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  • 1
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. A comprehensive cytogenetic characterization of the unusually large reindeer (Rangifer tarandus) sex chromosomes is presented for the purpose of studying the evolution of these atypical gonosomes. Sex chromosome idiograms were constructed from G-banded and C-banded chromosomes to illustrate the relative amounts and locations of euchromatin and heterochromatin. Hybridization with a Mazama gouazoubira X whole-chromosome paint revealed that essentially all reindeer X-linked euchromatin and most reindeer Y-linked euchromatin is conserved interspecifically. Subsequently, painting probes were generated from flow-sorted reindeer X chromosomes, flow-sorted reindeer Y chromosomes, and from microdissections of specific gonosomal regions to establish specific segment-to-segment homologies between these gonosomes. In particular, one microdissection-generated paint demonstrated that certain constituent repetitive DNAs, found in C-band region Xq31, were also present in essentially all heterochromatin blocks of the Y chromosome. Microdissection-generated paints from other X-linked heterochromatin blocks revealed the presence of DNA sequences that lacked homologous sequences on the Y chromosomes and were more specific for their region of origin. These characteristics of the reindeer sex chromosomes are consistent with the notion that mammalian sex chromosomes were derived from homologous progenitor chromosome pairs and provide insights into the evolution of these atypical mammalian gonosomes.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 2355-2364 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The technology of two-stage pneumatic pellet injectors represents by far the most reliable way to perform deep plasma fueling, with pipe gun devices capable of routinely launching small or medium size (up to 4 mm) D2 pellets at speeds in excess of 3 km/s, using rather small two-stage guns. It is still an open question, however, if scaling of the pellet size to the International Thermonuclear Experimental Reactor relevant values (6–8 mm) will or will not require a somewhat proportional increase in the physical size of the two-stage gun. In order to investigate this question, an extensive study was carried out at ENEA Frascati, using numerical simulation codes. It clearly indicated that a "compact" two-stage gun may have the potential to accelerate large size pellets at speeds up to 5 km/s. A low cost experiment was also scheduled. A spare pipe-gun cryostat of the single-shot two-stage pneumatic injector, previously used for high-speed pellet fueling of the Frascati tokamak upgrade, was modified in order to accommodate larger bore (up to 6 mm) launching barrels. In this article, we will mainly discuss the results of numerical simulations. A very early experimental campaign, carried out in 1996, will also be briefly reported, during which intact 6 mm D2 pellets were launched at speeds up to 2.5 km/s. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Over the past few years, several groups have used fluorescence in situ hybridization (FISH) to study aneuploidy in human sperm. Several important observations have derived from these studies, including the demonstration of chromosome-specific variation in non-disjunction frequencies, and the possible association of aneuploidy with environmental agents and with increasing paternal age. However, an important technical limitation of these studies has been the inability to distinguish between autosomal non-disjunction occurring at meiosis I and meiosis II. In the present report, we describe a simple FISH-based approach designed to overcome this limitation. Using oligonucleotide probes capable of distinguishing subtle differences in the alpha satellite sequences of chromosome 17, we demonstrate that (in appropriate heterozygotes) it is possible to simultaneously identify disomic sperm and to determine the meiotic stage of origin of the additional chromosome. This novel approach has important implications for future FISH sperm studies, since the ability to distinguish between meiosis I and meiosis II non-disjunction will make it possible to determine whether putative etiological agents affect chromosome segregation at both, or only one, of the two meiotic stages.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-7330
    Keywords: polymerase chain reaction ; single cell ; DNA amplification ; human preimplantation embryo ; preimplantation diagnosis ; sexing ; alphoid repeat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Introduction: Preimplantation diagnosis involves detecting genetic defects in one or two blastomeres biopsied from cleavage stage embryos followingin vitro fertilization (IVF). For X-linked recessive disease, identification of the sex of embryos allows transfer of only unaffected females. To examine how critical the preparation of the single blastomere is for amplification of a Y chromosome specific repeat sequence using the polymerase chain reaction (PCR), the incidence of amplification failure has been examined following two lysis protocols. Materials and Methods: Amplification of a Y alphoid repeat sequence from single blastomeres disaggregated from cleavage stage embryos was examined after either (1) lysis in distilled water and freeze-thawing twice or (2) a two-step lysis protocol involving an initial treatment in potassium hydroxide and dithiothreitol. Some of the embryos had been previously sexed by cleavage-stage biopsy and fluorescent in situ hybridization with X- and Y-specific probes. Results: Amplification failure occurred in 6 of 50 (12%) and 4 of 60 (7%) single blastomeres from male embryos following lysis in distilled water or using the two-step protocol, respectively. Conversely, amplification from contaminating DNA occurred in 5 of 63 (8%) single blastomeres from female embryos and 6 of 94 (6%) of control medium blanks. Conclusions: The incidence of amplification failure was improved but not eliminated using the two-step lysis protocol. At least two cells, therefore, would be necessary for accurate identification of males by amplification of Y-specific repeat sequences alone. Nevertheless, this protocol for preparing cleavage-stage blastomeres is likely to give more consistent amplification of any unique or repeat sequences.
    Type of Medium: Electronic Resource
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