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81.
The influence of sodium and potassium dynamics on excitability,seizures, and the stability of persistent states: I. Single neuron dynamics 总被引:1,自引:1,他引:0
John R. CressmanJr. Ghanim Ullah Jokubas Ziburkus Steven J. Schiff Ernest Barreto 《Journal of computational neuroscience》2009,26(2):159-170
In these companion papers, we study how the interrelated dynamics of sodium and potassium affect the excitability of neurons,
the occurrence of seizures, and the stability of persistent states of activity. In this first paper, we construct a mathematical
model consisting of a single conductance-based neuron together with intra- and extracellular ion concentration dynamics. We
formulate a reduction of this model that permits a detailed bifurcation analysis, and show that the reduced model is a reasonable
approximation of the full model. We find that competition between intrinsic neuronal currents, sodium-potassium pumps, glia,
and diffusion can produce very slow and large-amplitude oscillations in ion concentrations similar to what is seen physiologically
in seizures. Using the reduced model, we identify the dynamical mechanisms that give rise to these phenomena. These models
reveal several experimentally testable predictions. Our work emphasizes the critical role of ion concentration homeostasis
in the proper functioning of neurons, and points to important fundamental processes that may underlie pathological states
such as epilepsy.
相似文献
John R. Cressman Jr.Email: |
82.
Nicole M Gerardo Boran Altincicek Caroline Anselme Hagop Atamian Seth M Barribeau de Martin Vos Elizabeth J Duncan Jay D Evans Toni Gabaldón Murad Ghanim Adelaziz Heddi Isgouhi Kaloshian Amparo Latorre Andres Moya Atsushi Nakabachi Benjamin J Parker Vincente Pérez-Brocal Miguel Pignatelli Yvan Rahbé John S Ramsey Chelsea J Spragg Javier Tamames Daniel Tamarit Cecilia Tamborindeguy Caroline Vincent-Monegat Andreas Vilcinskas 《Genome biology》2010,11(2):1-17
83.
de Giuseppe PO Ullah A Silva DT Gremski LH Wille AC Chaves Moreira D Ribeiro AS Chaim OM Murakami MT Veiga SS Arni RK 《Biochemical and biophysical research communications》2011,409(4):6064-627
Phospholipases D (PLDs) are principally responsible for the local and systemic effects of Loxosceles envenomation including dermonecrosis and hemolysis. Despite their clinical relevance in loxoscelism, to date, only the SMase I from Loxosceles laeta, a class I member, has been structurally characterized. The crystal structure of a class II member from Loxosceles intermedia venom has been determined at 1.7 Å resolution. Structural comparison to the class I member showed that the presence of an additional disulphide bridge which links the catalytic loop to the flexible loop significantly changes the volume and shape of the catalytic cleft. An examination of the crystal structures of PLD homologues in the presence of low molecular weight compounds at their active sites suggests the existence of a ligand-dependent rotamer conformation of the highly conserved residue Trp230 (equivalent to Trp192 in the glycerophosphodiester phosphodiesterase from Thermus thermophofilus, PDB code: 1VD6) indicating its role in substrate binding in both enzymes. Sequence and structural analyses suggest that the reduced sphingomyelinase activity observed in some class IIb PLDs is probably due to point mutations which lead to a different substrate preference. 相似文献
84.
Sultana Juhara Mannan Mohammad Abul Kalam Azad Md. Ashik Ullah Abdullah Al Maruf Md. Israt Rayhan Mohammad Shamsul Ahsan Abul Hasnat 《Biological trace element research》2011,140(3):272-283
Drug abuser patients (n = 104), age ranging from 19 to 42 years, were randomly recruited to investigate the serum levels of trace elements (Cu, Zn,
Fe, and Mg), malondialdehyde (MDA), and immunoglobulin (IgG, IgA, and IgM) before and after clinical intervention. Control
group also included 104 healthy individuals. Blood samples were analyzed for determining trace elements, MDA, and immunoglobulin
using atomic absorption spectroscopy, Ultraviolet-Visible (UV-VIS) spectroscopy, and turbidimetry method, respectively. For
serum level of Zn and Fe, the differences between the groups (before intervention, after intervention, and control) were not
significant (p > 0.05). However, significant differences were found in serum copper levels between control group, drug abuser patients,
and before and after intervention (p < 0.05). The concentration of Mg was found to be significantly higher (p = 0.007) in drug abuser patients than the controls, and after intervention, the level was restored to control value. A displacement
of elemental homeostasis was observed in drug abuser patients compared to control, and it was improved after intervention.
An increase in serum concentration of MDA was found in drug abuser patients compared to control subjects (p > 0.05) but was not statistically significant. After intervention, the concentration was restored to control value (p > 0.05). The serum concentrations of IgA and IgM were found to be significantly higher (p < 0.05) in drug abuser patients before intervention than the controls, and the level tended to be restored to control level
after clinical intervention. Serum IgG level was found to be lower in drug abuser patients compared to controls and further
declined significantly (p < 0.05) after intervention. These findings may suggest a possible imbalance in the levels of micronutrients, antioxidants,
and immunoglobulin in drug abuser patients, which tend to be restored to control values after detoxification. 相似文献
85.
We investigated the effect of temperature on development and demographic parameters such as the intrinsic rate of natural
increase (r
m) of the two spider mite species Tetranychus merganser Boudreaux and T. kanzawai Kishida at eleven constant temperatures ranging from 15 to 40°C at intervals of 2.5°C. Both male and female T. merganser and T. kanzawai completed development from egg to adult at temperatures ranging from 15 to 37.5°C. The longest developmental duration of
immature stages was found at 15°C and the shortest developmental duration was found at 35°C for both species. Using linear
and non-linear developmental rate models, the lower thermal thresholds for egg-to-adult (female and male) and egg-to-egg development
were estimated as 12.2–12.3°C for T. merganser and as 10.8°C for T. kanzawai. The highest developmental rates were observed at around 35°C, whereas the upper developmental thresholds were around 40°C
for both species. In fact, at 40°C, a few eggs of either species hatched, but no larvae reached the next stage. The r
m-values of T. merganser ranged from 0.072 (15°C) to 0.411 day−1 (35°C), whereas those of T. kanzawai ranged from 0.104 (15°C) to 0.399 (30°C). The r
m-values were higher for T. kanzawai than for T. merganser at temperatures from 15 to 30°C, but not at 35°C (0.348 day−1). Total fecundity of T. merganser was also higher than that of T. kanzawai at 35°C. These results indicate that higher temperatures favor T. merganser more than T. kanzawai. 相似文献
86.
87.
88.
Background
Based on the ethnomedicinal uses and the effective outcomes of natural products in various diseases, this study was designed to evaluate Isodon rugosus as possible remedy in oxidative stress, alzheimer’s and other neurodegenerative diseases. Acetylecholinestrase (AChE) and butyrylcholinesterase (BChE) inhibitory activities of crude methanolic extract (Ir.Cr), resultant fractions (n-hexane (Ir.Hex), chloroform (Ir.Cf), ethyl acetate (Ir.EtAc), aqueous (Ir.Aq)), flavonoids (Ir.Flv) and crude saponins (Ir.Sp) of I. rugosus were investigated using Ellman’s spectrophotometric method. Antioxidant potential of I. rugosus was determined using DPPH, H2O2 and ABTS free radicals scavenging assays. Total phenolic and flavonoids contents of plant extracts were determined and expressed in mg GAE/g dry weight and mg RTE/g of dry sample respectively.Results
Among different fractions Ir.Flv and Ir.Cf exhibited highest inhibitory activity against AChE (87.44 ± 0.51, 83.73 ± 0.64%) and BChE (82.53 ± 0.71, 88.55 ± 0.77%) enzymes at 1 mg/ml with IC50 values of 45, 50 for AChE and 40, 70 μg/ml for BChE respectively. Activity of these fractions were comparable to galanthamine causing 96.00 ± 0.30 and 88.61 ± 0.43% inhibition of AChE and BChE at 1 mg/ml concentration with IC50 values of 20 and 47 μg/ml respectively. In antioxidant assays, Ir.Flv, Ir.Cf, and Ir.EtAc demonstrated highest radicals scavenging activities in DPPH and H2O2 assays which were comparable to ascorbic acid. Ir.Flv was found most potent with IC50 of 19 and 24 μg/ml against DPPH and H2O2 radicals respectively. Whereas antioxidant activates of plant samples against ABTS free radicals was moderate. Ir.Cf, Ir.EtAc and Ir.Cr showed high phenolic and flavonoid contents and concentrations of these compounds in different fractions correlated well to their antioxidant and anticholinestrase activities.Conclusion
It may be inferred from the current investigations that the Ir.Sp, Ir.Flv and various fractions of I. rugosus are good sources of anticholinesterase and antioxidant compounds. Different fractions can be subjected to activity guided isolation of bioactive compounds effective in neurological disorders. 相似文献89.
Background
Isodon rugosus is used traditionally in the management of hypertension, rheumatism, tooth-ache and pyrexia. Present study was arranged to investigate I. rugosus for phytoconstituents, phytotoxic and cytotoxic activities to explore its toxicological, pharmacological potentials and to rationalize its ethnomedicinal uses. Briefly, qualitative phytochemical analysis of the plant extracts were carried out for the existence of alkaloids, flavonoids, saponins, oils, glycosides, anthraquinones, terpenoids, sterols and tannins. Plant crude methanolic extract (Ir.Cr), its subsequent fractions; n-hexane (Ir.Hex), chloroform (Ir.Chf), ethyl acetate (Ir.EtAc), aqueous (Ir.Aq) and saponins (Ir.Sp) in different concentrations were tested for phytotoxic and cytotoxic activities using radish seeds and brine shrimps (Artemia salina) respectively. The phytotoxic activity was determined by percent root length inhibition (RLI) and percent seeds germination inhibition (SGI) while the cytotoxicity was obtained with percent lethality of the brine shrimps.Results
Ir.Cr was tested positive for the presence of alkaloids, glycosides, flavonoids, oils, terpenoids, saponins, tannins and anthraquinones. Among different fractions Ir.Sp, Ir.Chf, Ir.EtAc, and Ir.Cr were most effective causing 93.55, 89.32, 81.32 and 58.68% inhibition of seeds in phytotoxicity assay, with IC50 values of 0.1, 0.1, 0.1 and 52 μg/ml respectively. Similarly, among all the tested samples, Ir.Sp exhibited the highest phytotoxic effect causing 91.33% root length inhibition with IC50 of 0.1 μg/ml. Ir.Sp and Ir.Chf were most effective against brine shrimps showing 92.23 and 76.67% lethality with LC50 values of 10 and 12 μg/ml respectively.Conclusions
It may be inferred from the current investigations that I. rugosus contains different secondary metabolites and is a potential source for the isolation of natural anticancer and herbicidal drug molecules. Different fractions exhibited phytotoxic and cytotoxic activities, thus providing pharmacological basis for ethnomedicinal uses of this plant. 相似文献90.
Adnan Daud Khan Sultan Daud Khan Rehan Ullah Khan Naveed Ahmad 《Plasmonics (Norwell, Mass.)》2014,9(2):461-475
The presence of plasmonic Fano-like resonances in the optical response of isolated and dimer metal-dielectric-metal nanostructures are investigated theoretically. The nanostructures are engineered in such a way to support multiple Fano-like resonances that are induced by the interference of bright and dark plasmon modes. It is found that the dimer resonators exhibit different types of Fano resonances for both the transverse and longitudinal polarizations unlike conventional nanodimers. Several configurations of the dimer Fano resonator are analyzed with special emphasis on the Fano spectral line shape. Breaking the symmetry of the dimer nanostructure in various directions control the asymmetric line shape and provides different kinds of unique Fano resonances. In certain cases, the Fano resonators exhibit multiple Fano resonances that are particularly significant for plasmon line shaping and can serve as platforms for multi-wavelength sensing applications. 相似文献