The stable actin core of mechanosensory stereocilia features continuous turnover of actin cross-linkers

Stereocilia are mechanosensitive protrusions on the surfaces of sensory hair cells in the inner ear that detect sound, gravity, and head movement. Their cores are composed of parallel actin filaments that are cross-linked and stabilized by several actin-binding proteins, including fascin-2, plastin-1, espin, and XIRP2. The actin filaments are the most stable known, with actin turnover primarily occurring at the stereocilia tips. While stereocilia actin dynamics has been well studied, little is known about the behavior of the actin cross-linking proteins, which are the most abundant type of protein in stereocilia after actin and are critical for stereocilia morphogenesis and maintenance. Here, we developed a novel transgenic mouse to monitor EGFP-fascin-2 incorporation . In contrast to actin, EGFP-fascin-2 readily enters the stereocilia core. We also compared the effect of EGFP-fascin-2 expression on developing and mature stereocilia. When it was induced during hair cell development, we observed increases in both stereocilia length and width. Interestingly, stereocilia size was not affected when EGFP-fascin-2 was induced in adult stereocilia. Regardless of the time of induction, EGFP-fascin-2 displaced both espin and plastin-1 from stereocilia. Altering the actin cross-linker composition, even as the actin filaments exhibit little to no turnover, provides a mechanism for ongoing remodeling and repair important for stereocilia homeostasis

QSPR Modeling of Odor Threshold of Aliphatic Alcohols Using Extended Topochemical Atom (ETA) Indices

The present work establishes a quantitative structure-property relationship (QSPR) between top¬ochemical features and odor threshold (OT) of aliphatic alcohols. A data set of 53 aliphatic alcohols was chosen for the analysis employing different chemometric techniques, among which, genetic function ap¬proximation with spline option (GFA-spline) showed the most acceptable results in terms of internal and external validation metric values. The extended topochemical atom (ETA) indices, developed by the pre¬sent authors’ group, were considered as descriptors for model development. Additionally, selected non-ETA descriptors were also tried for model development. It was observed that the models with ETA indi¬ces significantly surpass the predictive ability of the models developed using other descriptors. The final model suggests that molecular branching and electronic parameters significantly influence the odor poten-cy of the molecules. Additionally, increased lipophilicity and reduced electronegativity increase the odor-ant property. The model thus developed may effectively be used for prediction of odor threshold of any untested aliphatic alcohols. (doi: 10.5562/cca2284

Stereocilia Morphogenesis and Maintenance is Dependent on the Dynamics of Actin Cytoskeletal Proteins

Indiana University-Purdue University Indianapolis (IUPUI)Age-related hearing loss is an acute health problem affecting people worldwide, often arising due to defects in the proper functioning of sensory hair cells in the inner ear. The apical surface of sensory hair cells contains actin-based protrusions known as stereocilia, which detect sound and head movements. Since hair cells are not regenerated in mammals, it is important to maintain the functioning of stereocilia for the life of an organism to maintain hearing ability. The actin filaments within a stereocilium are extensively crosslinked by various actin crosslinking proteins, which are important for stereocilia development and maintenance. Multiple studies have shown that the stereocilia actin core is exceptionally stable whereas actin is dynamic only at the tips of stereocilia. However, whether the actin crosslinking proteins, which are nearly as abundant as actin itself, are similarly stable or can freely move in and out of the core remains unknown. Loss or mutation of crosslinkers like plastin-1, fascin-2, and XIRP2 causes progressive hearing loss along with stereocilia degeneration while loss of espin prevents stereocilia from even developing properly. Do these phenotypes stem from an unstable stereocilia core? Does crosslinking confer stability to the core? To address these questions, we generated novel transgenic reporter lines to monitor the dynamics of actin in mice carrying fascin-2R109H mutation and espin null mice and also to study the dynamics of actin crosslinkers, in vivo and ex-vivo. We established that actin crosslinkers readily exchange within the highly stable F-actin structure of the stereocilia core. In addition, we determined that stereocilia degeneration in mice carrying fascin-2R109H mutation and espin null mice could possibly occur due to a less stable actin core. These studies suggest that dynamic crosslinks stabilize the core to maintain proper stereocilia functioning. Future work warrants understanding the reason behind the importance of dynamic crosslinks within a stable stereocilia core. Actin stability not only depends on actin crosslinkers, but also on actin filament composition as evident from distinct stereocilia degeneration and progressive hearing loss patterns in hair-cell specific knockout of actin isoforms. Although beta- and gamma- actin polypeptide sequences differ by only 14 four amino acids, whether the latter determine the unique function of each cytoplasmic actin isoform was previously unknown. Here we determined that these four critical amino acids determine the unique functional importance of beta-actin isoform in sensory hair cells. Taken together, our study demonstrates that actin cytoskeletal proteins are important for the morphogenesis and maintenance of stereocilia

“You drowned me in tears, where did you go?” Narratives of Reproductive Loss and Grief in Middle-Class India

This study is an analysis of middle-class couples’ experiences of reproductive loss, the ensuing grief, and their relentless struggles in order to achieve reproductive success in Kolkata, India. Based on ethnographic engagements, the study explains how the increasingly biomedicalised setting and middle-class ethos of 21st century, urban India shape such profoundly disruptive reproductive experiences. In doing so, the study illustrates how the couple’s experiences of loss and grief were constituted by multiple and intricately entangled enactments of gender roles, gendered emotions, entities, and normative concepts. Finally, the study pays attention to the processual utilisation of constrained agency by the actors, particularly, by the women, in order to show how they coped with their loss as well as their disrupted conjugal lives

Stereocilia morphogenesis and maintenance through regulation of actin stability

Stereocilia are actin-based protrusions on auditory and vestibular sensory cells that are required for hearing and balance. They convert physical force from sound, head movement or gravity into an electrical signal, a process that is called mechanoelectrical transduction. This function depends on the ability of sensory cells to grow stereocilia of defined lengths. These protrusions form a bundle with a highly precise geometry that is required to detect nanoscale movements encountered in the inner ear. Congenital or progressive stereocilia degeneration causes hearing loss. Thus, understanding stereocilia hair bundle structure, development, and maintenance is pivotal to understanding the pathogenesis of deafness. Stereocilia cores are made from a tightly packed array of parallel, crosslinked actin filaments, the length and stability of which are regulated in part by myosin motors, actin crosslinkers and capping proteins. This review aims to describe stereocilia actin regulation in the context of an emerging "tip turnover" model where actin assembles and disassembles at stereocilia tips while the remainder of the core is exceptionally stable

An experimental study of the swelling properties of spherical hydro-gel immersed in water and the formulation of a simple theoretical model for its explanation

The mechanism of variation of mass and volume, through the absorption of water, by the most commonly used and abundantly available spherical hydro-gel beads of various colors has been studied. Immersing the beads in distilled water, both mass and volume were measured at regular intervals. By an analysis of mass-versus-time data, using standard theoretical methods, the mechanism of diffusion of water has been studied. Relaxation controlled transport was found to be the predominant process of diffusion of water into the materials under study. The diffusion coefficient has been determined for hydro-gels of different colors. Various swelling related parameters such as equilibrium water content, equilibrium swelling ratio, characteristic time, initial rate of water absorption etc. were determined for these hydro-gels. The maximum attainable mass and the maximum number of water molecules that can be attached to active polymer sites in a single bead have been calculated. In this regard, the number of such active sites per unit volume and mass of dry hydro-gel was determined. A theoretical model has been developed, based on the consideration of water absorption through the occupation of vacant polymer sites in a highly porous hydro-gel. Considerations of cylindrical and spherical pores in this model predicted almost the same swelling behavior. Expressions relating mass and volume with time have been formulated and they agreed well with experimental observations. The dependence of characteristic time () upon structural parameters have been established. Values of swelling related parameters have been determined by a numerical fitting of theoretical model to experimental data. The agreement of experimental findings with theoretical predictions has been depicted graphically

Functional dissection of the catalytic carboxyl-terminal domain of Origin Recognition Complex Subunit 1 (PfORC1) of the human malaria parasite Plasmodium falciparum

Origin Recognition Complex subunit 1 (ORC1) is essential for DNA replication in eukaryotes. The deadly human malaria parasite Plasmodium falciparum contains an ORC1/CDC6 homolog with several interesting domains at the catalytic carboxyl-terminal region that include a putative nucleoside triphosphate-binding and hydrolysis domain, a putative PCNA-Interacting-Protein (PIP) motif and an extreme C-terminal region that shows poor homology with other ORC1 homologs. Due to the unavailability of a dependable inducible gene expression system, it is difficult to study the structure and function of essential genes in Plasmodium. Using a genetic yeast complementation system and biochemical experiments, here we show that the putative PIP domain in ORC1 that facilitates in vitro physical interaction with PCNA is functional in both yeast (Saccharomyces cerevisiae) and Plasmodium in vivo, confirming its essential biological role in eukaryotes. Furthermore, despite having less sequence homology, the extreme C-terminal region can be swapped between S. cerevisiae and P. falciparum and it binds to DNA directly, suggesting a conserved role of this region in DNA replication. These results not only provide us a useful system to study the function of the essential genes in Plasmodium, they help us to identify the previously undiscovered unique features of replication proteins in general

An experimental study of the swelling properties of spherical hydro-gel immersed in water and the formulation of a simple theoretical model for its explanation

The mechanism of variation of mass and volume, through the absorption of water, by the most commonly used and abundantly available spherical hydro-gel beads of various colors has been studied. Immersing the beads in distilled water, both mass and volume were measured at regular intervals. By an analysis of mass-versus-time data, using standard theoretical methods, the mechanism of diffusion of water has been studied. Relaxation controlled transport was found to be the predominant process of diffusion of water into the materials under study. The diffusion coefficient has been determined for hydro-gels of different colors. Various swelling related parameters such as equilibrium water content, equilibrium swelling ratio, characteristic time, initial rate of water absorption etc. were determined for these hydro-gels. The maximum attainable mass and the maximum number of water molecules that can be attached to active polymer sites in a single bead have been calculated. In this regard, the number of such active sites per unit volume and mass of dry hydro-gel was determined. A theoretical model has been developed, based on the consideration of water absorption through the occupation of vacant polymer sites in a highly porous hydro-gel. Considerations of cylindrical and spherical pores in this model predicted almost the same swelling behavior. Expressions relating mass and volume with time have been formulated and they agreed well with experimental observations. The dependence of characteristic time () upon structural parameters have been established. Values of swelling related parameters have been determined by a numerical fitting of theoretical model to experimental data. The agreement of experimental findings with theoretical predictions has been depicted graphically

Herbs Having Analgesic Activity

Healthcare maintains a high priority on pain management, and research to develop safer and more potent analgesics is ongoing. Natural goods, especially plants, have recently attracted renewed interest as potential sources of analgesic medications. In this study, various techniques are used to measure pain. The rich source of analgesics found in medicinal plants includes Moringa oleifera, Aloe barbadensis, Curcuma longa, Eugenia caryophyllata, Adhatoda vasica, Mentha piperita, Ocimum sanctum, Zingiber officinale, Lavandula angustifolia, Epilobium angustifolium, Dialium guineense, Sida acuta, Stylosanthes fruticose, Bougainvilla spectabilis, Ficus glomerata, Polyalithia longifolia, Calotropis gigantea, Tinospora cordifolia, Ageratina glabrata, Mangifera indica, Peperomia pellucida, Jatropha gossypifolia, Leonotis leonurus, Mimosa rubicaulis, Cussonia paniculate, Biebersteinia multifida, Alternanthera sessislis, Mentha arvensis, Oroxylum indicum, Tamarindus indica, Cucurbita maxima, Cucumis sativus, Emblica officinalis, Angiopteris evecta, Parastrephia lephidophylla, Peperomia pellucida, Scoparia dulcis, Ficus racemose, Eremostachys laciniata, Phlogacanthus thyrsiflorus, Kigelia pinnata, Molineria capitulate, Manihot esculenta, Ficus religiosa, Dalbergia sissoo, Grangea maderaspatana, Nothospondias staudtii, Rhodiola rosea, Juniperus communis, Erythrina variegate etc. The results reported in this review paper represent scientific knowledge that may be applied in the future to isolate potentially active molecules from some of these medicinal plants

Essential nucleotide- and protein-dependent functions of Actb/β-actin

The highly similar cytoplasmic β- and γ-actins differ by only four functionally similar amino acids, yet previous in vitro and in vivo data suggest that they support unique functions due to striking phenotypic differences between Actb and Actg1 null mouse and cell models. To determine whether the four amino acid variances were responsible for the functional differences between cytoplasmic actins, we gene edited the endogenous mouse Actb locus to translate γ-actin protein. The resulting mice and primary embryonic fibroblasts completely lacked β-actin protein, but were viable and did not present with the most overt and severe cell and organismal phenotypes observed with gene knockout. Nonetheless, the edited mice exhibited progressive high-frequency hearing loss and degeneration of actin-based stereocilia as previously reported for hair cell-specific Actb knockout mice. Thus, β-actin protein is not required for general cellular functions, but is necessary to maintain auditory stereocilia