The genome of the protist parasite Entamoeba histolytica

Entamoeba histolytica is an intestinal parasite and the causative agent of amoebiasis, which is a significant source of morbidity and mortality in developing countries. Here we present the genome of E. histolytica, which reveals a variety of metabolic adaptations shared with two other amitochondrial protist pathogens: Giardia lamblia and Trichomonas vaginalis. These adaptations include reduction or elimination of most mitochondrial metabolic pathways and the use of oxidative stress enzymes generally associated with anaerobic prokaryotes. Phylogenomic analysis identifies evidence for lateral gene transfer of bacterial genes into the E. histolytica genome, the effects of which centre on expanding aspects of E. histolytica's metabolic repertoire. The presence of these genes and the potential for novel metabolic pathways in E. histolytica may allow for the development of new chemotherapeutic agents. The genome encodes a large number of novel receptor kinases and contains expansions of a variety of gene families, including those associated with virulence. Additional genome features include an abundance of tandemly repeated transfer-RNA-containing arrays, which may have a structural function in the genome. Analysis of the genome provides new insights into the workings and genome evolution of a major human pathogen.     

Collapse of stiff conjugated polymers with chemical defects into ordered, cylindrical conformations

The optical, electronic and mechanical properties of synthetic and biological materials consisting of polymer chains depend sensitively on the conformation adopted by these chains. The range of conformations available to such systems has accordingly been of intense fundamental as well as practical interest, and distinct conformational classes have been predicted, depending on the stiffness of the polymer chains and the strength of attractive interactions between segments within a chain. For example, flexible polymers should adopt highly disordered conformations resembling either a random coil or, in the presence of strong intrachain attractions, a so-called 'molten globule'. Stiff polymers with strong intrachain interactions, in contrast, are expected to collapse into conformations with long-range order, in the shape of toroids or rod-like structures. Here we use computer simulations to show that the anisotropy distribution obtained from polarization spectroscopy measurements on individual poly[2-methoxy-5-(2'-ethylhexyl)oxy-1,4-phenylenevinylene] polymer molecules is consistent with this prototypical stiff conjugated polymer adopting a highly ordered, collapsed conformation that cannot be correlated with ideal toroid or rod structures. We find that the presence of so-called 'tetrahedral chemical defects', where conjugated carbon-carbon links are replaced by tetrahedral links, divides the polymer chain into structurally identifiable quasi-straight segments that allow the molecule to adopt cylindrical conformations. Indeed, highly ordered, cylindrical conformations may be a critical factor in dictating the extraordinary photophysical properties of conjugated polymers, including highly efficient intramolecular energy transfer and significant local optical anisotropy in thin films.     

Decondensation of nuclear chromatin under the influence ofTris buffer

Résumé Des petits fragments de foie de rat ont été maintenus dans un tampon 2 mM tris HCl avec ou sans saccharose (concentration final 0,25M). L'incubation du tissus pendant au moins 1 h dans le tampontris cause une décondensation de la chromatine, qui peut être retardée par le saccharose. Les changements morphologiques des types de chromatine n'ont pas l'effet d'incorporer l'uridine dans le noyaux interphasiques du foie.     

Adaptation to histamine. histaminase activity

Résumé L'activité de l'histaminase de cobayes n'est pas modifiée par l'adaptation à l'histamine, soit par voie inhalatoire soit par voie intrapéritonéale.     

A correlation of the ionization energies of water and ethers with the polar and inductive substituent constants

Résumé On démontre que les énergies d'ionisation des ethers, R₂O, sont une fonction linéaire des constantes substituentes polaires et inductives. Les groupes alkyls qui donnent des électrons abaissent l'énergie d'ionisation du «lone-pair» de l'atome d'oxygène. L'eau est inclue dans la corrélation de même que lether le plus simple. On trouve qu'avec bonne approximationE _I =10,00+ 2,57 ^* ouE _I =12,59+28,0 _I .     

Changes in the T4/T3 molar ratio following thyrotrophin releasing hormone injection in cattle

Summary The injection of thyrotropin releasing hormone into cattle resulted in a rapid decrease in the T₄/T₃ molar ratio. 2 breeds of cattle, Shorthorn and Africander Cross were studied. The decrease in the T₄/T₃ molar ratio was significantly greater in the Shorthorn breed. It is concluded that acute stimulation of the thyroid gland with TRH results in enhanced release of both T₃ and T₄ and that T₃ is discharged more rapidly than T₄.     

Inactivation of vasotocin by hen's tissues in vitro

Zusammenfassung In vitro wurde die Inaktivation von Vasotocin in einigen Gewebehomogenaten (Leber, Niere, Eileitersegmenten, Magnum, Isthmus Uterus, Vagina) festgestellt. Die grösste Inaktivation wurde bei den Homogenaten von Leber und Utersus gefunden.