Biomedical subjects
Publications and source records attributed to D C Smith.
By use of a scanning microdensitometer, a simple quantitative method of radiograph evaluation is made available for assessing the extent of bone healing after treatment of fractures or surgery. The surgeon is thus able to quantitatively determine the degree of healing and to choose a clinically desirable value of X at which he feels confident immobilization may be terminated.
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The colonization of host cells by modern symbionts is surveyed. The morphological distinction between extracellular and intracellular symbionts is not sharp, and the various kinds of association can be arranged in a graded series of increasing morphological integration of the symbiont into the host cell. Apart from some aggressive parasitic infections, the great majority of symbionts are enclosed by a host membrane in a vacuole. Those not enclosed in a host vacuole usually cannot be cultivated outside the cell. It is therefore surmised that encirclement by a vacuolar membrane would only disappear, if at all, in the later stages of the evolution of intracellular symbiosis. Recognition mechanisms between host and symbiont occur, but have been little studied. In some associations, recognition at surface contact occurs, and there is evidence for the involvement of lectins in certain cases. In other associations, recognition may occur wholly or in part after the entry of symbiont into host cells. After entry, special mechanisms for the biotrophic transfer of nutrients from symbiont to host develop. Both the symbiont population size and its rate of increase are strictly regulated by the host cell; symbiont metabolism may be controlled likewise. Rates of evolution of intracellular symbionts are probably very rapid, owing in part to responses of the host cell to its symbiont.
Three cases of pyloric diaphragm in elderly patients are reported. The finding of these patients within a 2-year period (1976-8) suggests that the condition is not as rare as previously thought. Diagnosis was achieved endoscopically and the condition managed surgically. While there has been controversy in the past over whether the disorder is acquired or congenital, the histological evidence of the cases presented here tends to suggest that it is a late presentation of a congenital abnormality.
Bonding resins to enamel requires some form of mechanical attachment. Currently the dissolution of the outermost enamel layer is involved in etching with phosphoric acid. A new approach to mechanical bonding is described using a crystalline interface which itself bonds chemically to enamel. The crystals can be removed from the enamel with an ultrasonci or sickle-scaler followed by pumice prophylaxis. Many variations of the crystal growth principle may be visualized, including the development of fluoride-containing crystals.
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Widening of the mediastinum after blunt, deceleration injuries to the chest in three patients suggested thoracic aortic lacerations. In each patient, the aorta was found to be intact and the iatrogenic hydromediastinum was caused by malpositioned central venous pressure lines. The radiographic appearance of the central venous pressure catheter is illustrated and clinical characteristics of the malpositioned catheter are discussed.
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Atria isolated from rats after 7 weeks of exercise training beat at a slower rate than did atria from sedentery controls. Atria from exercised rats showed a significant acceleration in response to atropine.