Search results for "sperm"
showing 10 items of 658 documents
Silene crassiuscula (Caryophyllaceae), a new species from Sicily
2015
Silene crassiuscula,, a new species of S. sect. Dipterosperma, is described and illustrated from North-Western Sicily. It is an annual halophyte with succulent growing on carbonatic or calcarenitic rocks of coastal stands. From the morphological point of view , S. crassiuscula appears to be similar to the species belonging to the S. colorata group especially to S. nummica, from Sardinia, from which it differs in several features chiefly regarding the habit, leaves, inflorescences, floral pieces and seed micro-morphology. An analytical key of the taxa belonging to this section is also provided.
Aberrant methylation patterns at the two-cell stage as an indicator of early developmental failure
2002
The fertilized mouse egg actively demethylates the paternal genome within a few hours after fertilization, whereas the maternal genome is only passively demethylated by a replication-dependent mechanism after the two-cell stage. This evolutionarily conserved assymetry in the early diploid mammalian embryo may have a role in methylation reprogramming of the two very different sets of sperm and egg chromatin for somatic development and formation of totipotent cells. Immunofluorescence staining with an antibody against 5-methylcytosine (MeC) showed that the incidence of abnormal methylation patterns differs between mouse two-cell embryos from superovulated females, nonsuperovulated matings, an…
Perspectives of the encapsulation technology in the nursery activity of Citrus
2007
The genetic and phytosanitary certification has to guarantee the quality of the propagation material also in Citrus. Traditional methods can be assisted by the techniques of in vitro culture, which are fundamental for the mass production of high quality plants. The encapsulation technology represents an innovative tool to combine the advantages of micropropagation with handling ease, storability, reduced size of the propagules, mechanization potentiality, transportability of the gamic seeds. In this work somatic embryos obtained from in vitro anther culture of the cultivar Mandarino Tardivo di Ciaculli (Citrus reticulata Blanco) were encapsulated in a sodium alginate matrix and synthetic se…
Preliminary research on conversion of encapsulated somatic embryos of Citrus reticulata Blanco, cv. Mandardino Tardivo di Ciaculli.
2006
Somatic embryogenesis was obtained through anther culture of Citrus reticulata, cv. Mandarino Tardivo di Ciaculli. The work was carried out to evaluate the response of somatic embryos inside a sodium alginate coating to different storage periods, and to the effects of the germicide PPM (1 ml l(-1) stop) and the fungicide Thiophanate-methyl (100 mg l(-1) stop). The effect of these alone or in combination, added to the artificial endosperm on the performance of the encapsulated somatic embryos was tested. After 45 days of culturing, sprouting, root development and conversion were recorded. The encapsulated somatic embryos can be conveniently stored at 4 degrees C, but not for a period longer …
The evolutionary history of the Arabidopsis arenosa complex: diverse tetraploids mask the Western Carpathian center of species and genetic diversity.
2012
The Arabidopsis arenosa complex is closely related to the model plant Arabidopsis thaliana. Species and subspecies in the complex are mainly biennial, predominantly outcrossing, herbaceous, and with a distribution range covering most parts of latitudes and the eastern reaches of Europe. In this study we present the first comprehensive evolutionary history of the A. arenosa species complex, covering its natural range, by using chromosome counts, nuclear AFLP data, and a maternally inherited marker from the chloroplast genome [trnL intron (trnL) and trnL/F intergenic spacer (trnL/F-IGS) of tRNA(Leu) and tRNA(Phe), respectively]. We unravel the broad-scale cytogeographic and phylogeographic pa…
Production of Norspermidine Contributes to Aminoglycoside Resistance in pmrAB Mutants of Pseudomonas aeruginosa
2019
Emergence of resistance to polymyxins in Pseudomonas aeruginosa is mainly due to mutations in two-components systems, that promote addition of 4-amino-4-deoxy-L-arabinose to the lipopolysaccharide (LPS) through upregulation of operon arnBCADTEF-ugd (arn) expression. Here, we demonstrate that mutations occurring in different domains of histidine kinase PmrB or in response regulator PmrA result in coresistance to aminoglycosides and colistin. All seventeen clinical strains tested exhibiting such a cross-resistance phenotype were found to be pmrAB mutants. As shown by gene deletion experiments, the decreased susceptibility of the mutants to aminoglycosides was independent from operon arn but r…
Concentration of glutathione and expression of glutathione peroxidases 1 and 4 in fresh sperm provide a forecast of the outcome of cryopreservation o…
2004
Oxidative stress imbalance potentially leads to damage of the structure of the cell and macromolecules such as plasma membrane components, proteins, and DNA. The plasma membrane of the sperm cell, which has high levels of polyunsaturated fatty acids, renders it particularly sensitive to free radical–mediated attacks. The freezing and subsequent thawing of sperm is a physically stressful process carried out during routine procedures in assisted reproduction techniques, which results in a highly variable and unpredictable reduction in the number of motile sperm cells. Subsequently, oxidative status can positively or negatively affect the motility, viability, and fertilizing capacity of thawed…
La utilización de marfil de cachalote en el Calcolítico de Portugal
2013
Scientific analysis were undertaken within a research project concerning ivory objects from the Chalcolithic to Early Bronze Age of the Iberian Peninsula. In several of the analyses of objects from Portuguese Estremadura, especially V-perforated buttons, we could detect for the first time the presence of sperm whale ivory. This highlights the advantage and necessity of scientific analysis of ivory. It also clearly demonstrates that not all ivory used was ivory from African or Asian elephants, but we also did find ivory from the extinct Elephas antiquus, the hippopotamus and in this case sperm-whale. Thus, already in the Chalcolithic the raw material provenience was highly diverse, which in …
Factors which influence sperm ability to fertilize.
2005
Different facrors influence animal sperm abiÌiry ro fertilizc- Some ofthem are revieu'ed here, spermmotiliry block to polyspermy, chemioattracrìon, sperm cornpetition lor fcrtilization. Old and new data are report-ed, as lor exanplc the new notions on sperm moriliry derived from sitc directed mutagenesis in rodents, the newnotions on thc odour receptors in m:rrnmalian sperm attr-action and ncw notions on sperm competìtion, which isvariable in diflerent species
Regulation of PCAF Activity by Spermidine
2011
Histones and polyamines are important determinants of chromatin structure. Histones are the core of nucleosome particles and their modification by acetylation of N-terminal tails is involved in chromatin structural changes and transcriptional modulation. Polyamines also, including spermidine, are targets of both nuclear and cytoplasmic acetylation, which in turn alters their affinity for DNA and nucleosomes. Previous studies report an interplay existing between polyamines metabolism and levels, and histone acetylation. The relationship between polyamines and histone epigenetics in vivo has been considered in various models of ageing through epigenetic modifications, induction of autophagy a…