The influence of viscous hydrodynamics on the fish lateral-line system

Fish exhibit many behaviors that involve sensing water flows with their lateral-line system. In many situations, viscosity affects how the flow interacts with the body of the fish and the neuromasts of the lateral line. Here we discuss how viscosity influences the stimulus to the fish lateral-line system. The movement of a fish's body creates flows that can interfere with the detection of external signals, but these flows can also serve as a source of information about nearby obstacles and the fish's own hydrodynamic performance. The viscous boundary layer on the surface of the skin alters external signals by attenuating the low-frequency components of stimuli. The stimulus to each neuromast depends on the interaction of the fluid surrounding the neuromast and the structural properties of that neuromast, including the number of mechanosensory hair cells it contains. A consideration of the influences of viscosity on flow, at both the whole-body and receptor levels, offers the promise of a more comprehensive understanding of the signals involved in behaviors mediated by the lateral-line system.     

The influence of transposable elements on genome size

Genome size displays an important variability between species without any direct link to complexity. This paradox, so-called "C value paradox", now becomes understood as resulting from a differential abundance of numerous repeated sequences, among which transposable elements. Genomes indeed contain a important proportion of such sequences (95 % of DNA in man, about 45 % of which are transposable elements, up to 99 % of DNA in some plants). While most investigations until now are focalized on genes or coding sequences, which thus represent a small part of the genome, more attention now is dedicated on so-called non-coding sequences. Transposable elements, which are capable of moving around in genomes, inducing mutations, chromosomal rearrangements, gene expression regulations, thus appear as major actors in diversity and evolution. We present here a brief review of the most prominent acquisition in this expanding domain.     

The influence of transposable elements on animal colouration

Transposable elements (TEs) are mobile genetic sequences present within host genomes. TEs can contribute to the evolution of host traits, since transposition is mutagenic and TEs often contain host regulatory and protein coding sequences. We review cases where TEs influence animal colouration, reporting major patterns and outstanding questions. TE-induced colouration phenotypes typically arise via introduction of novel regulatory sequences and splice sites, affecting pigment cell development or pigment synthesis. We discuss if particular TE types may be more frequently involved in the evolution of colour variation in animals, given that examples involving long terminal repeat (LTR) elements appear to dominate. Currently, examples of TE-induced colouration phenotypes in animals mainly concern model and domesticated insect and mammal species. However, several influential recent examples, coupled with increases in genome sequencing, suggest cases reported from wild species will increase considerably.     

The effect of hypothyroidism on myocardial contractility and sarcoplasmic reticulum function in rats

Changes in contractility and ATPase activity of SR from hearts of hypothyroid rats were investigated. Rats were made hypothyroid by daily injection of 100 mg/kg methimazole for 14 days. In methimazole-treated rats, the contractile force, the maximum velocity of tension development and relaxation were significantly decreased, however, the time to peak tension remained unchanged. Function of SR was studied by determining of Ca2+-activated ATPase activity, which was significantly decreased after methimazole treatment. This diminution may be partially responsible for a slower reduction of the free Ca2+ in the surroundings of contractile proteins and thus decrease the rate of relaxation.     

Effects of magnesium depletion on myocardial high-energy phosphates and contractility

The effect of prolonged magnesium depletion on contractility, phosphorylating activity, and organic phosphates of spontaneously beating isolated rat atria was studied. Rats were fed a Mg-deficient diet for 8 weeks, during which serum Mg fell from 1.85 +/- 0.02 to 0.52 +/- 0.10 mg/dl. Atrial contractile activity was measured for 1 hr and at the end of this period tissue samples were taken for the determination of the phosphorylated intermediates. Mg depletion was associated with (a) reduced intracellular inorganic phosphorus and adenine nucleotides; (b) elevated creatine phosphate; (c) reduction in contractile force (CF) with no change in atrial beat rate (BR). There were no significant differences in the activities of creatine phosphokinase and adenylate kinase in control and Mg-depleted rat atrial homogenates determined in the presence of 5 mM MgCl2. Addition of various concentrations of MgCl2 to the medium resulted in an immediate reduction in both CF and BR of normal and Mg-depleted rat atria. Intraperitoneal administration of MgCl2 to Mg-depleted rats resulted in complete recovery of CF of isolated atria. This improvement in CF occurred without changes in the levels of inorganic phosphate and adenine nucleotides. The reduced intracellular level of high-energy phosphate or inorganic phosphate cannot therefore be responsible for the impaired contractility seen in Mg-depleted heart muscle. On the other hand, the fact that the creatine phosphate levels were higher in magnesium depletion suggests that myofibrillar utilization of creatine phosphate is more impaired than production, analogous to phenomena seen in postanoxic recovery.     

The influence of macro and trace elements on sperm quality

The aim of this study was to examine the association between combined concentrations of macro and trace elements and markers of oxidative stress and antioxidative defense system function together with selected cytokine levels. Based on the combined medians of the seminal plasma levels of calcium, magnesium, zinc, copper, iron, and selenium, the study subjects (88 fertile male volunteers) were divided into the following two subgroups: the Me-L group (low level of metals) and the Me-H group (high level of metals). There was a tendency toward reduced motility in the Me-H group compared to that in the Me-L group. The total protein, albumin, and total oxidation status (TOS) levels were significantly higher in the Me-H group than in the Me-L group. The total superoxide dismutase (SOD), Mn-SOD, and CuZn-SOD, activity in spermatozoa were significantly lower in the Me-H group than in the Me-L group. In seminal plasma, the Mn-SOD activity was significantly higher in the Me-H group, whereas the CuZn-SOD activity was significantly lower. Additionally, the activity levels of glutathione peroxidase (GPx) and glutathione-S-transferase (GST) were lower in the Me-H group. The medians of IL-1β, IL-10, and IL-12 were significantly higher in the Me-H group than in the Me-L group, whereas the medians of IL-2, IL-5, and IL-13 were significantly lower. Higher levels of macro and trace elements in the seminal plasma of fertile males may be associated with decreased motility. Higher levels of the examined metals are associated with elevated oxidative stress accompanied by decreased activities of some of the antioxidant enzymes and increased pro-inflammatory cytokine levels.     

Effect of calmodulin inhibitors on rat and guinea pig myocardial contractility

The effects of phenothiazine drugs with different affinities for calmodulin (trifluoperazine, frenolone, majeptile and aminazine) on the contractility of rat and guinea pig papillary muscles were studied. The phenothiazine-induced changes in the contraction-relaxation parameters were shown to correlate with the degree of calmodulin inhibition. These parameters are relaxation-onset index, relaxation index and terminal relaxation index in rats, and relaxation index and maximal developed tension in guinea pigs. An essential role of calmodulin in myocardium relaxation in both animal species is postulated.