摘要:

AbstractThe effects of intranasal zinc sulfate (ZnSO4) irrigation on the morphology of the olfactory epithelium and olfactory bulb were studied in mice with short survival times (as early as 1 day) and with long survival times (up to 593 days) after the irrigation procedure. As in several previous studies, the olfactory epithelium was completely destroyed within a few days after the ZnSO4treatment. Within 2–4 days, the septum and turbinates were covered by a new, cuboidal epithelium, the cells of which differed significantly from any cells normally seen in the olfactory epithelium. Slowly, over several months, small areas of the olfactory epithelium regenerated in many of the animals.The ultrastructural changes occurring in the olfactory bulb from 1 to 25 days (the reactive stage) were characterized by degenerating olfactory axons and axon terminals, hypertrophy of astroglial cell processes, and proliferation of or extravasation by phagocytic cells. By 25 days after intranasal ZnSO4irrigation, the number of reactive glial processes and phagocytic cells returned to normal. In some mice with survival times of 150 days or longer, there was reinnervation of small areas of the olfactory bulb by regenerated olfactory axons. These new olfactory axons innervated only superficial glomeruli or the outer portions of deeper glomeruli, but they formed synaptic contacts with mitral/tufted cells and periglomerular cells that did not differ from control animals. These findings were supported by tract‐tracing experiments with3H‐amino acids and by behavioral analysis.In summary, the ultrastructural changes observed in the olfactory bulb in this study were not significantly different from those observed after surgical lesions of the olfactory epithelium or nerve. The olfactory bulb, however, never fully recovered; glomeruli remained shrunken (though with normal dendro‐dendritic synaptic connections), and there was minimal olfactory axon reinnervation. © 1993 Wiley

ISSN:1059-910X    

DOI:10.1002/jemt.1070240302

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe anatomical organization of the olfactory system of terrestrial snails and slugs is described in this paper, primarily on the basis of experiments using the African snailAchatina fulica. Behavioral studies demonstrate the functional competence of olfaction in mediating food finding, conspecific attraction, and homing. The neural substrate for olfaction is characterized by an extraordinarily large number of neurons relative to the rest of the nervous system, and by the fact that many of them are unusually small. There exist multiple serial and parallel pathways connecting the olfactory organ, located at the tip of the tentacle, with integrative centers in the central nervous system. Our methods of studying these pathways have relied on the selective neural labels horseradish peroxidase and hexamminecobaltous chloride. One afferent pathway contains synaptic glomeruli whose ultrastructure is similar to that of the glomeruli seen in the mammalian olfactory bulb and the insect olfactory lobe. All of the olfactory neuropils, but especially the tentacle ganglion, contain large numbers of morphologically symmetrical chemical synapses. The procerebrum is a unique region of the snail brain that possesses further features analogous with olfactory areas in other animal groups. Olfactory axons from the tentacle terminate in the procerebrum, but the intrinsic neurons do not project outside of it. An output pathway from the procerebrum to the pedal ganglion has been identified and found to consist of inter‐ganglionic dendrites. The major challenge for future studies is to elucidate the pattern of connectivity within, rather than between, the various olfactory neuropils. © 1993 Wiley‐Liss,

ISSN:1059-910X    

DOI:10.1002/jemt.1070240303

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

年代:1993

数据来源: WILEY

摘要:

AbstractLittle knowledge is available concerning the detailed anatomy of the crusctacean central olfactory pathway. We are using radiolabeling, Golgi and biocytin/neurobiotin tracer methodologies, at the correlated light and electron microscopical levels, to study the olfactory midbrain of the freshwater crayfish. We have found that primary afferent fibers from the antennular olfactory receptor cells branch extensively throughout the length of the glomerular columns within the olfactory lobes in the midbrain. Globuli cells of the lateral cell clusters ramify as dendritic arborizations within both the olfactory and accessory lobes; their axons project out the olfactory‐globular tracts to the lateral protocerebrum, often branching to both sides. Developmental plasticity involving the connections made by afferent fibers within the olfactory lobes may permit detailed examination of organizational changes within the midbrain as the animal grows and adds new afferent input from the periphery. © 1993 Wiley‐Liss,

ISSN:1059-910X    

DOI:10.1002/jemt.1070240304

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

年代:1993

数据来源: WILEY

摘要:

AbstractMany insects possess a highly developed sense of smell. This paper summarizes the cellular and synaptic organization of the antennal (olfactory) lobe of the insect brain and then reviews morphological and fine‐structural aspects of the development of the lobe. Visualization of synapses between classes of neurons identified by physiological, morphological, or transmitter‐cytochemical properties has provided insights into arrangements of contacts and their possible roles in information processing. Studies of development have revealed the requirement for afferent axons from the antenna for the formation of olfactory glomeruli, where virtually all of the synapses in the lobe occur, and have suggested the possibility that glial cells play a role in the instructive influence of the axons on their target neurons in the lobe. The findings reviewed in this paper are primarily from one representative hemimetabolous insect, the American cockroach, and one representative holometabolous insect, a hawkmoth, and comparisons are made with vertebrate systems when appropriate. © 1993 Wiley‐Lis

ISSN:1059-910X    

DOI:10.1002/jemt.1070240305

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe transverse (T) tubules and the sarcoplasmic reticulum (SR) at the myotendinous junction of stretched rat skeletal muscle were examined by conventional and intermediate voltage electron microscopy. Stretching induced a large cytoplasmic space devoid of myofibrils at the ends of lengthening fibers. In this space, irregularly running tubular elements were seen. They were connected both with subsarcolemmal caveolae and with T tubules traversing to the A‐I junctional level of the preexisting myofibrils. The SR was arranged at regular interverals which were narrower than those of the adult sarcomere. This orderly spacing of the SR seems to indicate that they may play some role(s) in myofibril assembly and/or T tubule arrangement. © 1993 Wiley‐Liss,

ISSN:1059-910X    

DOI:10.1002/jemt.1070240306

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

年代:1993

数据来源: WILEY

ISSN:1059-910X    

DOI:10.1002/jemt.1070240301

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

年代:1993

数据来源: WILEY