Paternal exposures and the question of birth defects.

Compared to maternal exposures, little attention has been paid to the possibility of paternally induced adverse effects on fetal development. There is increasing concern, however, about the potential for male-mediated developmental toxicity brought about by exposure to teratogenic agents. This is evidenced by the number of calls regarding paternal exposures that are received by teratogen information services. In this paper, we report the experience of the state of Florida's Teratogen Information Services regarding questions asked about paternal exposures, and briefly review what is known about the risk of paternal exposure to the 10 agents which are most frequently queried.

Analysis of repeated-measure multicycle unilateral mastication in children.

This study examined systematic and random errors associated with repeated-measure, multiple-cycle unilateral mastication in children during single recording sessions with the Replicator system. Twenty-six recording sessions with 17 children (10 boys, 7 girls) were examined. Nine of these children had a functional-shift unilateral crossbite malocclusion and were recorded before and after crossbite correction. Repeated recordings (trials) of mandibular movement during each session were made of right-side chewing of similar-sized pieces of cheese. The following variables were computed for each chewing cycle (stroke): time closed, maximum closure velocity, maximum opening velocity, chewing rate, vertical opening, and lateral deviation. From the multiple cycles of each trial, two pattern descriptors--the average and standard deviation--were determined for each variable. In addition, the mean and variance of these pattern descriptors were determined from the multiple trials of each recording session and were the dependent variables in a stepwise multiple regression analysis, with treatment status, sex, age, dentition stage, crossbite presence, and right side status the independent variables. The results disclosed bias in repeated measures of human chewing in response to adaptation to the recording session; this was evident in the average response but not in the variability of the measures. Sex and functional status of the subjects were associated with the mean and variance of measures describing the chewing pattern.

Internal derangement of the TMJ: changes associated with mandibular repositioning and orthodontic therapy.

Because of its apparent success in relieving symptoms, especially pain, anterior mandibular repositioning therapy is a popular mode of nonsurgical treatment for patients with painful, clicking internal derangement of the temporomandibular joint. Posterior open bites are a frequent consequence of such therapy and may necessitate either continued appliance wear or closure by equilibration, prosthetics, or orthodontics. The anatomic and functional changes that occur subsequent to mandibular repositioning during orthodontic closure of the posterior open bite are not well understood. A case of a patient with a Class II, deep bite malocclusion and painful internal derangement of the TMJ is presented. Transcranial and cephalometric radiographs, arthrograms, and mandibular movement recordings were obtained before treatment and after both repositioning therapy and orthodontic treatment. Regarding occlusal improvement and pain relief, the treatment was successful. However, not all of the changes that occurred during repositioning therapy were maintained after orthodontic treatment. The strategy used in this case (mandibular repositioning/orthodontic finishing) was evaluated by an examination of these anatomic and functional changes with a discussion centered on the possible mechanisms involved.

Evaluation of a three-dimensional reconstruction to compute left ventricular volume and mass.

This study tests the accuracy of a model to calculate left ventricular volume (LVV) and muscle volume (MV) when optimal data were used. These volumes were calculated using endocardial and epicardial borders traced from photos of cross sections of 20 animal (dog, goat and pig) hearts. A pyramid summation algorithm was used to perform a 3-dimensional (3-D) reconstruction based on 5 short-axis views, thus providing computer volume estimates. These were compared with the true (T) ventricular volumes determined by water filling of the cavity and the true MV based on weight. Because each heart was sliced in 5 planes, the appropriateness of the algorithm for MV could be tested for 6 regions. The pyramid summation algorithm consistently underestimated MV at the base and apex, but was accurate from the midmitral valve to the inferior papillary muscle region. Consequently, the total MV was computed as the midventricular MV, plus base and apex volumes computed from regression equations. Results showed that 3-D reconstruction resulted in a regression of LVVT = 1.02LVV3D + 10.30 ml with r = 0.987 for the chamber of MVT = 1.05 MV3D - 9.78 ml, with r = 0.967. It is concluded that the pyramid summation algorithm can accurately estimate volumes from spatially registered short-axis data with 95% prediction limits about the mean of the data of +/- 10 ml for left ventricular chamber volume and +/- 17.6 ml for MV.

Determination of ideal body weight for drug dosage calculations.

Formulas for ideal body weight (IBW) in men and women were derived from the Metropolitan Life Insurance Company height and weight tables. Regression determinations of median weight versus height were performed for men and women. A program for a minicomputer was developed to generate plots for small, medium, and large frame sizes and for subjects of all frame sizes. Equations for ideal body weight were derived from the resulting data. For men of all frame sizes, IBW = 51.65 kg + 1.85 kg/inch of height greater than 5 feet. For women of all frame sizes, IBW = 48.67 kg + 1.65 kg/inch of height greater than 5 feet. More accurate estimates of IBW by frame size can be obtained using equations derived from the plots for men and women of each frame size. Estimates of IBW obtained by the widely used empirical method probably contain only minor errors. However, formulas derived from actual height and weight data should be used in pharmacokinetic determination of dosage regimens for some drugs.

Prediction of theophylline dosage regimens from limited serum sampling.

Intravenous aminophylline was administered to 13 subjects (6 normal, 7 with chronic obstructive pulmonary disease), and multiple blood specimens were drawn over an 8-hour period for theophylline analysis. Half of the samples were obtained during the distribution phase of the drug and the remainder during the elimination phase. These data were entered into a computer program that both calculates and graphically displays individual two-compartment pharmacokinetic data, and recommends a dosing regimen. Analysis of these data demonstrates wide variability in the theophylline volume of distribution, half-life, and predicted dosage regimen. Dosage regimens can be individualized by obtaining two specimens for theophylline analysis during the elimination phase after intravenous administration of the drug; these regimens correlate extremely well (r2 = 0.95) with those designed using all the data points.

The instantaneous hinge axis - its reproducibility and use as an indicator for dysfunction.

This study investigated irregularities in hinge movement in 113 subjects. These irregularities were analyzed by computer with an instantaneous three-dimensional "screw axis method." The variation in hinge movement was measured by the dispersion of the hinge axis instant centers. Dispersion of instant centers was greater for muscle pain patients than for the normal, indicating that instant center data could make a contribution to diagnosis and treatment planning.

Computer-simulated conversion from intravenous to sustained-release oral theophylline.

A computer equipped with a pharmacokinetic program was used to theoretically determine the proper time to administer the first dose of a commonly prescribed, sustained-release oral theophylline product (Theo-Dur) in patients maintained on a continuous intravenous aminophylline infusion. Four conversion methods were tested. They included giving the first oral dose (1) immediately upon discontinuation of the iv infusion, (2) two hours after discontinuing the iv infusion, (3) four hours after discontinuing the iv infusion, and (4) two hours before discontinuing the iv infusion. Each of the four methods was simulated in three groups of patients: smokers, nonsmokers, and patients with cirrhosis. Results showed that, in most situations, given the first oral dose immediately upon discontinuation of the intravenous infusion provided minimal deviation from eventual steady-state levels. In addition, this computer simulation suggests that the initial 12-hour maintenance dose recommended by the FDA may result in toxicity in certain patient groups.