Enzymatic modifications of human plasma fibronectin in relation to opsonizing activity

Plasma fibronectin is one of the largest plasma proteins (Mr approximately 440 000), comprising two approximately equal polypeptide chains which are held together by a disulfide linkage near the C-terminal end of the molecule. The binding of gelatinized latex beads to liver slices as well as the internalization of these particles by macrophages, in the presence of heparin, is greatly enhanced by fibronectin. The question as to whether the entire covalent structure of fibronectin was necessary for opsonizing activity was approached by limited proteolytic degradations of the molecule. Patterns of controlled digestion with trypsin, cathepsin D, Staphylococcus aureus protease, and plasmin all indicate that the minimal unit necessary for retention of opsonic activity is some large (Mr 200 000 and 190 000) single-chain entity. Treatment with plasmin proved to be the most reliable procedure for generating the active split product which could be readily separated from the inactive, disulfide-containing C-terminal fragment. Incorporation of dansylcadaverine into plasma fibronectin (3.5 mol/mol of protein) by fibronoligase (coagulation factor XIIIa) did not affect the opsonic activity of the protein.     

Reversible hyperphosphorylation and reorganization of vimentin intermediate filaments by okadaic acid in 9L rat brain tumor cells.

Okadaic acid (OA), a protein phosphatase inhibitor, was found to induce hyperphosphorylation and reorganization of vimentin intermediate filaments in 9L rat brain tumor cells. The process was dose dependent. Vimentin phosphorylation was initially enhanced by 400 nM OA in 30 min and reached maximal level (about 26-fold) when cells were treated with 400 nM OA for 90 min. Upon removal of OA, dephosphorylation of the hyperphosphorylated vimentin was observed and the levels of phosphorylation returned to that of the controls after the cells recovered under normal growing conditions for 11 h. The phosphorylation and dephosphorylation of vimentin induced by OA concomitantly resulted in reversible reorganization of vimentin filaments and alteration of cell morphology. Cells rounded up as they were entering mitosis in the presence of OA and returned to normal appearance after 11 h of recovery. Immuno-staining with anti-vimentin antibody revealed that vimentin filaments were disassembled and clustered around the nucleus when the cells were treated with OA but subsequently returned to the filamentous states when OA was removed. Two-dimensional electrophoresis analysis further revealed that hyperphosphorylation of vimentin generated at least seven isoforms having different isoelectric points. Furthermore, the enhanced vimentin phosphorylation was accompanied by changes in the detergent-solubility of the protein. In untreated cells, the detergent-soluble and -insoluble vimentins were of equal amounts but the solubility could be increased when vimentins were hyperphosphorylated in the presence of OA. Taken together, the results indicated that OA could be involved in reversible hyperphosphorylation and reorganization of vimentin intermediate filaments, which may play an important role in the structure-function regulation of cytoskeleton in the cell.     

In vitro metabolism or testosterone by breast microcysts

Breast microcysts are considered to be a normal findings in the adult female breast without any increased risk of developing carcinomatous change. Breast cysts fluid contains steroid but not studies have been reported on the ability of breast microcysts to metabolise steroid hormones. It was, therefore, the aim of this study to identify the metabolites formed on incubation of radiolabelled testosterone with microcysts. In all instances dihydrotestosterone and androstenedione were formed. Oestrogens were not identified. Tis study, therefore, provides evidence for th presence of 5-alpha-reductase and 17-oxidoreductase enzyme systems in breast microcysts.     

Fetal-maternal transfer of [H3]-6 beta-hydroxycortisol in the pregnant ewe

Distribution and fetomaternal transfer of 6 beta-hydroxycortisol (6 beta-OHF) was studied using serial sampling following injection of tritium labelled 6 beta-OHF into various fluid compartments in the chronically cannulated unaesthesized pregnant ewe. There was a rapid transfer of 6 beta-OHF from the fetal circulation into amniotic fluid and maternal blood. In contrast, the maternal----fetal transfer of this steroid metabolite was considerably less. The sequence of appearance of 6 beta-OHF in fetal blood and amniotic fluid following injection into maternal blood suggests that this steroid is first transferred across the placenta to fetal blood before gaining entry into the amniotic fluid space. The half-lives of 6 beta-OHF after initial equilibration in maternal plasma, fetal plasma and amniotic fluid were 2.0 h, 5.1 h and 8.9 h respectively. The amniotic sac appears to contain a relatively static pool of 6 beta-OHF and may act as a "trap" for 6 beta-OHF in the ovine conceptus.     

Hypotensive and vasodilatory activity of (+/-) 1-o-octadecyl-2-acetyl glyceryl-3-phosphorylcholine in the normotensive rat

Synthetic (+/-) 1-O-octadecyl-2-acetyl-glyceryl-3-phosphorylcholine (octadecyl-AGPC) in microgram/kg doses given intravenously effectively and potently lowered mean arterial blood pressure in conscious and anesthetized normotensive rats. The hypotensive activity was much more pronounced in the anesthetized rat than in the conscious rat. The hypotension was associated with a significant elevation in plasma renin activity (PRA). In the rat in which the hindquarters were perfused, octadecyl-AGPC given intraarterially effectively decreased the perfusion and systemic pressures in a dose-dependent manner. Pharmacological blockade with specific cholinergic, histaminergic or beta-adrenergic receptor antagonists, did not block or attenuate the octadecyl-AGPC-induced reduction in perfusion or systemic pressure. These results suggest that the hypotensive activity of octadecyl-AGPC in the normotensive rat is the result of direct vasodilation and not the result of cholinergic, histaminergic or beta-adrenergic receptor interaction.     

Adherence Patterns and DNA Probe Types of Escherichia coli Isolated from Diarrheal Patients in China

One hundred and seventy-two strains of Escherichia coli isolated from diarrheal patients in Beijing, P. R. China, were analyzed for plasmid DNA profile, HEp-2 cell adherence ability and reactivity to 10 previously described DNA probes. They had not been recognized as pathogenic E. coli in China. Of the 110 strains tested, 76 (69%) contained one or multiple large plasmids. Of the 71 strains with the large plasmids 64 could adhere to HEp-2 cells. Of the 172 strains, 102 (59.3%) were hybridized with at least one of the 10 probes. Of those, seven strains hybridized with enteroaggregative E. coli (EAggEC) probe. Their serotypes were O128 (two strains), O6 (one strain), and O111 (one strain). Three strains were untypable. Six and three strains were hybridized with enteropathogenic E. coli (EPEC) attaching and effacing genes (eae) or EPEC adherence factor (EAF) probe, respectively. Two non-O157: H7 strains hybridized with enterohemorrhagic E. coli (EHEC) probe. Seventy-two strains (41.9%) hybridized with shiga-like toxin 2 or 1 (SLT2 or SLT1) probes. Among the SLT1 or SLT2 probe-positive strains, 54 hybridized with invasive (INV) plasmid probe developed for identification of enteroinvasive E. coli (EIEC) and Shigella species. The INV and SLT probe-positive strains might represent a new variety of verotoxin-producing E. coli (VTEC).     

Morphometric Analysis of Hepatocellular carcinoma

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An analysis of the unconfined compression of articular cartilage

Analytical solutions have been obtained for the internal deformation and fluid-flow fields and the externally observable creep, stress relaxation, and constant strain-rate behaviors which occur during the unconfined compression of a cylindrical specimen of a fluid-filled, porous, elastic solid, such as articular cartilage, between smooth, impermeable plates. Instantaneously, the "biphasic" continuum deforms without change in volume and behaves like an incompressible elastic solid of the same shear modulus. Radial fluid flow then allows the internal fluid pressure to equilibrate with the external environment. The equilibrium response is controlled by the Young's modulus and Poisson's ratio of the solid matrix.