Bounding Global Aerosol Radiative Forcing of Climate Change.

Aerosols interact with radiation and clouds. Substantial progress made over the past 40 years in observing, understanding, and modeling these processes helped quantify the imbalance in the Earth's radiation budget caused by anthropogenic aerosols, called aerosol radiative forcing, but uncertainties remain large. This review provides a new range of aerosol radiative forcing over the industrial era based on multiple, traceable, and arguable lines of evidence, including modeling approaches, theoretical considerations, and observations. Improved understanding of aerosol absorption and the causes of trends in surface radiative fluxes constrain the forcing from aerosol-radiation interactions. A robust theoretical foundation and convincing evidence constrain the forcing caused by aerosol-driven increases in liquid cloud droplet number concentration. However, the influence of anthropogenic aerosols on cloud liquid water content and cloud fraction is less clear, and the influence on mixed-phase and ice clouds remains poorly constrained. Observed changes in surface temperature and radiative fluxes provide additional constraints. These multiple lines of evidence lead to a 68% confidence interval for the total aerosol effective radiative forcing of -1.6 to -0.6 W m-2, or -2.0 to -0.4 W m-2 with a 90% likelihood. Those intervals are of similar width to the last Intergovernmental Panel on Climate Change assessment but shifted toward more negative values. The uncertainty will narrow in the future by continuing to critically combine multiple lines of evidence, especially those addressing industrial-era changes in aerosol sources and aerosol effects on liquid cloud amount and on ice clouds.

Priming of grasping muscles when viewing a safety handle is diminished with age.

Merely viewing objects within reachable space can activate motor cortical networks and potentiate movement. This holds potential value for smooth interaction with objects in our surroundings, and could offer an advantage for quickly generating targeted hand movements (e.g. grasping a support rail to maintain stability). The present study investigated if viewing a wall-mounted safety handle resulted in automatic activation of motor cortical networks, and if this effect changes with age. Twenty-five young adults (18-30 years) and seventeen older adults (65+ years) were included in this study. Single-pulse, transcranial magnetic stimulation was applied over the motor cortical hand representation of young and older adults shortly after they viewed a safety handle within reaching distance. Between trials, vision was occluded and the environment was unpredictably altered to reveal either a safety handle, or no handle (i.e. covered). Modulation of intrinsic hand muscle activity was evident in young adults when viewing a handle, and this was selective in terms of both the muscles activated and the time at which it emerged. By contrast, older adults failed to show any changes when viewing the safety handle. Specifically, the presence of a handle increased corticospinal activity in hand muscles of young adults when TMS was applied 120 ms after opening the goggles (p = .014), but not in the older adults (p > .954). The fact that the visual priming observed in younger adults was absent in older adults suggests that aging may diminish the ability to quickly put our visual world into automatic motor terms.

Predicting language production in children and adolescents with Down syndrome: the role of comprehension.

Predictors of language production skills in 12-minute narratives are investigated cross-sectionally in 48 children and adolescents with Down syndrome (trisomy 21), aged 5 to 20 years, in comparison to 48 control children aged 2 to 6 years matched statistically for nonverbal mental age and mother's years of education. Two models were evaluated by hierarchical regression analyses using predictors drawn from the domains of group membership, chronological age, cognition, socioeconomic status, and hearing screening status (Model I) and, additionally, comprehension performance (Model II). Results showed that Model II was more successful. In the DS group, it explained 68% of the variability in number of different words, 80% in MLU, and 32% in intelligibility. Corresponding percentages for the control group were 72%, 71%, and 26%. A mechanism linking comprehension of input to early stages of production practice through activation of the early speech motor area is proposed.

Language skills of children and adolescents with Down syndrome: II. Production deficits.

Hypotheses that children and adolescents with Down syndrome show (a) a specific expressive language impairment, (b) a "critical period" for language acquisition, (c) a "simple sentence syntactic ceiling" in production, and (d) deficit in grammatical morphology were investigated cross-sectionally. Conversational and narrative language samples from 47 children and adolescents with Down syndrome (Trisomy 21), aged 5 to 20 years, were compared to those from 47 control children aged 2 to 6 years matched statistically for nonverbal mental age. Children with Down syndrome appear to have a specific language impairment, compared to control children, in number of different words and total words (in the first 50 utterances) and in mean length of utterance (MLU). Total utterance attempts per minute were more frequent in the Down syndrome group. Narrative samples contained more word tokens, more word types, and longer MLU than conversation samples, for both groups. Intelligibility of narratives was significantly poorer for the Down syndrome group than controls. Analyses of narrative language sample by age sub-group showed no evidence of a critical period for language development ending at adolescence, nor of a "syntactic ceiling" at MLUs corresponding to simple sentences for the Down syndrome group. Omissions of word tokens and types were more frequent in the older Down syndrome than the younger control sample, matched on MLU.

Pharmacodynamics of racemic and S(-)-atenolol in humans.

The cardiovascular actions of racemic atenolol (RSATN) have been well characterized in humans, but the actions of S(-)-atenolol (SATN) when administered alone are unknown. In this study, responses of heart rate (HR) and Doppler-derived aortic blood flow profiles to upright treadmill exercise were compared after oral administration of 50 mg SATN and 100 mg RSATN in eight healthy, adult, male volunteers. After a single-blind, placebo run-in period, subjects were randomly allocated in a double-blind, crossover fashion to receive SATN and RSATN. Each study period was separated by a 7-day washout period. Multiple submaximal exercise tests were performed and data were collected over the 24 hours after each treatment. Both SATN and RSATN significantly (P < .05) blunted peak exercise HR by 38 +/- 3 and 37 +/- 3 beats/min, respectively. Aortic blood flow acceleration measured during peak exercise decreased after SATN and RSATN, by 13 +/- 4 and 13 +/- 3 m/sec2, respectively (P < .05). No difference in hemodynamic effect was observed between treatments. Pharmacodynamic parameters derived from plasma S(-)-atenolol concentration-effect (HR) curves after SATN, RSATN, and total atenolol plasma concentrations after RSATN did not differ significantly. Predicted maximum reductions in heart rate (Emax) and EC50 for S(-)-atenolol after SATN were 39.6 +/- 5.8 beats/min and 38.4 +/- 40.9 ng/ml versus 34.5 +/- 8 beats/min and 25.9 +/- 29.9 ng/ml for RSATN, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Climate forcing by anthropogenic aerosols.

Although long considered to be of marginal importance to global climate change, tropospheric aerosol contributes substantially to radiative forcing, and anthropogenic sulfate aerosol in particular has imposed a major perturbation to this forcing. Both the direct scattering of shortwavelength solar radiation and the modification of the shortwave reflective properties of clouds by sulfate aerosol particles increase planetary albedo, thereby exerting a cooling influence on the planet. Current climate forcing due to anthropogenic sulfate is estimated to be -1 to -2 watts per square meter, globally averaged. This perturbation is comparable in magnitude to current anthropogenic greenhouse gas forcing but opposite in sign. Thus, the aerosol forcing has likely offset global greenhouse warming to a substantial degree. However, differences in geographical and seasonal distributions of these forcings preclude any simple compensation. Aerosol effects must be taken into account in evaluating anthropogenic influences on past, current, and projected future climate and in formulating policy regarding controls on emission of greenhouse gases and sulfur dioxide. Resolution of such policy issues requires integrated research on the magnitude and geographical distribution of aerosol climate forcing and on the controlling chemical and physical processes.

Language skills of children and adolescents with Down syndrome: I. Comprehension.

This study investigates the development of vocabulary and syntax comprehension skills cross-sectionally in 48 children and adolescents with Down syndrome (Trisomy 21), aged 5-20 years, in comparison to 48 control children aged 2-6 years matched statistically for nonverbal mental age and mother's years of education. Age-equivalent scores on vocabulary (PPVT-R) and syntax (TACL-R) comprehension tests differed in the Down syndrome group but not the control group; vocabulary comprehension was relatively more advanced than syntax. Age-equivalent scores on nonverbal cognitive subtests of pattern analysis and short-term memory for bead arrangements (Stanford-Binet, 4th ed.) also differed for the Down syndrome group but not the control group, indicating an unusual pattern of nonverbal cognitive function in the Down syndrome group. Stepwise multiple regression analyses showed that chronological age and mean mental age, collectively, accounted for 78% of the variability in vocabulary comprehension and 80% of the variability in syntax comprehension in the Down syndrome group, with total passes on a hearing screening accounting for an additional 4% in each case. Implications for research are discussed.

Fast mapping of words in event contexts by children with Down syndrome.

Fast mapping of novel words for objects was compared in 48 children and adolescents with Down syndrome (ages 5:6-20:6), who were delayed in expressive language acquisition compared to mental age, and 48 normally developing children matched for mental age (chronological ages 2:0-6:0). Normal and Down syndrome groups did not differ in their ability to infer a connection between the novel word and referent (100% vs. 100%), to comprehend the novel word after a single exposure (83% vs. 73%), and to recall the location in which they hid the novel referent (83% vs. 75%). Nor did they differ in their ability to produce the novel word correctly (at least two out of three phonemes in order: 48% vs. 40%). When retested after an hour of other activity, only the production task showed a significant, and comparable, decrement. Comparing youngest and oldest quarters of each group showed improved memory for location in both, improved comprehension in the Down syndrome group, and improved production in the control group. Adults (n = 12), in contrast, performed perfectly on all tasks except the delayed word production. Neither intelligibility differences nor use of real word labels accounts for the failure to find a difference between groups. Fast mapping skills were unrelated to expressive language deficit in these children with Down syndrome.

Acid deposition: unraveling a regional phenomenon.

Because sources of sulfur and nitrogen oxides distributed broadly across eastern North America have greatly overlapping zones of influence, it is difficult to determine detailed relations between emissions and the resulting acid deposition. Although substantial progress has been made in the past decade in understanding the pertinent atmospheric processes and in describing them in numerical models, because of the complexities of these processes and the wide range of the time and space scales involved, credible source-receptor relations for regional-scale acid deposition are not yet at hand. Consequently, near-term strategies for reducing acid deposition should be based on considerations other than detailed atmospheric source-receptor relations, but with confidence that regional deposition will be reduced equivalently to any reduction in regional emissions.

Sustained pectin ingestion: effect on gastric emptying and glucose tolerance in non-insulin-dependent diabetic patients.

The effects of sustained pectin ingestion on gastric emptying, glucose tolerance, and hormone responses were studied in 12 stable, non-insulin-dependent (type 2) diabetic patients. Patients were placed on a 2400 kcal, low-fiber (3 g) diet for 2 wk, followed by 4 wk of an isocaloric diet supplemented with 20 g apple pectin/d. Gastric-emptying half-time, plasma glucose, glucagon, and human pancreatic polypeptide levels were determined. Gastric-emptying half-time was prolonged 43% (p less than 0.025) by pectin supplementation and returned to normal 3 d after its discontinuation. Fiber supplementation decreased the incremental area under the glucose tolerance curve from 34.8 +/- 3.0 to 27.9 +/- 3.2 mmol/L (p less than 0.01) but did not affect hormonal responses to a meal. Sustained pectin ingestion slowed the gastric-emptying rate and improved glucose tolerance; however, a direct relationship could not be demonstrated between changes in gastric emptying and changes in the incremental area under the glucose curve (r = 0.22).

Prevention of aspirin-induced gastric mucosal injury by histamine H2 receptor antagonists: a crossover endoscopic and intragastric pH study in the dog.

Histamine H2 receptor antagonists have been reported to protect the gastric mucosa of animals and humans against aspirin-induced damage. It is unclear, however, whether this protective effect can be observed at doses less than those needed to markedly inhibit gastric acid secretion. We have developed a single-dose endoscopic assay system of aspirin-induced gastric mucosal injury in normal conscious dogs. In this model, severe gastric mucosal injury and a decrease in the pH of the gastric luminal contents were consistently demonstrated 2 h after the oral administration of 100 mg/kg of aspirin. Pretreatment with three histamine H2 receptor antagonists (cimetidine, ranitidine, BMY-25271), prevented both of these effects in a dose-related manner. All three H2 receptor antagonists reduced gastric mucosal injury only at doses that were greater than those required to prevent the aspirin-induced decrease in gastric luminal pH or to inhibit histamine-stimulated gastric acid secretion in Heidenhain pouch dogs. Plasma levels of aspirin were not altered by histamine H2 receptor antagonism. These results indicate that acid inhibition is an important component of the mechanisms whereby histamine H2 receptor antagonists protect the gastric mucosa from aspirin-induced damage in the dog.

Analysis of publication output of internal medicine faculty members.

The number of publications per year produced by a department of internal medicine faculty is analyzed. The output of the younger faculty members (40 years or less) averaged 1.4 publications a year, and the annual output of the older faculty (over 40 years) averaged 2.3 publications (p less than 0.05). The site of their primary clinical responsibilities did not significantly affect their publication productivity. In all subspecialty sections, the output of older faculty members correlated well with that of younger faculty members (p less than 0.005). The productivity of section chiefs correlated well with the productivity of younger faculty members in their respective sections (p less than 0.001). Younger faculty members who later entered private practice had a lower (p less than 0.02) publication output than those who left for another academic position. The output of faculty members is related to the age of the faculty members, overall sectional productivity, and productivity of the section chief.

Indomethacin enhances histamine-stimulated acid production in rabbit isolated fundic glands.

The effects of 10(-4)M indomethacin on tissue prostaglandin E2 levels, cyclic AMP concentrations, and acid secretion as measured by the intraglandular accumulation of [14C]aminopyrine were evaluated in unstimulated and histamine-stimulated isolated rabbit fundic glands. Indomethacin (10(-4)M) reduced endogenous prostaglandin E2 content by 52% in unstimulated glands. Indomethacin tripled histamine (10(-6)-10(-4)M-stimulated aminopyrine uptake while not affecting aminopyrine accumulation in unstimulated glands. Indomethacin did not affect cyclic AMP levels in either the unstimulated or stimulated condition.

Dietary fiber decreases cholesterol and phospholipid synthesis in rat intestine.

The effects of fiber ingestion on the incorporation of oleic acid into triglyceride and lecithin, acetate incorporation into cholesterol, and monosaccharide and amino acid transport were determined in rat intestine. Prolonged pectin (10% by weight) ingestion caused a decrease in jejunal and ileal cholesterol synthesis (33% and 52%, respectively). Pectin ingestion reduced cholesterol synthesis by 60% in ileal crypt cells, but did not affect cholesterol synthesis in the jejunal or ileal villus cells or in jejunal crypt cells. Cholesterol synthesis in isolated crypt cells was markedly less than in isolated villus cells. Prolonged ingestion of a fiber-free diet supplemented with either cellulose or pectin (10% and 5% by weight, respectively) decreased jejunal lecithin glucose and leucine absorption but did not affect jejunal triglyceride synthesis.

Patterns of diagnostic testing in the academic setting: the influence of medical attendings' subspecialty training.

Internists with subspecialty training (subspecialists) constitute the majority of the medical faculty members and the test-ordering behavior of these subspecialists influences how house officers and students solve clinical problems. To assess whether test-ordering patterns are influenced by the ward attendings' subspecialty status, we identified the number of gastrointestinal endoscopic procedures, bone marrow procedures and exercise stress tests that were ordered on 9608 patients admitted to a medical service during a 3 year period. The patient management was supervised by attendings, 8 of whom were generalists and 37 of whom were subspecialists. House officers supervised by generalists ordered 23% fewer gastrointestinal procedures, 47% fewer bone marrow procedures, 43% fewer exercise stress tests and 29% fewer total procedures than house staff supervised by subspecialists (P--not significant, P less than 0.001, P less than 0.05 and P less than 0.01, respectively). House officers perceive a difference between the test-ordering patterns of subspecialists and generalists. They attribute this difference to post-residency training and believe that the use of more tests indicates a greater compulsion toward an exhaustive evaluation.