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71.
Little is known about how temporal stimulus factors influence perceptual learning. Here we demonstrate an essential role of stimulus temporal patterning in enabling perceptual learning by showing that 'unlearnable' contrast and motion-direction discrimination (resulting from random interleaving of stimuli) can be readily learned when stimuli are practiced in a fixed temporal pattern. This temporal patterning does not facilitate learning by reducing stimulus uncertainty; further, learning enabled by temporal patterning can later generalize to randomly presented stimuli. 相似文献
72.
Systematic changes in gene expression in postmortem human brains associated with tissue pH and terminal medical conditions 总被引:8,自引:0,他引:8
73.
Virus-inhibiting surgical glove to reduce the risk of infection by enveloped viruses 总被引:4,自引:0,他引:4
Bricout F Moraillon A Sonntag P Hoerner P Blackwelder W Plotkin S 《Journal of medical virology》2003,69(4):538-545
Needle puncture and other accidents that occur during surgery and other procedures may lead to viral infections of medical personnel, notably by hepatitis C (HCV) and human immunodeficiency virus (HIV), now that hepatitis B can be prevented by vaccination. A new surgical glove called G-VIR, which contains a disinfecting agent for enveloped viruses, has been developed. Herpes simplex type 1 (HSV) was used as a standard enveloped virus in both in vitro and in vivo tests of the virucidal capacity of the glove. Bovine viral diarrhea virus (BVDV) and feline immunodeficiency virus (FIV) were used as models for HCV and HIV, respectively. For in vitro study, a contaminated needle was passed through a glove and residual virus was titrated; for in vivo studies, animals were stuck with a contaminated needle through a glove. Despite variation in virus enumeration inherent in the puncture technique, statistical evaluation showed that infection was reproducibly and substantially reduced by passage through the virucidal layer. For BVDV, the amount of virus passing through the virucidal glove was reduced in 82% of pairwise comparisons with control gloves that lacked the virucidal agent; when plaque counts were adjusted to a common dilution, the median count for the virucidal glove was on the average reduced >10-fold. In experiments in which the proportion of wells infected with FIV was measured, the ratio of TCID(50) values (control glove to G-VIR) was >15, and probably much higher. For HSV, the amount of virus passing through the virucidal glove was reduced in 81% of comparisons with control gloves; the median of adjusted plaque counts was reduced on the average approximately eightfold or ninefold. In vivo tests with FIV and HSV in cats and mice, respectively, found smaller percentage reductions in infection than the in vitro tests but confirmed the virucidal effect of the gloves. 相似文献
74.
Stanley K. Sessions Matthias Stöck David R. Vieites Ryan Quarles Mi-Sook Min David B. Wake 《Chromosome research》2008,16(4):563-574
A cytogenetic analysis, including the karyotype, C-bands, silver-stained nucleolus organizer regions and genome size, was performed on the recently discovered species, Karsenia koreana, the first plethodontid salamander from Asia. The karyotype consists of 14 pairs of bi-armed chromosomes, with no evidence of heteromorphic sex chromosomes. C-banding reveals a concentration of heterochromatin at the centromeres as well as at interstitial locations. The smallest chromosome (pair number 14) has symmetrical interstitial C-bands in each arm, resembling chromosome no. 14 of North American species of its sister group taxon, supergenus Hydromantes. Acomparative analysis of C-band heterochromatin and silver-stained nucleolus organizer regions of Karsenia and other plethodontid genera reveals that chromosomal evolution may have featured chromosome 'repatterning' within the context of conserved chromosome number and shape in this clade. Genome size is correlated with geographic distribution in plethodontids and appears to have important phenotypic correlates as well. The genome size of Karsenia is relatively large, and resembles that of the geographically closest plethodontids from western North America, especially species of the genus Hydromantes. The biological significance of these cytogenetic characteristics of plethodontid salamanders is discussed within an evolutionary context. 相似文献
75.
76.
There is evidence that membrane proteins can serve as the functional units of ionic transport in biological membranes. Laser Raman spectroscopy has been used to probe specific molecular interactions inside two models of transport membrane proteins, valinomycin and gramicidin A. Conformational changes of these molecules, as well as specific interactions with ions, can be detected and may help elucidate how membrane transport proteins such as Na+ minus K+ ATPase and rhodopsin function. Resonance Raman spectroscopy has also been used to study conformational changes and protein-chromophore interactions in rhodopsin, the membrane protein that acts as the primary unit of visual excitation in the eye. 相似文献
77.
Altered production of tumour necrosis factors alpha and beta and interferon gamma by HIV-infected individuals. 总被引:4,自引:5,他引:4 下载免费PDF全文
A Vyakarnam P Matear A Meager G Kelly B Stanley I Weller P Beverley 《Clinical and experimental immunology》1991,84(1):109-115
In vitro studies shows that recombinant tumour necrosis factor (TNF) alpha and beta, and interferon-gamma (IFN-gamma) can enhance HIV replication, and peripheral blood mononuclear cells (PBMC) infected with HIV in vitro secrete high levels of the same cytokines. As T cells secrete all three mediators, the capacity of T cell activation signals to trigger cytokine production in PBMC from HIV-infected individuals was investigated as such patients may be immunocompromised. We demonstrate that asymptomatic seropositives in CDC group II/III as well as patients who have progressed to CDC group IV of the disease proliferate efficiently to anti-CD3 antibody, recombinant interleukin-2 (rIL-2), phytohaemagglutinin (PHA), PHA plus phorbol 12,13 dibutyrate (PMA) but secrete significantly (P less than 0.05) higher amounts of TNF-alpha, TNF-beta and IFN-gamma compared with controls in response to the same stimulants. We also show a difference between group II/III and group IV patients with the latter secreting more TNF-alpha and IFN-gamma. The kinetics of TNF-alpha and -beta, and IFN-gamma production was stimulus dependent with overall levels varying in time for each stimulus. Furthermore, the kinetics of the response to all three stimulants were altered in seropositives; CDC group II/III and group IV patients secreted higher levels of cytokines over several time points compared to controls. The altered production of these mediators by HIV-infected patients may contribute to disease progression and to the pathogenesis of AIDS. 相似文献
78.
The concept that prions are novel pathogens which are different from both viroids and viruses has received increasing support from many avenues of investigation over the past decade. Enriching fractions from Syrian hamster (SHa) brain for scrapie prion infectivity led to the discovery of the prion protein (PrP). Prion diseases of animals include scrapie and “mad cow” disease; those of humans present as inherited, sporadic and infectious neurodegenerative disorders, two of which are called Creutzfeldt-Jakob disease (CJD) and Gerstmann-Sträussler-Scheinker disease (GSS). The inherited human prion diseases are genetically linked to mutations in the PrP gene that result in non-conservative amino acid substitutions. Transgenic (Tg) mice expressing PrP carrying a GSS mutation developed neurodegeneration spontaneously and produced prions de novo. In other studies, Tg mice expressing both SHa and mouse (Mo) PrP genes were used to demonstrate that the “species barrier” for scrapie prions resides in the primary structure of PrP. This concept was strengthened by the results of studies in which mice expressing chimeric Mo/human (Hu) PrP transgenes were constructed which differ from MoPrP by nine amino acids between residues 96 and 167. All of the Tg(MHu2M) mice developed neurologic disease ~200 days after inoculation with brain homogenate from three patients who died of CJD. About 10% of Tg(HuPrP) mice expressing HuPrP and non-Tg mice developed neurologic disease >500 days after inoculation with CJD prions. The different susceptibilities of Tg(HuPrP) and Tg(MHu2M) mice to human prions indicate that additional species specific factors such as chaperone proteins are involved in prion replication. Diagnosis, prevention and treatment of human prion diseases should be facilitated by study of Tg(MHu2M) mice. Our findings and those from other studies suggest that mutant and wtPrP interact, perhaps through a chaperone-like protein, during the pathogenesis of the prion diseases. 相似文献
79.
Production of Macrophage Migration Inhibition Factors by Virus-Infected Cell Cultures 总被引:3,自引:3,他引:3 下载免费PDF全文
Macrophage migration inhibitory (MIF-like) activity was demonstrated in the supernatant fluids from cultures of African green monkey kidney cells (BGM) infected with mumps virus or Newcastle disease virus. We could detect no such activity in noninfected cultures. The virus-induced activity reported here is not due to nonspecific cytotoxic material released by dead or dying cells, and it does not require cell replication for its production. Preliminary estimates of molecular weight by Sephadex G-100 chromatography revealed a broad band of activity associated with the 45,000 and 65,000 markers. These are significantly smaller than previously reported chemotactic substances from virus-infected cultures, and thus appear to represent different cell products. These MIF-like factors may be produced concomitantly with interferon. However, ultraviolet irradiation of appropriate duration abolishes the ability of viruses to induce substances with MIF-like activity while preserving the ability to induce interferon. This strongly suggests that interferon is not the agent responsible for the macrophage migration inhibition effect. The functional properties of these various cell products induced by virus infection suggest that they all may play a role in the response to virus infection in vivo. 相似文献
80.
Quantification of Human Immunodeficiency Virus Type 1 RNA Levels in Plasma by Using Small-Volume-Format Branched-DNA Assays 总被引:2,自引:0,他引:2 下载免费PDF全文
Torange Yeghiazarian Yuqi Zhao Stanley E. Read William Kabat Xiaoyi Li Sarah J. Hamren Patrick J. Sheridan Judith C. Wilber David N. Chernoff Ram Yogev 《Journal of clinical microbiology》1998,36(7):2096-2098
We have developed small-volume (50 or 250 μl)-format branched-DNA assays for human immunodeficiency virus type 1 (HIV-1) RNA for use with specimens in which the volume is limited and/or a high viral load is anticipated. These formats exhibited good correlation with the standard 1-ml format; high specificity, reproducibility, and linearity; and no significant difference in the quantification of HIV-1 subtypes. 相似文献