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At least 865 records · Page 48Linked to original sources
PubMed1994

Correlations between amino acid hydrophobicity scales and stain exclusion capacity of type 1 collagen fibrils.

The relationship between the negative staining band pattern of type 1 native collagen fibrils and the amino acid distribution along the fibril axis was studied by comparing averaged microdensitograms with theoretical traces calculated on the basis of different amino acid parameters. As well as the spatial parameter "bulkiness" (volume/length, ratio), various literature-reported scales of "hydrophobicity" were tested. Two "hydrophobicity" sets allowed a better fit with the actual patterns than "bulkiness" values. However, a general improvement in simulations was achieved by associating most "hydrophobicity" sets with the "bulkiness" set. These results suggest that amino acid "hydrophobicity" plays a key role in the appearance of negative staining patterns but a composite mechanism would seem to occur: the accessibility of available intermolecular interstices may be conditioned by molecular hindrance, corresponding to amino acid "bulkiness" as well as by water-repulsion effect, which correlates with amino acid "hydrophobicity." Moreover, a detailed comparison of actual and simulated patterns suggests that a modulation exists in the effectiveness of these two factors along each D-period according to the different molecular packing and concentration of hydrophobic amino acid clusters within overlap regions and gap regions, respectively.

Amino Acids↗
PubMed1990

Effects of PGE2, carbenoxolone, cholecystokinin, and the thromboxane-mimetic U46619 on protein and glycoprotein production by isolated pig gastric mucosal cells.

We studied the effects of prostaglandin (PG) E2, carbenoxolone, cholecystokinin-octapeptide (CCK-OP), and the thromboxane-mimetic U46619, all known to stimulate gastric mucus secretion in vivo, on protein and glycoprotein synthesis in and release from isolated and enriched pig gastric mucous cells, as measured by the incorporation of [3H]L-leucine and N-acetyl-[14C]D-glucosamine respectively into cellular and released acid insoluble material. PGE2 stimulated glycoprotein and protein synthesis (EC50 7 and 30 nmol/L, respectively) and release (EC50 50 and 140 nmol/L, respectively) in a concentration-dependent manner, whereas carbenoxolone, CCK-OP and U46619 failed to enhance the incorporation of the tracers. We conclude that stimulation of mucus secretion by PGE2 is related to direct effects on protein and glycoprotein production of gastric non-parietal cells, whereas indirect effects may be involved in the stimulation by carbenoxolone, CCK-OP, and U46619.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed2007

Lipolysis in cheddar cheese made from raw, thermized, and pasteurized milks.

The evolution of free fatty acids (FFA) was monitored over 168 d of ripening in Cheddar cheeses manufactured from good quality raw milk (RM), thermized milk (TM; 65 degrees C x 15 s), and pasteurized milk (PM; 72 degrees C x 15 s). Heat treatment of the milk reduced the level and diversity of raw milk microflora and extensively or wholly inactivated lipoprotein lipase (LPL) activity. Indigenous milk enzymes or proteases from RM microflora influenced secondary proteolysis in TM and RM cheeses. Differences in FFA in the RM, TM, and PM influenced the levels of FFA in the subsequent cheeses at 1 d, despite significant losses of FFA to the whey during manufacture. Starter esterases appear to be the main contributors of lipolysis in all cheeses, with LPL contributing during production and ripening in RM and, to a lesser extent, in TM cheeses. Indigenous milk microflora and nonstarter lactic acid bacteria appear to have a minor contribution to lipolysis particularly in PM cheeses. Lipolytic activity of starter esterases, LPL, and indigenous raw milk microflora appeared to be limited by substrate accessibility or environmental conditions over ripening.

Animals↗
PubMed2004

Multifocal rhabdomyosarcomas within the tongue and oral cavity of a dog.

A 10-year-old terrier crossbreed presented with a change in bark intonation of 3-4 month's duration and pronounced panting. Four variably sized masses were observed within the oral cavity. The largest mass was located within the parenchyma at the caudal region of the tongue. Others were located on the left arytenoid, within the soft palate, and in the oropharynx above the soft palate. Histopathologic specimens consisted of large round to polygonal cells occasionally containing multiple nuclei and rare faint cytoplasmic cross striations. Staining was weakly positive with periodic acid-Schiff. Immunocytochemistry was strongly diffusely positive for muscle-specific actin, myoglobin, and desmin and scattered positive for S-100 and vimentin. Phosphotungstic acid-hematoxylin staining enhanced cytoplasmic cross striations. The cytoplasm of all neoplastic cells was filled with mitochondria on electron microscopy. The final diagnosis was multifocal/metastatic rhabdomyosarcoma.

Animals↗
PubMed1997

Morphology and histochemistry of human hair.

This chapter is concerned with the structure of the mature human hair shaft and the chemical composition of its subcomponents as adduced from the examination of fibres mainly with the conventional transmission electron microscope (TEM). The broad outlines of the techniques used in the study of hair are reviewed, with particular attention being paid to the processes of chemical staining which enable one to define various aspects of the chemical composition of the hair's microscopic sub-components. Against this background the internal structure of normal undamaged hair is described.

Carboxylic Acids↗
PubMed1971

Helical nucleocapsid structure of the oncogenic ribonucleic acid viruses (oncornaviruses).

Negative staining of virions and isolated nucleoids from avian myeloblastosis virus, murine leukemia virus, murine mammary tumor virus, and feline leukemia virus reveals common internal structures. The majority of virions that are penetrated by phosphotungstate show spherical nucleoids with no apparent symmetry. In a small percentage of virions, two distinctive structures are found: (i) single strands (3 to 5 nm in diameter) which are presumed to be the nucleoprotein and are found randomly oriented throughout the viral interior and (ii) helical structures (7 to 9 nm in diameter) which contain these nucleoprotein strands and are observed at the periphery of the nucleoid. The finding of helical nucleocapsid segments at the periphery of the nucleoid, as well as the hollow spherical structure observed in thin section of budding virions, has led to the hypothesis that the nucleocapsid of the freshly budded oncornavirus is supercoiled as a hollow sphere. This symmetry, however, is considered transient, as the internal structure of the extracellular virus undergoes a conformational rearrangement; thus, due to structural instability, the nucleocapsid uncoils and the nucleoprotein strands fill the interior of the virion. The extracellular virion is therefore considered degenerate in respect to symmetry, explaining the difficulty in detecting a helical nucleocapsid.

Avian Leukosis Virus↗
PubMed1984

Arginine-rich proteins in spherical inclusions of human locus coeruleus neurons demonstrated by benzil modification.

Previous studies have shown that aminergic neurons in the normal human brain contain acidophilic cytoplasmic inclusions--called protein bodies (PBs)--that are reduced or absent in parkinsonism and disrupted in depression. The purpose of the present study was to elucidate the constitution of PBs in five formalin-fixed normal human brains using histochemical methods specific for histones, protamines, and the amino acid arginine. PBs were revealed with alkaline fast green and bromphenol blue, exhibiting a high content in histones and in protamines. They developed blue metachromasia with phosphotungstic acid-hematoxylin and green fluorescence with phenanthrenequinone, which established the presence of arginyl residues. Using benzil, which selectively modifies the guanido group of arginine, staining was blocked for each of the above two methods. The application of Mallory's trichrome procedure after benzil differentiated the PBs into an unstained core and a still fuchsinophilic rim. Since the fuchsinophilia of the rim was shown to persist after acetylation as well, we suggest that this rim probably contains acidic macromolecules that attach to the basic charges of the amphoteric acid fuchsin. We conclude that the PB are complex structures consisting of a core segregating arginine-rich proteins and a rim which probably contains macromolecules of an acidic nature.

Aldehydes↗