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The present study aimed to evaluate the dependence of growth dynamics of toxigenic B. cereus on rice type, inoculum type, storage time, and temperature using appropriate mathematical models. Samples of cooked white (milled) and brown (husked) rice inoculated with vegetative cell/spore suspension of B. cereus were stored for 48 h at 4 °C (correct storage) and 24 °C (inappropriate storage method). No growth of B. cereus was observed during 48 hours of storage at 4 °C and was characterised by a linear model. To assess the growth of B. cereus in the cooked rice stored at 24 °C, the Baranyi-Roberts, Gompertz and Buchanan mathematical models were used. The Gompertz model characterized the growth of B. cereus best. The type of rice and the type of inoculum did not have a significant effect on the bacterial growth. After 48 h of storage at 24°C, the B. cereus counts were in the range of 8-9 log cfu.g-1, critical value of 5 log cfu.g-1 was reached in less than 10 hours of storage. The study results indicate that cooked rice stored at 24 °C quickly becomes a health risk for consumers due to the rapid multiplication of B. cereus within a few hours. In conclusion, it is crucial to cool cooked rice immediately to 4 °C if it is not to be consumed right after cooking. [ABSTRACT FROM AUTHOR]

In the last two decades, rapid range expansions of the invasive Ponto-Caspian round goby (Neogobius melanostomus) have been reported from many large waterbodies in Europe and North America. A high invasion potential of this species has been reported through its opportunistic life-history traits and high phenotypic plasticity. Nevertheless, it appears that unlike many other invasive fish species, N. melanostomus has not been able to colonize small and mid-size tributaries of large rivers (streams of order higher than two or three). Given that the invasion history of N. melanostomus in Europe is still rather short, and its invasion potential so high, its future possible expansion represents a big question with important ecological, conservation and management implications. One of the ways to answer this question is to identify the key environmental parameters important for further expansion of N. melanostomus, and to compare these with other successful invaders with longer histories, e.g. topmouth gudgeon (Pseudorasbora parva) and pumpkinseed (Lepomis gibbosus). In this study, basic environmental, physicochemical and chemical parameters, biological elements and human disturbances in all types of streams in Slovakia were analysed in order to identify the key factors that discriminate habitats where the three invasive species were present relative to those where they were not. Random Forest Analysis was used to predict and assess the relationship among the large number of potential predictor variables and a dependent variable. This method is useful especially when large numbers of correlated predictors are evaluated and both quantitative and qualitative predictors are involved. The main aim of this study was to estimate potential for further spread of the three invasive species, with an emphasis on the possibility of further expansion of N. melanostomus into small and mid-size tributaries of large rivers. The habitat parameters that characterize current distribution limits of N. melanostomus were found to be the wetted width, slope, pH, temperature and conductivity. The species was found to prefer wider wetted width and shallower slope, higher oxygen saturation and slightly alkaline pH. Nevertheless, the altitude (often considered a surrogate of several habitat parameters) limits current distribution of N. melanostomus both in Slovakia and other regions of Europe. Thus, in contrast to other successful invaders (L. gibbosus and P. parva) the analysis of key factors regulating current distributions of N. melanostomus suggests that its future spread into small and mid-size tributaries of large rivers is unlikely. [ABSTRACT FROM AUTHOR]

The cyanobacterial species Planktothrix rubescens is known to preferably inhabit deep, stratified, oligo- to mesotrophic lakes. It is also known for the production of diverse bioactive peptides, including the hepatotoxic microcystins. A number of studies showed that P. rubescens populations generally consist of multiple distinct genotypes or chemotypes, respectively. In the present study, variability of chemotype diversity was analysed. Filaments of P. rubescens were isolated from water samples originating from 10 European lakes and analysed by MALDI-TOF mass spectrometry. In most of the analysed filaments multiple peptides belonging to multiple peptide classes could be detected. A resulting data matrix of 964 filaments and 37 individual peptides was subjected to correspondence analysis and K-means clustering. From the latter analysis the distribution of chemotypes among the lakes was established and diversity estimated by computing Shannon-Indices. Diversity varied strongly among lakes with the lowest diversity found in non-alpine lakes. Further, chemotype diversity was strongly correlated to the maximum depth of the sampled lakes in alpine and non-alpine lakes. The possible influence of both factors, geographic isolation and water column depth, on the observed patterns of chemotype diversity of P. rubescens populations is discussed. [ABSTRACT FROM AUTHOR]

The aim of this article was to evaluate the amount of salt dosed in various proportions into minced pork and beef. Determination of salt was conducted by the atomic absorption spectrometry (AAS) method and, for comparison, by the near infrared spectroscopy (NIR) method. The meat (beef neck and pork topside) was ground through a plate with a hole size of 8 mm. Salt doses were from 0 to 2.0%, at intervals of 0.2%. Each sort of meat was divided into two parts of 350 g: 1) with initial grinding (coarse grinding), and 2) with subsequent grinding through a plate with a hole size of 3 mm (fine grinding). The salt content in fresh pork meat (0% salt) ranged between 0.13 and 0.16%, whereas the content in beef ranged from 0.14 to 0.19% (as analysed by the AAS method). The proportion of added salt had a statistically significant effect on the salt content in meat. No significant differences were found between coarse and fine grinding and between pork and beef meat. The predicted natural salt content in meat was 0.15 and 0.19% for pork, and 0.20 and 0.21% for beef. The proportion of analysed salt was then determined as 0.99-1.06 times the dosed salt. The authors do not recommend the use of the NIR method, which provides reliable results for the main chemical components of meat, i.e. protein and fat, for the determination of the proportions of salt in meat. [ABSTRACT FROM AUTHOR]

In this study, selected biochemical markers - cytochrome P450 (CYP 450), ethoxyresorufin-O-deethylase (EROD), glutathione S-transferase (GST) and glutathione (GSH) - were measured in chub (Leuciscus cephalus L.) liver samples obtained from three locations on the Vltava river (Podolí, Podbaba and Vranany) and from a control location nmicals commonly known as their inducers. These include polychlorinated biphenyls, hexachlorobenzene and octachlorostyrene measured in chub muscle and polyaromatic hydrocarbons measured in bear Vodnany. The levels of selected biomarkers should correlate with the concentration of cheottom sediments obtained from the same locations. The highest EROD activity (median 101.37 pmol·min-1·mg-1 protein), GST activity (median 42.82 nmol·min-1·mg-1 protein), and GSH concentration (median 8.01 nmol·mg-1 protein) were found in fish liver from the Podbaba location. There were no significant differences in CYP P450 level or EROD activity among the different locations. In Podbaba, GST activity (P < 0.01) and GSH concentrations (P < 0.001) were significantly higher than in the control location. The results of these analyses were correlated and a significant correlation was found between biochemical markers and their inducers. The results show that the use of biochemical markers in water quality assessment is a convenient method that can supplement classical chemical monitoring. [ABSTRACT FROM AUTHOR]

The aims of the study were to determine total mercury concentrations in "rainbow trout Oncorhynchus mykiss (Walbaum)" at their embryo-larval and juvenile stages and to assess mercury concentration dynamics in individual tissues. Samples of rainbow trout were collected at two-month intervals over a period of 18 months (one stock production cycle) at the Velká Losenice trout farm. Feedstuff samples were collected at the same time and analyzed for mercury concentrations. Tissue mercury concentrations were determined in muscle, liver, and kidneys. Analyses were performed using the AMA 254 atomic absorption spectrophotometer. The lowest mercury concentration was found in 14-day-old embryos (hard roe), and the highest concentrations in muscle tissue, liver, and kidneys at the end of monitoring, that is, in rainbow trout aged 18 months. The amount of mercury in feedstuffs showed an increasing trend and ranged between 0.0126 and 0.0859 mg kg(-1). A significant effect (P < 0.001) of mercury intake on mercury concentrations in muscle tissue, liver, and kidneys was demonstrated. Muscle mercury concentrations in 18-month-old market-ready rainbow trout of 0.128 ± 0.048 mg kg(-1) met the criteria for fish meat hygiene.