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PubMed2006

Reasoning about complex probabilistic concepts in childhood.

The competencies of children, particularly their understanding of the more complex probabilistic concepts, have not been thoroughly investigated. In the present study participants were required to choose the more likely of two events, a single event, and a joint event (conjunctive or disjunctive). It was predicted that the operation of the representativeness heuristic would result in erroneous judgements when children compared an unlikely component event with a likely-unlikely conjunction (the conjunction fallacy) and when a likely component event was compared to a likely-unlikely disjunction. The results supported the first prediction with both older children aged between 9 and 10 years and younger children aged between 4 and 5 committing the conjunction fallacy. However, the second prediction was not confirmed. It is proposed that the basis of representativeness judgements may differ between the conjunctive and disjunctive cases with absolute frequency information possibly playing a differential role.

Child↗

PubMed1981

The origin of human trisomy: a study of heteromorphisms and satellite associations.

The origin of the additional chromosome was studied in 45 trisomic-21 Down-syndrome patients. In 17 patients the additional chromosome was maternal, in 2 it was paternal and in the remaining 26 the parental origin could not be determined. Acrocentric chromosome association was studied in parents of Down-syndrome offspring and in parents of spontaneous abortions that were trisomic for an acrocentric chromosome. Parents of trisomic 16 abortuses and parents of triploid and chromosomally normal abortuses were used as controls. No increased association index was found for the specific acrocentric chromosome involved in the trisomy, either for the liveborn or for the aborted trisomics. However, the overall association index of the parent in whom the non-disjunctional event leading to the acrocentric trisomy occurred was increased by comparison with that of the parent in whom non-disjunction did not occur and with that of the controls. The reasons why we consider satellite associations to play an insignificant role in the aetiology of non-disjunction are discussed.

Analysis of Variance↗

PubMed1990

Sex-chromosome segregation in inbred Drosophila melanogaster XXY females. I. Influence of closely related Y chromosome derivatives.

In tests of XXYder hybrids from two inbred lines of Drosophila melanogaster, a non-random distribution of various Yder chromosomes was found at regular X disjunction. This non-random Yder distribution was dependent on differences within the proximal X chromosome region (forked--centromere) of these particular lines, with a limited influence of the Yder,s. The Yder,s (originating from BsYy+ chromosome) showed a large influence on both level and brood pattern of secondary non-disjunction. There was no correlation between secondary non-disjunction and non-random Yder distribution, indicating different mechanisms. Cytological examination of the five Yder chromosomes disclosed no relation between the composition or configuration of the Yder,s and the observed distribution effects. Various parts of the present results show inconsistencies with either of the two existing segregation models (Grell, Novitski), suggesting that the mechanistic understanding of the meiotic process requires additional assumptions and/or alternatives.

Animals↗

PubMed1987

Retrograde effects of target atrophy on submandibular ganglion neurons.

1. To study the retrograde effects of changes in target tissue upon the innervating nerve supply, we have examined the parasympathetic submandibular ganglion of the adult rat. Neurons of this ganglion innervate the submandibular and sublingual salivary glands. 2. Ligating the salivary ducts leads to rapid and prolonged salivary gland cell atrophy. 3. Duct ligations, without direct injury to the glandular nerve supply, initially produced few alterations in the ganglion. After 8 wk, however, neuron number was reduced by 50%. The numbers of presynaptic inputs/neuron and synapses/neuron perimeter were not affected by the cell loss. 4. After 1 wk of duct ligation in which the glandular nerve supply was intentionally damaged, some ganglionic neurons have lost all presynaptic inputs, suggesting synaptic disjunction. This is followed at 3 wk by a 40% decrease in neuron number and an increase in the number of inputs per (remaining) ganglion cell. However, the number of synapses/neuronal profile was unchanged. 5. Thus axotomy plus target atrophy causes synaptic disjunction, neuron cell death, and input rearrangement, presumably due to a combination of direct injury effects and an abrupt loss of peripheral trophic supplies. 6. In contrast, target atrophy alone produced more gradual changes in submandibular ganglion neurons. Only prolonged target atrophy leads to a decrease in the number of ganglionic neurons, perhaps due to the gradual loss of peripheral trophic supplies. However, other features, such as the number of inputs/cell and the number of synapses/neuron perimeter, remain unaltered. Evidently, the gradual loss of trophic support does not result in synaptic disjunction to the degree needed to produce presynaptic input rearrangement.

Animals↗

PubMed1977

Geographic distribution and habitat diversity of the Barbary Macaque sylvanus L.

During a 15-month behavioral study in Morocco and a 3-month survey in Morocco and Algeria, the present distribution of the Barbary macaque was determined. In Algeria, monkeys are found in seven constricted and disjunct localities in the Grande and Petite Kabylie mountain ranges. These localities are severely restricted in space and are located in remote or inaccessible areas which support only small populations. Their habitats include mixed cedar and holm oak forests, humid Portuguese and cork oak mixes and gorges dominated by scrub vegetation. In only two regions (Guerrouch and Agfadou) can population of reasonable size be found; even there they do not approach the abundance found in the central Middle Atlas zone of Morocco. Distribution was more extensive earlier in this century and some areas have become unoccupied within the past 15 years. Today, their absolute numbers and population densities are low in all but two locations. Algeria contains approximately 23% (5,500 maximum) of the total number of surviving Barbary macaques in North Africa. About 77% of the total number of Barbary macaques occur in Morocco. Moroccan habitats include high cedar forests, cedar/holm-oak mixtures and pure holm oak forests. Macaque distribution in the High Atlas is restricted to the Ourika valley where only a small relict population survives. There are between five and eight small, disjunct forest pockets in the Rif which support small groups of monkeys. In the Middle Atlas, monkeys are found in high numbers and in relatively wide stretches of distribution, although there are constricted areas of low densities in this region also. 65% (14,000 maximum) of the animals and their highest densities occur in the high mixed cedar forests of the Central zone, and mixed cedar forest appears to be the preferred habitat for the species. With the exception of the Central zone, their remaining distribution is typically disjunct and constricted, and population densities aer low. As in Algeria, distribution in Morocco was wider earlier this century, and several areas have recently become unoccupied.

Algeria↗

PubMedDate not supplied

Anatomic aspects of epididymis and tunica vaginalis in patients with testicular torsion.

OBJECTIVE: To analyze the morphology of epididymis and tunica vaginalis as well as their anatomical anomalies in patients with testicular torsion. MATERIALS AND METHODS: We studied 25 patients (50 testes) aged between 12 and 23 years (mean 15.6). Torsion length ranged from 2 hours to 2 days (mean 8 hours). Epididymal anatomy was classified in 6 groups: Type I--epididymis united to the testis by its head and tail; Type II--epididymis totally united to the testis; Type III--disjunction of epididymal tail; Type IV--disjunction of epididymal head; Type V--total disjunction between testis and epididymis, and Type VI--epididymal atresia. The type of torsion was classified in 3 groups: Group A--intravaginal torsion; Group B--extravaginal torsion and Group C--torsion due to long mesorchium. RESULTS: Of the 50 analyzed testes, 40 (80%) presented bell clapper deformity (with 21 presenting intravaginal torsion); 8 testes (16%) had long mesorchium (4 with torsion), and only 2 (4%) presented normal anatomy in the tunica vaginalis. The most frequently found anatomical relationship between testis and epididymis was Type I--38 cases (76%); Type II relationship was found in 6 cases (12%) and Type III relationship was found in 6 cases (12%). CONCLUSIONS: Intravaginal torsion is the most frequent type, and torsion due to long mesorchium is associated with cryptorchism. The most frequently found anatomical relation between testis and epididymis in the study group was Type I.

Adolescent↗

PubMed2001

Searching for two things at once: evidence of exclusivity in semantic and autobiographical memory retrieval.

We examined whether retrieval from semantic memory (Experiment 1) and autobiographical memory (Experiment 2) is exclusive, or whether people can search for two things at once. In Experiment 1, participants retrieved items as quickly as possible over 4 ruin from single categories (e.g., foods, countries) and from disjunctive categories (e.g., foods or countries). In Experiment 2, participants retrieved autobiographical episodes associated with single cue words (e.g., flower, ticket) or with disjunctive cue words (e.g., flower or ticket). In both experiments, retrieval of items from the disjunctive category did not exceed predictions based on optimal sequencing of retrieval from the corresponding two single categories. That is, exclusivity was observed to occur in retrieval from among multiple nonoverlapping categories in both semantic and autobiographical memory.

Adolescent↗

PubMed1999

Allozyme and morphological variation in two subspecies of Dryas octopetala (Rosaceae)in Alaska.

The Alaskan endemic shrub Dryas octopetala ssp. alaskensis and its circumpolar conspecific ssp. octopetala are adapted to closely adjacent habitats in alpine areas of Alaska. These alpine areas form geographically disjunct "islands" among which there are limited opportunities for gene flow. Allozyme electrophoresis and a common garden experiment were used to examine genetic variation between subspecies and among disjunct populations of each subspecies. Overall, allozyme variation in D. octopetala is low with little differentiation among populations or between subspecies. Morphological differences, however, are greater between subspecies than among populations within subspecies. Divergence for a few morphological and life-history characters has apparently occurred in response to strong selection, but without divergence at allozyme loci. The ancestors of both subspecies of D. octopetala in Alaska were isolated during the Pleistocene in the glacial refugia of Alaska and Yukon, which may explain low overall variation. Dryas. o. alaskensis is thought to be a Pleistocene derivative of ssp. octopetala, which may account for the low allozyme divergence between subspecies. Recent restriction to alpine areas may explain the low differentiation among disjunct populations.

Journal Article↗

PubMed1976

[On the origin of meiotic errors with special reference to trisomy 21 (author's transl)].

The origin of the supernumetary chromosome 21 in Down's syndrome was traced by the use of polymorphic regions of this chromosome. The present results interpretated in the light of the extensive literature may be summarized as follows; 1. The meiotic error involved in trisomy 21 can take place in both sexes and occurs at random. It occurs twice as frequently in the female than in the male. This situation is paralleled by the 2:1 ratio found in XXY-syndrome concerning the supernumerary X. 2. In both sexes non-disjunction occurred twice as frequently in the first than in the second meiotic division. 3. The rate of meiotic errors is largely dependent on age. The present study confirms the increase in meiotic errors with age of mother; moreover, increasing age of the father seems to enhance non-disjunction in spermatogenesis. Trisomy 21 on the basis of sporadic translocation in the child seems to be independent of the parental age. The present study includes two cases of translocation 21/21. In both cases the errors took place in mothers aged 18 and 19, respectively. 4. A new finding consists in the observation that previous pregnancies and deliveries may influence errors in oogenesis. In cases of maternal origin significantly more previous pregnancies and deliveries were found than in cases of trisomy of paternal origin. 5. A study of quinacrine polymorphism of chromosome numbers 1, 3, 9, 13, 14, 15, 16, 21, 22 and Y showed no significant difference between parents of children with Down's syndrome and controls. Moreover, the parents in whom the non-disjunction exists in parents of trisomic children, it cannot be detected by such methods. Recent observations made in the course of prenatal diagnosis contradict such an individual predisposition. The present results, after confirmation and augmentation, especially by implementation of biochemical methods, should prove of importance in genetic counseling and as guidelines in the indications for prenatal diagnosis.

Adolescent↗

PubMed1992

The chromosome complement of human gametes.

The comparisons of observed and predicted rates of chromosomally abnormal gametes for two major classes of abnormality and for three specific trisomies are summarized in Table 2.10. As can be seen there is not very good agreement between the two sets of data. For sperm the observed abnormality rates are, with the exception of polyploidy, all in excess of those predicted. For structural abnormalities the excess is absurd and suggests that most structural abnormalities seen in sperm chromosomes may be preparation artefacts. On the other hand, it could be argued that the excess of hyperhaploidy among sperm is real and represents those trisomic conceptuses lost in the early stages of pregnancy. However, both chromosome 21 and the sex chromosomes are represented more often than any other chromosomes. Recent observations among all clinically recognized pregnancies do not suggest an excess of trisomy 21 conceptions arising from non-disjunction in spermatogenesis. As can be seen from Table 2.10, the observed frequencies of trisomy 21 is 10 times greater than that predicted, a difference that seems too great to be accounted for by early pregnancy wastage. While the X chromosome does appear to undergo non-disjunction much more frequently than the autosomes during spermatogenesis, the increase is restricted to non-disjunction of the XY bivalent at the first male meiotic division. In this class the observed and predicted frequencies are rather similar and it is even possible that the observed excess in sperm is accounted for by early post-zygotic loss. However, with the exception of the 24, XY class, the distribution of individual chromosomes among the hyperhaploid sperm bears little relation to that predicted. The most likely explanation for this is that banding of sperm chromosomes is of such poor quality that there are many errors in the identification of individual chromosomes. Most authors use some form of Q banding and this technique should give unequivocal identification of the highly-fluorescent Y chromosome even when other chromosomes are not clearly distinguishable. An increased accuracy of Y-chromosome identification may account for the relative concordance between observed and predicted rates of 24, XY sperm. By the same argument, 24, YY sperm might be expected to be accurately enumerated.(ABSTRACT TRUNCATED AT 400 WORDS)

Abortion, Spontaneous↗

PubMed1987

[Heterochromatic regions and chromosome 21 nondisjunction in man. II. A comparative analysis of the polymorphism of the C bands of chromosomes 1, 9 and 16 in the fathers and mothers of Down's disease children].

To test a hypothesis on potential role of large heterochromatic regions in chromosome non-disjunction, a comparative analysis of C segment lengths of chromosomes 1, 9, and 16 in fathers and mothers of children with Down's syndrome was carried out. No difference was found between the two groups. The non-disjunction in mothers is known to occur 4 times as frequently as in fathers. This fact does not allow to suppose that the heterochromatic regions may play a certain part in non-disjunction of chromosome 21.

Adult↗

PubMed1982

Visible changes of the lens with age.

Slit lamp photographs taken along the optical axis of human eyes were examined with a microdensitometer. This showed an increasing opacity in the lens nucleus, an increased opacity and thickness of the cortex and the anterior lens capsule with age. However, the opacity and width of the anterior disjunction zones decreases with age. Patients with clear lenses but who had chronic uveitis, retinal detachment and glaucoma treated with medication, showed large deviations in the behavior of the disjunction zone as compared with other lenses of the same age. In incipient cataract in the aged, the fogging in the lens cortex is greatest when vestiges of the disjunction zone still remain. The cortex is less affected if the disfunction zone is absent.

Adolescent↗

PubMedDate not supplied

[The cytogenetic characteristics of subjects with menstrual function disorders].

The frequency and the pattern of chromosomal aberrations as well as the frequency of metaphase plates with premature chromatid disjunction, polyploidy and endoreduplication were studied in lymphocyte cultures of women with disturbances of the menstrual function and in healthy women. The frequency of metaphase plates was significantly increased in persons with Turner's syndrome and reduced in the groups with amenorrhea 1 and 2 in comparison with the group of healthy women. There was no difference in chromosomal aberration pattern. Premature chromatid disjunction is characteristic of patients with disturbances of the menstrual function and healthy women. The frequency of metaphase plates with premature chromatid disjunction was elevated in groups with Turner's syndrome, amenorrhea 1 and premature sexual maturation in comparison with the control.

Adult↗

PubMed1995

[Primary headache and orthognathorhinodontia in childhood].

The aim of the research was to study the interrelationship between the primary neurovascular headaches, the various levels dimension of nasal pyramid and the rapid palatal expansion. Twenty-five patients, of both sexes and on developmental age, were studied before and after the rapid palatal expansion. All patients showed palatal hypoplasia and were suffering from primary neurovascular headache. The research was based on the cephalometric and rhinomanometric data. The radiographic documentation of each patient consisted of three postero-anterior teleradiographic projection; the first before application of the disjunction device, the second immediately after disjunction and the third at the end of the contention period. The rhinomanometric evaluation studied the reduction of nasal resistance values before and after palatal expansion. In all patients a constant increase in the values relating both skeletal and dental structures was observed. The nasal septum, if deviated, appeared straightend. The nasal resistances were decreased. The concomitant headache symptomatology presented resolution or recovery in the 98% of treated patients. The results should confirm the hypothesis of the central-peripheral theory of "primary headaches" and the possibility to treat the primary headaches by rapid palatal disjunction in eliminating the stenosis at various levels of nasal pyramid.

Adolescent↗

PubMed1997

A cytogenetic study of G1-chromosomes in one-cell stage mouse embryo and in corresponding second polar body. Evaluation of aneuploidy originated in females heterozygous for translocation T[14;15]6Ca.

Meiotic chromosomes in ovulated oocytes and G1-chromosome sets visualized in the 2nd PB and in the pronuclei of one-cell stage embryos treated with okadaic acid were studied in female mouse heterozygous for reciprocal translocation T[14;15]6Ca. It was found that 61.5% of oocytes were haploid, 14.9% hyperhaploid and 23.6% hypohaploid. Unpaired chromatid (a half-dyad), in addition to (or replacing) a whole chromosome (a dyad), was detected in 20% of oocytes. G1-chromosome complements in the 2nd PB and in the MPN expected in the case of aneuploidy due to chromosome non-disjunction or to chromatid abnormal segregation at the first and second meiotic division were detected in one-cell stage embryos. The hypo- and hyperhaploidy caused by non-disjunction was revealed in 17.6% of embryos. Aneuploidy due to abnormal segregation of a chromatid in the first and the second meiotic division was in 20% and 4.4% of all cases respectively. The incidence of different classes of aneuploid oocytes were almost fully conformable to that of corresponding types of aneuploidy detected in one-cell stage embryos. The main advantage of the proposed new approach based on cytogenetic analysis of G1-chromosomes in the 2nd PB and in the corresponding MPN is that it allows to study not only the chromosome non-disjunction, but also abnormal segregation of chromatids in the first and in the second meiotic divisions, and to estimate accurately the incidence of these maternal meiotic errors.

Aneuploidy↗

PubMed2000

Dissecting the role of molecular motors in the mitotic spindle.

Accurate segregation of genetic material during both mitosis and meiosis is essential for the viability of future cellular generations. Genetic material is packaged in the form of chromosomes during cell division, and chromosomes are segregated equally into two daughter cells by a dynamic, microtubule-based structure known as the spindle. Molecular motor proteins of the kinesin and dynein superfamilies are essential players in the functional microanatomy of cell division. They power various aspects of spindle assembly and function, including establishing spindle bipolarity, spindle pole organization, chromosome alignment and segregation, regulating microtubule dynamics, and cytokinesis. This review highlights the roles that various members of the kinesin and dynein motor superfamilies play during mitosis and meiosis. Understanding how microtubule motors function during cell division will unravel how the spindle precisely segregates chromosomes, and may offer insights into the molecular basis of disease states that arise from spindle malfunctions. For example, chromosome non-disjunction during meiosis causes such disorders as Klinefelter, Turner, and Down Syndromes. Chromosome non-disjunction during mitosis is an important contributing mechanism for tumor progression. In addition, since motor proteins are essential for spindle assembly and function, they provide obvious targets for intervention into the cell division cycle, and compounds that specifically block motor functions during mitosis may prove to be valuable chemotherapeutic agents. Anat Rec (New Anat) 261:14-24, 2000.

Animals↗

PubMed1996

Prenatal diagnosis of uniparental disomy 15 following trisomy 15 mosaicism.

Maternal uniparental disomy 15 (UPD15), responsible for approximately 25 per cent of Prader-Willi syndrome cases, is usually caused by maternal meiosis I non-disjunction associated with advanced maternal age. These cases may initially be detected as mosaic trisomy 15 during routine prenatal diagnostic studies. In such cases, PCR (polymerase chain reaction) microsatellite analysis of uncultured cells makes prospective prenatal diagnosis for UPD15 possible with results available in 2-4 days. We have performed molecular analyses on a series of seven cases of mosaic trisomy 15 identified in amniotic fluid (AF, n = 3) or chorionic villus samples (CVS, n = 4) from patients initially referred for advanced maternal age or abnormal triple screen. In all cases, the maternal ages were > or = 35 years and maternal meiosis I non-disjunction was documented as the cause of the trisomy in all informative cases (n = 5). Of the three case with mosaic trisomy 15 at amniocentesis, two showed the presence of the trisomy in the fetus. Molecular analysis showed one case with maternal UPD15 in the euploid cell line and one case with biparental inheritance. Both of these families elected to terminate the pregnancies based on the presence of true fetal mosaicism. In the third case, low-level trisomy 15 mosaicism in the amniotic fluid was not confirmed in a follow-up amniotic fluid sample and molecular analysis indicated biparental inheritance in the fetus. For the four trisomy 15 mosaics detected at CVS, molecular analysis was performed on direct amniotic fluid cell lysates for prospective diagnosis of UPD at 14-16 weeks' gestation. Follow-up cytogenetic analysis of the amniotic fluid in all four cases was normal, indicating confined placental mosaicism. Molecular analysis showed one of these four cases to have maternal heterodisomy 15. Based on the likelihood of Prader-Willi syndrome due to maternal UPD15, the couple chose to terminate the pregnancy. The total of two of seven cases of trisomy 15 mosaicism resulting in UPD15 is consistent with the theoretical expectation of one-third and indicates a high risk of UPD in such pregnancies. Therefore, UPD testing should be offered in all cases of mosaic trisomy 15 encountered in CVS or amniocentesis.

Adult↗

PubMed2000

Prenatal diagnosis and genetic analysis of double trisomy 48,XXX,+18.

Prenatal diagnosis of simultaneous occurrence of double trisomy involving chromosomes 18 and X is extremely rare. We report on the prenatal diagnosis, genetic analysis and clinical manifestations of a fetus with both trisomy 18 and trisomy X. A 26-year-old, para 1 woman was referred for genetic counselling at 36 weeks' gestation with the sonographic findings of intrauterine growth retardation (IUGR), polyhydramnios, ventricular septal defect, and an enlarged cisterna magna. Both cordocentesis and amniocentesis revealed a consistent karyotype of 48,XXX,+18. Quantitative fluorescent polymerase chain reaction using polymorphic small tandem repeat markers specific for chromosomes 18 and X rapidly determined that both aneuploidies arose as a result of non-disjunction in maternal meiosis II. Our case shows that two non-disjunction events can occur not only in the same parent, but also in the same cell division. Our case also shows that double trisomy, 48,XXX,+18, can demonstrate an enlarged cisterna magna, IUGR and polyhydramnios in prenatal ultrasound.

Adult↗