Cellulose orientation determines mechanical anisotropy in onion epidermis cell walls

The role of cellulose microfibril orientation in determining cell wall mechanical anisotropy and in the control of the wall plastic versus elastic properties was studied in the adaxial epidermis of onion bulb scales using the constant-load (creep) test. The mean or net cellulose orientation in the outer periclinal wall of the epidermis was parallel to the long axis of the cells. In vitro cell wall extensibility was 30-90% higher in the direction perpendicular to the net microfibril orientation than parallel to it. This was the case for the size of the initial deformation occurring just after the load application and for the rate of time-dependent creep. Loading/unloading experiments confirmed the presence of a real irreversible component in cell wall extension. The plastic component of the time-dependent deformation was higher perpendicular to the net cellulose orientation than parallel to it. An acid buffer (pH 4.5) increased the creep rate by 25-30% but this response was not related to cellulose orientation. The present data provide direct evidence that the net orientation of cellulose microfibrils confers mechanical anisotropy to the walls of seed plants, a characteristic that may be relevant to understanding anisotropic cell growth.     

Challenging the model for induction of metallothionein gene expression

Metallothioneins (MTs) are low-molecular-weight, cysteine-rich metal-binding proteins found in a wide variety of organisms including bacteria, fungi and all eukaryotic plant and animal species. MTs bind essential and non-essential heavy metals. In mammalian cells MT genes are highly inducible by many heavy metals including Zn, Cd, Hg, and Cu. Aquatic systems are contaminated by different pollutants, including metals, as a result of man's activities. Bivalve molluscs are known to accumulate high concentrations of heavy metals in their tissue and are widely used as bioindicators for pollution in marine and freshwater environments, with MTs frequently used as a valuable marker of metal contamination. We here describe the MT isoform gene expression patterns of marine and freshwater molluscs and fish species after Cd or Zn contamination. Contamination was carried out at a river site polluted by a zinc ore extraction plant or in the laboratory at low, environmentally relevant metal concentrations. A comparison for each species based on the accumulated MT protein levels often shows discrepancies between gene expression and protein level. In addition, several differences observed in the pattern of MT gene expression between mollusc and mammalian species enable us to discuss and challenge a model for the induction of MT gene expression.     

Comparison of chaetognath mitochondrial genomes and phylogenetical implications

Two complete mitochondrial genomes (mtDNAs) of chaetognaths, Spadella cephaloptera and Paraspadella gotoi, have been recently published. These genomes are highly unusual. They are the smallest metazoan mtDNAs so far known; atp6 and atp8 genes are missing; lastly, our reanalysis has evidenced that, contrarily to what has been previously published for one sequence, both contain a unique transfer RNA (tRNA(Met)) evidencing that both have the same gene content. Indeed, even if the gene order seems very different, two gene blocks are conserved. In addition, comparison of gene arrangement suggests phylogenetical relationships between chaetognaths and some lophotrochozoa like annelids and molluscs.     

Prion dynamics with size dependency-strain phenomena

Models for the polymerization process involved in prion self-replication are well-established and studied [H. Engler, J. Pruss, and G.F. Webb, Analysis of a model for the dynamics of prions II, J. Math. Anal. Appl. 324 (2006), pp. 98-117; M.L. Greer, L. Pujo-Menjouet, and G.F. Webb, A mathematical analysis of the dynamics of prion proliferation, J. Theoret. Biol. 242 (2006), pp. 598-606; J. Pruss, L. Pujo-Menjouet, G.F. Webb, and R. Zacher, Analysis of a model for the dynamics of prions, Discrete Cont. Dyn. Sys. Ser. B 6(1) (2006), pp. 215-225] in the case where the dynamics coefficients do not depend on the size of polymers. However, several experimental studies indicate that the structure and size of the prion aggregates are determinant for their pathological effect. This motivated the analysis in Calvez et al. [Size distribution dependence of prion aggregates infectivity, Math Biosci. 217 (2009), pp. 88-99] where the authors take into account size-dependent replicative properties of prion aggregates. We first improve a result concerning the dynamics of prion aggregates when a pathological state exists (high production of the normal protein). Then we study the strain phenomena and more specifically we wonder what specific replicative properties are determinant in strain propagation. We propose to interpret it also as a dynamical property of size repartitions.     

Degree of sex reversal as related to plasma steroid levels in genetic female chickens (Gallus domesticus) treated with Fadrozole

The objectives of this work were to determine whether or not plasma levels of testosterone and estradiol reflect the various grades of sex reversal in genetic female chickens treated with Fadrozole (CGS 16949 A), a nonsteroidal aromatase inhibitor, and whether gonadal aromatase activity and plasma levels of testosterone and estradiol in treated females can or not be modified by post-hatch treatments with Fadrozole or Fadrozole + testosterone. Eggs were injected with 1 mg Fadrozole on day 4 of incubation. In females having developed sex-reversed gonads, endocrine parameters (estradiol and testosterone) at and after 13 weeks of age were indicative of the degree of sex reversal, with, for example, sex-reversed females with two testes having the highest levels of testosterone and the lowest levels of estradiol. Among these females, eight (from a total of 13) produced ejaculates with scarce and abnormal spermatozoa. Some motility was observable in the ejaculates from five of them. None of the post-hatch treatments had a significant effect on plasma levels of testosterone or estradiol (measured at 3-week intervals from week 4 to week 28 post-hatch) or on gonadal aromatase activity (measured at 12 and 28 weeks). In conclusion, these results indicate that plasma levels of testosterone and estradiol at and after 13 weeks of age are valuable indicators of the degree of sex reversal in female chickens treated with Fadrozole prior to gonadal sex differentiation. In pre-cited conditions, post-natal treatments with either Fadrozole or Fadrozole + testosterone had no apparent effect on the degree of sex reversal in these birds. Finally, the occurrence of ejaculates with motile although scarce and abnormal spermatozoa, revealed that epididymes and ducti deferens can develop and become functional in sex-reversed female chickens.     

3′-(N-Hydroxyimino)-2′,3-dideoxynucleosides and Their Derivatives: Synthesis,Broad Spectrum Antiviral Properties and Synthetical Application for the Preparation of Other Nucleoside Analogues

Abstract

A series of 3′-(N-hydroxyimino)-2′,3′-dideoxynucleosides bearing different nucleic bases has been prepared. In vitro antiviral activity studies showed that among these compounds the thymine derivative possesses significant activity against HIV, HSV, EBV and HBV. Conveniently 5′-protected 3′-(N-hydroxyimino)-2′,3′-dideoxythymidine was further used as a synthon for the preparation of other nucleoside analogues.     

Differential effectiveness of berry polyphenols as anti-giardial agents

Following previous work on the anti-giardial effect of blueberry polyphenols, a range of polyphenol-rich extracts from berries and other fruits was screened for their ability to kill Giardia duodenalis, an intestinal parasite of humans. Polyphenol-rich extracts were prepared from berries using solid-phase extraction and applied to trophozoites of Giardia duodenalis grown in vitro. All berry extracts caused inhibition at 166 μg gallic acid equivalents (GAE)/ml phenol content but extracts from strawberry, arctic bramble, blackberry and cloudberry were as effective as the currently used drug, metronidazole, causing complete trophozoite mortality in vitro. Cloudberry extracts were found to be the most effective causing effectively complete trophozoite mortality at 66 μg GAE/ml. The polyphenol composition of the more effective berry extracts suggested that the presence of ellagitannins could be an important factor. However, the potency of cloudberry could be related to high ellagitannin content but also to the presence of substantial amounts of unconjugated p-coumaric acid and benzoic acid. These in vitro effects occur at concentrations easily achievable in the gut after berry ingestion and we discuss the likelihood that berry extracts could be effective anti-giardial agents in vivo.