摘要:

AbstractSo far as known this is the first portrayal of the detailed structure of a pulmonary acinus as seen both from within its cavities and from without. Some 200 serial sections (× 50) were traced upon transparent plastic plates and then viewed as translucent objects in packets of ten. This method was supplemented by wax‐plate and graphic reconstructions of the whole and of its parts.The pulmonary acinus is a terminal bronchiole and all its branches. In this example there were three generations of respiratory bronchioles and from two to five generations of alveolar ducts ending in saccules. This acinus had a volume of 15.6 mm3, comparable to a cube measuring 2.5 mm on each side. The two halves (medial and lateral semiacini) interdigitated. Only the lateral, forming 53.4% of the whole, was analyzed in detail. It consisted of aroofhaving three portions with varying patterns (namely a proximal wing, a distal wing extending to the connective tissue septum, and a rudimentary lateral component); aseptal portionresting on the septum and consisting of four pairs of alternating small and large clusters of alveolar ducts, to the lower half of which acluster of vesicleswas appended; and apaired lateral envelopeof ducts which in one place communicated with an adjacent acinus, thereby revealing a third mode of collateral ventilation.This acinus, reconstructed over a period of three years, is replete with numerous variations such as dilated atria and saccules, supernumerary structures, recurrent ducts, irregular branches and differing lengths of airways. Thus, it records the “fight for space” in earlier periods of growth. Knowing the pattern of this particular acinus, it has been possible to calculate the rate of diffusion of gases between the terminal bronchiole and the peripheral saccules, andvice versa. Yet the impression persists that no two acini are alike in either proximal or distal portions; therefore, it is questionable whether diffusion of gases in the peripheral airways of the living individual are really subject to precise mathematical measu

ISSN:0002-9106    

DOI:10.1002/aja.1001320302

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

年代:1971

数据来源: WILEY

摘要:

AbstractThe fine structure of the epidermis of the external gills of the larval frog,Rana pipiens, was observed during the period of gill degeneration. Many of the epidermal cells underwent morbid alterations. In typical degenerating epidermal cells the nucleus became irregular in outline, chromatin formed electron‐dense clumps and the nuclear envelope increased in width. Lysosomes became prevalent in the cytoplasm of these cells and progressively larger autophagic vacuoles appeared. As degeneration continued, apical epidermal cells were found embedded deeper within the epidermis. In some instances cell processes from two neighboring epidermal cells extended partially around the relocated degenerating apical epidermal cells probably contributing to their translocation; phagocytosis was completed by a single cell in other instances. The degree of participation of the phagocytic epidermal cells in the degenerative process was uncertain. The distribution of acid phosphatase activity was followed in specimens treated by the Gomori technique. Profiles of cisterna‐like elements, positive for the enzyme, suggested that perhaps entire Golgi cisternae contributed to the formation of autophagic vacuoles in combination with small vesicles. Heterophils and macrophages observed in the degenerating gills were believed to participate in the removal of the dying ce

ISSN:0002-9106    

DOI:10.1002/aja.1001320303

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

年代:1971

数据来源: WILEY

摘要:

AbstractIn suckling rats absorptive cells in the distal two‐thirds of the small intestine ingest colloids by pinocytosis. In the middle third of the intestine pinocytosis ceases 17 to 21 days after birth and can be halted prematurely by glucocorticoids. The adrenal cortex is relatively inactive in newborn rats and begins to secrete glucocorticoids two weeks after birth; this secretion has been suspected to cause the termination of pinocytosis.Glucocorticoids do not stop pinocytosis in absorptive cells already present on the villi but induce the renewing population of cells in the crypts to replace the cells on the villi with new ones that do not engage in pinocytosis. Therefore, glucocorticoids act by inducing a new direction of cellular differentiation.BUDR (5‐bromodeoxyuridine) is reported to inhibit cellular differentiation reversiblyin vitro. When injected into 8 to 9‐day‐old rats, simultaneously with cortisol, it inhibited the change in cellular differentiation induced by cortisol; that is, pinocytosis continued unabated. BUDR did not appear to be toxic and did not interfere with cellular replacement in the small intestine, as judged autoradio‐graphically.Thus it appears that BUDR inhibits the initiation of cellular differentiation by cortisol but does not interfere with cellular proliferation or the pre‐established program of cellular differentiation that leads to pinocytosis. The mechanism of action of BUDR is still unknown; it is discussed in light of the possibility that BUDR may after cellular differentiation without acting directly on

ISSN:0002-9106    

DOI:10.1002/aja.1001320304

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

年代:1971

数据来源: WILEY

摘要:

AbstractThe ultrastructure of the atrioventricular node and Purkinje fibers of the guinea pig heart was studied. The atrioventricular node consists of slender, irregularly shaped muscle cells which are arranged in a complex network with frequent interdigitation. Nodal cells contact with each other by means of many desmosomes (maculae adherentes) and rare intercalated discs that contain short nexal regions (gap junctions). The Purkinje fibers are much larger and show less cellular interdigitation than the fibers of the atrioventricular node. Desmosomes are infrequent but there are many intercalated discs with rather a long nexus between the Purkinje fibers. The T‐system is not present in the atrioventricular node or in the Purkinje fibers. The most pronounced morphological differences between the atrioventricular node and Purkinje fibers are the size of the cells and the mode of intercellular connection, which may be related to different conduction velocities in these two region

ISSN:0002-9106    

DOI:10.1002/aja.1001320305

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

年代:1971

数据来源: WILEY

摘要:

AbstractThe purpose of this study was to examine whether a short term chemical insult to neuroepithelial cells (the matrix cells of neurons) causes a clearly defined neuronal deficit in the neocortex and hippocampal region. In the first experiment 15‐day pregnant mice were given a single dose of 5‐azacytidine (4 mg/kg); 30–60 minutes later they were injected with tritiated thymidine (6 μc/g). The fetuses were sacrificed at various hours and days after treatment. No cellular abnormalities were observed one or two hours after treatment with 5‐azacytidine, but at three to four hours abnormal mitotic figures became visible at the lumen. Usually the chromosomes were clumped together, forming commaand circle‐shaped structures. Sometimes chromosome breaks were observed. The number of cells with chromosomal abnormalities increased during the following hours, but ten hours after treatment a few normal mitotic figures appeared again. In the meantime the affected cells moved from the lumen toward the cortical plate. Their number gradually decreased and 48 hours after treatment all had disappeared. Since in the controls many labeled cells reached the cortex but in the experimental animals none, a neuronal deficit resulted from the treatment. It was difficult, however, to pinpoint the type of neuron lacking in the brain of the treated newborn. In the second experiment pregnant animals were given several doses of 5‐azacytidine (2 mg/kg on days 13, 14 and 15 of gestation) and sacrificed at various days after birth. The neocortex as well as the hippocampal region of the treated animals contained fewer cells than the same structures in the controls. In addition many neurons both in the cortex and hippocampus were morphologically abnormal. It is thus concluded that single and repeated shortterm chemical insults to neuroepithelial cells during the later stages of fetal life, result in a shortage of neurons and the presence of morphologically abno

ISSN:0002-9106    

DOI:10.1002/aja.1001320306

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

年代:1971

数据来源: WILEY

摘要:

AbstractThe neonatal line in developing human primary teeth was examined by means of phase contrast microscopy, microradiography and transmission electron microscopy. When thin sections were observed by light microscopy, the lateral dimensions of the line were not as extensive as had been previously reported. The line had a “staircase” configuration and appeared to be identical to published light micrographs of the stria of Retzius. On radiograms, the lateral extent of the hypomineralization was also decreased. The ultrastructural basis for the neonatal line appeared to be a localized change in configuration of enamel prisms along with a possible reduction in crystal concentration. The possibility that some rods actually end at the line could not be excluded, howe

ISSN:0002-9106    

DOI:10.1002/aja.1001320307

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

年代:1971

数据来源: WILEY

摘要:

AbstractThe incorporation of14C‐leucine into the cytoplasm and nuclei of the motor neurons in the spinal cords of control mice and of mice given total‐body X‐irradiation was studied with the use of autoradiography. A decrease in isotope incorporation into the cell cytoplasm of the motor neurons in the spinal cords of irradiated mice was observed. The incorporation of14C‐leucine into the nuclei of the motor neurons of spinal cords of irradiated animals was increased significantly as compared to the appropriate control

ISSN:0002-9106    

DOI:10.1002/aja.1001320308

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

年代:1971

数据来源: WILEY

ISSN:0002-9106    

DOI:10.1002/aja.1001320301

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

年代:1971

数据来源: WILEY