Use of the Weibull model to describe inactivation of dry-harvested conidia of different Penicillium species by ethanol vapours.

AIMS: This study aimed at modelling the effect of ethanol vapours, in the range 0.7-7.5 kPa, on the inactivation of dry-harvested conidia of Penicillium chrysogenum, Penicillium digitatum and Penicillium italicum. METHODS AND RESULTS: Survival curves were modelled by a Weibull model: log (N/N(0)) = -1/2.303 (t/alpha)(beta). The shape parameter beta was different from one in all cases, indicating that the classical first-order kinetics approach is the exception rather than the rule. Survival curves exhibited upward concavity (beta < 1) with the notable exception of P. chrysogenum at ethanol vapour pressures 0.7 and 1.5 kPa. The scale parameter alpha (h) varied greatly depending on the ethanol vapour pressure and on the species. CONCLUSIONS: For safety reasons, it is recommended not to exceed an ethanol vapour pressure of 3.3 kPa. At 2.8 kPa, more than 4 log(10) reductions in viable conidia were achieved for all the species after 24-h exposure. SIGNIFICANCE AND IMPACT OF THE STUDY: Ethanol has GRAS status in the USA and represents an interesting alternative to fungicides. The effectiveness of ethanol vapours to inactivate dry-harvested conidia of some Penicillium was demonstrated in this study.

Nonlinear response of the electric birefringence of polyelectrolyte solutions.

A theoretical approach for the nonlinear ac electro-optical response in polyelectrolytes is developed in the case where a weak ac electric field superimposed on a strong dc bias electric field is applied to these electrically charged systems. By restricting ourselves to an assembly of noninteracting and nonpolar rodlike macroions, we use a perturbation procedure and establish expressions for the first two harmonic components of the electric birefringence up to the second order in the electric field strength. An attempt is also made to extend this theory to the (non-Markovian) subdiffusive regime based on a fractional kinetic equation written in a configuration space where angular and linear displacements are taken into account. The results obtained are illustrated by three-dimensional dispersion and absorption plots together with Cole-Cole-like diagrams to show the importance of the coupling effect between translation and rotation. Besides considering the stationary ac response, we have also derived, in the context of subdiffusion, new expressions for the transient electric birefringence in the presence of a constant electric field, both for the buildup and the reversing pulse. All these results are illustrated by plots demonstrating the effect of the coupling (rotation-translation) parameter a and the critical exponent α (subdiffusion). A comparison of our theoretical model with experimental measurements of the ac Kerr effect response of a polyelectrolyte solution of NaCMC appears to be quite satisfactory.

A novel subgenomic murine leukemia virus RNA transcript results from alternative splicing.

Here we show the existence of a novel subgenomic 4.4-kb RNA in cells infected with the prototypic replication-competent Friend or Moloney murine leukemia viruses (MuLV). This RNA derives by splicing from an alternative donor site (SD') within the capsid-coding region to the canonical envelope splice acceptor site. The position and the sequence of SD' was highly conserved among mammalian type C and D oncoviruses. Point mutations used to inactivate SD' without changing the capsid-coding ability affected viral RNA splicing and reduced viral replication in infected cells.

Introduction of a cis-acting mutation in the capsid-coding gene of moloney murine leukemia virus extends its leukemogenic properties.

Inoculation of newborn mice with the retrovirus Moloney murine leukemia virus (MuLV) results in the exclusive development of T lymphomas with gross thymic enlargement. The T-cell leukemogenic property of Moloney MuLV has been mapped to the U3 enhancer region of the viral promoter. However, we now describe a mutant Moloney MuLV which can induce the rapid development of a uniquely broad panel of leukemic cell types. This mutant Moloney MuLV with synonymous differences (MSD1) was obtained by introduction of nucleotide substitutions at positions 1598, 1599, and 1601 in the capsid gene which maintained the wild-type (WT) coding potential. Leukemias were observed in all MSD1-inoculated animals after a latency period that was shorter than or similar to that of WT Moloney MuLV. Importantly, though, only 56% of MSD1-induced leukemias demonstrated the characteristic thymoma phenotype observed in all WT Moloney MuLV leukemias. The remainder of MSD1-inoculated animals presented either with bona fide clonal erythroid or myelomonocytic leukemias or, alternatively, with other severe erythroid and unidentified disorders. Amplification and sequencing of U3 and capsid-coding regions showed that the inoculated parental MSD1 sequences were conserved in the leukemic spleens. This is the first report of a replication-competent MuLV lacking oncogenes which can rapidly lead to the development of such a broad range of leukemic cell types. Moreover, the ability of MSD1 to transform erythroid and myelomonocytic lineages is not due to changes in the U3 viral enhancer region but rather is the result of a cis-acting effect of the capsid-coding gag sequence.

Transient nonlinear dielectric relaxation and dynamic Kerr effect from sudden changes of a strong dc electric field: polar and polarizable molecules.

The nonlinear transient response of polar and polarizable particles (macromolecules) diluted in a nonpolar solvent to a sudden change both in magnitude and in direction of a strong external dc field is considered. By averaging the underlying Langevin equation, the infinite hierarchy of differential-recurrence equations for ensemble averages of the spherical harmonics is derived for an assembly of polar and anisotropically polarizable molecules pertaining to the noninertial rotational Brownian motion. On solving this hierarchy, the relaxation functions and relaxation times appropriate to the transient dynamic Kerr effect and nonlinear dielectric relaxation are calculated. The calculations are accomplished using the matrix continued fraction method, which allows us to express exactly the solution of the infinite hierarchy of differential-recurrence relations for the first- and second-order transient responses of the ensemble averages of the spherical harmonics (relaxation functions). The results are then compared with available experimental data and solutions previously obtained for various particular cases.

Evidence that the amino acid composition of the particle proteins of plant viruses is characteristic of the virus group. I. Multidimensional classification of plant viruses.

The amino acid (AA) contents of the coat proteins of 134 plant viruses and strains were classified by principal components analysis. The virus groupings that were obtained correlated well with the classification of Matthews. The relationships of each virus were dependent on the number of AA residues (axis 1) and on the percentage composition of each AA in the proteins (axes 2-4). The classification indicated which data were anomalous and needed confirmation. There seemed to be more anomalies in estimates of protein size than of protein composition.

Evidence that the amino acid composition of the particle proteins of plant viruses is characteristic of the virus group. II. Discriminant analysis according to structural biological and classification properties of plant viruses.

The amino acid composition (AAC) of the coat proteins (CPs) of 126 plant viruses or strains were analyzed by stepwise discriminant analysis. The criteria chosen for discrimination were: the structure of virus particles (3 clusters); the mode of of transmission of the viruses (6 clusters); and the grouping of viruses according to the classification of the International Committee on Taxonomy of Viruses (23 groups). Statistically significant correlations were obtained with different groups of discriminant amino acids. The results confirm that the AAC of the CPs contains all the information needed for a quantitative classification of plant viruses. These results and possible explanations of these clustering patterns are discussed.

Treatment of dental decay by CO2 laser beam: preliminary results.

Results obtained from two clinical cases, representative of 1,140 human teeth treated by CO2 laser beam during 3 years, announce a new conception of treatment of dental caries. The beam (P = 4 - 5 W, energy density of 9 to 25 kw/cm2) causes a dentin healing which becomes sterile, chemically and physically more resistant than pathological dentin. In addition, this exposure leads to an activation of the dentinogenesis supported by X-ray, confirming histo-pathological results obtained from experiments performed on animals.

[Technical note on the isolation of arboviruses by inoculation in young mice: preparation of the mosquito brei]. / Note technique sur l'isolement des arbovirus par inoculation au souriceau: préparation des broyats de moustiques.

Studying the effects of centrifugation and deep freezing on the quantity of yellow fever virus in a grinded pool of mosquitoes, the authors followed the mortality rate of inoculated baby mice with twenty five artificially infected mosquitoes treated in four different ways. The statistical analysis of the results show that centrifugation and deep freezing have both an effect on the titer of virus and that the addition of the two treatments have an effect superior to the addition of the separate effects of each of them. The authors propose a new technic for the preparation of pools of mosquitoes, without centrifugation or deep freezing.