Measurement of gingival crevicular fluid conductivity, in vivo.

It has been shown that the ionic concentration of gingival crevicular fluid (GCF) rises with increases in the inflammation of the surrounding tissue. Because measurement of this increase might be useful for clinical assessment of periodontal status and because the sampling of this fluid is difficult in the typical clinical environment, attempts were made to measure the conductivity of GCF in vivo using a fabricated conductivity probe. Preliminary results suggest that statistically significant correlations may exist between certain clinical indices and GCF conductivity. A correlation could be shown when comparing the Gingival Index and the measured conductivity of GCF, but the correlation may be too low to be of biologic relevance, possibly due to the use of pooled samples. The use of an ion-specific probe and the study of site-specific periodontal lesions are suggested to develop more definitive data than this pilot study provided.

Factors affecting the exchange of apoproteins between human high density lipoprotein subclasses in vitro.

We have presented evidence that apoproteins may exchange, in vitro, between all HDL subclasses tested, including HDL2b, HDL2a, HDL3, and HDL4. This exchange process is influenced by various factors including the concentrations of the subclasses and the presence of added apoprotein. This exchange process should be considered when designing experiments using HDL subclasses in vitro, and the importance of exchange in the in vivo situation should be a subject of further investigation.

Influence of physicochemical parameters on adsorption of Actinomyces viscosus to hydroxyapatite surfaces.

Adsorption of Actinomyces viscosus strains T14V and T14AV to saliva-treated and untreated hydroxyapatite (HA) under various environmental conditions was studied. Strain T14V adsorption to saliva-treated HA was not influenced by pH, whereas strain T14AV adsorbed in higher numbers under acidic conditions. The addition of cations inhibited adsorption of strains T14V and T14AV to saliva-treated HA. Strain T14V possessed a greater affinity for hydrophobic gels than did strain T14AV, but incorporation of non-ionic detergents, which inhibit hydrophobic interactions, did not influence adsorption of strain T14V to saliva-treated HA. Adsorption of strain T14V to saliva-treated HA increased in the presence of an anionic detergent; however, strain T14AV adsorption was not affected. Strain T14V adsorption decreased in the presence of a cationic detergent, whereas strain T14AV adsorption increased. Collectively, these data suggest that electrostatic interactions, but not hydrophobic interactions, are of major importance in the adsorption of strain T14V to saliva-treated HA.

Interchange of apoprotein components between the human plasma high density lipoprotein subclasses HDL2 and HDL3 in vitro.

The major apoproteins of human high density lipoproteins (HDL) labeled with 125I have been shown to exchange between the two major HDL subclasses HDL2 and HDL3 in vitro. This bidirectional exchange process is inhibited by cross-linking with bifunctional reagents and is apparently dependent upon the formation of collision complexes. This exchange has been demonstrated both when the subclasses of HDL are free in solution and also when one of them is covalently bound to Sepharose. Using system involving Sepharose-bound HDL, it could be shown that not only free apoprotein molecules but subunits consisting of lipid-apoprotein combinations were exchanged between HDL2 and HDL3. The rate of exchange in these processes is significant in the lifetime of the protein particles in vivo equalling approximately 2.5% per h for apoprotein exchange. These experiments suggest that there is a dynamic relationship between HDL2 and HDL3 even though each of them exists alone in vitro as stable separate entities; when they are placed together in solution significant interaction occurs between the particles. Apoprotein exchange occurs between HDL2:HDL2 and HDL3:HDL3 as well as between HDL2 and HDL3 molecules. These data also suggest that the interconversion of HDL2 and HDL3 may be affected by the availability of lipids.

Turbidimetric method for the assay of antiviral antibodies.

A rapid, simple assay method has been developed for antiviral antibodies. The technique has been applied to antisera, immune gamma-globulins, and immunospecifically purified antibody for two strains of influenza virus, Asian 305 and PR8, and to antisera to tobacco mosaic virus. Turbidity changes due to the specific interaction of a virus with its antibody were measured by the increase in optical density in a sensitive wavelength region, e.g., 436 nm. Successful application of the method required that nonspecific effects which give rise to turbidity changes be eliminated. This was accomplished by proper choice of ionic strength (0.3 m) and pH (5.5), and by the addition of normal serum or serum albumin to the virus before contact with the antibody. Sensitivity of the method allowed quantitation of antibody down to the level of 10 mug of antibody protein per ml. The specificity of the reaction causing the turbidity change was established by experiments which showed that precipitation of virus-antibody complexes removed the reactive component in the serum, and by the absence of turbidity changes for nonspecific pairs (virus plus unrelated antisera).