The Ruff degradation: a review of previously proposed mechanisms with evidence that the reaction proceeds by a Hofer-Moest-type reaction.

The Ruff degradation reaction is critically reviewed. Based on available information, the Hofer-Moest decarboxylation mechanism is presented as the mechanism for it. Cu(III) is proposed as the active species of the copper variant of the Ruff degradation, which is the most efficient form of the reaction.

The Hofer-Moest decarboxylation of D-glucuronic acid and D-glucuronosides.

Research was undertaken to effect the oxidative decarboxylation of glycuronosides. Experiments with free D-glucuronic acid and aldonic acids were also executed. Both anodic decarboxylation and variants of the Ruff degradation reaction were investigated. Anodic decarboxylation was found to be the only successful method for the decarboxylation of glucuronosides. It was, therefore, proposed that glycuronosides can only undergo a one-electron oxidation to form an acyloxy radical, which decomposes to form carbon dioxide and a C-5 radical, that is, a Hofer-Moest decarboxylation. The radical is subsequently oxidized to a cation by means of a second one-electron oxidation. The cation undergoes nucleophilic attack from the solvent (water), whose product (a hemiacetal) undergoes a spontaneous hydrolysis to yield a dialdose (xylo-pentodialdose from D-glucuronosides).

Lessons learned from a regional strategy for resource allocation.

Two qualitative case studies focus on the allocation of CDC funds distributed during 2002 for bioterrorism preparedness in two Texas public health regions (each as populous and complex as many states). Lessons learned are presented for public health officials and others who work to build essential public health services and security for our nation. The first lesson is that personal relationships are the cornerstone of preparedness. A major lesson is that a regional strategy to manage funds may be more effective than allocating funds on a per capita basis. One regional director required every local department to complete a strategic plan as a basis for proportional allocation of the funds. Control of communicable diseases was a central component of the planning. Some funds were kept at the regional level to provide epidemiology services, computer software, equipment, and training for the entire region. Confirmation of the value of this regional strategy was expressed by local public health and emergency management officials in a focus group 1 year after the strategy had been implemented. The group members also pointed out the need to streamline the planning process, provide up-to-date computer networks, and receive more than minimal communication. This regional strategy can be viewed from the perspective of adaptive leadership, defined as activities to bring about constructive change, which also can be used to analyze other difficult areas of preparedness.

Imatinib mesylate resistance through BCR-ABL independence in chronic myelogenous leukemia.

Imatinib mesylate (IM) binds to the BCR-ABL protein, inhibiting its kinase activity and effectively controlling diseases driven by this kinase. IM resistance has been associated with kinase mutations or increased BCR-ABL expression. However, disease progression may be mediated by other mechanisms that render tumor cells independent of BCR-ABL. To demonstrate this potential, IM-resistant cells were found in chronic myelogenous leukemia patients with continuous BCR-ABL gene expression but undetectable BCR-ABL protein expression. These cells were unresponsive to IM and acquired BCR-ABL-independent signaling characteristics. IM resistance in some patients may be mediated through loss of kinase target dependence.

BCR-ABL independence and LYN kinase overexpression in chronic myelogenous leukemia cells selected for resistance to STI571.

Clinical studies have shown that the tyrosine kinase inhibitor STI571 effectively controls BCR-ABL-positive chronic myelogenous leukemia (CML). However, disease progression while on STI571 therapy has been reported, suggesting de novo or intrinsic resistance to BCR-ABL-targeted therapy. To investigate possible mediators of acquired STI571 resistance, K562 cells resistant to 5 microM STI571 (K562-R) were cloned and compared to the parental cell population. K562-R cells had reduced BCR-ABL expression and limited activation of BCR-ABL signaling cascades (Stat 5, CrkL, MAPK). STI571 failed to activate caspase cascades or to suppress expression of survival genes (bcl-xL) in resistant cells. Gene sequencing and tyrosine kinase activity measurements demonstrated that K562-R cells retained wild-type and active BCR-ABL tyrosine kinase that was inhibitable by in vitro incubation with STI571, suggesting that BCR-ABL was not coupled to proliferation or survival of K562-R cells. The src-related kinase LYN was highly overexpressed and activated in K562-R cells, and its inhibition reduced proliferation and survival of K562-R cells while having limited effects of K562 cells. Specimens taken from patients with advanced CML that progressed on STI571 therapy also were analyzed for LYN kinase expression, and they were found to be elevated to a level similar to that of K562-R cells. Comparison of samples from patients taken prior to and following STI571 failure suggested that expression and/or activation of LYN/HCK occurs during disease progression. Together, these results suggest that acquired STI571 resistance may be associated with BCR-ABL independence and mediated in part through overexpression of other tyrosine kinases.