1,721,008 research outputs found
Effects of cytochalasin B on the morphology of secretory cells of rana esculenta fungiform papilla.
No full textThe effects of cytochalasin B on the three types of secreting cells (apical, paracoronal and parietal cells) present in the fungiform papilla of the frog's tongue were studied. Cytochalasin B induced morphological modifications only in the apical secreting cells, localized in the sensorial area, without affecting the paracoronal cells or the parietal cells. The morphological features of treated apical cells showed that the drug induces two different effects: a disappearance of microfilaments and an increase in the exocytotic process. The results are related to previous experimental findings which showed that cytochalasin B produces actin depolymerization and interferes with calcium transport
Natural and synthetic biodegradable polymers: different scaffolds for cell expansion and tissue formation
No full textThe formation of tissue produced by implanted cells is influenced greatly by the scaffold onto which
they are seeded. In the long term it is often preferable to use a biodegradable material scaffold so
that all the implanted materials will disappear, leaving behind only the generated tissue. Research in
this area has identified several natural biodegradable materials. Among them, hydrogels are receiv-ing increasing attention due to their ability to retain a great quantity of water, their good biocom-patibility, their low interfacial tension, and the minimal mechanical and frictional irritation that they
cause. Biocompatibility is not an intrinsic property of materials; rather it depends on the biological
environment and the tolerability that exists with respect to specific polymer-tissue interactions. The
most often utilized biodegradable synthetic polymers for 3D scaffolds in tissue engineering are satu-rated poly-a-hydroxy esters, including poly(lactic acid) (PLA) and poly(glycolic acid) (PGA), as well
as poly(lactic-co-lycolide) (PLGA) copolymers. Hard materials provide compressive and torsional
strength; hydrogels and other soft composites more effectively promote cell expansion and tissue
formation. This review focuses on the future potential for understanding the characteristics of the
biomaterials considered evaluated for clinical use in order to repair or to replace a sizable defect by
only harvesting a small tissue sample
Paracoronal cavity system and papillary water uptake
No full textIn the research it has been carried out a morphological investigation of the paracoronal area of the fungiform papillae. By means of scanning, transmission and light microscopy it has been observed in this area a series of superficial openings around and external to the ciliary crown; and in the epithelium corresponding cavitary system. Each cavity on the other hand appears surrounded by extremely narrow epithelial cells and thus appears able to facilitate the papillary exchange activity. This paracoronal cavitary system is proposed as morphological candidate for the conspicuous water entry in the papillae during osmotic phenomena
Morphology of epiphyseal apparatus of a ranid frog (Rana Esculenta)
No full textMorphological, histochemical and ultrastructural investigations on epiphyseal apparatus of Rana Esculenta were made. The most important findings were the following: 1) metaphyseal cartilage is localized inside proximal diaphyseal compact bone as a plug; 2) metaphyseal cartilage do not reduce in thickness during ageing; 3) metaphyseal cartilage do not show vascular invasion and do not mineralize in degenerative zone; 4) trabecular bone was not at all evident in this animal; 5) external periosteum is well vascularized and proliferates in correspondence to marginal epiphyseal end of the diaphyseal. From these results the hypothesis that the ranid frog bone growth is not due to metaphyseal metabolism (as in avian and mammals) but to bone periosteal marginal mineralization is reached
Can a Bacterial Endotoxin be a Key Factor in the Kinetics of Amyloid Fibril Formation?
No full textData found in literature have reported that bacterial endotoxins may be involved in the inflammatory and pathological processes associated with amyloidosis and Alzheimer's disease (AD). In fact, it has been observed that the chronic infusion of the bacterial lipopolysaccharide, the outer cell wall component of Gram negative bacteria, into the fourth ventricle of rats reproduces many of the inflammatory and pathological features seen in the brain of AD patients. In this context, a key player in the pathogenesis of AD is the amyloid-β peptide (Aβ) that is capable of aggregating in fibrils that represent the main component of amyloid plaques. These deposits that accumulate among brain cells are indeed one of the hallmarks of AD. This aggregation in fibrils seems to correlate with Aβ toxic effects. However, recent data have shown that amyloid fibril formation not only results in toxic aggregates but also provides biologically functional molecules; such amyloids have been identified on the surface of fungi and bacteria. The aim of this work was to gain insight into the influence of bacterial endotoxins on Aβ fibrillogenesis; factors that influence fibril formation may be important for Aβ toxic potential. Following three days of incubation at 37°C, Aβ was organized in compact fibrils and the in vitro Aβ fibrillogenesis was potentiated by the Escherichia coli endotoxin. This suggests the importance of infectious events in the pathogenesis of AD and proposes a new aspect related to the putative pathological factors that can be implicated in the mechanisms involved in Aβ25-35 fibrillogenesis
Expression of proteins involved in calcium homeostasis during crista ampullaris regeneration
No full textMost of the events related to the mechano-transduction process in hair cell are regulated by cytoplasmic Ca++ concentrations. Ca++ influx trough the mechano-transduction channels regulates the adaptation process in the stereocilia, while Ca++ entering into the cell through the voltage gated channels regulates the neurotransmitter release. Moreover Ca++ activates the K+ channels that dominate the inhibitory postsynaptic potential at efferent synapses.
Cytoplasmic Ca++ concentration is regulated by a complex system of proteins, including the Na+/Ca++ exchanger, Ca++ pumps (PMCAs, SERCAs) and a copious supply of diffusible proteins that buffers free Ca++ in specific cell compartments. These proteins intercept Ca++ near its sites of entry and restrict the spread of the free ion. Moreover this buffering limits the period during which Ca++ local concentration are high enough to trigger its physiological effects.
In frog crista ampullaris PMCAs seems to be the most relevant mechanism of Ca++ extrusion since the lack of a functional Na+/Ca++ exchanger. We investigated the distribution of different subtypes of PMCAs finding that each isoform has its specific expression domain along the crista. We also demonstrate a similar compartmentalization for the IP3R, which is involved in Ca++ release from the IP3-sensitive intracellular stores, and for some buffering proteins.
These data and the morphological identification of diverse hair cell types differentially distributed along the crista ampullaris, suggest the presence in the sensory epithelium of distinct functional domains where the mechanisms of Ca++ homeostasis regulation are not completely overlapping.
This hypothesis is confirmed by the observation that the different regions of the crista ampullaris show a different sensibility to the ototoxic damage induced by gentamicin treatment: although the mechanism of actions of this drug has not jet completely understood, aminoglycosides are known to interfere with Ca++ homeostasis.
Our studies on frog crista ampullaris regeneration showed that the complete crista functional activity is restored well afterwards its morphological recovery. Indeed, while the appearance of a stereociliary apparatus expressing a correct pattern of Ca++ pumps seems to be sufficient to restore hair cell basal activity, the recovery of the evoked sensory discharge seems to need also the expression of Ca++ buffering proteins. This study try to correlate the appearance of the different proteins involved in Ca++ homeostasis with the complete functional recovery of the sensory epithelium
Exposure to reduced gravity impairs junctional transmission at the semicircular canal in the frog labyrinth.
No full textThe effects of microgravity on frog semicircular canals have been studied by electrophysiological and morphological approaches. Reduced gravity (microG) was simulated by a random positioning machine (RPM), which continually and randomly modified the orientation in space of the anesthetized animal. As this procedure stimulates the semicircular canals, the effect of altered gravity was isolated by comparing microG-treatment with an identical rotary stimulation in the presence of normal gravity (normoG). Electrophysiological experiments were performed in the isolated labyrinth, extracted from the animals after the treatment, and mounted on a turntable. Junctional activity was measured by recording quantal events (mEPSPs) and spikes from the afferent fibers close to the junction, at rest and during rotational stimulation. MicroG-treated animals displayed a marked decrease in the frequency of resting and evoked mEPSP discharge, vs. both control and normoG (mean decrease approximately 50%). Spike discharge was also depressed: 57% of microG-treated frogs displayed no spikes at rest and during rotation at 0.1 Hz, vs. 23-31% of control or normoG frogs. Among the firing units, during one cycle of sinusoidal rotation at 0.1 Hz microG-treated units emitted an average of 41.8 +/- 8.06 spikes, vs. 77.2 +/- 8.19 in controls. Patch-clamp analysis on dissociated hair cells revealed altered Ca(2+) handling, after microG, consistent with and supportive of the specificity of microG effects. Marked morphological signs of cellular suffering were observed after microG, mainly in the central part of the sensory epithelium. Functional changes due to microgravity were reversible within a few days
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