【摘要】：1前言 人類胼胝體是連接大腦兩側(cè)半球最大的白質(zhì)連合。隨著年齡增加,胼胝體前部會(huì)明顯減少,嘴和膝比壓部的比例下降,干部和壓部的厚度變薄,胼胝體的前后長(zhǎng)度和最大高度增高。胼胝體內(nèi)包含有髓神經(jīng)纖維和無(wú)髓神經(jīng)纖維,胼胝體的大小由纖維的數(shù)量和直徑的大小決定。衰老是否引起了胼胝體神經(jīng)纖維直徑的改變呢?目前的研究主要集中在出生前和出生后240天以內(nèi),但對(duì)于成年后一直到老年時(shí)期的胼胝體超微形態(tài)學(xué)的研究較少。有研究表明胼胝體接受來(lái)自顳葉后部包括顳極和顳上、下回的纖維,胼胝體干部的后部和壓部接受顳-頂-枕的連接區(qū)域以及頂上小葉和枕葉皮質(zhì)的纖維,胼胝體的干部和壓部可能與顳皮質(zhì)及顳皮質(zhì)相關(guān)的感覺(jué)功能有關(guān);聽(tīng)區(qū)位于顳上回,聽(tīng)力的不對(duì)稱性與胼胝體的大小,尤其胼胝體前部和后部的大小呈明顯的負(fù)相關(guān)。所以胼胝體的干部和壓部與顳皮質(zhì)相聯(lián)系,并與感覺(jué)功能相關(guān)。為了解老化對(duì)于胼胝體中段和壓部的影響,本研究將應(yīng)用新的體視學(xué)方法和電子顯微鏡技術(shù)來(lái)測(cè)定胼胝體中段(anterriormidbody,posterior midbody and isthmus)和壓部體積及其內(nèi)有髓神經(jīng)纖維的老年改變。 2目的 運(yùn)用新的體視學(xué)方法定量研究成年、中老年和老年雌性Long-Evans大鼠胼胝體中段和壓部的體積、有髓神經(jīng)纖維的長(zhǎng)度密度、總長(zhǎng)度、有髓神經(jīng)纖維的直徑、有髓神經(jīng)纖維體積、髓鞘體積、髓鞘厚度、髓鞘的內(nèi)周長(zhǎng)、外周長(zhǎng)的老年改變。 3方法 選擇成年組(7月齡,250±20 g)、中老年組(18月齡,350±25 g)和老年組(27月齡,380±40 g)雌性Long-Evans大鼠各5只。將大鼠麻醉灌注固定后,從每只大鼠隨機(jī)抽取一側(cè)大腦半球。以Witelson(1989)的工作為基礎(chǔ),將胼胝體分為三部分,前5/15為前部(包括Rostrum,Genu and Rostral Body),后3/15為后部(包括Splenium),中間剩下的部分為中段(包括Anterior Midbody,Posterior Midbody and Isthmus)。制作1 mm厚的連續(xù)腦組織塊。常規(guī)電鏡標(biāo)本制備。在放大14400倍的透射電子顯微鏡下,隨機(jī)選取視野進(jìn)行拍照,每個(gè)組織塊拍攝5～6張電鏡照片,因此每只大鼠胼胝體中段和壓部各得到10～12張電鏡照片。運(yùn)用新的體視學(xué)方法定量研究成年、中老年和老年雌性Long-Evans大鼠胼胝體中段和壓部的體積、有髓神經(jīng)纖維的長(zhǎng)度密度、總長(zhǎng)度、有髓神經(jīng)纖維的直徑、有髓神經(jīng)纖維體積、髓鞘體積、髓鞘厚度、髓鞘的內(nèi)周長(zhǎng)、外周長(zhǎng)的老年改變。 4結(jié)果 4.1老年組大鼠的胼胝體中段體積較成年組下降21.5%(p0.05),老年組較中老年組下降18.1%(p0.01)。壓部體積未見(jiàn)明顯老年性改變(p0.05)。 4.2老年組胼胝體中段有髓神經(jīng)纖維總長(zhǎng)度較成年組和中老年組分別降低28.8%和27.7%,但差異沒(méi)有統(tǒng)計(jì)學(xué)意義(p0.05)。胼胝體壓部有髓神經(jīng)纖維總長(zhǎng)度也未見(jiàn)明顯老年性改變(p0.05)。 4.3 3個(gè)年齡組之間,胼胝體中段和壓部?jī)?nèi)的有髓神經(jīng)纖維平均直徑均不存在顯著差異。 4.4在胼胝體中段,直徑為0.3～0.9μm的有髓神經(jīng)纖維的總長(zhǎng)度在老年組比成年組和中老年組有所降低,其中直徑為0.7～0.8μm的有髓神經(jīng)纖維的總長(zhǎng)度在老年組(3.152 km)比成年組(6.602 km)降低52.3%(p0.05),其他直徑段有髓神經(jīng)纖維長(zhǎng)度的變化沒(méi)有統(tǒng)計(jì)學(xué)意義;直徑為1.5～1.6μm的有髓神經(jīng)纖維的總長(zhǎng)度在老年組(0.614 km)比成年組(0.114 km)增加4.55倍(p0.05)。在胼胝體壓部,直徑為0.4～0.7μm的有髓神經(jīng)纖維總長(zhǎng)度在老年組比成年組和中老年組有所增加,但差異沒(méi)有統(tǒng)計(jì)學(xué)意義;直徑為1.2～1.3μm的有髓神經(jīng)纖維總長(zhǎng)度在老年組(0.189 km)比成年組(0.066 km)和中老年組(0.074 km)分別增加1.86倍(p0.05)和1.55倍(p0.05);直徑為1.4～1.5μm的有髓神經(jīng)纖維的總長(zhǎng)度在老年組(0.113 km)比成年組(0.005 km)增加21.6倍(p0.05)。 4.5胼胝體中段的有髓神經(jīng)纖維的體積,在年輕組為27.84±1.29mm~3;在中老年組為29.09±1.39 mm~3;老年組為20.12±1.41 mm~3。中段內(nèi)老年組有髓神經(jīng)纖維的體積明顯比成年組和中老年組小(p0.05)。而胼胝體壓部的有髓神經(jīng)纖維的體積沒(méi)有明顯的老年改變。中段內(nèi)有髓神經(jīng)纖維的體積與胼胝體中段體積存在正相關(guān)(r = 0.869, p0.01),壓部?jī)?nèi)有髓神經(jīng)纖維的體積與胼胝體壓部體積存在正相關(guān)(r = 0.931, p0.01)。 4.6中段內(nèi)老年組有髓神經(jīng)纖維的髓鞘體積明顯低于成年組和中老年組(p0.01)。壓部?jī)?nèi)有髓神經(jīng)纖維的髓鞘體積沒(méi)有明顯老年性改變。 4.7胼胝體中段和壓部?jī)?nèi)有髓神經(jīng)纖維的直徑,軸突直徑和髓鞘厚度的平均值均無(wú)明顯的老年改變。根據(jù)不同的有髓神經(jīng)纖維直徑,對(duì)有髓神經(jīng)纖維進(jìn)行分段,不同直徑段的髓鞘厚度存在明顯老年改變。直徑相對(duì)較大的有髓神經(jīng)纖維的髓鞘厚度隨著年齡的增加而增加。在胼胝體中段,直徑為0.9～1.0μm和1.2～1.3μm的有髓神經(jīng)纖維的髓鞘厚度在中老年組比成年組均顯著增加(p0.01,p0.05);直徑為1.5～1.6μm的有髓神經(jīng)纖維的髓鞘厚度在中老年組比成年組小(p0.05),老年組比中老年組小(p0.05)。在胼胝體壓部,直徑為0.9～1.0μm和1.1～1.2μm的有髓神經(jīng)纖維的髓鞘厚度在老年組比成年組顯著增加(p0.05)。 4.8胼胝體中段與壓部的外周長(zhǎng)與內(nèi)周長(zhǎng)之差,以及兩者之間的比值的平均值均無(wú)顯著的老年改變。在胼胝體中段,當(dāng)與成年組比較時(shí),直徑大于0.9μm的多個(gè)直徑段的有髓神經(jīng)纖維的髓鞘外、內(nèi)周長(zhǎng)之差在老年組和中老年組均增加;當(dāng)與成年組比較時(shí),直徑大于0.9μm的多個(gè)直徑段的有髓神經(jīng)纖維的髓鞘外、內(nèi)周長(zhǎng)的比值在老年組和中老年組均增加。髓鞘外、內(nèi)周長(zhǎng)之差和之比的改變均表明,在中段內(nèi)直徑相對(duì)較大的有髓神經(jīng)纖維的髓鞘隨年齡的增加而變厚。在胼胝體壓部,髓鞘外、內(nèi)周長(zhǎng)之差和之比的改變均表明,在中段內(nèi)直徑相對(duì)較大的有髓神經(jīng)纖維的髓鞘隨年齡的增加而變厚。 5結(jié)論 5.1本研究顯示老年大腦胼胝體壓部體積沒(méi)有發(fā)生顯著性改變,老年大腦胼胝體中段體積顯著性下降。 5.2胼胝體中段內(nèi)小直徑的有髓神經(jīng)纖維總長(zhǎng)度顯著性降低可能是老年胼胝體中段體積顯著性下降的重要原因之一。 5.3胼胝體壓部較大直徑有髓神經(jīng)纖維長(zhǎng)度隨年齡增加而增加。 5.4胼胝體中段和壓部?jī)?nèi)較大直徑有髓神經(jīng)纖維髓鞘厚度隨年齡增加而增加,而較小直徑有髓神經(jīng)纖維髓鞘厚度變化不明顯。
[Abstract]:1 Preface
The corpus callosum is the largest white matter connected to the two hemispheres of the brain. As the age increases, the anterior part of the corpus callosum decreases obviously, the ratio of the mouth to the knee is reduced, the thickness of the cadres and the pressure part is thinner, the length and maximum height of the corpus callosum increases. The corpus callosum contains myelinated and unmyelinated nerve fibers, and the corpus callosum is large. The size of the fibers depends on the size and size of the fibers. Does senescence cause changes in the diameter of the corpus callosum fibers? The current study is mainly focused on the 240 days before and after birth, but there are few studies on the ultrastructure of the corpus callosum in the adult period. The branches of the temporomandibular and inferior temporal and inferior gyrus, the posterior part of the corpus callosum and the pressure part of the corpus callosum accepted the junction of the temporo top occipital and the upper lobule and the occipital cortex. The corpus callosum may be associated with the sensory function of the temporal cortex and the temporal cortex; the auditory area is located in the upper temporal gyrus, the asymmetry of hearing and the size of the corpus callosum. In particular, the anterior and posterior portion of the corpus callosum is negatively correlated with the size of the posterior part of the corpus callosum. Therefore, the corpus callosum is associated with the temporal cortex and is associated with the sensory function. In order to understand the effect of aging on the middle segment and pressure of the corpus callosum, a new stereological method and a microscopical technique will be used to determine the median corpus callosum (anterriormidbod Y, posterior midbody and isthmus) and compression volume and the changes of myelinated nerve fibers in the aged.
2 purposes
A new stereological method was used to quantify the volume of the middle and pressure parts of the corpus callosum in adult, middle-aged and old female Long-Evans rats, with the length density of the myelinated nerve fibers, the total length, the diameter of the myelinated nerve fibers, the volume of myelinated nerve fibers, the volume of myelin sheath, the thickness of myelin sheath, the inner circumference of medullary sheath, and the external circumference of the elderly.
3 method
The adult group (7 month old, 250 + 20 g), the middle and old age group (18 month old, 350 + 25 g) and the old group (27 month old, 380 + 40 g) of the female Long-Evans rats each. After the rats were instilled, the rats were randomly selected from each rat. The corpus callosum was divided into three part with Witelson (1989) working as the basis, and the front 5/15 was the front part (including Rostru). M, Genu and Rostral Body), after 3/15 as the back part (including Splenium), the remaining part of the middle part is the middle section (including Anterior Midbody, Posterior Midbody and). Making 1 thick continuous brain tissue blocks. Preparation of conventional electron microscopy specimens. Under the amplification of 14400 times the transmission electron microscope, random selection of visual field is taken to take pictures, each tissue block is taken. 5~6 electron microscopic photographs were taken, and 10~12 electron microscopic photographs were taken in each rat's corpus callosum and the pressure part. A new stereological method was used to quantify the volume of the middle and pressure parts of the corpus callosum of adult, middle-aged and old female Long-Evans rats, with the length of the myelinated nerve fiber, the total length, the diameter of the myelinated nerve fibers, and the medullary God. The age-related changes of myelin sheath volume, myelin sheath volume, myelin sheath thickness, myelin sheath inner perimeter and peripheral length were observed.
4 Results
4.1 the volume of the corpus callosum in the aged group was 21.5% lower than that in the adult group (P0.05), and that in the elderly group was 18.1% (P0.01) compared with the middle aged group (P0.05).
4.2 the total length of the medullary nerve fibers in the middle segment of the corpus callosum in the elderly group was 28.8% and 27.7% lower than that in the adult and middle age groups, but the difference was not statistically significant (P0.05). The total length of the myelinated nerve fibers in the corpus callosum was not significantly changed (P0.05).
4.3 There was no significant difference in the average diameter of myelinated nerve fibers between the three age groups.
4.4 in the middle segment of the corpus callosum, the total length of the myelinated nerve fibers with a diameter of 0.3 to 0.9 m decreased in the elderly group than in the adult and middle aged groups. The total length of the myelinated nerve fibers with a diameter of 0.7 to 0.8 micron m decreased by 52.3% (6.602 km) in the elderly group (6.602 km), and the length of the myelinated nerve fibers in the other diameter segments was changed. The total length of myelinated nerve fibers with a diameter of 1.5 ~ 1.6 mu m increased by 4.55 times (P0.05) in the elderly group (0.614 km) than in the adult group (0.114 km). In the corpus callosum, the total length of the myelinated nerve fibers with a diameter of 0.4 to 0.7 um m increased in the elderly group than in the adult and middle aged groups, but the difference was not statistically significant; The total length of myelinated fibers with a diameter of 1.2 to 1.3 m (0.189 km) increased 1.86 times (P0.05) and 1.55 times (P0.05) in the elderly group (0.066 km) and in the middle and old age group (0.074 km), and the total length of the myelinated fibers with the diameter of 1.4 to 1.5 mu (0.113 km) increased by 21.6 times (P0.05) in the elderly group (0.113 km) than in the adult group (0.005 km).
4.5 the volume of myelinated nerve fibers in the middle segment of the corpus callosum was 27.84 + 1.29mm~3 in the young group and 29.09 + 1.39 mm~3 in the middle and old age group; the volume of myelinated nerve fibers in the elderly group was 20.12 + 1.41 mm~3.. The volume of myelinated nerve fibers was significantly smaller than that in the adult and middle aged groups (P0.05). There was a positive correlation between the volume of medullary nerve fibers in the middle segment and the volume of the corpus callosum (r = 0.869, P0.01). There was a positive correlation between the volume of myelinated nerve fibers in the pressure part and the volume of the corpus callosum (r = 0.931, P0.01).
4.6 the medullary sheath volume of the myelinated nerve fibers in the elderly group was significantly lower than that in the adult group and the middle aged group (P0.01). The myelin sheath volume of the myelinated nerve fibers in the press did not change significantly.
4.7 the diameter of the myelinated nerve fibers, the diameter of the axon and the thickness of the myelin sheath in the middle part of the corpus callosum and the average value of the medullary sheath thickness were no obvious old changes. According to the diameter of the myelinated nerve fibers, the myelinated fibers were segmented and the myelin thickness in different diameter segments had obvious aging changes. The pulp of the myelinated nerve fibers with relatively large diameter was the pulp. The thickness of the sheath increased with age. The myelin thickness of the myelinated nerve fibers in the middle and old age groups increased significantly (P0.01, P0.05) in the middle of the corpus callosum and in the middle-aged and old age groups. The myelin thickness of the myelinated nerve fibers with the diameter of 1.5 ~ 1.6 m in the middle and old age group was smaller than that of the adult group (P0.05), and the older group was compared with the middle age group (P0.01, P0.05). In the elderly group (P0.05), the myelin thickness of myelinated nerve fibers in the aged group increased significantly (P0.05) at the corpus callosum pressure, with the medullary sheath thickness of the myelinated nerve fibers with the diameter of 0.9 to 1 mu and 1.1 ~ 1.2 mu m.
4.8 the difference between the outer circumference and the internal circumference of the middle corpus callosum and the pressure part, and the average value of the ratio between the two groups were not significantly changed. In the middle of the corpus callosum, the difference in the length of the circumferential length increased in the elderly and the middle aged and old groups when compared with the adult group, and the myelinated nerve fibers with the diameter more than 0.9 m in diameter were increased. In the adult group, the myelin sheath of the myelinated nerve fibers with a diameter greater than 0.9 m in diameter increased the ratio of the inner circumference in both the elderly and the middle and old groups. The difference in the length of the medullary and the change of the ratio of the intramedullary sheath to the medullary sheath thickened with the increase of age. The change of the ratio of the difference of the inner circumference and the outer circumference of the compression part and the outer part of the myelin sheath showed that the myelin sheath of the myelinated nerve fibers with relatively large diameter in the middle part thickened with the increase of age.
5 Conclusion
5.1 This study showed that there was no significant change in the pressure volume of the corpus callosum in the aged, and the middle volume of the corpus callosum decreased significantly in the aged.
5.2 A significant decrease in the total length of small-diameter myelinated nerve fibers in the middle part of the corpus callosum may be one of the important reasons for the significant decrease in the volume of the middle part of the corpus callosum in the elderly.
5.3 The length of the larger diameter myelinated nerve fibers in the corpus callosum increased with age.
5.4 the medullary sheath thickness of the medullary nerve fibers in the middle and pressure parts of the corpus callosum increased with age, but the thickness of the myelinated myelin sheath in the smaller diameter was not obvious.
【學(xué)位授予單位】：重慶醫(yī)科大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2011
【分類號(hào)】：R322.81

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