Aspects of interastrocytic gap junctions in blood-brain barrier in the experimental penumbra area, revealed by transmission electron microscopy and freeze-fracture

1984 ◽  
Vol 40 (5) ◽  
pp. 471-473 ◽  
Author(s):  
P. Cuevas ◽  
J. A. Gutierrez Diaz ◽  
D. Reimers ◽  
M. Dujovny ◽  
F. G. Diaz ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Gap Junctions ◽  
Blood Brain Barrier ◽  
Freeze Fracture ◽  
Brain Barrier ◽  
Blood Brain ◽  
Transmission Electron

scholarly journals Blood-Brain Barrier Dysfunction in Idiopathic Intracranial Hypertension

2019 ◽  
Vol 78 (9) ◽  
pp. 808-818 ◽  
Author(s):  
Md Mahdi Hasan-Olive ◽  
Hans-Arne Hansson ◽  
Rune Enger ◽  
Erlend A Nagelhus ◽  
Per Kristian Eide
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Intracranial Hypertension ◽  
Blood Brain Barrier ◽  
Idiopathic Intracranial Hypertension ◽  
Basement Membranes ◽  
Brain Barrier ◽  
Aqp4 Expression ◽  
Blood Brain ◽  
Transmission Electron

Abstract Idiopathic intracranial hypertension (IIH) is traditionally considered benign and characterized by symptoms related to increased intracranial pressure, including headache and impaired vision. We have previously demonstrated that brains of IIH patients exhibit patchy astrogliosis, increased perivascular expression of the water channel aquaporin-4 (AQP4) as well as degenerating pericyte processes and capillary basement membranes. Given the established association between pericyte degeneration and blood-brain barrier (BBB) dysfunction, we investigated blood protein leakage by light microscopic immunohistochemistry. We also assessed perivascular AQP4 expression by immunogold transmission electron microscopy. The study included 14 IIH patients and 14 reference (REF) subjects undergoing neurosurgery for epilepsy, aneurysm, or tumor. Evidence of BBB dysfunction, measured as area extravasated fibrinogen/fibrin, was significantly more pronounced in IIH than REF individuals. The extent of extravasated fibrinogen was positively correlated with increasing degree of astrogliosis and vascular AQP4 immunoreactivity, determined by light microscopy. Immunogold transmission electron microscopy revealed no overall changes in AQP4 expression at astrocytic vascular endfeet in IIH (n = 8) compared to REF (n = 11) individuals. Our results provide evidence of BBB leakage in IIH, signifying that IIH is a more serious neurodegenerative disease than previously considered.

scholarly journals Inhibition of Gap Junctions Sensitizes Primary Glioblastoma Cells for Temozolomide

Cancers ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 858 ◽  
Author(s):  
Anna-Laura Potthoff ◽  
Dieter Henrik Heiland ◽  
Bernd O. Evert ◽  
Filipe Rodrigues Almeida ◽  
Simon P. Behringer ◽  
...  
Keyword(s):  
Gap Junctions ◽  
Gap Junction ◽  
Blood Brain Barrier ◽  
Brain Barrier ◽  
Glioblastoma Cells ◽  
Primary Glioblastoma ◽  
Blood Brain ◽  
Elevated Activity ◽  
Essential Contribution ◽  
Gap Junction Inhibitor

Gap junctions have recently been shown to interconnect glioblastoma cells to a multicellular syncytial network, thereby allowing intercellular communication over long distances as well as enabling glioblastoma cells to form routes for brain microinvasion. Against this backdrop gap junction-targeted therapies might provide for an essential contribution to isolate cancer cells within the brain, thus increasing the tumor cells’ vulnerability to the standard chemotherapeutic agent temozolomide. By utilizing INI-0602—a novel gap junction inhibitor optimized for crossing the blood brain barrier—in an oncological setting, the present study was aimed at evaluating the potential of gap junction-targeted therapy on primary human glioblastoma cell populations. Pharmacological inhibition of gap junctions profoundly sensitized primary glioblastoma cells to temozolomide-mediated cell death. On the molecular level, gap junction inhibition was associated with elevated activity of the JNK signaling pathway. With the use of a novel gap junction inhibitor capable of crossing the blood–brain barrier—thus constituting an auspicious drug for clinical applicability—these results may constitute a promising new therapeutic strategy in the field of current translational glioblastoma research.

scholarly journals Applicability of Freeze-Fracture and Cryo-TEM to Complex Liquids

1992 ◽  
Vol 00 (7) ◽  
pp. 9-9
Author(s):  
Janet L. Burns ◽  
Richard J. Spontak
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Sample Preparation ◽  
Freeze Fracture ◽  
Traditional Methods ◽  
Conventional Transmission Electron Microscopy ◽  
Transmission Electron ◽  
Multicomponent Complex ◽  
Complex Liquids

Traditional methods of sample preparation and analysis in conventional transmission electron microscopy (TEM) are not readily applicable to multicomponent complex liquids which may contain a wealth of microstructural information. Two techniques which facilitate the study of structure in such liquids are freeze-fracture (FF) TEM and cryo-TEM.

scholarly journals A circadian clock in the blood-brain barrier regulates xenobiotic efflux from the brain

2017 ◽  
Author(s):  
Shirley L. Zhang ◽  
Zhifeng Yue ◽  
Denice M. Arnold ◽  
Amita Sehgal
Keyword(s):  
Gap Junctions ◽  
Blood Brain Barrier ◽  
Time Of Day ◽  
Brain Barrier ◽  
Circadian Regulation ◽  
List Type ◽  
Intracellular Magnesium ◽  
Therapeutic Implications ◽  
Blood Brain ◽  
The Central Nervous System

HighlightsThe Drosophila BBB displays a circadian rhythm of permeabilityCyclic efflux driven by a clock in the BBB underlies the permeability rhythmCircadian control is non-cell-autonomous via gap junction regulation of [Mg2+]iAn anti-seizure drug is more effective when administered at nightSummaryEndogenous circadian rhythms are thought to modulate responses to external factors, but mechanisms that confer time-of-day differences in organismal responses to environmental insults / therapeutic treatments are poorly understood. Using a xenobiotic, we find that permeability of the Drosophila “blood”-brain barrier (BBB) is higher at night. The permeability rhythm is driven by circadian regulation of efflux and depends upon a molecular clock in the perineurial glia of the BBB, although efflux transporters are restricted to subperineurial glia (SPG). We show that transmission of circadian signals across the layers requires gap junctions, which are expressed cyclically. Specifically, during nighttime gap junctions reduce intracellular magnesium ([Mg2+]i), a positive regulator of efflux, in SPG. Consistent with lower nighttime efflux, nighttime administration of the anti-epileptic phenytoin is more effective at treating a Drosophila seizure model. These findings identify a novel mechanism of circadian regulation and have therapeutic implications for drugs targeted to the central nervous system.

Identification and distribution of gap junctions in the mesoderm of the developing chick limb bud

Development ◽  
1978 ◽  
Vol 46 (1) ◽  
pp. 99-110
Author(s):  
Robert O. Kelley ◽  
John F. Fallon
Keyword(s):  
Electron Microscopy ◽  
Gap Junctions ◽  
Limb Development ◽  
Freeze Fracture ◽  
Mesenchymal Cells ◽  
Limb Bud ◽  
Metabolic Coupling ◽  
Transmission Electron ◽  
Communicating Junctions ◽  
Cell Processes

Sub-ridge, core, anterior and posterior borders of mesoderm were dissected from stages 22–24 chick wing buds to investigate whether structures for intercellular coupling develop between mesenchymal cells. Fine structure was examined using techniques of transmission electron microscopy, freeze-fracture and scanning electron microscopy. Gap (communicating) junctions which were observed between mesenchymal cells of all limb bud regions were distributed between apposed cell bodies, points of contact between cell processes and other cell bodies, and between contacting tips of slender cell projections. In addition, particularly in the subridge region, filopodia were observed to extend through the intercellular matrix to contact other cells several micrometers distant. The observations reported in this paper show that mesodermal cells throughout the limb have the structural capability for electrotonic and metabolic coupling during a critical period of morphogensisis in the avian limb. Whether intercellular signals which are thought to be transmitted through gap junctions are active in normal limb development remains to be investigated.

scholarly journals An Electron Microscopic Immunogold Analysis of Developmental Up-Regulation of the Blood—Brain Barrier GLUT1 Glucose Transporter

1993 ◽  
Vol 13 (5) ◽  
pp. 841-854 ◽  
Author(s):  
Eain M. Cornford ◽  
Shigeyo Hyman ◽  
William M. Pardridge
Keyword(s):  
Electron Microscopy ◽  
Blood Brain Barrier ◽  
Glucose Transporter ◽  
Polyclonal Antiserum ◽  
Brain Barrier ◽  
Rabbit Brain ◽  
Immunogold Electron Microscopy ◽  
Electron Microscopic ◽  
Brain Capillary ◽  
Blood Brain

Electron microscopy was used to quantitate blood–brain barrier (BBB) glucose transporters in newborn, 14-day-old suckling, 28-day-old weanling, and adult rabbits. A rabbit polyclonal antiserum to a synthetic peptide encoding the 13 C-terminal amino acids of the human erythrocyte glucose transporter (GLUT1) was labeled with 10-nm gold particle–secondary antibody conjugates and localized immunoreactive GLUT1 molecules in rabbit brain capillary endothelia. Three distinct populations of brain capillary profiles were identified in newborn rabbits: prepatent capillary buds, partially patent capillaries with highly amplified luminal membranes, and patent capillaries. Immunogold analyses indicated that the GLUT1 transporter abundance positively correlated with capillary developmental status. The mean number of gold particles per capillary profile increased at each developmental age examined, suggesting that developmental up-regulation of the BBB glucose transporter occurred in rabbits. GLUT1 immunoreactivity was three- to fourfold greater on the abluminal than luminal capillary membranes among all ages examined. Changes in the proportions of GLUT1 transporter were also seen, and possible reasons for the postnatal decrease in the percentage of cytoplasmic GLUT1 transporter are discussed. The numbers of cytoplasmic and membrane-associated immunogold particles increased with age. We conclude that regulatory modulations of BB glucose transport may be characterized by increases in BBB glucose transporter density with age and state of development. In addition, modulation of glucose transporter activity may be reflected by minor postnatal shifts of GLUT1 from cytoplasmic to membrane compartments, which can be demonstrated with quantitative immunogold electron microscopy.

A freeze-fracture study of the cuticle of adult Nippostrongylus brasiliensis (Nematoda)

Parasitology ◽  
1993 ◽  
Vol 107 (5) ◽  
pp. 545-552 ◽  
Author(s):  
D. L. Lee ◽  
K. A. Wright ◽  
R. R. Shivers
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Freeze Fracture ◽  
Surface Coat ◽  
Nippostrongylus Brasiliensis ◽  
Freeze Fracturing ◽  
Transmission Electron ◽  
Fracture Study ◽  
20 Nm

SUMMARYThe surface of the cuticle of adult Nippostrongylus brasiliensis has been studied by means of the freeze-fracture technique and by transmission electron microscopy. Some of the surface coat appears to have been shed from the surface of the cuticle of adults fixed in situ in the intestine of its host and from the surface of individuals removed from the intestine and freeze-fractured. Freeze-fracturing the cuticle of individuals removed from the host has shown that this surface coat varies in thickness from 30 to 90 nm. The epicuticle is about 20 nm thick and cleaves readily to expose E- and P-faces. The P-face of the epicuticle possesses a small number of particles, similar to intra-membranous particles, whilst the E-face possesses a few, widely scattered depressions. Despite the presence of these particles the epicuticle is not considered to be a true membrane. Freeze-fracturing the remainder of the cuticle has confirmed its structure as described by conventional transmission electron microscopy. Clusters of particles on the P-face of the outer epidermal (hypodermal) membrane and corresponding depressions on the E-face of the membrane are thought to be associated with points of attachment of the cuticle to the epidermis (hypodermis). No differences in appearance of the cuticle and its surface layers were observed in individuals taken from 7-, 10-, 13- and 15-day infections.

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