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21.
Topp H Lengger C Schöch G Werner J Mietzsch E 《Archives of biochemistry and biophysics》2000,376(2):328-332
DNA damage by reactive oxygen species is of special interest in the development of cancer and in aging. The renally excreted amount of 8-oxo-7,8-dihydro-2'-deoxyguanosine (oxo(8)dG) is a potential noninvasive marker of oxidative DNA damage. The respiratory chain of mitochondria is one source for the formation of reactive oxygen species. In the present study we investigated in Wistar rats (n = 7; mean body weight at start, 307.4 +/- 11 g) the effect of an increased O(2) consumption, i.e., energy expenditure, due to cold stress on the renally excreted amount of oxo(8)dG. First, the rats were housed for 4 days at 23.5 degrees C (basic period, BP), and then for 6 days at 10 degrees C (cold stress period, CSP), and finally for 3 days at 23.5 degrees C (recovery period, RP). The O(2) consumption (L O(2)/day/kg weight) was significantly (P < 0.0001) on average 50% higher in CSP (69.0 +/- 3.9) than in BP (45.8 +/- 4.8), and similar in BP and RP (44.3 +/- 5.4). The average renal excretion of oxo(8)dG (pmol/day/kg weight) was significantly (P < 0.025) on average 13% higher in CSP (375.5 +/- 27.7) than in BP (333.2 +/- 47. 4) and similar in BP and RP (331.8 +/- 34.3). Maximum increase in oxo(8)dG excretion of on average 17% was on the third to fifth day of the CSP. This study reveals that an increase in O(2) consumption of 50% resulted in a much lower increase in the renal excretion of oxo(8)dG. 相似文献
22.
Influence of readily metabolizable carbon on pentachlorophenol metabolism by a pentachlorophenol-degrading Flavobacterium sp. 下载免费PDF全文
The influence of high concentrations of pentachlorophenol (PCP) and readily metabolizable carbon on the activity and viability of a PCP-degrading Flavobacterium sp. was examined in a mineral salts medium. Lags preceding PCP removal by glutamate-grown Flavobacterium cells were greatly attenuated by the addition of glutamate, aspartate, succinate, acetate, glucose, or cellobiose. The effect of these supplementary carbon sources on the apparent lag was not mediated entirely through the stimulation of growth since PCP metabolism accompanied the onset of growth. The specific activity of PCP-degrading cells in the absence of supplementary carbon was 1.51 x 10(-13) +/- 0.08 x 10(-13) g of PCP per cell per h and in the presence of supplementary carbon was 0.92 x 10(-13) +/- 0.09 x 10(-13) g of PCP per cell per h. Glutamate in combination with glucose or cellobiose partially repressed PCP metabolism. PCP removal by PCP-induced, glutamate-grown cells suspended in the presence of 4 g of sodium glutamate per liter was sensitive to shock loads of PCP, with a Ki of about 86.8 micrograms/ml. Subsequent removal rates, however, were more resistant to PCP. Optimal stimulation of PCP removal by sodium glutamate required 3.0 g/liter, about the same concentration as that which saturated growth in the absence of PCP. PCP removal rates decayed within minutes following the transfer of PCP-induced, glutamate-grown cells to media containing PCP without supplementary carbon, and increasing PCP concentrations accelerated the decay.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
23.
24.
Fibrillation of Human Calcitonin and Its Analogs: Effects of Phosphorylation and Disulfide Reduction
Harshil K. Renawala Karthik B. Chandrababu Elizabeth M. Topp 《Biophysical journal》2021,120(1):86-100
Some therapeutic peptides self-assemble in solution to form ordered, insoluble, β-sheet-rich amyloid fibrils. This physical instability can result in reduced potency, cause immunogenic side effects, and limit options for formulation. Understanding the mechanisms of fibrillation is key to developing rational mitigation strategies. Here, amide hydrogen-deuterium exchange with mass spectrometric analysis (HDX-MS) coupled with proteolytic digestion was used to identify the early stage interactions leading to fibrillation of human calcitonin (hCT), a peptide hormone important in calcium metabolism. hCT fibrillation kinetics was sigmoidal, with lag, growth, and plateau phases as shown by thioflavin T and turbidity measurements. HDX-MS of fibrillating hCT (pH 7.4; 25°C) suggested early involvement of the N-terminal (1–11) and central (12–19) fragments in interactions during the lag phase, whereas C-terminal fragments (20–32 and 26–32) showed limited involvement during this period. The residue-level information was used to develop phosphorylated hCT analogs that showed modified fibrillation that depended on phosphorylation site. Phosphorylation in the central region resulted in complete inhibition of fibrillation for the phospho-Thr-13 hCT analog, whereas phosphorylation in the N-terminal and C-terminal regions inhibited but did not prevent fibrillation. Reduction of the Cys1-Cys7 disulfide bond resulted in faster fibrillation with involvement of different hCT residues as indicated by pulsed HDX-MS. Together, the results demonstrate that small structural changes have significant effects on hCT fibrillation and that understanding these effects can inform the rational development of fibrillation-resistant hCT analogs. 相似文献
25.
报道了内蒙古清水河黄土丘陵地区发现的紫萼藓科1新变种——缨齿藓菱形变种[Jaffueliobryum wrightii(Sull.)Thér.var.rhombicumX.L.BaiSarula],该变种与干旱山地岩面生境中的原变种缨齿藓[Jaffueliobryum wrightii(Sull.)Thér.]相似,生境的变化导致其形态发生变化,主要表现在上部细胞菱形和细胞壁背部强烈加厚,未分化的叶上部边缘细胞、中肋横切面细胞不分化,叶片长0.7~0.8mm,毛尖长0.8~1.3mm。文中对缨齿藓及其新变种的形态学特征,分布和生境进行了描述,并提供了显微照片,另外,列出了缨齿藓属5个种的检索表。 相似文献
26.
Anonymous nuclear DNA markers in the American oyster and their implications for the heterozygote deficiency phenomenon in marine bivalves 总被引:4,自引:0,他引:4
A puzzling population-genetic phenomenon widely reported in allozyme
surveys of marine bivalves is the occurrence of heterozygote deficits
relative to Hardy-Weinberg expectations. Possible explanations for this
pattern are categorized with respect to whether the effects should be
confined to protein-level assays or are genomically pervasive and expected
to be registered in both protein- and DNA-level assays. Anonymous nuclear
DNA markers from the American oyster were employed to reexamine the
phenomenon. In assays based on the polymerase chain reaction (PCR), two
DNA-level processes were encountered that can lead to artifactual genotypic
scorings: (a) differential amplification of alleles at a target locus and
(b) amplification from multiple paralogous loci. We describe symptoms of
these complications and prescribe methods that should generally help to
ameliorate them. When artifactual scorings at two anonymous DNA loci in the
American oyster were corrected, Hardy-Weinberg deviations registered in
preliminary population assays decreased to nonsignificant values.
Implications of these findings for the heterozygote-deficit phenomenon in
marine bivalves, and for the general development and use of PCR-based
assays, are discussed.
相似文献
27.
Elucidating protein structure in amorphous solids is central to the rational design of stable lyophilized protein drugs. Hydrogen/deuterium (H/D) exchange with electrospray ionization mass spectrometry was applied to lyophilized powders containing calmodulin (17 kDa) and exposed to D(2)O vapor at controlled relative humidity (RH) and temperature. H/D exchange was influenced by RH and by the inclusion of calcium chloride and/or trehalose in the solid. The effects were not exhibited uniformly along the protein backbone but occurred in a site-specific manner, with calcium primarily influencing the calcium-binding loops and trehalose primarily influencing the alpha-helices. The results demonstrate that the method can provide quantitative and site-specific structural information on proteins in amorphous solids and on changes in structure induced by protein cofactors and formulation excipients. Such information is not readily available with other techniques used to characterize proteins in the solid state, such as Fourier transform infrared, Raman, and near-infrared spectroscopy. 相似文献
28.
We investigated the distribution pattern of centipedes (Chilopoda) in four primeval forests of the western Carpathians, central
Slovakia. The forests are located in two different mountain ranges (Kremnické vrchy and Pol’ana Mountains), which are exposed
on either the southern (Boky, Rohy) or northern slopes (Pol’ana, Badín). In these forests, the influence of coarse woody debris
(CWD) on centipede distribution was studied, by distinguishing sampling sites on the forest floor, close to CWD (c-CWD) and
distant from CWD (d-CWD). In total, we collected 2,706 individuals from 20 species of centipedes. Average species richness
and number of individuals per forest ranged from 8 to 12 species/m2 and from 244 to 486 individuals/m2. The oak forests on south facing slopes harboured several species, which did not occur in the more northern exposed fir-beech
forests. Number of species as well as individuals, however, varied more within than between individual forests. Increase of
species number and density was mainly caused by CWD and was more pronounced on the southern slopes (P<0.001), characterized by high temperatures and low precipitation, than on the northern slopes (n.s. to P<0.01), characterized by low temperatures and high precipitation. It was found that CWD did not generally increase (species)
diversity. 相似文献
29.
30.
Lanthier M Scott A Zhang Y Cloutier M Durie D Henderson VC Wilkes G Lapen DR Topp E 《Journal of applied microbiology》2011,110(2):407-421