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At least 847 records · Page 47Linked to original sources
PubMed1971

Dissociation by chelating agents and substructure of the thermophilic bacteriophage TP84.

The thermophilic bacteriophage TP84 is dissociated into its head, tail, and released deoxyribonucleic acid (DNA) by chelating agents such as ethylenediaminetetraacetic acid (EDTA) and phosphate. The phage is more sensitive to EDTA than to phosphate, and dialysis against either agent causes more effective dissociation than standing in their presence. The tail possesses a knobbed structure which is inserted into the head of the intact phage and to which the DNA appears to be attached. The method of dissociating TP84 described in this paper provides a source of undamaged structural components and intact strands of DNA for subsequent investigations. A possible mechanism of chelate inactivation is discussed.

Acetates↗
PubMedDate not supplied

[Inclusion compounds of collagen (author's transl)].

Small angle X-ray diagrams of collagen of rat tail treated with phospho tungstic acid or mercury chloride or cobalt- and uranyl-nitrate, osmiumoxide or hydroxy apatite show the same characteristic new reflections and reflection lines. The only remarkable difference exists between fibers treated under stress or relaxed. These experiments give new evidence for the paracrystallinity of collagen. More than 100 parallel aligned ca. 40 A thick octafibrils consist of 670 A long microparacrystals with 5 ca. 25 A thick soft segment layers. In these soft segments the holes of the octafibrils build up a lattice of vacancies with lattice cells of 38,5 x 35 x 135 A3 length. The above mentioned molecules penetrate from the lateral sides through the soft segments into these vacancies building up complexes with peptide groups of collagen. Under stress only a small amount of vacancies is occupied, statistically distributed over the vacancy-lattice, because the soft segments of the octafibrils are constricted. Without stress about 10 to 25% of the octafibrils within one paracrystal are filled up with sediments in the soft regions. With increasing precipitation finally 500 A long needles are formed of the inclusive material as detected by Höhling with the electron microscope in collagen of turkey tendon. The importance of the paracrystalline collagen model is emphasized to understand the biological process like the mineralisation of collagen and beta-keratin in organism or the activity of bone apatite in exchanging calcium ions.

Amino Acid Sequence↗
PubMed1986

Ultrastructural location of complex carbohydrates in developing rat incisor enamel.

The ultrastructural distribution of complex carbohydrates in an early formation stage of rat incisor enamel was investigated by staining with the periodic acid-thiocarbohydrazide-silver proteinate reaction (PA-TCH-SP) for vicinal glycol-containing glycoconjugates, the phosphotungstic acid-chromic acid mixture (PTA) for glycoproteins, and the cationic dyes alcian blue or bismuth nitrate for sulfated glycoconjugates. In order to remove selectively sulfated complex carbohydrates, half of the serial sections obtained were digested with a bovine testicular hyaluronidase prior to staining. Far fewer electron-dense deposits were observed with the PA-TCH-SP method on hyaluronidase-treated sections, especially those subsequently treated for 48 hours with TCH. On the other hand, the minimal staining obtained with PTA was much more intense on sections treated with hyaluronidase where linear fiberlike structures were observed. With cationic dyes, staining of dotlike alignment structures and ground substance was obtained but was completely abolished by hyaluronidase treatment. Cuprolinic blue in a critical electrolyte concentration, ruthenium hexamine trichloride used with aldehyde during fixation, as well as rapid-freezing followed by freeze-substitution validate that this dotlike distribution is not an artefact of processing. The staining results demonstrated that the glycoproteins and sulfated complex carbohydrates in developing rat incisor enamel each display a specific distribution pattern. The glycoproteins were present as fiberlike structures and the sulfated carbohydrates appeared as dotlike formations located close to the surface of the fiberlike structures, and/or in the spaces between them.

Animals↗
PubMed1992

Human cytomegalovirus nuclear and cytoplasmic dense bodies.

One of the characteristic features of cytomegalovirus (CMV) replication is the formation of cytoplasmic dense bodies. Recent findings revealed similar structures also in the nuclei of CMV-infected cells. By transmission electron microscopy, immuno electronmicroscopy, and cytochemistry, we have studied the morphogenetic steps and macromolecular composition of both structures. Our results show that both structures contain DNA, RNA and viral antigenic proteins. Nuclear dense bodies are probably an expression of a stimulated cellular metabolism, while cytoplasmic dense bodies may represent the site where surplus cellular and viral molecules are stored before being eliminated.

Cell Nucleus↗
PubMed1974

Replication of measles virus: distinct species of short nucleocapsids in cytoplasmic extracts of infected cells.

Cytoplasmic extracts of Vero cells infected with wild-strain Edmonston measles virus were found to contain two and probably three distinct species of nucleocapsids. Species sedimenting at 200 and 110S contained RNA which sedimented at 50 and 16 to 18S, respectively. The third nucleocapsid species which sedimented at 170S was not present in all experiments and was not characterized in detail. Essentially all 200 and 170S, as well as a portion of the 110S, nucleocapsids were membrane associated and probably present in part in cell-associated virions. Five of six plaque purified strains derived from wild-type Edmonston virus produced only 200S nucleocapsids. One of these five plaque-purified strains subsequently produced both 200 and 110S nucleocapsids after being passaged by using undiluted inocula. These results suggest that measles virus may produce distinct classes of defective virus containing short nucleocapsids and subgenomic viral RNA.

Animals↗
PubMed1976

New types of islet cells in a cyclostome, Petromyzon marinus L.

Four types of acidophilic granular cells, in addition to B-cells, are identified in the islet organ of anadromous specimens of two subspecies of Petromyzon marinus by light and electron microscopy. Three of these acidophils (PI, PII and PIV-cells) occur in both the cranial and hepatic islets while a fourth type (PIII-cell) has only been found in the hepatic islet of some animals. The granules of the PI-cells stain with ponceau de xylidine, give a distinct tryptophan reaction and in ultrastructural examination show large, dense granules. The PII-cells contain unusual crystals and appear to be a non-secretory stage of the PI. The PIII-cells stain deep-red and acid fuchsin. They contain very large, dense granules and some lysosomes. PIV-cells stain selectively with phosphotungstic acid-hematoxylin and ultrastructurally, contain small, more or less dense granules. It appears that PI- and PIV-cells develop directly from B-cells, while the PIII-cells derive from PI-cells. despite their direct or indirect origin from B-cells, the PI-, PIII- and PIV-cells show characteristic features of functionally independent endocrine cells. Petromyzon marinus may be an ideal model for the understanding of phylogenetic and pathological interrelationships between islet and gastrointestinal hormones. It is clear that the interpretation of the islet organ of the cyclostomes, which has been generally considered a source of insulin only, requires a revaluation.

Animals↗
PubMed1989

A newly modified isolation method of single muscle fibers--especially useful in histological, histochemical and electron microscopic studies on branched fibers.

The nitric acid muscle fiber digestion method has generally been used to determine total numbers of muscle fibers and branched fibers. However, it is not suitable for further studies because nitric acid causes protein denaturation known as the xanthoproteic reaction which make it difficult to examine the fiber types and morphology of muscle fibers. Therefore, we attempted to modify this method to preserve the morphology of muscle fibers as much as possible. Our modifications were as follows: (1) samples were immersed in ion exchanged water before nitroc acid treatment; (2) mammalian relaxing solution was used as the post- incubation solution; (3) the temperature of nitric acid was maintained at 4 degrees C; and (4) the nitric acid concentration was reduced to 10% from 15%. The samples obtained by this method were stained with phosphotungstic acid-hematoxylin and their striations were examined by a differential interference contrast method using light microscopy. The cell organella i.e. actin filaments, myosin filaments, T-tubules and mitochondria, were also examined electron microscopy. Actin and myosin filaments in these samples were also stained immunohistochemically to clarify the preservation of antigenicity. As a result, this modified method made it possible to examine actin and myosin filaments of a single muscle fiber light-microscopically and immunohistochemically and also to examine cell organella of a single muscle by electron microscopy. These results indicate that our method is useful for studies on branched muscle fibers such as stereological analysis and innervation of a single branched muscle fiber, in addition to obtaining muscle fiber numbers.

Actins↗
PubMed1971

Dissociation and reassembly of Escherichia coli outer membrane and of lipopolysaccharide, and their reassembly onto flagellar basal bodies.

Purified lipopolysaccharide vesicles dissociate when treated with ethylenediaminetetraacetic acid (EDTA) and then reassemble when dialyzed against Mg(2+). Purified outer, lipopolysaccharide membrane (L membrane) is partially dissociated by treatment with EDTA and fully dissociated upon further treatment with Triton X-100. Both the partially and fully dissociated L membrane can be reassembled by dialysis against Mg(2+). Reassembly of lipopolysaccharide or L membrane in the presence of intact flagella results in specific attachment of flagellar basal bodies to vesicles via the L and sometimes the M ring. Lipopolysaccharide and L membrane appear to be composed of substructures bound together by both Mg(2+) (divalent cation)-mediated and hydrophobic bonds.

Bacterial Proteins↗