The transcriptome of Toxoplasma gondii

Background  

Toxoplasma gondii gives rise to toxoplasmosis, among the most prevalent parasitic diseases of animals and man. Transformation of the tachzyoite stage into the latent bradyzoite-cyst form underlies chronic disease and leads to a lifetime risk of recrudescence in individuals whose immune system becomes compromised. Given the importance of tissue cyst formation, there has been intensive focus on the development of methods to study bradyzoite differentiation, although the molecular basis for the developmental switch is still largely unknown.     

Cost-effective G-CSF therapy strategies for cyclical neutropenia: mathematical modelling based hypotheses

Using computer simulations of a mathematical model for the regulation of stem cell and neutrophil production in dogs, we have studied the efficacy of four different treatment protocols for cyclical neutropenia involving granulocyte colony stimulating factor (G-CSF). The first treatment scheme is based on the bifurcation analysis of the mathematical model and proposes a daily, phase-dependent, protocol. The second involves alternate day administration of G-CSF. The third triggers G-CSF administration whenever neutrophil levels fall below a predetermined level, and the fourth one follows a random administration protocol. The computer simulations predict that clinically desirable results can be achieved with the three last methods, using far less G-CSF than would be needed with the standard daily treatment. If the results of this modelling are borne out clinically, they will entail a considerable financial savings for patients.     

A multivariate,osteological approach to Towa culture history

Eleven cranial measurements on 14 archeological populations from the American Southwest support the archeologically derived reconstruction of Towa population movements. The supposed (linguistic) relationship between Pecos and the Towa speaking villages is questioned.     

18S rRNA data indicate that Aschelminthes are polyphyletic in origin and consist of at least three distinct clades

The Aschelminthes is a collection of at least eight animal phyla, historically grouped together because the absence of a true body cavity was perceived as a pseudocoelom. Analyses of 18S rRNA sequences from six Aschelminth phyla (including four previously unpublished sequences) support polyphyly for the Aschelminthes. At least three distinct groups of Aschelminthes were detected: the Priapulida among the protostomes, the Rotifera-Acanthocephala as a sister group to the protostomes, and the Nematoda as a basal group to the triploblastic Eumetazoa.      

Unstable dynamics of a periodically driven oscillator in the presence of noise

Two qualitatively different unstable dynamical behaviours are shown to arise from the application of a periodic input to a simple mathematical model of an oscillator in the presence of noise. Rhythms similar to quasiperiodic dynamics may arise when there is a low amplitude periodic input, while with high amplitude inputs, patterns with irregular skipped or intercalated beats are found. These two qualitatively different types of unstable dynamics are similar to those observed in the respiratory activity of mechanically ventilated cats. A number of numerical simulations are performed to illustrate the quantitative properties of the two unstable patterns and to show how the quantitative properties can be compared with experimental data.     

The relationship between the base composition of bacterial DNA and its intracellular melting temperature as determined by differential scanning calorimetry

The correlation between the melting temperature of intracellular DNA, determined by differential scanning calorimetry (DSC) of whole bacteria, and its guanine + cytosine (G + C) content, was examined for 58 species of bacteria. Samples of vegetative cells were heated in a Perkin-Elmer DSC-2C at 10 degrees C min-1 from 5 to 130 degrees C, cooled to 5 degrees C and then re-heated as before. Literature values for the mole fraction of G + C, XGC, were linearly related to the temperature, Tmax, at which the reversible peak, pr, observed on the second heating run was at a maximum, via the equation XGC = (Tmax -73.8)/41.0. This equation accounted for 91.9% of the variance in XGC with 95% confidence limits of +/- 7.3%, approximately 1.6 times the corresponding uncertainty (+/- 4.5%) quoted by De Ley (Journal of Bacteriology 101, 738-754, 1970) for estimates based on the spectroscopically determined melting temperature of purified DNA. Random errors of measurement of Tmax did not greatly limit the precision of the prediction and it was concluded that factors additional to base composition affected the temperature of DNA melting within the bacterial cell. Displacement of Tmax values from the fitted line was particularly noticeable in Campylobacter, Corynebacterium and Bacterionema species and part of the residual variation appeared to be species specific, possibly caused by differences in intracellular solute concentration.