Effect of a covalently attached synergistic anion on chelator-mediated iron-release from ovotransferrin: additional evidence for two concurrent pathways.

The mechanism by which the iron-transport protein transferrin releases its iron in vivo is presently unclear. In vitro studies have implicated two concurrent chelator-mediated iron-release pathways: one which is hyperbolic in nature, involving a conformational change in the protein as a rate limiting step, and a second which has been proposed to be first-order in nature and to involve initial release of a synergistic anion. We have examined the effect that an affinity-label analog of the synergistic anion has on chelator-mediated iron-release from this protein. A covalently attached anion would inhibit iron-release via any pathway in which anion release is a prerequisite to iron release. The present investigation examined the effect that the covalently attached anion had on iron-release to pyrophosphate (PPi) and N, N-bis(phosphonomethyl)glycine (DPG), two chelators which are believed to utilize both pathways concurrently. Results show that when the affinity-label anion is utilized, strictly hyperbolic data are obtained, with similar observed kmax values. This is strong support for the hypothesis of a common, chelator-independent rate-limiting step for the one available pathway. These results also support strongly the hypothesis that synergistic anion removal is a prerequisite step to iron-release via the second pathway.

[Mucocele of the appendix. Some diagnostic features]. / Su un caso di mucocele appendicolare. Alcuni aspetti diagnostici.

The description of a case of mucocele of the appendix shows the difficulties of arriving at a preoperative diagnosis. Following an analysis of the diagnostic features it's possible to affirm that only surgery can confirm the diagnosis with the histological result. Careful surgical dissection is very important when a malignant tumor is suspected.