摘要:

AbstractThe fine structure of adrenal cortices of opossums maintained on a sodium deficient diet for 21 days has been examined. After this treatment, the thickness of the zona glomerulosa is increased due to hypertrophy and hyperplasia of the parenchymal cells. After 21 days on the low sodium diet, the glomerulosa cells are characterized by large accumulations of smooth surfaced endoplasmic reticulum. This appearance is in marked contrast to the sparse representation of smooth surfaced reticulum in control animals. The rough surfaced endoplasmic reticulum becomes organized into long flattened cisternal profiles in parallel array and appears to be increased in quantity. The Golgi complex is also hypertrophied but marked changes in other organelles were not observed. Cells of the zona fasciculata appear to be unaffected by sodium depletion. Large lipid droplets accumulate in the zona reticularis of experimental animals but this zone is otherwise comparable to control animals. The bearing of these results on hypotheses of physiological control of secretion of the zona glomerulosa are discussed.

ISSN:0003-276X    

DOI:10.1002/ar.1091660102

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

年代:1970

数据来源: WILEY

摘要:

AbstractThe present morphological investigation of the developing thymus of the rabbit during early embryogenesis differs with our previous studies concerning thymus lymphopoiesis in the chick and hamster which suggested that embryologically the first lymphocytes appearing in the thymus arisein situby the direct transformation of undifferentiated epithelial cells comprising the organ parenchyma. Significantly, in the rabbit and in contrast with the chick and hamster, a few cells morphologically resembling but not completely identical to medium‐size and large lymphocytes were evident in the mesenchyme near the thymus at a time just prior to the appearance of lymphocytes or lymphocytic precursors within the thymus parenchyma (twelve and one‐half days of gestation). Within a few hours after the appearance of these extrathymic lymphocytic cells both medium‐size and large lymphocytic cells were observed both in the thymus parenchyma and in the mesenchyme (thirteen and one‐half days of gestation); these cells remain more numerous in the mesenchyme than in the thymus during the next several days. In some instances, only a thin basement membrane separated the lymphocytic cells within the thymus from the surrounding mesenchyme. In contrast with our earlier studies, several examples have been encountered between the fifteenth and seventeenth days of gestation of lymphocytic cells extending through the basement membrane seperating the thymus parenchyma from the surrounding capsular connective tissue. Morphologically cellular modulations between thymus undifferentiated epithelial cells and lymphocytic precursors have not been as convincing in the developing rabbit thymus as in the chick and hamster. In contrast with thymus development in the chick few mature or developing granulocytes are found near the embryonic rabbit thymus indicating that the primitive extrathymic lymphocytic cells are not myeloblasts.The morphological evidence of this investigation is consistent with the thesis that the first lymphocytes present in the embryonic thymus probably are derived from the invasion of extrathymic lymphocytic cells into the organ parenchyma rather than formingin situfrom modulating undifferentiated epithelial cells. The presence of rare lymphocytic cells observed in the small vascular channels near the time of appearance of the lymphocytic cell population in the mesenchyme and within the thymus primordium would be consistent with the view that these primitive lymphocytic cells immigrate to the region of the thymus via the blood vascular

ISSN:0003-276X    

DOI:10.1002/ar.1091660103

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

年代:1970

数据来源: WILEY

摘要:

AbstractA small patch of immature‐testis‐like tubules is described from the ovary of a sexually mature, fertile hippopotamus. It is compared with similar tubules described in the literature from other species and it is concluded that the tubules are derived either from cords formed in the foetal ovary or are an early granulosa‐cell

ISSN:0003-276X    

DOI:10.1002/ar.1091660104

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

年代:1970

数据来源: WILEY

摘要:

AbstractElectron micrographs of dog papillary muscle fibers show the sarco‐plasmic reticulum (SR) as an extensive three‐dimensional network of diverging and converging tubules that is continuous throughout each sarcomere and in successive sarcomeres. The network surrounds each myofibril and is continuous across the fiber. Tubules of the SR network are oriented transversely and longitudinally. Interconnections of transversely and longitudinally oriented SR tubules form circular pathways in the network. A structural relationship appears to exist between the Z line and longitudinally and transversely oriented tubules of the SR network at their points of apposition with the Z line. A rather constant space approximately 100 Å wide is seen between SR tubules apposed at the Z line in cross‐sections and in favorable longitudinal sections of fibrils. This space is traversed by electron‐opaque strands which appear to be connections between SR tubules and the Z line. Other lines of evidence support the view that Z lines and SR tubules are connected. One of these is the change of position of Z line SR tubules in relation to the change of position of Z lines in adjacent fibrils. Another line of evidence is the continuity of SR apposed at the Z line and SR connected to the sa

ISSN:0003-276X    

DOI:10.1002/ar.1091660105

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

年代:1970

数据来源: WILEY

摘要:

AbstractThe pancreas of the batEptesicus fuscuswas investigated with respect to the normal ultrastructure of the islet cells, and structural alterations induced by alloxan. The ultrastructure of normal active and hibernating bat islet cells was similar. Through serial sections, B granules were shown to be disc‐shaped, and some B granules were observed to consist of up to three component plates. Vesicular configurations found in both A and B cells suggest that the Golgi complex is essential to granule formatio

ISSN:0003-276X    

DOI:10.1002/ar.1091660106

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

年代:1970

数据来源: WILEY

摘要:

AbstractThe prenatal development of rodent nasal mucous membrane has been examined histochemically (lactate dehydrogenase, succinate dehydrogenase, glucose‐6‐phosphate dehydrogenase, alkaline phosphatase, PAS and PAS with diastase digestion). Localization and intensity of the enzyme systems studied were distinctly different in respiratory and olfactory areas. These differences were demonstrable by at least the second half of gestation in the animals studied. Findings in Jacobson's organs were parallel to those in olfactory areas. Each of the pathways of carbohydrate metabolism examined was present in respiratory epithelium. However, intensity was less, appeared later and was more variable in intracellular localization than that found in olfactory areas. Based on enzyme staining olfactory epithelium seemed metabolically more active than respiratory mucosa. Apical portions of olfactory epithelium stained most intensely for oxidative enzyme systems, particularly the glucose‐6‐phosphate dehydrogenase system. These areas of high activity were thought to represent apices of supporting cells rather than receptor cells. This localization of a pentose phosphate shunt enzyme system was related speculatively to ion transport in these cells. Alkaline phosphatase was relatively slight in respiratory areas during the ages studied. The basal portions of olfactory epithelium stained positively for alkaline phosphatase. Since hydrolytic enzymes have been thought to be important in the mechanism of olfaction, its demonstration in these tissues suggests that this portion of the olfactory mechanism is present by midgestation in the rodents

ISSN:0003-276X    

DOI:10.1002/ar.1091660107

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

年代:1970

数据来源: WILEY

摘要:

AbstractTritiated thymidine was injected into adult female A/J mice at 24, 20, and 16 hours before transection of the left hypoglossal nerve. These animals and uninjured controls that received the same sequence of tritiated thymidine injections were sacrificed by perfusion fixation at either 4, 8, 16 or 35 days after the time of the injury. At all time intervals after injury there were several times more labeled cells in the nucleus of the injured nerve than were found in the right hypoglossal nucleus of the same animals. However, the right hypoglossal nucleus of the injured animals had significantly more labeled cells than were found in the hypoglossal nuclei of the uninjured control animals. Labeled mitotic figures were present in the nucleus of the injured nerve on the fourth day after injury. Since no tritiated thymidine should have been available at the time of injury or afterward to label cells that proliferated in response to the injury, the difference in the number of labeled cells between the injured animals and the controls is attributed to an infiltration of labeled mononuclear leucocytes.

ISSN:0003-276X    

DOI:10.1002/ar.1091660108

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

年代:1970

数据来源: WILEY

摘要:

AbstractCerebellar and cerebral cortices were frozen under various conditions; within 30 seconds of circulatory arrest, after eight minutes of asphyxiation, after ten minutes of perfusion with glutaraldehyde and after perfusion with this fixative and osmium tetroxide postfixation. Ethanol was used as the solvent in freeze substitution of these tissues. The resulting EMs closely resembled those of similar material freeze substituted in acetone. There were no differences in extracellular space even though differences have been reported between the space in EMs of conventionally fixed material dehydrated with ethanol or acetone.

ISSN:0003-276X    

DOI:10.1002/ar.1091660109

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

年代:1970

数据来源: WILEY

ISSN:0003-276X    

DOI:10.1002/ar.1091660101

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

年代:1970

数据来源: WILEY