Basal Processes Research Articles

A unique mating pattern of Panorpodes kuandianensis (Mecoptera: Panorpodidae)

Sexually reproductive insects exhibit diverse mating behaviors. However, the mating pattern remains unknown for Panorpodes of Panorpodidae to date. In this study, we investigated the mating behavior and copulatory mechanism of the short-faced scorpionfly Panorpodes kuandianensis Zhong, Zhang and Hua, 2011 for the first time. The results show that the male provides a salivary mass as a nuptial gift to the female and starts to copulate with the female in a V-shaped position, then changes to an end-to-end position by temporarily twisting the female abdominal segments VII−IX by 180°. During mating the basal processes and the basal teeth of the gonostyli and the hypandrium are used to obtain copulation and sustain the coupling of genitalia to secure successful sperm transfer. This unique mating pattern is greatly different from that of other Mecoptera reported and is likely evolved as an adaptation in the context of sexual conflict.

Molecular components and polarity of radial glial cells during cerebral cortex development.

Originating from ectodermal epithelium, radial glial cells (RGCs) retain apico-basolateral polarity and comprise a pseudostratified epithelial layer in the developing cerebral cortex. The apical endfeet of the RGCs faces the fluid-filled ventricles, while the basal processes extend across the entire cortical span towards the pial surface. RGC functions are largely dependent on this polarized structure and the molecular components that define it. In this review, we will dissect existing molecular evidence on RGC polarity establishment and during cerebral cortex development and provide our perspective on the remaining key questions.

Magnetic characteristics of polymorphic single crystal compounds DyIr2Si2

We have confirmed that the tetragonal ternary compound DyIr2Si2 shows polymorphism; the ThCr2Si2-type structure as a low temperature phase (I-phase) and the CaBe2Ge2-type one as a high temperature phase (P-phase) exist. A comparative study on magnetic characteristics of the morphs was performed on the I- and P-phase single crystals in order to elucidate how magnetic properties are influenced by crystallographic symmetry. The magnetic behavior changes drastically depending on the structure. The DyIr2Si2(I) shows an antiferromagnetic ordering below TN = 30K, additional magnetic transitions of T1 = 17K and T2 = 10K, and a strong uniaxial magnetic anisotropy with the easy [001] direction. The [001] magnetization shows four metamagnetic transitions at low temperatures. On the other hand, the DyIr2Si2(P) has comparatively low ordering temperature of TN1 = 9.4K and an additional transition temperature of TN2 = 3.0K, and exhibits an easy-plane magnetic anisotropy with the easy [110] direction. Two metamagnetic transitions appear in the basal plane magnetization processes. In both the morphs, the χ-T behavior suggests the existence of component-separated magnetic transitions. The ab-component of magnetic moments orders at the higher transition temperature TN1 for the P-phase compound, which is contrast to the I-phase behavior; the c-component orders firstly at TN. The crystalline electric field (CEF) analysis was made, and the difference in magnetic behaviors between both the morphs is explained by the CEF effects.

Diodonopsis ramiromedinae (Orchidaceae: Pleurothallidinae), a new species from Colombia

A new species, Diodonopsis ramiromedinae, is described, illustrated, and compared with similar species. A brief history of Masdevallia sect. Pygmaeae and the genus Diodonopsis is provided. Diodonopsis ramiromedinae is most similar to D. anachaeta, but differs by sepals with apices acute or acuminate-triangular vs. narrowly caudate; longer petals with a descending, narrowly linear, rounded basal process vs. with an acute, retrorse basal process; and the larger lip, obovate with the apex very broadly rounded vs. oblong-subpandurate with the apex acute.

Expression of Calcium-Binding Proteins, Calbindin D28k and Calretinin, in the Frog Taste Receptor Structures

Considering that information on the expression of calcium-binding proteins (CaBPs) in different cells of the taste receptors is rather limited, we investigated the distribution of such proteins, calbindin D28k (CB) and calretinin (CR), in the taste disc (TD) of the frog Lithobates catesbeianus. Western blot analysis revealed that CB and CR are expressed in cells of the fungiform papillae. CB-immunoreactive (ir) and CR-ir cell somata were located in the middle layer of the TD. Most CB-ir and CR-ir cells possessed one rod-shaped apical process and one basal process; in some cells there were several extended basal processes. Apical processes of CR-ir cells were thinner than those of CB-ir units, and CR-ir nerve fibers were ramified in the lamina propria directly below the TD. Most CR-ir fiber branches surrounded the TD; however, some penetrated this region, with both types of branches approaching the surface. CB and CR immunoreactivities did not co-occur in TD cells. In the TDs examined, the number of CB-ir cells was significantly greater than that of CR-ir units. Our observations suggest that CB-ir and CR-ir cells in the frog TD correspond to type-II and type-III cells, respectively.

Discovery of stress responsive TATA-box binding protein associated Factor6 (TAF6) from finger millet (Eleusine coracana (L.) Gaertn)

Drought is one of the major abiotic factors affecting plant growth mainly in the tropical regions. During stress acclimation response, basal transcriptional process is critical which is coordinated by several cofactors, among which TATAbox Binding Protein (TBP) - Associated Factors (TAFs) are the major proteins involved in pre-initiation complex assembly. In search of novel transcriptional regulators, we identified one of the factors, TAF6, in a drought cDNA library generated from an adapted crop, finger millet (Eleusine coracana (L.) Gaertn). RTPCR analysis in leaf tissues of finger millet experiencing different levels of drought, revealed its stress responsiveness in three different genotypes. The gene is also induced under salt, osmotic and oxidative stresses at seedling stage. Analysis of its promoter in model plants indicated the presence of cis-elements associated with diverse stress responses. Down regulation of NbTAF6 by virus induced gene silencing (VIGS) approach resulted in a developmentally defective and stress sensitive phenotype in Nicotiana benthamiana. This is the first report on the up-regulation of EcTAF6 under abiotic stresses and the gene probably has a crucial role in safeguarding the stress related transcription process. The basal regulators like TAF6 can thus be considered as prospective candidates associated with stress acclimation in plants.

Mitochondria as a target of cardioprotection in models of preconditioning.

Over the recent years the view on mitochondria in the heart as a cellular powerhouse providing ATP supply needed to sustain contractile function, basal metabolic processes, and ionic homeostasis has changed radically. At present it is known that dysfunctions of these organelles are essential in the development of a large number of diseases, including cardiovascular diseases. Moreover, mitochondria are considered to be a very promising target of endogenous strategies that are essential in the protection of the myocardium from acute ischemia/reperfusion injury. These strategies including ischemic preconditioning, remote ischemic preconditioning as well as the acute phase of streptozotocin-induced diabetes mellitus, provide a similar effect of protection. Alterations observed in the functional and structural properties of heart mitochondria caused by short-term pathological impulses are associated with endogenous cardioprotective processes. It seems that the extent of mitochondrial membrane fluidization could be an active response mechanism to injury with a subtle effect on membrane-associated processes which further affect the environment of the whole organelle, thus inducing metabolic changes in the heart. In this review article, we provide an overview of endogenous protective mechanisms induced by hypoxic, pseudohypoxic and ischemic conditions with special consideration of the role of heart mitochondria in these processes.

Heart heat separation.

The human heart requires a considerable amount of energy (10 W at rest to 100 W during exercise) for basal metabolism, activation processes and work to circulate blood (heart rate × stroke volume × arterial blood pressure). This article is protected by copyright. All rights reserved

The intestinal tuft cell nanostructure in 3D

Once referred to as “peculiar,” tuft cells are enigmatic epithelial cells. Here, we reasoned that future functional studies could be derived from a complete account of the tuft cell ultrastructure. We identified and documented the volumetric ultrastructure at nanometer resolution (4–5 nm/pixel) of specific intestinal tuft cells. The techniques used were Serial Block-Face (SBF) and Automated Tape-collecting Ultra-Microtome (ATUM) Scanning Electron Microscopy (SEM). Our results exposed a short (~15 µm) basal cytoplasmic process devoid of secretory vesicles. Volume rendering of serial sections unveiled several thin cytospinules (~1 µm). These cytospinules project from the tuft cell into the nuclei of neighboring epithelial cells. Volume rendering also revealed within the tuft cell an elegant network of interconnected tubules. The network forms a passage from the base of the microvilli to the rough endoplasmic reticulum. Based on their location and microanatomy, the tuft cells’ cytospinules, and tubular network, might facilitate the exchange of molecular cargo with nuclei of neighboring cells, and the gut lumen.

Rediscovery and redescription of Laelaps lignicola G. & R. Canestrini, a remarkable myrmecophilous mite of the genus Cosmolaelaps Berlese(Acari: Mesostigmata: Laelapidae) from Italy.

Laelaps lignicola G. & R. Canestrini, 1882 is redescribed on the basis of numerous adults and deutonymphs, collected from Italy more than a century after its description. Despite its setiform setae without a discernible asymmetric swelling, this species fits the current concept of the genus Cosmolaelaps Berlese for all remaining diagnostic characters. Males of L. lignicola and Cosmolaelaps vacuus (Michael) share the presence of a basal process bearing seta av on telefemur II. This attribute is apparently not described in other laelapid mites. Also, males of L. lignicola are similar to those of some European species of Cosmolaelaps in having a distinct masticatory ridge on the fixed digit of chelicera. The ecological preference for decaying wood microhabitats, where L. lignicola is closely associated with Lasius emarginatus (Olivier) (Hymenoptera Formicidae), also suggests a close affinity with Cosmolaelaps species. Consequently, this species is provisionally placed in Cosmolaelaps and the new combination C. lignicolus (G. & R. Canestrini, 1882) comb. nov. is proposed.

Dynamic behaviour of human neuroepithelial cells in the developing forebrain

To understand how diverse progenitor cells contribute to human neocortex development, we examined forebrain progenitor behaviour using timelapse imaging. Here we find that cell cycle dynamics of human neuroepithelial (NE) cells differ from radial glial (RG) cells in both primary tissue and in stem cell-derived organoids. NE cells undergoing proliferative, symmetric divisions retract their basal processes, and both daughter cells regrow a new process following cytokinesis. The mitotic retraction of the basal process is recapitulated by NE cells in cerebral organoids generated from human-induced pluripotent stem cells. In contrast, RG cells undergoing vertical cleavage retain their basal fibres throughout mitosis, both in primary tissue and in older organoids. Our findings highlight developmentally regulated changes in mitotic behaviour that may relate to the role of RG cells to provide a stable scaffold for neuronal migration, and suggest that the transition in mitotic dynamics can be studied in organoid models.

An improved method for the detection of nucleotide excision repair factors at local UV DNA damage sites

Among different DNA repair processes that cells use to face with DNA damage, nucleotide excision repair (NER) is particularly important for the removal of a high variety of lesions, including those generated by some antitumor drugs. A number of factors participating in NER, such as the TFIIH complex and the endonuclease XPG are also involved in basal processes, e.g. transcription. For this reason, localization of these factors at DNA damage sites may be difficult. Here we have applied a mild digestion of chromatin with DNase I to improve the in situ extraction necessary to detect chromatin-bound proteins by immunofluorescence. We have compared this method with different extraction protocols and investigated its application on different cell types, and with different antibodies. Our results show that a short DNase I treatment before the immunoreaction, enhances the fluorescence signal of NER proteins, such as XPG, DDB2 and XPC. In addition, our findings indicate that the antibody choice is a critical factor for accurate localization of DNA repair proteins at DNA damage sites. In conclusion, a mild DNA digestion with DNase I improves the immunofluorescence detection of the recruitment of NER factors at local DNA damage sites by enhancing accessibility to the antibodies, independently of the cell type.

Differences in the Cellular Response to Acute Spinal Cord Injury between Developing and Mature Rats Highlights the Potential Significance of the Inflammatory Response.

There exists a trend for a better functional recovery from spinal cord injury (SCI) in younger patients compared to adults, which is also reported for animal studies; however, the reasons for this are yet to be elucidated. The post injury tissue microenvironment is a complex milieu of cells and signals that interact on multiple levels. Inflammation has been shown to play a significant role in this post injury microenvironment. Endogenous neural progenitor cells (NPC), in the ependymal layer of the central canal, have also been shown to respond and migrate to the lesion site. This study used a mild contusion injury model to compare adult (9 week), juvenile (5 week) and infant (P7) Sprague-Dawley rats at 24 h, 1, 2, and 6 weeks post-injury (n = 108). The innate cells of the inflammatory response were examined using counts of ED1/IBA1 labeled cells. This found a decreased inflammatory response in the infants, compared to the adult and juvenile animals, demonstrated by a decreased neutrophil infiltration and macrophage and microglial activation at all 4 time points. Two other prominent cellular contributors to the post-injury microenvironment, the reactive astrocytes, which eventually form the glial scar, and the NPC were quantitated using GFAP and Nestin immunohistochemistry. After SCI in all 3 ages there was an obvious increase in Nestin staining in the ependymal layer, with long basal processes extending into the parenchyma. This was consistent between age groups early post injury then deviated at 2 weeks. The GFAP results also showed stark differences between the mature and infant animals. These results point to significant differences in the inflammatory response between infants and adults that may contribute to the better recovery indicated by other researchers, as well as differences in the overall injury progression and cellular responses. This may have important consequences if we are able to mirror and manipulate this response in patients of all ages; however much greater exploration in this area is required.

Bi- and uniciliated ependymal cells define continuous floor-plate-derived tanycytic territories

Multiciliated ependymal (E1) cells line the brain ventricles and are essential for brain homeostasis. We previously identified in the lateral ventricles a rare ependymal subpopulation (E2) with only two cilia and unique basal bodies. Here we show that E2 cells form a distinct biciliated epithelium extending along the ventral third into the fourth ventricle. In the third ventricle floor, apical profiles with only primary cilia define an additional uniciliated (E3) epithelium. E2 and E3 cells’ ultrastructure, marker expression and basal processes indicate that they correspond to subtypes of tanycytes. Using sonic hedgehog lineage tracing, we show that the third and fourth ventricle E2 and E3 epithelia originate from the anterior floor plate. E2 and E3 cells complete their differentiation 2–3 weeks after birth, suggesting a link to postnatal maturation. These data reveal discrete bands of E2 and E3 cells that may relay information from the CSF to underlying neural circuits along the ventral midline.

Apical and basal epitheliomuscular F-actin dynamics duringHydrabud evagination

ABSTRACTBending of 2D cell sheets is a fundamental morphogenetic mechanism during animal development and reproduction. A critical player driving cell shape during tissue bending is the actin cytoskeleton. Much of our current knowledge about actin dynamics in whole organisms stems from studies of embryonic development in bilaterian model organisms. Here, we have analyzed actin-based processes during asexual bud evagination in the simple metazoan Hydra. We created transgenic Hydra strains stably expressing the actin marker Lifeact-GFP in either ectodermal or endodermal epitheliomuscular cells. We then combined live imaging with conventional phalloidin staining to directly follow actin reorganization. Bending of the Hydra epithelial double layer is initiated by a group of epitheliomuscular cells in the endodermal layer. These cells shorten their apical-basal axis and arrange their basal muscle processes in a circular configuration. We propose that this rearrangement generates the initial forces to bend the endoderm towards the ectoderm. Convergent tissue movement in both epithelial layers towards the centre of evagination then leads to elongation and extension of the bud along its new body axis. Tissue movement into the bud is associated with lateral intercalation of epithelial cells, remodelling of apical septate junctions, and rearrangement of basal muscle processes. The work presented here extends the analysis of morphogenetic mechanisms beyond embryonic tissues of model bilaterians.

Characterization of Cytosine Methylation and the DNA Methyltransferases of Toxoplasma gondii.

DNA methylation is a key epigenetic modification which confers phenotypic plasticity and adaptation. Cyst-forming strains of Toxoplasma gondii undergo tachyzoite to bradyzoite conversion after initial acute infection of a host, and the reverse conversion may occur in immune-suppressed hosts. The formation of m5C is catalyzed by DNA methyltransferase (DNMT). We identified two functional DNA methyltransferases, TgDNMTa and TgDNMTb, in T. gondii that may mediate DNA methylation. The recombinant proteins showed intrinsic methyltransferase activity; both have higher transcription levels in bradyzoites than that in tachyzoites. We performed genome-wide analysis of DNA methylation in tachyzoites and bradyzoites. The results showed more methylation sites in bradyzoites than that in tachyzoites. The most significantly enriched GO-terms of genes with DNA methylation were associated with basal cellular processes such as energy metabolism and parasite resistance to host immunity. Tachyzoite proliferation in parasitophorous vacuoles (PV) can be inhibited by the DNA methyltransferase inhibitor 5-azacytidine, a chemical analogue of the nucleotide cytosine that can inactivate DNA methyltransferases. These findings provide the first confirmation of DNA methylation in T. gondii.

TNF-alpha Is not a Miscreant: A Hero for Basal Nrf2-Antioxidant Signaling.

About three decades of intensive research suggest that tumor necrosis factor-alpha (TNF-α) is a "miscreant". Although it is obvious that supra-physiological TNF-α levels are deleterious to cellular activities leading to a variety of pathological conditions, it is unlikely that complete removal of TNF-α is cytoprotective. Are we rejecting the basal physiological role of TNF-α as a reactive oxygen species (ROS) producer that is key and essential for numerous basal cell signaling processes? We believe that there are important protective roles for TNF-α under basal/physiological conditions. We propose that one such role is that of signaling through nuclear erythroid 2 p45 related factor-2/antioxidant response element (Nrf2/ARE). Confirming our hypothesis that TNF-α is necessary and sufficient for the basal activation of Nrf2/ARE transcriptional pathways, will change the existing paradigms on the function of TNF-α. This article briefly reviews the canonical role of TNF-α as miscreant and introduces a new role as a hero in the context of Nrf2-antioxidant signaling.

Interkinetic nuclear migration and basal tethering facilitates post-mitotic daughter separation in intestinal organoids.

ABSTRACTHomeostasis of renewing tissues requires balanced proliferation, differentiation and movement. This is particularly important in the intestinal epithelium where lineage tracing suggests that stochastic differentiation choices are intricately coupled to the position of a cell relative to a niche. To determine how position is achieved, we followed proliferating cells in intestinal organoids and discovered that the behaviour of mitotic sisters predicted long-term positioning. We found that, normally, 70% of sisters remain neighbours, while 30% lose contact and separate after cytokinesis. These post-mitotic placements predict longer term differences in positions assumed by sisters: adjacent sisters reach similar positions over time; in a pair of separating sisters, one remains close to its birthplace while the other is displaced upward. Computationally modelling crypt dynamics confirmed that post-mitotic separation leads to sisters reaching different compartments. We show that interkinetic nuclear migration, cell size and asymmetric tethering by a process extending from the basal side of cells contribute to separations. These processes are altered in adenomatous polyposis coli (Apc) mutant epithelia where separation is lost. We conclude that post-mitotic placement contributes to stochastic niche exit and, when defective, supports the clonal expansion of Apc mutant cells.

Importance of basal boundary conditions in transient simulations: case study of a surging marine-terminating glacier on Austfonna, Svalbard

ABSTRACTWe assess the importance of basal boundary conditions for transient simulations of Basin 3, Austfonna ice cap between January 1995 and December 2011 and for the surge starting in 2012 by carrying out simulations with the full-Stokes model Elmer/Ice and the vertically-integrated model BISICLES. Time-varying surface mass-balance data from the regional climate model HIRHAM5 are downscaled according to elevation. Basal friction coefficient is varied through time by interpolating between two data-constrained inversions of surface velocity fields, from 1995 and 2011. Evolution of the basal boundary condition appears to be much more important for mass discharge and the dynamic response of the fast flowing unit in Basin 3 than either model choice or the downscaling method for the surface mass balance. In addition, temporally linear extrapolation of the evolution of basal friction coefficient beyond the 2011 distribution could not reproduce the expansion of the acceleration observed in southern Basin 3 between January 2012 and June 2013. This implies that changes in basal friction patterns, and in turn basal processes that are not currently represented in either model, are among the most important factors for the 2012 acceleration.

Dynamic mRNA Transport and Local Translation in Radial Glial Progenitors of the Developing Brain

In the developing brain, neurons are produced fromneural stem cells termed radial glia [1, 2]. Radial glial progenitors span the neuroepithelium, extending long basal processes to form endfeet hundreds of micrometers away from the soma. Basal structures influence neuronal migration, tissue integrity, and proliferation [3-7]. Yet, despite the significance of these distal structures, theircell biology remains poorly characterized, impeding our understanding of how basal processes and endfeet influence neurogenesis. Here we use live imaging of embryonic brain tissue to visualize, for the first time, rapid mRNA transport in radial glia, revealing that the basal process is a highway for directed molecular transport. RNA- and mRNA-binding proteins, including the syndromic autism protein FMRP, move in basal processes at velocities consistent with microtubule-based transport, accumulating in endfeet. We develop an exvivo tissue preparation to mechanically isolate radial glia endfeet from the soma, and we use photoconvertible proteins to demonstrate that mRNA is locally translated. Using RNA immunoprecipitation and microarray analyses of endfeet, we discover FMRP-bound transcripts, which encode signaling and cytoskeletal regulators, including many implicated in autism and neurogenesis. We show FMRP controls transport and localization of one target, Kif26a. These discoveries reveal a rich, regulated local transcriptome in radial glia, far from the soma, and establish a tractable mammalian model for studying mRNA transport and local translation invivo. We conclude that cytoskeletal and signaling events at endfeet may be controlled through translation of specific mRNAs transported from thesoma, exposing new mechanistic layers within stem cells of the developing brain.