红光和Ca~(2 )对与绿豆下胚轴伸长有关的细胞壁酶的影响

作为去黄化过程中的一个反应——植物茎伸长受光抑制的现象,已有不少研究。人们发现,胚轴长度受光的调节,对红光尤其敏感（lion1982）。红光抑制绿豆下胚轴切段伸长（王小菩和潘瑞炽1990）,却促进绿豆下胚轴原生质体膨大,钙在此过程中起第二信使的作用（龙程等1994a,b）,但红光促进原生质体膨大却抑制切段伸长的机理尚不清楚。我们认为问题的症结可能在细胞壁,因为植物细胞的生长（伸长和扩大）在很大程度上取决于细胞壁的松弛和伸展。植物细胞只有当细胞壁酶作用于细胞壁使之松弛时,才能在膨压的作用下吸水长大（Taiz1984）。因…     

Activation of the melanocortin-4 receptor causes enhanced excitation in presympathetic paraventricular neurons in obese Zucker rats

Sympathetic nerve activity is increased in obesity-related hypertension. However, the central mechanisms involved in the increased sympathetic outflow remain unclear. The hypothalamic melanocortin system is important for regulating energy balance and sympathetic outflow. To understand the mechanisms by which the melanocortin systems regulates sympathetic outflow, we investigated the role of melanocortin 4 receptors (MC4R) in regulating presympathetic paraventricular nucleus (PVN) neurons. We performed whole-cell patch-clamp recordings on retrogradely labeled PVN neurons projecting to the rostral ventrolateral medulla in brain slices from obese zucker rats (OZRs) and lean zucker rats (LZRs). The MC4R agonists melanotan II (MTII) and α-melanocyte-stimulating hormone (α-MSH) increased the firing activity and depolarized the labeled PVN neurons from both LZRs and OZRs in a concentration-dependent manner. MTII produced significant greater increase in the firing activity in OZRs than in LZRs. Blocking MC4R with the specific antagonist SHU9119 had no effect on the basal firing rate but abolished the MTII-induced increase in the firing rate in both OZRs and LZRs. Furthermore, intracellular dialysis of guanosine 5'-O-(2-thodiphosphate), but not bath application of kynurenic acid and bicuculline, eliminated the MTII-induced increase in firing activity. In addition, MTII had no effect on the frequency and amplitude of glutamatergic excitatory postsynaptic currents and GABAergic inhibitory postsynaptic currents in labeled PVN neurons. Collectively, our findings suggest that MC4R contributes to the elevated excitability of PVN presympathetic neurons, which may be involved in obesity-related hypertension.     

Role of Cell Wall Calcium in Red Light- inhibited Elongation of Hypocotyls of Etiolated Phaseolus radiatus

When the hypocotyl segments of Phaseolus radiatus L. were incubated in CaC12 (1 mmol/L) medium, the cell wall calcium was increased over threefold more than those incubated in a Ca2+ -free medium. However, red light inhibited elongation of the hypocotyl was 20% to 25% both in the medium with or without Ca2 + . The amount of calcium removed from the wall by ethylene glycol-bis (2-aminoethyl ether)-N, N, N', N'-tetraacetic acid (EGTA) ( 1 to 10 mmol/L) was 58.13 % to 75.33%, which offset the red light-inhibited elongation of the hypocotyl by 61.29% to 87.1%. Moreover, treatment with the channel blocker, verapamil ( 10 to 100 μ mol/L), wall calcium was the same as that of the darkness control, by which the red light-inhibited growth was also offset. La3 + ( 100 to 1 000 μmol/L) had no effect on wall calcium as compared to hypocotyl segments treated with red light alone, but eliminated the inhibitory effect of red light. Treatment with the calcium ionophore, A23187 (10 to 100 μmol/L), red light-inhibited elongation was abolished by 66.67% to 142.45% while wall calcium was reduced by 24.53% to 42.81%. In addition, calmodulin antagonist chlorpromazine (1 to 10 μmol/L) also counter acted the red light-induced elongation inhibition. These data indicated that exogenous Ca2+ was involved in the red light-inhibition effect, but that' did not mean that Ca2 + was not required. Perhaps Ca2 + in the wall itself was sufficient for red light-induced inhibition of hypocotyl elongation. The role of wall calcium might be quite complex, it not only acted as a signal of influx Ca2 + from the Ca2 + pool, but also played a regulatory role in the cell wall.     

上海市几条黑臭河道治理效果的比较与分析

随着上海市经济的突飞猛进和城市化的日新月异,随之而来的城市水污染问题也愈演愈烈.据上海市2003年水资源公报反映:全市16条主要骨干河道中,Ⅱ、Ⅲ类水断面占13.11%,Ⅳ类水断面占28.17%,V类和劣于V类水断面占58.12%[1].     

营养液缺钙或缺钾对糜子幼苗抗旱性的影响

糜子幼苗生长于完全、缺钙、缺钾、缺钙并缺钾４种营养液中。水分胁迫下,各种幼苗相对含水量均下降,造性增强。其中,单缺钾及缺钙并缺钾时相对合水量比完全及单缺钙时下降较大,单缺钙时透性更易增强。水分胁迫下,完全营养苗游离脯氨酸含量明显高于对照,而其它３种苗的游离脯氨酸含量与其对照之间差异不显著。水分胁迫４８ｈ,缺钾苗和缺钙并缺钾苗叶肉细胞有质壁分离现象,叶绿体受到一定程度的损伤,单缺钾时超微结构损伤尤甚。另外,钙调蛋白抑制剂实验表明,干旱胁迫引起的幼苗体内游离脯氨酸含量的增加可能与钙调蛋白无关。     

矮牵牛叶肉原生质体再生壁多糖的形成及转化

用~3H—葡萄糖饲喂矮牵牛叶肉原生质体,发现放射性集中在半纤维素部分,占整个再生壁的83％～90％,而纤维素中约占9％。纸层析分析证明,葡萄糖占半纤维素部分中性糖总量的70％,再生壁主要是由非纤维素葡聚糖组成。原生质体在含有~3H—葡萄糖的培养基中培养4d后,24h追踪表明,部分半纤维素转化成纤维素。加入香豆素,至少3d之内抑制半纤维素向纤维素转化;除去抑制剂,半纤维素含量迅速降低而纤维素增加。所以认为矮牵牛叶向原生质体壁再生过程中半纤维素是合成纤维素的前体。     

Casein kinase 2-mediated synaptic GluN2A up-regulation increases N-methyl-D-aspartate receptor activity and excitability of hypothalamic neurons in hypertension

Increased glutamatergic input, particularly N-methyl-D-aspartate receptor (NMDAR) activity, in the paraventricular nucleus (PVN) of the hypothalamus is closely associated with high sympathetic outflow in essential hypertension. The molecular mechanisms underlying augmented NMDAR activity in hypertension are unclear. GluN2 subunit composition at the synaptic site critically determines NMDAR functional properties. Here, we found that evoked NMDAR-excitatory postsynaptic currents (EPSCs) of retrogradely labeled spinally projecting PVN neurons displayed a larger amplitude and shorter decay time in spontaneously hypertensive rats (SHRs) than in Wistar-Kyoto (WKY) rats. Blocking GluN2B caused a smaller decrease in NMDAR-EPSCs of PVN neurons in SHRs than in WKY rats. In contrast, GluN2A blockade resulted in a larger reduction in evoked NMDAR-EPSCs and puff NMDA-elicited currents of PVN neurons in SHRs than in WKY rats. Blocking presynaptic GluN2A, but not GluN2B, significantly reduced the frequency of miniature EPSCs and the firing activity of PVN neurons in SHRs. The mRNA and total protein levels of GluN2A and GluN2B in the PVN were greater in SHRs than in WKY rats. Furthermore, the GluN2B Ser(1480) phosphorylation level and the synaptosomal GluN2A protein level in the PVN were significantly higher in SHRs than in WKY rats. Inhibition of protein kinase CK2 normalized the GluN2B Ser(1480) phosphorylation level and the contribution of GluN2A to NMDAR-EPSCs and miniature EPSCs of PVN neurons in SHRs. Collectively, our findings suggest that CK2-mediated GluN2B phosphorylation contributes to increased synaptic GluN2A, which potentiates pre- and postsynaptic NMDAR activity and the excitability of PVN presympathetic neurons in hypertension.     

红光抑制绿豆下胚轴伸长时富含羟脯氨酸蛋白质的含量变化

红光能增加细胞壁的Hyp含量和细胞各部分的Hyp／Pro,绿豆下胚轴切段伸长被红光抑制的程度与两者是正相关。环己酰亚胺和放线菌素D明显降低细胞壁的Hyp含量,提高WSFC和CWRSE中的Hyp／Pro,抑制切段伸长。香豆素不仅显著减少细胞壁的Hyp含量,而且降低WSFC和CWRSE中的Hyp／Pro,促进下胚轴伸长。α,α．二吡啶降低细胞壁的Hyp含量和WSFC中的Hyp／Pro,解除红光对切段伸长的抑制。EGTA、verapamil、La3 和A23187均可解除红光抑制切段伸长的作用,但对细胞壁的Hyp含量和细胞三部分蛋白质中Hyp／Pro影响较小。     

Soil carbon stocks,deforestation and land‐cover changes in the Western Ghats biodiversity hotspot (India)

Habitat loss and soil organic carbon (SOC) stock variations linked to land‐cover change were estimated over two decades in the most densely populated biodiversity hotspot in the world, in order to assess the possible influence of conservation practices on the protection of SOC. For a study area of 88 484 km², 70% of which lie inside the Western Ghats Biodiversity Hotspot (WGBH), land‐cover maps for two dates (1977, 1999) were built from various data sources including remote sensing images and ecological forest maps. SOC stocks were calculated from climatic parameters, altitude, physiography, rock type, soil type and land‐cover, with a modelling approach used in predictive learning and based on Multiple Additive Regression Tree. The model was trained on 361 soil profiles data, and applied to estimate SOC stocks from predictor variables using a Geographical Information System (GIS). Comparison of 1977 and 1999 land‐cover maps showed 628 km² of dense forests habitat loss (6%), corresponding to an annual deforestation rate of 0.44%. This was found consistent with other studies carried out in other parts of the WGBH, but not with FAO figures showing an increase in forest area. This could be explained by the different forest definitions used, based on ecological classification in the former, and on percentage tree cover in the latter. Unexpectedly, our results showed that despite ongoing deforestation, overall SOC stock was maintained (～0.43 Pg). But a closer examination of spatial differences showed that soil carbon losses in deforested areas were compensated by sequestration elsewhere, mainly in recent plantations and newly irrigated croplands. This suggests that more carbon sequestration in soils could be achieved in the future through appropriate wasteland management. It is also expected that increasing concerns about biodiversity loss will favour more conservation and reinforce the already prevailing protective measures, thus further maintaining C stocks.     

玉米胚芽鞘细胞伸长生长与富含羟脯氨酸蛋白质的关系

玉米胚芽鞘细胞伸长生长进程中,富含羟脯氨酸蛋白质的合成速率同细胞的伸长生长呈负相关,迅速伸长期较低,而伸长近终止阶段出现活性高峰。生长素促进的伸长生长与富含羟脯氨酸蛋白质的合成、累积相关。IAA使胚芽鞘高体切段细胞的伸长生长增加4倍多,细胞中较低的羟脯氨酸蛋白质的合成速率似有利于生长素的促进效应。生长素对伸长细胞中羟脯氨酸蛋白质的转运和在壁中累积有抑制作用。