Membrane alterations during cornification of mammalian squamous epithelia: A freeze‐fracture, tracer, and thin‐section study
Membrane alterations during cornification of mammalian squamous epithelia: A freeze‐fracture, tracer, and thin‐section study
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哺乳动物鳞状上皮角质化过程中的膜变化：冷冻断裂、示踪剂和薄片研究
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发表时间：
1977
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影响因子：
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通讯作者：
D. Friend
中科院分区：
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作者：
P. Elias;N. Mcnutt;D. Friend
紧密连接（闭合小带）为非角化哺乳动物上皮中的大分子扩散形成细胞周屏障。然而，在角化上皮如表皮中，紧密连接元件与分泌的细胞间脂质对屏障功能的重要性尚不确定。为了解决这个问题，我们比较了正常和各种实验条件下新生儿和成年人和小鼠的表皮、食管和阴道的颗粒层和角质层的膜结构。我们在器官培养中孵育表皮片，并在体内和体外用镧或辣根过氧化物酶灌注组织。对所有样品进行冷冻断裂复制品或薄切片的电子显微镜检查。在检查的所有组织中，镧向外渗出至颗粒层-皮肤中的板层体内容物阻止了进一步的顶端迁移。在所有研究的上皮细胞中发生了类似的细胞间层状脂质沉积和膜结构。这些阻塞区域的冷冻断裂复制品显示偶见不完整的连接链（特别是在潮湿的上皮中）和丰富的板层物质，但从未遇到完整的闭锁小带。水分和紧密连接的形成之间可能存在的关系，进一步提出了器官培养实验期间，短暂的孵育刺激的连接链的数量增加和数量减少的板层体。我们的结论是，在研究的上皮细胞中，分泌的板层体内容物的沉积形成了水溶性示踪剂损失的屏障：紧密连接元件要么不存在，要么过于零碎，无法构成有效的屏障。
Tight junctions (zonulae occludentes) create a pericellular barrier to the diffusion of large molecules in non‐keratinizing mammalian epithelia. However, in cornifying epithelia such as the epidermis, the importance of tight‐junctional elements versus secreted intercellular lipid for barrier function is uncertain. In an attempt to resolve this question, we compared membrane structure in the stratum granulosum and stratum corneum of epidermis, esophagus, and vagina of newborn and adult humans and mice under both normal and various experimental conditions. We incubated pieces of epidermis in organ culture and infused tissues with lanthanum or horseradish peroxidase in vivo and in vitro. All were processed for electron microscopy of freeze‐fracture replicas or thin sections. Lanthanum seeped outward to the stratum granulosum in all tissues examined‐further apical migration was halted by lamellar‐body contents in skin. A similar pattern of intercellular lamellar lipid deposition and membrane structure occurred in all epithelia studied. Freeze‐fracture replicas of these obstructive regions revealed occasional, incomplete junctional strands (particularly in moist epithelia) and abundant lamellar material, but complete zonulae occludentes were never encountered. A possible relationship between moisture and tight junction formation was further suggested by organ culture experiments during which brief incubations stimulated an increase in the number of junctional strands and diminished numbers of lamellar bodies. We conclude that, in the epithelia studied, the deposition of secreted lamellar body contents forms the barrier to water‐soluble tracer loss: tight‐junctional elements are either absent or too fragmentary to constitute an effective barrier.