Interakcije nekih plijesni i aflatoksinogenog soja Asspergillus flavus NRRL 3251

The objective of this study was to evaluate biotic interaction between some mould species and active producer of aflatoxin B1 Aspergillus flavus NRRL 3251, co-cultured in yeast-extract sucrose (YES) broth. Twenty-five mould strains of Alternaria spp., Cladosporium spp., Mucor spp., A. flavus and A. niger, used as biocompetitive agents, were isolated from outdoor and indoor airborne fungi, scrapings of mouldy household walls, and from stored and post-harvest maize. Aflatoxin B1 was extracted from mould biomasses with chloroform and detected using the multitoxin TLC method. The results confirm antagonistic interaction between all strains tested. With Alternaria spp. and Cladosporium spp., aflatoxin B1 production decreased 100 %, compared to detection in a single culture of A. flavus NRRL 3251 (Cmean=18.7 µg mL-1). In mixed cultures with Mucor spp., aflatoxin B1 levels dropped to (5.6-9.3) µg mL-1, and the inhibition was from 50 % to 70 %. Four of five aflatoxin non-producing strains of A. flavus interfered with aflatoxin production in mixed culture, and reduced AFB1 productivity by 100 %. One strain showed a lower efficacy in inhibiting AFB1 production (80 %) with a detectable amount of AFB1 3.7 µg mL-1 when compared to control. A decrease in toxin production was also observed in dual cultivation with A. niger strains. It resulted in 100 % reduction in three strains), 90 % reduction in one strain (Cmean=1.9 µg mL-1) and 80 % reduction in one strain (Cmean=3.7 µg mL-1) inhibition.Cilj rada bio je procijeniti biotske interakcije između sojeva različitih vrsta plijesni i kontrolnog soja Aspergillus flavus NRRL 3251, producenta aflatoksina B1 (AFB1). Inhibitorno djelovanje u miješanim kulturama na tvorbu AFB1 ispitano je na dvadeset pet sojeva Alternaria, Cladosporium, Mucor i Aspergillus vrsta izoliranih iz zraka, strugotina pljesnivih zidova te uskladištenog i prezimljenog kukuruza. Biosinteze su provedene u tekućoj hranjivoj podlozi s kvaščevim ekstraktom (YESbujon). Ekstrakcije AFB1 iz biomase izvršene su multitoksinskom metodom tankoslojne kromatografije. Rezultati biotskih interakcija pokazali su antagonistički odnos svih testiranih sojeva. Alternaria i Cladosporium vrste simultano inokulirane sporama A. flavus NRRL 3251 inhibirale su tvorbu AFB1 100 % u odnosu na dokazani toksin u kontrolnoj biosintezi (konc. 18,7 µg mL-1). U miješanim kulturama vrstama roda Mucor dokazane su padajuće koncentracije AFB1 (9,3 µg mL-1, 7,5 µg mL-1 i 5,6 µg mL-1), odnosno inhibicija tvorbe toksina 50 % do 70 %. Atoksinogeni sojevi A. flavus inhibirali su tvorbu AFB1 80 % (1 soj, konc. 3,7 µg mL-1) i 100 % (4 soja). Antagonističko djelovanje prema toksinogenom soju, smanjujući tvorbu AFB1 u rasponu 80 % do 100 % (konc. 1,9 µg mL-1 i 3,7 µg mL-1), dokazano je u uzgojnim biosintezama s A. niger

The female menstrual cycle does not influence testosterone concentrations in male partners

<p>Abstract</p> <p>Background</p> <p>The time of ovulation has since long been believed to be concealed to male heterosexual partners. Recent studies have, however, called for revision of this notion. For example, male testosterone concentrations have been shown to increase in response to olfactory ovulation cues, which could be biologically relevant by increasing sexual drive and aggressiveness. However, this phenomenon has not previously been investigated in real-life human settings. We therefore thought it of interest to test the hypothesis that males' salivary testosterone concentrations are influenced by phases of their female partners' menstrual cycle; expecting a testosterone peak at ovulation.</p> <p>Methods</p> <p>Thirty young, healthy, heterosexual couples were recruited. During the course of 30-40 days, the women registered menses and ovulation, while the men registered sexual activity, physical exercise, alcohol intake and illness (confounders), and obtained daily saliva samples for testosterone measurements. All data, including the registered confounders, were subjected to multiple regression analysis.</p> <p>Results</p> <p>In contrast to the hypothesis, the ovulation did not affect the testosterone levels, and the resulting testosterone profile during the menstrual cycle was on the average flat. The specific main hypothesis, that male testosterone levels on the day of ovulation would be higher than day 4 of the cycle, was clearly contradicted by a type II error(β)-analysis (< 14.3% difference in normalized testosterone concentration; β = 0.05).</p> <p>Conclusions</p> <p>Even though an ovulation-related salivary testosterone peak was observed in individual cases, no significant effect was found on a group level.</p