Spatial and temporal patterns of intracellular calcium in colonic smooth muscle

Summary Intracellular calcium [Ca²⁺] _i measurements in cell suspension of gastrointestinal myocytes have suggested a single [Ca²⁺] _i transient followed by a steady-state increase as the characteristic [Ca²⁺] _i response of these cells. In the present study, we used digital video imaging techniques in freshly dispersed myocytes from the rabbit colon, to characterize the spatiotemporal pattern of the [Ca²⁺] _i signal in single cells. The distribution of [Ca²⁺] _i in resting and stimulated cells was nonhomogeneous, with gradients of high [Ca²⁺] _i present in the subplasmalemmal space and in one cell pole. [Ca²⁺] _i gradients within these regions were not constant but showed temporal changes in the form of [Ca²⁺] _i oscillations and spatial changes in the form of [Ca²⁺] _i waves. [Ca²⁺] _i oscillations in unstimulated cells (n = 60) were independent of extracellular [Ca²⁺] and had a mean frequency of 12.6 +1.1 oscillations per min. The baseline [Ca²⁺], was 171 ± 13 nm and the mean oscillation amplitude was 194 ± 12 nm. Generation of [Ca²⁺] _i waves was also independent of influx of extracellular Ca²⁺. [Ca²⁺] _i waves originated in one cell pole and were visualized as propagation mostly along the subplasmalemmal space or occasionally throughout the cytoplasm. The mean velocity was 23 +3 m per sec (n = 6). Increases of [Ca²⁺] _i induced by different agonists were encoded into changes of baseline [Ca²⁺] _i and the amplitude of oscillations, but not into their frequency. The observed spatiotemporal pattern of [Ca²⁺] _i regulation may be the underlying mechanism for slow wave generation and propagation in this tissue. These findings are consistent with a [Ca²⁺] _i regulation whereby cell regulators modulate the spatiotemporal pattern of intracellularly generated [Ca²⁺] _i oscillations.The authors thank Debbie Anderson for excellent technical assistance with the electron microscopy and Dr. M. Regoli for providing the NK-1 agonist [Sar⁹,Met(O₂)¹¹]-SP. This work was supported by National Institutes of Health Grants DK 40919 and DK 40675 and Veterans Administration Grant SMI.     

Cloning and sequencing of a human pancreatic tumor mucin cDNA

A monospecific polyclonal antiserum against deglycosylated human pancreatic tumor mucin was used to select human pancreatic mucin cDNA clones from a lambda gt11 cDNA expression library developed from a human pancreatic tumor cell line. The full-length 4.4-kilobase mucin cDNA sequence included a 72-base pair 5'-untranslated region and a 307-base pair 3'-untranslated region. The predicted amino acid sequence for this cDNA revealed a protein of 122,071 daltons containing 1,255 amino acid residues of which greater than 60% were serine, threonine, proline, alanine, and glycine. Approximately two-thirds of the protein sequence consisted of identical 20-amino acid tandem repeats which were flanked by degenerate tandem repeats and nontandem repeat sequences on both the amino-terminal and carboxyl-terminal ends. The amino acid sequence also contained five putative N-linked glycosylation sites, a putative signal sequence and transmembrane domain, and numerous serine and threonine residues (potential O-linked glycosylation sites) outside and within the tandem repeat position. The cDNA and deduced amino acid sequence of the pancreatic mucin sequence was over 99% homologous with a mucin cDNA sequence derived from breast tumor mucin, even though the native forms of these molecules are quite distinct in size and degree of glycosylation.     

Mycobacteria glycolipids as potential pathogenicity effectors: alteration of model and natural membranes

Four mycobacterial wall glycolipids were tested for their effects on phospholipidic liposome organization and passive permeability and on oxidative phosphorylation of isolated mitochondria. From fluorescence polarization of diphenylhexatriene performed on liposomes it was concluded that the two trehalose derivatives (dimycoloyltrehalose and polyphthienoyltrehalose) rigidified the fluid state of liposomes, the triglycosyl phenolphthiocerol slightly fluidized the gel state, while the peptidoglycolipid ("apolar" mycoside C) just shifted the phase transition temperature upward. Dimycoloyltrehalose was without effect on liposome passive permeability, as estimated from dicarboxyfluorescein leak rates, and polyphthienoyltrehalose and triglycosyl phenolphthiocerol slightly decreased leaks, while mycoside C dramatically increased leaks. Activity of these lipids on mitochondrial oxidative phosphorylation was examined. The two trehalose derivatives have been tested previously: both had the same type of inhibitory activity, dimycoloyltrehalose being the most active. Triglycosyl phenolphthiocerol was inactive. Mycoside C was very active, with effects resembling those of classical uncouplers: this suggested that its activity on mitochondria was related to its effect on permeability. All these membrane alterations were called nonspecific because it is likely that they result from nonspecific lipid-lipid interactions, and not from recognition between specific molecular structures. Such nonspecific interactions could be at the origin of some of the effects of mycobacteria glycolipids on cells of the immune system observed in the last few years.     

Effects of protease treatment on growth,morphology, adhesion,and cell surface proteins of secondary chick embryo fibroblasts

Several proteolytic enzymes have been studied with regard to their ability to induce DNA synthesis and cell proliferation in resting chick embryo fibroblasts. Of the enzymes examined, thrombin, bromelin, and trypsin exhibit potent mitogenic activity, elastase has significant but less marked activity, whereas thermolysin, papain, and α-protease are inactive. The enzymes were also tested for their ability to induce morphological change or to remove two iodinatable proteins of 250,000 and 205,000 daltons. Although the larger protein is removed by some but not all of the proteases examined, every protease tested removed the smaller cell surface protein. The ability of proteases to stimulate cell growth could not be correlated directly with removal of either of these cell surface proteins; however, loss of the smaller protein does correlate with the reduction of both cytoplasmic spreading and cell-cell interactions observed after protease treatment. A secondary, later event of migration of cells into clumps is observed in those instances when protease treatment did not result in a loss of the 250K protein. A role for each of these proteins in the processes of cellular adhesion is discussed.     

Ecological studies on Indonesian lakes. Overturn and restratification of Ranu Lamongan

In July 1974 Ranu Lamongan overturned. The resulting deoxygenation of this small tropical crater lake killed some of its fishes. This paper describes the recovery of stratification of temperature and oxygen and follows short-term changes in the plankton during the three weeks after overturn. The lake is fringed with a floating mat of Eichhornia whose submerged roots support and shelter a rich community of invertebrates on which much of the fishery depends. Comparison of our findings with those of the German Sunda Expedition in 1928 show remarkably few changes in the lake or its biota during the 45-year interval, despite a marked increase in the human population and the introduction of four species of fishes.     

Solitary thyroid metastasis from clear-cell renal carcinoma.

A 58-year-old woman underwent nephrectomy because of clear-cell renal carcinoma. Seven years later a solitary thyroid metastasis was detected. She is alive and well 17 months after thyroidectomy. The rarity of this manifestation is well known but its explanation is not clear. The long metastasis-free interval, a characteristic shared by other hormonally dependent neoplasms, has been explained in part by the concept of "dormant cells", which do not undergo division. The stimulus that provokes these cells into division is at present not known.     

基于结构方程模型的森林生态系统空气负离子影响机制分析

空气负离子(Negative air ion, NAI)是衡量空气质量的重要指标之一,受到植被和环境的共同影响。然而,森林生态系统作为NAI产生的重要来源,森林中的植被和环境之间的相互作用以及对NAI的影响机制和贡献潜力仍难以捉摸。以暖温带森林生态系统中广泛分布的栓皮栎(Quercus variabilis BI.)为对象,基于自动观测设备长期定位观测获取了气象、土壤性质、空气洁净度以及植被光合等数据,利用皮尔逊相关系数分析和偏最小二乘结构方程模型分析了森林植被和环境要素对NAI的影响机制和贡献潜力。结果表明,环境要素和植被光合对NAI的贡献差异显著,植被光合对NAI的贡献潜力为62.65%,环境要素对NAI的贡献率为37.35%。环境要素中太阳辐射和饱和水汽压差的影响程度最大,分别为68.94%和16.55%。植被光合和PM_2.5主要通过直接效应影响NAI,而光合有效辐射、紫外辐射、土壤温湿度和饱和水汽压差主要通过间接效应影响NAI。因此,利用结构方程模型可以阐明植被光合与环境要素的变化对NAI的影响趋势,从而全面揭示了森林生态系统中植被产生NAI的作用机制以及...     

萎缩芽胞杆菌CKL1促盐胁迫下燕麦生长活性及其功能基因分析

【背景】青海省特殊生境孕育了特殊微生物资源。【目的】探究适合生活于高原生境的芽胞杆菌菌源。【方法】采用平板对峙法、显色法对萎缩芽胞杆菌（Bacillus atrophaeus） CKL1的拮抗、产吲哚乙酸活性进行测定,并检测耐低温、耐盐性及菌株对盐胁迫下燕麦品种（Avena sativa）“青燕1号”种子萌发、幼苗生长效应及叶绿素、脯氨酸、丙二醛的含量变化,利用二代测序技术对菌株进行基因组测序并分析相关功能基因。【结果】菌株CKL1对禾谷镰孢菌（Fusarium graminearum）、锐顶镰孢菌（Fusarium acuminatum）表现出显著的拮抗活性（抑菌圈直径>15 mm）;与Salkowski比色液反应变红,能在NaCl浓度为13%的LB培养基及4℃低温下生长,表现出一定的产吲哚乙酸、耐盐及耐低温活性;盐胁迫下,菌株CKL1对“青燕1号”种子萌发及幼苗生长具有显著促进作用,叶绿素及脯氨酸含量显著增加,丙二醛含量下降,增强了燕麦的抗盐性。菌株CKL1基因组全长为14 281 280 bp,与GO功能数据库比对注释到3 303个功能基因;基因组编码与脂肽类化合物itur...     

海岛碳排放核算与时空特征——以东山岛为例

把握地区碳信息发展动态是开展区域碳平衡规划的科学基础。以统计年鉴数据为基础,对东山岛2012—2021年整体及各产业的直接碳排放量进行核算,同时,将产业与土地利用结合,分析其空间表现形态,运用核密度分析和克里金法分析碳排放源的空间影响,采用高斯烟羽模型对工业点源的碳排放扩散进行空间模拟,通过渔网和人口修正的方法分析海岛碳排放的空间分异,以此探讨海岛碳排放的空间分布和空间影响特征。结果显示,工业是东山岛的首要碳排放源,2021年工业碳排放量的大幅下降表明能源种类的转换对于工业碳减排具有重要作用;渔业碳排放量总体占比25%左右,是海岛地区不容忽视的碳排放源之一。在空间分布方面,东山岛综合碳排放的空间分布呈“点状聚集,面状扩散”的基本特征,工业碳排放对周围地区的影响最大,往往形成以工业碳排放源点为中心的碳排放热点核心区,其次碳排放量较高的地区为人口聚集区,丘陵区的碳排放量最低,不同土地利用类型之间形成碳排放的交叉过渡区。最后,本文从碳排放空间影响的视角出发,根据不同形态的碳排放源提出“包围”、“伴随”和“介入”的碳汇空间规划策略,这对区域的低碳规划具有一定参考意义。     

亚热带杉木径向生长对气候因子的响应

杉木(Cunninghamia lanceolata)是亚热带地区主要造林树种之一,其在区域碳循环和缓解气候变化中起着重要的作用。以亚热带地区6个站点(荆关、马鬃岭、分宜、将乐、东风、高峰)杉木人工林为研究对象,建立树轮标准化年表,分析树木年轮年表与气候因子的关系,解析不同研究区杉木径向生长对气候变化的响应机制,探讨不同站点杉木对干旱事件的响应策略,为该地区杉木人工林的经营管理提供理论依据。研究结果表明,6个研究区杉木树轮宽度对气候变化的平均敏感度大于0.15,样本总体代表性大于0.85,均处于可接受水平,表明6个站点的杉木样本具有区域代表性,适用于进行气候相关分析。杉木径向生长主要与生长季的平均温度和降水量、上一年夏季的最低温度正相关,与当年夏季最高温度负相关,高峰站点的径向生长与7—10月的相对湿度显著正相关,其他地点径向生长与月相对湿度相关性较弱,分宜、东风和高峰站的径向生长与干旱指数显著正相关,其他地点的杉木树轮宽度与干旱指数相关性较弱。干旱事件对6个站点杉木生长均产生了负面影响,胸高断面积增长(Basal area increment, BAI)呈先上升后下降的趋势,在生长后...