Recycling of CO2 via Crassulacean acid metabolism in the rock outcrop succulent Sedum pulchellum Michx. (Crassulaceae)

Under well-watered conditions in the laboratory, Sedum pulchellum assimilated CO₂ only during the day, yet exhibited small nocturnal increases in tissue acid content followed by deacidification in the light (CAM-cycling). When drought-stressed, little CO₂ was fixed in the day and none at night, yet even greater acid fluctuations were observed (CAM-idling). Calculations indicate that water savings associated with CAM-cycling when water is available are small. Water saving is more likely to be significant during CAM-idling when water supply is limited and stomata are closed day and night. Thus, in this species, CAM-idling may be of greater benefit to the plant, relative to CAM-cycling, in surviving habitats prone to frequent drought stress.Abbreviations A CO₂ exchange rate - CAM Crassulacean acid metabolism - c_i shoot internal CO₂ concentration - g_c shoot conductance to CO₂ - PPFD photosynthetic photon flux density - WUE water-use efficiency Supported by National Science Foundation Grant No. DMB 8506093.     

Microtubule and microfilament distribution and tubulin content in the cell cycle of Indian muntjac cells

Using DAPI, rabbit antitubulin antibody, FITC-labeled goat anti-rabbit IgG, and TRITC-phalloidin to stain individual cells, the microspectrophotometric analysis showed that three markers that represent the nucleus, microtubules (MT), and microfilaments (MF), respectively, could be recognized in individual cells without interference. The phase of the cell cycle was determined by DNA content. We found that in Indian muntjac (IM) cells, the amount of tubulin in G2 and M phases was about twice as much as that in G1 phase. In G2 cells, the cytoplasmic microtubule complex (CMTC) became denser than in G1 cells. The cytoplasmic MT extent in basically the same orientation as MF bundles in interphase. The regions where the MT is denser also have a denser MF distribution.     

紫茎泽兰的化学成分初报

紫茎泽兰(Eupalorium adenophorum Spreng)原产中美墨西哥,现在滇南一带广泛分布,对林、牧业生产造成严重危害。其化学成分研究未见报道。 从紫茎泽兰的叶和花序中,分到九个单体,经详细的光谱解析和与标准品对照,其中五个成分的化学结构分别为:正三十二烷n-dotriacontane(1),β-谷甾醇β-sitosterol(2),豆甾醇stigmasterol(3),蒲公英醇棕榈酸酯taraxasteryl palmitate(4),蒲公英醇乙酸酯taraxastcryl acetate(5)。     

向日葵幼胚培养中体细胞胚胎发生的观察

1.向日葵不同品种体细胞胚胎发生的情况不同。2.较高浓度的蔗糖有利于向日葵幼胚的体细胞胚胎发生。3.在同样条件下,2mm长的幼胚较其它时期的幼胚体细胞胚胎发生的频率高。4.在蔗糖浓度为17.5％并分别加入0.5—10.0ppm玉米素的Nitsch培养基中,向日葵幼胚产生体细胞胚胎发生的频率随着玉米素浓度的增高而增加。5. 2,4-D能使体细胞胚胎发生,但不能分化器官。6.切片观察表明:在含玉米素的培养基上,幼胚产生了胚性细胞团和胚状体。并多数发生于子叶与下胚轴的深层。胚性细胞团周围细胞退化,使其与周围组织之间形成间隙。     

兰萼丙素的结构

从北京地区产兰萼香茶菜[Rabdosia japonica (Burm. f.)Hara var.glaucocalyx(Maxim.)Hara]叶中分得三个对映-贝壳杉烯二萜化合物,其中二个为已知物兰萼甲素(2)和乙素(3),另一个为新化合物,命名为兰萼丙素,经光谱和化学方法证明,其结构为对映-7β,14α,15α-三羟基-16-贝壳杉烯-3-酮(1)。     

高黎贡山鼠兔一新种

1985年10月,云南省流行病防治研究所调查队在云南西北部高黎贡山北段的贡山地区相继采到3只体色特殊的鼠兔,经与该属各已知种比较均不同,鉴定为一新种,描述如下:     

皱纹盘鲍的染色体研究

本文报道皱纹盘鲍的染色体制备方法及核型分析结果。皱纹盘鲍的2n=36,可配为18对,中央着丝点(M)的11对,即1,3,6,7,9,11,12,13,14,16,17号染色体。亚中央着丝粒(Sm)的7对,即2,4,5 8,15,18号染色体,NF=72。染色体的长度呈连续递变。其中相对长度最长的1号染色体为7.09,最短的18号染色体4.11,单倍体总长687.05。     

Effect of Chronic Lithium Treatment on 5-Hydroxytryptamine Autoreceptors and Release of 5-[3H]Hydroxytryptamine from Rat Brain Cortical, Hippocampal, and Hypothalamic Slices

The effect of acute and chronic lithium treatments on 5-hydroxytryptamine (5-HT, serotonin) release and on its regulation by presynaptic 5-HT autoreceptors was studied in [3H]5-HT preloaded superfused rat brain slices. The [3H]5-HT overflow evoked by a 30-s exposure to 65 mM K+ was increased after 3 weeks of ingestion of lithium-containing diet in the three brain areas examined. Acute injection of 4 mEq/kg lithium chloride did not affect 5-HT release. The K+-induced release observed in both control and chronically lithium-treated animals was Ca2+-dependent. Chronic lithium treatment was also found to be associated with a decrease in basal [3H]5-HT overflow in the cortex and hypothalamus but not in hippocampus [corrected]. The Ca2+-independent overflow induced by fenfluramine was also decreased in cortical slices from lithium-treated animals. The sensitivity of the inhibitory 5-HT autoreceptors was assessed by the response to the 5-HT agonist 5-methoxytryptamine. The results indicate a marked reduction in the maximal inhibition of [3H]5-HT release induced by 5-methoxytryptamine in slices obtained from animals which have been treated with lithium for 3 weeks. These data suggest that the functional down regulation of the prejunctional 5-HT sites may be responsible for the increase in K+-stimulated 5-HT overflow in brain slices of animals treated chronically with lithium.     

An adenovirus mRNA which encodes a 14,700-Mr protein that maps to the last open reading frame of region E3 is expressed during infection.

The E3 regions of adenovirus types 2 and 5, respectively, are known to synthesize proteins of 19,000 Mr (19K) and 11.6K, but information regarding the identity and characterization of other potential E3 proteins encoded by the six remaining open reading frames (ORFs) is lacking. In this study, we show that the last ORF of region E3, which encodes a 14.7K protein, is expressed in adenovirus-infected cells. This information was largely derived from analysis of an E3 deletion mutant (H2dl801) in which an extensive deletion (1,939 base pairs) was found to eliminate all ORFs except for two proteins of 12.5K and 14.7K. The 14.7K protein was translated from RNA isolated from H2dl801-infected cells that had been hybridization selected to E3 DNA; hybridization-selected RNA from wild-type adenovirus type 5-infected cells translated both the 19K and the 14.7K proteins. Moreover, an antiserum directed against a bacterial 14.7K fusion protein (A. E. Tollefson and W. S. M. Wold, J. Virol. 62:33-39, 1988) immunoprecipitated the 14.7K translation product synthesized by wild-type and mutant H2dl801 adenovirus mRNAs.