艾氏腹水癌细胞核糖核酸体外对C_(57)BL/6脾自然杀伤活性的影响

本文采用~(51)Cr释放法,研究了艾氏腹水癌细胞核糖核酸(EAC-RNA)体外对C_(57)BL/6小鼠脾自然杀伤细胞(NK)对YAC-1靶细胞杀伤活性的影响。结果表明,EAC-RNA能显著抑制NK活性。经RNase处理后,其抑制活性消失,DNase或Pronase的处理不改变其抑制活性。     

Molecular biology of K transport across the plant cell membrane: What do we learn from comparison between plant species?

Cloning and characterizations of plant K⁺ transport systems aside from Arabidopsis have been increasing over the past decade, favored by the availability of more and more plant genome sequences. Information now available enables the comparison of some of these systems between species. In this review, we focus on three families of plant K⁺ transport systems that are active at the plasma membrane: the Shaker K⁺ channel family, comprised of voltage-gated channels that dominate the plasma membrane conductance to K⁺ in most environmental conditions, and two families of transporters, the HAK/KUP/KT K⁺ transporter family, which includes some high-affinity transporters, and the HKT K⁺ and/or Na⁺ transporter family, in which K⁺-permeable members seem to be present in monocots only. The three families are briefly described, giving insights into the structure of their members and on functional properties and their roles in Arabidopsis or rice. The structure of the three families is then compared between plant species through phylogenic analyses. Within clusters of ortologues/paralogues, similarities and differences in terms of expression pattern, functional properties and, when known, regulatory interacting partners, are highlighted. The question of the physiological significance of highlighted differences is also addressed.     

Phenological studies on the wing dimorphism of a semi-aquatic bug,Microvelia douglasi (Heteroptera: Veliidae)

Seasonal changes in the percentage of macropterous individuals in natural population of Microvelia douglasi in permanent habitats were investigated in Shimane, western part of Japan. Macropterous forms of 5th instar nymphs occurred most frequently from late June to early July. However, the seasonal appearance of macropterous adults differed between habitats and years. There were significant effects of density, temperature, photoperiod and food availability on the percentage of macropters under laboratory conditions. The percentage of macropterous forms generally increased with density, but the mode of the response was modified by temperature, photoperiod and food availability. When insects were reared under long day photperiod (16L8D) with abundant food (0.5–1.0 g/container/day), the percentage of macroptery varied most among the different density treatments at the intermediate temperature (24°C) and the difference was reduced at higher temperature (28° and 32°C). Effects of temperature were small under the short day photoperiod (12L12D). Under 12L12D photoperiod sensitivity of density responses were higher at 32°C and lower at 24°C than those under 15L8D photoperiod. When the insects were supplied with food every other day, the density response became obscure. Ecological significance of environmental responses in the wing morph determination was discussed in relation to the heterogeneous environment of water surface.     

Nodal基因的第一内含子中存在着顺式调控增强子元件

小鼠ｎｏｄａｌ基因是在胚胎发育时期表达的一个基因,它在原肠期起着重要作用,并且参与左－右体轴的决定,４１３－ｄ小鼠胚胎干细胞系３５６３在ｎｏｄａｌ基因的第一内含子中含有单拷贝逆转录病毒的插入。采用定量ＲＮａｓｅ保护法比较了该细胞系及其母源ＥＳ细胞ＣＣＥ中ｎｏｄａｌ基因的表达量,ＣＣＥ细胞中ｎｏｄａｌ ｍＲＮＡ的含量是３５６３ＥＳ细胞含量的２．３倍。这一结果提示原病毒在ｎｏｄａｌ基因第一内含子中的整     

Enrichment planting does not improve tree restoration when compared with natural regeneration in a former pine plantation in Kibale National Park,Uganda

Given the high rates of deforestation and subsequent land abandonment, there are increasing calls to reforest degraded lands; however, many areas are in a state of arrested succession. Plantations can break arrested succession and the sale of timber can pay for restoration efforts. However, if the harvest damages native regeneration, it may be necessary to intervene with enrichment planting. Unfortunately, it is not clear when intervention is necessary. Here, we document the rate of biomass accumulation of planted seedlings relative to natural regeneration in a harvested plantation in Kibale National Park, Uganda. We established two 2‐ha plots and in one, we planted 100 seedlings of each of four native species, and we monitored all tree regeneration in this area and the control plot. After 4 years, naturally regenerating trees were much taller, larger and more common than the planted seedlings. Species richness and two nonparametric estimators of richness were comparable between the plots. The cumulative biomass of planted seedlings accounted for 0.04% of the total above‐ground tree biomass. The use of plantations facilitated the growth of indigenous trees, and enrichment planting subsequent to harvesting was not necessary to obtain a rich tree community with a large number of new recruits.     

SEASONAL SUCCESSION OF ALGAL PERIPHYTON FROM A WASTEWATER TREATMENT FACILITY1

Attached algal populations were sampled at weekly or biweekly to characterize successional changes in the secondary clarifiers of a wastewater treatment plant. Three communities were compared from areas of slow, medium and rapid current velocities. In general, the algae resembled those reported for other hypereutrophic flowing water. Of the twenty-three algae recorded, Stigeoclonium, Oedogonium, Oscillatoria, Lyngbya, and Pleurocapsa were dominant at some point in the 15 month sampling period. Nutrient concentrations were consistently high (N = 1.1–21.4 mg·L⁻¹; P = 0.1–10.4 mg·L⁻¹); therefore, changes in temporal distribution of algae were probably dependent on seasonal changes in light and temperature. Colonization of artificial substrates was also observed. Small unicellular algae were the first autotrophs to attach and these were followed by larger filamentous forms.     

陕北撂荒地上优势蒿类叶片解剖结构及其生态适应性

对陕北丘陵区撂荒地上处于自然恢复演替不同时期的3种优势种蒿类铁杆蒿（Artemisia gmelinii Web．）、茭蒿（Artemisia giraldii Pamp．）、猪毛蒿（Artemisia scoparia）的叶片解剖结构进行了观察研究的结果表明,随着演替序列的发展,3种蒿类的栅栏组织随演替时间的推移呈现出全栅型-环栅型-过渡型的趋势,叶片解剖结构说明越靠近演替前期的蒿类对干旱的适应性越强。此外,3种蒿类的栅栏组织排列都很紧密,表皮细胞排列不规则,且具有表皮毛和腺毛等旱生适应结构;在猪毛蒿和茭蒿中还发现了特化的气腔结构。这些特征均能说明这些蒿类植物具有很好的抗旱适应性,作为环境改造的先锋物种,它们在当地的自然植被恢复演替中起着积极的正向推动作用。     

Influence of a non-native invasive tree on primary succession at Mt. Koma, Hokkaido, Japan

The slopes of Mt. Koma in Japan are undergoing primary succession as a result of a 1929 eruption. Understory vegetation below a non-native invasive tree species, Larix kaempferi, a native tree, Betula ermanii, and in the open were compared to determine if the non-native tree species was influencing species composition. Larix canopies are significantly larger than Betula canopies. Vegetation under Larix canopies had significantly greater richness and diversity than vegetation in the open, vegetation under Betula was intermediate but was significantly greater than the open in diversity. Vegetation cover was highest under Betula and significantly lower in the open. Larix canopy size was positively correlated with size and number of Salix reinii shrubs. Betula canopy size was positively correlated with size but not with number of Salix reinii shrubs. Species assemblages in the three sites are slightly different as shown by DCA. Due to the limited species pool on Mt. Koma the greatest possible extent of differences between the three microsites is not large. At this point Larix certainly appears to be accelerating succession for the non-tree species. If Larix persists on the slopes then succession would be permanently deflected towards a Larix forest. This would be a case of succession being deflected towards dominance by the introduced species. This revised version was published online in June 2006 with corrections to the Cover Date.     

广东始兴南山自然保护区的植物资源及珍稀植物

对南山自然保护区的初步调查结果显示,区内有野生维管植物179科565属1039种,国家二级野生保护植物9种,其他珍稀濒危的种类7种。由此可见,南山自然保护区植物资源极其丰富,野生维管植物及珍稀保护植物是其重要组成部分。其中野生维管植物资源种类繁多,蕴藏量较大,而且不少种类具有开发和可持续利用的价值,具有巨大的经济价值和生态价值。     

Secondary succession in Acacia nilotica (L.) savanna in the Hluhluwe Game Reserve,South Africa

Analysis of aerial photographs indicates that woody plant biomass has rapidly increased in Hluhluwe Game Reserve over the last 40 years. Open Acacia nilotica savanna is being replaced by broadleaf species, especially Euclea spp. We were interested in whether this secondary successional shift was due to high numbers of seedlings establishing and growing to maturity under acacias (facilitation) or due to the release of already established, but suppressed individuals (gullivers) of the resprouting broadleaf species. We examined the recruitment patterns and size-class distributions (height, basal diameter) of important species in this savanna.Densities of euclea seedlings (<0.6 cm basal diameter) under Acacia nilotica were low (median of 0 and mean of 0.06 m²) below adult canopies and effectively zero in adjacent interspaces. No differences in numbers of other broadleaf species were found between open sites and under Acacia nilotica sites. Few large eucleas or other broadleaf species occurred under Acacia nilotica. Few Acacia nilotica recruits were found either under adults or in the open whereas Acacia karroo recruits were more common.The overall size class distribution for eucleas was dominated by individuals in the intermediate size class, suggesting that recruitment is not the dominant demographic process. We propose that the escape of intermediate sized eucleas from the fire trap has caused the increase in woody plants.Analysis of a time sequence of aerial photographs shows that invasion occurred rapidly between 1954 and 1975. A common feature for sites where woody plant invasion has taken place, was the presence of barriers to fire (especially roads). We suggest that the recent and rapid increase in woody vegetation is due to a decrease in the frequency of intense fires, rather than the recent absence of megaherbivores which allowed Acacia nilotica establishment. Few intense fires allow suppressed tree or shrub individuals, ('gullivers'), to escape the grass/fire layer and thereby become tall and fire-resistant. This release may explain the rapid rate of invasion by inherently slow growing broad-leaf species.