Hypersensitivity of abscisic acid-induced cytosolic calcium increases in the Arabidopsis farnesyltransferase mutant era1-2.

Cytosolic calcium increases were analyzed in guard cells of the Arabidopsis farnesyltransferase deletion mutant era1-2 (enhanced response to abscisic acid). At low abscisic acid (ABA) concentrations (0.1 microM), increases of guard cell cytosolic calcium and stomatal closure were activated to a greater extent in the era1-2 mutant compared with the wild type. Patch clamping of era1-2 guard cells showed enhanced ABA sensitivity of plasma membrane calcium channel currents. These data indicate that the ERA1 farnesyltransferase targets a negative regulator of ABA signaling that acts between the points of ABA perception and the activation of plasma membrane calcium influx channels. Experimental increases of cytosolic calcium showed that the activation of S-type anion currents downstream of cytosolic calcium and extracellular calcium-induced stomatal closure were unaffected in era1-2, further supporting the positioning of era1-2 upstream of cytosolic calcium in the guard cell ABA signaling cascade. Moreover, the suppression of ABA-induced calcium increases in guard cells by the dominant protein phosphatase 2C mutant abi2-1 was rescued partially in era1-2 abi2-1 double mutant guard cells, further reinforcing the notion that ERA1 functions upstream of cytosolic calcium and indicating the genetic interaction of these two mutations upstream of ABA-induced calcium increases.

Risk factors for proximal humerus fracture.

This case-control study of proximal humerus fracture included 448 incident female and male cases and 2,023 controls aged 45 years or older identified in five Northern California Kaiser Permanente Medical Centers in 1996-2001. Data were collected by using an interviewer-administered questionnaire. Some factors related to low bone mass, including number of fractures since age 45 years and low dietary calcium intake, were associated with increased risks of fracture, and factors thought to protect against bone loss, such as menopausal hormone therapy and calcium carbonate tablet use, were associated with reduced risks. Fall-related risk factors included previous falls, diabetes mellitus, and difficulty walking in dim light. Possible fall-related risk factors suggested for the first time in this study were seizure medication use (adjusted odds ratio (OR) = 2.80, 95% confidence interval (CI): 1.45, 5.42), depression (OR = 1.34, 95% CI: 0.98, 1.84), almost always using a hearing aid (OR = 1.92, 95% CI: 1.12, 3.31 vs. never prescribed), and left-handedness (OR = 2.36, 95% CI: 1.51, 3.68 vs. right-handedness). Difficulty with activities of daily living and lack of physical activity tended to be associated with increased risk. Prevention of falls among frail, osteoporotic persons would likely reduce the frequency of proximal humerus fracture.