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21.
Josiane Arnaud Pierre Bourlard Bernard Denis Alain E. Favier 《Biological trace element research》1996,53(1-3):129-136
This study was carried out to assess manganese (Mn) status after an acute episode of myocardial infarction. Plasma and erythrocyte
Mn concentrations were measured from admission to hospital to day 15 postadmission in 21 patients suffering from acute myocardial
infarction and in three control groups. The determination of Mn in these biological fluids was performed by electrothermal
atomic absorption spectrometry. Plasma Mn was higher (p<0.01) and erythrocyte Mn was similar in the acute myocardial infarction group compared to healthy age-matched control group.
Plasma and erythrocyte Mn remained unchanged during the 2 wk after acute myocardial infarction and were not correlated to
enzyme activities. A decrease of erythrocyte Mn with age, expressed in nmol/L, was noted (p<0.02). These results suggest that plasma and erythrocyte Mn do not provide an indication of myocardial damage. Nonetheless,
Mn status in elderly merits further attention. 相似文献
22.
Dr. Arthur K. Satterley 《Facies》1994,30(1):119-149
Summary The Upper Triassic Dachsteinkalk of the Hochk?nig Massif, situated 50 km south of Salzburg in the Northern Calcareous Alps,
corresponds to a platform margin reef complex of exceptional thickness. The platform interior limestones form equally thick
sequences of the well known cyclic Lofer facies. Sedimentation in the reef complex was not so strongly controlled by low-amplitude
sea-level oscillations as was the Lofer facies. The westernmost of the 8 facies of the reef complex is an oncolite-dominated
lagoon, in which wave-resistant stromatolite mounds with a relief of a few metres were periodically developed. The transition
to the central reef area is accomplished across the back-reef facies. In the back-reef facies patch reefs and calcisponges
appear. The proportion of coarse bioclastic sediment increases rapidly over a few hundred metres before the central reef area
is encountered. The central reef area consists of relatively widely spaced small patch reefs that did not develop wave-resistant
reef framework structures. The bulk of the sediment in the central reef area is coarse bioclastic material, provided by the
dense growth of reef organisms and the wave-induced disintegration of patch reefs. Collapse of the reef margin is recorded
by the supply of large blocks of patch reef material to the upper reef slope. Additionally, coarse, loose bioclastic debris
was supplied to the upper reef slope and this was incorporated into debris flows on the reef slope and turbidites found at
the base of the slope and in the off-reef facies. Partially lithified packstones and wackestones of the lower to middle reef
slope were modified by mass movement to form breccia and rudstone sheets. The latter reach out hundreds of metres into the
off-reef facies environment. A reef profile is presented which was derived by the restoration of strike and dip information.
In conjunction with constraints imposed by sedimentary facies related to slope processes, the angle of slope in the reef margin
area ranged from 11° to 5°, forming a concave (dished downwards) slope. Water depth estimations require that the central reef
area did not develop in water of less than 10 metres depth. At the reef margin water depths were about 30 metres, at the base
of the reef slope 200 metres and deepening in the off-reef facies to 250 metres. While previous work on reef complexes from
this type of setting suggests growth in a heavily storm-dominated environment, the present author finds little evidence for
the storm generation of the fore reef breccias, although there is good evidence for storm-influenced sedimentation and reworking
in the central reef area.
Post-depositional processes were characterised by continued slope processes causing brecciation and hydraulic injection of
red internal sediments downwards into the reef slope and off-reef limestones. Hydrothermal circulation caused a number of
phases of post-depositional (diagenetic) brecciation. There appears not to have been an important period of emergence at the
Triassic/Jurassic boundary. 相似文献
23.
RNase P in both prokaryotes and eukaryotes is a ribonucleoprotein that cleaves tRNA precursors to generate the 5 termini of the mature tRNAs. Many patients with autoimmune diseases produce antibodies against a 40 kDa protein (designatedTo orTh antigen) which is an integral component of eukaryotic RNaseP as well as nucleolar 7-2 RNP which is identical to the mitochondrial RNA processing (MRP) RNP. Interestingly, theTo antigen found in human cells and the C5 protein, the only protein component ofE. coli RNaseP, are antigenically related. In this study, we show that a 56 nucleotide-long sequence, corresponding to nucleotides 20–75 near the 5 end of human RNaseP RNA, is sufficient to bind theTo antigen. We previously showed that the humanTo antigen binds to a short distinct structural domain near the 5 end of human 7-2/MRP RNA. There is no obvious primary sequence homology between theTo antigen binding sites in RNaseP RNA and 7-2/MRP RNA; however, these sequences are capable of assuming a similar secondary structure which corresponds to the recently proposed cage structure for RNaseP RNAs and 7-2/MRP RNA (Forster and Altman (1989) Cell 62: 407–409). These data are supportive of the idea that these two RNAs may have evolved from a common progenitor molecule. 相似文献
24.
Many deterministic models of sexually transmitted diseases, as well as population models in general, contain elements of stochastic or statistical reasoning. An example of such a model is that of Dietz and Hadeler (1988) concerning sexually transmitted diseases in which there is partnership formation and dissolution. Among the interesting formulas in this paper, which enter into the analysis of the model, are those for the expected number of partners a male or female has during a lifetime. To a probabilist such formulas suggest the possibility that some stochastic process may be constructed so as to yield these formulas as well as others that may be of interest. The principal purpose of this paper is to demonstrate that such a stochastic process does indeed exist in the form of a three state semi-Markov process in continuous time with stationary laws of evolution and with a one-step density matrix determined by four parameters which were interpreted as constant latent risk functions in the classical theory of competing risks. This construction of a semi-Markov process not only provides a framework for the systematic derivation of the formulas of Dietz and Hadeler but also suggests pathways,for extensions to the age-dependent case.This research was partially supported by NATO Grant D.890350 相似文献
25.
As previously reported, mitochondrial malate dehydrogenase (MDH) binds to purified complex I of the electron transport system. With conditions used in previous reports, MDH binds even more extensively, but probably predominantly non-specifically, to the matrix side of the inner mitochondrial membrane of submitochodrial particles (SMP). Herein we report experimental conditions for highly specific binding of malate dehydrogenase to complex I within SMP. These conditions permit us to demonstrate NADH channelling from malate dehydrogenase to complex I using the completing reaction test. This test, though not ideal for all situations, has several advantages over the enzyme buffering test previously used. These advantages should facilitate further studies elucidating NADH channeling to complex I from MDH and other dehydrogenases. Independent evidence of NADH channelling to the electron transport chain and the potential advantages of substrate channelling in general are also discussed. Substrate channelling from MDH in particular may be especially beneficial because of the unfavourable equilibrium and kinetics of this enzyme reaction. 相似文献
26.
R. C. Roverud 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1994,174(5):559-565
A stereotypical approach phase vocalization response of the lesser bulldog bat, Noctilio albiventris, to artificial echoes simulating a virtual approaching object was used to assess the ability of the bat to analyze and extract distance information from the artificial echoes. The performance of the bat was not significantly different when presented with naturally structured CF/FM echoes containing FM elements that sweep continuously from about 75-55 kHz in 4 ms or with CF/FM echoes containing FM components constructed from a series of 98 pure tone frequency steps, each with a duration of 0.04 ms. The performance of the bat remained unchanged when the duration of the tone steps was increased up to 0.08 ms but declined sharply to a level that was significantly below that seen with a naturally structured echo when the steps were 0.09 ms or longer. The performance of the bat depended on the duration of the individual tone steps, which could not exceed a specific upper limit of about 0.08 ms. The study suggests that the bats have adaptations for processing individual narrow band segments of FM signals over specific time intervals.Abbreviations CF
constant frequency
- FM
frequency modulation 相似文献
27.
Lev G. Goldfarb Paul Brown Larisa Cervenakova D. Carleton Gajdusek 《Molecular neurobiology》1994,8(2-3):89-97
Genetic study of over 200 cases of Creutzfeldt-Jakob disease (CJD), Gerstmann-Sträussler-Scheinker disease (GSS), fatal familial insomnia (FFI), and kuru have brought a reliable body of evidence that the familial forms of CJD and all known cases of GSS and FFI are linked to germline mutations in the coding region of the PRNP gene on chromosome 20, either point substitutions or expansion of the number of repeat units. No pathogenic mutations have so far been found in sporadic or infectious forms of CJD, although there are features of genetic predisposition in iatrogenic CJD and kuru. In FFI and familial CJD, clinically and pathologically distinct syndromes that are both linked to the 178Asp→Asn substitution, phenotypic expression is dependent on a polymorphism at codon 129. Synthetic peptides homologous to several regions of PrP spontaneously form insoluble amyloid fibrils with unique morphological characteristics and polymerization tendencies. Peptides homologous to mutated regions of PrP exhibit enhanced fibrilogenic properties and, if mixed with the wild-type peptide, produce even more abundant and larger fibrous aggregates. A similar process in vivo may lead to amyloid accumulation and disease, and transmission of “baby fibrils” may induce disease in other hosts. 相似文献
28.
Ian M. Møller Allan G. Rasmusson Kenneth M. Fredlund 《Journal of bioenergetics and biomembranes》1993,25(4):377-384
Plant (and fungal) mitochondria contain multiple NAD(P)H dehydrogenases in the inner membrane all of which are connected to the respiratory chain via ubiquinone. On the outer surface, facing the intermembrane space and the cytoplasm, NADH and NADPH are oxidized by what is probably a single low-molecular-weight, nonproton-pumping, unspecific rotenone-insensitive NAD(P)H dehydrogenase. Exogenous NADH oxidation is completely dependent on the presence of free Ca2+ with aK
0.5 of about 1 µM. On the inner surface facing the matrix there are two dehydrogenases: (1) the proton-pumping rotenone-sensitive multisubunit Complex I with properties similar to those of Complex I in mammalian and fungal mitochondria. (2) a rotenone-insensitive NAD(P)H dehydrogenase with equal activity with NADH and NADPH and no proton-pumping activity. The NADPH-oxidizing activity of this enzyme is completely dependent on Ca2+ with aK
0.5 of 3 µM. The enzyme consists of a single subunit of 26 kDa and has a native size of 76 kDa, which means that it may form a trimer. 相似文献
29.
天花粉蛋白与FMP复合物的晶体结构 总被引:6,自引:1,他引:5
用浸泡法得到了天花粉蛋白(TCS)与FMP复合物的晶体,在SIMENNSX-200B面探测器系统上收集了一套2.0分辨率的X射线衍射数据。用同晶差值傅立叶法解析了复合物的结构,经X—PLOR程序修正得到了TCS—FMP复合物的分子结构并找出了197个水分子,最后的R因子为0.172,键长和键角的RMS偏差分别为0.015和2.922度。TCS—FMP复合物中,FMP与天花粉蛋白分子有较好的结合,其结合位置正处于根据三维结构和突变体信息推测的N一糖苷酶活性口袋之中。它的类嘌呤环夹在Y70和Y111两个侧链环之间,与Y70环近乎平行,其N7和N6分别与TCS分子的G1094羰基氧和I71的N成氢键,N3靠近R163的侧链,其磷酸根则伸向活性口袋的底部,与E189、E160和R163等残基作用。 相似文献
30.
Age-Dependent Impairment of Mitochondrial Function in Primate Brain 总被引:11,自引:2,他引:9
Allen C. Bowling Elizabeth M. Mutisya Lary C. Walker† Donald L. Price†‡§ Linda C. Cork† M. Hint Beal 《Journal of neurochemistry》1993,60(5):1964-1967
Abstract: It has been hypothesized that some of the functional impairments associated with aging are the result of increasing oxidative damage to mitochondrial DNA that produces defects in oxidative phosphorylation. To test this hypothesis, we examined the enzymes that catalyze oxidative phosphorylation in crude mitochondrial preparations from frontoparietal cortex of 20 rhesus monkeys (5-34 years old). Samples were assayed for complex I, complex II-III, complex IV, complex V, and citrate synthase activities. When enzyme activities were corrected for citrate synthase activities (to account for variable degrees of mitochondrial enrichment), linear regression analysis demonstrated a significant negative correlation of the activities of complex I (p < 0.002) and complex IV (p < 0.03) with age but no significant change in complex II-III or complex V activities. Relative to animals 6.9 ± 0.9 years old (n = 7), the citrate synthase-corrected activity of complex I was reduced by 17% in animals 22.5 ± 0.9 years old (n = 6) (p < 0.05) and by 22% in animals 30.7 ± 0.9 years old (n = 7) (p < 0.01). Similar age-related reductions in the activities of complexes I and IV were obtained when enzyme activities were corrected for complex II-III activity. These findings show an age-associated progressive impairment of mitochondrial complex I and complex IV activities in cerebral cortices of primates. 相似文献