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Food Uptake (food + uptake)
Selected AbstractsFood uptake in the mixotrophic Dinophysis acuminataTHE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 2 2005LUCIE MARANDA Evidence of food uptake in the photosynthetic genus Dinophysis comes solely from the presence of food vacuoles, as no photosynthetic cells have ever been observed in the act of feeding. We examined the feeding ecology of D. acuminata in natural populations and under laboratory conditions. Using depth-integrated sampling of the water column, we determined the frequency of food vacuolated cells at 2-h intervals over a 24-h period in a shallow marine embayment. Food vacuoles in preserved cells were enumerated using Nomarski differential interference contrast microscopy; ultrastructural characters were recorded by transmission electron microscopy. A peak in the feeding activity was observed toward dusk for an abundant June population, with 26% of cells with at least one food vacuole. Mechanisms of concurrent carbon acquisition were evident from the presence of chloroplasts with starch grains and food vacuoles within the same cell. Vacuole content could not be identified. In a preliminary 2-wk long simulated grazing experiment, a mixture of two hypothesized preys, Rhodomonas salina and Dunaliella tertiolecta, was offered to D. acuminata; the Dinophysis populations decreased steadily and at the same rate, whether food was present or not. The evaluation of the food vacuole frequency will be repeated in the coming season to verify the observed pattern, while grazing experiments will include a variety of food items and incubation conditions. Our current inability to successfully culture any photosynthetic Dinophysis limits ecophysiological approaches, either at the population or cellular level, to manipulation of field samples. Supported by National Institutes of Health Grant GM62126-01A1. [source] Drosophila neuropeptide F mediates integration of chemosensory stimulation and conditioning of the nervous system by foodDEVELOPMENTAL NEUROBIOLOGY, Issue 1 2001Ping Shen Abstract The conserved neuropeptide Y (NPY) signaling pathway has been strongly implicated in the stimulation of food uptake in vertebrates as well as in the regulation of food conditioned foraging behaviors of Caenorhabditis elegans. Using in situ RNA hybridization and immunocytochemistry, we report the neuronal network of Drosophila neuropeptide F (dNPF), a human NPY homologue, in the larval central nervous system and its food-dependent modifications. We provide indications that gustatory stimulation by sugar, but not its ingestion or metabolism, is sufficient to trigger long-term, dose-dependent alterations of the dNPF neuronal circuit through both dnpf activation and increased synaptic transmission. Our results strongly suggest that the dNPF neuronal circuit is an integral part of the sensory system that mediates food signaling, providing the neural basis for understanding how invertebrate NPY regulates food response. © 2001 John Wiley & Sons, Inc. J Neurobiol 47: 16,25, 2001 [source] The effects of continuous and pulsed exposures of suspended clay on the survival, growth, and reproduction of Daphnia magnaENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2010Sarah E. Robinson Abstract Suspended sediments are a natural component of aquatic ecosystems, but anthropogenic activity such as land development can result in significant increases, especially after rain events. Continuous exposures of suspended clay and silt have been shown to affect growth and reproduction of Cladocera, leading to a decrease in population growth rate. The mechanism of clay toxicity in these filter-feeding organisms is clogging of the gut tract, resulting in decreased food uptake and assimilation. When placed in clean water, daphnids can purge clay from their gut and recover. In many surface waters, aquatic organisms experience episodic exposures of high concentrations of suspended solids driven by rain events. However, little is known about the consequences of pulsed exposures on individuals and populations. The objective of the present study was to characterize the effects of continuous and pulsed exposures of natural and defined clays on survival, growth, and reproduction of Daphnia magna. Two defined clays, montmorillonite and kaolinite, as well as clay isolated from the Piedmont region of South Carolina, USA, were used. Continuous exposures of clays elicited a dose dependent decrease in survival. Toxicity varied depending on clay source with montmorillonite,>,natural clay,>,kaolinite. Pulsed exposures caused a decrease in survival in a 24 h exposure of 734 mg/L kaolinite. Exposure to 73.9 mg/L also caused an increase in the time to gravidity, although there was not a corresponding decrease in neonate production over 21 d. No significant effects resulted from 12 h exposures even at 730 mg/L, almost 10 times the 24-h reproductive effects concentration. This suggests that exposure duration impacted toxicity more than exposure concentration in these pulsed exposures. Environ. Toxicol. Chem. 2010;29:168,175. © 2009 SETAC [source] Identification of breast cancer biomarkers in transgenic mouse models: A proteomics approachPROTEOMICS - CLINICAL APPLICATIONS, Issue 6-7 2010Wendy Rodenburg Abstract Purpose: Transgenic mouse models for cancer circumvent many challenges that hamper human studies aimed at biomarker discovery. Lower biological variances among mice combined with controllable factors such as food uptake and health status may enable the detection of more subtle protein expression differences. This is envisioned to result in the identification of biomarkers better discriminating cancer cases from controls. Experimental design: The current study used two innovative mouse models for breast-cancer to identify new serum biomarkers. Multi-analyte profiling technique was used to analyze 70 proteins in individual serum samples of non-tumor and mammary tumor-bearing Tg.NK (MMTV/c-neu) mice. Results: A small set of proteins fully differentiated tumor samples from controls. These comprised osteopontin, interleukin-18, cystatin C and CD40 antigen. Comparison of protein expression in another breast-cancer mouse model, the humanized p53.R270H mice, showed common discriminatory expression of osteopontin. However, other biomarkers showed distinct expression in the two different breast-cancer models, indicating that different mammary tumor sub-types with respect to molecular and estrogen receptor status reveal divergent serum biomarker sets. Conclusions and clinical relevance: The current study supports the concept that serum proteins can discriminate mammary tumor cases from controls, and yielded interesting biomarkers that need further testing and validation in human studies. [source] Food uptake in the mixotrophic Dinophysis acuminataTHE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 2 2005LUCIE MARANDA Evidence of food uptake in the photosynthetic genus Dinophysis comes solely from the presence of food vacuoles, as no photosynthetic cells have ever been observed in the act of feeding. We examined the feeding ecology of D. acuminata in natural populations and under laboratory conditions. Using depth-integrated sampling of the water column, we determined the frequency of food vacuolated cells at 2-h intervals over a 24-h period in a shallow marine embayment. Food vacuoles in preserved cells were enumerated using Nomarski differential interference contrast microscopy; ultrastructural characters were recorded by transmission electron microscopy. A peak in the feeding activity was observed toward dusk for an abundant June population, with 26% of cells with at least one food vacuole. Mechanisms of concurrent carbon acquisition were evident from the presence of chloroplasts with starch grains and food vacuoles within the same cell. Vacuole content could not be identified. In a preliminary 2-wk long simulated grazing experiment, a mixture of two hypothesized preys, Rhodomonas salina and Dunaliella tertiolecta, was offered to D. acuminata; the Dinophysis populations decreased steadily and at the same rate, whether food was present or not. The evaluation of the food vacuole frequency will be repeated in the coming season to verify the observed pattern, while grazing experiments will include a variety of food items and incubation conditions. Our current inability to successfully culture any photosynthetic Dinophysis limits ecophysiological approaches, either at the population or cellular level, to manipulation of field samples. Supported by National Institutes of Health Grant GM62126-01A1. [source] Lipid and Fatty Acid Composition of Diatoms Revisited: Rapid Wound-Activated Change of Food Quality Parameters Influences Herbivorous Copepod Reproductive SuccessCHEMBIOCHEM, Issue 10 2007Thomas Wichard Dr. Abstract Lipid and fatty acid composition are considered to be key parameters that determine the nutritive quality of phytoplankton diets for zooplanktonic herbivores. The fitness, reproduction and physiology of the grazers are influenced by these factors. The trophic transfer of lipids and fatty acids from algal cells has been typically studied by using simple extraction and quantification approaches, which, as we argue here, do not reflect the actual situation in the plankton. We show that cell disruption, as it occurs during a predator's grazing on diatoms can drastically change the lipid and fatty acid content of the food. In some algae, a rapid depletion of polyunsaturated fatty acids (PUFAs) is observed within the first minutes after cell disruption. This fatty acid depletion is directly linked to the production of PUFA-derived polyunsaturated aldehydes (PUA); these are molecules that are thought to be involved in the chemical defence of the algae. PUA-releasing diatoms are even capable of transforming lipids from other sources if these are available in the vicinity of the wounded cells. Fluorescent staining reveals that the enzymes involved in lipid transformation are active in the foregut of copepods, and therefore link the depletion processes directly to food uptake. Incubation experiments with the calanoid copepod Temora longicornis showed that PUFA depletion in PUA-producing diatoms is correlated to reduced hatching success, and can be compensated for by externally added single fatty acids. [source] | ||||||||||