摘要:

AbstractThe relationship of nascent albumin and hepatocyte organelles was studied with the immunoperoxidase reaction in rats given various drugs to alter cellular albumin content. Colchicine was used to increase intracellular albumin. Cycloheximide inhibited synthesis but allowed nascent albumin to remain with its ribosome of origin. Puromycin also inhibited synthesis but released albumin from its ribosome. There was no difference in the appearance of attached ribosomes in hepatocytes from saline‐injected rats and those given colchicine or cycloheximide. In these cases, membranes of the endoplasmic reticulum were consistently decorated with ribosomes positive for the presence of albumin antigenicity on their cytosolic surface. The cisternal and cytosolic compartments were negative. The situation after puromycin was different. Here the membranes appeared to be denuded of ribosomes and reaction product, indicative of albumin, was present only on the lumenal surface. To determine whether puromycin had caused the release of ribosomes, sections from puromycin‐treated cells were stained nonspecifically with uranyl acetate. This showed that the normal amount of ribosomes was still bound but that they could not be seen when a probe specific only for albumin was used. It appears that nascent albumin can associate with its ribosome within the cytosol. Also, apparently after albumin passes through the membrane of the rough endoplasmic reticulum, it remains attached to its lumenal surface. A model incorporating cytosolic folding of albumin followed by its entropic membrane transit is presen

ISSN:0003-276X    

DOI:10.1002/ar.1092010202

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

年代:1981

数据来源: WILEY

摘要:

AbstractUrea and dithiothreitol can decondense the chromatin in some of rat sperm heads. By this treatment, we have observed that in the nuclei of rat sperm the chromatin is organized into two morphologically distinct portions, namely: the compact chromatin rods of about 450 to 1,000 Å thick, and the interlacing fibers about 250–290 Å in thickness. When these treated sperm are further digested with micrococcal nuclease, the small fibers disappear, whereas the chromatin rods are still present in the “urea‐nuclease pellet.” From the available evidence, we suggest that the chromatin rods represent the highly packed nucleoprotamine, whereas the small fibers represent the more loosely organized nucl

ISSN:0003-276X    

DOI:10.1002/ar.1092010203

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

年代:1981

数据来源: WILEY

摘要:

AbstractWe reinvestigated the still controversial existence of arterial pathways by‐passing glomeruli within kidneys of rats from weaning to more than 12 months old (i.e., body weight ranging from 39 g to 643 g). For this purpose, the arterial injection of microspheres 7.5 μm to 17 μm in diameter was combined to corrosion‐replication of the arterial bed of a vasodilated perfused kidney preparation. This procedure allowed easy detection of arterial by‐passes with light microscope and detailed observation with scanning electron microscope. Our results clearly demonstrate the existence of various categories of arterial by‐passes throughout renal cortex regardless of age. Some of them had never been described before. These vascular by‐passes were found with increased frequency from superficial to juxtamedullary cortex. In the latter area, frequency was not agedependent, and approximately 10% (range 4–22%) of juxtamedullary glomeruli were involved. Data derived from previous microsphere studies would suggest that these structures are (partially) nonfunctioning in basal physiological conditions, but more information is needed to assess their possible functional ro

ISSN:0003-276X    

DOI:10.1002/ar.1092010204

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

年代:1981

数据来源: WILEY

摘要:

AbstractIn order to determine the location of sensory nerve endings in cat teeth,3H‐proline and3H‐leucine were injected into the left trigeminal ganglion of eight cats aged 6.5–10 months; 24 hours was allowed for axonal transport of radioactive protein to dental nerve endings, and the endings were then detected by autoradiography. The pulps of most ipsilateral (left) teeth contained some labeled axons. These axons ended in the odontoblastic layer and predentin of roots and crown; at the tip of the pulp horn of each cusp, nerve endings also extended as far as 150 μm into dentinal tubules.Labeled nerve endings were extremely rare in contralateral (right) teeth; only one tooth of 83 studied (eight cats) contained heavily labeled axons, and one other had faintly labeled axons. Both labeled contralateral teeth were central maxillary incisors. Their labeled axons were unbranched in the root and arborized in the crown to end among odontoblasts and many adjacent dentinal tubules.Labeled periodontal nerve endings were most numerous in the apical one‐third of the ligament, with some endings extending as far as the gingiva. The nerve endings in the periodontal ligament were often clustered and appeared to end freely between the collagen bundles; their radioactivity varied in the same way as that of pulp nerves in the adjac

ISSN:0003-276X    

DOI:10.1002/ar.1092010205

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

年代:1981

数据来源: WILEY

摘要:

AbstractRuthenium red (RR) and cetylpyridinium chloride (CPC) were used to demonstrate the distribution of cell surface coat material (SCM) on the free epithelial surface of the developing lens vesicle in stages 14–17 (50–64 hours) chick embryos. Observations were made by light microscopy and transmission (TEM) and scanning (SEM) electron microscopy. A progressive increase in SCM is observed on cellular apices within the epithelium of the lens vesicle by means of RR staining, particularly at the margins of the aperture which are the sites of presumptive fusion. In contrast, a relatively thin layer of SCM persists on the adjacent surface ectoderm. Ruthenium red‐positive SCM extends across the aperture of the lens vesicle prior to initial contact between the advancing epithelial surfaces. The presence of abundant SCM is interpreted as a possible significant prerequisite to invagination and to epithelial adhesion and fusion prior to detachment of the lens from surface ectoderm. When CPC is added to the fixative, a flocculent precipitate over the aperture of the lens visicle and an associated band of modified surface ectoderm which extends ventrally from its lower margin are observed. The modified ectoderm and associated SCM likely represent a presumptive region of active coordinated cellular migr

ISSN:0003-276X    

DOI:10.1002/ar.1092010206

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

年代:1981

数据来源: WILEY

摘要:

AbstractAn improved method is presented for processing single cells for electron microscopy. Agarose, which has a low (30°C) gelling temperature, was used as an initial embedding medium for single cells (spermatozoa and oocytes) and dissociated cell preparations (luteal cells and spleen cells). Dispersed cells of corpus luteum, spleen, and epididymal spermatozoa were placed in 1.5% agarose after aldehyde fixation. These fixed cells, embedded in agarose, were packed into a dense pellet by centrifugation, postfixed, then embedded in Epon. Mammalian eggs were not centrifuged; instead, they were embedded in agarose discs. Cells embedded in agarose were cooled below 30°C to allow for gelling, then processed for electron microscopy. Because agarose has a low gelling temperature, some heat‐labile substances were preserved, as demonstrated by retention of peroxidase activity using the DAB histochemical method. The agarose embedding procedure is both rapid and facile, and has proven to be of value in the handling of fragile single cells for electron microscopic stud

ISSN:0003-276X    

DOI:10.1002/ar.1092010207

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

年代:1981

数据来源: WILEY

摘要:

AbstractThe bronchiolar Clara cells of rats contain characteristic rodshaped granules always surrounded by a unit membrane. These granules contain thin filaments about 9 to 10 nm in diameter lying in a pale matrix. Our morphological results suggest that the filamentary rod‐shaped granules originate from the common, round‐to‐oval, electron‐dense Clara cell granules, as we found different intermediate structures between these two kinds of granules. The electron‐dense granules are digested by pepsin, whereas the filamentary rod‐shaped granules are apparently not affected. The biochemical nature and the possible function of the filamentary rod‐shaped granules are also discussed in relation to the secretory activity of th

ISSN:0003-276X    

DOI:10.1002/ar.1092010208

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

年代:1981

数据来源: WILEY

摘要:

AbstractThe muscle‐tendon junctions of the extensor carpi radialis longus and brevis muscles from adult Balb C Bailey/J mice have been examined tensiometrically and ultrastructurally following removal of cellular membrane and soluble cytoplasm by exposure to nonionic detergent. As judged by the ability of the extracted muscle to generate tension upon exposure to ATP and to transmit the generated tension to the tendon, detergent extraction leaves the muscle‐tendon junction functionally intact. Electron microscopic analysis of the extracted muscle‐tendon junctions reveals that the relationship between the terminal myofilaments and the lamina densa of the basal lamina is retained, despite the extensive extraction of the plasma membrane. Fine filaments (2–7 nm) are seen to connect the lamina densa with an electron‐dense intracellular layer into which terminal actin filaments appear to insert. These fine filaments are considered to represent an important component of the structural linkage between myofilaments and connective tissue and hence to be a significant component of the tension transmitting mechanism. Their precise nature is not known, but some part of the filaments must pass through the hydrophobic compartment of the plasma membrane and thus must be a transmembrane component of considerable tensile strength. These studies suggest that detergent‐extractable membrane lipids play no significant role in the transmission of tension at the muscle–tendon junction, and that fine filaments, probably protein, are responsible for transmitting tension from myofilaments, through the plasma membrane, to the lamina densa of the

ISSN:0003-276X    

DOI:10.1002/ar.1092010209

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

年代:1981

数据来源: WILEY

摘要:

AbstractSlices or sections through the bursa cloacalis and thymus of chick embryos at 7–21 days of incubation were observed by light and electron microscopy to determine whether major differences existed in the surface morphologies of lymphoid cells in these organs, and whether the surface morphologies of these cells changed during ontogeny. These organs were fixed concurrently and identically at each stage.The thymus was packed at all stages with spherical cells having fine structures characteristic of those of lymphoid cells. Many irregularly shaped, epithelial cell processes were present between lymphoid cells.The bursa contained many irregularly shaped stromal cells as well as spherical cells. The latter were few in number during early development, but became the predominant type of cell near the end of incubation. Spherical cells in the bursa consisted of three types based on fine structure: lymphoid cells, granulocytic cells, and cells which were probably precursors of granulocytic cells. Spherical cells in the bursa could not be classified into these three types by their surface morphologies, however, because the latter at any one stage of development were similar. At 7–8 days of incubation, spherical cells in the bursa could not be differentiated consistently from neighboring stromal cells by scanning electron microscopy alone, but by 9 days, spherical cells could be identified routinely by this method.At 9–10 days of incubation, only minor differences existed in the surface morphologies of the spherical cells in the bursa and thymus: Bursal cells displayed long, ridgelike processes, whereas thymic cells exhibited fine surface undulations and large blebs. At 11 days, the surfaces of the spherical cells in the bursa were covered by numerous short microvilli, but the surfaces of thymic cells were unchanged. Bursal cells retained their microvilli through 14 days of incubation, but between 15 and 21 days progressively lost their microvilli, becoming essentially bald near the end of this period. Likewise, thymic cells gradually lost their surface wrinkles and blebs. Near the time of hatching, both types of cells were smoothsurfaced and tightly packed, with individual cells assuming polyhedral configura

ISSN:0003-276X    

DOI:10.1002/ar.1092010210

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

年代:1981

数据来源: WILEY

ISSN:0003-276X    

DOI:10.1002/ar.1092010211

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

年代:1981

数据来源: WILEY