摘要:

AbstractThe rat incisor is an excellent model system in which to study amelogenesis. However, the information obtained has not been extrapolated to the human because of alleged structural differences between the teeth. The obvious differences include continuous eruption in rat incisors and an enamel rod pattern in rats which seemingly differs from the keyhole pattern of human enamel. A comprehensive analysis was made of those features of enamel structure considered fundamental to the understanding of its formation. This was done by applying the knowledge of amelogenesis obtained in rat incisors to the teeth of monkey and man. The following points of basic similarity were established between these species: (1) Interrod enamel is secreted first. It forms the side walls of cavities which are initially occupied by Tomes' processes. (2) The formation of interrod cavities is followed by deposition of enamel rods within these spaces. (3) The rods conform to the shape of the cavities and are secreted from one surface of Tomes' process. (4) At the initial site of rod deposition its enamel is continuous with the interrod enamel wall. (5) Growth of the rod compresses the process to one side of the cavity resulting in an arcade‐shaped “space” between the rod and the remaining interrod walls. This study demonstrates that it is no longer necessary to postulate a keyhole structure for primate enamel, and it has established that a fundamental similarity exists in the basic structure and in the mode of formation of enamel in all three sp

ISSN:0003-276X    

DOI:10.1002/ar.1092000402

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

年代:1981

数据来源: WILEY

摘要:

AbstractThe membranous systems of the “chloride cell” were studied in teleostean fish gills stained in ferrocyanide‐reduced osmium (Karnovsky, '71). Three distinct systems were observed: (1)the tubular system, densely stained with ferrocyanide‐reduced osmium, was made up of anastomosed tubules opening in the latero basal intercellular space; (2) theendoplasmic reticulum, faintly stained, and continuous with the nuclear envelope; (3) thevesiculotubular system, the staining of which was intermediate between those of both previously cited systems, was made up of vesicles and short tubules. These membranous systems underwent modifications according to the salinity of the exterior medium: (1) the tubular system formed a broad and loose network in fresh water adapted fishes; in salt water, the meshes of the network became small, tight, and regular thus increasing the cell surface area. (2) the endoplasmic reticulum, which in fresh water, consisted of dilated cisternae often studded with ribosomes; in salt water, it developed in a network of anastomosed smooth sheets interdigitated with the tubular system. (3) the vesiculotubular system seems to be also more developed in salt water than in fresh water‐adapt

ISSN:0003-276X    

DOI:10.1002/ar.1092000403

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

年代:1981

数据来源: WILEY

摘要:

AbstractEumelanosomes from the developing chick pigment epithelium have been isolated, solubilized, and the residue collected. Examination of this material in the electron microscope provides evidence for new structural entities in the eumelanosome and information on the organization of the melanosome. This evidence suggests that there are (1) 190‐Å fibers arranged in a zigzag fashion, surrounding 240‐Å–diameter electron‐lucent spaces and (2) an internal gridwork enclosing 40–50‐Å‐diameter spaces. These two structures are probably alternately layered

ISSN:0003-276X    

DOI:10.1002/ar.1092000404

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

年代:1981

数据来源: WILEY

摘要:

AbstractGlomeruli and tubules were isolated from rabbit kidney cortex by mild homogenization and sieving. Mixtures of these renal components were treated with detergents to prepare pellets of morphologically intact and easily distinguishable tubular (TBM) and glomerular basement membranes (GBM). These BMs were prepared for electron microscopy after: (1) no treatment; (2) treatment with buffer alone; or (3) treatment with enzyme (pronase, trypsin, pepsin, collagenase or testicular hyaluronidase). Mixtures of TBMs and GBMs were treated in the same incubation medium to keep constant the enzyme concentration, temperature, pH, and duration of the treatment. Untreated TBMs showed collapsed, highly folded sheets of electron‐dense material. In contrast, control GBMs were thinner and strikingly resistant to changes in in vivo histoarchitecture. In all enzymatic treatments except hyaluronidase, TBM was more susceptible to digestion than GBM. In general, the effect of pepsin was greater than trypsin, which was greater than pronase. Collagenase also solubilized TBM but was only slightly effective in attacking GBM. Hyaluronidase‐treated BMs were indistinguishable from controls. TBMs and GBMs were both affected least by the enzyme on their epithelial surfaces, which generally remained crisp and sharply demarcated. In contrast, fibrillar materials and BM fragments were released from connective tissue surfaces of TBMs and endothelial‐mesangial surfaces of GBMs. Data in the present study indicate that various BMs are morphologically heterogeneous and that a “non‐unitary” concept of BM is most appropriate. Moreover, the BM “sidedness” demonstrated following enzymatic digestions strongly suggests that macromolecular complexes within laminae densae may be arranged such a manner that opposing surfaces of the same BM are compositio

ISSN:0003-276X    

DOI:10.1002/ar.1092000405

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

年代:1981

数据来源: WILEY

摘要:

AbstractThe incidence of multiple processes within the tubules of the cuspal dentin of the cat's canine has been measured by counting directly from ultrathin sections examined in the electron microscope. The incidence is highly variable. The greatest incidence was found 1 mm below the cuspal dentino enamel junction where up to 75% of tubules in some areas contain more than one process. On average 33.6% of the tubules at this level contain multiple processes. The incidence declines linearly toward the apex with virtually no multiple processes occurring at 4 mm below the tip dentino enamel junction or beyond. Half of the “second processes” contain either mitochondria and/or vesicles. They are restricted to predentin where many of them end and to inner calcified dentin. Their distribution is similar to that described for nerve fibers in other studies. None of the processes participated in specialized juncti

ISSN:0003-276X    

DOI:10.1002/ar.1092000406

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

年代:1981

数据来源: WILEY

摘要:

AbstractThe nature of the trophic response of the mouse submandibular gland to thyroxine (T4) was examined. Adult female Swiss‐ Webster mice were given daily subcutaneous injections of T4 (1 μg/gm body weight) for two or four days; two injections of tritiated thymidine (3H‐ TdR) were given 24 and 29 hours after the last injection of hormone, and the mice were killed one hour after the last injection of 3H‐ TdR. One gland was analyzed chemically for DNA content and for incorporation of 3H‐ TdR, while the other was used to prepare autoradiograms. The cellular composition of each gland was analyzed by counting 1000 nuclei, and the frequency and labelling index (LI) of six cell types were established. A rise in specific activity of DNA and a fall in its concentration were seen in response to T4. The LI for the entire gland more than doubled. The LIs and frequencies of granular convoluted tubule and granular intercalated duct cells were increased more than those of acinar and nongranular intercalated duct cells; striated and excretory duct cells were not affected. It is concluded that the enlargement of the submandibular gland of the mouse caused by T4 is due to both hyperplastic and hypertrophic

ISSN:0003-276X    

DOI:10.1002/ar.1092000407

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

年代:1981

数据来源: WILEY

摘要:

AbstractThe purpose of this study was to determine the organization of collagen in the wall of the human pulmonary alveolus. Samples of human lung obtained at surgery were processed for light and electron microscopy. Light microscopy confirmed the general findings of Orsos ('36): there were 3 common fibers called primary, secondary, tertiary in this study in order of their increasing size. Primary fibers (called “pericapillary” by Orsos) formed a continuous mesh in the alveolar wall and were often confluent within the intercapillary regions of the wall (“knötenpunkten,” or nodes, Orsos). The tortuous secondary fibers (“circulatory fibers,” Orsos) passed frequently across the thickness of the alveolar wall and were closely applied to capillary walls. Tertiary fibers (“respiratory fibers,” Orsos) were continuous with the alveolar ostia and formed the supportive struts of the alveolar wall as they crossed the wall in a more direct course than the serpiginous secondary fibers.Electron microscopy (serial sections and stereo pairs) showed that the primary fibers inserted near the edge of an intercapillary region, where they were attached to the endothelial or epithelial basal lamina directly or by a smaller fiber or microfibril resembling the fibrous component of elastin or oxytalan. Primary fibers passed through a typical intercapillary region while describing a helix or a portion thereof. Secondary fibers were more coarse than primary, and both secondary and tertiary fibers resem

ISSN:0003-276X    

DOI:10.1002/ar.1092000408

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

年代:1981

数据来源: WILEY

摘要:

AbstractC‐cell complexes are special cell groups consisting of a mass of C‐cells associated with other epithelial elements and cysts. They are remnants of ultimobranchial bodies retaining fetal characteristics. In the C‐cell complexes there are follicular cells in various stages of differentiation, i.e., the cell clusters not yet organized into follicles, primordial follicles with small lumens and comparatively enlarged follicles storing plentiful amounts of colloid. They have a morphology similar to follicular cells of fetal thyroid glands and react to antiserum to 19S thyroglobulin. In order to determine whether or not the follicles in these complexes have the ability to incorporate radioiodine, autoradiography after a single injection of125I was combined with immunoperoxidase staining using specific anti‐calcitonin, anti‐C‐thyroglobulin, and anti‐19S thyroglobulin antisera. The 19S‐positive cells not yet organized into follicles did not take up radioiodine. Primordial follicles showed a heavy accumulation of silver grains over their follicular lumens storing new 19S thyroglobulin as colloid. Comparatively enlarged follicles revealed a strong autoradiographic reaction and their labeling patterns were identical with those of typical thyroid follicles. These results confirm that the follicles in C‐cell complexes, as well as thyroid follicles, can incorporate radioiodine and are related to thyroid hormone synthesis. That is, functional thyroid follicles can arise from the ultim

ISSN:0003-276X    

DOI:10.1002/ar.1092000409

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

年代:1981

数据来源: WILEY

摘要:

AbstractThe blood and bone marrow of New Hampshire chicks were analyzed quantitatively from the time of hatch to 8 weeks of age. Hormonal bursectomy was performed by treating embryonating eggs on the 11th day of incubation with testosterone propionate (TP) which resulted in severe hypogammaglobulinemia and complete atrophy of the bursa of Fabricius. TP‐treated birds exhibited some lymphocytopenia, reduced splenic weight, and lack of plasma cells in their bone marrow. The number of cells per milligram bone marrow was comparable in normal and TP‐treated birds, falling in the range reported for laboratory rodents. The chick medullary hemopoiesis is characterized by the predominance of erythroblasts throughout early development; granulocytes and lymphocytes represent much smaller cellular compartments than in rodents. In the chick granulocytes tend to decrease after hatch, whereas in rodents they tend to increase. The normal chick shows a temporary increase in marrow lymphocytes after hatch, similar to that observed in some young rodents, but on a much smaller scale. Hormonal bursectomy did not prevent the development of a lymphocyte population in the bone marrow. These cells were fewer in TP‐treated birds at hatch and at 4 weeks than in normal birds, but at 8 weeks of age normal and bursectomized chicks had comparable numbers of lymphocytes in their marrow. Although some lymphocytes in avain bone marrow may depend on the bursa of Fabricius for their development, a substantial proportion of bone marrow lymphocytes in the chick are bursa independent. The cell surface phenotype and site of origin of these cells remains to be investi

ISSN:0003-276X    

DOI:10.1002/ar.1092000410

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

年代:1981

数据来源: WILEY

摘要:

AbstractMorphology of guinea‐pig thymic fragments was studied sequentially during in vitro organ culture by using light and electron microscopy and3H‐thymidine autoradiography. In culture the fragments became alymphoid. Thymic lymphocytes started to disappear first at the corticomedullary border, which gradually broadened, giving rise to alymphoid epithelial fragments. As the lymphoid cells disappeared the thymic epithelium began to transform into a keratinized squamous epithelium. The keratinization started in the cells surrounding the Hassall's corpuscles, causing the enlargement of the corpuscles and finally total keratinization of the cultured epithelial fragments. In autoradiographic studies cell proliferation could be observed in uncultured thymuses at the cortical pericapsular area. In cultured alymphoid fragments labelled cells were distributed diffusely in the epithelium. Later labelling was concentrated to epithelial cells transforming to keratinized epithelium. Ultrastructural studies similarly showed transformation of the epithelial cells to squamous keratinized epithelium. The observation support the view that Hassall's corpuscles are derived from the keratinized thymic epithelium and that their existence is connected to the normal function of the epithel

ISSN:0003-276X    

DOI:10.1002/ar.1092000411

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

年代:1981

数据来源: WILEY