Nearshore and pelagic abundances of Artemia monica in Mono Lake,California

The spatial distribution and abundance of the brine shrimp, Artemia monica, in Mono Lake, California were determined during 1982 and 1983. Peak abundances of shrimp occur in midsummer and reach densities of 15–17 individuals l^-1 in the nearshore regions and 6–8 individuals 1^-1 in the pelagic region. The brine shrimp were non-uniformly distributed both vertically and horizontally. The coefficient of variation in shrimp abundance among stations within the nearshore region was similar to that found in the pelagic region. On two of the nine dates, nearshore densities were 3 to 4 times greater than those in the pelagic zone, and on average the brine shrimp appear to be slightly over-dispersed to the nearshore region. However, including nearshore abundances in lakewide estimates will usually result in a change of less than a 10%.     

Distribution pattern of the dinoflagellateCeratium hirundinella (O. F. Müller) Bergh in a reservoir

Horizontal distribution of the dinoflagellateCeratium hirundinella (O. F. Müller) Bergh in the Ishitegawa Reservoir, Ehime Prefecture, Japan, was investigated. Water quality was also surveyed. It was observed that the population ofC. hirundinella exponentially decreased in number from the head of the reservoir to the dam site. Further investigation proved thatC. hirundinella initiated growth at the head of the reservoir, and later gradually expanded downstream. It was found during the period of increase in water temperature that the cell density ofC. hirundinella at the uppermost station exponentially increased.     

Spatial patterns and feeding of meiobenthic harpacticoid copepods in relation to resident microbial flora

Distributional and feeding relationships of harpacticoid copepods and their microbial prey were examined in a tidal channel at Great Sippewissett Marsh. A horizontal zonation of photosynthetic microorganisms was composed of: 1) a diatom area; 2) a purple sulfur bacterial (Thiocapsa sp.) area; and 3) a clear area. Four species of harpacticoid copepods were associated with given areas. Leptocaris brevicornis occurred in very high densities in the diatom area but in relatively low densities in other areas. Mesochra lilljeborgi occurred in significantly higher densities in the purple and clear areas.Feeding experiments, using resident microbial flora labelled with NaH¹⁴CO₃ and ³H-thymidine, were conducted to determine which foods are 1) ingested but simply pass through the gut and 2) ingested, and retained. These experiments indicated that L. brevicornis ingested diatoms and the heterotrophs associated with the diatoms, but only retained the heterotrophic portion. Microscopic examination indicated that diatoms were passed out intact in feces. Oscillatoria sp. (cyanobacterium) was not ingested. Mesochra lilljeborgi ingested Spirulina sp. (cyanobacterium), Thiocapsa sp., and the heterotrophs associated with Thiocapsa but only retained the Thiocapsa label.These data for harpacticoids suggest that spatial distributions of meiofauna may be closely coupled with microbial food organisms which they consume. Also, that while several microbial foods may be ingested, only certain microbes are digested and assimilated as a food resource, further indicating the complexity of feeding relationships among the meiofauna.     

Chlorophyll differences in Mono Lake (California) observable on Landsat imagery

In Mono Lake (California), a large saline lake, chlorophyll concentrations in the euphotic zone increased from 4 to 45 µg l^–1 between July and October 1979. These seasonal changes in chlorophyll are detectable on imagery obtained with the multispectral scanner on Landsat. Computer-compatible tapes of Landsat images were normalized for solar zenith and corrected for atmospheric scatter and absorption to obtain Landsat band 4 emittances (W m^–2 str^–1) of 13.4 ± 0.5 when chlorophyll was 4 µg l^–1 and 4.6 ± 0.3 when chlorophyll was 45 µg l^–1. Lake wide, spatial heterogeneity of chlorophyll of 2 µg l^–1 in July and 8 µg l^–1 in October was not detectable on the Landsat imagery.     

The response of stream macroinvertebrates to substrate size and heterogeneity

Manipulations of substrate size and components of heterogeneity were designed to test their independent effects and interactions on the abundance and species richness of stream macroinvertebrates. Two components of substrate heterogeneity, variation in size class proportions and number of size classes, had no independent effect on abundance or richness; and in general did not interact with median particle size. Median particle size, stream current, and detritus accounted for most of the significant variation in macroinvertebrates colonizing the experimental substrates. Rocks with high surface heterogeneity (roughness) were colonized by more individuals (but not taxa) than rocks with low surface heterogeneity.     

Implications of cytochromeb 6/f location for thylakoidal electron transport

The cytochromeb ₆/f complex of higher plant chloroplasts is uniformly distributed throughout both appressed and nonappressed thylakoids, in contrast to photosystem II and photosystem I, the other major membrane protein complexes involved in electron transport. We discuss how this distribution is likely to affect interactions of the cytochromeb ₆/f complex with other electron transport components because of the resulting local stoichiometries, and how these may affect the regulation of electron transport.     

牛生长激素结构不均一性的研究

本文报导用常规方法分离纯化的牛生长激素,在还原性SDS-11％聚丙烯酰胺凝胶电泳中呈分子量很接近的两条主带(22KD,21.5KD)。用单克隆抗体和多克隆抗体亲和层析技术分析了不同分子量形式的牛生长激素的转化,结果表明:牛生长激素可能在pH5.5条件下转化为21.5KD分子,在pH8.3条件下则转化18KD分子。这几种形式的牛生长激素均保留与抗体的结合力,但亲和力不尽相同,如在亲和层析的洗脱性质上存在差异。已检验分离并部分纯化了18KD分子以备作进一步的研究。     

Structural basis of hierarchical multiple substates of a protein. II: Monte Carlo simulation of native thermal fluctuations and energy minimization

Conformational fluctuations in a globular protein, bovine pancreatic trypsin inhibitor, in the time range between picoseconds and nanoseconds are studied by a Monte Carlo simulation method. Multiple energy minima are derived from sampled conformations by minimizing their energy. They are distributed in clusters in the conformational space. A hierarchical structure is observed in the simulated dynamics. In the time range between 10(-14) and 10(-10) seconds dynamics is well represented by a superposition of vibrational motions within an energy well with transitions among minima within each cluster. Transitions among clusters take place in the time range of nanoseconds or longer.     

氨甲酰胆碱和Impromidine对CFU—S细胞周期的影响

正常情况下处于S期的CFU-S比例低于10％。氨甲酰胆碱(Cach 10~(-13)—10~(-9)mol/L)和Impromidine(Impro 10~(-9)—10~(-4)mol/L)在体外与小鼠骨髓细胞短时培育后,增加了CFU-S对细胞毒剂羟基脲的敏感性。反应最大时,9d和13dCFU-S的减少率分别是32.8和60.6％(Cach)以及38.4和49.5％(Impro)。这种效应可分别被胆碱能N受体阻断剂筒箭毒(10~(-6)mol/L)和组胺H_2受体阻断剂甲氰咪呱(10~(-6)mol/L)所阻断,表明9d和13d CFU-S表面胆碱能N受体和组胺H_2受体的密度或活性存在差别,再次证实了CFU-S是一个不均一的细胞群。