摘要:

AbstractRana pipienslarval beaks consist of column cells, sheath cells and basal cells which supply cells to column and sheath. Each column consists of disk‐like precone cells, cone cells and keratinized cone cells; they are cells in different stages of the process of keratinization.Beaks first appear externally at embryonic stage 24. Epidermal cells align at the tip of the jaw at stage 21. They increase in number and change in shape. Keratinization starts at stage 23. By stage 24, the apical column cells are keratinized and the histological organization is set for the whole larval period.During the larval period, the numbers of column cells increase until stages VIII or IX, stay relatively constant during mid‐larval stages, and decrease at late larval stages. The beak is completely shed at stage XX. The widening of the beaks goes on during the entire larval period. Along the cutting edge of the jaw the booth spikes increase in number and in individual width as the animal grows older and larger.Thyroid hormone causes a premature reduction of the column cell number and a precocious beak loss. The loss of beak at metamorphic climax is a thyroid dependent ev

ISSN:0003-276X    

DOI:10.1002/ar.1091820402

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

年代:1975

数据来源: WILEY

摘要:

AbstractBoth the NZW and NZB mice exhibit an elevated fasting blood sugar level when compared to Swiss white mice. The NZB/NZW F1hybrid mouse shows still a higher fasting serum glucose level than either of its parental strains. This elevated glucose level is noted very early in the animals' life, long before definitive signs or symptoms of pathology are evident, and remains elevated at least until the fortieth week of life, the last testing period in our series before sacrificing the animals. There are two major peaking periods for the glucose levels, namely at 4–10 weeks of age and then again at 31–40 weeks of age. These age periods correspond to the very young animal and to the animal that is beyond its prime and most likely sick and near the end of its lifespan due to the animals' inherent disease processes. The NZB and NZB/NZW F1hybrid succumb to their disease processes at approximately 8–10 months of age. The NZW usually lives until 18 months.The questions are raised: does the altered immunologic state in the NZB and/or the NZB/NZW F1hybrid produce the elevated blood sugar levels and the pancreatic histopatholgy or is it the early hyperglycemic condition coupled with pancreatic pathology which are in some measure instrumental in producing the lesions discussed and observed, in the beginning of the three to four month period of age, in the various organs? Is there a relationship between the hyperglycemic condition and the immune state or are these independent phenomena in a genetically “mixed up

ISSN:0003-276X    

DOI:10.1002/ar.1091820403

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

年代:1975

数据来源: WILEY

摘要:

AbstractThe tibial tuberosity develops by a concomitant, and juxtaposed, outgrowth of hyaline cartilage and ingrowth of fibrovascular tissue. During the fetal period this hyaline cartilage outgrowth is progressively distally displaced to become situated adjacent to the anterior portion of the tibial metaphysis. About four to six months post‐natally a growth plate develops under the tibial tuberosity. This growth plate shows structural adaptations that permit accommodation of large tensile stresses. The growth plate of the tibial tuberosity has three distinct regions — (a) a zone of endochondral bone formation, (b) a zone of intramembranous bone formation through fibrocartilage, and (c) a zone of intramembranous bone formation through fibrous tis

ISSN:0003-276X    

DOI:10.1002/ar.1091820404

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

年代:1975

数据来源: WILEY

摘要:

AbstractPotassium pyroantimonate has been employed in this study to localize calcium in the vascular smooth muscle of the thoracic aorta of the rabbit. The pyroantimonate ion precipitates sodium, magnesium and calcium. Incubation of the isolated thoracic aorta in a high potassium bathing medium which does not contain sodium, magnesium or calcium depletes the tissue of sodium. Addition of 10.8 mM CaCl2to the incubation medium results in welllocalized depositions of reaction product, presumably that of calcium pyroantimonate, in mitochondria, sarcoplasmic reticulum, and at the plasma membrane. Some or all of these organelles may, therefore, play a vital role in the contractionrelaxation cycle of vascular smooth muscle.

ISSN:0003-276X    

DOI:10.1002/ar.1091820405

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

年代:1975

数据来源: WILEY

摘要:

AbstractTo study the role of certain organelles in steroidogenesis, dissociated rat adrenocortical cells were incubated for two hours with ACTH at a concentration that induces a high level of steroid production. Sections of ACTH treated and untreated cells were photographed in the electron microscope, and morphometric analysis was undertaken to assess possible ACTH‐induced changes in total cell volume, volume density and numerical density of lipid droplets and mitochondria.There was no change in total cell volume. Lipid droplet volume density and numerical density decreased. Mitochondrial volume density did not change, but numerical density increased.The decrease in lipid droplet volume density indicates a rapid depletion of cholesterol for steroid production. This depletion is almost entirely due to the disappearance of lipid droplets, rather than to an overall diminution in their size, as shown by the decrease in lipid droplet numerical density. The mitochondrial data suggest that the adrenocortical cell has an adequate mitochondrial apparatus to respond to acute ACTH stimulation with increased steroid output without an increase in mitochondrial volum

ISSN:0003-276X    

DOI:10.1002/ar.1091820406

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

年代:1975

数据来源: WILEY

摘要:

AbstractMuscle fibers of the sternomastoid and the tongue of the rat were characterized histochemically according to mitochondrial distribution (succinic dehydrogenase), as well as reactivity for the alkali‐ and acid‐stabile “myofibrillar” adenosine triphosphatases. The principal fiber types of the sternomastoid were the large, “white” AαβM fibers and the smaller, “intermediate” BβD and “red” CαL fibers (figs. 1, 2, 3). The unusual musculature of the tongue was populated by diminutive AαM and CαM fibers, and variants thereof; all with relatively high mitochondrial content (figs. 4, 5, 6).Reinnervation of the sternomastoid muscle by the hypoglossal nerve caused most fibers of the sternomastoid to assume histochemical profiles reminiscent of those commonly observed in the tongue. However, the BβD fibers of the sternomastoid persisted in near usual numbers and disposition (fig. 17), despite their reinnervation by a nerve normally destined for a muscle lacking that particular fiber type. Thus, there are as yet unrecognized factors, possibly of neural origin, though more likely of muscle origin (genetic), that impose restrictions on the metabolism‐regulating functio

ISSN:0003-276X    

DOI:10.1002/ar.1091820407

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

年代:1975

数据来源: WILEY

摘要:

AbstractBile canaliculi in the rat liver have been studied by scanning electron microscopy. They appear as half tubules carved out of the hepatocytes' surface. In several cases the bile channel bifurcates to form two or three long branches running on the same face of the cell. Therefore, by SEM it seems obvious that the same side of an hepatocyte may be used for bounding two or more bile canaliculi.Some bile canaliculi display a flexuous course and show lateral sacculations. Some of them are large and apparently similar to the short lateral branches of the bile canaliculus; others are smaller and arise obliquely from the subjacent cortical areas of the hepatocyte cytoplasm. These latter structures are best observed in stereo‐views in which they appear as narrow intracellular projections bordered with a few microvilli, actually opening into the lumen of the bile canaliculus. The SEM results suggest that these sacculations probably correspond to short intracellular branches of the bile canaliculi.Zones of minimal distance (0.1 μ) between the space of Disse and the bile channel have been frequently observed. They are actually the zones where the intercellular clefts arising from the subendothelial space of Disse come into closest contact with the bile canaliculus and might serve as sites of simple diffusion of substanc

ISSN:0003-276X    

DOI:10.1002/ar.1091820408

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

年代:1975

数据来源: WILEY

ISSN:0003-276X    

DOI:10.1002/ar.1091820401

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

年代:1975

数据来源: WILEY