ABSTRACT
A major determinant of tooth architecture is the arrangement of lines in dentin and in the enamel following the contour of the surface. Since the original description of these lines in the 19th century, they have been attributed to recurring events during tooth development. They have also attracted the attention of dental scientists and anthropologists; however, to date, studies of these structures have been largely theoretical and microscopic. We show here that the statistical properties of the spacing between the lines are similar in teeth from both ancient and modern humans and from extinct archosaurs, reptiles that lived tens or hundreds of millions of years ago-they also resemble heart rate variability of living humans. We propose that the deposition of these recurring structures is controlled by the autonomic nervous system. This control accounts for their regularity and recurrent nature and implies that the lines are an expression of a biologic rhythm which has been conserved throughout evolution. Details of the rhythms give clues to life styles in ancient civilizations and to the physiology of extinct archosaurs.
Subject(s)
Autonomic Nervous System/physiology , Models, Biological , Odontogenesis/physiology , Tooth/growth & development , Animals , Heart Rate/physiology , History, Ancient , Humans , Paleodontology/methods , Reptiles , Statistics, NonparametricABSTRACT
Verofylline, a long-acting polysubstituted methylxanthine bronchodilator, was taken orally by eight adult patients with asthma in a double-blind, crossover tolerance study. Peak expiratory flow, forced vital capacity, and its subdivisions were measured weekly 2, 4, and 6 hr after oral dosing with drug or placebo. Peak drug activity developed between 4 and 6 hr after dosing. Subject tolerance was good at the doses used. Dose-response curves for mean forced expiratory volume in one second, peak expiratory flow rate, and forced expiratory flow at the end of 4 hr were greater after 0.05 mg/kg verofylline than after placebo or higher doses of verofylline. Mean percent change in forced vital capacity remained increased as long as 6 hr after 0.15 mg/kg active drug. Verofylline was not very effective as a bronchodilator at the doses used.
Subject(s)
Asthma/drug therapy , Bronchodilator Agents/therapeutic use , Theophylline/analogs & derivatives , Administration, Oral , Adult , Bronchi/drug effects , Bronchodilator Agents/pharmacology , Clinical Trials as Topic , Double-Blind Method , Drug Evaluation , Female , Humans , Male , Maximal Expiratory Flow Rate , Maximal Midexpiratory Flow Rate , Middle Aged , Peak Expiratory Flow Rate , Spirometry , Theophylline/therapeutic use , Vital CapacityABSTRACT
For the first time in almost 30 years, new Middle Paleocene primate specimens have been discovered in the San Juan Basin, New Mexico. They are from the 'Pantolambda zone' in the type area, Arroyo Torrejon, and are referable to Palaechthon woodi and Torrejonia wilsoni. The only other known association of these two species is in the Shotgun Local Fauna from Wyoming.
