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Fong H, Zhou B, Feng H, Luo C, Bai B, Zhang J, Wang Y. Recapitulation of Structure-Function-Regulation of Blood-Brain Barrier under (Patho)Physiological Conditions. Cells 2024; 13:260. [PMID: 38334652 PMCID: PMC10854731 DOI: 10.3390/cells13030260] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2023] [Revised: 01/12/2024] [Accepted: 01/19/2024] [Indexed: 02/10/2024] Open
Abstract
The blood-brain barrier (BBB) is a remarkable and intricate barrier that controls the exchange of molecules between the bloodstream and the brain. Its role in maintaining the stability of the central nervous system cannot be overstated. Over the years, advancements in neuroscience and technology have enabled us to delve into the cellular and molecular components of the BBB, as well as its regulation. Yet, there is a scarcity of comprehensive reviews that follow a logical framework of structure-function-regulation, particularly focusing on the nuances of BBB regulation under both normal and pathological conditions. This review sets out to address this gap by taking a historical perspective on the discovery of the BBB and highlighting the major observations that led to its recognition as a distinct brain barrier. It explores the intricate cellular elements contributing to the formation of the BBB, including endothelial cells, pericytes, astrocytes, and neurons, emphasizing their collective role in upholding the integrity and functionality of the BBB. Furthermore, the review delves into the dynamic regulation of the BBB in physiological states, encompassing neural, humoral, and auto-regulatory mechanisms. By shedding light on these regulatory processes, a deeper understanding of the BBB's response to various physiological cues emerges. This review also investigates the disruption of the BBB integrity under diverse pathological conditions, such as ischemia, infection, and toxin exposure. It elucidates the underlying mechanisms that contribute to BBB dysfunction and explores potential therapeutic strategies that aim to restore the BBB integrity and function. Overall, this recapitulation provides valuable insights into the structure, functions, and regulation of the BBB. By integrating historical perspectives, cellular elements, regulatory mechanisms, and pathological implications, this review contributes to a more comprehensive understanding of the BBB and paves the way for future research and therapeutic interventions.
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Affiliation(s)
- Hin Fong
- Faculty of Medicine, International School, Jinan University, Guangzhou 510632, China; (H.F.); (C.L.); (B.B.)
| | - Botao Zhou
- Department of Physiology, Basic Medical and Public Health School, Jinan University, Guangzhou 510632, China;
| | - Haixiao Feng
- Gies College of Business, University of Illinois Urbana-Champaign, Urbana-Champaign, IL 61801, USA;
| | - Chuoying Luo
- Faculty of Medicine, International School, Jinan University, Guangzhou 510632, China; (H.F.); (C.L.); (B.B.)
| | - Boren Bai
- Faculty of Medicine, International School, Jinan University, Guangzhou 510632, China; (H.F.); (C.L.); (B.B.)
| | - John Zhang
- Department of Physiology and Pharmacology, Loma Linda University, Loma Linda, CA 92350, USA;
- Department of Neurosurgery, Loma Linda University, Loma Linda, CA 92350, USA
| | - Yuechun Wang
- Department of Physiology, Basic Medical and Public Health School, Jinan University, Guangzhou 510632, China;
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Menaceur C, Gosselet F, Fenart L, Saint-Pol J. The Blood-Brain Barrier, an Evolving Concept Based on Technological Advances and Cell-Cell Communications. Cells 2021; 11:cells11010133. [PMID: 35011695 PMCID: PMC8750298 DOI: 10.3390/cells11010133] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2021] [Revised: 12/27/2021] [Accepted: 12/30/2021] [Indexed: 02/07/2023] Open
Abstract
The construction of the blood–brain barrier (BBB), which is a natural barrier for maintaining brain homeostasis, is the result of a meticulous organisation in space and time of cell–cell communication processes between the endothelial cells that carry the BBB phenotype, the brain pericytes, the glial cells (mainly the astrocytes), and the neurons. The importance of these communications for the establishment, maturation and maintenance of this unique phenotype had already been suggested in the pioneering work to identify and demonstrate the BBB. As for the history of the BBB, the evolution of analytical techniques has allowed knowledge to evolve on the cell–cell communication pathways involved, as well as on the role played by the cells constituting the neurovascular unit in the maintenance of the BBB phenotype, and more particularly the brain pericytes. This review summarises the key points of the history of the BBB, from its origin to the current knowledge of its physiology, as well as the cell–cell communication pathways identified so far during its development, maintenance, and pathophysiological alteration.
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MacAulay N. Molecular mechanisms of K + clearance and extracellular space shrinkage-Glia cells as the stars. Glia 2020; 68:2192-2211. [PMID: 32181522 DOI: 10.1002/glia.23824] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Revised: 02/28/2020] [Accepted: 03/04/2020] [Indexed: 12/17/2022]
Abstract
Neuronal signaling in the central nervous system (CNS) associates with release of K+ into the extracellular space resulting in transient increases in [K+ ]o . This elevated K+ is swiftly removed, in part, via uptake by neighboring glia cells. This process occurs in parallel to the [K+ ]o elevation and glia cells thus act as K+ sinks during the neuronal activity, while releasing it at the termination of the pulse. The molecular transport mechanisms governing this glial K+ absorption remain a point of debate. Passive distribution of K+ via Kir4.1-mediated spatial buffering of K+ has become a favorite within the glial field, although evidence for a quantitatively significant contribution from this ion channel to K+ clearance from the extracellular space is sparse. The Na+ /K+ -ATPase, but not the Na+ /K+ /Cl- cotransporter, NKCC1, shapes the activity-evoked K+ transient. The different isoform combinations of the Na+ /K+ -ATPase expressed in glia cells and neurons display different kinetic characteristics and are thereby distinctly geared toward their temporal and quantitative contribution to K+ clearance. The glia cell swelling occurring with the K+ transient was long assumed to be directly associated with K+ uptake and/or AQP4, although accumulating evidence suggests that they are not. Rather, activation of bicarbonate- and lactate transporters appear to lead to glial cell swelling via the activity-evoked alkaline transient, K+ -mediated glial depolarization, and metabolic demand. This review covers evidence, or lack thereof, accumulated over the last half century on the molecular mechanisms supporting activity-evoked K+ and extracellular space dynamics.
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Affiliation(s)
- Nanna MacAulay
- Department of Neuroscience, University of Copenhagen, Copenhagen, Denmark
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Inhibition of brain swelling after ischemia-reperfusion by β-adrenergic antagonists: correlation with increased K+ and decreased Ca2+ concentrations in extracellular fluid. BIOMED RESEARCH INTERNATIONAL 2014; 2014:873590. [PMID: 25478577 PMCID: PMC4247955 DOI: 10.1155/2014/873590] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/31/2014] [Revised: 09/03/2014] [Accepted: 09/10/2014] [Indexed: 12/11/2022]
Abstract
Infarct size and brain edema following ischemia/reperfusion are reduced by inhibitors of the Na+, K+, 2Cl−, and water cotransporter NKCC1 and by β1-adrenoceptor antagonists. NKCC1 is a secondary active transporter, mainly localized in astrocytes, driven by transmembrane Na+/K+ gradients generated by the Na+,K+-ATPase. The astrocytic Na+,K+-ATPase is stimulated by small increases in extracellular K+ concentration and by the β-adrenergic agonist isoproterenol. Larger K+ increases, as occurring during ischemia, also stimulate NKCC1, creating cell swelling. This study showed no edema after 3 hr medial cerebral artery occlusion but pronounced edema after 8 hr reperfusion. The edema was abolished by inhibitors of specifically β1-adrenergic pathways, indicating failure of K+-mediated, but not β1-adrenoceptor-mediated, stimulation of Na+,K+-ATPase/NKCC1 transport during reoxygenation. Ninety percent reduction of extracellular Ca2+ concentration occurs in ischemia. Ca2+ omission abolished K+ uptake in normoxic cultures of astrocytes after addition of 5 mM KCl. A large decrease in ouabain potency on K+ uptake in cultured astrocytes was also demonstrated in Ca2+-depleted media, and endogenous ouabains are needed for astrocytic K+ uptake. Thus, among the ionic changes induced by ischemia, the decrease in extracellular Ca2+ causes failure of the high-K+-stimulated Na+,K+-ATPase/NKCC1 ion/water uptake, making β1-adrenergic activation the only stimulus and its inhibition effective against edema.
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Lasansky A, Wald F. THE EXTRACELLULAR SPACE IN THE TOAD RETINA AS DEFINED BY THE DISTRIBUTION OF FERROCYANIDE : A Light and Electron Microscope Study. ACTA ACUST UNITED AC 2010; 15:463-79. [PMID: 19866612 PMCID: PMC2106175 DOI: 10.1083/jcb.15.3.463] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Measurements of the uptake of compounds that ordinarily do not penetrate into cells have been a source of data on the size of the extracellular space in nervous tissue. The distribution of one such compound, ferrocyanide, has been studied in the toad retina by means of the light and electron microscopes. At the level of the light microscope, ferrocyanide, detected as Prussian blue, appears to penetrate predominantly within the inner processes of Müller cells. A diffuse background staining by Prussian blue can be noticed also at the inner retinal layers. At the level of the electron microscope, Müller cells exhibit an extensively developed system of channels which are formed by infoldings of the plasma membrane. Ferrocyanide, detected as copper ferrocyanide deposits, is found occupying the lumina of these channels and in the narrow intercellular gaps of the retina. These observations indicate that in the toad retina the extracellular medium includes the intercellular spaces plus a glial compartment formed by the infoldings of the plasma membrane of the Müller cells.
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Affiliation(s)
- A Lasansky
- Instituto de Anatomía General y Embriología, Facultad de Ciencias Médicas, Buenos Aires, Argentina
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Siesjö BK. THE BICARBONATE/CARBONIC ACID BUFFER SYSTEM OF THE CEREBRAL CORTEX OF CATS, AS STUDIED IN TISSUE HOMOGENATES. Acta Neurol Scand 2009. [DOI: 10.1111/j.1600-0404.1962.tb01082.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Abstract
Neurons have long held the spotlight as the central players of the nervous system, but we must remember that we have equal numbers of astrocytes and neurons in the brain. Are these cells only filling up the space and passively nurturing the neurons, or do they also contribute to information transfer and processing? After several years of intense research since the pioneer discovery of astrocytic calcium waves and glutamate release onto neurons in vitro, the neuronal-glial studies have answered many questions thanks to technological advances. However, the definitive in vivo role of astrocytes remains to be addressed. In addition, it is becoming clear that diverse populations of astrocytes coexist with different molecular identities and specialized functions adjusted to their microenvironment, but do they all belong to the umbrella family of astrocytes? One population of astrocytes takes on a new function by displaying both support cell and stem cell characteristics in the neurogenic niches. Here, we define characteristics that classify a cell as an astrocyte under physiological conditions. We will also discuss the well-established and emerging functions of astrocytes with an emphasis on their roles on neuronal activity and as neural stem cells in adult neurogenic zones.
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Ribatti D, Nico B, Crivellato E, Artico M. Development of the blood-brain barrier: a historical point of view. ACTA ACUST UNITED AC 2006; 289:3-8. [PMID: 16437552 DOI: 10.1002/ar.b.20087] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Although there has been considerable controversy since the observation by Ehrlich more than 100 years ago that the brain did not take up dyes from the vascular system, the concept of an endothelial blood-brain barrier (BBB) was confirmed by the unequivocal demonstration that the passage of molecules from blood to brain and vice versa was prevented by endothelial tight junctions (TJs). There are three major functions implicated in the term "BBB": protection of the brain from the blood milieu, selective transport, and metabolism or modification of blood- or brain-borne substances. The BBB phenotype develops under the influence of associated brain cells, especially astrocytic glia, and consists of complex TJs and a number of specific transport and enzyme systems that regulate molecular traffic across the endothelial cells. The development of the BBB is a complex process that leads to endothelial cells with unique permeability characteristics due to high electrical resistance and the expression of specific transporters and metabolic pathways. This review article summarizes the historical background underlying our current knowledge of the cellular and molecular mechanisms involved in the development and maintenance of the BBB.
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Affiliation(s)
- Domenico Ribatti
- Department of Human Anatomy and Histology, University of Bari Medical School, Piazza G. Cesare, Bari, Italy.
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11
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Eisner I, Colombo JA. Detection of a novel pattern of connexin 43 immunoreactivity responsive to dehydration in rat hypothalamic magnocellular nuclei. Exp Neurol 2002; 177:321-5. [PMID: 12429234 DOI: 10.1006/exnr.2002.7953] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Immunocytochemical expression of Connexin 43 (Cx 43) in the rat Supraoptic Nucleus was analyzed following dehydration, using sequence-specific anti-Cx 43 antibodies (designated 13-8300, 71-0700, and sc-9059) that exhibit differential recognition of Cx 43. Punctate and longitudinally arranged immunostaining patterns of Cx 43 labeling, as evidenced by antibody sc-9059, was detected overlaying the nucleus of magnocellular neuroendocrine cells. This novel form of longitudinally arranged Cx 43 immunoreactivity was modified by dehydration and halothane exposure, but not lactation.
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Affiliation(s)
- Ines Eisner
- Unidad de Neurobiologia Aplicada (CEMIC-CONICET), Av. Galván 4102, 1431, Buenos Aires, Argentina
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Plesnila N, Muller E, Guretzki S, Ringel F, Staub F, Baethmann A. Effect of hypothermia on the volume of rat glial cells. J Physiol 2000; 523 Pt 1:155-62. [PMID: 10673552 PMCID: PMC2269776 DOI: 10.1111/j.1469-7793.2000.00155.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
1. The cell volume of suspended C6 glioma cells and primary cultured rat astrocytes was measured at normothermia (37 degrees C), and at mild (32 degrees C) and moderate (27 degrees C) hypothermia by flow cytometry with electrical cell sizing. 2. Under control conditions (37 degrees C), C6 glioma cells had a volume of 809 +/- 29 microm3. Moderate hypothermia (27 degrees C) led to rapid cell swelling, with a maximum volume of 113.1 +/- 1.3 % of control being achieved after 50 min. After rewarming to 37 degrees C, cell volume recovered very slowly and incompletely (to 107.2 +/- 0.4 % of control). Less severe hypothermia (32 degrees C) led to a smaller increase in cell volume (108.7 +/- 0.5 % of control). 3. The maximal cell swelling response and the kinetics of swelling were similar in C6 glioma cells and primary cultured astrocytes. 4. Hypothermia-induced cell swelling was dependent on the presence of extracellular Na+ and was reduced by the Na+-H+ antiporter inhibitor EIPA. 5. The underlying mechanisms of hypothermia-induced cell swelling are an intracellular accumulation of Na+ by (1) differential effects of hypothermia on the membrane permeabilities of Na+ and K+ and (2) activation of the Na+-H+ antiporter by a shift of its activation curve to a more alkaline value.
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Affiliation(s)
- N Plesnila
- Institute for Surgical Research, Klinikum Grosshadern, Ludwig-Maximilians-University, Munich, Germany.
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13
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VILAR O, PEREZ DEL CERRO MI, MANCINI RE. The Sertoli cell as a "bridge cell" between the basal membrane and the germinal cells. Histochemical and electron microscope observations. Exp Cell Res 1998; 27:158-61. [PMID: 13925948 DOI: 10.1016/0014-4827(62)90056-3] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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15
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LASANSKY A. Morphological bases for a nursing role of glia in the toad retina. Electron microscope observations. J Biophys Biochem Cytol 1998; 11:237-43. [PMID: 14462570 PMCID: PMC2225124 DOI: 10.1083/jcb.11.1.237] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Key Words] [MESH Headings] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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WALD F, DE ROBERTIS E. The action of glutamate and the problem of the "extracellular space" in the retina. An electron microscope study. Cell Tissue Res 1998; 55:649-61. [PMID: 14004517 DOI: 10.1007/bf00384504] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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17
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BUNGE RP, BUNGE MB. Electron microscopic study of demyelination in an experimentally induced lesion in adult cat spinal cord. J Biophys Biochem Cytol 1998; 7:685-96. [PMID: 13805917 PMCID: PMC2224890 DOI: 10.1083/jcb.7.4.685] [Citation(s) in RCA: 117] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Plaques of subpial demyelination were induced in adult cat spinal cords by repeated withdrawal and reinjection of cerebrospinal fluid. Peripheral cord was fixed by replacing cerebrospinal fluid available at cisternal puncture with 3 per cent buffered OsO4. Following extirpation, surface tissue was further fixed in 2 per cent buffered OsO4, dehydrated in ethanol, and embedded in araldite. Normal subpial cord consists mainly of myelinated axons and two types of macroglia, fibrous astrocytes and oligodendrocytes. Twenty-nine hours after lesion induction most myelin sheaths are deteriorating and typical macroglia are no longer visible. Phagocytosis of myelin debris has begun. In 3-day lesions, axons are intact and their mitochondria and neurofibrils appear normal despite continued myelin breakdown. All axons are completely demyelinated by 6 days. They lack investments only briefly, however, for at 10 and 14 days, macroglial processes appear and embrace them. These macroglia do not resemble either one of the normally occurring glia; their dense cytoplasm contains fibrils in addition to the usual organelles. It is proposed that these macroglia, which later accomplish remyelination, are the hypertrophic or swollen astrocytes of classical neuropathology. The suggestion that these astrocytes possess the potential to remyelinate axons in addition to their known ability to form cicatrix raises the possibility of pharmacological control of their expression.
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Aschner M, Vitarella D, Allen JW, Conklin DR, Cowan KS. Methylmercury-induced astrocytic swelling is associated with activation of the Na+/H+ antiporter, and is fully reversed by amiloride. Brain Res 1998; 799:207-14. [PMID: 9675283 DOI: 10.1016/s0006-8993(98)00399-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Astrocytes are a known 'sink' for brain methylmercury (MeHg) deposition. Yet, the significance of the preferential accumulation of MeHg within these cells is imprecisely defined. To determine whether MeHg in isotonic buffer has the potential to interfere with homeostatic functions, we measured its effect on astrocytic volume using an electrical impedance method [E.R. O'Connor, H.K. Kimelberg, C.R. Keese, I. Giaever, Electrical impedance method for measuring volume changes in astrocytes, Am. J. Physiol. 264 (1993) C471-C478.]. In addition, we have characterized the alterations in astrocytic ion permeability associated with exposure to this organometal. The results show that MeHg rapidly induces astrocytic swelling, and that this effect is secondary to increased astrocytic Na+ uptake. Furthermore, the effect of MeHg on astrocytic swelling is completely inhibited by amiloride, but not by SITS (4-acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic acid), furosemide, or bumetanide. Accordingly, increased cellular permeability to Na+ via the Na+/H+ antiporter is invoked as the primary mechanism of MeHg-induced astrocytic swelling.
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Affiliation(s)
- M Aschner
- Departments of Physiology and Pharmacology, Wake Forest University School of Medicine, Winston-Salem, NC, USA.
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Tamada Y, Tanaka M, Munekawa K, Hayashi S, Okamura H, Kubo T, Hisa Y, Ibata Y. Neuron-glia interaction in the suprachiasmatic nucleus: a double labeling light and electron microscopic immunocytochemical study in the rat. Brain Res Bull 1998; 45:281-7. [PMID: 9510420 DOI: 10.1016/s0361-9230(97)00403-6] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The morphological interactions between astroglial and neuronal elements were elucidated in the rat suprachiasmatic nucleus (SCN) by light and electron microscopic immunocytochemistry using antibodies against glial fibrillary acidic protein (GFAP), vasoactive intestinal peptide (VIP) and arginine-vasopressin (AVP). Throughout the SCN, particularly in its ventral portion, GFAP-like-immunoreactive (GFAP-LI) astroglial elements were found. These astrocytes displaying GFAP-like immunoreactivity occasionally contained fairly well-developed organelles. Some of these astrocytes were found as satellite cells in close contact with non-immunoreactive neuronal perikarya and processes. Around the neurons, GFAP-LI astroglial processes were also observed to cover some portions of presynaptic and postsynaptic elements. In addition, these astroglial elements were seen between two neuronal somata and pericytes of blood capillaries as glial endfeet. By double labeling immunoelectron microscopy using antibodies against GFAP/VIP and GFAP/AVP, some portions of VIP-like-immunoreactive or AVP-like-immunoreactive neuronal somata and processes were found to be engulfed by GFAP-LI astroglial processes. The possible functional roles of the morphological interactions between astroglial and neuronal elements are discussed.
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Affiliation(s)
- Y Tamada
- Department of Anatomy & Neurobiology, Kyoto Prefectural University of Medicine, Japan
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Silver IA, Deas J, Erecińska M. Ion homeostasis in brain cells: differences in intracellular ion responses to energy limitation between cultured neurons and glial cells. Neuroscience 1997; 78:589-601. [PMID: 9145812 DOI: 10.1016/s0306-4522(96)00600-8] [Citation(s) in RCA: 156] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Intracellular concentrations of sodium, potassium and calcium together with membrane potentials were measured in cultured murine cortical neurons and glial cells under conditions which mimicked in vivo hypoxia, ischemia and hypoglycemia. These included; glucose omission with and without added pyruvate, addition of rotenone in the presence and absence of glucose and substitution of 2-deoxyglucose for glucose with and without rotenone. Cellular energy levels ([ATP], [ADP], [phosphocreatine], [creatine]) were measured in suspensions of C6 cells incubated in parallel under identical conditions. [Na+]i and [Ca2+]i rose while [K+]i fell and plasma membrane depolarized when energy production was limited. Intracellular acidification was observed when glycolysis was the sole source for ATP synthesis. There was a positive correlation between the extent of energy depletion in glial cells and the magnitude and velocity of alterations in ion levels. Neither glycolysis alone nor oxidative phosphorylation alone were able to ensure unaltered ion gradients. Since oxidative phosphorylation is much more efficient in generating ATP than glycolysis, this finding suggests a specific requirement of the Na pump for ATP generated by glycolysis. Changes in [Na+]i and [K+]i observed during energy depletion were gradual and progressive whereas those in [Ca2+]i were initially slow and moderate with large elevations occurring only as a late event. Increases in [Na+]i were usually smaller than reductions in [K+]i, particularly in the glia, suggestive of cellular swelling. Glia were less sensitive to identical insults than were neurons under all conditions. Results presented in this study lead to the conclusion that the response to energy deprivation of the two main types of brain cells, neurons and astrocytes, is a complex function of their capacity to produce ATP and the activities of various pathways which are involved in ion homeostasis.
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Affiliation(s)
- I A Silver
- Department of Anatomy, School of Veterinary Science, University of Bristol, U.K
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Abstract
The physicochemical properties of water enable it to act as a solvent for electrolytes, and to influence the molecular configuration and hence the function--enzymatic in particular--of polypeptide chains in biological systems. The association of water with electrolytes determines the osmotic regulation of cell volume and allows the establishment of the transmembrane ion concentration gradients that underlie nerve excitation and impulse conduction. Fluid in the central nervous system is distributed in the intracellular and extracellular spaces (ICS, ECS) of the brain parenchyma, the cerebrospinal fluid, and the vascular compartment--the brain capillaries and small arteries and veins. Regulated exchange of fluid between these various compartments occurs at the blood-brain barrier (BBB), and at the ventricular ependyma and choroid plexus, and, on the brain surface, at the pia mater. The normal BBB is relatively permeable to water, but considerably less so to ions, including the principal electrolytes Brain fluid regulation takes place within the context of systemic fluid volume control, which depends on the mutual interaction of osmo-, volume-, and pressure-receptors in the hypothalamus, heart and kidney, hormones such as vasopressin, renin-angiotensin, aldosterone, atriopeptins, and digitalis-like immunoreactive substance, and their respective sites of action. Evidence for specific transport capabilities of the cerebral capillary endothelium, for example high Na+K(+)-ATPase activity and the presence at the abluminal surface of a Na(+)--H+ antiporter, suggests that cerebral microvessels play a more active part in brain volume regulation and ion homoeostasis than do capillaries in other vascular beds. The normal brain ECS amounts to 12-19% of brain volume, and is markedly reduced in anoxia, ischaemia, metabolic poisoning, spreading depression, and conventional procedures for histological fixation. The asymmetrical distributions of Na+ K+ and Ca2+ between ICS and ECS underlie the roles of these cations in nerve excitation and conduction, and in signal transduction. The relatively large volume of the CSF, and extensive diffusional exchange of many substances between brain ECS and CSF, augment the ion-homeostasing capacity of the ECS. The choroid plexus, in addition to secreting CSF principally by biochemical mechanisms (there is an additional small component from the extracellular fluid), actively transports some substances from the blood (e.g. nucleotides and ascorbic acid), and actively removes others from the CSF. In contrast with CSF secretion, CSF reabsorption is principally a biomechanical process, passively dependent on the CSF-dural sinus pressure gradient. Pathological increases in intracranial water content imply development of an intracranial mass lesion. The additional water may be distributed diffusely within the brain parenchyma as brain oedema, as a cyst, or as increase in ventricular volume due to hydrocephalus. Brain oedema is classified on the basis of pathophysiology into four categories, vasogenic, cytotoxic, osmotic and hydrostatic. The clinical conditions in which brain oedema presents the greatest problems are tumour, ischaemia, and head injury. Peritumoural oedema is predominantly vasogenic and related to BBB dysfunction. Ischaemic oedema is initially cytotoxic, with a shift of Na+ and CI- ions from ECS to ICS, followed by osmotically obliged water, this shift can be detected by diffusion-weighted MRI. Later in the evolution of an ischaemic lesion the oedema becomes vasogenic, with disruption of the BBB. Recent imaging studies in patients with head injury suggest that the development of traumatic brain oedema may follow a biphasic time course similar to that of ischaemic oedema. Hydrocephalus is associated in the great majority of cases with an obstruction to the circulation or drainage of CSF, or, occasionally, with overproduction of CSF by a choroid plexus papilloma. In either case, the consequence is a ris
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Affiliation(s)
- K G Go
- Department of Neurosurgery, University of Groningen, The Netherlands
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TORACK RM. THE EXTRACELLULAR SPACE OF RAT BRAIN FOLLOWING PERFUSION FIXATION WITH GLUTARALDEHYDE AND HYDROXYADIPALDEHYDE. Cell Tissue Res 1996; 66:352-64. [PMID: 14312247 DOI: 10.1007/bf00334717] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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KIBLER RF, O'NEILL RP, ROBIN ED. INTRACELLULAR ACID-BASE RELATIONS OF DOG BRAIN WITH REFERENCE TO THE BRAIN EXTRACELLULAR VOLUME. J Clin Invest 1996; 43:431-43. [PMID: 14135494 PMCID: PMC441936 DOI: 10.1172/jci104928] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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ROBERTSON JD, BODENHEIMER TS, STAGE DE. THE ULTRASTRUCTURE OF MAUTHNER CELL SYNAPSES AND NODES IN GOLDFISH BRAINS. ACTA ACUST UNITED AC 1996; 19:159-99. [PMID: 14069792 PMCID: PMC2106865 DOI: 10.1083/jcb.19.1.159] [Citation(s) in RCA: 297] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
An electron microscope study of goldfish Mauthner cells is reported.1 The cell is covered by a synaptic bed ∼ 5 µ thick containing unusual amounts of extracellular matrix material in which synapses and clear glia processes are implanted. The preterminal synaptic neurites are closely invested by an interwoven layer of filament-containing satellite cell processes. The axoplasm of the club endings contains oriented mitochondria, neurofilaments, neurotubules, and relatively few synaptic vesicles. That of the boutons terminaux contains many unoriented mitochondria and is packed with synaptic vesicles and some glycogen but no neurofilaments or neurotubules. The bare axons of club endings are surrounded by a moderately abundant layer of matrix material. The synaptic membrane complex (SMC) in cross-section shows segments of closure of the synaptic cleft ∼ 0.2 to 0.5 µ long. These alternate with desmosome-like regions of about the same length in which the gap widens to ∼ 150 A and contains a condensed central stratum of dense material. Here, there are also accumulations of dense material in pre- and postsynaptic neuroplasm. The boutons show no such differentiation and the extracellular matrix is largely excluded around them. The axon cap is a dense neuropil of interwoven neural and glial elements free of myelin. It is covered by a closely packed layer of glia cells. The findings are interpreted as suggestive of electrical transmission in the club endings.
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MCDONALD TF. THE IMPORTANCE OF OEDEMA IN ACUTE RADIATION INJURY TO THE CEREBRAL CORTEX OF RATS: AN ELECTRON MICROSCOPE STUDY. Cell Tissue Res 1996; 64:119-28. [PMID: 14316644 DOI: 10.1007/bf00339191] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Newman GC, Hospod FE, Qi H, Patel H. Effects of dextran on hippocampal brain slice water, extracellular space, calcium kinetics and histology. J Neurosci Methods 1995; 61:33-46. [PMID: 8618423 DOI: 10.1016/0165-0270(95)00020-u] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Hippocampal brain slices are valuable models for studying brain function but are compromised by several artifacts, including significant water gain and histologic injury, which occur under certain incubation conditions. Addition of colloid to Krebs-Ringer buffer (K-R) has been shown to eliminate water gain but has not achieved widespread acceptance. We confirm prior observations that dextran and PEG lessen the increase in slice mass during incubation in a dose-dependent manner with no water gain occurring at 4% concentrations. However, we also observe that addition of colloid to standard K-R induces severe neuronal pyknosis. Fortunately, the pyknosis can be eliminated by reduction in buffer osmolarity through adjustment of NaCl, producing markedly improved slice histology in dextran buffer, especially in the CA3 and CA4 regions of the hippocampus which are severely injured when incubated submerged in K-R at 37 degrees C. Extracellular space markers are not affected by either colloid. The volume of distribution for 45Ca is much larger in dextran buffers than in K-R and variability of 45Ca kinetics is also reduced. In the presence of dextran, hypoxia induces significant slice water gain, a relatively selective histologic injury and an alteration of tissue Ca2+ kinetics. Use of dextran buffers may eliminate many troubling brain slice artifacts.
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Affiliation(s)
- G C Newman
- Department of Neurology, HSC T12-020, SUNY at Stony Brook 11794-8121, USA
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Newman GC, Hospod FE, Qi H, Patel H, Trowbridge SD, Patlak CS. Effects of K+, pH and glutamate on 45Ca kinetics in hippocampal brain slices. J Neurosci Methods 1995; 59:111-20. [PMID: 7475241 DOI: 10.1016/0165-0270(94)00201-q] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Altered calcium homeostasis is likely to play a pathogenetic role in cerebral ischemia. In order to further understand which factors associated with ischemia contribute to disturbances of calcium metabolism, the influence of 3 isolated insults, 8 mM K+, pH 6.1 and 1 mM glutamate, on total tissue calcium were studied by analysis of steady-state kinetics of 45Ca in 500 microns hippocampal brain slices. 45Ca kinetics were analyzed with 2 bi-exponential models by non-linear least-squares analysis. Tissue wet weight/protein was measured simultaneously. Each experimental condition produced a unique tissue response. Raising K+ had no effect on tissue water but increased the rate of uptake of Ca2+ into the larger, rapidly equilibrating tissue Ca2+ space. Acidosis reduced tissue water and the amount of Ca2+ in the slowly equilibrating compartment due to enhanced efflux from that space. Glutamate increased tissue water in a time-dependent manner and increased the influx and amount of Ca2+ in the slowly equilibrating space. Combined insults revealed minimal interaction between K+ and acidosis or glutamate, but glutamate with acidosis worsened tissue injury. We discuss the relationship of this technique to other methods for studying tissue calcium and the significance of the observations regarding ischemia.
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Affiliation(s)
- G C Newman
- Department of Neurology, SUNY at Stony Brook 11794-8121, USA
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Affiliation(s)
- I Klatzo
- Stroke Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD
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Aschner M, LoPachin RM. Astrocytes: targets and mediators of chemical-induced CNS injury. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH 1993; 38:329-42. [PMID: 8450560 DOI: 10.1080/15287399309531721] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
It is now well established that a reciprocal relationship exists between neurons and astrocytes, and that this association is vital for mutual differentiation, development, and functioning of both cell types. It had also become apparent that perturbations in astrocytic function may lead to deleterious consequences in juxtaposed neurons. It is therefore possible that neuronal damage induced by chemicals or neuropathic disease involves dissociation of astrocytic-neuronal interactions. The purpose of this review is to explore astrocytic-neuronal interactions, focusing on potential sites of neurotoxicant actions. In developing this thesis, we briefly examine the functional interactions between astrocytes and neurons, followed by specific examples of astrocyte-mediated neurotoxicity.
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Affiliation(s)
- M Aschner
- Department of Pharmacology and Toxicology, Albany Medical College, New York
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Abstract
Perfusion experiments with horseradish peroxidase have established that the morphological substrate of the blood-brain barrier is represented by microvascular endothelial cells. They are characterized by complexly arranged tight junctions and a very low rate of transcytotic vesicular transport. They express transport enzymes, carrier systems and brain endothelial cell-specific molecules of unknown function not expressed by any other endothelial cell population. These blood-brain barrier properties are not intrinsic to these cells but are inducible by the surrounding brain tissue. Type I astrocytes injected into the anterior eye chamber of the rat or onto the chick chorioallantoic membrane are able to induce a host-derived angiogenesis and some blood-brain barrier properties in endothelial cells of non-neural origin. Recently we have shown that this cellular interaction is due to the secretion of a soluble astrocyte derived factor(s). Astrocytes are also implicated in the maintenance, functional regulation and the repair of the blood-brain barrier. Complex interactions between other constituents of the microenvironment surrounding the endothelial cells, such as the basement membrane, pericytes, nerve endings, microglial cells and the extracellular fluid, take place and are required for the proper functioning of the blood-brain barrier, which in addition is regionally different as reflected by endothelial cell heterogeneity.
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Affiliation(s)
- R C Janzer
- Institut Universitaire de Pathologie, Division de Neuropathologie, Lausanne, Switzerland
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Effects of Swelling on Glial Cell Function. ADVANCES IN COMPARATIVE AND ENVIRONMENTAL PHYSIOLOGY 1993. [DOI: 10.1007/978-3-642-77124-8_6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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Lee CM, Tung WL, Young JD. Tachykinin-stimulated inositol phospholipid hydrolysis and taurine release from human astrocytoma cells. J Neurochem 1992; 59:406-14. [PMID: 1378485 DOI: 10.1111/j.1471-4159.1992.tb09386.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The activation of NK1 receptors on U373 MG human astrocytoma cells by substance P (SP) and related tachykinins was accompanied by an increase in taurine release and an accumulation of inositol phosphates. Both of these effects could be inhibited by spantide, a SP receptor antagonist. The relative potency of tachykinins in stimulating 3H-inositol phosphate accumulation correlated very well with their effects in stimulating the release of [3H]-taurine and inhibition 125I-Bolton-Hunter reagent-conjugated SP binding. The effect on [3H]taurine release was mimicked by a protein kinase C (PKC) activator, phorbol 12-myristate 13-acetate (PMA). The inactive phorbol ester analogue 4-alpha-phorbol 12,13-didecanoate, however, was without effect. Both SP- and PMA-induced releases of [3H]-taurine were markedly inhibited by staurosporine, a potent PKC inhibitor. Pretreatment of U373 MG cells with 10 microM PMA for 19 h to down-regulate PKC activity also markedly inhibited both SP- and PMA-induced releases of [3H]-taurine. Treatment of cells with 100 nM SP induced a time-dependent translocation of PKC from the cytosolic fraction to the membrane fraction. These findings are consistent with the hypothesis that an activation of NK1 receptors on U373 MG cells results in the release of inositol phosphates and activation of PKC, which in turn may regulate the release of taurine.
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Affiliation(s)
- C M Lee
- Department of Biochemistry, Faculty of Medicine, Chinese University of Hong Kong, Shatin, New Territories
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Tower DB. A century of neuronal and neuroglial interactions, and their pathological implications: an overview. PROGRESS IN BRAIN RESEARCH 1992; 94:3-17. [PMID: 1287720 DOI: 10.1016/s0079-6123(08)61735-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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Aschner M, Aschner JL. Cellular and molecular effects of trimethyltin and triethyltin: relevance to organotin neurotoxicity. Neurosci Biobehav Rev 1992; 16:427-35. [PMID: 1480339 DOI: 10.1016/s0149-7634(05)80184-8] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Many of the neurotoxic aspects of organotin exposure have been described. Organotin exposure culminates in its accumulation in the CNS and PNS. The clinical picture is dominated by neurological disturbances; yet, the primary basis for their neurotoxicity is unknown. Trimethyltin (TMT) is primarily a CNS neurotoxin affecting neurons within the hippocampal pyramidal band and the fascia dentata. Triethyltin (TET) is a neurotoxin that produces a pathological picture dominated by brain and spinal cord edema. The first part of this review summarizes the current understanding of the interaction of TMT and TET with biologically active sites in the induction of neurotoxicity. In the second part, several hypotheses for the differential neurotoxic effects of these organotins and their shortcomings are discussed.
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Affiliation(s)
- M Aschner
- Department of Pharmacology and Toxicology, Albany Medical College, NY 12208
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Kimelberg HK. Swelling and Volume Control in Brain Astroglial Cells. ADVANCES IN COMPARATIVE AND ENVIRONMENTAL PHYSIOLOGY 1991. [DOI: 10.1007/978-3-642-76226-0_4] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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Abstract
Reye syndrome is an acute non-inflammatory encephalopathy that can be precipitated by toxic, infective, metabolic or hypoxic upsets. The biochemical changes point to mitochondrial dysfunction and this is substantiated by structural changes in mitochondria on electron microscopy. The toxic metabolites that accumulate are similar to those incriminated in hepatic encephalopathy and other metabolic diseases. These metabolites exert their deleterious effects by direct neuronal damage, neurotransmitter blockade, vascular damage, cerebral oedema, hypoxic ischaemic damage, demyelination, retardation of brain growth and neuronal storage. Brain capillary endothelial cells are very rich in mitochondria and mitochondrial disorders can effect the central nervous system primarily, and not just as a consequence of systemic metabolic upset.
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Affiliation(s)
- J K Brown
- Department of Paediatric Neurology, Royal Hospital for Sick Children, Edinburgh, Scotland
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Wolpaw EW, Martin DL. Sulfate-chloride exchange transport in a glioma cell line. BIOCHIMICA ET BIOPHYSICA ACTA 1986; 855:302-11. [PMID: 3947627 DOI: 10.1016/0005-2736(86)90178-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Transport of SO4(2-) was studied in the glioma cell line LRM55 to determine whether it is mediated by the Cl-/HCO3- exchanger or the K+/Cl- cotransporter previously described in these cells (Wolpaw, E.W. and Martin, D.L. (1984) Brain Res. 297, 317-327). 35SO4(2-) influx was saturable with SO4(2-). External SO4(2-) stimulated 35SO4(2-) efflux, indicating an exchange mechanism. External Cl- was a competitive inhibitor of 35SO4(2-) influx. Internal Cl- stimulated 35SO4(2-) influx and external Cl- stimulated 35SO4(2-) efflux, indicating that Cl- is an exchange substrate for the SO4(2-) carrier. Also, SO4(2-) flux was sensitive to SITS, DIDS and furosemide. However, saturating external SO4(2-) did not inhibit 36Cl- influx and did not inhibit 36Cl- efflux via the Cl-/HCO3- exchanger. Moreover, K+ did not stimulate 36Cl- efflux via the Cl-/HCO3- exchanger. Moreover, K+ did not stimulate 35SO4(2-) influx as it does Cl- influx. These findings indicate that SO4(2-) transport into these cells is mediated by an exchange carrier distinct from both the Cl-/HCO3- exchanger and the K+/Cl- cotransporter. While Cl- is an alternative substrate for the SO4(2-) porter, this carrier is responsible for only a minor fraction of total Cl- flux in these cells.
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Hertz L, Kjeldsen CS. Functional role of the potassium-induced stimulation of oxygen uptake in brain slices studied with cesium as a probe. J Neurosci Res 1985; 14:83-93. [PMID: 4020900 DOI: 10.1002/jnr.490140108] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The potassium-induced stimulation of oxygen consumption in brain slices has a threshold value of 15-20 mM potassium, and it reaches its maximum at 35-50 mM. Although this phenomenon now has been known for almost 50 years, its physiological role remains undetermined. One reason for this may be that the high concentrations of potassium that are required for this response also have many other consequences, e.g., a depolarization of the cells, and that the different effects to some extent may mask each other. For this reason this investigation studied the effects of cesium, which evokes a maximal stimulation of oxygen consumption already at 15 mM. Like potassium, concentrations of cesium that stimulate oxygen consumption also lead to an enhanced swelling. Unlike potassium, the sodium content is affected very little by these concentrations of cesium, whereas cesium and chloride contents are increased. On this basis it is concluded that the cesium-induced stimulation of oxygen uptake is a metabolic manifestation of an active uptake of cesium and chloride, which secondarily leads to an uptake of water, i.e., the cesium-induced swelling. Analogously, it is suggested that the potassium-induced stimulation of oxygen uptake represents an active accumulation of potassium and chloride.
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Abstract
Cl- transport was studied in the glioma cell line LRM55 . Our results indicate that LRM55 cells contain two major Cl- transporters, an anion exchanger and a K+/Cl- cotransporter , and that these are similar to the Cl- porters found in primary cultures of astrocytes. The exchanger was studied by measuring fluxes of Cl- (as 36Cl-). 36Cl- flux was trans-stimulated by Cl- or HCO-3 and was inhibited by SITS or furosemide. The K+/Cl- cotransporter was studied by measuring fluxes of 36Cl- and K+ (as 86Rb+). External K+ stimulated 36Cl- influx, and external Cl- stimulated 86Rb+ influx. Furosemide, but not SITS, inhibited the K+/Cl- cotransporter . As in primary cultures of astrocytes, the steady-state concentration of Cl- in LRM55 cells was higher than that predicted from passive equilibration according to the membrane potential. LRM55 cells appear to be a good in vitro model for glial Cl- transport.
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Cervós-Navarro J, Artigas J, Mrsulja BJ. Morphofunctional aspects of the normal and pathological blood-brain barrier. ACTA NEUROPATHOLOGICA. SUPPLEMENTUM 1983; 8:1-19. [PMID: 6346777 DOI: 10.1007/978-3-642-68970-3_1] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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Glial and Neuronal Na+,K+ Pump. ACTA ACUST UNITED AC 1983. [DOI: 10.1016/b978-0-12-008304-6.50011-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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Bosley TM, Woodhams PL, Gordon RD, Balázs R. Effects of anoxia on the stimulated release of amino acid neurotransmitters in the cerebellum in vitro. J Neurochem 1983; 40:189-201. [PMID: 6129287 DOI: 10.1111/j.1471-4159.1983.tb12670.x] [Citation(s) in RCA: 112] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The effect of anoxia and ischemia on the release of amino acid transmitters from cerebellar slices induced by veratridine or high [K+] was studied. Synaptic specificity was tested by examining the tetradotoxin (TTX)-sensitive and the Ca2+-dependent components of stimulated release. Evoked release of endogenous amino acids was investigated in addition to more detailed studies on the stimulated efflux of preloaded [14C]GABA and D-[3H]aspartate (a metabolically more stable anologue of acidic amino acids). [14C]GABA release evoked by either method of stimulation was unaffected by periods of up to 35 min of anoxia and declined moderately by 45 min. In contrast, induced release of D-[3H]Asp increased markedly during anoxia to a peak at about 25 min, followed by a decline when anoxia was prolonged to 45 min. Evidence was obtained that the increased evoked efflux of D'[3H]Asp from anoxic slices was not due to impaired reuptake of the released amino acid and that it was completely reversible by reoxygenation of the slices. Results of experiments examining the evoked release of endogenous amino acids in anoxia were consistent with those obtained with the exogenous amino acids. Only 4 of the 10 endogenous amino acids studied exhibited TTX-sensitive veratridine-induced release under aerobic conditions (glutamate, aspartate, GABA, and glycine). Anoxia for 25 min did not affect the stimulated efflux of these amino acids with the exception of glutamate, which showed a significant increase. Compared with anoxia, effects of ischemia on synaptic function appeared to be more severe. Veratridine-evoked release of [14C]GABA was already depressed by 10 min and that of D-[3H[Asp showed a modest elevation only a 5 min. Stimulated release of D-Asp and labelled GABA declined progressively after 5 min. These findings were compared with changes in tissue ATP concentrations and histology. The latter studies indicated that in anoxia the earliest alterations are detectable in glia and that nerve terminals were the structures by far the most resistant to anoxic damage. The results thus indicated that evoked release of amino acid transmitters in the cerebellum is compromised only by prolonged anoxia in vitro. In addition, it would appear that the stimulated release of glutamate is selectively accentuated during anoxia. This effect may have a bearing on some hypoxic behavioral changes and, perhaps, also on the well-known selective vulnerability of certain neurons during hypoxia.
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Hertz L. Features of astrocytic function apparently involved in the response of central nervous tissue to ischemia-hypoxia. J Cereb Blood Flow Metab 1981; 1:143-53. [PMID: 6120175 DOI: 10.1038/jcbfm.1981.17] [Citation(s) in RCA: 106] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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Roberts F, Hill RG, Osborne RH, Mitchell JF. The effect of depolarizing potassium concentrations on the efflux of GABA from rat dorsal medulla in vivo and from slices and synaptosomes. Brain Res 1979; 178:467-77. [PMID: 509214 DOI: 10.1016/0006-8993(79)90707-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The efflux of [3H]GABA from the dorsal surface of adult rat medulla overlying the dorsal column nuclei (DCN) was found not be influenced by increasing the concentration of potassium in the superfusing solution to 40 mequiv. Similarly, raised potassium was found not to influence the efflux from slices of the dorsal region of the caudal medulla containing the dorsal column nuclei. This lack of effect of raised potassium is not thought to be due to lack of GABAergic terminals in this region because there is good pharmacological evidence for their presence and bacause both electrical stimulation and 100 microM veratridine increased the efflux of [3H]GABA from such slices. Also, 40 mequiv potassium was found to increase the efflux of both endogenous and [3H]GABA from crude synaptosome preparations of this region without influencing the efflux of [14C]sucrose or [3H]leucine. This release of [3H]GABA was calcium-dependent, and was similar whether produced by 20, 40 of 60 mequiv potassium and occurred whether eos or AOAA was used to inhibit GABA metabolism. Release from synaptosomes could also be induced with 100 microM veratridine. Raised potassium was additionally found to prevent the increased efflux from slices produced by electrical stimulation and to increase the efflux from slices prepared from the brains of rats 14 days old. It is suggested that the astrocytic swelling produced by raised potassium concentration restricts the diffusion of GABA away from depolarized terminals.
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Abstract
The introduction of the concept of blood-ocular barriers in the ophthalmic literature is briefly reviewed. Two main blood-ocular barriers are proposed: the blood-aqueous barrier and the blood-retinal barrier. The blood-aqueous barrier is formed by an epithelial barrier located in the nonpigmented layer of the ciliary epithelium and in the posterior iridial epithelium, and by the endothelium of the iridial vessels. Both these layers have tight junctions of the "leaky" type. The pereability of the blood-aqueous barrier shows a significant degree of pressure-dependent diffusion associated with transport activity, resembling the standing gradient osmotic flow model. The blood-retinal barrier is located at two levels, forming an outer barrier in the retinal pigment epithelium and an inner barrier in the endothelial membrane of the retinal vessels. Both these membranes have tight junctions of the "nonleaky" type. The permeability of the blood-retinal barrier resembles cellular permeability in general, diffusion being directly related to the predominant roles of lipid solubility and transport mechanisms. Finally, the clinical significance of the blood-ocular barrier is analyzed. The metabolism of cornea and lens and the regulation of intraocular fluids are directly influenced by the blood-aqueous barrier. Similarly, an alteration of the blood-retinal barrier appears to play an important role in the development of vascular retinopathies, pigment epitheliopathies, and retinal edema.
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Benjamin AM, Okamoto K, Quastel JH. Effects of ammonium ions on spontaneous action potentials and on contents of sodium, potassium, ammonium and chloride ions in brain in vitro. J Neurochem 1978; 30:131-43. [PMID: 621504 DOI: 10.1111/j.1471-4159.1978.tb07044.x] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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