scholarly journals Brain Sensory Organs of the Ascidian Ciona robusta: Structure, Function and Developmental Mechanisms

2021 ◽  
Vol 9 ◽  
Author(s):  
Paola Olivo ◽  
Antonio Palladino ◽  
Filomena Ristoratore ◽  
Antonietta Spagnuolo
Keyword(s):  
Photoreceptor Cells ◽  
Building Blocks ◽  
Sister Group ◽  
Low Complexity ◽  
Pigment Cells ◽  
Sensory Organs ◽  
Larval Brain ◽  
Gravity Perception ◽  
Good Opportunity ◽  
Simplified Approach

During evolution, new characters are designed by modifying pre-existing structures already present in ancient organisms. In this perspective, the Central Nervous System (CNS) of ascidian larva offers a good opportunity to analyze a complex phenomenon with a simplified approach. As sister group of vertebrates, ascidian tadpole larva exhibits a dorsal CNS, made up of only about 330 cells distributed into the anterior sensory brain vesicle (BV), connected to the motor ganglion (MG) and a caudal nerve cord (CNC) in the tail. Low number of cells does not mean, however, low complexity. The larval brain contains 177 neurons, for which a documented synaptic connectome is now available, and two pigmented organs, the otolith and the ocellus, controlling larval swimming behavior. The otolith is involved in gravity perception and the ocellus in light perception. Here, we specifically review the studies focused on the development of the building blocks of ascidians pigmented sensory organs, namely pigment cells and photoreceptor cells. We focus on what it is known, up to now, on the molecular bases of specification and differentiation of both lineages, on the function of these organs after larval hatching during pre-settlement period, and on the most cutting-edge technologies, like single cell RNAseq and genome editing CRISPR/CAS9, that, adapted and applied to Ciona embryos, are increasingly enhancing the tractability of Ciona for developmental studies, including pigmented organs formation.

scholarly journals INHERITED RETINAL DYSTROPHY IN THE RAT

1962 ◽  
Vol 14 (1) ◽  
pp. 73-109 ◽  
Author(s):  
John E. Dowling ◽  
Richard L. Sidman
Keyword(s):  
Pigment Epithelium ◽  
Light And Electron Microscopy ◽  
Retinal Dystrophy ◽  
Photoreceptor Cells ◽  
Pigment Cells ◽  
Membrane Thickness ◽  
Outer Segments ◽  
Progressive Loss ◽  
Retinal Rods ◽  
Microscopy Data

Retinal dystrophies, known in man, dog, mouse, and rat, involve progressive loss of photoreceptor cells with onset during or soon after the developmental period. Functional (electroretinogram), chemical (rhodopsin analyses) and morphological (light and electron microscopy) data obtained in the rat indicated two main processes: (a) overproduction of rhodopsin and an associated abnormal lamellar tissue component, (b) progressive loss of photoreceptor cells. The first abnormality recognized was the appearance of swirling sheets or bundles of extracellular lamellae between normally developing retinal rods and pigment epithelium; membrane thickness and spacing resembled that in normal outer segments. Rhodopsin content reached twice normal values, was present in both rods and extracellular lamellae, and was qualitatively normal, judged by absorption maximum and products of bleaching. Photoreceptors attained virtually adult form and ERG function. Then rod inner segments and nuclei began degenerating; the ERG lost sensitivity and showed selective depression of the a-wave at high luminances. Outer segments and lamellae gradually degenerated and rhodopsin content decreased. No phagocytosis was seen, though pigment cells partially dedifferentiated and many migrated through the outer segment-debris zone toward the retina. Eventually photoreceptor cells and the b-wave of the ERG entirely disappeared. Rats kept in darkness retained electrical activity, rhodopsin content, rod structure, and extracellular lamellae longer than litter mates in light.

Bond analyses of borates from the Inorganic Crystal Structure Database

2006 ◽  
Vol 62 (5) ◽  
pp. 702-709 ◽  
Author(s):  
Daqiu Yu ◽  
Dongfeng Xue
Keyword(s):  
Crystal Structure ◽  
Building Blocks ◽  
Low Complexity ◽  
Bond Valence ◽  
Inorganic Crystal Structure Database ◽  
Bonding Structure ◽  
Structural Evaluation ◽  
Structure Database ◽  
Inorganic Crystal ◽  
Crystal Structure Database

Various fundamental building blocks (FBBs) are observed in the crystallographic structures of oxoborates available in the Inorganic Crystal Structure Database, Version 1.3.3 (2004); the occurrence of borate groups with low complexity is dominant. Bond-valence parameters d 0 of B—O bonds in 758 oxoborates with various FBBs have been calculated using the bond-valence sum model. Some discrepancies in the d 0 values obviously occur if the detailed configurations of FBBs in borate crystals are considered; d 0 is sensitive to the chemical bonding structure of B atoms in the crystallographic framework. Moreover, d 0 values are affected by the existence of interstitial atoms and the substitution of other anionic groups. In addition, the d 0 parameters for B—N, B—S, B—P and B—F bonds are also calculated statistically. Some suitable d 0 data for various borate FBBs are recommended according to their particular configurations, especially for those with low complexity. On the basis of the proposed linear relationship between calculated nonlinear optical (NLO) coefficients of borates and the current d 0 values for various FBBs, it is found that the d 0 values may be regarded as a useful parameter for pre-investigating the NLO properties of borates, leading to an efficient structural evaluation and design of novel borates.

scholarly journals From spiral cleavage to bilateral symmetry: the developmental cell lineage of the annelid brain

BMC Biology ◽  
2019 ◽  
Vol 17 (1) ◽  
Author(s):  
Pavel Vopalensky ◽  
Maria Antonietta Tosches ◽  
Kaia Achim ◽  
Mette Handberg-Thorsager ◽  
Detlev Arendt
Keyword(s):  
Gene Expression ◽  
Cell Lineage ◽  
Cholinergic Neurons ◽  
Bilateral Symmetry ◽  
Specific Cell ◽  
Cleavage Pattern ◽  
Spiral Cleavage ◽  
Sensory Organs ◽  
Larval Brain ◽  
Larval Stages

Abstract Background During early development, patterns of cell division—embryonic cleavage—accompany the gradual restriction of blastomeres to specific cell fates. In Spiralia, which include annelids, mollusks, and flatworms, “spiral cleavage” produces a highly stereotypic, spiral-like arrangement of blastomeres and swimming trochophore-type larvae with rotational (spiral) symmetry. However, starting at larval stages, spiralian larvae acquire elements of bilateral symmetry, before they metamorphose into fully bilateral juveniles. How this spiral-to-bilateral transition occurs is not known and is especially puzzling for the early differentiating brain and head sensory organs, which emerge directly from the spiral cleavage pattern. Here we present the developmental cell lineage of the Platynereis larval episphere. Results Live-imaging recordings from the zygote to the mid-trochophore stage (~ 30 hpf) of the larval episphere of the marine annelid Platynereis dumerilii reveal highly stereotypical development and an invariant cell lineage of early differentiating cell types. The larval brain and head sensory organs develop from 11 pairs of bilateral founders, each giving rise to identical clones on the right and left body sides. Relating the origin of each bilateral founder pair back to the spiral cleavage pattern, we uncover highly divergent origins: while some founder pairs originate from corresponding cells in the spiralian lineage on each body side, others originate from non-corresponding cells, and yet others derive from a single cell within one quadrant. Integrating lineage and gene expression data for several embryonic and larval stages, we find that the conserved head patterning genes otx and six3 are expressed in bilateral founders representing divergent lineage histories and giving rise to early differentiating cholinergic neurons and head sensory organs, respectively. Conclusions We present the complete developmental cell lineage of the Platynereis larval episphere, and thus the first comprehensive account of the spiral-to-bilateral transition in a developing spiralian. The bilateral symmetry of the head emerges from pairs of bilateral founders, similar to the trunk; however, the head founders are more numerous and show striking left-right asymmetries in lineage behavior that we relate to differential gene expression.

scholarly journals The ‘division of labour’ model of eye evolution

2009 ◽  
Vol 364 (1531) ◽  
pp. 2809-2817 ◽  
Author(s):  
Detlev Arendt ◽  
Harald Hausen ◽  
Günter Purschke
Keyword(s):  
Visual Information ◽  
Photoreceptor Cells ◽  
Cell Types ◽  
Division Of Labour ◽  
Pigment Cells ◽  
Sensory Cells ◽  
Cell Type ◽  
Eye Evolution ◽  
Residual Functions ◽  
Light Shading

The ‘division of labour’ model of eye evolution is elaborated here. We propose that the evolution of complex, multicellular animal eyes started from a single, multi-functional cell type that existed in metazoan ancestors. This ancient cell type had at least three functions: light detection via a photoreceptive organelle, light shading by means of pigment granules and steering through locomotor cilia. Located around the circumference of swimming ciliated zooplankton larvae, these ancient cells were able to mediate phototaxis in the absence of a nervous system. This precursor then diversified, by cell-type functional segregation, into sister cell types that specialized in different subfunctions, evolving into separate photoreceptor cells, shading pigment cells (SPCs) or ciliated locomotor cells. Photoreceptor sensory cells and ciliated locomotor cells remained interconnected by newly evolving axons, giving rise to an early axonal circuit. In some evolutionary lines, residual functions prevailed in the specialized cell types that mirror the ancient multi-functionality, for instance, SPCs expressing an opsin as well as possessing rhabdomer-like microvilli, vestigial cilia and an axon. Functional segregation of cell types in eye evolution also explains the emergence of more elaborate photosensory–motor axonal circuits, with interneurons relaying the visual information.

A New Simplified Approach to the Kinematic Analysis and Design of Epicyclic Gearboxes

1995 ◽  
Vol 209 (1) ◽  
pp. 49-53 ◽  
Author(s):  
A A Fogarasy ◽  
M R Smith
Keyword(s):  
Kinematic Analysis ◽  
Building Blocks ◽  
Kinematic Constraint ◽  
Simplified Approach ◽  
Analysis And Design ◽  
Constraint Equations ◽  
Epicyclic Gear ◽  
Simplified Method ◽  
New Type ◽  
Gear Drives

The present paper introduces a much simplified method for the kinematic analysis of epicyclic gear drives. It is based on the concept of the existence of only two basic building blocks and their kinematic constraint equations. These can easily be found by inspection of the relevant kinematic structural diagram. A new type of notation is used which is simpler and more versatile than those of previous methods and is adaptable to depicting the kinematic alternatives of any particular drive without the need for drawing structural diagrams.

scholarly journals Eyes in Staurozoa (Cnidaria): a review

PeerJ ◽  
2019 ◽  
Vol 7 ◽  
pp. e6693
Author(s):  
Lucília Souza Miranda ◽  
Allen Gilbert Collins
Keyword(s):  
Light Intensity ◽  
Recent Literature ◽  
Image Formation ◽  
Photoreceptor Cells ◽  
Pigment Cells ◽  
Light Perception ◽  
Dark Pigment ◽  
Single Origin ◽  
Synchronous Spawning ◽  
Shared Ancestry

The presence of dark pigment spots associated with primary tentacles (or structures derived from them, i.e., rhopalioids) in Staurozoa was recently overlooked in a study on the evolution of cnidarian eyes (defined as a “region made of photoreceptor cells adjacent to pigment cells”, irrespective of image formation, i.e., including all photoreceptive organs). Review of old and recent literature on Staurozoa shows that dark pigment spots are present in virtually all species ofManania, as well as some species ofHaliclystus,Stylocoronella, and probablyCalvadosia. The known ultrastructure of ocelli seems to be compatible with light perception, but no immediate response to changes in light intensity have been observed in the behavior of staurozoans. Therefore, although further studies addressing photic behavior are required, we discuss an earlier hypothesis that the dark spots in some stauromedusae may be related to synchronous spawning, as well as the possible sensorial function of rhopalioids. Observations summarized here suggest a possible ninth independent origin of eyes in Cnidaria, within a lineage of benthic medusae. Alternatively, documented similarity across medusae of Cubozoa, Scyphozoa, and Staurozoa—with eyes being topologically associated with primary tentacles in each of these taxa—could indicate shared ancestry and a single origin of eyes in this clade known as Acraspeda. Information on Staurozoa, one of the least studied groups within Cnidaria, is often neglected in the literature, but correctly recognizing the characters of this class is crucial for understanding cnidarian evolution.

scholarly journals Distributed Video Coding for Video Communication on Mobile Devices and Sensors

2010 ◽  
pp. 375-402
Author(s):  
Peter Lambert ◽  
Stefaan Mys ◽  
Jozef Škorupa ◽  
Jürgen Slowack ◽  
Rik Van de Walle ◽  
...  
Keyword(s):  
Video Coding ◽  
Side Information ◽  
Building Blocks ◽  
Low Complexity ◽  
Distributed Video Coding ◽  
Channel Noise ◽  
Virtual Channel ◽  
Important Research ◽  
Coding Schemes ◽  
Information Generation

In the context of digital video coding, recent insights have led to a new video coding paradigm called Distributed Video Coding, or DVC, characterized by low-complexity encoding and high-complexity decoding, which is in contrast to traditional video coding schemes. This chapter provides a detailed overview of DVC by explaining the underlying principles and results from information theory and introduces a number of application scenarios. It also discusses the most important practical architectures that are currently available. One of these architectures is analyzed step-by-step to provide further details of the functional building blocks, including an analysis of the coding performance compared to traditional coding schemes. Next to this, it is demonstrated that the computational complexity in a video coding scheme can be shifted dynamically from the encoder to the decoder and vice versa by combining conventional and distributed video coding techniques. Lastly, this chapter discusses some currently important research topics of which it is expected that they can further enhance the performance of DVC, i.e., side information generation, virtual channel noise estimation, and new coding modes.

scholarly journals Eyes in Staurozoa (Cnidaria): a review

2019 ◽  
Author(s):  
Lucília Souza Miranda ◽  
Allen Gilbert Collins
Keyword(s):  
Light Intensity ◽  
Recent Literature ◽  
Image Formation ◽  
Photoreceptor Cells ◽  
Pigment Cells ◽  
Light Perception ◽  
Dark Pigment ◽  
Single Origin ◽  
Synchronous Spawning ◽  
Shared Ancestry

The presence of dark pigment spots associated with primary tentacles (or structures derived from them, i.e., rhopalioids) in Staurozoa was recently overlooked in a study on the evolution of cnidarian eyes (defined as a “region made of photoreceptor cells adjacent to pigment cells”, irrespective of image formation, i.e., including all photoreceptive organs). Review of old and recent literature on Staurozoa shows that dark pigment spots are present in virtually all species of Manania, as well as some species of Haliclystus, Stylocoronella, and probably Calvadosia. The known ultrastructure of ocelli seems to be compatible with light perception, but no immediate response to changes in light intensity have been observed in the behavior of staurozoans. Therefore, although further studies addressing photic behavior are required, we discuss an earlier hypothesis that the dark spots in some stauromedusae may be related to synchronous spawning, as well as the possible sensorial function of rhopalioids. Observations summarized here suggest a possible ninth independent origin of eyes in Cnidaria, within a lineage of benthic medusae. Alternatively, documented similarity across medusae of Cubozoa, Scyphozoa, and Staurozoa – with eyes being topologically associated with primary tentacles in each of these taxa – could indicate shared ancestry and a single origin of eyes in this clade known as Acraspeda. Information on Staurozoa, one of the least studied groups within Cnidaria, is often neglected in the literature, but correctly recognizing the characters of this class is crucial for understanding cnidarian evolution.

scholarly journals Eyes in Staurozoa (Cnidaria): a review

2019 ◽  
Author(s):  
Lucília Souza Miranda ◽  
Allen Gilbert Collins
Keyword(s):  
Light Intensity ◽  
Recent Literature ◽  
Image Formation ◽  
Photoreceptor Cells ◽  
Pigment Cells ◽  
Light Perception ◽  
Dark Pigment ◽  
Single Origin ◽  
Synchronous Spawning ◽  
Shared Ancestry

The presence of dark pigment spots associated with primary tentacles (or structures derived from them, i.e., rhopalioids) in Staurozoa was recently overlooked in a study on the evolution of cnidarian eyes (defined as a “region made of photoreceptor cells adjacent to pigment cells”, irrespective of image formation, i.e., including all photoreceptive organs). Review of old and recent literature on Staurozoa shows that dark pigment spots are present in virtually all species of Manania, as well as some species of Haliclystus, Stylocoronella, and probably Calvadosia. The known ultrastructure of ocelli seems to be compatible with light perception, but no immediate response to changes in light intensity have been observed in the behavior of staurozoans. Therefore, although further studies addressing photic behavior are required, we discuss an earlier hypothesis that the dark spots in some stauromedusae may be related to synchronous spawning, as well as the possible sensorial function of rhopalioids. Observations summarized here suggest a possible ninth independent origin of eyes in Cnidaria, within a lineage of benthic medusae. Alternatively, documented similarity across medusae of Cubozoa, Scyphozoa, and Staurozoa – with eyes being topologically associated with primary tentacles in each of these taxa – could indicate shared ancestry and a single origin of eyes in this clade known as Acraspeda. Information on Staurozoa, one of the least studied groups within Cnidaria, is often neglected in the literature, but correctly recognizing the characters of this class is crucial for understanding cnidarian evolution.

scholarly journals Meso-Scale Digital Materials: Modular, Reconfigurable, Lattice-Based Structures

2016 ◽  
Author(s):  
Benjamin Jenett ◽  
Daniel Cellucci ◽  
Christine Gregg ◽  
Kenneth Cheung
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Building Blocks ◽  
Simplified Approach ◽  
Large Structures ◽  
Reconfigurable System ◽  
Structural Applications ◽  
Meso Scale ◽  
Good Agreement

We present a modular, reconfigurable system for building large structures. This system uses discrete lattice elements, called digital materials, to reversibly assemble ultralight structures that are 99.7% air and yet maintain sufficient specific stiffness for a variety of structural applications and loading scenarios. Design, manufacturing, and characterization of modular building blocks are described, including struts, nodes, joints, and build strategies. Simple case studies are shown using the same building blocks in three different scenarios: a bridge, a boat, and a shelter. Field implementation and demonstration is supplemented by experimental data and numerical simulation. A simplified approach for analyzing these structures is presented which shows good agreement with experimental results.

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