三氧化二砷对食管癌细胞增殖和热休克蛋白70表达的影响

目的：研究三氧化二砷（As2O3）对食管癌细胞增殖和热休克蛋白70（HSP70）表达的影响。方法：通过相差显微镜、流式细胞术、免疫细胞化学染色和免疫印迹分析等方法观察As2O3对人食管癌细胞株EC1的作用效果和作用机制。结果：与对照组相比,经2μmol/L和5μmol/Las2O3作用的细胞出现明显的生长抑制,G2/M期细胞比例增加;2μmol/Las2O3作用48h后经Ecl细胞HSP70（heat shock protein70）及HSC70(heat shock cognate protein70)表达均增加。结论：As2O3诱导食管癌细胞G2/M期阻滞抑制细胞增殖和生长;HSP70的升高是细胞对As2O3作用后出现的应激反应,并与细胞周期阻滞相关。     

Intragenic duplication and divergence in the spectrin superfamily of proteins

Many structural, signaling, and adhesion molecules contain tandemly repeated amino acid motifs. The alpha-actinin/spectrin/dystrophin superfamily of F-actin-crosslinking proteins contains an array of triple alpha-helical motifs (spectrin repeats). We present here the complete sequence of the novel beta-spectrin isoform beta(Heavy)- spectrin (beta H). The sequence of beta H supports the origin of alpha- and beta-spectrins from a common ancestor, and we present a novel model for the origin of the spectrins from a homodimeric actin-crosslinking precursor. The pattern of similarity between the spectrin repeat units indicates that they have evolved by a series of nested, nonuniform duplications. Furthermore, the spectrins and dystrophins clearly have common ancestry, yet the repeat unit is of a different length in each family. Together, these observations suggest a dynamic period of increase in repeat number accompanied by homogenization within each array by concerted evolution. However, today, there is greater similarity of homologous repeats between species than there is across repeats within species, suggesting that concerted evolution ceased some time before the arthropod/vertebrate split. We propose a two-phase model for the evolution of the spectrin repeat arrays in which an initial phase of concerted evolution is subsequently retarded as each new protein becomes constrained to a specific length and the repeats diverge at the DNA level. This evolutionary model has general applicability to the origins of the many other proteins that have tandemly repeated motifs.      

Operant behavior in dwarf hamsters (Phodopus campbelli): Effects of rate of reinforcement and reinforcer flavor variety

We investigated operant behavior in a novel species, the dwarf hamster (Phodopus campbelli). In two experiments, hamsters were trained to lever-press for food reinforcement. In Experiment 1, rate of reinforcement was manipulated across conditions using four variable-interval schedules of reinforcement (delivering one to eight reinforcers per min). As predicted, within-session decreases in responding were steepest on the richest schedule. In Experiment 2, lever-pressing was reinforced by either a constant or a variety of flavored food pellets. Within-session decreases in responding were steeper when the reinforcer flavor remained constant than when it was varied within the session. In both experiments, subjects hoarded most reinforcers in their cheek pouches rather than consuming them in the operant chambers. These results are incompatible with post-ingestive satiety variables as explanations for within-session decreases in operant responding and suggest that habituation to repeatedly presented reinforcers best accounts for subjects’ response patterns. Additionally, a mathematical model that describes behavior undergoing habituation also described the present results, thus strengthening the conclusion that habituation mediates the reinforcing efficacy of food.     

Comparison of laser Doppler imaging, fingertip lacticemy test, and nailfold capillaroscopy for assessment of digital microcirculation in systemic sclerosis

Introduction  

Laser Doppler imaging (LDI) is a relatively new method for assessing the functional aspect of superficial skin blood flow in systemic sclerosis (SSc) and Raynaud's phenomenon. The present study investigated the dynamic behavior of digital skin microvascular blood flow before and after cold stimulus (CS) in SSc patients and in healthy controls by means of a comprehensive approach of the functional (LDI), morphological (nailfold capillaroscopy (NFC)), and biochemical (fingertip lacticemy (FTL)) microcirculation components.     

Mitochondrial DNA and bindin gene sequence evolution among allopatric species of the sea urchin genus Arbacia

Sea urchins of the genus Arbacia (order Stirodonta) have discontinuous allopatric distributions ranging over thousands of kilometers. Mitochondrial DNA (mtDNA) sequences were used to reconstruct phylogenetic relationships of four Arbacia species and their geographic populations. There is little evidence of genetic structuring of populations within species, except in two cases at range extremes. The mtDNA sequence differentiation between species suggests that divergence occurred about 4-9 MYA. Gene sequences encoding the sperm protein bindin and its intron were obtained and compared with the mtDNA phylogeny. Sea urchins among the well-studied echinoid order Camarodonta, with degrees of mtDNA divergence similar to those of Arbacia species, are known to have remarkable variation in bindin. However, in Arbacia, little variation in deduced amino acid sequences of bindin was found, indicating that purifying selection acts on the protein. In contrast, bindin intron sequences showed much differentiation, including numerous insertion/deletions. Fertilization experiments performed between a divergent pair of Arbacia species from the Atlantic and Pacific Oceans revealed no evidence of blocks to gamete recognition. In Arbacia, fertilization specificities may have evolved relatively slowly as a result of extensive gene flow within species, greater functional constraint on the bindin polypeptide, or reduced selective pressure for species recognition in singly occurring species.      

Direct immobilization of gangliosides onto gold-carboxymethyldextran sensor surfaces by hydrophobic interaction: applications to antibody characterization

We describe a novel immobilization technique to investigate interactions between immobilized gangliosides (GD3, GM1, and GM2) and their respective antibodies, antibody fragments, or binding partners using an optical biosensor. Immobilization was performed by direct injection onto a carboxymethyldextran sensor chip and did not require derivatization of the sensor surface or the ganglioside. The ganglioside appeared to bind to the sensor surface by hydrophobic interaction, leaving the carbohydrate epitope available for antibody or, in the case of GM1, cholera toxin binding. The carboxyl group of the dextran chains on the sensor surface did not appear to be involved in the immobilization as evidenced by equivalent levels of immobilization following conversion of the carboxyl groups into acyl amino esters, but rather the dextran layer provided a hydrophilic coverage of the sensor chip which was essential to prevent nonspecific binding. This technique gave better reactivity and specificity for anti- ganglioside monoclonal antibodies (anti-GD3: KM871, KM641, R24; and anti-GM2: KM966) than immobilization by hydrophobic interaction onto a gold sensor surface or photoactivated cross-linking onto carboxymethydextran. This rapid immobilization procedure has facilitated detailed kinetic analysis of ganglioside/antibody interactions, with the surface remaining viable for a large number of cycles (>125). Kinetic constants were determined from the biosensor data using linear regression, nonlinear least squares and equilibrium analysis. The values of kd, ka, and KAobtained by nonlinear analysis (KAKM871 = 1.05, KM641 = 1.66, R24 = 0.14, and KM966 = 0.65 x 10(7) M- 1) were essentially independent of concentration and showed good agreement with data obtained by other analytical methods.      

HIV-particles in spermatozoa of patients with AIDS and their transfer into the oocyte

By immunocytochemistry and in situ hybridization at the electron microscopy level, and by the PCR technique, we have shown that HIV-1 binds and enters normal sperm; that viral particles, their antigens, and nucleic acid are present in sperm from HIV-1 infected men; and that such sperm can transfer HIV-1 like particles to normal human oocytes. We also present evidence that a galactosylceramide-like compound is present on the sperm membrane and could function as an alternative receptor for HIV.     

Impact of growth conditions on the occurrence of<Emphasis Type="Italic">Fusarium</Emphasis> spp. and the mycotoxin content of wheat

In 1997–99 the occurrence ofFusarium spp. on winter wheat and the contamination with mycotoxins was investigated at three locations in the Rhineland, Germany. All cultivation methods investigated had an effect on the level ofFusarium infection, however, rainfall during flowering was the most important factor. The choice of cultivar and soil cultivation proved to be the most promising tools to reduce head scab severity and mycotoxin contamination.     

Scats and den contents as indicators of the diet of stoats (Mustela erminea) in the Tasman Valley,South Canterbury,New Zealand

Stoats are significant predators of native fauna in New Zealand. They occur in many habitat types and consume a wide range of prey. The diet of stoats in the Tasman River, South Canterbury, was studied by analysis of scats and den contents. Analysis of 206 scats showed that stoats ate mainly lagomorphs, birds and invertebrates. Minor components included mice, lizards, fish and hedgehogs. Stoats ate more birds in spring than in autumn, and female stoats ate more invertebrates than did males. The contents of 219 dens collected in the same area at the same time provided further information. Birds and lagomorphs occurred at high frequency in dens, and other components were minor. Remains in dens were larger than in scats and allowed identification of many more prey items to species level. Den contents revealed a potentially substantial impact of stoats on threatened shorebirds locally; this impact was not detected by analysis of scats.     

Turning a corner on HIV neutralization?

HIV vaccine development has been hampered by the inability of conventional immunogens to elicit antibodies capable of neutralizing primary isolates of the virus. Recent studies using 'fusion-competent' immunogens that capture transitional intermediate structures of the functioning envelope protein suggest that this goal may now be achievable.