摘要:

AbstractIntrasphenoid and intrasellar segments of the cerebral carotid arteries were dissected in 82 specimens of birds, representing 21 avian orders. The configuration and branching of these carotid segments and the intercarotid anastomosis were observed.A well develop intercarotid anastomosis unites the two carotids directly caudal to the hypophysis in all birds examined except for five specimens of passeriform birds of the Suborder Tyranni. Three principal patterns occur: an H‐type having a lengthy transverse anastomosis connecting the carotids; an X‐type with the carotids anastomosing side‐to‐side; and an I‐type with the carotids merged into a single longitudinal vessel. Patterns for each species are illustrated.Since ordinarily birds lack a cerebral arterial circle comparable to that of mammals. the intercarotid anastomosis obviously serves as its substitute. Evidence of correlation between asymmetry of caudal rami of the cerebral carotids and form of the intercarotid anastomosis is presented.A communication between cerebral carotids caudal to the hypophysis seems to be a deep‐rooted vertebrate characteristic. An intercarotid anastomosis, apparently homologous to that of birds, occurs in a number of cartilaginous fishes, reptiles, and mammals. In mammals the intercarotid anastomosis is a communication between right and left posterior hypophyse

ISSN:0002-9106    

DOI:10.1002/aja.1001220102

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

年代:1968

数据来源: WILEY

摘要:

AbstractThis paper describes the ultrastructural phenomena occurring during the differentiation of cilia in the epidermis and trachea ofXenopus laevis. The sequence of developmental events seems to begin with thede novoformation of clusters of small, dense “procentriole precursor bodies” which are apparently transformed into procentrioles under the influence of dense amorphous masses here termed “procentriole organizers.” The procentriole so formed is a cylinder 150 mm̈ in diameter with nine single microtubules in its wall which probably give rise to the nine “triplet” microtubles in the wall of the definite centrioles (200 mm̈ in diameter). The appearance of multiple centrioles in the apical cytoplasm is correlated with disappearance of procentriole precursor bodies and procentrioles. Smooth‐surfaced vesicles seemingly produced in the well developed Golgi zones may contribute to the development of the ciliary membrane. Following their formation in the supranuclear cytoplasm, the centrioles or presumptive basal bodies align with their longitudinal axes perpendicular to the apical plasmalemma. A ciliary shaft then appears distal to each basal body and simultaneously small, dense bodies like those termed “procentriole precursor bodies” reappear. At this time we call the dense bodies, “axonemal precursor bodies,” because they probably provide material for the synthesis of new axial microtubules at the tip end of the growing cilium. Centriolar rootlets develop during centriolar alignment and ciliary shaft formation from a distinct, low electron‐op

ISSN:0002-9106    

DOI:10.1002/aja.1001220103

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

年代:1968

数据来源: WILEY

摘要:

AbstractThe behaviour of glycogen in the rat liver under conditions of fasting, refeeding, and cortisone administration has been investigated in a combined chemical and histochemical study. In contrast to the observations of others the distribution of glycogen in the liver was found to be reasonably uniform. Histochemically, the periodic acid‐Schiff reaction was considered to be the method of choice for the assessment of glycogen, particularly at low levels. In sections from frozen dried liver, however, reasonably good results could also be obtained with Best's carmine stain, although this stain was not very sensitive at the lower, and was thought to be too dense for accurate visual assessment at the higher levels of glycogen. As far as the intralobular distribution of glycogen was concerned, no fixed zones of “glycogen deposition” and “glycogen withdrawal” were found, since the intralobular gradient could be altered by varying the experimental conditions. This observation led to the postulate of a “glycogenic wave,” which not only helps to explain some of the contradictory findings in the literature on the localization of glycogen in the liver, but which can also be reconciled with the traditional concept of the liver lobule. The “heterogeneity of the cell population” in the liver lobule was considered to be a function of time rather than of fixed an

ISSN:0002-9106    

DOI:10.1002/aja.1001220104

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

年代:1968

数据来源: WILEY

摘要:

AbstractThe ultrastructure of the cells of the enamel organ related to enamel formation was studied using the lower incisors of adult male rats. In the region of enameldeposition, stratum intermedium cells are stabilized by a system of intercellular bridges and intracellular fibrils. The mitochondria in these cells are positioned toward the extracellular channels through which any direct intercellular exchange between the capillaries and ameloblasts must occur. Tentatively, the mitochondrial arrangement is considered to be related to the movements of electrolytes and water across the capillary‐ameloblast interval.In the region oftransition, enamel deposition ceases and the ergastoplasm of the ameloblasts is removed, apparently by cytosegresomes, with an accompanying reduction in the height of the ameloblasts. Here, vesicles containing stippled material are infrequent compared to their occurrence in ameloblasts concerned with enamel deposition. Other vesicles, characteristically found in ameloblasts related to maturing enamel, first appear in the transition region and seem to originate from the cell membrane abutting on the enamel.In the region ofmaturation, cytosomes are common in the Golgi region whereas vesicles and mitochondria predominate in the distal ends of the ameloblasts. The papillary cells contain an unusually large number of mitochondria, elaborate microvilli and vesicles, which suggests that these cells are extremely active, presumably in the movement of materials related to enamel maturation.The changes in structure of the papillary cells, which occur concomitantly with those of the ameloblasts during enamel formation, are indicative of interrelated functional changes and strongly support the concept of ameloblasts and papillary cells acting together as a functional uni

ISSN:0002-9106    

DOI:10.1002/aja.1001220105

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

年代:1968

数据来源: WILEY

摘要:

AbstractIn sheep, the gastrosplenic and mesenteric veins converge at an angle of about 140° to form the portal vein, which is joined, along its right ventral border, by the gastroduodenal vein. At the porta, right and left branches of the portal vein diverge at an angle of 65–70° to supply separate areas that join along a line between the fossa for the gall bladder, and the middle of the left branch. Right dorsal branches leave the portal vein or its right branch near the point of bifurcation.When131I‐albumin that had been heated was injected into the right ruminal vein and entered the portal stream in the gastrosplenic vein, no significant differences existed in the levels of radioactivity between the areas supplied by the different portal branches. When the131I‐albumin entered the portal stream from either the gastroduodenal or mesenteric veins, the area supplied by the right branch contained a significantly higher level of radioactivity than the remainder of the liver. When corrections were made for an unequal distribution of blood, it was found that blood from the gastrosplenic vein was distributed preferentially to the left branch, blood from the gastroduodenal vein to the right branch, and that blood from the mesenteric vein enters the right and left branches in preference to the right dorsal branches of the port

ISSN:0002-9106    

DOI:10.1002/aja.1001220106

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

年代:1968

数据来源: WILEY

摘要:

AbstractThe ultrastructural details of human oocytes from four primordial follicles and one early primary follicle are presented. A fifth primordial follicle is represented by a paraffin section stained by hematoxylin and eosin. The paranuclear Balbiani vitelline body, contsisting of a centrosome surrounded by endoplasmic reticulum, Golgi complexes, compound aggregates, annulate lamellae, and mitochondria is described. The annulate lamellae arise as an evagination from the outer leaflet of the nuclear envelope and interdigitate with folds of the endoplasmic reticulum which also is continuous with the outer leaflet of the nuclear envelope. Structural aspects of annulate lamellae are discussed in relationship to current ideas of nuclear membrane ultrastructure and to their possible role in nucleo‐cytoplasmic transfer. A biographical note on the life of Edouard Gérard Balbiani is present

ISSN:0002-9106    

DOI:10.1002/aja.1001220107

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

年代:1968

数据来源: WILEY

摘要:

AbstractRegional binding of norepinephrine to tissue structures occurs in sections of brain tissue incubatedin vitrowith tritiated norepinephrine, followed by radioautography. The binding probably represents one of the mechanisms involved in the uptake and storage of catecholamines by nerve cells. Applying this method to a study of human brains showed excessively strong binding of norepinephrine at the surface membranes of pigmented nerve cells in the substantia nigra, nucleus coeruleus, nucleus dorsalis vagi, and others. Such excessive binding was not found in nonpigmented nuclei in the human brain nor in rat brain. The arrangement of sites of binding at the cell membranes strongly suggested synaptic endings. Melanin pigmentation of nerve cells may be related to the amount of catecholamine‐containing synapses at the surface of the neuron

ISSN:0002-9106    

DOI:10.1002/aja.1001220108

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

年代:1968

数据来源: WILEY

摘要:

AbstractThe myofibrillar ATPase histochemical reaction was utilized to determine the proportion of the two basic histochemical fiber types in three “mixed” skeletal muscles of guinea pig after denervation. In five normal control animals, there was no significant difference in the proportion of fiber types on the two sides. In 12 experimental animals from 6–27 weeks after right sciatic neurectomy, the intensity of the myosin ATPase activity was not appreciably altered in the denervated muscle fibers but the type II (dark) fibers underwent preferential atrophy. The fiber type ratio between denervated and control sides in the experimental animals was not significantly different from the same values in the normal control animals. This allowed the conclusion that, up to 27 weeks after denervation, the histochemical typing of a fiber by the myofibrillar ATPase reaction probably reflects the original fiber type. This reaction is the preferred method for fiber typing in denervated guinea pig muscle, especially since most other histochemical reactions show markedly reduced activity of muscle enzymes after denervation and are unsuitable for fiber typing. The soleus, which normally contains only type I fibers, showed numerous type II fibers at 27 weeks after denervation and this was interpreted as a dedifferentiating pr

ISSN:0002-9106    

DOI:10.1002/aja.1001220109

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

年代:1968

数据来源: WILEY

摘要:

AbstractNumerous microtubules of nerve cells and gliocytes in the toad are found, in electron micrographs, to contain a dense core. Such content is granular in nature, the granules being irregularly disposed in the lumen of the microtubules. Comparative observations on dense‐core microtubules in peripheral and central nerve cells indicate that they are consistent cell components in the entire nervous system of the toad. The functional significance of the granular content of the microtubles is discusse

ISSN:0002-9106    

DOI:10.1002/aja.1001220110

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

年代:1968

数据来源: WILEY

ISSN:0002-9106    

DOI:10.1002/aja.1001220101

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

年代:1968

数据来源: WILEY