Mitochondrial and sex steroid hormone crosstalk during aging

Decline in circulating sex steroid hormones accompanies several age-associated pathologies which may influence human healthspan. Mitochondria play important roles in biosynthesis of sex steroid hormones, and these hormones can also regulate mitochondrial function. Understanding the cross talk between mitochondria and sex steroid hormones may provide insights into the pathologies associated with aging. The aim of this review is to summarize the current knowledge regarding the interplay between mitochondria and sex steroid hormones during the aging process. The review describes the effect of mitochondria on sex steroid hormone production in the gonads, and then enumerates the contribution of sex steroid hormones on mitochondrial function in hormone responsive cells. Decline in sex steroid hormones and accumulation of mitochondrial damage may create a positive feedback loop that contributes to the progressive degeneration in tissue function during aging. The review further speculates whether regulation between mitochondrial function and sex steroid hormone action can potentially influence healthspan

Duality Symmetry in Kaluza-Klein n+D+dn+D+d Dimensional Cosmological Model

It is shown that, with the only exception of $n=2$, the Einstein-Hilbert action in $n+D+d$ dimensions, with $n$ times, is invariant under the duality transformation $a\to \frac{1}{a}$ and $b\to \frac{1}{b}$, where $a$ is a Friedmann-Robertson-Walker scale factor in $D$ dimensions and $b$ a Brans-Dicke scalar field in $d$ dimensions respectively. We investigate the $2+D+d$ dimensional cosmological model in some detail.Comment: 23 pages, Late

Stochastic pump of interacting particles

We consider the overdamped motion of Brownian particles, interacting via particle exclusion, in an external potential that varies with time and space. We show that periodic potentials that maintain specific position-dependent phase relations generate time-averaged directed current of particles. We obtain analytic results for a lattice version of the model using a recently developed perturbative approach. Many interesting features like particle-hole symmetry, current reversal with changing density, and system-size dependence of current are obtained. We propose possible experiments to test our predictions.Comment: 4 pages, 2 figure

Diverse roles of actin in C. elegans early embryogenesis

<p>Abstract</p> <p>Background</p> <p>The actin cytoskeleton plays critical roles in early development in <it>Caenorhabditis elegans</it>. To further understand the complex roles of actin in early embryogenesis we use RNAi and <it>in vivo </it>imaging of filamentous actin (F-actin) dynamics.</p> <p>Results</p> <p>Using RNAi, we found processes that are differentially sensitive to levels of actin during early embryogenesis. Mild actin depletion shows defects in cortical ruffling, pseudocleavage, and establishment of polarity, while more severe depletion shows defects in polar body extrusion, cytokinesis, chromosome segregation, and eventually, egg production. These defects indicate that actin is required for proper oocyte development, fertilization, and a wide range of important events during early embryogenesis, including proper chromosome segregation. <it>In vivo </it>visualization of the cortical actin cytoskeleton shows dynamics that parallel but are distinct from the previously described myosin dynamics. Two distinct types of actin organization are observed at the cortex. During asymmetric polarization to the anterior, or the establishment phase (Phase I), actin forms a meshwork of microfilaments and focal accumulations throughout the cortex, while during the anterior maintenance phase (Phase II) it undergoes a morphological transition to asymmetrically localized puncta. The proper asymmetric redistribution is dependent on the PAR proteins, while both asymmetric redistribution and morphological transitions are dependent upon PFN-1 and NMY-2. Just before cytokinesis, actin disappears from most of the cortex and is only found around the presumptive cytokinetic furrow. Finally, we describe dynamic actin-enriched comets in the early embryo.</p> <p>Conclusion</p> <p>During early <it>C. elegans </it>embryogenesis actin plays more roles and its organization is more dynamic than previously described. Morphological transitions of F-actin, from meshwork to puncta, as well as asymmetric redistribution, are regulated by the PAR proteins. Results from this study indicate new insights into the cellular and developmental roles of the actin cytoskeleton.</p

Connexin-Based Channels and RhoA/ROCK Pathway in Angiotensin II-Induced Kidney Damage

The incidence of chronic kidney diseases is increasing worldwide, and there is no efficient therapy to reduce this phenomenon. The main therapies currently available focus on the control of blood pressure and the optimization of the blockade of the renin-angiotensin system (RAS). In addition, it is known that in several models of kidney damage, the amounts of connexins are altered. On the other hand, fasudil, a selective ROCK blocker, has shown renoprotective effects. The beneficial effects of blocking the RhoA/ROCK pathway in renal function may be related to its action of reducing macrophage infiltration, inflammation, and oxidative stress (OS), its expression of extracellular matrix genes and proteinuria, or to its effects on connexin abundance. Even though a correlation has been found between renal damage, caused by an increase in the RAS activity, connexins, and the RhoA/ROCK signaling pathway, it has not yet been possible to clearly determine its functional significance. Moreover, it has not been possible to identify the preponderance of this signaling pathway in the development of chronic kidney diseases. Here, we describe the advances in this subject