Salt-dependent DNA superhelix diameter studied by small angle neutron scattering measurements and Monte Carlo simulations

Using small angle neutron scattering we have measured the static form factor of two different superhelical DNAs, p1868 (1868 bp) and pUC18 (2686 bp), in dilute aqueous solution at salt concentrations between 0 and 1.5 M Na+ in 10 mM Tris at 0% and 100% D2O. For both DNA molecules, the theoretical static form factor was also calculated from an ensemble of Monte Carlo configurations generated by a previously described model. Simulated and measured form factors of both DNAs showed the same behavior between 10 and 100 mM salt concentration: An undulation in the scattering curve at a momentum transfer q = 0.5 nm-1 present at lower concentration disappears above 100 mM. The position of the undulation corresponds to a distance of approximately 10-20 nm. This indicated a change in the DNA superhelix diameter, as the undulation is not present in the scattering curve of the relaxed DNA. From the measured scattering curves of superhelical DNA we estimated the superhelix diameter as a function of Na+ concentration by a quantitative comparison with the scattering curve of relaxed DNA. The ratio of the scattering curves of superhelical and relaxed DNA is very similar to the form factor of a pair of point scatterers. We concluded that the distance of this pair corresponds to the interstrand separation in the superhelix. The computed superhelix diameter of 16.0 +/- 0.9 nm at 10 mM decreased to 9.0 +/- 0.7 nm at 100 mM salt concentration. Measured and simulated scattering curves agreed almost quantitatively, therefore we also calculated the superhelix diameter from the simulated conformations. It decreased from 18.0 +/- 1.5 nm at 10 mM to 9.4 +/- 1.5 nm at 100 mM salt concentration. This value did not significantly change to lower values at higher Na+ concentration, in agreement with results obtained by electron microscopy, scanning force microscopy imaging in aqueous solution, and recent MC simulations, but in contrast to the observation of a lateral collapse of the DNA superhelix as indicated by cryo-electron microscopy studies.     

Investigation on the mechanism of adsorption and desorption behavior in cerium ions modified Y-type zeolite and improved hydrocarbons conversion

Different types of Y zeolites(HY, USY and Na Y) containing various amounts of cerium(Ce) were prepared with the method of liquid ion exchange and characterized by X-ray diffraction(XRD), intelligent gravimetric analyzer(IGA), and a molecular simulation technology(grand canonical Monte Carlo simulation, GCMC). A novel calculation method of desorption index(DI) was proposed and the influence of cerium cationic species on the processes of adsorption-desorption of hydrocarbon molecules(n-octane) on the cerium modified Y zeolites(Ce Y) was studied. The results indicated that Ce ion species played a key role in reducing desorption activation energy of n-octane on Y type zeolites, leading to an improvement of the desorption ability of the Ce Y and the regulation of the adsorption state of n-octane from aggregation to decentralization. These findings are essential factors for enhancing the product selectivity of light hydrocarbon component and the catalytic activity of rare earth modified Y zeolites(REY) catalysts in fluid catalytic cracking(FCC) process.     

Protein conformational changes determined by matrix-assisted laser desorption mass spectrometry

Caldesmon is an actin/calmodulin/tropomyosin protein located in the thin filaments of smooth muscle cells and microfilaments of nonmuscle cells. Two isoforms of caldesmon, h- and l-types, shown to exist in vertebrate smooth and nonmuscle cells respectively, are produced by alternative splicing of the caldesmon mRNA encoded by a single gene. To study the expression of smooth muscle specific h-caldesmon during the differentiation of mesenchymal cells into smooth muscle cells, soluble protein and total RNA from the gizzard primordium in the gut region of 5-day and gizzards of 7-, 9-, 13-, 17- and 21-day embryos and 2-days post-hatch chicks were extracted and analyzed for caldesmon expression at both protein and mRNA levels. Western blot analysis of proteins and immunofluorescence microscopy of tissue section were carried out using an antibody specific for h-caldesmon. Total RNA was analyzed by Northern blotting using a caldesmon cDNA probe, and h- and l-caldesmon cDNAs were identified due to the difference in their molecular sizes (4.8 and 4.1 kb respectively). The mRNA was also analyzed by reverse transcribed-polymerase chain reaction (RT-PCR) and Southern blot analysis. Our results show that the I-caldesmon mRNA was expressed at higher levels in the gizzard primordium during the early stages of development, and decreased gradually during growth. The h-caldesmon protein and mRNA, not expressed at day 5, is minimally expressed at day 7 and is fully turned on by day 9. Additionally, sequence analyses of the RT-PCR products of I-caldesmon showed that it lacked the spacer region, as predicted. RT-PCR analysis of total RNA gave two h-caldesmon fragments. These two fragments were identified as two different isoforms of h-caldesmon since they both contained the spacer region. They also showed homology in the region of exon 4 had differences in the region of exon 3b.     

Oxygen adsorption/desorption behavior of YBaCo4O7+δ and its application to oxygen removal from nitrogen

A new medium-temperature (200-400℃) adsorbent material for oxygen removal and air separation, YBaCo4O7+β, was prepared by the solid-state reaction method. This new adsorbent could adsorb a large quantity of oxygen in the temperature range of 200-370 ℃. Ad-sorbed oxygen could be released by raising temperature over 400 ℃ or by switching the atmosphere from oxygen to nitrogen. This oxygen adsorption and desorption process had good reproducibility. Taking advantage of this unique oxygen intake/release behavior, a nitrogen puri-fication process was investigated. The results showed that YBaCo4O7+δ material was a promising candidate for the oxygen sorption process and could be used to produce high-purity nitrogen or to remove trace oxygen from other gases.     

Cell density-dependent DNA fragmentation and its suppression by heparin in primary culture of adult rat hepatocytes

We show here that the internucleosomal DNA fragmentation, which is a biochemical hallmark of apoptosis, was induced in a cell density-dependent manner in primary culture of adult rat hepatocytes. This DNA fragmentation could be suppressed by a gene expression inhibitor, indicating the active nature of this process. Moreover, the viability changes in high and low cell density cultures showed a tendency corresponding with the incidence of the DNA fragmentation in them. These results suggest that in hepatocytes there may be a cell density-dependent apoptosis mechanism. In this report, we also show that heparin could suppress this DNA fragmentation with high specificity, and the cell death to some extent.     

Genetic changes in intraductal breast cancer detected by comparative genomic hybridization

Ductal carcinoma in situ (DCIS) is considered a direct precursor of invasive ductal breast cancer (IDC). We combined tissue microdissection and comparative genomic hybridization to identify genetic changes in five DCIS lesions with no invasion and in two that were adjacent to IDC. Extensive genetic changes characterized pure DCIS cases with gains of 1q, 6q, 8q, and Xq as well as losses of 17p and chromosome 22 being most often involved. Except for the Xq gain, these changes are also common to IDC. Separate analysis of DCIS and IDC components in the same tumor revealed an almost identical pattern of genetic changes in one case, whereas substantial differences were found in another. We conclude that many of the common genetic changes in IDC may take place before development of invasive growth. However, a simple linear progression model may not always account for the DCIS-IDC transition.     

萃淋树脂吸附金解脱及再生研究

萃淋树脂在酸性介质中能很好的吸附金，吸附后用硫脲容易解脱并且树脂可以再生重复使用。     

Two cases of gastroesophageal achalasia detected by radioiodide or pertechnetate imaging

Simultaneous primary tumors (tumors found at the same time or within 1 month of each other) are not uncommon in head and neck cancer. Most frequently, one lesion is small relative to the other; however, this is not always the case When two anatomically separate simultaneous primary tumors are large, a challenge for the reconstructive surgeon exists. The authors present a case of simultaneous primary tumors arising along the left and right mandibular gingiva. Following extirpation of the tumors, the defects were reconstructed with bilateral free radial forearm flaps. They conclude that this procedure is an excellent option for reconstruction of anatomically separate simultaneous defects of the head and neck region. This reconstruction provides an excellent tissue match for the intraoral region, and can be accomplished with minimal morbidity in a relatively short operative time.     

Age-related and vasomotor stimuli-induced changes in renal vascular resistance detected by Doppler ultrasound

Indirect measurement of renal vascular resistance by duplex Doppler waveform analysis was evaluated in relation to aging and some pathophysiological conditions. Baseline renal resistive index (RRI) (peak systolic frequency shift - lowest diastolic frequency shift/peak systolic frequency shift) was measured in healthy controls aged 20 to 85 years by analyzing the blood flow velocity waveform of interlobar arteries. RRI changes induced by sympathetic activation (cold pressor test and handgrip test) or by fluid load were evaluated. Both repeatability and reproducibility were very good, as the intra and interoperator variations were all less than their reproducibility coefficients. RRI showed a significant increase with aging (ANOVA P < .001), particularly evident in subjects older than 50 years. Both the cold pressor test and handgrip test induced in all the subjects (n = 16) a significant increase in RRI (P < .001), from 0.59 +/- 0.04 to 0.69 +/- 0.04 (12 +/- 6%) for the cold pressor test and from 0.57 +/- 0.03 to 0.66 +/- 0.03 (15 +/- 2%) for the handgrip test. In eight subjects intravenous fluid load (0.25 mL/kg/min of 0.9% NaCl for 120 min) caused a significant decrease in RRI (P < .001), from 0.62 +/- 0.02 to 0.53 +/- 0.01 (17 +/- 2%), which was inversely related to mean blood pressure rise (r = 0.71, P < .001). These data show that pulsed wave Doppler analysis is an accurate method for an indirect evaluation of changes in renal vascular resistance induced by common vasomotor stimuli.     

改性壳聚糖对Ag^＋的吸附性能研究

利用壳聚糖与氯丙酸反应,制备了改性壳聚糖,并研究了改性壳聚糖对Ag^＋的吸附性能。试验结果表明,在pH值为4-6,吸附时间为240rain,温度为40℃,氯丙酸一壳聚糖对Ag^＋的吸附率达到95％以上。通过运用相关数学模型对试验数据进行拟合表明,氯丙酸一壳聚糖对Ag^＋的吸附符合Langmuir和Freundlich等温方程式,最大吸附量为216．9197mg／g,吸附过程符合一级动力学方程。     

Surface energy, adsorption, and wetting transitions in ternary liquid alloys

Surface energy measurements have been performed on liquid Ga-Sn binary and on Ga-Pb-Sn as well as Ga-Pb-Tl ternary alloys, by the sessile drop technique under ultrahigh vacuum conditions. The purpose of these measurements was to investigate the change in adsorption behavior of Pb in Garich alloys as a consequence of ternary additions. In order to aid in the interpretation of the results, a multilayer model of surface segregation was formulated in the regular solution approximation. The results show evidence of site competition effects between the two solutes, which reduce the surface concentration of Pb in relation to binary Ga-Pb alloys. The effects of Sn on previously studied wetting-related adsorption transitions in Ga-Pb were also investigated. It was concluded that Sn additions are likely to raise the wetting temperature of the Ga-Pb alloy.     

Epidermization in the esophageal mucosa: unusual epithelial changes clearly detected by Lugol's staining

A 58-year-old Japanese man with superficial esophageal cancer accompanied by unusual epithelial changes, including esophageal mucosal epidermization, is reported. Staining with Lugol's iodine clearly showed irregular unstained lesions, which could not be seen clearly macroscopically, in the resected specimen. Histologic examination of the irregular unstained areas showed definite granular and horny layers regarded as epidermization, acanthosis with slight nuclear enlargement, and epithelial atrophy. The immunohistochemical staining patterns of keratins in the epidermized and atrophic lesions were similar to those in the epidermis, and the keratin staining patterns of the acanthotic lesion were similar to those of the oral epithelium.     

Cell density-dependent changes in the insulin action pathway: evidence for involvement of protein-tyrosine phosphatases

Three gas chromatographic procedures for the determination of ethanol in postmortem blood using alternative internal standards to n-propanol are presented: a direct injection procedure using t-butanol, and two headspace methods using t-butanol and methyl ethyl ketone. t-Butanol and methyl ethyl ketone were well resolved from ethanol, acetone, methanol and other commonly observed putrefactive volatiles using direct injection or headspace analysis. CVs for the direct injection method were below 5% for ethanol and below 10% for the other volatiles. The lower limits of detection (LOD) were 25-50 mg/L. The CVs for the headspace methods were below 5% for ethanol and below 6% for the other volatiles. The LODs were 10 mg/L using either t-butanol or methyl ethyl ketone as internal standards. The use of t-butanol or methyl ethyl ketone as alternatives to n-propanol avoids the possibility of error in the quantitation of ethanol due to the presence of n-propanol and allows for the identification of other volatiles that may aid in distinguishing antemortem ingestion from postmortem production of ethanol.