In electrically nonexcitable cells the activity of the plasma membrane calcium channels is controlled by events occurring in mitochondria, as well as in the lumen of the endoplasmic reticulum. Thapsigargin, a specific inhibitor of endoplasmic reticulum Ca 2+ -ATPase, produces the release of calcium from the endoplasmic reticulum and thus, activation of store-operated calcium channels in the plasma membrane. However, thapsigargin failed to produce significant activation of the channels in Jurkat cells that had been pretreated with mitochondria-directed agents: an uncoupler (carbonyl cyanide m-chlorophenylhydrazone) and oligomycin. This is in spite of the fact that Jurkat cells pretreated with carbonyl cyanide m-chlorophenylhydrazone plus oligomycin are otherwise energetically competent, due to a high rate of glycolysis and the inhibition of mitochondrial F 1 F o -ATPase by oligomycin. The pool of intracellular ATP was found not to be influenced by the pretreatments of cells with oligomycin or with oligomycin plus carbonyl cyanide m-chlorophenylhydrazone. In the control cells, we found that the ATP pool amounted to 23.2^1.9 nmoles per 10 7 cells (n = 4). In cells pretreated with oligomycin the level of ATP was 21.8^1.9 nmoles per 10 7 cells (n = 4), and in cells pretreated with both oligomycin and an uncoupler the level of ATP was 22.1^0.2 nmoles per 10 7 cells (n = 3). Moreover, in cells pretreated with oligomycin plus carbonyl cyanide m-chlorophenylhydrazone and suspended in a nominally calcium-free medium, thapsigargin produces transient increases in cytosolic calcium identical to those in the control cells. Thus, this pretreatment does not modify either the content of intracellular calcium stores and/or the activity of calcium ATPase in the plasma membrane. Similar results were obtained when Jurkat cells were challenged by myxothiazol, a potent inhibitor of mitochondrial cytochrome bc 1 oxidoreductase. Thapsigargin, although producing calcium release from intracellular stores, was ineffective in triggering the activation of calcium channels in the plasma membrane in the case of cells pretreated with myxothiazol and oligomycin. Our results suggest that coupled mitochondria participate directly in the control of calcium channel activity in the plasma membrane of Jurkat cells. When the mitochondrial protonmotive force is collapsed, either by carbonyl cyanide m-chlorophenylhydrazone or myxothiazol, the channel remains inactive even under conditions of empty intracellular calcium stores.
The potential of potato juice in relieving gastrointestinal disorders has already been proven. Work continues on implementation of this active component into products that are widely consumed. In this article, results of an attempt to fortify pasta with potato juice are presented and discussed. Fortification is performed using fresh and dried juice. The influence of the addition on culinary properties of the final product, such as cooking weight and cooking loss, as well as microstructure, color, texture, and consumer acceptance were evaluated. It was found that potato juice can be used for fortification of pasta both in its fresh and dried forms, however the effects on different responses depend on the potato juice form used. The addition of potato juice influenced the color of the product reducing its lightness and shifting color balances from green to red, yellow color saturation was decreased as well. Changes in color were more significant in the case of fresh juice addition. The firmness and microstructure of pasta was also influenced. The surface microstructure of pasta containing fresh potato juice was different from that of the other 2 products being a likely explanation of the lower cooking loss observed in its case. In contrast, the consistency of dough was strengthened by addition of dried potato juice. Principal components analysis indicated that the color change had the most pronounced effect on consumer acceptance. Other physicochemical changes were slightly less significant. Nevertheless, sensory evaluation proved that functional pasta produced with fresh potato juice finds consumer acceptance comparable with that of classic pasta.
The distribution of Ca 2+ in intact cells was monitored with fluorescent probes: fura-2 for cytosolic [Ca 2+ ] and rhod-2 for mitochondrial [Ca 2+ ]. It was found that in neoplastic cells, such as Ehrlich ascites tumour and Zajdela hepatoma, but not in non-malignant cells, such as fibroblasts, glucose and deoxyglucose elicited release of Ca 2+ from endoplasmic reticulum stores and an increase in Ca 2+ concentration in the cytosol. Parallel to this, a decrease in the rate of Ca 2+ extrusion from the cell and an enhanced uptake of Ca 2+ by mitochondria were observed. The increase in mitochondrial [Ca 2+ ] was accompanied by an increase in the mitochondrial membrane potential and the reduction state of nicotinamide nucleotides. F 1 F o -ATPase in submitochondrial particles of Zajdela hepatoma was strongly inhibited in the presence of micromolar Ca 2+ concentrations, whereas this activity in submitochondrial particles from rat liver appeared to be less sensitive to Ca 2+ . Indications of glycosylation of Ehrlich ascites tumour cell proteins were also obtained. These data strengthen the proposal [Bogucka, K., Teplova, V.V., Wojtczak, L. and Evtodienko, Y. V. (1995) Biochim. Biophys. Acta 1228, 261±266] that the Crabtree effect is produced by mobilization of cell calcium, which is subsequently taken up by mitochondria and inhibits F 1 F o -ATP synthase.Keywords: Calcium; Crabtree effect; Ehrlich ascites tumour; mitochondrial membrane potential; Zajdela hepatoma.Many kinds of tumour exhibit an unusual reaction towards glucose: addition of millimolar concentrations of glucose to the culture medium results in a decrease in the cell respiration rate. This behaviour, known by the name of its discoverer as the Crabtree effect [1], has also been observed in some non-malignant cells and tissues, such as spermatozoa [2,3], proliferating thymocytes [4], intestinal mucosa [5] and mammalian embryos at their very early developmental stage [6]. Common features of all these tissues, both malignant and normal, are a high proliferation rate and/or a high glycolytic rate. Although the Crabtree effect has been known for seven decades (for an early review see [7]), its molecular mechanism is not fully understood. First attempts to explain it pointed to the competition between respiration and glycolysis for precursors of ATP production, i.e. ADP [8,9] and inorganic phosphate [10±12]. However, this explanation is not satisfactory because deoxyglucose, which is phosphorylated in the cytoplasm but not further metabolized and therefore does not generate ATP, produced even stronger inhibition of respiration than did glucose [13] and phosphate transport into the cell has been shown to be fast enough [13].Other possible explanations of the mechanisms of the Crabtree effect were a shift in intracellular pH [7], a change in permeability properties of the inner mitochondrial membrane [14], a specific isoenzyme pattern of the glycolytic pathway and regulatory behaviour of key enzymes of this pathway [15], and specific topography of enzymes in rap...
Triticale is a hybrid obtained by crossing wheat with rye. One of the factors limiting its application into food industry is still a lack of knowledge about this cereal. The aim of this study was to characterize and compare features of triticale starch obtained from grain of five new Polish triticale varieties: Madilo, Baltiko, CHD 3012/99, Pizarro and Fredro. Starch content in grain of analyzed cultivars varied in narrow range, while differences of falling number values, in spite of the same growing condition, varied more significantly. All the investigated triticale starches had a bimodal size distribution of granules. This was confirmed by both laser diffraction methods and scanning electron microscopy. Tested starches differed in terms of their amylose content and particle size distribution, thermal and pasting properties, as well as molecular weights. Starches of higher molecular mass (Mw) underwent gelatinization at higher temperature, according to DSC analysis. Values of pasting temperatures recorded by RVA were higher than those obtained by DSC. Relative proportion of A‐type to B‐type starch granules affected pasting properties measured by RVA. Starches of higher Mw underwent gelatinization at higher temperature. Tested triticale starches did not differ much in terms of hydrodynamic properties, offset and peak temperatures (DSC). Differences between samples show that physicochemical properties and the structure of triticale starch are variety‐dependent. PCA analysis indicated that starches obtained from Madilo and CHD 3099/12 as well as Baltiko and Fredro form separate groups with similar characteristics. Starch of cv. Pizarro differs significantly from those of the other cultivars.
The objective of the present work was to determine the effect of pretreatment by extrusion on the biogas and biomethane yield of lignocellulosic substrates such as maize silage and maize straw silage. The biogas yields of the substrates before and after treatment were compared. Moreover, energy efficiency of pretreatment by extrusion was analyzed in order to assess the applicability of the process in an agricultural biogas plant. Extrusion tests were carried out in a short single-screw extruder KZM-2 in which the length-to-diameter ratio of the screw was 6:1 and rotational speed was 200 rpm. The biogas yield tests of the plant substrates after extrusion were carried out in a laboratory scale, using 15 biofermenters operated in a periodic manner, at a constant temperature of 39°C (mesophilic digestion) and controlled pH conditions. The gas-emission analysis was performed using a certified gas analyzer from Geotech GA5000. Pretreatment by extrusion was observed to improve the quantity of methane generated: in terms of fresh matter for maize silage subjected to extrusion, the methane yield was 16.48% higher than that of the non-extruded silage. On the other hand, maize straw silage after extrusion gave 35.30% more methane than did the same, non-extruded, material. Differences in yields relative to dry organic matter are also described in this paper. Taking into account the amount of energy that is spent on pretreatment and the generated amount of methane, the energy balance for the process gives an idea of the economics of the operation. For maize silage, energy efficiency was lower by 13.21% (-553.2 kWh/Mg), in contrast to maize straw silage, where the increase in energy was 33.49% (678.4 kWh/Mg). The obtained results indicate that more studies on the pretreatment and digestion of maize silage are required in order to improve the efficiency of its use for making biogas. To fully utilize its potential, it is necessary to know thoroughly the effect of the extrusion process and of biogas production on energy efficiency at different conditions.
Grain growth conditions related to location and nitrogen fertilisation level had the most noticeable effect on grain starch content, while grain yield per hectare had the most significant effect on ethanol productivity.
Summary Soybean sprouts cultured in 20 mm FeSO4 were introduced into corn snacks (1.75–3.50%) to supplement iron. The effect of extrusion process on the ferritin iron stability and on product quality was studied. Iron stability in these fortified snacks depended mainly on feed moisture levels, with the best results seen when the feed moisture and temperature were 12% and 110 °C, respectively. Lower feed moisture was beneficial to hardness, expansion ratio and bulk density, while lower temperature increased snack hardness and density, while worsening the expansion ratio. The snacks’ water absorption was strongly and directly dependent on the temperature, while their solubility mainly depended inversely on feed moisture. All of the variables tested altered the colour of the snacks. The conditions that were best for producing the ferritin‐fortified snacks – 12% feed moisture, and temperature equal than or less to 140 °C – may yield a product with the desired quality features.
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