Agrochemicals: Effect on genetic resistance in yeasts colonizing winter wheat kernels.

Crop protection agents are widely used in modern agriculture and exert direct effects on non-target microorganisms such as yeasts. Yeasts abundantly colonize wheat grain and affect its chemical composition. They can also limit pathogen growth. This study evaluated the sensitivity of yeast communities colonizing winter wheat kernels to benzimidazole, strobilurin, triazole and morpholine fungicides, trinexapac-ethyl, a commercial mixture of o-nitrophenol+p-nitrophenol+5-nitroguaiacol, and chitosan applied during the growing season of winter wheat and in vitro in a diffusion test. A molecular identification analysis of yeasts isolated from winter wheat kernels was performed, and nucleotide polymorphisms in the CYTb gene (G143A) conferring resistance to strobilurin fungicides in yeast cells were identified. The size of yeast communities increased during grain storage, and the total counts of endophytic yeasts were significantly (85%) reduced following intensive fungicide treatment (fenpropimorph, a commercial mixture of pyraclostrobin, epoxiconazole and thiophanate-methyl). This study demonstrated that agrochemical residues in wheat grain can drive selection of yeast communities for reduced sensitivity to xenobiotics. A mutation in the CYTb gene (G143A) was observed in all analyzed isolates of the following azoxystrobin-resistant species: Aureobasidium pullulans, Debaryomyces hansenii, Candida albicans and C. sake. Agrochemicals tested in vitro were divided into four classes of toxicity to yeasts: (1) tebuconazole and a commercial mixture of flusilazole and carbendazim - most toxic to yeasts; (2) fenpropimorph and a commercial mixture of pyraclostrobin and epoxyconazole; (3) propiconazole, chitosan, thiophanate-methyl and a commercial mixture of o-nitrophenol, p-nitrophenol and 5-nitroguaiacol; (4) trinexapac-ethyl and azoxystrobin - least toxic to yeasts. It was found that agrochemicals can have an adverse effect on yeast abundance and the composition of yeast communities, mostly due to differences in fungicide resistance between yeast species, including the clinically significant C. albicans.

The effect of pyrimethanil on the growth of wine yeasts.

AIMS: The toxicity of the fungicide pyrimethanil on the growth of wine yeasts was evaluated using in vivo and in vitro experimentation. METHODS AND RESULTS: The effect of pyrimethanil in the must was studied during the spontaneous wine fermentation of three consecutive vintages and by the cultivation of Hanseniaspora uvarum and Saccharomyces cerevisiae yeasts in a liquid medium. The residues of the fungicide were measured using gas chromatography-mass spectrometry system and the sugar concentration in the must using HPLC-RI. Molecular and standard methods were used for identifying the yeast species. Although the pyrimethanil residues in grapes were below the maximum residue limits, they significantly affected the reduced utilization of sugars in the first days of fermentation. Its residues controlled the growth of H. uvarum during the fermentation and during in vitro cultivation as well. CONCLUSIONS: The fungicide pyrimethanil had an effect on the course and successful conclusion of spontaneous wine fermentation that was correlated with the initial concentration of yeasts in the must. SIGNIFICANCE AND IMPACT OF THE STUDY: The impact of pyrimethanil on the indigenous mixed yeast flora in fermenting must was investigated for the first time. The results showed that its residues might play an important role in the growth and succession of yeast during spontaneous wine fermentation.

ErbB2 receptor tyrosine kinase signaling mediates early demyelination induced by leprosy bacilli.

Demyelination is a common pathologic feature in many neurodegenerative diseases including infection with leprosy-causing Mycobacterium leprae. Because of the long incubation time and highly complex disease pathogenesis, the management of nerve damage in leprosy, as in other demyelinating diseases, is extremely difficult. Therefore, an important challenge in therapeutic interventions is to identify the molecular events that occur in the early phase before the progression of the disease. Here we provide evidence that M. leprae-induced demyelination is a result of direct bacterial ligation to and activation of ErbB2 receptor tyrosine kinase (RTK) signaling without ErbB2-ErbB3 heterodimerization, a previously unknown mechanism that bypasses the neuregulin-ErbB3-mediated ErbB2 phosphorylation. MEK-dependent Erk1 and Erk2 (hereafter referred to as Erk1/2) signaling is identified as a downstream target of M. leprae-induced ErbB2 activation that mediates demyelination. Herceptin (trastuzumab), a therapeutic humanized ErbB2-specific antibody, inhibits M. leprae binding to and activation of ErbB2 and Erk1/2 in human primary Schwann cells, and the blockade of ErbB2 activity by the small molecule dual ErbB1-ErbB2 kinase inhibitor PKI-166 (ref. 11) effectively abrogates M. leprae-induced myelin damage in in vitro and in vivo models. These results may have implications for the design of ErbB2 RTK-based therapies for both leprosy nerve damage and other demyelinating neurodegenerative diseases.

In vitro and in vivo activity of K-130, a dihydrofolate reductase inhibitor, against Mycobacterium leprae.

The antimicrobial effects of a new dihydrofolate reductase inhibitor, K-130 (2,4-diaminodiphenyl sulfone substituted 2,4-diamino-5-benzylpyrimidine), alone and in combination with dapsone (CAS 80-08-0) against both dapsone-sensitive and dapsone-resistant strains of Mycobacterium leprae were evaluated in vitro, in cell-free culture system, and in vivo, in mouse foot pads. The minimal inhibitory concentration of K-130 against dapsone-sensitive as well as dapsone resistant strains of M, leprae was 0.03 microgram/ml, and the activity was bactericidal in both cases. However, when combined with dapsone, K-130 exhibited synergism in case of dapsone-sensitive M. leprae, while in case of dapsone-resistant M. leprae, the effect was merely additive. Similar synergistic effects were also observed in the mouse foot pad system for both types of M. leprae strains.

[Pharmacological basis of the action of isaxonine (author's transl)]. / Bases pharmacologiques de l'action de l'isaxonine.

The author reviews previous therapeutic attempts to stimulate regeneration of peripheral nerves. Since 1971 he has been studying a synthetic compound, isaxonine, which in rats accelerates nerve regeneration and functional recovery. Stimulation of axonal regeneration and collateral sprouting has been demonstrated in tissue cultures. The therapeutic activity of the compound has been demonstrated in man in leprous neuropathy and in vincristine neuropathy. Isaxonine has specific affinity for peripheral nerves. Its acts directly on the neuron or indirectly by stimulating production of a growth factor remains unknown. In vitro and in vivo studies isaxonine have shown that isaxonine antagonizes the noxious effects of Vinca alkaloids on neurotubular structure. Research in progress suggest a possible action of this new compound in other diseases related to tubulin anomaly.

Further investigations on M. leprae. Growth promotion and inhibition by organic substances and observations on antagonistic and syntergistic effects.

The multiplication of 2 strains of M. leprae on a medium containing a sonic extract (SE), prepared from M. smegmatis, was promoted by cysteine, tryptophane and dimethylasulfoxide (DMSO), while glutamic acid, glutamine and histidine exerted variable effects. The final effects of glutamic acid and glutamine were determined by the total concentration of both compounds together. The presence of cysteine and glutamic acid alone or together with DMSO abolished all inhibitory effects. Desferal did not enable the multiplication of M. leprae on media devoid of SE prepared from M. smegmatis. However with SE and 0.005 per cent and 0.002 per cent concentrations of Desferal its initial growth was accelerated. Its final counts, noted after an 8-month incubation, did not exceed those observed without Desferal. Puring and pyrimidine compounds promoted markekly the multiplication of M. leprae (counts greater than 3 times 10-7/ml). The highest counts were observed with pyrimidines (thymine, thymidine, cytosine) applied single or combined.