摘要:

AbstractDirect observation of unstained, 1 mm thick blocks of fresh epiphyseal cartilage from tibia of 15‐ and 18‐day‐old chick embryos revealed shrunken chondrocytes on its cut surfaces but unshrunken chondrocytes deep within the tissue blocks. The unshrunken hypertrophied chondrocytes are rimmed with refractile substance identified as chondroitin sulfate removable with hyaluronidase. This substance is stained metachromatically red with toluidine blue, and is stained with ruthenium red and with ruthenium red‐OsO4. The latter, observed with the electron microscope, is present as an electron dense rim, specifically about the unshrunken, hypertrophied chondrocytes between the plasma membrane and lacunar wall. By rendering the chondroitin sulfate electron dense with RR‐OsO4, electron lucent bodies (ELB) were revealed specifically about the hypertrophied chondrocytes. The ELB contain an electron dense core with radiating fibrils. The content and source of ELB, also found in the intercellular matrix, are not known. The 0.1% toluidine blue solution containing 0.2 m MgCl2or 0.4% NaCl or KCl stained juxtanuclear clusters of granules metachromatically red. The location of intracellular granules was believed to represent a cluster of Golgi‐derived vesicles. The pericellular metachromatic, RR‐OsO4‐positive rim is believed to be an accumulation of externalized juxtanuclear metachromatic granules. The possibility that the ELB may also be externalized content of Golgi vesicles

ISSN:0003-276X    

DOI:10.1002/ar.1091830302

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

年代:1975

数据来源: WILEY

摘要:

AbstractThe authors' previous report (Savostin‐Asling and Asling, 1973) demonstrated that Meckel's cartilage is a favorable site for study of calcified cartilage resorption. In the present study the ultrastructural features at this resorption front have been examined by transmission and scanning electron microscopes (19‐day rat fetus). Multinucleated giant cells (chondroclasts) dominated the erosion front. The many features which they showed in common with osteoclasts included abundant mitochondria, vacuolation, lysosomes, sparsity of roughsurfaced endoplasmic reticulum, and deep infoldings at loci of contact with calcified matrix. Crumbling of matrix (with mineral crystals penetrating between these foldings) and fragmentation of collagen fibrils were also seen. The propensity of chondroclasts for spanning several opened lacunae provided special opportunity to demonstrate cell surface modifications in presence or absence of matrix contact. Ameboid processes extending into lacunae were seen by both transmission and scanning procedures; they were sometimes tipped with a veil of filamentous processes as small as 0.3 μm in diameter. Most hypertrophic chondrocytes, when released from lacunae, appeared to be disintegrating. However, in accord with previous evidence of their possible merger with chondroclasts (in light microscopic studies) there was also evidence for breakdown of cell walls between a chondroclast and a chondrocyte in intimate contact, with possibility of cytoplasmic contin

ISSN:0003-276X    

DOI:10.1002/ar.1091830303

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

年代:1975

数据来源: WILEY

摘要:

AbstractAutoradiographic methods were used to analyze cell kinetics in peripheral epithelium of the fetal mouse lung, days 15‐18. The3H labeling index decreased in proportion to increases in fetal lung and body weight from day 15 to day 18. Cell‐cycle determination estimated from the percent of labeled metaphases at intervals after3H thymidine injection showed the shortest cell‐cycle time (12.25 hours) on day 15 during the precenal stage of growth. Total cycle time (Tc) increased by approximately one hour on each subsequent day. Between days 15 and 16 Tc increased due to a 1‐hour increase in the post mitotic interphase (G1); thereafter increases in Tc could be ascribed almost entirely to lengthening of the DNA synthetic period. A comparison of cell‐cycle time in central and peripheral tubules of the same lungs on day 15 showed a slower cell cycle in the central tubules than in the peripheral branches. An estimate of the growth fraction (GF) on each day based on calculated and observed cell‐cycle times showed that GF was 1 on days 15 and 16, decreasing to 0.69 on day 17 and 0.27 on day 18. Thus cell‐cycle time increases with lung maturation and it increases from peripheral to central zones of the bronchial tree. The greater part of the observed decline in growth rate as the prenatal phase of growth is completed was due largely to a decrease in the fraction of cells in t

ISSN:0003-276X    

DOI:10.1002/ar.1091830304

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

年代:1975

数据来源: WILEY

摘要:

AbstractThe synthesis of zymogen‐like secretory granules in convoluted tubules of mouse submandibular gland (SMG) was investigated by histometry, light microscopy and electron microscopy. In normal males secretory granules in the SMG increased greatly from 25 days after birth and reached a maximum level 50 days after birth. Castration of adult male mice markedly decreased the level, but it was completely restored by testosterone administration. A parallel was found between change in the granule level and the amount of rough endoplasmic reticulum (RER) in the convoluted tubular cells during development or after various treatments. Development of the Golgi apparatus was also observed in the cells when the granules increased. Both the increase in the granules and in the RER induced by testosterone were prevented by actinomycin D or puromycin. These results indicate that the granule contents are synthesized on the RER under the control of testosterone, and then condensed in the Golgi apparatu

ISSN:0003-276X    

DOI:10.1002/ar.1091830305

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

年代:1975

数据来源: WILEY

摘要:

AbstractThis study is concerned with the morphogenesis of the carpal elements in the regenerating forelimb of the adult newt. Blastema cells surrounding the remnant bony stumps begin to differentiate into cartilage on the twentieth post‐amputation day. Subsequently, masses of cartilage build up from the radial and ulnar stumps. The radial mass is larger and differentiates more rapidly than the ulnar mass. By the fifty‐fifth post‐amputation day, the eight basic carpal elements are formed, with fusion of two of the units, intermedium with ulnare, occurring by the seventieth day. The complexed regenerate possesses the seven carpal elements characteristic of the normal adult limb. The present results show that during limb regeneration in the adult newt the carpal elements are restored to their original number and position and that the pattern of such carpal differentiation proceeds in a proximodistal direction influenced by the stump remnants of the radius and

ISSN:0003-276X    

DOI:10.1002/ar.1091830306

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

年代:1975

数据来源: WILEY

摘要:

AbstractA simple, inexpensive method of making accurate permanent casts of brain dissections is described. Dissected brain preparations are used to produce silicone rubber molds. Methyl methacrylate is used to make the hard plastic models.

ISSN:0003-276X    

DOI:10.1002/ar.1091830307

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

年代:1975

数据来源: WILEY

摘要:

AbstractThe effects of magnesium deficiency in ovariectomized and estrogen‐treated rats were examined in histological sections of bones and various soft tissues. The changes observed in the femora ofintactrats deprived of magnesium for three weeks were: 1. a general increase in diaphyseal thickness, 2. the presence of localized fibrous or bony‐like masses in subperiosteal and metaphyseal sites, and 3. the occurrence, although rare, of endosteal hyperplasia. Inovariectomized, magnesium‐deprived animals, the incidence and location of fibrous masses were similar to that in the femora of magnesium‐deficientintactrats; however, no increase in diaphyseal thickness was noted. Daily injections of 25 μgestradiolcaused a reduction of the frequency of skeletal hyperplasia from 80% to 20%, as well as a reduction in femoral diaphyseal thickness. Estradiol hormone administration also brought about a marked alleviation of the dermal and neural manifestations of magnesium deficiency, but, at the same time, caused an exacerbation of renal ca

ISSN:0003-276X    

DOI:10.1002/ar.1091830308

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

年代:1975

数据来源: WILEY

摘要:

AbstractChanges in physiological reproductive states of female Long‐Evans hooded rats were directly correlated with changes in the concentration of acidophilic and basophilic connective tissue granulated cells in the lamina propria of the duodenum. Acidophilic granulated cell numbers were significantly higher at estrus and metestrus than at other stages of the estrous cycle or in the immature state. Acidophilic granulated cell numbers during pregnancy were not significantly different from cell numbers quantified during metestrus, diestrus, or proestrus, but were significantly lower than cell numbers during estrus. Late lactation (21‐25 days) was associated with significant decreases in the numbers of acidophilic granulated cells from numbers observed during the estrous cycle and during pregnancy. Basophilic granulated cell numbers did not differ significantly during the estrous cycle, although the highest numbers were observed during proestrus. Basophilic granulated cell numbers were significantly higher during pregnancy than during the estrous cycle. Basophilic granulated cell counts in late lactation were comparable to numbers quantified in estrus, metestrus, and diestrus, but were significantly lower than during proestrus and pregna

ISSN:0003-276X    

DOI:10.1002/ar.1091830309

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

年代:1975

数据来源: WILEY

摘要:

AbstractThe ultrastructure of the median eminence of neonatal (newborn, 1‐, 3‐, 5‐, and 10‐day old) and adult guinea pigs was studied to determine the dynamic changes occurring in this structure during early life. At birth the portal vasculature consists of the Mantelplexus and a few, non‐fenestrated capillary loops. The number of ansae and the degree of fenestration increase rapidly after birth. The abundance of cytoplasmic and ciliary projections into the ventricular recess and the large numbers of organelles indicate that the ependymal cells are more active in the neonatal period than in the adult male. Moreover, the ependymal endfeet cover most of the surface area of the primary portal plexus during this time. The neuronal layers of the median eminence are difficult to distinguish at birth due to the lack of myelinated fibers in the zona interna. Significant myelination appears on day 3 but is not complete until day 10. There is a progressive increase in the numbers of Herring bodies and large neurosecretory granules (1,500‐1,700 Å) during this same time period. In the zona externa, few nerve terminals abut on the perivascular space until day 3. Increases in numbers of granules per axon profile were noted for each day after birth. Despite the relatively long gestation period of the guinea pig (68‐72 days), the morphologic appearance of the median eminence at birth suggests that the neurovascular link controlling anterior pituitary function is no

ISSN:0003-276X    

DOI:10.1002/ar.1091830310

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

年代:1975

数据来源: WILEY

摘要:

AbstractThe ultrastructure of the intercellular junctions of rat endocardium has been characterized following lanthanum exposure in vitro and uranyl acetate stainingen bloc. The interendothelial clefts of the endocardium run either a relatively straight or convoluted course and possess one or two loci where the plasma membranes are in close apposition or form punctate fusions. Elongate restrictions, that exhibit hexagonal arrays of subunits following lanthanum immersion (gap junctions), are also present in the intercellular endocardial clefts. The occurrence of interendothelial clefts of endocardium lacking occlusive foci can account for the permeability properties of ventricular endocardium, where the direction of diffusion of macromolecules has been attributed to pressure gradients between ventricular cavity and myocardium. The relationship of gap junctions to possible electrical phenomena within the endocardium is also discussed.

ISSN:0003-276X    

DOI:10.1002/ar.1091830311

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

年代:1975

数据来源: WILEY