Impact of sea-ice dynamics on the spatial distribution of diatom resting stages in sediments of the Pacific Arctic region

Author Posting. © American Geophysical Union, 2021. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 126(7), (2021): e2021JC017223, https://doi.org/10.1029/2021JC017223.The Pacific Arctic region is characterized by seasonal sea-ice, the spatial extent and duration of which varies considerably. In this region, diatoms are the dominant phytoplankton group during spring and summer. To facilitate survival during periods that are less favorable for growth, many diatom species produce resting stages that settle to the seafloor and can serve as a potential inoculum for subsequent blooms. Since diatom assemblage composition is closely related to sea-ice dynamics, detailed studies of biophysical interactions are fundamental to understanding the lower trophic levels of ecosystems in the Pacific Arctic. One way to explore this relationship is by comparing the distribution and abundance of diatom resting stages with patterns of sea-ice coverage. In this study, we quantified viable diatom resting stages in sediments collected during summer and autumn 2018 and explored their relationship to sea-ice extent during the previous winter and spring. Diatom assemblages were clearly dependent on the variable timing of the sea-ice retreat and accompanying light conditions. In areas where sea-ice retreated earlier, open-water species such as Chaetoceros spp. and Thalassiosira spp. were abundant. In contrast, proportional abundances of Attheya spp. and pennate diatom species that are commonly observed in sea-ice were higher in areas where diatoms experienced higher light levels and longer day length in/under the sea-ice. This study demonstrates that sea-ice dynamics are an important determinant of diatom species composition and distribution in the Pacific Arctic region.This work was conducted by the Arctic Challenge for Sustainability (ArCS) project, Arctic Challenge for Sustainability II (ArCSII) project and ArCS program for overseas visits by young researchers. In addition, this work was partly supported by the Japan Society for the Promotion of Science (JSPS) KAKENHI Grant Number JP20J20410 and JP21H02263. We thank Anderson laboratory members for their support of our study at WHOI, and also thank Robert Pickart, Leah McRaven, and Jacqueline Grebmeier for their support and assistance on the Healy cruises. Funding for DA, EF, and MR was provided by the NOAA Arctic Research Program through the Cooperative Institute for the North Atlantic Region (CINAR Award NA14OAR4320158), by the NOAA ECOHAB Program (NA20NOS4780195) and by the National Science Foundation Office of Polar Programs (OPP-1823002). This is ECOHAB contribution number ECO986.2021-12-1

Dynamic Trend of Myocardial Edema in Takotsubo Syndrome: A Serial Cardiac Magnetic Resonance Study

BACKGROUND The wall motion abnormalities of the left ventricle (LV) in takotsubo syndrome (TTS) are known to be transient and completely recover within a few weeks. However, there is little information about the relationship between functional recovery and tissue characteristics. The aim of this study was to investigate the recovery process of TTS using cardiovascular magnetic resonance (CMR). METHODS Consecutive patients with TTS were prospectively enrolled. We performed serial CMR in the acute phase (<72 h after admission), the subacute phase (7-10 days after admission) and the chronic phase (3 months later). To assess the degree of myocardial edema quantitatively, we evaluated the signal intensity of myocardium on T2-weighted images and calculated the signal intensity ratio compared with the skeletal muscle. RESULTS Fifteen patients with TTS were enrolled. CMR demonstrated reduced LV ejection fraction in the acute phase, and it recovered almost completely by the subacute phase. On the other hand, severe myocardial edema was still observed in the subacute phase, associated with increased LV mass. The highest signal intensity ratio in the subacute phase was correlated with the maximum voltage of negative T wave on electrocardiogram (r = 0.57, p = 0.03). CONCLUSIONS In patients with TTS, myocardial edema associated with increased LV mass still remained in the subacute phase despite functional recovery of the LV. Electrocardiogram may be useful to assess the degree of myocardial edema in the subacute phase. Our study suggests that myocardial ischemia might have a central role in developing TTS

Prognostic factors for progression of visual field deterioration in patients with primary open-angle glaucoma

Regulatory T cells (Tregs) play an important role in the maintenance of self-tolerance and immune homeostasis. Interleukin-2 (IL-2) is critical for Treg expansion, activity and survival. Previous studies have demonstrated that low-dose IL-2 resulted in the selective expansion of Tregs and the clinical improvement of auto-immune disease. To examine the mechanisms whereby IL-2 affects Treg apoptosis through the intrinsic pathway, we used BH3 profiling, and quantitated mitochondrial apoptotic priming. This pattern suggests that Tregs were more primed than conventional CD4 T cells (Tcons) in a BCL2-dependent manner. Tregs expressed lower levels of BCL2 than Tcons. To examine the functional effects of IL-2, sorted Tregs and Tcons were cultured with different concentrations of IL-2. Low-dose IL-2 (10 IU/mL) lowered priming and increased BCL2 expression in Tregs. However, higher concentrations of IL-2 (>100 IU/mL) were required to increase BCL2 expression and decrease priming in Tcons. Apoptosis assays also revealed that low-dose IL-2 reduced susceptibility to apoptosis only in Tregs. ABT-199, a selective BCL2 inhibitor, enhanced the priming and apoptosis of both Tcells. IL-2 reversed the effects of ABT-199 for Tregs only. This provides further evidence that the inhibition of intrinsic pathway apoptosis mediated by IL-2 in Tregs is dependent on BCL2

Neoadjuvant chemotherapy with docetaxel, nedaplatin, and fluorouracil for resectable esophageal cancer : A phase II study

Cisplatin plus 5‐fluorouracil is regarded as standard neoadjuvant chemotherapy for esophageal squamous cell carcinoma (ESCC) in Japan, but the prognosis remains poor. We have previously described how definitive chemoradiotherapy with docetaxel, nedaplatin, and 5‐fluorouracil (DNF) led to a very high response rate and promising survival times. We therefore undertook a phase II trial to evaluate the feasibility and efficacy of neoadjuvant DNF. The study included patients with clinical stage Ib‐III ESCC. Chemotherapy consisted of i.v. docetaxel (30 mg/m2) and nedaplatin (50 mg/m2) on days 1 and 8, and a continuous infusion of 5‐fluorouracil (400 mg/m2/day) on days 1‐5 and 8‐12, every 3 weeks. After three courses of chemotherapy, esophagectomy was carried out. The primary end‐point was the completion rate of the protocol treatment. Twenty‐eight patients were enrolled (cStage Ib/II/III, 2/3/23) and all received at least two cycles of chemotherapy. Twenty‐five patients underwent surgery, all of whom achieved an R0 resection, leading to a completion rate of 89.3%. The overall response rate was 87.0%. A pathological complete response was confirmed in eight (32.0%) cases. Grade 3/4 adverse events included leukopenia (32.1%), neutropenia (39.3%), febrile neutropenia (10.7%), thrombocytopenia (10.7%), and diarrhea (14.3%), but were manageable. Treatment‐related deaths and major surgical complications did not occur. Estimated 2‐year progression‐free and overall survival rates were 70.4% and 77.2%, respectively. Thus, DNF therapy was well tolerated and deemed feasible, with a strong tumor response in a neoadjuvant setting for ESCC. This trial is registered with the University Hospital Medical Information Network (UMIN ID: 000014305)

Formation of Proton Motive Force Under Low-Aeration Alkaline Conditions in Alkaliphilic Bacteria

In Mitchell’s chemiosmotic theory, a proton (H+) motive force across the membrane (Δp), generated by the respiratory chain, drives F1Fo-ATPase for ATP production in various organisms. The bulk-base chemiosmotic theory cannot account for ATP production in alkaliphilic bacteria. However, alkaliphiles thrive in environments with a H+ concentrations that are one-thousandth (ca. pH 10) the concentration required by neutralophiles. This situation is similar to the production of electricity by hydroelectric turbines under conditions of very limited water. Alkaliphiles manage their metabolism via various strategies involving the cell wall structure, solute transport systems and molecular mechanisms on the outer surface membrane. Our experimental results indicate that efficient ATP production in alkaliphilic Bacillus spp. is attributable to a high membrane electrical potential (ΔΨ) generated for an attractive force for H+ on the outer surface membrane. In addition, the enhanced F1Fo-ATPase driving force per H+ is derived from the high ΔΨ. However, it is difficult to explain the reasons for high ΔΨ formation based on the respiratory rate. The Donnan effect (which is observed when charged particles that are unable to pass through a semipermeable membrane create an uneven electrical charge) likely contributes to the formation of the high ΔΨ because the intracellular negative ion capacities of alkaliphiles are much higher than those of neutralophiles. There are several variations in the adaptation to alkaline environments by bacteria. However, it could be difficult to utilize high ΔΨ in the low aeration condition due to the low activity of respiration. To explain the efficient ATP production occurring in H+-less and air-limited environments in alkaliphilic bacteria, we propose a cytochrome c-associated “H+ capacitor mechanism” as an alkaline adaptation strategy. As an outer surface protein, cytochrome c-550 from Bacillusclarkii possesses an extra Asn-rich segment between the region anchored to the membrane and the main body of the cytochrome c. This structure may contribute to the formation of the proton-binding network to transfer H+ at the outer surface membrane in obligate alkaliphiles. The H+ capacitor mechanism is further enhanced under low-aeration conditions in both alkaliphilic Bacillus spp. and the Gram-negative alkaliphile Pseudomonas alcaliphila

Targeting Notch-1 positive acute leukemia cells by novel fucose-bound liposomes carrying daunorubicin

Complete remission by induction therapy in acute myelogenous leukemia (AML) can be achieved due to improvements in supportive and optimized therapy. However, more than 20% of patients will still need to undergo salvage therapy, and most will have a poor prognosis. Determining the specificity of drugs to leukemia cells is important since this will maximize the dose of chemotherapeutic agents that can be administered to AML patients. In turn, this would be expected to lead to reduced drug toxicity and its increased efficacy. We targeted Notch-1 positive AML cells utilizing fucose-bound liposomes, since activation of Notch-1 is required for O-fucosylation. Herein, we report that intravenously injected, L-fucose-bound liposomes containing daunorubicin can be successfully delivered to AML cells that express fucosylated antigens. This resulted in efficient tumor growth inhibition in tumor-bearing mice and decreased proliferation of AML patient-derived leukemia cells. Thus, biological targeting by fucose-bound liposomes that takes advantage of the intrinsic characteristics of AML cells could be a promising new strategy for Notch-1 positive-AML treatment

A dehydrated space-weathered skin cloaking the hydrated interior of Ryugu

Without a protective atmosphere, space-exposed surfaces of airless Solar System bodies gradually experience an alteration in composition, structure and optical properties through a collective process called space weathering. The return of samples from near-Earth asteroid (162173) Ryugu by Hayabusa2 provides the first opportunity for laboratory study of space-weathering signatures on the most abundant type of inner solar system body: a C-type asteroid, composed of materials largely unchanged since the formation of the Solar System. Weathered Ryugu grains show areas of surface amorphization and partial melting of phyllosilicates, in which reduction from Fe3+ to Fe2+ and dehydration developed. Space weathering probably contributed to dehydration by dehydroxylation of Ryugu surface phyllosilicates that had already lost interlayer water molecules and to weakening of the 2.7 µm hydroxyl (–OH) band in reflectance spectra. For C-type asteroids in general, this indicates that a weak 2.7 µm band can signify space-weathering-induced surface dehydration, rather than bulk volatile loss

Photophysiological response of diatoms in surface sediments to light exposure : A laboratory experiment on a diatom community in sediments from the Chukchi Sea

Diatoms form dense blooms in the Pacific Arctic region from spring to summer, supporting the unique benthic-pelagic coupling ecosystems. Although the Arctic has a severe light-limited season from autumn to winter, diatoms can proliferate in spring when sufficient light becomes available for photosynthesis. One of the crucial strategies for diatoms to survive in unfavorable growing conditions is to form resting stages. Because of enhanced primary and export production in the Pacific Arctic shelves, many viable diatom resting stages can be detected in the surface sediments. However, little is known about the photophysiological response of viable diatom cells, including resting stages, in sediments to light availability. We conducted a laboratory experiment investigating the photophysiological capabilities of the diatom cells containing resting stages using surface sediments from the Chukchi Sea shelf. As a result, diatoms grew dramatically after light exposure, and Chaetoceros socialis complex highly contributed to the enhanced diatom abundance. Their photophysiological changes were also evident from the maximum quantum efficiency (F-v/F-m) of photochemistry in photosystem II, C-13-based photosynthetic-energy (PE) parameters, diadinoxanthin (DD)-diatoxanthin (DT) pool size, and the de-epoxidation state (DES) of DD. Even after the excess light exposure suppressed the photosynthetic activity in the microalgal cells, the diatoms recovered quickly, indicating the high photophysiological plasticity to dynamic light changes. Therefore, our results suggest that diatoms in surface sediments have a high seeding potential for blooms in the Pacific Arctic shelf region