摘要:

AbstractThe spheno‐occipital synchondroses of 20 cynomolgus monkeys have been examined histologically and radiographically. The findings by these two methods have been compared and correlated with the dental age of the monkeys. The radiographic examination was carried out on the isolated clivus region while serial sections were used for histological examination. Comparison of the synchondrosis by the two methods resulted in six disagreements when the synchondroses were classified as open, partly closed or closed. It is suggested that this difficulty is due to superimposition of shadows on the radiographs and small degrees of histological union not being recognised radiographically. It is further suggested that care should be taken in determining the age at closure when radiographs alone are used as the criterion. The dental age at initial closure appeared to vary widely in some cases occurring at an early mixed dentition stage and in others as late as the adolescent dentition. The closure of the synchondrosis was not related to the eruption time of any particular tooth. The pattern of closure did not conform to the classical type, i.e., from above downwards nor indeed was any consistent pattern revealed in either the radiographs or histological section

ISSN:0003-276X    

DOI:10.1002/ar.1091720201

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

年代:1972

数据来源: WILEY

摘要:

AbstractSeventy‐five‐ to one‐hundred‐micron slices of undemineralized human teeth were examined by transmitted light, incident light and polarized light microscopy, to determine the nature of Tomes' granular layer in root dentine. Transmitted light examination showed that the granules occupied differing levels within the section. Incident light microscopy showed that the granules were true spaces and polarized light microscopy showed that fibre orientation was not the cause of the granular layer. When thin sections (1 μ‐0.75μ) of a tooth slice containing Tomes' granular layer were examined by light and electron microscopy no evidence of any spaces were found in the region where they had been demonstrated in the thick 75‐100 μ section. Looping of the terminal portions of the dentinal tubules was found. A model system has been used to show that sectioning of this loop region could produce a space visible in thick sections and corresponding to a granule of Tomes' layer. It is suggested that this looping of dentinal tubules in root dentine, and not in the dentine beneath enamel, is the result of different rates of dentine deposition in t

ISSN:0003-276X    

DOI:10.1002/ar.1091720202

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

年代:1972

数据来源: WILEY

摘要:

AbstractFragments of liver were successfully transplanted to an ectopic site in the kidney cortex of the mouse. Survival was followed for varying periods of time. In some cases both syngeneic grafts and allogeneic grafts placed in mice previously made immunologically tolerant to the genotype of the donor were still alive one year later. However, extensive amounts of liver tissue would not survive, at the best, strips of about 30 cells thick grew, and various measures tried to promote an increase in this amount were not successful.

ISSN:0003-276X    

DOI:10.1002/ar.1091720203

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

年代:1972

数据来源: WILEY

摘要:

AbstractThe tongue of the echidna,Tachyglossus aculeatusis divided structurally and functionally into two distinct parts; a free rostral portion covered by stratified squamous epithelium bearing filiform papillae and a fixed caudal portion formed by a trapezoidal pad which bears highly specialized keratinized spines. These spines are similar in their morphology to the horny teeth of the living cyclostomeMyxineand the hard keratin of rat filiform papillae.The gross and light microscopic structure of the lingual spines is described and their use as a masticatory organ (by occlusion with a similar set of spines on the palate) is discussed in relation to the animal's diet and method of feeding.

ISSN:0003-276X    

DOI:10.1002/ar.1091720204

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

年代:1972

数据来源: WILEY

摘要:

AbstractExamination of serial histologic sections of the head and neck regions of rats at selected age intervals from 14 daysin uteroto 100 days postnatally revealed that at 16 daysin utero, a second salivary gland arises from the rudimentary parotid (Stensen's) duct. This gland develops more rapidly than the parotid gland; its acini are essentially mature prior to weaning, preceding parotid acini in this respect by several days. All cells of the secretory units of the mature gland stain positively with both alcian blue and periodic acid‐Schiff, indicating that the gland is of pure mucous type. The body of the gland occupies a space lateral and mostly superior to the maxillary buccal sulcus, nestled beneath the anterior bulge of the masseter muscle, near the point where the buccal and mandibular marginal branches of the facial nerve cross paths. It is the only salivary gland in the buccal wall anterior to the third molar; hence, the proposed name ofanterior buccal gland.These observations suggest: (1) Samples of rat parotid saliva collected proximally and distally to the junction of the ducts of the parotid and anterior buccal glands are likely to differ significantly in the quality and quantity of mucosubstances which they contain. (2) The divergent differentiation of two branches of the same glandular primordium in this instance implies differences in the inductive qualities of their respective mesenchymal bed

ISSN:0003-276X    

DOI:10.1002/ar.1091720205

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

年代:1972

数据来源: WILEY

摘要:

AbstractThe morphogenetic tissue interactions between epithelium and mesenchyme of male accessory sexual gland primordia were investigated by standard culture methods. Seminal vesicle (SV), urogenital sinus (UGS), and preputial gland (PP) rudiments were excised from 13‐ to 19‐day old embryonic mice. After tryptic‐separation, the epithelium and mesenchyme of these rudiments were recombined into control (homotypic) and experimental (heterotypic) recombinants which were subsequently grown in the anterior chamber of the eye of adult male hosts.In recombinants composed of accessory sexual gland epithelium (SV, UGS, or PP) and urogenital gland mesenchyme (SV or UGS), the histotypic pattern of the recombinants reflected the source of the epithelium. Normal differentiation of SV, UGS, and PP epithelium occurred consistently when these epithelia were associated with SV or UGS mesenchyme. On the other hand, urogenital gland epithelium (SV or UGS) did not develop normally when associated with the integumentally‐derived preputial gland mesenchyme. Instead, seminal vesicle epithelium was maintained as a columnar epithelium arranged in a simple tubular structure, while urogenital sinus epithelium formed a keratinized epithelium despite the presence of androgens. These data illustrate (1) the supportive properties common to urogenital mesenchyme, (2) the stability of accessory sexual gland epithelium, and (3) the lack of strict mesenchymal requirements of these epithelia. Furthermore, the data suggest that urogenital and integumental mesenchyme differ significantly in their ability to mediate hormonally‐dependent developmental

ISSN:0003-276X    

DOI:10.1002/ar.1091720206

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

年代:1972

数据来源: WILEY

摘要:

AbstractDeep splenic lymphatics, studied in five marmots, entwine major arteries of white pulp. Lymphatics vary in prominence from spleen to spleen and within a spleen.These lymphatics constitute efferent channels likely draining splenic fluid flowing within the spleen counter‐current to blood.The endothelium is irregular, thin and imperforate, beset with vacuoles and containing filaments. Its hyaloplasm is light or dark. Flap‐like inter‐endothelial cell junctions without membranous specializations are typical. Endothelial cells richly interdigitate with one another resulting in extensive, closely‐spaced intercellular junctions. Long endothelial processes extend into subjacent connective tissue.The lymphatics lie in an extracellular ground substance, continuous with that surrounding arteries and with the fibrous reticulum of white pulp. Filaments, about 100 Å in width, lie in the ground substance close upon the basal endothelial surface. The filaments appear to attach to the endothelium and run out into surrounding collagenous fibers. The collagen is abundant, occurring in thick layers around lymphatics and extending, with the ground substance, into the white pulp.Macrophages, replete with phagosomes, surround lymphatic vessels and extend processes toward them, penetrating the peri‐lymphatic connective tissue. Erythrocytes lie outside these vessels and within their lumen. Sheets of plasma cells may surround the lymphatics. Lymphocytes, in large number, are present around the lymphatics, cross their wall between endothelial cells, and lie in t

ISSN:0003-276X    

DOI:10.1002/ar.1091720207

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

年代:1972

数据来源: WILEY

摘要:

AbstractInTadarida, the diffuse endotheliodichorial placenta is established over the parietal area of the uterus and is prominent, for an extended period of time during midgestation, both prior to and during the development of the definitive discoidal structure. A transitory yolk sac placenta precedes the establishment of the diffuse placenta. The tissues of the yolk sac are displaced from the trophoblast through collapse, and by the advance of the allantoic mesoderm. Allantoic vessels infiltrate the cords of cellular trophoblast that extend into the syncytium that, in turn, has penetrated deeply into the maternal endometrium. The syncytium progressively phagocytizes the maternal tissues, leaving the superficial maternal blood vessels and attendant pericytes intact, but destroys many of the deeper maternal vessels. Several morphological changes occur in the pericytes during the period that the superficial maternal capillaries retain their integrity, suggesting that they play an important role in maintaining these vessels which are eventually destroyed also.The cytotrophoblast is the most undifferentiated cell type throughout gestation. The syncytium, on the other hand, contains a large array of organelles that vary in concentration from one area to another within this tissue. Particular attention was paid to cytoplasmic structures potentially related to transport phenomena. Among those described are (1) coated vesicles and tubules in the syncytium at its interface with the cellular trophoblast, (2) microvilli extending from the cytotrophoblast into the syncytium some of which contained lines of pinocytotic vesicles, (3) coated vesicles along the plasma membrane of the syncytium toward the maternal tissues, and (4) pinocytotic vesicles associated with the endothelium of both the allantoic and maternal blood vessels.

ISSN:0003-276X    

DOI:10.1002/ar.1091720208

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

年代:1972

数据来源: WILEY

ISSN:0003-276X    

DOI:10.1002/ar.1091720209

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

年代:1972

数据来源: WILEY