Mechanisms of developmental robustness

We present a review of noise buffering mechanisms responsible for developmental robustness. We focus on functions of chaperone Hsp90, miRNA, and cross-regulation of gap genes in Drosophila. The noise buffering mechanisms associated with these functions represent specific examples of the developmental canalization, reducing the phenotypical variability in presence of either genetic or environmental perturbations. We demonstrate that robustness often appears as a function of a network of interacting elements and that the system level approach is needed to understand the mechanisms of noise filtering.     

Escalating Plasmodium falciparum antifolate drug resistance mutations in Macha, rural Zambia

Background

Artemisinin and its derivatives have been used for falciparum malaria treatment in China since late 1970s. Monotherapy and uncontrolled use of artemisinin drugs were common practices for a long period of time. In vitro tests showed that the susceptibility of Plasmodium falciparum to artemisinins was declining in China. A concern was raised about the resistance to artemisinins of falciparum malaria in the country. It has been reported that in vitro artemisinin resistance was associated with the S769N mutation in the PfATPase6 gene. The main purpose of this study was to investigate whether that mutation has occurred in field isolates from China.

Methods

Plasmodium falciparum field isolates were collected in 2006–2007 from Hainan and Yunnan provinces, China. A nested PCR-sequencing assay was developed to analyse the genotype of the PfATPase6 S769N polymorphism in the P. falciparum field isolates.

Results

The genotyping results of six samples could not be obtained due to failure of PCR amplification, but no S769N mutation was detected in any of the 95 samples successfully analysed.

Conclusion

The results indicate that the S769N mutation in the PfATPase6 gene is not present in China, suggesting that artemisinin resistance has not yet developed, but the situation needs to be watched very attentively.     

Methods for acquisition of quantitative from confocal images of gene expression in situ

In this review we summarize original methods for the extraction quantitative information from the confocal images of gene expression patterns. These methods include image segmentation, extraction of quantitative numerical data on gene expression, removal of background signal and spatial registration. Finally it is possible to construct a spatiotemporal atlas of gene expression form individual images obtained at each developmental stage. Initially all methods were developed to extract quantitative numerical information form confocal images of segmentation gene expression in Drosophila melanogaster. Application of these methods to Drosophila images makes it possible to reveal new mechanisms of formation of segmentation gene expression domains, as well as to construct the quantitative atlas of segmentation gene expression. Most image processing procedures can be easily adapted to process a wide range of biological images.     

Methods for acquisition of quantitative data from confocal images of gene expression in situ

In this review, we summarize original methods for the extraction of quantitative information from confocal images of gene-expression patterns. These methods include image segmentation, the extraction of quantitative numerical data on gene expression, and the removal of background signal and spatial registration. Finally, it is possible to construct a spatiotemporal atlas of gene expression from individual images recorded at each developmental stage. Initially all methods were developed to extract quantitative numerical information from confocal images of segmentation gene expression in Drosophila melanogaster. The application of these methods to Drosophila images makes it possible to reveal new mechanisms in the formation of segmentation gene expression domains, as well as to construct a quantitative atlas of segmentation gene expression. Most image processing procedures can be easily adapted to process a wide range of biological images.     

Phage typing of the coagulase-positive staphylococci isolated from various species of animals

More than 200 coagulase-positive strains of animal origin have been studied by means of Staphylococcus aureus typing phages, belonging to two international sets and intended for typing staphylococci isolated from large cattle and humans, and experimental "chicken" phage A 1591. Among S. aureus strains the cultures isolated from swine, cows, chickens, and belonging to biotypes B1, C1, B2, respectively, have been mostly (in 78.5-90.0% of cases) determined by phage typing. The strains belonging to one biotype have proved to be sensitive predominantly to the same phages. In this connection further differentiation of staphylococci within individual biotypes by means of the phages used in these experiments seems to be impracticable. S. intermedius strains have been found to be completely resistant to the above phages, which confirms that S. intermedius is rightly considered to be an independent species of coagulase-positive staphylococci.     

Effect of diazepam on electrical activity and Na,K-ATP-ase level in a penicillin-induced epileptic focus in the rat cerebral cortex

Application of penicillin solution to the motor cortex in rats evoked the appearance of interictal discharges and epileptic seizures. After administration of diazepam in a dose of 2 mg/kg, Na,K-ATPase activity in the unpurified synaptosomes fraction of the cortex in the zone of the focus was increased by practically 100% compared with the level of activity of the enzyme in the focus without diazepam. Interictal discharges and epileptic seizures underwent different changes following intramuscular injection of diazepam. The frequency and variability of amplitude of the interictal discharges increased after administration of diazepam, whereas epileptic seizures were depressed. This effect was potentiated with an increase in the dose of diazepam. It is suggested that the opposite action of diazepam on epileptic seizures and interictal discharges may be evidence that the mechanisms lying at the basis of the development of these phenomena are different.Institute of General Pathology and Pathological Physiology, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 12, No. 4, pp. 349–357, July–August, 1980.