Accumulation and Spatial Distribution of Poly(A)+RNA in Oocytes and Early Embryos of Drosophila melanogaster

We describe the accumulation and distribution of poly (A)⁺RNA during oogenesis and early embryogenesis as revealed by in situ hybridization with a radio-labeled poly (U) probe. The amount of poly (A)⁺RNA in nurse cell cytoplasm continuously increased untill mid-vitellogenic stage (st. 10), then decreased with the rapid increase of poly (A)⁺RNA in the oocyte (st. 11). The localization of poly (A)⁺RNA at stage 10 was in the anterior region of the oocyte, where it is connected by cytoplasmic bridge to the nurse cells. These observations indicate that most of the poly (A)⁺RNA synthesized in the nurse cells is transferred to the oocyte through the cytoplasmic bridges at stage 10–11. During the remainder of oogenesis (st. 11–14) and during preblastodermal embryogenesis, poly (A)⁺RNA was evenly distributed over the cytoplasm of oocytes and embryos. At blastoderm stage, poly(A)⁺RNA became concentrated in the peripheral region of embryos. Though the somatic nuclei of the blastoderm contained a detectable amount of poly (A)⁺ RNA, the pole cell nuclei did not. The cytoplasmic RNA visualised by acridine orange staining and the poly (A)⁺RNA detected by hybridization with [³H]poly (U) exhibited identical distributions during oogenesis and early embryogenesis. These observations provide a basis to assess the unique distributions of specific RNA sequences involved in early development.     

Maternal Messenger RNA as a Determinant of Pole Cell Formation in Drosophila Embryos

Some polar plasm components are UV-sensitive. Messenger RNA extracted from oocytes or cleavage embryos can to induce pole cells in embryos that have been deprived of ability to form pole cells by UV-irradiation. This article reviews studies on the role of this mRNA in the developmental pathway leading to germ cell formation.     

基于Rag1基因序列变异的鲤形目鱼类系统发育重建:采样策略对生命之树的影响

The phylogenetic relationships of species are fundamental to any biological investigation, including all evolutionary studies. Accurate inferences of sister group relationships provide the researcher with an historical framework within which the attributes or geographic origin of species (or supraspecific groups) evolved. Taken out of this phylogenetic context, interpretations of evolutionary processes or origins, geographic distributions, or speciation rates and mechanisms, are subject to nothing less than a biological experiment without controls. Cypriniformes is the most diverse clade of freshwater fishes with estimates of diversity of nearly 3,500 species. These fishes display an amazing array of morphological, ecological, behavioral, and geographic diversity and offer a tremendous opportunity to enhance our understanding of the biotic and abiotic factors associated with diversification and adaptation to environments. Given the nearly global distribution of these fishes, they serve as an important model group for a plethora of biological investigations, including indicator species for future climatic changes. The occurrence of the zebrafish, Danio rerio, in this order makes this clade a critical component in understanding and predicting the relationship between mutagenesis and phenotypic expressions in vertebrates, including humans. With the tremendous diversity in Cypriniformes, our understanding of their phylogenetic relationships has not proceeded at an acceptable rate, despite a plethora of morphological and more recent molecular studies. Most studies are pre-Hennigian in origin or include relatively small numbers of taxa. Given that analyses of small numbers of taxa for molecular characters can be compromised by peculiarities of long-branch attraction and nodal-density effect, it is critical that significant progress in our understanding of the relationships of these important fishes occurs with increasing sampling of species to mitigate these potential problems. The recent Cypriniformes Tree of Life initiative is an effort to achieve this goal with morphological and molecular (mitochondrial and nuclear) data. In this early synthesis of our understanding of the phylogenetic relationships of these fishes, all types of data have contributed historically to improving our understanding, but not all analyses are complementary in taxon sampling, thus precluding direct understanding of the impact of taxon sampling on achieving accurate phylogenetic inferences. However, recent molecular studies do provide some insight and in some instances taxon sampling can be implicated as a variable that can influence sister group relationships. Other instances may also exist but without inclusion of more taxa for both mitochondrial and nuclear genes, one cannot distinguish between inferences being dictated by taxon sampling or the origins of the molecular data.     

Quantitative aspects of heterogeneity in soil organic matter dynamics in a cool-temperate Japanese beech forest: a radiocarbon-based approach

Soil is the largest carbon reservoir in terrestrial ecosystems; it stores twice as much carbon as the atmosphere. It is well documented that global warming can lead to accelerated microbial decomposition of soil organic carbon (SOC) and enhance the release of CO₂ from the soil to the atmosphere; however, the magnitude and timing of this effect remain highly uncertain due to a lack of quantitative data concerning the heterogeneity of SOC biodegradability. Therefore, we sought to identify SOC pools with respect to their specific mean residence times (MRTs), to use those SOC pools to partition soil respiration sources, and to estimate the potential response of the pools to warming. We collected surface soil and litter samples from a cool-temperate deciduous forest in Japan, chemically separated the samples into SOC fractions, estimated their MRTs based on radiocarbon (¹⁴C) isotope measurements, and used the data to construct a model representing the soil as a complex of six SOC pools with different MRT ranges. We estimate that a minor, fast-cycling SOC pool with an MRT of less than 10 years (corresponding to the O horizon and recognizable plant leaf fragments in the A1 horizon) is responsible for 73% of annual heterotrophic respiration and 44% of total soil respiration. However, the predicted response of these pools to warming demonstrates that the rate of SOC loss from the fast-cycling SOC pool diminishes quickly (within several decades) because of limited substrate availability. In contrast, warming will continue to accelerate SOC loss from slow-cycling pools with MRTs of 20–200 years over the next century. Although using a ¹⁴C-based approach has drawbacks, these estimates provide quantitative insights into the potential importance of slow-cycling SOC dynamics for the prediction of positive feedback to climate change.     

Larvicidal toxicity of Japanese Bacillus thuringiensis against the mosquito Anopheles stephensi

Japanese isolates of Bacillus thuringiensis were screened for larvicidal activity against the mosquito Anopheles stephensi , the urban malaria vector of the Indian subcontinent. Among more than 30 strains identified, larvicidal activity causing >80% mortality in 72 h was demonstrated for 41/1449 (2.8%) isolates. The majority of strains and isolates (97.2%) exhibited little or no larvicidal activity. Anopheles -active strains belonged to more than 12 H serotypes, especially H3ade (serovar fukuokaensis ) and H44 (serovar higo ). SDS-PAGE profiles of inclusion proteins showed 4 distinct types among 6 active strains examined. The most active Japanese isolates were H20 strain 89-T-34-14 (LC₅₀ 4.4 μg/ml) and H44 serovar higo strain 74-E-45-24 (LC₅₀ 7.6 μg/ml), respectively, 13-fold and 23-fold less active than the international standard H14 serovar israelensis (LC₅₀ 0.33 μg/ml).     

Herbivory in canopy gaps created by a typhoon varies by understory plant leaf phenology

1. Availabilities of light and soil nitrogen for understory plants vary by extent of canopy gap formation through typhoon disturbance. We predicted that variation in resource availability and herbivore abundance in canopy gaps would affect herbivory through variation in leaf traits among plant species. We studied six understory species that expand their leaves before or after canopy closure in deciduous forests. We measured the availabilities of light, soil nitrogen, soil water content, and herbivore abundance in 20 canopy gaps (28.3–607.6 m²) formed by a typhoon and in four undisturbed stands. We also measured leaf traits and herbivory on understory plants. 2. The availabilities of light and soil nitrogen increased with increasing gap size. However, soil water content did not. The abundance of herbivorous insects (such as Lepidoptera and Orthoptera) increased with increasing gap size. 3. Concentrations of condensed tannins, total phenolics, and nitrogen in leaves and the leaf mass per area increased in late leaf expansion species with increasing gap size, whereas none of the leaf traits varied by gap size in early leaf expansion species. 4. Herbivory increased on early leaf expansion species with increasing gap size, but decreased on late leaf expansion species. In these late leaf expansion species, total phenolics and C : N ratio had negative relationships with herbivory. 5. These results suggested that after typhoon disturbance, increased herbivory on early leaf expansion species can be explained by increased herbivore abundance, whereas decreased herbivory on late leaf expansion species can be explained by variation in leaf traits.     

INSTABILITY OF MESSENGER AND RIBOSOMAL RNA IN A GLUE-PROTEIN MUTANT OF Bombyx mori

The mucous glands of Bombyx pupae secrete glue proteins which attach deposited eggs to the mounting sheet. A mutant of a dominant gene, named no glue (Ng) , produces nonadhesive eggs which have a low capacity for glue-protein synthesis. In the present study it was shown that the mucous glands of Ng silkworms showed rapid degradation of mRNA as well as rRNA during development; this may cause the low capacity for glue-protein synthesis in the mutant organ. In contrast, the mucous glands of normal silkworms showed a significant increase in content of RNA's until the maximum rate of glue-protein synthesis was achieved. The degradation of RNA in the Ng mucous gland was inhibited by actinomycin D injected into the body fluid. Thus it is supposed that the Ng gene codes for a presumptive controller RNA, which would be the mediator of RNA instability in the mucous glands of Ng pupae.     

Tissue Distribution of an Immunogenic Melanoma Associated Antigen,D-1

A human melanoma-associated antigen immunogenic in patients was recently identified by screening an expression cDNA library constructed from cultured human melanoma cell line with sera from patients with melanoma. The nucleic acid sequence of the cloned D-1 cDNA has no significant homology with previously reported mammalian genes. The cDNA D-1 encodes a peptide of about 37 kDa, which showed fivefold higher reactivity with sera from patients with melanoma than with sera from normal donors. In order to detect D-1 gene expression in vivo, in-situ hybridization and immunostaining with cRNA probe and murine anti-D-1 sera were carried out on surgically removed tissues. Digoxigenin-labeled cRNA D-1 was exclusively hybridized with mRNA in the cytoplasm of melanoma cells but not with keratinocytes and fibroblasts adjacent to melanoma nests. Polyclonal anti-D-1 antibodies were obtained by immunization of Balb/c mice with recombinant D-1 peptide and clearly reacted with melanoma cells but not with keratinocytes and fibroblasts, similar to the results of in-situ hybridization. The above information will help to assess the suitability of recombinant D-1 peptide to implement active specific immunotherapy in patients with melanoma.     

Culling Versus Density Effects in Management of a Deer Population

Abstract: Wildlife managers often manipulate hunting regulations to control deer populations. However, few empirical studies have examined the level of hunting effort (hunter-days) required to limit population growth and demographic effects through harvesting of females. Moreover, the relative importance of density effects on population growth has not been quantified. We reconstructed a sika deer [Cervus nippon] population over a period of 12 years (1990–2001) using age- and sex-specific harvest data. Using cohort analysis, we analyzed population dynamics, focusing on 1) the relationship between hunting effort and hunting-induced mortality rate, 2) relative contributions of hunting mortality and recruitment of yearlings to annual changes in population growth rate, and 3) annual variation in recruitment rate. Population size increased until 1998 and declined thereafter. The population growth rate changed more in response to annual changes in recruitment rate than hunting mortality rate. Temporal variation in recruitment rate was not controlled by birth rate alone; direct density dependence, intensities of hunting mortality for fawns, and for females (≥2 yr of age), which accounted for the fawn survival rate, were required as factors to explain temporal variation. Density effects on the recruitment rate were not strong enough to regulate the population within the study period; high hunting mortality, with intensive female harvesting, was necessary to prevent population growth. Hunting effort was a good predictor of the hunting mortality rate, and female harvest had a negative effect on the recruitment rate through fawn survival. We suggest that >3,500 hunter-days and prioritization of female harvesting are required to prevent increases in this deer population.