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 28,634 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A time sequence study was performed on experimental animals to investigate long-term effects of intravenously administered glycerol on the epithelial cell activity in the endolymphatic sac (ES) and on the ES volume. Fifteen to 60 min after systemic glycerol administration, the ES volume decreased. During this time, the ES lumen was often obliterated. Subsequently, the lumen dilated. Meanwhile, many light epithelial cells showed granules with floccular and/or lamellar contents. Concomitant deposition of floccular material into the luminal space suggested secretion of macromolecular substances, presumably from these transformed light cells. The number of granule-containing cells was significantly increased 2 h (p < 0.01) and 4 h (p < 0.01) after glycerol administration. The ES was significantly dilated after 4 h (p < 0.01) and 6 h (p < 0.05). Thus systemic alterations in osmotic pressure led to a reversible change in ES volume, with initial collapse followed by dilation and normalization after 8 h. The secretory response of the ES preceded the volume increase. A great variability in ES volume indicated high compliance of this organ system. A secretion/degradation system or turnover of osmotically active macromolecular complexes in the epithelial lining and ES lumen seems to be linked to the ability of the ES to hold fluid volumes within a wide range. This may serve as a micromechanical pressure-volume-regulating device for monitoring endolymph fluid homeostasis.
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PMID:Effects of glycerol on the endolymphatic sac. A time sequence study. 148 3

A technique for real-time in vitro observation of cavitation on a prosthetic heart valve operating in a ventricular assist device under normal physiologic conditions has been developed. Considering the documented observation of cavitation erosion in heart valve components from human explants, and the potential risk of blood damage that cavitation presents, the technique developed in this study may prove useful in the design of prosthetic heart valves and ventricular assist devices. Cavitation of a glycerol blood analog fluid has been documented for a Medtronic/Hall prosthetic heart valve operating in a Penn State Electric Ventricular Assist Device. The ventricular assist device was operated in a mock circulatory system under normal physiologic conditions. The valve was located in the mitral position, with the cavitation occurring on the inlet side after valve closure. Bubble cavitation was seen on the valve occluder face, and vortex cavitation was observed at two locations in the vicinity of the valve occluder and housing. The cavity growth and collapse cycle for these forms of vaporous cavitation was less than 1 msec. Stroboscopic photography and stroboscopic videography with frame grabbing were used to document the cavity life cycle. With beat rate held constant, the cavity duration time was found to decrease with increasing mean venous return pressure.
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PMID:Real-time in vitro observation of cavitation in a prosthetic heart valve. 175 Nov 82

The fine structure of the plasma membrane in spores of the microsporidium Nosema algerae, a pathogen of mosquitoes, was examined in the resting condition and after the spores were stimulated to germinate in vitro. Slow penetration of resin caused collapse of the germinated spores. Thin sections of germinated spores showed peculiar membrane infoldings that were never found in ungerminated samples. Analogous germination-dependent configurations of the plasma membrane were observed in freeze-fractured preparations of spores either fixed and impregnated with glycerol prior to freezing, or rapidly frozen with liquid propane while in the process of germination. In every case, the replicas presented germinated spores with indentations in the protoplasmic face of the plasma membrane, and apparently complementary blunt spines on the external face, that were absent in ungerminated spores. It suggests that these alterations of the plasma membrane result from a structural adjustment to a spontaneous contraction of the spore case after germination. We discuss this interpretation with regard to conflicting views on the nature of such morphological features.
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PMID:Structural alteration of the plasma membrane in spores of the microsporidium Nosema algerae on germination. 192 Jan 52

A method for inducing a partial dysfunction of the endolymphatic sac and its effect was investigated. Acetazolamide as well as amiloride caused collapse of the lateral intercellular spaces in the endolymphatic sac epithelium and a subsequent mild endolymphatic hydrops. These changes indicate a decreased absorption rate of endolymph in the endolymphatic sac. Colchicine caused a disturbed secretory activity of the sac induced by glycerol. Animals treated with colchicine showed marked signs of inner ear malfunction after additional treatment with glycerol, which might indicate that the secretory activity in the sac is closely related to the regulation of inner ear fluid homeostasis and functional disturbance.
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PMID:Modulation of the endolymphatic sac function. 192 64

The penetration rate of glycerol across lipid bilayers can be assayed dispersing liposomes filled with a 0.1 M glucose solution in an isotonic or a hypertonic solution of glycerol. The kinetic of glycerol permeation is found to be different in each of those cases. Liposomes dispersed above the phase transition temperature in hypertonic solutions show an increase in the surface polarization as measured by means of merocyanine 540. Under this condition, the permeation of glycerol shows a two-step kinetic which is indicative of a non-fickean diffusion process. In contrast, liposomes dispersed in isotonic solutions of the permeant show a fickean behavior. The changes in polarization of the membrane interface are ascribed to variations in the surface potential due to the osmotic collapse and the glycerol concentration in contact with the outer surface. The permeability of polar molecules can, in consequence, be considered as a function of the surface potential of the liposome which is congruent with previous data in literature reporting that water permeability increases as a function of the zeta potential of liposomes shrunken in hypertonic solutions.
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PMID:Surface changes induced by osmotic stress and its influence on the glycerol permeability in lipid bilayers. 193 49

Recombinant mouse thymidylate synthase (TS) expressed at high levels in Escherichia coli was purified to homogeneity in greater than 70% yield by a rapid three-step procedure. Both 0.1% Triton X-100 and 10% glycerol were required to stabilize the enzyme whose activity remained unchanged after 1 month when stored at -20 degrees C. Thermal inactivation of the enzyme was a first-order process at 37 degrees C, with t1/2 values of 6.9, 15.6 and 3.0 min at pH 5.5, 7.0 and 8.5, respectively. The presence of saturating levels of dUMP at pH 8.5 increased the t1/2 of inactivation of 38 min. The pH profile for enzyme activity showed a narrow optimum region centered at pH 7.0, which was mirrored by the shape of the Km, dUMP/Vmax plot. The pH dependence of Kd for the covalent inhibitory ternary complex of enzyme, 5-fluoro-2'-deoxyuridylate and 5,10-methylenetetrahydrofolate exhibited a broad minimum between pH 5.5 and 8.5, and ranged between 3.1, 0.8 and 1.1 nM at pH 5.5, 7.0 and 8.5, respectively. The UV/VIS spectrum of the native enzyme exhibited a maximum at 280 nm (epsilon = 98,200 M-1 cm-1), while that of the inhibitory ternary complex showed an additional maximum at 320 nm. The 19F-NMR spectrum of the mouse enzyme:FdUMP binary complex revealed two new resonances at -2.8 and -34.8 ppm. The most deshielded resonance represented the noncovalent binary complex while the other resonance was assigned to the nucleotide covalently bound to the enzyme. The alteration of nucleotide binding equilibria produced by addition of H4 folate was exemplified by both an increase in intensity and a 5 ppm deshielding of the resonance attributed to the covalent FdUMP-enzyme complex. Addition of formaldehyde to the latter mixture produced the covalent ternary complex which resulted in the collapse of the resonances at -2.8 and -39.5 ppm and the appearance of a new resonance at -12.4 ppm.
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PMID:Purification and characterization of recombinant mouse thymidylate synthase. 200 93

Onchocerca volvulus worms, extracted from nodules by collagenase digestion, stained with haematoxylin and cleared in glycerol, were unravelled for longitudinal examination and later embedded in brain blocks for study of serial transverse sections. A classification system for female worms is proposed, based on the reproductive status of 446 worms from Guatemala, 94 from Liberia and 125 from Mali. They were categorized into fecund, inseminated specimens; uninseminated, but potentially fertile specimens, shedding ova destined to degenerate; worms changing from the uninseminated to the inseminated state and vice versa, which were few in number; old worms, with degenerate ovaries, whose genital tracts were either empty or had disappeared; and moribund or dead worms, characterized by loss of turgor, collapse and degeneration, calcification, or invasion by polymorphic, basophilic cells. Potentially fertile worms shed oocytes continuously and, when they were inseminated, embryonic development ensured. No evidence was found of a periodic cycle of reproduction. Inseminated worms were found in nodules without a male worm, and uninseminated worms in nodules harbouring male worms. Measurements are recorded of portions of the female reproductive tract and of the length of uterus occupied by the various embryonic stages in fully fecund worms. A significant difference in the length of the body behind the first and second ovaries was observed as between worms from West African savanna (Mali) and forest (Liberia). Limited observations were also made on meiosis in the oocyte, penetration of the oocyte by sperm, formation of the ovum, syngamy and zygote formation.
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PMID:On the reproductive activity of the female Onchocerca volvulus. 207 83

NMR, calorimetric, and optical spectroscopic studies have been performed on a trifluoromethyl-substituted styryl molecular probe bound to vesicles and multilamellar suspensions formed from dimyristoylphosphatidylcholine (DMPC). In the fluorine NMR spectrum at 35 degrees C there are two partially resolved resonances, but these collapse to an apparently single resonance at temperatures above 60 degrees C. However, a line-shape analysis is not consistent with exchange between two sites on an NMR time scale, and the two resonances are assumed to be due to probe sites in the inner and outer leaflets of the vesicles. Two fluorescence lifetimes, each associated with one of these sites, characterize the decay curves for the molecular probe bound to DMPC vesicles. The shift reagent Eu(FOD)3 and several nitroxide spin labels covalently bound to lipophilic structures strongly attenuate the lower frequency component of the fluorine NMR spectrum and also shift the other resonance to higher frequencies. The effect of two spin labels on the probe fluorine T2 relaxation time has been used to estimate the distance between the spin label unpaired electron and the trifluoromethyl group. The location of the spin label site in the membrane was determined from the effect of the unpaired electron on the lipid 13C linewidths. A model for the location of the probe in the bilayer was developed from the above information and refined using molecular mechanics calculations on a probe-DMPC lipid complex. The long axis of the probe parallels the bilayer normal; the styryl-group portion of the optical chromophore is located slightly below the glycerol backbone, and the remainder of the chromophore extends well into the hydrophobic region of the bilayer. Therefore, the optical properties of the probe should not be significantly influenced by alterations of the membrane surface charge density. Parameters derived from DSC studies in the gel-to-lipid crystal phase transition of DMPC are extremely sensitive to the probe. Even at 0.0001 mol fraction of probe, the transition is substantially broadened, and the delta H for the transition has increased, just as one predicts for the formation of a tight complex described above.
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PMID:NMR, calorimetric, spin-label, and optical studies on a trifluoromethyl-substituted styryl molecular probe in dimyristoylphosphatidylcholine vesicles and multilamellar suspensions: a model for location of optical probes. 215 5

The pressure difference between the perilymph and the endolymph following administration of 50% glycerol (12 ml/kg) was studied in guinea pigs. The perilymphatic and endolymphatic pressures were measured simultaneously with two sets of a servo-nulling system. Glycerol was administered for about one minute via a gastrocatheter. Both the perilymphatic and endolymphatic pressures began to decrease about 5 min after the administration of glycerol, and thereafter the decrease continued for about one hour with no significant difference between the two pressures. We concluded from the results that the glycerol-induced pressure difference between the perilymph and the endolymph, if present, is only a very small one, although a collapse of the scala media after glycerol intake was reported in guinea pigs and chinchillas.
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PMID:Effect of glycerol on pressure difference between perilymph and endolymph. 238 35

The combined effects of glycerol and colchicine on the endolymphatic sac were investigated in mice. Glycerol induced signs of secretion from the epithelium with formation of secretory granules in the light epithelial cells. Other characteristics of the epithelial lining were also changed resulting in an increased widening of the lateral intercellular spaces, a partial collapse of the lumen and with a deposition of a stainable substance within the lumen. This reaction lasted from 30 min to 24 h following the injection. Pretreatment with colchicine was found to decrease or inhibit the glycerol-induced secretion of macromolecules into the sac. The lumen collapsed but frequently there was no presence of stainable substance. Animals treated with both glycerol and colchicine showed marked signs of inner ear malfunction which could indicate that the secretory activity in the sac might be closely related to the regulation of inner ear fluid homeostasis and that functional disturbances in this system may lead to disorders of inner ear function.
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PMID:The endolymphatic sac and inner ear homeostasis. I: Effect of glycerol on the endolymphatic sac with or without colchicine pretreatment. 276 75


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