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Embryo development in vitro of cat oocytes cryopreserved at different maturation stages
No full textThe purpose of this study was to evaluate the ability of cat oocytes, at different stages of maturation, to survive after cryopreservation and to assess their subsequent development following IVM and IVF. In the initial toxicity trial, immature oocytes were exposed to different concentrations of DMSO and ethylene glycol (EG). Resumption of meiosis and metaphase II were evaluated after removal of the cryoprotectant and IVM. The highest rates of resumption of meiosis (51.4%) were achieved after exposure to 1.5 mol l-1 of cryoprotectants, and no difference was observed with control oocytes. Metaphase II was obtained in 25.7% (P<0.01) and 22.9% (P<0.005) of oocytes exposed to 1.5 mol l-1 of DMSO and ethylene glycol, although at lower rates than in control oocytes (54.4%). On the basis of this finding, 1.5 mol l-1 of cryoprotectant was chosen for freezing cat oocytes at the germinal vesicle stage (immature) or at metaphase II stage (mature). Post-thaw viability was assessed by the evaluation of the embryo development in vitro. After fertilization, mature oocytes frozen in ethylene glycol cleaved in better proportions (38.7%) than immature oocytes (6.8%, P<0.001), and no differences were observed in the cleavage rate of oocytes frozen at different maturation stages with DMSO (immature 12.8%; mature 14.1%). Embryonic development beyond the 8-cell stage was obtained only when mature oocytes were frozen with ethylene glycol (11.3%). This study suggests that cryopreserved cat oocytes can be fertilized successfully and that their development in vitro is enhanced when mature oocytes are frozen with ethylene glycol. The stage of maturation may be a key element in improving cat oocyte cryopreservation. (C) 2000 by Elsevier Science Inc
Embryo development of in-vitro matured cat oocytes cryopreserved by slow and ultrarapid freezing
No full textEffects of slow and ultrarapid freezing on morphology and resumption of meiosis in immature cat oocytes
No full textThis study examined the ability of immature cat oocytes to survive after cryopreservation by evaluating their subsequent development following maturation in vitro. The effect of slow and ultrarapid freezing using one of two cryoprotectants dimethylsulphoxide (DMSO) or 1,2-propanediol (PROH) at different concentrations (1.5 or 3.0 mol-1) and the slow freezing with the cryoprotectant ethylene glycol (EG 1.5 mol l-1 and 3.0 mol l-1) were tested. Morphology, resumption of meiosis and metaphase II rates of oocytes were recorded after thawing. Freshly collected oocytes were used as controls. Results indicate that immature cat oocytes can survive, resume meiosis and achieve metaphase II in vitro after freezing. The highest rates of resumption of meiosis and metaphase II were achieved with slow freezing and 1.5 mol DMSO or EG l-1 (DMSO: 47.4%, 18/38 and 23.7%, 9/38 and EG: 52%, 13/25 and 20%, 5/25, respectively). The ultrarapid procedure did not result in resumption of meiosis in vitro, despite intact morphology of the oocytes after thawing. These results suggest that morphology of oocytes after freezing and thawing has no predictive value for their ability to resume meiosis
Effects of slow and ultrarapid freezing on morphological appearance and meiosis resumption of cat immature oocytes
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VALIDITA’ DELL’INDAGINE ECOGRAFICA ED ISTEROSCOPICA NELLE METRORRAGIE IN MENOPAUSA: DATI PRELIMINARI
No full textNegli ultimi anni si e' andato affermando l'impiego dell'isteroscopia, che consente una visualizzazione diretta della cavita' uterina, con possibilita' di ottenere prelievi nelle aree piu' a rischio. Numerosi sono anche gli studi che propongono l'ecografia transvaginale come metodica di studio dell'endometrio in menopausa, ritenendola utile per la diagnosi di alterazioni endometriali e soprattutto nel predirre l'atrofia endometriale
Il gatto come specie modello per lo studio dei felini selvatici: produzione in vitro di embrioni
No full textFertilization and in vitro development of cat oocytes cryopreserved before and after maturation in vitro
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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