Random-hopping approach to fluctuation phenomena in quantum dots with chiral symmetry.

We propose a numerical approach to study mesoscopic fluctuations in quantum dots with chiral symmetry. Our method involves applying the random-hopping model to a tight-binding Hamiltonian, allowing us to calculate the conductance and shot-noise power distributions for systems belonging to the three chiral symmetry classes of random matrix theory. Furthermore, we demonstrate that the spectral fluctuations of quantum dots belonging to the Wigner-Dyson symmetry classes of random matrix theory can be obtained by applying the random-hopping model to a scattering region that was originally integrable, thus bypassing the need to use the boundaries of chaotic billiards.

Multifractal magnetoconductance fluctuations in mesoscopic systems.

We perform a multifractal detrended fluctuation analysis of the magnetoconductance data of two standard types of mesoscopic systems: a disordered nanowire and a ballistic chaotic billiard, with two different lattice structures. We observe in all cases that multifractality is generally present and that it becomes stronger in the quantum regime of conduction, i.e., when the number of open scattering channels is small. We argue that this behavior originates from correlations induced by the magnetic field, which can be characterized through the distribution of conductance increments in the corresponding "stochastic time series," with the magnetic field playing the role of a fictitious time. More specifically, we show that the distributions of conductance increments are well fitted by q Gaussians and that the value of the parameter q is a useful quantitative measure of multifractality in magnetoconductance fluctuations.

Bos taurus papillomavirus activity in peripheral blood mononuclear cells: demonstrating a productive infection.

Bovine papillomavirus (BPV) is an oncogenic virus with mucous and epithelial tropism. Possible productive virus infection in other tissues, such as blood, has been hypothesized. In order to investigate this possibility, three samples of skin papillomas and blood were collected from bovines with BPV infection and five samples of peripheral blood and one sample of normal tissue were collected from a calf without BPV infection. Peripheral blood mononuclear cells (PBMCs) were isolated from whole blood and examined by reverse transcription-polymerase chain reaction, immunofluorescence, in situ hybridization, and electron microscopy. The tissue samples were examined for histopathological and immunohistochemical features. The skin papillomas showed the presence of DNA sequences of BPV-2, BPV-11, and a putative virus type. The blood samples showed DNA sequences of BPV-1, 2, and 4 simultaneously. Immunohistochemistry showed BPV L1 protein in both epithelium and stroma and BPV E2 protein in koilocytes. In situ hybridization confirmed the presence of BPV DNA in PBMCs and immunofluorescence showed nuclear labeling of E2 and L1 BPV proteins in PBMCs. The transcription analysis revealed transcripts of BPV-1 L1, BPV-2 L2, and BPV-4 E7 in blood and papilloma samples of BPV-infected cattle. The comet assay revealed high levels of host cell DNA damage upon BPV infection. Electron microscopy analysis of PBMCs identified the presence of particles in the cytoplasm that are consistent with papillomavirus in size and shape. The productive infection of PBMCs with BPV has been previously discussed and this study provides evidence indicating that PBMCs are a target of BPV.

Out-of-season sperm cryopreserved in different media of the Amazonian freshwater fish pirapitinga (Piaractus brachypomus).

The pirapitinga (Piaractus brachypomus) is a freshwater fish that inhabits the Amazon and Orinoco River basins. The use of cryopreserved sperm has been considered to facilitate procedures during the artificial reproduction. The aim of the present study was to develop a freezing protocol for pirapitinga sperm collected outside the spawning season. Sperm samples were diluted in four freezing media prepared by a combination of two extenders (glucose and BTS-Beltsville Thawing Solution) and two cryoprotectant agents (DMSO and methylglycol) loaded into 0.5-mL straws, frozen in a nitrogen-vapor shipping dewar (dry-shipper) and stored in liquid nitrogen at -196 degrees C. Post-thaw sperm motility was evaluated both subjectively using a light microscope and by a computer-assisted sperm analyzer (CASA). Curvilinear, average path and straight-line velocities were also determined. There were no differences (P>0.05) in post-thaw sperm motility between evaluations performed subjectively and using the CASA. Sperm samples cryopreserved in glucose-methylglycol yielded the greatest post-thaw sperm motility (81%) and fastest sperm velocities when compared to the samples frozen in the other three media (P<0.05). Out-of-season sperm cryopreserved in glucose and methylglycol under the conditions described above is of high quality and can therefore be used to facilitate artificial reproduction procedures, as only females will need handling for hormonal induction and gamete collection during the spawning season. Although the CASA system provides precise data on sperm motility, the subjective evaluation is practical and can be conducted by well-trained personnel at commercial fish farms as an acceptable evaluation of sperm quality.

Appearance of 'natural' antisperm autoantibodies after sexual maturation of normal Lewis rats.

Serum antisperm antibodies were assessed quantitatively with an ELISA in normal male Lewis rats at intervals between ages 10 and 128 days, spanning the onset of puberty. Antisperm antibodies rose between 56 and 91 days, and were significantly higher in 91- and 128-day old rats than at earlier intervals. The animals underwent normal pubertal development as indicated by increases in weights of the seminal vesicles and ventral prostate. The rise in antisperm antibodies correlated temporally with events in the postnatal development of the male reproductive system, with the increase in antisperm antibodies most closely following the time when spermatozoa reach the epididymis and proximal vas deferens at approximately 56 days. The observation that serum antisperm antibodies increased only after sexual maturation suggests that some differentiation antigens of sperm are processed and presented to the immune system under normal circumstances in this strain. Western blot analysis showed that the sera from normal postpubertal Lewis rats bound several proteins, including bands of > 100, 82-75, 78, 68, 65, 63, 54-55, 42, 37, 35, 26, and 20-22 kDa. The majority of these autoantibodies were sperm-specific as shown by the absence of comigrating bands in western blots of somatic tissue extracts, although antibodies in postpubertal sera recognized certain other proteins in somatic tissues. Several protein autoantigens, defined by sera from postpubertal animals, matched dominant autoantigens recognized by antibodies produced in response to vasectomy, prepubertal vas obstruction, or immunization with spermatozoa. This finding indicates that the antisperm antibody responses following sperm immunization, vasectomy or prepubertal vasal obstruction represent accentuation of an autoantibody response to sperm that develops normally following puberty.