Modelling the inhibitory effect of copper sulfate on the growth of Penicillium expansum and Botrytis cinerea.

AIMS: This study aimed to investigate the effect of copper sulfate (from 0 to 8 mmol kg(-1)) on radial growth rate and lag time of two moulds responsible for vine grapes spoilage: Penicillium expansum strain 25·03 and Botrytis cinerea, strains BC1 and BC2. METHODS AND RESULTS: A new model was developed to describe tailing and shoulders in the inhibition curves. Because of tailing, the minimum inhibitory concentration (MIC), was not defined as the concentration at which no growth was observed, but as the concentration at which the lag time was infinite. The concentrations at which µ = µ(opt)/2, (Cu50), were in the range of 2·2-2·6 mmol kg(-1). Radial growth rate of P. expansum and the reciprocal of the lag time were linearly correlated (r = 0·84). In contrast, in the range 0-4 mmol kg(-1), an inhibition of growth of B. cinerea was observed whereas germination remained unaffected (i.e. the lag time was constant). In the range 4-8 mmol kg(-1) , the radial growth rate of B. cinerea was almost constant (c. 1 mm day(-1)), but germination was inhibited (i.e. the lag time was increased). CONCLUSIONS: The MIC values were 4·7 mmol kg(-1) for P. expansum, 8·2 and 7·3 mmol kg(-1) for B. cinerea strain BC1 and BC2, respectively, demonstrating that some isolates of these moulds are resistant to copper. SIGNIFICANCE AND IMPACT OF THE STUDY: Copper concentrations at 4 mmol kg(-1) would be sufficient to control the development of these isolates, but the toxicity of copper should be extended to other isolates and evaluated in vineyards.

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.

Antagonist effect of a receptor-mimicking peptide encoded by human angiotensin II complementary RNA.

This article reports on the binding and the angiotensin II (Ang II) antagonistic properties of a peptide, referred to as hIIA, encoded by an RNA strand complementary to the human Ang II messenger RNA. Although Ang II and hIIA (H2N-Glu-Gly-Val-Tyr-Val-His-Pro-Val-COOH) share four amino acids, the iodinated and tritiated forms of hIIA were unreactive with seven monoclonal antibodies defining four distinct epitopes on the Ang II molecule and failed to bind to Ang II hepatic and mesangial receptors. However, hIIA did inhibit binding of 125I-Ang II to rat hepatocyte membranes (IC50, 2 x 10(-7) M) and to the various monoclonal antibodies. The lowest IC50 (5 x 10(-7) M) was measured with the monoclonal antibody specific for the Ang II sequence generally considered as implicated in receptor recognition. As predicted from the binding studies, hIIA was further shown to antagonize some biological properties of Ang II. On mesangial cells, hIIA alone had no effect on intracellular calcium concentration ([Ca2+]i) and prostaglandin E2 synthesis but did abolish the transient increase in [Ca2+]i in response to 100 nM Ang II and did induce a specific dose-dependent inhibition of the Ang II-stimulated prostaglandin E2 release. Furthermore, intravenous infusion of hIIA (200 micrograms.kg-1.min-1) inhibited by 66 +/- 3% the rat hypertensive response to 100 ng.kg-1 Ang II but had no effect on the pressor activity of agents such as alpha 1-adrenergic and HT2 serotonin agonists. Our data suggest that the "complementary" peptide hIIA interacts directly with Ang II by mimicking the Ang II complementary site on the receptor and can inhibit the physiological effects of Ang II. This type of Ang II complementary peptide may serve as a model for a new class of antihypertensive drugs.

In vitro development of resistance of Streptococcus pneumoniae to beta-lactam antibiotics.

In recent years, increasing numbers of Streptococcus pneumoniae strains displaying relative resistance to penicillin have been reported. Epidemiological studies have shown a correlation between aminopenicillin administration and resistance. We investigated the development of resistance in six strains (four sensitive and two intermediate-resistant to penicillin) by serial daily passages in subinhibitory concentrations of amoxicillin (AMX), amoxicillin + clavulanic acid (AMC), imipenem (IMP), cefixime (CFM), cefatrizine (CTZ), cefadroxil (CDX), and cefuroxime (CXM). MICs were determined by the macrodilution method in brain-heart broth for each daily passage. The number of daily passages needed to increase the MIC by a factor of 8 was achieved with AMX, AMC, and CFM for most of the strains after a mean of 24, 20, and 11 passages, respectively, and for one-third of the strains, with CDX, IMP, and CTZ after 11, 11, and 21 passages, respectively. Decreased susceptibility to breakpoints for intermediate-resistant S. pneumoniae populations was noted for all strains with CFM, AMX, and AMC after a mean of 10, 18, and 21 serial passages, respectively, and for four of five strains with IMP and CTZ after 12 and 13 passages. CTZ-, CDX-, and CXM-passaged variants had increased MIC values only for cephalosporins, while AMX-, AMC-, IMP-, and CFM-passaged variants exhibited increased MICs to all antibiotics tested. These in vitro data appear to be in agreement with epidemiological studies and warrant further exploration with respect to possible clinical implications.

Immunological reactivity of angiotensin II receptor antagonists: possible implications for receptor binding sites.

In the present study, we assessed the reactivity with seven anti-angiotensin II monoclonal antibodies of three nonpeptide and one peptide compounds described as selective antagonists of angiotensin II for AT1 (DuP 753, 2-n-butyl-4-chloro-5-(hydroxymethyl)-1-[[2'-(1H-tetrazol-5-yl) biphenyl-4-yl] methyl] imidazole; EXP 3174, 2-n-butyl-4-chloro-5-(carboxylic acid)-1-[[2'-(1H-tetrazol-5-yl) biphenyl-4-yl] methyl] imidazole) and AT2 receptor sites (CGP42112A, nicotinyl-Tyr-(N alpha-benzyloxycarbonyl-Arg)Lys-His-Pro-Ile-OH; PD123177, 1-[(4-amino-3-methylphenyl) methyl]-5-(diphenyl-acetyl)-4,5,6,7-tetrahydro-1H-imidazol[4,5-c] pyridine 6-carboxylic acid), respectively. These studies were undertaken because the reactivity of the monoclonal antibodies with peptide analogs of angiotensin II and the three-dimensional structure of an angiotensin II-immunoglobulin Fab fragment complex strongly suggested that the conformations identified by the monoclonal antibodies were relevant to those involved in receptor binding as defined by biophysical models supported by structure activity studies. Surprisingly although three of the compounds were described as competitive inhibitors of angiotensin II, binding of the various monoclonal antibodies to either ovalbumin-coupled angiotensin II adsorbed to plastic wells or 125I-labeled angiotensin II in liquid phase was unaffected by any of the nonpeptide antagonists and CGP42112A up to 10(-4) M concentration. The antagonists also failed to bind to rabbit polyclonal anti-angiotensin II antibodies. Direct binding experiments in which solid phase-immobilized angiotensin II and DuP 753 conjugates were incubated with anti-angiotensin II or anti-DuP 753 monoclonal antibodies, did not show any cross-reactivity.(ABSTRACT TRUNCATED AT 250 WORDS)

A temperature-type model for describing the relationship between fungal growth and water activity.

Growth of Penicillium chrysogenum, Aspergillus flavus, Cladosporium cladosporioides and Alternaria alternata at their respective optimum temperatures was studied in Potato Dextrose Agar (PDA) medium at different water activities (a(w)) adjusted with glycerol. The growth rate (mu) was expressed as the increase in colony radius per unit of time. This paper extends the model that showed the relationship between temperature and bacterial growth rate developed by Rosso et al. [J. Theor. Biol. 162 (1993) 447] to describe the influence of a(w) on fungal development. An excellent correlation between the experimental data and the model predictions was obtained, the regression coefficients (r2) were greater than 0.990, with the exception of that for A. flavus (r2 = 0.982). In addition, the use of such a model allows predictions of the cardinal water activities: a(wmin), a(wopt) and a(wmax). The estimation of the minimum water activity (a(wmin)) was in accordance with data literature for all the moulds considered here, but seemed to be slightly underestimated for P. chrysogenum and A. flavus when compared to our experimental values. The estimations of the optimal water activity (a(wopt)) and the optimal growth rate (muopt) were in excellent agreement to the experimental results for the four moulds. Through this example, it is suggested that the same approach for modelling can be used for various microorganisms (e.g. bacteria and moulds), and different environmental parameters (e.g. temperature and water activity).

Comparison of volatile compound production in fruit body and in mycelium of Pleurotus ostreatus identified by submerged and solid-state cultures.

Comparative analyses of the production of volatile compounds by Pleurotus ostreatus JMO.95 fruit body and its corresponding mycelium grown in liquid, on agar surface, and on solid support cultures were carried out by dynamic headspace concentration using gas chromatography/mass spectrometry and gas chromatography sniffing. The aroma produced by fruit body was owing essentially to the presence of octan-3-one and, to a lesser extent, to octan-3-ol. Other compounds, such as oct-1-en-3-ol, oct-1-en, 2-methylbutanol, and alpha-pinene were also present in low concentrations. Comparison of aromatic spectra of the fruit body with that of mycelia obtained under different culture conditions indicated that the main aromatic compounds present in the P. ostreatus fruit body and mycelium were produced in the same proportions on agar surface and on solid support culture, but not under submerged conditions.

[Pollen counts (from Ambrosia and Artemisia) in Lyon-Bron from 1982 to 1985]. / Les comptes polliniques de Lyon-Bron de 1982 à 1985 (dont ambroisies et armoises).

The purpose of this work is to distinguish the broad outlines of the pollen calendar in the Lyons area for the 5th year, using the same method (P. COUR) and the same location--Lyon-Bron weather station. Weekly data is given for 1982, 1983, 1984, 1985 (1986 data was not complete at the time of the conference, October 1986). This work is the fruit of numerical counts integrated into a data processing program which enables pollens tested and not tested in allergology to be identified. In Lyon, we observe 3 pollen seasons: early Spring (TREES), Spring (TREES and GRAMINEAE) and Summer-Autumn (TREES, GRAMINEAE, and COMPOSITAE). During the late the following are present: Artemisia vulgaris (last 10 days of July), RAGWEED (mid-August-1st fortnight of October), Artemisia annua (end September-early October). The particularity of our region is that not only ragweed pollen is collected but also two categories of Mugwort pollen, at different periods.

Influence of the water activity of a solid substrate on the growth rate and sporogenesis of filamentous fungi.

The water activity (a(w)) of substrates has been related to the mycelial growth and the sporogenesis of two molds. In the absence of other limiting factors, optimal a(w) values were determined for growth and sporogenesis as 0.99 and 0.98, respectively, for Trichoderma viride TS and 0.97 and 0.96 for Penicillium roqueforti. In all cases, the accuracy of the optimal value would justify the regulation of this parameter. A model was proposed which establishes a relationship between the mycelial growth and the water activity value of the substrate.

Influence of inoculum preparation on the growth of Penicillium chrysogenum.

AIMS: The influence of the spore preparation on subsequent fungal growth of Penicillium chrysogenum was assessed. METHODS AND RESULTS: The influence of four factors [the nature of the diluting solution (physiological water and physiological water added with Tween-80), the age of the sporulating culture (4, 8 and 12 days), the strain (737, 738 and 740) and the inoculum size (102, 103, 104 and 105 spores ml(-1)] on two responses (i.e. the radial growth rate, mu, and the lag time, lambda) was studied using an experimental screening methodology. CONCLUSIONS: The main conclusion was the strong effect of the inoculum size on lambda. In contrast, the diluting solution had no effect on both the experimental responses. In order to obtain the highest growth rates, it is recommended to use 4-day-old sporulating cultures with an inoculum size of 102 spores ml(-1). SIGNIFICANCE AND IMPACT OF THE STUDY: There is a need for standardizing spore preparation in predictive mycology. The screening methodology is a powerful tool to determine the influence of qualitative and quantitative factors on various biological responses and can be applied widely in microbiology.