Genotoxicity of 5-azacytidine in somatic cells of Drosophila

The newly developed somatic mutation and recombination test, utilizing the wing-hair mutations mwh and flr3, was used to evaluate the genotoxicity of the base analog 5-azacytidine in larvae of Drosophila melanogaster. Third instar larvae were fed media wetted with various concentrations of the compound, and wings of surviving adults were removed and scored for the presence of clones of cells possessing malformed hairs. Wings of exposed flies trans-dihybrid for mwh and flr3 had significantly increased frequencies of twin spots, small single spots and large single spots. Significant linear regression of twin-spot frequencies upon concentration was also obtained. Induction of twin spots by 5-azacytidine unambiguously demonstrates its recombinogenic activity in somatic cells of Drosophila. Significantly increased frequencies of large single spots on wings of inversion-heterozygous flies were also observed and suggest that 5-azacytidine may also be inducing somatic gene mutations (or deletions).     

Comparative study of effect of infrared, submillimeter, and millimeter electromagnetic radiation on wing somatic mutations in Drosophila melanogaster induced by gamma-irradiation

It was shown that the number of spontaneous and gamma-radiation-induced somatic mutations in wing cells of fruit flies (third instar larvae) exposed to laser irradiation of submillimeter range (lambda = 81.5 microns) was significantly lower than in control. Laser irradiation did not affect the number of recombinations. Exposure to laser radiation in the infrared range and electromagnetic waves of the millimeter range (lambda = 3.8 mm) enhanced the effect of gamma-irradiation.     

电穿孔法可用于家蚕基因功能分析

[目的]明确基于电穿孔的基因功能分析方法在家蚕Bombyx mori活体内的应用实效.[方法]针对调控家蚕幼虫体表斑纹黑色素合成的靶基因Wnt1(Wingless),人工合成特异性siRNA,向4龄第3天家蚕幼虫注射Wnt1 siRNA并进行电穿孔作为处理组(ERFA-RNAi),以注射Wnt1 siRNA但未进行电穿...     

Spermiogenesis of the testes of juvenile hormone-treated silkworm larvae,Bombyx mori

• 1.1. To examine changes in the percentages of testicular cells such as 1C cells (spermatids and spermatozoa), 2C cells (G1 somatic cells, spermatogonia and secondary spermatocytes), 2–4C cells (somatic and germinal cells in S phase) and 4C cells (G2 somatic cells and primary spermatocytes), we isolated nuclei from the testes of silkworm larvae and subjected them to flow cytometric analysis.
• 2.2. In control testes, 1C cells appeared at day 0 of the fifth instar, increased gradually by spinning and increased steeply at 2 days later still spinning. The percentage of 2C cells decreased gradually after ecdysis to the fifth instar. The percentage of 4C cells increased from day 2 to day 5 of the fifth instar and decreased after day 11 of this instar. Cells in S phase remained constant through the fifth instar.
• 3.3. An injection of juvenile hormone analog, methoprene, at day 0 of the fifth instar did not inhibit spermiogenesis, but resulted in increased 2C cells and decreased 4C cells dose-dependently. In contrast, the same treatment at day 2 of the fifth instar did not change the percentages of 1C, 2C and 4C cells of the testes at all, suggesting that the testes changed sensitivity to the hormone at larval development.
• 4.4. Repeated injections of methoprene to induce the appearance of dauer larvae resulted in a complete block of the development of 1C cells.

     

Juvenoid action on the total body metabolism in larvae of a noctuid moth

A juvenoid compound known as methoprene has no effect on growth and respiratory metabolism in penultimate instar larvae that contain endogenous juvenile hormone. In the last larval instar the juvenoid induces enormously large somatic growth and postpones pupal ecdysis although it does not increase the overall metabolic intensity beyond certain limits.The metabolic changes caused by the juvenoid were more pronounced when connected with formation of the supernumerary larval instars. After this developmental change the larvae further continued to grow on and turned finally into the conspicuous giants. The overall metabolic capacity of the supernumerary larval tissues surpassed the above limitations determined by the body of a normal last instar larva. However, unlike in some other species, there was no hypermetabolic response to juvenoid treatments in this material.     

Ontogenetic divergence in the phytoparasitic nematodes Macroposthonia nainitalensis and M. tenuiannulata (Criconematidae, Tylenchia)

Promorphogenesis, egg cleavage, and gastrulation proceed in Macroposthonia nainitalensis similarly to other phytonematodes of the subclass Tylenchia. Before the onset of gastrulation, the greatest similarity was observed in a descendant of the micromere 2b, which separates macromeres of the third division. Deviations from the general line of development started in this species during embryonal organogenesis with the formation of an external epithelium with a special rough surface layer, which was absent in the embryos of other phytonematodes. In addition, during this period of acceleration, the digestive system developed, while peristaltic changes in body shape appeared at the tadpole stage. Later, somatic muscle development was enhanced in the first instar larvae of M. nainitalensis, while in the second instar larvae of Macroposthonia spp. somatic muscle cells were located at an acute angle to the longitudinal body axis. In addition, denticles--microchaetae appeared in the second to fifth instar larvae of these nematodes. All these features, which have not been observed in other phytonematodes of the subclass Tylenchia, help the peristaltic crawling of Macroposthonia spp. In contrast to other Tylenchia, the musculocutaneous sac did not develop in Macroposthonia spp. However, there are similarities in the development of the digestive and genital systems.     

Ontogenetic divergence of the phytoparasitic nematodesMacroposthonia nainitalensis andM. tenuiannulata (Criconematidae, tylenchia)

Promorphogenesis, egg cleavage, and gastrulation proceed inMacroposthonia nainitalensis similarly to other phytonematodes of the subclass Tylenchia. Before the onset of gastrulation, the greatest similarity was observed in a descendant of the micromere 2b, which separates macromeres of the third division. Deviations from the general line of development started in this species during embryonal organogenesis with the formation of an external epithelium with a special rough surface layer, which was absent in the embryos of other phytonematodes. In addition, during this period of acceleration, the digestive system developed, while peristaltic changes in body shape appeared at the tadpole stage. Later, somatic muscle development was enhanced in the first instar larvae ofM. nainitalensis, while in the second instar larvae ofMacroposthonia spp., somatic muscle cells were located at an acute angle to the longitudinal body axis. In addition, denticles—microchaetae—appeared in the second to fifth instar larvae of these nematodes. All of these features, which have not been observed in other phytonematodes of the subclass Tylenchia, help the peristaltic crawling ofMacroposthonia spp. In contrast to other Tylenchia, the musculocutaneous sac did not develop inMacroposthonia spp. However, there are similarities in the development of the digestive and genital systems.     

Isolation of temperature sensitive mutations blocking clone development inDrosophila melanogaster,and the effects of a temperature sensitive cell lethal mutation on pattern formation in imaginal discs

Summary A method of isolating temperature-sensitive (ts) mutations blocking clone development, based on the analysis of twin spots produced by X-ray induced somatic recombination is reported. From this screen 10 ts mutations were recovered which caused an absence of the lethal-bearing clone at the restrictive temperature. Eight of these mutations were analyzed. Seven proved to be autonomous ts cell lethals and one was an autonomous ts mutation which reversibly affected cell division and growth of imaginal disc cells and growth of larval cells. The effects on development of one of the cell lethal mutations,l(1)ts-504, are described. Heat pulses (29°C) 24–72 hrs long caused a high frequency (up to 90%) of morphologically abnormal animals. The abnormalities observed were of two major kinds: deficiencies and duplications of imaginal disc derivatives. In addition, alterations of tarsal segmentations occurred. Heat pulses to larvae also delayed pupariation and eclosion by as much as four days. In general, longer pulses led to a greater delay in pupariation and eclosion and a higher frequency of deficiencies and duplications than shorter pulses. Exposure to restrictive temperature early in larval development delayed pupariation and resulted in mostly normal animals; exposure during the second and early third larval instar also delayed pupariation and led to a high frequency of duplications; exposure later in larval life, i.e. mid and late third larval instar, caused no delay in pupariation but led to a high frequency of deficiencies. These results can be explained by the occurrence of areas of cell death, which can be seen in the imaginal discs of larvae exposed to restrictive temperature by staining with trypan blue. This conclusion is further supported by the observation in gynandromorphs of duplications of female nonmutant tissue. These results are discussed in relation to current theories of pattern formation.     

Development of terminal filaments and ovariole envelopes in Thermobia domestica (Insecta, Zygentoma) larvae

The 3rd instar female larvae of Thermobia domestica have five pairs of gonad primordia, each enclosed within a basal lamina (tunica propria). At the end of the 3rd instar some somatic cells scattered on the outer surface of the lamina are seen. During the 4th larval instar the gonad primordia start to form the ovarioles. Each ovariole is elongated and polarized, having anterior and posterior ends. The anterior group of outer somatic cells proliferate to form the terminal filament. At the 6th larval stage the ovarioles are already formed. The terminal filament is separated from the germarium by a thick basal lamina (transverse septum). There are three types of cell building the terminal filament. 1/Basal cells with numerous fingerlike projections; 2/Cells with electron lucent cytoplasm and large nuclei, and 3/Cells with darker cytoplasm containing bundles of fibers and more compact nuclei. The outer surface of the filament is covered by a thick, fibrous basal lamina. The somatic cells that in the previous stages were scattered on the tunica propria as distinct cells, in the 6th larval stage form a cellular envelope (tunica externa). This envelope is formed by a layer of flat cells, and contains numerous tracheae.     

The Effect of Oxygen on the Frequency of Somatic Recombination in DROSOPHILA MELANOGASTER

The influence of oxygen on the frequency of somatic recombination in the yellow singed system on the X chromosome of Drosophila melanogaster was studied under a variety of experimental conditions. Flies raised from egg to adult in atmospheres containing 70-90% oxygen were found to have significantly more mosaic spots on their abdominal tergites than were observed in flies which developed in air. First instar larvae X-rayed in from 0 to 100% oxygen demonstrated the existence of an oxygen effect for somatic recombination in the cells which form the abdominal hypoderm. The mosaic spot counts, beginning with the lowest numbers which were found in flies X-rayed in nitrogen, increased rapidly with rising oxygen tensions until the percentage in air was reached, then leveled off at the higher concentrations. Post-treatment with nitrogen of larvae X-rayed in air or oxygen created a substantially higher number of mosaic spots than were found when larvae, after being similarly irradiated, were instead placed into air or oxygen.     

Genetic effects of cosmic radiation in Drosophila melanogaster]

To examine possible effects of space radiation on living organism, we have analyzedtwo types of mutations, sex-linked recessive lethal mutations and somatic mutations, in fruit fly of the species Drosophila melanogaster. Drosophila strains used were wild type strains and a radiation-sensitive strain mei-41. Two different developmental stages of samples were sent into space; young adult males to analyze sex-linked recessive lethal mutations and about 30hr-old larvae to detect somatic mutations in wing epidermal cells. For wild type and mei-41 strains each, about 200 adult male flies and about 6,000 larvae were loaded on space shuttle Endeavour. The male flies returned from space were mated to virgin female flies of a tester strain, and the presence of the lethal mutations was analyzed at F2 generation. The frequencies of sex-linked recessive lethal mutations in flight groups were 2 and 3 times higher for wild type Canton-S and mei-4 1, respectively, than those in ground control groups. Most larvae sent to space emerged as adult flies within about 10 days after the landing. The presence of wing-hair somatic mutations, which give morphological change in hairs growing on the surface of wing epidermal cells, was analyzed under microscope. In wild type strain Muller-5, the frequency of wing hair mutant spots in flight group was about 1.5-fold higher than that in ground control, and in Canton-S-derived wild type strain the frequencies were similar between the two groups. By contrast, for mei-41 strain the mutation frequency was lower in flight group than in control group. The observed higher frequency of lethal mutations in the flight group might be due to a possibility that radiation effects on reproductive cells could be greatly enhanced under micro gravity. However, if this would be the case, we do not have appropriate explanation for the apparent absence of such synergistic effects on somatic wing-hair mutation system.     

转Bt基因抗虫棉对棉铃虫拒食作用及其机理研究

转Bt基因抗虫棉对 3 ,4,5龄棉铃虫幼虫的抗性表现形式为拒食作用 ,且随幼虫龄期的增加拒食作用明显降低 ,其中对 5龄幼虫的拒食作用很低。取食Bt棉后 ,3 ,4,5龄棉铃虫幼虫中肠消化酶比活力均较对照有所减退 ,且随幼虫龄期的增加减退率明显降低 ,其中对 5龄幼虫减退率最低。由此 ,解释了Bt棉对 3龄及 3龄以上棉铃虫幼虫抗性表现形式、抗性随不同幼虫龄期的差异性 ,及其抗性差异性的消化机理。     

Larval rearing conditions affect kin-mediated cannibalism in a treehole mosquito

Cannibalistic behavior among Ochlerotatus triseriatus larvae was studied to determine whether cannibals are able to alter their attack behavior based on their relatedness to newly hatched conspecific prey larvae. Fourth instar larvae, reared in one of four different initial densities, were placed with newly emerged first instars and, after 48 h, the number of first instar larvae remaining was recorded. Our data suggest a Type III functional response of non-kin fourth instar larvae to first instar prey density. Several significant effects emerged from our analysis model, namely that the number of first instar prey available, the relationship of the first instar larvae with the cannibals, and the density at which the fourth instar cannibals were reared all affected the number of first instar larvae consumed.     

Vulnerability of larvae of two species of aphidophagous ladybirds, Adalia bipunctata Linnaeus and Harmonia axyridis Pallas, to cannibalism and intraguild predation

Vulnerability of larvae of two species of aphidophagous ladybirds, Adalia bipunctata Linnaeus and Harmonia axyridis Pallas, to cannibalism and intraguild predation was assessed in the laboratory. In the first experiment, a first instar of one of the two above species was kept with a fourth instar of the other species in a Petri dish. The number of times each first instar larva was encountered by the fourth instar larva and the fate of the first instar was determined over a period of 10 min. The fourth instar larvae captured and killed all the first instar larvae of their own species at the first encounter. However, when presented with fourth instar larvae of the other species the first instar larvae of A. bipunctata and H. axyridis were encountered 6.4 ± 1.3 ( n  = 10) and 19.4 ± 2.1 ( n  = 10), respectively. In this experiment no first instar larvae of H. axyridis , whereas all those of A. bipunctata , were killed.     

Stimulated synthesis of the female-specific storage protein in male larvae of the silkworm Bombyx mori treated with juvenile hormone analog

Application of methoprene to fourth (penultimate) instar larvae of the silkworm Bombyx mori induced the appearance of the feeding dauer larvae at the fifth (last) instar and prevented pupal metamorphosis. Methoprene also increased the protein concentrations of hemolymph last instar larvae by preventing sequestration of storage proteins by the fat body. Usually, the female-specific storage protein 1 (SP1)* disappears from the male hemolymph at the time of the last larval instar. However, exposure of male larvae to methoprene at the penultimate instar enhanced the accumulation of SP1 in the hemolymph. The SP1 accumulated in males did not differ in molecular weight and immunoreactivity from the SP1 produced in female larvae. Both sexes of fourth instar larvae allatectomized on day 1 instantly accumulated SP1 in the hemolymph, and methoprene application after allatectomy suppressed the hemolymph accumulation of the SP1. In contrast, if allatectomy was carried out at a later stage of the fourth larval instar, SP1 concentration in hemolymph of fifth instar larvae did not increase, suggesting the different juvenile hormone action for regulation of SP1 synthesis in the penultimate instar larvae of silkworms.     

Synthesis of satellite DNA in Rhynchosciara hollaenderi

During the latter part of the fourth instar development of Rhynchosciara larvae, DNA synthesis occurs in both germ cells and somatic cells, even though these cells do not undergo mitosis. CsCl density gradient analysis has revealed the synthesis of d(AT) satellite DNAs in the testis and in somatic tissues such as salivary gland, fat body, and gastric cecum. In these studies it has been shown that there is a tissue-specific variation in the relative proportions of synthesis of d(AT) satellite and main-band DNA in the testis during the fourth instar. The initiation of synthesis of the d(AT) satellite in the testis corresponds with the appearance and formation of the highly characteristic mitochondria which develop during the maturation of the spermatocytes. This satellite DNA has been shown to be circular and has a density of 1.681 gm/cm³ in CsCl. Synthesis of a similar circular DNA cannot be detected in somatic tissues, although these tissues do synthesize a d(AT) satellite of similar density.     

Desiccation resistance in pre-diapause, diapause and post-diapause larvae of Choristoneura fumiferana (Lepidoptera: Tortricidae)

Desiccation resistance was examined in pre-diapause, diapause and post-diapause larvae of the spruce budworm, Choristoneura fumiferana (Clemens), in terms of passive water evaporation under three desiccation conditions: freeze-drying, desiccant-drying at 2 degrees C and desiccant-drying at 18 degrees C. Diapausing second instar larvae and post-diapause non-feeding second instar larvae showed strongest desiccation resistance: a significant amount of water was retained after repeated drying under desiccating conditions, while pre-diapause first instar larvae and post-diapause feeding second instar larvae lost almost all their water content after one or two drying cycles. A hibernaculum covering had no effect on water evaporation. While dead larvae tended to lose significantly more water than their living counterparts, particularly among first instar larvae, such an impact was much weaker among diapausing second instar larvae. Desiccation resistance was lost when post-diapause second instar larvae were allowed access to water while the level of desiccation resistance was maintained or enhanced when the larvae did not have access to water. These results are discussed in the context of overwintering ecology of the species and possible mechanisms for the desiccation resistance are also discussed.     

Buthionine sulfoximine mediated enhancement of γ-radiation induced mutation frequency in Drosophila melanogaster

Experiments were carried out to investigate whether or not depletion of the glutathione (GSH) level in Drosophila melanogaster larvae with buthionine sulfoximine (BSO) treatment can result in the modulation of the frequency of sex-linked recessive lethal (SLRL) mutations induced by γ-radiation. Third instar larvae were fed on BSO for 24 h before exposure to 10 Gy γ-radiation. Immediately after this the larvae were divided into two batches, which were used to determining the GSH level and the induction of SLRL mutations respectively. The results obtained suggest that the depletion of the GSH level with BSO can lead to an enhancement in the frequency of SLRL mutations (significant at the 5% level). In a subsequent experiment in which adult Drosophila melanogaster male flies were fed on BSO for 72 h before irradiation, a significant increase was observed in the incidence of SLRL mutations.     

黄玛草蛉幼虫对草地贪夜蛾卵和低龄幼虫的捕食能力

【目的】明确本地优势天敌黄玛草蛉Mallada basalis对入侵我国的重大农业害虫草地贪夜蛾Spodoptera frugiperda卵及低龄幼虫的捕食能力和生防潜力。【方法】在实验室条件下采用功能反应模型评价了黄玛草蛉2和3龄幼虫对草地贪夜蛾卵及1和2龄幼虫的捕食能力。【结果】黄玛草蛉幼虫对草地贪夜蛾卵和低龄幼虫的捕食量均随猎物密度的升高而增加,最后趋于捕食饱和状态,而其捕食率随猎物密度的升高而逐步下降,对不同发育阶段的草地贪夜蛾均表现为Ⅱ型功能反应。黄玛草蛉2龄幼虫对草地贪夜蛾卵及1和2龄幼虫的瞬时攻击率a分别为0.150, 0.084和0.094,处理时间Th分别为0.282, 0.333和0.519 h,理论日最大捕食量T/Th分别为85106粒、72072头和46.242头;黄玛草蛉3龄幼虫对草地贪夜蛾卵及1和2龄幼虫的瞬时攻击率分别为2.018, 0.288和0.259,处理时间分别为0.102, 0.311和0.375 h,理论日最大捕食量分别为235294粒、77170头和64000头。【结论】黄玛草蛉2和3龄幼虫对草地贪夜蛾卵和低龄幼虫均具较强的捕食能力,其中黄玛草蛉3龄幼虫比2龄幼虫具有更强的捕食效率。