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Physical changes of possible biological significance occurring in the cooling and the rewarming of aqueous solutions
348
ABSTI/ACTS OF I N T E R E S T
to l)revenL any supercooling of h.,aves in autumn and sl)ring , n)lhough (h, tnehed h, avos could readily supercool to --,t°C. On the other lmnd, ice formation in winter twi~s took plat:(.' at --3.5 10 --5.5°(3 without tee ,-:ceding in enid room as well as in frosty nights. Freezing in a Ipafy twig was found to (levelop from a nuelealion point alcmg the xylem vessels St~l)ercooled to a tOllll)f.w~tl.tlr(" l)elow --1°O. The progress of freezing througll twigs was observt,d under controlled l emperature eomlitions in a eolcl room. "Flu" velocity of freezing in twigs was found t0 be hi)proximately prol)ortionall lo the degree of supercooling of the twig. It was al)out 34 em per rain 1)or degree Cenligrqde. Even in tilt: field trees during d,,fotiation l)eriods, freezing procee(led along l,he vessels from a few nuelt,:~tion points and rapidly reaelmd all parls in twigs. An oeeurren(,e of freezing in the tissu(.,, indue(,(l by n s~.vere frost in Into aululnn, resulted in :t ralfi(l increase in frost hardiness within a few days. On the other h:m(1, a warm spell in early spring was followed by the deharth, ning of mu.iberry tree without freezing of twigs.
Sulfhydryls and Freezing Resistance. L~vtT'r, ,1. The sulfhydo'l theory at, tempts to explain the mechanism of freezing injury, lts usefulness is best tested 173" attempting to relate it to freezing re.sistanee. Oil the ba.,-is of l.his theory 1) the changes that occur when a plant's freezing resistance increases should be predictaide and explainable, and 2) it should be possible Io control freezing reslst-ulce artificially in the absence of lhe n:ttural ehanges. ~ec'ent results in these two are'ts are described.
Physic:d Changes of l'ossiblc Biological Significance. Occurring in the Cooling and the Rewarming of Aqueous Solutions. LUrgT, B. Cryobiologists have examined closely the various aspects of the drastic change that occurs in the cooling of solutions, nalnely, crystallization; but they have generally ignored less conspicuous
changes in the motilib" of the component molecules or particles (and therefore in the stability of the solution) which take place at various temperatures (h'l)ending on the at(fur,., and concentrations of the
solutes anti on the (ale of cooling and rewarming. Tl~ese changes are best observed when a rapi~lly cooled solution is being rewarmed, but their occurrence is not limited to such conditions. Five cases will be mentioned here: 1) gelatin .gels of 53 to 65% concentration, cooled rapidly, lose their stabilit.~ when rewarmed to aboul,-37.°(3; 2) gels of 20 to 50% concentration do so only when rewarmed to about - 1 2 ° C ; 3) a 60% solulion of
glycerol, cooled to --150°O, undergoes a loosening of its molecules (corresponding to a sudden (le-
c,r(,~ls~, in density) wht,n it is n:wnrme~l to al~out -110°(3: ,1) if ]taro Ms'cerol, precooh,~l to --IOWC or l,elow, is gradu'dly rewnrmeti, its molecules will aC(luire enough mobilit,y to form mu'loi wiwn the temperature reaches --50°C; but 5) they require a t(,mp(,rature of --5°C to parti('il)ate a('liw.,ly in tile construction of crystals. Vte ~,re now trying to coordinate the:~o :lml similar data :m~l it> ~,.-tabli.-h a
l'hysicai-Chemical Basis of Injury front int;'acellular Freezing in Yea~l. Mazutt, P. "l'ho death of ('ells of ,~ru'c]~artmtyc'es cerevixioc vooh,~l :tt rnlos nl)ove 1 to 10"'C per rain is corn:]:tied with tim forlmttion of ice m'ysials witllin lhe coils, Tilts view is base,l on the following evide;we: 1) the cooling rates that produce (ieal,ll coincide wilh l,llose I]mt, cause intr'tcelhllar water to l~,come SUl)ercoolcd; 2) lho volume of ralfidly coolo~l cells is muell larger than it would b e i f they eontain~_(l no ice; and 3) alt:,rnativc, hypolheso.-, do not atcount for the observe(t dale. Cells that, "tr¢, killt,d under conditions yielding inlracpllular ice slmw extt,nsive permeability danmge immedialely :~l't(..: l,lutwin~. Igx'idr,n,o is presented to SUl)t)ort tlw view tirol iniracelluhu' freezing is ;t c:mse of ~lenth and not a eonseqtt[,nce of (h,aLl~ from some oilmr cause. Tills vivw is based chiefly on flu' ol)sm'va~ion (hal, survival is proportional to warn~ing velocit,y. Twc~ expl,lnttlions for tl~e lethal action of intr.'lcr,lhllar freezing :(re discussed. One is that inj u w is (lue to the removal of water l)y in(recellular ice; the otl~er is that injury Js a.'-sociated with the tenth,hey of ice crystals to attqil~ a minimum surface energy (i.e., a maximt,m radius of curvature). The evidenee with yeast, favors the latter. T h e R e l a t i o n s h i p between D e h y d r a t i o n and F r e e z i n g I n j u r y in the M a m m a l i a n E r y t h r o cytc. MEnY.xbx,x, ]-I. T. An'tlyses have l,oo,n ma(ie of the reI'tLimMlil) between ]mmolysis, temper'tture, glycerol c()nccllI,l'ation, and the proportion of water converted to ice. This Ires made i~ possible to designate a certain proportion of the water in oryt, hrocyles ns "vital" and has enabled the formulation of a .-.'ingle hypothesis which explains the survival of ted coils following both rapid and slow freezing in tlm l~resenee of either diffusable or nomliffusable additives.
ABSTI/ACTS OF I N T E R E S T
to l)revenL any supercooling of h.,aves in autumn and sl)ring , n)lhough (h, tnehed h, avos could readily supercool to --,t°C. On the other lmnd, ice formation in winter twi~s took plat:(.' at --3.5 10 --5.5°(3 without tee ,-:ceding in enid room as well as in frosty nights. Freezing in a Ipafy twig was found to (levelop from a nuelealion point alcmg the xylem vessels St~l)ercooled to a tOllll)f.w~tl.tlr(" l)elow --1°O. The progress of freezing througll twigs was observt,d under controlled l emperature eomlitions in a eolcl room. "Flu" velocity of freezing in twigs was found t0 be hi)proximately prol)ortionall lo the degree of supercooling of the twig. It was al)out 34 em per rain 1)or degree Cenligrqde. Even in tilt: field trees during d,,fotiation l)eriods, freezing procee(led along l,he vessels from a few nuelt,:~tion points and rapidly reaelmd all parls in twigs. An oeeurren(,e of freezing in the tissu(.,, indue(,(l by n s~.vere frost in Into aululnn, resulted in :t ralfi(l increase in frost hardiness within a few days. On the other h:m(1, a warm spell in early spring was followed by the deharth, ning of mu.iberry tree without freezing of twigs.
Sulfhydryls and Freezing Resistance. L~vtT'r, ,1. The sulfhydo'l theory at, tempts to explain the mechanism of freezing injury, lts usefulness is best tested 173" attempting to relate it to freezing re.sistanee. Oil the ba.,-is of l.his theory 1) the changes that occur when a plant's freezing resistance increases should be predictaide and explainable, and 2) it should be possible Io control freezing reslst-ulce artificially in the absence of lhe n:ttural ehanges. ~ec'ent results in these two are'ts are described.
Physic:d Changes of l'ossiblc Biological Significance. Occurring in the Cooling and the Rewarming of Aqueous Solutions. LUrgT, B. Cryobiologists have examined closely the various aspects of the drastic change that occurs in the cooling of solutions, nalnely, crystallization; but they have generally ignored less conspicuous
changes in the motilib" of the component molecules or particles (and therefore in the stability of the solution) which take place at various temperatures (h'l)ending on the at(fur,., and concentrations of the
solutes anti on the (ale of cooling and rewarming. Tl~ese changes are best observed when a rapi~lly cooled solution is being rewarmed, but their occurrence is not limited to such conditions. Five cases will be mentioned here: 1) gelatin .gels of 53 to 65% concentration, cooled rapidly, lose their stabilit.~ when rewarmed to aboul,-37.°(3; 2) gels of 20 to 50% concentration do so only when rewarmed to about - 1 2 ° C ; 3) a 60% solulion of
glycerol, cooled to --150°O, undergoes a loosening of its molecules (corresponding to a sudden (le-
c,r(,~ls~, in density) wht,n it is n:wnrme~l to al~out -110°(3: ,1) if ]taro Ms'cerol, precooh,~l to --IOWC or l,elow, is gradu'dly rewnrmeti, its molecules will aC(luire enough mobilit,y to form mu'loi wiwn the temperature reaches --50°C; but 5) they require a t(,mp(,rature of --5°C to parti('il)ate a('liw.,ly in tile construction of crystals. Vte ~,re now trying to coordinate the:~o :lml similar data :m~l it> ~,.-tabli.-h a
l'hysicai-Chemical Basis of Injury front int;'acellular Freezing in Yea~l. Mazutt, P. "l'ho death of ('ells of ,~ru'c]~artmtyc'es cerevixioc vooh,~l :tt rnlos nl)ove 1 to 10"'C per rain is corn:]:tied with tim forlmttion of ice m'ysials witllin lhe coils, Tilts view is base,l on the following evide;we: 1) the cooling rates that produce (ieal,ll coincide wilh l,llose I]mt, cause intr'tcelhllar water to l~,come SUl)ercoolcd; 2) lho volume of ralfidly coolo~l cells is muell larger than it would b e i f they eontain~_(l no ice; and 3) alt:,rnativc, hypolheso.-, do not atcount for the observe(t dale. Cells that, "tr¢, killt,d under conditions yielding inlracpllular ice slmw extt,nsive permeability danmge immedialely :~l't(..: l,lutwin~. Igx'idr,n,o is presented to SUl)t)ort tlw view tirol iniracelluhu' freezing is ;t c:mse of ~lenth and not a eonseqtt[,nce of (h,aLl~ from some oilmr cause. Tills vivw is based chiefly on flu' ol)sm'va~ion (hal, survival is proportional to warn~ing velocit,y. Twc~ expl,lnttlions for tl~e lethal action of intr.'lcr,lhllar freezing :(re discussed. One is that inj u w is (lue to the removal of water l)y in(recellular ice; the otl~er is that injury Js a.'-sociated with the tenth,hey of ice crystals to attqil~ a minimum surface energy (i.e., a maximt,m radius of curvature). The evidenee with yeast, favors the latter. T h e R e l a t i o n s h i p between D e h y d r a t i o n and F r e e z i n g I n j u r y in the M a m m a l i a n E r y t h r o cytc. MEnY.xbx,x, ]-I. T. An'tlyses have l,oo,n ma(ie of the reI'tLimMlil) between ]mmolysis, temper'tture, glycerol c()nccllI,l'ation, and the proportion of water converted to ice. This Ires made i~ possible to designate a certain proportion of the water in oryt, hrocyles ns "vital" and has enabled the formulation of a .-.'ingle hypothesis which explains the survival of ted coils following both rapid and slow freezing in tlm l~resenee of either diffusable or nomliffusable additives.