Auditory versus visual processing of three sets of simultaneous digit pairs

Two experiments were conducted to determine whether the auditory and visual systems process simultaneously presented pairs of alphanumeric information differently. In Experiment 1, different groups of subjects were given extensive practice recalling pairs of superimposed visual or auditory digits in simultaneous order (the order of arrival) or successive order (one member of each digit pair in turn, followed by the other pair member). For auditory input, successive order of recall was more accurate, particularly for the last two of three pairs presented, whereas for visual input, simultaneous order of recall was more accurate. In Experiment 2, subjects were cued to recall in one or the other order either immediately before or after stimulus input. Recall order results were the same as for Experiment 1, and precuing did not facilitate recall in either order for both modalities. These results suggest that processing in the auditory system can only occur successively across time, whereas as in the visual system processing can only occur simultaneously in space.

Early response of lung to low levels of ozone

The epithelial response in the terminal bronchioles and alveoli was examined after exposure to approximately 0.5 and 0.9 ppm ozone (O(3)). Loss of ciliated cells from the terminal bronchiole was pronounced after 6 to 10 hours of exposure; however, nonciliated cells were resistant to injury from O(3). In contrast, type 1 alveolar lining cells were very sensitive to O(2) and were severely damaged or removed from significant areas of the proximal alveoli after as little as 2 hours of exposure to 0.5 ppm. The basement lamina was left devoid of an epithelium with the exception of type 2 cells, which were very resistant and retained a relatively normal appearance. Under continuous exposure, repair of the lesion area was accomplished in approximately 48 hours through proliferation of the type 2 cells. The new cells were cuboidal at first but subsequently became more squamous in appearance. Exposure for 8 to 10 hours followed by residence in clean air resulted in a proliferative response at 48 hours, about equal to that observed after continuous exposure.

Renewal of alveolar epithelium in the rat following exposure to NO2

This research was undertaken to study the kinetics of Type 2 cell division and the fate of the Type 2 sister cell following exposure to NO(2). To accomplish this, male rats were exposed to NO(2). Dividing cells were labeled with (3)H-TdR and studied with autoradiographic technics in the light and electron microscopes for up to 72 hours after labeling. The kinetics of cell division were determined from a curve constructed from the percent of labeled mitotic figures. The fate of the Type 2 sister cells was determined by studying tissues at 24, 48 and 72 hours after labeling with (3)H-TdR. The results show that Type 2 cells may divide and the sister cells transform into Type 1 cells. These data support an interpretation of the mechanism for cell renewal of the alveolar epithelium in which Type 2 cells are the progenitor cells for Type 1 cells.

Cell division of alveolar macrophages in rat lung following exposure to NO2

The purpose of this research was to study cell division of alveolar macrophages following exposure of rats to NO(2). Dividing cells were labeled with (3)H-TdR and studied for 12 hours after labeling. The kinetics of cell division were determined from a curve constructed from the percent of labeled mitotic figures. Dividing alveolar macrophages were localized in alveoli near the openings of terminal bronchioles. There were no morphologic differences observed between labeled and unlabeled macrophages. Estimates of the durations of the various phases of the cell cycle gave approximate values of: G(2), 1 hour; t(2), 1.8 hour; M, 2.8 hours; and S, 5.8 hours. This evidence, combined with that of others, is compatible with an interpretation for alveolar cell renewal in which marrow-derived cells enter the alveoli and become macrophages. While in the alveoli, the cells may divide and thus increase their numbers. Eventually the macrophages are extruded from the alveoli. Alveolar macrophages were classified as a dividing, transient renewing cell population.

Early response of mouse foot pads to Mycobacterium laprae

The purpose of these experiments was to study the early response of mouse foot pads to Mycobacterium leprae. To accomplish this, mice were inoculated in both foot pads with large and small numbers of organisms. The animals were sacrificed at intervals from 2 hr to 27 days after inoculation. The microscopical results, which utilized normal BALB/c and thymectomized-irradiated B6C3F(1) mice, showed that the tissue responded first with an influx of polymorphonuclear cells and later lymphocytes and monocytes. The latter formed a diffuse infiltrate in the tissues. Under conditions where growth normally occurred, the mononuclear cell infiltrate did not persist. The organisms were found within phagocytic cells and the interstitial space. They were always contained within a phagosome and often fused with lysosomes. Most of the organisms appeared to be degenerating at all of the times studied. No organisms were observed in striated muscle fibers of tissues studied.

Ultrastructural changes in cells of the mouse footpad infected with Mycobacterium leprae

Ultrastructural changes in cells of the mouse footpad are described which occurred during the log phase of multiplication, the plateau, and the stationary phase of growth of Mycobacterium leprae.BALB/c mice were inoculated in the right hind footpad with 5 x 10(3) organisms and sacrificed in pairs at 86 to 173 days after inoculation. Tissue samples were prepared for electron microscopy by standard techniques. During the early growth phase of M. leprae in the mouse footpad, few organisms can be detected. Those present are in macrophages and are bound by a single membrane. The cytoplasm of the macrophage is less dense around the organism. There are few lysosomes, and the bacteria do not appear to be degenerating. At the peak of the growth phase, the organisms within a macrophage are bound by either a single or double membrane. There is an increased number of vacuoles, which are also bound by a double membrane, and lysosomes. During the stationary phase, most of the macrophages have taken on a vacuolar appearance and contain lysosomes. The vacuoles are bound by a double membrane, as are most of the organisms within the macrophage. Many of these organisms appear to be degenerating. Occasionally, organisms are encountered in the sarcoplasm of striated muscle. They are usually bound by a single membrane and do not appear to be degenerating.