Fractal Analysis of Plant Root Systems

The morphology of root systems of crop plants was analysed byfractal geometry using an image processing system. Results indicatethat these root systems have a fractal structure (D; 1.48     

FIRST RECORD OF THE CIRRIPEDE GENUS STRAMENTUM (THORACICA, SCALPELLIFORMES) FROM THE UPPER CRETACEOUS OF JAPAN

Abstract:  The scalpelliform genus Stramentum is described from upper Turonian–Coniacian (Upper Cretaceous) strata in the Mikasa area, Hokkaido (Japan), documenting the first record of the genus from the north-west Pacific Realm. The single articulated skeleton, which is horizontally embedded in a dark grey laminated mudstone, is specifically indeterminate because capitular plates are missing. However, peduncular morphology resembles that of S. ( S .) pulchellum (Sowerby Jr), which has been described from the Cenomanian–Turonian of Europe. The present record from Japan demonstrates that this cirripede genus had a wider geographic distribution than previously assumed during the youngest phase of its radiation.     

玉米大斑病菌(Exserohilum turcicum)原生质体的分离及转化

玉米大斑病是严重危害玉米生产的一个世界性真菌病害。由于玉米大斑病菌(Exserohilum turcicum)在无性生长过程中迅速产生黑色素,致使原生质体难以分离。测试了包括Fungase、Funcelase、Novozyme、Glucanex、Driselase、Uskizyme、Kitalase在内的7种细胞壁降解酶及其组合、病原菌菌株和培养基对原生质体分离效果的影响。结果表明菌株的培养形态和菌丝的生长状态显著影响原生质体的分离效率;酶组合Kitalase Glucanex Driselase,Kitalase Glucanex和Kitalase Uskizyme能够有效地分离玉米大斑病菌的原生质体。初步的转化试验表明,质粒pAN71可以用于该病原菌的转化。这些结果将为E．turcicum和Exserohium属其它真菌的基因克隆提供一些有用的信息。     

家蚕抑前胸腺肽类似物的活性鉴定和结构分析

以家蚕Bombyx mori抑前胸腺肽的氨基酸序列作为基础,通过氨基酸残基的添加、减少和置换,人工合成了一组与家蚕抑前胸腺肽结构类似的多肽。利用家蚕前胸腺体外培养技术,结合蜕皮激素放射免疫分析方法,鉴定了与抑前胸腺肽结构类似的多肽的生理活性,并对它们的活性特征、化学参数、结构和功能、信号传导途径进行了综合的比较和分析。类似物899808的生物学功能与抑前胸腺肽的相同而且活性近似;类似物899805和899809对家蚕前胸腺蜕皮激素的生物合成表现出随浓度增加而增加的促进作用,而低浓度下几乎不促进;899803、899804、899806和899807类似物对家蚕前胸腺蜕皮激素的生物合成的促进和抑制作用与它们的浓度有着依赖关系。实验结果表明,对抑前胸腺肽的氨基酸序列作任何改变,都导致其生理活性的下降、丧失甚至相反的活性。     

Effects of temperature on body color change in the grasshopper Atractomorpha lata (Orthoptera: Pyrgomorphidae) with reference to sex differences in color morph frequencies

The effects of five environmental factors, background color, density, humidity, photoperiod and temperature, on the body color of a pyrgomorphid green/brown polymorphic grasshopper, Atractomorpha lata, were examined in rearing experiments, in which the differences in color morph frequencies between males and females were also examined. Field censuses were conducted to determine whether the sex difference in body‐color polymorphism occurs under field conditions. Among the environmental factors examined, temperature was the only factor that significantly affected body color: the frequency of brown morphs tended to be higher at higher temperatures. The frequency of brown morphs in the female was higher than in the male, a consistent finding in both the rearing experiments and the field censuses. The threshold temperature at which body color changes may be lower in the female than in the male.     

Examination of the relationships between jaw opener and closer rhythmical muscle activity in an in vitro brainstem jaw-attached preparation

An in vitro jaw-attached brainstem preparation was developed to investigate the relationship between jaw opener and closer muscle activity during chemically induced rhythmical jaw movements in neonatal rats. In the majority of preparations examined, where a defined region of brainstem was isolated and the neuronal innervation of the jaw opener and closer muscles was left intact, bath application of the excitatory amino acid agonist N -methyl-D,L-aspartate (NMA, 20-40 muM) in combination with bicuculline (BIC 10 muM), a GABAA antagonist, produced rhythmical electromyogram (EMG) activity in jaw opener and closer muscles, bilaterally, in conjunction with rhythmical jaw movements. Low concentrations of NMA (20 muM) in combination with BIC produced temporally coordinated activity between the jaw opener and closer muscles, ipsilaterally. With higher doses of NMA (40 muM), each muscle group exhibited bursting, but temporal coordination between them was difficult to establish. Similarly, NMA application in combination with the glycine antagonist strychnine (STR, 10 muM), also produced rhythmical EMG activity from both opener and closer muscles, ipsilaterally, but showed no temporal coordination between the antagonist muscle pair. However, coordination of opener and closer muscle discharge could be restored by the addition of BIC to the bath. We suggest that there exist separate, but coordinated, rhythm generator circuits for opener and closer motoneuronal discharge located in close proximity to the trigeminal motor nucleus and under GABAergic control for production of temporal coordination between rhythmogenic circuits.     

DEVELOPMENT OF ENDOTHELIA AND ERYTHROID CELLS IN THE MOUSE METANEPHROGENIC MESENCHYME IN CULTURE WITH THE FETAL LIVER

Histogenetic response in vitro of cells of the mouse metanephrogenic mesenchyme to different kinds of tissues was studied by means of transfilter induction technique. When the metanephrogenic mesenchyme obtained from 11-day mouse embryos was cultivated for 7 days in combination with the fetal liver or the primary differentiated hepatoma tissue, cell islets in which cells were arranged in a pavement-like or radial fashion, sinusoid endothelia and erythroid cells were induced in the culture, while in combination with the adult liver, no particular structures were. The number of the cell islets, which were absolutely absent in the initial culture, increased with time of the fetal liver-combined cultivation.
When the mesenchyme was cultivated for 7 days in combination with the spinal cord and simultaneously with the fetal liver, new structures which were somewhat different from but faintly reminiscent of tubules and glomeruli were formed. Such structures seemed to be intermediate in appearance between the tubules and the sinusoids, and were formed largely at the expense of normal development of cell islets, sinusoid endothelia, erythroid cells, tubules and glomeruli.     

Group size affects the metabolic rate of a tropical beetle

ABSTRACT. . Dormancy is metabolically very costly for insects and other poikilotherms of the tropics because energy reserves are rapidly utilized at high temperature. Yet, the beetle Stenotarsus rotundus Arrow spends up to 10 months each year in a tropical lowland forest as a non-feeding adult, dependent upon its fat reserve as an energy source. While in this dormant state, the beetles aggregate in huge numbers and the size of the group greatly influences the metabolic rate. As group size increases, the metabolic rate decreases, and the minimum rate observed in the field (22 μ l O₂ g^-1 h^-1) is estimated to occur when group size reaches about 300 individuals. A decrease in metabolic rate can also be achieved by elevating relative humidity, thus suggesting that one function of the aggregation is to increase humidity within the group and thereby decrease metabolic rate.     

Seasonal variation in embryonic diapause of the striped ground cricket, Allonemobius fasciatus

ABSTRACT. The incidence and intensity of embryonic diapause in the striped ground cricket, Allonemobius fasciatus DeGeer (Gryllidae), is influenced by the date of oviposition and the incubation temperature. At 20C, embryos develop normally until the end of the appendage-formation stage when diapause occurs. The intensity of 'winter' diapause at this stage is greatest in eggs laid early in the season. Incubation at higher temperature induces a different and earlier 'summer' diapause. The higher the temperature the earlier the stage at which this developmental suppression is imposed. At 27 and 30C, some individuals develop without any interruption and hatch within 20 days. The proportion of these fast-developing eggs is low in summer but increases towards the end of the laying season. In nature, this species is univoltine and precocious hatching before winter is unlikely.
When embryos diapausing at an early stage at 27C are transferred to low temperatures, they resume development and enter winter diapause. The time required to reach the winter-diapause stage after transfer is inversely related to the temperature (30-30C). At 30C, sunmer diapause is neither induced nor maintained.     

Determination of effective light pulse and classical Bünsow experiment in the larval diapause of the Indian meal moth Plodia interpunctella

Plodia interpunctella Hübner (Lepidoptera: Pyralidae) comprises a model insect to analyse the photoperiodic time‐measuring system controlling its larval diapause. In the present study, the effective length of light pulse in night interruption experiments is determined at 25 °C. Various lengths of light pulse are tested by inserting them at the midnight of an LD 12 : 12 h photoperiod. When the light pulse is 15 or 30 min, the incidence of diapause is 86%. To inhibit the induction of diapause effectively, a light pulse of 1.75–2 h is needed. The incidence of diapause is 12% under an LD 12 : 5 : 2 : 5 h photoperiod. To determine the precise role of the light pulse, 2‐h light pulses placed at the midnight of an LD 12 : 12 h photoperiod are disrupted systematically by darkness. When a 2‐h light pulse is disrupted by 15 min of darkness, diapause is generally prevented (< 29%) regardless of the temporal position of darkness. Longer disruption by darkness induces diapause moderately (37–67%). A Bünsow experiment is also conducted at 25 and 20 °C, in which the main photophase of 12 h of light is combined with 24–72‐h scotophases scanned by a 2‐h light pulse. The photoperiodic cycle length tested, therefore, varies in the range 36–84 h. In each cycle length, the incidence of diapause fluctuates as the light pulse moves toward dawn. However, no regular and circadian changes in the percentage diapause are observed in relation to diapause determination.