How good are the fits to the experimental velocity profiles in vivo?

This paper was presented at the 3rd Micro and Nano Flows Conference (MNF2011), which was held at the Makedonia Palace Hotel, Thessaloniki in Greece. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, Aristotle University of Thessaloniki, University of Thessaly, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute.A new velocity profile equation for the description of microcirculatory blood flow in vivo was proposed in 2009. However various recently published papers still use the assumption of parabolic velocity profile (Poiseuille flow). The purpose of this work was to evaluate the performance of 3 different fitting cases: 1) best parabolic fit, 2) axial fit with the proposed equation and 3) best fit with the proposed equation. Twelve experimental velocity profiles measured by particle image velocimetry in mouse venules were used to compare the fitting efficiency of the 3 cases on the basis of the velocity relative error (RE) expressed as average ± SE (standard error) at ten different radial segments (REj with 1 ≤ j ≤ 10). The parabolic best fit (case 1) leads to serious deviations from the real velocity distribution (RE10 = - 65% ± 2%). The proposed equation axial fit (case 2) slightly overestimates blood velocity distribution near the vessel wall but the was below + 12% and it requires only one experimental value near the vessel axis, measurable using the Doppler Effect. The proposed equation best fit (case 3) approximates the experimental data without any serious bias but requires a complete velocity profile data set

KLJUČNI DOGAĐAJI U POVIJESTI DJEČJE KIRURGIJE ZA VRIJEME BIZANTA

During the Byzantine Times, medicine and surgery developed as Greek physicians continued to practice in Constantinople. Healing methods were common for both adults and children, and pediatrics as a medical specialty did not exist. Already Byzantine hospitals became institutions to dispense medical services, rather than shelters for the homeless, which included doctors and nurses for those who suffered from the disease. A major improvement in the status of hospitals as medical centers took place in this period, and physicians were called archiatroi. Several sources prove that archiatroi were still functioning in the late sixth century and long afterward, but now as xenon doctors. Patients were averse to surgery due to the incidence of complications. The hagiographical literature repeated allusions to doctors. Concerns about children with a surgical disease often led parents to seek miraculous healings achieved by Christian Protectors – Saints. This paper is focused on three eminent Byzantine physicians and surgeons, Oribasius, Aetius of Amida, Paul of Aegina, who dealt with pediatric operations and influenced the European Medicine for centuries to come. We studied historical and theological sources in order to present a comprehensive picture of the curative techniques used for pediatric surgical diseases during the Byzantine Times.U bizantsko doba medicina i kirurgija razvijali su se dok su grčki liječnici nastavili s praksom u Carigradu. Metode liječenja i za odrasle i za djecu se nisu razlikovale, a pedijatrija kao medicinska specijalizacija nije postojala. Bizantske bolnice postale su ustanove, a ne skloništa za beskućnike, u kojima su liječnici i medicinske sestre pružali medicinske usluge za sve oboljele. U ovom se razdoblju dogodilo veliko poboljšanje statusa bolnica kao medicinskih centara, a liječnici su prozvani archiatroi. Nekoliko izvora dokazuje da su archiatroi još uvijek djelovali u kasnom šestom stoljeću i dugo nakon toga, ali sada kao ksenonski liječnici. Pacijenti nisu bili skloni operacijama zbog učestalosti komplikacija. U hagiografskoj literaturi su se učestalo spominjali liječnici. Zabrinutost za djecu s kirurškom bolešću roditelje je često tjerala da traže čudesna ozdravljenja koja su prakticirali kršćanski sveci zaštitnici. Ovaj rad govori o tri ugledna bizantska liječnika i kirurga. Oribazije, Aecije iz Amide i Pavao iz Aegine bavili su se pedijatrijskim operacijama i utjecali na europsku medicinu u idućim stoljećima. Proučavali smo povijesne i teološke izvore kako bismo predstavili sveobuhvatnu sliku kurativnih tehnika koje su korištene za dječje kirurške bolesti u bizantsko doba

Castrati singers: surgery for religion and art

The act of castration was practiced from ancient times. In countries of Middle and Far East, castration was often done to provide eunuchs as guardians of the harems. In Europe and especially in Italy, it was carried out to preserve the male voice unbroken into adult life. From 16th century till the end of 18th century, castrati singers dominated opera with their supernatural voices. Boys were castrated mainly before the age of 9 years and when they grew up they had feminine characteristics, such as smooth, hairless bodies, breasts, infantile penis. The training procedure to become a castrato singer was very intense and lasted up to ten years. The most common surgical technique was either to sever the spermatic cords or crush the testis with the fingers. The voice of a castrato was the outcome of a larynx the size of a child’s combined with the lung volume of an adult male. The castrati singers became superstars who dominated opera, singing both male and female roles for more than 200 years. Castrated for art, the beauty, range and flexibility of their voices raised them to mythical status

Fluid shear stress modulation of hepatocyte like cell function

Freshly isolated human adult hepatocytes are considered to be the gold standard tool for in vitro studies. However, primary hepatocyte scarcity, cell cycle arrest and the rapid loss of cell phenotype limit their widespread deployment. Human embryonic stem cells and induced pluripotent stem cells provide renewable sources of hepatocyte-like cells (HLCs). Despite the use of various differentiation methodologies, HLCs like primary human hepatocytes exhibit unstable phenotype in culture. It has been shown that the functional capacity can be improved by adding back elements of human physiology, such as cell co-culture or through the use of natural and/or synthetic surfaces. In this study, the effect of fluid shear stress on HLC performance was investigated. We studied two important liver functions, cytochrome P450 drug metabolism and serum protein secretion, in static cultures and those exposed to fluid shear stress. Our study demonstrates that fluid shear stress improved Cyp1A2 activity by approximately fivefold. This was paralleled by an approximate ninefold increase in sensitivity to a drug, primarily metabolised by Cyp2D6. In addition to metabolic capacity, fluid shear stress also improved hepatocyte phenotype with an approximate fourfold reduction in the secretion of a foetal marker, alpha-fetoprotein. We believe these studies highlight the importance of introducing physiologic cues in cell-based models to improve somatic cell phenotype

Overcoming the blood–brain barrier: the role of nanomaterials in treating neurological diseases

Therapies directed toward the central nervous system remain difficult to translate into improved clinical outcomes. This is largely due to the blood–brain barrier (BBB), arguably the most tightly regulated interface in the human body, which routinely excludes most therapeutics. Advances in the engineering of nanomaterials and their application in biomedicine (i.e., nanomedicine) are enabling new strategies that have the potential to help improve our understanding and treatment of neurological diseases. Herein, the various mechanisms by which therapeutics can be delivered to the brain are examined and key challenges facing translation of this research from benchtop to bedside are highlighted. Following a contextual overview of the BBB anatomy and physiology in both healthy and diseased states, relevant therapeutic strategies for bypassing and crossing the BBB are discussed. The focus here is especially on nanomaterial‐based drug delivery systems and the potential of these to overcome the biological challenges imposed by the BBB. Finally, disease‐targeting strategies and clearance mechanisms are explored. The objective is to provide the diverse range of researchers active in the field (e.g., material scientists, chemists, engineers, neuroscientists, and clinicians) with an easily accessible guide to the key opportunities and challenges currently facing the nanomaterial‐mediated treatment of neurological diseases

Loss of field of view due to optical mismatch at the inner diametric plane of cylindrical artificial microvessels

In the experimental research with cylindrical artificial microvessels it may not be possible to view the entire inner diameter, due to optical mismatch between the microvessel material and the inside liquid suspension. A quantification of the field of view loss (FOVL) at the inner diametric plane is proposed, when the liquid suspension has a lower refractive index than the microvessel material and imaging is performed by a dry objective lens. A graphical model shows the optical ray tracing, utilizing 3 different refractive indices (η1, η2 and η3) for the microvessel material, the liquid suspension and the air. The numerical aperture (NA) of the objective lens defines the maximum ray output angle received by the lens and corresponds to a certain FOVL. Output angles were estimated for 8 different input angles and the corresponding FOVLs ranged from 71% down to 2%. The graphical model theoretical estimations were assessed experimentally for the cases of a water suspension and a plasma diluted blood sample (5% hematocrit). The theoretical estimations deviated only ±3% from the experimental assessments, showing that the graphical model could be a valuable tool for research on cylindrical artificial microvessels with dry objective lenses. © 202