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11.
Protoplasts of Bacillus stearothermophilus NCA 1503-4R are resistant to osmotic rupture and are not sensitive to mechanical manipulation. Protoplast stability is maintained by divalent cations. The thermostability of protoplasts is enhanced when the cells are grown at elevated temperatures. The membrane content of the cell and the protein-to-lipid ratio of the membrane increases as the growth temperature is increased. The membrane-bound nicotinamide adenine dinucleotide (reduced form) oxidase system from cultures grown at 70 C was more thermostable than the same enzyme system from cultures grown at 55 C. Alkaline phosphatase was resistant to thermal inactivation in the intact protoplast. The extent of this protection is dependent on protoplast stability. 相似文献
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A comparison of phenotypic plasticity between two species occupying different positions in a successional sequence 总被引:1,自引:0,他引:1
Yingxin Huang Xueyong Zhao Hongxuan Zhang Gang Huang Yayong Luo Wisdom Japhet 《Ecological Research》2009,24(6):1335-1344
We compared the phenotypic plasticity of two greenhouse-grown species (Corispermum macrocarpum and Salsola collina) occupying different positions in a successional sequence in Horqin Sandy Land, by treating with different population density
and the availability of soil nutrients and water. The same species can exhibit different patterns of plasticity in response
to different environmental factors. In the soil nutrient treatments, the plasticity pattern of S. collina could be described as “master-of-some”. However, in the soil-water and population-density treatments, it showed no significant
difference from C. macrocarpum in the reaction norm for plasticity. It was similar to a “jack-of-all-trades” plasticity pattern. Contrary to the previous
conclusion that late successional species had higher reproductive allocation than early successional species, in this successional
sequence, the late species had lower reproductive allocation in all treatments. Reproductive allocation of both species increased
with the increase in water availability and also increased with a decrease in nutrient levels. However, density had no effect
on reproductive allocation. Although the root:shoot ratio increased with decreasing water availability, there were no differences
in the plasticity pattern for this trait in both species. Root:shoot ratio was, however, not significantly affected by nutrient
availability and density. In a word, the plasticity patterns of invaders are adapted to the analyses of succession. 相似文献
15.
Xiaojing Dang Thu Giang Tran Thi Guanshan Dong Hui Wang Wisdom Mawuli Edzesi Delin Hong 《Planta》2014,239(6):1309-1319
Key message
Twenty-seven QTLs were identified for rice seed vigor, in which 16 were novel QTLs. Fifteen elite parental combinations were designed for improving seed vigor in rice.Abstract
Seed vigor is closely related to direct seeding in rice (Oryza sativa L.). Previous quantitative trait locus (QTL) studies for seed vigor were mainly derived from bi-parental segregating populations and no report from natural populations. In this study, association mapping for seed vigor was performed on a selected sample of 540 rice cultivars (419 from China and 121 from Vietnam). Population structure was estimated on the basis of 262 simple sequence repeat (SSR) markers. Seed vigor was evaluated by root length (RL), shoot length (SL) and shoot dry weight in 2011 and 2012. Abundant phenotypic and genetic diversities were found in the studied population. The population was divided into seven subpopulations, and the levels of linkage disequilibrium (LD) ranged from 10 to 80 cM. We identified 27 marker–trait associations involving 18 SSR markers for three traits. According to phenotypic effects for alleles of the detected QTLs, elite alleles were mined. These elite alleles could be used to design parental combinations and the expected results would be obtained by pyramiding or substituting the elite alleles per QTL (apart from possible epistatic effects). Our results demonstrate that association mapping can complement and enhance previous QTL information for marker-assisted selection and breeding by design. 相似文献16.
Priscilla K. Coe Bruce K. Johnson Michael J. Wisdom John G. Cook Martin Vavra Ryan M. Nielson 《The Journal of wildlife management》2011,75(1):159-170
Knowledge of how landscape features affect wildlife resource use is essential for informed management. Resource selection functions often are used to make and validate predictions about landscape use; however, resource selection functions are rarely validated with data from landscapes independent of those from which the models were built. This problem has severely limited the application of resource selection functions over larger geographic areas for widely distributed species. North American elk (Cervus elaphus) is an example of a widely-distributed species of keen interest to managers and for which validation of resource selection functions over large geographic areas is important. We evaluated the performance of resource selection functions developed for elk on one landscape in northeast Oregon with independent data from a different landscape in the same region. We compared predicted versus observed elk resource use for 9 monthly or seasonal periods across 3 yr. Results showed strong, positive agreement between predicted and observed use for 2 spring and 3 late summer-early fall models (3-yr r = 0.81–0.95). Predicted versus observed use was negatively or weakly positively correlated for 3 summer models and 1 mid-fall model (3-yr r = −0.57–0.14). Predicted and observed use correlated well when forage was limited (spring and late summer or early fall), corresponding to important biological stages for elk (parturition and breeding seasons). For these seasonal periods, model covariates such as rate of motorized traffic and canopy closure often were effective predictors of elk resource selection. The models we validated for spring and late summer-early fall may be used to evaluate management activities in areas with similar landscape characteristics. © 2010 The Wildlife Society. 相似文献
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Denham M. Wisdom Gines M. Salido Lisa M. Baldwin Jaipaul Singh 《Molecular and cellular biochemistry》1996,154(2):123-132
This study investigates the effect of magnesium (Mg2+) on the secretory responses and the mobilization of calcium (Ca2+) and Mg2+ evoked by cholecystokinin-octapeptide (CCK-8) in the exocrine rat pancreas. In the isolated intact perfused pancreas CCK-8 (10–10 M) produced marked increases in juice flow and total protein output in zero and normal (1.1 mM) extracellular Mg2+ [Mg2+]o compared to a much reduced secretory response in elevated (5 mM and 10 mM) [Mg2+]o Similar effects of perturbation of [Mg2+]o on amylase secretion and 45Ca2+ uptake (influx) were obtained in isolated pancreatic segments. In pancreatic acinar cells loaded with the fluorescent bioprobe fura-2 acetomethylester (AM), CCK-8 evoked marked increases in cytosolic free Ca2+ concentration [Ca2+]i in zero and normal [Mg2+]o compared to a much reduced response in elevated [Mg2+]o Pretreatment of acinar cells with either dibutyryl cyclic AMP (DB2 cAMP) or forskolin had no effect on the CCK-8 induced changes in [Ca2+]i. In magfura-2-loaded acinar cells CCK-8 (10–8 M) stimulated an initial transient rise in intracellular free Mg2+ concentration [Mg2+]i followed by a more prolonged and sustained decrease. This response was abolished when sodium Na+ was replaced with N-methyl-D-glucamine (NMDG). Incubation of acinar cells with 10 mM Mg2+ resulted in an elevation in [Mg2+]i. Upon stimulation with CCK-8, [Mg2+]i. decreased only slightly compared with the response obtained in normal [Mg2+]o. CCK-8 caused a net efflux of Mg2+ in pancreatic segments; this effect was abolished when extracellular sodium [Na+]o was replaced with either NMDG or choline. The results indicate that Mg2+ can regulate CCK-8-evoked secretory responses in the exocrine pancreas possibly via Ca2+ mobilization. Moreover, the movement of Mg2+ in pancreatic acinar cells is dependent upon extracellular Na+. 相似文献
18.
Revertants of v-fos-transformed rat fibroblasts: suppression of transformation is dominant. 总被引:6,自引:3,他引:3
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Phenotypic revertants of Finkel-Biskis-Riley (FBR)-murine sarcoma virus-transformed rat fibroblasts were isolated on the basis of their adherence to plastic tissue culture dishes in the absence of divalent cations. Some revertants had sustained deletions or inactivating mutations of the v-fos gene. However, two revertants expressed a functional v-fos gene at levels equal to that in the transformed parental cells, and therefore phenotypic reversion was due to mutations in nonviral genes. These revertants were considered nontransformed according to four criteria: (i) they were flat and had a nontransformed morphology, (ii) they were contact inhibited when grown to confluence, (iii) they did not display anchorage-independent growth in soft agar, and (iv) they did not form tumors in nude mice. Somatic-cell hybrids between the revertants and the transformed parental cells were nontransformed, suggesting that the revertants had sustained an activating mutation of a gene capable of suppressing transformation. The expression of c-jun, junB, and junD was not altered in the revertants, and they could not be transformed by transfection with a c-jun expression vector. The revertants were resistant to transformation by an activated c-Ha-ras gene but were susceptible to transformation by simian virus 40. Our results demonstrate the existence of a class of revertants that harbor genes capable of suppressing transformation by v-fos and some other oncogenes. This contrasts with previously described revertants of transformation by v-fos that contain recessive mutations. 相似文献
19.
Li G Gustafson-Brown C Hanks SK Nason K Arbeit JM Pogliano K Wisdom RM Johnson RS 《Developmental cell》2003,4(6):865-877
The migration of epithelial layers requires specific and coordinated organization of the cells at the leading edge of the sheet. Mice that are conditionally deleted for the c-jun protooncogene in epidermis are born at expected frequencies, but with open eyes and with defects in epidermal wound healing. Keratinocytes lacking c-Jun are unable to migrate or elongate properly in culture at the border of scratch assays. Histological analyses in vitro and in vivo demonstrate an inability to activate EGF receptor at the leading edge of wounds, and we demonstrate that this can be rescued by supplementation with conditioned medium or the EGF receptor ligand HB-EGF. Lack of c-Jun prevents EGF-induced expression of HB-EGF, indicating that c-jun controls formation of the epidermal leading edge through its control of an EGF receptor autocrine loop. 相似文献
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