1,942 research outputs found
Caracterización cromosómica de Hoplias malabaricus (Pisces, Erythrinidae) del Río Paraná, Argentina
Hoplias malabaricus presenta una amplia distribución geográfica, encontrándose en varias cuencas hidrográficas de algunos países de la región neotropical de América del Sur, donde asume valor económico. Dada su diversidad cariotípica, el objetivo del presente trabajo fue establecer la estructura cromosómica de esta especie en ejemplares provenientes del Río Riachuelo, afluente del Río Paraná en la localidad de Corrientes, Argentina. La población estudiada presentó un número diploide (2n) de 40 cromosomas del tipo meta–submetacéntricos, denominado “citotipo C” en estudios previos. No se evidenció ningún sistema de cromosomas sexuales. A través del bandeo C se localizó la heterocromatina constitutiva en posiciones pericentroméricas y teloméricas. Por medio de la coloración con nitrato de plata, en la región telomérica de seis cromosomas del complemento, se observaron marcaciones Ag–NOR (regiones organizadoras de nucléolos) positivas. Los resultados obtenidos proporcionan información adicional a los conocimientos preexistentes, corroborando la hipótesis que H. malabaricus formaría parte de un complejo de especies.
Rendimento de milho (Zea mays) em sucessão a diferentes adubos verdes em sistemas orgânicos de produção de grãos.
Corneal Posterior Curvature Changes After Phacoemulsification Cataract Surgery with 2.75 mm Corneal Incision
The aim of this study was to evaluate the corneal posterior curvature changes after phacoemulsification cataract surgery, with intraocular lens implantation, with a temporal limbal self-sealing 2.75 millimeters (mm) corneal incision, using a Placido-dual rotating Scheimpflug device. In this prospective intervention study, corneal posterior curvature changes were evaluated in fifty-six patients (56 eyes). All patients underwent corneal tomography using the Galilei G2 (Ziemer Ophthalmic System AG, Port, Switzerland) preoperatively (PRE) and with two weeks (RP15), one month (RP30), and three months (RP90) after phacoemulsification cataract surgery with a temporal limbal self-sealing 2.75 mm incision. Tomographic parameters analyzed in the posterior cornea were the steep curvature (K2), flat curvature (K1), mean curvature (average K), and posterior corneal astigmatism. We did not observe any statistically significant change in the K2, K1, average K, and posterior corneal astigmatism in any postoperative follow-up measurements (RP15, RP30, RP90), showing that the postoperative values tend to be the same as the preoperative ones when measured with the Galilei G2 tomography. In conclusion, the 2.75 mm temporal limbal self-sealing corneal incision in phacoemulsification cataract surgery does not induce significant changes in the posterior corneal curvature parameters of K2, K1, average K, and astigmatism
Chromosome analysis in Saccodon wagneri (Characiformes) and insights into the karyotype evolution of Parodontidae
Parodontidae is a relatively small group of Neotropical characiform fishes
consisting of three genera (Apareiodon, Parodon, and Saccodon) with 32 valid
species. A vast cytogenetic literature is available on Apareiodon and Parodon, but
to date, there is no cytogenetic data about Saccodon, a genus that contains only
three species with a trans-Andean distribution. In the present study the karyotype
of S. wagneri was described, based on both conventional (Giemsa staining, Ag-
NOR, C-bands) and molecular (repetitive DNA mapping by fluorescent in situ
hybridization) methods. A diploid chromosome number of 2n = 54 was observed
in both sexes, and the presence of heteromorphic sex chromosomes of the ZZ/
ZW type was detected. The W chromosome has a terminal heterochromatin band
that occupies approximately half of the long arm, being this band approximately
half the size of the Z chromosome. The FISH assay showed a synteny of the
18S-rDNA and 5S-rDNA genes in the chromosome pair 14, and the absence
of interstitial telomeric sites. Our data reinforce the hypothesis of a conservative
karyotype structure in Parodontidae and suggest an ancient origin of the sex
chromosomes in the fishes of this family
Rainfall Erosivity: Gap-Filling Method Differences in the Brazilian Pantanal and Cerrado Biomes
To improve the use of soil and its conservation, precipitation data are necessary. With the Universal Soil Loss Equation (USLE), the study of historical precipitation series is a main factor, but in these series, there are gaps that need to be filled. This study had, as a basis, the methods of weighted likelihood, multiple regression, and weighted likelihood based on multiple regression to fill the gaps of the rainfall data for the rainfall gauges in the Brazilian biomes (Cerrado and Pantanal, municipalities of Campo Grande, Bandeirantes, Sidrolândia, Miranda, Fazenda Ponte, and Ribas do Rio Pardo). With this, it became possible to calculate the rainfall erosivity (R factor in the USLE). Therefore, the consistency of the filled rainfall data was analyzed by the double mass method. The value of the rainfall erosivity calculated varies from 2304.80 to 13562.10 MJ mm ha−1 h−1 year. With this data, it was possible to identify particular results that differed from the rainfall erosivity. Comparing all the gap-filling methods, numbers varying from 0–12% at the same rainfall gauge were obtained
Specific heat and magnetic measurements in Nd0.5Sr0.5MnO3, Nd0.5Ca0.5MnO3 and Ho0.5Ca0.5MnO3 samples
We studied the magnetization as a function of temperature and magnetic field
in the compounds Nd0.5Sr0.5MnO3, Nd0.5Ca0.5MnO3 and Ho0.5Ca0.5MnO3. It allowed
us to identify the ferromagnetic, antiferromagnetic and charge ordering phases
in each case. The intrinsic magnetic moments of Nd3+ and Ho3+ ions experienced
a short range order at low temperatures. We also did specific heat measurements
with applied magnetic fields between 0 and 9 T and temperatures between 2 and
300 K in all three samples. Close to the charge ordering and ferromagnetic
transition temperatures the specific heat curves showed peaks superposed to the
characteristic response of the lattice oscillations. Below 10 K the specific
heat measurements evidenced a Schottky-like anomaly for all samples. However,
we could not successfully fit the curves to either a two level nor a
distribution of two-level Schottky anomaly. Our results indicated that the peak
temperature of the Schottky anomaly was higher in the compounds with narrower
conduction band.Comment: submitted to PR
Unusual magnetic relaxation behavior in La0.5Ca0.5MnO3 and Nd0.5Sr0.5MnO3
We have carried out a systematic magnetic relaxation study, measured after
applying and switching off a 5 T magnetic field to polycrystalline samples of
La0.5Ca0.5MnO3 and Nd0.5Sr0.5MnO3. The long time logarithmic relaxation rate
(LTLRR), decreased from 10 K to 150 K and increased from 150 K to 195 K in
La0.5Ca0.5MnO3. This change in behavior was found to be related to the complete
suppression of the antiferromagnetic phase above 150 K and in the presence of a
5 T magnetic field. At 195 K, the magnetization first decreased, and after a
few minutes increased slowly as a function of time. Moreover, between 200 K and
245 K, the magnetization increased throughout the measured time span. The
change in the slope of the curves, from negative to positive at about 200 K was
found to be related to the suppression of antiferromagnetic fluctuations in
small magnetic fields. A similar temperature dependence of the LTLRR was found
for the Nd0.5Sr0.5MnO3 sample. However, the temperature where the LTLRR reached
the minimum in Nd0.5Sr0.5MnO3 was lower than that of La0.5Ca0.5MnO3. This
result agrees with the stronger ferromagnetic interactions that exist in
Nd0.5Sr0.5MnO3 in comparison to La0.5Ca0.5MnO3. The above measurements
suggested that the general temperature dependence of the LTLRR and the
underlying physics were mainly independent of the particular charge ordering
system considered. All relaxation curves could be fitted using a logarithmic
law at long times. This slow relaxation was attributed to the coexistence of
ferromagnetic and antiferromagnetic interactions between Mn ions, which
produced a distribution of energy barriers.Comment: Accepted to PRB as a regular article, 10 figures, Scheduled Issue: 01
June 200
Sympatric occurrence of two cytotypes of Astyanax scabripinnis (Characiformes, Characidae)
Cytotaxonomy of Parodon nasus and Parodon tortuosus (Pisces, Characiformes): A case of synonymy confirmed by cytogenetic analyses
Evaluation of the proteomic profiles of ejaculated spermatozoa from Saanen bucks (Capra hircus).
Abstract: The Saanen goat breed has been widely explored in breeding programmes; however, there are few reports about the breed?s genetic and molecular composition. Thus, this study aimed to characterize the proteomic profile of spermatozoa from Saanen breeding goats. Five breeding animals with proven fertility were selected, the spermatozoa were collected, and the protein was extracted. Subsequently, the proteins were separated and analysed by two-dimensional electrophoresis and mass spectrometry; the proteins were then identified with the SwissProt database. A total of 31 proteins involved in reproduction were identified, including binding proteins on spermatozoa for fusion with the egg, acrosomal membrane proteins, metabolic enzymes, heat shock proteins, cytoskeletal proteins and spermatozoa motility proteins. The characterization of such proteins clarifies the molecular mechanisms of spermatogenesis and the modifications that ensure the success of fertilization
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