摘要:

AbstractAn electron dense material is found in the extracellular space of the nervous system ofAplysia, a marine mollusc whose ganglia are widely studied by neurobiologists. This material appears to consist of irregular electron‐dense granules, with diameters of approximately 600 Å. This material is found between the glial cells that surround the neuronal perikarya. It is not found in other regions of the nervous system. Because it is found in the ganglion cell layer of the nervous system and because the neurons contain what may be the precursor of this substance, the electron‐dense material is regarded as most probably being a neuronal product. The importance of this material is that it is one of the few examples of visible structure in the extracellular space of the nervous sy

ISSN:0003-276X    

DOI:10.1002/ar.1091870302

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

年代:1977

数据来源: WILEY

摘要:

AbstractThe initiation of Wallerian degeneration in the severed optic nerve of the newt(Triturus viridescens)was very rapid and intense. Significant degeneration of nonmyelinated axons was observed as early as six hours after lesion (h.a.l.) and was almost complete by 48 h.a.l. Initial degeneration of non‐myelinated axons began in “extracellular digestion chambers” formed between burgeoning ependymoglial processes. The remaining fragments and debris were later phagocytized by surrounding ependymoglial processes.Many axons of myelinated fibers have degenerated as early as 6 h.a.l. However, the overall population of myelinated axons degenerates at a much slower rate than nonmyelinated ones, for many of them appear intact as late as 48 h.a.l.Some myelin sheaths show significant signs of degeneration by 6 h.a.l. Indeed, by this time a number of myelinated fibers have completely degenerated leaving only large vacuolated spaces in the nerve parenchyma. Swelling and vacuolization of the sheath are among the earliest signs of myelin degeneration.The ependymoglial cell response to optic nerve lesion is manyfold and dramatic. By 6 h.a.l. there are signs of burgeoning ependymoglial processes which begin to resemble scar formation (gliosis) by 48 h.a.l. The morphological evidence is consistent with the concept of an important phagocytic role of ependymoglial cells during the early stages of optic nerve degener

ISSN:0003-276X    

DOI:10.1002/ar.1091870303

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

年代:1977

数据来源: WILEY

摘要:

AbstractThe distribution of actin and myosin in the rat ovary at different stages of postnatal development was studied by examination of cryostat sections treated with antibodies to chicken smooth muscle (gizzard) myosin or to chicken (pectoral muscle) actin and subsequently with fluoresceinated goat anti‐rabbit γ‐globulins. Staining with either antiserum revealed several layers of intensely fluorescent elongated cells within the theca externa, forming a coherent band around the larger Graafian follicles. In smaller follicles, this band of fluorescent cells was incomplete, and ovaries of immature (6‐day‐old) rats were devoid of strongly fluorescent cells. Corpora lutea contained only scattered fluorescent cells at their circumference. Sections of mature ovaries incubated with antibodies raised against striated (pigeon pectoral) muscle myosin generated no significant fluorescence. Large oocytes stained with either anti‐actin or anti‐smooth muscle myosin showed a thin fluorescent band just beneath the zona pellucida, suggesting that actin and myosin are associated with the oolemma. The distribution of the two antigens in serial sections of follicles coincided, suggesting that the same cells contained both actin and myosin. It is suggested that follicular growth and maturation is attended by the development of a smooth muscle layer in the theca and that contraction of this layer in response to catecholamines and/or prostaglandins may play a role in the extrusion of the oocyte. The rǒle of contractile elements in the oocyte remains to

ISSN:0003-276X    

DOI:10.1002/ar.1091870304

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

年代:1977

数据来源: WILEY

摘要:

AbstractScanning electron microscopy of permanent tooth buds of the monkey confirmed that mineralizing interrod enamel surrounds Tomes' processes on three sides, forming pits that restrict enamel rod formation. The forming face of the enamel rod, which is the floor of the pit, angled toward the tooth surface at the apical edge of the pit, the side nearest the cervical region of the tooth. Consequently, the apical edge of each pit was the only site where both rod and interrod enamel were formed at the nascent tooth surface.The ameloblasts had two secretory surfaces. One was the microvillous surface of the short Tomes' process abutting the forming face of the enamel rod. The other surface, closer to the ameloblast, was between Tomes' processes, abutting the crests of interrod enamel which formed the pits. At each site forming enamel crystallites had specific orientations.Due to the angle of the forming face of the rod and the short Tomes' process, crystallites with both rod and interrod orientation form at the same time and the same plane within the apical (cervical) margin of each rod. It is hypothesized that indistinct boundaries between rod and interrod enamel at the apical margin of each rod are due to both secretory surfaces of ameloblasts secreting at the same time and at the same site.

ISSN:0003-276X    

DOI:10.1002/ar.1091870305

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

年代:1977

数据来源: WILEY

摘要:

AbstractThe effects of denervation on the gastrocnemius muscle of the frog were studied by histologic and histochemical methods. ThirteenRana pipiensunderwent unilateral sciatic neurotomy and were sacrificed weekly as long as 46 days. Of the three normal populations of muscle fibers, the small fibers underwent atrophy, the intermediate sized fibers remained unchanged in size, and the large fibers either did not change or underwent hypertrophy between 21 and 46 days. Necrosis of muscle fibers did not occur. Histochemical stains showed persistence of the normal pattern after denervation. The small fibers continued to have a high concentration of both oxidative and glycolytic enzyme activity (NADH‐TR, SDH, phosphorylase), and the large fibers continued to have a low concentration of these enzymes. Depletion of glycogen stores was seen with PAS. Hypertrophic muscle fibers had mostly subsarcolemmal nuclei and few internal nuclei, suggesting that they may be physiologically tonic rather than twitch fibers. Achilles tenotomy at the time of denervation prevented the hypertrophy of large fibers. Abnormal inclusions have been demonstrated in mammalian muscle following tenotomy alone, but were not seen in the fro

ISSN:0003-276X    

DOI:10.1002/ar.1091870306

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

年代:1977

数据来源: WILEY

摘要:

AbstractIn normal adult rats some germ cells degenerate at several vulnerable steps of spermatogenesis. These are the type A spermatogonia, midpachytene spermatocytes, primary and secondary spermatocytes which degenerate during their respective maturation divisions and step 7 and 19 spermatids. In the present study, these degenerating cells were examined under the electron microscope, and their frequency was determined in toluidine blue stained semithin sections of testes from normal, hypophysectomized (at 5.5 days after operation) and hypophysectomized rats injected with FSH and LH separately or in combination. With the exception of the step 19 spermatids, the degenerating germ cells underwent necrosis in vacuolated spaces delimited by Sertoli cells. In the case of the affected step 19 spermatids, an apical cytoplasmic process of the Sertoli cell initially ensheathed a long segment of their flagellum, and then each degenerating cell was drawn deep in the seminiferous epithelium where it was phagocytozed by the Sertoli cell. Soon after hypophysectomy the incidence of degenerating mid‐pachytene spermatocytes, step 7 and 19 spermatids which are present in stages VII or VIII of the cycle of the seminiferous epithelium, increased significantly. In contrast the number of degenerating primary or secondary spermatocytes during the meiotic divisions seen in stage XIV of the cycle or of any other germinal cell was not significantly modified. While the injection of FSH alone had no influence on the number of degenerating cells in hypophysectomized rats, injections of LH at the two doses administered (0.7 μg or 20 μg) reduced significantly the number of degenerating cells seen in stages VII‐VIII of the cycle; combined injections of FSH and LH (20 μg) reduced the number of these degenerating cells to the normal low values. Thus it appeared that the mid‐pachytene spermatocytes and the step 7 and 19 spermatids, all present in the adluminal compartment of the seminiferous epithelium in stages VII or VIII of the cycle, were more sensitive to the presence of absence of gonadotropic hormones than the other germ cells present in the seminiferous ep

ISSN:0003-276X    

DOI:10.1002/ar.1091870307

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

年代:1977

数据来源: WILEY

摘要:

AbstractUptake of H3‐leucine into secretory product and its subsequent intracellular transport was analyzed by electron microscopic autoradiographic techniques in the rat submandibular gland acinar cells in vitro. The route and kinetic timetable of intracellular transport was established for the acinar cell secretory product by calculating the percent of silver grains and relative grain density associated with the various organelles on a time sequence basis. Radioactivity was first associated with the rough endoplasmic reticulum; then the convex surface of the Golgi apparatus; the concave surface of the Golgi apparatus; and finally with the secretory granules. Comparison of the kinetics of intracellular transport in the rat submandibular gland acinar cell with other established systems revealed only a difference in the exit of radioactivity from the concave surface of the Golgi apparatu

ISSN:0003-276X    

DOI:10.1002/ar.1091870308

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

年代:1977

数据来源: WILEY

摘要:

AbstractMyotomes of the caudal one‐third of the body of 26‐day‐old larval lampreys,Lampetra japonica, were studied by electron microscopy. Each myotome consists of horizontally stacked muscle lamellae. The myotomes are covered laterally by a single layer of flattened cells called here “lateral cells,” and the other aspect is covered by an external lamina. The myotomes are mid‐segmentally innervated.Each muscle lamella usually contains two single cortical layers of myofibrils along the dorsal and ventral sarcolemma with a nucleus and mitochondria interposed between two layers. Numerous peripheral couplings are observed with relatively less developed triads. There are no membrane specializations to connect adjacent muscle lamellae within a myotome. Intermyotomal junctions are, however, noted between tips of cytoplasmic processes of muscle lamellae of adjoining myotomes. They resemble tight or gap junctions. No myofibrils are present in these cytoplasmic processes. Myotendinous junctions, with “terminal couplings” (Nakao, 1975), are seen under development at the myoseptal ends of muscle lamellae.Lateral cells contain only ordinary organelles and no special structures such as myofibrils are found in the cytoplasm. They are connected to each other and to muscle lamellae by primitive desmosomes. They generally have no external la

ISSN:0003-276X    

DOI:10.1002/ar.1091870309

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

年代:1977

数据来源: WILEY

ISSN:0003-276X    

DOI:10.1002/ar.1091870301

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

年代:1977

数据来源: WILEY