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S Findlay

Publications and source records attributed to S Findlay.

At least 19 recordsLinked to original sources
PubMed2006

Large-scale variation in subsurface stream biofilms: a cross-regional comparison of metabolic function and community similarity.

We examined bacterial metabolic activity and community similarity in shallow subsurface stream sediments distributed across three regions of the eastern United States to assess whether there were parallel changes in functional and structural attributes at this large scale. Bacterial growth, oxygen consumption, and a suite of extracellular enzyme activities were assayed to describe functional variability. Community similarity was assessed using randomly amplified polymorphic DNA (RAPD) patterns. There were significant differences in streamwater chemistry, metabolic activity, and bacterial growth among regions with, for instance, twofold higher bacterial production in streams near Baltimore, MD, compared to Hubbard Brook, NH. Five of eight extracellular enzymes showed significant differences among regions. Cluster analyses of individual streams by metabolic variables showed clear groups with significant differences in representation of sites from different regions among groups. Clustering of sites based on randomly amplified polymorphic DNA banding resulted in groups with generally less internal similarity although there were still differences in distribution of regional sites. There was a marginally significant (p = 0.09) association between patterns based on functional and structural variables. There were statistically significant but weak (r2 approximately 30%) associations between landcover and measures of both structure and function. These patterns imply a large-scale organization of biofilm communities and this structure may be imposed by factor(s) such as landcover and covariates such as nutrient concentrations, which are known to also cause differences in macrobiota of stream ecosystems.

Bacteria↗
PubMed2002

A cross-system comparison of bacterial and fungal biomass in detritus pools of headwater streams.

The absolute amount of microbial biomass and relative contribution of fungi and bacteria are expected to vary among types of organic matter (OM) within a stream and will vary among streams because of differences in organic matter quality and quantity. Common types of benthic detritus [leaves, small wood, and fine benthic organic matter (FBOM)] were sampled in 9 small (1st-3rd order) streams selected to represent a range of important controlling factors such as surrounding vegetation, detritus standing stocks, and water chemistry. Direct counts of bacteria and measurements of ergosterol (a fungal sterol) were used to describe variation in bacterial and fungal biomass. There were significant differences in bacterial abundance among types of organic matter with higher densities per unit mass of organic matter on fine particles relative to either leaves or wood surfaces. In contrast, ergosterol concentrations were significantly greater on leaves and wood, confirming the predominance of fungal biomass in these larger size classes. In general, bacterial abundance per unit organic matter was less variable than fungal biomass, suggesting bacteria will be a more predictable component of stream microbial communities. For 7 of the 9 streams, the standing stock of fine benthic organic matter was large enough that habitat-weighted reach-scale bacterial biomass was equal to or greater than fungal biomass. The quantities of leaves and small wood varied among streams such that the relative contribution of reach-scale fungal biomass ranged from 10% to as much as 90% of microbial biomass. Ergosterol concentrations were positively associated with substrate C:N ratio while bacterial abundance was negatively correlated with C:N. Both these relationships are confounded by particle size, i.e., leaves and wood had higher C:N than fine benthic organic matter. There was a weak positive relationship between bacterial abundance and streamwater soluble reactive phosphorus concentration, but no apparent pattern between either bacteria or fungi and streamwater dissolved inorganic nitrogen. The variation in microbial biomass per unit organic matter and the relative abundance of different types of organic matter contributed equally to driving differences in total microbial biomass at the reach scale.

Bacteria↗
PubMed1999

Influence of Three Contrasting Detrital Carbon Sources on Planktonic Bacterial Metabolism in a Mesotrophic Lake.

Abstract Lakes receive organic carbon from a diversity of sources which vary in their contribution to planktonic microbial food webs. We conducted a mesocosm study to test the effects of three different detrital carbon sources (algae, aquatic macrophytes, terrestrial leaves) on several measures of microbial metabolism in a small meso-eutrophic lake (DOC approximately 5 mg/L). Small DOC additions (DeltaC < 1 mg/L) affected bacterial numbers, growth, and pathways of carbon acquisition. Macrophyte and leaf detritus significantly increased TDP and color, but bacterial densities initially (+12 h) were unaffected. After 168 h, densities in systems amended with terrestrial detritus were 60% less than in controls, while production rates in mesocosms with macrophyte detritus were 4-fold greater. Detritus treatments resulted in greater per-cell production rates either through stable cell numbers and greater growth rates (macrophyte-C) or lower densities with stable production rates (terrestrial-C). After only 12 h, rates of leucine aminopeptidase (LAPase) activity were 2.5x greater in macrophyte-C systems than in controls, but LAPase and beta-N-acetylglucosamindase activities in systems amended with terrestrial-C were only 50% of rates in controls. After 168 h, beta-xylosidase rates were significantly greater in communities with terrestrial and phytoplankton detritus. Microbial utilization of >20% of 102 carbon sources tested were affected by at least one detritus addition. Macrophyte-C had positive (6% of substrates) and negative (14%) effects on substrate use; terrestrial detritus had mainly positive effects. An ordination based on carbon-use profiles (+12 h) revealed a cluster of macrophyte-amended communities with greater use of psicose, lactulose, and succinamic acid; controls and algal-detritus systems were more effective in metabolizing two common sugars and cellobiose. After 168 h, communities receiving terrestrial detritus were most tightly clustered, exhibiting greater use of raffinose, pyroglutamic acid, and sebacic acid. Results suggest that pelagic bacterial communities respond to changes in organic carbon source rapidly and by different routes, including shifts in per-cell production rates and variations in degradation of a variety of compounds comprising the DOC pool.

Journal Article↗
PubMed1998

Effects of budesonide by means of the Turbuhaler on the hypothalmic-pituitary-adrenal axis in asthmatic subjects: a dose-response study.

BACKGROUND: As a general phenomenon, corticosteroids may suppress the activity in the hypothalamic-pituitary-adrenal (HPA) axis. The adrenal stimulation test is a commonly used method to assess the relative risk of exogenous corticosteroids to induce systemic side effects. OBJECTIVES: This clinical trial was performed to assess the effects of budesonide on the HPA axis (at 800, 1600, or 3200 microg/day, given as a twice daily regimen, administered by means of the Turbuhaler) in adult patients with mild, non-steroid-dependent asthma. METHODS: Sixty-four asthmatic patients received budesonide or placebo by inhalation or 10 mg/day oral prednisone once daily as a positive control in a double-blind, double-dummy, randomized, placebo-controlled, parallel-group, multicenter study. Plasma cortisol concentration was measured to assess the effect on the HPA axis before and during a 6-hour infusion of synthetic adrenocorticotropic hormone (ACTH), cosyntropin. RESULTS: After 6 weeks of treatment, plasma cortisol concentrations after adrenal stimulation by cosyntropin infusion had fallen by 4% in the placebo group; by 13%, 11%, and 27% in the budesonide groups (800, 1600, and 3200 microg/day, respectively); and by 35% in the prednisone group. The decrease was significant only in the 3200 microg/day budesonide (p = 0.03) and prednisone (p = 0.005) groups. Over the same time period, decreases in basal plasma cortisol concentrations were 1% in the placebo group; 19%, 19%, and 34% in the three budesonide groups; and 37% in the prednisone group. Only in the prednisone group was the decrease significant (p = 0.03 vs placebo). CONCLUSIONS: In this study budesonide inhaled by means of the Turbuhaler, at doses recommended for clinical use (800 or 1600 microg/day), did not produce any statistically significant suppression of the HPA axis compared with placebo.

Administration, Inhalation↗
PubMed1996

Comparison of efficacy, safety, and skin test inhibition of cetirizine and astemizole.

BACKGROUND: Astemizole, an H1-histamine-receptor antagonist prescribed for seasonal allergic rhinitis, has a slow onset of action and a strong suppressive effect on the wheal and flare reaction, which interferes with skin testing results. The newer antihistamine cetirizine appears to have a rapid onset of action and a low potential to interfere with posttreatment skin testing results. OBJECTIVE: To compare the efficacy, safety, and skin test inhibition of astemizole and cetirizine in the treatment of seasonal allergic rhinitis. METHODS: In a double-blind, parallel-group study conducted at six sites during ragweed pollination season, 263 subjects were randomized to receive 10 mg of astemizole, 5 mg of cetirizine, or 10 mg of cetirizine daily for 2 weeks. The subjects rated seven allergic rhinitis symptoms daily, the subjects and investigators provided global assessments of the responses to the treatments, and the subjects rated their satisfaction with the treatments. Thirty-nine subjects at one study site underwent quantitative skin testing before and after treatment. RESULTS: As measured by reduction from baseline in total symptom severity score, which was the primary efficacy measure in the study, all three treatments significantly relieved the symptoms of allergic rhinitis (P less than .05). This finding was supported by the global ratings and the subject satisfaction ratings. There were no significant differences among the three treatments for reduction from baseline in total symptom severity score. The mean subject satisfaction score with 10 mg of cetirizine was significantly greater than that with astemizole (P less than .05). In the skin tests performed 3, 7, and 14 days after the end of antihistamine treatment, the subjects who had received the cetirizine doses had significantly greater mean sum of wheal and mean sum of erythema values than those who had received the astemizole dose (P less than .05). Sensitivity to ragweed pollen extract returned to 90% of baseline within three days of the end of cetirizine treatment. Both drugs were well tolerated and their adverse event profiles were similar. CONCLUSIONS: Astemizole and cetirizine are effective and well tolerated in alleviating the symptoms of ragweed-induced allergic rhinitis. Cetirizine inhibits skin test results to a much lesser extent than does astemizole. Physicians may wish to consider the potential for skin test inhibition when selecting an antihistamine for patients with allergic rhinitis.

Adolescent↗