DNA-based Electrochemical Biosensor for Imipramine Detection

AbstractThe main aim of our research was development of a novel selective electrochemical method for imipramine (IMI) detection. This substance enable to interact with DNA and it is also electrochemically active. Two major groups of electrochemical sensors were used in the experiments with bare gold electrodes and DNA-modified. Determination of imipramine by means of non-modified electrodes was not selective and limit of detection was shifted towards higher concentrations of IMI. The sensitivity of mixed and mono-GC sequence DNA-modified electrodes was much higher than for the bare gold ones

Differential Levels of Stress Proteins (HSPs) in Male and Female Daphnia magna in Response to Thermal Stress: A Consequence of Sex-Related Behavioral Differences?

In two independent experiments, we compared: (1) water depth selection (and accompanying temperature selection) by male and female Daphnia magna under different kinds of environmental stress, including the presence of filamentous cyanobacteria, the risk of predation from fish, and the presence of toxic compounds; and (2) sex-dependent production of heat shock proteins (HSP60, 70, and 90) in response to a sudden change in temperature. Male D. magna selected deep water strata, which offer a relatively stable environment, and thereby avoided the threat of predation and the presence of toxic compounds in surface waters. Correlated with this behavior, males reduce their molecular defenses against stress, such as the production of heat shock proteins (HSPs), and do not maintain the physiological machinery that triggers an increase in HSP levels in response to stress. In contrast, female D. magna actively select habitats that offer optimal conditions for growth and production of offspring. Consequently, females are exposed to variable environmental conditions that may be associated with increased stress. To permit survival in these different habitats, D. magna females require molecular mechanisms to protect their cells from rapid changes in stress levels. Thus, they maintain high constitutive levels of the heat shock proteins from HSP 60, 70, and 90 families, and they have the potential to further enhance the production of the majority of these proteins under stress conditions. The results of this study indicate that the separate habitats selected by male and female D. magna result in different patterns of HSP production, leading us to hypothesize that that male and female Daphnia magna adopt different strategies to maximize the fitness of the species

Acute aquatic toxicity of arsenic-based chemical warfare agents to Daphnia magna

Sea dumping of chemical warfare (CW) took place worldwide during the 20th century. Submerged CW included metal bombs and casings that have been exposed for 50-100 years of corrosion and are now known to be leaking. Therefore, the arsenic-based chemical warfare agents (CWAs), pose a potential threat to the marine ecosystems. The aim of this research was to support a need for real-data measurements for accurate risk assessments and categorization of threats originating from submerged CWAs. This has been achieved by providing a broad insight into arsenic-based CWAs acute toxicity in aquatic ecosystems. Standard tests were performed to provide a solid foundation for acute aquatic toxicity threshold estimations of CWA: Lewisite, Adamsite, Clark I, phenyldichloroarsine (PDCA), CWA-related compounds: TPA, arsenic trichloride and four arsenic-based CWA degradation products. Despite their low solubility, during the 48 h exposure, all CWA caused highly negative effects on Daphnia magna. PDCA was very toxic with 48 h D. magna LC50 at 0.36 mu g x L-1- and Lewisite with EC50 at 3.2 mu g x L-1 . Concentrations at which no immobilization effects were observed were slightly above the analytical Limits of Detection (LOD) and Quantification (LOQ). More water-soluble CWA degradation products showed no effects at concentrations up to 100 mg x L-1.Peer reviewe

Alarm signals in Daphnia?

Daphnia magna can respond to chemical cues from freshly crushed conspecifics with various behavioural reactions. A shift in vertical distribution towards the bottom, the formation of aggregations and direct escape responses can all be induced by water-borne signals released from crushed Daphnia. The pattern and strength of the first two behavioural responses (i.e. the persistent tendency to occupy deeper strata in the experimental columns and to stay within patches) indicate that Daphnia perceive the signal from crushed conspecifics as nonspecific information, not necessarily associated with any particular kind of danger from either vertebrate or invertebrate predators. The adaptive value and possible costs associated with performing these two behavioural reactions are discussed. The adaptive value of the induced escape response was directly tested: Daphnia which had experienced the presence of a cue from crushed conspecifics avoided attacks by common bream more efficiently than naive Daphnia. The recognition of the signal originating from crushed conspecifics can be especially adaptive in encounters with unfamiliar predators and with predators that undergo ontogenetic shifts in their diet. Under natural conditions, the combination of such a signal with a predator cue can, very reliably, advertise the local scale of the predatory impact

Diel vertical migration in zooplankton: fixed or inducible behavior?

Inducible migratory behavior can be favored over fixed behavioral patterns under the changing predation regime in a lake when the risk of a contact with a predator is highly unpredictable. Since the strength of behavioral response can be adjusted to predation intensity, and behavioral defensive traits can be reversible along the predator recession, behavioral plasticity is less costly than constant maintenance of fixed defensive traits. An inducible migratory behavior can be favored if the time necessary to complete a phenotypic change is brief enough as related to the time scale of environmental change, fitness costs of producing plastic responses and of displaying such a response do not exceed the gained benefits, and reliable cues which announce the approaching danger are available to individual prey. The sensitivity to different environmental cues depends on lag time between the cue and anticipated danger in relation to the time required to display a defensive response. Whereas complicated and time consuming defenses which require deep morphological and physiological changes should be rather triggered by environmental predictors of predation onsets, unpredictable onset of predation, usually not announced by any of environmental cues, should be recognized directly, via the stimulus coming from a predator itself

Cues from injured Daphnia and from cyclopoids feeding on Daphnia can modify life histories of conspecifics

Size, age and number of offspring at the first and subsequent two reproductions were compared in Daphnia treated with cues from invertebrate predators (adult Cyclopoida fed Daphnia) and from crushed conspecifics. Daphnia in the presence of invertebrate predators had earlier maturation, greater size at first and subsequent reproductions and a larger number of offspring than control animals, while the opposite (later maturation and smaller size at subsequent reproductions) happened when Daphnia were treated with homogenate from crushed conspecific

Summer diapause in Daphnia as a reaction to the presence of fish

A chemical signal, released by a fish predator under summer-like high water temperature and long-day photoperiod, caused the formation of resting eggs in a clone of Daphnia magna. No ephippial females were recorded and no ephippia were released in the control treatment during 45 days of the experiment. When exposed to fish water, the fraction of ephippial females reached a maximum of 3.7%,a value comparable to that registered in summer in the Grosser Binnensee (Northern Germany), a hypertrophic lake inhabited by fish, which was the source lake for our experimental clone. The number of ephippia released within 45 days was on average 34 +/- 22. Ephippia formation could not result from the between-treatment differences in population density, and related patterns of food depletion, since no substantial difference between control and fish treatment was observed. Instead, specific information on the presence of a predator provided a cue which induced the formation of resting eggs in Daphnia. Under heavy predation and very low survival probability of parthenogenetic females, ephippia formation in summer can be adaptive, i.e. higher fitness can be achieved through survival in the diapausing state than through the immediate reproductive gain via parthenogenesi