Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: DrugBank:APRD00080 (Leaf)
 21,685 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The ultrastructure of Acinetobacter sp. strain HO1-N grown on hydrocarbon and nonhydrocarbon substrates was compared using thin sections and freeze-etching. Hydrocarbon-grown cells were characterized by the presence of intracytoplasmic membrane-bound hexadecane inclusions. This membrane did not exhibit a typical unit membrane structure but appeared as a monolayer. The freeze-etch technique revealed the internal structure of the hexadecane inclusions and provided evidence for the presence of a smooth-surfaced limiting membrane. Freeze-etching also revealed intracytoplasmic membranes in the hexadecane-grown cells. These ultrastructural modifications were not present in nonhydrocarbon-grown cells. The hexadecane inclusions were isolated from Acinetobacter. Negative-staining of the inclusions revealed electron-transparent vesicles approximating the size of the inclusions seen in whole cells. Freeze-etching of the purified inclusions revealed membrane-bound vesicles. The purified inclusions exhibited a relatively high value of lipid phosphorus to protein. The lipid composition and the electrophoretic banding pattern of the inclusions on sodium dodecyl sulfate-polyacrylamide gels were determined and compared with other membrane fractions (outer membrane and cytoplasmic membrane) previously isolated from this organism.
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PMID:Characterization of intracytoplasmic hydrocarbon inclusions from the hydrocarbon-oxidizing Acinetobacter species HO1-N. 17 78

Deuterium (2H) and phosphorus (31P) nuclear magnetic resonance (NMR) and freeze-fracture electron microscopy were used to study spontaneous vesiculation in model membranes composed of POPC:POPS with or without cholesterol. The NMR spectra indicated the presence of a central isotropic line, the intensity of which is reversibly and linearly dependent upon temperature in the L alpha phase, with no hysteresis when cycling between higher and lower temperatures. Freeze-fracture microscopy showed small, apparently connected vesicles that were only present when the samples were frozen (for freeze-fracture) from an initial temperature of 40-60 degrees C, and absent when the samples are frozen from an initial temperature of 20 degrees C. Analysis of motional narrowing was consistent with the isotropic lines being due to lateral diffusion in (and tumbling of) small vesicles (diameters approximately 50 nm). These results were interpreted in terms of current theories of shape fluctuations in large unilamellar vesicles which predict that small daughter vesicles may spontaneously "erupt" from larger parent vesicles in order to expel the excess area created by thermal expansion of the bilayer surface at constant volume. Assuming that all the increased area due to increasing temperature is associated with the isotropic lines, the NMR results allowed a novel estimate of the coefficient of area expansion alpha A in multilamellar vesicles (MLVs) which is in good agreement with micromechanical measurements upon giant unilamellar vesicles of similar composition. Experiments performed on unilamellar vesicles, which had been placed upon glass beads, confirmed that alpha A determined in this way is unchanged compared with the MLV case. Addition of the highly positively charged (extrinsic) myelin basic protein (MBP) to a POPC:POPS system showed that membrane eruptions of the type described here occur in response to the presence of this protein.
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PMID:Temperature-reversible eruptions of vesicles in model membranes studied by NMR. 160 85

The effect of the volatile anaesthetic halothane on the structure and dynamics of lipid multilayers (dimyristoyl- and dipalmitoylphosphatidylcholine, DM- and DP-PC, aqueous dispersions) was studied using Differential Scanning Calorimetry (DSC), Freeze Fracture Electron Microscopy and solid state phosphorus-31 Nuclear Magnetic Resonance (31P-NMR). The action of the drug depends upon the halothane-to-lipid molar ratio, Ri, and temperature. With DPPC lipids, three main regions can be distinguished: i) 0 less than Ri less than 0.7, ii) 0.7 less than Ri less than 2 and iii) Ri greater than 2. As Ri increases in the first region, a linear decrease in the main gel-to-fluid phase transition temperature (Tc), a broadening in the DSC transition peak and a lowering in the enthalpy variation (delta H), are observed. A minimum in delta H is reached at Ri = 0.7. In this region, 31P-NMR spectra indicate that the multibilayer structure is maintained. In the second region, Tc still decreases with the same slope, but delta H increases up to a plateau value for Ri = 2. In the lipid fluid phase, an isotropic NMR line appears superimposed on the powder pattern that corresponds to a lamellar phase. For Ri greater than 2, Tc and delta H remain almost constant. At values of temperature that are greater than Tc, a growing isotropic line occurs in 31P-NMR spectra. This means a new supramolecular structure made of lipids and halothane is stabilized. This structure has been characterized as small vesicles of about 400 A to 600 A diameter by Freeze Fracture electron microscopy observations. With DMPC and low ratios (Ri less than or equal to 2), DSC and NMR results are similar to those obtained for DPPC. However, the minimum delta H is reached at Ri = 0.2 and the decrease in Tc is faster than for DPPC when Ri increases from 0. For Ri greater than 2, while Tc and delta H remain constant as in the case of DPPC, 31P-NMR spectra of DMPC systems show a superimposition of an isotropic line and two powder patterns, which correspond to small tumbling vesicles, a possible hexagonal phase and a lamellar phase respectively. Halothane, thus acts on model membranes in two different steps: at low Ri the bilayer is disturbed but keeps its structure. Whereas for higher drug concentrations, a new organization of lipids seems to be stabilized for T greater than Tc.
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PMID:Halothane-induced membrane reorganization monitored by DSC, freeze fracture electron microscopy and 31P-NMR techniques. 206 Apr 97

Bullfrog heart muscle trabecula are shock-frozen in liquid propane cooled by liquid nitrogen and then processed for X-ray microanalysis in two different ways: 1. Freeze-drying followed by vacuum embedding. 2. Cryoultramicrotomy and freeze-drying. Stained sections of freeze-dried, embedded tissue exhibit detailed ultrastructure, but are useless for X-ray microanalysis. Unstained, dry cut plastic-sections are suitable for X-ray microanalysis, but the ultrastructure appears faint. Higher electron optical contrast and peak-to-background ratio of X-ray spectra are generally obtained in freeze-dried cryosections. Both preparation methods show that the X-ray spectra are influenced by the quality of cryofixation. The phosphorus/potassium ratio in nuclei increases with increasing ice crystal size.
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PMID:The influence of different cryopreparations on the distribution of ions in bullfrog myocard cells. 240 23

The interaction of the bile salt cholate with unilamellar vesicles was studied. At low cholate content, equilibrium binding measurements with egg yolk lecithin membranes suggest that cholate binds to the outer vesicle leaflet. At increasing concentrations, further bile salt binding to the membrane is hampered. Before the onset of membrane solubilization, diphenylhexatriene fluorescence anisotropy decreases to a shallow minimum. It then increases to the initial value in the cholate concentration range of membrane solubilization. At still higher cholate concentrations, a drop in fluorescence anisotropy indicates the transformation of mixed disk micelles into spherical micelles. Perturbation of the vesicle membranes at molar ratios of bound cholate/lecithin exceeding 0.15 leads to a transient release of oligosaccharides from intravesicular space. The cholate concentrations required to induce the release depend on the size of the entrapped sugars. Cholesterol stabilizes the membrane, whereas, in spite of enhanced membrane order, sphingomyelin destabilizes the membrane against cholate. Freeze-fracture electron microscopy and phosphorus-31 nuclear magnetic resonance (31P NMR) also reflect a change in membrane structure at maximal cholate binding to the vesicles. In 31P NMR spectra, superimposed on the anisotropic line typically found in phospholipid bilayers, an isotropic peak was found. This signal is most probably due to the formation of smaller vesicles after addition of cholate. The results were discussed with respect to bile salt/membrane interactions in the liver cell. It is concluded that vesicular bile salt transport in the cytoplasm is unlikely and that cholate binding is restricted to the outer leaflet of the canalicular part of the plasma membrane.
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PMID:Structural changes in membranes of large unilamellar vesicles after binding of sodium cholate. 242 97

The effects of a high dose of acetylcholine (ACh) on oxygen consumption (VO2) and changes in phosphorus energy metabolites during secretion were studied in isolated perfused mandibular gland of rats at 24 degrees C. Sugar phosphates (SP), Pi, phosphocreatine (PCr), and ATP were identified by phosphorus-31 nuclear magnetic resonance spectroscopy. One micromole ACh induced a tachyphylactic secretory response, a persistently elevated VO2, and decreased PCr and ATP; 1 mM ACh caused an initial burst of secretion that was followed by suppression of secretion and a rapid increase in the VO2 to the same level as that with 1 microM ACh. These findings indicate a dissociation between secretion and VO2. During stimulation with 1 mM ACh, the level of PCr first decreased and then partially recovered, but the level of ATP continued to decrease and the levels of Pi and SP increased markedly. These findings suggest compartmentalization of creatine phosphokinase (CPK) systems and the possibility that a high concentration of ACh interferes with the transport of PCr between one CPK system near adenosinetriphosphatase and another system near mitochondria in acinar cells.
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PMID:Dissociation of fluid secretion and energy supply in rat mandibular gland by high dose of ACh. 283 65

Five different brands of instant dry whole milk that are most commonly used, and freeze dried milk were analyzed for nitrogen, fat, ash and 4 inorganic constituents and compared with human milk. The composition of the milks differed considerably. The protein content varied widely, ranging from 11.6 to 24.5%. Fat content did not differ widely, ranging from 24.9 to 29.5%. Freeze dried milk had the highest fat content (42.6%). Three out of the five brands of dry milk studied were spray dried and the remaining two were roller dried. All milks tested contained considerably more sodium, potassium, calcium and phosphorus solid than human milk, some of them the four fold amount of calcium and phosphorus.
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PMID:Effect of the drying process on the nutritive value of milk. Part 1. Biochemical composition. 323 Dec 48

Freeze-dried rat incisors were examined by high-resolution scanning electron microscopy (SEM) combined with energy-dispersive x-ray microanalysis (EDX) for determination of the correlation between the morphology of the enamel organ and the concentrations in the adjacent developing enamel matrix of calcium (Ca), phosphorus (P), and sulfur (S), as well as the Ca/P ratio. In SEM examination of the freeze-dried enamel organ, it was possible to identify the stages of enamel secretion, transition, and maturation, and furthermore to identify ruffle-ended and smooth-ended maturation ameloblasts. EDX analysis of the outer layer of forming and maturing enamel was carried out from the apical to the incisal end at interval points of approximately 50 micron. Ca and P concentrations increased gradually and continuously from the secretion zone to the end of the maturation zone, but never showed a steep rise in any of the zones examined. Maturing enamel overlaid by either ruffle-ended or smooth-ended maturation ameloblasts showed similar Ca and P concentrations. Throughout the outer enamel layer, the Ca/P molar ratio was fairly constant. Sulfur concentration began to decrease in the zone of enamel secretion, and was no longer detected in the middle of the maturation zone.
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PMID:Ameloblast modulation and changes in the Ca, P, and S content of developing enamel matrix as revealed by SEM-EDX. 347 11

Fast-growing heavy (White Rock) chicks, fed a vitamin D-deficient diet, exhibited a higher activity of kidney 25-hydroxycholecalciferol-1-hydroxylase (1-hydroxylase) than slow-growing light (White Leghorn x Rhode Island Red) chicks fed the same diet. 1-Hydroxylase and duodenal calcium-binding protein (CaBP) declined with age. Feeding of low energy diets with or without vitamin D resulted in a slower rate of growth and reduced 1-hydroxylase activity and CaBP concentration. Severe dietary restriction of either calcium or phosphorus resulted in a lower growth rate as well as a duodenal CaBP as compared to a moderate mineral restriction. The severe dietary calcium restriction also resulted in a lower 1-hydroxylase activity than that resulting from a moderate restriction. The results clearly indicate that high 1-hydroxylase activity and a high intestinal CaBP are associated with a high growth rate.
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PMID:Relationships between cholecalciferol metabolism and growth in chicks as modified by age, breed and diet. 625 6

The pH of cool drinks and fruit juices is very low and ranges from 2,4 (Pepsi Cola) to 3,7 (fresh orange juice). The osmotic concentration of most cool drinks and fruit juices is considerably higher than that of blood and, with the exception of Isotonic Game, ranges from 430 mOsm/kg (Coca Cola) to 1 297 mOsm/kg (Liquifruit Grape). Glucose, fructose and sucrose contribute from 72% to 98% of the osmotically active particles in cool drinks and fruit juices and their high carbohydrate content causes concern about substrates for oral bacteria to produce acid as well as daily energy intake. The sodium (Na), potassium (K), calcium (Ca) and phosphorus (P) content of cool drinks is low although K and P may contribute significantly to dietary intake when most fruit juices are consumed. K is virtually absent in Coca Cola and its use in replacing lost minerals, e.g. in infantile gastro-enteritis, is disputed. The relatively high levels of K and P in fruit juices could be harmful to patients suffering from chronic uraemia. The selected cool drinks and fruit juices analysed contain very little Na and should not pose problems to hypertensive patients.
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PMID:Chemical analysis of cool drinks and pure fruit juices--some clinical implications. 649 27


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