Croatian medical journal
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Croatian medical journal · Aug 2014
ReviewA proposed role for efflux transporters in the pathogenesis of hydrocephalus.
Hydrocephalus is a common brain disorder that is treated only with surgery. The basis for surgical treatment rests on the circulation theory. However, clinical and experimental data to substantiate circulation theory have remained inconclusive. ⋯ The location of p-gp along the pathways of macromolecular clearance and the broad substrate specificity of this abundant transporter to a variety of different macromolecules are reviewed. Involvement of p-gp in the transport of amyloid beta in Alzheimer disease and its relation to normal pressure hydrocephalus is reviewed. Finally, individual variability of p-gp expression might explain the variability in the development of hydrocephalus following intraventricular hemorrhage.
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Croatian medical journal · Aug 2014
ReviewVirchow-Robin space and aquaporin-4: new insights on an old friend.
Recent studies have strongly indicated that the classic circulation model of cerebrospinal fluid (CSF) is no longer valid. The production of CSF is not only dependent on the choroid plexus but also on water flux in the peri-capillary (Virchow Robin) space. Historically, CSF flow through the Virchow Robin space is known as interstitial flow, the physiological significance of which is now fully understood. ⋯ Autoregulation of brain blood flow serves to maintain a constant inner capillary fluid pressure, allowing fluid pressure of the Virchow Robin space to regulate regional cerebral blood flow (rCBF) based on AQP-4 gating. Excess heat produced by neural activities is effectively removed from the area of activation by increased rCBF by closing AQP-4 channels. This neural flow coupling (NFC) is likely mediated by heat generated proton channels.
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Croatian medical journal · Aug 2014
Case ReportsLong lasting near-obstruction stenosis of mesencephalic aqueduct without development of hydrocephalus--case report.
The aim of this study is to present the five-year longitudinal magnetic resonance imaging (MRI) follow up of a patient with incidental finding of near-obstruction stenosis of the aqueduct of Sylvius due to a large pineal cyst. The patient was scanned 3 times on a 3T MR device using a set of standard structural sequences supplemented with high-resolution constructive interference of steady state (CISS) T2 sequence for precise delineation of the aqueduct of Sylvius and cardiac-gated phase-contrast sequences for the analysis of cerebrospinal fluid (CSF) movement. ⋯ Our findings are contradictory to the classic hypothesis of CSF physiology based on secretion, circulation, and absorption of CSF, which states that the impairment of CSF circulation through the aqueduct of Sylvius inevitably leads to a hypertensive hydrocephalus development involving the third and the lateral ventricle. Our research group previously proposed a new hypothesis of CSF physiology, which offers more suitable explanation for such clinical cases.
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Croatian medical journal · Aug 2014
Fluid filtration and reabsorption across microvascular walls: control by oncotic or osmotic pressure? (secondary publication).
Relationships between hydrostatic and oncotic (colloid osmotic) pressures in both capillaries and interstitium are used to explain fluid filtration and reabsorption across microvascular walls. These pressures are incorporated in the Starling oncotic hypothesis of capillaries which fails, however, to explain fluid homeostasis when hydrostatic capillary pressure is high (in feet during orthostasis) and low (in lungs), or when oncotic plasma pressure is significantly decreased in experiments and some clinical states such as genetic analbuminaemia. ⋯ The osmotic counterpressure hypothesis explains fluid homeostasis at high, mean and low capillary hydrostatic pressures. Plasma proteins and inorganic electrolytes contribute 0.4% and 94% to plasma osmolarity, respectively, so that plasma proteins have low osmotic (oncotic) pressure and despite high restriction of their passage across microvascular wall they contribute little to build up of osmotic counterpressure in comparison to electrolytes. However, absence or very low concentration of plasma proteins increases microvascular wall permeability to water and osmolytes compromising build up of osmotic counterpressure leading to development of interstial oedema.