Okadaic acid: the archetypal serine/threonine protein phosphatase inhibitor.

As the first recognized member of the "okadaic acid class" of phosphatase inhibitors, the marine natural product okadaic acid is perhaps the most well-known member of a diverse array of secondary metabolites that have emerged as valuable probes for studying the roles of various cellular protein serine/threonine phosphatases. This review provides a historical perspective on the role that okadaic acid has played in stimulating a broad spectrum of modern scientific research as a result of the natural product's ability to bind to and inhibit important classes of protein serine / threonine phosphatases. The relationships between the structure and biological activities of okadaic acid are briefly reviewed, as well as the structural information regarding the particular cellular receptors protein phosphatases 1 (PP1) and 2A. Laboratory syntheses of okadaic acid and its analogs are thoroughly reviewed. Finally, an interpretation of the critical contacts observed between okadaic acid and PP1 by X-ray crystallography is provided, and specific molecular recognition hypotheses that are testable via the synthesis and assay of non-natural analogs of okadaic acid are suggested.

Expedient access to the okadaic acid architecture: a novel synthesis of the C1-C27 domain.

A newly designed synthetic entry to the C1-C27 domain of okadaic acid has been developed. This incorporates substantial improvements in the preparations of the key okadaic acid building blocks representing the C3-C8, C9-C14, and C16-C27 portions. The synthesis of the C3-C8 lactone used (R)-glycidol as the origin of the C4 stereogenic center and featured a late-stage optional incorporation of the C7 hydroxyl group. The complementary C9-C14 fragment was synthesized in a concise route from (R)-3-tert-butyldimethylsilyloxy-2-methylpropanal and propargyl bromide. Assembly of the C3-C14 spiroketal-containing intermediate from the constitutent fragments revealed a dramatic effect of C7 functionalization upon spiroketalization efficiency. In contrast, both (9E)- and (9Z)-enones converged readily to the C8 spiroketal upon treatment with acid. Modifications to the central C16-C27 fragment of okadaic acid included the early replacement of benzylic protecting groups by more suitable functionalities to facilitate both the generation of the C15-C27 intermediate and the deprotection of the final products. These modular building blocks were deployed for the synthesis of the C1-C27 scaffold of 7-deoxyokadaic acid. This work demonstrates improvements in the formation of versatile okadaic acid intermediates, as well as a reordering of fragment couplings. This alternative order of coupling was designed to promote the late stage incorporation of nonnatural lipophilic extensions from the C27 terminus.

Anticancer activity of synthetic analogues of the phorboxazoles.

The phorboxazoles are recently described natural products that are extremely cytostatic towards the National Cancer Institute's panel of 60 tumor cell lines. We report here the results of preliminary structure-activity studies of synthetic analogues of the phorboxazoles against BT-20 breast cancer, NALM-6 B-lineage ALL, U373 brain tumor, and U373 glioblastoma cell lines. These data indicate the importance of several of the natural products' structural moieties for potent anticancer activity.

Importance of the C28-C38 hydrophobic domain of okadaic acid for potent inhibition of protein serine-threonine phosphatases 1 and 2A.

Okadaic acid is a potent inhibitor of select serine/threonine protein phosphatases. The importance of the C28-C38 hydrophobic domain of okadaic acid for inhibition of PP1 and PP2A was investigated. The hydrophobic domain is required but not sufficient for potent inhibition, and it also contributes to differential inhibition between PP1 and PP2A.

Synthetic studies toward the C5-C20 domain of the azaspiracids.

[structure: see text]. An approach toward the C5-C20 THF-fused trioxadispiroketal portion of the azaspiracids is reported. The highly substituted azaspiracid D ring (C16-C19) was prepared by the one-pot conversion of a tetraol into a tetrahydrofuran. Efforts to establish the C10 and C13 spiroketal centers via an oxonium-initiated bis-spiroketalization under both kinetic and thermodynamic conditions have yielded the (10R,13S)-trioxadispiroketal 19 as the major product, which is diastereomeric with the (10R,13R) relative configuration assigned to the azaspiracids.

Synthesis of a 2,9-dioxabicyclo[3.3.1]nonane via double intramolecular hetero-Michael addition: entry to the F-G ring system of the azaspiracids.

[structure: see text]. An effective approach to form a 1,3-disubstituted 2,9-dioxabicyclo[3.3.1]nonane system representing the core of the F and G rings (C28-C34) of the azaspiracid natural products has been developed. The double intramolecular hetero-Michael addition (DIHMA) of a diol upon an ynone generated the bicyclic ketal in a highly diastereoselective fashion.

Novel total synthesis of the anticancer natural product dysidiolide.

The marine natural product dysidiolide has been synthesized in a highly diastereoselective fashion that features the sequential transfer of chirality from a cyclohexenone precursor.

Novel synthesis of the C1-C15 polyether domain of the thyrsiferol and venustatriol natural products.

[formula: see text] A convergent construction of the C1-C15 domain of the thyrsiferol-related natural products has been developed. This involved the separate construction of C1-C7 and C8-C15 fragments, their organochromic-mediated coupling, and subsequent reductive closure of the B ring. This synthetic A-B-C ring construct will be useful for the total synthesis of the biologically active polyether squalenoid natural products, as well as their non-natural analogues.

Abbreviated synthesis of the C3-C14 (substituted 1,7-dioxaspiro[5.5]undec-3-ene) system of okadaic acid.

[formula: see text] Described is a novel, concise, and flexible synthesis of the C3-C14 portion of okadaic acid. A substituted valerolactone (C3-C8) was prepared in three steps and alpha-hydroxylated using Davis' oxaziridine. Conjugate addition of dimethylcuprate upon ynones derived from the C3-C8 lactones followed by intramolecular ketalization provided the C3-C14 fragment and revealed a significant role of the C7 alpha'-ketone substituent upon the efficiency of spiroketalization.

Childhood sexual trauma and substance misuse: a pilot study.

This research investigates the type of and extent to which additional problematic experiences and behaviors are associated with a history of both substance misuse and childhood sexual abuse. In a recent study of women undergraduate students, 30 years and older, 15 disclosed a history of problematic alcohol and/or drug use. Of these, 10 had experienced sexual trauma as children; five had not. This report compares these two subsamples with respect to problematic experiences and behavior. Implications for counseling and research are discussed.

The meaning of college for survivors of sexual abuse: higher education and the older female college student.

A study of the general college experience of 44 female undergraduates, 30 years of age and older, revealed a high prevalence of childhood sexual abuse. The impact of this abuse on these women and the meaning of higher education in resolving the negative sequelae of their earlier traumatic experiences are examined, and implications for counseling are discussed.

Thalidomide responsive chronic pulmonary GVHD.

A 29-year-old male underwent allogeneic bone marrow transplantation for progressive multiple myeloma. His post-transplant course was complicated by severe chronic pulmonary graft-versus-host disease (GVHD) resistant to cyclosporin A, corticosteroids and azathioprine. The introduction of thalidomide resulted in a dramatic improvement in his lung function which has been maintained even after cessation of thalidomide. He remains well 40 months after transplantation.

Oral L-arginine inhibits platelet aggregation but does not enhance endothelium-dependent dilation in healthy young men.

OBJECTIVES: Our aim was to assess the effect of oral L-arginine on endothelial or platelet physiology in humans. BACKGROUND: L-Arginine is the substrate for nitric oxide synthesis, and in cholesterol-fed rabbits, oral L-arginine improves endothelium-dependent dilation, inhibits platelet aggregation and reduces atheroma. In hypercholesterolemic humans, intravenous L-arginine immediately improves endothelium-dependent dilation; however, the vascular effects of oral L-arginine in healthy humans have not previously been investigated. METHODS: In a prospective, double-blind, randomized crossover trial, 12 healthy young men 27 to 37 years old took L-arginine (7 g three times daily) or placebo for 3 days each, separated by a washout period of 7 to 14 days. RESULTS: After L-arginine, plasma levels of arginine (mean +/- SEM 303 +/- 36 vs. 128 +/- 12 mumol/liter, p = 0.01) and urea (6.7 +/- 0.5 vs. 5.2 +/- 0.2 mmol/liter, p < 0.01) were higher than levels measured after placebo, and platelet aggregation in response to adenosine diphosphate was markedly impaired (37 +/- 12% vs. 81 +/- 3%, p = 0.02). The inhibition of platelet aggregation correlated with the plasma level of L-arginine (r = 0.74, p = 0.01), and it could be completely or partially reversed by ex vivo incubation with N-monomethyl-L-arginine, a specific nitric oxide synthase inhibitor. Platelet cyclic guanosine monophosphate levels were higher after oral L-arginine than at baseline (1.91 +/- 0.46 vs. 1.38 +/- 0.40 pmol/10(9) platelets, p = 0.04). No changes were seen in fasting lipid levels, heart rate, blood pressure, endothelium-dependent dilation of the brachial artery (measured in response to reactive hyperemia, using external vascular ultrasound) (6.1 +/- 0.7% vs. 6.5 +/- 0.7%, p = NS) or in plasma levels of nitrosylated proteins (a marker of in vivo nitric oxide production) (3.5 +/- 0.5 vs. 3.3 +/- 0.4 mumol/liter, p = NS) 1 to 1.5 h after the last dose of L-arginine. CONCLUSIONS: In these healthy young adult men, oral L-arginine inhibited platelet aggregation by way of the nitric oxide pathway. However, it had no effect on systemic hemodynamic variables, plasma nitrosylated protein levels or endothelium-dependent dilation. Therefore, at certain doses, oral L-arginine may result in a relatively platelet-specific increase in nitric oxide production.

Biotherapy of B-cell precursor leukemia by targeting genistein to CD19-associated tyrosine kinases.

B-cell precursor (BCP) leukemia is the most common form of childhood cancer and the second most common form of acute leukemia in adults. Human BCP leukemia was treated in a severe combined immunodeficient mouse model by targeting of the tyrosine kinase inhibitor Genistein (Gen) to the B cell-specific receptor CD19 with the monoclonal antibody B43. The B43-Gen immunoconjugate bound with high affinity to BCP leukemia cells, selectively inhibited CD19-associated tyrosine kinases, and triggered rapid apoptotic cell death. At less than one-tenth the maximum tolerated dose more than 99.999 percent of human BCP leukemia cells were killed, which led to 100 percent long-term event-free survival from an otherwise invariably fatal leukemia. The B43-Gen immuno-conjugate might be useful in eliminating leukemia cells in patients who have failed conventional therapy.

Grieving men: thoughts, feelings, and behaviors following deaths of wives.

Despite the growing body of literature on bereavement, grief, and mourning, little attention has been given to the impact of bereavement on men. This is particularly true for studies on the impact of death of spouse on the survivor. Using in-depth interviews, we explored the thoughts, feelings, and behaviors of twenty men following the deaths of their wives. The findings do not support prevailing assumptions that men are less likely to be emotionally involved in the conjugal relationship and, thus, less likely to grieve than women; or, if emotionally involved, less likely to experience grief. This research suggests that men may be emotionally involved in the conjugal relationship and that the death of a wife may evoke intense feelings. The majority of the men in this study both hurt and knew they hurt. What they did not do was to reach out to others for help. This finding has important implications for bereavement program development.