MEASUREMENTOFERYTHROCYTESDEFORMABILITYWITHCOUNTER−ROTATINGPARALLELDISKSYSTEM

Shigehiro＝ashimotol，＝iroshiOkul，MasayoshiOmoril，ⅦkiMatsumotol，KoichiSakauel，KazuhiroIkegamll，HajimeOtani2，HirojiImamura2

1BiomedicalSystems，Dept・OfElectronics，InformationandCommunicationEngineerlng，OsakaInstituteofTechnology，Osaka，Japan，hasimoto伝）elc・Oit・aC・b

2Dept▲OfThoracicandCardiovascularSurgery，KansaiMedicalUniversity
INTRODUCTIONRESULTSANDDISCUSSION

Erythrocytes deform to pass through capillary in

Thedextranconcentrationinmediumdoesnotaffectonshear

micro−Circulation． Deformability of erythrocytesis an
important parameter to maintain blood circulation・ To

StreSS reSPOnSiveness． Erythrocytes deformationis notgoverned by shear rate，but by shear stressin these shear

measureerythrocytesdeformation，SeVeralmethodologyhave
been designedin the previous studies．Measurement oferythrocytesdeformability1SaVailabletodetecttheirsublethal
damage and to design micro−CaPSulelike artincialCOndition．Couette−typeflow has an advantage to quantify

erythrocytes．In this study，erythrocytes deformabilitywas

theshear，becauseuniformshearrateisappliedtothewhole
SpaCe．ThecounterrotatlngrheoscopeisadevisetoobserveShearedcells，Whicharesuspendedatthestationaryplanein
themiddlepartofCouette−tyPeflowwithoutcontactbetween

quantitatively evaluated with shear stress responsiveness incells and surfaces．1ncrease of stifhess of the disks

thecounter−rOtatlngParalleldisksystem．

minimizes secondary flow.

disksat25degreesC．

0．02

0．04

0．0

0．08

Viscosity（P且S）

Figurel：Relationbetweenmediumviscosltyandshearstressresponsiveness．
SUMMARY

The designed experimental system has enough geometricalaccuracytoevaluateshearstressresponsiveness．Thepresent
Studyshowsthaterythrocytedeformationisnotgovernedby
Shearrate，butbyshearstress．
REFERENCES

Hashimoto，S．，Hikita，S．，Sasada，T．（1992）．T［ans．4′′，勒rldβわ∽αJerJαJ∫Co〃g′℃∫∫，347・

Erythrocytes deform from biconcave to ellipsoid in
Couette−type Ofshear neld．Erythrocytes deformation wasquanti茄edwithanelongationindex（E），Whichwascalculated
丘omthelengthofmajoraxis（L）andthatoftheminoraxis（W）by E＝（L−W）／（L＋W）．E becomes zeroin a sphere（L＝W），andapproachestounityasthedeformationadvances（L＞＞W）．Theelongationindex（E）wasplottedasafunction
Ofshearstress（S），andthenttingexponentialcurve．

elongationandRistheshearstressresponsiveness．

爪じSOlution（hematocritofO・5％，viscositybetweenO．02PasandO．06Pa s）and were sheared between two counter rotating

5

Human erythrocytes were suspended in a dextran water∧UO．001s，With avideo tape recorder，and with a computer．

1

With a charge coupled device camera at a shutter speed of5hasalongfocallengthof6．9mm．ThepLCtureWaSreCOrdedlmicroscopeWithanobjectivelensof20magnifications，Which−mm斤omtherotationalaxisthroughanoptLCal−Phase−COntraSt

5

betweentwodisks，isconstantregardlessofthedistancefrom
the disk．An erythrocyte can be observed under shearWithouttranslationalmovement，Whenitissuspendedatthe
Stationary planein the middle part of the shear neld．
Deformationoferythrocyteswasviewedatadistanceof27︵d已ss冨ぎ叫Suedsむ虔Aparallel−disk−tyPerheoscopesystemhasbeendesignedand
manufactured．In the system，Couette−tyPe Shear茄eldis
inducedinthefluidbetweentwocounter−rOtatlngdisks，Whicharemadeoftransparentsilicaglass（5mmthickness，80mmdiameter）．The distance was maintained O．1mm between
two disks supportedwithballbearings（100mm diameter）．
Therotatingspeed（＜0．4rad／s）wasregulatedwithastepping
motor，Whichis controlled by a computer．The shear rate
（く2001／s），Whichiscalculatedfromthevelocitydeferece（く20mm／s）between two disks and ftom the dimens10n

つ▲METHODS

Hashimoto，S．，（2000）．T［ans．6（h vbrld BiomaleriaLyCo〃gre∫∫，2，929・Schmit−Schoenbein，H．，Wells，R．（1969）．Science，165，288．
Sutera，S．P．，etal．（1983）．BloodCelLs，9，485−495．
ACKNOWLEDGEMENTS

This work was supportedin part by a Grant−in−Aid for

ScientincResearchfromtheJapaneseMinistryofEducation．
Culture，Sports，ScienceandTechmology．