1,721,039 research outputs found
Fine structure of the afferent synapses in the paratympanic organ of the chicken, with special reference to the synaptic bodies.
No full textThe afferent synapses of the paratympanic organ in the chicken were studied by TEM. These synapses were formed by non-myelinated fibres which reached the basal part of the hair cells. The fibres contained a number of irregular mitochondria and a few pale vesicles. In the hair cells, near the presynaptic membrane, typical synaptic bodies formed by an electron-dense core surrounded by several small pale vesicles were present. The core was connected with the vesicles by numerous thin filaments, and at same time with the presynaptic membrane by some dense projections. Moreover, we have observed that the connections between the core and the adjacent vesicles also consisted of similar structures to the dense projections. We suggest that this device is involved in the movement of the vesicles towards the presynaptic membrane. Our hypothesis is in agreement with that formulated by some authors who believe that the electron-dense core of the synaptic bodies is able to channel the vesicles to the presynaptic membrane (conveyor-belt hypothesis). Moreover, our work showed that the synaptic bodies of the paratympanic organ in the chicken are variable in density and in shape. These morphological aspects might be linked to regression-reconstitution cycles of the SBs and to the functional level of the afferent synapses
Fine structure of the middle ear epithelium in the chicken (Gallus gallus).
No full textThe epithelium lining the tympanic cavity of the chicken possesses distinct morphological characteristics. Its ultrastructure was studied using 2 preparative techniques. (1) After fixation in Karnovsky's solution, postfixation in osmium tetroxide and embedding in Epon, the epithelium was observed to contain 2 kinds of cell: secretory and basal. The secretory cells (which we refer to as mixed granulated cells) showed numerous secretory vesicles that varied in appearance, some containing paracrystalline formations. The basal cells, located close to the basement membrane, showed no evidence of secretory activity. (2) Other specimens were immersed in Karnovsky fixative and subsequently in a mixture of glutaraldehyde and tannic acid. They were then osmicated and embedded in polar Epon mix. With this method, the epithelium was seen to be covered by electron-dense material made up of thin intertwined tubules. In addition, the secretory cells contained vesicles with concentrically arranged lamellae; such vesicles resembled the multilamellar bodies of mammalian type II pneumocytes. The hypothesis is advanced that tubules and lamellar vesicles are related to the presence of surfactant substances
Tubular structures revealed using tannic acid on the surface of the epithelium of the tympanic cavity of the chicken
No full textWe have studied the ultrastructure of the epithelium lining the tympanic cavity of chicken, using two embedding techniques. In certain cases, the epithelium was minced in Karnovsky fixative, post-fixed in osmium, dehydrated and embedded in Epon, following the usual methods. No morphologically detectable structures were seen at the level of the epithelium surface. In other cases, the epithelium was immersed in Karnovsky fixative and subsequently in glutaraldehyde (1%) to which, however, tannic acid (1%) was added; the specimens were then osmicated, dehydrated with Epon and embedded in polar Epon mix. This method was sometimes used to study the alveolar surfactant, since this makes it possible to preserve its phospholipid fraction. The epithelium, in this way, is seen to be covered by an electron-dense material made up of thin, intertwined tubules. The hypothesis formulated is that the tubules are related to the presence of surfactant substances
The ultrastructure of the sensory hairs of the paratympanic organ receptor cells in chicken.
No full textThe hair bundle of the receptor cells in the paratympanic organ of the chicken was studied by TEM, after fixation in aldehydes/osmium tetroxide or in aldehydes/osmium tetroxide/tannic acid. The bundles are formed by a kinocilium and by 40-70 stereocilia. The stereocilia are linked to each other by an extensive network of filaments. Three types of these connectors are present: basal, shaft and apical; the latter consist of side-to-side and tip-to-side connectors. We observed that the shaft connectors are well-highlighted only when tannic acid was used, while the other connectors are to be found in the conventionally fixed specimens also. The tip-to-side connector consists of a filament which joins the tip of a stereocilium with the side of an adjacent taller stereocilium; we suggest that the distortion of this filament would give rise to the mechanosensory transduction. The other connectors probably serve to maintain the regular spatial arrangement of the hair bundle and the mechanical coupling of the stereocilia. Our study shows that the general conformation of the hair bundle and the stereociliary links of the hair cells in the paratympanic organ of chicken are similar to those previously described in the hair cells of the acoustico lateralis system
Effects of chronic ethanol administration on the NOS-related NADPH-diaphorase activity in the mouse Leydig cells
No full textINTRODUCTION - Nitric oxide (NO) is a free radical involved in several physiological and pathological processes (1). NO appears to be involved in crucial aspects of male genital physiology, including relaxation of corpora cavernosa and inhibition of sperm mobility and testosterone secretion (2). The gonadotoxic effects of the alcohol were well documented in humans and in animal models (2, 3). In-deed, ethanol administration has been shown to cause morphological alterations on seminiferous tubules (2) and Leydig cells (3) and to decrease testosterone and LH plasmatic levels (4). We examined by TEM the effects of chronic ethanol treatment on the NADPH-diaphorase (NADPH-d) activity in the mouse Leydig cells.
MATERIAL AND METHODS - Ten adult Wistar mice were treated with ethanol 0.5g/Kg/die intragastrically for two weeks. The animals were anaesthetised, perfused by aldehydes and treated for NADPH-d histochemistry (5). Specimens incubated with NADPH-free medium were utilised as controls. In order to test the specificity of NADPH-d staining for NOS activity, some specimens were immersed in the medium containing 0.3 mM iodonium diphenyl (6). The specimens were post-fixed in osmium tetroxide, and embedded in Epon 812.
RESULTS AND DISCUSSION - About 20% of Leydig cells of the ethanol-treated mice showed morphological alterations. The cells were characterised by irregular protrusions of the plasmatic membrane, rarefaction of the cytoplasmic matrix and increased number of lipid droplets. Irregular mitochondria were also observed. Some Leydig cells (about 10%) showed signs of degeneration. As regards the enzymatic study, the controls animals exhibited the NADPH-d activity in the nuclear cistern, mitochondria and SER. In the ethanol treated-mice the enzymatic reaction was strongly reduced both in apparently normal and injured Leydig cells. A moderate reactivity was detected only in the SER. These findings suggest that chronic ethanol treatment inhibits the NOS-related NADPH-d activity in the Leydig cells of mouse. This effect could be a consequence of the impaired synthesis of the testosterone, inducing an inhibition of NO production through a negative feedback mechanism. However it can not be excluded a direct action of the alcohol on the NOS/cGMP enzymatic pathway
THE ULTRASTRUCTURAL LOCALIZATION OF NADPH-DIAPHORASE ENZYMATIC ACTIVITY IN THE LEYDIG CELLS OF MOUSE. EFFECTS OF ETHANOL ADMINISTRATION
No full textAbstract
The effects of the chronic ethanol treatment on the NOS-related NADPH-diaphorase activity were described in the mouse Leydig cells by means of transmission electron microscope. The recovery of the Leydig cells was also examined during a period of four weeks. About 10% of the Leydig cells showed various degrees of morphological alterations, consisting in increased number of lipid droplets, rarefaction and vacuolization of the cytoplasmic matrix. Other groups of Leydig cells (about 10%) revealed evident signs of degeneration. The NADPH-d activity was reduced both in apparently normal and injured Leydig cells and a moderate enzymatic reaction was only detected in the smooth endoplasmic reticulum. A week after the treatment an increased number of the degenerating Leydig cells and a further reduction of the enzymatic reaction were observed. Then, the Leydig cells showed a progressive recovery and four weeks after the treatment they exhibited a normal morphology and NADPH-d enzymatic reaction. These results demonstrated for the first time the inhibition of NOS activity in the Leydig cells after chronic ethanol administration
Ultrastructure of the supporting cells in the paratympanic organ of chicken, Gallus gallus domesticus
No full text
- …
