Study of the dynamics of the electrode plasma in a high-current magnetically insulated transmission line

A series of experiments was carried out in the S-300 facility (3 MA, 0.15 Θ, 100 ns) to study the behavior of a section of a magnetically insulated transmission line (MITL) at current densities of up to 500 MA/cm² and linear current densities of up to 6 MA/cm (i.e., at parameters close to those expected in a fast Z-pinch fusion reactor projected in Sandia National Laboratories). The surface explosion of the ohmically heated MITL electrode is accompanied by the formation of a plasma layer on its surface. This can deteriorate of the transmission properties of the line because the vacuum gap is short-circuited by the plasma produced. The parameters of the electrode plasma and its effect on the MITL transmission properties were investigated experimentally. Possible consequences of the above effects are evaluated, and MHD simulations of the electrode explosion and the subsequent spread of the plasma layer are performed. It is shown that the time during which an MITL segment preserves its transmission properties conforms to the requirements of the conceptual fusion reactor.     

Synthesis of 4-hydroxyisoleucine by the aldolase-transaminase coupling reaction and basic characterization of the aldolase from Arthrobacter simplex AKU 626

Arthrobacter simplex AKU 626 was found to synthesize 4-hydroxyisoleucine from acetaldehyde, alpha-ketobutyrate, and L-glutamate in the presence of Escherichia coli harboring the branched chain amino acid transaminase gene (ilvE) from E. coli K12 substrain MG1655. By using resting cells of A. simplex AKU 626 and E. coli BL21(DE3)/pET-15b-ilvE, 3.2 mM 4-hydroxyisoleucine was produced from 250 mM acetaldehyde, 75 mM alpha-ketobutyrate, and 100 mM L-glutamate with a molar yield to alpha-ketobutyrate of 4.3% in 50 mM Tris-HCl buffer (pH 7.5) containing 2 mM MnCl(2) x 4H(2)O at 28 degrees C for 2 h. An aldolase that catalyzes the aldol condensation of acetaldehyde and alpha-ketobutyrate was purified from A. simplex AKU 626. Mn(2+) and pyridoxal 5'-monophosphate were effective in stabilizing the enzyme. The native and subunit molecular masses of the purified aldolase were about 180 and 32 kDa respectively. The N-terminal amino acid sequence of the purified enzyme showed no significant homology to known aldolases.     

Cryptic freshwater amoeba species in the bottom sediments of Nivå Bay (Øresund, Baltic Sea)

An aquarium containing a portion of freshly collected brackish-water sediment from Nivå Bay (Øresund, Baltic Sea) was sampled to determine the species of amoebae present and refilled with inorganic salt medium to achieve freshwater salinity. After 2 months incubation, the diversity of amoebae was again studied, and the salinity was restored to the original level. The aquarium was incubated for a further 2 months and the amoeba fauna was studied for the last time. A number of freshwater species appeared in the sample after the first salinity shift, while some marine species disappeared. Most marine species did not re-appear after the salinity in the aquarium was restored, but one marine species not noted previously was recorded. The experiment illustrates the presence of ‘cryptic diversity’ of amoebae in natural habitats and demonstrates that laboratory manipulation of the salinity of a sample prior to inoculation may achieve an increased recovery of species from a brackish-water habitat.     

Mortality Caused by Bath Exposure of Zebrafish (Danio rerio) Larvae to Nervous Necrosis Virus Is Limited to the Fourth Day Postfertilization

Nervous necrosis virus (NNV) is a member of the Betanodavirus genus that causes fatal diseases in over 40 species of fish worldwide. Mortality among NNV-infected fish larvae is almost 100%. In order to elucidate the mechanisms responsible for the susceptibility of fish larvae to NNV, we exposed zebrafish larvae to NNV by bath immersion at 2, 4, 6, and 8 days postfertilization (dpf). Here, we demonstrate that developing zebrafish embryos are resistant to NNV at 2 dpf due to the protection afforded by the egg chorion and, to a lesser extent, by the perivitelline fluid. The zebrafish larvae succumbed to NNV infection during a narrow time window around the 4th dpf, while 6- and 8-day-old larvae were much less sensitive, with mortalities of 24% and 28%, respectively.     

The effect of the coded amino acids on meso- and ectodermal tissue development in organotypic culture

The effect of L-amino acids was investigated in organotypic tissue culture ofmesodermal tissue (spleen, myocardium) and ectodermal tissue (brain cortex) in mature rats. The low hydrophobic amino acids: asparagine, hystidine, serine, lysine, arginine and glutamine acid, induced the proliferation stimulation. The high hydrophobic amino acids had both the apoptose effect (spleen) and no effect at all (myocardium). The proliferation stimulation occurred in the ectodermal tissue under the effect of the high hydrophobic amino acids (asparagines acid, valine, threonine, methionine, leucine, isoleucine), whereas the low hydrophobic amino acids had no effect on the nervous tissue development. The combination of two amino acids one of which stimulated and another one inhibited the explant growth zone (or was not active in myocardium) lead to an increase of the stimulatory effect in meso- and ectodermal tissue. The amino acid modulated properties can be taken in consideration in synthesis of new regulatory peptides.     

Comparative estimation of the EGFP effects on the development of embryos obtained by reciprocal crossing of C57BL/6-Tgn(ACTbEGFP)1Osb/J and C57BL/6 mice

The effect of enhanced green fluorescent protein (EGFP) on the in vitro viability of early embryos of C57BL/6-Tgn(ACTbEGFP)1Osb/J mice has been studied. The number of viable ova in hemizygous females (−/egfp) has been shown to decrease. Irrespective of the EGFP level, it has no deleterious effect on the early development of embryos obtained by reciprocal crossing of hemizygous (−/egfp) and wild-type (−/−) mice.     

DNA or RNA oligonucleotide 2'-hydrazides for chemoselective click-type ligation with carbonyl compounds

An efficient method for the synthesis of DNA or RNA oligonucleotide 2'-hydrazides is described. Fully deprotected oligonucleotides containing a hydrazide group at the 2'-position of a uridine residue were obtained by a novel two-step procedure: periodate cleavage of an oligonucleotide with 1,2-diol group followed by conversion of the aldehyde to hydrazide with an extended linker arm using a homobifunctional reagent succinic dihydrazide and NaBH(3)CN. The resulting oligonucleotide 2'-hydrazides were efficiently conjugated by a click-type reaction at acidic pH to aliphatic or aromatic aldehydes with or without NaBH(3)CN reduction to afford novel 2'-conjugates.     

Biocenotic characteristics of some Yucatan lentic water bodies based on invertebrate remains in sediments

The Yucatan Peninsula is a karstic environment with almost no permanent surface water flows. All freshwater lentic systems here are supported by underground water. We examined sediments, obtained with an Eckman dredge, from 25 different types of water bodies (sinkholes or cenotes, lagoons, and wetlands), to investigate their biocenotic characteristics. All systems showed differences in their zoocenoses, ostracods being the dominant group in most. Cladocera were scarce in the sediments, represented by only eight genera. It can be partially related to the near absence of a littoral zone in cenotes, due to vertical walls, and the lack of submersed vegetation. In spite of their importance, relatively little work has been done on ostracods from this region of the world.     

Dynamics of replication foci in early S phase as visualized by cross-correlation function

To monitor gradual changes in the replication foci distribution during early S phase, different segments of newly synthesized DNA were visualized by immunocytochemical mapping of two consecutively incorporated deoxythymidine analogs in pulse-chase-pulse experiments in HeLa cells. The resulting dual-labeled fluorescence images were evaluated using cross-correlation function (CCF) analysis. General changes of CCF shape due to image deterioration caused by blur, noise, and lateral sampling (pixel size) were also discussed. Using CCF analysis of model images simulating either random initiation of new replication foci, or the firing of new foci in close proximity to completed ones, we were able to ascribe the changes in the early S replication foci distribution to the latter mechanism. In contrast to the data published previously, we monitored the dynamics of all replication foci for up to 3 h. In addition, we showed that the replication foci dynamics is well described by random walk model, so that the average de-localization of individual foci is proportional to square root of the applied chase.