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991.
992.
Brevetoxin-3 (PbTx-3), described to increase the open probability of voltage-dependent sodium channels, caused trains of action potentials and fast oscillatory changes in fluorescence intensity of fluo-3-loaded rat skeletal muscle cells in primary culture, indicating that the toxin increased intracellular Ca(2+) levels. PbTx-3 did not elicit calcium transients in dysgenic myotubes (GLT cell line), lacking the alpha1 subunit of the dihydropyridine receptor (DHPR), but after transfection of the alpha1DHPR cDNA to GLT cells, PbTx-3 induced slow calcium transients that were similar to those of normal cells. Ca(2+) signals evoked by PbTx-3 were inhibited by blocking either IP(3) receptors, with 2-aminoethoxydiphenyl borate, or phospholipase C with U73122. PbTx-3 caused a tetrodotoxin-sensitive increase in intracellular IP(3) mass levels, dependent on extra-cellular Na(+). A similar increase in IP(3) mass was induced by high K(+) depolarization but no action potential trains (nor calcium signals) were elicited by prolonged depolarization under current clamp conditions. The increase in IP(3) mass induced by either PbTx-3 or K(+) was also detected in Ca(2+)-free medium. These results establish that the effect of the toxin on both intracellular Ca(2+) and IP(3) levels occurs via a membrane potential sensor instead of directly by Na(+) flux and supports the notion of a train of action potentials being more efficient as a stimulus than sustained depolarization, suggesting that tetanus is the physiological stimulus for the IP(3)-dependent calcium signal involved in regulation of gene expression. 相似文献
993.
994.
Marsillach J Ferré N Camps J Rull A Beltran R Joven J 《Molecular and cellular biochemistry》2008,308(1-2):101-109
Chronic liver diseases are accompanied by changes in the biochemical pathways related to the regulation of apoptosis and extra-cellular
matrix deposition. The present study was designed to investigate, using low density arrays, changes in the hepatic gene expression
together with hepatic biochemical and histological alterations in rats that had liver impairment induced by chronic exposure
to CCl4. Further, we examined the possible recovery of genetic and pathological changes following the cessation of the hepatotoxic
injury. Experimental fibrosis was induced in male Wistar rats by CCl4 administration. Animals were subdivided into two groups. One group was given CCl4 and animals were killed at 8 and 12 weeks of treatment. The other group was treated with CCl4 for 6 weeks, the CCl4 was then stopped and, subsequently, subgroups of animals were killed after 1 and 2 weeks of recovery. CCl4 administration over 12 weeks was associated with significant changes in B-cell leukemia/lymphoma 2, procollagen type I α
2, matrix metalloproteinases 3 and 8, tissue inhibitors of metalloproteinases 1, 2, and 3 and the inhibitor of apoptosis 4
gene expressions. Recovery after CCl4 cessation was associated with changes in procollagen type I α 2, matrix metalloproteinase 7, tissue inhibitors of metalloproteinases
1 and 2, inhibitor of apoptosis 4, and survivin gene expressions. This study shows an association between changes in the expression
of several genes regulating hepatic cell apoptosis, the fibrosis process, and the recovery of the hepatic function after removal
of the toxic injury. 相似文献
995.
Hernández-Alcántara G Rodríguez-Romero A Reyes-Vivas H Peon J Cabrera N Ortiz C Enríquez-Flores S De la Mora-De la Mora I López-Velázquez G 《Biochimica et biophysica acta》2008,1784(11):1493-1500
In the native state several proteins exhibit a quenching of fluorescence of their tryptophans. We studied triosephosphate isomerase from Giardia lamblia (GlTIM) to dissect the mechanisms that account for the quenching of fluorescence of its Trp. GlTIM contains four Trp per monomer (Trp75, Trp162, Trp173, and Trp196) distributed throughout the 3D structure. The fluorescence of the denatured enzyme is 3-fold higher than that of native GlTIM. To ascertain the origin of this phenomenon, single and triple mutants of Trp per Phe were made. The intrinsic fluorescence was determined, and the data were interpreted on the basis of the crystal structure of the enzyme. Our data show that the fluorescence of all Trp residues is quenched through two different mechanisms. In one, fluorescence is quenched by aromatic-aromatic interactions due to the proximity and orientation of the indole groups of Trp196 and Trp162. The magnitude of the quenching of fluorescence in Trp162 is higher than in the other three Trp. Fluorescence quenching is also due to energy transfer to the charged residues that surround Trp 75, 173 and 196. Further analysis of the fluorescence of GlTIM showed that, among TIMs from other parasites, Trp at position 12 exhibits rather unique properties. 相似文献
996.
Soliz J Soulage C Borter E van Patot MT Gassmann M 《American journal of physiology. Regulatory, integrative and comparative physiology》2008,295(2):R649-R658
Proteins harboring a Per-Arnt-Sim (PAS) domain are versatile and allow archaea, bacteria, and plants to sense oxygen partial pressure, as well as light intensity and redox potential. A PAS domain associated with a histidine kinase domain is found in FixL, the oxygen sensor molecule of Rhizobium species. PASKIN is the mammalian homolog of FixL, but its function is far from being understood. Using whole body plethysmography, we evaluated the ventilatory response to acute and chronic hypoxia of homozygous deficient male and female PASKIN mice (Paskin-/-). Although only slight ventilatory differences were found in males, female Paskin-/- mice increased ventilatory response to acute hypoxia. Unexpectedly, females had an impaired ability to reach ventilatory acclimatization in response to chronic hypoxia. Central control of ventilation occurs in the brain stem respiratory centers and is modulated by catecholamines via tyrosine hydroxylase (TH) activity. We observed that TH activity was altered in male and female Paskin-/- mice. Peripheral chemoreceptor effects on ventilation were evaluated by exposing animals to hyperoxia (Dejours test) and domperidone, a peripheral ventilatory stimulant drug directly affecting the carotid sinus nerve discharge. Male and female Paskin-/- had normal peripheral chemosensory (carotid bodies) responses. In summary, our observations suggest that PASKIN is involved in the central control of hypoxic ventilation, modulating ventilation in a gender-dependent manner. 相似文献
997.
Kaba NK Schultz J Law FY Lefort CT Martel-Gallegos G Kim M Waugh RE Arreola J Knauf PA 《American journal of physiology. Cell physiology》2008,295(5):C1454-C1463
Ischemia-reperfusion injury is a common pathological occurrence causing tissue damage in heart attack and stroke. Entrapment of neutrophils in the vasculature during ischemic events has been implicated in this process. In this study, we examine the effects that lactacidosis and consequent reductions in intracellular pH (pH(i)) have on surface expression of adhesion molecules on neutrophils. When human neutrophils were exposed to pH 6 lactate, there was a marked decrease in surface L-selectin (CD62L) levels, and the decrease was significantly enhanced by inclusion of Na(+)/H(+) exchanger (NHE) inhibitor 5-(N,N-hexamethylene)amiloride (HMA). Similar effects were observed when pH(i) was reduced while maintaining normal extracellular pH, by using an NH(4)Cl prepulse followed by washes and incubation in pH 7.4 buffer containing NHE inhibitors [HMA, cariporide, or 5-(N,N-dimethyl)amiloride (DMA)]. The amount of L-selectin shedding induced by different concentrations of NH(4)Cl in the prepulse correlated with the level of intracellular acidification with an apparent pK of 6.3. In contrast, beta(2)-integrin (CD11b and CD18) was only slightly upregulated in the low-pH(i) condition and was enhanced by NHE inhibition to a much lesser extent. L-selectin shedding was prevented by treating human neutrophils with inhibitors of extracellular metalloproteases (RO-31-9790 and KD-IX-73-4) or with inhibitors of intracellular signaling via p38 MAP kinase (SB-203580 and SB-239063), implying a transmembrane effect of pH(i). Taken together, these data suggest that the ability of NHE inhibitors such as HMA to reduce ischemia-reperfusion injury may be related to the nearly complete removal of L-selectin from the neutrophil surface. 相似文献
998.
Pleurotus species are recognized for producing beta-glucans with important medicinal properties as a constituent of the cellular wall of the fruiting body or of the mycelium. The aims of this work were to select a culture medium that maximized the production of biomass and polysaccharides produced by Pleurotus ostreatus DSM 1833 and to evaluate the selected medium in two values of initial oxygen transfer rate -K(L)a (10.2 and 19.3 h(-1)). A 2* *4 factorial design was constructed to evaluate the supplementation of wheat extract with corn steep liquor--CSL (10 or 20 g L(-1)), yeast extract--YE (2 or 5gL(-1)), ammonium sulfate--AS (0 or 5 g L(-1)) and glucose (20 or 40 g L(-1)). In terms of maximum productivity in biomass and global productivity in polysaccharides, the best values were obtained when 5 g L(-1) of YE and 40 g L(-1) of glucose were used. In terms of maximum concentration of biomass, the best results were obtained when 20 g L(-1) of CSL and 40 g L(-1) of glucose were used. The best results in terms of production of biomass and polysaccharides were achieved when lower initial K(L)a (10.2 h(-1)) was used. 相似文献
999.
Torres-Gómez H Hernández-Núñez E León-Rivera I Guerrero-Alvarez J Cedillo-Rivera R Moo-Puc R Argotte-Ramos R Rodríguez-Gutiérrez Mdel C Chan-Bacab MJ Navarrete-Vázquez G 《Bioorganic & medicinal chemistry letters》2008,18(11):3147-3151
A series of ten novel hybrids from benzimidazole and pentamidine were prepared using a short synthetic route. Each compound was tested in vitro against the protozoa Trichomonas vaginalis, Giardia lamblia, Entamoeba histolytica, Leishmania mexicana, and Plasmodium berghei, in comparison with pentamidine and metronidazole. Some analogues showed high bioactivity in the low micromolar range (IC(50)<1 microM) against the first four protozoa, which make them significantly more potent than either standard. 1,5-bis[4-(5-methoxy-1H-benzimidazole-2-yl)phenoxy]pentane (2) was 3- and 9-fold more potent againstG. lamblia than metronidazole and pentamidine, respectively. This compound was 23-, 108-, and 13-fold more active than pentamidine against T. vaginalis, E. histolytica and L. mexicana, respectively. Studying further structure-activity relationships through the use of bioisosteric substitution in these hybrids should provide new leads against protozoal diseases. 相似文献
1000.
Carlos E. Aragón Maritza Escalona Iris Capote Danilo Pina Inaudis Cejas Roberto Rodriguez Maria Jesus Cañal Jorge Sandoval Sophe Roels Pierre Debergh Justo Gonzalez-Olmedo 《In vitro cellular & developmental biology. Plant》2005,41(4):550-554
Summary The photosynthetic capacity changes and the main enzymatic systems related to carbon metabolism were investigated during the
in vitro culture of plantain shoots (Musa AAB cv. CEMSA 3/4) in temporary immersion bioreactors (TIB) and their subsequent acclimatization.
The maximal rate of photosynthesis (Pn), transpiration, and the activity of the carbon metabolism enzymes phosphoenolpyruvate
carboxylase (PEPC), acid invertase (AI), pyruvate kinase (PK) and sucrose phosphate synthase (SPS) were measured every 7 d
during the 21 d of elongation in TIB, and the following 42 d of acclimatization. Sucrose content in the liquid medium and
in the leaves was also determined. The most significant changes in plant growth were observed during acclimatization. During
the in vitro stage photosynthesis was limited (4–6 μmol CO2m−2s−1); the photosynthetic rate however increases rapidly and significantly as soon as in vitro culture is over during acclimatization. PEPC activity increased during the whole evaluation period. The highest levels were
achieved around days 42 and 56. PK and SPS activities were optimal during the first weeks in acclimatization (28–35 d), while
AI increased at the beginning of the elongation phase (7 d), and later at the end of the acclimatization (49–63 d). The relationships
between morphological parameters, photosynthetic capacity of the plantlets and the carbon metabolism enzymes during both phases
of the culture are discussed. 相似文献