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Csercsik D Farkas I Hrabovszky E Liposits Z 《Journal of computational neuroscience》2012,32(1):119-136
In this paper a modular model of the GnRH neuron is presented. For the aim of simplicity, the currents corresponding to fast time scales and action potential generation are described by an impulsive system, while the slower currents and calcium dynamics are described by usual ordinary differential equations (ODEs). The model is able to reproduce the depolarizing afterpotentials, afterhyperpolarization, periodic bursting behavior and the corresponding calcium transients observed in the case of GnRH neurons. 相似文献
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Summary The absolute concentration of zinc in the Purkinje cells of the rat cerebellum was determined by means of energy dispersive X-ray microanalysis (EDAX). Gelatine blocks with known zinc concentrations were stained by Timm's sulphide-silver method, and their silver concentrations were measured by EDAX. A linear correlation was found between the zinc and silver concentrations and this linear function was used as a quantitative calibration for evaluation of sulphide-silver staining, after perfusion with sodium-sulphide solution, fixation with glutaraldehyde, cryostat sectioning and staining of cerebellar samples in Timm's reagent. 相似文献
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Gerd Wallukat Gyorgy Nemecz Tibor Farkas Hartmut Kuehn Albert Wollenberger 《Molecular and cellular biochemistry》1991,102(1):35-47
Incubation of rocker-cultured neonatal rat heart cells with 3 mM L(+)-lactate led to a sharp increase in the sensitivity of cardiomyocytes to the beta-adrenergic agonist isoprenaline, as measured by their chronotropic response. This effect was accompanied by a reduction in the arachidonic acid content of the total phospholipids. The phospholipase A2-activator melittin as well as free arachidonic acid induced this supersensitivity to the same degree. On the other hand, the L(+)-lactate-evoked supersensitivity could be blocked by the phospholipase A2 inhibitors mepacrine and n-bromophenacyl-bromide, suggesting an involvement of phospholipase A2 in the process of beta-adrenergic sensitization. The sensitizing action of arachidonic acid was blocked by the lipoxygenase inhibitors esculetin and nordihydroguaiaretic acid, but not by the cyclooxygenase inhibitor indomethacin. Supersensitivity was likewise evoked by 15-S-hydroxyeicosatetraenoic acid (15-S-HETE), but not by 5-S-HPETE or 5-S-HETE. These findings suggest that the phospholipase A2-15-lipoxygenase pathway plays a role in the induction of beta-adrenergic supersensitivity in the cultured cardiomyocytes and point to a new physiological role of the lipoxygenase product 15-S-HETE.Abbreviations NDGA
nordihydroguaiaretic acid
- HETE
hydroeicosatetraenoic acid
- HPETE
hydroperoxyeicosatetraenoic acid 相似文献
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Farkas G. A.; Decramer M.; Rochester D. F.; De Troyer A. 《Journal of applied physiology》1985,59(2):528-535
To have some insight into the functional coupling between the parasternal intercostals (PS) and the diaphragm (DPM), we have examined the isometric contractile properties of bundles from canine PS and DPM muscles. Bundles of external (EXT) and internal (INT) interosseous intercostals were studied for comparison. In addition we have related sonometrically measured length of the intercostals in vivo at supine functional residual capacity (FRC) to in vitro optimal force-producing length (Lo). We found that 1) intercostal twitch speed is significantly faster than DPM, thus displacing their relative force-frequency curve to the right of that of the DPM; 2) the ascending limb of the active length-tension curve of all intercostals lies below the DPM curve; i.e., at 85% Lo, PS force is 46% of maximal force (Po), whereas DPM force is still 87% Po; 3) for any given length change beyond Lo, all intercostals generate greater passive tension than the DPM; 4) Po is greater for the intercostals than the DPM; and 5) at supine FRC, both EXT and INT in dogs are nearly operating at Lo, whereas the PS are operating at a length greater than Lo. We conclude that 1) PS produce less force than DPM during breathing efforts involving low- (10-20 Hz) stimulation frequencies, but they generate more force than DPM when high- (greater than 50 Hz) stimulation frequencies are required; and 2) the pressure-generating ability of the PS is better preserved than that of the DPM with increases in lung volume.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
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A novel experimental method was developed which allows the determination of the threshold concentration of sucrose by use of a linear sucrose gradient in water. With this method a continuous tasting of the test-liquid is possible. A panel of 15 persons experienced in taste-testing was used. Three gradients of different steepness were applied: 0 to 1.5% (w/w) sucrose in 2 min (I), 3 min (II) and 4 min (III). The results of the new method were compared with those of the standard method (DIN). With gradients I and II we found values which were significantly higher than those of the standard method (I: 0.49% (w/w); II: 0.46% (w/w); DIN: 0.31% (w/w)), whereas with gradient III the same threshold value was found as with the DIN-Method (III: 0.32% (w/w)). 相似文献
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Pig brain tRNA was assayed for the presence of queuosine in the first position of the anticodon for each of the Q-family of tRNAs (aspartyl, asparaginyl, histidyl and tyrosyl). The brain tRNA was aminoacylated with each of the four amino acids and the aminoacylated tRNA's analyzed by RPC-5 chromatography. The results of this study show that for all four tRNAs of the family, queuine is substituted for guanine in virtually 100% of the anticodons. Therefore, it can be concluded that queuine is able to cross the blood-brain barrier and that brain contains quanine-queuine tRNA transglycosylase, the enzyme responsible for the excision of guanine from the orginal transcipts of these tRNAs and insertion of queuine. The determination of whether the tRNA contained queuine was made from the elution profile of the RPC-5 chromatrograms and the results confirmed by a change in the RPC-5 elution profile when the tRNAs were reacted with BrCN or NaIO4. 相似文献
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Mária Wollemann Judit Farkas Géza Tóth Sándor Benyhe 《Journal of neurochemistry》1994,63(4):1460-1465
Abstract: A tritiated heptapeptide, [3 H]Tyr-Gly-Gly-Phe-Met-Arg-Phe ([3 H]Met-enkephalin-Arg6 -Phe7 ), with high specific radioactivity has been synthesized in order to characterize its opioid binding activity to frog brain membrane fractions. The apparent K D value of the radioligand calculated from homologous displacement experiments was 3.4 n M , and the maximal number of specific binding sites was 630 fmol/mg of protein. The K D determined from equilibrium saturation binding studies was found to be 3.6 n M . However, the Hill coefficient was far below unity ( n H = 0.43), which suggests the presence of a second, lower affinity binding site. The presence of this binding component is strengthened by the displacement experiments performed with levorphanol and some other ligands. It is assumed that the lower affinity site has no opiate character. The rank order of potency of the applied ligands in competing reversibly with [3 H]Met-enkephalin-Arg6 -Phe7 binding reflects a κ2 - and/or δ-subtype specificity of the heptapeptide. Binding to a κ1 and/or μ site of opioid receptors is excluded, but the existence of a novel endogenous opiate receptor subtype for Met-enkephalin-Arg6 -Phe7 in frogs cannot be ruled out. The [3 H]Met-enkephalin-Arg6 -Phe7 binding was inhibited by both sodium ions and GppNHp, which suggests the opioid agonist character of the heptapeptide. 相似文献