Relationship between plasma volume reduction and plasma electrolyte changes after prolonged bicycle exercise, passive heating and diuretic dehydration

Plasma volume was decreased by prolonged bicycle exercise, by passive heating in warm water, by sauna dehydration, and by diuretically induced dehydration in eleven well trained subjects. Blood samples from an arm vein were taken before and after this pre-treatment, as well as after a subsequent standard exercise test (SET) on a bicycle ergometer (50%, 70% and 105% of max VO2; the SET with no pre-treatment was used as a control condition. The changes in plasma concentration of Na+, K+ and Cl- were not proportional to the calculated plasma volume changes. The Na+ and Cl- concentrations always increased in the plasma, while plasma potassium concentration was increased after prolonged exercise, but decreased after the other types of dehydrations. The standard exercise test produced a pronounced fall in total calculated plasma potassium and in K+ concentration measured 3-5 min after exercise in all types of experiments. In the standard exercise test the calculated water loss from the plasma volume was relatively large. It amounted to about 2/3 of the total water loss in the standard exercise test and was independent of the pre-treatments.     

The effect of nucleosides on the induced synthesis of β-galactosidase in non-growing cells ofEscherichia coli

The induced synthesis of β-galactosidase in non-growing cells ofEscherichia coli starving for exogenous carbon and nitrogen sources was stimulated markedly by the addition of any of four nucleosides tested: adenosine, guanosine, cytidine, and uridine. Adenosine was used as a representative of this group of compounds in most experiments. The decrease of ability of the cells to synthesize β-galactosidase, resulting from a prolonged starvation for exogenous carbon and nitrogen, was removed by adenosine. This compound also considerably reduced the inhibitory effect of metabolic poisons on the induced synthesis of β-galactosidase. The blockade of induced β-galactosidase synthesis evoked in aerobically grown cells by anaerobic starvation for exogenous sources of carbon and nitrogen was also significantly reduced by adenosine. The weak transient catabolic repression of induced synthesis of β-galactosidase evoked by glucose in non-growing cells ofEscherichia coli deprived of exogenous carbon and nitrogen sources was prevented by adenosine. The total repression caused by higher glucose concentrations was not influenced by this compound. The results are discussed from the point of view of the role of the energy state ofEscherichia coli cells in the regulation of β-galactosidase synthesis.     

Rapid reorganization of microtubular cytoskeleton accompanies early changes in nuclear ploidy and chromatin structure in postmitotic cells of barley leaves infected with powdery mildew

Summary Post-mitotic epidermal cells of barley leaves were found to contain, in addition to cortical microtubules (CMTs), distinct arrays of endoplasmic microtubules (EMTs). These encircle nuclei and continuously merge into the CMT arrays that underly the plasmalemma. Detailed three-dimensional reconstruction of both types of MTs during fungal infection showed that profound and very rapid MT rearrangements occurred especially in the case of incompatible (resistant) barley-powdery mildew genotype combination. The most early MT responses, followed by their subsequent complete disintegration, were recorded around nuclei. These events might be relevant for the induction of such nuclear processes as onset of DNA synthesis and nuclear chromatin condensation. Observed pattern of early infection events, as well as less prominent responses in the case of compatible (susceptible) barley-powdery mildew genotype combination, both findings suggest that rapid reorganization of the MT cytoskeleton could be involved in recognition of the fungus by host cells and in the initiation of resistance responses in barley leaves. We hypothesize that the integrity and dynamics of the MT cytoskeleton, especially of its perinuclear part, might participate in control mechanisms involved in activation of resistance genes.Abbreviations CMTs cortical microtubules - EMTs endoplasmic microtubules - MT microtubules - PI propidium iodide - SC sensitive combination - RC resistant combination     

Conceptual design of integrated microfluidic system for magnetic cell separation,electroporation, and transfection

For the purposes of a successful ex vivo gene therapy we have proposed and analyzed a new concept of an integrated microfluidic system for combined magnetic cell separation, electroporation, and magnetofection. For the analysis of magnetic and electric field distribution (given by Maxwell equations) as well as dynamics of magnetically labeled cell and transfection complex, we have used finite element method directly interfaced to the Matlab routine solving Newton dynamical equations of motion. Microfluidic chamber has been modeled as a channel with height and length 1 mm and 1 cm, respectively. Bottom electrode consisted of 100 parallel ferromagnetic straps and the upper electrode was plate of diamagnetic copper. From the dynamics of magnetic particle motion we have found that the characteristic time-scales for the motion of cells (mean capture time ～ 4 s) and gene complexes (mean capture time ～ 3 min), when permanent magnets are used, are in the range suitable for efficient cell separation and gene delivery. The largest electric field intensity (～10 kV/m) was observed at the edges of the microelectrodes, in the close proximity of magnetically separated cells, which is optimal for subsequent cell electroporation.     

The effects of using lactic acid bacteria inoculants in maize silage on the formation of biogenic amines

Silages from five ripened varieties of silage maize with dry matter contents ranging between 275 and 410 g/kg were prepared in five laboratory experiments. Whole-plant maize was fermented at 22°C and silages were then stored at the same temperature for 4 months. Spontaneously fermented silages were prepared as control variants and compared with silages inoculated with commercial strains of Lactobacillus plantarum, Lactobacillus buchneri and a mixed preparation Microsil containing L. plantarum, Lactobacillus casei, Enterococcus faecium and Pediococcus pentosaceus. The starter cultures were applied at doses 5·10⁵ and 5·10⁶ CFU/g of chopped maize. Seven biogenic amines and polyamines were extracted from silages with perchloric acid and determined as N-benzamides by micellar electrokinetic capillary chromatography. Common chemical criteria of silage quality were also determined. All three inoculants, mainly at the higher dose, decreased significantly contents of tyramine, putrescine and cadaverine, three undesirable amines occurring at the highest levels. L. plantarum was the most effective. Contents of histamine and tryptamine were low in all experimental silages. Also relatively low were levels of polyamines spermidine and mainly of spermine.     

The dependence of Fluorescein-PE fluorescence intensity on lipid bilayer state. Evaluating the interaction between the probe and lipid molecules

The degree of dependence of a lipid bilayer's surface properties on its conformational state is still an unresolved question. Surface properties are functions of molecular organization in the complex interfacial region. In the past, they were frequently measured using fluorescence spectroscopy. Since a fluorescent probe provides information on its local environment, there is a need to estimate the effect caused by the probe itself. In this paper, we address this question by calculating how lipid head-group orientation effects the fluorescence intensity of Fluorescein-PE (a probe that is sensitive to surface potential). In the theoretical model assumed the lipid bilayer state and the interactions between the charged fluorescent probe and the surrounding lipid molecules was evaluated. The results of this theoretical analysis were compared with experimentally obtained data. A lipid bilayer formed from DPPC was chosen as the experimental system, since it exhibits all the major conformational states within a narrow temperature range of 30 degrees C-45 degrees C. Fluorescein-PE fluorescence intensity depends on local pH, which in turn is sensitive to local electrostatic potential in the probe's vicinity. This local electrostatic potential is generated by lipid head-group dipole orientation. We have shown that the effect of the probe on lipid bilayer properties is limited when the lipid bilayer is in the gel phase, whereas it is more pronounced when the membrane is liquid-crystalline. This implies that Fluorescein-PE is a good reporter of local electrostatic fields when the lipid bilayer is in the gel phase, and is a poor reporter when the membrane is in the liquid-crystalline state.