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71.
A new general equation simulating irreversible DSC transitions of multimeric proteins was developed. The equation put forward here is the result of an improved mathematical re-elaboration of the classical Lumry-Eyring models, where no restrictive a priori assumptions are made on the kinetic constraints of the denaturation process, or on the enthalpy of the final denatured state. In order to test the wide applicability of this new effective theoretical tool, a series of DSC transitions were simulated with the aim of determining the effects of all relevant thermodynamic, kinetic or experimental parameters on the shape of DSC profiles. Moreover, the classical equations used widely in DSC investigations for the calculus in both kinetic parameters and changes of molecularity, were studied in the light of the model developed here, highlighting, in each case, their rather limited applicability. The new approach proposed in this article was applied to study the thermal denaturation of an hexameric protein (Glucosamine-6-phosphate deaminase), putting in evidence the practical applicability of the theoretical equations developed. 相似文献
72.
Caridad Rojas Susana Cadenas Mónica López-Torres Rosa Pérez-Campo Gustavo Barja 《Free radical biology & medicine》1996,21(7):907-915
Dietary treatment with three diets differing in vitamin E, Low E (15 mg of vitamin E/kg diet), Medium E (150 mg/kg), or High E (1,500 mg/kg), resulted in guinea pigs with low (but nondeficient), intermediate, or high heart a-tocopherol concentration. Neither the antioxidant enzymes superoxide dismutase, catalase, glutathione peroxidase, and reductase, nor the nonenzymatic antioxidants, GSH, ascorbate, and uric acid were homeostatically depressed by increases in heart a-tocopherol. Protection from both enzymatic (NADPH dependent) and nonenzymatic (ascorbate-Fe2+) lipid peroxidation was strongly increased by vitamin E supplementation from Low to Medium E Whereas no additional gain was obtained from the Medium E to the High E group. The GSH/GSSG and GSH/total glutathione ratios increased as a function of the vitamin E dietary concentration closely resembling the shape of the dependence of heart a-tocopherol on dietary vitamin E. The results show the capacity of dietary vitamin E to increase the global antioxidant capacity of the heart and to improve the heart redox status in both the lipid and water-soluble compartments. This capacity occurred at levels six times higher than the minimum daily requirement of vitamin E, even in the presence of optimum dietary vitamin C concentrations and basal unstressed conditions. The need for vitamin E dietary supplementation seems specially important in this tissue due to the low constitutive levels of endogenous enzymatic and nonenzymatic antioxidants present of the mammalian heart in comparison with those of other internal organs. 相似文献
73.
74.
Molecular cytogenetic analysis of a duplication Xp in a male: further delineation of a possible sex influencing region on the X chromosome 总被引:3,自引:0,他引:3
P. Nagesh Rao Kurt Klinepeter William Stewart Rosa Hayworth Robin Grubs Mark J. Pettenati 《Human genetics》1994,94(2):149-153
We describe a male infant with severe mental retardation and autism with a duplication of the short arm of the X chromosome. Chromosome painting confirmed the origin of this X duplication. Molecular cytogenetic analysis with fluorescence in situ hybridization (FISH) identified one copy of the zinc finger protein on the X chromosome (ZFX) and two copies of the steroid sulfatase gene (STS), further delineating the breakpoints. Based on cytogenetic and molecular comparisons of cases from the literature of sex-reversal in dup(X),Y patients and our patient, we suggest that a possible secondary sexinfluencing gene involved in the regulation of sex determination or testis morphogenesis is present at the distal Xp21.1 to p21.2 region. 相似文献
75.
E. Petrangeli C. Lubrano F. Ortolani L. Ravenna A. Vacca S. Sciacchitano L. Frati A. Gulino A. Vacca S. Sciacchitano L. Frati A. Gulino 《The Journal of steroid biochemistry and molecular biology》1994,49(4-6):327-331
The imbalance between proliferative and differentiative estrogenic effect, caused by quantitative and qualitative alteration of the estrogen receptor (ER) expression, may play a determinant role in mammary neoplastic transformation. Our studies demonstrate that ER levels are significantly higher in human mammary neoplastic tissues when compared to perineoplastic tissues and that increased ER expression is associated with ER gene hypomethylation. During progressive multifactorial carcinogene, ER overexpression may represent an early step in neoplastic transformation. In fact, high levels of ER represent good markers of differentiation and can predict the likelihood of benefiting from anti-estrogen therapy. Nevertheless, about 35% of ER-positive breast cancers are resistant to endocrine therapy and 10% of ER-negative tumors behave as hormone-sensitive tumors. Recent studies on ER mRNA variants, which naturally occur in human breast tumors, demonstrated mutations, deletions and alternative splicings, yielding deletions of exons 3, 4, 5 and 7. ER variants exhibited altered functions or changed the responsiveness to hormonal therapy. Analysis of these variants could be a useful parameter to better predict tumor responsiveness to anti-estrogen therapy. Recently, a regain of hormonal responsiveness by ER-negative breast cancer cells has been reported following ER gene transfection. However, estradiol treatment inhibits rather than stimulates cell growth as well as the metastatic and invasive potential of the ER gene transduced cells. Transfer of the ER gene may be considered as a new therapeutic approach in the management of hormone-independent breast cancer. 相似文献
76.
Physical Mapping of Meiotic Crossover Events in a 200-Kb Region of Neurospora Crassa Linkage Group I 总被引:1,自引:1,他引:0
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We propose a general restriction fragment length polymorphism-based strategy to analyze the distribution of meiotic crossover events throughout specific genetic intervals. We have isolated 64 recombinant chromosomes carrying independent meiotic crossover events in the genetic interval eth-1-un-2 on linkage group I of Neurospora crassa. Thirty-eight crossover events were physically mapped with reference to a 200-kb region cloned by chromosome walking, using N. crassa λ and cosmid libraries. Crossovers were homogeneously distributed at intervals of 5.0 +/- 2.3 kb along the entire cloned interval. The ratio of physical to genetic distance appears to be higher in the region than in the overall N. crassa genome, suggesting that recombinational activity is less in large chromosomes than in small ones. The present work provides a method for defining the centromeric-telomeric orientation of single cloned DNA fragments. Their physical distance can also be estimated with respect to linked loci, provided that crossover events are distributed homogeneously in the interval. This strategy overcomes typical difficulties in defining the position and direction of chromosome walking steps on conventional linkage maps. 相似文献
77.
Armengol-Díaz Javier Esparcia Angeles Vicente Eduardo Miracle Maria Rosa 《Hydrobiologia》1993,255(1):381-388
Vertical distribution of planktonic rotifers is described in relation to temperature and oxygen in Lake La Cruz, a single-doline, closed karstic lake (121 m diameter and 25 m maximum depth) which shows iron meromixis. Samples were taken by peristaltic pumping at 10 cm depth intervals in the oxycline zone from June 1987 to September 1988. A model of rotifer vertical structure in stratified lakes is proposed. Rotifers concentrate their populations at the depths with intense gradients. As stratification develops some rotifer populations show a downward migration following the thermocline and some others show an upward migration following the oxycline. The production-respiration balance in the lake, and so the position of the oxycline with respect to the thermocline and the layer of maximum production, depends on meteorological conditions. A shift in the dominance of congeneric or related species can occur in consecutive years. In Lake La Cruz, mixing conditions and subterranean inflow in spring were much more intense in 1988 than 1987, and the distance between production and decomposition depths was smaller in 1988. Anuraeopsis miraclei, an oxycline-bound species with high abundance in 1987, was displaced by A. fissa in 1988. A. fissa, which was a metalimnetic species during early summer, reached peak densities (3 × 104 ind l–1) at the oxycline, equaling the abundance of A. miraclei the preceeding year. 相似文献
78.
Estaras Matias Ortiz-Placin Candido Castillejo-Rufo Alba Fernandez-Bermejo Miguel Blanco Gerardo Mateos Jose M. Vara Daniel Gonzalez-Cordero Pedro L. Chamizo Sandra Lopez Diego Rojas Adela Jaen Isabel de Armas Noelia Salido Gines M. Iovanna Juan L. Santofimia-Castaño Patricia Gonzalez Antonio 《Journal of physiology and biochemistry》2023,79(1):235-249
Journal of Physiology and Biochemistry - We have investigated the effects of melatonin on major pathways related with cellular proliferation and energetic metabolism in pancreatic stellate cells.... 相似文献
79.
Simone Baumann-Pickering Jennifer S. Trickey Alba Solsona-Berga Ally Rice Erin M. Oleson John A. Hildebrand Kaitlin E. Frasier 《Diversity & distributions》2023,29(4):478-491
Aim
Understanding cetacean species' distributions and population structure over space and time is necessary for effective conservation and management. Geographic differences in acoustic signals may provide a line of evidence for population-level discrimination in some cetacean species. We use acoustic recordings collected over broad spatial and temporal scales to investigate whether global variability in echolocation click peak frequency could elucidate population structure in Blainville's beaked whale (Mesoplodon densirostris), a cryptic species well-studied acoustically.Location
North Pacific, Western North Atlantic and Gulf of Mexico.Time period
2004–2021.Major taxa studied
Blainville's beaked whale.Methods
Passive acoustic data were collected at 76 sites and 150 cumulative years of data were analysed to extract beaked whale echolocation clicks. Using an automated detector and subsequent weighted network clustering on spectral content and interclick interval of clicks, we determined the properties of a primary cluster of clicks with similar characteristics per site. These were compared within regions and across ocean basins and evaluated for suitability as population-level indicators.Results
Spectral averages obtained from primary clusters of echolocation clicks identified at each site were similar in overall shape but varied in peak frequency by up to 8 kHz. We identified a latitudinal cline, with higher peak frequencies occurring in lower latitudes.Main conclusions
It may be possible to acoustically delineate populations of Blainville's beaked whales. The documented negative correlation between signal peak frequency and latitude could relate to body size. Body size has been shown to influence signal frequency, with lower frequencies produced by larger animals, which are subsequently more common in higher latitudes for some species, although data are lacking to adequately investigate this for beaked whales. Prey size and depth may shape frequency content of echolocation signals, and larger prey items may occur in higher latitudes, resulting in lower signal frequencies of their predators. 相似文献80.
Vincenzo La Bella Filippo Brighina Prof. Federico Piccoli Rosa Guarneri 《Neurochemical research》1993,18(2):171-175
Beta-N-oxalylamino-l-alanine (BOAA), a non-protein amino acid present in the seeds of Lathyrus Sativus (LS), is one of several neuroactive glutamate analogs reported to stimulate excitatory receptors and, in high concentrations, cause neuronal degeneration. In the present study, the in vivo acute effects of synthetic BOAA and LS seed extract were investigated on rat cerebellar cyclic GMP following intraperitoneal (10–100 mg/kg) or oral (100 mg/kg) administration of subconvulsive doses of toxin. Furthermore, the BOAA content in LS seeds and in the cerebellum of injected rats was determined by high performance liquid chromatograph analysis. A dose- and time-dependent increase of cerebellar cyclic guanosine monophosphate (cGMP) level was observed after intraperitoneal administration of synthetic BOAA or LS extract. The neurotoxin evoked a maximum stimulation 90 min after injection within the dose range of 50–75 mg/kg, elevating cGMP from basal levels of 5.3±0.5 pmol/mg protein to 15±1.3 pmol/mg protein. Similarly, the oral intake of LS-extracted neurotoxin resulted in the elevation of cGMP content. Kynurenic acid (300 mg/kg i.p.), a non specific excitatory amino acid antagonist, was effective in blocking LS BOAA-elicited cGMP enhancement. The data suggest that in the cerebellum acute administration of low concentrations of BOAA exert in vivo activation of glutamate receptors involved in the regulation of cGMP level. 相似文献