scholarly journals JUNCTIONS BETWEEN INTIMATELY APPOSED CELL MEMBRANES IN THE VERTEBRATE BRAIN

1969 ◽  
Vol 40 (3) ◽  
pp. 648-677 ◽  
Author(s):  
M. W. Brightman ◽  
T. S. Reese
Keyword(s):  
Gap Junctions ◽  
Tight Junctions ◽  
Preparative Method ◽  
Uranyl Acetate ◽  
Structural Basis ◽  
Ependymal Cells ◽  
Cerebral Ventricles ◽  
Vertebrate Brain ◽  
Intercellular Movement ◽  
The Brain

Certain junctions between ependymal cells, between astrocytes, and between some electrically coupled neurons have heretofore been regarded as tight, pentalaminar occlusions of the intercellular cleft. These junctions are now redefined in terms of their configuration after treatment of brain tissue in uranyl acetate before dehydration. Instead of a median dense lamina, they are bisected by a median gap 20–30 A wide which is continuous with the rest of the interspace. The patency of these "gap junctions" is further demonstrated by the penetration of horseradish peroxidase or lanthanum into the median gap, the latter tracer delineating there a polygonal substructure. However, either tracer can circumvent gap junctions because they are plaque-shaped rather than complete, circumferential belts. Tight junctions, which retain a pentalaminar appearance after uranyl acetate block treatment, are restricted primarily to the endothelium of parenchymal capillaries and the epithelium of the choroid plexus. They form rows of extensive, overlapping occlusions of the interspace and are neither circumvented nor penetrated by peroxidase and lanthanum. These junctions are morphologically distinguishable from the "labile" pentalaminar appositions which appear or disappear according to the preparative method and which do not interfere with the intercellular movement of tracers. Therefore, the interspaces of the brain are generally patent, allowing intercellular movement of colloidal materials. Endothelial and epithelial tight junctions occlude the interspaces between blood and parenchyma or cerebral ventricles, thereby constituting a structural basis for the blood-brain and blood-cerebrospinal fluid barriers.

Membranous alterations in the cytoplasm and nucleus in a primitive neuroectodermal tumor of the brain

1978 ◽  
Vol 36 (2) ◽  
pp. 628-629
Author(s):  
C. N. Sun ◽  
C. Araoz ◽  
H. J. White
Keyword(s):  
Nuclear Envelope ◽  
Tumor Cells ◽  
Osmium Tetroxide ◽  
Primitive Neuroectodermal Tumor ◽  
Uranyl Acetate ◽  
Neuroectodermal Tumor ◽  
Annulate Lamellae ◽  
Lead Citrate ◽  
Thin Sections ◽  
The Brain

The ultrastructure of a cerebral primitive neuroectodermal tumor has been reported previously. In the present case, we will present some unusual previously unreported membranous structures and alterations in the cytoplasm and nucleus of the tumor cells.Specimens were cut into small pieces about 1 mm3 and immediately fixed in 4% glutaraldehyde in phosphate buffer for two hours, then post-fixed in 1% buffered osmium tetroxide for one hour. After dehydration, tissues were embedded in Epon 812. Thin sections were stained with uranyl acetate and lead citrate.In the cytoplasm of the tumor cells, we found paired cisternae (Fig. 1) and annulate lamellae (Fig. 2) noting that the annulate lamellae were sometimes associated with the outer nuclear envelope (Fig. 3). These membranous structures have been reported in other tumor cells. In our case, mitochondrial to nuclear envelope fusions were often noted (Fig. 4). Although this phenomenon was reported in an oncocytoma, their frequency in the present study is quite striking.

Ultrastructural morphology of neurosecretory neurons in the barnacle Balanus amphitrite

1990 ◽  
Vol 48 (3) ◽  
pp. 434-435
Author(s):  
Grazia Tagliafierro ◽  
Cristiana Crosa ◽  
Marco Canepa ◽  
Tiziano Zanin
Keyword(s):  
Nervous System ◽  
Ultrastructural Level ◽  
Uranyl Acetate ◽  
Balanus Amphitrite ◽  
Neurosecretory Neurons ◽  
The Central Nervous System ◽  
Ultrathin Sections ◽  
Dense Core Granules ◽  
The Brain ◽  
Ocellar Nerve

Barnacles are very specialized Crustacea, with strongly reduced head and abdomen. Their nervous system is rather simple: the brain or supra-oesophageal ganglion (SG) is a small bilobed structure and the toracic ganglia are fused into a single ventral mass, the suboesophageal ganglion (VG). Neurosecretion was shown in barnacle nervous system by histochemical methods and numerous putative hormonal substances were extracted and tested. Recently six different types of dense-core granules were visualized in the median ocellar nerve of Balanus hameri and serotonin and FMRF-amide like substances were immunocytochemically detected in the nervous system of Balanus amphitrite. The aim of the present work is to localize and characterize at ultrastructural level, neurosecretory neuron cell bodies in the VG of Balanus amphitrite.Specimens of Balanus amphitrite were collected in the port of Genova. The central nervous system were Karnovsky fixed, osmium postfixed, ethanol dehydrated and Durcupan ACM embedded. Ultrathin sections were stained with uranyl acetate and lead citrate. Ultrastructural observations were made on a Philips M 202 and Zeiss 109 T electron microscopy.

scholarly journals Enhanced resolution of histochemical distribution of glucose-6-phosphate dehydrogenase activity in rat neural tissue by use of a semipermeable membrane.

1991 ◽  
Vol 39 (7) ◽  
pp. 937-943 ◽  
Author(s):  
M A Philbert ◽  
C M Beiswanger ◽  
T L Roscoe ◽  
D K Waters ◽  
H E Lowndes
Keyword(s):  
Vestibular Nucleus ◽  
Neural Tissue ◽  
Semipermeable Membrane ◽  
G6pd Activity ◽  
Ependymal Cells ◽  
Regional Localization ◽  
Enhanced Resolution ◽  
Membrane Technique ◽  
Glucose 6 Phosphate Dehydrogenase ◽  
The Brain

We examined the histochemical distribution of glucose-6-phosphate dehydrogenase (G6PD) activity in neural tissue using different diffusion barriers. Although polyvinyl alcohol and agar overlays permitted regional localization of G6PD, a semipermeable membrane revealed cellular differences in G6PD activity within populations of neurons. Distribution of G6PD activity in selected regions of the nervous system was examined using the membrane technique. White matter usually exhibited strong G6PD activity. The neuronal somata of the dorsal root ganglia (L4-L6) and anterior horns of the spinal lumbar enlargement demonstrated a variation in activity which was independent of somal size. Satellite cells showed intense activity when the membrane technique was used. Hippocampal pyramidal and granular cells of the dentate gyrus exhibited moderate, uniform G6PD activity, but only weak activity was seen in hippocampal and dentate molecular layers. High levels of activity were observed in the vascular endothelial cells of the brain, spinal cord, and choroid plexus, and in the ependymal cells of the spinal central canal and ventricles of the brain. The superior vestibular nucleus appeared to have little G6PD activity in either the neuron cell bodies or the surrounding parenchyma. The use of a semipermeable membrane for localization of G6PD activity in neural tissues permits enhanced resolution of neuron elements and may provide a more accurate assessment of G6PD activity in histological preparations.

A study of the properties, morphogenetic potencies and prospective fate of outer and inner layers of ectodermal and chordamesodermal regions during gastrulation, in various Anuran amphibians

Development ◽  
1983 ◽  
Vol 75 (1) ◽  
pp. 67-86
Author(s):  
T. A. Dettlaff
Keyword(s):  
Outer Layer ◽  
Normal Development ◽  
Neural Plate ◽  
Ependymal Cells ◽  
Epithelial Layer ◽  
Bombina Bombina ◽  
Cell Layers ◽  
The Brain ◽  
Early Gastrula

In both the ectodermal and the chordamesodermal regions of Anuran embryos, the outer layer of cells possesses epithelial properties and has the same restricted morphogenetic potencies. It is thus interchangeable between the regions, capable of epiboly and, when underlain by notochord material, of the formation of bottle-shaped cells as at the blastoporal groove, and invagination. When taken from the chordamesoderm region, this outer layer has no inducing effect on the ectoderm of the early gastrula. In normal development the outer layer of the neural plate takes an active part in forming the neural tube cavity. It gives rise to the neuroepithelial roof of the diencephalon and medulla oblongata and, when underlain by neuroblasts that develop from the inner cell layers, to ependymal cells of the brain wall. The outer layer of the notochord material is included in the epithelial layer underlying the roof of the gastrocoel - the hypochordal plate. The inner layers of these regions consist of loosely arranged cells and normally have no epithelial properties although, when taken from the ectoderm region, they may acquire such properties upon long-term contact with the environment. However they have wide morphogenetic potencies; the differences in these potencies between cells taken from the various presumptive regions being less than the differences between outer and inner cell layers in each region. Maps are provided which show the arrangement of presumptive rudiments in the ectoderm and chordamesoderm on sagittal sections through Bombina bombina embryos in early and late gastrulation.

Retinal input influences pace of neurogenesis but not cell-type configuration of the visual forebrain

2021 ◽  
Author(s):  
Shachar Sherman ◽  
Koichi Kawakami ◽  
Herwig Baier
Keyword(s):  
Visual Information ◽  
Visual Stimulation ◽  
Ganglion Cells ◽  
Neuronal Cell ◽  
Cell Types ◽  
Vertebrate Brain ◽  
Relative Contribution ◽  
Retinal Input ◽  
And Migration ◽  
The Brain

The brain is assembled during development by both innate and experience-dependent mechanisms1-7, but the relative contribution of these factors is poorly understood. Axons of retinal ganglion cells (RGCs) connect the eye to the brain, forming a bottleneck for the transmission of visual information to central visual areas. RGCs secrete molecules from their axons that control proliferation, differentiation and migration of downstream components7-9. Spontaneously generated waves of retinal activity, but also intense visual stimulation, can entrain responses of RGCs10 and central neurons11-16. Here we asked how the cellular composition of central targets is altered in a vertebrate brain that is depleted of retinal input throughout development. For this, we first established a molecular catalog17 and gene expression atlas18 of neuronal subpopulations in the retinorecipient areas of larval zebrafish. We then searched for changes in lakritz (atoh7-) mutants, in which RGCs do not form19. Although individual forebrain-expressed genes are dysregulated in lakritz mutants, the complete set of 77 putative neuronal cell types in thalamus, pretectum and tectum are present. While neurogenesis and differentiation trajectories are overall unaltered, a greater proportion of cells remain in an uncommitted progenitor stage in the mutant. Optogenetic stimulation of a pretectal area20,21 evokes a visual behavior in blind mutants indistinguishable from wildtype. Our analysis shows that, in this vertebrate visual system, neurons are produced more slowly, but specified and wired up in a proper configuration in the absence of any retinal signals.

scholarly journals Modulating the Blood-Brain Barrier by Light Stimulation of Molecular-Targeted Nanoparticles

2020 ◽  
Author(s):  
Xiaoqing Li ◽  
Vamsidhara Vemireddy ◽  
Qi Cai ◽  
Hejian Xiong ◽  
Peiyuan Kang ◽  
...  
Keyword(s):  
Tight Junction ◽  
Tight Junctions ◽  
Blood Brain Barrier ◽  
Therapeutic Interventions ◽  
Brain Barrier ◽  
Light Stimulation ◽  
Targeted Nanoparticles ◽  
Blood Brain ◽  
The Brain ◽  
Stimulation Of

AbstractThe blood-brain barrier (BBB) tightly regulates the entry of molecules into the brain by tight junctions that seals the paracellular space and receptor-mediated transcytosis. It remains elusive to selectively modulate these mechanisms and to overcome BBB without significant neurotoxicity. Here we report that light stimulation of tight junction-targeted plasmonic nanoparticles selectively opens up the paracellular route to allow diffusion through the compromised tight junction and into the brain parenchyma. The BBB modulation does not impair vascular dynamics and associated neurovascular coupling, or cause significant neural injury. It further allows antibody and adeno-associated virus delivery into local brain regions. This novel method offers the first evidence of selectively modulating BBB tight junctions and opens new avenues for therapeutic interventions in the central nervous system.One Sentence SummaryGentle stimulation of molecular-targeted nanoparticles selectively opens up the paracellular pathway and allows macromolecules and gene therapy vectors into the brain.

scholarly journals Reovirus Neurotropism and Virulence Are Dictated by Sequences in the Head Domain of the Viral Attachment Protein

2018 ◽  
Vol 92 (23) ◽  
Author(s):  
Danica M. Sutherland ◽  
Pavithra Aravamudhan ◽  
Melanie H. Dietrich ◽  
Thilo Stehle ◽  
Terence S. Dermody
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Ependymal Cells ◽  
Attachment Protein ◽  
Newborn Mice ◽  
Viral Attachment ◽  
Head Domain ◽  
Serotype 1 ◽  
The Central Nervous System ◽  
The Brain

ABSTRACTViral capsid components that bind cellular receptors mediate critical functions in viral tropism and disease pathogenesis. Mammalian orthoreoviruses (reoviruses) spread systemically in newborn mice to cause serotype-specific disease in the central nervous system (CNS). Serotype 1 (T1) reovirus infects ependymal cells to cause nonlethal hydrocephalus, whereas serotype 3 (T3) reovirus infects neurons to cause fulminant and lethal encephalitis. This serotype-dependent difference in tropism and concomitant disease is attributed to the σ1 viral attachment protein, which is composed of head, body, and tail domains. To identify σ1 sequences that contribute to tropism for specific cell types in the CNS, we engineered a panel of viruses expressing chimeric σ1 proteins in which discrete σ1 domains have been reciprocally exchanged. Parental and chimeric σ1 viruses were compared for replication, tropism, and disease induction following intracranial inoculation of newborn mice. Viruses expressing T1 σ1 head sequences infect the ependyma, produce relatively lower titers in the brain, and do not cause significant disease. In contrast, viruses expressing T3 σ1 head sequences efficiently infect neurons, replicate to relatively higher titers in the brain, and cause a lethal encephalitis. Additionally, T3 σ1 head-expressing viruses display enhanced infectivity of cultured primary cortical neurons compared with T1 σ1 head-expressing viruses. These results indicate that T3 σ1 head domain sequences promote infection of neurons, likely by interaction with a neuron-specific receptor, and dictate tropism in the CNS and induction of encephalitis.IMPORTANCEViral encephalitis is a serious and often life-threatening inflammation of the brain. Mammalian orthoreoviruses are promising oncolytic therapeutics for humans but establish virulent, serotype-dependent disease in the central nervous system (CNS) of many young mammals. Serotype 1 reoviruses infect ependymal cells and produce hydrocephalus, whereas serotype 3 reoviruses infect neurons and cause encephalitis. Reovirus neurotropism is hypothesized to be dictated by the filamentous σ1 viral attachment protein. However, it is not apparent how this protein mediates disease. We discovered that sequences forming the most virion-distal domain of T1 and T3 σ1 coordinate infection of either ependyma or neurons, respectively, leading to mutually exclusive patterns of tropism and disease in the CNS. These studies contribute new knowledge about how reoviruses target cells for infection in the brain and inform the rational design of improved oncolytic therapies to mitigate difficult-to-treat tumors of the CNS.

The distribution of non-synaptic intercellular junctions during neurone differentiation in the developing spinal cord of the clawed toad

Development ◽  
1975 ◽  
Vol 33 (2) ◽  
pp. 403-417
Author(s):  
Brian P. Hayes ◽  
Alan Roberts
Keyword(s):  
Spinal Cord ◽  
Gap Junctions ◽  
Neural Differentiation ◽  
Electrical Coupling ◽  
Intercellular Junctions ◽  
Ependymal Cells ◽  
Freedom Of Movement ◽  
Ventricular Cells ◽  
Vertebrate Embryos ◽  
Developing Spinal Cord

The distribution of intercellular junctions, other than synapses and their precursors, has beendescribed in the developing spinal cord of Xenopus laevis between the neurula andfree swimming tadpole stages. At the neurocoel, ventricular cells are joined in the apical contactzone by a sequence of junctions which usually has one or more intermediate junctions but often also includes close appositions, gap junctions and desmosomes. This apical complex is more diverse than that reported in other vertebrate embryos and between ependymal cells in the adult central nervous system. Gap junctions are also found between ventricular cells and their processes near the external cord surface. However, no other special junctions occur in this location under the basementlamella which surrounds the cord. Punctate intermediate junctions are generally distributed between undifferentiated and differentiating cells and their processes but were not found in neuropil after stage 28. These results are discussed in relation to cell movements during neural differentiation, possible effects on the freedom of movement of ions and molecules through extracellular pathways in the embryo, and possible intercytoplasmic pathways via gap junctions which may be responsible for the physiologically observed electrical coupling between neural tube cells.

The skull

2013 ◽  
Author(s):  
Martin E. Atkinson
Keyword(s):  
Soft Tissues ◽  
Clinical Importance ◽  
Dental Students ◽  
Structural Basis ◽  
Facial Skeleton ◽  
Lower Jaw ◽  
Temporomandibular Joints ◽  
Maxilla And Mandible ◽  
And Function ◽  
The Brain

Dental students and practitioners require a sound knowledge of the structure, growth, and development of the skull as a whole. The structure of the skull can be examined and studied more efficiently if you have access to a dried skull or one of the very good plastic replica skulls which are now available; you can identify the structures on the diagrams accompanying the following descriptions and examine a skull at the same time to appreciate the size and relationships of individual components. This chapter outlines the basic principles of the development and structure of the skull and includes some reference to individual bones where this makes understanding easier. The more detailed aspects of particular regions of the skull will be covered in the appropriate chapter describing the whole anatomy of that region; it is much easier to learn the parts of the skull in context of overall structure and function rather than learning a long list of bones, foramina, and muscle attachments in isolation from the related soft tissue structures. Only the maxilla and mandible which are bones of significant clinical importance are described as separate bones. As already demonstrated in Chapter 20, the skull is the structural basis f or the anatomy of the head. The skull has many functions. • It encloses and protects the brain. • It provides protective capsules for the eyes and middle and inner ear. • It forms the skeleton of the entrances to the respiratory and gastrointestinal tracts (GIT) through the nose and mouth, respectively. Those skull components that form the entrance to the GIT also house and support the teeth and soft tissues of the oral region as part of this function. As already outlined in Chapter 20, the skull is made up of several bones joined together to form the cranium which articulates with the separate mandible forming the lower jaw at the temporomandibular joints. The cranium specifically refers to the skull without the mandible; the terms ‘skull’ and ‘cranium’ are not strictly synonymous but they are frequently used as though they are. The cranium can be subdivided into the braincase enclosing the brain and the facial skeleton.

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