Apical Processes Research Articles

Hippocampal neural stem cells facilitate access from circulation via apical cytoplasmic processes.

Blood vessels (BVs) are considered an integral component of neural stem cells (NSCs) niches. NSCs in the dentate gyrus (DG(have enigmatic elaborated apical cellular processes that are associated with BVs. Whether this contact serves as a mechanism for delivering circulating molecules is not known. Here we uncovered a previously unrecognized communication route allowing exclusive direct access of blood-borne substances to hippocampal NSCs. BBB-impermeable fluorescent tracer injected transcardially to mice is selectively uptaken by DG NSCs within a minute, via the vessel-associated apical processes. These processes, measured >30 nm in diameter, establish direct membrane-to-membrane contact with endothelial cells in specialized areas of irregular endothelial basement membrane and enriched with vesicular activity. Doxorubicin, a brain-impermeable chemotherapeutic agent, is also readily and selectively uptaken by NSCs and reduces their proliferation, which might explain its problematic anti-neurogenic or cognitive side-effect. The newly-discovered NSC-BV communication route explains how circulatory neurogenic mediators are 'sensed' by NSCs.

Autofluorescent Granules of the Human Retinal Pigment Epithelium: Phenotypes, Intracellular Distribution, and Age-Related Topography.

PurposeThe human retinal pigment epithelium (RPE) accumulates granules significant for autofluorescence imaging. Knowledge of intracellular accumulation and distribution is limited. Using high-resolution microscopy techniques, we determined the total number of granules per cell, intracellular distribution, and changes related to retinal topography and age.MethodsRPE cells from the fovea, perifovea, and near-periphery of 15 human RPE flat mounts were imaged using structured illumination microscopy (SIM) and confocal fluorescence microscopy in young (≤51 years, n = 8) and older (>80 years, n = 7) donors. Using custom FIJI plugins, granules were marked with computer assistance, classified based on morphological and autofluorescence properties, and analyzed with regard to intracellular distribution, total number per cell, and granule density.ResultsA total of 193,096 granules in 450 RPE cell bodies were analyzed. Based on autofluorescence properties, size, and composition, the RPE granules exhibited nine different phenotypes (lipofuscin, two; melanolipofuscin, five; melanosomes, two), distinguishable by SIM. Overall, lipofuscin (low at the fovea but increases with eccentricity and age) and melanolipofuscin (equally distributed at all three locations with no age-related changes) were the major granule types. Melanosomes were under-represented due to suboptimal visualization of apical processes in flat mounts.ConclusionsLow lipofuscin and high melanolipofuscin content within foveal RPE cell bodies and abundant lipofuscin at the perifovea suggest a different genesis, plausibly related to the population of overlying photoreceptors (fovea, cones only; perifovea, highest rod density). This systematic analysis provides further insight into RPE cell and granule physiology and links granule load to cell autofluorescence, providing a subcellular basis for the interpretation of clinical fundus autofluorescence.

Knockdown of IP3R1 disrupts tubulobulbar complex-ectoplasmic reticulum contact sites and the morphology of apical processes encapsulating late spermatids†.

Tubulobulbar complexes (TBCs) internalize intercellular junctions during sperm release. One of the characteristic features of TBCs is that they form "bulbs" or swollen regions that have well-defined membrane contact sites (MCS) with adjacent cisternae of endoplasmic reticulum. Previously, we have localized the IP3R calcium channel to the TBC bulb-ER contacts and have hypothesized that fluctuations in local calcium levels may facilitate the maturation of TBC bulbs into putative endosomes, or alter local actin networks that cuff adjacent tubular regions of the TBCs. To test this, we injected the testes of Sprague Dawley rats with small interfering RNAs (siRNAs) against IP3R1 and processed the tissues for either western blot, immunofluorescence, or electron microscopy. When compared to control testes injected with nontargeting siRNAs, Sertoli cells in knocked-down testes showed significant morphological alterations to the actin networks including a loss of TBC actin and the appearance of ectopic para-crystalline actin bundles in Sertoli cell stalks. There also was a change in the abundance and distribution of TBC-ER contact sites and large internalized endosomes. This disruption of TBCs resulted in delay of the withdrawal of apical processes away from spermatids and in spermiation. Together, these findings are consistent with the hypothesis that calcium exchange at TBC-ER contacts is involved both in regulating actin dynamics at TBCs and in the maturing of TBC bulbs into endosomes. The results are also consistent with the hypothesis that TBCs are part of the sperm release mechanism.

A phenetic analysis of Philippine Rubus species (Rosaceae) by morphology

The taxonomy of the Philippine Rubus species was studied through a phenetic analysis of the morphological data from preserved specimens. After recording the character states, the data were analyzed using cluster analysis and PCA, and the resulting analysis allowed the delimitation of morphologically similar Rubus species. Specimens of the Rubus genus collected in the country were separated into two clusters distinguished by leaf structure. Specimens of the same species are often found in multiple sub-clusters, which suggests the high degree of variation within a species. PCA of morphological data from Rubus species show that leaf and floral characters, which include the maximum number of lobes, pedicel pubescence, outside pubescence of the hypanthium, apex of the simple leaf blade, and the apical process of the sepals, explain the variation in Rubus species in the Philippines.

Taxonomic study of the genus Promalactis Meyrick, 1908 (Lepidoptera: Oecophoridae) VIII. The densimacularis species group, with descriptions of four new species.

The densimacularis species group of the genus Promalactis Meyrick, 1908 is proposed based on the forewing patterns. These species are diagnostic by the forewing having three black patches on the costal margin, the gnathos usually with a membranous apical process in the male genitalia, and the ductus bursae with denticles or spines in the female genitalia. Four new species are described: P. costispinata sp. nov., P. trimaculata sp. nov., P. simingshana sp. nov. and P. yongjiana sp. nov. All the 14 described species of the densimacularis-group are listed. Photographs of adults and genitalia of the new species are provided.

Description of the larvae of three species of the genus Mordellistena(Coleoptera: Mordellidae) with notes on their ecology.

The mature larvae of Mordellistena luteipalpis Schilsky, 1895, M. koelleri Ermisch, 1956 and M. brevicauda (Bohemann, 1849) are described for the first time. The descriptions are illustrated with photographs of habitus and drawings of the key characters of the larvae. The larva of M. brevicauda differs significantly from the other known larvae of Mordellistena species by fused apical processes and 2-segmented antennae. Ecological data of all three species are presented and discussed. M. luteipalpis is recorded for the first time from Ukraine and Belarus.

Description of two new species of Regalana and a new genus of Gyponini (Hemiptera: Cicadellidade: Iassinae).

Two new species of Regalana DeLong Freytag, 1975 are described and illustrated: Regalana jamari sp. nov. and Regalana madeira sp. nov., both from State of Rondônia, Northern Brazil. Delongiana gen. nov. is described within Gyponini, based on two new species from Brazil: Delongiana ramosa sp. nov., designated as type-species, from Minas Gerais and Paraná states and Delongiana baiana sp. nov. from Bahia and Rio de Janeiro states. The new genus can be distinguished from other Gyponini genera based on the combination of the following features: crown slightly produced, parallel striated; crown-face transition distinct, thick and striated; male pygofer with an oblique integument thickening near dorsal margin; subgenital plate very narrow and elongated; connective Y-shaped; style elongated with apex foot-shaped; aedeagus with dorsal apodemes strongly developed, shaft cylindrical and curved dorsally, with processes near mid-length and without apical processes. Additionally, new country records are given for Regalana bobbyi and R. dianae and state records to R. sheilae.

CT evaluation of elbow congruity in dogs: radial incisure versus apical medial coronoid process fragmentation.

To compare elbow congruity in two cohorts of Labrador retrievers affected with either radial incisure or apex fragmentation of the medial coronoid process. Dogs were included if they had elbow lameness and a CT diagnosis of a fissure or fragmentation of the medial coronoid process occurring either along the radial incisure or at the coronoid apex. Radioulnar joint space was measured incrementally from the lateral to the medial coronoid process on transverse slice images. Axial radioulnar congruency was also measured at the apex and mid-coronoid in the dorsal plane and at the base of the coronoid in the sagittal plane. We studied 99 elbows (in 66 dogs) of which 56 had a fissure or fragmentation along the radial incisure and 43 had an apical fragment. No difference was found between the two groups at the different measuring points - with the exception of a transverse plane radioulnar joint space measurement in the radial incisure group that was smaller adjacent to the lateral coronoid process. Abnormal ulnar morphology in the radial incisure group could result in a fulcrum effect within the radioulnar joint, overloading the radial incisure and predisposing to osteochondral damage at this site.

Mesoderm and endoderm internalization in the Xenopus gastrula.

Mesoderm and endoderm internalization in the Xenopus embryo are based on a number of region-specific morphogenetic processes that co-act in the vegetal half of the gastrula. In the multilayered wall surrounding the blastocoel, the apical layer engages in bottle cell formation and associated invagination and involution movements, and in cell intercalation in the plane of the layer. Of these epithelial-type processes, only bottle cell formation has been analyzed mechanistically. In the deep layers of the blastocoel wall, cell-on-cell migration drives the internalization of mesoderm by various forms of involution and of the endodermal cell mass by vegetal rotation. In the mesoderm, cells migrate in a mesenchymal mode with the aid of locomotory protrusions, whereas cells of the vegetal cell mass resemble free bottle cells that engage in ingression-type amoeboid migration. Cells rearrange by differential migration leading to parallel or orthogonal forms of intercalation and respective types of convergent extension. The interaction of the various apical and deep layer processes gives rise to dorsal multilayer invagination, ventrolateral internal involution, peak involution and orthogonal convergent extension of the dorsal posterior mesoderm, vegetal rotation, and blastopore constriction. It is speculated how these multilayer gastrulation movements could be derived from mechanisms in invertebrate single-epithelium gastrulae.

A Transcriptome Analysis Identifies Biological Pathways and Candidate Genes for Feed Efficiency in DLY Pigs.

Feed cost accounts for approximately 65–75% of overall commercial pork production costs. Therefore, improving the feed efficiency of pig production is important. In this study, 12 individuals with either extremely high (HE) or low (LE) feed efficiency were selected from 225 Duroc × (Landrace × Yorkshire) (DLY) pigs. After the pigs were slaughtered, we collected small intestine mucosal tissue. Next, RNA sequencing (RNA-seq) analysis was used to reveal the presence and quantity of genes expressed between these extremely HE- and LE-groups. We found 433 significantly differentially expressed genes (DEGs) between the HE- and LE-groups. Of these, 389 and 44 DEGs were upregulated and downregulated in the HE-group, respectively. An enrichment analysis showed that the DEGs were mainly enriched in functions related to apical plasma membrane composition, transporter activity, transport process and hormone regulation of digestion and absorption. Protein network interaction and gene function analyses revealed that SLC2A2 was an important candidate gene for FE in pigs, which may give us a deeper understanding of the mechanism of feed efficiency. Furthermore, some significant DEGs identified in the current study could be incorporated into artificial selection programs for increased feeding efficiency in pigs.

The polarity and properties of radial glia-like neural stem cells are altered by seizures with status epilepticus: Study using an improved mouse pilocarpine model of epilepsy.

In the adult mouse hippocampus, new neurons are produced by radial glia-like (RGL) neural stem cells in the subgranular zone, which extend their apical processes toward the molecular layer, and express the astrocyte marker glial fibrillary acidic protein, but not the astrocyte marker S100β. In rodent models of epilepsy, adult hippocampal neurogenesis was reported to be increased after acute and mild seizures, but to be decreased by chronic and severe epilepsy. In the present study, we investigated how the severity of seizures affects neurogenesis and RGL neural stem cells in acute stages of epilepsy, using an improved mouse pilocarpine model in which pilocarpine-induced hypothermia was prevented by maintaining body temperature, resulting in a high incidence rate of epileptic seizures and low rate of mortality. In mice that experienced seizures without status epilepticus (SE), the number of proliferating progenitors and immature neurons were significantly increased, whereas no changes were observed in RGL cells. In mice that experienced seizures with SE, the number of proliferating progenitors and immature neurons were unchanged, but the number of RGL cells with an apical process was significantly reduced. Furthermore, the processes of the majority of RGL cells extended inversely toward the hilus, and about half of the aberrant RGL cells expressed S100β. These results suggest that seizures with SE lead to changes in the polarity and properties of RGL neural stem cells, which may direct them toward astrocyte differentiation, resulting in the reduction of neural stem cells producing new granule cells. This also suggests the possibility that cell polarity of RGL stem cells is important for maintaining the stemness of adult neural stem cells.

A new species of the genus Polyphena Solovyev, 2014 (Lepidoptera: Limacodidae) from China.

Polyphena chongzuoensis sp. nov. is described from China, as the twelfth species of Polyphena Solovyev, 2014. This new species is morphologically similar to P. bana (Cai, 1983), but differs in male genitalia from the latter by short spurs of anellus and aedeagus without obvious apical processes. Male adult and its genitalia are illustrated. The new species is supported molecularly by the analysis of pairwise genetic distances from a 658 bp of the mitochondrial cytochrome c oxidase subunit I gene, with the minimum distance value of 6.4% from its allied species P. annae.

A new species of the sharpshooter genus Dasmeusa (Hemiptera: Cicadellidae: Cicadellini) from Central Amazon

A new species of the genus Dasmeusa Melichar, 1926 is described and illustrated from specimens collected in the State of Amazonas, Northern Brazil. Dasmeusa imperialis sp. nov. can be distinguished from the five known species of the genus, as well as from those of closely related genera, by the following combination of features: dorsum yellow with orange, preapical transverse irregular stripe on forewing; male pygofer moderately produced posteriorly, with posterior margin broadly rounded; style without preapical lobe, narrow and truncate apically; aedeagus with robust apical process directed ventrally, ventral margin of this process dentate; paraphyses with pair of dorsal dentiform projections on stalk, rami slender and directed posterodorsally; posterior margin of female sternite VII with small quadrate lobe; first ovipositor valvula with dentiform apex; second ovipositor valvula with apical third directed ventrally. This paper includes the first detailed description and illustrations of the female terminalia of a Dasmeusa species. In addition, the known geographic distribution of the genus is presented; D. pauperata (Fabricius, 1803) is newly recorded from the Brazilian states of Roraima, Amazonas, Pará, Sergipe, and Bahia; the records from the last two states are interesting because they are from areas of Atlantic Forest. Previously, the genus was known only from the Amazon Forest.

Genes and Mechanisms Involved in the Generation and Amplification of Basal Radial Glial Cells.

The development of the cerebral cortex relies on different types of progenitor cell. Among them, the recently described basal radial glial cell (bRG) is suggested to be of critical importance for the development of the brain in gyrencephalic species. These cells are highly numerous in primate and ferret brains, compared to lissencephalic species such as the mouse in which they are few in number. Their somata are located in basal subventricular zones in gyrencephalic brains and they generally possess a basal process extending to the pial surface. They sometimes also have an apical process directed toward the ventricular surface, similar to apical radial glial cells (aRGs) from which they are derived, and whose somata are found more apically in the ventricular zone. bRGs share similarities with aRGs in terms of gene expression (SOX2, PAX6, and NESTIN), whilst also expressing a range of more specific genes (such as HOPX). In primate brains, bRGs can divide multiple times, self-renewing and/or generating intermediate progenitors and neurons. They display a highly specific cytokinesis behavior termed mitotic somal translocation. We focus here on recently identified molecular mechanisms associated with the generation and amplification of bRGs, including bRG-like cells in the rodent. These include signaling pathways such as the FGF-MAPK cascade, SHH, PTEN/AKT, PDGF pathways, and proteins such as INSM, GPSM2, ASPM, TRNP1, ARHGAP11B, PAX6, and HIF1α. A number of these proteins were identified through transcriptome comparisons in human aRGs vs. bRGs, and validated by modifying their activities or expression levels in the mouse. This latter experiment often revealed enhanced bRG-like cell production, even in some cases generating folds (gyri) on the surface of the mouse cortex. We compare the features of the identified cells and methods used to characterize them in each model. These important data converge to indicate pathways essential for the production and expansion of bRGs, which may help us understand cortical development in health and disease.

A new genus and four new species of Cylindropsyllidae Sars, 1909 (Copepoda: Harpacticoida) from the Great Meteor Seamount plateau (North-East Atlantic Ocean), with remarks on the phylogeny and the geographical distribution of the taxon

The Great Meteor Seamount plateau comprises three regions (north, middle, south), and sampling across the whole area, six species of Cylindropsyllidae Sars, 1909 were discovered. These species were homogenously distributed, indicating that the community of Cylindropsyllidae on the plateau was not zonated according to geographical features, but might be influenced by the presence of microhabitats. The new genus Monsmeteoris gen. nov. is characterized by the presence of two segments distally inserted to the swollen segment with aesthetasc on the male antennule, five elements on the antennal enp2, and completely reduced P4 endopod. Two new species, M. wiesheuorum sp. nov. and M. reductus sp. nov. are hereby described. Additionally, two closely related species belonging to Cylindropsyllus Brady, 1880 are described: C. valentini sp. nov. and C. flexibilis sp. nov., having at most two distal setae on the mandibular endopod, the inner seta of P4 enp2 lost, strongly pronounced styliform proximal part of seta V on the caudal rami, and an apical process on the female P3 enp2.

<p class="Body">Ivoria taiensis gen. nov., sp. nov., a remarkable new mite genus from West Africa (Acari: Mesostigmata: Urodinychidae)

A new monotypic genus, Ivoria taiensis gen. nov., sp. nov. (Mesostigmata: Uropodina: Uropodinychidae) is described on the basis of seven females collected in soil samples from Ivory Coast. The new genus has large and robust chelicerae, but it differs from the other Uropodina genera having similar chelicerae in several characters, which are presented in a comparative table. The new genus is placed in the family Urodinychidae based on its long setae h1, chelicerae with an internal sclerotized node, fixed digit of chelicerae apically smooth and devoid of apical processes, corniculi smooth.

Neural Stem Cell Regulation by Adhesion Molecules Within the Subependymal Niche.

In the mammalian adult brain, neural stem cells persist in neurogenic niches. The subependymal zone is the most prolific neurogenic niche in adult rodents, where residing stem cells generate large numbers of immature neurons that migrate into the olfactory bulb, where they differentiate into different types of interneurons. Subependymal neural stem cells derive from embryonic radial glia and retain some of their features like apico-basal polarity, with apical processes piercing the ependymal layer, and a basal process contacting blood vessels, constituting an epithelial niche. Conservation of the cytoarchitecture of the niche is of crucial importance for the maintenance of stem cells and for their neurogenic potential. In this minireview we will focus on extracellular matrix and adhesion molecules in the adult subependymal zone, showing their involvement not only as structural elements sustaining the niche architecture and topology, but also in the maintenance of stemness and regulation of the quiescence-proliferation balance.

Regulation of the apical extension morphogenesis tunes the mechanosensory response of microvilliated neurons.

Multiple types of microvilliated sensory cells exhibit an apical extension thought to be instrumental in the detection of sensory cues. The investigation of the mechanisms underlying morphogenesis of sensory apparatus is critical to understand the biology of sensation. Most of what we currently know comes from the study of the hair bundle of the inner ear sensory cells, but morphogenesis and function of other sensory microvilliated apical extensions remain poorly understood. We focused on spinal sensory neurons that contact the cerebrospinal fluid (CSF) through the projection of a microvilliated apical process in the central canal, referred to as cerebrospinal fluid-contacting neurons (CSF-cNs). CSF-cNs respond to pH and osmolarity changes as well as mechanical stimuli associated with changes of flow and tail bending. In vivo time-lapse imaging in zebrafish embryos revealed that CSF-cNs are atypical neurons that do not lose their apical attachment and form a ring of actin at the apical junctional complexes (AJCs) that they retain during differentiation. We show that the actin-based protrusions constituting the microvilliated apical extension arise and elongate from this ring of actin, and we identify candidate molecular factors underlying every step of CSF-cN morphogenesis. We demonstrate that Crumbs 1 (Crb1), Myosin 3b (Myo3b), and Espin orchestrate the morphogenesis of CSF-cN apical extension. Using calcium imaging in crb1 and espin mutants, we further show that the size of the apical extension modulates the amplitude of CSF-cN sensory response to bending of the spinal cord. Based on our results, we propose that the apical actin ring could be a common site of initiation of actin-based protrusions in microvilliated sensory cells. Furthermore, our work provides a set of actors underlying actin-based protrusion elongation shared by different sensory cell types and highlights the critical role of the apical extension shape in sensory detection.

A new species of Clinodiplosis (Diptera: Cecidomyiidae) causing galls on Banisteriopsis membranifolia (Malpighiaceae), an endemic plant in Brazil

Clinodiplosisquartelensis sp. nov. (holotype male in MNRJ: Brazil, Minas Gerais State), a new gall midge species causing leaf galls on Banisteriopsismembranifolia (A. Juss.) B. Gates (Malpighiaceae), an endemic liana in Brazil, is described based on larva, pupa, adult male and female and its gall is characterized. Galls were collected in Quartel de São João, state of Minas Gerais, Southeastern Brazil. Larvae were removed from the galls and pupae and adults were obtained by rearing. Pupation takes place in the gall. The most important morphological characters were illustrated. The new species is compared with other Neotropical species of Clinodiplosis and belongs to the group with simple tarsal claws, curved beyond tarsus midlength. Clinodiplosisquartelensis sp. nov. shares the male cercus secondarily lobed, the 12th female flagellomere with setulose apical process, the deeply bilobed male hypoproct with convergent lobes, pupa lacking dorsal spines on abdominal segments, and larva with four pairs of setose terminal papillae with C.bellum from that might be distinguished by size of palpus, wing venation, level of sclerotization of eighth abdominal segment in the adults, as well as, by the pupal cephalic dorsal plate and larval spatula.

In Vivo Knockdown of the IP3R1 Calcium Channel Disrupts ER and Actin Morphology, as well as TBC Bulb Maturation in the Apical Processes of Sertoli Cells in Rat Testes

Spermatogenesis is the process by which sperm cells are produced, but at one phase of this process, late stage spermatids are temporarily attached to the apex of Sertoli cells in the seminiferous epithelium. Late spermatids are anchored by large adhesion like junction complexes termed ‘ectoplasmic specializations’ (ESs) that are proposed to be disassembled by novel endocytic structures only found in mammalian Sertoli cells, called ‘tubulobulbar complexes’ (TBCs). Both ESs and TBCs are heavily actin related, with parallel actin arrays and dendritic actin networks respectively being hallmarks of their identities. The endoplasmic reticulum (ER) in the Sertoli cell apical processes surrounding the late spermatids forms an extensive and continuous network. Cisternae of this network form part of the structure of the ESs, participate in a membrane contact site with the bulbs of TBCs, and have a parallel alignment with the surrounding Sertoli cell plasma membrane. Previously, we've localized the IP3R calcium channel to the TBC bulb‐ER contacts as well as other calcium exchange machinery to various parts of the ER in the apical process. Calcium release and exchange have been implicated in processes related to both actin dynamics as well as in fusion and acidification of endocytic components such as endosomes. We've proposed that calcium exchange may be a crucial mechanism in regulating both the actin networks of ESs and TBCs, as well as in facilitating the maturation and fusion of TBC bulbs as they develop into putative endosomes. If calcium exchange from the ER is responsible for regulating the local actin networks and maturation of endocytic components in the apical process, then knocking down the primary calcium release channel of the ER should alter local actin and TBC bulb morphology. To test this, we injected the testes of Sprague Dawley rats with siRNAs against IP3R1 (ITPR1) and collected tissues at 1 day, 2 day, and 3 days post injection and processed the tissues for either western blot, immunofluorescence, or electron microscopy. ITPR1 siRNA treated tissues showed significant morphological alterations to the ER, actin, and TBC bulbs in the apical processes of late spermatids compared to controls. This data supports the hypothesis that ER calcium exchange is an integral component to actin dynamics and TBC bulb maturation in the apical processes of Sertoli cells.Support or Funding InformationNatural Sciences and Engineering Research Council of Canada (NSERC) Discovery Grant awarded to AWV; Alexander Graham Bell Scholarship (NSERC) awarded to AAThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.