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21.
R. G. Northcutt H. Bleckmann 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1993,172(4):439-446
The lateral line system of axolotls (Ambystoma mexicanum) consists of mechanoreceptive neuromasts and electroreceptive ampullary organs. All neuromasts in salamanders are located superficially and are organized into lines that are homologous to canal neuromasts in fishes. Ampullary organs are confined to the head and generally are located adjacent to the lines of superficial neuromasts. Axolotls, however, also possess a third class of receptors; these form restricted patches on the head and are possibly homologous to the superficial pit organs in fishes. In order to test this hypothesis the morphology of the suspected pit organs was examined with scanning electron microscopy, and a number of their physiological properties were determined. Pit organs are approximately half the size of neuromasts and have fewer hair cells, although these hair cells do possess kinocilia and stereocilia like those of neuromasts. Pit organs also possess cupulae and exhibit a pattern of innervation identical to that of neuromasts. Pit organs and neuromasts also exhibit similar rates of spontaneous activity, are excited by weak water currents but not weak electric stimuli, and are not inhibited by magnesium ions. Pit organs appear to have slightly lower rates of spontaneous discharge than neuromasts, however, and have slightly lower displacement thresholds to low frequency wave stimuli. These data support the contention that the pit organs of axolotls constitute a second class of neuromasts homologous to the pit organs of fishes. 相似文献
22.
23.
Shigeko Ishimatsu Toshihiro Kawamoto Koji Matsuno Yasushi Kodama 《Biological trace element research》1995,49(1):43-52
In this study, eight kinds of nickel (Ni) compounds were orally administered to Wistar male rats and the distribution of each
compound was investigated 24 h after the administration. The Ni compounds used in this experiment were nickel metal [Ni−M],
nickel oxide (green) [NiO(G)], nickel oxide (black) [NiO(B)], nickel subsulfide [Ni3S2], nickel sulfide [NiS], nickel sulfate [NiSO4], nickel chloride [NiCl2], and nickel nitrate [Ni(NO3)2]. The solubilities of the nickel compounds in saline solution were in the following order; [Ni(NO3)2>NiCl2>NiSO4]≫[NiS>Ni3S2]>[NiO(B)>Ni−M>NiO(G)]. The Ni level in the visceral organs was higher in the rats given soluble Ni compounds; Ni(NO3)2, NiCl2, NiSO4, than that in the rats receiving other compounds. In the rats to which soluble Ni compounds were administered, 80–90% of
the recovered Ni amounts in the examined organs was detected in the kidneys. On the other hand, the Ni concentration in organs
administered scarcely soluble Ni compounds; NiO(B), NiO(G), and Ni−M were very low. The estimated absorbed fraction of each
Ni compounds was increased with the increase of the solubility. These results suggest that the kinetic behavior of Ni compounds
administered orally is closely related with the solubility of Ni compounds, and that the solubility of Ni compounds is one
of the important factors for determining the health effect of Ni compounds. 相似文献
24.
The short term effect of NO3 − (12 mM) on nitrate reductase (NR. EC 1.6.6.1) activity has been studied in the roots, nodules and leaves of different genotypes of Vicia faba L. at the end of vegetative growth. Root and leaf NR activity responded positively to NO3 − while nodule activity, where detected, proved to he strongly inhibited. The withdraw of this NO3 − from the solution consistently reduced activity in the roots and leaves but surprising, promoted a significant increase in nodule activity, which matched or surpassed that of control plants On the other hand, nodules developed in the presence of 8 mM NO3 − expressed an on average 141% higher level of NR activity than did controls. This effect was observed even in nodules with negligible control activity. In any case, a naturally occurring mutant (VF17) lacking root and nodule NR activity is described. The results indicate that in V. faba. the effects of NO3 − and plant genotype on NR activity depended on plant organ and time of NO3 − application, hut the distribution of NO3 − reduction through the plain was mainly dependent on plant genotype, and to a lesser extent on NO: supply and plant age. 相似文献
25.
An unusual testicular structure in the white grunt, Haemulon plumieri , and the French grunt, H. flavolineatum , and a urinary exocrine gland in H. flavolineatum are described. The testes of both species are comprised predominantly of efferent ducts, with spermatogenetic tissue restricted to the gonadal periphery. The epithelial cells of the efferent ducts produce glycogen which may serve a role in the storage and nutrition of sperm. The urinary gland is a male accessory gland thought to be associated with reproduction. The gland is mesonephric in origin and the epithelial cells of the gland produce mucins which may be involved in intraspecific chemical communication. 相似文献
26.
B. Le Rü Sophie Renard Marie-Rose Allo J. Le Lannic J. P. Rolland 《Entomologia Experimentalis et Applicata》1995,77(1):31-36
The ultrastructure of the sensory receptors located on the labium of the cassava mealybugPhenacoccus manihoti Matile-Ferrero (Homoptera, Pseudococcidae) was studied with scanning and transmission electron microscopes. Trichoid hairs
of probable mechanoreceptive function are distributed over the labium. Uniporous chemosensilla which possess a mechanoreceptive
dendrite, multiporous chemosensilla and mechanoreceptive pegs are present on the tip of the labium. The presence of contact
and olfactory chemoreceptors on the labial tip ofP. manihoti suggests that tapping it on the cassava leaf provides the pest with information about the chemical nature of the leaf surface.
ORSTOM 相似文献
27.
R D Farley 《Tissue & cell》1984,16(4):577-588
The light and electron microscopes were used to examine possible hemocytopoietic tissue in the desert scorpion, Paruroctonus mesaensis. Results agree with earlier light microscopic studies that cells are released into the blood from the two lateral lymphoid organs and the supraneural gland. The former are sacciform structures attached by their anterior ends to the diaphragm. The supraneural gland forms the thickened wall of the supraneural artery in the mesosoma from the first to the third abdominal ganglia. The lateral lymphoid glands have an acellular stroma in which are embedded granular and agranular cells. The stroma is apparently formed by specialized cells which release membranous cell fragments that become the matrix of the gland. Cells are released into the body cavity from the periphery of the two organs. The supraneural gland has a fibrous stroma in which are embedded a variety of cell types. The cells appear to be released in greatest abundance into the blood in the lumen of the gland. The gland has cells with opaque granules (0.9-1.4 micron diameter) and agranular cells of variable shape. The most abundant cell, possibly the stem-cell for the others, is about 10 micron diameter and often has processes of variable length. In addition, muscle cells at various stages of differentiation are found at the inner margin of the gland. These cells have thick and thin myofilaments (24-32 and 5-8 nm diameter) and dense bodies which sometimes become organized into sarcomeres with Z-bands before the cells are released into the gland lumen. The function of these muscle cells is unknown, but possibly they contribute to the maintenance of blood pressure and the release of cells into the blood from the inner margin of the gland. 相似文献
28.
E. Gelinek 《Cell and tissue research》1978,190(2):357-369
Summary Ampullary organs were found in the epidermis of the paddle-fish Sorubim lima; they are distributed all over the skin surface of the fish but are particularly densely grouped in the head region and on the dorsal surface of the paddle. Histological and electron microscopical observations show that their structure is similar to the type of cutaneous ampullary organs characteristic of other Siluroidea. Composed of a relatively large mucus-filled ampulla, the organ possesses a short and narrow canal which leads to the outer epidermal surface. The wall of the ampulla is formed of several layers of flat epidermal cells. In general four sensory cells, each one surrounded by supporting cells, compose the sensory epithelium at the bottom of the ampulla. The inner surface of the sensory cells in contact with the ampullary mucus bears only microvilli. The contact between the nerve endings and the sensory cells show the characteristic structure of an afferent neuro-sensory junction. Two ampullae are innervated in some cases by the same afferent nerve fibre.The author expresses her gratitude to Dr. Szabo for his scientific advice during her stay in Gif sur Yvette 相似文献
29.
Prof. H. -D. Dellmann 《Cell and tissue research》1978,186(2):361-374
Summary The ventricular surface of the subfornical organ of the frog is made up of ependymal cells with numerous apical microvilli, occasional cytoplasmic protrusions and many vacuoles projecting into the lumen of the third ventricle. Between these cells dendrites of cerebrospinal fluid-contacting neurons reach the ventricle to terminate in bulbous enlargements. In addition, flask-shaped encephalo-chromaffin cells, containing granulated vesicles and aggregates of filaments in their cytoplasm, project into the cerebrospinal fluid. Surrounding the centrally located capillaries are enlarged dendrites and axons of heterogeneous morphology, some of which appear to originate within the subfornical organ, intermingled with dendrites and axons of normal structure. The glial cells in this region, especially the microglial cells, often contain large lipofuscin inclusions, suggestive of degeneration and subsequent phagocytosis of some of the enlarged dendrites and axons. The normally scarce neurosecretory peptidergic axons become more evident and form typical Herring bodies in stalk-transected animals. Neuronal perikarya of varying morphology are predominantly located peripheral to the region of enlarged dendrites and axons. Supraependymal macrophages are particularly numerous on the subfornical organ.Abbreviations used
CSF
cerebrospinal fluid
-
SEM
scanning electron microscope, scanning electron microscopy
-
SFO
subfornical organ
-
TEM
transmission electron microscope, transmission electron microscopy
Supported, in part, by NIH grant NB 07492The skillful technical assistance of J.G. Linner and the secretarial assistance of Ann Gerdom are gratefully acknowledged. The SEM studies were made possible through a grant from the Graduate College of Iowa State University and the use of the SEM facility in the Department of Botany 相似文献
30.
Summary The rhombencephalic recess, an ependymal organ, has been studied for the first time by light- and electron microscopy. It is situated mediosagittally on the floor of the rhomboid fossa at the level of the colliculus facialis. The recess and the superimposed tissue are built up by tanycytes, their apices being connected by tight junctions. HRP, injected into the c.s.f., does not penetrate into the intercellular clefts of the recess area. The recess area reveals a certain autonomy regarding its supply with arteries and capillaries. A bloodbrain barrier exists, but shows slight leakage in circumscribed areas as a result of intense transendothelial vesicular transport. The organization of the recess area is compared with that of other ependymal organs, especially circumventricular organs.The skilful technical assistance of Miss K. Bielenberg, Mrs. H. Prien, Mrs. E. Schöngarth and Mrs. H. Schöning is thankfully acknowledgedSupported by the Deutsche Forschungsgemeinschaft (Kr 569/1 and SFB 34/D4) and Stiftung Volkswagenwerk
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