Effect of temperature and cell density on cellular protein content in temperature-sensitive mutants of rat 3Y1 diploid fibroblasts

Summary We examined cellular protein content in four temperature-sensitive (ts) mutants of rat 3Y1 fibroblasts (3Y1tsD123, 3Y1tsF121, 3Y1tsG125, and 3Y1tsH203) under various conditions of culture that affect cell proliferation. When proliferation of the ts mutants was inhibited at a nonpermissive temperature (39.8°C) in the G₁ phase, prominent accumulation of cellular protein occurred in three mutants (3Y1tsF121, 3Y1tsG125, and 3Y1tsH203) but not in 3Y1tsD123. The over-accumulation of protein at 39.8°C in the former three mutants was inhibited at high cell densities. At low cell densities there was an upper limit in the protein accumulation at 39.8°C. When the three mutants, proliferation-arrested at high cell densities at 33.8°C, were replated sparsely in fresh medium and shifted to 39.8°C, proliferation was completely inhibited whereas over-accumulation of protein occurred. These results indicating dissociation of protein accumulation and cell proliferation suggest that the two events are regulated by different mechanisms. This work was supported in part by a Grant-in-Aid for Encouragement of Young Scientists (1984) to K. Y. from the Ministry of Education, Science, and Culture, Japan.     

Predation byCheilomenes vicina [Coleoptera: Coccinellidae] on the cowpea aphid,Aphis craccivora [Homoptera: Aphididae]: Effect of prey stage and density

Consumption of larvae and females ofAphis craccivora Koch by 1st and 4th larvae and adults ofCheilomenes vicina (Muls.) was studied under fluctuating temperature (24–30°C). The early aphid instars were consumed in significantly greater numbers than later instars and females. The feeding rates ofC. vicina were significantly positively correlated with the population density of prey. The number of prey consumed daily by each predator stage tested, increased more steeply at lower than at higher prey densities, exhibiting thus the type 2 functional response

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Résumé Consommation des larves et des ♀ d'Aphis craccivora par les11^e stades, les 4^e stades et les adultes deCheilomenes vicina a été étudiée à une température variant de 24 à 30°C. Les jeunes stades du puceron sont consommés en nombre plus grand significativement que les derniers stades et les ♂. Les taux d'alimentation deC. vicina manifestent une corrélation hautement significative avec la densité de population de la proie. Le nombre de proies consommées quotidiennement par chaque stade considéré du prédateur augmentait plus brusquement aux faibles qu'aux fortes densités de proies, manifestant ainsi chez le prédateur le type 2 de réponse fonctionnelle.

     

Critical nuclear DNA size and distribution associated with S phase initiation

Using HeLa S-3 cells synchronized by selective detachment, in this paper we report a parallel study of nuclear morphology and autoradiography grain patterns between middle G₁ and middle S phases: Our results show two distinct [³H]-thymidine labeling patterns. The first “peripheral” labeling pattern has a characteristic nuclear size distribution, in contrast to the heterogeneous and varying size distributions of Feulgen-stained nuclei, and apparently is characteristic of very early S phase. The sizes of the second labeling pattern—homogeneous or inhomogeneous grain distribution throughout the nucleus—are equal or larger than the first and vary with S phase progression. Together, the corresponding nuclear sizes of the labeled nuclei represent the larger extreme of nuclear areas, and the labeling index closely parallels the fraction of nuclei with areas larger than the minimum size of the labeled nuclei. These results suggest a characteristic nuclear size (reflecting unique intranuclear DNA distribution) as a necessary, if not sufficient, requirement for S phase initiation. Parallel experimentation with rat liver cells—synchronized in vivo by partial hepatectomy and analyzed by thin section autoradiography—confirms the existence of a peripheral labeling pattern in both the very early part and the very late part of S phase, which reconciles our data with previous results and points to the fact that both initiation and termination sites for DNA replication are near the nuclear periphery.     

Vegetation responses to past climatic variation

Vegetation responses to climatic change can be studied retrospectively by utilizing the Quaternary fossil record. There has been controversy over the extent to which major changes in vegetation patterns at the continental scale lag behind the climatic changes that drive them, and to what extent vegetation can ever be said to be in equilibrium with climate. The equilibrium question has no single answer. The predominant mode of vegetation response to climatic change depends on the space and time frame and resolution of the data set in which the response is observed.Vegetation (as observed on particular space and time scales) can be in dynamic equilibrium with climate if its response time is sufficiently fast in relation to the rate of climatic change to which it is observed to be responding. Several processes can be involved in the response: successional, migrational, edaphic, and evolutionary. Successional response times can be deduced from forest succession models. The other processes are less well understood and different ideas exist concerning their rates. According to one hypothesis, migrational lags caused delays of thousands of years in the postglacial dynamics of forest composition. The alternative hypothesis explains these changes as dynamic equilibrium responses to changes in climatic seasonality and climatic anomaly patterns. Neither hypothesis need be universally true; gradient analysis and forest succession models are among the techniques that can be used in inferential tests of these hypotheses for particular space-time regions.Dynamic equilibrium may often be a reasonable approximation for the responses of the broadest continental-scale forest patterns to orbitally induced climatic changes. But as spatial and temporal frames of observation are diminished and resolution increased, biotic processes must eventually come to dominate. At sufficiently fine scales the main observable phenomena are successional responses to natural disturbance events. The late-Quaternary record of vegetation change allows a choice of observation scales and thus provides a continuum of possibilities for study, ranging from long-term dynamic bioclimatology to more conventional vegetation dynamics.I thank Margaret Davis, Honor Prentice, Jim Ritchie, Al Solomon, Geoff Spaulding and Tom Webb for their reviews of earlier drafts. Research supported by a US Department of Energy, Carbon Dioxide Research Division, grant to Brown University and a Swedish Natural Science Research Council grant to the project SlsSimulation of Natural Forest Dynamics.I thank Margaret Davis, Honor Prentice, Jim Ritchie, Al Solomon, Geoff Spaulding and Tom Webb for their reviews of earlier drafts. Research supported by a US Department of Energy, Carbon Dioxide Research Division, grant to Brown University and a Swedish Natural Science Research Council grant to the project SlsSimulation of Natural Forest Dynamics.     

Ca~(++)促进大麦根K~+吸收的过程分析

吸收溶液中CaCl_2促进了大麦根K~+净吸收,Ca~(++)本身对H~+分泌无影响,Cl~-减少了H~+净分泌量。 含有~(86)Rb的大麦根在1m mol/L KCl溶液中发生~(86)Rb外流,在H_2O、1m mol/L NaCl或0.5 m mol/L CaCl_2中没有明显外流。VO_4~(3-)、NaN_3和4℃低温均可以减少根段在1m mol/L KCl溶液中的~(86)Rb外流量。Ca~(++)抑制K~+(~(86)Rb~+)的外流,EDTA加剧外流,Ca~(++)可以逆转EDTA的效应。 Ca~(++)抑制K~+(~(86)Rb)外流和促进K~+净吸收的趋势相吻合。K~+吸收的通量分析结果表明,Ca~(++)抑制K~+通过质膜的外流,促进K~+由细胞质向液泡中转运,而不影响K~+通过质膜的内流速率。     

二氧化硫熏气对小麦叶片中1-氨基环丙烷-1-羧酸、1-(丙二酰氨基)环丙烷-1-羧酸含量的影响及与乙烯产生的关系

在SO_2熏气9h过程中,小麦叶片中乙烯先上升,约6h达高峰,后下降;ACC含量则随熏气时间的延长而上升。停止熏气,乙烯继续下降,ACC含量也明显降低。MACC含量从熏气3h后不断上升,脱离接触后仍继续增加。6-BA预处理对SO_2引起的乙烯和ACC上升有促进作用,但对MACC含量无明显影响。SO_2熏气提高了乙烯形成酶活性。6-BA预处理对SO_2伤害有保护作用。对逆境乙烯的产生与调节作用进行了讨论。     

光合能量代谢对C_3植物光呼吸的调节作用

C_3植物光呼吸与光合作用关系受光合能量代谢状况的调节。在外界无CO_2和照光条件下,贮藏性光合产物经某种转化途径能“回迁”光合与光呼吸碳循环并显著地受到光合能量代谢的影响。在无CO_2或低CO_2浓度、高光强条件下,此碳素“回迁”过程对协调光合能量代谢与光合碳素代谢平衡,可能起重要作用。     

体外分化的人体巨噬细胞抑制天然杀伤(NK)细胞的研究

本文继先前工作后,进一步应用正常健康人外周血单个核细胞(PBMNC)经塑料培皿粘附技术把单核细胞分离出来,经培养进一步纯化,随后动态观察培养0,2,4,6和8天的单核-巨噬细胞的形态变化和对新鲜分离同种异基因个体PBMNC中NK活性的影响。实验表明,体外分化6天和8天的巨噬细胞质/核比例和胞浆内空泡显著增加,细胞直径约为0天时的2倍。这些细胞和PBMNC之比为0.5:1时,引起了NK细胞活性的50%以上抑制(4小时~(51)Cr标记K 562肿瘤的同位素释放试验)。这种抑制效应不为过氧化氢酶(Catalase 4000单位/毫升)和前列腺素合成酶的抑制剂(Indom 1×10~(-5)M)所阻断。实验证明,同种异基因个体的NK细胞不能识别巨噬细胞表面抗原,从而排除了巨噬细胞和K562肿瘤抗原竞争的可能性。实验还表明,巨噬细胞对NK活性的抑制是不受HLA约束的。应用高频超声振荡破碎巨噬细胞膜方法和免疫调变技术进一步提示,人体巨噬细胞对NK活性的抑制与巨噬细胞体积无关,而与体外分化所赋有的固有特性和它们分泌的免疫调节分子有关。     

Stimulation and inhibition of secretion by phorbol myristate acetate in different cell types

In washed human platelets and in HL60 granulocytes phorbol myristate acetate (PMA, 1-2000nM) synergised with threshold concentrations of secretogogues to induce a sustained maximum secretory response. Likewise, superoxide production from HL60 cells maintained a maximal response at PMA concentrations between 30-300nM. At concentrations up to 10nM PMA also augmented calcium ionophore, A23187, stimulated histamine release from rat peritoneal mast cells. However, in the mast cell PMA concentrations above 10nM reduced maximum histamine release in a dose-dependent manner.