Evaluation of the quality of duplicated radiographs

This experiment evaluated the image quality of duplicated radiographs made at different ultraviolet light exposures. Image quality was measured in terms of "residual" film fog, film density, mottle, image contrast, and resolution. The "residual" fog density of duplicates decreased with increases in ultraviolet exposures until it was less than the fog density of the original. The density of duplicates decreased with increases in ultraviolet exposures until it leveled off at a certain density, depending on the density of the original film. Mottle was less on lighter duplicates than on darker duplicates. Contrast of duplicates increased initially with increases in ultraviolet exposures and later decreased with further increases in ultraviolet exposures. Resolution of duplicates was nearly the same as the original as long as the duplicate had acceptable "residual" fog density.

A comparison of attitudes and final grades among freshman dental students

A study was conducted to determine if a change in dental students' attitudes toward three preselected concepts would occur as a result of a traditionally difficult gross anatomy course. In addition, an attempt was made to determine the predictive value of a student's attitudes in determining his or her final grade. The study employed Campbell and Stanley's one group pretest-posttest design. The results indicated that students' attitudes toward a difficult course and themselves did not change significantly, but that a significant negative change did occur in their attitude toward the entire dental educational experience. The results also indicated that students' attitudes toward specific concepts can be successfully employed to predict a portion of their final grade.

Comparison of films processed in automatic and manual processors

This study compared the quality of Kodak RP X-Omat, Kodak Blue Brand, and Kodak periapical films processed in manual tank. Auveloper, P-10, All-Pro, Philips 810, and RP X-Omat processors. Film quality was evaluated in terms of film fog, image contrast, and resolution. For Kodak RP X-Omat and periapical films, automatic processors produced less film fog and were more consistent in fog production than manual tank processor. The difference in fog production between automatic and manual processors was not clinically significant; indeed, it was visuially undetectable. The difference disappeared when Kodak Blue Brand film was used. For Kodak RPX-Omat and Kodak Blue Brand films, at high film densities, the RP X-Omat processor produced films of the highest image contrast. For periapical films, the manual processor produced the highest image contrast. Image contrast at low densities was nearly the same for all processors. For each type of film, resolution was nearly the same for all processors.

Thrombosis of the spermatic vein in children

We describe 3 children in whom thrombosis of the spermatic vein vessels caused swelling of the spermatic cord and epididymis with edema of the scrotum. Venography of the spermatic vein demonstrated the thrombosis and, therefore unnecessary exploration was avoided.

Competition trait anxiety, state anxiety, and performance

This study tested predictions about social facilitation using a competitive (evaluation) vs non-competitive setting. In addition, subjects who exhibited low, moderate, or high anxiety concerning competition were selected to determine the relation of anxiety to social facilitation. The design was 2 (competition/no competition) X 3 (competition trait anxiety), with state anxiety and performance as the major dependent variables. In a significant main effect of anxiety about competition subjects high in competitive anxiety displayed higher levels of state anxiety than subjects moderate or low in anxiety about competition. Performance differences were non-significant although means were as predicted.

Path analysis of environmental and genetic influences on blood pressure

Familial aggregation of a trait (determined by the intraclass correlation coefficient) may result from genetic influence or from environment common to a household. The authors used path analysis to separate aggregation into the proportion of population variability due to genetic influence (h2 = heritability) and the proportion due to environment common to a household (c2). They used data from full siblings and maternal half siblings, aged two to 18 years, from Bogalusa, Louisiana, a biracial community. The statistically significant aggregation they found could be explained by either h2 or c2 except for two cases: systolic measurement in the pooled (black and white) sample requires h2; diastolic measurement in the white sample requires c2. The authors present a simplified explanation of the techniques they used.

Computer graphics in support of Space Shuttle simulation

Electronic scene generation plays an important role in simulation of the Space Shuttle at the Johnson Space Center in Houston, Texas. Simulators for astronaut training, system integration and engineering development utilize both a moving camera/map board system as well as computer generated images. Launch, on-orbit, payload handling and landing tasks are simulated with shaded computer graphics to provide realtime visual feedback. An overview of these simulators is presented.

Childhood sibling aggregation of coronary artery disease risk factor variables in a biracial community

To analyze aggregation of risk factors for coronary artery disease (CAD), the authors studied 4538 children from the biracial community of Bogalusa, Louisiana. Of these children ranging in age from two to 18 years, 2535 had at least one sibling, permitting the calculation of F-ratios and intraclass correlation coefficients. Those calculations revealed statistically signigicant F-ratios for all anthropometric, blood pressure and lipid variables studied. Of the lipoprotein variables studied only alpha-lipoprotein showed no statistically significant aggregation (for black children). The analysis failed to reveal any significant differences in intraclass correlations between black and white children.

Poor predictability of lactose malabsorption from clinical symptoms for Chilean populations

Clinical symptoms and lactose malabsorption may occur in persons intolerant to lactose. To predict malabsorption from symptoms and age, the authors used simple regression, multiple regression, and discrimant analysis on data from 436 Chileans. All individual r2 values from simple regression were less than 0.05. For the best stepwise multiple regression program, R2 was only 0.09, indicating that 91% of the variability in malabsorption was "unexplained" by the five best predictor variables. Because of so much unexplained variability, the authors could detect (using multiple regression) only 56 of 90 (62%) malabsorbers and only 14 of 38 (37%) absorbers. In conclusion, for their Chilean populations the authors poorly predicted malabsorption from symptoms.

Estimates of the heritability of serum lipoprotein and lipid concentrations

Heritability (h2) of a serum lipid or a serum lipoprotein concentration is the proportion of variability in that concentration, among individuals, which is associated with heredity. We derive a familiar formula for estimating heritability (h2) from a simple linear model for inheritance. The formula was implied by Fisher (1918) and by Wright (1921); it was derived from a consideration of variances by Jensen (1967), and from a consideration of path coefficients by Rao et al. (1974). The estimate of heritability (ĥ2) is ĥ2 = 2(rMZ - rDZ) for twin studies, where rMZ and rDZ are the sample intraclass correlation coefficients among monozygous and dizygous twins, respectively. We calculate ĥ2 for some published twin data (Heiberg 1974) on serum lipoprotein and serum lipid concentrations.

Translation of mRNA from simian virus 40-infected cells into simian virus 40 capsid protein by cell-free extracts

Messenger RNA was isolated from simian virus 40 (SV40)-infected and mock-infected cells by chromatography on poly(U) sepharose. When added to cell-free extracts from Chinese hamster ovary cells or rabbit reticulocytes, RNA from the infected cells, but not from mock-infected cells, stimulated synthesis of the major SV40 capsid protein. Identification of this species was done by sodium dodecyl sulfate gel electrophoresis, peptide mapping, and immunoprecipitation. The in vitro synthesized capsid protein was slightly different from virion assembled capsid protein, as shown by separation upon chromatography on hydroxylapatite and by minor differences in the peptide map.

Mechanism of induction of RNA tumor viruses by halogenated pyrimidines

Frome these studies on JLS V-9 cells, a number of conclusions can be drawn about the mechanism of MuLV induction by halogenated pyrimidines. The compounds can induce virus from otherwise healthy cells as long as deoxycytidine is present along with the inducing agent. The compounds must be present during the S phase of the cell cycle and must be incorporated into DNA in order to induce virus (Teich et al. 1973). Only one strand of DNA need be substituted by BrdU or IdU in order to induce virus, because a one-hour period of incorporation leads to induction. From these results it is possible to construct a model for how halogenated pyrimidines are able to induce viruses from otherwise uninfected cells. Because the critical period for the incorporation of the compound is a restricted segment of the S phase of the cell, there would appear to be a critical segment of the genetic information of the cell which, when substituted with BrdU or IdU, leads to a transcriptional derepression. Presumably the critical segment of DNA is either a controlling element of the integrated provirus or it is a separate gene which controls the expression of the integrated provirus. Whichever is true, these results strongly imply that the search for specific repressors of the segments of mammalian DNA is likely to be successful and that RNA tumor viruses may offer a system in which such repression systems can be identified and investigated.

The selective interruption of nucleolar RNA synthesis in HeLa cells by cordycepin

Cordycepin is an analogue of adenosine lacking the 3'-OH. When incorporated into a growing RNA molecule, cordycepin prevents further elongation, thus producing a prematurely terminated RNA molecule. When HeLa cells are exposed to low concentrations of cordycepin, DNA and protein synthesis are unaffected during short exposure periods. The synthesis of completed ribosomal and ribosomal-precursor (45S) RNA is significantly depressed. Partially completed 45S ribosomal precursor molecules accumulate in the nucleolus. 18S ribosomal RNA can be cleaved from these incomplete precursors, while 32S ribosomal precursor cannot be produced from partially snythesized 45S molecules. The synthesis of transfer RNA is also reduced in the presence of cordycepin. The synthesis of the nuclear heterogeneous RNA species is unaffected by the drug while the cytoplasmic heterogeneous RNA is slightly reduced.