Possible role of sarcolemmal Ca2+/Mg2+ ATPase in heart function

The Ca2+/Mg2+ ATPase, which is activated by millimolar concentrations of Ca2+ or Mg2+, has been found to exist in the heart sarcolemmal membrane. Although a great deal of work has been carried out to characterize the enzyme activity as well as to purify the enzyme, the physiological function of the enzyme remains to be elucidated. This enzyme has been shown to be different from other known ion transport ATPases such as Na(+)-K+ ATPase and Ca2(+)-stimulated ATPase in terms of the activation kinetics of various cations, the sensitivity towards specific inhibitors, and the molecular weights. In view of the existing data and circumstantial evidence, it has been proposed that the Ca2+/Mg2+ ATPase is involved in the entry of Ca2+ into the cardiac cells, the transport of Mg2+ across the cell membrane, and extracellular ATP signal transduction.     

Strategies to improve the signal and noise performance of active matrix, flat-panel imagers for diagnostic x-ray applications

A theoretical investigation of factors limiting the detective quantum efficiency (DQE) of active matrix flat-panel imagers (AMFPIs), and of methods to overcome these limitations, is reported. At the higher exposure levels associated with radiography, the present generation of AMFPIs is capable of exhibiting DQE performance equivalent, or superior, to that of existing film-screen and computed radiography systems. However, at exposure levels commonly encountered in fluoroscopy, AMFPIs exhibit significantly reduced DQE and this problem is accentuated at higher spatial frequencies. The problem applies both to AMFPIs that rely on indirect detection as well as direct detection of the incident radiation. This reduced performance derives from the relatively large magnitude of the square of the total additive noise compared to the system gain for existing AMFPIs. In order to circumvent these restrictions, a variety of strategies to decrease additive noise and enhance system gain are proposed. Additive noise could be reduced through improved preamplifier, pixel and array design, including the incorporation of compensation lines to sample external line noise. System gain could be enhanced through the use of continuous photodiodes, pixel amplifiers, or higher gain x-ray converters such as lead iodide. The feasibility of these and other strategies is discussed and potential improvements to DQE performance are quantified through a theoretical investigation of a variety of hypothetical 200 microm pitch designs. At low exposures, such improvements could greatly increase the magnitude of the low spatial frequency component of the DQE, rendering it practically independent of exposure while simultaneously reducing the falloff in DQE at higher spatial frequencies. Furthermore, such noise reduction and gain enhancement could lead to the development of AMFPIs with high DQE performance which are capable of providing both high resolution radiographic images, at approximately 100 microm pixel resolution, as well as variable resolution fluoroscopic images at 30 fps.     

Improved typing procedure for the polymorphic single-copy RLA-DQA gene of the rabbit reveals a new allele

The DQA gene of the rabbit major histocompatibility complex (MHC, RLA) is highly polymorphic and, in contrast to those reported for other mammalian species, is present as a single copy. These properties allow use of this gene in a method to type the class II locus of RLA by a combination of single-stranded conformational polymorphism (SSCP) and heteroduplex (HD) analysis. Familial segregation of RLA-DQA was shown and RLA class II types for rabbits of unknown pedigree were determined using migration patterns of amplified genomic DNA. Typing results were confirmed in experiments where unknown samples were mixed with products from rabbits of RLA types defined by sequence analysis. These analyses detected an RLA-DQA allele in addition to the five previously described; this new allele is designated RLA-DQA-F.     

NF-κB在人肝细胞肝癌中的表达及与HBV X蛋白的关系

目的：研究核转录因子NF－-κB在人肝细胞肝癌组织中的表达及其与乙型肝炎病毒（HBV ）X蛋白的关系。方法；用免疫组织化学S－P法，检测52例人肝细胞肝癌组织中核转录因子NF－-κB及HBV X蛋白的表达；用脂质体介导的基因转染法将HBV x基因真核表达载体pcDNA3.1-HBX转染入人肝癌细胞系HCC－9204，检测肝癌细胞内核转录因子NF－-κB的表达。结果：52例人肝细胞肝癌组织均有核转录因子NF－-κB的广泛表达，并且在11例HBV X蛋白阳性的肝癌组织，核转录因子NF－-κB位于细胞胞质和胞核，而在41例HBV X蛋白阴性的肝癌组织，核转录因子NF－-κB位于肝癌细胞的胞质。将HBV x基因真核表达载体pcDNA3.1-HBX转染 入人肝癌细胞系HCC－9204，并在稳定表达X蛋白 的肝癌细胞，核转录因子NF－-κB定位于其胞质和胞核，而未进行基因转染的亲体细胞，核转录因子NF－-κB仅定位于细胞质，细胞核无核转录因子NF－-κB的表达。结论：核转录因子NF－-κB在人肝细胞肝癌组织中广泛表达，人肝细胞肝癌中存在着核转录因子NF－-κB的异常激活，并且核转录因子NF－-κB的异常激活与HBV X蛋白有关，X蛋白激活核转录因子NF－-κB， 使其从细胞转位于细胞核，这可能在HBV相关的人原发性肝癌肝癌的发生中起一定作用。     

Homozygosity by descent for a rare mutation in the myophosphorylase gene is associated with variable phenotypes in a Druze family with McArdle disease.

We examined a large consanguineous Druze family with McArdle disease for mutations in the glycogen myophosphorylase (PYGM) gene. All affected subjects were autozygous for a single G to A transition that abolishes the 5' consensus splice site in the first nucleotide of intron 14. The G to A transition is a rare mutation, with only one previous report in a single white subject heterozygous for this mutation and another, more common, mutation at codon 49. The kindred in our study is the first family reported in which disease is caused by homozygosity for this rare mutation. This kindred was originally reported as the first familial case of McArdle disease in the Druze.     

The x-ray sensitivity of amorphous selenium for mammography

A study of the x-ray sensitivity of amorphous selenium (a-Se) for digital mammography has been performed. A uniform layer of a-Se was deposited on a glass substrate with electrodes on both surfaces. The deposition procedure was identical to that used for a-Se flat-panel detectors. A high voltage was applied to the top surface of the a-Se layer in order to establish an electric field E(Se). Then the sample was exposed to x rays with 27 kVp spectra generated from an x-ray tube with a molybdenum (Mo) target. The mean x-ray energy of the spectrum used was approximately 16.6 keV. The x-ray current generated by the a-Se layer was measured as a function of E(Se). From the current measurement and the estimation of total x-ray energy absorbed in the a-Se, the energy required to create one electron-hole pair (EHP), W, was determined as a function of E(Se). It was found that at the most commonly used E(Se) of 10 V/microm, W was measured as 64 eV. This is considerably higher than the widely accepted typical value of W = 50 eV measured at higher x-ray photon energies (e.g., 50 keV). The dependence of W as a function of E(Se) can be best fitted using the empirical expression of E(Se)-gamma. This relationship is consistent with the results obtained at higher x-ray energies. This article provides an accurate measurement of x-ray sensitivity of a-Se at mammographic energies independent of detector operation, such as the most recently developed flat-panel detectors. The results will be a useful tool for investigation and optimization of a-Se-based x-ray imaging detectors, such as determination of pixel fill-factor and optimal E(Se) during operation.     

A novel method for making "tissue" microarrays from small numbers of suspension cells.

Tissue microarrays (TMAs) are a highly efficient method for large-scale protein expression studies. To date most TMAs have been constructed using paraffin-embedded specimens. The authors developed a method that allows construction of TMAs from small numbers of cells in suspension. Spun pellets of 1x10 to 1x10 cells are directly processed and embedded in paraffin in an Eppendorf tube. Cylindrical cores of 0.6 mm are taken from these tubes and embedded in a recipient paraffin block to create a TMA. This relatively simple but versatile method enables very small numbers of cells in suspension to be analyzed using the TMA technology and allows for the study of hematolymphoid and related disorders of the blood and bone marrow for which solid tissue samples cannot be readily obtained. With the increasing trend toward obtaining small samples for screening and diagnostic purposes, this method provides a means to manipulate small volume samples for high-throughput immunohistochemical analysis. This method is also amenable for use for cultured cells.     

Phenotypic switching of Cryptococcus neoformans can produce variants that elicit increased intracranial pressure in a rat model of cryptococcal meningoencephalitis

Increased intracranial pressure (ICP) plays an important role in the morbidity and mortality of cryptococcal meningoencephalitis. The microbial and host factors that contribute to the development of increased ICP are poorly understood. We found that phenotypic switch variants of Cryptococcus neoformans (smooth and mucoid) differed in their abilities to promote increased ICP in a rat model of cryptococcal meningitis. Rats infected with the mucoid variant developed increased ICP, whereas rats infected with the smooth parent did not. This trend correlated with a shorter survival time and a higher cerebrospinal fluid (CSF) fungal burden for mucoid variant-infected rats, although brain fungal burdens were comparable between mucoid variant- and smooth parent-infected rats. Magnetic resonance imaging revealed enhanced T2 signal intensity over the surfaces of the brains of mucoid variant-infected rats. In addition, more polysaccharide accumulated in the CSF and brains of mucoid variant-infected rats. The accumulation of glucorunoxylomannan was associated with elevated levels of MCP-1 (CCL2) and, accordingly, a more pronounced but ineffective monocytic inflammatory response in the meninges of mucoid variant-infected rats. In summary, these findings suggest that strain-specific characteristics can influence the development of increased ICP and indicate a manner in which phenotypic switching could influence the outcome of a central nervous system infection.     

Novel micro-crosslinked poly(organophosphazenes) with improved mechanical properties and controllable degradation rate as potential biodegradable matrix

As biodegradable materials, linear polyphosphazenes undergo rapid hydrolysis degradation but exhibit poor mechanical properties. Blending with biodegradable polyesters or inorganic particles strengthen their mechanical properties but give rise to slower degradation rate. To balance the mechanical properties and the degradation rate, micro-crosslinked polyphosphazenes were synthesized in this study. Their glass transition temperatures, mechanical properties, and in vitro degradation behavior were investigated. 2-hydroxyethyl methacrylate (HEMA) was firstly attached to the side chain along with glycine ethyl ester to prepare co-substituted poly(organophosphazene) with pendant ethenyl substituents. The co-substituted poly(organophosphazene) was blended with HEMA or acrylic acid (AA) followed by a free radical polymerization to prepare micro-crosslinked poly(organophosphazenes). The resulting crosslinked polymers showed two separate glass transition temperatures depending on the HEMA or AA feed. Incorporation of crosslinking affected the mechanical properties positively. Crosslinked poly(organophosphazenes) showed an approximately 11-17 fold increase in terms of modulus of elasticity when compared to the linear counterpart. In vitro degradation tests indicated that HEMA-crosslinked polymers hydrolyzed at a retarded rate while AA-crosslinked polymers hydrolyzed at a moderate rate compared to linear polymers.     

Characterization of antimicrobial resistance among Escherichia coli O111 isolates of animal and human origin

Fifty isolates of Escherichia coli serogroup O111 recovered from humans and various animal species over a 24-year period (1976-1999) were examined for typical virulence-associated factors and susceptibilities to antimicrobials of human and veterinary significance. Nine H (flagellar) types were identified including nonmotile (n = 24), 32 (n = 12), negative (n = 5), and 56 (n = 3). Thirty-five (70%) isolates possessed at least one Shiga-toxin-producing E. coli (STEC)-associated virulence determinants (eae, stxl, stx2, hlyA) via PCR analysis. Of these 35 isolates, 20 possessed eae, stxl, and hlyA genes, whereas three isolates possessed eae, stxl, stx2, and hylA genes. Multiple antibiotic resistance was observed in 70% of the 50 E. coli O111 isolates. The majority of isolates displayed resistance to streptomycin, sulfamethoxazole, tetracycline, and kanamycin. Bacterial resistance to ampicillin, gentamicin, chloramphenicol, trimethoprim and apramycin was also observed. Integrons were identified in 23 (46%) of the E. coli isolates assayed, with a 1-kb amplicon being most frequently observed. DNA sequencing of these integrons revealed the presence of the aadA gene, encoding resistance to streptomycin. Two integrons of 1.5 and 2 kb contained the aadA2 and either dfrI or dfrXII genes, encoding resistance to streptomycin and trimethoprim, respectively. Integrons were also identified from isolates dating back to 1982. Isolates were further genetically characterized via ribotyping, which identified 15 distinct ribogroups, with 62% of isolates clustering into four major ribogroups. Certain riboprint patterns from different animal species, including humans, were observed in isolates spanning the 24-year collection period, suggesting the dissemination of specialized pathogenic O111 clones.