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141.
142.
Inositol 1,4,5-trisphosphate receptors (IP3R) are intracellular Ca2+ channels. Most animal cells express mixtures of the three IP3R subtypes encoded by vertebrate genomes. Adenophostin A (AdA) is the most potent naturally occurring agonist of IP3R and it shares with IP3 the essential features of all IP3R agonists, namely structures equivalent to the 4,5-bisphosphate and 6-hydroxyl of IP3. The two essential phosphate groups contribute to closure of the clam-like IP3-binding core (IBC), and thereby IP3R activation, by binding to each of its sides (the α- and β-domains). Regulation of the three subtypes of IP3R by AdA and its analogues has not been examined in cells expressing defined homogenous populations of IP3R. We measured Ca2+ release evoked by synthetic adenophostin A (AdA) and its analogues in permeabilized DT40 cells devoid of native IP3R and stably expressing single subtypes of mammalian IP3R. The determinants of high-affinity binding of AdA and its analogues were indistinguishable for each IP3R subtype. The results are consistent with a cation-π interaction between the adenine of AdA and a conserved arginine within the IBC α-domain contributing to closure of the IBC. The two complementary contacts between AdA and the α-domain (cation-π interaction and 3″-phosphate) allow activation of IP3R by an analogue of AdA (3″-dephospho-AdA) that lacks a phosphate group equivalent to the essential 5-phosphate of IP3. These data provide the first structure-activity analyses of key AdA analogues using homogenous populations of all mammalian IP3R subtypes. They demonstrate that differences in the Ca2+ signals evoked by AdA analogues are unlikely to be due to selective regulation of IP3R subtypes. 相似文献
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Adrian J. Cutler Mohammed Saleem Hong Wang 《In vitro cellular & developmental biology. Plant》1991,27(3):104-111
Summary Cereal leaf protoplasts are extremely difficult to culture (recalcitrant) in vitro. There have been few reports of division
and the protoplasts typically exhibit excessive enlargement and vacuolization with reduced cell wall deposition. Inasmuch
as leaf base explants are capable of callus formation in vitro, protoplasts derived from this tissue must have lost the ability
to divide as a consequence of changes induced by the wall-digestion process. We review evidence suggesting that the inhibition
of mitosis in these protoplasts is a consequence of a cascade of events initiated at the plasma membrane. The enzyme treatment
necessary for wall removal triggers membrane depolarization and other changes that can lead to the initiation of lipid peroxidation
and oxidative stress. Mitotically inactive cereal leaf protoplasts are unable to mount a protective response to these degradative
processes. Consequently, the resulting membrane perturbations and permeabilization give rise to secondary effects on the cytoskeleton
and the cell wall. These effects include reduced or absent microtubules as well as reduced and uneven wall deposition. Such
abnormalities are observed in cereal leaf protoplasts and are sufficient to account for recalcitrance because the occurrence
of mitosis is strongly dependent on a normal cell wall and cytoskeleton.
This paper is NRCC number 32475. 相似文献
146.
We generalise the model of [21] in which the author considered a predator-prey system with predators eating only the young ones (or eggs) of the prey species. The prime assumption of the present paper is that the birth rate (per unit individual per unit time) of predators depends not only on the current prey egg-level but also on all previous prey egg-levels. It is seen that under this assumption an otherwise stable system may be stable as well as unstable leading to the conclusion that young predation with time delay is less stable than without it. Finally for the model of [21] we prove a result which shows that large predation rates help in the co-existence of both predator and prey species. 相似文献
147.
AbstractFour organic solvents along with water were applied for the conventional extraction of Eucalyptus camaldulensis (Myrtaceae), phenolic contents and antioxidant activities were investigated through variable protocols and correlation coefficients were considered, the phenolic composition was also characterized by Gas chromatography-mass spectrometry (GC-MS). Using solvents with dissimilar polarities affected the phenolic yields extracted from E. camaldulensis and their related antioxidant activities varied significantly among the four investigated plant organs. The leaf extract of acetone 70% contained the highest amount of phenolic compounds (46.56?mg/g dry weight); while the bud-water boiled extract maintained the maximum value of tannins (45.68?mg/g dry weight). Correlation coefficients indicated that phenolic compounds were mostly accountable for the phosphomolybednum antioxidant potentials (0.520), followed by tannins (0.460). Also, both the reducing power activities and hydrogen peroxide scavenging of E. camaldulensis extracts positively correlated with tannins, but at different significance degrees. However, the GC-MS analysis revealed that most of the detected phenolic constituents were more abundant in the plant seed. So, the existence of some other compounds such as organic acids, along with phenolics, may have increased the antioxidant potentials of leaf and bud. Undeniably, the optimization of extraction conditions could stimulate the antioxidant capabilities of the plant extracts of E. camaldulensis. 相似文献
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Genomic screens for small RNA candidates in Enterobacteriacae genomes were carried out with existing small RNA sequences, conserved flanking genes, and genomic backbone information. The small RNA sequences and contexts from E. coli K12 formed the basis of the search. Sequence identity identified 117 additional small RNA homologs in related genomes. Motifs of continuous sequence stretches added another 48 sRNA regions, termed partial homologs. However, this study is unique in identifying 160 nonhomologous sRNA loci in related genomes based on the conserved flanking gene synteny and the backbone retention information obtained from KEGG-SSDB. Gene synteny and genomic backbone continuity were observed to be correlated with all of the sRNAs in related genomes. This search is the first of its kind toward identification of functionally important regions using gene order and back-bone information. A disruption in flanking gene order or genomic backbone indicates a possible hotspot for alien gene pool integration. This study reports both occurrence of multiple copies of a sRNA and co-occurrence of different sRNAs between a pair of conserved flanking genes. In general, synteny and genomic backbone retention information can be added as additional search criteria toward the design of precise bioinformatics tools for sRNA, gene identification, and gene functional annotations in related genomes. 相似文献
150.
Abdul Rouf Khawaja Tanveer Iqbal Dar Sajad Maik Javaid Magray Ashiq Bhat Arif Hameed Bhat Mohd.Saleem Wani Baldev Singh Wazir 《Reviews in urology》2015,17(4):241-245
Inaccessible urethra with no retrograde endoscopic access due to multiple/diffuse strictures or multiple urethrocutaneous fistulas with acute urinary retention due to posturethral instrumentation (transurethral resection of bladder tumor [TURBT], or TURBT with transurethral resection of the prostate [TURP]), is a rare entity. Management of such a case with a bladder tumor for TURBT/surveillance cystoscopy poses a great challenge. The authors present 12 cases of bladder tumor with inaccessible urethra, 10 cases due to multiple strictures (post-TURBT and/or TURP), and 2 cases due to urethrocutaneous fistulas (post-TURBT), who presented to our emergency department with acute urinary retention. Emergent suprapubic catheterization was used as a temporary treatment method.Key words: Suprapubic cystostomy, Inaccessible urethra, Bladder tumors, Tract seedlingBladder tumors are the most common neoplasm of the lower urinary tract, comprising 6% of all malignancies in men and 2% of those in women.1 A majority of patients present with gross painless hematuria, usually as the sole presenting symptom.2 Bladder carcinoma is unique among human neoplasms in that many of its etiologic factors are known; the urologist should be aware of the possible occupational exposures to urothelial carcinogens.3 Initial symptoms of urothelial carcinoma of the bladder (UCB) include microhematuria, painless macrohematuria, and/or irritative voiding symptoms, and require further investigation. Carcinoma in situ of the bladder causes irritative lower urinary tract symptoms (LUTS) more often than does papillary UCB. Histopathologic evaluation is necessary to assess stage and grade with sufficient certainty after the appearance of bladder tumors.4 Bladder tumors spread by implantation in abdominal wounds, denuded epithelium, resected prostatic fossa, or traumatized urethra5; implantation occurs most often with high-grade tumors. 相似文献