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1.
Greseth MD Boyle KA Bluma MS Unger B Wiebe MS Soares-Martins JA Wickramasekera NT Wahlberg J Traktman P 《Journal of virology》2012,86(11):6197-6209
Vaccinia virus, the prototypic poxvirus, efficiently and faithfully replicates its ~200-kb DNA genome within the cytoplasm of infected cells. This intracellular localization dictates that vaccinia virus encodes most, if not all, of its own DNA replication machinery. Included in the repertoire of viral replication proteins is the I3 protein, which binds to single-stranded DNA (ssDNA) with great specificity and stability and has been presumed to be the replicative ssDNA binding protein (SSB). We substantiate here that I3 colocalizes with bromodeoxyuridine (BrdU)-labeled nascent viral genomes and that these genomes accumulate in cytoplasmic factories that are delimited by membranes derived from the endoplasmic reticulum. Moreover, we report on a structure/function analysis of I3 involving the isolation and characterization of 10 clustered charge-to-alanine mutants. These mutants were analyzed for their biochemical properties (self-interaction and DNA binding) and biological competence. Three of the mutant proteins, encoded by the I3 alleles I3-4, -5, and -7, were deficient in self-interaction and unable to support virus viability, strongly suggesting that the multimerization of I3 is biologically significant. Mutant I3-5 was also deficient in DNA binding. Additionally, we demonstrate that small interfering RNA (siRNA)-mediated depletion of I3 causes a significant decrease in the accumulation of progeny genomes and that this reduction diminishes the yield of infectious virus. 相似文献
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不受欢迎的生物多样性:香港的外来植物物种 总被引:44,自引:2,他引:44
香港早在19世纪中叶开始就有外来植物入侵的记录,迄今为止,已发现多达238种已归化的外来或怀疑为外来的植物,其中又以薇甘菊(Mikania micrantha)、五爪金龙(Ipomoea cairica)、假臭草(Eupatorium catarium)、大黍(Panicum maximum)等最常见,外来植物最常见于受人为干扰的生境,例如荒废农田及路旁等,而较少在天然林地生境及贫瘠的灌草丛中发现,外来植物的对本地生态系统的影响主要局限于低地生境,它们常形成单优种群,减少了生境及贫瘠的灌草丛中发现,外来植物对本地生态系统的影响主要局限于低地生境,它们常形成单优种群,减少少了生境及动植物的多样性,外来动物对香港原生植物影响最大的是于20世纪70年代入侵的松树线虫(Bur-saphelenchus xylophilus)。外来的脊椎动物也有可能对香港的植物被演替产生影响,目前香港的外来植物当中,有些在大陆较少分布或没有记录,作为华南最大的港口,香港对外来物种的引入扮演着重要的角色,因此制定控制外来种在香港及华南地区的引入及传播的政策及措施非常重要。 相似文献
3.
How Does Biofeedback Reduce Clinical Symptoms and Do Memories and Beliefs Have Biological Consequences? Toward a Model of Mind-Body Healing 总被引:1,自引:0,他引:1
Wickramasekera I 《Applied psychophysiology and biofeedback》1999,24(2):91-105
Changes in the magnitude and direction of physiological measures (EMG, EEG, temperature, etc.) are not strongly related to the reduction of clinical symptoms in biofeedback therapy. Previously, nonspecified perceptual, cognitive, and emotional factors related to threat perception (Wickramasekera, 1979, 1988, 1998) may account for the bulk of the variance in the reduction of clinical symptoms. The mean magnitude of these previously nonspecified or placebo factors is closer to 70% whenboththe therapist and patient believe in the efficacy of the therapy. This powerful placebo effect is hypothesized to be anelicitedconditioned response (Wickramasekera, 1977a, 1977c, 1980, 1985) based on the memory of prior healings. These memories of healing are more resistant to extinction if originally acquired on a partial rather than continuous reinforcement schedule. High and low hypnotic ability in interaction with threat perception (negative affect) is hypothesized to contribute to both the production and reduction of clinical symptoms. High and low hypnotic ability respectively are hypothesized to be related to dysregulation of the sympathetic and parasympathetic arms of the autonomic nervous system. Biofeedback is hypothesized to be most effective for reducing clinical symptoms in people of low to moderate hypnotic ability. For people high in trait hypnotic ability, training in self-hypnosis or other instructional procedures (e.g., autogenic training, progressive muscle relaxation, mediation, CBT, etc.) will produce the most rapid reduction in clinical symptoms. 相似文献
4.
Nucleotide polymorphism in the acidic chitinase locus (ChiA) region of the wild plant Arabidopsis thaliana 总被引:3,自引:0,他引:3
To investigate DNA variation in natural plant populations, a 1.8-kb region
of the acidic chitinase locus (ChiA)was analyzed for 17 ecotypes of
Arabidopsis thaliana sampled worldwide and 3 Arabis species in Japan. As in
the Adh region, dimorphism was detected throughout the investigated ChiA
region, suggesting the possibility that dimorphic DNA variation exists in
the entire nuclear genome of A. thaliana. The ChiA region was divided into
two blocks by an intragenic recombination between two parental sequence
types, which diverged 7.4 MYA under the assumption that nucleotide mutation
rate per site per year is mu = 10(- 9). Nucleotide diversity in the entire
ChiA region was 0.0104. Tajima's test was significantly negative for both
nucleotide and indel variations, which was manifested as an excess of
unique polymorphisms. However, the level and pattern of polymorphism in the
ChiA region were inconsistent with simple theoretical explanations. The HKA
test detected no difference in the levels of intra- and interspecific
variations between the ChiA and Adh regions. In the ChiA coding region, no
difference in the patterns of synonymous and replacement variation was
found in intra- and interspecific comparisons by the MK test. Although it
was difficult to determine the exact genetic mechanism acting on the ChA
locus, these results suggested that the ChA locus region was under the same
genetic mechanism before and after the establishment of A. thaliana as a
species.
相似文献
5.
Ian E. Wickramasekera Paul Kolm Alan Pope Marsha Turner 《Applied psychophysiology and biofeedback》1998,23(4):233-241
A total of 224 chronic pain somatoform disorder patients without obvious pathophysiology or psychopathology were found to have colder hands than nonpatients. A paradoxical temperature increase (PTI) in response to a cognitive stressor (mental arithmetic) was noted in a subset of these chronic pain patients. Patients were defined as PTI responders if, during cognitive stress, an increase in digital temperature occurred over a prior eyes closed resting condition. It was found that 49.4% of males and 42.6% of females in a total sample of 224 patients demonstrated PTI. The PTI patients had significantly colder hands than non-PTI patients prior to stress. A concurrent SCL measure of sympathetic activation found no difference between the PTI and non-PTI groups either at baseline or during cognitive stress. It appears from this data that PTI is specific to the peripheral vascular system of these patients and may be a marker of psychophysiological dissociation or trauma blocked from consciousness. 相似文献
6.
A conditioned response model of the placebo effect 总被引:1,自引:0,他引:1
A model of the placebo response as a conditioned response(CR) is presented and predictions from this model are listed. Through association with active ingredients(UCS), neutral(CS) places, persons, procedures, and things can come to acquire the ability to reduce pain, anxiety, and depressive responses. One major counterintuitive prediction from the model is that therapists who routinely use active ingredients(UCS) or powerful drugs will get stronger placebo effects than those who routinely use inert ingredients(CS) or weak drugs. Developmentally, placebo responding appears to involve two successive conditioning stages, which may involve first the left and later the right hemisphere in right-handed subjects. The relationship between placebo responding and hypnotizability is discussed.This paper was first presented at the San Diego Biomedical Symposium (invited paper), San Diego, California, November 1977. Later it was presented at a symposium on Non-Specific Effects in Biofeedback, Biofeedback Society of America, Albuquerque, New Mexico, February 1978. It has been published in abbreviated form inProceedings of the San Diego Biomedical Symposium, New York: Academic Press, 1977. I would like to thank G. E. Schwartz for encouraging me to repackage this model for left brain (critical analytic) consumers, and particularly for his encouragement and critical comments during the review process. 相似文献
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Debebe Gebremedhin Maia Terashvili Nadi Wickramasekera David X. Zhang Nicole Rau Hiroto Miura David R. Harder 《PloS one》2013,8(7)
The present study examined the level of generation of reactive oxygen species (ROS) and roles of inactivation of the phosphatase PTEN and the PI3K/Akt signaling pathway in response to an increase in intramural pressure-induced myogenic cerebral arterial constriction. Step increases in intraluminal pressure of cannulated cerebral arteries induced myogenic constriction and concomitant formation of superoxide (O2
.−) and its dismutation product hydrogen peroxide (H2O2) as determined by fluorescent HPLC analysis, microscopic analysis of intensity of dihydroethidium fluorescence and attenuation of pressure-induced myogenic constriction by pretreatment with the ROS scavenger 4,hydroxyl-2,2,6,6-tetramethylpiperidine1-oxyl (tempol) or Mito-tempol or MitoQ in the presence or absence of PEG-catalase. An increase in intraluminal pressure induced oxidation of PTEN and activation of Akt. Pharmacological inhibition of endogenous PTEN activity potentiated pressure-dependent myogenic constriction and caused a reduction in NPo of a 238 pS arterial KCa channel current and an increase in [Ca2+]i level in freshly isolated cerebral arterial muscle cells (CAMCs), responses that were attenuated by Inhibition of the PI3K/Akt pathway. These findings demonstrate an increase in intraluminal pressure induced increase in ROS production triggered redox-sensitive signaling mechanism emanating from the cross-talk between oxidative inactivation of PTEN and activation of the PI3K/Akt signaling pathway that involves in the regulation of pressure-dependent myogenic cerebral arterial constriction. 相似文献
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Phagocytosis of bacteria by polymorphonuclear leukocytes: a freeze-fracture, scanning electron microscope, and thin-section investigation of membrane structure 总被引:2,自引:2,他引:0 下载免费PDF全文
The changes in membrane structure of rabbit polymorphonuclear (PMN) leukocytes during bacterial phagocytosis was investigated with scanning electron microscope (SEM), thin-section, and freeze-fracture techniques. SEM observations of bacterial attachment sites showed the involvement of limited areas of PMN membrane surface (0.01-0.25μm(2)). Frequently, these areas of attachment were located on membrane extensions. The membrane extensions were present before, during, and after the engulfment of bacteria, but were diminished in size after bacterial engulfment. In general, the results obtained with SEM and thin-section techniques aided in the interpretation of the three-dimensional freeze-fracture replicas. Freeze-fracture results revealed the PMN leukocytes had two fracture faces as determined by the relative density of intramembranous particles (IMP). Membranous extensions of the plasma membrane, lysosomes, and phagocytic vacuoles contained IMP's with a distribution and density similar to those of the plasma membrane. During phagocytosis, IMPs within the plasma membrane did not undergo a massive aggregation. In fact, structural changes within the membranes were infrequent and localized to regions such as the attachment sites of bacteria, the fusion sites on the plasma membrane, and small scale changes in the phagocytic vacuole membrane during membrane fusion. During the formation of the phagocytic vacuole, the IMPs of the plasma membrane appeared to move in with the lipid bilayer while maintaining a distribution and density of IMPs similar to those of the plasma membranes. Occasionally, IMPs were aligned to linear arrays within phagocytic vacuole membranes. This alignment might be due to an interaction with linearly arranged motile structures on the side of the phagocytic vacuole membranes. IMP-free regions were observed after fusion of lysosomes with the phagocytic vacuoles or plasma membrane. These IMP-free areas probably represent sites where membrane fusion occurred between lysosomal membrane and phagocytic vacuole membrane or plasma membrane. Highly symmetrical patterns of IMPs were not observed during lysosomal membrane fusion. 相似文献