Meiosis is a critical stage of gametogenesis in which alignment and synapsis of chromosomal pairs occur, allowing for the recombination of maternal and paternal genomes. Here we show that FK506 ...binding protein (Fkbp6) localizes to meiotic chromosome cores and regions of homologous chromosome synapsis. Targeted inactivation of Fkbp6 in mice results in aspermic males and the absence of normal pachytene spermatocytes. Moreover, we identified the deletion of Fkbp6 exon 8 as the causative mutation in spontaneously male sterile as/as mutant rats. Loss of Fkbp6 results in abnormal pairing and misalignments between homologous chromosomes, nonhomologous partner switches, and autosynapsis of X chromosome cores in meiotic spermatocytes. Fertility and meiosis are normal in Fkbp6 mutant females. Thus, Fkbp6 is a component of the synaptonemal complex essential for sex-specific fertility and for the fidelity of homologous chromosome pairing in meiosis.
Mammalian MutL homologues function in DNA mismatch repair (MMR) after replication errors and in meiotic recombination. Both functions are initiated by a heterodimer of MutS homologues specific to ...either MMR (MSH2-MSH3 or MSH2-MSH6) or crossing over (MSH4-MSH5). Mutations of three of the four MutL homologues (Mlh1, Mlh3, and Pms2) result in meiotic defects. We show herein that two distinct complexes involving MLH3 are formed during murine meiosis. The first is a stable association between MLH3 and MLH1 and is involved in promoting crossing over in conjunction with MSH4-MSH5. The second complex involves MLH3 together with MSH2-MSH3 and localizes to repetitive sequences at centromeres and the Y chromosome. This complex is up-regulated in Pms2⁻superscript /⁻ males, but not females, providing an explanation for the sexual dimorphism seen in Pms2⁻superscript /⁻ mice. The association of MLH3 with repetitive DNA sequences is coincident with MSH2-MSH3 and is decreased in Msh2⁻superscript /⁻ and Msh3⁻superscript /⁻ mice, suggesting a novel role for the MMR family in the maintenance of repeat unit integrity during mammalian meiosis.
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In this paper, we report the encapsulation of near-infrared emitting Ag2S quantum dots (QDs) in the phospholipid nanostructures with different functional head-groups of phospholipids. ...Ag2S QDs were prepared using single-source precursor approach by thermal decomposition of silver diethyldithiocarbamate (Ag(DDTC)). Water dispersion of the QDs were accomplished by their encapsulation within cationic, anionic, neutral or PEGylated phospholipid nanostructures. The influence of different head-groups of phospholipids on physicochemical properties, encapsulation efficiency, luminescence efficiency, type of aggregates and stability of phospholipid nanostructures containing Ag2S QDs was determined and discussed. The basic biocompability of Ag2S QDs preparates was tested in vitro using NIH3T3 and HCT116 cell lines. In this regard the viability was assessed using MTS assay along with induction of apoptosis in cultures treated with selected phospholipid formulations of Ag2S. The anionic and PEGylated phospholipids showed greater encapsulation efficacy, stability and lower cytotoxicity than neutral and cationic phospholipids used for QDs encapsulation. Such low-toxic phospholipid structures can be used as carriers for different types of QDs. Our study revealed that the DSPE-PEG2000-based formulations of Ag2S QDs are well suited for applications in living biological systems Combination of outstanding optical properties of QDs and phospholipids biocompatibility makes such particles potentially useful in fluorescent microscopy as fluorescent contrast agents.
Genetic modifications causing germ cell death during meiotic prophase in the mouse frequently have sexually dimorphic phenotypes where oocytes reach more advanced stages than spermatocytes. To ...determine to what extent these dimorphisms are due to differences in male versus female meiotic prophase development, we compared meiotic chromosome events in the two sexes in both wild-type and mutant mice. We report the abundance and time course of appearance of structural and recombination-related proteins of fetal oocyte nuclei. Oocytes at successive days post coitus show rapid, synchronous meiotic prophase development compared with the continuous spermatocyte development in adult testis. Consequently, a genetic defect requiring 2-3 days from the onset of prophase to reach arrest registers pachytene as the developmental endpoint in oocytes. Pachytene spermatocytes, on the other hand, which normally accumulate during days 4-10 after the onset of prophase, will be rare, giving the appearance of an earlier endpoint than in oocytes. We conclude that these different logistics create apparent sexually dimorphic endpoints. For more pronounced sexual dimorphisms, we examined meiotic prophase of mice with genetic modifications of meiotic chromosome core components that cause male but not female sterility. The correlations between male sterility and alterations in the organization of the sex chromosome cores and X-Y chromatin may indicate that impaired signals from the XY domain (XY chromosome cores, chromatin, dense body and sex body) may interfere with the progression of the spermatocyte through prophase. Oocytes, in the absence of the X-Y pair, do not suffer such defects.
An effective ontology architecture enables the development of a geospatial semantic system that forges multiple geospatial data sources into a powerful cross-discipline knowledge source. This paper ...suggests types of ontologies that could support a geospatial semantic system. Motivations of each of the ontology types will be expounded, as well as potential areas for standardization by the geospatial community. Finally, the use of this approach within the OGC GSW Interoperability Experiment will be discussed.
The article discusses the key challenges associated with the economic development of the oilfield service industry within the climatic, geological, and infrastructural conditions of the Arctic. The ...evaluation of the Arctic's contribution to the total hydrocarbon production in Russia is an important research problem, which is particularly relevant amidst the current international political tensions. The study aims to unveil aspects of research and development (R&D) prospects of oilfield services in Russia's Arctic regions and adjacent territories. The research identifies characteristic features of economic development associated with economic activity risks. These include infrastructure and technological constraints linked to the distance from federal R&D and industrial centers; insufficient financial resources and experience for large project implementation by local authorities; the intricacy and labor intensity of work, coupled with a shortage of specialists possessing the necessary skills. The study establishes that the complexity of developing Arctic oil and gas fields is mitigated by the application of innovations and highlights the vulnerability of domestic companies to import supplies, which are currently inaccessible due to Western sanctions. The results presented offer a comprehensive view of the promising facets of the innovation-driven and technological development of the oilfield services industry in the Arctic. They propose specific measures geared towards enhancing production efficiency in the oil and gas and oilfield services sectors for implementation by the government. The study's conclusions constitute its scientific novelty and affirm that the sector under consideration is characterized by the following aspects: 1) the demanding nature of work necessitating substantial financial assets and professional competencies of often scarce labor market participants, alongside the utilization of innovative technologies to curtail production costs; and 2) a constrained pool of oil and gas market participants diminishing competition in the oilfield services market and enabling vertically integrated oil companies to dictate prices to service organizations, thus limiting opportunities for the industry's innovation-driven and technological development. The study's conclusions hold significant practical potential and are recommended for incorporation into territorial, regional, and federal programs for the social and economic development of Arctic regions. These findings contribute to the innovation-driven and technological revitalization of the oilfield services industry, an integral element in developing the resource base of Northern territories. Additionally, they provide avenues for further scientific exploration, delving into logistic, financial, technological, corporate, and other economic aspects specific to participants in forthcoming development processes.
On the assumption that Rad51 protein plays a role in early meiotic chromosomal events, we examine the location and time of appearance of immuno-reactive Rad51 protein in meiotic prophase chromosomes. ...The Rad51 foci in mouse spermatocytes appear after the emergence of, and attached to, short chromosomal core segments that we visualize with Cor1-specific antibody. These foci increase in number to about 250 per nucleus at the time when core formation is extensive. The numbers are higher in mouse oocytes and lower in rat spermatocytes, possibly correlating with recombination rates in those cases. In the male mouse, foci decrease in number to approximately 100 while chromosome synapsis is in progress. When synapsis is completed, the numbers of autosomal foci decline to near 0 while the X chromosome retains about 15 foci throughout this time. This stage coincides with the appearance of testis-specific histone H1t at mid- to late pachytene. Electron microscopy reveals that at first Rad51 immunogold-labeled 100 nm nodules are associated with single cores, and that they come to lie between the chromosome cores during synapsis. It appears that these nodules may be the homologs of the Rad51-positive early nodules that are well documented in plants. The reciprocal recombination-correlated late nodules appear after the Rad51 foci are no longer detectable. The absence of Rad51 foci in the chromatin loops suggests that in wild-type mice Rad51/DNA filaments are restricted to DNA at the cores/synaptonemal complexes. The expected association of Rad51 protein with Rad52 could not be verified immunocytologically.
En Algérie, la gouvernance hospitalière et l’évaluation des performances des hôpitaux s’inscrit dans un axe de priorité du gouvernement dans le cadre de la réforme du secteur de la santé. Son ...importance s’est encore plus marqué suite à la conjoncture économique que vit le pays depuis 2015, et ce en raison des grands moyens financiers alloué par l’état àce dernier secteur.Ce papier testequelques principes dela gouvernance et les perspectives d’application du nouveau management public décrit par les spécialistes sur un centre hospitalo-universitaire Algérien et en conclut de sérieusesinsuffisances en matière de pratiques managériales qui découlent des effets de la transition du modèle socialet économiquedu pays, entamée depuis le début des années quatre-vingt-dix.
Lateral variations of seismic anisotropy investigated by body waves allow us to detect the Archean–Proterozoic boundary in the upper mantle beneath the south-eastern Fennoscandia, though isotropic ...P-velocity perturbations in teleseismic P tomography or shear-velocity variations retrieved by inversion of surface waves by other authors do not noticeably differ in the Proterozoic and Archean mantle beneath the SVEKALAPKO array. The boundary seems to be inclined to the SW, in general, and very complex, forming a broad transition zone. This zone appears in the P residuals, which accumulate the velocity deviations along the ray path, as almost isotropic structure due to superposition of pieces of the mantle lithosphere with differently oriented anisotropy. The shear-wave splitting is consistent for groups of stations within the Archean and Proterozoic domains, and detects anisotropy even in the central transitional domain, which may reflect anisotropy of the thickest lithosphere wedge. In general, variations of the splitting parameters indicate a very complicated structure, which cannot be approximated by a single layer with horizontal symmetry axis or a simple contact of two mantle lithosphere blocks. We propose three potential candidates for a mantle lithosphere model around the Proterozoic–Archean contact.
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