The Internal Environment During Hibernation

7/29/2019 The Internal Environment During Hibernation

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XXIITHE INTI]IINAL ENVIRONMENTDTIRING HIBERNATIONIly I'Il,nvtN f;. lirnot:snr,

l)epartncrrt of Occupational llealth(:h'aduate School of Pu].r1ic. I{ealthUlir.ctsi.ty of Pittsbulgh, Pittsburgh, l'errri.i,onered boci;' tempc'lature ancl reclucecl metabolie rate fol anextendecl period of time are included in the simplest clescriptionof hibernation. liecentl1., ne have learnecl to expect numeronsbjochernical changes chiring liibernation. Riologieal proeessesale lecognizell as being subject to rnodi{ication by these threcfactors : ternperature, time anrl (:iicrnical envirorrment. Befor:econsidering the biochemical changes r'r.hich occur with hiberna-tion, let us consider briefl.v some examples of the interclependenceof these factors. The interclepenclence of time and chemicalenvironrnent iir biologitral processes is demonstratecl b1' thtrcatalytic actiorr of enzynres ancl ions. The interaction of temper:a-ture and chemical environnrent is iilustraterl b1- Rachtach'sstuclies (I3aclirach, 19,t6). TTe observcd a tlro1t ol 17"C in theolrtinurn lemperature for contraction of the snail (Hel'i:r a,speroL\Iull) healt rviien lireb's solution \vas rcplacec'l |11r ic6f6p's ryl'onesium chloride. The optimum temperature for contraction jnisotonic potassium aild sodiuni chlorjcie u'as intcrtnecliate. Othertlemonstrations of the interdependencl. of chernical ertvironmentturtl temperrature rr.ere macle b1r Conl'a1- aiitl Geoglregan (19;15)and bl Adolph ancl Richmond (1956). Thel'reltoltecl a gain irrrr-eiglrt rihen tissues \r'ele suspendecl in cold isotonic solutions.-\tlolph and Riehinontl liale strggested a reclefinitiort of isotoiric-itI- ltt ,.tirrr of tempc'r"ature antl time. Interclellcnrleitce of teru-

perattrle atrtl tirte is cletuonstrated 1t1' the effect of timc npotrthe optimum terirperature 0f enzl'111gs zrnd enzyrtte systellls (Spector, 1956; Dixon ancl \\rebb, 1958). Thc iirpoltatrrre of tinc irrr'lefining tolerance linrits of anirtrals to heat ancl colti is arlotherrc-xample of the interdependernce of time arttl tcirtllelaturc. Itappears that a stuciy of bioJogical processes dur:ing hibelnationrnust consicler the iirter:clcpericlence of tenperatnre, tjnre anclrlttttrit'lrI ettt'ilolttrtt'ttt.


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+22 Btu,rrETrN: trIrsE{IM oF ool{pARATrvE zoorroey Yol, 12.1Serum Electrolyte Levels Duling Hibematiorr

The relation of the uragnesiurn ion to temperature regulationhas given particular interest to the elevation of serum magnesiumduring hibernatioir. Three types of studies other than hiberna-tiorr have related the ruagnesiurn ion to heat loss. Parenteral in-jection of magnesiuni has been clemonstrated to facilitate hypo-thermia (Schutz, 1916; Heagy and Burton, 1948; Hall et al..1951) and elevated serllm rnagnesium has heen reported to bel)roduced with hypothermia in a nurnber of animals (Stead-nlan ei al., 1943; Piatner, 1950; Platner ancl l{osko, 1953). Theantipyretic ection of magnesium has been described in experi-rneutal animals and in human beings (Barbour antl Winter,1 9!8 : Sollman. 1957 ) .

'l,q.er,s IReltorts ou Senrnr Magnesiurn clurilg Hibernation

Coltnt orrNattr e Scientilic Increase over'Narne Controls InYestigatorThirteen-lineclground squir:relWoodchuchGolclen harnsterLittle brorvr batI3ig blown batI'IeclgehogJleclgehog

C,itcllus trid,eaenr 65/oIitr,eahts

.llo nnota moilt.t 637'Vesocriaetus 25%attralustr[yotis lztciJ'ug us 62%'Eyttesious seroti,nus 53%Er'tmaccu.seuropaeus l)2%Erirutcetts ?url9)(reus rlone

Rietlesel and Folk (1957)-\{cBirnie et al,. (1953)Riedesel and Folk (1957)'liieclesel ancl Folk (1957)Il,iedesel (1957)Suomalainen (1939){Jiiirck r:t rul. (1956)

Itrlevation of the seluln nlagnesium appears to be a character'-istic of hibernatiorr. Reports of eler,ated seruln magrlesium ha\:ebeen made on a lal'ge sample of ttre hibernators by several inde-penclent laboratories (Table I). The extent of the increase inselum maguesiuln is depenclent r.rpon the species of the hiber-nator'. Some of the details of the change in serum magnesium\r:ere deterlninecl in studies on the little brorvn bat. There $'as nosigtrilicant increase in the inagnesiurn $,hen esophageal teinper-ature had log'ered to 17"C, but an elevation of serum magnesiurnwas obsel'ved s,hen the esophageal temperature hacl dropped to13"C (Fig. I t. 'lhe elevation of serum magnesiunl appears to


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I 960 MA}IMAITIAN HIBERNATIONbe deperrdent upon cooling of cells. Bats raised their botly tern,perature to the semiactir,e ler.el of 18"C in fou.r to eight rninutesl-ithout altcring the hiberrration 'level of serum magnesium (Fig.2). The rnagnesium ler.cl appears to be inclcpenclent of tempera-ture clurirrg arousal from hiberiration. Then, rvhen the bod-vtemperature lras raisecl further b-y exposure in a l arm room forone hour'. thc selum mitEnesinnr l.as back to the basal le.r'el of

3Oo 25" 2Oo l5o lo" 50BODY TEMp. oC (Esophogeot)}-ig. 1. Setnnr uruguesiurrr ralucs il ltats cooled to ltrogrcssir-e11- los'erbotly tcrnpelaturcs. (Lightest shaded alcr rcll'csetts trro st:rntlarcl cleviatiols

lubove arncl beiol' thc tueern.)active bats. The eler.ation of bocly temperature r-ithout a redu(r-tion of the serurn lnagnesiuin contraindicates the role of lnagne-sium as a causative factor in hibernation. This arguiitent is$,eakened by the fact tirat awakening from hibelnation appealsto be a very differeirt process from "going into" this state.Ileports on serulll clectroll-tes other than maEnesium clescribeplimarily homeostasis of potassiuni, socliuru and calcium duringhibernation. There are some exceptions. I)epending upon thc

,{ oD

-oo)7Q'lEE^foal!zLD.


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421 BI]LITETIN : NI]SEUN{ OF CO\,IPARATIVE ZOOI]OCIY YOl- 124species stutlied, the serum potassium remains near control levelsor increases cluring hibernation. An 82 pel celt increase in theserttrn ler-el ofi potassiurn during lril,rcriration of the l'oorlchuclilras bcen reportecl (l{cl}irnie et a!.. 1.95:}) (Table TI). A con-sistent increase jn serum l)otassiilril has been observerl l.ithactive hamsters. g'r'orLncl squirrels aiirl bats in a colrl environ-ment (Ricclcscl anci lrollr. 'l 9i8). The cause antl effect relation-ship oI the changes in semm irotassiunr alcr not apparerrt, Jrut

)Z s.r"

z,s" 300BODY TEMP, oC. (Esophogeol)

-!'ig. 2. Selurn ruaglesiLrru Iet-cJs tlulirrg alonsll frorlActiveI hr.

hil rernation.thc charrges in selrm potassium tluring hibelnation rna)- bceffectecl b1' aclrenal cortical activity or utilization of glygsgsll.Fenrr ancl Asarro (.1 956) havc reported an increase in intracel-h.rlar lrotassiunr u'ith tlepositiorr of. gl1.cogen. Thus. the irrcreaseof serum 1rotassiunr ruav lesult flont tire i:ecluction in gl1-cogenstores rrhich occru's cluring hibernation (Zimiry. 1956). Ther-alues of serrn soclium clnring hibernatiou of the heclgehog l-eresimilar to those found- in actile aniilals (Suomalaineir, 1939,1953; BiiJlcli at al., 1956). Reports of seruni calciuni coucentra-tion cluring hibelnatior-r are controver:sial. No change has beenrepoltecl u.itli hibernatioir of the grouncl sqtirrel. hamster antlheilgehog, rvheleas hrpocalcenria has been obserretl u.itir hiber'-nation of the little brori'n bat ancl Eulopean marrnot. An 88


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1960 }TAMMAIIIAN HIBERNATIONper cent inerease in the serllrn calciurn was lepolted rvith hiber-nation of the Eruopean lnannot (tr'erdrlann and Feinscirmidt,1932). A more detailed stu.d1- of the little brol-n bat has givenrise to interesting speculation. The clata in Figure 3 suggest thatthc serum levels observed during hibemation mav varJr l'iththe body temperature and./or clepth of hibernation. The lot,er-ing of serum calcitul I'ith reclucecl body temperature cloes notappear to bc large, but jt is consistcnt. The lorvering of sertnr

'lAsln IIIteports on Selurri Electrol;'tes clurirrg Hiliernation

AnimaI Dlec trol)"te Concentrationsls Compared to Controls InvestigatorPotnssium Calciurn Soclium\{ooclehuckEuropean marmot

'l'hilteen-lineclgrouncl squinelIlarnstcrl,ittle brown batBig brown batI{eclgehog

int,reasecltlecreaseti

rro changeno changeircr eased'Flo changeclccreasedrro cLange

tlecreasertincreased

uci cha.ngeno ohangedecleasecl" tn

no changelo chauge

no changeno change

I[cBirnie et al. (7953)Adler (1926)X'ertlmann andX'einschmidt (1932)Rietlesel ancl Folk (1958)Rieriesel and Irolk (1958)Rierlesel and !'otk (1958)Riedesel ancl Folk (1958)Suomalainen(1e3e) (1e53)Bitirck cf ol. (195ti)

*'.lho itrcrease $'as collsistent but rot statisticallJ' signilicant.**'l'lro sellrrD cnlcinur trppears to rary with dcl)th of hillerntrtion.calciurn with hibernation of the little bror,vn bat receives furthersupport from the observation of a 54 per cent reduction inserum calcium in bats rvhich had hibernated for ten $'eeks and a34 per cent decrease after nine weeks of hibernation (Rieclesel,1957). The lorv and apparently fluctuating calcium levels withextended hibernation canrot be explained on the basis of the dataavailable. The calcium let'el may cycle during long-term hiber-nation, and the data cited here may have been taken at times\\'hen the calcium level happened to be at a low ebb of the cycle.Strch a cycle lila)' accoullt for the contraclictory reports on theca.lciunl content of thc selurn during hibernation $'hich appear


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.126 BULT,ETTN: MUSEUM oF coMPARATTvE zoorJocY Yol. 124in Tabie II. It m&;r [. that during hibernation the circulationt,o calcium stores and,/or hi


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1960 ilIAMMAIJIAN HIBERNATIONshifts of body rvater may account for the controversial herna-tological clata. The electroll.ts data citecl earlier indicate homeo-stasis 'n'ith regard to body fluid compartments since magnesium,potassium and calcium concentrations change independently ofeach other; for instance, if the elevation of serum magnesiumtluring hibernation rvere due to a decrease in plasma water, onervoulcl expect similar increases in serum potassium, calciumancl sodium values. The rrrine of hibernating glround. squirrelshas been reportecl to be of verl!' small volume and dilution

Taer,n IIIIndiees of Hemoconcentration during Hibernation

427

Animll Criteria Change withHiberlation Ifemo-colcentration Inrestigator'l'hirtecn-linedgroundsquirrelWoorlchuck

Europeanmarnot

I{a.rnster

l,ittle brombatBig brownlt:rtIleclgthog

Ir)r'ythrocyte count1h'.vthrocyte count[]IematocritllematocritSerum sp. gr.Elythrocyte countIlernatocritT,IermoglobinP'lood sp. gr.Rlootl sp. gr.Erythroeyte count\Vater content ofblood)Ir'-trthroeyte countI{ematoeritI{ematocritHema.tocritSerum sp. gl.Total Serump lotoirrsHematocritSenul sp. gr'.Ilenratocli tSt'runr sp. gr'.Ilernatoerit'I'otal serurrrploteins

d.ecreaserlincreaseilsl. increaseno changeno changedecleasedincreasedrro changeno changeilcrcaserlincreasecltl ec rea se rlincreaseriincleasedincreasedincreaseduo changeiucleaserlno changeno cirangeno changeincr eased.increasedno changc

Stuckey ancl Coco (1942)+ Svihla ancl Borvman (1953)+ Svihla ancl Bowman (1953)0 liieclesel (1957)0 Rieclesel (1957)R,asmussen (1916)+ McBirnie et aI. (1.953')0 Ra.smussen (1916)0 Rasmussen (1916)+ Dubois (1896)+ Dubois (1896)+ Aeby (1875)l)ubois (1896)+ Lyman ef al. (1957)+ Lyman af aI. (1957)+ ll,ieclesel (1957)+ Sorith ancl Jetray (1958)0 Riec'lesel (1957)+ South ancl Jetray (1958)0 .lliedesel (1957)0 liieclesel (1957)0 Riedesel (1957)+ Eiedesel (1957)+ Biiirck et oZ. (1956)0 Biiirck et al. (1956')


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428 BUI]I]ETIN: N,IUSDTTM OF CONIPARATI\TE ZOOITOGY YO]. 124(Holg, 19;8). Adclitional information on kidney fuirction l'ouldfacilitate an rrnderstancling of $'ater balance during hiberna-tion. No ruajor sliifts irr body nater cluring hibemation are ap-parent flom existing clata.

Other Changes in the Lrternal Environment'l'he sub jects of pII, pO2 and pCO2 of the bloocl, euergysollrccs, bJoorl srrgai' arrd enckrcrines liar-e been rcr,iewcd. recentl.yby Lynian and Chatfield (195' ) ancl I(ayser (1957). Theseclata accumulatecl on harnsters, s.ooclchucks ancl ground, stluirrelsindicate that hibernating animals maintain oxygenation of theblood, pH and pCO2 near the values of active animals. Dataon the respiratorv qlrotient ancl bloocl glucose levels indicatethat fat is the priircipal sortrce of energy cluring hibernation.The role of the endocrines as a causal factor in hibernation isrluestionabkr, but charrges in endocrine actirity may effect apre-conditioning of the animal for entrancc into hiberiration. Tliefacility of some animals to hibelnate jn the laboratory the ;'earround conttadicts the supposition that enclocrines have a causa-tive role in hibelrration (Rieclesel, 1957).

'I'heories on thc Der,elopment of HibernationThe eler,ation o[ serurn ruagnesiltrn antl the le]atiorr of theruragnesium iou to heat loss in othcl tl.ltes of stuclies suggestmagnesium as a causal factor in the


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1960 \'IAMMAI]IAN HIBERNA'IION'I'ire lirst is that a high level of rnagnesiurri \r,as observed beforetlte teniperatures of deep hibernation u'ere reached.. Thus, theelevatcd magnesinrn observed rvith 13"C esophageal temperaturemay faciiitate the development of the lorver temperatures. Thesecond line of evidence in support of this theory is that intra-venous and rnicro-injection of magnesium ion have been demon-stratecl to facilitate heat loss (Schutz, 1916; Heagy and Burton,1948 ; Hall et al., I95I).The "Additive-Influence" theory assumes that exposure to thecold and elevated. serllrn magnesium both influence the activityof the heat loss center and have an additive effect. The theoryimplies that cooling of tissues, endocrine and cerebral corticalactivitv ancl otlier factors initiate the lorvering of bocly tempera-ture ancl that the elevatecl serr-lnl magnesium facilitates theprocess by affecting the heat loss center. This theory receivessupport from the observation that the serllm magnesium had notincreased u,hen the esophageal temperature had dropped to 17"C.This evidence inclicates that a factor other than elevated mag-nesiurn is requirerl for initiating the clecrease in body tempera-ture.The author is of the opinion that the "Additive-Tnfluence"theory is the most acceptable in vies' of the evidence cited. EIe-vation of the esophageal temperature to 20"C during the arousalfrom hibernation rvithout reduction of the serum magnesiumlevel represents the major eviclence that contradicts this theory.This argument is Neakened by the fact that ar,r'akening fromhibernation appears to be a lerr. different process from "goinginto" this state. Irousal from hibernation can be initiated bydiscrete external stimuli, such as hanilling. Internal stimuli fromthirst, hunger or a full bladder are also uncloubtedll. involveclin arorrsal frorn hibernation. No srich stimuli have been relateclto the clevelopment of liibernation. ,\rousal from hibernationmust be the result of neural stimulation of the hypothalamus anclthis stimulation must be strong enough to overcome the influenceof magnesium on the heat loss eenter.To restate the "Aclditir.e-Influence" theory, the developmeritof hibernatiorr may proceecl in thc foliorving manner : Colclexposnre and reclu.cecl activitl' produce a cooling of peripheraltissues, anil a release of nlagnesium fron-r cells to plasma occurs.This may start lvhen the animal is asleep. The increase in serurirmagnesium affects the heat loss center so that bocly temperaturcand metabolism of the animals clrop to hibernation levels.

429


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430 BUTTTTETIN: IITISEIII{ o!' coMPARArrvE zoolocY Vo]. 124Questions and Suggestions for Future Research

Questions arrtl suggestions to be consiclered. when planningresealch on hibernation include the follorving:1. ]Iore information is needecl regarding the irrterdependenceof temperature, tirne ancl chemical environment in biologiealI)rocesses.2. ll'he ch.emical euvironment and temperature of in' uil'rosttrtlies should be similar to those clescribed in uiuo.3. Are changes in intracellular electrolyte concentrations auniversal response of cells to cooling?4. Iilclitional information is neecled. on 'water balance duringhibernation; for instauce, "\Vhat is the extent of the kidnel'activit.y cluring hibernatiorr ? "5. Additional information is neecled regarcling the possibleclclic changes in serutn calcium concentration during hiberna-tiou.6. \Ve need a bettel clefinition of hibernation in terms ofspt'cies iliffereuces aird stages of hibernation.

R,Ejr.ERENCESAnr,rn, Ir.1g26. l)er \Viltersclilaf. I{a1lcll)rrc]r cler norrnaltr untl pathologisclrelPhysioJogie, l7 : 105-133.Aunv, C.18?5. Tleber tlel Ejnfluss tles wintersclilafes auf die Zusammelsetzultgtler verscheitlenen Organe des Thierkiirpers' Arch' exp' Pathol'Pharmakol., 3 : 180-184.An()r,PH, E. F. ,t.ND J. B,rcnuomlr1956. Watel exehanEes of isolatec.l rnamnt:rlian tisstles at lorv temperatures. Am. .I. Ph;'siol., 187:137'444.Ij.\L-Hn-\cFr, E.

1946.Tacteurst'hitrriclueslriothertniqrres.Ar,clr.Irrternat.Physiol.'54:19-99.l:l-\riBouF., lI. G. ,\ND J. n' WrNt'nn1918. Autipyretic aetion ant[ toxicity of combination of Mg rvithphetryL cinclioninic irticl. J. Pharmacol' llxp' Thelapeutie s'

35 :425-439.llrdncK, G., B. JoH-\NSSoN AND S. YnrGE1956. Some laboratory clata on heclgehogs, hibernating and non-hiber-natirig. Acta physiol. scantl.. 37 :281-294'


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1960 MAMMATJTAN rlrBlRNArroN 487CoNl.lr, J. E. ,rno II. Grocnnc,rx:1955, X{olec:ular concentration of kitlney cor.tex slices. J. physiol.,

130 :438-445.Dr-rox, M.,rNt E. C. Wnnl1958. tr)nzyrnes. Neu' Yorli, i82 pp. (pp. lb0-120).I)usors, R.1896. Physiologie compa,r6e cle la rnarnotte. Ann. Univ. Lyon. pa.ris,268 pp. (Pp.82-105).l-nnw, W. O. auo T. Asano1956. Effects of carbon dioxicle inhalation on potassium liberatiorfrom the liver. Am. J. l,hysiol., lB5: i67-576.Frnuu,rxx, I). lNn O. FTTNSCrruTDT193:. I)er rvinter.schlaf . Ergebir. Biol., 8 :1-75.Il.rlr,, V. ll., R,. GR,\NII,r.lrl \\r. J. \Vrrrlltx1951. 'I'he influerrce of l{g arrcl p].rogens on teniperature r.egulation.AF Tech. Rt'por't No. 6682 (Wright Air Developrnent Center).Iir.rcv, ]'. (,'. ,rNn A. C. Bunrox1948. Hffert of IV injectiol of MgCl2 on the borlv tenperatur.e of theunanesthctizccl ilog, rvith some oLrselvations on X{g levels anclhoclr'tentperattle in man. Arr. J. Ph;,si0l., 152:407-416.IItrNc, S. K.1958. Rerral functiol cluring h1'pothermia anrl hibernatiol. Am. J.Physiol., 188 : 137-150.Ii.rvsrn, C.1957. Le somuteil hirelrral pr.olildrne cle thenuor6gulation. Re.r,. Canatl.Biol., l6:303-389.Lvrrlx, C. J). ,rnl P. O. Cn.r.rprnr,l19J5. Pliysiolog;' of hibernation ir mrtrnnal-s. Physiol. Rer., OS:403-125.Lr:-u.r-r. C. P., L. P. \Vrirss, R. C. O,BnrtN -LNo A. A. Bannn,tul95i. The effect of hiliernation on the replacenent of bloocl in thegolilen hanrster.. J: Erp. Zoo1., lS6:421-486.llcBrnxrn, J. !1., F. G. Ptrnsox, L:1. A. TBUSLER, H. tI. Ken.rcar,rNlW. G. BrGELorv19;3. Physiological stutl.ies of the groundho g (.Marmota ,tnonar).Canacl. J. \Iecl. Sci., 3l:421-430.Pl-rtNnn, W. S.19J0. Effects of lorv ternperature ol l1g content of btood, body fluictsancl tissues of golclfish ancl turtle. AnL. J. Physiol., 161:39g-40b.


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432 BUr,rrETrN: MUSEUIT oF coMpARATrvE zoorrocy Vol. 124Pr,-a.rNnn,'W. S. ,LNo tr,I. J. HosKo1953. I'Iobility of serurn magnesium in hypothermia. Am. J. Physiol.,174:273-276.R-+suussnr, A. '1.1916. The corpuscles, hemoglobin content and specifie gravity of theblootl during hiberna,tion in the wooclchtck (Marmota monan),Am. J. Physiol., 4l:464-482.Rrnonsnr,, trf. L.1957. Serum nagnesiurn levels i.n mammalian hibernation. Trans.Kansas Acacl. Sci., 60 :99-141.Rrornsnr,, XI .L. rxp G. E. For,ri, Jn.19J7. Ser,rm nragnesiurn changes in cold-exposetl mammals. J. Mant-mal., 38 :123-421.1958. Serum electrolyte levels in hibelnating mammals. Amer. Nat.,

92 :307-312.Scnurz, J.

'1 91(i. Zul Kelntnis cler Wirliung tles \Iagnesium auf die Korper-ternperatur. Arch. e-xp. Pathol. Pharmakol., 79:285-290.Sor,r,rrr-r.x, T.1957. A manual ot' phalruacology. Philadelphin, 1535 pp. (Pp. 1057-1062).Sou'r'u, F. E. .,lxn H. Jnrr.rv1958. Alterations in serum proteins of hibernating hamsters. Proc.

Soc. Exp. Bio1. Ilecl., 98 :885-887.Srlcron, W. S,1.956. Hanclbook of biological clata,. Philaclelphia ancl Lontlon, 584 pp.(Pp.28-29).Srnlorr-lx, L. '1., I. Anrnr, ,l,xl S. L. \Y.qnrrlN1943. Stuclies on the effect of hypothermia. I\-. The lise of serum llgin ral:rbits iluring the hypothermic states as sholvn by the spectro-chemictrl methocl, Calcer Res., 3:477'174.St'r.rcr


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1960Svrnl,t, A.

1 !i5 3.

Zrrrxr-, lI.l95ti.

433

l{etabolisrn of some calbohyalrate and phosphate compounalstluring hibernation in the ground squirrel. J. Oell. Comp.I'h1 siol., 48 :371 -39j.DISOI]SSION I'OI,IIIO\VING RIEDESEI,/'S PAPER

WIMSATT observecl that RIEDESELT'S serum measurementscolrl:l l'eflect cliscontirlrit). in hiLrelnatiot, aucl luight also lrrovidecvidence for arousal lf so, one nlaJi be able to malripulate mech-anisms in such a way as to eliminate arousal. lle also gal'e fur-ther evidence for cyclirrg of hiirerutrtion. In visiting bat caveset'ell tu,o \\reelis (huing thlee rvinters he observecl that tlieclnsters of bats tnovetl, and bauding stuclies s]rorvecl rnovementsof aninals betu'een ca\-es in the miclclle of l'inter. Even in anartificial hibernacnlrrrrr thc.re ale tiiiles \\.hen bats are active inthe liiberrrating seasrirr. ltlEDESEL thought this rvas true, arrdhe felt that the cJ'cle naJ' partly leflect tetlperature changes.With respect to moveurents of bats in caves. IiOI:K (G. Il. tr'olh,J. n'Iammai., 2l:306, 1940) rvas citecl as having reportecl changesin positions of bats in u'inter. cluite a bit of movement beingcharacteristic.

,\DOLPH therr asked if SIIOM,\LAINEN \vouicl give his pres-cnt vierv of tlic rolc of niagnesium in hibernation. SOIITH alsonslied if SIjO,\IAL,\INEN hekl to hjs olcl f is11'point. SI.|OX{A-L;\INEN rernarliec'l that it is a cliflicult question, but that he l'assrue rnagnesium is a typical irr


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+:14 BuLLETTN: rrusEUM op cor{l'ARATrvIt zoorrocy Vol. 124bloo


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I 960 trT AMMAI]IAN I]IB]trIiNATIONrncrease of serum rnagnesium in hibernation ancl in hypothermia.IIe ilelieves magnesiurn increase irr the serum is related to (isperhaps the corrsec3rence of) hypotherrnia. He said he rvas notconvincerl that magnesium hacl a causal effect on hibernation,but rather beiieved that elevatecl serum magnesium was a con-sequence of cold.

F OLK remarked that he felt the discussion was difficult be-cause there was not time enough to go into methods. Relativeto WINISATT'S and POPOVIC'S comments, he said it shouldlle emphasized that lneasurements u'ere rnaile after sacrifieinganimals in spontaneous hibernation.}}ARTFIOI,/OME W, t-'xtenclin g I(AYSEIi,'S remarlis, pointedout that hibernation-h;'pothermia discussions are impecled b-vthe chlonic problem of causation and correlation. FIe rvoulcl liketo separate hypotherrnia and iribemation. By experience with avariety' of forms, he hacl noted tliat hypothermia, per se, is nottin cssential causal factor for hibernation. Ife felt that peri-pheral cooling is a result rather than a cause. He asked that rve

release ourselves from dependencl- or1 the iclea that colcl exposlrreis a necessary prior condition to entering liibernation.RIIIDESEIT state

The Internal Environment During Hibernation

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