Frustrated Bearings.

In a bearing state, touching spheres (disks in two dimensions) roll on each other without slip. Here we frustrate a system of touching spheres by imposing two different bearing states on opposite sides and search for the configurations of lowest energy dissipation. If the dissipation between contacts of spheres is viscous (with random damping constants), the angular momentum continuously changes from one bearing state to the other. For Coulomb friction (with random friction coefficients) in two dimensions, a sharp line separates the two bearing states and we show that this line corresponds to the minimum cut. Astonishingly, however, in three dimensions intermediate bearing domains that are not synchronized with either side are energetically more favorable than the minimum-cut surface. Instead of a sharp cut, the steady state displays a fragmented structure. This novel type of state of minimum dissipation is characterized by a spanning network of slipless contacts that reaches every sphere. Such a situation becomes possible because in three dimensions bearing states have four degrees of freedom.

Do prune-belly syndrome and neural tube defects change testicular growth? A study on human fetuses.

BACKGROUND: There are no reports comparing testicular volume between normal fetuses, fetuses with prune-belly syndrome (PBS), and fetuses with anencephaly. The study hypothesis was that PBS and especially anencephaly alter the testicular volume during the human fetal period. AIM: The objective of the study was to compare the testicular growth in fetuses with anencephaly, with PBS, and without anomalies. STUDY DESIGN: This is a morphometric study of human fetuses. Seventy testes from fetuses without anomalies aged 11-22 weeks post-conception (WPC), 30 testes from fetuses with anencephaly aged 13-19 WPC, and eight testes from fetuses with PBS aged 13-16 WPC were studied. Testicular length, width, and thickness were evaluated with the aid of computer programs (Image Pro and ImageJ) (Figure). The fetal testicular volume was calculated using the ellipsoid formula: Testicular volume (TV) = [length × thickness × width] × 0.523. The Shapiro-Wilk test was used to ascertain the normality of the data and to compare quantitative data between normal fetuses vs. fetuses with anencephaly, while the Kruskal-Wallis test was used to assess gender and laterality differences. Simple linear correlations (LCs) were calculated for testicular volume according to fetal age, weight, and crown-rump length. RESULTS: All 108 testes studied were abdominal. The right (p = 0.0310) and left (0.0470) testicular volumes were significantly smaller in fetuses with anencephaly than those in the control group. The linear regression analysis indicated that the right and the left testis volume in the control group (right: r2 = 0.6665; left: r2 = 0.6707) and PBS group (right: r2 = 0.9937; left: r2 = 0.9757) increased with fetal age (p < 0.0001). This analysis also indicated that the testicular volume in fetuses with anencephaly did not increase with fetal age (right: r2 = 009816; left: r2 = 0.07643). DISCUSSION: This article is the first to report testicular volume correlations with fetal parameters in fetuses with anencephalic and fetuses with PBS. Significant alterations were observed in testicular growth in the anencephalic group compared with the control group, and it was also observed that the bilateral cryptorchidism in PBS does not alter the testicular development and growth during the fetal period. The unequal WPC distribution between fetuses with PBS, fetuses with anencephaly, and controls and the small sample size are limitations of this study. Further studies should be performed to confirm this study's findings. CONCLUSIONS: Testicular growth is slower and does not show significant correlations with fetal parameters in fetuses with anencephalic. Significant differences in testicular development in fetuses with PBS was not observed.

The effects of acrobatic exercise on brain plasticity: a systematic review of animal studies.

Acrobatic exercise is considered a complex motor activity and may promote motor learning and neuroplasticity. The objective of this systematic review was to verify possible plastic brain changes induced by acrobatic exercise in non-lesioned rat and mouse through the analysis of experimental studies. Manual and electronic searches were conducted in MEDLINE, EMBASE and ISI Web of Science databases, without restriction to language or publication date. Synaptogenesis and neurogenesis were selected as the primary outcomes. To evaluate the risk of bias of individual studies, we used the Systematic Review Centre for Laboratory Animal Experimentation (SYRCLE) RoB tool. We found 1780 studies, from which 18 fulfilled the inclusion criteria in this review. Seventeen studies evaluated the cerebellum, six the motor cortex, five the striatum and two evaluated the hippocampus. The results showed that acrobatic exercise promotes plastic changes in brain areas of rats, and such changes are dependent of training frequency and duration. However, studies were heterogeneous regarding the proteins analyzed and the training protocols, which made it difficult to compare and determine ideal acrobatic exercise parameters for neuroplasticity. Concerning the methodological quality of studies, most of them presented high risk of bias with absence of relevant study design information. New research with detailing training protocols and analysis might contribute to clarify the role of acrobatic exercise in neuroplasticity and how it could be used in translational research.

Confined sandpile in two dimensions: Percolation and singular diffusion.

We investigate the properties of a two-state sandpile model subjected to a confining potential in two dimensions. From the microdynamical description, we derive a diffusion equation, and find a stationary solution for the case of a parabolic confining potential. By studying the systems at different confining conditions, we observe two scale-invariant regimes. At a given confining potential strength, the cluster size distribution takes the form of a power law. This regime corresponds to the situation in which the density at the center of the system approaches the critical percolation threshold. The analysis of the fractal dimension of the largest cluster frontier provides evidence that this regime is reminiscent of gradient percolation. By increasing further the confining potential, most of the particles coalesce in a giant cluster, and we observe a regime where the jump size distribution takes the form of a power law. The onset of this second regime is signaled by a maximum in the fluctuation of energy.

BDNF receptor blockade hinders the beneficial effects of exercise in a rat model of Parkinson's disease.

Physical exercise is known to produce beneficial effects to the nervous system. In most cases, brain-derived neurotrophic factor (BDNF) is involved in such effects. However, little is known on the role of BDNF in exercise-related effects on Parkinson's disease (PD). The aim of this study was to investigate the effects of intermittent treadmill exercise-induced behavioral and histological/neurochemical changes in a rat model of unilateral PD induced by striatal injection of 6-hydroxydopamine (6-OHDA), and the role of BDNF in the exercise effects. Adult male Wistar rats were divided into two main groups: (1) injection of K252a (a blocker of BDNF receptors), and (2) without BDNF receptor blockade. These groups were then subdivided into four groups: control (CLT), sedentary (SED, non-exercised with induction of PD), exercised 3×/week during four weeks before and four weeks after the induction of PD (EXB+EXA), and exercised 3×/week during four weeks after the induction of PD (EXA). One month after 6-OHDA injections, the animals were subjected to rotational behavioral test induced by apomorphine and the brains were collected for immunohistochemistry and immunoblotting assays, in which we measured BDNF and tyrosine hydroxylase (TH) in the substantia nigra pars compacta (SNc) and the striatum (caudate-putamen, CPu). Our results showed a significant reduction of rotational asymmetry induced by apomorphine in the exercised parkinsonian rats. BDNF decreased in the SNc of the SED group, and exercise was able to revert that effect. Exercised groups exhibited reduced damage to the dopaminergic system, detected as a decreased drop of TH levels in SNc and CPu. On the other hand, BDNF blockade was capable of substantially reducing TH expression postlesion, implying enhanced dopaminergic cell loss. Our data revealed that physical exercise is capable of reducing the damage induced by 6-OHDA, and that BDNF receptors are involved in that effect.

Differential expression of AMPA-type glutamate receptor subunits during development of the chick optic tectum.

Glutamate receptors have been often associated with developmental processes. We used immunohistochemical techniques to evaluate the expression of the AMPA-type glutamate receptor (GluR) subunits in the chick optic tectum (TeO). Chick embryos from the 5th through the 20th embryonic day (E5-E20) and one-day-old (P1) chicks were used. The three types of immunoreactivity evaluated (GluR1, GluR2/3, and GluR4) had different temporal and spatial expression patterns in the several layers of the TeO. The GluR1 subunit first appeared as moderate staining on E7 and then increased on E9. The mature GluR1 pattern included intense staining only in layer 5 of the TeO. The GluR2/3 subunits presented low expression on E5, which became intense on E7. The staining for GluR2/3 changed to very intense on E14 in tectal layer 13. Staining of layer 13 neurons is the most prominent feature of GluR immunoreactivity in the adult TeO. The GluR4 subunit generally presented the lowest expression starting on E7, which was similar to the adult pattern. Some instances of transient expression of GluR subunits were observed in specific cell populations from E9 through E20. These results demonstrate a differential expression of the GluR subunits in the embryonic TeO, adding information about their possible functions in the developmental processes of the visual system.

Differential expression of AMPA-type glutamate receptor subunits during development of the chick optic tectum

Glutamate receptors have been often associated with developmental processes. We used immunohistochemical techniques to evaluate the expression of the AMPA-type glutamate receptor (GluR) subunits in the chick optic tectum (TeO). Chick embryos from the 5th through the 20th embryonic day (E5-E20) and one-day-old (P1) chicks were used. The three types of immunoreactivity evaluated (GluR1, GluR2/3, and GluR4) had different temporal and spatial expression patterns in the several layers of the TeO. The GluR1 subunit first appeared as moderate staining on E7 and then increased on E9. The mature GluR1 pattern included intense staining only in layer 5 of the TeO. The GluR2/3 subunits presented low expression on E5, which became intense on E7. The staining for GluR2/3 changed to very intense on E14 in tectal layer 13. Staining of layer 13 neurons is the most prominent feature of GluR immunoreactivity in the adult TeO. The GluR4 subunit generally presented the lowest expression starting on E7, which was similar to the adult pattern. Some instances of transient expression of GluR subunits were observed in specific cell populations from E9 through E20. These results demonstrate a differential expression of the GluR subunits in the embryonic TeO, adding information about their possible functions in the developmental processes of the visual system

Expression of endo-oligopeptidase A in the rat central nervous system: a non-radioactive in situ hybridization study.

Endo-oligopeptidase A (EOPA, formerly EC 3.4.22.19), a thiol-activated oligopeptidase, is able to degrade both bradykinin and neurotensin, and also to convert enkephalin-containing peptides into enkephalins. The expression of this enzyme was studied in the rat brain by in situ hybridization using non-radiotopic probes. The distribution of EOPA transcripts included many regions of the rat central nervous system, with higher expression in some regions, such as the hippocampus, cerebellum, and basal nucleus of Meynert. The marked EOPA expression in these areas could be anticipated, since they are rich in neuropeptides that are known to be EOPA substrates in vitro. The data characterize a widespread occurrence of EOPA in the rat brain and reinforce the suggestion of a critical role for EOPA in peptide processing.

Retinal lesions induce differential changes in the expression of flip and flop isoforms of the glutamate receptor subunit GluR1 in the chick optic tectum.

A sensitive RNase protection assay was employed to determine the levels of mRNA encoding the GluR1 subunit flip and flop isoforms in the chick optic tectum and forebrain. We found that the flip GluR1 mRNA predominates in the forebrain, whereas the flop variant is more strongly expressed in the optic tectum. A temporal analysis of GluR1 variants in the embryonic and adult chick brain revealed that the flip isoform is more highly expressed at E12 than at P15-21, whereas mRNA levels of the flop isoform are higher at P15-21 than at E12. To study the effect of deafferentation on GluR1 expression, unilateral retinal lesions were performed. Two days later the mRNA levels of GluR1 flip and flop variants were decreased in the deafferented tectum, especially for the flop isoform. However, 7 days after the lesion, the mRNA levels of both GluR1 isoforms were increased, especially for the flip isoform. These results reveal an important control of the retinal input upon the expression of the different GluR1 isoforms. Furthermore, they indicate a differential spatial and temporal regulation of the flip and flop splice variants, suggesting the existence of a mechanism regulating differential splicing or possibly differential RNA stability.

Expression of the AMPA-type glutamate receptor subunits in the chick optic tectum changes biphasically after retinal deafferentation.

Effects of retinal lesions on the expression of AMPA-type glutamate receptor (GluR) subunits in the chick optic tectum were evaluated with immunohistochemistry and immunoblotting. Expression of GluR1 and GluR2/3 subunits decreased in the deafferented tectum after 2 days and increased after 7 days postlesion. These results suggest biphasic effects of retinal lesions upon the expression of GluR subunits, possibly due to removal of the glutamatergic input from the retina.

Avaliaçäo morfométrica de fibras nervosas do nervo ulnar após reparaçäo cirúrgica com auto-enxerto e prótese tubular em cäes / Morphometric evaluation of nerve fibers after surgical repair by allograft and tubular prothesis of the ulnar nerve in dogs

O objetivo da investigaçäo foi o de comparar os resultados observados por meio de avaliaçäo morfométrica de fibras nervosas regeneradas, em cäes, após 26 semanas da reparaçäo cirúrgica de falhas do nervo ulnar, através de auto-enxertos e próteses tubulares de silicone. Para cada procedimento foram utilizados quatro animais. Dos nervos regenerados e dos enxertos foram retirados segmentos para avaliaçäo em nível de microscopia eletrônica. De cada corte foram amostrados seis campos distintos com 1,750µm elevado ao quadrado cada, que foram fotografados com aumentos de 1.880 vezes. Através de sistema computadorizado de morfometria (SigmaScan - Jandel Co., USA), obtiveram-se os seguintes parâmetros: diâmetros das fibras mielínicas; diâmetros dos axônios mielínicos; espessuras das bainhas de mielina e diâmetro dos axônios amielínicos. Os nervos regenerados no interior das próteses tubulares apresentaram diâmetros das fibras mielínicas com média de 5,12ñ1,67µm; média dos diâmetros dos axônios mielínicos de 4,08ñ1,52µm; média das espessuras das bainhas de mielina de 0,52ñ0,18µm; média dos diâmetros dos axônios amielínicos de 0,98ñ0,37µm. Os enxertos apresentaram os seguintes valores: média dos diâmetros das fibras mielínicas de 6,04ñ2,27µm; média dos diâmetros dos axônios mielínicos de 4,59ñ1,95µm; média das espessuras das bainhas de mielina de 0,72ñ0,23µm; média dos diâmetros dos axônios amielínios de 0,96ñ0,40µm. Estes resultados permitiram concluir que os procedimentos cirúrgicos utilizados, quando analisadas as fibras regeneradas no interior das próteses tubulares e dos auto-enxertos, näo apresentaram diferenças morfométricas significantes, decorridas 26 semanas de observaçäo pós-operatória

Distribution of AMPA-type glutamate receptor subunits in the chick visual system.

Several glutamate receptor (GluR) subunits have been characterized during the past few years. In the present study, subunit-specific antisera were used to determine the distribution of the AMPA-type glutamate receptor subunits GluR1-4 in retinorecipient areas of the chick brain. Six white leghorn chicks (Gallus gallus, 7-15 days old, unknown sex) were deeply anesthesized and perfused with 4% buffered paraformaldehyde and brain sections were stained using immunoperoxidase techniques. The AMPA-type glutamate receptor subunits GLuR1, GluR2/3 and GluR4 were present in several retinorecipient areas, with varying degrees of colocalization. For example perikarya in layers 2, 3, and 5 of the optic tectum contained GluR1, whereas GluR2/3 subunits appeared mainly in neurons of layer 13. The GluR4 subunit was only detected in a few cells of the tectal layer 13. GluR1 and GluR2/3 were observed in neurons of the nucleus geniculatus lateralis, whereas GluR4 was only present in its neuropil. Somata in the accessory optic nucleus appeared to contain GluR2/3 and GluR4, whereas GluR1 was the dominant subunit in the neuropil of this nucleus. These results suggest that different subpopulations of visual neurons might express different combinations of AMPA-type GluR subunits, which in turn might generate different synaptic responses to glutamate derived from retinal ganglion cell axons.

Distribution of AMPA-type glutamate receptor subunits in the chick visual system

Several glutamate receptor (GluR) subunits have been characterized during the past few years. In the present study, subunit-specific antisera were used to determine the distribution of the AMPA-type glutamate receptor subunits GluRl-4 in retinorecipient areas of the chick brain. Six white leghorn chicks (Gallus gallus, 7-15 days old, unknown sex) were deeply anesthetized and perfused with 4 per cent buffered paraformaldehyde and brain sections were stained using immunoperoxidase techniques. The AMPA-type glutamate receptor subunits GluRl, GluR2/3 and GluR4 were present in several retinorecipient areas, with varying degrees of colocalization. For example, perikarya in layers 2, 3, and 5 of the optic tectum contained GluRl, whereas GluR2/3 subunits appeared mainly in neurons of layer 13. The GluR4 subunit was only detected in a few cells of the tectal layer 13. GluRl and GluR2/3 were observed in neurons of the nucleus geniculatus lateralis ventralis, whereas GluR4 was only present in its neuropil. Somata in the accessory optic nucleus appeared to contain GluR2/3 and GluR4, whereas GluR1 was the dominant subunit in the neuropil of this nucleus. These results suggest that different subpopulations of visual neurons might express different combinations of AMPA-type GluR subunits, which in turn might generate different synaptic responses to glutamate derived from retinal gangliom cell axons.

Differential co-localization of nicotinic acetylcholine receptor subunits with calcium-binding proteins in retinal ganglion cells.

Immunohistochemistry was used to examine the co-occurrence of nicotinic acetylcholine receptor subunits with calcium-binding proteins in ganglion cells of the chick retina. The alpha3 subunit was rarely observed in ganglion cells containing calbindin, calretinin, or parvalbumin. On the other hand, the alpha8 subunit was more often co-localized with all calcium-binding proteins studied. These results may be related to the high calcium permeability of nicotinic receptors that contain the alpha8 subunit.