Purification and characterization of lymphocytic clonal growth factor (LCGF) derived from human-human hybridoma SH-76 cells

Human-human hybridoma SH-76 cells were found to produce a factor that supported the growth of lymphocytic cells at low densities. The factor was purified from serum-free conditioned medium of the hybridoma cells by a successive application of ammonium sulfate precipitation, DEAE-Toyopearl, TSK G3000 SW and DEAE-5PW column chromatograph. The purified factor was a 72K single protein. The factor showed marked growth stimulating effect on lymphocytic cell lines, but had no effect on the growth of human adhesive cancer cell lines. Thus, the factor is a lymphocytic clonal growth factor (LCGF), as found previously in human plasma (Miyata, 1988). The LCGF of SH-76 cells could be produced in growth factor-free RPMI medium and purified easily from the conditioned medium. The factor is inactivated by heating at over 80°C, but is much more stable than the LCGF in human plasma.     

Trophic level assessment of profundal sediments of the artificial Lake Campotosto (Central Italy), using midge larval community (Diptera: Chironomidae)

A study on the profundal chironomids of the artificial Lake Campotosto (Central Italy) was carried out during the summer/early autumn of 1983 and 1984, in order to analyse their composition and community structure in relation to the lake trophic level assessed by water chemical analysis.A total of about 2000 specimens belonging to 15 taxa were collected during the study.Chironomus plumosus group andTanytarsus spp. dominated in 1983 and 1984, respectively, showing a competitive relationship probably due to the larval size. The functional feeding organization was mostly composed of collectors (percentages greater than 90%), revealing the presence of abundant fine organic deposits (FPOM). Diversity and evenness appeared to be negatively affected by the monotony of food, which seems to constitute the key factor in governing both the taxonomic and the trophic structure of chironomid fauna.A clear discrepancy between water chemical data and profundal chironomid analyses was observed in the assessment of the lake trophic level. Sediments exhibited eutrophicated conditions, whereas overlying waters indicated an oligotrophic status. The relevance of profundal macrobenthic investigations in detecting eutrophication is stressed.     

Adaptive foraging by predators as a cause of predator-prey cycles

Summary When foraging has costs, it is generally adaptive for foragers to adjust their foraging effort in response to changes in the population density of their food. If effort decreases in response to increased food density, this can result in a type-2 functional response; intake rate increases in a negatively accelerated manner as prey density increases. Unlike other mechanisms for type-2 responses, adaptive foraging usually involves a timelag, because foraging behaviours do not often change instantaneously with changes in food density or risks. This paper investigates predator-prey models in which there are explicit dynamics for the rate of adaptive change. Models appropriate to both behavioural and evolutionary change are considered. Both types of change can produce cycles under similar circumstances, but under some evolutionary models there is not sufficient genetic variability for evolutionary change to produce cycles. If there is sufficient variability, the remaining conditions required for cycles are surprisingly insensitive to the nature of the adaptive process. A predator population that approaches the optimum foraging strategy very slowly usually produces cycles under similar conditions as does a very rapidly adapting population.     

Modulation of connexon densities in gap junctions of horizontal cell perikarya and axon terminals in fish retina: effects of light/dark cycles,interruption of the optic nerve and application of dopamine

Summary In the fish retina, connexon densities of gap junctions in the outer horizontal cells are modulated in response to different light or dark adaptation times and wavelengths. We have examined whether the connexon density is a suitable parameter of gap junction coupling under in situ conditions. Short-term light adaptation evoked low connexon densities, regardless of whether white or red light was used. Short-term dark adaptation evoked high connexon densities; this was more pronounced in the axon terminal than in perikaryal gap junctions. Under a 12 h red light/12 h dark cycle, a significant difference in connexon densities between the light and the dark period could be established in the gap junctions of the perikarya and axon terminals. Under a white light/dark cycle, only the gap junctions of axon terminals showed a significant difference. Crushing of the optic nerve resulted in an increase in connexon densities; this was more pronounced in axon terminals than in perikarya. Dopamine injected into the right eye of white-light-adapted animals had no effect. However, dopamine prevented the effect of optic-nerve crushing on connexon density. The reaction of axon-terminal gap junctions to different conditions thus resembles that of perikaryal gap junctions, but is more intense. Axon terminals are therefore thought to play an important role in the adaptation process.     

Interpopulation differences in pupal size and fecundity are not associated with occurrence of outbreaks in Epirrita autumnata (Lepidoptera, Geometridae)

Abstract.

• 1 Among-population differences in pupal mass were studied in a geometrid, Epirrita autumnata. Some Epirrita autumnata populations regularly reach outbreak densities while others are never known to do so. Because adults do not feed, pupal mass of females correlates strongly with fecundity.
• 2 Larvae were collected from twelve field sites. Ten of our sample populations originated within the outbreak range of the species and represented different phases of outbreaks. Two populations originated outside the outbreak range.
• 3 Pupal mass of field-collected E. autumnata varied significantly among populations. The peak phase populations had the smallest pupae and the biggest were found in low density populations outside the outbreak range.
• 4 Offspring of moths from each population were reared under identical conditions in two larval densities. Significant differences were not found in pupal mass among populations. That is, the inherent size, correlated with fecundity of moths, was not different between populations originating within and outside the outbreak range, nor among collections from different densities or phases of the outbreaks.
• 5 Rearing density did not interact in a consistent way with population.
• 6 As far as size and fecundity are concerned, the results do not support Chitty's hypothesis that differences in genetic composition of the population at low and high density phases generate cyclic fluctuations of population density.
• 7 Because no hereditary or maternal differences were found in size and fecundity between E.autumnata originating within and outside the outbreak range, variation in reproductive capacity cannot explain why outbreaks occur only in some populations.

     

Preferential inhibition of acetylcholinesterase molecular forms in rat brain

The effect of eight different acetylcholinesterase inhibitors (AChEIs) on the activity of acetylcholinesterase (AChE) molecular forms was investigated. Aqueous-soluble and detergent-soluble AChE molecular forms were separated from rat brain homogenate by sucrose density sedimentation. The bulk of soluble AChE corresponds to globular tetrameric (G₄), and monomeric (G₁) forms. Heptylphysostigmine (HEP) and diisopropylfluorophosphate were more selective for the G₁ than for the G₄ form in aqueous-soluble extract. Neostigmine showed slightly more selectivity for the G₁ form both in aqueous- and detergent-soluble extracts. Other drugs such as physostigmine, echothiophate, BW284C51, tetrahydroaminoacridine, and metrifonate inhibited both aqueous- and detergent-soluble AChE molecular forms with similar potency. Inhibition of aqueous-soluble AChE by HEP was highly competitive with Triton X-100 in a gradient, indicating that HEP may bind to a detergent-sensitive non-catalytic site of AChE. These results suggest a differential sensitivity among AChE molecular forms to inhibition by drugs through an allosteric mechanism. The application of these properties in developing AChEIs for treatment of Alzheimer disease is considered.Special issue dedicated to Dr. Morris H. Aprison.     

刺激隐神经中C类纤维诱发的小脑浦肯野细胞简单锋电位反应

用玻璃微电极记录了猫小脑浦肯野细胞的简单锋电位(PC-SS)。在标准化互协方差函数图中,PC-SS自发放电无明显波峰;弱刺激隐神经只引起A类纤维传入时,PC-SS出现A类诱发放电反应(A-CED),它包括潜伏期为16.7±0.9ms的早反应和270.8±12.8ms的晚反应。用极化电流选择性阻滞A类纤维传导后,强刺激只引起C类纤维单独传入时,出现潜伏期为142.4±4.3ms的C类诱发反应(C-CED)。强刺激同时引起A类和C类纤维传入时,只出现A-CED而不出现C-CED。按标准化功率谱密度函数分析,PC-SS自发放电可分为两种类型。一类为高峰型,最大能量峰值平均为15.7±4.7×10~(-3),峰频为4.07±1.67Hz;刺激A类纤维使峰值增大,而刺激C类纤维却使峰值减小。另一类为低峰型,峰值为8.4±1.4×10~(-3),峰频为3.67±2.90Hz。刺激A类和C类纤维均使峰值增大,前者增大更多,但峰频均无显著性变化。上述结果表明,C类纤维传入可以到达小脑浦肯野细胞,引起特异的PC-SS放电反应。     

Spawning tactics of paired males of the dark chub,Zacco temmincki,reflect potential fitness costs of satellites

Synopsis Paired males of the dark chub, Zacco temmincki, buried released eggs by vibrating their anal fin, but this behavior was prevented and eggs were cannibalized when many satellites (males and females) were present. A number of satellite males also caused a loss to paired males in sperm competition on spawning grounds far from shelters. Paired males followed repeating tactics, which were defined as successive spawning acts at the same redd, in most cases, but occasionally did shifting tactics which refer to spawning acts conducted successively at different redds. The proportion of the shifting tactic was not correlated with the dominance status of paired males. The shifting tactic was not advantageous in performing spawnings frequently. The calculation of the total advantage of both tactics indicated that the shifting tactic itself was not more beneficial than the repeating tactic at any density of satellites. Since a number of satellites stayed around the redd when no spawning pair was present, or pursued a pair or a single dominant male moving between spawning grounds, the occasional shifting tactics of paired males functioned to confuse and disperse satellites. The spawning tactics of paired males apparently reflected potential fitness costs of satellites. Paired males mainly spawned at the redds near shelters, despite the fact that more satellites were present to devour eggs, presumably because they could obtain many females and monopolize fertilizations.     

Studies of the relationship between isoprene emission rate and CO2 or photon-flux density using a real-time isoprene analyser

Abstract. Studies of the isoprene emission rate in response to changes in photon-flux density and CO₂ partial pressure were conducted using a recently developed on-line isoprene analyser combined with a gas exchange system and chlorophyll fluorometer. Upon darkening, the isoprene emission rate from leaves of aspen ( Populus tremuloides Michaux.) began to decline immediately, demonstrating that the internal pool of isoprene, or its precursors, is small and that the instantaneous emission rate is tightly coupled to the rate of synthesis. A post-illumination burst of isoprene was observed within 5 min after darkening and lasted for 15–20 min in four isoprene-emitting species that were examined. In leaves of eucalyptus ( Eucalyptus globulus Labill.), the magnitude of the post-illumination burst was dependent on the photon-flux density that existed before darkening, but not on ambient CO₂ partial pressure. The dependence of the post-illumination burst on photon-flux density paralleled that for the steady-state rate of isoprene emission. A step-wise increase in intercellular CO₂ partial pressure from 24.5 to 60 Pa resulted in an immediate decrease in isoprene emission rate and non-photochemical fluorescence quenching, but an increase in CO₂ assimilation rate. Given the several recent studies that link isoprene emission to chloroplastic processes, the results of this study indicate that the linkage is not dependent on the rate of CO₂ flux through the reductive pentose phosphate pathway, but rather on more complex relationships involving metabolites not appreciably influenced by CO₂ partial pressure.     

美洲蜚蠊机械感受器输出信号的计算机分析

对蜚蠊单个机械感受器诱发反应峰电位的历程及幅度,使用系列分析、栅分析、时序分布、累加密度函数、栅—频分析、特征参数的伪三维隐线显示、峰电位幅度概率密度函数、峰电位间隔概率密度函数等分析方法,获得较多的神经信号间隔编码信息,以揭示刺激和反应之间的复杂关系。峰电位间隔和栅—频分析图由函数经曲线拟合后,分别求得描述其动态过程的时间常数τ_1,τ_2和τ_3,应用上述多种分析显示方法,使研究者更为直观地观察和定量描述刺激—反应间的动态关系。