Two-phase phenomena, minority games, and herding models

The recently discovered two-phase phenomenon in financial markets [Nature 421, 130 (2003)] is examined with the German financial index DAX, minority games, and dynamic herding models. It is observed that the two-phase phenomenon is an important characteristic of financial dynamics, independent of volatility clustering. An interacting herding model correctly produces the two-phase phenomenon.

Preparation and characterization of polybutylcyanoacrylate magnetic nanoparticles

OBJECTIVE

To Prepare and characterize polybutylcyanoacrylate (PBCA) magnetic nanoparticles.

METHODS

The suspension of PBCA magnetic nanoparticles was prepared by emulsion polymerization method. The particle size, size distribution, polydispersity and other parameters were determined by photon correlation spectroscopy and transmission electron microscopy, and the iron content in the nanoparticles by ultraviolet spectroscopy.

RESULTS

The data of the particle size and size distribution of aqueous decanoic acid stabilized Fe3O4 magnetic fluids were acquired, and the influences of concentrations of butylcyanoacrylate (BCA) and Dextran-70 on the particle size and size distribution of PBCA magnetic nanoparticles were characterized.

CONCLUSION

We have for the first time successfully prepared stable suspension of PBCA magnetic nanoparticles by emulsion polymerization method at pH 6.3-6.4 in aqueous medium.

[Using chamber technique for studying the permeability of dexamethasone sodium phosphate liposome through rabbit colon mucosa in vitro]

OBJECTIVE

To investigate the features of liposome-mediated drug permeability through the colon mucosa in vitro.

METHODS

Dexamethasone sodium phosphate liposome (DSP) was prepared using orthogonal design. With in vitro Ussing chamber experiment, the accumulated amount of DSP permeated through rabbit colon mucosa into the receptor chamber and the distribution amount in the colon were determined at different time points during the experiment.

RESULTS

Compared with the prepared DSP solution, DSP liposome decreased the permeated amount of DSP through rabbit colon mucosa. The apparent permeability coefficient (Papp, x10(-6), cm/s1) of the DSP was 31.95+/-7.65, significantly lower than that of DSP solution (88.61+/-18.61). On the other hand, the distribution amount of DSP liposome in the colon mucosa was significantly higher than that of the DSP solution both at 120 and 300 min.

CONCLUSIONS

DSP liposome dosage form may induce less toxicity with better therapeutic effect in the treatment of colitis, which is worthy of further exploitation.

Corrections to scaling in two-dimensional dynamic XY and fully frustrated XY models

With large-scale Monte Carlo simulations, we investigate the two-dimensional dynamic XY and fully frustrated XY models. Dynamic relaxation starting from a disordered or an ordered state is carefully analyzed. It is confirmed that there is a logarithmic correction to scaling for a disordered start, but a power-law correction for an ordered start. Rather accurate values of the static exponent eta and the dynamic exponent z are estimated.

Treatment of corneal epithelial in-growth after excimer laser in situ keratomileusis

OBJECTIVE

To evaluate efficacy of photo therapeutic keratectomy (PTK) on corneal epithelial growth under the lamellar flap after excimer laser in situ keratomileusis (LASIK).

METHODS

In the 6 eyes with epithelial in-growth, the corneal cap was lifted, and the in-growing epithelium was removed from the interface. Five to 10 pulses of PTK being 7 mm in diameter were placed over the undersurface of the flap and the stromal bed, irrigation between the interface and replacing corneal flap were performed, and 50 to 75 pulses PTK being 3 mm in diameter were utilized to smooth the flap edge. The follow-up period ranged from 5 to 12 months.

RESULTS

In the follow-up, no epithelial implantation reoccurred in these 6 eyes. The uncorrected visual acuity achieved their best preoperative corrected visual acuity.

CONCLUSION

The results indicate that PTK can prevent recurrent epithelial in-growth after LASIK.

Performance of AlGaN/GaN high electron mobility transistors at nanoscale gate lengths

The DC and RF performance of AlGaN/GaN high electron mobility transistors with nanoscale gate lengths is presented. The layer structures were grown by either metal organic chemical vapor deposition or rf plasma-assisted molecular beam epitaxy. Excellent scaling properties were observed as a function of both gate length and width and confirm that these devices are well suited to both high speed switching and power microwave applications.

Constrained genomic and conformational variability of the hypervariable region 1 of hepatitis C virus in chronically infected patients

We analysed the genomic and conformational variability of the hypervariable region 1 (HVR1) of the hepatitis C virus (HCV) to evaluate the importance of its biological role. A total of 865 genotype 1b HVR1 subclones were collected from serially sampled sera in 11 patients with chronic hepatitis C, four of whom received interferon therapy. Consequently, 169 distinct sequences were examined for amino acid substitutions as well as hydrophilic or hydrophobic profile at each amino acid position within HVR1. Secondary structure of HVR1 was also predicted by the method of Robson in 90 distinct sequences from eight patients, including three interferon-treated patients. Some positions within the HVR1 were invariable or nearly so as to amino acid substitution. Hydrophilic or hydrophobic residues exclusively predominated at several positions. These constrained amino acid replacement and hydrophilic or hydrophobic profiles were conserved irrespective of interferon therapy, though the frequency of amino acid replacement was greater at almost all amino acid positions within the HVR1 in interferon-treated patients. The quasispecies of HCV showed various secondary structures of HVR1, but many sequences seemed to have common characteristics. beta sheet conformations around both the N-terminus and position 20 (numbered from the NH2 terminus of E2 envelope glycoprotein), and/or coil structures around the C-terminus of HVR1 could be identified. These results suggest that HVR1 amino acid replacements are strongly constrained by a well-ordered structure, in spite of being tolerant to amino acid substitutions, and imply an important biological role of the HVR1 protein in HCV replication.

Inference and prediction of courses of the diseases caused by pathologic viruses by estimating molecular evolution of within-host virus

A new approach for inferring the evolutionary process of within-host virus is presented in this study. This approach includes a sequential-linking algorithm developed by us that can deal with the sequential viral samples that are obtained at different time points from the same host, and reconstruct a longitudinal phylogenetic tree in which the evolutionary relations between viral variants can be shown. A codon-based model, which uses a Markov process to describe substitutions between codons, is also employed in this approach to calculate synonymous and non-synonymous substitution rates and to distinguish positive selection and neutral evolution. The approach is applied to a data set of the V3 region of the HIV-1 envelope genes sequenced in different years after infection of a single patient. The results suggest that this approach may provide a more realistic description of viral evolution than the traditional evolution models because it accounts for both neutral and adaptive evolution. Most important of all, since this approach make it possible to follow up the evolutionary process of within-host virus by analyzing the sequential viral samples, it could be used in inference and prediction of the course of the diseases caused by pathologic viruses and evaluation of the treatment.

Genotype may correlate with liver carcinogenesis and tumor characteristics in cirrhotic patients infected with hepatitis B virus subtype adw

To identify the influence of hepatitis B virus (HBV) genotype on development of hepatocellular carcinoma (HCC) and clinical outcome in chronic HBV infection, 26 consecutive cirrhotic patients infected with HBV subtype adw were investigated prospectively. HBV serology was undertaken using subtype-specific antibodies against hepatitis B surface antigens. The HBV genotype was determined by sequencing directly the polymerase chain reaction products of the HBV S gene. When HCC occurred, patients underwent transcatheter arterial embolization therapy. If tumor necrosis was incomplete, additional embolization therapy was carried out after a 3- to 4-month interval. At a median follow-up of 14.1 years (range 2.2 to 31.7), HCC occurred in 9 (35%) of 26 patients. Nineteen patients were infected with genotype B and 7 with genotype C. Four of the 19 genotype B patients (21%) and 5 of the 7 genotype C patients (71%) developed HCC (P = 0.058). Patient age (<45 years or 45 < or = ) at diagnosis of cirrhosis was the only significant independent factor influencing liver carcinogenesis by multiple logistic regression analysis and Cox's regression analysis (P = 0.0069 and 0.029, respectively). When analysis was limited to the age of 45 years or more at the last visit, genotype was the only contributory factor to HCC development by univariate analysis (P = 0.038). Whereas genotype B patients responded well to embolization therapy and had no recurrence of HCC for a prolonged period of time, genotype C patients showed poor responses and died of hepatic failure due to rapid HCC progression despite embolization therapy. The cumulative incidence of survival was significantly higher in the genotype B group (P = 0.0049). The HBV genotype correlated with the development of HCC, response to embolization therapy, and recurrence of HCC. Determination of HBV genotype may be useful in predicting outcomes in HBV subtype adw-related cirrhosis.

A new algorithm for analysis of within-host HIV-1 evolution

A new algorithm for inferring the evolution of within-host viral sequences is presented. A sequential-linking approach is developed so that a longitudinal phylogenetic tree can be reconstructed from sequential molecular data that are obtained at different time points from the same host. The algorithm employs a codon-based model, which uses a Markov process to describe substitutions between codons, to calculate nonsynonymous and synonymous substitution rates and to distinguish positive selection and neutral evolution. The algorithm is applied to a data set of the V3 region of the HIV-1 envelope genes sequenced at different years after the infection of a single patient. The results suggest that this algorithm may provide a more realistic description of viral evolution than traditional evolutionary models, because it accounts for both neutral and adaptive evolution, and reconstructs a longitudinal phylogenetic tree that describes the dynamic process of viral evolution.

Once a month administration of mifepristone improves bleeding patterns in women using subdermal contraceptive implants releasing levonorgestrel

It has been suggested that the administration of an anti-progesterone might improve bleeding patterns in women with irregular bleeding while using low-dose progestin-only contraception. We report the findings of a double-blind, randomized, placebo-controlled trial of mifepristone 50 mg taken once every 4 weeks in 100 Chinese women (50 subjects and 50 controls) complaining of frequent and irregular bleeding while using a levonorgestrel-releasing subdermal contraceptive implant. In all women, regardless of treatment, the frequency of bleeding decreased significantly over 360 days of observation. Women recorded significantly shorter episodes of bleeding (P: < 0.0002) during mifepristone treatment than during the 90 days before treatment started. In contrast, the duration of bleeding episodes fell more gradually in placebo-treated controls. Women using mifepristone were more likely to find treatment acceptable than women receiving a placebo tablet (P: < 0.01). Despite concern that anti-progestogenic effects may jeopardize contraception, there were no pregnancies. This approach may offer a useful strategy to improve continuation rates by alleviating unwanted side-effects until bleeding patterns improve spontaneously with time.

Design of experiment and data analysis by JMP (SAS institute) in analytical method validation

Validation of an analytical method through a series of experiments demonstrates that the method is suitable for its intended purpose. Due to multi-parameters to be examined and a large number of experiments involved in validation, it is important to design the experiments scientifically so that appropriate validation parameters can be examined simultaneously to provide a sound, overall knowledge of the capabilities of the analytical method. A statistical method through design of experiment (DOE) was applied to the validation of a HPLC analytical method for the quantitation of a small molecule in drug product in terms of intermediate precision and robustness study. The data were analyzed in JMP (SAS institute) software using analyses of variance method. Confidence intervals for outcomes and control limits for individual parameters were determined. It was demonstrated that the experimental design and statistical analysis used in this study provided an efficient and systematic approach to evaluating intermediate precision and robustness for a HPLC analytical method for small molecule quantitation.

Tea polyphenols down-regulate the expression of the androgen receptor in LNCaP prostate cancer cells

Androgens via their cognate receptor may be involved in the development and progression of prostate cancer. The aim of this study was to determine whether tea polyphenols have inhibitory effects on androgen action in an androgen-responsive, prostate cancer cell line, LNCaP. The tea polyphenol, EGCG, inhibited LNCaP cell growth and the expression of androgen regulated PSA and hK2 genes. Moreover, EGCG had a significant inhibitory effect on the androgenic inducibility of the PSA promoter. Immunoblotting detected a decrease in androgen receptor protein with treatments of the tea polyphenols EGCG, GCG and theaflavins. Northern blot analysis showed decreased levels of androgen receptor mRNA by EGCG. Transient transfections demonstrated that EGCG and theaflavins could repress the transcriptional activities of the androgen receptor promoter region. An Sp1 binding site in the androgen receptor gene promoter is an important regulatory component for its expression. This study suggests Sp1 is the target for the tea polyphenols because treatments of EGCG decreased the expression, DNA binding activity and transactivation activity of Sp1 protein. In conclusion, we have described a new property of tea polyphenols that inhibits androgen action by repressing the transcription of the androgen receptor gene.

Purification, characterization, and molecular cloning of the gene of a seed-specific antimicrobial protein from pokeweed

A small cysteine-rich protein with antimicrobial activity was isolated from pokeweed (Phytolacca americana) seeds and purified to homogeneity. The protein inhibits the growth of several filamentous fungi and gram-positive bacteria. The protein was highly basic, with a pI higher than 10. The entire amino acid sequence of the protein was determined to be homologous to antimicrobial protein (AMP) from Mirabilis jalapa. The cDNA encoding the P. americana AMP (Pa-AMP-1) and chromosomal DNA containing the gene were cloned and sequenced. The deduced amino acid sequence shows the presence of a signal peptide at the amino terminus, suggesting that the protein is synthesized as a preprotein and secreted outside the cells. The chromosomal gene shows the presence of an intron located within the region encoding the signal peptide. Southern hybridization showed that there was small gene family encoding Pa-AMP. Immunoblotting showed that Pa-AMP-1 was only present in seeds, and was absent in roots, leaves, and stems. The Pa-AMP-1 protein was secreted into the environment of the seeds during germination, and may create an inhibitory zone against soil-borne microorganisms. The disulfide bridges of Pa-AMP-1 were identified. The three-dimensional modeling of Pa-AMP-1 indicates that the protein has a small cystine-knot folding, a positive patch, and a hydrophobic patch.

The application of model-based complexity inference method to molecular evolution analysis

In this study, a new method based on the concept of complexity in inductive inference is proposed for reconstructing molecular phylogenetic tree. This method describes the complexity of molecular phylogenetic tree by three terms, which are related to tree topology, the branch lengths and fitness between the model and data measured by likelihood function. The computer simulation is used to investigate the efficiency of this method. The results suggest that this method is superior to the traditional methods because it avoids excess-complexity in the tree model estimation available from DNA sequence.

Topology selection in unrooted molecular phylogenetic tree by minimum model-based complexity method

In reconstruction of phylogenetic trees from molecular data, it has been pointed out that multifurcate phylogenetic trees are difficult to be correctly reconstructed by the conventional methods like maximum likelihood method(ML). In order to resolve this problem, we have been engaged in developing a new phylogenetic tree reconstruction method, based on the minimum complexity principle widely used in the inductive inference. Our method, which we call "minimum model-based complexity (MBC) method", has been proved so far to be efficient in estimating multifurcate branching when the tree is described in the form of rooted one. In this study, we make further investigations about the efficiency of MBC method in estimating the multifurcation in unrooted phylogenetic trees. To do so, we conduct computer simulation in which the estimations by MBC method are compared with those by ML, AIC and statistical test approach. The results show that MBC method also provides good estimations even in the case of multifurcate unrooted trees and suggest that it could be generally used for reconstruction of phylogenetic tree having arbitrary multifurcations.

[Relationship between change of erythrocyte membrane lipid composition and pregnancy induced hypertension]

OBJECTIVE

To study the cause of decreased erythrocyte deformability and its relation to pregnancy induced hypertension (PIH).

METHODS

The cholesterol and phospholipid content of erythrocyte membrane in 24 non-pregnant healthy women, 22 normotensive pregnant women and 36 cases with PIH were determined using automatic biochemical analysor, Gas chromatography and modified colorimetric method.

RESULTS

The cholesterol content and the cholesterol/phospholipid (C/P) ratio of the erythrocyte membrane were obviously higher in the group with moderate or severe PIH than that in the nonmotensive pregnancies (P < 0.01). There was no significant difference between mild PIH group and the normotensive pregnant group (P > 0.05).

CONCLUSION

The increase of cholesterol content and C/P ratio in the erythrocyte membrane might be involved in the pathophysiology of PIH. The alteration of cholesterol content in the erythrocyte membrane probaby reflected the disturbance of serum lipid metabolism.

[Studies on hepatitis B virus infection in blood donors with positive anti-HBc and negative HBsAg]

OBJECTIVE

To study if it is necessary to screen for core antibody against hepatitis B (anti-HBc) to prevent post-transfusion hepatitis B and what is its criteria for screening.

METHODS

Relationship between the titer of anti-HBc and HBV DNA in blood from qualified donors by routine testing was conducted. HBV DNA was detected in 297 units of blood with anti-HBc at various titers by immuno-nested polymerase chain reaction (RT-PCR).

RESULTS

HBV DNA was detected in one of four units of blood with positive anti-HBc at a dilution of equal to or greater than 1:128, and no HBV DNA was detected in other 75 units of blood with a dilution of anti-HBc less than 1:128. There was significant relationship between HBV DNA and the titer of anti-HBc. No HBV DNA was detected in 218 units of blood with both positive anti-HBc and anti-HBs and in 50 units with negative anti-HBc. Detection rate of HBV DNA in blood with positive anti-HBc was only 0.34% (1/297).

CONCLUSION

Blood containing higher titer of single anti-HBc may be infectious. It is suggested that sensitivity of the reagents for detecting HBsAg currently used (1 ng/ml) be improved with the limited budget.

Inference of molecular phylogenetic tree based on minimum model-based complexity method

In this study, starting with a newly introduced concept of data complexity ("empirical data complexity"), we specify the concept of complexity more concretely in relation to mathematical modeling and introduce "model-based complexity (MBC)". Inductive inference based on the minimum model-based complexity method is then applied to the reconstruction of molecular evolutionary tree from DNA sequences. We find that minimum MBC method has good asymptotic property when DNA sequence lengths approach to infinite and compensates the bias of maximum likelihood method due to the difference of tree topology complexity. The efficiency of minimum MBC method for reconstruction of molecular tree is studied by computer simulation, and results suggest that this method is superior to the traditional maximum likelihood method or its modification by Akaike's AIC.