흰쥐 대뇌피질의 모세혈관 구조에 관한 연구

Abstract

[한글]

중추신경계의 대뇌에 있어서 혈액과 뇌실질간의 투과성에 대하여 선택적 장벽이 개재한다는 사실이 알려진 후 많은 연구자들이 선택적 장벽과 관련성이 있는 대뇌 모세관의 형태학적 특이성을 규명하고저 미세구조에 대하여 조사해 왔다.

그러나 선택적 장벽의 투과성을 뒷받침 해줄만한 모세관 미세구조의 특이성 및 연령차이에 대한 투과성의 변화에 대하여는 상세히 규명되어 있지 않다.

저자는 흰쥐 대뇌의 혈액-뇌 장벽 (blood-brain harrier)을 구성해주는 모세관을 출생 전, 후 및 성숙 흰쥐에서 전자현미경적 관찰을 하여 선택적 장벽의 구조상 특성을 밝히고저 하였던 바 다음과 같은 결과를 얻었다.

태아 및 출생초기의 흰쥐에 있어서 대뇌피질 모세관의 내피세포와 외막세포의 세포질에서 볼 수 있었던 많은 유리 리보솜(ribosome)과 대소부동한 소포의 출현량은 출생후 3개월된 흰쥐에서 현저히 감소되었다.

태아기와 출생초기에서 모세관 내피세포의 많은 세포질돌기 혹은 미세융모 그리고 음소포(pinocytotic vesicles)등의 구조는 출생후 3개월 이상이 되면서 거의 관찰되지 않았다.

내피세포와 외막세포의 두께는 태아와 신생흰쥐에서는 두텁고 일정하지 않았으나 3개월된 흰쥐에서는 일정한 두께로 얇아졌다.

모세관 기저막의 구성요소인 3충 즉, lamina dense, lamina rara 및 zona diffuse는 출생후 7일된 흰쥐에서 처음으로 관찰되었고 출생후 3개월된 흰쥐에서는 lamina densa가 두터워졌고 lamina rara와 zona diffusa는 얇아졌다.

성상교세포 혈관주위소족(astrocytic perivascular feet)의 기저막과 접촉되는 면적은 성숙하며 따라 점차 넓어졌다.

이상의 결과로 미루어 흰쥐 대뇌피질의 모세관은 출생직후 부터 성숙된 형태를 구비하기 시작하는 것으로 생각한다.

Studies on the Fine Structure of Capillaries in the Cerebral Cortex of Albino Rats

Don Woo Choi

Department of Medical Science, The Graduate School. Yonsei University

(Directed by Prof. Soo Yun Pak)

The structure and the function of capillaries in the central nervous system have

been of special interest since the existence of a selective barrier in permeability

between the blood and brain was described by Ehrlich (1885). Thereafter the

morphology of thin barrier has become the main objective of numerous

investigations.

Patek (1944) reported that the morphological blood-brain harrier consisted only

of the et pillary wall itself and the surrounding sheath of astrocytic perivascular

feet. Van Breeman ca al. (1955) and Dempsey et al. (1955) studying rats, fed silver

nitrate in their drinking water, found that silver was deposited in the connective

tissue around the basement membrane of the capillaries of the body and in known

permeable sites in the central nervous system but not around the capillaries in

other areas of the central nervous system.

Based on the observations and results of many authors concerning this selective

barrier of the capillaries in the central nervous system, electron microscopic

examination of the cerebral cortex of prenatal and postnatal albino rata was

undertaken in order to studs the fine structure of the capillaries and their

investing sheaths to determine whether there are also morphological changes with

increasing age.

Albino rats of the Spraque-Dawley strain were used for the this study. The

prenatal rats were 12 and 16 days old and the postnatal rata were 7 and 16 days as

well as 3 months old.

Small pieces of the dorsal parasagittal cerebral cortex were placed in cold 1%

buffered osmic acid as described by Palade (1952). The tissue wart then cut into

blocks of approximately 1mm**3 in size and fixed for about 2 hours in 4%

glutaraldehyde in phosphate buffer (pH 7.4) and then postfixed in cold 1% osmium

tetroxide in phosphate buffer (pH 7.4) for about 2 hours.

The blocks were dehydrated through an ethanol series and embedded in Epon 812 by

means of the procedure used by Luft (1961). Thin sections were prepared with glass

knives on a Porter-Blum microtome and then stained with uranyl acetate and lead

nitrate as deseribed by Watson (1958) and Millonig (1961) respectively. These

sections were examined through a Hi-tachi HU-11 E type electron microscope.

Morphological alterations of the cerebral cortical capillaries and their

surroundings that were observed in the rots ranging in age from the 12th fetal to

the 16th postnatal day have been recorded and comparisons have been made with the

matured rats approximately 3 mouths of age.

Free ribosomes and vesicles in the cytoplasm of the endothelial cell and

pericyte, which were relatively rich in the fetal and the newborn rata, were

significantly diminished in the matured rats.

In the fetal and newborn rats the thickness as of the endothelial cell and

pericyte were usually thicker and less uniform than those of the matured rats.

However the intraluminal flaps or microvilli of the endothelial cell, which were

usually observed in the fetal and newborn rats, were markedly diminished in number

and size in the matured rats.

In the newborn rats, the thickness of the basement membrane became more or less

uniform and thereafter, the membrane could be readily divided into 3 layers by its

electron density a main central dense layer or lamina densa, a subendothelial layer

which is more translucent and called the lamina rara or lucida, and an outer fuzzy

layer or the bona diffusa.

Consequently it was concluded that the fine structure of the cerebral cortical

capillary of the albino rat was developed and becomes fixed into the matured or

adult form of the capillary in the early postnatal period.

[영문]

The structure and the function of capillaries in the central nervous system have been of special interest since the existence of a selective barrier in permeability between the blood and brain was described by Ehrlich (1885). Thereafter the

morphology of thin barrier has become the main objective of numerous investigations.

Patek (1944) reported that the morphological blood-brain harrier consisted only of the et pillary wall itself and the surrounding sheath of astrocytic perivascular feet. Van Breeman ca al. (1955) and Dempsey et al. (1955) studying rats, fed silver

nitrate in their drinking water, found that silver was deposited in the connective tissue around the basement membrane of the capillaries of the body and in known permeable sites in the central nervous system but not around the capillaries in

other areas of the central nervous system.

Based on the observations and results of many authors concerning this selective barrier of the capillaries in the central nervous system, electron microscopic examination of the cerebral cortex of prenatal and postnatal albino rata was

undertaken in order to studs the fine structure of the capillaries and their investing sheaths to determine whether there are also morphological changes with increasing age.

Albino rats of the Spraque-Dawley strain were used for the this study. The prenatal rats were 12 and 16 days old and the postnatal rata were 7 and 16 days as well as 3 months old.

Small pieces of the dorsal parasagittal cerebral cortex were placed in cold 1% buffered osmic acid as described by Palade (1952). The tissue wart then cut into blocks of approximately 1mm**3 in size and fixed for about 2 hours in 4%

glutaraldehyde in phosphate buffer (pH 7.4) and then postfixed in cold 1% osmium tetroxide in phosphate buffer (pH 7.4) for about 2 hours.

The blocks were dehydrated through an ethanol series and embedded in Epon 812 by means of the procedure used by Luft (1961). Thin sections were prepared with glass knives on a Porter-Blum microtome and then stained with uranyl acetate and lead nitrate as deseribed by Watson (1958) and Millonig (1961) respectively. These sections were examined through a Hi-tachi HU-11 E type electron microscope.

Morphological alterations of the cerebral cortical capillaries and their surroundings that were observed in the rots ranging in age from the 12th fetal to the 16th postnatal day have been recorded and comparisons have been made with the matured rats approximately 3 mouths of age.

Free ribosomes and vesicles in the cytoplasm of the endothelial cell and pericyte, which were relatively rich in the fetal and the newborn rata, were significantly diminished in the matured rats.

In the fetal and newborn rats the thickness as of the endothelial cell and pericyte were usually thicker and less uniform than those of the matured rats.

However the intraluminal flaps or microvilli of the endothelial cell, which were usually observed in the fetal and newborn rats, were markedly diminished in number and size in the matured rats.

In the newborn rats, the thickness of the basement membrane became more or less uniform and thereafter, the membrane could be readily divided into 3 layers by its electron density a main central dense layer or lamina densa, a subendothelial layer

which is more translucent and called the lamina rara or lucida, and an outer fuzzy layer or the bona diffusa.

Consequently it was concluded that the fine structure of the cerebral cortical capillary of the albino rat was developed and becomes fixed into the matured or adult form of the capillary in the early postnatal period.