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21.
Adenylate kinase (AK) from the sulphate-reducing bacterium Desulfovibrio gigas (AK) has been characterized earlier as a Co2+/Zn2+-containing enzyme, which is an unusual characteristic for adenylate kinases from Gram-negative bacteria, in which these enzymes are normally devoid of metal ions. AK was overexpressed in E. coli and homogeneous Co2+-, Zn2+- and Fe2+-forms of the enzyme were obtained under in vivo conditions. Their structural stability and spectroscopic and kinetic properties were compared. The thermal denaturation of Co2+- and Zn2+-forms of AK was studied as a cooperative two-state process, sufficiently reversible at pH 10, which can be correctly interpreted in terms of a simple two-state thermodynamic model. In contrast, the thermally induced denaturation of Fe2+-AK is irreversible and strongly dependent upon the scan rate, suggesting that this process is under kinetic control. Practically identical contents of secondary-structure elements were found for all the metal-chelated-forms of AK upon analysis of circular dichroism data, while their tertiary structures were significantly different. The peculiar tertiary structure of Fe2+-AK, in contrast to Co2+- and Zn2+-AK, and the consequent changes in the physico-chemical and enzymatic properties of the enzyme are discussed.  相似文献   
22.
The thermal stability of peroxidase from leaves of the African oil palm tree Elaeis guineensis (AOPTP) at pH 3.0 was studied by differential scanning calorimetry (DSC), intrinsic fluorescence, CD and enzymatic assays. The spectral parameters as monitored by ellipticity changes in the far-UV CD spectrum of the enzyme as well as the increase in tryptophan intensity emission upon heating, together with changes in enzymatic activity with temperature were seen to be good complements to the highly sensitive but integral method of DSC. The data obtained in this investigation show that thermal denaturation of palm peroxidase is an irreversible process, under kinetic control, that can be satisfactorily described by the two-state kinetic scheme, N -->(k) D, where k is a first-order kinetic constant that changes with temperature, as given by the Arrhenius equation; N is the native state, and D is the denatured state. On the basis of this model, the parameters of the Arrhenius equation were calculated.  相似文献   
23.
Nine out of 22 microsatellite primers tested were successfully amplified on three samples of cod Gadus morhua L. (two contemporary and one archived otolith samples). All loci were polymorphic (5–23 alleles/locus). The average observed heterozygosity across loci and samples was 0.625, ranging from 0.294 to 0.895 at each locus. All loci were under Hardy–Weinberg equilibrium, except PGmo56 that showed significant excess of heterozygotes in all studied samples. The isolated loci were suitable for degraded DNA and therefore useful for conducting a long‐term temporal study with DNA obtained from archived otoliths of cod.  相似文献   
24.
The structure and location of the diaphragm (gular membrane) was studied in five families of Terebelliformia: Terebellidae, Trichobranchidae, Pectinariidae, Ampharetidae and Alvinellidae, using dissections, histology, and scanning and transmission electron microscopy. Position, shape, and structure of the diaphragm differ in these taxa. In Terebellidae and Pectinariidae the diaphragm is straight. In Trichobranchidae, Ampharetidae and Alvinellidae it is funnel-shaped. Diaphragm possesses two contractile sacs in Terebellidae and Pectinariidae, one in Alvinellidae and none at all in Trichobranchidae. The relative size and form of the sacs varied. Representatives of the family Ampharetidae have one or two sacs or none at all. Four kinds of the diaphragm can be distinguished: strait with two sacs, funnel-shaped with two sacs, funnel-shaped with one sac, funnel-shaped without sacs. In some Alvinellidae, the diaphragm is fenestrated, while in all other taxa it is continuous. The wall of the sacs is more muscular than the wall of the remaining diaphragm. The diaphragm is attached to the body wall at different levels: between the third and fourth segments in pectinariids or between the fourth and fifth in terebellids, ampharetids, alvinellids and trichobranchids. In most cases, the diaphragm contains two coelothelial layers with a well-developed extra-cellular matrix in between, and one or two muscle layers. The maximum development of the muscle fibres occurs in Terebellidae; probably related to the length of buccal tentacles. Significance of morphological and ultrastructural peculiarities of the diaphragm is discussed.  相似文献   
25.

Background

Virus-induced exacerbations of Chronic Obstructive Pulmonary Disease (COPD) are a significant health burden and occur even in those receiving the best current therapies. Rhinovirus (RV) infections are responsible for half of all COPD exacerbations. The mechanism by which exacerbations occur remains undefined, however it is likely to be due to virus-induced inflammation. Given that phophodiesterase 4 (PDE4) inhibitors have an anti-inflammatory effect in patients with COPD they present a potential therapy prior to, and during, these exacerbations.

Methods

In the present study we investigated whether the PDE4 inhibitor piclamilast (10-6 M) could alter RV or viral mimetic (5 μg/mL of imiquimod or poly I:C) induced inflammation and RV replication in primary human airway smooth muscle cells (ASMC) and bronchial epithelial cells (HBEC). The mediators IL-6, IL-8, prostaglandin E2 and cAMP production were assayed by ELISA and RV replication was assayed by viral titration.

Results

We found that in ASMCs the TLR3 agonist poly I:C induced IL-8 release was reduced while induced IL-6 release by the TLR7/8 agonist imiquimod was further increased by the presence of piclamilast. However, in RV infected ASMCs, virus replication and induced mediator release were unaltered by piclamilast, as was also found in HBECs. The novel findings of this study reveal that although PDE inhibitors may not influence RV-induced cytokine production in ASMCs and replication in either ASMCs or HBECs, they have the capacity to be anti-inflammatory during TLR activation by modulating the induction of these chemotactic cytokines.

Conclusion

By extrapolating our in vitro findings to exacerbations of COPD in vivo this suggests that PDE4 inhibitors may have beneficial anti-inflammatory properties when patients are infected with bacteria or viruses other than RV.  相似文献   
26.
A novel adenylate kinase (AK) has recently been purified from Desulfovibrio gigas and characterized as a Co(2+)/Zn(2+)-containing enzyme: this is an unusual characteristic for AKs from Gram-negative bacteria, in which these enzymes are normally devoid of metals. Here, we studied the conformational stability of holo- and apo-AK as a function of temperature by differential scanning calorimetry (DSC), circular dichroism (CD), and intrinsic fluorescence spectroscopy. The thermal unfolding of AK is a cooperative two-state process, and is sufficiently reversible in the 9-11 pH range, that can be correctly interpreted in terms of a simple two-state thermodynamic model. The spectral parameters as monitored by ellipticity changes in the CD spectra of the enzyme as well as the decrease in tryptophan intensity emission upon heating were seen to be good complements to the highly sensitive but integral DSC-method.  相似文献   
27.
Oxaliplatin, in combination with 5-fluorouracil plus folinate (or capecitabine), has increased survival substantially in stage III colorectal cancer and prolonged life in stage IV patients, but its use is compromised because of severe toxicity. Chemotherapy-induced peripheral neuropathy (CIPN) is the most problematic dose-limiting toxicity of oxaliplatin. Oncologists included for years calcium and magnesium infusion as part of clinical practice for preventing CIPN. Results from a phase III prospective study published in 2014, however, overturned this practice. No other treatments have been clinically proven to prevent this toxicity. There is a body of evidence that CIPN is caused by cellular oxidative stress. Clinical and preclinical data suggest that the manganese chelate and superoxide dismutase mimetic mangafodipir (MnDPDP) is an efficacious inhibitor of CIPN and other conditions caused by cellular oxidative stress, without interfering negatively with the tumoricidal activity of chemotherapy. MnPLED, the metabolite of MnDPDP, attacks cellular oxidative stress at several critical levels. Firstly, MnPLED catalyzes dismutation of superoxide (O2??), and secondly, having a tremendous high affinity for iron (and copper), PLED binds and disarms redox active iron/copper, which is involved in several detrimental oxidative steps. A case report from 2009 and a recent feasibility study suggest that MnDPDP may prevent or even cure oxaliplatin-induced CIPN. Preliminary results from a phase II study (PLIANT) suggest efficacy also of calmangafodipir, but these results are according to available data obscured by a surprisingly low number of adverse events and a seemingly lower than expected efficacy of FOLFOX.  相似文献   
28.
Lentil lectin obtained from Lens culinaris collected in the La Armu?a area (Salamanca, Spain) was examined by high-sensitivity differential scanning calorimetry, fluorimetry and measurements of circular dichroism at pH 2.0 and 7.4. At pH 2.0 the lentil lectin is not in the native state; however, at this pH it does show signs of a residual structure that breaks down upon heating. The lentil lectin at pH 2 shares some similarities with what has become known as the molten globule state. The thermal denaturation of intact (pH 7.4) and partially unfolded (pH 2.0) lentil lectin was irreversible and strongly dependent upon the scan rate, suggesting that its denaturation is under kinetic control. The process of lentil lectin denaturation is interpreted in terms of the simple kinetic model, Nk --> D, where k is a first-order kinetic constant that changes with temperature, as given by the Arrhenius equation; N is the native state, and D is the denatured state.  相似文献   
29.
30.
In experiments on Black Sea skates (Raja clavata), the potential of the receptor epithelium of the ampullae of Lorenzini and spike activity of single nerve fibers connected to them were investigated during electrical and temperature stimulation. Usually the potential within the canal was between 0 and –2 mV, and the input resistance of the ampulla 250–400 k. Heating of the region of the receptor epithelium was accompanied by a negative wave of potential, an increase in input resistance, and inhibition of spike activity. With worsening of the animal's condition the transepithelial potential became positive (up to +10 mV) but the input resistance of the ampulla during stimulation with a positive current was nonlinear in some cases: a regenerative spike of positive polarity appeared in the channel. During heating, the spike response was sometimes reversed in sign. It is suggested that fluctuations of the transepithelial potential and spike responses to temperature stimulation reflect changes in the potential difference on the basal membrane of the receptor cells, which is described by a relationship of the Nernst's or Goldman's equation type.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. I. M. Sechenov, Institute of Evolutionary Physiology and Biochemistry, Academy of Sciences of the USSR, Leningrad. Pacific Institute of Oceanology, Far Eastern Scientific Center, Academy of Sciences of the USSR, Vladivostok. Translated from Neirofiziologiya, Vol. 12, No. 1, pp. 67–74, January–February, 1980.  相似文献   
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