Relative humidity: important modifier of pollutant uptake by plants.

Laboratory measurements of foliar uptake of sulfur dioxide and ozone by red kidney beans demonstrated a strong effect of relative humidity on internal pollutant dose. Foliar uptake was enhanced two- to threefold for sulfur dioxide and three- to fourfold for ozone by an increase in relative humidity from 35 to 75 percent. For the same exposure concentration, vegetation growing in humid areas (such as the eastern United States) may experience a significantly greater internal flux of pollutants than that in more arid regions.

An Atmosphere on Ganymede from Its Occultation of SAO 186800 on 7 June 1972.

On 7 June 1972 the third , Jovian satellite Ganymede occulted the eighth-magnitude star SAO 186800. Successful photoelectric observations obtained at Lembang, Java (Indonesia), and Kavalur, India, show nonabrupt immersions and emersions, indicating the presence of an atmosphere whose surface pressure is greater than about 10(-3) millibar. By fitting the two occultation durations as chords to a model disk, the diameter is found to be 5270 (+30, - approximately 200) kilometers, the major error contribution arising from the uncertain atmospheric thickness below the occultation layer. The derived mean density is 2.0 (-0.03, + approximately 0.2) grams per cubic centimeter.

Propranolol-augmented, exercise-induced human growth hormone release.

Serum growth hormone (HGH) responses to 20 minutes of exercise 90 minutes after orally given propranolol (0.5 mg/kg; maximum, 40 mg), were assessed in 15 short but otherwise normal children, in 2 obese teen-agers, in 3 hypopituitary children, and in 8 healthy adult volunteers. In six adults HGH responses to exercise alone were also assessed one week previously. Normal children responded with a peak serum HGH concentration of 10 ng/ml or greater, except one whose peak was 7 ng/ml (normal, greater than 7 ng/ml). The obese girls showed smaller responses to exercise with propranolol (ex/prop) (peak HGH, 6 ng/ml), to hypoglycemia, and to levodopa (peak HGH, 7 and 4 ng/ml). The three hypopituitary children did not respond to ex/prop or to two other stimuli. In the volunteer adults, the mean HGH responses were greater to ex/prop than to exercise alone, although two out of six did not have increased levels with exercise. There were also elevations of fasting serum HGH levels before exercise and propranolol on repeat testing. These results suggest that orally given propranolol improves the exercise-HGH stimulation test both in the number of responders and in the degree of response. Some individuals have an anticipatory HGH secretion before exercise due to a conditioned response.

High levels of mercury contamination in multiple media of the Carson River drainage basin of Nevada: implications for risk assessment.

Approximately 5.5 x 109 g (4.0 x 105) of mercury was discharged into the Carson River Drainage Basin of west-central Nevada during processing of the gold- and silver-rich Comstock ore in the late 1800s. For the past 13 decades, mercury has been redistributed throughout 500 km2 of the basin, and concentrations are some of the highest reported values in North America. This article documents the concentrations of mercury in the air, water, and substrate at both contaminated and noncontaminated sites within the basin and discusses the implications for risk assessment. At contaminated areas, the range of mercury concentrations are as follows: mill tailings, 3-1610 micrograms/g; unfiltered reservoir water, 53-591 ng/l; atmospheric vapor, 2-294 ng/m3. These values are three to five orders of magnitude greater than natural background. In all media at contaminated sites, concentrations are spatially variable, and air and water mercury concentrations vary temporally. The study are in situated in a natural mercuriferous belt, and regional background mercury concentrations in all environmental media are higher than values typically cited for natural background. As a mercury-contaminated site in North America, the Carson River Drainage Basin is unusual for a number of reasons, including its location in a natural mercuriferous belt, high and sustained levels of anthropogenic mercury inputs, long exposure time, aridity of the climate, and the riparian setting in an arid landscape, where biological activity is concentrated in the same areas that contain high levels of mercury in multiple media.

Serotonin increases excitability of rabbit C-fiber neurons by two distinct mechanisms.

Serotonin (5-HT) increases impulse activity in visceral afferent C-fibers in vivo. A 5-HT-induced membrane depolarization may partially account for this effect. Here, we examined the potential contribution of an additional mechanism to the 5-HT-mediated increase in impulse activity. Approximately 40% of rabbit visceral C-fiber neurons exhibit a protracted (greater than 3 s) spike afterhyperpolarization (AHPslow) that is a major determinant of repetitive firing properties in these neurons. Intracellular recording methods were applied to rabbit nodose ganglion neurons in vitro to assess whether 5-HT could increase excitability through effects on the AHPslow. Results revealed a concentration-dependent 5-HT-mediated depression of the AHPslow amplitude and duration that was accompanied by decreased accommodation of action potential firing. Experiments with 5-HT receptor antagonists further showed that this autacoid depressed the AHPslow through a different 5-HT receptor subtype than that subserving the 5-HT-induced depolarization. Thus the AHPslow represents a distinct locus where 5-HT can increase the impulse activity of these visceral C-fiber afferents.

Promethazine or DPPD pretreatment attenuates oleic acid-induced injury in isolated canine lungs.

Oleic acid causes pulmonary edema by increasing capillary endothelial permeability, although the mechanism of this action is uncertain. We tested the hypothesis that the damage is an oxidant injury initiated by oleic acid, using isolated blood-perfused canine lung lobes. The lobes were dilated with papaverine and perfused in zone III with a constant airway pressure of 3 cmH2O. Changes in isogravimetric capillary pressure (Pc,i) and capillary filtration coefficient (Kf,C) were used as indices of alterations in microvascular permeability in lungs treated with silicone fluid (n = 3), oleic acid (n = 11), oleic acid after pretreatment with the antioxidants promethazine HCl (n = 11) or N,N'-diphenyl-p-phenylenediamine (DPPD; n = 4), or oleic acid following pretreatment with methylprednisolone (n = 4). Kf,C averaged 0.21 +/- 0.02 ml X min-1 X cmH2O-1 X 100 g-1 in control and increased to 0.55 +/- 0.05 and 0.47 +/- 0.05 when measured 20 and 180 min after the administration of oleic acid. When oleic acid was infused into lungs pretreated with promethazine, Kf,C increased to only 0.38 +/- 0.05 ml X min-1 X cmH2O-1 X 100 g-1 after 20 min and had returned to control levels by 180 min. Pretreatment with DPPD, but not methylprednisolone, similarly attenuated the increase in Kf,C following oleic acid. Silicone fluid had no effect on Kf,C. That oleic acid increases vascular permeability was also evidenced by a fall (P less than 0.05) in Pc,i from control when measured at 180 min in every group.(ABSTRACT TRUNCATED AT 250 WORDS)

Foliar δ13C within a temperate deciduous forest: spatial, temporal, and species sources of variation.

Foliar 13C-abundance (δ13C) was analyzed in the dominant trees of a temperate deciduous forest in east Tennessee (Walker Branch Watershed) to investigate the variation in foliar δ13C as a function of time (within-year and between years), space (canopy height, watershed topography and habitat) and species (deciduous and coniferous taxa). Various hypotheses were tested by analyzing (i) samples collected from the field during the growing season and (ii) foliar tissues maintained in an archived collection. The δ13C-value for leaves from the tops of trees was 2 to 3%. more positive than for leaves sampled at lower heights in the canopy. Quercus prinus leaves sampled just prior to autumn leaf fall had significantly more negative δ13C-values than those sampled during midsummer. On the more xeric ridges, needles of Pinus spp. had more positive δ13C-values than leaves from deciduous species. Foliar δ13C-values differed significantly as a function of topography. Deciduous leaves from xeric sites (ridges and slopes) had more positive δ13C-values than those from mesic (riparian and cove) environments. On the more xeric sites, foliar δ13C was significantly more positive in 1988 (a dry year) relative to that in 1989 (a year with above-normal precipitation). In contrast, leaf δ13C in trees from mesic valley bottoms did not differ significantly among years with disparate precipitation. Patterns in foliar δ13C indicated a higher ratio of net CO2 assimilation to transpiration (A/E) for trees in more xeric versus mesic habitats, and for trees in xeric habitats during years of drought versus years of normal precipitation. However, A/E (units of mmol CO2 fixed/mol H2O transpired) calculated on the basis of δ13C-values for leaves from the more xeric sites was higher in a wet year (6.6±1.2) versus a dry year (3.4±0.4). This difference was attributed to higher transpiration (and therefore lower A/E) in the year with lower relative humidity and higher average daily temperature. The calculated A/E values for the forest in 1988-89, based on δ13C, were within ±55% of estimates made over a 17 day period at this site in 1984 using micrometeorological methods.

Physiology of ecotypic plant response to sulfur dioxide in Geranium carolinianum L.

Populations of Geranium carolinianum, a winter annual plant common in disturbed habitats, vary in their foliar response to sulfur dioxide, and pollution resistance is characteristic of populations sampled from areas in which SO2 has been a prominent stress. The physiological basis of this ecotypic response was investigated using a whole-plant gaseous exchange system in which leaf resistance to H2O efflux and SO2 influx were concurrently monitored. Individual plants of distinct SO2 susceptibility were exposed to pollutant concentrations of either 0.4, 0.6 or 0.8 µl 1-1 in both the dark and light. Total SO2 flux (µg cm-2 h-1) to the plant, which is the sum of leaf adsorptive and absorptive loss, varied as an inverse function of leaf resistance (s cm-1), and the relationship was modeled using linear regression techniques. Total SO2 flux was partitioned to leaf surface and internal fractions using estimation procedures with the regression analysis. SO2 flux into the leaf interior, the pollutant fraction responsible for causing foliar injury, was strikingly similar for resistant and sensitive plants at each concentration. Resistant plants must absorb 30% more SO2 than their sensitive counterparts in order to exhibit comparable levels of foliar injury. Therefore, in G. carolinianum the predominant explantation for genetically controlled and quantitatively inherited differences in plant résponse to SO2 is not variable pollutant flux but rather disparate physiological-biochemical processes affecting pollutant toxicity, cellular perturbation and repair. This conclusion is relevant to understanding how populations of G. carolinianum respond over time to elevated levels of SO2 and may explain the inherent susceptibility of this species compared with plants with which it co-exists.

Photosynthesis, carbon allocation, and growth of sulfur dioxide ecotypes ofGeranium carolinianum L.

This study investigated ways in which genetically determined differences in SO2 susceptibility resulting from ecotypic differentiation inGeranium carolinianum were expressed physiologically. The SO2-resistant and SO2-sensitive ecotypes were exposed to a combination of short- and long-term SO2 exposures to evaluate the responses of photosynthesis, H2S efflux from foliage (sulfur detoxification), photoassimilate retention, leaf-diffusive resistance to CO2, and growth. When exposed to SO2, both ecotypes re-emit sulfur in a volatile, reduced form, presumably as H2S. Because H2S efflux rates at various SO2 concentrations were comparable between ecotypes, genetic differences inG. carolinianum could not be attributed to a re-emission of excess sulfur as H2S. Incipient SO2 effects on photosynthesis were observed as cumulative SO2 flux into the leaf interior excecded 0.40 nmol·m-2 in the resistant ecotype and 0.26 nmol·m-2 in the sensitive ecotype. Although initial SO2-induced changes in photosynthesis in both ecotypes were mediated through an increase in stomatal resistance to CO2, the ecotype-specific patterns as a function of pollutant concentration and exposure time were associated with marked increases in residual resistance to CO2. Patterns in photosynthesis, photoassimilate retention, and growth following long-term SO2 exposures were also ecotype-specific. Although physiological accommodation of SO2 stress was observed in both ecotypes, it was more pronounced in the resistant ecotype. The physiological mechanisms underlying genetic differences inG. carolinianum in response to SO2 stress were concluded to be (1) dissimilar threshold levels of response to SO2 and/or its toxic derivatives and (2) differences in homeostatic processes governing the rate of repair or compensation for physiological injury.

Ozone flux in Glycine max (L.) Merr.: Sites of regulation and relationship to leaf injury.

Hood and Dare cultivars of soybean, Glycine max (L.) Merr., vary in their foliar response to ozone. The physiological basis of this variation was investigated as a function of leaf age through an analysis of ozone flux data, leaf developmental morphology, and analogue modelling techniques. At all concentrations (0.25-0.58 µl l-1) and exposure times (1-4 h), resistance to O3 flux in the gas phase of the diffusive pathway (i.e., boundary layer and stomate) did not account fully for variation in pollutant uptake rates into the leaf interior. Ozone molecules experienced a residual resistance to diffusion that is not shared by effluxing water vapor molecules. Residual resistance to O3 flux increased with pollutant concentration and exposure time and was associated with age-dependent differences in foliar O3 response. Leaf morphology data, including stomatal frequency and the ratio of internal to external surface area, did not help explain cultivar or age-dependent differences in O3 flux. The extent of foliar injury was not consistently related to the magnitude of O3 flux into the leaf interior. An analysis of the residual resistance to O3 flux suggests that the gas and liquid phase pathways for O3, water vapor, and carbon dioxide are not identical.

Carbon dioxide assimilation and growth of red spruce (Picea rubens Sarg.) seedlings in response to ozone, precipitation chemistry, and soil type.

The influence of ozone, mist chemistry, rain chemistry, and soil type on CO2 assimilation and growth of red spruce (Picea rubens Sarg.) seedlings was investigated over a 4-month period under controlled laboratory and glasshouse conditions. Growth was evaluated through interval estimates of aboveground relative growth rates (RGR) and the partitioning of biomass components at harvest to root, stem, and needle fractions. Precipitation chemistry treatments and O3 exposure dynamics were based on reported characteristics of air chemistry and/or deposition in high-elevation forests of eastern North America. The two soils were collected from Camels Hump in the Green Mountains of Vermont and Acadia National Park on the Maine coast. Soil from Acadia had higher organic content, higher levels of extractable base cations, and lower levels of extractable aluminum and heavy metals. The only treatment variables that consistently influenced the growth of P. rubens were soil type and rain chemistry. In comparison with seedlings grown in soil from Acadia National Park, those grown in Camels Hump soil had significantly less needle (27%), stem (33%), and root (26%) biomass at harvest and statistically lower aboveground RGR within 2 months after initiation of the treatments. Seedlings grown in Camels Hump soil had significantly higher levels of aluminum (6.5X), copper (1.4X), and nickel (2.7X) in new needle tissue. The only influence of precipitation chemistry on the growth of P. rubens was a pattern of greater root and shoot biomass in seedlings experiencing the more acidic rain treatments. Interactive effects among the main treatment variables (e.g., acidic mist and O3, acidic rain and soil type) on seedling growth were not notable. Rates of CO2 assimilation and transpiration on a per gram needle dry weight basis [mol·g-1·s-1] were not influenced by any of the main treatment variables or their interaction. Because neither soil type nor precipitation chemistry influenced the efficiency of CO2 assimilation per gram dry weight of needle tissue, the physiological mechanism underlying the growth response of P. rubens is attributed to a change in either whole-plant allocation of carbon resources or a direct toxic effect in the rhizosphere on root growth.

Pneumococcal vaccination in a remote population of high-risk Alaska Natives.

In response to an increasing prevalence of serious pneumococcal disease among adult Alaska Natives of northwest Alaska, a 3-year program was begun in 1987 to identify residents of that remote region who were at high risk for developing invasive pneumococcal disease, to determine their pneumococcal vaccination status, and to deliver vaccine to at least 80 percent of those at risk. After reviewing public health nursing and Indian Health Service data bases, the authors identified 1,337 persons, 20 percent of the 6,692 residents of the region, at high risk for invasive pneumococcal infection, defined either by having a specific chronic disease or by age criteria. Cardiovascular disease and alcoholism were the two most common chronic diseases. Only 30 percent of those determined to be at high risk had received one or more doses of pneumococcal vaccine previously. Half of those persons had received their most recent vaccination 6 or more years earlier. The program used both customary and innovative methods to deliver 23-valent polysaccharide vaccine to 1,046 of those at high risk (78 percent), including 388 persons who were revaccinated. At the completion of the project, 1,123 persons, 84 percent of those at high risk, had received at least 1 dose. They included 1,088 persons, 81 percent of those at high risk, with vaccination within the previous 5 years as a result of the project, compared with a 15-percent rate prior to the vaccination phase of the project. The program demonstrated that high levels of vaccination against pneumococcal disease, exceeding Year 2000 objectives of 60 percent, are attainable in a remote rural Alaskan population.

Preliminary measurements of summer nitric acid and ammonia concentrations in the Lake Tahoe Basin air-shed: implications for dry deposition of atmospheric nitrogen.

Over the past 50 years, Lake Tahoe, an alpine lake located in the Sierra Nevada mountains on the border between California and Nevada, has seen a decline in water clarity. With significant urbanization within its borders and major urban areas 130 km upwind of the prevailing synoptic airflow, it is believed the Lake Tahoe Basin is receiving substantial nitrogen (N) input via atmospheric deposition during summer and fall. We present preliminary inferential flux estimates to both lake surface and forest canopy based on empirical measurements of ambient nitric acid (HNO3), ammonia (NH3), and ammonium nitrate (NH4NO3) concentrations, in an effort to identify the major contributors to and ranges of atmospheric dry N deposition to the Lake Tahoe Basin. Total flux from dry deposition ranges from 1.2 to 8.6 kg N ha-1 for the summer and fall dry season and is significantly higher than wet deposition, which ranges from 1.7 to 2.9 kg N ha-1 year-1. These preliminary results suggest that dry deposition of HNO3 is the major source of atmospheric N deposition for the Lake Tahoe Basin, and that overall N deposition is similar in magnitude to deposition reported for sites exposed to moderate N pollution in the southern California mountains.

Octreotide does not prevent bacterial translocation in an infant piglet model of intestinal ischemia-reperfusion.

The process of bacterial translocation (BT) after ischemia/reperfusion (I/R) injury is reported to be mediated by local mucosal factors, the effects of pancreatic enzymes, epithelial disruption, and by dysfunctional intestinal motility. Octreotide (OCT), a somatostatin analog, has been postulated to protect against BT by influencing one or more of these factors. Twenty-two formula-fed piglets (weight, 3.5 +/- 0.5 kg; age, 20 +/- 5 days) were divided into four groups: control (no drug given; no I/R; n = 6), I/R (no drug given; n = 5), I/R plus low-dose OCT (LD OCT, 0.08 microgram/kg; n = 6), and I/R plus high-dose OCT (HD OCT, 8 micrograms/kg; n = 5). All experimental subjects had nonocclusive mesenteric ischemia induced by reversible pericardial tamponade with mesenteric flow decreased to 25 +/- 5% of baseline for 5 hours followed by 15 +/- 5 hours of reperfusion. Mesenteric lymph nodes (MLN), liver, spleen, blood, and peritoneum were harvested for blind microbial analysis. None of the animals in the control group experienced translocation to the tissues tested. All of the animals in the I/R group experienced BT to the MLN. The subjects in the LD OCT and HD OCT groups experienced BT to the MLN 66% and 80% of the time, respectively. Despite the reported clinical evidence that OCT can protect the intestinal mucosa from injury and increase the clearance of bacteria from the gastrointestinal tract, in this study in which variables other than I/R known to promote bacterial translocation were eliminated, OCT failed to modify or prevent the occurrence of translocation to the MLN after I/R injury.

Physiological Site of Ethylene Effects on Carbon Dioxide Assimilation in Glycine max L. Merr.

The physiological site of ethylene action on CO(2) assimilation was investigated in intact plants of Glycine max L., using a whole-plant, open exposure system equipped witha remotely operated single-leaf cuvette. The objective of the study was met by investigating in control and ethylene-treated plants the (a) synchrony in response of CO(2) assimilation, stomatal conductance to water vapor, and substomatal CO(2) partial pressure; (b) response of CO(2) assimilation as a function of a range of substomatal CO(2) partial pressures; and (c) response of CO(2) assimilation as a function of a range of photon flux densities. After exposure to 410 micromoles per cubic meter of ethylene for 2.0 hours, CO(2) assimilation and stomatal conductance declined in synchrony, while substomatal CO(2) partial pressure remained unchanged until exposure times equaled and exceeded 3.0 hours. Because incipient changes in CO(2) assimilation occurred without a change in the CO(2) partial pressure in the leaf interior, it is concluded that both stomatal physiology and the chloroplast's CO(2) assimilatory capacity were initial sites of ethylene action. After 3.5 hours the effect of ethylene on stomatal conductance and CO(2) assimilation exhibited saturation kinetics, and the effect was substantially more pronounced for stomatal conductance than for CO(2) assimilation. Based on the response of CO(2) assimilation to a range of substomatal CO(2) partial pressures, ethylene did not affect either the CO(2) compensation point or carboxylation efficiency at subsaturating CO(2) partial pressures. Above-ambient supplies of CO(2) did not alleviate the diminished rates of CO(2) assimilation. In partitioning the limitations imposed on CO(2) assimilation in control and ethylene-treated plants, the stomatal component accounted for only 16 and 4%, respectively. The response of CO(2) assimilation to a range of photon flux densities suggests that ethylene reduced apparent quantum yield by nearly 50%. Thus, the pronounced decline in net photosynthetic CO(2) assimilation in the presence of ethylene was due more to a loss in the mesophyll tissue's intrinsic capacity to assimilate CO(2) than to a reduction in stomatal conductance.