Phosphorus and nitrogen cycling in forest soils depending on long-term nitrogen inputs

Foliar phosphorus (P) contents have been decreasing in a range of temperate forests in Europe and North America during the last decades, and one reason for this might be atmospheric nitrogen (N) deposition (1,2,3). Therefore, we studied the effect of N inputs on P and N cycling in long-term N fertilization experiments in temperate forests. The aim of the study was to test how increased N inputs affect P and N cycling in forest soils. We sampled the organic layer of three N fertilization experiments in the USA (Harvard Forest, Cary Institute and Bear Brook), that are between 17 and 25 years old. Net N and P mineralization rates were determined along with microbial biomass, enzyme activities and soil C, N and P stoichiometry. Total C and N concentrations in the organic layer (Oe+Oa horizon) increased significantly due to long-term fertilization in Harvard Forest and the same trend was observed in the two other experiments that are based on lower N fertilization rates. Contrariwise, total P concentrations in the organic layer decreased on average by 15% due to N fertilization, while C:P ratios increased by 60%. Phosphatase activity was elevated in the N fertilized soils in all experiments by a factor of 2 to 5, and the ratio of chitinase:phosphatase activity was on average decreased by 30%, indicating that specifically phosphatase production was upregulated. The results imply that trees and/or microorganisms invested more N in the production of phosphatases in the N fertilized soils than in the non-fertilized controls. Net P mineralization did not change consistently with N inputs, indicating that mineralized P was quickly taken up by the plants in most of the N fertilized soils. In contrast, net N mineralization increased in all experiments in response to N fertilization, while microbial biomass C was only little affected by N fertilization In conclusion, the experiments indicate that high inputs of N in temperate forest ecosystems lead to increased P demand and hence to increased phosphatase activity. Moreover, the decreased P concentration and the elevated C:P ratio of the organic layer indicate that P is preferentially mineralized and taken up by plants. Our results support the hypothesis that increased atmospheric N inputs are the reason for an emerging P limitation in temperate forests

Application of Automatic Speech Recognition Technology for Dysphonic Speech Assessment

Dysphonia is a communication disorder secondary to a problem with voice production. Speakers with dysphonia often report decreased intelligibility, particularly in a noisy communication environment. Intelligibility is the primary measure of a speaker’s communicative ability; however, it is not routinely assessed in clinical settings today. This lack of intelligibility assessment can be partly attributed to the time-consuming, labor-intensive nature of manually transcribing a speaker’s utterance. Recent advances in automatic speech recognition technology have significantly increased the ease and accuracy of speech-to-text transcription, and incorporation of this technology may dramatically increase efficiency in clinical intelligibility assessment. Therefore, this project examined the feasibility of an automatic speech-to-text transcription program for describing speech production abnormalities among speakers with dysphonia. Audio recordings of the Rainbow Passage from 30 adult female speakers with normal voice and 23 adult female speakers with dysphonic voice were transcribed using IBM Watson speech-to-text transcription service. Differences between the groups were evaluated based on three measures: 1) error rate in transcribed words, 2) confidence level of transcribed words, and 3) number of possible alternatives for transcribed words. The results indicated that the confidence level was significantly lower, and the number of possible alternatives was significantly higher in the dysphonic group. Interestingly, there was no significant between-group difference in the error rate. Clinical implications of these findings and future direction will be discussed.Ope

Structural insights into Clostridium perfringens delta toxin pore formation

Clostridium perfringens Delta toxin is one of the three hemolysin-like proteins produced by C. perfringens type C and possibly type B strains. One of the others, NetB, has been shown to be the major cause of Avian Nectrotic Enteritis, which following the reduction in use of antibiotics as growth promoters, has become an emerging disease of industrial poultry. Delta toxin itself is cytotoxic to the wide range of human and animal macrophages and platelets that present GM2 ganglioside on their membranes. It has sequence similarity with Staphylococcus aureus β-pore forming toxins and is expected to heptamerize and form pores in the lipid bilayer of host cell membranes. Nevertheless, its exact mode of action remains undetermined. Here we report the 2.4 Å crystal structure of monomeric Delta toxin. The superposition of this structure with the structure of the phospholipid-bound F component of S. aureus leucocidin (LukF) revealed that the glycerol molecules bound to Delta toxin and the phospholipids in LukF are accommodated in the same hydrophobic clefts, corresponding to where the toxin is expected to latch onto the membrane, though the binding sites show significant differences. From structure-based sequence alignment with the known structure of staphylococcal α-hemolysin, a model of the Delta toxin pore form has been built. Using electron microscopy, we have validated our model and characterized the Delta toxin pore on liposomes. These results highlight both similarities and differences in the mechanism of Delta toxin (and by extension NetB) cytotoxicity from that of the staphylococcal pore-forming toxins

Daratumumab monotherapy for patients with intermediate-risk or high-risk smoldering multiple myeloma: a randomized, open-label, multicenter, phase 2 study (CENTAURUS)

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