Search

Understanding the age and dynamics of the overriding plates allows an assessment of competing subduction initiation hypotheses. The Izu‐Bonin‐Mariana margin in the Western Pacific is a key example of initiation and hence it is important to constrain the age and origin of the oldest igneous crust of the supra‐subduction Philippine Sea Plate. We present geochronological and geochemical data of igneous rocks from the oldest ocean basins of the Philippine Sea Plate: the West Philippine and Palau Basins. Basalts from these basins have enriched geochemical characteristics similar to the EM‐2‐like mantle component found in OIB‐like basalts associated with the Oki‐Daito mantle plume. Ages of basalts from the northernmost West Philippine Basin (WPB) and the Palau Basin range from 43.5 to 50.5 Ma, which is similar to the oldest samples associated with the Oki‐Daito mantle plume (48–50 Ma). This implies that the plume contributed to magmatism from the onset of basin formation. It also provides support for the proposition that rifting of the Mesozoic arc terrane and subsequent seafloor spreading of the WPB was triggered by the arrival of the Oki‐Daito mantle plume at the base of the lithosphere. The age of these Philippine Sea Basins implies that only the Mesozoic Daito Ridge Group and the Gagua Ridge existed as Philippine Sea Plate crust before subduction initiation. A major fault activity after 37 Ma in the northernmost WPB demonstrates that careful reconstruction of the Eocene Philippine Sea Plate is critical to understanding plate dynamics during subduction initiation in the Western Pacific. Plain Language Summary: This study investigates the formation of the crust beneath the Philippine Sea Plate. An outcome of this research is a clearer understanding of the plate tectonic configuration in the Western Pacific at the point when volcanic activity started. We collected rock samples from what is thought to be the oldest sections of the West Philippine Basin and the Palau Basin, and determined their age and chemical composition. These rocks were erupted between 43.5 and 50.5 million years ago, and are of a similar age and composition to the volcanic rocks known to be associated with the Oki‐Daito mantle plume (48–50 million years old). These similarities imply that the initial volcanism on the Philippine Sea Plate was triggered by the arrival of the upwelling Oki‐Daito mantle plume. A consequence of the hot and buoyant mantle plume was to stretch the existing crust and develop a new ocean basin by volcanic activity. The new ages for the oldest ocean basins in the Philippine Sea Plate reveal that only the Mesozoic arc terrane existed as the Philippine Sea Plate crust before subduction initiation. This provides new constraints on the conditions under which subduction can initiate between the two plates. Key Points: New dating indicates that a major part of the oldest Philippine Sea Plate basins formed after c. 51 MaOcean crust of the oldest Philippine Basins is affected by the Oki‐Daito mantle plumeOnset of spreading of the West Philippine Basin could have been triggered when the Oki‐Daito plume hit the base of preexisting lithosphere [ABSTRACT FROM AUTHOR]

The Totten Ice Shelf (TIS) and Moscow University Ice Shelf (MUIS), along the Sabrina Coast of Wilkes Land, are the floating seaward terminuses of the second-largest freshwater reservoir in the East Antarctic Ice Sheet. Being a marine ice sheet, it is vulnerable to the surrounding ocean conditions. Recent comprehensive oceanographic observations, including bathymetric measurements off the Sabrina Coast, have shed light on the widespread intrusion of warm modified Circumpolar Deep Water (mCDW) onto the continental shelf and the intense ice–ocean interaction beneath the TIS. However, the spatiotemporal coverage of the observation is very limited. Here, we use an ocean–sea ice–ice shelf model with updated bathymetry to better understand the regional ocean circulations and ocean–cryosphere interactions. The model successfully captured the widespread intrusions of mCDW, local sea ice production and the ocean heat and volume transports into the TIS cavity, facilitating an examination of the overturning ocean circulation within the ice shelf cavities and the resultant basal melting. We found notable differences in the temporal variability in ice shelf basal melting across the two adjacent ice shelves of the TIS and the western part of the MUIS. Ocean heat transport by mCDW controls the low-frequency interannual-to-decadal variability in ice–ocean interactions, but the sea ice production in the Dalton Polynya strongly modifies the signals, explaining the regional difference between the two ice shelves. The formation of a summertime eastward-flowing undercurrent beneath the westward-flowing Antarctic Slope Current is found to play an important role in the seasonal delivery of ocean heat to the continental shelf. [ABSTRACT FROM AUTHOR]

Transanal total mesorectal excision is a relatively new approach for treating lower rectal cancer. Carbon dioxide embolism is a critical complication of this procedure. We report the case of a 69‐year‐old man with lower rectal cancer who underwent transanal total mesorectal excision followed by laparoscopic low anterior resection. He had a sudden intraoperative carbon dioxide embolism during the transanal mesorectal excision. During the ventral dissection of the rectum, end‐tidal carbon dioxide and blood oxygen saturation suddenly decreased. We stopped the insufflation of carbon dioxide and suspended the procedure. There was no circulatory collapse, and the vital signs gradually recovered; therefore, we resumed the surgery approximately 30 minutes later and completed it without additional complications. Upon reviewing the video, we found a small injured vein that would aspirate carbon dioxide. These findings suggested that careful hemostasis is essential to prevent carbon dioxide embolus during transanal total mesorectal excision. [ABSTRACT FROM AUTHOR]

Accumulating evidence suggests that the intrarenal renin-angiotensin system may be involved in the progression of diabetic nephropathy. Chymase is a potent local angiotensin II-forming enzyme in several species, including humans and hamsters. However, the pathophysiological role of chymase is not fully understood. Here, we report a causal role of chymase in diabetic nephropathy and the therapeutic effectiveness of chymase inhibition. In the present study, renal chymase expression was markedly upregulated in streptozotocin-induced diabetic hamsters. Oral administration of a specific chymase inhibitor, TEI-F00806, completely ameliorated proteinuria, the overexpression of transforming growth factor-[beta] and fibronectin in glomeruli, and renal mesangial expansion, by normalizing the increase in intrarenal angiotensin II levels in diabetic hamsters independently of blood pressure levels. In contrast, ramipril did not show such sufficient effects. These effects occurred in parallel with improvements in superoxide production and expression of NAD(P)H oxidase components [NAD(P)H oxidase 4 and [p22.sup.phox]] in glomeruli. This study showed for the first time that chymase inhibition may protect against elevated intrarenal angiotensin II levels, oxidative stress, and renal dysfunction in diabetes. These findings suggest that chymase offers a new therapeutic target for diabetic nephropathy. angiotensin II; NAD(P)H oxidase doi: 10.1152/ajprenal.00337.2010

The southern Indian Ocean has several prominent aseismic ridges recognized as oceanic large igneous provinces (i.e., the Madagascar Ridge, Del Cano Rise, Crozet Plateau, and Conrad Rise) in the off‐axis areas of the Southwest Indian Ridge (SWIR). However, previously obtained magnetic survey lines are sparse and not correctly aligned with the seafloor spreading direction; thus, the detailed spreading history, including the formation of these aseismic ridges, remains an open question. We reconstructed the tectonic history of two segments between the Discovery II and Gallieni fracture zones in the SWIR using newly obtained magnetic data (total and vector magnetic field) and an open‐source magnetic data set. We revealed that the southern Madagascar Ridge and the Del Cano Rise once formed a single bathymetric high and separated by at least Chron 30y, which is quite different from the global age model. In addition, the rises may have formed before Chron 34y, assuming an extinct ridge south of the Del Cano Rise. The two rises have been recognized as having formed by Marion hotspot plume‐induced excess volcanism around the active spreading ridge of the SWIR, which can explain locally isostatically compensated thicker‐than‐normal crust. However, linear magnetic anomalies have not been observed across the main part of these rises, suggesting that magmatic activity controlled by seafloor spreading is unlikely. Like other aseismic ridges in the southern Indian Ocean, these two rises may possibly have been formed partly by continental fragments rather than plume‐induced excess volcanism. Plain Language Summary: The southern Indian Ocean contains several bathymetric high regions previously interpreted as oceanic large igneous provinces. Hotspot‐ridge interaction is considered as the key factor in the formation of such large volcanic structures. However, the detailed seafloor spreading history and origin of these large volcanic structures are not understood as well as those in other oceans because of the vast and remote Indian Ocean. We conducted magnetic surveys and reconstructed a new tectonic history of two segments along the Southwest Indian Ridge (SWIR). We found that the southern Madagascar Ridge and the Del Cano Rise once formed a single bathymetric high and that they separated by at least 66 million years ago. Moreover, the rises may have formed before 84 million years ago, assuming an extinct ridge south of the Del Cano Rise. The two rises might have formed by interaction between the Marion hotspot and SWIR; however, linear magnetic anomalies implying seafloor spreading are not observed in the main parts of these rises. This absence suggests that hotspot‐ridge interaction cannot fully explain the origin of these rises. We cannot exclude the possibility that the two rises are partly continental fragments rather than products of hotspot‐induced excess volcanism. Key Points: Revised seafloor ages up to Chron 31 in the Indian Ocean are obtained by new total and vector magnetic dataOur new tectonic scenario indicates that the Madagascar Plateau and Del Cano Rise once formed a single bathymetric highThe tectonics of oceanic plateaus in the Indian Ocean need to be reexamined, including continental fragment origin [ABSTRACT FROM AUTHOR]

Basal melting of Antarctic ice shelves accounts for more than half of the mass loss from the Antarctic ice sheet. Many studies have focused on active basal melting at ice shelves in the Amundsen–Bellingshausen seas and the Totten ice shelf, East Antarctica. In these regions, the intrusion of Circumpolar Deep Water (CDW) onto the continental shelf is a key component for the localized intensive basal melting. Both regions have a common oceanographic feature: southward deflection of the Antarctic Circumpolar Current brings CDW toward the continental shelves. The physical setting of the Shirase Glacier tongue (SGT) in Lützow-Holm Bay corresponds to a similar configuration on the southeastern side of the Weddell Gyre in the Atlantic sector. Here, we conduct a 2–3 km resolution simulation of an ocean–sea ice–ice shelf model using a recently compiled bottom-topography dataset in the bay. The model can reproduce the observed CDW intrusion along the deep trough. The modeled SGT basal melting reaches a peak in summer and a minimum in autumn and winter, consistent with the wind-driven seasonality of the CDW thickness in the bay. The model results suggest the existence of an eastward-flowing undercurrent on the upper continental slope in summer, and the undercurrent contributes to the seasonal-to-interannual variability in the warm water intrusion into the bay. Furthermore, numerical experiments with and without fast-ice cover in the bay demonstrate that fast ice plays a role as an effective thermal insulator and reduces local sea ice formation, resulting in much warmer water intrusion into the SGT cavity. [ABSTRACT FROM AUTHOR]

We determined the mineralogical and petrological characteristics of ultramafic rocks dredged from two oceanic core complexes: the Mado Megamullion and 23°30′N non‐transform offset massif, which are located within the Shikoku back‐arc basin in the Philippine Sea. The ultramafic rocks are strongly serpentinized, but can be classified as harzburgite/lherzolite or dunite, based on relict primary minerals and their pseudomorphs. Strongly elongated pyroxene porphyroclasts with undulatory extinction indicate high‐temperature (≥700 °C) strain localization on a detachment fault within the upper mantle at depths below the brittle–viscous transition. During exhumation, the peridotites underwent impregnation by magmatic or hydrothermal fluids, lizardite/chrysotile serpentinization at ≤300 °C, antigorite crystallization, and silica metasomatism that formed talc. These features indicate that the detachment fault zones formed a fluid pathway and facilitated a range of fluid–peridotite interactions. [ABSTRACT FROM AUTHOR]

Discriminating magnetic minerals of different origins in natural samples is useful to reveal their associated geological and environmental processes, which can be achieved by the analysis of remanent magnetization curves. The analysis relies on the choice of the model distribution to unmix magnetic components. Three model distributions were proposed in past studies, namely, the lognormal, skew normal, and skewed generalized Gaussian distributions, which are related to the normal distribution. In this study, the Burr type XII distribution is tested and compared with existing model distributions. An automated protocol is proposed to assign parameters necessary to initiate the component analysis, which improves the efficiency and objectivity. Results show that the new model distribution exhibits similar flexibility to the skew normal and skewed generalized Gaussian distributions in approximating skewed coercivity distributions and can fit end‐member components better than the commonly used lognormal distribution. We demonstrate that the component analysis is sensitive to model distribution as well as measurement noise. As a consequence, the decomposition is subject to bias that is hard to identify due to the lack of ground‐truth data. It is therefore recommended to compare results derived from various model distributions to identify spurious components. Key Points: The Burr type XII distribution is suitable as a model distribution to statistically separate the magnetic mixture in geological samplesAn automated procedure for randomly choosing initial guesses is proposed to improve the objectivity and efficiency of decompositionComparing results derived from different model distributions is useful to assess the reliability of interpretations [ABSTRACT FROM AUTHOR]

The evolution of seafloor spreading of Africa, South America, and Antarctica is key to understanding the initial break-up of Gondwana. Vector geomagnetic surveys were conducted in the Natal Valley and Mozambique Ridge, off South Africa. We summarize the nature of the crust using the results of dense vector geomagnetic anomaly data, as well as satellite gravity data. Based on both inversion and forward analytical results, we identified areas of stretched continental crust, with basaltic magma intrusion in parts, as the northern Natal Valley, north part of the Mozambique Ridge, and north part of the southern Natal Valley. Oceanic crust was identified in the south part of the southern Natal Valley and south part of the Mozambique Ridge. Magnetic isochrons M0–M10 were identified in the south part of the southern Natal Valley. Clear magnetic lineations were observed in the south part of the Mozambique Ridge, where some areas were distorted by hotspot volcanism. The location of the continental ocean boundary in the Natal Valley, along with a four-stage model of tectonic evolution of the study area since about 183 Ma, are newly proposed. [ABSTRACT FROM AUTHOR]

High-resolution vector magnetic measurements were performed on an inactive ultramafic-hosted hydrothermal vent field, called Yokoniwa Hydrothermal Field (YHF), using a deep-sea manned submersible Shinkai6500 and an autonomous underwater vehicle r2D4 . The YHF has developed at a non-transform offset massif of the Central Indian Ridge. Dead chimneys were widely observed around the YHF along with a very weak venting of low-temperature fluids so that hydrothermal activity of the YHF was almost finished. The distribution of crustal magnetization from the magnetic anomaly revealed that the YHF is associated with enhanced magnetization, as seen at the ultramafic-hosted Rainbow and Ashadze-1 hydrothermal sites of the Mid-Atlantic Ridge. The results of rock magnetic analysis on seafloor rock samples (including basalt, dolerite, gabbro, serpentinized peridotite, and hydrothermal sulfide) showed that only highly serpentinized peridotite carries high magnetic susceptibility and that the natural remanent magnetization intensity can explain the high magnetization of Yokoniwa. These observations reflect abundant and strongly magnetized magnetite grains within the highly serpentinized peridotite. Comparisons with the Rainbow and Ashadze-1 suggest that in ultramafic-hosted hydrothermal systems, strongly magnetized magnetite and pyrrhotite form during the progression of hydrothermal alteration of peridotite. After the completion of serpentinization and production of hydrogen, pyrrhotites convert into pyrite or nonmagnetic iron sulfides, which considerably reduces their levels of magnetization. Our results revealed origins of the magnetic high and the development of subsurface chemical processes in ultramafic-hosted hydrothermal systems. Furthermore, the results highlight the use of near-seafloor magnetic field measurements as a powerful tool for detecting and characterizing seafloor hydrothermal systems. [ABSTRACT FROM AUTHOR]

Highlights: [•] CTLA-4Ig completely alleviates HFD-induced insulin resistance. [•] CTLA-4Ig reduces epididymal and subcutaneous fat tissue weight and adipocyte size. [•] CTLA-4Ig alters ATM polarization from inflammatory M1 to anti-inflammatory M2. [•] CTLA-4Ig may lead to a novel anti-obesity/inflammation/insulin resistance agent. [•] We identified the mechanism of the novel favorable effects of CTLA-4lg. [ABSTRACT FROM AUTHOR]

A combination of zinc triflate and pyridine in a nitrile medium was found to act as an effective catalytic system for dehydrogenative silylation with flexible pieces of terminal alkynes and hydrosilanes, thereby producing diverse alkynylsilanes in high to excellent yields. [ABSTRACT FROM AUTHOR]

We recently found a markedly lower prevalence of vascular complications, including kidney disease, in diabetic patients with Gilbert syndrome, a congenital form of hyperbilirubinemia, suggesting a beneficial effect of bilirubin (BIL) on diabetic nephropathy. To directly examine this, we determined whether hereditary hyperbilirubinemic Gunn j/j rats and biliverdin (BVD)-treated diabetic db/db mice were resistant to the development of renal disease. Both rodent models had less albuminuria and complete protection against the progression of mesangial expansion accompanied by normalization of transforming growth factor-β1 and fibronectin expression. Simultaneously, there was normalization of urinary and renal oxidative stress markers, and the expression of nicotinamide adenine dinucleotide phosphate (NAD(P)H) oxidase subunits in the kidney. In cultured vascular endothelial and mesangial cells, BIL and BVD significantly inhibited NADPH-dependent superoxide production, and both high glucose- and angiotensin II-induced production of reactive oxygen species. Collectively, our findings suggest that BIL and BVD may protect against diabetic nephropathy and may lead to novel antioxidant therapies for diabetic nephropathy. [ABSTRACT FROM AUTHOR]

Abstract: With recent technical advancements, the number of operative manipulations in the knee joint by minimally invasive surgery–total knee arthroplasty (MIS-TKA) is now considered to be the same as that using standard TKA (S-TKA). The question still remains, however, if MIS-TKA improves recovery compared to S-TKA. We compared MIS-TKA and S-TKA patients'' physical activity as measured by an accelerometer. Physical activity expressed as cumulative acceleration was significantly higher in the MIS-TKA than in the S-TKA group on postoperative days (POD1, 2, 3, 4, 5, 10, 11) (P < .05). The recovery time, defined as the number of days required to achieve cumulative acceleration of 80% of the preoperative level, was significantly shorter (P < .05) in the MIS-TKA (3.0 ± 3.3 days) group than in the S-TKA (7.0 ± 3.5 days) group. Minimally invasive surgery–total knee arthroplasty appears to allow an earlier recovery after the operation than S-TKA. Less invasion to muscle during the surgery appears to contribute to shorter convalescence. [Copyright &y& Elsevier]

Necrotizing soft tissue infection (NSTI) of the chest wall is a rare, rapidly spreading, highly lethal surgical disease. Radical debridement interferes with the important anatomical function of the chest wall. We report a case of chest wall NSTI that was successfully managed with early diagnosis and serial debridement. A 43-year-old, previously healthy woman presented with severe malaise and worsening right axillary pain. She was severely lethargic and had a painful, large, pale lesion with surrounding erythema of the right chest and trunk. Computed tomography revealed NSTI, with diffuse soft tissue inflammation extending from the axilla to the lower abdomen. There was no obvious entry portal. Prompt surgical drainage was established. Group A streptococcus infection was diagnosed. During her 3-month postoperative course, she underwent four more surgeries, including two debridements. This treatment proved successful and avoided the need for complicated muscle flap reconstruction. She was discharged on postoperative day 109. Group A streptococcus can cause NSTI even in immunocompetent patients without an entry portal. Radical debridement is recommended for infection control. Preserving anatomical chest wall function, however, is also important. Serial debridement with close follow-up solved the problem in this patient. Serial debridement with close follow-up enabled to avoid large tissue deficits and complicated reconstruction in the case of NSTI of the chest wall. • Necrotizing soft tissue infection of the chest wall is rare and lethal. • Radical debridement could interfere with the anatomical function of the chest wall. • Adequate drainage with minimum skin incision avoids large tissue defects. • Serial debridement with close follow-up enabled to avoid complicated reconstruction [ABSTRACT FROM AUTHOR]