Arginase,an s-phase enzyme in a human cell line

Suspension cultures of ‘Chang liver’ cells were synchronized by preincubation in a glutamine-deficient medium or by thymidine blockade. Specific arginase activity varied in the synchronized cultures, being high when the number of S-phase cells was maximal. A relationship between high arginase activity and a high percentage of (S+G₂) cells was also found when unsynchronized cells were separated by velocity sedimentation. The increase in arginase activity near the G₁/S border was totally inhibited in the presence of cycloheximide. The rate of decrease in activity after addition of the drug indicated that the variations in the rate of synthesis of the enzyme, while the rate of degradation was more or less constant, corresponding to 4–6% per h. The role of arginase in cells lacking a urea cycle and the regulation of arginase activity in ‘Chang liver’ cells is discussed.     

刺叶柄棘豆的一个新变型--白花刺叶柄棘豆

描述了棘豆属(豆科)刺叶柄棘豆(Oxytropis acipblla Ledeb．)的一个新变型：白花刺叶柄棘豆O．aciphylla Ledeb．f．albiflora Z．Y．Chang,Z．H．Wu et L．R．Xu。原变型的花冠为红紫色或蓝紫色,而新变型的花冠为白色。     

濒危植物长柄双花木开花物候与生殖特性

研究了长柄双花木开花过程中花部表型的变化。连续4a对其野生种群、1a对人工种群的开花物候进行了观察,并运用相对开花强度和同步性等开花物候指数分析了开花物候对其生殖的影响。结果如下：长柄双花木开花时间为9月上、中旬至11月中、下旬;单花花期一般为6～7d,单花依其形态和散粉特征可以分为4个时期：散粉前期、散粉初期、散粉盛期和凋谢期。个体开花持续时间49～55d,种群花期历时63～71d。种群内不同年度间开花物候指数没有显著差异,而种群间则存在显著差异,野生种群开花进程为渐进式单峰曲线。人工种群则为“钟”形曲线,二者均属于“集中开花模式”。长柄双花木具有2个相对开花强度的分异趋势,这种分异趋势具有进化意义。开花物候指数与生殖间的相关分析表明,始花时间与开花数量、座果率及花期长度之间均具显著负相关关系,而开花数量与花期长度之间则呈显著正相关,但均为线性相关。长柄双花木开花物候在种群间的差异和种群内年度间的相似性说明,其开花时间可能是由与其相关的复杂的微生境特征和(或)由其遗传因子决定的,同时也反映了种群间的遗传分异和种群内个体间的遗传一致性。作为一种濒危物种,长柄双花木在这种环境的选择压力之下,形成了“大量、集中开放的花”的开花模式,吸引到更多的传粉者的访问,从而达到生殖成功。     

南岭大东山长柄双花木群落物种组成与种群结构特征分析

采用样方法以及用基径结构代替年龄结构的方法,对位于南岭大东山不同海拔的3个长柄双花木(Disanthus cercidifolius var.longipes Chang)样带(包括小洞、大洞和鸡子场样带,海拔分别为1 010、1 170和1 260 m)进行了调查,并编制了种群静态生命表和生存曲线,对其群落物种组成、种群年龄结构和生殖力现状进行了分析。结果显示:3个样带群落乔木层优势种数量及种类组成差异明显,共包含26个种类,但共有种仅3种,除长柄双花木外还有多花杜鹃(Rhododendron cavaleriei Lévl.)和两广杨桐(Adinandra glischroloma Hand.-Mazz.)2种;小洞样带长柄双花木种群的重要值(46.116%)明显高于另2个样带。根据基径可将长柄双花木种群分为68个龄级,3个样带的种群年龄结构基本一致,但小洞样带个体数量更多且基径31.0 mm以下的幼体所占比例最高;总体上长柄双花木种群中5 a以下的幼苗数量偏少,其他龄级的个体数量呈现随株龄增大波动但整体下降的趋势。种群的个体死亡率在5~10 a和10~15 a龄级较高(分别为20.30%和20.50%),并随年龄增长总体呈逐渐下降的趋势;且不同龄级个体生命期望值为4.49~0.50,总体偏低。种群生存曲线为Ⅰ型,种群净增殖率、内禀增长率、周限增长率和世代平均周期分别为0.504、-0.018、0.982和38.351 a,显示该种群在当前状态下自我更新不良,属缓慢的负增长型种群。根据研究结果,对该区域长柄双花木种群提出了相应的保护对策和建议。     

羌塘国家级自然保护区地表土壤冻结天数时空变化特征

利用1981—2018年羌塘自然保护区周边5个气象台站的地表逐日最低温度和平均气温资料,采用线性回归和Mann-Kendall非参数检验方法,分析了近38 a以及全球变暖1.5℃和2℃阈值时羌塘自然保护区地表土壤冻结天数的时空变化特征。结果表明:(1)近38 a近地表土壤冻结开始日期呈推迟趋势,变化率为7.72 d·10 a^-1,冻结终止日期以8.17d·10 a^-1的速率显著提早;冻结持续时间和冻结天数均呈显著缩短趋势,平均每10年分别缩短14.69和11.19 d;同时段内,自然保护区大部分土壤冻结参数的变化率均大于青藏高原。(2)在年代际变化上,自然保护区呈现土壤冻结开始日期推迟、冻结终止日期提前、冻结持续时间和冻结天数缩短的变化特征。(3)土壤冻结参数在21世纪初均发生了气候突变,较青藏高原土壤冻融时间的突变点偏晚。(4)在全球变暖1.5℃时,RCP4.5和RCP8.5情景下的自然保护区土壤冻结参数变化值相同,冻结开始日期推迟25 d,冻结终止日期提早22 d,冻结持续时间和冻结天数分别缩短46和28 d;变暖2.0℃时,RCP4.5和RCP8.5情景下的土壤冻结开始日期推迟35和33 d,冻结终止日期提早30和29 d,冻结持续时间减少64和62 d,冻结天数缩短40和39 d。     

羌塘高原藏羚羊栖息地分布及影响因素

藏羚羊作为羌塘高原草食性野生动物的典型代表,明确其栖息地的准确分布将有利于识别藏羚羊种群保护关键区域,协调羌塘高原人与野生动物冲突。采用野外调查与物种分布模型相结合的办法,以藏羚羊栖息地选择偏好和迁徙规律为基础,利用Maxent模型模拟其在繁殖季节和非繁殖季节的栖息地分布,并通过栖息地质量模型辅以GIS空间分析方法,识别受人类干扰的栖息地范围。结果表明：藏羚羊在非繁殖季节主要分布在羌塘高原东南部,围绕在色林错等水系周围,其越冬区面积约为26万km²。倾向选择海拔4800m以上、气候温暖、靠近水源且食物资源丰富的区域。藏羚羊在繁殖季节栖息地明显呈现由南向北扩散的趋势,多在水系周围呈小片状分布于羌塘东北、中北、昆仑山南麓部分区域,产羔区面积约为30万km²。选择产羔地时则注重坡度、水源、海拔、气温日较差等,对植被资源的选择倾向较非繁殖季弱,重视迁徙通道连贯性和产羔区域安全性。羌塘高原人类活动整体较弱,北部羌塘国家级自然保护区是藏羚羊理想栖息地,但南部地区社会经济较发达,尤其是那曲地区南部和阿里西南部,居民地、道路和牧业等人类活动对栖息地干扰较大,受干扰面积分别占藏羚羊越冬区的39.7%,产羔区的34.9%。     

红金麻——木槿属一个新杂种

<正> 红金麻 新杂种 Hibiscus×hongjinma Y. T. Chang, hybr. nov. H. cannabinus L. ♀× H. radiatus Cav.♂ Hybrida hortensis ( 2n=30+6sat) θ Hibisco cannabino L. ( 2n=32+4sat) et H. ranndiato Cav. (2n=70+2sat) exorta, Habitu illo simil, characteribus ad hoc magis accedit; ab illo differt floribus purpureis, folio prope basin 3—5     

异裂菊属两新种

异裂菊属两新种梁健英（广西植物研究所,桂林５４１００６）关键词菊科;异裂菊属;新种ＴＷＯＮＥＷＳＰＥＣＩＥＳＯＦＨＥＴＥＲＯＰＬＥＸＩＳＣＨＡＮＧ（ＣＯＭＰＯＳＩＴＡＥ）￥ＬｉａｎｇＪｉａｎｇｙｉｎｇ（ＧｕａｎｇｘｉＩｎｓｔｉｔｕｔｅｏｆＢｏｔａｎｙ...     

The stimulation of metallothionein synthesis in neuroblastoma IMR-32 by zinc and cadmium but not dexamethasone

Metallothioneins are a class of cysteine-rich and low molecular weight, metal-binding proteins that are inducible by a wide variety of agents, including metal ions, such as cadmium and zinc, glucocorticoid hormones, interferon, and tumor promoters. In an effort to delineate the regulation of the synthesis of the recently identified brain metallothionein-like protein, a study was undertaken to compare the induction of metallothionein in human neuroblastoma IMR-32 cells by zinc, cadmium, and dexamethasone using the human Chang liver cells as a control. Both cadmium (1 microM) and zinc (100 microM) significantly enhanced the incorporation of [35S]cysteine into metallothioneins isolated from both neuroblastoma and Chang liver cells. Dexamethasone in concentrations of 10 microM stimulated the synthesis of metallothionein in the Chang cells, whereas it had no effects on the synthesis of metallothionein in the neuroblastoma cells at concentrations ranging from 2.5--100 microM. The degree of stimulation of metallothionein synthesis in the Chang cells by cadmium and zinc was significantly higher than seen in neuroblastoma cells. The neuroblastoma IMR-32 exhibited less tolerance to the toxicity of both cadmium and zinc than the Chang cells, which may correlate with the inherent ability of these ions to induce metallothioneins in these dissimilar cells. The results of these studies are interpreted to indicate that the factors regulating the synthesis of metallothioneins in the Chang and neuroblastoma cells are not identical, suggesting also of the presence of dissimilar regulatory mechanisms in the liver and brain.     

Cholecystokinin receptor mediated hydrolysis of inositol phospholipids in guinea pig gastric glands

CCK-octapeptide (CCK-8) (EC50 = 0.5 nM), in the presence of Li+, increased 3H-inositol phosphate (IP) accumulation in guinea pig gastric glands prelabeled with 3H-inositol. CCK-8 desulfate, human gastrin I and pentagastrin were much less potent than CCK-8. Antagonists of CCK receptors such as proglumide, dibutyryl-c-GMP and CBZ-Tyr (SO3H)-Met-Gly-Trp-Met-AspNH2 shifted the CCK dose response curve to the right. However, histamine (H1 and H2), cholinergic, substance P and alpha- and beta-adrenergic receptor antagonists had no effect on 3H-IP accumulation induced by CCK. The results suggest that CCK receptor activation in gastric glands leads to an enhanced breakdown of inositol phospholipids which may relate to calcium mobilization and pepsinogen secretion.