Pharmacogenetics of caffeine and caffeine-halothane contractures in biopsies of human skeletal muscle.

In vitro pharmacological responses of fresh biopsy specimens of human skeletal muscle were used as indicators of some intrinsic muscle properties. The measured parameters that were utilized for the current study were contractures induced in vitro by caffeine or by caffeine plus halothane. The opportunity to study such specimens arose from clinical testing for diagnosing the genetic predisposition to malignant hyperthermia, a potentially fatal complication of anaesthesia. The current analysis covers data from over 1,000 subjects, most of whom were clinical suspects and relatives of these. Responsiveness of the muscle specimens varied over two orders of magnitude. The frequency distribution curves suggest that the variation does not represent a continuum but that there are three or more clusters of functional variants. Muscle specimens from males were on average more responsive to caffeine than were those from females. Correlations within father-son and brother-brother pairs indicated complete heritability of responsiveness; this might have been expected but the surprise was a lack of correlation within mother-daughter pairs. There was an intermediate correlation in father-daughter pairs. The sex difference in heritability could be due to gender-related modifying genes or due to secondary modification of the muscle response in females by sex-related, perhaps hormonal factors. Among the effects of age appeared to be poor development in early childhood of the potentiation of the caffeine contracture by halothane.

The analysis of picomole amounts of L(+)- and D(-)-lactic acid in samples of dental plaque using bacterial luciferase.

L(+)-Lactic acid (5 pmol) and D(-)-lactic acid (20 pmol) were assayed by coupling the generation of NADH with the use of bacterial luciferase. The binding of NADH to L(+)-lactic dehydrogenase made it necessary to denature the protein so that the assay with bacterial luciferase was effective. The coupled luciferase assay of L(+)-lactic acid was 400 times more sensitive than the fluorometric assay. The luciferase coupled assay was used to analyze the L(+)- and D(-)-lactic acid contents of small samples of dental plaque.

Application of a competition model to the growth of Streptococcus mutans and Streptococcus sanguis in binary continuous culture.

Streptococcus mutans 6715-15 and Streptococcus sanguis 10558 were grown together in continuous culture with glucose as the limiting carbon source. The relationship of growth rate to substrate concentration was determined for pure cultures of each organism in continuous and batch cultures. A model based on competition for a growth-limiting substrate (glucose) was used to predict the proportions of each organism when grown in binary cultures. The results indicate that interactions other than competition for glucose carbon exist between S. mutans and S. sanguis grown under these conditions.