Marked Strain Research Articles

Calcium affects the competitiveness of acid-sensitive and acid-tolerant strains of Bradyrhizobium japonicum in nodulating and fixing nitrogen with two soybean cultivars in acid soil

A glasshouse experiment studied the role of calcium and pH on competitiveness of acid-sensitive and acid-tolerant Bradyrhizobium japonicum strains with similar N 2-fixation effectiveness in nodulating two soybean ( Glycine max L. Merr) cultivars selected for tolerance of aluminium (PI416937) or for manganese (Manta). Liming provides calcium (Ca) as well as increasing soil pH. Thus the effect of Ca and pH of soil are difficult to separate. We examined the effects of Ca per se by comparing the response to gypsum and lime amendment on the competitiveness of acid-tolerant and acid-sensitive strains in nodulating soybean in an acid soil. Acid soil was treated with either CaSO 4 or CaCO 3 and incubated for 2 weeks before sowing soybean seed. Two acid-sensitive and two acid-tolerant B. japonicum strains were mixed with each other (one acid-sensitive plus one acid-tolerant) and were inoculated onto soybean seeds at the rate of 10 6cfu seed −1. Soil pH, as amended by lime addition, had more effect on nodulation than Ca addition in the form of gypsum. The response was affected by cultivar and strain in a complicated fashion with a marked strain × cultivar interaction. One acid-tolerant strain formed most nodules with both cultivars in the unamended soil of pH 4.36 in competition with one acid-sensitive strain. The same acid-tolerant strain was not competitive against the second acid-sensitive strain with Manta but was with PI416937. The second acid-tolerant strain was not competitive with either acid-sensitive strain in unamended and gypsum treated soils. It was only competitive with PI416937 in limed soil, a rather surprising result. Inoculation of this soil with no native soybean nodulating strains, increased shoot weight, %N, N uptake. N 2-fixation was greatly increased by inoculation and lime addition, and to a lesser extent by gypsum addition for Manta. This experiment indicates that addition of Ca per se as gypsum to an acid soil has little effect on symbiotic performance, but changing pH by liming has a major effect, that both soybean cultivar and B. japonicum strain influence the competitiveness of strains in acid soil and that acid-tolerance does not necessarily increase a strain's competitiveness.

Preparation of fluorescent labeled nodule bacteria strains of wild legumes for their detection in vivo and in vitro

A series of expression vectors containing genes of fluorescent proteins TurboGFP and TurboRFP under the phage T5 constitutive promoter regulation, intended for lifetime marking of nodule bacteria is created: a series of vectors based on a broad-host-range replicon BBRI, for marking strains with an expression of reporter gene from a transformed plasmid and a series of vectors based on a plasmid pRL765gfp for marking strains by introduction genes of fluorescent proteins in a bacterial chromosome. It was shown that transformation is the most preferable method of constructions transfer in nodule bacteria cells, as in the presence of mob locus in the vectors necessary for conjugation, exists the possibility of occasional plasmid mobilization and its transition from marked strain cells in other soil bacteria. With application of the created vector constructions we obtained fluorescent tagged strains of Rhizobium sp., Mesorhizobium sp., Ensifer (Sinorhizobium) sp., Bradyrhizobium sp., Phyllobacterium sp., Agrobacterium sp. Also their suitability for experiments in vivo and in vitro is shown.

Hydroxyurea Enhances Post-Fusion Hyphal Extension During Sexual Development in C. neoformans var. grubii

Mating and sexual development in C. neoformans var. grubii strains of the H99 background is often less robust than that laboratory generated isogenic C. neoformans var. neoformans strains in the JEC21 background. In Candida albicans and Saccharomyces serevisiae, slowing of DNA synthesis and engagement of the replication stress response, such as that caused by treatment with hydroxyurea (HU), induces filamentation and pseudohyphal growth, respectively. In this study, we investigated the effect of HU treatment on C. neoformans var. grubii morphogenesis. Treatment with HU did not induce filamentation of yeast cells either in liquid culture or on solid YPD or V8 agar. In the presence of the opposite mating partner, we observed early emergence of hyphae in the presence of HU. Semi-quantitative analysis of fusion using marked strains demonstrated that no significant enhancement of fusion in the presence of HU. Transfer of fusion colonies from crosses performed in the absence of HU to V8 + HU revealed enhanced hyphal growth in the presence of HU. Analysis of expression of the target of HU, ribonucleotide reductase, revealed that a phylogenetically divergent catalytic subunit is replication stress responsive in C. neoformans. These results suggest that induction of replication stress promotes post-fusion hyphal growth of C. neoformans var. grubii strains in the H99 background.

Different susceptibility to 1-methyl-4-phenylpyridium (MPP+)-induced nigro-striatal dopaminergic cell loss between C57BL/6 and BALB/c mice is not related to the difference of monoamine oxidase-B (MAO-B)

Subcutaneous and intraperitoneal administrations of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) induce selective dopaminergic (DA-ergic) neuronal death in many animal species. After passing through the blood-brain barrier (BBB), MPTP is converted to 1-methy-4-phenylpiridinium (MPP(+)) by astrocytic monoamine oxidase-B (MAO-B). MPP(+) then induces the dopaminergic neuronal death. In mice, marked strain differences in the susceptibility to MPTP-injection have been reported. To clarify which factor(s) cause the strain differences, MPTP or MPP(+) was intracerebroventricularly (icv) injected into adult C57BL/6 (highly susceptible to MPTP) and BALB/c (resistant to MPTP) mice. The brain tissues including the striatum and substantia nigra pars compacta (SNpc) were examined immunohistochemically using an antibody to tyrosine hydrocyrase (TH). MPP(+)-injected C57BL/6 mice showed a significant decrease in TH-immunopositive areas in the striatum at Day 3 post injection (p<0.01), and TH-positive cells in the SNpc at Days 1 and 3 (p<0.01), respectively, compared to saline-injected control mice. In addition, MPP(+)-injected BALB/c mice showed a significant decrease in TH-positive areas in the striatum at Days 1 and 3, and SNpc TH-positive cells in the SNpc at Day 3, respectively (p<0.05). However, the decrease rates in the BALB/c mice were lower than that in C57BL/6 mice. MPTP-injected C57BL/6 mice, however, showed no lesions in the striatum and SNpc at Days 1 and 7 after icv injection. All the present findings indicate that factors other than MAO-B can influence the strain susceptibility between C57BL/6 and BALB/c mice after the conversion from MPTP to MPP(+).

Microbial removal from the separated liquid fraction of anaerobically digested pig manure in meso-scale integrated constructed wetlands

The aim was to investigate microbial removal from the liquid fraction of anaerobically digested pig manure in meso-scale integrated constructed wetlands (ICW’s) over a 13month period. Four treatments were investigated: T1 (standard), T2 (effluent recycling), T3 (high nutrient loading), and T4 (high flow rate). Mean counts of yeasts and moulds and spore-forming bacteria were higher in T3 and T4 than in T1 and T2 (P<0.05). Flow through the cells reduced mean counts of coliform, yeasts and moulds and spore-forming bacteria across all treatments (P<0.01). Counts varied with season; coliform were highest in the Summer (P<0.001), with yeasts and moulds highest in the Summer and Autumn (P<0.01) and spore-formers lowest in the Autumn (P<0.001). As Salmonella was undetectable in the influent and Escherichia coli and Enterococcus were rarely detected it is difficult to make conclusions regarding pathogen removal. Further investigations using marked strains would allow pathogen tracking within the ICW’s.

Neuronal or inducible nitric oxide synthase (NOS) expression level is not involved in the different susceptibility to nigro-striatal dopaminergic neurotoxicity induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) between C57BL/6 and BALB/c mice

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) induces severe degeneration of dopaminergic (DA-ergic) neurons when administrated to C57BL/6 mice, but such lesions are not observed in BALB/c mice. To clarify the factors which influence such marked strain differences in the susceptibility to MPTP, the involvement of neuronal NOS (nNOS) and inducible NOS (iNOS) was investigated. MPTP was intraperitoneally (ip) administrated to adult C57BL/6 (highly sensitive) and BALB/c (resistant) mice. Immunohistochemical analysis using an antibody to tyrosine hydroxylase (TH) showed a significant decrease in TH-immunopositive areas in the striatum and TH-positive cells in the substantia nigra pars compacta (SNpc) of MPTP-treated C57BL/6 mice at 1 and 7 days (d) after administration, compared to control C57BL/6 mice. On the other hand, MPTP-treated BALB/c mice showed no significant changes. By Western blot analysis, TH, MAO-B, DAT, nNOS and iNOS protein expression levels were examined in intact and MPTP-treated mice. Intact BALB/c mice showed higher DAT protein expression in the striatum and TH protein expression in the midbrain than intact C57BL/6 mice. In addition, MPTP-treated BALB/c mice showed a more significant increase of MAO-B expression than MPTP-treated C57BL/6 mice at 12 h. The increase of nNOS and iNOS protein expressions in MPTP-treated BALB/c mice was more pronounced in the striatum and midbrain than in MPTP-treated C57BL/6 mice at 12 h and 2 d. These results indicate that MAO-B, DAT, nNOS or iNOS expression levels do not influence the different strain susceptibility to MPTP.

Marked strain and substrain differences in induction of status epilepticus and subsequent development of neurodegeneration, epilepsy, and behavioral alterations in rats: Strain and substrain differences in an epilepsy model in rats

Outbred rat strains such as Sprague-Dawley (SD) or Wistar are widely used in epilepsy models, including popular models of temporal lobe epilepsy in which spontaneous recurrent seizures (SRS), hippocampal damage, and behavioral alterations develop after status epilepticus (SE). Such rats are randomly outbred, hence allelic variations can occur across separate colonies, so that outbred rats from different sources may have little in common with each other besides their names and similarities in pelage. Although such intrastrain differences may be an important reason for discrepancies between studies from different laboratories, the extent to which such differences affect development of seizures, neurodegeneration, and psychopathology in post-SE models of epilepsy has received little attention as yet. In the present study, we induced SE by sustained electrical stimulation of the basolateral amygdala in SD and Wistar rats from different breeders (Harlan, Charles River, Janvier, Taconic) as well as different breeding locations of the same breeder (Harlan-Winkelmann in Germany vs. Harlan in the Netherlands). Several marked inter- and intrastrain differences in induction of SE and its long-term consequences were found. Wistar rats from different vendors were all strikingly less sensitive to SE induction than SD rats from Harlan-Winkelmann or Harlan. Within the SD strain, SD rats from Charles River exhibited markedly lower sensitivity to SE induction than all other groups of SD rats. The majority of SD rats from different vendors developed SRS after SE except SD rats from Charles River. The latter rats also markedly differed in basal behavior, SE-induced behavioral alterations and neurodegeneration from other SD substrains. These marked inter- and intrastrain differences provide an interesting tool to study the impact of genetic and environmental factors on seizure susceptibility, epileptogenesis, and the relationship between behavior and epilepsy and vice versa.

The Awesome Power of Yeast Evolutionary Genetics: New Genome Sequences and Strain Resources for theSaccharomyces sensu strictoGenus

High-quality, well-annotated genome sequences and standardized laboratory strains fuel experimental and evolutionary research. We present improved genome sequences of three species of Saccharomyces sensu stricto yeasts: S. bayanus var. uvarum (CBS 7001), S. kudriavzevii (IFO 1802T and ZP 591), and S. mikatae (IFO 1815T), and describe their comparison to the genomes of S. cerevisiae and S. paradoxus. The new sequences, derived by assembling millions of short DNA sequence reads together with previously published Sanger shotgun reads, have vastly greater long-range continuity and far fewer gaps than the previously available genome sequences. New gene predictions defined a set of 5261 protein-coding orthologs across the five most commonly studied Saccharomyces yeasts, enabling a re-examination of the tempo and mode of yeast gene evolution and improved inferences of species-specific gains and losses. To facilitate experimental investigations, we generated genetically marked, stable haploid strains for all three of these Saccharomyces species. These nearly complete genome sequences and the collection of genetically marked strains provide a valuable toolset for comparative studies of gene function, metabolism, and evolution, and render Saccharomyces sensu stricto the most experimentally tractable model genus. These resources are freely available and accessible through www.SaccharomycesSensuStricto.org.

Understanding the role of agricultural practices in the potential colonization and contamination by Escherichia coli in the rhizospheres of fresh produce.

To better protect consumers from exposure to produce contaminated with Escherichia coli, the potential transfer of E. coli from manure or irrigation water to plants must be better understood. We used E. coli strains expressing bioluminescence (E. coli O157:H7 lux) or multiantibiotic resistance (E. coli²(+)) in this study. These marked strains enabled us to visualize in situ rhizosphere colonization and metabolic activity and to track the occurrence and survival of E. coli in soil, rhizosphere, and phyllosphere. When radish and lettuce seeds were treated with E. coli O157:H7 lux and grown in an agar-based growth system, rapid bacterial colonization of the germinating seedlings and high levels of microbial activity were seen. Introduction of E. coli²(+) to soil via manure or via manure in irrigation water showed that E. coli could establish itself in the lettuce rhizosphere. Regardless of introduction method, 15 days subsequent to its establishment in the rhizosphere, E. coli²(+) was detected on the phyllosphere of lettuce at an average number of 2.5 log CFU/g. When E. coli²(+) was introduced 17 and 32 days postseeding to untreated soil (rather than the plant surface) via irrigation, it was detected at low levels (1.4 log CFU/g) on the lettuce phyllosphere 10 days later. While E. coli²(+) persisted in the bulk and rhizosphere soil throughout the study period (day 41), it was not detected on the external portions of the phyllosphere after 27 days. Overall, we find that E. coli is mobile in the plant system and responds to the rhizosphere like other bacteria.

Establishment of lacZ marked strain of phosphate solubilizing bacterium in the rhizosphere and its effect on plant growth in mungbean

The establishment of lacZ marked strain of P-solubilizing bacterium Pseudomonas in the rhizosphere of mungbean (Vigna radiata) under pothouse conditions was studied. The lacZ marker was transferred to Pseudomonas P-36 on LB medium using donor strain of E. coli. The lacZ marked strain formed blue colonies on selective media and could be identified from soil on the basis of this character. The lacZ marked strain was able to survive in rhizosphere of mungbean under pothouse conditions and maintained a population of about 10(4) g(-1) of rhizosphere soils up to 60 days study period. Positive effect of inoculation with P-solubilizing bacterium on dry matter yield, P and N-uptake was observed using rock phosphate and single super phosphate as P sources with and without farmyard amendment.

Crystal Structures of Ethanolamine Ammonia-lyase Complexed with Coenzyme B12 Analogs and Substrates

N-terminal truncation of the Escherichia coli ethanolamine ammonia-lyase beta-subunit does not affect the catalytic properties of the enzyme (Akita, K., Hieda, N., Baba, N., Kawaguchi, S., Sakamoto, H., Nakanishi, Y., Yamanishi, M., Mori, K., and Toraya, T. (2010) J. Biochem. 147, 83-93). The binary complex of the truncated enzyme with cyanocobalamin and the ternary complex with cyanocobalamin or adeninylpentylcobalamin and substrates were crystallized, and their x-ray structures were analyzed. The enzyme exists as a trimer of the (alphabeta)(2) dimer. The active site is in the (beta/alpha)(8) barrel of the alpha-subunit; the beta-subunit covers the lower part of the cobalamin that is bound in the interface of the alpha- and beta-subunits. The structure complexed with adeninylpentylcobalamin revealed the presence of an adenine ring-binding pocket in the enzyme that accommodates the adenine moiety through a hydrogen bond network. The substrate is bound by six hydrogen bonds with active-site residues. Argalpha(160) contributes to substrate binding most likely by hydrogen bonding with the O1 atom. The modeling study implies that marked angular strains and tensile forces induced by tight enzyme-coenzyme interactions are responsible for breaking the coenzyme Co-C bond. The coenzyme adenosyl radical in the productive conformation was modeled by superimposing its adenine ring on the adenine ring-binding site followed by ribosyl rotation around the N-glycosidic bond. A major structural change upon substrate binding was not observed with this particular enzyme. Glualpha(287), one of the substrate-binding residues, has a direct contact with the ribose group of the modeled adenosylcobalamin, which may contribute to the substrate-induced additional labilization of the Co-C bond.

DNA watermarking of infectious agents: progress and prospects.

DNA watermarking of infectious agents: progress and prospects.

Genetic diversity in Campylobacter jejuni is associated with differential colonization of broiler chickens and C57BL/6J IL10-deficient mice

Previous studies have demonstrated that Campylobacter jejuni, the leading causative agent of bacterial food-borne disease in the USA, exhibits high-frequency genetic variation that is associated with changes in cell-surface antigens and ability to colonize chickens. To expand our understanding of the role of genetic diversity in the disease process, we analysed the ability of three C. jejuni human disease isolates (strains 11168, 33292 and 81-176) and genetically marked derivatives to colonize Ross 308 broilers and C57BL/6J IL10-deficient mice. C. jejuni colonized broilers at much higher efficiency (all three strains, 23 of 24 broilers) than mice (11168 only, 8 of 24 mice). C. jejuni 11168 genetically marked strains colonized mice at very low efficiency (2 of 42 mice); however, C. jejuni reisolated from mice colonized both mice and broilers at high efficiency, suggesting that this pathogen can adapt genetically in the mouse. We compared the genome composition in the three wild-type C. jejuni strains and derivatives by microarray DNA/DNA hybridization analysis; the data demonstrated a high degree of genetic diversity in three gene clusters associated with synthesis and modification of the cell-surface structures capsule, flagella and lipo-oligosaccharide. Finally, we analysed the frequency of mutation in homopolymeric tracts associated with the contingency genes wlaN (GC tract) and flgR (AT tracts) in culture and after passage through broilers and mice. C. jejuni adapted genetically in culture at high frequency and the degree of genetic diversity was increased by passage through broilers but was nearly eliminated in the gastrointestinal tract of mice. The data suggest that the broiler gastrointestinal tract provides an environment which promotes outgrowth and genetic variation in C. jejuni; the enhancement of genetic diversity at this location may contribute to its importance as a human disease reservoir.

Sexual reproduction in Aspergillus species of medical or economical importance: why so fastidious?

Heterothallism is dependent upon the obligatory cross-mating between self-sterile homokaryotic individuals and represents a common pattern of sexuality in yeasts and molds. Heterothallic reproductive cycles have recently been discovered in three Aspergillus species of medical and economic importance, namely Aspergillus fumigatus,A. parasiticus and A. flavus. Together with Aspergillus udagawae (Neosartorya udagawae), heterothallism has now been discovered in a total of four aspergilli that affect human health or economy. These fungi appear to express relatively low levels of fertility compared to other heterothallic or homothallic aspergilli and require unusually fastidious environmental parameters to complete the sexual cycle. Because the purpose of sex is to reproduce, we favor the hypothesis that while fertility of these species is on the decline this is compensated by their proficiency to reproduce asexually in a wider range of environmental conditions. Heterothallism in these species could provide an invaluable tool for the recombinational analysis of factors relevant to pathogenicity or toxin production. There is concern, however, whether extensive recombinational analysis can be very practical in light of the fact that formation of ascospores in these species requires a long period of time and the construction of genetically marked strains is likely to decrease fertility even further.

‘Nothing is permanent but change’†- antigenic variation in persistent bacterial pathogens

Pathogens persist in immunocompetent mammalian hosts using various strategies, including evasion of immune effectors by antigenic variation. Among highly antigenically variant bacteria, gene conversion is used to generate novel expressed variants from otherwise silent donor sequences. Recombination using oligonucleotide segments from multiple donors is a combinatorial mechanism that tremendously expands the variant repertoire, allowing thousands of variants to be generated from a relatively small donor pool. Three bacterial pathogens, each encoded by a small genome (< 1.2 Mb), illustrate this variant generating capacity and its role in persistent infection. Borrelia burgdorferi VlsE diversity is encoded and expressed on a linear plasmid required for persistence and recent experiments have demonstrated that VlsE recombination is necessary for persistence in the immunocompetent host. In contrast, both Treponema pallidum TprK and Anaplasma marginale Msp2 expression sites and donors are chromosomally encoded. Both T. pallidum and A. marginale generate antigenic variants in vivo in individual hosts and studies at the population level reveal marked strain diversity in the variant repertoire that may underlie pathogen strain structure and the capacity for re-infection and heterologous strain superinfection. Here, we review gene conversion in bacterial antigenic variation and discuss the short- and long-term selective pressures that shape the variant repertoire.

Non-linear Rheology Of Collagen Type I Gels Probed On The Length Scale Of A Migrating Cell

Recent investigations showed that the dimensionality of the environment in which living cells are cultured - flat 2D culture wells versus 3D biopolymer networks - has a strong effect on cell morphology, metabolism and migration. The reason for these differences are unclear. What is lacking is a fundamental understanding of the mechanical and morphological properties of 3D matrices at varying length scales.We probe the local microrheology of a series of reconstituted collagen gels with different concentrations (1.2 - 2.4 mg/ml) by applying a calibrated force on embedded magnetic particles (O4.5μm) using magnetic tweezers. The resulting strain field within the matrix is visualized by tracking the positions of polystyrene spheres (O1μm) embedded in the collagen gels. This strain field is compared to expectations from continuum theory. In addition, the local microrheology is compared to bulk rheological properties measured in a cone-plate rheometer. At low forces and strains below 3%, local and bulk rheological properties agree closely, and the strain field follows that of a continuum linear elastic material. At higher strains, marked non-linear strain stiffening occurs, showing an increase in modulus of nearly 20-fold until the material eventually yields. Because of the non-uniform shear conditions around magnetic beads in the local microrheology experiments, the non-linear stiffening appeared to be less pronounced, but the strain field spread much farther out than expected from continuum theory. These data suggest that the strain stiffening behavior of collagen gels, together with the well-documented ability of cells to sense the stiffness of their surroundings, could account for the differences in cell behavior seen in 2D versus 3D culture conditions.

Strain differences in proliferation of progenitor cells in the dentate gyrus of the adult rat and the response to fluoxetine are dependent on corticosterone

This paper investigates the role of differences in adrenal cortical function on the proliferation rate of progenitor cells in the dentate gyrus of the hippocampus in adult Sprague–Dawley (SD) and Lister-Hooded (LH) male rats. SD rats had around 60% more cells labeled with Ki67 (an index of mitosis) than LH rats under basal conditions. Bilateral adrenalectomy (ADX) increased levels in both strains, but by unequal amounts, such that post-ADX numbers of Ki67-labeled cells were similar in both strains. Daily injections of 5 mg/kg corticosterone for 7 days reduced levels to similar values in ADX rats of both strains. The activity of progenitor cells in either strain did not respond to daily i.p. injections of fluoxetine (10 mg/kg) for 14 days, but an equivalent dose administered by osmotic minipump stimulated proliferation in both by a similar proportional amount, such that strain differences persisted. S.c. implantation of a corticosterone pellet (75 mg), which flattens the diurnal rhythm in corticosterone, prevented fluoxetine delivered by minipump from activating progenitor cell mitosis in SD rats, as it had in the LH strain in a previous study. These results show that much, if not all, of the marked strain differences between SD and LH rats in progenitor cell activity, and hence rates of neurogenesis in the dentate gyrus may be ascribed to corresponding differences in adrenal cortical activity.

Serum S-100B Response to Moderate-Intensity Exercise-Heat Strain Before and After Acclimation

Intense exercise alone and in combination with environmental heat stress can elevate blood S-100β protein concentrations. Moderate intensity exercise with marked environmental heat stress has not been studied, nor has the potential for heat acclimation to alter the response. PURPOSE: Determine the S-100β response to moderate intensity exercise with marked heat strain in a population vulnerable to exercise-heat exhaustion before and after acclimation. METHODS: Nine healthy male volunteers completed a heat acclimation protocol consisting of up to 100 minutes of treadmill walking (1.56m/sec, 4% grade) in the heat (45°C, 20% relative humidity) for 10 consecutive days. Changes in heart rate (HR), rectal temperature (Tre), and sweat rate (SR) were examined to determine successful acclimation. Area under the curve (AUC) for Tre> 38.5°C was calculated to assess cumulative hyperthermia. Blood samples were taken before and after exercise on days 1 and 10 and analyzed for serum osmolality and S-100β concentration. RESULTS: All subjects displayed physiological adaptations to heat acclimation, including a significant (P<0.05) reduction in final HR (161 to 145 b/min) and Tre (39.0 to 38.4°C), as well as a modest (~10%) increase in SR (1.10 to 1.20 L/hr; p=0.09). No differences were observed in pre-to-post exercise serum S-100β concentrations on day 1 or day 10, nor were differences observed in S-100β values between days 1 and 10. No significant correlations were found between S100&β values and any variable of interest. CONCLUSIONS: S-100β concentrations were not increased in response to moderate intensity exercise with marked heat strain in this study, thus no effect of heat acclimation was observed despite other classical signs of adaptation. Factors other than hyperthermia alone may better explain the rise in S-100β often observed with moderate intensity exercise to exhaustion in the heat.

Deformation and kinematics in a melt-bearing shear zone from the Western Betic Cordilleras (Southern Spain)

This work deals with the structural evolution and kinematics of the basal dynamothermal aureole of the Ronda peridotites, located in the Sierra Bermeja massif of the Western Betic Cordilleras, in southern Spain. This aureole is characterized by: 1) a marked strain gradient towards the contact with the overlying peridotites; 2) the great angular dispersion, ≈90°, of stretching lineations; and 3) the intrusion of thin syn-kinematic granite sheets. These features are consistent with the aureole being a low-viscosity shear zone formed at temperatures high enough, ≈725 °C, to promote the partial melting of crustal metamorphic rocks. The high-temperature deformation is demonstrated by the activation of c-slip in quartz. We consider that the heat source came from the thrusting of the hot subcontinental mantle over metamorphic crustal rocks. The interaction of alternating events of melt-enhanced deformation and melt-enhanced embrittlement explains the heterogeneity of this ductile shear zone and the strong narrowing, to only 30 meters, of the deformed domain. The small thickness of this shear zone is in contradiction with classical conceptual models of shear zones suggesting a broadening of ductile shear zones with increasing depths and temperatures.

Influence of swift ions and proton implantation on the formation of optical waveguides in lithium niobate

Optically polished titanium doped congruent lithium niobate single crystals were implanted with protons of energy of 120keV (at fluences of 1×1015, 1×1016, and 1×1017ions∕cm2). Some loss of lithium from the surface upon ion implantation was recovered by irradiation with 50MeV lithium ions (at fluences varying from 1×1011to1×1013ions∕cm2). The near surface region defects created in the crystal were analyzed using high resolution x-ray diffraction technique, atomic force microscopy, fourier transform infrared, and optical transmittance (UV-visible) studies. The marked lattice strain induced by the energetic ions was characterized by high resolution x-ray diffraction measurements. Three-dimensional defect clusters were observed from atomic force microscopy with nanoscale resolution. Variations of O–H bond stretching vibrations as a function of fluences were observed. Optical transparency of these samples was found to depend on implantation, irradiation, and combined processes. Correlating the structural information with surface morphology experiments, the existence of a waveguide layer on lithium niobate surface has been ascertained.