The relationship between smoking and periodontal disease. Review of literature and case report.

Cigarette smoking has been associated with tooth loss from periodontal disease for a long time. Smoking cessation has been shown to reverse these effects. The purpose of this paper is to review the current literature regarding the possible mechanisms for destruction of the periodontium caused by smoking and to present a protocol for the implementation of a smoking cessation program at New York University College of Dentistry.

A unifying physically meaningful relativistic action.

The motion of an object under the influence of force fields and/or media is described by means of a world-line with least action in its influenced spacetime. For any spacetime point x and a four-vector u, measured in the frame of an inertial observer, a unifying and physically meaningful action function L(x, u) generating the action is defined. To ensure independence of the observer and of the parametrization on the world-line, L(x, u) must be Lorentz invariant and positive homogeneous of order 1 in u. The simplest such L(x, u) depends on two four-potentials. In most cases, these potentials can be defined directly from the sources of the fields without the need for field equations. The unified dynamics equation resulting from this action, properly describes the motion in any electromagnetic field, in any static gravitational field, in a combined electromagnetic and gravitational field, as well as the propagation of light and charges in isotropic media.

VTA dopamine neuron bursting is altered in an animal model of depression and corrected by desipramine.

Ventral tegmental area (VTA) neuronal activity plays an important role in reward-related learning and motivation. Tracing the bursting signal is important for understanding neural state and understanding communication between individual neurons. The dopaminergic system, which projects from the VTA to other regions in the mesolimbic system, is involved in hedonia and motivation. However, the role of this system in the pathophysiology of depression and its manipulation for treatment of depression has received little attention. Inter-spike interval time series were recorded from the VTA of control Sprague-Dawley and Flinders sensitive line (FSL) rats with or without 14 days of desipramine (5 mg/kg) treatment. Comparison of the firing modes of control and desipramine-treated FSL rats reveals dissimilar patterns. Desipramine treatment normalized depressive-like behavior and elevated the dopaminergic mesolimbic activity, although not to control levels. Mesolimbic neuronal activity is known to occur either in burst or in single-spike firing mode. Herein, we suggest a third mode that is characterized as a "cluster" formed from burst and post-burst activity. A significant reduction in the activity of both bursts and cluster was detected in FSL rats, which was restored by desipramine treatment.

Decoding of dopaminergic mesolimbic activity and depressive behavior.

Dopaminergic mesolimbic and mesocortical systems are involved in hedonia and motivation, two core symptoms of depression. However, their role in the pathophysiology of depression and their manipulation to treat depression has received little attention. Previously, we showed decreased limbic dopamine (DA) neurotransmission in an animal model of depression, Flinder sensitive line (FSL) rats. Here we describe a high correlation between phase-space algorithm of bursting-like activity of DA cells in the ventral tegmental area (VTA) and efficiency of DA release in the accumbens. This bursting-like activity of VTA DA cells of FSL rats is characterized by a low dimension complexity. Treatment with the antidepressant desipramine affected both the dimension complexity of cell firing in the VTA and rate of DA release in the accumbens, as well as alleviating depressive-like behavior. Our findings indicate the potential usefulness of monitoring limbic dopaminergic dynamics in combination with non-linear analysis. Decoding the functionality of the dopaminergic system may help in development of future antidepressant drugs.

Relativistic acceleration of charged particles in uniform and mutually perpendicular electric and magnetic fields as viewed in the laboratory frame.

We obtain exact solutions in the laboratory frame for the relativistic position, velocity, and energy of a charged particle moving in constant, uniform, and mutually perpendicular electromagnetic fields. We also obtain an exact equation relating the proper time and the laboratory time, and examine all these quantities in the large and small time limits. Working in the laboratory frame makes the accelerated motion that can occur when /E/ > or = c/B/ easier to analyze and understand.