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1.
Summary Enzymatic hydrolysis of racemic 3-acetylthio-2-methylpropionic methyl ester catalyzed by bovine pancreatic protease and Mucor javanicus lipase showed opposite enantioselecivity. A tandem hydrolysis of the ester catalyzed by these two enzymes gives enantiomerically enriched (S)-3-acetylthio-2-methylpropionic acid, a building block of captopril.  相似文献   
2.
The mitochondrial selenoprotein is a major structural protein of the keratinous mitochondrial capsule in mammalian sperm, a structure that functions in shaping mitochondria into the helical sheath surrounding the flagellum. A cDNA clone (Kleene et al., 1990) was isolated previously encoding a protein whose predicted size and amino acid content of > 20% cysteine and proline closely resembled a selenoprotein in the bull mitochondrial capsule. The sequences of additional cDNAs and genomic DNA reported here reveal that the mouse mitochondrial capsule selenoprotein reading frame begins 54 codons further upstream than previously reported. Significantly, these 54 codons contain three in-phase UGA codons, which normally signify stop but encode selenocysteine in bacterial and mammalian selenoproteins. The coding region of the mitochondrial capsule selenoprotein gene is interrupted by a single intron. S1 mapping and primer extension demonstrate that the vast majority of MCS mRNAs are spliced using consensus 5' and 3' slice junctions in mammalian cells. However, two cDNAs have been identified that apparently represent rare mRNA variants produced by use of cryptic splice sites.  相似文献   
3.
Rapid identification of the expression of oncogene products in specific cell types could potentially be useful in the diagnosis and treatment of human malignancy. We have now observed that through the use of lysolecithin permeabilization and fluorescence-activated flow cytometry, cells expressing high levels of the v-Ha-ras oncogene product, p21, can readily be distinguished from the nontransformed parent cells in a rapid and quantitative manner.  相似文献   
4.
Water-deficit induction of a tomato H1 histone requires abscisic acid   总被引:5,自引:0,他引:5  
Many genes are induced by periods of water deficit, and a subset of these are dependent on elevated ABA content for expression. A number of drought-induced genes are not induced in leaves of the ABA-deficient mutant flacca from tomato (Lycopersicon esculentum) but are induced in detached, wilted wild-type leaves and ABA-treated leaves of both genotypes. The nucleotide sequence of the cDNA and corresponding genomic DNA fragment of one of these genes, his1-s (formerly called le20), encodes an amino acid sequence that is rich in Lys, Ala, and Ser. The predicted protein contains the tripartite structure of H1 histone and is similar to other H1 histones, especially in the globular domain. Since, his1-s is more closely related to a stress-induced gene from Lycopersicon pennellii than to another H1 histone in the tomato genome it is considered a stress-induced variant of H1 histone. his1-s mRNA accumulated in vegetative plants in response to other abiotic stress treatments, including application of polyethylene glycol, and salt. The mRNA preferentially accumulated in leaves as compared to roots. his1-s mRNA accumulation was controlled during development; the level was higher in developing seeds of mature green fruit than in detached wilted leaves. H1 histones have been implicated in the general repression of gene expression and in the regulation of specific genes. The rapid accumulation of his1-s mRNA during stress may indicate that this unique, stress-induced H1 histone is involved in controlling gene expression during plant stress.  相似文献   
5.
The switching on-and-off of I-kappaB kinase (IKK) and NF-kappaB occurs rapidly after signaling. How activated IKK becomes down-regulated is not well understood. Here we show that following tumor necrosis factor-alpha stimulation, protein phosphatase 2A (PP2A) association with IKK is increased. A heptad repeat in IKKgamma, helix 2 (HLX2), mediates PP2A recruitment. Two other heptad repeats downstream of HLX2, termed coiled-coil region 2 (CCR2) and leucine zipper (LZ), bind HLX2 and negatively regulate HLX2 interaction with PP2A. HTLV-1 transactivator Tax also binds HLX2, and this interaction is enhanced by CCR2 but reduced by LZ. In the presence of Tax, PP2A-IKKgamma binding is greatly strengthened. Interestingly, peptides spanning CCR2 and/or LZ disrupt IKKgamma-Tax and IKKgamma-PP2A interactions and potently inhibit NF-kappaB activation by Tax and tumor necrosis factor-alpha. We propose that when IKK is resting, HLX2, CCR2, and LZ form a helical bundle in which HLX2 is sequestered. The HLX2-CCR2-LZ bundle becomes unfolded by signal-induced modifications of IKKgamma or after Tax binding. In this conformation, IKK becomes activated. IKKgamma then recruits PP2A via the exposed HLX2 domain for rapid down-regulation of IKK. Tax-PP2A interaction, however, renders PP2A inactive, thus maintaining Tax-PP2A-IKK in an active state. Finally, CCR2 and LZ possibly inhibit IKK activation by stabilizing the HLX2-CCR2-LZ bundle.  相似文献   
6.
A new subfamily Rudisiricinae Gao, Rasnitsyn, Ren & Shih, n. subfam. and a new genus Rudisiricius Gao, Rasnitsyn, Ren & Shih, n. gen. with three new species R. belli Gao, Rasnitsyn, Ren & Shih n. sp., R. crassinodus Gao, Rasnitsyn, Ren & Shih, n. sp., and R. celsus Gao, Rasnitsyn, Ren & Shih, n. sp. are described and illustrated from the family Praesiricidae. The type specimens were collected from the Late Jurassic to Early Cretaceous Yixian Formation, northeastern China. The new subfamily also includes Aulidontes Rasnitsyn from the Upper Jurassic of Karatau in Kazakhstan. This is the first record of Praesiricidae in China. These well-preserved nearly-complete new fossils reported here provide additional material and structure characters about this family, which helps filling some gap in the evolution of Lower Hymenoptera.  相似文献   
7.
8.
The NK1 and NK2 receptor activity of a series of 5-[(3,5-bis(trifluoromethyl)phenyl)methoxy]-3-(3,4-dichlorophenyl)-4(Z)-(methoxyimino)pentyl-1-piperidines was evaluated. Compounds 11d, 11e, 11f, 12a, and 12k were found to be our most potent inhibitors.  相似文献   
9.
ABSTRACT: BACKGROUND: Traditional electroencephalography provides a critical assessment of pain responses. The perception of pain, however, may involve a series of signal transmission pathways in higher cortical function. Recent studies have shown that a mathematical method, the neuronal avalanche model, may be applied to evaluate higher-order network dynamics. The neuronal avalanche is a cascade of neuronal activity, the size distribution of which can be approximated by a power law relationship manifested by the slope of a straight line (i.e., the alpha value). We investigated whether the neuronal avalanche could be a useful index for nociceptive assessment. FINDINGS: Neuronal activities were recorded with 4 X 8 multichannel electrode arrays in the primary somatosensory cortex (S1) and anterior cingulate cortex (ACC). Under light anesthesia, peripheral pinch stimulation increased the slope of the alpha value in both the ACC and S1, whereas brush stimulation increased the alpha value only in the S1. The increase in alpha values was blocked in both regions under deep anesthesia. The increase in alpha values in the ACC induced by peripheral pinch stimulation was blocked by medial thalamic lesion, but the increase in alpha values in the S1 induced by brush and pinch stimulation was not affected. CONCLUSIONS: The neuronal avalanche model shows a critical state in the cortical network for noxious-related signal processing. The alpha value may provide an index of brain network activity that distinguishes the responses to somatic stimuli from the control state. These network dynamics may be valuable for the evaluation of acute nociceptive processes and may be applied to chronic pathological pain conditions.  相似文献   
10.
Androgens have important physiological effects in women. Not only are they the precursor hormones for estrogen biosynthesis in the ovaries and extragonadal tissues, but also act directly via androgen receptors (ARs) throughout the body. Studies of the role of androgens on breast cancer development are controversial and the mechanisms involved are not fully understood. In this report we demonstrate that a non-aromatizable androgen metabolite, dihydrotestosterone (DHT), stimulated cell proliferation in vitro of both estrogen receptor-α (ER-α)-positive MCF-7 cells and ER-α-negative MDA-MB-231 human breast cancer cells. A contribution of ER to the proliferative effect of DHT in MCF-7 cells was supported by actions of small interfering RNA (siRNA) ER-α transfection and of the specific inhibitor of ER, ICI 182,780 to block DHT-induced proliferation. A contribution of the possible conversion of DHT to androstane-3α, 17β-diol was not excluded in these MCF-7 cell studies. In MDA-MB-231 cells, a novel mechanism was implicated, in that anti-integrin αvβ3 or an Arg-Gly-Asp (RGD) peptide targeted at a small molecule binding domain of the integrin eliminated the DHT effect on cell proliferation. Anti-integrin αvβ3 did not affect DHT action on MCF-7 cells. A contribution from classical androgen receptor to the DHT effect in each cell line was excluded. A proliferative DHT signal is transduced in both ER-α-positive and ER-α-negative breast cancer cells, but by discrete mechanisms.  相似文献   
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