Patients with heart failure frequently exhibit abnormal skeletal muscle metabolic responses to exercise, as assessed with 31P NMR. To investigate whether these metabolic abnormalities are due to intrinsic skeletal muscle changes, we performed gastrocnemius muscle biopsies on 22 patients with heart failure (peak Vo2, 15.4±4.7 ml/kg/min; ejection fraction, 20±7%) and on eight normal subjects. Biopsies were analyzed for fiber type and area, capillarity, citrate synthase, phosphofructokinase, lactate dehydrogenase, and ,B-hydroxyacyl CoA dehydrogenase activity. All patients with heart failure also underwent 31P NMR studies of their calf muscle during plantarflexion at three workloads. Muscle pH responses and the relation of the ratio of inorganic phosphate to phosphocreatine (Pi/PCr) to systemic Vo2 were then evaluated.Compared with normal subjects, patients with heart failure exhibited a shift in fiber distribution with increased percentage of the fast twitch, glycolytic, easily fatigable type Ilb fibers (normal subjects, 22.7± 10.1; heart failure, 33.1 ± 1. 1%; p <0.05), atrophy of type lla (normal subjects, 5,477±1,109; heart failure, 4,239±1,247 ALm2; p<0.05) and type lIb fibers (normal subjects, 5,957±1,388; heart failure, 4,144±945 um2; p<0.01), and decreased activity of j-hydroxyacyl CoA dehydrogenase (normal subjects, 5.17±1.44; heart failure, 3.67±1.68 mol/kg protein/hr; p<0.05). No significant linear correlation could be identified between the slope of the Pi/PCr to Vo2 relation and muscle histochemistry or enzyme activities. Similarly, no linear relation was found between intracellular pH at peak exercise and any muscle variable. These data suggest that patients with heart failure develop intrinsic skeletal muscle changes but that these intrinsic muscle changes do not contribute significantly to the abnormal skeletal muscle 31P NMR metabolic responses observed in such patients. (Circulation 1989;80:1338-1346 E xertional fatigue in patients with heart failure has traditionally been attributed to skeletal muscle underperfusion. However, recent investigations suggest that intrinsic skeletal muscle abnormalities may be operative, as well. Abnormal forearm 31P NMR responses to forearm exercise in patients with heart failure have been

Few studies have focused on broad scale biogeographic patterns of ammonia oxidizers in coastal systems, yet understanding the processes that govern them is paramount to understanding the mechanisms that drive biodiversity, and ultimately impact ecosystem processes. Here we present a meta-analysis of 16 years of data of ammonia oxidizer abundance, diversity, and activity in New England (NE) salt marshes and 5 years of data from marshes in the Gulf of Mexico (GoM). Potential nitrification rates were more than 80x higher in GoM compared to NE marshes. However, nitrifier abundances varied between regions, with ammonia-oxidizing archaea (AOA) and comammox bacteria significantly greater in GoM, while ammonia-oxidizing bacteria (AOB) were more than 20x higher in NE than GoM. Total bacterial 16S rRNA genes were also significantly greater in GoM marshes. Correlation analyses of rates and abundance suggest that AOA and comammox are more important in GoM marshes, whereas AOB are more important in NE marshes. Furthermore, ratios of nitrifiers to total bacteria in NE were as much as 80x higher than in the GoM, suggesting differences in the relative importance of nitrifiers between these systems. Communities of AOA and AOB were also significantly different between the two regions, based on amoA sequences and DNA fingerprints (terminal restriction fragment length polymorphism). Differences in rates and abundances may be due to differences in salinity, temperature, and N loading between the regions, and suggest significantly different N cycling dynamics in GoM and NE marshes that are likely driven by strong environmental differences between the regions.

We investigated the impacts of drought on ammonia-oxidizing archaea (AOA) and bacteria (AOB) in a salt marsh and compared the response to the total bacterial community. We analyzed abundance and community composition of amoA genes by QPCR and TRFLP, respectively, in three vegetation zones in 2014 (pre-drought), 2016 (drought), and 2017 (post-drought), and analyzed bacterial 16S rRNA genes by QPCR, TRFLP, and MiSeq analyses. AOA and AOB abundance in the Spartina patens zone increased significantly in 2016, while abundance decreased in the tall S. alterniflora zone, and showed little change in the short S. alterniflora zone. Total bacterial abundance declined annually in all vegetation zones. Significant shifts in community composition were detected in 2016 in two of the three vegetation zones for AOA and AOB, and in all three vegetation zones for total bacteria. Abundance and community composition of AOA and AOB returned to pre-drought conditions by 2017, while bacterial abundance continued to decline, suggesting that nitrifiers may be more resilient to drought than other bacterial communities. Finding vegetation-specific drought responses among N-cycling microbes may have broad implications for changes in N availability and marsh productivity, particularly if vegetation patterns continue to shift as predicted due to sea level rise.

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