Single-channel response of hamster oocytes to fertilization with homologous spermatozoa.

Electrophysiological events occur early after fertilization, along with changes in intracellular Ca2+ concentration. Passive electrical parameters were determined in golden hamster oocytes by whole cell patch-clamp method. In separate experiments the effect of 4-aminopyridine on resting oocytes was tested. The single-channel patch clamp configuration was employed to assess the electrical response to fertilization with homologous sperm. Structure of oocytes submitted to patch clamp was evaluated with scanning electron microscopy and found to be preserved. Oocyte diameter was 70.2 +/- 2.2 microm; their resting parameters were: membrane potential 23.8 +/- 0.8 mV; total membrane specific resistance 519.1 +/- 94.6 ohms.cm2, and specific capacity 0.99 +/- 0.03 microF.cm(-2). Total membrane current was decreased by 42 % by 4-aminopyridine. Control oocytes and oocytes exposed to sperm differed in their membrane currents in response to a voltage ramp clamping membrane potential from - 100 mV to + 100 mV. In both cases, currents were largest at the most negative potentials, but sperm-exposed oocytes had larger currents. Additionally, while in control oocytes the current was inward at negative potentials but outward at positive potentials, in the presence of spermatozoa oocytes was inward within the whole voltage range tested. This latter current may represent Ca2+ entry.     

Seasonal variations in the heterologous binding of viscacha spermatozoa. A scanning electron microscope study.

Seasonal changes in the reproductive activity of the adult male viscacha (Lagostomus maximus maximus) were investigated during the annual reproductive cycle. Assays of heterologous in vitro binding between compatible gametes were used to evaluate the ability of viscacha spermatozoa to achieve primary binding during its annual reproductive cycle. Sperm were collected by mincing cauda epididymis in HECM-3 medium and the sperm concentration and motility were evaluated. Cumulus-free and zona-free oocytes obtained from superovulated hamsters were inseminated in vitro with capacitated sperm suspensions, incubated at 37 degrees C, 5% CO2 for 3 h, and then processed for studies by scanning electronic microscopy. Statistical analysis was used to compare the quantitative differences. The number of spermatozoa significantly decreases during the regression period, while sperm motility was progressive speed in both periods. During the active period elevated sperm binding to cumulus-free and zona-free oocytes was observed, while the binding during the regression period decreased drastically. In both periods, oocyte microvilli covered sperm heads and tails. These results suggest that the ability of viscacha spermatozoa to participate in gamete recognition is profoundly affected. This would likely be related to different functional stages of the spermatozoa and their epididymal microenvironment during the annual reproductive cycle of viscacha.     

The actin filament network associated to Sertoli cell ectoplasmic specializations

Junctional devices in Sertoli cells conform the blood-testis barrier and play a key role in maturation and differentiation of germ cells. The spacial distribution of ectoplasmic specializations of Sertoli cells was studied by beta-actin immunolabelling, using laser confocal and transmission electron microscopy. For confocal microscopy, beta-actin immunolabelling of ectoplasmic specializations was studied over the background of either prosaposin or glutaredoxin immunolabelling of the Sertoli cytoplasm. Labelling was found near the basal lamina, surrounding early spermatocytes (presumably in leptotene-zygotene) or at one of two levels in the seminiferous epithelium: (1) around deep infoldings of the Sertoli cell cytoplasm, in tubular stages before spermiation, and (2) in the superficial part of the seminiferous epithelium, in tubular stages after or during spermiation. For transmission electron microscopy, beta-actin immunolabelling of ectoplasmic specializations was also used. Ectoplasmic specializations were found at two different levels of the seminiferous epithelium. We also used freeze fracture to analyze the characteristics of tubulo-bulbar complexes, a known component of apical ectoplasmic specializations. Also, these different approaches allowed us to study the complex arrangement of the actin cytoskeleton of Sertoli cells branches, which surround germ cells in different stages of the spermatogenic cycle. Our results show a consistent labelling for beta-actin before, during and after the release of spermatozoa in the tubular lumen (spermiation) suggesting a significant role of the actin network in spermatic cell differentiation. In conclusion, significant interrelations among the beta-actin network, the junctional complexes of the blood-testis barrier and the ectoplasmic specializations were detected at different stages of the seminiferous cycle.     

Self-labeling techniques for semi-supervised time series classification: an empirical study

An increasing amount of unlabeled time series data available render the semi-supervised paradigm a suitable approach to tackle classification problems with a reduced quantity of labeled data. Self-labeled techniques stand out from semi-supervised classification methods due to their simplicity and the lack of strong assumptions about the distribution of the labeled and unlabeled data. This paper addresses the relevance of these techniques in the time series classification context by means of an empirical study that compares successful self-labeled methods in conjunction with various learning schemes and dissimilarity measures. Our experiments involve 35 time series datasets with different ratios of labeled data, aiming to measure the transductive and inductive classification capabilities of the self-labeled methods studied. The results show that the nearest-neighbor rule is a robust choice for the base classifier. In addition, the amending and multi-classifier self-labeled-based approaches reveal a promising attempt to perform semi-supervised classification in the time series context.     

Words from "Sesame Street": Learning vocabulary while viewing.

The present study was a longitudinal investigation of preschool children's viewing of "Sesame Street" and their vocabulary development. Five 1-week diaries of television viewing were collected for 2 years from 2 cohorts of children; 1 group was followed from ages 3 to 5 (n?=?160) and another from ages 5 to 7 (n?=?166). Child and family measures included children's vocabulary skills, gender, presence of siblings, parent education, parent encouragement of "Sesame Street" viewing, and parent positive attitudes about television. Cross-age multiple regressions, in conjunction with within-age regressions, suggested a positive effect of "Sesame Street" viewing from ages 3 to 5, with declining benefits from ages 5 to 7. Neither positive nor negative effects were evident for viewing other kinds of children's programs, such as cartoons. Results suggest that the content and presentation formats of "Sesame Street" are well suited to preschoolers' vocabulary development, independent of parent education, family size, child gender, and parental attitudes. The findings suggest the feasibility of tutorial uses of the video medium. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Functional Chia Oil‐in‐Water Emulsions Stabilized with Chia Mucilage and Sodium Caseinate

The objective of this research was to study the effect of adding different concentrations of chia mucilage (0%, 0.30%, or 0.80%, wt/wt) and sodium caseinate (NaCas) as emulsifying agents (0.1%, 0.5%, 2.0%, or 5.0%, wt/wt) on the stability of oil‐in‐water (O/W) emulsions (10:90, wt/wt) as a function of storage time, at room temperature. The emulsions were characterized by determining the evolution of backscattering profiles, the particle‐size distribution, and microscopic observations. The most stable emulsions over the storage period were those with 0.80% of the chia mucilage concentration. These emulsions also presented a bimodal particle‐size distribution, while the emulsions without chia mucilage exhibited a monomodal distribution. The De Brouker mean diameter (D) [4,3] of all the emulsions decreased with increasing NaCas concentrations and they increased with storage time, mainly for the emulsions with the lowest chia mucilage and the emulsifying agent concentrations. The optical micrographs showed a high destabilization in the emulsions with low concentrations of chia mucilage and NaCas. The results suggest that the addition of chia mucilage to O/W emulsions confers more stability to the emulsions, as a function of increase in the mucilage concentration. The addition of NaCas also showed a greater stability with increasing concentration for both emulsions (with and without chia mucilage).     

Fatty Acid Composition of Irvingia gabonensis and Treculia africana Seed Lipids and Phospholipids

Lipid compositions of two non-conventional oilseeds (Irvingia gabonensis and Treculia africana) were studied. Total lipids were extracted by the Folch method and phospholipids were isolated by solid phase extraction. Fatty acid compositions of total lipids and phospholipids were determined by gas chromatography. Phospholipid classes and tocopherols were quantified by HPLC. The major fatty acids in I. gabonensis seed total lipids were myristic (41.4–48.9 %) and lauric (39.8–46.8 %) while those in T. africana seed were linoleic (29.1–31.4 %) and oleic (22.9–25.9 %). The principal fatty acid at the sn-2 position of I. gabonensis seed triacylglycerols was myristic (49.5 %) while that of T. africana was linoleic (50.6 %). Phospholipid content of crude T. africana seed oil was 3.3 % and that of I. gabonensis was 0.1–0.3 %. The composition and distribution of saturated fatty acids in I. gabonensis seed lipids suggest that it may contribute to cardiovascular disease risk factors among the Igbo people in Nigeria that use the seed as food ingredient.     

PERFORMANCE EVALUATION OF PCA TESTS IN SERIAL ELIMINATION STRATEGIES FOR GROSS ERROR IDENTIFICATION

In this paper, the performance of the Principal Component Measurement Test (PCMT) is evaluated when used for the identification of multiple biases. A serial elimination strategy is implemented where a statistical test based on principal component analysis is used to identify the measurement to eliminate. A simulation procedure involving random measurement errors and fixed gross error sizes is applied to evaluate its performance. This performance is compared with the one obtained using serial elimination using the conventional Measurement Test (MT), as it is performed in some commercial simulators. The analysis indicates that principal component tests alone, without the aid of other collective tests, do not significantly enhance the ability in identification features of this strategy, performing worse in some cases. A few cases of severe failure of this strategy are shown and a suggestion to test other strategies is offered.     

Poly(acrylonitrile)-montmorillonite nanocomposites: Effects of the intercalation of the filler on the conductivity of composite polymer electrolytes

In this work, a series of composite polymer electrolytes (CPEs) basically constituted by polyacrylonitrile (PAN) and a clay, montmorillonite (Bentonite), as filler have been developed, in which the clay in its lithiated form was used both as prepared and intercalated with PAN .The effect of these two forms of nanoceramic active filler on the properties of the CPEs was analyzed. Results show that the ionic conductivity of the CPEs using as filler Bentonite-Li⁺-polyacrylonitrile nanocomposite is about one order of magnitude higher than that using Bentonite-Li⁺ under the same conditions. The effect of the concentration of the filler on the conductivity of the products is discussed.