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W B STEWART

Publications and source records attributed to W B STEWART.

22 records · Page 2Linked to original sources
PubMed1950

Radioiron absorption in anemic dogs; fluctuations in the mucosal block and evidence for a gradient of absorption in the gastrointestinal tract.

The control of iron absorption appears to reside in the mucosa of the gastrointestinal tract. The normal dog absorbs very little iron, but the anemic iron-depleted dog may absorb 10 to 20 times as much. This "mucosal block" of the normal dog probably is due largely to iron stores in the mucosa. "Mucosal block" can be effected in the anemic iron-depleted dog by feeding of iron salts, but the degree of "mucosal block" under these conditions never reaches the high degree of "mucosal block" in the normal dog. Rapid movement of iron through the mucosa may explain the short duration of "mucosal block" due to iron feeding in the anemic iron-depleted dogs (18 to 20 hours, Fig. 1). The colon absorbs very little iron under the conditions described. The stomach and duodenum seem to be most active in its absorption. This suggests the existence of a gradient in the capacity of the gastrointestinal tract to absorb iron.

Anemia↗
PubMed1950

Passage of radioactive erythrocytes from the peritoneal cavity into the blood stream during experimental ascites.

Intraperitoneal injection of red cells tagged with radioiron into dogs with experimental ascites demonstrated that such cells were rapidly transferred into the circulating blood. When the experimental animals were not actively producing ascitic fluid, 43.4, 67.0, and 56.4 per cent respectively, of the administered radioactive red cells passed to the blood in 72 hours. In the same three dogs during active ascitic fluid formation, 25.9, 51.2, and 38.8 per cent of the administered radioactivity was removed in a similar period. The amount of radioactivity in the blood stream, consequent on the passage of red cells from the peritoneal cavity into the circulation, becomes nearly constant in 48 hours, whereas for radioactive plasma proteins the plateau is attained in 24 hours (Fig. 1). In normal dogs (16), the passage of red cells from the peritoneal cavity was complete in 72 hours, while in ascitic dogs, 5 to 47 per cent of the injected tagged red cells remained behind in the peritoneum after the same period.

Animals↗
PubMed1950

Age as effecting the osmotic and mechanical fragility of dog erythrocytes tagged with radioactive iron.

Radioactive iron was administered to three normal dogs, two of which had previously been bled, in order to tag a group of erythrocytes of approximately known age. The osmotic fragility of the newly formed tagged cells was significantly greater than that of the general cell population during the first few days after injection of the iron, while the mechanical fragility of the young cells was less than that of the general red cell population. As the cells aged and approached the end of their life span, their susceptibility to destruction by trauma inflicted by rolling glass beads exceeded that of the general cell population. The osmotic behavior of the old cells was not distinctive. The increased mechanical fragility of senescent cells suggests that the life span of erythrocytes may be limited at least in part by changes within the cell which render it more susceptible to destruction by mechanical wear and tear in the circulation. It is emphasized, however, that the trauma produced by rolling glass beads may be quite unlike that inflicted upon red cells in vivo. A decrease in circulating radioactive iron was observed in each experiment soon after the mechanical fragility of the tagged cells began to exceed that of the total cell population. The lowest point on the curve representing circulating radioiron was noted at 119, 119, and 122 days respectively after injection of iron in the three experiments. Estimates of the life span of dog erythrocytes obtained in this way agree with those provided by other methods.

Age Factors↗