Biomedical subjects
Publications and source records attributed to M N Smith.
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Clara cells in the terminal bronchoiles of mouse, rat, rabbit, calf and human were compared by light, transmission and scanning microscopy, and species-differences were clearly present. Mouse Clara cells were most numerous and mouse and rabbit Clara cells had large dense mitochondria. Rabbit and calf had glycogen in Clara cells and rat Clara cells had the most variability in secretory granules, some of which had a crystalline structure. Calf Clara cells had deeply indented nuclei. Human Clara cells had the most prominent nucleoli and lacked smooth endoplasmic reticulum, which was a prominent feature of most other species. No evidence of apical extrusion or apocrine secretion of Clara cell secretory granules was observed.
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In freezing, competitive interaction between ice and hydrophilic plant substances causes an energy of adhesion to develop through the interstitial liquid. The thermodynamic basis for the adhesion energy is discussed, with estimates of the energies involved. In this research, effects of adhesion energy were observed microscopically in conjunction with energies of crystallization and frost desiccation. The complex character of ice in intact crown tissue of winter barley (Hordeum vulgare L.) and the problems of sectioning frozen tissue without producing artifacts led to an alternative study of single barley cells in a mesh of ice and cell wall polymers. Adhesions between ice, cell wall polymers, and the plasmalemma form a complexly interacting system in which the pattern of crystallization is a major factor in determination of stress and injury.
An alteration consisting of widening of the inner membrane space (approximately 240 A) of the human heart mitochondria was studied and compared in surgical and autopsy material. The presence of these changes in well-preserved surgical material suggests that it may be a morphologic manifestation of an unknown biochemical alteration.
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Bronchiolo-alveolar carcinoma is the least common of the primary pulmonary carcinomas, and there is controversy as to its cell of origin. In this light- and electron microscopic study of five bronchiolo-alveolar carcinomas, at least two cell types were found, both of bronchiolar origin. One cell type is a metaplastic bronchiolar mucous cell and the other a bronchiolar stem cell that has ultrastructural features of both the respiratory ciliated and the respiratory nonciliated ("Clara") cell. It would not be unusual if tumors of the bronchiolo-alveolar region differentiate into cells of either the bronchiole or the alveolus, for embryologically they have a common origin. However, as information about the ultrastructure of these tumors accumulates, it is becoming apparent that an alveolar-cell carcinoma must be a rare occurrence. Hyperplastic Type II aleveolar epithelial cells may be found about the margins of these tumors and can be mistaken for the neoplastic cells.
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Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
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Twenty asthmatic volunteers, most with mild disease, underwent dose-response studies with sulfur dioxide (SO2) under three pretreatment conditions: (1) drug (metaproterenol sulfate in aerosolized saline solution), (2) placebo (aerosolized saline only), and (3) no pretreatment. Sulfur dioxide exposure concentrations were 0.0, 0.3, and 0.6 ppm. Experimental conditions were presented in random order at 1-wk intervals. Exposures lasted 10 min with heavy continuous exercise. Lung function was measured at baseline, after pretreatment (immediately pre-exposure), immediately post-exposure, and during a 2-hr follow-up. Subjects could elect to take bronchodilators during follow-up. Symptoms were monitored before, during, and for 1 wk after exposure. With no pretreatment, subjects exhibited typical exercise-induced bronchospasm at 0.0 ppm, slightly increased responses at 0.3 ppm, and more marked increases at 0.6 ppm. Seven subjects took bronchodilator after 0.6-ppm exposures, compared to 2 at lower concentrations. Within 30 min post-exposure, most subjects' symptoms and lung function had returned to near pre-exposure levels. A similar sequence was observed when subjects received placebo. Drug pretreatment improved lung function relative to baseline, prevented bronchoconstrictive responses at 0.0 and 0.3 ppm, and greatly mitigated responses at 0.6 ppm. Thus, typical bronchodilator usage by asthmatics is likely to reduce their response to ambient SO2 pollution.
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