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Query: UNIPROT:P50583 (asymmetrical)
 12,197 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The otic, the lens and the nasal placodes have been examined in chick embryos between stages 10 and 18 of Hamburger and Hamilton. At the stage when each placode first becomes visible conspicuous differences have been seen in the surface morphology between those cells which will invaginate and form the placode and those which will remain on the surface of the head, forming the epidermis. The differences become more pronounced with increasing development. The placode cells possess many surface projections whilst the epidermal cells do not. These differences in surface morphology are related to other differences which are visible in TEM sections, the placode cells being highly columnar and extending the full depth of the placode, whilst the epidermal cells are cuboidal or even squamous. This modification in cell shape of the placode cells is correlated with the presence of longitudinally orientated microtubules. The mechanism of invagination is discussed and evidence is presented which supports the idea that there is a migration of cells into the placode from one side. Such a phenomenon would help to explain the asymmetrical structure of the placode, including the presence of the overhanging lip.
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PMID:Placodes of the chick embryo studied by SEM. 90 1

The fine structure of hibernating bat spermatozoa (Vesperugo savi and Rinolophus f.e.) has been studied by SEM and TEM, during their prolonged storage in female reproductive tract. The main morphological aspects of sperm portions: head, neck, middle piece, principal piece and terminal piece have been described. The Author besides comparisons with other mammalian species and Chiroptera, suggests some typical ultrastructural features of these Chiroptera, as the complete absence of vacuoles in the nuclear chromatin and corrugated structures in the post-acrosomal zone. Moreover electron-dense material in the subacrosomal space and three mitochondria in the neck were observed. Two areas of fusion between outer dense fibers 3 and 8 and the inner ends of the respective longitudinal columns of the fibrous sheath and asymmetrical arrangement of the outer dense fibers of the principal piece were found.
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PMID:[The fine structure of spermatozoa from Chiroptera]. 624 6

The response of ependyma to injury was investigated in rats following placement of bilateral lesions in the floor of the fourth ventricle. Animals were sacrificed from 2-60 days post-operatively and the brains were prepared in the conventional manner for comparative LM, SEM and TEM examination. For LM radioautography, randomly selected lesioned rats received either a single i.p. injection (5 muCi/g BW) or multiple injections (2 muCi/g) of 3H-thymidine prior to sacrifice. Focal disruption of the lining resulted in significant qualitative and quantitative changes in the ependyma at the wound margins. Labelling of normally quiescent ependymal cells occurred from day 2-6 post-operatively, however, the level of turnover was relatively low. Labelling was maximum on day 2 and was greater at the medial than lateral margin of the wound. During the first postoperative week, a gradual increase was observed in the number of ependymal cells per unit length at the margins of the wound concomitant with an abrupt reduction in wound diameter. This was consistent with the assumption that newly formed cells were added to the ependymal sheet at the leading edges of the wound. From 14-60 days after injury, further repair resulted from asymmetrical spreading and thinning of the ependymal sheet in the absence of mitotic activity. Quantitatively, this was reflected in a reduction in cell number at the leading edges of the wound that was most pronounced at the lateral margin. At day 60 neither epithelialization nor wound closure was complete and the normal architecture of the lining had not been fully restored. These results suggest that ependyma in the fourth ventricle of the postnatal rat undergoes a process of only limited repair following injury.
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PMID:Ependymal cells of the rat fourth ventricle: response to injury. 663 67

It is well known that arginine vasopressin (AVP) produces up to a 40-fold increase (0.1 to 4.0 microL/min.cm2) in net water flux across the amphibian urinary bladder under an osmotic gradient (mucosal side 10% hypotonic). No AVP effect is observed when the gradient is in the opposite direction (serosal hypotonic). Similar asymmetrical behavior to osmotic gradients occurs in the frog corneal epithelium. This rectification phenomenon has not been satisfactorily explained. We measured net water fluxes in bladder sacs and confirmed that AVP has no effect when the serosal bath is hypotonic. We reasoned that the 'abnormal' serosal osmolarity was inducing changes in membrane water permeability, the very parameter being measured. Thus, we studied the effect of solution osmolarity on diffusional water flow (Jdw) across the frog bladder using 3H2O. As expected, AVP doubled Jdw (in either direction from 12 to 21 microL/min.cm2) when the serosal solution was iso-osmolar regardless of mucosal osmolarity. However, in the AVP-stimulated bladders, hypo-osmolarity of the serosal solution reduced Jdw by 42%, an effect that was reversible when normal osmolarity was re-established. Amphotericin B (instead of AVP) was used to irreversibly increase the permeability to water of the apical membrane. Under these conditions, basolateral hypotonicity also reversibly decreased Jdw by 32%, suggesting the basolateral membrane as the site where permeability is reduced. SEM and TEM of the tissue shows extreme swelling when it was exposed to serosal hypotonicity with or without AVP and typical surface morphology changes following hormone stimulation. We conclude that this swelling may initiate a signaling mechanism that reduces basolateral water permeability. These findings constitute evidence of basolateral water channel permeability regulation, which can also contribute to cell volume regulation.
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PMID:Evidence of basolateral water permeability regulation in amphibian urinary bladder. 946 4

The aim of the study was to analyse in TEM the evolution of changes in structural elements of synaptic junctions of the cerebellar cortex in rats in valproate encephalopathy induced by chronic 12-month administration of sodium valproate - VPA (once daily intragastrically, in a dose of 200 mg/kg b.w.) and after withdrawal of this antiepileptic for 1 and 3 months. After 9 and 12 months of the experiment, synaptic endings of both the symmetrical and asymmetrical synapses in the neuropil of the cerebellar cortex, especially in the molecular layer, showed signs of severe damage (mainly swelling) and even disintegration. They were mostly observed in axodendritic endings and axospinal endings on the dendritic spines of Purkinje cells, being manifested in the presence of large vacuolar structures, electron lucent areas and swollen mitochondria within the cytoplasm. A reduced number of axonal synaptic vesicles (with more type F vesicles preserved) could be seen. One and 3 months after the end of chronic application of VPA, the synaptic junctions did not show morphological exponents of the repair processes. The alterations observed in the synapticjunctions of the cerebellar cortex may suggest disorders in neurotransmission processes, such as exhaustion and damage caused by ischaemia due to damage to the blood-brain barrier induced by VPA and/or its toxic metabolites.
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PMID:Ultrastructure of synaptic junctions in the cerebellar cortex in experimental valproate encephalopathy and after terminating chronic application of the antiepileptic. 1223 Feb 60

Hyperactivated motility, a swimming pattern of mammalian sperm in the oviduct, is essential for fertilization in vivo. It is characterized by high-amplitude flagellar waves and, usually, highly asymmetrical flagellar beating. It had been suggested, but not tested, that Ca2+ and cAMP switch on hyperactivation by directly affecting the flagellar axoneme. In this study, the direct affects of these agents on the axoneme were tested by using detergent-demembranated bull sperm. As confirmed by TEM, treatment of sperm with 0.2% Triton X-100 disrupted the plasma, acrosomal, and inner mitochondrial membranes, leaving axonemes intact. In the presence of 2 mM ATP, the percentage of reactivated sperm that were hyperactivated increased to 80% when free Ca2+ was increased from 50 to 400 nM. The effect of the Ca2+ in this range was to increase beat asymmetry by increasing the curvature of the principal bend. No additional increases were observed above 400 nM free Ca2+, but motility was suppressed at 1 mM. The ability of Ca2+ to produce hyperactivation depended on ATP availability, such that more ATP was required to produce the high amplitude flagellar bends characteristic of hyperactivated motility than to produce activated motility. Cyclic AMP was not required for reactivation, nor for hyperactivation. Production of hyperactivated motility also required an alkaline environment (pH 7.9-8.5). These results suggest that, provided sufficient ATP is present and pH is sufficiently alkaline, Ca2+ switches on hyperactivation by enabling curvature of the principal bends to increase.
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PMID:Hyperactivated motility of bull sperm is triggered at the axoneme by Ca2+ and not cAMP. 1229 7

The quiescent Artemia cysts of seven geographical origins in China were examined with scanning and transmission electron microscopes. SEM observations on cysts of these Artemia strains showed that the surface topography of cyst shells could be categorized into 6 types: complete smooth surface; smooth surface with sparsely distributed glabrate humps; surface with densely arranged wart-like humps that are composed of packed minute tubercles; rugged surface, with densely arranged tubercles not piling up to form larger humps; shallow-pocked surface; and surface with numerous and densely spaced pore-like fossulae. Some of the patterns were strain specific [e.g., cysts from Ga Hai (GH) are characterized by having a surface with wart-like ornaments that are composed of packed minute tubercles, rugged surface is only found in Chengkou (CK) cysts], and apparent intrastrain variation of cyst surface topography was found in Xizang (XZ), Jingyu Hu, and Xie Chi (SIN) strains. TEM studies on the ultrastructure of cyst shells revealed an apparent divergence in the structure of outer cuticular membrane (OCM) among Artemia strains. In CK, Aqqikkol Hu (AQK), SIN, and GH strains, it is a normal, asymmetrical, and multi-layered structure similar to those described in previous works. In XZ, JYH, and Lagkor Co (LGC) strains, however, the OCM is not obviously multi-layered and the borderlines between OCM and adjacent layers seem indistinct. The present results suggest that the diversity of the surface topography of Artemia cysts may be an available tool for identifying certain Artemia strains as well as for tracking the origins of some Artemia cysts, and the hypoplastic OCM may be a characteristic of the species A. tibetiana.
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PMID:Comparative observations on the cyst shells of seven Artemia strains from China. 1739 78

The nanostructure of titanate nanotubes known as a one-dimensional catalytic/electric subject is combinatorially characterized using x-ray diffraction (XRD), micro-Raman, photoluminescence (PL) and advanced electron microscopy. The micro-Raman and PL spectra prove the successful synthesis of TiO6 octahedron units in macroscopic scale. Cryo-high-angle annular dark-field (HAADF)-STEM and aberration-corrected (AC) TEM visualize in real-space the TiO6 octahedron unit formed as a TiO2-based tubular structure prepared by the alkaline hydrothermal methods. The chirality and scrolling-up mechanism of the TiO6 octahedron nanosheets in relation to an asymmetrical chemical environment and mechanical tensions are discussed.
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PMID:Direct observation of TiO6 octahedron forming titanate nanotube by advanced transmission electron microscopy. 1975

There are several reports indicating a linkage between exposures to 50-60 Hz electromagnetic fields and abnormalities in the early stages of embryonic development of chicken embryos. The present study was designed to demonstrate whether electromagnetic fields could be an environmental factor invoking histopathological and ultra-structural changes in livers of preincubated chicken embryos exposed to EMFs. Following other researchers and our previous results from different groups of Developmental Biology at the Animal Sciences, Faculty of Biological Sciences, Shahid-Beheshti University, effects of most effective intensities (1.33, 2.66, 5.52, and 7.32 mT) of electromagnetic fields (EMFs, 50 Hz ) on livers of pre-incubated white leghorn chicken embryos were investigated . 150 healthy, fresh, and fertilized eggs (55-65 gr) were divided into 6 groups of experimental(1-4, n = 30), control (n = 60), and sham (n = 50). Experimental eggs (inside coil) were exposed to 4 different intensities (1.33, 2.66, 5.52, and 7.32 mT). Sham groups were located inside same coil, with no exposure, for 24 h before incubation. Control, sham, and experimental groups (1-4) were then incubated in an incubator (38 +/- 0.5 degrees C, 60% humidity) for 17 days. At the end of this period, livers of experimental, sham, and control groups were processed for light and transmission electrom microscopes (TEM and SEM) studies. So, livers of 17-day old chicken embryos were removed by C-sections, fixed in formalin 10%, stained with H&E and reticulin, and studied under light microscope. Others were prepared for electron microscopes (TEM and SEM) investigations. Morphological observations indicated exencephalic embryos, embryos with asymmetrical faces, crossed beak, shorter upper beak, deformed hind limbs, gastroschesis, anophthalmia, and microphthalmia. H&E and reticulin stainings, TEMS, and SEMs studies indicated EMFs would create hepato-cytes with fibrotic bands, severe steatohepatitis, vacuolizations, swollen and extremely electron-dense mitochondria, reduced invisible cristae, crystalized mitochondria with degenerated cristae, myelin-like figures, macrophages engulfing adjacent cells, dentated nuclei, nuclei with irregular envelopes, degenerated hepatocytes, abnormal lipid accumulations, lipid droplets pushing hepatocytes' nuclei to the corner of the cells, abundant cellular infiltrations cellular infiltrations inside sinusoid and around central veins, disrupted reticulin plexus, and release of chromatin into cytosol,, with partially regular water layers. An elevated oxyradical generation and, subsequently, cell membrane disruptions were the reasons for electromagnetic fields inducing cell damages.
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PMID:Histopathological and ultrastructural studies on the effects of electromagnetic fields on the liver of preincubated white Leghorn chicken embryo. 2001 30

Highly ordered mesoporous CdS nanowire arrays were synthesized by using mesoporous silica as hard template and cadmium xanthate (CdR(2)) as a single precursor. Upon etching silica, mesoporous CdS nanowire arrays were produced with a yield as high as 93 wt%. The nanowire arrays were characterized by XRD, N(2) adsorption, TEM, and SEM. The results show that the CdS products replicated from the mesoporous silica SBA-15 hard template possess highly ordered hexagonal mesostructure and fiber-like morphology, analogous to the mother template. The current-voltage characteristics of CdS nanoarrays are strongly nonlinear and asymmetrical, showing rectifying diode-like behavior.
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PMID:Ordered Mesostructured CdS Nanowire Arrays with Rectifying Properties. 2059 34


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