a1_The day-night variation of food intake and alkaline phosphatase (AP) activity was studied in the duodenum of rats neonatally treated with monosodium glutamate (MSG) and saline-treated (control) rats. The animals were kept under light-dark conditions (light phase from 09:00 h to 21:00 h) with free access to food. AP activity was cytophotometrically analyzed in the brush-border of enterocytes separated from the tip, middle and cryptal part of the villi every 6 h over a 24-hour period. In comparison with the controls, MSG-treated rats consumed about 40 % less food during the dark period and their 24-hour food intake was thus significantly lowered (P<0.001). On the other hand, the nocturnal feeding habit showed a similar pattern: food consumption was high during the night (65 % vs. 75 %) and the lowest consumption was found during the light phase (35 % vs. 25 %) in MSG-treated and control rats, respectively. In agreement with the rhythm of food intake, the highest AP activity was observed during the dark phase and was lowest during the light phase in both groups of animals. These significant day-night variations showed nearly the same pattern in the enterocytes of all observed parts along the villus axis. In comparison with the controls, a permanent increase of AP activity was observed in neonatal MSG-treated rats. This increase was more expressive during the dark phase of the day in the cryptal (P<0.001) and middle part of the villus (P<0.01). From the viewpoint of feeding, this enzyme in MSG-treated rats was enhanced in an inverse relation to the amount of food eaten i.e. despite sustained hypophagia the mean AP activity in the enterocytes along the villus axis was higher than in the control animals during all investigated periods., a2_The present results suggest that the increased AP activity in MSG-treated rats is probably not a consequence of actual day-night eating perturbations but could be a component of a more general effect of MSG. This information contributes to better understanding of the function of intestinal AP and its relation to day-night feeding changes especially in connection with the MSG syndrome., A. Martinková, Ľ. Lenhardt, Š. Mozeš., and Obsahuje bibliografii
The present investigation was directed to study the effect of in vitro or ex vivo NO donors, sodium nitroprusside and molsidomine, using isolated sliced adipose tissue or in the form of immobilized and perfused adipocytes on the basal and isoprenaline-stimulated lipolysis. The results demonstrated that 1) in vitro application of sodium nitroprusside to perfused adipocytes or molsidomine to sliced adipose tissues affects isoprenaline-induced lipolysis in two ways, an increase in lipolysis at low isoprenaline concentrations (which means the sensitization of adipose tissues to adrenergic effect by NO) and decreased adrenergic agonist-stimulated lipolysis at higher concentration of isoprenaline (a decrease in the maximum lipolytic effect of isoprenaline), 2) low concentrations of molsidomine alone induced lipolysis from adipose tissue which attained more than 60 % of that by isoprenaline (pD2 value for molsidomine = 11.2, while pD2 for isoprenaline = 8.17) while sodium nitroprusside did not affect the basal lipolysis significantly, 3) in vivo administration of molsidomine for 2 days reduced the maximum lipolytic effect of isoprenaline and (only non-significantly) increased the sensitivity to low doses of isoprenaline. In conclusion the present data demonstrate that NO plays an important role in adrenergic lipolysis in adipose tissues and further investigations are needed to unravel the exact role of NO in lipolysis., D. Lincová, D. Mišeková, E. Kmoníčková, N. Canová, H. Farghali., and Obsahuje bibliografii
As nitric oxide is considered a mediator of liver oxid ative metabolism during sepsis, we studied the effects of exogenous nitric oxide, produced by NO-donor, (±)-(E)-4-ethyl-2-[(E)-hydroxyimino]-5-nitro-3-hexenamide (NOR-3), on cell viability, urea biosynthesis and oxygen consumption in rat hepatocyte cultures. Nitric oxide release from NOR-3 was studied using 4,5-diaminofluorescein diacetate. Urea levels were measured by the spectrophotometric method. Cell viability was determined by the MTT test and trypan blue exclusion test, whereas oxygen consumption was measured by a polarographic technique. After 2 h treatment, NOR-3 induced an increase in the levels of nitric oxide. After 2 h of treatment and 24 h after the end of the treatment with NOR-3, both cell viability and urea synthesis were significantly reduced in comparison to the controls for NOR-3 concentrations equal to or greater than 50 μM. A reduction in oxygen consumption was observed in hepatocytes after 40 min treatment with 100 μM NOR-3, even if the cell viability was unchanged. Reduction of oxygen consumption is an early indicator of the metabolic alterations in hepatocytes exposed to nitric oxide. These findings suggest that nitric oxide accumulation acts on hepatocyte cultures inducing cell death and reduction of urea synthesis after 2 hours., R. Chimenti, G. Martino, S. Mazzulla, S. Sesti., and Obsahuje bibliografii a bibliografické odkazy
Nitrogen (N) availability is a critical factor affecting photosynthetic acclimation of C3 plants under elevated atmospheric CO2 concentration ([CO2]e). However, current understanding of N effects on photosynthetic electron transport rate and partitioning, as well as its impact on photosynthesis under [CO2]e, is inadequate. Using controlled environment open-top chambers, wheat (Triticum aestivum L.) was grown at two N levels (0 and 200 mg(N) kg-1 soil) and two atmospheric CO2 concentrations of 400 ([CO2]a) and 760 μmol mol-1([CO2]e) during 2009 and 2010. Under [CO2]e high N availability increased stomatal conductance and transpiration rate, reduced limitations on the activity of triose phosphate isomerase, a Calvin cycle enzyme, and increased the rate of net photosynthesis (PN). Considering photosynthetic electron transport rate and partitioning aspects, we suggest that greater N availability increased PN under [CO2]e due to four following reasons: (1) higher N availability enhanced foliar N and chlorophyll concentrations, and the actual photochemical efficiency of photosystem (PS) II reaction centers under irradiance increased, (2) increase of total electron transport rate and proportion of open PSII reaction centers, (3) enhancement of the electron transport rate of the photochemical and carboxylation processes, and (4) reduced limitations of the Calvin cycle enzymes on the photosynthetic electron transport rate. Consequently, sufficient N improved light energy utilization in wheat flag leaves under [CO2]e, thus benefiting to photosynthetic assimilation. and X. C. Zhang, X. F. Yu, Y. F. Ma.
Effects of nitrogen (N)-deficiency on midday photoinhibition in flag leaves were compared between two contrastive Japanese rice cultivars, a traditional japonica cultivar with low yield, cv. Shirobeniya (SRB), and a japonica-indica intermediate type with high yield, cv. Akenohoshi (AKN). Both cultivars were grown under high-N and low-N conditions. At midday, low-N supply resulted in more intensive reductions in net photosynthetic rate, stomatal conductance, maximal quantum yield of photosystem II (PSII) and quantum yield of PSII electron transport in SRB than in AKN, indicating that SRB was more strongly photoinhibited than AKN under low-N condition. At midday, the low-N plants of two cultivars showed higher superoxide dismutase (SOD) activities than the high-N plants. However, ascorbate peroxidase (APX) activity was maintained in AKN but significantly decreased in SRB under low-N condition (N-deficiency). In contrast, hydrogen peroxide (H2O2) content in SRB significantly increased under low-N condition, indicating that the susceptibility to midday photoinhibition in the low-N plants of SRB is related to the increased H2O2 accumulation. It is suggested that the midday depression in photosynthesis may be a result of oxidative stress occurring in the low-N plants in which antioxidant capacity is not enough to cope with the generation of H2O2. Therefore, H2O2-scavenging capacity could be an important factor in determining the cultivar difference of midday photoinhibition in flag leaves of rice under low-N condition. and E. Kumagai, T. Araki, O. Ueno.
To examine the role of sink size on photosynthetic acclimation under elevated atmospheric CO2 concentrations ([CO2]), we tested the effects of panicle-removal (PR) treatment on photosynthesis in rice (Oryza sativa L.). Rice was grown at two [CO2] levels (ambient and ambient + 200 μmol mol-1) throughout the growing season, and at full-heading stage, at half the plants, a sink-limitation treatment was imposed by the removal of the panicles. The PR treatment alleviated the reduction of green leaf area, the contents of chlorophyll (Chl) and Rubisco after the full-heading stage, suggesting delay of senescence. Nonetheless, elevated [CO2] decreased photosynthesis (measured at current [CO2]) of plants exposed to the PR treatment. No significant [CO2] × PR interaction on photosynthesis was observed. The decrease of photosynthesis by elevated [CO2] of plants was associated with decreased leaf Rubisco content and N content. Leaf glucose content was increased by the PR treatment and also by elevated [CO2]. In conclusion, a sink-limitation in rice improved N status in the leaves, but this did not prevent the photosynthetic down-regulation under elevated [CO2]. and H. Shimono ... [et al.].
The partial shading effect on the photosynthetic apparatus of the sunflower (Helianthus annuus L.) was examined by monitoring oxygen evolution, maximum quantum yield of PSII photochemistry in dark-adapted leaves (Fv/Fm), the chlorophyll (Chl) concentrations and the Rubisco contents, and leaf mass per area (LMA) at the leaf level and by determining the concentrations of cytochrome (Cyt) f and the reaction centres of photosystem (PS) I and PSII at the thylakoid level. In this experiment, partial shading was defined as the shading of 2nd leaves with shade cloths, and the whole treatment was defined as the covering of the whole individuals with shade cloths. In the leaf level responses, oxygen evolution, LMA, Chl concentrations and Rubisco contents decreased in all shade treatments administered for six days. Fv/Fm remained constant irrespective of the shade treatments. On the other hand, in the thylakoid-level responses, the concentrations of the thylakoid components per unit Chl and the stoichiometry of the two photosystems showed no statistical difference among the shade treatments. The data obtained from the present study indicate that the partial shading affected the leaf-level responses rather than the thylakoid-level responses. The light received at the lower leaves might serve as a factor in the regulation of the leaf properties of the upper leaves due to the whole plant photosynthesis, while this factor did not have an effect at the thylakoid level., J. Ymazaki, Y. Shinomiya., and Obsahuje bibliografii
a1_Two experiments were performed to compare the effect of pectin and its hydrophobic derivatives on homeostasis of cholesterol and cecal metabolism in male young rats. Control rats were fed a diet supplemented with palm fat and cholesterol (50 and 10 g/kg, respectively). Rats of other gro ups were fed the same diet containing citrus pectin or octadecylpectinamide (60 g/kg). Diets were fed for 4 weeks. In experiment I, pectinamide of lower degree of amidation (30 %) increased serum HDL cholesterol from 1.20 to 1.43 μmol/ml (p>0.05) at the expense of other cholesterol fractions. In experiment II, pectinamide of a higher degree of amidation (53 %) significantly decreased total serum cholesterol from 2.08 to 1.67 μmol/ml. Amidated pectins at both levels of substitution significantly decreased hepatic concentrations of cholesterol and fat. In both experiments the relative weight of cecum in the pectinamide group was significantly lower than in pectin group. The highest cecal concentrations of short-chain fatty acids (SCFA) were found in rats fed a diet with pectin (133.2 and 129.3 μmol/g in experiment I and II, respectively). In other groups, cecal SCFA was significantly (pectinamide groups) or non-significantly (controls) lower. In wet feces, SCFA concentrations were higher and butyrate molar proportions lower than in corresponding cecal contents., a2_Pectinamide of a lower or higher degree of substitution significantly increased fecal content of cholesterol from 18.5 and 17.3 μmol/g in controls to 31.8 and 28.0 μmol/g, respectively. Corresponding concentrations of coprostanol were decreased. Effects of pectin on cholesterol homeostasis were absent or marginal. Histological examination revealed that hepatic tissue of control and pectin-fed rats was infiltrated with lipids. The Sudan black-positive material was absent in the liver of rats fed pectinamides. No pathological changes of liver tissue were apparent. In summary, hydrophobic amidated pectins significantly altered cholesterol homeostasis in rats and might be considered as a clinically effective hypocholesterolemic agent. Low cecal SCFA concentrations in rats fed pectinamides suggest that amidation of pectin had decreased its fermentability., M. Marounek, Z. Volek, A. Synytsya, J. Čopíková., and Obsahuje bibliografii a bibliografické odkazy
a_1 In this study, we have determined power output reached at maximal oxygen uptake during incremental cycling exercise (PI,max) performed at low and at high pedaling rates in nineteen untrained men with various myosin heavy chain composition (MyHC) in the vastus lateralis muscle. On separate days, subjects performed two incremental exercise tests until exhaustion at 60 rev . min-1 and at 120 rev . min-1. In the studied group of subjects PI,max reached during cycling at 60 rev . min-1 was significantly higher (p=0.0001) than that at 120 rev . min-1 (287±29 vs. 215±42 W, respectively for 60 and 120 rev . min-1). For further comparisons, two groups of subjects (n=6, each) were selected according to MyHC composition in the vastus lateralis muscle: group H with higher MyHC II content (56.8±2.79 %) and group L with lower MyHC II content in this muscle (28.6±5.8 %). PI,max reached during cycling performed at 60 rev . min-1 in group H was significantly lower than in group L (p=0.03). However, during cycling at 120 rev . min-1, there was no significant difference in PI,max reached by both groups of subjects (p=0.38). Moreover, oxygen uptake (VO2), blood hydrogen ion [H+], plasma lactate [La-] and ammonia [NH3] concentrations determined at the four highest power outputs completed during the incremental cycling performed at 60 as well as 120 rev . min-1, in the group H were significantly higher than in group L. We have concluded that during an incremental exercise performed at low pedaling rates the subjects with lower content of MyHC II in the vastus lateralis muscle possess greater power generating capabilities than the subjects with higher content of MyHC II. Surprisingly, at high pedaling rate, power generating capabilities in the subjects with higher MyHC II content in the vastus lateralis muscle did not differ from those found in the subjects with lower content of MyHC II in this muscle., a_2 We have concluded that during an incremental exercise performed at low pedaling rates the subjects with lower content of MyHC II in the vastus lateralis muscle possess greater power generating capabilities than the subjects with higher content of MyHC II. Surprisingly, at high pedaling rate, power generating capabilities in the subjects with higher MyHC II content in the vastus lateralis muscle did not differ from those found in the subjects with lower content of MyHC II in this muscle, despite higher blood [H+], [La-] and [NH3] concentrations. This indicates that at high pedaling rates the subjects with higher percentage of MyHC II in the vastus lateralis muscle perform relatively better than the subjects with lower percentage of MyHC II in this muscle., J. Majerczak, Z. Szkutnik, K. Duda, M. Komorowska, I. Kolodziejski, J. Karasinski, J. A. Zoladz., and Obsahuje bibliografii a bibliografické odkazy
A series of experiments have been undertaken to determine the effect of water extracts from pine bark (Pinus radiata) on the inhibition of the sporulation of oocysts of three species of avian coccidia. Tubes containing coccidian oocysts isolated from droppings of coccidia-infected chickens were randomly assigned to 0, 250, 500 and 1000 µg/ml pine bark extract (PBE). The tubes were incubated at 25-29 oC for 48 h depending on the species of Eimeria. Sporulation inhibition bioassay was used to evaluate the activity of PBE on the sporulation of coccidian oocysts. The oocysts were gently aerated with an air pump away from sun light. The results show for the first time that water-soluble extracts from pine bark containing 35% condensed tannins have anticoccidial activity as evidenced by their ability to decrease significantly the sporulation of the oocysts of three species of Eimeria, namely Eimeria tenella (Railliet et Lucet, 1891), E. maxima Tyzzer, 1929 and E. acervulina Tyzzer, 1929, under laboratory conditions. Incubation of unsporulated oocysts of these parasites in water containing 500 µg PBE per ml resulted in inhibition of sporulation of these oocysts by about 28-84% relative to the oocysts in the control incubations. In addition, up to 12% of E. maxima oocysts exposed to 500-1000 µg pine bark/ml were containing abnormal sporocysts in terms of size, number and shape.