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At least 793 records · Page 44Linked to original sources
PubMed1964

ELECTRON MICROSCOPIC AND BIOCHEMICAL STUDIES OF PYRUVATE DEHYDROGENASE COMPLEX OF ESCHERICHIA COLI.

Examination with the electron microscope of the pyruvate dehydrogenase complex and its component enzymes from Escherichia coli indicates that the complex has a polyhedral structure with a diameter of about 300 to 350 angstroms and a height of 200 to 250 angstroms. The reconstituted complex closely resembles the native complex in appearance. A tentative model of this multienzyme complex is proposed on the basis of the correlated biochemical and electron-microscopic data

Acetates↗
PubMed1971

Autolytic activity associated with competent group H streptococci.

Competent cells of group H streptococci strains Wicky and Challis autolyzed markedly when placed at 37 C in 0.05 m tris(hydroxymethyl)methyl-amino-propane sulfonic acid buffer (pH 9.0 to 9.1) containing 0.02 m 2-mercaptoethanol, whereas noncompetent cells autolyzed slightly. Autolysis of competent Wicky cells did not occur at 0 C or after the cells were heated at 100 C for 5 min. Culture fluids derived from strain Challis that contained competence factor (CF) activity did not contain lytic activity. Addition of native deoxyribonucleic acid (DNA) to competent Wicky cells caused a retardation in the rate of autolysis; ribonucleic acid and alkali-denatured DNA had less of an effect. Supernantant fluids derived from competent cell lysates lysed noncompetent Wicky cells but were inactive against cells of Hydrogenomonas eutropha, a group A Streptococcus, and against a commercial lysozyme substrate (Micrococcus lysodeikticus). This lytic activity was inactivated by heat (5 min at 100 C). Electron microscopic observations of autolyzed cells showed that autolysis occurs only at the site of cross-wall formation. A close relationship between the development of competence and autolysis is suggested by the fact that certain conditions that prevent the establishment of the competent state in Wicky populations (such as no CF, addition of CF simultaneously with chloramphenicol, and addition of trypsin-inactivated CF) also prevent autolysis. This observation emphasizes the indirect or inductive nature of CF on these processes.

Autolysis↗
PubMed1973

Isolation, chemical composition, and ultrastructural features of the cell membrane of the mycoplasma-like organism Spiroplasma citri.

Thin sections of Spiroplasma citri, a mycoplasma-like organism isolated from citrus infected with "Stubborn" disease, showed the organisms to be limited by a single trilaminar plasma membrane. An additional outer layer could, however, be frequently seen in freeze-etched preparations of unwashed cells. The organisms were found to be extremely sensitive to lysis by osmotic shock. The cell membrane of S. citri isolated in this way resembled that of mycoplasmas in ultrastructure and gross chemical composition. The isolated membranes showed the characteristic trilaminar shape in section and the typical particle-studded fracture faces in freeze-etched preparations. Protein and lipid formed over 80% of the total dry weight of the membrane, which had a density of ~1.180 g/cm(3). Cholesterol constituted over 20% of the total membrane lipid. Phosphatidyl-glycerol, synthesized by the organisms, was the major phospholipid. Significant amounts of hexosamine (15 to 35 mug/mg of membrane protein) could be found in the membrane preparations. Our results support the thesis that S. citri does not possess a cell wall, either of the gram-positive or the gram-negative type, though it may be coated by some other type of an envelope or by a slime layer, at least temporarily.

Bacterial Proteins↗
PubMed1973

Human cytomegalovirus. I. Purification and characterization of viral DNA.

Two human strains (AD-169 and C87) and one simian strain (GR2757) of cytomegalovirus (CMV) have been purified from the extracellular fluids of virus-infected cultures by sedimentation through a sucrose gradient followed by brief centrifugation in a preformed gradient of CsCl. Enveloped virus particles were located in the density region, 1.219 g/cm(3), and nucleocapsids at 1.263 g/cm(3). Purified viral DNA, both human and simian, sedimented in the region of 55S in neutral sucrose gradients with herpes simplex type I DNA as a marker; the molecular weight of the CMV DNA was estimated as approximately 10(8). The density of the viral DNA determined by analytical ultracentrifugation was 1.716 g/cm(3) for the human strains and 1.710 g/cm(3) for the simian strain. Tritiated viral complementary RNA synthesized in vitro with Escherichia coli transcriptase has been used for detection and localization of viral genome in membrane hybridization and in situ cytohybridization. Newly synthesized viral DNA appeared 24 h after infection and localized at two acrocentric areas; later the viral DNA distributed in a band resembling intranuclear inclusions 48 to 70 h after infection. Total DNA synthesis began to increase 24 h after infection and reached its peak at 70 h; RNA synthesis increased at 13 h, and reached its peak at 24 to 33 h. The viral DNA was also labeled with (3)H-TTP by repair-synthesis in vitro with Kornberg's enzyme in order to analyze the purity of the DNA and for detection of viral DNA by DNA-DNA reassociation kinetics.

Animals↗
PubMed1972

Morphology and physical properties of Staphylococcus bacteriophage P11-M15.

The Group B Staphylococcus phage P11-M15 is shown to be 51% protein and 49% deoxyribonucleic acid (DNA). The intact virion has a molecular weight of 66.7 x 10(6) daltons. The purified viral DNA has a molecular weight of 32.7 x 10(6) daltons. The intact virion is shown to be composed of a polyhedral head which is attached at one of its vertices to a flexible tail having helical symmetry. The tail structure is terminated by a complex baseplate which has sixfold symmetry. The virion contains a single molecule of double-stranded DNA which has no apparent single-strand nicks or single-stranded terminal redundancies.

Centrifugation, Density Gradient↗
PubMed1995

Fixation and staining of planaria for histological study.

Fixation and staining of planaria can affect the interpretation of histopathological changes following their exposure to various agents. We assessed several fixation protocols with various stains in planaria to determine an optimal combination. Planaria were fixed in each of the following: 10% neutral buffered formalin, 2.5%, glutaraldehyde, Bouin's, Zenker's, 70% ethanol, and relaxant. In addition, planaria were fixed in relaxant and postfixed in each of the fixatives above. Paraffin embedded sections from each fixation protocol were stained with hematoxylin and eosin (H & E), toluidine blue, periodic acid-Schiff (PAS), or phosphotungstic acid-hematoxylin (PTAH). Relaxant fixed planaria were also stained with Steiner's, Holmes, trichrome, Giemsa, Grocott's methenamine silver (GMS) and antibodies for intermediate filaments (cytokeratin, vimentin and desmin). Relaxant and Zenker's gave the best fixation with minimal artifacts. Formalin, glutaraldehyde, and ethanol were unacceptable because they caused contortions of the body, crenation, and a darkly pigmented epidermis. Gastroderm could be differentiated from stroma best when stained with H & E, toluidine blue and PTAH. Other organ systems differentially stained included the epidermis, marginal adhesion gland, nervous tissue, and muscle. PAS, Steiner's, Holmes, trichrome and the intermediate filament stains were not useful for planaria staining. The most morphological information was obtained with relaxant fixative and a combination of sections stained with H & E and PTAH.

Animals↗
PubMed2005

Influence of starters on chemical, biochemical, and sensory changes in Turkish White-brined cheese during ripening.

Turkish White-brined cheese was manufactured using Lactococcus strains (Lactococcus lactis ssp. lactis NCDO763 plus L. lactis ssp. cremoris SK11 and L. lactis ssp. lactis UC317 plus L. lactis ssp. cremoris HP) or without a starter culture, and ripened for 90 d. It was found that the use of starters significantly influenced the physical, chemical, biochemical, and sensory properties of the cheeses. Chemical composition, pH, and sensory properties of cheeses made with starter were not affected by the different starter bacteria. The levels of soluble nitrogen fractions and urea-PAGE of the pH 4.6-insoluble fractions were found to be significantly different at various stages of ripening. Urea-PAGE patterns of the pH 4.6-insoluble fractions of the cheeses showed that considerable degradation of alpha(s1)-casein occurred and that beta-casein was more resistant to hydrolysis. The use of a starter culture significantly influenced the levels of 12% trichloroacetic acid-soluble nitrogen, 5% phosphotungstic acid-soluble nitrogen, free amino acids, total free fatty acids, and the peptide profiles (reverse phase-HPLC) of 70% (vol/vol) ethanol-soluble and insoluble fractions of the pH 4.6-soluble fraction of the cheeses. The levels of peptides in the cheeses increased during the ripening period. Principal component and hierarchical cluster analyses of electrophoretic and chromatographic results indicated that the cheeses were significantly different in terms of their peptide profiles and they were grouped based on the use and type of starter and stage of ripening. Levels of free amino acid in the cheeses differed; Leu, Glu, Phe, Lys, and Val were the most abundant amino acids. Nitrogen fractions, total free amino acids, total free fatty acids, and the levels of peptides resolved by reverse phase-HPLC increased during ripening. No significant differences were found between the sensory properties of cheeses made using a starter, but the cheese made without starter received lower scores than the cheeses made using a starter. It was found that the cheese made with strains NCDO763 plus SK11 had the best quality during ripening. It was concluded that the use of different starter bacteria caused significant differences in the quality of the cheese, and that each starter culture contributed to proteolysis to a different degree.

Amino Acids↗
PubMed1976

[Ultrastructural localization of acid phosphatase and thiamine pyrophosphatase activities and of phosphotungstic staining at low pH in the placental labyrinth of the cat].

The localizations of acid phosphatase (ACPase) and thiamine pyrophosphatase (TPPase) activities were studied in the placental labyrinth of the cat during the last days of gestation. ACPase activities were observed essentially in the syncytiotrophoblast and in the "interstitial inert substance" (S.I.I.) that separates maternal from foetal tissues. Reaction product was localized in lysosomes, multivesicular bodies, and in the network of smooth-membraned tubules which open on the cell surface of the syncytiotrophoblast facing the S.I.I. The S.I.I. exhibit a strong activity, probably of syncytiotrophoblastic origin. TPPase activities were found in the syncytiotrophoblast, rarely in the Golgi apparatus but always in the lumen of the network of smooth-membrande tubules. The S.I.I. shows a moderate activity. These TPPase positive tubules being frequently observed very close to the Golgi cisternae, it is proposed that they arise from the Golgi complex and convey phosphatases to the S.I.I. After phosphotungstic acid staining at low pH, luminal surface coat of maternal endothelium is always strongly and continuously visualized, while the plasma membrane of the syncytiotrophoblast facing the S.I.I. is never stained. Staining is intense in the lumen of tubules, and continuous with the stain of the S.I.I. ACPase activity of the S.I.I. could be implicated in enzymatic degradation of maternal molecules during their transfer from maternal to foetal blood. The S.I.I. may correspond to the immunological buffer zone at the interface between maternal and foetal tissues.

Acid Phosphatase↗
PubMed1982

Membrane histochemistry of Physarum polycephalum myxamoebae.

Myxamoebae of Physarum polycephalum are the uninucleate, haploid stage of the organism. Histochemical studies were undertaken to characterize intracellular and plasma membranes, and to provide a basis for assaying subcellular fractions for enrichment in plasma membranes. Lead salts deposition techniques were employed for hydrolytic enzymes. Alcian blue-ruthenium red, osmium tetroxide-potassium ferrocyanide, and phosphotungstic acid-chromic acid stains were evaluated for specificity for plasma membranes. Glucose 6-phosphatase was localized in endoplasmic reticulum, Golgi apparatus, and perinuclear space. 5'-Nucleotidase was localized in food vacuoles, chromatin, and plasmalemma. Acid phosphatase was in food vacuoles and Golgi apparatus. Alkaline phosphatase was in food vacuoles and endoplasmic reticulum. We conclude that none of the above enzymes is suitable as a cytochemical marker for plasma membranes of Physarum myxamoebae, but recommend instead staining ultrathin sections of membrane pellets with phosphotungstic acid-chromic acid, which stains plasma membranes selectively.

5'-Nucleotidase↗
PubMed2001

Clinicopathological correlation in exudative age-related macular degeneration: recurrent choroidal neovascularization.

PURPOSE: To report the pathology of surgically removed submacular tissue in recurrent choroidal neovascularization after laser photocoagulation of classic choroidal neovascularization in age-related macular degeneration. METHODS: A recurrent subfoveal choroidal neovascular membrane was surgically removed in two patients. The recurrence was identified as a classic membrane on fluorescein angiography at the foveal border of the laser scar. A net was visualized in the early venous phase of the indocyanine green angiogram, with associated late hyperfluorescence. Both patients had undergone laser photocoagulation for a classic interpapillomacular choroidal neovascular membrane about 1 1/2 years earlier. The specimens were serially sectioned and stained with hematoxylin-eosin, periodic acid-Schiff, Masson trichrome and phosphotungstic acid-hematoxylin. RESULTS: The two specimens consisted of subretinal fibrovascular tissue with fibrin exudation. Fibrovascular tissue bordered subretinal fibrous tissue adherent to Bruch's membrane and remnants of the choroid in one patient. The fibrovascular portion most likely corresponded to the recurrence, whereas the fibrous portion represented the original membrane, being obliterated after photocoagulation. Some peripapillary tissue was additionally removed in the other patient. The latter lesion was invisible on fluorescein angiography but stained in the late phase of indocyanine green angiography and corresponded histopathologically to poorly vascularized intra-Bruch's fibrovascular tissue. Granular deposits, periodic acid-Schiff positive and metachromatically purple on Masson trichrome stain, representing diffuse drusen (basal laminar/linear deposits), were identified in the three specimens. CONCLUSION: A subretinal fibrovascular membrane corresponded with the classic recurrent choroidal neovascularization.

Aged↗
PubMed1969

Uric acid and plasma lipids in cerebrovascular disease. I. Prevalence of hyperuricaemia.

Serum uric acid levels measured by the phosphotungstic sodium cyanide method have been estimated in 60 patients suffering from a cerebrovascular incident. Patients with diseases known to predispose to hyperuricaemia were excluded. Twenty-five per cent. of patients with acute strokes had hyperuricaemia, and this did not appear to be a transitory phenomenon. These findings suggest that hyperuricaemia may be one of the factors in the pathogenesis of atheroma.

Adult↗
PubMed2002

Comparative ultracytochemical study of the acrosome in four different Veneroida species from the Turkish coast.

Cytoplasmic acidic phosphoproteins and complex polysaccharides were stained with ammoniacal silver nitrate-formalin and phosphotungstic acid-chromic acid, respectively. In Cerastoderma glaucum (Cardiacea), acrosomal vesicle contents are differentiated into an apical intermediate-dense component and a basal dense region. PTA stained the apical component and silver stained the basal region and the apex of the acrosome. In Spisula subtruncata (Mactracea) the acrosome showed a PTA-stained apical component and a silver-positive basal dense region. In the Veneracea, Chamelea gallina and Pitar rudis show a tripartite acrosomal vesicle, with apical light, outer dense and inner intermediate-dense regions. In both species, the apical and inner components were stained by PTA, whereas silver stained all regions of the acrosomal vesicle in C. gallina and the apical and outer regions in P. rudis. In midpiece, only C. glaucum showed a positive silver reaction at the centriolar fossa.

Acrosome↗