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排序方式: 共有125条查询结果,搜索用时 187 毫秒
31.
Sandra Regina B. R. Sella Belquis P. Guizelini Luciana P. S. Vandenberghe Adriane B. P. Medeiros Carlos Ricardo Soccol 《Applied microbiology and biotechnology》2009,82(6):1019-1026
Bacillus atrophaeus’ spores are used in the preparation of bioindicators to monitor the dry heat, ethylene oxide, and plasma sterilization processes
and in tests to assess sterilizing products. Earlier production methods involved culture in chemically defined medium to support
sporulation with the disadvantage of requiring an extended period of time (14 days) besides high cost of substrates. The effect
of cultivation conditions by solid-state fermentation (SSF) was investigated aiming at improving the cost–productivity relation.
Initial SSF parameters such as the type of substrate were tested. Process optimization was carried out using factorial experimental
designs and response surface methodology in which the influence of different variables—particle size, moisture content, incubation
time, pH, inoculum size, calcium sources, and medium composition—was studied. The results have suggested that soybean molasses
and sugarcane bagasse are potential substrate and support, respectively, contributing to a 5-day reduction in incubation time.
Variables which presented significant effects and optimum values were mean particle size (1.0 mm), moisture content (93%),
initial substrate pH (8.0), and water as a solution base. The high-yield spore production was about 3 logs higher than the
control and no significant difference in dry heat resistance was observed. 相似文献
32.
G. Sella A. Marin A. Santovito M. Girotti P. Cervella M. Delpero 《Russian Journal of Genetics》2010,46(8):1009-1015
The isonymic method has been generally accepted in population genetic studies and surnames have been successfully used to
investigate human populations as if they were genetic markers associated to the Y chromosome. In this study we analysed the
microevolution dynamics of Postua, a mountain village of North Western Italy, by means of demographic methods. The uniqueness
of this community is due to its past geographical and cultural isolation and to the high frequency of marriage between relatives.
During the study period considered (1640–1989) the population underwent several fluctuations in size and other demographic
parameters such as the endogamy, isonimy and consanguinity rates. Until the first half of the XIX century Postua appears to
be a village characterised by a closed and isolated community, with high endogamy (80–90%) and isonimy (up to 34.4%). Only
at the beginning of the XX century, when the population started to be subjected to significant immigration fluxes, data show
a progressive reduction of the isolation. The population showed two demographic peaks, the first around the second half of
the XVIII century (1639 inhabitants) and the second at the end of the XIX century (1464 inhabitants). The S/N ratio was low (0.2–0.3) and relatively constant until the beginning of the last century, and only in the last three decades
of the XX century, when the population was subjected to immigration, Postua showed a significant increase in the S/N ratio values (to about 0.9). The surname frequency was constant until the 1850 when almost all surnames were the same as
those already present in the XVII century. From the first half of the XIX century, the founder surnames decreased, whereas
new surnames started to increase and became persistent in the population. 相似文献
33.
34.
Dawei Jiang Peter P Jones Darryl R Davis Robert Gow Martin S Green David H Birnie SR Wayne Chen Michael H Gollob 《Channels (Austin, Tex.)》2010,4(4):302-310
Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an arrhythmogenic disease that manifests as syncope or sudden death during high adrenergic tone in the absence of structural heart defects. It is primarily caused by mutations in the cardiac ryanodine receptor (RyR2). The mechanism by which these mutations cause arrhythmia remains controversial, with discrepant findings related to the role of the RyR2 binding protein FKBP12.6. The purpose of this study was to characterize a novel RyR2 mutation identified in a kindred with clinically diagnosed CPVT.Single-strand conformational polymorphism analysis and direct DNA sequencing were used to screen the RyR2 gene for mutations. Site-directed mutagenesis was employed to introduce the mutation into the mouse RyR2 cDNA. The impact of the mutation on the interaction between RyR2 and a 12.6 kDa FK506 binding protein (FKBP12.6) was determined by immunoprecipitation and immunoblotting and its effect on RyR2 function was characterized by single cell Ca2+ imaging and [3H]ryanodine binding.A novel CPVT mutation, E189D, was identified. The E189D mutation does not alter the affinity of the channel for FKBP12.6, but it increases the propensity for store-overload-induced Ca2+ release (SOICR). Furthermore, the E189D mutation enhances the basal channel activity of RyR2 and its sensitivity to activation by caffeine.The E189D RyR2 mutation is causative for CPVT and functionally increases the propensity for SOICR without altering the affinity for FKBP12.6. These observations strengthen the notion that enhanced SOICR, but not altered FKBP12.6 binding, is a common mechanism by which RyR2 mutations cause arrhythmias.Key words: arrhythmia, calcium, death sudden, genetics, ion channels 相似文献
35.
Sex allocation theory predicts that, in hermaphroditic organisms,individuals allocate a fixed amount of resources divided amongmale and female functions to reproduction and that the proportiondevoted to each sex depends on the mating group size. As themating group size increases, hermaphrodites are predicted toallocate proportionally more resources to the male and lessresources to the female function (approaching equal allocationto both sexes) to face increased sperm competition. Up to nowlittle experimental evidence has been provided to support thetheory in hermaphroditic animals. Facultative shift betweenmale and female allocation in response to variation in localgroup size does occur in several taxa but not always in theexpected direction and not with similar patterns. In the protandricand then simultaneously hermaphroditic polychaete worm Ophryotrochadiadema reproductive resources are flexibly allocated in theprotandrous and the hermaphroditic phase. The cost of male reproductionduring adolescence is spread over the whole energy budget ofthe animal as shown by the shortening of lifespan and the loweringof growth rate in individuals with enhanced male expenditureduring the protandrous phase. Moreover, in this species, shortterm sex allocation adjustments differ from those describedin other taxa. Individuals regulate their reproductive outputso that where reproductive competitors are present, the numberof female gametes is strongly reduced but the number of malegametes (although it changes) is not significantly increased.Resources subtracted from the female function are not directlyallocated to sperm production, but to expensive male behaviorsthat are likely to enhance male reproductive success. Theseresults are discussed in the light of the relevance of sexualselection in large populations of hermaphrodites. 相似文献
36.
Aluminum (Al) and iron (Fe) have been implicated as playing a toxic role in the pathologic lesions of Alzheimer's disease. In the following report we describe the uptake and toxicity of Al, the effect of Al on Fe uptake, and the expression of neurofibrillary tangle (NFT) protein in murine neuroblastoma cells (Neuro 2A). Significant cell Al uptake and inhibition of cell growth were seen in Neuro 2A cells at 24, 48, 72, and 96 h after plating in medium containing Al transferrin (Al-Tf) and Al citrate. Al-loaded Neuro 2A cells showed increased rates of 59Fe and 125I-Tf uptake and total cellular Fe content at 24, 48, 72, and 96 h after plating compared with control cultures. Significant increases in NFT protein staining were detected in Al-exposed cells at 72 and 96 h in culture compared with controls. The intensity of NFT staining in Al-loaded cells was directly proportional to the time in culture. There was no difference in malonyldialdehyde levels measured in control versus Al-loaded Neuro 2A cells. These results suggest that the accumulation of Al in Neuro 2A cells resulted in increased uptake of Fe, inhibition of cell growth, and expression of NFT protein, partially mimicking the pathological hallmarks of Alzheimer's disease. This model system may also be applicable for Al-induced dialysis dementia, because the Al concentrations at which cell toxicity occurred can be found in dialysis patients. 相似文献
37.
Cellular Al accumulation has been shown to alter iron metabolism and induce peroxidative injury. Therefore antioxidants could potentially reduce or prevent peroxidative injury in Al-loaded cells. To test this hypothesis we assessed the effect of the antioxidants N-acetyl cysteine (NAC), catalase, superoxide dismutase (SOD), and tetramethylpiperidine 1-oxyl (TEMPO) in abrogating Al-associated cell toxicity and melonyldialdehyde (MDA) accumulation in mouse hepatocytes. Mouse hepatocytes (MH) were grown in media containing the minimum toxic concentration of Al (100 microg/L as Al-transferrin). All antioxidants protected MH from injury as assessed by cell growth and enzyme leakage into media. The antioxidants did not affect Al uptake by MH, protect MH from lipid peroxidation or decrease the reactive iron content of MH. Although antioxidants protected Al loaded MH from injury the mechanisms of this effect are unknown. 相似文献
38.
The murid rodent subfamily Sigmodontinae contains 79 genera which are
distributed throughout the New World. The time of arrival of the first
sigmodontines in South America and the estimated divergence time(s) of the
different lineages of South American sigmodontines have been controversial
due to the lack of a good fossil record and the immense number of extant
species. The "early-arrival hypothesis" states that the sigmodontines must
have arrived in South America no later than the early Miocene, at least 20
MYA, in order to account for their vast present-day diversity, whereas the
"late-arrival hypothesis" includes the sigmodontines as part of the
Plio-Pleistocene Great American Interchange, which occurred approximately
3.5 MYA. The phylogenetic relationships among 33 of these genera were
reconstructed using mitochondrial DNA (mtDNA) sequence data from the ND3,
ND4L, arginine tRNA, and ND4 genes, which we show to be evolving at the
same rate. A molecular clock was calibrated for these genes using published
fossil dates, and the genetic distances were estimated from the DNA
sequences in this study. The molecular clock was used to estimate the dates
of the South American sigmodontine origin and the main sigmodontine
radiation in order to evaluate the "early-" and "late-arrival" scenarios.
We estimate the time of the sigmodontine invasion of South America as
between approximately 5 and 9 MYA, supporting neither of the scenarios but
suggesting two possible models in which the invading lineage was either (1)
ancestral to the oryzomyines, akodonts, and phyllotines or (2) ancestral to
the akodonts and phyllotines and accompanied by the oryzomyines. The
sigmodontine invasion of South America provides an example of the advantage
afforded to a lineage by the fortuitous invasion of a previously
unexploited habitat, in this case an entire continent.
相似文献
39.