Tracheal instillation of urban PM2.5 suspension promotes acute cardiac polarization changes in rats

The mechanisms by which PM2.5 increases cardiovascular mortality are not fully identified. Autonomic alterations are the current main hypotheses. Our objective was to determine if PM2.5 induces acute cardiac polarization alterations in healthy Wistar rats. PM2.5 samples were collected on polycarbonate filters. Solutions containing 10, 20, and 50 µg PM2.5 were administered by tracheal instillation. P wave duration decreased significantly at 20 µg (0.99 ± 0.06, 0.95 ± 0.06, and 0.96 ± 0.07; P < 0.001), and 50 µg (0.98 ± 0.06, 0.98 ± 0.07, and 0.96 ± 0.08; 60, 90 and 120 min, respectively) compared to blank filter solution (P < 0.001). PR interval duration decreased significantly at 20 µg (0.99 ± 0.06, 0.98 ± 0.07, and 0.97 ± 0.08) and 50 µg (0.99 ± 0.05, 0.97 ± 0.0, and 0.95 ± 0.05; 60, 90, and 120 min, respectively) compared to blank filter and 10 µg (P < 0.001). QRS interval duration decreased at 20 and 50 µg in relation to blank filter solution and 10 µg (P < 0.001). QT interval duration decreased significantly (P < 0.001) with time in animals receiving 20 µg (0.94 ± 0.12, 0.88 ± 0.14, and 0.88 ± 0.11) and 50 µg (1.00 ± 0.13; 0.97 ± 0.11 and 0.98 ± 0.16; 60, 90 and 120 min, respectively) compared to blank filter solution and 10 µg (P < 0.001). PM2.5 induced reduced cardiac conduction time, within a short period, indicating that depolarization occurs more rapidly across ventricular tissue.

Group cognitive training in old age: paper-and-pencil tasks of processing speed

Psychometric models attribute cognitive aging to decline in executive fuctions: processing speed(PS) or PS plus coordination of operations, both related to theprefrontal lobes. In a first study, healthy aged subjets (mean age: 68.42 years, range: 59-81; mean formalschooling: 6.47 years, range: 2-15) were divided into two groups. Group 1 (n=9) trained six VP paper-and-pencil tasks (letter and symbol recognizing speed) for five 1-hour daily sessions. Group 2 (n=8) received the same amount of training in a face-name association task. Measures of working memory employed in the pre-and post-tests were digit span, word span sentence comprehension. Group 1 improved significantly both in VP for letters and in the sentence comprehension measure. Group 2 improvement only in the paired associates learning task. Training old individuals on processing speed tasks may thus improve their working memory performance. In second training study, it was possible to assess coordination-related measures of working memory in the pre-and post-tests. Group 3 trained VP and was composed of 15 subjects with mean a age of 68.33 years (SD=6.36) and a mean formal schooling of 7.00 years (SD=3.22). Group 4, wich trained paired associates, consisted of 17 individuals with a mean age of 66.42 years (SD=8.38), who had a mean schooling of 7.77 years (SD=3.68). Contrary to our expectations, only training Group 4 exhibited generalization effects related to coordinatio of operations in working memory. These results confirm only partially unifactorial models of working memory