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PubMed1984

Induction of somatic segregation by halogenated aliphatic hydrocarbons in Aspergillus nidulans.

8 halogenated aliphatic hydrocarbons were assayed for their ability to induce somatic segregation in the mould Aspergillus nidulans. Induction of haploidization, mitotic non-disjunction and mitotic crossing-over was studied in heterozygous colonies exposed to the tested chemicals through the detection and phenotypic analysis of segregated sectors. The results obtained show that 1,2-dibromoethane induced all kinds of segregated sectors; 1,2-dichloroethane, allyl chloride, 2-chloroethanol, 2,2-dichloroethanol and 2,2-dichloroacetaldehyde significantly increased the frequency of haploid sectors and diploid non-disjunctional sectors; chloroform and 1,2-dichloropropane were ineffective.

Aspergillus nidulans↗

PubMed1986

X-ray-induced chromosome aberrations in immediately preovulatory oocytes.

The effects of relatively small doses of X-rays (up to 100 cGy) to immediately preovulatory mouse oocytes have been examined by screening chromosome aberrations at metaphase I. Dose-related responses for the induction of aberrations were found. These were mainly of the quadratic or power-law types, and therefore similar in nature to the dose-responses described elsewhere for dictyate oocytes. The frequencies of the various categories of structural aberration have been compared to the previously determined rates of radiation-induced non-disjunction in immediately preovulatory oocytes in order to examine the potential involvement of structural chromosome aberrations in radiation-induced non-disjunction.

Animals↗

PubMed1991

A case of spontaneous trisomy in the spermatocytes of Microtus arvalis.

A triple synaptomal complex was observed between 3 small-sized chromosomes in 4 spermatocytes closely connected by intercellular bridges, of the common vole (Microtus arvalis L.). Other spermatocytes from the same and from 2 other males had a normal chromosome complement and pairing patterns. This finding was interpreted as the result of a single act of non-disjunction taking place in a spermatogonium. These data suggest that chromosome non-disjunction in premeiotic germ cells can be considered one of the causes of aneuploidy in mammals.

Animals↗

PubMed1996

Purification and functional characterization of type II DNA topoisomerase from rat testis and comparison with topoisomerase II from liver.

A number of studies in yeast have shown that DNA topoisomerase II is essential for chromosome condensation and disjunction during mitosis at the metaphase/anaphase transition and meiosis I. Accordingly, kinetic and mechanistic studies have implied a role for topoisomerase II in chromosome disjunction. As a step toward understanding the nature and role of topoisomerase II in a mammalian germline in vivo, we have purified topoisomerase II from rat testis to homogeneity and ascertained several of its catalytic activities in conjunction with that of the purified enzyme from liver. The purified enzymes appeared to be monomers under denaturing conditions; however, they differed in their relative molecular mass. Topoisomerase II from testis and liver have apparent molecular masses of 150 +/- 10 kDa and 160 +/- 10 kDa, respectively. The native molecular mass of testis topoisomerase II as assayed by immunoblot analysis of cell-free extracts, prepared in the presence of SDS and a number of protease inhibitors, corroborated with the size of the purified enzyme. Both enzymes are able to promote decatenation and relax supercoiled DNA substrates in an ATP and Mg(2+)-dependent manner. However, quantitative comparison of catalytic properties of topoisomerase II from testis with that of the enzyme from liver displayed significant differences in their efficiencies. Optimal pH values for testis enzyme are 6.5 to 8.5 while they are 6 to 7.5 for the liver enzyme. Intriguingly, the relaxation activity of liver topoisomerase II was inhibited by potassium glutamate at 1 M, whereas testis enzyme required about half its concentration. These findings argue that topoisomerase II from rat testis is structurally distinct from that of its somatic form and the functional differences between the two enzymes parallels with the physiological environment that is unique to these two tissues.

Animals↗

PubMed2005

Evaluation of EST-data using the genome assembly.

Using expressed sequence tag (EST) data for genomewide studies requires thorough understanding of the nature of the problems that are related to handling these sequences. We investigated how EST clustering performs when the genome is used as guidance as compared to pairwise sequence alignment methods. We show that clustering with the genome as a template outperforms sequence similarity methods used to create other EST clusters, such as the UniGene set, in respect to the extent ESTs originating from the same transcriptional unit are separated into disjunct clusters. Using our approach, approximately 80% of the RefSeq genes were represented by a single EST cluster and 20% comprised of two or more EST clusters. In contrast, approximately 25% of all RefSeq genes were found to be represented by a single cluster for the UniGene clustering method. The approach minimizes the risk for overestimations due to the amount of disjunct clusters originating from the same transcript. We have also investigated the quality of EST-data by aligning ESTs to the genome. The results show how many ESTs are not adequately trimmed in respect of vector sequences and low quality regions. Moreover, we identified important problems related to ESTs aligned to the genome using BLAT, such as inferring splice junctions, and explained this aspect by simulations with synthetic data. EST-clusters created with the method are available upon request from the authors.

Base Sequence↗

PubMed2003

The meiosis I-to-meiosis II transition in mouse oocytes requires separase activity.

Faithful segregation of homologous chromosomes during the first meiotic division is essential for further embryo development. The question at issue is whether the same mechanisms ensuring correct separation of sister chromatids in mitosis are at work during the first meiotic division. In mitosis, sister chromatids are linked by a cohesin complex holding them together until their disjunction at anaphase. Their disjunction is mediated by Separase, which cleaves the cohesin. The activation of Separase requires prior degradation of its associated inhibitor, called securin. Securin is a target of the APC/C (Anaphase Promoting Complex/Cyclosome), a cell cycle-regulated ubiquitin ligase that ubiquitinates securin at the metaphase-to-anaphase transition and thereby targets it for degradation by the 26S proteasome. After securin degradation, Separase cleaves the cohesins and triggers chromatid separation, a prerequisite for anaphase. In yeast and worms, the segregation of homologous chromosomes in meiosis I depends on the APC/C and Separase activity. Yet, it is unclear if Separase is required for the first meiotic division in vertebrates because APC/C activity is thought to be dispensable in frog oocytes. We therefore investigated if Separase activity is required for correct chromosome segregation in meiosis I in mouse oocytes.

Animals↗

PubMed2004

Nucleotide excision repair deficiency causes elevated levels of chromosome gain in Saccharomyces cerevisiae.

Aneuploidy is the most frequent aberration observed in tumor cells, and underlies many debilitating and cancer-prone congenital disorders. Aneuploidy most often arises as a consequence of chromosomal non-disjunction, however, little is known about the genetic and epigenetic factors that affect the chromosomal segregation process. As many cancer-prone syndromes are associated with defects in DNA repair pathways we decided to investigate the relationship between DNA repair in mutation avoidance pathways, namely base and nucleotide excision, and mismatch repair (MMR), and aneuploidy in the yeast Saccharomyces cerevisiae. Isogenic haploid and diploid DNA repair deficient yeast strains were constructed, and spontaneous levels of intra- and inter-chromosomal recombination, forward mutation, chromosome gain, and loss were measured. We show that the nucleotide excision repair (NER) pathway is required for accurate chromosomal disjunction. In the absence of Rad1, Rad2, or Rad4, spontaneous levels of chromosome XV gain were significantly elevated in both haploid and diploid mutant strains. Thus, chromosome gain may be an additional cancer predisposing event in NER deficient patients.

Aneuploidy↗

PubMed2004

[Chromosome abnormalities of spermatozoa].

Chromosome meiotic pairing during male meiosis is a major event for chromosome segregation during anaphase I and spermatogenesis normal process. Chromosome non-disjunctions responsible for aneuploidy in male gametes can be observed during the first and the second meiotic divisions. The analysis of sperm nuclei chromosome constitution is a major and indirect tool for assessing male meiotic non-disjunctions and the genesis of chromosomal abnormalities. This evaluation has been performed initially by the human sperm/hamster oocyte fusion assay and more recently by fluorescence in situ hybridisation (FISH). Therefore, male populations with increased risk of aneuploidy for their progeny could be identified before entering an in vitro fertilization procedure, and depending on the potential risk a preimplantation or prenatal genetic diagnosis could be performed. For males with constitutional chromosome abnormalities, a specific genetic counselling could also be proposed.

Aneuploidy↗

PubMed2004

Trichlorfon predisposes to aneuploidy and interferes with spindle formation in in vitro maturing mouse oocytes.

The pesticide trichlorfon (TCF) has been implicated in human trisomy 21, and in errors in chromosome segregation at male meiosis II in the mouse. We previously provided evidence that TCF interferes with spindle integrity and cell-cycle control during murine oogenesis. To assess the aneugenic activity of TCF in oogenesis, we presently analysed maturation, spindle assembly, and chromosome constitution in mouse oocytes maturing in vitro in the presence of 50 or 100 microg/ml TCF for 16 h or in pulse-chase experiments. TCF stimulated maturation to meiosis II at 50 microg/ml, but arrested meiosis in some oocytes at 100 microg/ml. TCF at 100 microg/ml was aneugenic causing non-disjunction of homologous chromosomes at meiosis I, a significant increase of the hyperploidy rate at metaphase II, and a significant rise in the numbers of oocytes that contained a 'diploid' set of metaphase II chromosomes (dyads). TCF elevated the rate of precocious chromatid segregation (predivision) at 50 and 100 microg/ml. Pulse-chase experiments with 100 microg/ml TCF present during the first 7 h or the last 9 h of maturation in vitro did not affect meiotic progression and induced intermediate levels of hyperploidy at metaphase II. Exposure to > or =50 microg/ml TCF throughout maturation in vitro induced severe spindle aberrations at metaphase II, and over one-third of the oocytes failed to align all chromosomes at the spindle equator (congression failure). These observations suggest that exposure to high concentrations of TCF induces non-disjunction at meiosis I of oogenesis, while lower doses may preferentially cause errors in chromosome segregation at meiosis II due to disturbances in spindle function, and chromosome congression as well as precocious separation of chromatids prior to anaphase II. The data support evidence from other studies that TCF has to be regarded as a germ cell aneugen.

Aneuploidy↗

PubMed2005

Orthovanadate increased the frequency of aneuploid mouse sperm without micronucleus induction in mouse bone marrow erythrocytes at the same dose level.

The objective of the current study was to investigate the ability of orthovanadate to induce aneuploidy in mouse sperm and micronuclei in mouse bone marrow cells at the same dose levels. The BrdU-incorporation assay was performed to test if the chemical treatment altered the duration of the meiotic divisions. It was found that orthovanadate (25mg/kg bw) treatment did not cause meiotic delay. To determine the frequencies of hyperhaploid and diploid sperm, male mice were treated by intraperitoneal (i.p.) injection with 5, 15 or 25mg/kg bw orthovanadate and sperm were sampled from the Caudae epididymes 22 days later. Fluorescence in situ hybridization (FISH) was performed with DNA-probes for chromosomes 8, X or Y. Significant increases in the frequencies of total hyperhaploid sperm (p<0.01) were found with 15 and 25mg/kg bw orthovanadate, indicating induced non-disjunction during male meiosis. The dose-response was described best by a linear equation. Orthovanadate did not significantly increase the frequencies of diploid sperm at any of the three doses tested, indicating that no complete meiotic arrest occurred. Orthovanadate was investigated also by the micronucleus test at i.p. doses of 1, 5, 15 or 25mg/kg bw, followed by bone marrow sampling 24h after treatment. None of the orthovanadate doses caused a significant increase in the rates of micronuclei (MN). Since the results show that orthovanadate induced non-disjunction during male meiosis without an accompanying induction of MN in bone marrow erythrocytes under the present experimental conditions and doses, it is concluded that male germ cells (meiosis) are more sensitive to the aneugenic effects of orthovanadate than somatic cells (mitosis). However, induction of micronuclei was reported in the literature with orthovanadate, vanadylsulfate and ammonium metavanadate, which contradicts the notion that vanadium compounds might be unique germ cell aneugens.

Aneugens↗

PubMed2006

Phylogeny and biogeography of Altingiaceae: evidence from combined analysis of five non-coding chloroplast regions.

The Altingiaceae consist of approximately 15 species that are disjunctly distributed in Asia and North America. The genus Liquidambar has been employed as a biogeographic model for studying the Northern Hemisphere intercontinental disjunctions. Parsimony and Bayesian analyses based on five non-coding chloroplast regions support that (1) Liquidambar is paraphyletic; (2) the temperate Liquidambar acalycina and Liquidambar formosana are nested within a large tropical to subtropical Asian clade; (3) Semiliquidambar is scattered in the eastern Asian clade and is of hybrid origin involving at least two maternal species: L. formosana and L. acalycina; and (4) the eastern North American Liquidambar styraciflua groups with the western Asian Liquidambar orientalis, but is highly distinct from other lineages. Biogeographically, our results demonstrate the complexity of biogeographic migrations throughout the history of Altingiaceae since the Cretaceous, with migration across both the Bering and the North Atlantic land bridges.

Asia↗

PubMed2006

Intercontinental biogeography of subfamily Orontioideae (Symplocarpus, Lysichiton, and Orontium) of Araceae in Eastern Asia and North America.

Symplocarpus, Lysichiton, and Orontium (Orontioideae) are three of the few north temperate genera of the primarily tropical Araceae. Symplocarpus is disjunctly distributed in eastern Asia (3 spp.) and eastern North America (1 sp.); Lysichiton has an intercontinental discontinuous distribution in eastern Asia (1 sp.) and northwestern North America (1 sp.); and the monotypic Orontium is restricted to eastern North America. Phylogenetic analysis of the trnL-F and ndhF sequences supports (1) the monophyly of both Symplocarpus and Lysichiton, (2) the sister-group relationship of Symplocarpus and Lysichiton, and (3) the clade of Orontium, Symplocarpus, and Lysichiton. Although Symplocarpus shows a much wider disjunction than Lysichiton, the estimated divergence time of the former [4.49+/-1.69 or 6.88+/-4.18 million years ago (mya)] was similar to that of the latter (4.02+/-1.60 or 7.18+/-4.33 mya) based on the penalized likelihood and the Bayesian dating methods, respectively. Eastern Asia was suggested to be the ancestral area of the Symplocarpus-Lysichiton clade based on the dispersal-vicariance analysis. Our biogeographic results support independent migrations of Symplocarpus and Lysichiton across the Bering land bridge in the late Tertiary (Pliocene/late Miocene). Fossil evidence suggests Orontioideae dated back to the late Cretaceous in the temperate Northern Hemisphere (72 mya). The relative rate test shows similar substitution rates of the trnL-F sequences between the proto and the true aroids, although the latter has substantially higher species diversity. The proto Araceae perhaps suffered from a higher rate of extinction in the temperate zone associated with periods of climatic cooling in the Tertiary.

Animals↗

PubMed2004

[Neurological damage in pelvic injuries: a continuous prospective series of 50 pelvic injuries treated with an iliosacral lag screw].

PURPOSE OF THE STUDY: The purpose of this study was to analyze lesions to the lumbosacral plexus related to pelvic injury and its treatment. MATERIAL AND METHODS: Forty-four patients presented 50 posterior osteoligamentary lesions of the pelvic girdle. All patients except eight had other injuries. Mean ISS was 27/75. Posterior lesions were: iliosacral disjunction (n=23), extra-foraminal fracture of the sacrum (n=4), transforaminal fracture (n=22), intra-foraminal fracture (n=1). Vertical posterior displacement was > 1 cm for 24 posterior lesions. Orthopedic reduction was performed at admission for all patients. Fluoroscopy-guided percutaneous lag screw fixation was performed in all cases, on the average eight days after the accident. Neurological involvement was evaluated at admission, after surgery, and at last follow-up. Data were recorded for skeletal muscles, lower limb dermatomes, tendon reflexes, and anal tone. Screw emplacement was checked on the CT-scan. Outcome was assessed subjectively with the Majeed score, a self-administered visual analog scale, and use of antalgesic drugs according to the WHO classification. RESULTS: The neurological examination could not be performed for ten patients at admission. Postoperatively, there was a neurological deficit associated with 26 osteoligamentary lesions (23 lesions of the lumbosacral trunk, 14 lesions of the S1 spinal nerve, 3 lesions of the pudendal nerve, 12 lesions of the superior gluteal nerve, and 10 lesions of the femoral nerve). Patients with neurological involvement had experienced more severe trauma. The iliosacral screw was partially extra-osseous in thirteen cases, with an associated iatrogenic neurological deficit in seven. At mean follow-up of 20 Months (range 4-50) there persisted ten major sequelae including eight cases of hallux extensor deficit. DISCUSSION: Neurological involvement is underestimated during the acute phase of trauma. After recovery, only the manifestations of major injuries persist. The prognosis is poor in the event of a stretched lumbosacral trunk or gluteal nerve due to iliosacral disjunction. Prognosis is good for nerve contusion due to sacral fracture because of early reduction. The femoral nerve is generally injured by compression due to a peri-fracture hematoma; recovery is the rule. Iliosacral screwing requires rigorous technique by a skilled and experienced surgeon. CONCLUSION: About 52% of posterior osteoligamentary injuries are associated with neurological symptoms. After recovery, permanent deficit persists in 21.7%. The most common sequelae are hallux extensor and gluteus medius palsy due to stretching of the lumbosacral trunk.

Adolescent↗

PubMed2005

[Osteocartilaginous autograft after proximal resection of the scaphoid for radioscaphoid osteoarthritis].

PURPOSE OF THE STUDY: Radioscaphoid osteoarthritis is usually a complication of scaphoid pseudarthrosis or chronic scapholunate disjunction. As an alternative to the classical surgical techniques used for this lesion, we propose a novel reconstruction method consisting In partial proximal resection of the scaphoid associated with interposition of a biological spacer composed of a osteocartilaginous rib graft. The purpose of this study was to present the technical aspects of this procedure and to report preliminary results in ten patients with radioscapular osteoarthritis treated between 1994 and 2001. MATERIAL AND METHODS: We performed a retrospective analysis of the ten patients who underwent surgery from 1994 to 2001 for early-stage radioscaphoid osteoarthritis associated with scaphoid osteoarthritis in eight and chronic scapholunate disjunction in two. The procedure consisted in partial resection of the proximal portion of the scaphoid and insertion of an osteocartilaginous autograft harvested from a rib. Outcome was based on the clinical results (pain, motion, grip force, activity) and patient satisfaction. Bone healing was measured with plain x-rays and vitality of the osteocartilaginous graft with MRI. RESULTS: Mean follow-up was 4.6 years. Clinical outcome was considered excellent or good in eight patients, fair in one and poor in one (graft dislocation). All patients were satisfied or very satisfied except one (one failure). Radiological healing was achieved at three months in nine patients. Four patients underwent an MRI examination at thirteen months which demonstrated, in all patients: no sign of necrosis, healing of the graft-scaphoid interface, and no bony metaplasia in the cartilage. DISCUSSION: Compared with partial carpal arthrodesis and resection of the first row of the carpus, this palliative technique can be used to reconstruct the proximal portion of the carpal scaphoid in young patients with early-stage radioscaphoid osteoarthritis. As for arthroplasty or scaphoid implants, our goal was to achieve a satisfactory scaphoid height using a biological spacer after resection of the proximal 3/4 of the bone. The results of this technique are encouraging but must be examined with precaution due to the small number of patients and the short follow-up to date.

Adult↗

PubMed1996

Direct evidence of a role for heterochromatin in meiotic chromosome segregation.

We have investigated the mechanism that enables achiasmate chromosomes to segregate from each other at meiosis I in D. melanogaster oocytes. Using novel cytological methods, we asked whether nonexchange chromosomes are paired prior to disjunction. Our results show that the heterochromatin of homologous chromosomes remains associated throughout prophase until metaphase I regardless of whether they undergo exchange, suggesting that homologous recognition can lead to segregation even in the absence of chiasmata. However, partner chromosomes lacking homology do not pair prior to disjunction. Furthermore, euchromatic synapsis is not maintained throughout prophase. These observations provide a physical demonstration that homologous and heterologous achiasmate segregations occur by different mechanisms and establish a role for heterochromatin in maintaining the alignment of chromosomes during meiosis.

Animals↗

PubMed2003

The expression and experience of emotion in schizophrenia: a study of social interactions.

Previous studies on emotional expression and experience in schizophrenia indicate that patients show significantly fewer outward displays of emotion than controls despite similar self-reports of emotional experience in response to various non-social stimuli (e.g. film clips, flavored drinks). However, it is unclear if this disjunction between emotional experience and expression in schizophrenia extends to the interpersonal domain. This study compared 33 patients with schizophrenia and 15 non-psychiatric controls on emotional expression and experience during a social role play. Results showed that patients were significantly less expressive than controls but the two groups reported equal levels of emotional experience. Neither clinical blunting ratings nor behavioral ratings of facial expressivity were related to emotional experience in patients. These results extend prior findings of an expression/experience disjunction in schizophrenia to a social domain. Implications for understanding social dysfunction in schizophrenia and directions for future study are discussed.

Adult↗

PubMed1998

Unaltered meiotic chromosome segregation in Drosophila melanogaster raised on a 5% quercetin diet.

Flavonoid plant pigments are an integral part of the human diet. Although potentially negative mitotic effects of flavonoids have been observed in model organisms, investigation into meiotic effects of flavonoids has been neglected. As flavonoids affect cell signalling and DNA replication, and because the flavonoid content of the human food supply is being increased, determining the effects of flavonoids on meiotic fidelity is important. Here, the effect of the human food supply's most prevalent flavonoid, quercetin, on the level of meiotic recombination and the amount of X and 4th chromosome non-disjunction in Drosophila melanogaster females was determined. This model organism was chosen since Drosophila melanogaster and Homo sapiens share a remarkable number of commonalities in the meiotic processes of oogenesis and because genetic techniques allow a detailed analysis of meiotic processes in Drosophila. No significant effect on either non-disjunction levels or the percentage distribution of exchange bivalents was observed. A significant effect was observed on the number of offspring; F1 and F2 generations of flies raised on a quercetin diet produced over 10% more progeny than flies raised on a control diet. In this investigation, high quercetin consumption by Drosophila melanogaster females did not pose a threat to meiotic fidelity.

Animals↗

PubMed2003

Stress and the urge to drink.

OBJECTIVE: Understanding why people drink alcohol is important for the health and safety of individuals and the public. The aim of this study was to examine from a cognitive point of view the hypothesized link between drinking and stress. METHODS: 25 scenarios were constructed by combining two items, either two life-change events or a social situation and an emotional state. In the initial three experiments, 159 male and 43 female alcoholics and 157 male and 93 female nonalcoholics in France judged the degree to which these scenarios were stressful and subsequently the degree to which they stimulated an urge to drink. In the final experiment, 126 of the male alcoholics were studied at the beginning and end of an inpatient alcohol rehabilitation program. RESULTS: The alcoholics and nonalcoholics, regardless of gender, assigned similar stress values to the scenarios and used the same cognitive rules for combining the stress associated with two items (disjunctive rules for two life-change events and additive ones for a personal emotion combined with a social situation). They differed, however, in how they judged the urge to drink. The nonalcoholics reported little stimulus to drink from any combination of items, whereas the alcoholics not only perceived the individual items as stimulating an urge to drink but also used the same cognitive rule in judging the combined urge to drink of two items as they used in judging the combined stress. After completing rehabilitation, the alcoholics judged the combinations of life-change events as stimulating less stress and less urge to drink. Nevertheless, they continued to use a disjunctive combination rule. CONCLUSIONS: Stress and drinking are linked at a fundamental cognitive level among alcoholics, though not among nonalcoholics. Alcoholics should be helped to recognize this link, to reduce their feelings of stress, and to find outlets other than drink.

Adult↗