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31.
Isaac Sadnik Scott J. Petersen Nazli Oktay Calvin S. McLaughlin Kivie Moldave 《Biochimica et Biophysica Acta (BBA) - Gene Structure and Expression》1984,782(2):220-227
The effects of incubation of yeast spheroplasts at elevated temperature (40°C) on a number of activities involved in protein biosynthesis have been examined in preparations obtained from wild-type cells (wt A364A) and a temperature-sensitive mutant (ts 7–45) derived from it. With wild-type cells, preincubation of spheroplasts at the elevated temperature had little or no effect on the following: (1) the ribosomal subunit-polysome pattern; (2) the translation of exogenous natural mRNA in postpolysomal extracts devoid of endogenous mRNA; (3) the translation of poly(U) in postpolysomal extracts; (4) the incorporation of methionine into 40 S preinitiation and 80 S initiation complexes; (5) the synthesis of Met-tRNA in postribosomal (cytosol) extracts; and (6) the formation of eIF-2·GTP·Met-tRNAf ternary complex in the cytosol. With temperature-sensitive spheroplasts that had not been preincubated at the elevated temperature, the concentration of free, native 40 S subunits appeared to be lower and that of 60 S subunits higher than in wild-type cells; translation of exogenous natural mRNA in postpolysomal extracts was somewhat lower than in wild-type preparations, but all of the other reactions and components measured were comparable to those in wild-type preparations. Preincubation of temperature-sensitive spheroplasts at 40°C resulted in: (1) a further decrease in the level of 40 S subunits; (2) disaggregation of polysomes; (3) loss of ability to translate natural mRNA but not poly(U); (4) decreased ability to form 40 S preinitiation intermediates; and (5) production of an activity, found in the cytosol, that inhibited Met-tRNA synthetase reversibly. The inhibitor had the characteristics of a protein and did not appear to be a proteinase, nuclease, or nucleotidase. 相似文献
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Inferior temporal (IT) cortex as the final stage of the ventral visual pathway is involved in visual object recognition. In our everyday life we need to recognize visual objects that are degraded by noise. Psychophysical studies have shown that the accuracy and speed of the object recognition decreases as the amount of visual noise increases. However, the neural representation of ambiguous visual objects and the underlying neural mechanisms of such changes in the behavior are not known. Here, by recording the neuronal spiking activity of macaque monkeys’ IT we explored the relationship between stimulus ambiguity and the IT neural activity. We found smaller amplitude, later onset, earlier offset and shorter duration of the response as visual ambiguity increased. All of these modulations were gradual and correlated with the level of stimulus ambiguity. We found that while category selectivity of IT neurons decreased with noise, it was preserved for a large extent of visual ambiguity. This noise tolerance for category selectivity in IT was lost at 60% noise level. Interestingly, while the response of the IT neurons to visual stimuli at 60% noise level was significantly larger than their baseline activity and full (100%) noise, it was not category selective anymore. The latter finding shows a neural representation that signals the presence of visual stimulus without signaling what it is. In general these findings, in the context of a drift diffusion model, explain the neural mechanisms of perceptual accuracy and speed changes in the process of recognizing ambiguous objects. 相似文献
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Evidence from clinical and epidemiological studies indicates that women are disproportionately susceptible to sexually transmitted viral infections. To understand the underlying biological basis for this increased susceptibility, more studies are needed to examine the acute events in the female reproductive tract following exposure to viruses during sexual transmission. The epithelial lining of the female reproductive tract is the primary barrier that sexually transmitted viruses, such as HIV-1 and HSV-2 need to infect or traverse, in order to initiate and establish productive infection. We have established an ex-vivo primary culture system to grow genital epithelial cells from upper reproductive tract tissues of women. Using these cultures, we have extensively examined the interactions between epithelial cells of the female genital tract and HSV-2 and HIV-1. In this review, we describe in detail the experimental protocol to grow these cultures, monitor their differentiation and inoculate with HSV-2 and HIV-1. Prospective use of these cultures to re-create the microenvironment in the reproductive tract is discussed. 相似文献
35.
In this study, our aim was to investigate the association of methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism on the vitamin B12 therapy response in 95 patients with vitamin B12 deficiency and 92 healthy control subjects using vitamin B12, plasma total homocysteine (tHcy), and folate as the main measure of outcome. MTHFR C677T genotypes were determined by polymerase chain reaction-restriction fragment length polymorphism techniques. There were no differences in the distribution of MTHFR genotypes in the cases versus the controls. Mean concentrations of plasma tHcy and B12 vitamin were 18.84 μM and 142.47 pg/mL in patients with TT (10.5%) genotypes. Furthermore, mean concentrations of B12 vitamin after cobalamin therapy were 697.62, 656.64, and 488.76 pg/mL in patients with the CC, CT, and TT genotypes, respectively. The MTHFR 677 TT genotype has decreasing effect in B12 vitamin and increasing effect in tHcy. In comparison with the patients having CC and CT genotypes, patients with the TT genotype had a lower response to vitamin B12 therapy. 相似文献
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Barlow CA Kitiphongspattana K Siddiqui N Roe MW Mossman BT Lounsbury KM 《Apoptosis : an international journal on programmed cell death》2008,13(5):681-692
Oxidant stress plays a role in the pathogenesis of pulmonary diseases, including fibrotic lung disease and cancer. We previously
found that hydrogen peroxide (H2O2) initiates an increase in Ca2+/cAMP-response element binding protein (CREB) phosphorylation in C10 alveolar type II cells that requires activation of extracellular
regulated kinases 1/2 (ERK1/2). Here, we investigated the role of crosstalk between protein kinase A (PKA) and epidermal growth
factor receptor (EGFR) in oxidant-induced signaling to ERK1/2 and CREB in C10 cells. Application of H2O2 increased nuclear accumulation of PKA, and inhibition of PKA with H89 reduced oxidant-mediated phosphorylation of both CREB
and ERK1/2. Single cell measurements of cAMP and redox status, using a FRET-based biosensor and a redox-sensitive GFP, respectively,
indicated that H2O2 increases production of cAMP that correlates with redox state. Inhibition of EGFR activity decreased both H2O2-induced CREB phosphorylation and translocation of PKA to the nucleus, suggesting that crosstalk between PKA and EGFR underlies
the oxidant-induced CREB response. Furthermore, knockdown of CREB expression using siRNA led to a decrease in bcl-2 and an
increase in oxidant-induced apoptosis. Together these data reveal a novel role for crosstalk between PKA, ERK1/2 and CREB
that mediates cell survival during oxidant stress. 相似文献
37.
Genetic determinants of phenotypic diversity in humans 总被引:1,自引:0,他引:1
New technologies for rapidly assaying DNA sequences have revealed that the degree and nature of human genetic variation is far more complex then previously realized. These same technologies have also resulted in the identification of common genetic variants associated with more than 30 human diseases and traits. 相似文献
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Johnathan Cooper-Knock Tobias Moll Tennore Ramesh Lydia Castelli Alexander Beer Henry Robins Ian Fox Isabell Niedermoser Philip Van Damme Matthieu Moisse Wim Robberecht Orla Hardiman Monica P. Panades Abdelilah Assialioui Jesus S. Mora A. Nazli Basak Karen E. Morrison Christopher E. Shaw Pamela J. Shaw 《Cell reports》2019,26(9):2298-2306.e5
40.
Yagmur Unver Melike Yildiz Nazli Pinar Arslan Serkan Ortucu 《Biocatalysis and Biotransformation》2015,33(2):105-110
The present study was performed to produce the protease using free and immobilized cells of locally isolated cold-adapted psychrotolerant yeast Cryptococcus victoriae CA-8. Cell immobilization was performed using sodium alginate as entrapping agent. The best conditions for enzyme production by both free and immobilized cells of the yeast were temperature of 15°C and initial pH of 8.0. The optimal incubation times were 72 and 96 h for immobilized and free cells, respectively. Immobilized cells were reused in 3 successive reaction cycles without any loss in the maximum protease activity. Little decreases in the protease activity were observed in 4 and 5 cycles. Under the optimized conditions, the maximum enzyme activities were determined as 12.1 and 13.5 U/mL for free and immobilized cells, respectively. This is a first attempt on cold-active alkaline protease production by free and/or immobilized cells of yeasts. Besides, the protease activity of the yeast C. victoriae CA-8 was investigated for the first time in the present study. 相似文献