鄂西南后河自然保护区植物区系研究

后河自然保护区共人维管植物１４１６种,尿属５６８属１６０科。其中蕨类、拟蕨类４１种２８属２０科;裸子植物１８种１１属６科;被子植物１３５７种５２９属１３４科。在科、属、种不同水平上对后河自然保护区植物区系特点进行了较深入的统计和分析。结果显示了该区系的丰富性。复杂性。古老、遗、原始性、温带成分的集中性,古特珍稀危植物群落繁荣的特殊性等特点。因此有理由认为后河植物区系对湖北乃至华中植物区系具有典型的     

Visualization of chromatin folding patterns in chicken erythrocytes by atomic force microscopy （AFM）

The organization of the higher order structure of chromatin in chicken erythrocytes has been examined with tapping-mode scanning force microscopy under conditions close to their native envirinment.Reproducible highresolution AFM images of chromatin compaction at several levels can be demonstrated.An extended beads-on-astring (width of - 15-20nm,height of - 2-3nm for each individual nucleosome) can be consistently observed.Furthermore,superbeade (width of - 40nm,height of - 7nm) are demonstrated.Visualization of the solenoid conformation at the level of 30nm chromatin fiber is attained either by using AFM or by using electron microscopy.In addition,tightly coiled chromatin fibers (- 50-60nm and - 90-110nm) can be revealed.Our data suggest that the chromatin in the interphase nucleus of chicken erythrocyte represents a high-order conformation and AFM provides useful high-resolution structural information concerning the folding pattern of interphase chromatin fibers.     

中药91—4对抗生素相关性腹泻小鼠肠道膜菌群影响的电镜研究

实验用菌群检查和光、电镜相结合的方法,观察了中药９１—４对抗生素相关性腹泻（ＡＡＤ）小鼠肠道膜菌为及其病理学变化的影响。由林可霉素灌胃致小鼠腹泻模型并证实菌群紊乱后,给各治疗组分别灌喂中药,并设自然恢复组,一个疗程后,时各组小鼠进行肠道膜菌群检测分析,同时取回盲部组织标本,分别用光镜及电镜观察肠粘膜结构。结果表明,ＡＡＤ模型组大多数小鼠肠粘膜出现不同程度的损害,治疗一个疗程后,病理组织学及超微结构改变基本恢复正常。９１－４不仅对肠道膜菌群有调整作用,对肠粘膜也有一定的修复作用。     

Sex ratio in populations of Silene otites in relation to vegetation cover,population size and fungal infection

Abstract. In contrast to populations of most dioecious Silene species (which usually are female-biased), populations of Silene otites have been frequently reported to be male-biased. We describe sex ratio variation in 34 natural S. otites populations in Central Germany in relation to vegetation cover, population size and fungal infection. The overall sex ratio was unbiased in 1994 and only slightly male-biased in 1995. Sex ratio varied among the populations from 26.6 % to 72.6 % females. The sex ratio of small populations varied strongly due to stochastic processes. Furthermore, we found that populations in habitats with high vegetation cover contained a higher percentage of females. Hermaphroditic plants, theoretically, could increase male bias as they only produce male or hermaphroditic offspring. Their frequency in the populations, however, was far too low to affect sex ratio. In 1994 12.1 % and in 1995 17.0 % of the plants were infected by the smut fungus Ustilago major. Disease incidence in the population was not related to sex ratio, suggesting equal susceptibility of males and females. The sex ratio of partially infected plants did not deviate from the population sex ratio, both under field conditions and in a greenhouse laboratory experiment. The results suggest that the frequently reported male bias in Silene otites populations is not a general pattern, but is mainly caused by environmental conditions.     

PHYSIOLOGICAL STRESS REACTION OF CHINESE CABBAGE, BRASSICA CHINENSIS, INFESTED BY DIAMONDBACK, PLUTELLA XYLOSTELLA

Abstract The enzymatic activities of superoxidae dismutase (SOD), hydrogen peroxidae(CAT), peroxidase (POD), polyphenol oxidase (PPO), and the content of phenol in the leaves of Chinese cabbage, Brassica chinensis , changed rapidly after the cabbage leaves were infested by the larvae of diamondback moth (DBM), Plutella xyhstetta . Variations of the SOD, CAT, POD and PPO activities and the phenol content of damaged leaves within a day are generally different from that of undamaged normal leaves, which might result from the excessive stress caused by DBM infestation. The content of phenol and the activity of PPO are negatively correlated in the normal leaves, but the change is not the same as that in the damaged leaves. It is thus evident that the physiological disorder was caused by feeding activity of DBM in the cabbage plants, and the physiological stress response of the Chinese cabbage is prone systematically to the feeding of DBM. The defensive system of the Chinese cabbage could be destroyed by the infestation of DBM larvae, and there might be other defensive mechanisms in the cabbage resistant to the damage of DBM.     

Decoupling cell growth and product formation in Chinese hamster ovary cells through metabolic control.

The development of a strategy for the culture of Chinese hamster ovary (CHO) cells producing tissue plasminogen activator (t-PA) is investigated. This strategy is based on the replacement of the main carbon source, glucose, by another compound that is slowly metabolizable, particularly galactose. The introduction of this change allows for acute change in cell behavior at various levels. Cell growth is stopped after this nutrient shift, and the cells can be kept in long-duration culture at a low growth rate and high viability as compared with a culture strategy based solely on glucose utilization. Moreover, the capability of cells to produce recombinant proteins (t-PA in this work) can be maintained over the entire period of galactose feeding. From the metabolic point of view, use of a slowly metabolizable carbon source (galactose) introduces important changes in the production of lactate, ammonia, and some amino acids. The use of this metabolic shift enables the generation of biphasic processes, with a first phase with cell growth on glucose and a second stationary phase on galactose, which is particularly suited to perfusion systems.     

Rational Design of Pyrrolo[1,2-a]benzimidazole-Based Antitumor Agents Targeting the DNA Major Groove

Models have been developed for the interaction of the pyrrolo[1,2-a]benzimidazole (PBI) antitumor agents with the two-electron activating enzyme DT-diaphorase and the DNA major groove. The DT-diaphorase model and experimental results indicate that the S-enantiomer of 3-carbamido PBI can enantioselect ovarian cancers. The reduced PBI interacts with the DNA major groove at AT base pairs by forming Hoogsteen-like hydrogen bonds. The reduced 3-amino PBI forms three hydrogen bonds in the major groove with the amino group acting as an H-bond donor to the thymine carbonyl. The DNA-binding model will permit the design of major groove recognition agents.     

Covalent structure and some pharmacological features of native and cleaved α‐KTx12−1, a four disulfide‐bridged toxin from Tityus serrulatus venom

A toxin with four disulfide bridges from Tityus serrulatus venom was able to compete with ¹²⁵I‐kaliotoxin on rat brain synaptosomal preparations, with an IC₅₀ of 46 nM . The obtained amino acid sequence and molecular mass are identical to the previously described butantoxin. Enzymatic cleavages in the native peptide followed by mass spectrometry peptide mapping analysis were used to determine the disulfide bridge pattern of α‐KTx_12?1. Also, after the cleavage of the first six N‐terminal residues, including the unusual disulfide bridge which forms an N‐terminus ring, the potency of the cleaved peptide was found to decrease about 100 fold compared with the native protein. Copyright © 2003 European Peptide Society and John Wiley & Sons, Ltd.     

Effects of nutrient loading and extreme rainfall events on coastal tallgrass prairies: invasion intensity, vegetation responses, and carbon and nitrogen distribution

Soil fertility and precipitation are major factors regulating transitions from grasslands to forests. Biotic regulation may influence the effects of these abiotic drivers. In this study, we examined the effects of extreme rainfall events, anthropogenic nutrient loading and insect herbivory on the ability of Chinese tallow tree ( Sapium sebiferum ) to invade coastal prairie to determine how these factors may influence woody invasion of a grassland. We manipulated soil fertility (NPK addition) and simulated variation in frequency of extreme rainfall events in a three growing season, full factorial field experiment. Adding water to or pumping water out of plots simulated increased and decreased rainfall frequencies. We added Sapium seeds and seedlings to each plot and manipulated insect herbivory on transplanted Sapium seedlings with insecticide. We measured soil moisture, Sapium performance, vegetation mass, and carbon and nitrogen in vegetation and soils (0–10 cm deep, 10–20 cm deep). Fertilization increased Sapium invasion intensity by increasing seedling survival, height growth and biomass. Insect damage was low and insect suppression had little effect in all conditions. Recruitment of Sapium from seed was very low and independent of treatments. Vegetation mass was increased by fertilization in both rainfall treatments but not in the ambient moisture treatment. The amount of carbon and nitrogen in plants was increased by fertilization, especially in modified moisture plots. Soil carbon and nitrogen were independent of all treatments. These results suggest that coastal tallgrass prairies are more likely to be impacted by nutrient loading, in terms of invasion severity and nutrient cycling, than by changes in the frequency of extreme rainfall events.