摘要:

AbstractThe present study utilizes the scanning electron microscope (SEM) to reveal the surface morphology of proximal tubular cells and the parietal cells of Bowman's capsule of the adult rabbit nephron. To facilitate the examination of the basal surface of these cells, proximal tubules were dissected free and treated with collagenase to remove the basememt membrane. Other blocks of tissue were cryofractured to expose the lateral cell surfaces of the proximal tubules. Our investigation has shown that the lateral and basal surfaces of both the convoluted and straight segments of the proximal tubule have numerous processes. However, the arrangement and degree of branching is distinctly different in the two segments. The convoluted segment has large lateral ridges which form at the base of the microvilli and fan out to divide into lateral‐basal processes. Many of the lateral‐basal processes reach the basement membrane intact, interdigitating with complementary processes from adjacent cells. However, some of the lateral‐basal processes branch into short, knobby projections (basal villi) which may also reach the basement membrane. Patches of basal villi are interspersed between broad regions of interdigitating lateralbasal processes. Therefore, in the convoluted segment, the lateral‐basal processes form the major part of the basal cell surface. In tubular cells of the pars recta, unlike convoluted tubular cells, the majority of the ridges remain unbranched and pass directly to the basal surface where they divide into elaborate basal villi. Thus the basal surface of the pars recta cells is highly complex, appearing leaf‐like, being a composite of numerous basal villi with a few lateral ridges.The basal surface of some parietal cells of Bowman's capsule have parallel ridges, which results in patches of s

ISSN:0003-276X    

DOI:10.1002/ar.1091910402

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractMorphological and functional differentiation of the mucosal surface epithelium of the bursa Fabricii was studied in White Leghorn chicken fetuses and newly hatched chickens. First signs of differentiation towards two types of epithelial cells appeared on the thirteenth day of incubation: The apical cells of the epithelial buds projected towards the lumen, and an increase in the number of Golgi regions was observed in the epithelial cells between the buds. On day 15 the follicle‐associated epithelium contained small apically situated vacuoles, and large mucin granules appeared in the interfollicular surface epithelium. Towards the day of hatching both epithelial cell types were arranged to a monolayered or pseudostratified cylindrical epithelium. The follicle‐associated epithelium had invaginations and small vacuoles in the apical cytoplasm, whereas the interfollicular surface epithelium had numerous microvilli on its apical surface and large mucin granules in the apical cytoplasm. In functional studies, endocytosis of colloidal carbon was demonstrated in four out of ten 19‐day‐old fetuses and in all chickens studied immediately after h

ISSN:0003-276X    

DOI:10.1002/ar.1091910403

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractThe anatomy of parts of the pelvic outlet and perineum is described in an adult male gorilla. Two previously undescribed muscles are presented: (1) The puborectalis muscle, completely separated from the levator ani, arises from the region of the symphysis and forms a sling for the rectum while it also substitutes for the perineal membrane. (2) The puboampullaris muscle, a paired smooth muscle, arises from the pubis and inserts into the rectum to elevate the rectum while additionally providing support for the urogenital viscera. The levator ani muscle is recounted to point out its lack of attachment to the pelvic viscera while allowing a hiatus in which the rectum is exposed within the perineum. The sphincter urethrae muscle is presented emphasizing its true sphincteric characteristics, its absence of lateral attachments and its similarity to man. Other muscles of the pelvis and perineum as well as urogenital viscera are described or modified where necessary. The manner in which these structures enter into the support of the pelvic viscera is considered.

ISSN:0003-276X    

DOI:10.1002/ar.1091910404

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractAt the 7–8 somite stage of embryonic chick development (29‐31 hours of incubation), a slightly elliptical island of thickened ectoderm appears laterally on either side of the most distal constricture of the rhombencephalon at the level of the anterior intestinal portal. The appearance and extent of this auditory placode is precisely correlated with the subjacent accumulation of neural crest cells. By 33 hours of incubation, there is a distinct depression in the developing otic placode, and by 40 to 45 hours, the placode is visibly invaginated, forming an epithelial vesicle or otocyst. Carefully staged embryos were serially sectioned, and the area underlying the developing otic placode was traced with a planimeter. It was found that placode size (area 60,000 μm2) is nearly unchanged from 30 to 42 hours of development. During this time interval, the placode cells first become columnar, show nuclear orientation, and then pseudostratify. The increase in placode cell number during this time interval is not likely to be the result of localized, accelerated cell division: the population doubling time of placode cells is eight and one‐half hours and the mitotic index of 2.5% is similar to that of cells in an equivalent area of adjacent, non‐placode forming head ectoderm. A model of otic placode formation is proposed which suggests that by 30 hours of development, a discrete population of placode forming cells is segregated from head ectoderm. Subsequent epithelial pseudostratification results from accumulation of this dividing population within the limits of the

ISSN:0003-276X    

DOI:10.1002/ar.1091910405

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractThe otic placode takes its origin from surface ectoderm. Prior to the arrival of neural crest cells, surface epithelial cells adjacent to the neural folds are squamous in shape and synthesize primarily interstitial bodies. However, by 26 hours of development, neural crest cells, using the undersurface of the epithelium as a substratum, migrate away from the neural tube. Cells of surface epithelium above the neural crest cells assume a columnar shape, and the amount of intercellular space between adjacent epithelial cells is consequently reduced. Placode cells show extensive interdigitation apically as they pseudostratify and invaginate, while it appears that many of the basal cells contribute components to the underlying extracellular matrix. This extracellular matrix interface between surface epithelium and neural crest cells is distinctly fibrillar and less granular than that found between ordinary head ectoderm and primary mesenchymal cells. Just prior to complete invagination as an otocyst, otic placode cells in a region near the ventrolateral wall of the hindbrain extend cell processes through discontinuities in the basal lamina and leave the otocyst. These are likely to be the cells which contribute to the formation of the acoustico‐facialis ganglion. These observations support the hypothesis that the development of the otic placode is the result of a tissue interaction between surface epithelium and neural crest cell

ISSN:0003-276X    

DOI:10.1002/ar.1091910406

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractCircadian rhythms in DNA synthesis are described for the tongue epithelium, five different regions of the alimentary canal (gut) –esophagus, stomach, duodenum, jejunum and rectum– and bone marrow in a group of BDF1male mice. A circadian rhythm is also described for the mitotic index in the corneal epithelium in the same mice. The data document for the first time in the same animals the dramatic variation in cell division encountered from one region of the gut to another. This variation is seen in the amplitudes of the rhythms as well as in the over‐all 24‐hour means. On the contrary, the phasings of the rhythms in the different regions of the gut are remarkably similar. In this study, where the mice were standardized to 12 hours of light (0600‐1800) alternating with 12 hours of darkness, the peak of the DNA‐synthesis rhythm occurred around the time of transition from dark to light, and the trough around the time of transition from light to dark. The implications of these findings, and those of others, to the study of cell kinetics and to cancer chemotherapy ar

ISSN:0003-276X    

DOI:10.1002/ar.1091910407

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractThe labial ridge epidermis of the anuran tadpole, which is the formative site of horny teeth, was studied with the electron microscope. The triangular epidermis covering the apex of the labial ridge was composed of horny teeth cells arranged in a columnar shape, keratinocytes, secretory epidermal cells, two kinds of non‐epidermal cells and Merkel cells. Individual non‐epider‐mal cells were identified as neutrophils and macrophages respectively.In addition, the fine structure, distribution and cytochemistry of the Merkel cell were studied. The fine structure of Merkel cells in the labial ridge epidermis was not so different from those of other vertebrates reported previously by other workers, except for the presence of numerous glycogen particles. The presence of Merkel cells in the labial ridge epidermis was very frequent, and they were arranged in a line at a uniform level of the triangular epidermis. They were usually located in the third cell layer from the base of the epidermis.PAS and azure A stains were used on semithin epoxy sections to reveal the Merkel cells, and both stained them intensely. On the other hand, though glutaraldehyde‐silver techniques and permanganate fixation were used to detect monoamines in the Merkel cells ultracytochemically, a positive reaction was observed on the pigment g

ISSN:0003-276X    

DOI:10.1002/ar.1091910408

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

摘要:

AbstractIntercellular junctions of the excurrent duct system of the adult rat testis were studied by freeze‐fracture. In the terminal segment of the seminiferous tubule, where there are no spermatogenic cells, the tight junctions of Sertoli cells consist of many parallel strands of particles. The particles of the junctions predominantly appear on the E face instead of the P face, similar to those of the seminiferous tubules reported previously. From the rete testis to the ductus deferens, the tight junctional particles or smooth strands are mainly found on the P face, and the tight junctions show anastomosing networks. In the ductuli efferentes, whose epithelial lining consists of ciliated and nonciliated cells, the tight junctions between two adjacent nonciliated cells and between nonciliated and ciliated cells are poorly developed. In the former, belt‐like gap junctions are often associated with segmented tight junctions. In such area, there are tiny regions, where no junctional elements are observed. Between two ciliated cells, several strands of the tight junctions can be seen. The result of the tracer experiment suggests that the barrier of the ductuli efferentes is weak. In the epididymis, the tight junctions are well developed throughout the duct. Corresponding with the regional variation of the epi‐didymal epithelium, the geometrical organization of the tight junction networks varies along the duct. In the ductus deferens, many strands of the tight junctions are scattered throughout the lateral cell surface in addition to the belt‐like network of the tight junction in the adluminal area.The number of the tight junctional strands is presented graphically in the various segments of the excurrent duct of the

ISSN:0003-276X    

DOI:10.1002/ar.1091910409

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY

ISSN:0003-276X    

DOI:10.1002/ar.1091910401

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1978

数据来源: WILEY