藏鹀的自然历史、威胁和保护

藏鹀(Emberiza koslowi)是我国青藏高原东部的特有珍稀鸟种,目前关于它的资料非常匮乏.为了解藏鹀的分布、数量和基本生活史特征,促进对于该物种的有效保护,自2005年起以青海省果洛州久治县白玉乡为中心对藏鹀进行了持续6年的观察,并针对其面临的威胁采取了相应的保护措施.结果显示,藏鹀主要分布在青海的玉树、果洛和四川的阿坝一带海拔3 500～4 700 m范围内的适宜栖息地,该分布区比原有认知更靠东北,更为狭小且海拔更高.用样线法开展的藏鹀数量监测,在7.4 km2的调查范围内记录到一个18 ～33只的稳定种群.此外,还对藏鹀的筑巢、育雏和争斗等行为进行了详细描述.食肉动物的捕食、冬季食物缺乏和牲畜踩踏鸟卵是藏鹀面临的最直接威胁.通过持续监测、与当地牧民协商、建立保护小区并开展有针对性的保护,藏鹀种群趋于稳定.     

The topology of the C-terminal sections of the NCX1 Na+/Ca2+ exchanger and the NCKX2 Na+/Ca2+-K+ exchanger

Mammalian Na⁺/Ca²⁺ (NCX) and Na⁺/Ca²⁺-K⁺ exchangers (NCKX) are polytopic membrane proteins that play critical roles in calcium homeostasis in many cells. Although hydropathy plots for NCX and NCKX are very similar, reported topological models for NCX1 and NCKX2 differ in the orientation of the three C-terminal transmembrane segments (TMS). NCX1 is thought to have 9 TMS and a re-entrant loop, whereas NCKX2 is thought to have 10 TMS. The current topological model of NCKX2 is very similar to the 10 membrane spanning helices seen in the recently reported crystal structure of NCX_MJ, a distantly related archaebacterial Na⁺/Ca²⁺ exchanger. Here we reinvestigate the orientation of the three C-terminal TMS of NCX1 and NCKX2 using mass-tagging experiments of substituted cysteine residues. Our results suggest that NCX1, NCKX2 and NCX_MJ all share the same 10 TMS topology.     

High genetic differentiation and low genetic diversity in Incarvillea younghusbandii, an endemic plant of Qinghai-Tibetan Plateau,revealed by AFLP markers

Incarvillea younghusbandii Sprague (Bignoniaceae) is a perennial herbaceous plant endemic to Qinghai-Tibetan Plateau. As a species of medical and horticulture importance, I. younghusbandii is threatened by over exploitation and habitat fragmentation. In this study, we analyze the genetic diversity and population structure of I. younghusbandii using amplified fragment length polymorphism (AFLP) markers. Our data reveal very low levels of genetic diversity in seven natural populations across Tibet. Specifically, at population level, the average Nei's genetic diversity index (H_E) and Shannon's diversity index (I) were 0.063 and 0.096, respectively. In contrast, high genetic differentiation among populations (Gst = 0.6238, Φ_ST = 0.614) is detected. The results of Neighbor-joining cluster, PCO, and STRUCTURE assignment reveal consistent pattern, suggesting seven well-defined genetic groups that are concordant with their geographical origins. The possible mechanisms and implications of these findings for conservation are discussed.     

Interactions among Vascular-Tone Modulators Contribute to High Altitude Pulmonary Edema and Augmented Vasoreactivity in Highlanders

Background

The interactions among various biomarkers remained unexplored under the stressful environment of high-altitude. Present study evaluated interactions among biomarkers to study susceptibility for high altitude pulmonary edema (HAPE) in HAPE-patients (HAPE-p) and adaptation in highland natives (HLs); both in comparison to HAPE-free sojourners (HAPE-f).

Methodology/Principal Findings

All the subjects were recruited at 3500 m. We measured clinical parameters, biochemical levels in plasma and gene expression using RNA from blood; analyzed various correlations between and among the clinical parameters, especially arterial oxygen saturation (SaO₂) and mean arterial pressure (MAP) and biochemical parameters like, asymmetric dimethylarginine (ADMA), serotonin (5-HT), 8-iso-prostaglandin F2α (8-isoPGF2α), endothelin-1 (ET-1), plasma renin activity (PRA), plasma aldosterone concentration (PAC), superoxide dismutase (SOD) and nitric oxide (NO) in HAPE-p, HAPE-f and HLs. ADMA, 5-HT, 8-isoPGF2α, ET-1 levels, and PAC were significantly higher (p<0.0001, each), whereas SOD activity and NO level were significantly lower in HAPE-p than HAPE-f (p≤0.001). Furthermore, ADMA, 5-HT, 8-isoPGF2α, NO levels and PAC were significantly higher (p<0.0001), whereas ET-1 level significantly (p<0.0001) and SOD activity non-significantly (p>0.05) lower in HLs than HAPE-f. The expression of respective genes differed in the three groups. In the correlations, SaO₂ inversely correlated with ADMA, 5-HT and 8-isoPGF2α and positively with SOD in HAPE-p (p≤0.009). MAP correlated positively with 5-HT and 8-isoPGF2α in HAPE-p and HLs (p≤0.004). A strong positive correlation was observed between ADMA and 5-HT, 5-HT and 8-isoPGF2α (p≤0.001), whereas inverse correlation of SOD with ET-1 in HAPE-p and HLs (p≤0.004), with 5-HT and 8-isoPGF2α in HAPE-p (p = 0.01) and with 5-HT in HLs (p = 0.05).

Conclusions/Significance

The interactions among these markers confer enhanced vascular activity in HLs and HAPE in sojourners.     

Site-directed disulfide mapping of residues contributing to the Ca2+ and K+ binding pocket of the NCKX2 Na+/Ca2+-K+ exchanger

The Na+/Ca2+-K+ exchanger (NCKX) gene products are polytopic membrane proteins that utilize the existing cellular Na+ and K+ gradients to extrude cytoplasmic Ca2+. NCKX proteins are made up of two clusters of hydrophobic segments, both thought to consist of five putative membrane-spanning alpha-helices, and separated by a large cytoplasmic loop. The two most conserved regions within the NCKX sequence are known as the alpha1 and alpha2 repeats, and are found within the first and second set of transmembrane domains, respectively. The alpha repeats have previously been shown to contain residues critical for transport function. Here we used site-directed disulfide mapping to report that the alpha repeats are found in close proximity in three-dimensional space, bringing together key functional NCKX residues, e.g., the two critical acidic residues, Glu188 and Asp548. Glu188Cys in the alpha1 repeat could form a disulfide cross-link with Asp548Cys in the alpha2 repeat. Surprisingly, cysteine substitutions of Ser185 in the alpha1 repeat could form disulfide cross-links with cysteine substitutions of three residues in the alpha2 repeat (Ser545, Asp548, and Ser552), thought to cover close to two full turns of an alpha helix, implying an area of increased flexibility. Using the same method, Asp575, a residue critical for the K+ dependence of NCKX, was shown to be in the proximity of Ser185 and Glu188, consistent with its role in enabling K+ to bind to a single Ca2+ and K+ binding pocket.     

Steps towards sustainable harvest of Ophiocordyceps sinensis in Bhutan

The insect-pathogenic fungus Ophiocordyceps sinensis (better known as Cordyceps sinensis) is harvested over much of the Himalayan plateau as a highly prized remedy in traditional Oriental medicine. Over the past 10 years its financial value has increased dramatically, with collectors paid as much as US $12,500 kg⁻¹ for top-quality material. This is causing significant distortion to local economies, and there is widespread concern that the current rate of collection is unsustainable. This paper introduces the fungus and its insect hosts, documents some of the biological and social constraints to achieving sustainability, describes the socioeconomic climate within which harvest and sale occurs in Bhutan, and details the measures put in place by the Royal Government of Bhutan to promote wise management of this valuable natural resource.

藏雪鸡的人工饲养与繁殖初报

报道了原产地为西藏自治区白朗县马乡地区(海拔4500m以上)的藏雪鸡(Tetraogallus tibetanus)在人工条件下(在拉萨市区海拔3650m)为期4年的饲养繁殖情况,以及藏雪鸡在人工条件下所产的卵和野生卵的大小及重量的差异显著性分析结果。