scholarly journals Metabolic mechanisms of development and compensation of osmotic stress in the brain

2017 ◽  
Vol 14 (4) ◽  
pp. 73-76 ◽  
Author(s):  
Ekaterina A. Pigarova ◽  
Larisa K. Dzeranova
Keyword(s):  
Cerebrospinal Fluid ◽  
Osmotic Stress ◽  
Interstitial Fluid ◽  
Rapid Change ◽  
Extracellular Fluid ◽  
Plasma Osmolality ◽  
Compensatory Mechanisms ◽  
Passive Permeability ◽  
Mechanisms Of Development ◽  
The Brain

Extracellular fluid of the brain, consisting of cerebrospinal fluid and interstitial fluid, is normally isotonic to blood plasma. Problems arise with a rapid change in osmolality of circulating blood or interstitial brain fluid. The permeability of the blood-brain barrier is lower than in the peripheral capillaries, but this permeability is still several times greater than the passive permeability for electrolytes or glucose. Because of this difference, it is believed that the brain is like an osmometer: it swells with reduced plasma osmolality and contracts (dehydrated) when the plasma becomes hypertonic. Osmotic stress has a direct effect on the functioning of the brain and triggers physiological compensatory mechanisms, in the absence of which due to the intensity or duration of stress, irreversible serious complications may develop. Knowledge and understanding of these processes are the basis for preventing their development and treatment.

Volume influences on thirst and vasopressin secretion in dehydrated sheep

1986 ◽  
Vol 251 (3) ◽  
pp. R621-R626
Author(s):  
R. G. Park ◽  
M. Congiu ◽  
D. A. Denton ◽  
M. J. McKinley
Keyword(s):  
Water Intake ◽  
Water Consumption ◽  
Interstitial Fluid ◽  
Extracellular Fluid ◽  
Plasma Osmolality ◽  
Fluid Volume ◽  
Experimental Protocol ◽  
Vasopressin Secretion ◽  
Total Body ◽  
Reduced Water

The contribution of extracellular fluid volume (ECFV) to water consumption and plasma vasopressin concentration (PAVP) after water deprivation for 52 h was examined in sheep. Intravenous infusion of isotonic NaCl, equivalent to either estimated ECFV loss or total body water loss, significantly reduced water intake by 37% when water was offered 3 h after infusion but not when water was offered 1 h after infusion. Plasma osmolality (POsm) was reduced after 3 h. Infusion of 200 mM NaCl, which maintained POsm, decreased water consumption by the same degree as isotonic NaCl infusion. Thus large decreases in POsm had no effect on water intake in this experimental protocol. Lack of inhibition of drinking 1 h after infusion suggests that the decrease observed after 3 h may have been mediated by receptors in the interstitial fluid (ISF) compartment and not the intravascular compartment. PAVP was reduced 3 h after infusion of NaCl but not at 1 or 2 h after infusion. POsm was also decreased at 3 h. Thus reduction of PAVP by NaCl infusion may have been caused by either ISF or intracellular fluid volume expansion.

Changes in brain surface pH during acute isocapnic metabolic acidosis and alkalosis

1981 ◽  
Vol 51 (2) ◽  
pp. 276-281 ◽  
Author(s):  
S. Javaheri ◽  
A. Clendening ◽  
N. Papadakis ◽  
J. S. Brody
Keyword(s):  
Cerebrospinal Fluid ◽  
Metabolic Acidosis ◽  
Interstitial Fluid ◽  
Acid Base ◽  
Surface Ph ◽  
Brain Surface ◽  
Arterial Blood ◽  
Anesthetized Dogs ◽  
The Mean ◽  
The Brain

It has been thought that the blood-brain barrier is relatively impermeable to changes in arterial blood H+ and OH- concentrations. We have measured the brain surface pH during 30 min of isocapnic metabolic acidosis or alkalosis induced by intravenous infusion of 0.2 N HCl or NaOH in anesthetized dogs. The mean brain surface pH fell significantly by 0.06 and rose by 0.04 pH units during HCl or NaOH infusion, respectively. Respective changes were also observed in the calculated cerebral interstitial fluid [HCO-3]. There were no significant changes in cisternal cerebrospinal fluid acid-base variables. It is concluded that changes in arterial blood H+ and OH- concentrations are reflected in brain surface pH relatively quickly. Such changes may contribute to acute respiratory adaptations in metabolic acidosis and alkalosis.

Cerebrospinal fluid formation and absorption in dehydrated sheep

1998 ◽  
Vol 275 (2) ◽  
pp. F235-F238 ◽  
Author(s):  
Adam Chodobski ◽  
Joanna Szmydynger-Chodobska ◽  
Michael J. McKinley
Keyword(s):  
Cerebrospinal Fluid ◽  
Adaptive Response ◽  
Venous Pressure ◽  
Extracellular Fluid ◽  
Cerebral Ventricles ◽  
Central Venous ◽  
Ventriculocisternal Perfusion ◽  
Fluid Formation ◽  
The Brain ◽  
Csf Production

Cerebrospinal fluid (CSF) plays an important role in the brain’s adaptive response to acute osmotic disturbances. In the present experiments, the effect of 48-h dehydration on CSF formation and absorption rates was studied in conscious adult sheep. Animals had cannulas chronically implanted into the lateral cerebral ventricles and cisterna magna to enable the ventriculocisternal perfusion. A 48-h water deprivation altered neither CSF production nor resistance to CSF absorption. However, in the water-depleted sheep, intraventricular pressure tended to be lower than that found under control conditions. This likely resulted from decreased extracellular fluid volume and a subsequent drop in central venous pressure occurring in dehydrated animals. In conclusion, our findings provide evidence for the maintenance of CSF production during mild dehydration, which may play a role in the regulation of fluid balance in the brain during chronic hyperosmotic stress.

scholarly journals Cerebrospinal Fluid and Interstitial Fluid Motion via the Glymphatic Pathway Modelled by Optimal Mass Transport

2016 ◽  
Author(s):  
Vadim Ratner ◽  
Yi Gao ◽  
Hedok Lee ◽  
Maikan Nedergaard ◽  
Helene Benveniste ◽  
...  
Keyword(s):  
Cerebrospinal Fluid ◽  
Interstitial Fluid ◽  
Initial Conditions ◽  
Fluid Motion ◽  
Flow Patterns ◽  
Brain Parenchyma ◽  
Fluid Exchange ◽  
Waste Products ◽  
Glymphatic Pathway ◽  
The Brain

It was recently shown that the brain-wide cerebrospinal fluid (CSF) and interstitial fluid exchange system designated the `glymphatic pathway' plays a key role in removing waste products from the brain, similarly to the lymphatic system in other body organs [1,2]. It is therefore important to study the flow patterns of glymphatic transport through the live brain in order to better understand its functionality in normal and pathological states. Unlike blood, the CSF does not flow rapidly through a network of dedicated vessels, but rather through peri-vascular channels and brain parenchyma in a slower time-domain, and thus conventional fMRI or other blood-flow sensitive MRI sequences do not provide much useful information about the desired flow patterns. We have accordingly analyzed a series of MRI images, taken at different times, of the brain of a live rat, which was injected with a paramagnetic tracer into the CSF via the lumbar intrathecal space of the spine. Our goal is twofold: (a) find glymphatic (tracer) flow directions in the live rodent brain; and (b) provide a model of a (healthy) brain that will allow the prediction of tracer concentrations given initial conditions. We model the liquid flow through the brain by the diffusion equation. We then use the Optimal Mass Transfer (OMT) approach [3] to model the glymphatic flow vector field, and estimate the diffusion tensors by analyzing the (changes in the) flow. Simulations show that the resulting model successfully reproduces the dominant features of the experimental data.

scholarly journals The Brain-Nose Interface: A Potential Cerebrospinal Fluid Clearance Site in Humans

2022 ◽  
Vol 12 ◽  
Author(s):  
Neel H. Mehta ◽  
Jonah Sherbansky ◽  
Angela R. Kamer ◽  
Roxana O. Carare ◽  
Tracy Butler ◽  
...  
Keyword(s):  
Cerebrospinal Fluid ◽  
Animal Species ◽  
Immune Surveillance ◽  
Cranial Nerves ◽  
Extracellular Fluid ◽  
Olfactory Nerve ◽  
Brain Functions ◽  
Treatment Considerations ◽  
Physiological Homeostasis ◽  
The Brain

The human brain functions at the center of a network of systems aimed at providing a structural and immunological layer of protection. The cerebrospinal fluid (CSF) maintains a physiological homeostasis that is of paramount importance to proper neurological activity. CSF is largely produced in the choroid plexus where it is continuous with the brain extracellular fluid and circulates through the ventricles. CSF movement through the central nervous system has been extensively explored. Across numerous animal species, the involvement of various drainage pathways in CSF, including arachnoid granulations, cranial nerves, perivascular pathways, and meningeal lymphatics, has been studied. Among these, there is a proposed CSF clearance route spanning the olfactory nerve and exiting the brain at the cribriform plate and entering lymphatics. While this pathway has been demonstrated in multiple animal species, evidence of a similar CSF egress mechanism involving the nasal cavity in humans remains poorly consolidated. This review will synthesize contemporary evidence surrounding CSF clearance at the nose-brain interface, examining across species this anatomical pathway, and its possible significance to human neurodegenerative disease. Our discussion of a bidirectional nasal pathway includes examination of the immune surveillance in the olfactory region protecting the brain. Overall, we expect that an expanded discussion of the brain-nose pathway and interactions with the environment will contribute to an improved understanding of neurodegenerative and infectious diseases, and potentially to novel prevention and treatment considerations.

Cerebrospinal Fluid, Brain Electrolytes Balance, and the Unsuspected Intrinsic Property of Melanin to Dissociate the Water Molecule

2018 ◽  
Vol 17 (10) ◽  
pp. 743-756 ◽  
Author(s):  
Arturo Solís Herrera ◽  
Ghulam Md Ashraf ◽  
María del Carmen Arias Esparza ◽  
Vadim V. Tarasov ◽  
Vladimir N. Chubarev ◽  
...  
Keyword(s):  
Cerebrospinal Fluid ◽  
Extracellular Fluid ◽  
Intrinsic Property ◽  
Fluid Secretion ◽  
Current View ◽  
Formidable Challenge ◽  
Fluid Production ◽  
Fluid Transfer ◽  
The Brain

Background & Objective: Regulation of composition, volume and turnover of fluids surrounding the brain and damp cells is vital. These fluids transport all substances required for cells and remove the unwanted materials. This regulation tends to act as barrier to prevent free exchange of materials between the brain and blood. There are specific mechanisms concerned with fluid secretion of the controlled composition of the brain, and others responsible for reabsorption eventually to blood and the extracellular fluid whatever their composition is. The current view assumes that choroidal plexuses secrete the major part of Cerebrospinal Fluid (CSF), while the Blood-Brain Barrier (BBB) has a much less contribution to fluid production, generating Interstitial Fluid (ISF) that drains to CSF. The skull is a rigid box; thereby the sum of volumes occupied by the parenchyma with its ISF, related connective tissue, the vasculature, the meninges and the CSF must be relatively constant according to the Monroe-Kellie dogma. This constitutes a formidable challenge that normal organisms surpass daily. The ISF and CSF provide water and solutes influx and efflux from cells to these targeted fluids in a quite precise way. Microvessels within the parenchyma are sufficiently close to every cell where diffusion areas for solutes are tiny. Despite this, CSF and ISF exhibit very similar compositions, but differ significantly from blood plasma. Many hydrophilic substances are effectively prevented from the entry into the brain via blood, while others like neurotransmitters are extremely hindered from getting out of the brain. Anatomical principle of the barrier and routes of fluid transfer cannot explain the extraordinary accuracy of fluids and substances needed to enter or leave the brain firmly. There is one aspect that has not been deeply analyzed, despite being prevalent in all the above processes, it is considered a part of the CSF and ISF dynamics. This aspect is the energy necessary to propel them properly in time, form, space, quantity and temporality. Conclusion: The recent hypothesis based on glucose and ATP as sources of energy presents numerous contradictions and controversies. The discovery of the unsuspected intrinsic ability of melanin to dissociate and reform water molecules, similar to the role of chlorophyll in plants, was confirmed in the study of ISF and CSF biology.

scholarly journals Epithelial Pathways in Choroid Plexus Electrolyte Transport

Physiology ◽  
2010 ◽  
Vol 25 (4) ◽  
pp. 239-249 ◽  
Author(s):  
Helle H. Damkier ◽  
Peter D. Brown ◽  
Jeppe Praetorius
Keyword(s):  
Cerebrospinal Fluid ◽  
Chemical Composition ◽  
Choroid Plexus ◽  
Interstitial Fluid ◽  
Electrolyte Transport ◽  
Molecular Pathways ◽  
Choroid Plexus Epithelium ◽  
Neuronal Function ◽  
The Brain

A stable intraventricular milieu is crucial for maintaining normal neuronal function. The choroid plexus epithelium produces the cerebrospinal fluid and in doing so influences the chemical composition of the interstitial fluid of the brain. Here, we review the molecular pathways involved in transport of the electrolytes Na+, K+, Cl−, and HCO3− across the choroid plexus epithelium.

scholarly journals Interstitial and cerebrospinal fluid exchanging process revealed by phase alternate labeling with null recovery MRI

2021 ◽  
Author(s):  
Anna M Li ◽  
Jiadi Xu
Keyword(s):  
Cerebrospinal Fluid ◽  
Fluid Flow ◽  
Interstitial Fluid ◽  
Interstitial Fluid Flow ◽  
Cerebrospinal Fluid Flow ◽  
Recovery Curves ◽  
Ependymal Layer ◽  
Apparent Diffusion ◽  
The Difference ◽  
The Brain

Purpose: To develop Phase Alternate LAbeling with Null recovery (PALAN) MRI methods for the quantification of interstitial to cerebrospinal fluid flow (ICF) and cerebrospinal to interstitial fluid flow (CIF) in the brain. Method: In both T1-PALAN and apparent diffusion coefficient (ADC)-PALAN MRI methods, the cerebrospinal fluid (CSF) signal was nulled, while the residual interstitial fluid (ISF) was labeled by alternating the phase of pulses. ICF was extracted from the difference between the recovery curves of CSF with and without labeling. Similarly, CIF was measured by the T2-PALAN MRI method by labeling CSF, which took advance of the significant T2 difference between CSF and parenchyma. Results: Both T1-PALAN and ADC-PALAN observed a rapid occurrence of ICF at 67±56 ms and 13±2 ms interstitial fluid transit times, respectively. ICF signal peaked at 1.5 s for both methods. ICF was 1153±270 ml/100ml/min with T1-PALAN in the third and lateral ventricles, which was higher than 891±60 ml/100ml/min obtained by ADC-PALAN. The results of the T2-PALAN suggested the ISF exchanging from ependymal layer to the parenchyma was extremely slow. Conclusion: The PALAN methods are suitable tools to study ISF and CSF flow kinetics in the brain.

scholarly journals Fluid Dynamics Inside the Brain Barrier: Current Concept of Interstitial Flow, Glymphatic Flow, and Cerebrospinal Fluid Circulation in the Brain

2018 ◽  
Vol 25 (2) ◽  
pp. 155-166 ◽  
Author(s):  
Tsutomu Nakada ◽  
Ingrid L. Kwee
Keyword(s):  
Fluid Dynamics ◽  
Cerebrospinal Fluid ◽  
Interstitial Fluid ◽  
Systemic Circulation ◽  
Free Access ◽  
Alternative Mechanism ◽  
Interstitial Flow ◽  
Fluid Circulation ◽  
Brain Interstitial Fluid ◽  
The Brain

The discovery of the water specific channel, aquaporin, and abundant expression of its isoform, aquaporin-4 (AQP-4), on astrocyte endfeet brought about significant advancements in the understanding of brain fluid dynamics. The brain is protected by barriers preventing free access of systemic fluid. The same barrier system, however, also isolates brain interstitial fluid from the hydro-dynamic effect of the systemic circulation. The systolic force of the heart, an essential factor for proper systemic interstitial fluid circulation, cannot be propagated to the interstitial fluid compartment of the brain. Without a proper alternative mechanism, brain interstitial fluid would stay stagnant. Water influx into the peri-capillary Virchow-Robin space (VRS) through the astrocyte AQP-4 system compensates for this hydrodynamic shortage essential for interstitial flow, introducing the condition virtually identical to systemic circulation, which by virtue of its fenestrated capillaries creates appropriate interstitial fluid motion. Interstitial flow in peri-arterial VRS constitutes an essential part of the clearance system for β-amyloid, whereas interstitial flow in peri-venous VRS creates bulk interstitial fluid flow, which, together with the choroid plexus, creates the necessary ventricular cerebrospinal fluid (CSF) volume for proper CSF circulation.

scholarly journals Distribution of Glycylsarcosine and Cefadroxil among Cerebrospinal Fluid, Choroid Plexus, and Brain Parenchyma after Intracerebroventricular Injection is Markedly Different between Wild-Type and Pept2 Null Mice

2010 ◽  
Vol 31 (1) ◽  
pp. 250-261 ◽  
Author(s):  
David E Smith ◽  
Yongjun Hu ◽  
Hong Shen ◽  
Tavarekere N Nagaraja ◽  
Joseph D Fenstermacher ◽  
...  
Keyword(s):  
Cerebrospinal Fluid ◽  
Choroid Plexus ◽  
Interstitial Fluid ◽  
Brain Parenchyma ◽  
Wild Type ◽  
Septal Region ◽  
Biodistribution Studies ◽  
Choroid Plexuses ◽  
Clearance Kinetics ◽  
The Brain

The purpose of this study was to define the cerebrospinal fluid (CSF) clearance kinetics, choroid plexus uptake, and parenchymal penetration of PEPT2 substrates in different regions of the brain after intracerebroventricular administration. To accomplish these objectives, we performed biodistribution studies using [14C]glycylsarcosine (GlySar) and [3H]cefadroxil, along with quantitative autoradiography of [14C]GlySar, in wild-type and Pept2 null mice. We found that PEPT2 deletion markedly reduced the uptake of GlySar and cefadroxil in choroid plexuses at 60 mins by 94% and 82% ( P<0.001), respectively, and lowered their CSF clearances by about fourfold. Autoradiography showed that GlySar concentrations in the lateral, third, and fourth ventricle choroid plexuses were higher in wild-type as compared with Pept2 null mice ( P<0.01). Uptake of GlySar by the ependymal–subependymal layer and septal region was higher in wild-type than in null mice, but the half-distance of penetration into parenchyma was significantly less in wild-type mice. The latter is probably because of the clearance of GlySar from interstitial fluid by brain cells expressing PEPT2, which stops further penetration. These studies show that PEPT2 knockout can significantly modify the spatial distribution of GlySar and cefadroxil (and presumably other peptides/mimetics and peptide-like drugs) in brain.

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