182 research outputs found
Selection of highly fertilization-competent bovine spermatozoa through adhesion to the Fallopian tube epithelium in vitro
Mammalian spermatozoa undergo a marked reduction in number during their journey through the female reproductive tract. One of the checkpoints in the selection of fertilizing spermatozoa may be the transient adhesion to the Fallopian tube epithelium, an event previously shown to play a key role in sperm storage. Bovine spermatozoa adhering to the Fallopian tube epithelium in vitro may be synchronously released by sulphated glycoconjugates. In the present study, experiments were designed to quantify the number of spermatozoa selected through adhesion, and to compare the zona pellucida (ZP) binding and fertilization competence of the initial sperm suspension versus the bound and unbound sperm subpopulations. Results showed that: (1) a fraction accounting for about 30% of the initial sperm suspension was selected by in vitro adhesion to oviductal epithelial cell monolayers; (2) selected spermatozoa, collected after heparin-induced release, had a significantly superior ZP binding and fertilization competence (mean +/- SD: 110 +/- 28 bound spermatozoa per oocyte; % cleavage, mean +/- SEM: 89 +/- 4) compared with both the initial sperm suspension (45 +/- 10 bound spermatozoa per oocyte, P < 0.001; % cleavage: 69 +/- 3, P < 0.05) and the unselected subpopulation (30 +/- 4 bound spermatozoa per oocyte, P < 0.001; % cleavage: 58 +/- 3, P < 0.01). These findings support the hypothesis that binding to oviductal cells is not only beneficial for sperm survival but also represents a crucial step for the selection of spermatozoa endowed with superior fertilization competence
String Breaking in Quenched QCD
We present preliminary quenched results on a new operator for the
investigation of string-breaking within SU(2)-colour QCD. The ground-state of a
spatially-separated static-light meson-antimeson pair is a combination of a
state with two distinct mesons, expected to dominate for large separations, and
a state where the light-quarks have annihilated, which contributes for short
distances. The crossover between these two regimes provides a measure of the
string-breaking scale length.Comment: LATTICE98(confine), 3 pages, 4 figure
Mitochondrial dysfunction and oxidative stress caused by cryopreservation in reproductive cells
Mitochondria, fundamental organelles in cell metabolism, and ATP synthesis are respon-sible for generating reactive oxygen species (ROS), calcium homeostasis, and cell death. Mitochon-dria produce most ROS, and when levels exceed the antioxidant defenses, oxidative stress (OS) is generated. These changes may eventually impair the electron transport chain, resulting in decreased ATP synthesis, increased ROS production, altered mitochondrial membrane permeability, and dis-ruption of calcium homeostasis. Mitochondria play a key role in the gamete competence to facilitate normal embryo development. However, iatrogenic factors in assisted reproductive technologies (ART) may affect their functional competence, leading to an abnormal reproductive outcome. Cry-opreservation, a fundamental technology in ART, may compromise mitochondrial function leading to elevated intracellular OS that decreases sperm and oocytes’ competence and the dynamics of fertilization and embryo development. This article aims to review the role played by mitochondria and ROS in sperm and oocyte function and the close, biunivocal relationships between mitochon-drial damage and ROS generation during cryopreservation of gametes and gonadal tissues in different species. Based on current literature, we propose tentative hypothesis of mechanisms involved in cryopreservation-associated mitochondrial dysfunction in gametes, and discuss the role played by antioxidants and other agents to retain the competence of cryopreserved reproductive cells and tissues
New taxa in the paleocene flora from the cross Valley-Wiman Formation, Marambio (=Seymour) Island, Antarctica
The Paleocene at the Marambio Island (James Ross Basin) is represented by three marine sedimentary units. The uppermost unit corresponds to the Cross Valley-Wiman Formation (CVWF), which overlies previous units by a strong erosive discordance. Contrary to the underlayed units, the CVWF is characterized by the preservation of a rich flora of compressions and petrifications; preserving leaves and seeds at it uppermost section (BahÃa Pingüino Allomember), that corresponds to lagoon or protected bay facies and which age has been dated as upper Paleocene (C25n, Thanetian). Its fossil records are known since the Dusén studies from 1908, who proposed 87 leaf taxa. Despite its Southern Hemisphere importance, few studies has revised the plant type materials, recognizing a richness reduction from the originally proposed to three fern species, two conifers, and 14 angiosperms. New Argentina field works has permitted identify the 19 previous taxa, recognized two more from Dusén (Mollinedia seymourensis and Phyllites sp. 14), and adds seven new findings (a fertile fern, a filmy fern, and five angiosperms). The unbiased collection of 282 exemplars allows to measure the taphoflora relative abundance. It indicates the dominance (35 %) of ferns (Cladophlebis and Sphenopteris). The most common angiosperm families were: Atherospermathaceae, Lauraceae, Moraceae?, Nothofagaceae, and Winteraceae. The Araucariaceae also were well represented, in agreement with wood studies. The CVWF taphoflora overpass the Paleocene known richness in all the Antarctic Peninsula, adds new elements, and quantify the relative proportion of taxa.Fil: Iglesias, Aimé Lucila. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Gallardo, R.. Departamento de Geologia y Petroleo ; Centro Regional Universitario Bariloche ; Universidad Nacional del Comahue;Fil: Pipo, MarÃa Laura. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Santillana, Sergio Nestor. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; ArgentinaFil: Talevi, Marianella. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación en PaleobiologÃa y GeologÃa; ArgentinaReunión anual de comunicaciones de la Asociación Paleontológica ArgentinaArgentinaAsociación Paleontológica Argentin
Protective effects of a SIRT1 inhibitor on primordial follicle activation and growth induced by cyclophosphamide: insights from a bovine in vitro folliculogenesis system
Purpose: Although oncological advances have improved survival rates of female cancer patients, they often suffer a reduced fertility due to treatment side effects. In the present study, we evaluated the potential fertoprotective effects of the specific inhibitor of SIRT1, EX-527, on the gonadotoxic action exerted by cyclophosphamide (CPM) on loss of primordial follicles (PFs). Methods: The effects of the CPM metabolite phosphoramide mustard (PM) on follicle activation, growth and viability and the protective action of EX-527 against PM effects were evaluated on bovine ovarian cortical strips in vitro cultured for 1 or 6Â days. To understand whether PFs exposed to PM plus EX-527 were able to activate and grow to the secondary stage after suspension of the treatment, strips cultured for 3Â days in PM plus EX-527 for 3Â days were transferred to plain medium until day 6. Follicle growth and health were evaluated through histology and viability assay at a confocal microscope. In order to investigate the molecular pathways underlying the ovarian response to PM in the presence of EX-527, we analysed the protein level of SIRT1, HuR, PARP1 and SOD2 after 1Â day of in vitro culture. Results: We found that (1) PM, the main CPM active metabolite, promotes PF activation; (2) the ovarian stress response induced by PM includes a SIRT1-dependent pathway; and (3) EX-527 reduces PF activation and growth induced by PM. Conclusion: SIRT1 can represent a candidate molecule to be targeted to protect ovarian follicles from alkylating agents and EX-527 could represent a potential fertoprotective agent for cancer patients
Light hadron spectroscopy with O(a) improved dynamical fermions
We present the first results for the static quark potential and the light
hadron spectrum using dynamical fermions at using an O(a) improved
Wilson fermion action together with the standard Wilson plaquette action for
the gauge part. Sea quark masses were chosen such that the pseudoscalar-vector
mass ratio, m_PS/m_V$, varies from 0.86 to 0.67. Finite-size effects are
studied by using three different volumes, 8^3\cdot 24, 12^3\cdot 24 and
16^3\cdot 24. Comparing our results to previous ones obtained using the
quenched approximation, we find evidence for sea quark effects in quantities
like the static quark potential and the vector-pseudoscalar hyperfine
splitting.Comment: 38 pages, 14 Postscript figure, LaTe
Speeding up finite step-size updating of full QCD on the lattice
We propose various improvements of finite step-size updating for full QCD on
the lattice that might turn finite step-size updating into a viable alternative
to the hybrid Monte Carlo algorithm. These improvements are noise reduction of
the noisy estimator of the fermion determinant, unbiased inclusion of the
hopping parameter expansion and a multi-level Metropolis scheme. First
numerical tests are performed for the 2 dimensional Schwinger model with two
flavours of Wilson fermions and for QCD two flavours of Wilson fermions and
Schr"odinger functional boundary conditions.Comment: 22 pages, 1 figur
String Breaking in Lattice Quantum Chromodynamics
The separation of a heavy quark and antiquark pair leads to the formation of
a tube of flux, or string, which should break in the presence of light
quark-antiquark pairs. This expected zero temperature phenomenon has proven
elusive in simulations of lattice QCD. We present simulation results that show
that the string does break in the confining phase at nonzero temperature.Comment: 11 pages RevTeX, including 4 encapsulated Postscript figures.
version2: minor corrections to reference
Is there a role for endocannabinoids in sperm–oviduct interaction?
The endocannabinoid system (ECS) has been found in reproductive cells and tissues in several mammals. Spermatozoa are able to respond to anandamide, and the oviduct is able to synthesize and modulate the concentration of this endocannabinoid along the isthmic and ampullary regions. The main aim of this study was to understand whether the ECS has a role during sperm storage and release within the oviduct in cattle. Data showed that 1) the endocannabinoid receptors 1 and 2 (CB1 and CB2) are present in bovine spermatozoa both in the initial ejaculate and in spermatozoa bound to the oviduct in vitro; 2) CB1 receptor is still detectable in spermatozoa released from the oviduct through penicillamine but not in those released through heparin; 3) arachidonylethanolamide (AEA) does not affect sperm viability, whereas it depresses sperm progressive motility and kinetic values; 4) sperm–oviduct binding and release in vitro are not influenced by AEA; 5) AEA depresses sperm–zona pellucida (ZP) binding; 6) binding of heparin-capacitated spermatozoa to the ZP is not affected by AEA; 7) N-acylphosphatidylethanolamine-selective phospholipase D, the main enzyme involved in anandamide synthesis, is expressed in oviductal epithelial cells. In conclusion, secretion of AEA from epithelial cells might contribute to the oviduct sperm-reservoir function, prolonging the sperm fertile life through the depression of motility and capacitation. Capacitation signals, such as heparin, that promote sperm release, might remodel the sperm surface and cause a loss of the sperm sensitivity to AEA
The Kaon B-parameter with the Wilson Quark Action using Chiral Ward Identities
A lattice QCD calculation of the kaon parameter is carried out with
the Wilson quark action in the quenched approximation at .
The mixing problem of the four-quark operators is solved
non-perturbatively with full use of chiral Ward identities employing four
external quarks with an equal off-shell momentum in the Landau gauge. This
method, without invoking any effective theory, enables us to construct the weak
four-quark operators exhibiting good chiral behavior. Our results for
with the non-perturbative mixing coefficients show small scaling violation
beyond the lattice cut-off GeV. Our estimate concludes
at GeV, which agrees with the value
obtained with the Kogut-Susskind quark action. For comparison we also calculate
with one-loop perturbative mixing coefficients. While this yields
incorrect values at finite lattice spacing, a linear extrapolation to the
continuum limit as a function of leads to a result consistent with those
obtained with the Ward identity method.Comment: 42 pages, 22 Postscript figures, added a new reference[26
- …