Basic limnological study in an alpine Lake Puma Yumco, the pre-Himalayas, China

Lake Puma Yumco is a typical alpine lake (altitude; 5,030m) located in the pre-Himalayas of Tibet, China. This study was the first limnologicak investigation. Puma Yumco (28°34'N,90°24'E) has the following morphometric properties: maximum length of 31 km; maximum width of 14 km; mean width of 9 km; shoreline of 90 km; surface area of 280 km²; shoreline development of 1.5. Transparency was approximately 10 m. Dissolved oxygen was l7 mg O₂ L⁻¹ and showed saturated values. Saljnity was 360 mg L⁻¹. The chemical type of the lake water was Mg-Ca-HCO₃-SO₄. Total nitrogenous nutrients and phosphate were extremely low at 1μM and 0.02 μM, respetively. Chlorophyll-a concentration was 0.2 mg chl.a m⁻³. Phytoplankton and zooplankton were dominated by Aphanocapsa. and Diaptomidae. The grain size of lake sediment was that of silt in most cases.Article信州大学山地水環境教育研究センター研究報告 2: 83-90(2004)departmental bulletin pape

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Recent studies have shown that the cellular immune response to the hypoxic microenvironment constructed by vascular remodeling development modulates the resulting pathologic alterations. A major mechanism mediating adaptive responses to reduced oxygen availability is the regulation of transcription by hypoxia-inducible factor１（HIF‐１）. Impairment of HIF‐１‐ dependent inflammatory responses in T cells causes an augmented vascular remodeling induced by arterial injury, which is shown as prominent neointimal hyperplasia and increase in infiltration of inflammatory cells at the adventitia in mice lacking Hif‐１α specifically in T cells. Studies to clarify the mechanism of augmented vascular remodeling in the mutant mice have shown enhanced production of cytokines in activated T cells and augmented antibody production in response to a T-dependent antigen in the mutant mice. This minireview shows that HIF‐１α in T cells plays a crucial role in vascular inflammation and remodeling in response to cuff injury as a negative regulator of the T cell-mediated immune response and suggests potential new therapeutic strategies that target HIF‐１α

Rho-associated protein kinase and cyclophilin a are involved in inorganic phosphate-induced calcification signaling in vascular smooth muscle cells

Arterial calcification, a risk factor of cardiovascular events, develops with differentiation of vascular smooth muscle cells (VSMCs) into osteoblast-like cells. Cyclophilin A (CypA) is a peptidyl-prolyl isomerase involved in cardiovascular diseases such as atherosclerosis and aortic aneurysms, and rho-associated protein kinase (ROCK) is involved in the pathogenesis of vascular calcification. CypA is secreted in a ROCK activity-dependent manner and works as a mitogen via autocrine or paracrine mechanisms in VSMCs. We examined the involvement of the ROCK-CypA axis in VSMC calcification induced by inorganic phosphate (Pi), a potent cell mineralization initiator. We found that Pi stimulated ROCK activity, CypA secretion, extracellular signal-regulated protein kinase (ERK) 1/2 phosphorylation, and runt-related transcription factor 2 expression, resulting in calcium accumulation in rat aortic smooth muscle cells (RASMCs). The ROCK inhibitor Y-27632 significantly suppressed Pi-induced CypA secretion, ERK1/2 phosphorylation, and calcium accumulation. Recombinant CypA was found to be associated with increased calcium accumulation in RASMCs. Based on these results, we suggest that autocrine CypA is mediated by ROCK activity and is involved in Pi-induced ERK1/2 phosphorylation following calcification signaling in RASMCs

Drug efficacy against aortic dissection

Objective: Aortic dissection is a life-threatening disease. At present, the only therapeutic strategies available are surgery and antihypertensive drugs. Moreover, the molecular mechanisms underlying the onset of aortic dissection are still unclear. We established a novel aortic dissection model in mice using pharmacologically induced endothelial dysfunction. We then used the Japanese Adverse Drug Event Report database to investigate the role of pitavastatin in preventing the onset of aortic dissection. Methods and results: To induce endothelial dysfunction, Nω-nitro-L-arginine methyl ester, a nitric oxide synthase inhibitor, was administered to C57BL/6 mice. Three weeks later, angiotensin II (Ang II) and β-aminopropionitrile (BAPN), a lysyl oxidase inhibitor, were administered with osmotic mini-pumps. False lumen formation was used as the pathological determinant of aortic dissection. The incidences of aortic dissection and death from aneurysmal rupture were significantly higher in the Nω-nitro-L-arginine methyl ester, Ang II, and BAPN (LAB) group than they were in the Ang II and BAPN (AB) group. Pitavastatin was administered orally to LAB mice. It significantly lowered the incidences of dissection and rupture. It also decreased inflammation and medial degradation, both of which were exacerbated in the LAB group. The Japanese Adverse Drug Event Report database analysis indicated that there were 113 cases of aortic dissection out of 95 090 patients (0.12%) not receiving statins but only six cases out of 16 668 patients receiving statins (0.04%) (odds ratio: 0.30; P=0.0043). Conclusion: Our results suggest that endothelial dysfunction is associated with the onset of aortic dissection and pitavastatin can help prevent this condition

Limnological characteristics of an oxbow lake in a lower reach of the Shibetsu River in Hokkaido Island, Japan

Limnological characteristics of a shallow oxbow lake (maximum depth about 2 meters) were investigated in a lower reach of the Shibetsu River in Hokkaido Island, Japan. Water temperatures, under-water light attenuation coefficients, and concentrations of dissolved oxygen, nitrogen, phosphorus and chlorophyll-a were measured on July 21 and November 17 in 2001 and July 30 in 2002. Water temperature varied among sampling stations and depths, ranging from 10°C to 24°C in July, while all measurements were constant at about 5°C in November. Dissolved oxygen concentrations at all stations on all sampling dates were 10 mg L-1 or more. Its maximum concentration reached 25 mg L-1 with 250% saturation at the lake bottom on July 21 in 2001. The depths of sampling stations that obtained high concentrations of dissolved oxygen were between 50 cm and 60 cm. Water temperatures at these depths ranged from 10°C to 15°C, which were lower than surface water by 5°C to 10°C. A large filamentous green alga, Spirogyra sp., propagated in these depths. Concentrations of dissolved nitrogen in lake water varied from 11 μg L-1 to 250 μg L-1, which declined in July at all stations and depths. Concentrations of PO43--P showed a range from 7 μg L-1 to 14 μg L-1, not so different among stations, depths and sampling dates. Particulate phosphorus and chlorophyll-a concentrations were approximately constant between 33 μg L-1 and 35 μg L-1 and 10 μg L-1 and 13 μg L-1, respectively. The concentrations of total phosphorus and chlorophyll-a on 21 July 2001 indicate that trophic status of the oxbow lake is in meso-eutrophic conditions. Under-water light attenuation coefficients (k) ranged from 1 m-1 to 2 m-1 at all stations and sampling dates. These values are comparable to the maximum value for eutrophic lakes with water-bloom of phytoplankton. However, because chlorophyll-a concentrations in this oxbow lake were lower than those in the eutrophic lakes, under-water light seemed to be attenuated by non-living particles and dissolved organic matter. Therefore, there is a possibility that the oxbow lake is in dystrophic conditions. These results suggested that the limnological characteristics of the oxbow lake were greatly different from those of the main channel of the Shibetsu River. It is believed that the oxbow lake maintains the characteristics of a low-land marsh, which was former landscape of the lower region of the Shibetsu River watershed

Highly efficient silica sink in monomictic Lake Biwa in Japan

In order to clarify the mechanisms underlying high efficiency of the silica sink in monomictic Lake Biwa in Japan, vertical flux of biogenic silica (BSi) was measured using sediment traps over a period of 15 months. The sediment traps were deployed at depths of 30 and 70 m. On a global scale, BSi fluxes in Lake Biwa were very high, ranging from 20 to 1087 mg Si.m−2.d−1 at the 30 m trap and 12–999 mg Si.m−2.d−1 at the 70 m trap throughout the observation period. The BSi fluxes at both traps increased significantly during the winter period and the ratio of BSi fluxes in the winter period to annual BSi fluxes ranged from 27 to 62%. In the winter period, when nutrients are supplied from the hypolimnion to the epilimnion, the distribution of photosynthetically active diatoms was almost homogeneous in all layers, including the aphotic layer. At this time, the diatoms assimilated dissolved silica (DSi) in a wider layer containing a part of aphotic layer in order to produce rigid frustules, which accumulated rapidly in bottom sediments as DSi concentration in the water column decreased. Thus, size of the silica sink in Lake Biwa is enhanced during the winter holomictic mixing period through interaction between physical (thermocline disruption: transfer of diatoms to deep layers by vertical convection), chemical (nutrient supply from deep layers) and biological (dominance of active diatoms in all layers) processes