMJ), thus revealing the possibility of a yet, little known morphogenic influence on the genesis of TMJ disorders.

Adolescent↗

PubMed2002

Cytogenetic and cellular events during radiation-induced thymic lymphomagenesis in the p53 heterozygous (+/-) B10 mouse.

PURPOSE: Cellular and cytogenetic events in radiation-induced thymic lymphomagenesis were investigated in the p53 heterozygous (+/-) mouse following a single dose of whole-body irradiation. MATERIALS AND METHODS: The loss of the wild-type p53 allele and microsatellite markers of chromosome 11 in thymic lymphomas that developed in the p53 heterozygous (+/-) mouse after irradiation, and the stage at which prelymphoma cells appeared were analysed. RESULTS: The p53 heterozygous mouse developed thymic lymphomas in a dose-dependent manner. The loss of the wild-type p53 allele (loss of heterozygosity; LOH) occurred in almost all thymic lymphomas induced in the irradiated p53 heterozygous mouse. Cytogenetic analysis for the mechanism of LOH strongly suggested that the loss of the wild-type p53 gene in the lymphomas was caused by duplication of the disrupted allele through either homologous recombination or non-disjunctional chromosome duplication. The assay for prelymphoma cells suggested that a critical event in the development of prelymphoma cells occurred at least 3 weeks after irradiation. CONCLUSIONS: The loss of the wild-type p53 gene in thymocytes of the p53 heterozygous mouse may precede the development of prelymphoma cells after irradiation and be a valuable marker of radiation-induced leukemogenesis.

Animals↗

PubMed1983

The effects of lead and X-rays, alone or in combination, on blastocyst formation and cell kinetics of preimplantation mouse embryos in vitro.

Two-cell embryos in late G2-phase (cytofluorometrically determined) at 32 hours post-conception were treated in vitro with PbC12 (0 . 1 or 1 . 0 micrograms per ml). An additional group was X-irradiated 1 hour later (0 . 94 Gy) with or without lead treatment. Lead alone impaired formation and hatching of blastocysts. The combined treatment increased this deleterious effect on preimplantation development but synergism was not observed. Cell proliferation was disturbed by lead alone but to a higher degree by lead plus X-rays. A pronounced reduction of cell number per embryo was found during the period after reaching the morula stage although the labelling index increased. Apparently cell death occurred. Unlabelled S-phase cell nuclei (comparison between autoradiographic results and cytofluorometric DNA-determinations on the same isolated cell nuclei) and cell nuclei with a hyperploid (0 . 1 microgram PbC12 + 0 . 94 Gy) or hypoploid (1 . 0 microgram PcC12 + 0 . 94 Gy) DNA-content may have contributed to this cell loss. Labelling of cell nuclei which according to their DNA-content were not in S-phase was only observed when 0 . 1 microgram PbC12 alone or in combination with X-rays was used. This effect may be due to unscheduled DNA-repair synthesis or to the induction of chromosome aberrations (acentric fragments or non-disjunction).

Animals↗

PubMed1994

Construction of mouse chromosome-specific DNA libraries and their use for the detection of X-ray-induced aberrations.

We describe here the development of mouse chromosome-specific DNA libraries and their use in the detection of radiation-induced chromosome aberrations by fluorescence in situ hybridization. Large metacentric chromosomes, resulting from a translocation involving chromosomes 1, 11 and 13, were flow-sorted. Using a slit-scan technique for morphometric analysis, metacentric chromosomes were separated from normal acrocentric chromosomes and their aggregates. DNA from the metacentric chromosomes was amplified by PCR using the linker/adaptor method. In this pilot study, mouse was whole-body irradiated with 1, 2 and 3 Gy and aberrations were scored in metaphase spreads of splenocytes cultured in vitro. The results indicate that directly after radiation exposure, stable and unstable aberrations are induced at about equal frequencies in the splenocytes. The availability of chromosome-specific probes for mouse may prove very useful when analysing the behaviour of stable aberrations, as well as the testing of many suspected mutagenic carcinogens and aneugens in vivo for induction of chromosomal translocations and non-disjunction, respectively.

Animals↗

PubMed2004

Southern hemisphere biogeography inferred by event-based models: plant versus animal patterns.

The Southern Hemisphere has traditionally been considered as having a fundamentally vicariant history. The common trans-Pacific disjunctions are usually explained by the sequential breakup of the supercontinent Gondwana during the last 165 million years, causing successive division of an ancestral biota. However, recent biogeographic studies, based on molecular estimates and more accurate paleogeographic reconstructions, indicate that dispersal may have been more important than traditionally assumed. We examined the relative roles played by vicariance and dispersal in shaping Southern Hemisphere biotas by analyzing a large data set of 54 animal and 19 plant phylogenies, including marsupials, ratites, and southern beeches (1,393 terminals). Parsimony-based tree fitting in conjunction with permutation tests was used to examine to what extent Southern Hemisphere biogeographic patterns fit the breakup sequence of Gondwana and to identify concordant dispersal patterns. Consistent with other studies, the animal data are congruent with the geological sequence of Gondwana breakup: (Africa(New Zealand(southern South America, Australia))). Trans-Antarctic dispersal (Australia <--> southern South America) is also significantly more frequent than any other dispersal event in animals, which may be explained by the long period of geological contact between Australia and South America via Antarctica. In contrast, the dominant pattern in plants, (southern South America(Australia, New Zealand)), is better explained by dispersal, particularly the prevalence of trans-Tasman dispersal between New Zealand and Australia. Our results also confirm the hybrid origin of the South American biota: there has been surprisingly little biotic exchange between the northern tropical and the southern temperate regions of South America, especially for animals.

Africa↗

PubMed2006

Dating dispersal and radiation in the gymnosperm Gnetum (Gnetales)--clock calibration when outgroup relationships are uncertain.

Most implementations of molecular clocks require resolved topologies. However, one of the Bayesian relaxed clock approaches accepts input topologies that include polytomies. We explored the effects of resolved and polytomous input topologies in a rate-heterogeneous sequence data set for Gnetum, a member of the seed plant lineage Gnetales. Gnetum has 10 species in South America, 1 in tropical West Africa, and 20 to 25 in tropical Asia, and explanations for the ages of these disjunctions involve long-distance dispersal and/or the breakup of Gondwana. To resolve relationships within Gnetum, we sequenced most of its species for six loci from the chloroplast (rbcL, matK, and the trnT-trnF region), the nucleus (rITS/5.8S and the LEAFY gene second intron), and the mitochondrion (nad1 gene second intron). Because Gnetum has no fossil record, we relied on fossils from other Gnetales and from the seed plant lineages conifers, Ginkgo, cycads, and angiosperms to constrain a molecular clock and obtain absolute times for within-Gnetum divergence events. Relationships among Gnetales and the other seed plant lineages are still unresolved, and we therefore used differently resolved topologies, including one that contained a basal polytomy among gymnosperms. For a small set of Gnetales exemplars (n = 13) in which rbcL and matK satisfied the clock assumption, we also obtained time estimates from a strict clock, calibrated with one outgroup fossil. The changing hierarchical relationships among seed plants (and accordingly changing placements of distant fossils) resulted in small changes of within-Gnetum estimates because topologically closest constraints overrode more distant constraints. Regardless of the seed plant topology assumed, relaxed clock estimates suggest that the extant clades of Gnetum began diverging from each other during the Upper Oligocene. Strict clock estimates imply a mid-Miocene divergence. These estimates, together with the phylogeny for Gnetum from the six combined data sets, imply that the single African species of Gnetum is not a remnant of a once Gondwanan distribution. Miocene and Pliocene range expansions are inferred for the Asian subclades of Gnetum, which stem from an ancestor that arrived from Africa. These findings fit with seed dispersal by water in several species of Gnetum, morphological similarities among apparently young species, and incomplete concerted evolution in the nuclear ITS region.

Base Sequence↗

PubMed1995

Testing the mental model theory of propositional reasoning.

Johnson-Laird, Byrne, and Schaeken (1992) present a theory of propositional reasoning by mental models. The present study provides a comprehensive test of the predictions of that theory for the difficulty of simple disjunctive and conditional inferences. The results are largely consistent with the complex pattern of predictions. They are discussed in the light of recently proposed modifications of the original theory.

Adult↗

PubMed2000

The suppression of q card selections: evidence for deductive inference in Wason's selection task.

The results of three experiments investigating the role of deductive inference in Wason's selection task are reported. In Experiment 1, participants received either a standard one-rule problem or a task containing a second rule, which specified an alternative antecedent. Both groups of participants were asked to select those cards that they considered were necessary to test whether the rule common to both problems was true or false. The results showed a significant suppression of q card selections in the two-rule condition. In addition there was weak evidence for both decreased p selection and increased not-q selection. In Experiment 2 we again manipulated number of rules and found suppression of q card selections only. Finally, in Experiment 3 we compared one- and two-rule conditions with a two-rule condition where the second rule specified two alternative antecedents in the form of a disjunction. The q card selections were suppressed in both of the two-rule conditions but there was no effect of whether the second rule contained one or two alternative antecedents. We argue that our results support the claim that people make inferences about the unseen side of the cards when engaging with the indicative selection task.

Choice Behavior↗

PubMed1987

Synaptonemal complex antigen location and conservation.

The axial cores of chromosomes in the meiotic prophase nuclei of most sexually reproducing organisms play a pivotal role in the arrangement of chromatin, in the synapsis of homologous chromosomes, in the process of genetic recombination, and in the disjunction of chromosomes. We report an immunogold analysis of the axial cores and the synaptonemal complexes (SC) using two mouse monoclonal antibodies raised against isolated rat SCs. In Western blots of purified SCs, antibody II52F10 recognizes a 30- and a 33-kD peptide (Heyting, C., P. B. Moens, W. van Raamsdonk, A. J. J. Dietrich, A. C. G. Vink, and E. J. W. Redeker, 1987, Eur. J. Cell Biol., 43: 148-154). In spreads of rat spermatocyte nuclei it produces gold grains over the cores of autosomal and sex chromosomes. The cores label lightly during the chromosome pairing stage (zygotene) of early meiotic prophase and they become more intensely labeled when they are parallel aligned as the lateral elements of the SC during pachytene (55 grains/micron SC). Statistical analysis of electronically recorded gold grain positions shows that the two means of the bimodal gold grain distribution coincide with the centers of the lateral elements. At diplotene, when the cores separate, the antigen is still detected along the length of the core and the enlarged ends are heavily labeled. Shadow-cast SC preparations show that recombination nodules are not labeled. The continued presence suggests that the antigens serve a continuing function in the cores, such as chromatin binding, and/or structural integrity. Antibody III15B8, which does not recognize the 30- and 33-kD peptides, produces gold grains predominantly between the lateral elements. The grain distribution is bimodal with the mean of each peak just inside the pairing face of the lateral element. The antigen is present where and while the cores of the homologous chromosomes are paired. From the location and the timing, it is assumed that the antigen recognized by III15B8 functions in chromosome pairing at meiotic prophase. The two anti-rat SC antibodies label rat and mouse SCs but not rabbit or dog SCs. A positive control using human CREST (calcinosis, Raynaud's phenomenon, esophageal dysmotility, sclerodactyly, telangiectasia) anti-centromere serum gives equivalent labeling of SC centromeres in the rat, mouse, rabbit, and dog. It is concluded that the SC antigens recognized by II52F10 and III15B8 are not widely conserved. The two antibodies do not bind to cellular or nuclear components of somatic cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1990

In vitro reactivation of spindle elongation in fission yeast nuc2 mutant cells.

To investigate the mechanisms of spindle elongation and chromosome separation in the fission yeast Schizosaccharomyces pombe, we have developed an in vitro assay using a temperature-sensitive mutant strain, nuc2. At the restrictive temperature, nuc2 cells are arrested at a metaphase-like stage with short spindles and condensed chromosomes. After permeabilization of spheroplasts of the arrested cells, spindle elongation was reactivated by addition of ATP and neurotubulin both at the restrictive and the permissive temperatures, but chromosome separation was not. This suggests that the nuc2 cells are impaired in function at a stage before sister chromatid disjunction. Spindle elongation required both ATP and exogenous tubulin and was inhibited by adenylyl imidodiphosphate (AMPPNP) or vanadate. The ends of yeast half-spindle microtubules pulse-labeled with biotinylated tubulin moved past each other during spindle elongation and a gap formed between the original half-spindles. These results suggest that the primary mechanochemical event responsible for spindle elongation is the sliding apart of antiparallel microtubules of the two half-spindles.

Adenylyl Imidodiphosphate↗

PubMed1990

BIK1, a protein required for microtubule function during mating and mitosis in Saccharomyces cerevisiae, colocalizes with tubulin.

BIK1 function is required for nuclear fusion, chromosome disjunction, and nuclear segregation during mitosis. The BIK1 protein colocalizes with tubulin to the spindle pole body and mitotic spindle. Synthetic lethality observed in double mutant strains containing a mutation in the BIK1 gene and in the gene for alpha- or beta-tubulin is consistent with a physical interaction between BIK1 and tubulin. Furthermore, over- or underexpression of BIK1 causes aberrant microtubule assembly and function, bik1 null mutants are viable but contain very short or undetectable cytoplasmic microtubules. Spindle formation often occurs strictly within the mother cell, probably accounting for the many multinucleate and anucleate bik1 cells. Elevated levels of chromosome loss in bik1 cells are indicative of defective spindle function. Nuclear fusion is blocked in bik1 x bik1 zygotes, which have truncated cytoplasmic microtubules. Cells overexpressing BIK1 initially have abnormally short or nonexistent spindle microtubules and long cytoplasmic microtubules. Subsequently, cells lose all microtubule structures, coincident with the arrest of division. Based on these results, we propose that BIK1 is required stoichiometrically for the formation or stabilization of microtubules during mitosis and for spindle pole body fusion during conjugation.

Amino Acid Sequence↗

PubMed1992

A temperature-sensitive calmodulin mutant loses viability during mitosis.

Although rare, a recessive temperature-sensitive calmodulin mutant has been isolated in Saccharomyces cerevisiae. The mutant carries two mutations in CMD1, isoleucine 100 is changed to asparagine and glutamic acid 104 is changed to valine. Neither mutation alone conferred temperature sensitivity. A single mutation that allowed production of an intact but defective protein was not identified. At the nonpermissive temperature, the temperature-sensitive mutant displayed multiple defects. Bud formation and growth was delayed, but this defect was not responsible for the temperature-sensitive lethality. Cells synchronized in G1 progressed through the cell cycle and retained viability until the movement of the nucleus to the neck between the mother cell and the large bud. After nuclear movement, less than 5% of the cells survived the first mitosis and could form colonies when returned to permissive conditions. The duplicated DNA was dispersed along the spindle, extending from mother to daughter cell. Cells synchronized in G2/M lost viability immediately upon the shift to the nonpermissive temperature. At a semipermissive temperature, the mutant showed approximately a 10-fold increase in the rate of chromosome loss compared to a wild-type strain. The mitotic phenotype is very similar to yeast mutants that are defective in chromosome disjunction. The mutant also showed defects in cytokinesis.

Calmodulin↗