Taurodontism: A biometric study

This study has been carried out in order to clarify various aspects of the phenomenon known as taurodontism. Samples of both taurodont and non-taurodont teeth were measured and statistical analyses were performed on the resultant data from which various conclusions may be drawn. The most important conclusion is that this phenomenon may be defined metrically. The distributions have shown that the taurodont trait grades into the normal and it is quite difficult to make a subjective judgment at the low end of the taurodont range. It is for this reason that an accurate mathematical means for performing this task is so invaluable. The question of the nature of cuneiform single rooted molars was also investigated, and they were found not to be true taurodonts although the statistical procedure classed them as such. It was demonstrated that through the construction of simple plots these teeth could be eliminated from any group classed by analysis as taurodonts. Various metrical attributes were evaluated with respect to their ability to distinguish taurodonts, and two were found to be satisfactory for this purpose in most cases. Certain changes in molar morphology regarding caries and age were also investigated.     

Differential irreversible insertion of protein kinase C into phospholipid vesicles by phorbol esters and related activators.

Incubation of protein kinase C (PKC) alpha with phorbol 12,13-dibutyrate and phospholipid vesicles promoted a time-dependent irreversible insertion of the enzyme into the vesicles and the generation of a calcium-independent kinase activity. Calcium neither caused insertion nor influenced the insertion induced by the phorbol ester. The effect was strongly dependent on the phosphatidylserine concentration in the vesicle and could also be supported by other anionic phospholipids. An analysis of the structure-activity relations of PKC activators for the calcium-independent kinase activity revealed marked relative differences in potencies for binding and for insertion. Compounds such as phorbol 13-myristate 12-acetate and mezerein were very efficient at inducing insertion. In contrast, 12-deoxyphorbol esters and diacylglycerol were relatively inefficient at inducing insertion, requiring higher concentrations than expected from their binding affinities. The insertion of PKC alpha depended substantially on the length of the aliphatic esters in the 12- and 13-positions of the phorbol derivatives, and once again, potencies for insertion and binding were not directly proportional. Our findings suggest two different sites for ligand interaction on the molecule of PKC alpha with different structure-activity requirements. We speculate that the differential ability of compounds to promote insertion could contribute to the documented marked differences in the biological behavior of PKC activators.     

Comparison of subcellular activation of the human neutrophil NADPH-oxidase by arachidonic acid, sodium dodecyl sulfate (SDS), and phorbol myristate acetate (PMA)

The phorbol myristate acetate (PMA) stimulation of the human neutrophil NADPH-oxidase has been demonstrated through the activation of protein kinase C (PK-C), using light membrane fractions from nitrogen-cavitated cells. Both arachidonic acid (AA) and sodium dodecyl sulfate (SDS) can also generate an active oxidase in cellfree systems. That the source of O2- with AA and SDS activation is the same NADPH-oxidase as previously studied was confirmed by the similar pH optima and Km values for NADPH as those previously described for the O2- -generating activity harvested from pre-stimulated human neutrophils. In contrast to the stimulation by PMA, however, the stimulation of the NADPH-oxidase by AA and SDS does not appear to require protein kinase C activation: the action of AA and SDS is independent of the addition of PK-C cofactors to the system, and the inhibitor of PK-C activity, H-7, had no effect on the stimulation by AA or SDS. AA and SDS activation are comparable, but the level of NADPH-oxidase expression is sixfold greater with each of these agents than that obtained with a reconstituted PK-C system. The basis of this difference in oxidase expression is unclear, but these findings suggest strongly that although activated PK-C is capable of stimulating a dormant NADPH-oxidase in a cellfree system, this is not the sole pathway for oxidase activation.     

Investigation of neutral endopeptidases (EC 3.4.24.11) and of neutral proteinases (EC 3.4.24.4) using a new sensitive two-stage enzymatic reaction

A sensitive two-stage enzymatic reaction for mammalian and bacterial metalloendopeptidases has been developed using the substrate 3-carboxypropanoyl-alanyl-alanyl-leucine-4-nitroanilide supplemented with Streptomyces griseus amino-peptidase. Neutral endopeptidase EC 3.4.24.11 from bovine kidney hydrolyzes the substrate (pH 7.5, 25 degrees C) with a catalytic efficiency (kcat = 1.2 x 10(2) s-1, Km = 0.15 mM) of the highest ever reported for the enzyme acting on synthetic chromophoric and fluorogenic substrates. Thermolysin hydrolyzes the substrate at a faster rate (kcat = 1.2 x 10(3) s-1) but the overall efficiency is diminished by a higher Km (4.2 mM). Suspensions of human neutrophil cells and culture filtrates of Bacillus cereus have been assayed sensitively for their neutral endopeptidases and neutral proteinase activities, respectively. The assay provides a convenient tool for the kinetic investigation of neutral endopeptidases and neutral proteinases and for assessing their function in biological systems.