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排序方式: 共有376条查询结果,搜索用时 15 毫秒
61.
Arima J Uesugi Y Iwabuchi M Hatanaka T 《Protein engineering, design & selection : PEDS》2008,21(1):45-53
We purified and characterized the aminopeptidase P from Streptomyces costaricanus TH-4 (thAPP). This enzyme has a tetramer structure, a metal-ion preference toward Zn, broad substrate specificity and a narrow pH dependency for activity. The primary structure of thAPP, respectively, exhibits 91% and 65% identity with those of two other APPs-APP I and APP II-from Streptomyces lividans (slAPP I and slAPP II). We next overexpressed the genes encoding thAPP and slAPP II in Escherichia coli and characterized them. Two differences were apparent in their properties: slAPP II formed a dimer, whereas thAPP formed a tetramer; also, the alkaline side pKa for the catalytic action of slAPP II is higher than that of thAPP. Investigation using chimeras of both enzymes revealed that the N-terminal domain is associated with the determination of pKa values for catalytic action and quaternary structure. 相似文献
62.
Vinicius Ruan Neves dos Santos Maria Karolina Martins Ferreira Leonardo Oliveira Bittencourt Paulo Fernando Santos Mendes Deiweson Souza-Monteiro Karolyny Martins Balbinot Joo de Jesus Viana Pinheiro Senda Charone Juliano Pelim Pessan Rafael Rodrigues Lima 《International journal of molecular sciences》2022,23(13)
There is currently a controversial and heated debate about the safety and ethical aspects of fluoride (F) used for human consumption. Thus, this study assessed the effects of prenatal and postnatal F exposure of rats on the salivary glands of their offspring. Pregnant rats were exposed to 0, 10, or 50 mg F/L from the drinking water, from the first day of gestation until offspring weaning (42 days). The offspring rats were euthanized for the collection of the parotid (PA) and submandibular (SM) glands, to assess the oxidative biochemistry and to perform morphometric and immunohistochemical analyses. F exposure was associated with a decrease in the antioxidant competence of PA in the 10 mg F/L group, contrasting with the increase observed in the 50 mg F/L group. On the other hand, the antioxidant competence of the SM glands was decreased at both concentrations. Moreover, both 10 and 50 mg F/L groups showed lower anti-α-smooth muscle actin immunostaining area in SM, while exposure to 50 mg F/L was associated with changes in gland morphometry by increasing the duct area in both glands. These findings demonstrate a greater susceptibility of the SM glands of the offspring to F at high concentration in comparison to PA, reinforcing the need to adhere to the optimum F levels recommended by the regulatory agencies. Such findings must be interpreted with caution, especially considering their translational meaning. 相似文献
63.
PURPOSE: To evaluate the efficacy of positron emission tomography (PET) in aiding in the diagnosis of brainstem infarctions that cause abnormal eye movements. METHOD: Cerebral glucose metabolism was examined by PET with 18F-fluorodeoxyglucose as a tracer in five normal control subjects and six patients with abnormal eye movements. The PET images were registered to and superimposed on magnetic resonance images (MRIs). RESULTS: All control subjects showed little asymmetry of glucose metabolism in the brainstem, whereas all six patients demonstrated areas of low glucose metabolism in the brainstem. Areas of low metabolism seen by PET were wider than they appeared to be by MRI; MRIs even appeared normal in some patients. Asymmetry index measurements at the level of the ischemic lesion ranged between 19% and 45%. CONCLUSIONS: Positron emission tomography detected metabolic abnormality in patients with brainstem lesions that caused abnormal eye movements. Superimposing PET images on MRIs accurately localized abnormally low metabolism in the brainstem. Combined imaging with PET and MRI can be used to diagnose ischemic lesions in the brainstem from functional (PET) and morphologic (MRI) viewpoints. 相似文献
64.
The aim of this study was to explain the contribution of mitochondria to the accumulation of 99mTc-meso-hexamethyl propyleneamine oxime (HMPAO) in the brain, after examinations were performed. METHODS: We studied subcellular distribution of 99mTc-meso-HMPAO and glutathione (GSH) in normal and diethyl maleate (DEM)-administered mice. RESULTS: In normal brain, major radioactivity was found in the mitochondrial (49.0%) and cytosolic fractions (33.0%), while the GSH content was high in the cytosol (63.2%) and mitochondria (30.6%). The radioactivity in mitochondrial, cytosolic, microsomal and nuclear fractions was decreased in a dose-dependent manner by DEM, a GSH depleting agent, to 32.2% (mitochondrial) and 24.7% (cytosolic) of the control by a dose of 550 mg/kg. The GSH content in mitochondrial and cytosolic fractions also decreased in a dose-dependent manner on DEM treatment to 29.3% (mitochondrial) and 30.0% (cytosolic) of the control by 550 mg/kg of DEM. A good correlation was found between the uptake of 99mTc-meso-HMPAO and GSH content in mitochondrial, cytosolic and nuclear fractions, with a correlation coefficient (r) of 0.814, 0.834 and 0.784, respectively. CONCLUSION: Mitochondria are a major subcellular fraction for the uptake of 99mTc-meso-HMPAO by the brain, and GSH in mitochondria contributes to the accumulation of 99mTc-meso-HMPAO. 相似文献
65.
Shozaburo Nakashima Kunihide Takashima Jiro Harase 《Metallurgical and Materials Transactions A》1997,28(3):681-687
A study was made on the effect of the increase of silicon content and the addition of carbon on the primary recrystallization
of silicon steel sheet containing MnS and AlN as inhibitors. The increase of silicon content led to the reduction of the size
of primary grains and the intensity of {110} that is considered to represent the amount of {110}〈001〉-oriented nuclei, to
the gain of the size of precipitates, and to the coarse dispersion of the precipitates. The carbon addition promoted primary
recrystallization and decreased the size of primary grains. From the points mentioned earlier, the increase of silicon content
is considered disadvantageous, and the carbon addition is advantageous to the secondary recrystallization of the {110}〈001〉
texture. 相似文献
66.
This paper deals with the reliability considerations on a redundant system consist of two subsystems connected in series, in which they have a similar warm-standby subsystem, respectively. And these four subsystems are composed of several identical units in parallel redundancy, respectively and are connected with switching devices each other.The purpose of this paper is to attain the following two subjects; (1) to utilize the surviving units at any switch-over point of time, as many as possible, making use of the switching devices as mensioned above, and (2) to deal with various complex redundant systems with or without switching devices, simultaneously.In these considerations we have obtained the reliability function and mean time to system failure (MTSF) of this system. 相似文献
67.
The binding of anionic dye, p-(2-amino-6-sulfonyl-8-naphthylazo)benzene sulfonic acid disodium salt (ASANA) to bovine serum albumin (BSA) at pH 7.5 has been studied by spectrophotometric techniques. The values of the dissociation constants were obtained with the use of the Benesi-Hildebrand equation for ASANA. Competitive binding of polyanions, sodium poly(styrene sulfonate) (PSSNa), potassium poly(vinyl sulfonate) (PVSK), poly(acrylic acid) (PAA), and poly(methacrylic acid) (PMAA) and anionic dye to BSA was evaluated through the variations in the different spectra of BSA-dye-polymer systems. 相似文献
68.
69.
Jiro Kondo 《Nuclear Engineering and Design》1996,165(3):281-287
Failure of a large system causes disasters. However, after an accident, the causes are frequently attributed to human error when the operators do not survive the accident. It might be difficult to prove that the real cause of the accident is human error. Process decision program chart (PDPC) would be a useful tool in indicating the causes of an accident since it can clearly show that if the operator made the correct choice, the safety of the system could be maintained. The case of the incident of the nuclear reactor at Mihama Unit 2 is indicated by PDPC in which the sequence of events and the operations are indicated in this paper together with the safe operation. One can easily understand the cause of the incident and the way to avoid it. Also, PDPC for the Three Mile Island (TMI) accident is shown. Initially, in order to prevent an accident, mental training and safety culture is most important. The oriental safety culture based on Zentoism, a school of Buddhism is discussed. 相似文献
70.
Takashi Wakasugi Rikuo Ota Jiro Fukunaga 《Journal of the American Ceramic Society》1992,75(11):3129-3132
In order to evaluate the crystallization tendency of glasses, the ratio of the crystallization temperature to the liquidus temperature ( T c / T L ) was obtained by DTA measurement for the Na2 O–B2 O3 and Na2 O–B2 O3 –Al2 O3 systems. The critical cooling rate for glass formation ( Q *) was also measured. The measurements were performed in the composition range of (100 − x )Na2 O–( x )B2 O3 , ( x = 25–35 and 60–100 mol%), and (100 − y )0.5Na2 O·0.5B2 O3 −( y )Al2 O3 , ( y = 6–34 mol%). The relationship between T c / T L and Q * was discussed. A linear relationship between T c / T L and log Q * for these systems was found. Furthermore, the relationship between T c / T L and Q * was verified by computer simulation based on the crystallization kinetics of glass or supercooled liquid. 相似文献