42 research outputs found
Oligotrophication of Lake Balaton over a 20-year period and its implications for the relationship between phytoplankton and zooplankton biomass
Relationship between gill raker morphology and feeding habits of hybrid bigheaded carps (Hypophthalmichthys spp.)
Relationship between gill raker morphology and feeding habits of hybrid bigheaded carps (Hypophthalmichthys spp.)
Bigheaded carps and especially silver carp have been considered as an effective
biological control for algal blooms, thus were introduced to several countries in the last
decades, including Hungary. Our aim was to explore the feeding habits of bigheaded carps
in Lake Balaton (Hungary), where the stock consists mainly of hybrids (silver carp
× bighead carp). We examined
the relationship between filtering apparatus (gill raker) morphology and size-distribution
of planktonic organisms in the food. We failed to find any significant relationship
between gill raker parameters and plankton composition in the filtered material. Bigheaded
carps with various types of gill rakers consumed food within the same size-spectrum,
independently of the rate of hybridization. However, the linkage between the proportion of
different planktonic size classes in the water and in the diet of fish was detectable in
case of both phytoplankton and zooplankton consumption, suggesting that the seasonally
variable availability of different food items was an important factor in determining the
food composition of bigheaded carps. We can deduce that bigheaded carps consume high
amounts of zooplankton to meet their energy requirements, and the diet overlap among
bigheaded carps and other planktivores may exert negative effects on native fish
populations
Applicability of gill raker filtrates and foregut contents in the diet assessment of filter-feeding Asian carps
Fermented wheat germ extract inhibits glycolysis/pentoses cycle enzymes and induces apoptosis through poly(ADP-ribose) polymerase activation in Jurkat T cell leukemia tumor cells
The fermented extract of wheat germ, trade name Avemar, is a complex mixture of biologically active molecules with potent anti-metastatic activities in various human malignancies. Here we report the effect of Avemar on Jurkat leukemia cell viability, proliferation, cell cycle distribution, apoptosis, and the activity of key glycolytic/pentose cycle enzymes that control carbon flow for nucleic acid synthesis. The cytotoxic IC(50) concentration of Avemar for Jurkat tumor cells is 0.2 mg/ml, and increasing doses of the crude powder inhibit Jurkat cell proliferation in a dose-dependent fashion. At concentrations higher than 0.2 mg/ml, Avemar inhibits cell growth by more than 50% (72 h of incubation), which is preceded by the appearance of a sub-G(1) peak on flow histograms at 48 h. Laser scanning cytometry of propidium iodide- and annexin V-stained cells indicated that the growth-inhibiting effect of Avemar was consistent with a strong induction of apoptosis. Inhibition by benzyloxycarbonyl-Val-Ala-Asp fluoromethyl ketone of apoptosis but increased proteolysis of poly(ADP-ribose) indicate caspases mediate the cellular effects of Avemar. Activities of glucose-6-phosphate dehydrogenase and transketolase were inhibited in a dose-dependent fashion, which correlated with decreased (13)C incorporation and pentose cycle substrate flow into RNA ribose. This decrease in pentose cycle enzyme activities and carbon flow toward nucleic acid precursor synthesis provide the mechanistic understanding of the cell growth-controlling and apoptosis-inducing effects of fermented wheat germ. Avemar exhibits about a 50-fold higher IC(50) (10.02 mg/ml) for peripheral blood lymphocytes to induce a biological response, which provides the broad therapeutic window for this supplemental cancer treatment modality with no toxic effects
Applicability of gill raker filtrates and foregut contents in the diet assessment of filter-feeding Asian carps
Impact of the solvent capacity constraint on E. coli metabolism
<p>Abstract</p> <p>Background</p> <p>Obtaining quantitative predictions for cellular metabolic activities requires the identification and modeling of the physicochemical constraints that are relevant at physiological growth conditions. Molecular crowding in a cell's cytoplasm is one such potential constraint, as it limits the solvent capacity available to metabolic enzymes.</p> <p>Results</p> <p>Using a recently introduced flux balance modeling framework (FBAwMC) here we demonstrate that this constraint determines a metabolic switch in <it>E. coli </it>cells when they are shifted from low to high growth rates. The switch is characterized by a change in effective optimization strategy, the excretion of acetate at high growth rates, and a global reorganization of <it>E. coli </it>metabolic fluxes, the latter being partially confirmed by flux measurements of central metabolic reactions.</p> <p>Conclusion</p> <p>These results implicate the solvent capacity as an important physiological constraint acting on <it>E. coli </it>cells operating at high metabolic rates and for the activation of a metabolic switch when they are shifted from low to high growth rates. The relevance of this constraint in the context of both the aerobic ethanol excretion seen in fast growing yeast cells (Crabtree effect) and the aerobic glycolysis observed in rapidly dividing cancer cells (Warburg effect) should be addressed in the future.</p