摘要:

AbstractThe structure of the areas pellucida and vasculosa of the early chick embryo (stages 11–29) was examined by light, transmission and scanning electron microscopy. The most striking feature of the endodermal cells of these areas is the presence of large intracellular yolk drops which are characteristic of the regions in which they are found: lipid‐likehomogeneousdrops in the area pellucida, heterogeneously composedpleomorphicdrops in the mid‐region of the area vasculosa andgranulardrops at the periphery of the area vasculosa in the region of the sinus terminalis. On morphological criteria it is postulated that granular drops may arise by direct engulfment of extracellular yolk, but this does not appear to be true for pleomorphic or homogeneous drops. Since the apical junctions between endodermal cells across the yolk sac are tight, they seal off the extraembryonic compartment from the vitelline circulation and presumably prevent intercellular passage of the yolk constituents. Thus the endodermal epithelium must mediate the transport of nutrients from the yolk mass to the developing embryo. Endodermal cells exhibit a variation across the yolk sac in the presence and number of structures associated with uptake of extracellular materials. The mid‐region of the area vasculosa appears to be the most endocytotically active region with an abundance of microvilli, bristle‐coated pits and vesicles and apical canaliculi and vacuoles. There is a close association between the endoderm and vitelline blood vessels and this association is maintained, as the yolk sac develops, by the formation of small vessels juxtaposed between the vascular surface of the endoderm and the walls of the large vitellin

ISSN:0002-9106    

DOI:10.1002/aja.1001550302

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

年代:1979

数据来源: WILEY

摘要:

AbstractThe purpose of this research was to describe patterns of density variation throughout the cortex of the humeral shaft inMacacaand to attempt to explain these variations in terms of the gross anatomy and mechanical function of the bone. One hundred ninety transverse sections were taken from five sites along the humeral diaphyses of 38Macaca. The density at eight positions around each section was measured using radiographic and densitometric techniques. Analysis of variance indicated significant (p<0.02) differences among cross‐sectional levels and positions within each level. No sexual dimorphism in density could be demonstrated, although sexual dimorphism in density has been reported for the femora of this same sample. This relationship between humerus and femur parallels that found in humans. Density increased distally in the humerus, probably due to major areas of muscle attachment. Comparison with similar data from the femur ofMacacaindicated unexpected differences in density pattern which may underlie differences in the strength and mechanics of the upper and lower extremitie

ISSN:0002-9106    

DOI:10.1002/aja.1001550303

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

年代:1979

数据来源: WILEY

摘要:

AbstractExamination of longitudinally and transversely sectioned photoreceptor cells of the guinea pig retina revealed an aggregate of thin filaments forming a single cross‐striated fibril coursing through the full length of the non‐receptor portion of the cell. The fibril begins as the ciliary rootlet from the region of the basal body of the connecting cilium. From the basal body it passes between the mitochondria of the ellipsoid and along the Golgi zone of the myoid region of the inner segment, narrowing from an irregularly shaped bundle to a ribbon‐shaped aggregate. The fibril separates into discrete strands, each curving along the nucleus, reuniting into a single bundle to pass down the cell's axon, and terminating deep within the synaptic terminal. The fibril is flanked by two separate membranous saccules, each continuous along nearly its full length. The fibril's extensive course in the guinea pig and its association with continuous membranes necessitates a reexamination of earlier proposals for the function of cross‐striated filamentous structures in photorecepto

ISSN:0002-9106    

DOI:10.1002/aja.1001550304

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

年代:1979

数据来源: WILEY

摘要:

AbstractChondrocytes isolated from auricular cartilage of 7‐day‐old rabbits were grown in vitro until the onset of phase III, occurring after 10‐14 population doublings (PD). The size of cells and their dry mass were measured at various PD levels. These data were compared with results of analogous measurements of chondrocytes freshly isolated from 28‐day‐old rabbits.Both in vivo, during cartilage growth, and in vitro, some of the chondrocytes increased considerably in size and acquired two nuclei.Chondrocytes cultured in vitro for 4 population doublings were still capable of depositing elastic fibers in culture and forming cartilage after intramuscular transplantation. After longer periods of cultivation the ability of cells to produce a cartilage matrix declined.It is suggested that the auricular chondrocytes may represent a convenient model for comparative studies of cell aging in culture and in vivo, owing to the simplicity of matching senescent cells arising in both these s

ISSN:0002-9106    

DOI:10.1002/aja.1001550305

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

年代:1979

数据来源: WILEY

摘要:

AbstractThe cellular and cytoarchitectural features of the lateral superior olive, the medial superior olive, the superior paraolivary nucleus and the medial, lateral and ventral nuclei of the trapezoid body are described in C57BL/6 mice using Nissl, Bodian and Golgi techniques. Principal, spindle and marginal cells are present in a well‐defined lateral superior olive. The dendrites of these cells run primarily within rostrocaudal sheets as in the cat. The principal cells of the medial nucleus of the trapezoid body are similar to the principal cells in the cat. Large multipolar cells characterize the lateral nucleus of the trapezoid body and bipolar cells with a medial‐lateral orientation are found in the medial superior olive. The largest neurons are found in the superior paraolivary nucleus and the lateral superior olive, and the medial and ventral nuclei of the trapezoid body. While brain weight and neuronal packing density change with development, the characteristic location of cell groups and the shape and Nissl‐staining pattern of neurons in the youngest brains examined were essentially unchanged in the adult mice, although dendritic maturation had occurred. The homologies of the C57BL/6 superior olivary complex nuclei with the same areas described in other mouse strains, rat and cat are discussed.This study expands our understanding of the organization of the superior olivary complex in an inbred strain ofMus musculusand relates it to other species. The data about changes occurring during postnatal maturation may aid in the interpretation of behavioral and physiological studies of neonatal plasticity of the auditory s

ISSN:0002-9106    

DOI:10.1002/aja.1001550306

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

年代:1979

数据来源: WILEY

摘要:

AbstractIleum from rats 4, 9, 11, 12, and 15 days old can best be maintained for 24 hours in a system using Hanks' Balanced Salt Solution without fetal calf serum, at 25°C and 21% O2. Suckling rat duodenum and jejunum were difficult to maintain well for 24 hours in this system or a variety of other systems that were tried. A temperature of 37°C hastened deterioration of duodenum, jejunum or ileum. With ileum,3H‐thymidine and14C‐leucine were increasingly incorporated into DNA and protein over the 24‐hour period. Light microscopy, as well as scanning and transmission electron microscopy, showed very good preservation of the ileum after 24 hours. The addition to the medium of hydrocortisone, 1 μm, and thyroxine, 0.01 μm, alone or in combination, did not change DNA or protein synthesis, or morphology, possibly because of the relatively short (24 hour) time period. Our organ culture system emphasizes the differences between suckling rat ileum and the rest of the intestine, and provides a new tool for evaluating, over a 24‐hour period, the developing rat smal

ISSN:0002-9106    

DOI:10.1002/aja.1001550307

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

年代:1979

数据来源: WILEY

摘要:

AbstractWith the use of Golgi, horseradish peroxidase, and electron microscopic techniques, neurons within a broad region of the preoptic hypothalamus of the mouse were shown to have dendrites that projected well into the depths of the optic chiasm. Further experimental and ultrastructural investigation demonstrated synapses between these dendrites and retinal axonal boutons within the chiasm. All synapses located in the chiasm were classified as Gray's type I. The possible function of these dendritic projections is discussed.

ISSN:0002-9106    

DOI:10.1002/aja.1001550308

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

年代:1979

数据来源: WILEY

ISSN:0002-9106    

DOI:10.1002/aja.1001550301

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

年代:1979

数据来源: WILEY