[考古] 19号考试补充月读考古

2.1.4 冷血动物

V1 By luckyxmx

记起来那个长阅读了，好像是三四段，第一段说冷血动物（还是冬眠动物）为什么能够活在很冷的天气里而不死。因为它们有某种物质，这种物质可以阻止小冰晶结成大冰晶破坏组织什么的。比较长

第二段举了某动物的例子，说它还有另外一种物质帮助它在寒冷环境下存活，这种物质帮它减低细胞能量的消耗什么的，这段比较短

第三段说了这个原理在医学上的应用，墨迹了一会，但好像目前为止还没成功的样子。。。这段比上一段长一点点

V2 By 某贝

冷血动物靠什么机制过冬。说了2种方法。第二种方法还单独一断用wood frog举例来说。最后是说可以把这些方法运用到人的器官移植。。觉得这篇是最简单的。。记得比较清楚

V3 by njim

还有就是有一篇冷血动物怎么通过不同方法冬眠，而人们还无法这种应用到器官医学方面

V4 by syusuke02

树蛙整段高亮问作用

V5 by gaohongmin(Q50,V40)

很长的一篇，关于冷血动物防冻 的文章；大概共三/四段，先描述了冷血动物常用的两种防冻机制，一种是一种Protein，还有一种是利用什么antifreeze什么的；第二部分描述WOOD FROG的防冻机制，好像跟两两种都不太一样；最后一段将人类将此种机制应用在人体或者医学上，虽然还没有大的进展，但是很有借鉴意义。

V6 by  龍之哀伤(Q50,V35,700)

阅读是第一个是冷血动物, 问了那个青蛙的blood suger是干啥用的, 和第一段最后说到的那个东西有点容易混,小心点. 问了woodfrog这段是为了干嘛, 是为了说some animal need more than (第一段的物质) to survive in .....

V7 by  Cherry0225

冷血动物那片的题目：

1。主题题，A/B选项很像，大家考的时候注意

2。高亮wood frog,  as in order to

3. 树蛙没有那个腺体会怎样，选项，energy not suffient, 这个应该确定的

4。 第一段中有一个破折号的名词，题目文这个东西起什么作用，答案我选的是，controlfreezing 啥的，这个也确定，原文那个名词后面就可以定位到。

V8 by sky2  (700)

冷血动物那篇。比较长，但是不难

问题：树蛙的例子的作用。选项有说明有动物有除了anti-freezing和什么（忘了）以外的方法抗冻；还有说明树蛙在一种情况下用一个方法抗冻，另一种情况下用另一个方法抗冻。。。

主旨。选项有说明了冷血动物抗冻的process以及在器官移植上的dissimiliar啥的。。。

V9 by TTJudy 710

   冷血动物

第一段：介绍了冬眠hibernation，然后说冬眠是一种自然界里很多动物（freeze tolerantanimals）都会采取的过冬方法blabla，反正第一段不重要。下文两段分别介绍的是动物们普遍采取的两种方法。

第二段：介绍了一种通过anti-freezeprotein来保护身体的机制。首先用一个同位语解释了这种蛋白（一个术语cryoprotectant）可以control the formation of freeze，让动物结冻后安全解冻，然后说这种抗冻蛋白可以保护细胞，可以让细胞外体液结晶后均匀分布，不至于局部涨大损坏细胞的。

第三段：介绍了另外一种通过提高血糖浓度的方法来御寒的机制。以典型代表树蛙为例，高浓度血糖除了抗冻外可以有各种作用，比如降低冬眠期间的细胞耗能，还有些别的，后面考到过细节题，定位即可。

第四段：最后讲这两种抗冻机制给了科学家启示，在医学上的各种应用，没考点，可忽略。

V10 by  tina弯(Q51,V25,640)

第三篇是冷血动物。一题问的是a开头的一种物质的作用。还问了举青蛙例子的作用。最后一段关于医学应用的几乎没用，粗略看一下即可。

考古

冷血动物体内结晶

【已确认】

V1 by mopton(690)

1篇讲某些冷血动物（会冬眠的乌龟，青蛙。。）体内的ice-nucleating（冰晶）？（1段）帮助细胞crystalized，另外的anti-freezing帮助减少the cluster of crystalization。（2段）青蛙体内有种XX（忘了名字）帮助reduce energy needed formetabolism。（3段）医学应用。（4段）虽然这篇是比较长第三段，但很容易读懂。

V2 by yifeifan (700)

一篇长阅读，像托福的：冷血动物poikilotherm的一些用于防治自身被freeze的functions，题目都是原文能直接定位的。中间一段举了树蛙的例子，它和上文中提到的那些动物的functions不同，有问题

V3 by rayzero

动物过冬的那个 freeze crystal的题目 补充一下中间那段说树蛙的，他说树蛙是通过增加血液里的血糖来过冬的。（后面有到细节题问的是这里树蛙增加血糖的作用）。

V4 by angelfisher

我能补充的就是第二段它讲的是crystalized什么的原理，然后就说这个晶体会越来越大，所以就有antifreezing来帮助减少，这里有个考点。第三段讲wood frog好像跟前文说的那个不太一样，第三段不长，但是有两个考题。第四段是医学应用，很简单，没考点。

V5 by withtea （690）

冬眠动物体内结晶那篇。文章有点长但是细节题很多，定位很容易。

V6 by zhouchlcy

防冻的那篇，就记得第三段吧，讲一种青蛙能提高血糖浓度，延缓被冻

有两道题，一个是全段高亮，问这段的作用

一个是问这种青蛙的防冻跟上面讲的有什么不同

V7 by Johnnyli (750)

冷血动物结晶，记得好像有个问题都是关于某个anti-freezeproteide的作用，原文中说它可以控制体内冰块结晶的体积保持在小冰渣的状态，不会凝结成大块（大概是这个意思），答案是控制...某个词忘了

V8 by 加洛林 (710)

树蛙的那个：有一个问说作者提到这种树蛙是为了什么？定位树蛙例子上段结尾。还有问没有树蛙体内的那种腺体物质，树蛙会怎样？仔细理解那个腺体的作用很重要。我选了一个能量所需无法满足。还有一个问说一种t物质实干什么用的？选保持血液中冰晶结冻速率稳定那个。还有一个问题在结尾，问你科学家研究的一个物质有什么特性。

背景文

Freeze tolerance

The ability towithstand the long-term freezing of body fluids has developed in diverse groupsof animals

including some frogsand turtles, many types of insects, and a variety of intertidal marine molluscsand

barnacles (Storey andStorey, 1989, 1996). Freeze tolerance occurs in several species of woodlandfrogs

that hibernate in theleaf litter of the forest floor including the wood frog (Rana sylvatica)(Figure 3), the

gray tree frog (Hylaversicolor), the spring peeper (Pseudacris crucifer) and the chorus frog(Pseudacris

triseriata). TheSiberian salamander (Salamandrella keyserlingii) and two turtle species, theterrestrial box

turtle (Terrapenecarolina) and the painted turtle (Chrysemys picta) also survive freezing. Freezetolerance

by painted turtles islimited to the newly hatched juveniles that stay in their underground nests fortheir first

winter of life whereasthe adults winter under water.

The driving force forfreeze tolerance was probably an inability to mount an effective defense

against inoculativefreezing by environmental ice. For example, the water-permeable skin of frogsis no

barrier to icepropagation and although frogs chilled to -2°C may stay supercooled if they aresitting on a

dry substrate, they beginto freeze in less than 30 seconds if they touch ice crystals. Since frogs needto

hibernate in the humidthe leaf litter to keep from desiccating, they have virtually no chance ofavoiding

freezing if icepenetrates into their microenvironment.

Freezing can causemultiple types of damage to unprotected organisms (Figure 4). Ice formation

inside of cellsscrambles intracellular architecture and is lethal in virtually all instancesso even freeze

tolerant animals takeprecautions to limit ice formation to extracellular spaces. Extracellular icecan also do

physical damage bysqueezing or shearing cells, puncturing membranes or bursting microcapillariesso that

upon thawing, theintegrity of cells and organs is destroyed. Ice propagating through extracellularspaces

such as the abdominalcavity, blood stream, gut lumen and bladder also causes severe dehydration ofcells.

This is because theformation of ice, which is a crystal of pure water, excludes the solutes thatwere

dissolved in it andraises the concentration of the remaining unfrozen extracellular fluid. Thishighly

concentrated fluidputs an osmotic stress on cells and draws water out of them so that they shrinkin

volume. If shrinkageexceeds a critical minimum cell volume, irreversible damage is done to thelipid

membranes surroundingthe cell and the cells are not viable after thawing. Freezing of blood alsohalts the

delivery of oxygen andnutrients to organs which most organisms cannot tolerate for long.

Freeze tolerantanimals have developed defenses against these possible injuries withadaptations

that fall into severalcategories: (1) regulation of ice propagation through body tissues, (2) damagerepair to

deal with bleedinginjuries caused by ice, (3) minimizing cell volume reduction during freezing,(4)

membrane and proteinstabilization, (5) resistance to oxygen deprivation, and (6) reactivation ofvital signs

(breathing, heartbeat, nerve and muscle activity) after thawing (Storey and Storey, 1996).

To control iceformation, freeze tolerant animals use specific nucleators (Figure 4). Insteadof

lowering their SCP inwinter as freeze avoiding animals do, freeze tolerant animals raise their SCPby using

nucleators so thatfreezing occurs begins just below the FP. Some species introduce special icenucleating

proteins into theirblood whereas others use contact with environmental ice crystals or thepresence of

nucleating bacteria onthe skin or in the gut to stimulate ice formation. The slow freeze initiated by

nucleators allows thegreatest possible time for organs to make metabolic adjustments before blood

circulation halts andpermits a controlled dehydration of organs that sequesters most of the ice inextraorgan

spaces (such as theabdominal cavity). This reduces the chance of internal damage to organs such as

by ice expansionwithin the lumen of capillaries. Some freeze tolerant animals also appear tohave AFPs in

their body fluidswhich seems contradictory. However, it appears that the function of AFPs infreeze

tolerant systems is tohelp regulate crystal growth and inhibit recrystallization, the process wherebysmall

crystals regroup overtime into larger crystals. In addition, freeze tolerant animals enhance theirdamage

repair mechanisms sothat bleeding injuries can be dealt with rapidly upon thawing. In wood frogs,for

example, freezingstimulates the production of blood clotting proteins.

Controlled dehydrationof cells and organs can minimize ice damage but cell volume reduction

can only go so farbefore cell membranes collapse under compression stress. Generally, freezetolerant

animals can endure theconversion of up to ~65% of their total body water into extracellular ice butthe

remainder must remainliquid within cells. Water retention in cells is aided by the synthesis of highlevels

of glycerol or relatedcarbohydrates which provide the same protection to the intracellular milieu offreeze

tolerant animals thatthey do for all of the body water of freeze avoiding animals. Frogs use glucoseas their

cryoprotectant withlevels of this blood sugar rising by 50-100 fold or more whenever body fluidsbegin to

freeze (Storey andStorey, 1996) . Interestingly, frogs show no evidence of the debilitatingeffects of

hyperglycemia that areevident at much lower sugar levels (2-10 fold above normal) in diabetics. Other

cryoprotectants arealso produced that stabilize the structure of cell membranes so that they canresist

compression stress;the sugar, trehalose, and the amino acid, proline, are widely used for thisfunction.

They intercalatebetween the headgroups of membrane phospholipids to stabilize the bilayerstructure that

is key to biologicalfunction and prevent the lipids from collapsing into an amorphous gel.

Freeze tolerantanimals have also enhanced their ability to cope with oxygen deprivation forthere

is no breathing and noblood circulation while frozen. Again, high glycogen reserves are used toproduce

ATP energy viaglycolysis with lactate build-up tolerated during the freeze. Freeze tolerantanimals also

show enhanced antioxidantdefenses that can minimize damage due to the production of oxygen free

radicals whenbreathing resumes after thawing. The molecular mechanisms that reactivate vitalsigns

during thawing arestill largely unexplored. In frogs, a resumption of heart beat is the firstdetectable vital

sign, followed soonthereafter by breathing and later by a return of coordinated muscle movements.Studies

of the physiology andbiochemistry of natural freezing survival by frogs are revealing numeroussecrets that

are being applied inthe development of improved cryopreservation technology for the freezingstorage of

mammalian cells,tissues and organs.