Cation hexaammines are selective and potent inhibitors of the CorA magnesium transport system.

Cation hexaammines and related compounds are chemically stable analogs of the hydrated form of cations, particularly Mg(2+). We tested the ability of several of these compounds to inhibit transport by the CorA or MgtB Mg(2+) transport systems or the PhoQ receptor kinase for Mg(2+) in Salmonella typhimurium. Cobalt(III)-, ruthenium(II)-, and ruthenium(III)-hexaammines were potent inhibitors of CorA-mediated influx. Cobalt(III)- and ruthenium(III)chloropentaammines were slightly less potent inhibitors of CorA. The compounds inhibited uptake by the bacterial S. typhimurium CorA and by the archaeal Methanococcus jannaschii CorA, which bear only 12% identity in the extracellular periplasmic domain. Cation hexaammines also inhibited growth of S. typhimurium strains dependent on CorA for Mg(2+) uptake but not of isogenic strains carrying a second Mg(2+) uptake system. In contrast, hexacyano-cobaltate(III) and ruthenate(II)- and nickel(II)hexaammine had little effect on uptake. The inhibition by the cation hexaammines was selective for CorA because none of the compounds had any effect on transport by the MgtB P-type ATPase Mg(2+) transporter or the PhoQ Mg(2+) receptor kinase. These results demonstrate that cation hexaammines are potent and highly selective inhibitors of the CorA Mg(2+) transport system and further indicate that the initial interaction of the CorA transporter is with a fully hydrated Mg(2+) cation.

Ascending aortic aneurysm and dissection in young adults with bicuspid aortic valve: implications for echocardiographic surveillance.

Bicuspid aortic valve (BAV) is an independent risk factor for aneurysm and dissection of the ascending aorta. Despite this association, routine imaging of the aorta has not been recommended for patients with BAV. We describe two young men who developed life-threatening aneurysm or dissection of the ascending aorta; one had a normally functioning BAV and the other was 10 years after valve replacement. The pathology of this condition is very similar to that found in the Marfan syndrome. We recommend echocardiographic surveillance of the ascending aorta at regular intervals, and consideration of beta-adrenergic blockade among patients with significant dilation.

A comparison of palpable and nonpalpable breast cancers.

Chi-square statistics were used to compare prognostic factors of 60 patients with nonpalpable breast cancer (NPBC) and 112 patients with palpable breast cancer. Noninvasive cancers were more frequent, tumor size was smaller, and nodal metastasis was significantly less frequent in the NPBC group. However, the frequency of nodal metastasis was similar when adjusted for size and grade. There was no significant difference in the incidence of age and menopausal status of the patients, histologic types, hormone receptor status, and histologic/nuclear grade between these two groups. The findings were consistent with the hypothesis that NPBCs are potentially lethal tumors and that mammograms detect them earlier, ie, these tumors are smaller, localized, and, therefore, more curable.