The time of completion of a linear birth-growth model

Consider the following birth-growth model in ℝ. Seeds are born randomly according to an inhomogeneous space-time Poisson process. A newly formed point immediately initiates a bi-directional coverage by sending out a growing branch. Each frontier of a branch moves at a constant speed until it meets an opposing one. New seeds continue to form on the uncovered parts on the line. We are interested in the time until a bounded interval is completely covered. The exact and limiting distributions as the length of interval tends to infinity are obtained for this completion time by considering a related Markov process. Moreover, some strong limit results are also established.

-173G/C polymorphism in the promoter of MIF is associated with hepatitis B virus infection in a Chinese Han population

In addition to the host immune response, genetic and environmental factors play crucial roles in the manifestation of hepatitis B virus (HBV) infection. The macrophage migration inhibitory factor (MIF) -173G/C polymorphism (rs755622), located in the promoter region of MIF, may play integral roles in diverse processes, including the immune response. Thus, the MIF -173G/C polymorphism may influence the immune response to HBV during natural infection. We investigated whether the MIF -173G/C polymorphism was associated with susceptibility to HBV infection in a Chinese Han population. A total of 596 HBV infection cases and 612 age-matched controls were recruited for the study. Genotyping of the MIF -173G/C polymorphism was performed using the allele-specific polymerase chain reaction method. The frequencies of the alleles and genotypes in patients and controls were compared using the χ(2) test. Carriers of the variant C allele in MIF -173 G/C were at significantly higher risk of HBV infection than carriers of the wild-type allele (P = 0.032, odds ratio = 0.799, 95% confidence interval = 0.651-0.981). However, there was no significant difference in the distribution of MIF -173G/C genotypes between case and control groups in either population (P = 0.096, degrees of freedom = 2). Our findings indicate that the G to C base change in MIF -173 G/C confers an increased risk of development of HBV infection by altering the expression of MIF in our Chinese Han population.

Identification and expression analysis of components involved in rice Xa21-mediated disease resistance signalling

Rice Xa21 gene encodes a receptor-like kinase that confers broad-spectrum resistance against Xanthomonas oryzae pv. oryzae (Xoo). Recently, a number of genes involved in the Xa21-mediated disease resistance pathway have been identified. Based on our previous data and the literature, we chose 16 candidate proteins and made corresponding antibodies. Using Western blotting, we systematically investigated the expression profile of the proteins in Xa21-mediated disease resistance response. We found nine proteins with altered expression. We further compared their expression in resistance, susceptible and mock responses, and found that GST expression was up-regulated during the resistance process, indicating GST is a positive regulator in resistance responses. ATPsB expression was down-regulated during both the resistance and susceptible response processes, although it was higher in the resistance response than that in the susceptible response. The total amount of MYB, GAPDH, CatB, Trx and NB-ARC proteins was lower in the resistance than in the susceptible response, but their abundance per unit bacteria in the resistance response was still higher than in the susceptible response, suggesting that these proteins might be positive regulators in the resistance response. In addition, expression of another ERF was induced by inoculation with bacterial blight pathogen, and expression of Zf-LSD1 was activated by wounding stress alone. Interestingly, most proteins showed similar altered expression patterns in the resistance and susceptible responses, but differed to some extents, implying that both responses might share common molecular mechanisms. This study revealed evidence of resistance-related protein expression, providing a foundation for better understanding of their functions.

Recent advances in the diagnosis and classification of myeloid neoplasms--comments on the 2008 WHO classification

The fourth edition of the World Health Organization (WHO) classification of myeloid neoplasms refined the criteria for some previously described myeloid neoplasms and recognized several new entities based on recent elucidation of molecular pathogenesis, identification of new diagnostic and prognostic markers, and progress in clinical management. Protein tyrosine kinase abnormalities, including translocations or mutations involving ABL1, JAK2, MPL, KIT, PDGFRA, PDGFRB, and FGFR1, have been used as the basis for classifying myeloproliferative neoplasms (MPN). Two new entities - refractory cytopenia with unilineage dysplasia and refractory cytopenia of childhood have been added to the group of myelodysplastic syndromes (MDS), and 'refractory anemia with excess blasts-1' has been redefined to emphasize the prognostic significance of increased blasts in the peripheral blood. A list of cytogenetic abnormalities has been introduced as presumptive evidence of MDS in cases with refractory cytopenia but without morphologic evidence of dysplasia. The subgroup 'acute myeloid leukemia (AML) with recurrent genetic abnormalities' has been expanded to include more molecular genetic aberrations. The entity 'AML with multilineage dysplasia' specified in the 2001 WHO classification has been renamed 'AML with myelodysplasia-related changes' to include not only cases with significant multilineage dysplasia but also patients with a history of MDS or myelodysplasia-related cytogenetic abnormalities. The term 'therapy-related myeloid neoplasms' is used to cover the spectrum of disorders previously known as t-AML, t-MDS, or t-MDS/MPN occurring as complications of cytotoxic chemotherapy and/or radiation therapy. In this review, we summarize many of these important changes and discuss some of the diagnostic challenges that remain.

Detection of Quantitative Trait Loci Affecting Milk Production Traits on Bovine Chromosome 6 in a Chinese Holstein Population by the Daughter Design

Fourteen microsatellite markers with a coverage of 63.5 cM on bovine chromosome 6 were selected, and 26 sire families with 2,260 daughters were analyzed for mapping quantitative trait loci (QTL) affecting 5 milk production traits in a Chinese Holstein population. In the analyses across 26 families and within the largest significant families with a one-QTL model fitted, a QTL near BMS470 was detected that affected fat yield at the 5% experiment-wide significance level. When a 2-QTL model was fitted in the across-family analysis, it was found that there might exist 2 QTL affecting the 3 yield traits, although the exact or empirical thresholds for the significance testing were unknown. In all analyses, the results for milk yield and protein yield were generally consistent, which might have resulted from the same genetic background for milk and protein yield.

[Cloning and sequence analysis of the light chain variable region gene of monoclonal anti-idiotypic antibody NP30 of Schistosoma japonicum]

OBJECTIVE

To amplify and sequence the light chain of anti-idiotypic monoclonal antibody NP30 of Schistosoma japonicum.

METHODS

By comparing the conserved regions at each end of the nucleotide sequences of murine germ-line genes encoding FR1 and FR4 regions of immunoglobulin light chain variable regions, we designed a set of primers for amplification of VL gene. The hybridoma cells secreting anti-idiotypic monoclonal antibody NP30 of Schistosoma japonicum were cultured and their genome DNAs were extracted and used as templates for PCR. The PCR product was then cloned into pUC19 vector. The recombinants were sequenced by Sanger's method. The VL gene was compared with GenBank and published mouse VL genes.

RESULTS

The full-length of VL gene was 318 bp. The VL gene was a member of mouse Ig kappa light chain subgroup IV and generated from rearrangement of germ line V and J kappa 4 genes. The VL gene sequence has been registered by GenBank(accession No. AF206720).

CONCLUSION

The obtained VL gene was a potentially functional gene of anti-idiotypic monoclonal antibody NP30 of Schistosoma japonicum.

[Studies of mtDNA haplotype polymorphism of Rongcheng population in China]

The loss of one copy of two 9-bp repeats in mtDNA non-coding region V is often found in Asia and Pacific populations. Two hundred and ten samples from Rongcheng county, Shandong province were detected with the deletion frequency of 12.4%. A distribution map of frequencies of mtDNA 9-bp deletion among Asian and Pacific population was made with reference to other published data. Further discussion was made for the hypotheses of affinity and original model of those populations. PCR-RFLP was conducted to obtain the mtDNA polymorphism information in five other mtDNA regions except the 9-bp deletion in 95 samples. Twenty-seven different mtDNA haplotypes were found, and the relationships among these haplotypes have been analyzed by using MEGA2.0 and PHYLIP 3.57. Two new RFLP sites caused by point mutation were also found, which have not been reported in Chinese populations.

The quarternary molecular architecture of TetA, a secondary tetracycline transporter from Escherichia coli

TetA, a tetracycline cation/proton antiporter, was expressed in Escherichia coli with a C-terminal tag of six histidines, solubilized in dodecyl maltoside and purified in a single step using Ni2+ affinity chromatography. Two-dimensional crystals were obtained after reconstitution of purified protein with lipids. Electron microscopy of negatively stained crystals revealed a trigonal symmetry, from which we infer that this secondary transporter has a trimeric structure. An overall molecular envelope can be described by a triangle of side approximately 100 A enclosing a central stain-filled depression. These dimensions are consistent with those obtained from projection views of single, isolated TetA particles that also display a trimeric architecture, confirming that the threefold symmetry is not simply a consequence of crystal-packing interactions. These data represent the first direct view of the quarternary arrangement of any antibiotic efflux pump. They are fully consistent with biochemical data on TetA, which indicate that it functions as a multimer and that the monomer consists of two domains, one of which plays the major part in oligomerization interactions.

Intrinsic lattice formation by the ryanodine receptor calcium-release channel

Recent theoretical analysis of a model lattice of interacting transmembrane receptor proteins has indicated that such clustering in the membrane could provide a novel mechanism for regulating receptor signalling in cells. It has been calculated that cooperative interactions between receptors organized into a cluster, or array, in the membrane would dramatically increase their sensitivity to activation by ligand. Sensitivity to ligand would increase with the extent of spread of activity within the receptor lattice. Hence, formation of extensive receptor lattices in the membrane would allow a large population of receptors to be simultaneously switched on, or off, by a very small change in ligand concentration. We show here that lattice formation is an intrinsic property of an integral membrane protein, the ryanodine-sensitive calcium-release channel (RyR) of endoplasmic reticulum. The purified protein spontaneously assembled into two-dimensional lattices in solution, enabling the construction of a 25 A projection map that identifies the mode of interaction between RyR oligomers. Our observations on the RyR provide a new perspective on various properties of cell signalling via this and other receptors.

The association of BMI and WHR on blood pressure levels and prevalence of hypertension in middle-aged and elderly people in rural China

The purpose of this study was to examine the effects of BMI (Body Mass Index) and WHR (Waist Hip Ratio) on average blood pressure and the prevalence of hypertension in middle-aged and elderly population in rural China. A total of 12955 subjects including 6276 males and 6688 females over 40 years of age were surveyed. Height, weight, waist circumference, hip circumference and blood pressure were measured. The association of BMI and WHR on average blood pressure levels and prevalence of hypertension were analyzed by dividing BMI and WHR into tertiles. The average blood pressure levels and the prevalence of hypertension in males and females increased significantly with the increase of BMI or WHR (P < 0.01), as well as with the increase of both of them (P < 0.01). The average blood pressure and the prevalence of hypertension stopped increasing when WHR was > or = 0.76, suggesting that WHR > or = 0.80 could be used as a cut-off value for the prediction of hypertension risk for both males and females. Therefore hypertension could be effectively prevented and controlled by controlling BMI and WHR.

Purification, crystallization and preliminary X-ray diffraction studies on the thermostable catechol 2,3-dioxygenase of Bacillus stearothermophilus expressed in Escherichia coli

The thermostable catechol 2,3-dioxygenase of Bacillus stearothermophilus has been crystallized. The crystal is probably in the space group I222 with unit-cell dimensions of a = 70.87, b = 74.60 and c = 133.69 A. A native data set has been collected with a completeness of 96% at 2.22 A resolution and an Rmerge value of 0.091.

The effect of positive and negative pH-gradients on the stability of small unilamellar vesicles of negatively charged phospholipids

The stability of small unilamellar vesicles (SUV) made from negatively-charged phosphatidate by ultrasonication or pH-jump has been investigated. As criteria for the vesicle stability are used: (I) the bilayer integrity as judged from the permeability of the fluorescent probe carboxyfluorescein (CF) and (II) the susceptibility of the phospholipid vesicles to fusion as judged by gel filtration and freeze-fracture electron microscopy. Egg phosphatidate SUV (PA-SUV) whose internal cavity is in equilibrium with the dispersion medium are strictly speaking thermodynamically unstable by these criteria. They may, however, be regarded as stable from a practical point of view. CF-release is observed with a half-time of 14 days and also some vesicle fusion, particularly at low temperature (4 degrees C). The small effects observed, e.g., the small tendency of the vesicles to undergo fusion is probably due to the high surface charge density of PA bilayers. A main finding of this work is that the same positive pH-gradient which is used in the pH-jump method to drive the formation of SUV from large phosphatidic acid bilayer sheets has a stabilizing effect on the resulting PA-SUV. Stabilization is achieved by positive pH-gradients of about two pH-units or more with the pH of the external medium exceeding the pH of the vesicle cavity. Under these conditions, up to about 8 weeks no significant loss of entrapped CF and no fusion of SUV was observed both at 4 degrees C and room temperature. In contrast, a reverse or negative pH-gradient of several pH units applied to PA-SUV (with the external pH being lower than that of the vesicle cavity) destabilizes PA-SUV. Such a gradient can be shown to lead to a dramatic perturbation of the lipid bilayer packing as evident from a significant increase in CF permeability. The local perturbation of the phospholipid bilayer is accompanied by massive vesicle fusion which is prominent at low temperature (4 degrees C).

Monolayer characteristics and thermal behaviour of phosphatidic acids

The monolayer and thermal behaviour of different phosphatidic acids are presented. At neutral pH and 22 degrees C dilauroylphosphatidic acid and unsaturated phosphatidic acids form liquid-expanded monolayers, while dipalmitoyl- and distearoylphosphatidic acid form condensed monolayers. Dimyristoylphosphatidic acid undergoes a transition from the liquid-expanded to the condensed state. With long-chain saturated and unsaturated phosphatidic acids little change in molecular area is observed between pH 2 and 7. In contrast, the short chain saturated phosphatidic acids, dilauroyl- and dimyristoylphosphatidic acids, undergo a condensation in the pH range 2 to 7. This is so in spite of the fact that the phosphoric acid group dissociates and the phosphatidic acid molecule attains one negative charge over this pH range. This finding is interpreted to indicate that the electrostatic repulsion between negatively charged phosphatidic acid molecules is compensated for or even outweighed by other intermolecular forces. Hydrogen bonding at the lipid/water interface is supposed to play a major role. All phosphatidates studied exhibit a significant expansion in the pH range 7 to 12. The second apparent pK of the primary phosphate group of phosphatidic acids is 8.6 and the expansion observed in this pH range is therefore due to electrostatic repulsion. At neutral pH the ether analogues of saturated phosphatidic acids have monolayer properties similar to those of the ester compounds. Considering the total pH range of 2 to 12 studied the force-area curves of the ether analogues are more condensed compared to the ester compounds. Synthetic phosphatidates and their ether analogues give reversible sharp crystal(gel)-to-liquid crystal transitions while the naturally occurring egg phosphatidate gives a broad, asymmetric one. The transition temperature Tm of saturated phosphatidates increases with increasing hydrocarbon chain length and at a given chain length Tm decreases markedly with unsaturation. The Tm values of the ether analogues are about 10 degrees C higher and the delta H values are 10-15% lower than those of the corresponding esters.

The effect of monoacylglycerol on the phase behavior of egg phosphatidylcholine

Phosphatidylcholine bilayers can accommodate large quantities of monoacylglycerol. Incorporating up to 40% monoacylglycerol has little effect on the orientation and motion of the phosphatidylcholine polar group. Briefly heating mixed dispersions of 1-monooleoylglycerol/egg phosphatidylcholine (1:1, weight ratio; 2.1:1, mole ratio) to 50-60 degrees C induced spontaneous vesiculation: unilamellar and some oligolamellar vesicles bud off the large multilamellar particles. The size of the resulting vesicles ranges from 100 to 1000 nm, with the bulk of the vesicles having diameters between 100 and 500 nm. The spontaneous vesiculation process is reflected in the visual clearance of the mixed lipid dispersion and in the collapse of the 31P powder NMR spectrum to a sharp, asymmetric peak. The narrowing of the 31P-NMR spectrum is explained in terms of additional molecular and/or segmental motion of the lipid polar groups. In mixed dispersions of 1-monooleoylglycerol/egg phosphatidylcholine containing an excess of 1-monooleoylglycerol (greater than or equal to 50%) domain formation takes place, i.e., the formation of local clusters enriched in either of the two lipids. As a result the mechanical properties of these mixed lipid bilayers seem to be quite different from those of pure egg phosphatidylcholine.