摘要:

AbstractThe fine structure of differentiating ameloblasts was studied in the lower second molar of 1‐week‐old kittens after perfusion fixation with and without subsequent decalcification.The differentiation zone was divided into three phases. In Differentiation 1, ameloblasts are about 27 μm long and face an uninterrupted basal lamina. The predentin adjacent to the basal lamina contains a few collagen fibrils oriented mainly at right angles to the ameloblast surface. This specialized predentin forms a well‐defined layer, up to 1.5 μm thick, referred to as the junctional layer. In Differentiation 2, ameloblast processes extend through the basal lamina and the thickness of the junctional layer. The processes consist of cytoplasmic sheets forming a honeycomb‐like network. Dentin starts to calcify after process‐formation is underway. Two distinct types of odontoblast processes, having different shapes and contents, come in contact with the ameloblasts and push into the ameloblastic layer. In Differentiation 3, stippled material appears in the extracellular spaces between ameloblasts. Later, stippled material‐like substances appear in the predentin close to the ameloblast apex and close to odontoblast processes within the dentin. Ameloblasts now are up to 40 μm high. Enamel secretion starts in small circumscribed areas which gradually enlarge, leading to the disappearance of the ameloblast processes. These findings are compared with results obtained in other species, including man, and their possible functional significanc

ISSN:0002-9106    

DOI:10.1002/aja.1001450302

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

年代:1976

数据来源: WILEY

摘要:

AbstractThe structure of developing rat testes was studied by light and electron microscopy. Ultrastructural differentiation of Sertoli and Leydig cells was followed from 14 days of gestation through birth. Specialized morphology in Sertoli cells was first seen at 16 days of gestation. In these cells the rough endoplasmic reticulum increased and became organized as numerous short cisternae loaded with a homogenous material. Typical Leydig cells were found among the stromal cells, around day 17 of gestation.There is good correlation between the time of appearance of ultrastructural specialization and published data on secretory capacity of the fetal testes, in respect to the inhibition and differentiation of the Müllerian and Wolffian ducts

ISSN:0002-9106    

DOI:10.1002/aja.1001450303

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

年代:1976

数据来源: WILEY

摘要:

AbstractMorphological interactions of trophoblast and uterus from stages of preimplantation and implantation were studied in 14 western spotted skunks. In addition, the granulosa lutein cells and plasma progesterone levels were studied. In animals several days from implantation the height of epithelial cells decreased, but began to increase in animals approaching implantation. During the preimplantation period a few leucocytes infiltrated the epithelium, but in animals just prior to implantation many leucocytes infiltrated the epithelium. However, in the implanted animals leucocyte infiltration was not observed. The increased infiltration of epithelium was possibly in response to the proximity of trophoblast or due to some antigenic material from the trophoblast. The unimplanted blastocyst had a layer of trophoblast and the embryonic disc. As implantation approached, the trophoblast formed trophoblastic knobs which apposed the luminal epithelium. Subsequently microvilli of trophoblastic and epithelial cells interdigitated. Junctional complexes were observed between many adhering microvilli and/or cell processes. The first attachment of trophoblast and epithelium occurred in the abembryonic region. Later the trophoblastic cell processes and/or individual cells penetrated the epithelium and reached the basal lamina. In addition to the penetration of the trophoblast, sometimes individual trophoblastic and epithelial cells fused. In the fused cells, remnants of junctional complexes and plasma membranes were observed. The fused cells did not penetrate the basal lamina and were not observed in the stroma.During the delay period the corpus luteum contained predominantly small granulosa cells and some large granulosa lutein cells, but only large lutein cells were observed in the implanted animals. The plasma progesterone levels fluctuated during the time of implantation and should not be regarded as a basis to predict nidation in the skunk.

ISSN:0002-9106    

DOI:10.1002/aja.1001450304

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

年代:1976

数据来源: WILEY

摘要:

AbstractStandard techniques for performing carotid angiography in dogs and in man were adapted to the cat in order to study the vascularization of both intracranial and extracranial structures. Venous drainage was examined by venography of selected vessels. The carotid‐cerebral and the vertebral‐basilar arterial systems of the cat were studied, although no attempt was made to define the territory supplied by each system.In serial angiograms, vascularization of the rete mirabile conjugatum was visualized, and distinct arterial and venous retia were delineated. Large facial veins were seen approximately one second after the intra‐arterial injection of radio‐contrast material. The early filling of the large facial veins appeared to be the result of an artery‐to‐venous shunt. Contrast material flowed posteriorly in these veins and drained into the venous rete. When contrast material was injected either into the sagittal sinus or retrograde in the external jugular vein, the internal jugular vein was visible in four of ten cats. This vessel drained blood directly from intracranial contents before anastomosis with the vertebral and external ju

ISSN:0002-9106    

DOI:10.1002/aja.1001450305

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

年代:1976

数据来源: WILEY

摘要:

AbstractSnell‐Bagg pituitary dwarf mice are an autosomal recessive mutant, their dwarfism being the result of an anterior pituitary defect. A number of investigators have reported that these mice, in addition to having hormonal deficiencies, have immunological defects. Dwarf mice reject allogenic skin grafts slowly, show a reduced response to contact agents and decreased graft‐vs.‐host reactivity. Other investigators have suggested that these results indicate a thymus‐cell‐deficiency. Contrary to this conclusion, we have found that the thymuses in our dwarf mice have a normal cellular composition and the T‐cell‐dependent zones in the peripheral lymphoid tissues are not deficient in lymphocytes. Therefore, this investigation was undertaken to study the response of dwarf mice to the hapten, oxazolone, which produces one type of T‐cell‐dependent response, delayed hypersensitivity, and to compare this response to that of normal littermates in animals 15 to 90 days of age.The results of these studies indicate that the dwarf mice have the ability to develop delayed hypersensitivity, as shown by both a blastogenic response in the lymph node draining the site of sensitization (the induction phase of delayed hypersensitivity) and by a positive skin‐test. The magnitudes of the blastogenic response and the skin‐test reaction appear similar in dwarf and normal littermate animals, both histologically, and quantitatively. These results, which are in contrast to other studies, may be the result of the husbandry provided our colony of dwarf mice, and the immunological deficiencies that have been described previously may not be a necessary condition accompanying d

ISSN:0002-9106    

DOI:10.1002/aja.1001450306

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

年代:1976

数据来源: WILEY

摘要:

AbstractThe proliferative kinetics of the intraepithelial lymphocytes (IL) of the mouse intestine have been evaluated. By inducing mitotic arrest it was found that large IL — constituting about 50% of the IL — showed a mitotic rate of 2.3. Autoradiographic results obtained after two different schedules of3H‐thymidine injections showed that 30% of the large IL were in DNA synthesis, and that the large IL were renewed at a rate comparable to that of blast cells from Peyer's patches, mesenteric lymph nodes and thoracic duct lymph. The small IL were renewed very rapidly compared to small lymphocytes of peripheral lymphoid tissues, although small lymphocytes with lifespans of several weeks were also present in the epithelial sheet. By the use of intestinal perfusion, in vivo, it was estimated that the loss of lymphocytes from intestinal villi into the lumen of the gut was negligible, and it is concluded that the most probable kinetic model for the majority of IL is: B and T lymphoblasts invade the epithelium and undergo mitosis. B lymphoblasts give rise predominantly to plasma cells, and T lymphoblasts give rise to small lymphocytes — probably long‐lived — which reenter the

ISSN:0002-9106    

DOI:10.1002/aja.1001450307

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

年代:1976

数据来源: WILEY

ISSN:0002-9106    

DOI:10.1002/aja.1001450308

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

年代:1976

数据来源: WILEY

ISSN:0002-9106    

DOI:10.1002/aja.1001450301

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

年代:1976

数据来源: WILEY