Intact soil core experiments reveal that temperature and depth influence microbial community function and impact the fate of nitrogenous fertilizer amendments

The application of nitrogenous fertilizer to agricultural soil has potentially large impacts on environmental quality, including large scale emission of the potent greenhouse gas nitrous oxide and runoff of nitrates. Through their metabolic activities, including nitrification, denitrification and dissimilatory nitrate reduction to ammonium (DNRA), soil microbial communities play an active role in determining the fate of nitrogenous species, thus thorough knowledge of microbial community structure and function is important to understanding ecosystem scale N-fluxes. While much work has been done to understand the role of microbes in soil N-cycling, rarely are such communities studied in ecological context of depth and temperature combined and we hypothesize that diurnal temperature variation, large in surface soils and more narrow at depth, will result in a differential response to N-input. To investigate both the fate of exogenous N-inputs and microbial community and functional response, intact soil cores (0-10 cm and 10-30 cm depth) taken from an agricultural field site in Havana, IL were imbibed with 15N labelled NH4Cl and KNO3 to simulate fertilizer input. The unsaturated cores were then incubated under a summer diurnal temperature regime reflective of natural temperature profiles observed at specified depths (20-35°C shallow, 22-24°C deep). At nine time points over 21 days, replicate cores were deconstructively sampled for pH, NO3-, NH4+, and 15N isotopic analyses. Stable isotope pool dilution was used to calculate gross transformation rates and microbial community structure and function were assessed by T-RFLP and qPCR, respectively. Comparison of 16S rRNA based T-RFLP total community profiles revealed a distinct temporal succession across soil depths, with shifts in community structure corresponding to changes in soil NO3- and NH4+ concentration. While no significant difference in 16 rRNA based communities was evident between depths, a large temporal shift in nitrous oxide reductase gene (nosZ) based denitrifier community structure of was evident after 7 days, resulting in denitrifier communities that were significantly distinct. Additionally, qPCR analysis of relevant functional gene transcripts reveals differential trends in gene expression between depths. These results suggest that while diurnal temperature variation and depth may not significantly alter overall community structure, the functional response of community members to N-input is a function of temperature and these functional differences between soil communities has a direct impact on not only rates of transformation, but also for the timing and magnitude of N2O fluxes

Functional and Radiologic Outcomes of Degenerative Versus Traumatic Full-Thickness Rotator Cuff Tears Involving the Supraspinatus Tendon.

BACKGROUND Arthroscopic rotator cuff repair (ARCR) is among the most commonly performed orthopaedic procedures. Several factors-including age, sex, and tear severity-have been identified as predictors for outcome after repair. The influence of the tear etiology on functional and structural outcome remains controversial. PURPOSE To investigate the influence of tear etiology (degenerative vs traumatic) on functional and structural outcomes in patients with supraspinatus tendon tears. STUDY DESIGN Cohort study; Level of evidence, 2. METHODS Patients undergoing ARCR from 19 centers were prospectively enrolled between June 2020 and November 2021. Full-thickness, nonmassive tears involving the supraspinatus tendon were included. Tears were classified as degenerative (chronic shoulder pain, no history of trauma) or traumatic (acute, traumatic onset, no previous shoulder pain). Range of motion, strength, the Subjective Shoulder Value, the Oxford Shoulder Score (OSS), and the Constant-Murley Score (CMS) were assessed before (baseline) and 6 and 12 months after ARCR. The Subjective Shoulder Value and the OSS were also determined at the 24-month follow-up. Repair integrity after 12 months was documented, as well as additional surgeries up to the 24-month follow-up. Tear groups were compared using mixed models adjusted for potential confounding effects. RESULTS From a cohort of 973 consecutive patients, 421 patients (degenerative tear, n = 230; traumatic tear, n = 191) met the inclusion criteria. The traumatic tear group had lower mean baseline OSS and CMS scores but significantly greater score changes 12 months after ARCR (OSS, 18 [SD, 8]; CMS, 34 [SD,18] vs degenerative: OSS, 15 [SD, 8]; CMS, 22 [SD, 15]) (P < .001) and significantly higher 12-month overall scores (OSS, 44 [SD, 5]; CMS, 79 [SD, 9] vs degenerative: OSS, 42 [SD, 7]; CMS, 76 [SD, 12]) (P≤ .006). At the 24-month follow-up, neither the OSS (degenerative, 44 [SD, 6]; traumatic, 45 [SD, 6]; P = .346) nor the rates of repair failure (degenerative, 14 [6.1%]; traumatic 12 [6.3%]; P = .934) and additional surgeries (7 [3%]; 7 [3.7%]; P = .723) differed between groups. CONCLUSION Patients with degenerative and traumatic full-thickness supraspinatus tendon tears who had ARCR show satisfactory short-term functional results. Although patients with traumatic tears have lower baseline functional scores, they rehabilitate over time and show comparable clinical results 1 year after ARCR. Similarly, degenerative and traumatic rotator cuff tears show comparable structural outcomes, which suggests that degenerated tendons retain healing potential