Dynamics of sediment-associated nitrogen export from intermittent streams in subtropical forests of southeast China.

The significance of intermittent streams in nutrient loss within forest ecosystems is becoming increasingly critical due to changes in precipitation patterns associated with global climate change. However, few studies have focused on nutrient export from intermittent streams. We conducted continuous sediment collection from intermittent streams from March 2022 to February 2023 to investigate the export pattern and mechanism of sediment-associated nitrogen (N) from intermittent streams of different forest types (composed forest of Castanopsis carlesii (Cas. carlesii) and Cunninghamia lanceolata (C. lanceolata) forests, compared to Cas. carlesii forests). We measured the N concentrations and calculated the export amounts of four common forms of N associated with sediments: total N (TN), dissolved N (DN), nitrate, and ammonia. Our results showed that (1) the annual average exports of TN, DN, nitrate, and ammonia associated with sediments from intermittent streams from both forest types were 273, 1.62, 0.26, and 0.84 kg ha-1, respectively; (2) N export was significantly higher in composite forests of Cas. carlesii and C. lanceolata, compared to Cas. carlesii forests; (3) stream sediment export amount positively affected N export both in composite forests and Cas. carlesii forests; and (4) N export was also controlled by rainfall amount and stream characteristics. Our study quantified sediment-associated N export from intermittent streams among different subtropical forest types, which will enhance our understanding of N dynamics associated with stream hydrological processes in subtropical forests.

Global patterns and drivers of initial plant litter ash concentration.

Ash is a fundamental component of plant litter and plays a vital role in regulating litter decomposition. However, to date, global patterns and underlying mechanisms of initial litter ash concentrations remain unclear. Here, we used 570 observations collected from 104 independent publications to assess the global patterns of initial plant litter ash concentrations and evaluated the effects of mycorrhizal association [arbuscular mycorrhiza (AM) vs. ectomycorrhiza (ECM)], taxon group (gymnosperm vs. angiosperm), life form (tree vs. shrub vs. herb), leaf type (broadleaf vs. needle), and environmental factors such as climate and soil properties on initial litter ash concentration. The results showed that (1) global average ash concentrations varied significantly among different plant tissues and were 7.3, 4.5, 3.7, 3.5, 3.1, 2.4, and 1.5% in leaf, root, bark, reproductive tissue (flower and fruit), branch, stem, and wood litter, respectively; (2) in leaf litter, the initial ash concentrations of AM plants and species associated with both AM and ECM fungi were higher than those of ECM plants, and those of the tree species were lower than those of the herbs and shrubs; in root litter, the initial ash concentrations of the AM plants were lower than those of the species associated with both AM and ECM fungi but higher than those of the ECM plants; in both leaf and root litter, the initial ash concentrations of the angiosperms and broadleaf trees were higher than those of the gymnosperms and needle trees, respectively, while the effect of plant traits on branch litter was not obvious; and (3) the initial ash concentration of leaf litter was predominantly driven by mycorrhizal association and taxon group, while that of root litter tended to be driven by mycorrhizal association well as soil organic carbon. Our study clearly assessed the global patterns and underlying mechanisms of initial plant litter ash concentrations, which could help in better understanding the role of ash in litter decomposition and the related processes of carbon and nutrient cycling.

Application of intraoperative electrocorticography in bypass surgery for adult moyamoya disease: a preliminary study.

OBJECTIVE: Postoperative complications of surgical revascularization in moyamoya disease (MMD) are difficult to predict because of poor knowledge of the underlying pathophysiological process. Since the aim of surgery is to improve brain dynamics by increasing regional blood flow, we hypothesize that postoperative complications are closely related to aberrant electrophysiological changes. Thus, we evaluated the clinical significance of intraoperative electrocorticography (iECoG) in bypass surgery for adult MMD. METHODS: Ninety-one adult patients operated on by the same neurosurgeon in our institute were involved (26 in the iECoG group, 65 in the traditional group). Two 1 × 6 subdural electrode grids were placed parallel to the middle frontal gyrus and superior temporal gyrus to record ECoG data continuously during the procedure in the iECoG group. Selected from several M4 candidate arteries, the recipient artery was determined to be closer to the cortex with lower power spectral density (PSD) in the beta band. The PSD parameter we used was the (delta+theta)/(alpha+beta) (DTAB) ratio (DTABR). Next, the pre- and post-bypass PSD values were evaluated, and correlations between post-/pre-bypass PSD parameter ratios and neurological/neuropsychological performance (in terms of changes in National Institutes of Health Stroke Scale [NIHSS] and Mini-Mental State Examination [MMSE] scores) were analyzed. RESULTS: Postoperative complications (transient neurological events) in the iECoG group were significantly lower than those in the traditional group (p = 0.046). In the iECoG group, the post-/pre-bypass DTABR ratio in the bypass area was significantly correlated with postoperative NIHSS (p = 0.002, r2 = 0.338) and MMSE changes (p = 0.007, r2 = 0.266). In the nonbypass area, neither postoperative NIHSS nor MMSE changes showed a significant correlation with the post-/pre-bypass DTABR ratio (p > 0.05). Additionally, patients with postoperative complications exhibited significantly higher DTABR (1.67 ± 0.33 vs. 0.95 ± 0.08, p = 0.003) and PSD of the theta band (1.54 ± 0.21 vs. 1.13 ± 0.08, p = 0.036). CONCLUSIONS: This study is the first to explain and guide surgical revascularization from the perspective of electrophysiology. Intraoperative ECoG is not only sensitive in reflecting and predicting postoperative neurological and cognitive performance but also usable as a reference for recipient artery selection.

Immunological Responses to Transgene-Modified Neural Stem Cells After Transplantation.

Neural stem cell (NSC) therapy is a promising therapeutic strategy for stroke. Researchers have frequently carried out genetic modification or gene editing of stem cells to improve survival or therapeutic function. However, NSC transplantation carries the risk of immune rejection, and genetic modification or gene-editing might further increase this risk. For instance, recent studies have reported on manipulating the stem cell genome and transplantation via the insertion of an exogenous gene derived from magnetotactic bacteria. However, whether transgene-modified stem cells are capable of inducing immunological reactions has not been explored. Although NSCs rarely express the major histocompatibility complex (MHC), they can still cause some immunological issues. To investigate whether transgene-modified NSCs aggravate immunological responses, we detected the changes in peripheral immune organs and intracerebral astrocytes, glial cells, and MHC-I and MHC-II molecules after the injection of GFP-labeled or mms6-GFP-labeled NSCs in a rat model. Xenogeneic human embryonic kidney (HEK-293T) cells were grafted as a positive control group. Our results indicated that xenogeneic cell transplantation resulted in a strong peripheral splenic response, increased astrocytes, enhanced microglial responses, and upregulation of MHC-I and MHC-II expression on the third day of transplantation. But they decreased obviously except Iba-1 positive cells and MHC-II expression. When injection of both mms6-GFP-labeled NSCs and GFP-labeled NSCs also induced similar responses as HEK-293T cells on the third days, but MHC-I and MHC-II expression decreased 3 weeks after transplantation. In addition, mms6 transgene-modified NSCs did not produce peripheral splenic response responses as well as astrocytes, microglial cells, MHC-I and MHC-II positive cells responses when compared with non-modified NSCs. The present study provides preliminary evidence that transgenic modification does not aggravate immunological responses in NSC transplantation.

Chiral analysis of ammuxetine enantiomers in dog plasma using online SPE/liquid chromatography with tandem mass spectrometric detection after precolumn chiral derivatization.

Ammuxetine (AMT), a novel chiral antidepressant candidate compound, exhibits better antidepression effects than duloxetine in different animal models. In this article, a chiral derivatization method, combined with online solid phase extraction (online SPE) and liquid chromatography-tandem mass spectrometry (LC-MS/MS), was developed for the chiral separation of AMT enantiomers after administration of racemic AMT to dogs. The derivatization reaction employed 2,3,4,6-tetra-O-acetyl-b-glucopyr-anosyl isothiocyanate (GITC) as a precolumn chiral derivatization reagent. A SPE column Retain PEP Javelin (10 × 2.1 mm) was used to remove proteins and other impurities in plasma samples. The enantiomeric derivatives were separated on a ZORBAX SB-C18 column (50 × 2.1 mm × 3.5 µm) with an isocratic elution procedure. The selected multiple reaction monitoring mode of the positive ion was performed and the parent to the product transitions m/z 681.0/543.1 and m/z 687.4/543.1 were used to measure the derivatives of AMT and duloxetine (internal standard) with electrospray ionization. The method was validated in terms of specificity, linearity, sensitivity, precision, accuracy, matrix effect, and stability. The method was applied to a pharmacokinetics study of AMT racemate in dogs. The results suggested that the pharmacokinetic of AMT enantiomers might be stereoselective in dogs.

Cystic adventitial disease of the common femoral vein: A case report.

Adventitial cystic disease (ACD) of the common femoral vein is a rare vascular disorder. It becomes more difficult to recognize preoperatively especially when the femoral vein is affected. We report the case of a 62-year-old female patient who presented with a one-month history of painless swelling in her right lower extremity. She had no specific past medical history and no history of trauma, and had a full coagulopathy profile that was negative for any hypercoagulable syndrome. On examination, her lower right leg was significantly swollen with a palpable mass in her right inguinal region. A computerized tomography (CT) with contrast was performed to provide more information and revealed an eccentric compression over the medial wall of the right common femoral vein. During surgical exploration, adventitial cystic mucinous disease was enucleated and the patient underwent femoral exploration, excision of the cysts and reconstruction of iliac femoral vein graft using an artificial blood vessel. The pathological examination confirmed the diagnosis. The patient continued to do well, and she had an unremarkable venous duplex evaluation at her 6-month follow-up. The presentation, investigation, treatment, and pathology of this condition are discussed with a literature review.