We analyze the multifractal spectra of daily foreign exchange rates for Japan, Hong-Kong, Korea, and Thailand with respect to the United States in the period from 1991 until 2005. We find that the ...return time series show multifractal spectrum features for all four cases. To observe the effect of the Asian currency crisis, we also estimate the multifractal spectra of limited series before and after the crisis. We find that the Korean and Thai foreign exchange markets experienced a significant increase in multifractality compared to Hong-Kong and Japan. We also show that the multifractality is stronger related to the presence of high values of returns in the series.
The Gram-negative bacterium Burkholderia pseudomallei (Bp) is the causative agent of the human disease melioidosis. To understand the evolutionary mechanisms contributing to Bp virulence, we ...performed a comparative genomic analysis of Bp K96243 and B. thailandensis (Bt) E264, a closely related but avirulent relative.
We found the Bp and Bt genomes to be broadly similar, comprising two highly syntenic chromosomes with comparable numbers of coding regions (CDs), protein family distributions, and horizontally acquired genomic islands, which we experimentally validated to be differentially present in multiple Bt isolates. By examining species-specific genomic regions, we derived molecular explanations for previously-known metabolic differences, discovered potentially new ones, and found that the acquisition of a capsular polysaccharide gene cluster in Bp, a key virulence component, is likely to have occurred non-randomly via replacement of an ancestral polysaccharide cluster. Virulence related genes, in particular members of the Type III secretion needle complex, were collectively more divergent between Bp and Bt compared to the rest of the genome, possibly contributing towards the ability of Bp to infect mammalian hosts. An analysis of pseudogenes between the two species revealed that protein inactivation events were significantly biased towards membrane-associated proteins in Bt and transcription factors in Bp.
Our results suggest that a limited number of horizontal-acquisition events, coupled with the fine-scale functional modulation of existing proteins, are likely to be the major drivers underlying Bp virulence. The extensive genomic similarity between Bp and Bt suggests that, in some cases, Bt could be used as a possible model system for studying certain aspects of Bp behavior.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
abstract
Aflatoxin contamination of food and feed is a major concern due to the carcinogenic properties of this mycotoxin. Previous studies using classical approaches have identified a cluster of ...genes responsible for aflatoxin production under the control of the pathway-specific transcriptional regulator aflR, but it is unknown whether aflR controls expression of other genes within the genome. Transcription profiling comparing wild type and ΔaflR strains of Aspergillus parasiticus grown under conditions conducive for aflatoxin production identified only 23 upregulated genes in the wild type. These included 20 genes in the aflatoxin biosynthetic cluster, and three additional genes outside the aflatoxin biosynthetic cluster (nadA, hlyC, and niiA), all with AflR binding sites. This report is the first to demonstrate genes outside the biosynthetic cluster as being associated with aflR expression.
Two closely related species Burkholderia mallei (Bm) and Burkholderia pseudomallei (Bp) are serious human health hazards and are potential bio-warfare agents, whereas another closely related species ...Burkholderia thailandensis (Bt) is a non-pathogenic saprophyte. To investigate the genomic factors resulting in such a dramatic difference, we first identified the Bm genes responsive to the mouse environment, and then examined the divergence of these genes in Bp and Bt.
The genes down-expressed, which largely encode cell growth-related proteins, are conserved well in all three species, whereas those up-expressed, which include potential virulence genes, are less well conserved or absent notably in Bt. However, a substantial number of up-expressed genes is still conserved in Bt. Bm and Bp further diverged from each other in a small number of genes resulting from unit number changes in simple sequence repeats (ssr) in the homologs.
Our data suggest that divergent evolution of a small set of genes, rather than acquisition or loss of pathogenic islands, is associated with the development of different life styles in these bacteria of similar genomic contents. Further divergence between Bm and Bp mediated by ssr changes may reflect different adaptive processes of Bm and Bp fine-tuning into their host environments.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Proton nuclear magnetic resonance (1H NMR) experiments have been performed to measure the spin−lattice, T 1, and spin−spin, T 2, relaxation times of the three functional groups in water/methanol ...mixtures at different methanol molar fractions (X MeOH = 0, 0.04, 0.1, 0.24, 0.5, 1) as a function of temperature in the range 205 K < T < 295 K. The measured relaxation times in the mixtures, at all the methanol molar fractions, are faster than those of pure water and methanol because of strong interactions, resulting in a complex hydrogen bonding dynamics that determines their thermodynamic properties. In particular, we observe how the interplay between hydrophobicity and hydrophilicity changes with temperature and influences the peculiar thermal behavior of the NMR relaxation times of the solution. The obtained results are interpreted in terms of the existence of stable water−methanol clusters at high temperature whereas, upon cooling to low temperature, clusters of single species are present in the mixture.
For a comprehensive evaluation of genes that have their expression modulated during exposure of the mycelia to voriconazole, we performed a large-scale analysis of gene expression in Aspergillus ...fumigatus using a microarray hybridization approach. By comparing the expression of genes between the reference time and after addition of voriconazole (30, 60, 120, and 240 min), we identified 2,271 genes differentially expressed in the wild-type strain. To validate the expression of some of these genes during exposure to voriconazole, we analyzed 13 genes showing higher expression in the presence of voriconazole by real-time RT-PCR. Although the magnitudes of induction differed between the two experimental systems, in about 85% of the cases they were in good agreement with the microarray data. To our knowledge this is the first study of microarray hybridization analysis for a filamentous fungus exposed to an antifungal agent. In our study, we have observed: (i) a decreased mRNA expression of various ergosterol biosynthesis genes; (ii) increased mRNA levels of genes involved in a variety of cell functions, such as transporters, transcription factors, proteins involved in cell metabolism, and hypothetical proteins; and (iii) the involvement of the cyclic AMP-protein kinase signaling pathway in the increased mRNA expression of several of these genes.
Burkholderia mallei (Bm), the causative agent of the predominately equine disease glanders, is a genetically uniform species that is very closely related to the much more diverse species Burkholderia ...pseudomallei (Bp), an opportunistic human pathogen and the primary cause of melioidosis. To gain insight into the relative lack of genetic diversity within Bm, we performed whole-genome comparative analysis of seven Bm strains and contrasted these with eight Bp strains. The Bm core genome (shared by all seven strains) is smaller in size than that of Bp, but the inverse is true for the variable gene sets that are distributed across strains. Interestingly, the biological roles of the Bm variable gene sets are much more homogeneous than those of Bp. The Bm variable genes are found mostly in contiguous regions flanked by insertion sequence (IS) elements, which appear to mediate excision and subsequent elimination of groups of genes that are under reduced selection in the mammalian host. The analysis suggests that the Bm genome continues to evolve through random IS-mediated recombination events, and differences in gene content may contribute to differences in virulence observed among Bm strains. The results are consistent with the view that Bm recently evolved from a single strain of Bp upon introduction into an animal host followed by expansion of IS elements, prophage elimination, and genome rearrangements and reduction mediated by homologous recombination across IS elements.
.
We investigate the statistical properties of the cross-correlation matrix between individual stocks traded in the Korean stock market using the random matrix theory (RMT) and observe how these ...affect the portfolio weights in the Markowitz portfolio theory. We find that the distribution of the cross-correlation matrix is positively skewed and changes over time. We find that the eigenvalue distribution of original cross-correlation matrix deviates from the eigenvalues predicted by the RMT, and the largest eigenvalue is 52 times larger than the maximum value among the eigenvalues predicted by the RMT. The
coefficient, which reflect the largest eigenvalue property, is 0.8, while one of the eigenvalues in the RMT is approximately zero. Notably, we show that the entropy function
with the portfolio risk
σ
for the original and filtered cross-correlation matrices are consistent with a power-law function,
E
(
σ
) ~
, with the exponent
γ
~ 2.92 and those for Asian currency crisis decreases significantly.
Members of the Asm1p, Phd1p, Sok2p, Efg1p, and StuAp (APSES) family of fungal proteins regulate morphogenesis and virulence in ascomycetes. We cloned the Aspergillus fumigatus APSES gene encoding ...StuAp and demonstrated that stuA transcription is markedly up-regulated after the acquisition of developmental competence. A. fumigatus DeltastuA mutants were impaired in their ability to undergo asexual reproduction. Conidiophore morphology was markedly abnormal, and only small numbers of dysmorphic conidia were produced, which exhibited precocious germination. Whole genome transcriptional analysis during the onset of developmental competence was performed and identified a subset of developmentally regulated genes that were stuA dependent, including a cluster of putative secondary metabolite biosynthesis genes, genes encoding proteins implicated in the regulation of morphogenesis, and genes encoding allergens and other antigenic proteins. Additionally, hyphae of the DeltastuA mutant displayed reduced expression of the catalase gene CAT1 and were hypersusceptible to hydrogen peroxide.
We prospectively evaluated the safety and effectiveness of aggressive mechanical disruption of clot in conjunction with intra-arterial administration of a low-dose third-generation thrombolytic agent ...(reteplase) to treat ischemic stroke in patients who were considered poor candidates for intravenous alteplase therapy or who failed to improve after intravenous thrombolysis. Mechanical clot disruption was used if low-dose pharmacological thrombolysis was ineffective. This strategy was adopted to increase the recanalization rate without increasing the risk of intracerebral hemorrhage.
Patients were considered poor candidates for intravenous therapy because of severity of neurological deficits, interval from symptom onset to presentation of at least 3 hours, or recent major surgery. We administered a maximum total dose of 4 U of reteplase intra-arterially in 1-U increments via superselective catheterization. After the initial doses were administered, we performed mechanical angioplasty (for proximal occlusion) or snare manipulation (for distal occlusion) at the occlusion site if recanalization had not occurred. The remaining doses of thrombolytics were subsequently administered if required for further recanalization. Angiographic responses were graded using modified Thrombolysis in Myocardial Infarction (TIMI) criteria. Clinical evaluations were performed before and 24 hours, 7 to 10 days, and 1 to 3 months after treatment.
Nineteen consecutive patients were treated (mean age, 64.3 +/- 16.2 yr; 10 were men). Initial National Institutes of Health Stroke Scale scores ranged from 11 to 42. Time from onset to treatment ranged from 1 to 9 hours. Occlusion sites were in the following arteries: cervical internal carotid (n = 7), intracranial internal carotid (n = 1), middle cerebral (n = 9), and basilar (n = 2). Of the 19 patients, thrombolysis alone was used in 5 patients, angioplasty was performed in 11 patients, and snare maneuvers were used in 5 patients. Complete restoration of blood flow (modified TIMI Grade 4) was observed in 12 patients, near-complete restoration of flow (modified TIMI Grade 3) in 4 patients, minimal response (modified TIMI Grade 1) in 1 patient, and no response in 2 patients (modified TIMI Grade 0). Neurological improvement at 24 hours (decline of at least 4 points in National Institutes of Health Stroke Scale score) was observed in seven patients. Five other patients experienced further improvement in National Institutes of Health Stroke Scale score at 7 to 10 days. No vessel rupture, dissection, or symptomatic intracranial hemorrhages were observed. At the time of follow-up evaluation, 7 of 19 patients were functionally independent.
A high rate of recanalization and clinical improvement can be observed in patients with ischemic stroke using low-dose thrombolytic agents with adjunctive mechanical disruption of clot. Moreover, this strategy may reduce the risk of intracerebral hemorrhage observed with thrombolytics.
PDF
