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At least 19 recordsLinked to original sources
PubMedDate not supplied

Mechanisms of cellular interaction with monosodium urate crystals. IgG-dependent and IgG-independent platelet stimulation by urate crystals.

Monosodium urate crystals (MSU) stimulate suspensions of washed platelets or neutrophils. When MSU crystals are coated with IgG, as occurs in plasma, stimulation is markedly enhanced. These studies which use MSU-induced human platelet serotonin secretion as a model examine the nature of cellular recognition mechanisms for MSU crystals and IgG-coated MSU crystals. F(ab')2 fragments of specific anti-Fc antibody blocked and the lipopolysaccharide of Salmonella minnesota R595 enhanced human platelet secretion induced by IgG-coated urate crystals. These agents had little effect on stimulation by uncoated crystals. This indicated that urate crystals stimulate platelets independently of fluid phase IgG. Urate crystals directly stimulated suspensions of washed rabbit platelets which lack Fc receptors. In contrast to human cells, stimulation was blocked by IgG. This again demonstrated IgG-independent cell stimulation by urate crystals. Calcium pyrophosphate dihyrate crystals could trigger human platelet secretion only when coated with IgG. This suggests that when crystals are coated with IgG, the surface-bound IgG alone may be the stimulus to the cell. This was supported by the finding that polyvinylpyridine-N-oxide, a hydrogen acceptor, blocked human platelet stimulation by uncoated, but not IgG-coated, urate crystals. These data indicate that urate crystals (and potentially other surface or particles) can stimulate a mediator cell by at least two mechanisms: by direct stimulation without the mediation of adsorbed IgG or, when coated with IgG, by triggering the cell via immunoglobulin receptors.

Blood Platelets↗
PubMed1979

Crystallization studies in a urothelial-lined living test tube (the catheterized female rat bladder). I. Calcium oxalate crystal adhesion to the chemically injured rat bladder.

We developed an in vivo technique to study crystallization in a urothelial-lined "living test tube" by employing the catheterized female rat bladder. Calcium oxalate crystals adherent to the bladder urothelium were distinguished from free or intraluminal crystals. Chemical injuries of the urothelium induced by either 0.1 N HCL or 5 per cent Triton X 100 in saline resulted in marked calcium oxalate crystal adhesion to the injured urothelium. Control bladders without urothelial injury remained free of adherent crystals but formed large numbers of small free crystals relatively uniform in size. Histologic and fresh microscopic evaluations of urothelial injury and crystal adhesion are presented.

Animals↗
PubMed1976

Crystallization of human placental estradiol 17beta-dehydrogenase. A new method for crystallizing labile enzymes.

Estradiol 17beta-dehydrogenase from human placenta has been crystallized by a new technique, herein referred to as electrophoretic diffusion. This is the first crystallization of an enzyme from human placenta as well as the first crystallization of any steroid-converting enzyme of human source. A solution of the enzyme (specific activity 7.1 units/mg) in 1.5 ml of Tris-barbituric acid buffer, pH 7.0, containing 20% glycerol as stabilizer, was placed in an electrophoresis tube and the tube was closed at both ends with a dialysis membrane which permits the passage of substances of molecular weight less than 18,000. The tube was placed in a gel electrophoresis apparatus and the reservoirs filled with the Tris-barbituric acid buffer. A potential of 100 V was applied for 12 hours, then raised to 200 V for another 12 hours, and finally to 300 V until opalescence appeared at the bottom of the tube. Activity measurements showed that more than 90% of the enzyme had concentrated in the bottom 0.15-ml portion of the solution. When this section of the solution was removed and kept overnight at 4 degrees, gross and microscopic examination revealed a heavy crop of crystals which possessed a specific activity of 7.2 units/mg. The specific activity remained constant throughout three recrystallizations. The crystalline enzyme displayed a single band by analytical and sodium dodecyl sulfate-polyacrylamide gel analysis. Crystals of enzyme of high specific activity could also be obtained from an enzyme sample initially possessing a specific activity of only 4.5 units/mg. The new technique should be appliable for the crystallization of other labile enzymes and receptor proteins which have so far resisted crystallization by conventional methods.

Crystallization↗
PubMed1979

Clearance of calcium pyrophosphate dihydrate crystals in vivo. I. Studies using 169Yb labeled triclinic crystals.

Synthetic triclinic calcium pyrophosphate dihydrate crystals were uniformly trace-labeled with Ytterbium-169 (169Yb), a pure gamma-emitting isotope with a halflife of 31 days. The solubility of the labeled crystals was similar to that of cold synthetic crystals. The clearance rate of labeled sterile crystals, sieved to obtain the desired size, was determined after injection of microgram quantities into 4 arthritic huuman and 3 normal adult rabbit joints and corrected by the observed rate of clearance of free 169Yb. The derived rate constants were then used to calculate the time required for half of the injected dose of CPPD to be cleared from the joint. Crystal clearance was found in all instances. Crystal removal from normal rabbit joints was much more rapid than from the much larger human arthritic joints and was inversely proportional to the size of the crystals injected.

Animals↗
PubMed1975

Succinylsulfathiazole crystal forms. III: Crystal growth studies.

Crystal growth accompanying the transformation of succinylsulfathiazole crystal forms in aqueous suspensions was studied using a projecting microscope. The effects of increase of temperature, agitation, inclusion of seeds of Form II (the water-stable dihydrate), sulfathiazole, methylcellulose, and polysorbate 80 on the particle-size distribution of anhydrous succinylsulfathiazole Form I were examined. Rates of crystal growth, calculated as increase of diameter per unit time, were given under different experimental conditions. Increase of temperature, agitation, and seeding with nuclei of Form II had significant growth-accelerating effects. Sulfathiazole and polysorbate 80 had growth-retarding effects. Methylcellulose inhibited the crystal growth of Form I for over a year. Aqueous suspensions of Form II did not show any change in particle-size distribution. The crystal growth was shown to be a direct consequence of the transformation of the crystal form. Physical conditions and additives which had accelerating or retarding effects on the rate of succinylsulfathiazole in aqueous suspensions.

Chemical Phenomena↗
PubMed1979

CLearance of calcium pyrophosphate dihydrate crystals in vivo. II. Studies using triclinic crystals doubly labeled with 45Ca and 85Sr.

The clearance rate of isotopically labeled synthetic triclinic calcium pyrophosphate dihydrate (CPPD) crystals injection into rabbit joints was estimated by serial counting. Kinetic analysis using a four compartment model showed that half of the injected dose was cleared from 4 rabbit knee joints in 19.1 +/- 0.42 (SEM) days. Profound hypomagnesemia, produced in 2 rabbits with a low magnesium diet, did not affect the rate of crystal clearance detectably. Lavage of joints with solutions known to promote CPPD crystal solubility failed to remove detectable radioactivity. The previous finding of CPPD crystals in synovial phagocytes by electron microscopy, together with the finding of nuclide activity in the synovium and the failure to remove such activity by joint lavage, suggests that endocytosis by synovial cells is an important, effective mechanism controlling the synovial fluid concentration of crystals in patients with CPPD crystal deposition disease.

Animals↗
PubMed1992

Observations on the structural features and characteristics of biological apatite crystals. 2. Observation on the ultrastructure of human enamel crystals.

In a series of studies to investigate the structural features of biological crystals, using an electron microscope, we examined the ultrastructure of human enamel crystals at near atomic resolution through the cross and longitudinal sections of the crystals. The materials used for this study were the middle layer of the noncarious enamel from freshly extracted human erupted permanent molars. The small cubes of the enamel were fixed in glutaraldehyde and osmium tetroxide and embedded in epoxy resin using the routine methods. The ultrathin sections were cut with a diamond knife without decalcification. The sections were examined with HITACHI H-500 and H-700 types of transmission electron microscopes operated at 125-200 kV. Each crystal was observed at the initial magnification of 300,000 times and at the final magnification of 10,000,000 times and over. Using this approach, the authors have been able to show the configuration of the hydroxyapatite in the cross and longitudinal sections of the enamel crystals and observe the basic hexagonal pattern of the unit cell viewed down the c-axis. The authors sincerely believe that the electron micrograph shown in this report is the first atomic image to be obtained from a hydroxyapatite crystal from the human enamel, using the sections.

Dental Enamel↗
PubMed1976

[Protein crystals and tubuli bundles in yeast cells. IV. Biochemical and electron microscopic studies of the induction of alcohol dehydrogenase (ADH) crystals].

Cells of Saccharomyces carlsbergensis H 60 synthesize alcohol dehydrogenase (ADH) in media containing 2% lactat, 1% ethanol or 0.1% glucose. Crystals may be induced in protoplasts of these cells. Increase of glucose concentration in the medium results in diminished ADH synthesis and decreased tendency for crystal formation. Repression of ADH synthesis by glucose results in the formation of a protein (MG 110000 D), the significance of which is discussed. Early stages of crystal formation inside the cell are demonstrated electronmicroscopically. At first dense material accumulates between opposite membranes of neighbouring mitochondria. Within mitochondria frequently membrane bundles occur in close vicinity to crystals. These ADH-crystals arise from this material.

Alcohol Oxidoreductases↗
PubMed1975

Growth of calcium oxalate crystals. II. Inhibition by natural urinary crystal growth inhibitors.

A method is described for quantitatively determining the inhibitory activity of pure components, isolates, or mixtures of components (such as urine) on the growth of calcium oxalate crystals. Results with known calcium phosphate crystal growth inhibitors--magnesium, citrate, and pyrophosphate--suggest that these components contribute little to the ability to normal urine to inhibit the growth of calcium oxalate crystals. As yet unidentified urinary components seem to be responsible for most of this activity. The urinary crystal growth inhibitors appear to function by adsorbing on the surface of the growing crystals, thereby preventing the further incorporation of lattice ions. The fit of experimental data to the Langmuir absorption isotherm supports this conclusion.

Calcium↗
PubMed1977

Crystallization and preliminary crystal data of porcine pepsinogen.

Single crystals of porcine pepsinogen, suitable for x-ray diffraction studies, have been grown with lithium sulfate as the precipitant. These pepsinogen crystals were dissolved, activated, and assayed for proteolytic activity. The specific enzymic activity of the dissolved crystalline protein was nearly twice that of the commerical pepsinogen from which the crystals were grown. Incubation at pH 8 before assay demonstrated that the crystals are free of pepsin. This crystal form of pepsinogen belongs to the monoclinic space group C2 with 4 molecules in the unit cell. The unit cell dimensions are a = 104.8 +/- 0.5 A, b = 43.1 +/- 0.1 A, c = 88.4 +/- 0.3 A, and beta = 91.3 degrees.

Animals↗
PubMed1978

Crystallization, crystal structure analysis and atomic model of the complex formed by a human Fc fragment and fragment B of protein A from Staphylococcus aureus.

Crystals of the complex formed by human Fc fragment and fragment B (FB) of protein A from Staphylococcus aureus were prepared and the crystal structure determined at high resolution by multiple isomorphous replacement. Phase were improved considerably by combining these phases with calculated phases from the Fc component. FB is a small globular protein built of three parallel helices arranged in a triangular array. It binds by the first two helices of Fc and is attached to segments of CH2 and CH3. The CH3 module is unchanged between complex and Fc fragment crystals, but CH2 changes its position slightly relative to CH3. In addition, the upper third of CH2 is disordered in the complex crystals. Possible sources of this disorder are discussed.

Antigen-Antibody Complex↗
PubMed1977

[Protein crystals and tubuli bundles in yeast cells. VI. Light-and electron microscopy studies as well as biochemical studies on alcohol dehydrogenase activity of isolated crystals].

Isolated crystals from Saccharomyces carlsbergensis, stabilized by Cd2+ or Zn2+, retain their enzymatic activity as shown by topochemical reactions. During these reactions the crystals disintegrate characteristically. Stages of this disintegration and deposition of reaction products have been demonstrated by light and electron microscopy. Ground plasmatic and mitochondrial alcoholdhydrogenase has been solubilized by means of 0.01 M EDTA from Zn2+ stabilized crystals separated by gel electrophoresis and proved to be active.

Alcohol Oxidoreductases↗
PubMed1976

[Protein crystals and tubuli bundles in yeast cells. V. Enrichment of crystal and tubuli proteins during O2 limitation and anaerobiosis].

Cells of Saccharomyces carlsbergensis contain proteins assembling to crystals and bundles of tubules (tb) in the cyto- and karyoplasm by osmotic shock with hypertonic solutions. The cellular concentration of these proteins is regulated by oxygen pressure during growth. In cells grown at optimal aeration the protein level is low and crystals and tb cannot be induced. After a short period of O2-limitation or anerobic growth conditions the protein concentration increases and induction of crystals and tb is possible.

Anaerobiosis↗
PubMed1976

[Protein crystals and tubuli bundles in yeasts cells. III. Identification of crystals as alcohol dehydrogenase (ADH)].

Inducibility of alcohol dehydrogenase (ADH) crystals in yeast cells depends on the growth phase. They accumulate during exponential growth, a process that is parallelled by accumulation of a special protein (H protein). The following pieces of evidence show that crystals, H protein, and ADH are identical: (1) The three proteins have the same amino acid composition and subunit molecular weight; (2) active H protein and ADH exhibit the same electrophoretic mobility, indicating a common molecular weight of about 158 000 D; (3) the native H protein and a crystal fraction stabilized by Zn++ and dialyzed against EDTA possess ADH activity.

Alcohol Oxidoreductases↗
PubMedDate not supplied

Assembly of 2-D membrane protein crystals: dynamics, crystal order, and fidelity of structure analysis by electron microscopy.

Membrane protein reconstitution into two-dimensional (2-D) ordered arrays is described. The assembly of 2-D crystals may be modeled as a two-step process: the membrane protein is first integrated in the lipid bilayer and then crystallized by removal of excess detergent or lipid and/or by precipitating agents. Lipid-detergent, protein-detergent, and lipid-protein interactions are critical during the first step, while lipid-protein and protein-protein interactions dominate events in the second step. The evidence supporting this model results from quasielastic light scattering analyses and electron microscopy of different lipid-detergent systems and reconstitution experiments with Escherichia coli porin OmpF, Phormidium laminosum photosystem I reaction centers, and integral membrane proteins of mammalian lens fiber cells.

Animals↗
PubMed1979

Crystal structure analysis of the tetragonal crystal form are preliminary molecular model of pig-heart citrate synthase.

The crystal structure of pig heart citrate synthase was analyzed at 0.35-nm resolution. Chain tracing was possible and an initial molecular model constructed. The dimensions of the dimer molecule (located on a crystallographic diad) are 7.5 x 6.0 x 9.0 nm. The chain folding is characterized by the predominance of helices and the absence of sheet structure. The electron density accounts for 355 residues per monomer, so that about 80 residues must be disordered in the crystal. The disordered segment in probably N-terminal. The ordered part consists of two closely associated domains, a large domain with 300 residues and a C-terminal domain of 55 residues consisting of 3(anti)parallel helices. The large domain is built from 12 helical segments, some of which are buried in the interior of the molecule. Inhibitor binding studies with citrate and CoA revealed citrate binding sites but showed no electron density for CoA. It is suggested that CoA binds to the disordered, flexible N-terminal domain. Experiments of limited proteolysis with trypsin showed that under conditions a segment of Mr 9000 is cleaved off selectively. The remaining 35 000-Mr part is dimeric.

Animals↗
PubMed1977

[Effect of the crystallization conditions of tetracycline base on the properties of the powders and drug forms obtained. The dependence of the degree of dispersion of tetracycline base on the crystallization conditions].

Characteristics of the powder dispersity of tetracycline base samples prepared by directed crystallization with variation of the process conditions were determined by the sedimentation method. It was found that the speed of the solution agitation had the maximum effect on the level and nature of the dispersity. The rate of the solution temperature and pH changing during the crystallization process had also a significant effect at low agitation speed.

Chemistry, Pharmaceutical↗
PubMed1979

Acquired lipidosis of marrow macrophages: birefringent blue crystals and Gaucher-like cells, sea-blue histiocytes, and grey-green crystals.

Three varieties of compound lipid inclusions occurring as a secondary phenomenon in marrow macrophages are detectable and distinguishable by Romanowsky staining, ultraviolet fluorescence, and polarised light. Birefringent blue crystals and Gaucher-like cells form one variety, sea-blue granules another, and grey-green crystals a third. All occur chiefly in myeloid leukaemias, either acute or chronic.

Birefringence↗