Absence Of Other Nutrients Research Articles

Lipid droplets provide metabolic flexibility for cancer progression.

A hallmark of cancer cells is their remarkable ability to efficiently adapt to favorable and hostile environments. Due to a unique metabolic flexibility, tumor cells can grow even in the absence of extracellular nutrients or in stressful scenarios. To achieve this, cancer cells need large amounts of lipids to build membranes, synthesize lipid-derived molecules, and generate metabolic energy in the absence of other nutrients. Tumor cells potentiate strategies to obtain lipids from other cells, metabolic pathways to synthesize new lipids, and mechanisms for efficient storage, mobilization, and utilization of these lipids. Lipid droplets (LDs) are the organelles that collect and supply lipids in eukaryotes and it is increasingly recognized that the accumulation ofLDs is a new hallmark of cancer cells. Furthermore, an active role of LD proteins in processes underlying tumorigenesis has been proposed. Here, by focusing on three major classes of LD-resident proteins (perilipins, lipases, and acyl-CoA synthetases), we provide an overview of the contribution of LDs to cancer progression and discuss the role of LD proteins during the proliferation, invasion, metastasis, apoptosis, and stemness of cancer cells.

Sugar-Induced Cell Death in the Yeast S. cerevisiae Is Accompanied by the Release of Octanoic Acid, Which Does Not Originate from the Fatty Acid Synthesis Type II Mitochondrial System

Incubation of the yeast S. cerevisiae with glucose, in the absence of other nutrients, leads to Sugar-Induced Cell Death (SICD), accompanied by the accumulation of Reactive Oxygen Species (ROS). Yeast acidifies the environment during glucose metabolism not only as a result of the activity of the H+-ATPase of the plasma membrane but also due to the release of carboxylic acids. Acetic acid is known to induce apoptosis in growing yeast. We analyzed the composition of the incubation medium and found octanoic acid (OA) but no other carboxylic acids. Its concentration (0.675 µM) was significantly lower than the one at which OA had a toxic effect on the cell. However, the theoretically calculated concentration of OA inside the cell (about 200 μM) was found to be high enough to lead to cell necrosis. To test the hypothesis that OA might cause SICD, we used a ΔACP1 strain incapable of synthesizing OA in the yeast mitochondrial Fatty Acid Synthesis type II system (FAS-II). The deletion of the ACP1 gene did not affect the OA content in the medium. But, on the other hand, OA is a precursor of lipoic acid, which has antioxidant properties. However, strains with deleted genes for lipoic acid biosynthesis from OA (ΔPPT2, ΔLIP2, ΔLIP5, and ΔSGV3) showed no change in ROS and SICD levels. Thus, lipoic acid synthesized in FAS-II does not protect cells from ROS accumulated during SICD. We conclude that OA synthesized in the mitochondrial FAS-II system and its derivative lipoic acid are not involved in SICD in yeast S. cerevisiae.

Effects of temperature and nutrients on the emissions of biogenic volatile sulfur compounds from

Environmental context Blooms of Ulva prolifera have recurred annually in the Yellow Sea since 2007, causing economic losses and severe ecological problems. We conducted laboratory incubation experiments to examine the effects of temperature and nutrients on its biogenic sulfur emissions during its decline period. Increasing temperature and nutrients affected the decay of U. prolifera, resulting in respective decreased and increased emission of biogenic sulfur compounds. Abstract The Ulva prolifera blooms have recurred annually in the Yellow Sea (YS) since 2007, causing huge economic losses and severe ecological problems. So far, few studies have investigated the release of volatile biogenic sulfur compounds by the U. prolifera blooms. In this study, laboratory incubation experiments were conducted to examine the effects of temperature and nutrient concentrations on the emissions of biogenic sulfur compounds during the green tide decline period. Under simulated conditions, higher incubation temperatures and nutrient concentrations promoted the decay of U. prolifera. When the incubation temperature was increased from 20 °C to 25 °C, the mean concentrations of dimethylsulfide (DMS), dissolved dimethylsulfoniopropionate (DMSPd) and particulate dimethylsulfoniopropionate (DMSPp) in the culture medium decreased by ~20 %, 55 % and 20 % respectively; in addition, these values increased by ~40 %, 70 % and 240 % respectively when exogenous nutrients were added to the culture medium. Moreover, a high concentration of nitrate (NO3–) (>50 μM) could promote the release of biogenic sulfur by U. prolifera in the absence of other nutrients. The findings of this study provide insight into the roles of macroalgae on changes to the environment and shed light on the potential impact of DMSP and other degradation products of DMS produced by the green tide on the environment and ecosystem.

Toxicity, uptake and transport mechanisms of dual-modal polymer dots in penny grass (Hydrocotyle vulgaris L.)

The use of polymers such as plastic has become an important part of daily life, and in aqueous environments, these polymers are considered as pollutants. When macropolymers are reduced to the nanoscale, their small particle size and large specific surface area facilitate their uptake by plants, which has a significant impact on aquatic plants. Therefore, it is essential to study the pollution of nanoscale polymers in the aquatic environment. In this work, we prepared nanoscale polymer dots (Pdots) and explored their toxicity, uptake and transport mechanisms in penny grass. From toxicological studies, in the absence of other nutrients, the cell structure, physiological parameters (total soluble protein and chlorophyll) and biochemical parameters (malondialdehyde) do not show significant changes over at least five days. Through in vivo fluorescence and photoacoustic (PA) imaging, the transport location can be visually detected accurately, and the transport rate can be analyzed without destroying the plants. Moreover, through ex vivo fluorescence imaging, we found that different types of Pdots have various uptake and transport mechanisms in stems and blades. It may be due to the differences in ligands, particle sizes, and oil-water partition coefficients of Pdots. By understanding how Pdots interact with plants, a corresponding method can be developed to prevent them from entering plants, thus avoiding the toxicity from accumulation. Therefore, the results of this study also provide the basis for subsequent prevention work.

Saccharomyces cerevisiae ste20 Mutant Showing Resistance to Glucose-Induced Cell Death

Glucose is one of the most important nutrients for yeast growth, which induces cell death of S. cerevisiae in the absence of other nutrients to support growth. In the present study, we reported that the S. cerevisiae ste20 mutant was resistant to glucose-induced cell death. Cells of ste20 mutant that were treated with glucose maintained intact membrane and nuclei. Ste20 kinase phosphorylates histone H2B at serine 10 (S10) during hydrogen peroxide (H 2O 2)-induced cell death. Therefore, glucose-induced cell death (GICD) may be regulated via a similar pathway of H 2O 2-induced apoptosis.

Have Your DNA and Eat It Too

MICROBIOLOGY Bacteria readily consume extracellular DNA by various mechanisms. The acquisition of foreign DNA contributes to horizontal gene transfer and is of experimental utility. Finkel and Kolter now offer data to show that homo- and heterospecific DNA can fully support the growth of Escherichia coli in the absence of other nutrients. Not all bacteria, including E. coli, are naturally competent for genetic transformation; after all, recombination with heterologous DNA is risky. Tellingly, for several species, competence (mediated by the com family of genes) is induced only by starvation. Despite lacking natural competence, E. coli possesses com gene homologs that, if mutated, destroy its capacity to compete with wild-type bacteria during stationary phase, presumably because the mutants no longer can eat the DNA released into the medium from dying bacteria.— CA J. Bacteriol. 183 , 6288 (2001).

Taxol Production in Nodule Cultures of Taxus

The in vitro synthesis of secondary compounds from plants is one source of scarce and valuable phytopharmaceuticals. Often, some level of cellular or tissue differentiation is needed for the biosynthesis of many of these important compounds. Nodule cultures, consisting of cohesive multicellular units displaying a high degree of differentiation, were initiated from cultured needles of seven Taxus cultivars (Taxus cuspidata, Taxus x media 'Hicksii', Taxus x hunnewelliana 'Richard Horsey', Taxus x media 'Dark Green Spreader', Taxus x media 'L. C. Bobbick', and Taxus brevifolia). Under normal semicontinuous perfusion culture conditions (bimonthly refreshments to yield 0.2% sucrose), only trace amounts of taxol were detected from Taxus nodule cultures. However, with an elevated sucrose level (0.5% or 1.0%), taxol production was enhanced in T. cuspidata nodules to approximately 12 micrograms taxol/g nodule dry weight (dw). Stimulation of taxol production by elevated sucrose levels occurred even in the absence of other nutrients. The effect of increased sucrose on taxol induction does not appear to be due to an osmotic effect in the medium, suggesting that the increase in taxol production may be correlated with a metabolic process within the nodules. Although sucrose had a significant effect on taxol production, taxane precursors or elicitors of terpenes, as well as other plant secondary metabolites, had no effect on the production of taxol from these cultures. In addition to taxol, the higher sucrose levels also induced the production of 7-epi-10-deacetyltaxol, cephalomannine, and 7-epi-10-deacetylcephalomannine, so that total content of these taxanes equaled approximately 39 micrograms taxane/g dw nodules.

Effects of salinity, pH, organic solutes, anaerobic conditions, and the presence of other microbes on production and survival of Lagenidium giganteum (Oomycetes: Lagenidiales) zoospores

The effects of several environmental factors on the production of viable zoospores by Lagenidium giganteum were determined by counts of germlings produced after induction of zoosporogenesis by suspension of mycelium in various substances. NaCl at a concentration of 0.6 g/liter virtually eliminated zoosporogenesis. At 0.2 g/liter NaCl there was a significant reduction in four of the five fungal isolates tested. Transmission of fungus between mosquito larvae at 0.8 g/liter NaCl suggests that estimates of solute effects from in vitro studies are exaggerated. Zoosporogenesis took place from pH 4.5 to 8.4 by three isolates and from 4.5 to 8 by two other isolates (±0.2). Anaerobic conditions halted zoosporogenesis. Reintroduction of oxygen within 7 days allowed the process to resume, but with reduced production for each day under anaerobic conditions. Five species of bacteria inhibited zoosporogenesis at concentrations of 10 7–10 8 cells/ml. The yeast, Saccharomyces cerevisiae, was inhibitory at 10 6 cells/ml. Three sugars, a sugar alcohol, three amino acids, and peptone all reduced zoosporogenesis at levels that generally correlated positively with their nutritional values for the fungus. Peptone, which can support lush vegetative growth of L. giganteum in the absence of other nutrients, was far more effective in inhibiting zoosporogenesis than the other solutes.

Application of split-root technique in orthoposphate absorption experiments

SummaryThe absorption and translocation of phosphate by roots of intact seedlings of rape, oats, flax and buckwheat were studied. Two hydroponic experiments were conducted in the greenhouse. A split-root technique was used in which a single root of the culture plants was grown in one solution and the rest of the roots in another solution in a twocompartmented glass jar.The presence of other nutrients had a favourable effect on root growth and was essential for efficient phosphate absorption. There was a positive relation between the extent of root growth and phosphorus uptake. On the basis of unit weights of a single root, rape was not any better than oats and buckwheat. A single root of rape, in the presence of other nutrients, absorbed two-thirds of the phosphorus absorbed by all the other roots, whereas single roots of buckwheat, oats, and flax were much less efficient than the rest of the roots. In the absence of other nutrients, single roots of buckwheat, rape and oats absorbed 4·61, 0·18 and 3·49%, respectively, of the phosphorus supplied. However, in the presence of other nutrients, the corresponding values were 21·68, 43·86, and 7·62%, respectively. Both in the presence and absence of other nutrients the single root of flax did not absorb phosphorus from solutions high in phosphate. The results indicate that the age of the plant has an important bearing on the uptake and translocation of phosphorus.

Changes in the plasma membrane of Escherichia coli during magnesium starvation.

The effect of Mg(++) starvation on the structure of the Escherichia coli cell membrane was studied with the freeze-etch technique. Special attention was paid to changes within the plane of the membrane, which in normal exponentially growing cells has a netlike arrangement of particles 2 to 6 nm in diameter. During Mg(++) starvation, a paracrystalline particle pattern appeared on the plasma membrane, and large areas devoid of particles were seen. Although these changes are reproducibly associated with Mg(++) starvation of the bacteria, no decrease in the Mg(++) content of the cell envelope per se was detected, even after 24 hr of Mg(++) deprivation. The structural changes caused by Mg(++) deprivation appeared to involve specific and permanent alterations in membrane development. The absence of other nutrients or divalent cations did not induce similar alterations.

Larval feeding behaviour of the cabbage looper, Trichoplusia ni

The effects of dietary components on the feeding behaviour of first instar cabbage looper larvae were studied by means of a two-choice experimental technique. Larval feeding was stimulated by proteins, sugars, wheat germ oil, and inorganic salts. Ascorbic acid and cellulose deterred larval feeding. Of the proteins tested, casein was the best feeding stimulant. The order of effectiveness of sugars as feeding stimulants was: sucrose>fructose >dextrose. The response threshold to sucrose was found to be 5 × 10 −5 M. The phospholipid fraction of wheat germ oil stimulated larval feeding, and of the purified phospholipids tested, only the plant lecithins were found to be feeding stimulants. Wesson inorganic salt mixture stimulated feeding when incorporated in the complex meridic diet, but not when in the absence of other nutrients. The salt mixture was found to synergize the stimulatory effect of wheat germ oil. The synergism was shown to be attributable to the feeding stimulation produced by the combination of potassium ions and the neutral lipid fraction of wheat germ oil. The optimal concentration of potassium was found to be 0·1 M, and the synergistic effect was reduced when the anion was dihydrogen phosphate.