Thymoquinone reduces mouse colon tumor cell invasion and inhibits tumor growth in murine colon cancer models

We have shown that thymoquinone (TQ) is a potent antitumor agent in human colorectal cancer cells. In this study, we evaluated TQ's therapeutic potential in two different mice colon cancer models [1,2-dimethyl hydrazine (DMH) and xenografts]. We also examined TQ effects on the growth of C26 mouse colorectal carcinoma spheroids and assessed tumor invasion in vitro. Mice were treated with saline, TQ, DMH, or combinations once per week for 30 weeks and the multiplicity, size and distribution of aberrant crypt foci (ACF) and tumors were determined at weeks 10, 20 and 30. TQ injected intraperitoneally (i.p.) significantly reduced the numbers and sizes of ACF at week 10; ACF numbers were reduced by 86%. Tumor multiplicity was reduced at week 20 from 17.8 in the DMH group to 4.2 in mice injected with TQ. This suppression was observed at week 30 and was long-term; tumors did not re-grow even when TQ injection was discontinued for 10 weeks. In a xenograft model of HCT116 colon cancer cells, TQ significantly (P < 0.05) delayed the growth of the tumor cells. Using a matrigel artificial basement membrane invasion assay, we demonstrated that sub-cyto-toxic doses of TQ (40 microM) decreased C26 cell invasion by 50% and suppressed growth in three-dimensional spheroids. Apoptotic signs seen morphologically were increased significantly in TQ-treated spheroids. TUNEL staining of xenografts and immunostaining for caspase 3 cleavage in DMH tumors confirmed increased apoptosis in mouse tumors in response to TQ. These data should encourage further in vivo testing and support the potential use of TQ as a therapeutic agent in human colorectal cancer.     

Brucella suis histidinol dehydrogenase: Synthesis and inhibition studies of substituted N-L-histidinylphenylsulfonyl hydrazide

Histidinol dehydrogenase (HDH, EC EC1.1.1.23) catalyses the final step in the biosynthesis of histidine and constitutes an attractive novel target for the development of new agents against the pathogenous, bacteria Brucella suis. A small library of new HDH inhibitors based on the L-histidinylphenylsulfonyl hydrazide scaffold has been synthesized and their inhibitory activity investigated. The obtained results demonstrate that modification of the group between the histidinyl moiety and the phenyl ring constitutes an important structural factor for the design of effective HDH inhibitors.     

Estimation of protochlorophyll(ide) contents in plant extracts; re-evaluation of the molar absorption coefficient of protochlorophyll(ide)

In an attempt to solve the controversy about the evaluation of the molar absorption coefficient of PChl(ide), this coefficient is estimated in this work by using an original experimental approach. The calculated molar absorption coefficient of PChl(ide) is 30.4.10³ 1 mole^–1 cm^–1 at 626 nm in acetone 80%; it is close to that derived from the specific absorption coefficient of Koski and Smith when assuming that the pigment extracted by these authors was the esterified pigment: PChl. Sets of equations for the quantification of Chl(ide) a, Chl b and PChl(ide) in 80% acetone extracts are derived.Abbreviations PChl(ide) protochlorophyll(ide) - Chl(ide) chlorophyll(ide)     

Evaluating the performance of a successive-approximations approach to parameter optimization in maximum-likelihood phylogeny estimation

Almost all studies that estimate phylogenies from DNA sequencedata under the maximum-likelihood (ML) criterion employ an approximateapproach. Most commonly, model parameters are estimated on someinitial phylogenetic estimate derived using a rapid method (neighbor-joiningor parsimony). Parameters are then held constant during a treesearch, and ideally, the procedure is repeated until convergenceis achieved. However, the effectiveness of this approximationhas not been formally assessed, in part because doing so requirescomputationally intensive, full-optimization analyses. Here,we report both indirect and direct evaluations of the effectivenessof successive approximations. We obtained an indirect evaluationby comparing the results of replicate runs on real data thatuse random trees to provide initial parameter estimates. Forsix real data sets taken from the literature, all replicateiterative searches converged to the same joint estimates oftopology and model parameters, suggesting that the approximationis not starting-point dependent, as long as the heuristic searchesof tree space are rigorous. We conducted a more direct assessmentusing simulations in which we compared the accuracy of phylogeniesestimated using full optimization of all model parameters oneach tree evaluated to the accuracy of trees estimated via successiveapproximations. There is no significant difference between theaccuracy of the approximation searches relative to full-optimizationsearches. Our results demonstrate that successive approximationis reliable and provide reassurance that this much faster approachis safe to use for ML estimation of topology.     

PTB regulates the processing of a 3'-terminal exon by repressing both splicing and polyadenylation

The polypyrimidine tract binding protein (PTB) has been described as a global repressor of regulated exons. To investigate PTB functions in a physiological context, we used a combination of morpholino-mediated knockdown and transgenic overexpression strategies in Xenopus laevis embryos. We show that embryonic endoderm and skin deficient in PTB displayed a switch of the alpha-tropomyosin pre-mRNA 3' end processing to the somite-specific pattern that results from the utilization of an upstream 3'-terminal exon designed exon 9A9'. Conversely, somitic targeted overexpression of PTB resulted in the repression of the somite-specific exon 9A9' and a switch towards the nonmuscle pattern. These results validate PTB as a key physiological regulator of the 3' end processing of the alpha-tropomyosin pre-mRNA. Moreover, using a minigene strategy in the Xenopus oocyte, we show that in addition to repressing the splicing of exon 9A9', PTB regulates the cleavage/polyadenylation of this 3'-terminal exon.     

Mitochondrial genome transmission in Chlamydomonas diploids obtained by sexual crosses and artificial fusions: Role of the mating type and of a 1 kb intron

Summary The linear mitochondrial DNAs of the two infertile algal species Chlamydomonas smithii and C. reinhardtii are co-linear with the exception of a 1 kb intron ( intron) located in the cytochrome b gene of C. smithii. C. smithii also possesses an additional HpaI restriction site (H marker) located in the COXI gene, about 5 kb from the intron. In reciprocal crosses, C. smithii (H ⁺⁺) × C. reinhardtii (H ^––), the intron is transmitted to all diploid progeny, whereas the H marker is frequently transmitted either biparentally or paternally depending on whether the C. smithii parent is maternal (mt ⁺) or paternal (mt ^–). In diploids resulting from artificial fusion between vegetative cells, the absolute transmission of a is accompanied by the frequent transmission of the H ⁺ marker, irrespective of the mating type of the parental strains. Finally, in reciprocal crosses between C. smithii (H ⁺⁺) and recombinant H ^–+ clones, the transmission of the H marker is predominantly paternal or biparental. These results allow us to conclude that (1) the a intron behaves as a group I intron whose unidirectional conversion influences the transmission of the H marker; and (2) the mt ^– paternal mitochondrial genome is transmitted more often than the mt ⁺. The mating type has no effect in diploids obtained by artificial fusion.     

Temperature effects on oxygen consumption of two nocturnal geckos,Ptyodactylus hasselquistii (Donndorff) andBunopus tuberculatus (Blanford) (Reptilia: Gekkonidae) in Saudi Arabia

Summary Oxygen consumption rates of the lizardsPtyodactylus hasselquistii (adult and subadults) andBunopus tuberculatus (adult) were determined in relation to ambient temperatures ranging from 10 to 35°C using a double-chamber, volumetric closed system. The metabolic rate-temperature curves for both species were triphasic and similar in shape, but O₂ consumption differed between species.The low thermal dependence at temperatures between 15 and 25°C, common to both species, was correlated with the lizards' dual mode of thermoregulatory activity and ecology.