I n Memory of Dr.Rei j i Nat ori ,Pres i dent Emeri t us of The Ji kei Uni vers i t y School of Medi ci ne
Sat os hi K
URIHARA,M. D. ,Ph. D.
Pr esident and Chair man of the Depar tment of Physiology (II), The Jikei Univer sity School of Medicine
Dr .Rei j i Nat or i ,Pr es i dent Emer i t us of The Ji kei Uni ver s i t y School of Medi ci ne,pas s ed away on November 20,2006. A s peci al f uner al cer emony was hel d at The Ji kei Uni ver s i t y School of Medi ci ne on December 22,2006. About 1, 200 peopl e at t ended t he cer emony t o pay t hei r l as t r es pect s . Thi s s peci al i s s ue i s dedi cat ed t o Dr .Nat or i ,who publ i s hed t hr ee ar t i cl es r egar di ng s ki nned f i ber s i n t he f i r s t vol ume of Ji kei kai Medi cal Jour nal i n 1954. Hi s wor k was r ecogni zed ar ound t he wor l d,and s ki nned f i ber s have been us ed by many phys i ol ogi s t s .
Dr .Nat or i gr aduat ed f r om The Ji kei Uni ver s i t y School of Medi ci ne i n Mar ch 1936. Af t er gr aduat i on,
he j oi ned t he Depar t ment of Phys i ol ogy( whos e chai r - man at t he t i me was Pr of es s or Sei zabur ou Ur amot o) and s t ar t ed hi s r es ear ch wor k. At t he begi nni ng,he meas ur ed act i on pot ent i al s i n t he r es pi r at or y cent er of t he car p and i n per i pher al ner ves . He became i nt er - es t ed i n t he cont r act i on of s kel et al mus cl e f i ber s and i nt ended t o i nves t i gat e t he mechani s m of mus cl e cont r act i on at t he myof i br i l l evel . He at t empt ed t o i s ol at e myof i br i l s f r om ot her cel l ul ar component s . At t hat t i me,t he cel l was cons i der ed t he mi ni mal f unct i onal uni t ,and di s s oci at i on of i nt r acel l ul ar com-
ponent s f r om t he cel l was cons i der ed i mpos s i bl e.
However ,Dr .Nat or i at t empt ed t o peel of f t he cel l membr ane whi l e l eavi ng t he myof i br i l s i nt act and undamaged. However ,accompl i s hi ng t hi s f eat was qui t e di f f i cul t . I f t he cel l membr ane i s damaged,t he i oni c bar r i er of t he cel l membr ane di s appear s and t he mus cl e f i ber i s i r r ever s i bl y damaged. Dr .Nat or i cr eat ed s ever al s ol ut i ons whos e i oni c compos i t i on was s i mi l ar t o t hat of t he i nt er i or of t he cel l and at t empt ed t o r emove t he cel l membr ane of a s kel et al mus cl e
f i ber i n t he s ol ut i ons . Unf or t unat el y,hi s at t empt s wer e uns ucces s f ul .
I n ear l y s pr i ng 1949,Dr .Nat or i s pecul at ed t hat t he i nt r acel l ul ar envi r onment mi ght be mai nt ai ned i f t he cel l membr ane wer e peel ed of f i n oi l . Hi s i dea was t hat oi l cover s t he mus cl e f i ber and t hat t he i nt r acel l ul ar envi r onment coul d be mai nt ai ned even t hough t he cel l membr ane was r emoved. Thus , i nt r acel l ul ar i oni c condi t i on s houl d be mai nt ai ned wi t hout t he cel l membr ane. He t ook a bundl e of s kel et al mus cl e f r om t he s ar t or i us of a t oad and pl aced i t on a gl as s s l i de. Af t er put t i ng a dr op of machi ne oi l on t he pr epar at i on,he di s s ect ed a s i ngl e mus cl e f i ber under a bi nocul ar mi cr os cope. He t hen peel ed of f i t s cel l membr ane. Cont r act i on di d not occur ,and t he myof i br i l s wer e wel l mai nt ai ned even af t er t he membr ane was peel ed of f . Thi s was how Dr .Nat or i cr eat ed t he s ki nned f i ber( Nat or i ʼ s s ki nned f i ber ) . Hi s excel l ent i dea had never been cons i der ed by ot her r es ear cher s . Pr of es s or Umazume,Chai r - man of t he Depar t ment of Phys i ol ogy( I ) ,The Ji kei Uni ver s i t y School of Medi ci ne,des cr i bes t he phys i o-
l ogi cal i mpor t ance of s ki nned f i ber i n t hi s vol ume.
Dr .Nat or i pr es ent ed hi s r es ear ch about t he s ki n- ned f i ber at t he annual meet i ng of t he Phys i ol ogi cal Soci et y of Japan i n 1949 and des cr i bed t he s ki nned f i ber i n a t ext book( Kinseir igaku ［Mus cl e Phys i ol ogy］) i n 1951. I n 1954,Dr .Nat or i publ i s hed t hr ee ar t i cl es i n t he Ji kei kai Medi cal Jour nal . Thes e wer e t he f i r s t ar t i cl es r epor t i ng t he s ki nned f i ber i n Engl i s h. How-
ever ,t he s ki nned f i ber was not known i nt er nat i onal l y, becaus e t he Ji kei kai Medi cal Jour nal had a l i mi t ed ci r cul at i on. I n 1957,Pr of es s or Hi r os hi Kumagai ( Pr of es s or of Depar t ment of Phar macol ogy,Facul t y
Jikeikai Med J 2007;54:23‑4
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of Medi ci ne,The Uni ver s i t y of Tokyo)or gani zed a s ympos i um on “The Chemi s t r y of Mus cl e Cont r ac- t i on”i n Tokyo. Dr .Nat or i pr es ent ed hi s r es ear ch about t he s ki nned f i ber at t he meet i ng. Sci ent i s t s f r om t he abr oad wer e s ur pr i s ed at t he var i ous char ac- t er i s t i cs of t he s ki nned f i ber ,es peci al l y i t s r es pons e t o el ect r i cal s t i mul at i on and i t s mechani cal pr oper t i es .
I n 1960,Dr .Nat or i vi s i t ed Pr of es s or Si r Andr ew Huxl ey ( Nobel Pr i ze Wi nner f or Phys i ol ogy and Medi ci ne)at Uni ver s i t y Col l ege London and s howed movi es of t he s ki nned f i ber . Pr of es s or Huxl ey ad- mi r ed and pr ai s ed t he s ki nned f i ber ,whi ch s howed unexpect ed phenomena. Soon,t he s ki nned f i ber was known al l over t he wor l d,and mus cl e phys i ol ogi s t s began t o us e t hi s pr epar at i on t o s t udy t he mechani s ms of exci t at i on‑cont r act i on coupl i ng and t he pr oper t i es of myof i l ament s .
The or i gi nal met hod of s ki nni ng i nvol ves mechan- i cal r emoval of t he cel l membr ane wi t h a f i ne s ur gi cal s cal pel( mechani cal l y s ki nned f i ber ) . However ,s ome det er gent s can be us ed t o des t r oy t he cel l membr ane whi l e l eavi ng t he myof i br i l s i nt act . Det er gent ‑t r eat - ed s ki nned f i ber s ar e eas i er t o pr epar e t han ar e mechani cal l y s ki nned f i ber s . On t he ot her hand, Pr of es s or I wao Oht s uki( Pr of es s or Emer i t us ,Kyus hu Uni ver s i t y School of Medi ci ne;now Vi s i t i ng Pr of es - s or of t he Depar t ment of Phys i ol ogy( I I ) ,The Ji kei Uni ver s i t y School of Medi ci ne)f ound t hat s aponi n pr oduces por es i n t he cel l membr ane t hr ough whi ch s mal l mol ecul es can pas s wi t hout af f ect i ng t he s ar co-
pl as mi c r et i cul um membr ane. Saponi n and ot her det er gent s ar e now us ed t o pr epar e s ki nned car di ac and s moot h mus cl e f i ber s ,whi ch ar e di f f i cul t t o pr e- par e mechani cal l y. I n par t i cul ar ,s aponi n i s wi del y us ed f or s t udi es of t he Ca ‑handl i ng mechani s ms of t he s ar copl as mi c r et i cul um. Det er gent ‑or s aponi n‑
t r eat ed s ki nned f i ber s ar e cal l ed chemi cal l y s ki nned f i ber s . Thus ,s ki nned f i ber s ar e wi del y us ed f or var i ous exper i ment s and ar e a power f ul t ool f or t he s t udy of mus cl e phys i ol ogy.
I n t he Depar t ment of Phys i ol ogy( I )and( I I )of The Ji kei Uni ver s i t y School of Medi ci ne,s ki nned f i ber s of s kel et al ,car di ac,and s moot h mus cl es ar e now us ed t o i nves t i gat e t he mechani s ms of exci t at i on‑
cont r act i on coupl i ng and mechani cal pr oper t i es of t he mus cl e.
Thus ,Dr .Nat or i made a t r emendous cont r i but i on t o mus cl e phys i ol ogy by i nvent i ng t he s ki nned f i ber . For hi s cont r i but i ons t o s ci ence and cul t ur e,he was r ecogni zed as a per s on who had done di s t i ngui s hed s er vi ce i n t he f i el d of cul t ur e and awar ded t he As ahi Pr i ze,t he Or der of Cul t ur e,and t he Gr and Cor don of t he Or der of t he Sacr ed Tr eas ur e.
As a phys i ol ogi s t and t he Pr es i dent of The Ji kei Uni ver s i t y School of Medi ci ne,I woul d l i ke t o pay my r es pect s t o Dr .Nat or i and hi s r es ear ch. I hope t hat t hi s i s s ue wi l l r emi nd you of Dr .Nat or i ʼ s wor k i n mus cl e phys i ol ogy.
Febr uar y 11,2007
S.KURI HARA Vol.54,No.1
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