Scanning electron microscopy of Drosophila melanogaster embryogenesis: III. Formation of the head and caudal segments

The formation of both the anterior most and posterior most segments in higher dipteran embryos involves complex movements of primordia which can be best visualized with the scanning electron microscope. During head formation, the gnathocephalic segments partially involute through the stomodeum. The labial segment forms the floor of the mouth, and the fused maxillary and mandibular segments form the lateral sides of the mouth. The involuted clypeolabrum forms the roof of the mouth. Invaginations of cells for segmentally derived sense organs can be found prior to involution on all the gnathocephalic and thoracic segments as well as on the labrum. The antennal sense organ derives from the lateral surface of the procephalic lobe. Following involution of the mouth parts, the dorsal ridge, which arises just anterior to the first thoracic segment, is drawn over the dorsal procephalic lobe producing the deep dorsal sac. The optic lobes of the brain invaginate anterior to the dorsal ridge just prior to the covering over of the head. The formation of the anal segment is similarly complex. Two rudimentary segments are found posterior to the eighth abdominal segment. During shortening of the germ band, the posterior most segment is drawn around the posterior tip of the embryo to lie ventrally. Two large anal pads form lateral to the anus from this segment. The next segment, following dorsal closure, produces a pair of anal sense organs and a central tuft of setae. Finally, the eighth abdominal segment gives rise to the posterior spiracles. Following dorsal closure these three segments fuse to produce the terminal (anal) segment of the larva.     

Accelerated evolution of nervous system genes in the origin of Homo sapiens

Human evolution is characterized by a dramatic increase in brain size and complexity. To probe its genetic basis, we examined the evolution of genes involved in diverse aspects of nervous system biology. We found that these genes display significantly higher rates of protein evolution in primates than in rodents. Importantly, this trend is most pronounced for the subset of genes implicated in nervous system development. Moreover, within primates, the acceleration of protein evolution is most prominent in the lineage leading from ancestral primates to humans. Thus, the remarkable phenotypic evolution of the human nervous system has a salient molecular correlate, i.e., accelerated evolution of the underlying genes, particularly those linked to nervous system development. In addition to uncovering broad evolutionary trends, our study also identified many candidate genes--most of which are implicated in regulating brain size and behavior--that might have played important roles in the evolution of the human brain.     

CstF-64 and 3′-UTR cis-element determine Star-PAP specificity for target mRNA selection by excluding PAPα

Almost all eukaryotic mRNAs have a poly (A) tail at the 3′-end. Canonical PAPs (PAPα/γ) polyadenylate nuclear pre-mRNAs. The recent identification of the non-canonical Star-PAP revealed specificity of nuclear PAPs for pre-mRNAs, yet the mechanism how Star-PAP selects mRNA targets is still elusive. Moreover, how Star-PAP target mRNAs having canonical AAUAAA signal are not regulated by PAPα is unclear. We investigate specificity mechanisms of Star-PAP that selects pre-mRNA targets for polyadenylation. Star-PAP assembles distinct 3′-end processing complex and controls pre-mRNAs independent of PAPα. We identified a Star-PAP recognition nucleotide motif and showed that suboptimal DSE on Star-PAP target pre-mRNA 3′-UTRs inhibit CstF-64 binding, thus preventing PAPα recruitment onto it. Altering 3′-UTR cis-elements on a Star-PAP target pre-mRNA can switch the regulatory PAP from Star-PAP to PAPα. Our results suggest a mechanism of poly (A) site selection that has potential implication on the regulation of alternative polyadenylation.     

Developmental Genetics of the 2e-F Region of the Drosophila X Chromosome: A Region Rich in "Developmentally Important" Genes

We have analyzed the 2E1-3A1 area of the X chromosome with special attention to loci related to embryogenesis. Published maps indicate that this chromosomal segment contains ten bands. Our genetic analysis has identified 11 complementation groups: one recessive visible (prune), two female steriles and eight lethals. One of the female sterile loci is fs(1)k10 for which homozygous females produce both egg chambers and embryos with a dorsalized morphology. The second female sterile is the paternally rescuable fs(1)pecanex in which unrescued embryos have a hypertrophic nervous system. Of the eight lethal complementation groups two are recessive embryonic lethals: hemizygous giant (gt) embryos possess segmental defects, and hemizygous crooked neck (crn) embryos exhibit a twisted phenotype. Analysis of these mutations in the female germ line indicates that gt does not show a maternal effect, whereas normal activity of crn is required for germ cell viability. Analysis of the maternal effect in germ line clones of the remaining six recessive lethal complementation groups indicates that four are required for germ cell viability and one produces ambiguous results for survival of the germ cells. The remaining, l(1)pole hole, is a recessive early pupal lethal in which embryos derived from germ line clones and lacking wild-type gene activity exhibit the "torso" or "pole hole" phenotype.     

Effects of prenatal diclofenac sodium exposure on newborn testis: a histomorphometric study

Diclofenac sodium (DS) is used primarily to treat fever and to alleviate pain and inflammation. We investigated the effects of DS exposure during gestation on the testes of rat pups to investigate the safety of its use during the prenatal period. Pregnant rats were separated into control, saline, low dose, medium dose and high dose groups. DS was given between weeks 15 and 21 of gestation. Total numbers of spermatogonia and Sertoli cells were counted in the testes of 7-day-old male rats using the physical disector method. By the end of the study, the total number of Sertoli cells was decreased significantly in a dose dependent manner in the medium and high dose groups compared to controls. No significant differences were found in the total number of spermatogonia in the control, saline and low dose DS groups. Medium and high dose DS administration reduced the total number of spermatogonia compared to other groups. We suggest that prenatal administration of DS can cause deleterious effects on the testis development, especially in high doses.     

Intraspecific chemical variability of the leaf essential oil of Juniperus phoenicea subsp. turbinata from Corsica

The composition of 50 samples of essential oil of individual plants of Juniperus phoenicea subsp. turbinata from Corsica was investigated by GC, GC-MS and 13C NMR. alpha-Pinene, beta-phellandrene, alpha-terpinyl acetate, Delta-3-carene, myrcene and alpha-phellandrene were found to be the main constituents. The results were submitted to cluster analysis and discriminant analysis which allowed two groups of essential oils to be distinguished with respect to the content of alpha-pinene, beta-phellandrene and alpha-terpinyl acetate.     

An assessment of false discovery rates and statistical significance in label-free quantitative proteomics with combined filters

Background  

Many studies have provided algorithms or methods to assess a statistical significance in quantitative proteomics when multiple replicates for a protein sample and a LC/MS analysis are available. But, confidence is still lacking in using datasets for a biological interpretation without protein sample replicates. Although a fold-change is a conventional threshold that can be used when there are no sample replicates, it does not provide an assessment of statistical significance such as a false discovery rate (FDR) which is an important indicator of the reliability to identify differentially expressed proteins. In this work, we investigate whether differentially expressed proteins can be detected with a statistical significance from a pair of unlabeled protein samples without replicates and with only duplicate LC/MS injections per sample. A FDR is used to gauge the statistical significance of the differentially expressed proteins.     

Sequence and structure of Brassica rapa chromosome A3

Background

The species Brassica rapa includes important vegetable and oil crops. It also serves as an excellent model system to study polyploidy-related genome evolution because of its paleohexaploid ancestry and its close evolutionary relationships with Arabidopsis thaliana and other Brassica species with larger genomes. Therefore, its genome sequence will be used to accelerate both basic research on genome evolution and applied research across the cultivated Brassica species.

Results

We have determined and analyzed the sequence of B. rapa chromosome A3. We obtained 31.9 Mb of sequences, organized into nine contigs, which incorporated 348 overlapping BAC clones. Annotation revealed 7,058 protein-coding genes, with an average gene density of 4.6 kb per gene. Analysis of chromosome collinearity with the A. thaliana genome identified conserved synteny blocks encompassing the whole of the B. rapa chromosome A3 and sections of four A. thaliana chromosomes. The frequency of tandem duplication of genes differed between the conserved genome segments in B. rapa and A. thaliana, indicating differential rates of occurrence/retention of such duplicate copies of genes. Analysis of 'ancestral karyotype' genome building blocks enabled the development of a hypothetical model for the derivation of the B. rapa chromosome A3.

Conclusions

We report the near-complete chromosome sequence from a dicotyledonous crop species. This provides an example of the complexity of genome evolution following polyploidy. The high degree of contiguity afforded by the clone-by-clone approach provides a benchmark for the performance of whole genome shotgun approaches presently being applied in B. rapa and other species with complex genomes.     

The co-distribution of Plasmodium falciparum and hookworm among African schoolchildren

Background

On the island of Bioko (Equatorial Guinea), insecticide-treated nets (ITNs) have been the main tool used to control malaria over the last 13 years. In 2004, started an indoor residual spraying (IRS) campaign to control malaria. The purpose of this study is to asses the impact of the two control strategies on the island of Bioko (Equatorial Guinea), with regards to Plasmodium infection and anaemia in the children under five years of age.

Methods

Two transversal studies, the first one prior to the start of the IRS campaign and the second one year later. Sampling was carried out by stratified clusters. Malaria infection was measured by means of thick and thin film, and the packed cell volume (PCV) percentage. Data related to ITN use and information regarding IRS were collected. The Pearson's chi-square and logistic regression statistical tests were used to calculate odds ratios (OR)

Results

In the first survey, 168 children were sampled and 433 children in the second one. The prevalence of infection was 40% in 2004, and significantly lower at 21.7% in 2005. PCV was 41% and 39%, respectively. 58% of the children surveyed in 2004 and 44.3% in 2005 had slept under an ITN. 78% of the dwellings studied in 2005 had been sprayed. In the 2005 survey, sleeping without a mosquito net meant a risk of infection 3 times greater than sleeping protected with a net hanged correctly and with no holes (p < 0.05).

Conclusion

IRS and ITNs have proven to be effective control strategies on the island of Bioko. The choice of one or other strategy is, above all, a question of operational feasibility and availability of local resources.