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Starvation
Kinds of Starvation Terms modified by Starvation Selected AbstractsINFLUENCE OF STARVATION, TEMPERATURE, AND pH ON CULTURABILITY OF ESCHERICHIA COLI O157:H7JOURNAL OF FOOD SAFETY, Issue 3 2000LIQIANG ZHAO ABSTRACT In farm and food processing environments Escherichia coli O157:H7 can survive for days to months. In this study, we investigated the influence of starvation, pH (pH 4 or 7), temperature (4, 10 and 22C), and exposure to chlorine (50, 100, 150, 200 ppm) on culturability of E. coli O157:H7. The culturable cell population in PBS decreased to an undetectable level at 4C and 10C, but not at 22C during the experimental period. Cells suspended in PBS adjusted to pH 4 lost culturability more rapidly than at pH 7. Culturable cells were not detectable after exposure to chlorine, however, viable cell populations in the range of 1 , 2 log remained stable for 5 days. During loss of culturability two distinct morphological cell populations emerged; typical rod shaped and coccoid shaped cells. In this study, independent of exposure to chlorine, conditions of low temperature and low pH had the greatest influence on entry of E. coli O157:H7 into a VNC state. [source] PHOTOSYNTHETIC FUNCTION IN DUNALIELLA TERTIOLECTA (CHLOROPHYTA) DURING A NITROGEN STARVATION AND RECOVERY CYCLEJOURNAL OF PHYCOLOGY, Issue 5 2003Erica B. Young Phytoplankton can be exposed to periods of N starvation with episodic N resupply. N starvation in Dunaliella tertiolecta (Butcher) measured over 4 days was characterized by slow reduction in cell chl and protein content and chl/carotenoid ratio and a decline in photosynthetic capacity and maximum quantum yield of photosynthesis (Fv/Fm). In the early stages of N starvation, cell division was maintained despite reduction in cellular chl. Chl content was more sensitive than carotenoids to N deprivation, and cellular chl a was maintained preferentially over chl b under N starvation. NO3, resupply stimulated rapid and complete recovery of Fv/Fm (from 0.4 to 0.7) within 24 h and commencement of cell division after 10 h, although N-replete levels of cell chl and protein were not reestablished within 24 h. Recovery of Fv/Fm was correlated with increases in cell chl and protein and was more related to increases in Fm than to changes in F0. Recovery of Fv/Fm was biphasic with a second phase of recovery commencing 4,6 h after resupply of NO3,. Uptake of NO3, from the external medium and the recovery of Fv/Fm, cell chl, and protein were inhibited when either cytosolic or chloroplastic protein synthesis was inhibited by cycloheximide or lincomycin, respectively; a time lag observed before maximum NO3, uptake was consistent with synthesis of NO3, transporters and assimilation enzymes. When both chloroplastic and cytosolic translation was inhibited, Fv/Fm declined dramatically. Dunaliella tertiolecta demonstrated a capacity to rapidly reestablish photosynthetic function and initiate cell division after N resupply, an important strategy in competing for limiting inorganic N resources. [source] ACCUMULATION OF OLEIC ACID IN HAEMATOCOCCUS PLUVIALIS (CHLOROPHYCEAE) UNDER NITROGEN STARVATION OR HIGH LIGHT IS CORRELATED WITH THAT OF ASTAXANTHIN ESTERS1JOURNAL OF PHYCOLOGY, Issue 2 2002Mirash Zhekisheva The chlorophyte Haematococcus pluvialis accumulates large quantities of astaxanthin under stress conditions. Under either nitrogen starvation or high light, the production of each picogram of astaxanthin was accompanied by that of 5 or 3,4 pg of fatty acids, respectively. In both cases, the newly formed fatty acids, consisting mostly of oleic (up to 34% of fatty acids in comparison with 13% in the control), palmitic, and linoleic acids, were deposited mostly in triacylglycerols. Furthermore, the enhanced accumulation of oleic acid was linearily correlated with that of astaxanthin. Astaxanthin, which is mostly monoesterified, is deposited in globules made of triacylglycerols. We suggest that the production of oleic acid-rich triacylglycerols on the one hand and the esterification of astaxanthin on the other hand enable the oil globules to maintain the high content of astaxanthin esters. [source] Starvation in the midst of plentyEUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 5 2000Rennie No abstract is available for this article. [source] Starvation-induced changes in the cell surface of Azospirillum lipoferumFEMS MICROBIOLOGY ECOLOGY, Issue 1 2000Thelma Castellanos Abstract Three starvation regimes (a deficient culture medium, a saline buffer solution and distilled water) were evaluated for their possible effect on cell surface characteristics of Azospirillum lipoferum 1842 related to the initial adsorption of the bacterium to surfaces. The bacteria survived for 7 days in all media although they did not multiply. Upon transfer from a rich growth medium (nutrient agar) to starvation conditions, cell surface hydrophobicity dropped sharply but recovered its initial value within 24 to 48 h, except in phosphate-buffered saline, the length of the recovery period depending on the starvation medium. Starvation affected the sugar affinity of the A. lipoferum cell surface mainly towards p -aminophenyl-,- D -mannopyranoside, to a lesser extent to glucose, but not to other monosaccharides tested. Starvation changed the concentration of several cell surface proteins but did not induce the synthesis of new ones. The cell surface hydrophobic protein (43 kDa) of A. lipoferum 1842 was unaffected by any starvation treatment for a period of up to 48 h, but later disappeared. These data showed that starvation is not a major factor in inducing changes in the cell surface which lead to the primary phase of attachment of Azospirillum to surfaces. [source] Survival analysis of Little Penguin Eudyptula minor chicks on Motuara Island, New ZealandIBIS, Issue 4 2001MARTIN RENNER Chick survival of Little Penguins Eudyptula minor was studied on predator-free Motuara Island, Cook Strait, New Zealand (41d,05'S, 174d,15'E), in 1995 and 1996. We used the Kaplan-Meier estimator and robust Cox regression to estimate chick survival rate (pL se) at 0.325 pL 0.044, leading to an estimated survival from laying to fledging of 0.13 or a reproductive output of 0.26 chicks per pair and breeding attempt. Starvation posed the greatest mortality risk, followed by unknown factors and rain. Risk of death due to rain was restricted to the guard stage, whereas starvation occurred throughout the nesting period, though with a peak in the early guard stage. Significant seasonal differences in survival rate were detected in both years, but with reversed trends, survival decreasing with the season in 1995 and increasing in 1996. Failure of adults to relieve their partner on the nest after chicks hatched accounted for 16% mortality or 34% of all chick deaths. Differences in chick survival rate between nest types were significant in 1995, a year with high rainfall, but not in 1996. Nests in the base of hollow trees had the highest chick survival rate. Of chicks in open nests - a nest type that is unusual for this species - 5.4% fledged. Our results suggest that on Motuara Island good breeding sites are scarce and that the food supply has been poor during the years of this study. [source] Transcriptional signatures in response to wheat germ agglutinin and starvation in Drosophila melanogaster larval midgutINSECT MOLECULAR BIOLOGY, Issue 1 2009H.-M. Li Abstract One function of plant lectins such as wheat germ agglutinin is to serve as defences against herbivorous insects. The midgut is one critical site affected by dietary lectins. We observed marked cellular, structural and gene expression changes in the midguts of Drosophila melanogaster third instar larvae that were fed wheat germ agglutinin. Some of these changes were similar to those observed in the midguts of starved D. melanogaster. Dietary wheat germ agglutinin caused shortening, branching, swelling, distortion and in some cases disintegration of the midgut microvilli. Starvation was accompanied primarily by shortening of the microvilli. Microarray analyses revealed that dietary wheat germ agglutinin evoked differential expression of 61 transcripts; seven of these were also differentially expressed in starved D. melanogaster. The differentially transcribed gene clusters in wheat germ agglutinin-fed larvae were associated with (1) cytoskeleton organization; (2) digestive enzymes; (3) detoxification reactions; and (4) energy metabolism. Four possible transcription factor binding motifs were associated with the differentially expressed genes. One of these exhibited substantial similarity to MyoD, a transcription factor binding motif associated with cellular structures in mammals. These results are consistent with the hypothesis that wheat germ agglutinin caused a starvation-like effect and structural changes of midgut cells of D. melanogaster third-instar larvae. [source] Correcting the short-term effect of food deprivation in a damselfly: mechanisms and costsJOURNAL OF ANIMAL ECOLOGY, Issue 1 2008Melina Campero Summary 1Mass at emergence is a life-history trait strongly linked to adult fitness. Therefore, when faced with transient food shortage in the larval stage, mass-correcting mechanisms are common. 2These correcting mechanisms may carry costs with them. On one hand, these costs may be overestimated because they can be confounded with the direct effects of the transient food shortage itself. On the other hand, costs may be underestimated by ignoring physiological costs. Another largely neglected topic is that correcting mechanisms and costs may critically depend upon other stressors that often co-occur. 3Here, we identify the mass-correcting mechanisms and their associated costs at emergence in the damselfly Coenagrion puella, after being stressed by a transient period of starvation and a subsequent exposure to pesticide stress during the larval stage. We introduce path analysis to disentangle direct costs of starvation and the mass-correcting mechanisms in terms of immune response. 4As predicted, we found no differences in mass at emergence. Starvation directly resulted in a costly delayed emergence and a decreased immune response at emergence. Mass-correcting mechanisms included a prolonged post-starvation period, reduced mass loss at emergence and compensatory growth, although the latter only in females under pesticide stress. 5The mass-correcting mechanisms were associated with beneficial effects on investment in immune response, but only in the absence of pesticide stress. Under pesticide stress, these beneficial effects were mostly undone or overruled, resulting in negative effects of the mass-correcting mechanisms in terms of immune response. 6Our results stress the importance of and introduce a statistical way of disentangling direct costs of starvation and the mass-correcting mechanisms themselves, and the importance of including physiological endpoints in this kind of studies. [source] Influence of Starvation on Flesh Quality of Farmed Dentex, Dentex dentexJOURNAL OF THE WORLD AQUACULTURE SOCIETY, Issue 4 2010María Dolores Suárez Dentex (mean initial weight 324 ± 5 g) from a fish farm were divided into two groups (control and fasted). At the end of experimental period (5 wk), dentex were sampled for gross muscle composition and quality analysis. For post mortem muscle analysis, after death, fish were kept in a cold chamber at 4 C, and muscle samples were taken at 4 (prerigor state), 24 (rigor state), and 82 (postrigor state) h after slaughtering. In each fish, textural and biochemical parameters were determined. During starvation, there was a drastic reduction in muscle lipid content and a relative increase of the proteolysis. There were little qualitative changes in the fatty-acid profile of muscle lipids, although a significant increase in n3/n6 ratio in the starved dentex was detected. Starved fish also showed higher muscle firmness, but no differences in pH and water holding capacity were observed. Total and myofibrillar protein and collagen content increased significantly in starved dentex. Firmness during post mortem storage was significantly higher in starved fish, compared with control group. Preslaughtering feeding status showed decisive influence on the evolution dentex muscle quality parameters during cold storage. [source] The cell differentiation protein SpoIIE contains a regulatory site that controls its phosphatase activity in response to asymmetric septationMOLECULAR MICROBIOLOGY, Issue 4 2002Andrea Feucht Summary Starvation induces Bacillus subtilis to initiate a simple, two-cell developmental process that begins with an asymmetric cell division. Activation of the first compartment-specific transcription factor, ,F, is coupled to this morphological event. SpoIIE, a bifunctional protein, is essential for the compartment-specific activation of ,F and also has a morphogenic activity required for asymmetric cell division. SpoIIE consists of three domains: a hydrophobic N-terminal domain, which targets the protein to the membrane; a central domain, involved in oligomerization of SpoIIE and interaction with the cell division protein FtsZ; and a C-terminal domain comprising a PP2C protein phosphatase. Here, we report the isolation of mutations at the very beginning of the central domain of spoIIE, which are capable of activating ,F independently of septum formation. Purified mutant proteins showed the same phosphatase activity as the wild-type protein in vitro. The mutant proteins were fully functional in respect of their localization to sites of asymmetric septation and support of asymmetric division. The data provide strong evidence that the phosphatase domain of SpoIIE is tightly regulated in a way that makes it respond to the formation of the asymmetric septum. [source] Akt1-mediated Intracellular Oxidation after UVB Irradiation Suppresses Apoptotic Cell Death Induced by Cell Detachment and Serum StarvationPHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 1 2008Yuko Ibuki Apoptosis is an important cell death system that deletes damaged and mutated cells to prevent cancer. We have previously reported that a certain dose of UVB irradiation inhibited the apoptosis induced by serum starvation and cell detachment, leading to cell transformation. This antiapoptotic effect was partially inhibited by phosphatidylinositol 3-kinase (PI3-kinase) inhibitors. UVB irradiation is known to cause the phosphorylation of Akt via the activation of PI3-kinase; however, the Akt isoform-specific relationship has not yet been clarified. Notably, the role in antiapoptotic effect of UVB has yet to be elucidated. In this study, the role of Akt1 in the UVB-induced inhibition of apoptosis was examined by Akt1 knockdown using small interfering RNA (siRNA). NIH3T3 cells showed typical apoptotic cell death by serum starvation and cell detachment, which was significantly inhibited by UVB irradiation. Akt1 knockdown decreased the antiapoptotic effect of UVB. Hydrogen peroxide-induced suppression of cell death was also decreased in Akt1 knockdown cells. An antioxidant, N -acetylcysteine, inhibited the antiapoptotic effect by UVB irradiation, whereas no inhibition was observed in Akt1 knockdown cells. Furthermore, UVB-induced intracellular peroxidation was not observed in the knockdown cells, indicating that Akt1 played an important role in mediating the intracellular redox status. Treatment with insulin had a similar antiapoptotic effect as UVB irradiation involving intracellular peroxidation, which was also attenuated in Akt1 knockdown cells. These findings suggest that appropriate intracellular oxidation after UVB irradiation prevented apoptosis, a process which might be partially regulated by the production of reactive oxygen species mediated by Akt1. [source] Quantification of cockroach allatostatin-like peptide and its myotropic effects in males of the earwig Euborellia annulipesPHYSIOLOGICAL ENTOMOLOGY, Issue 1 2001Roy Phitayakorn Summary A monoclonal antibody to allatostatin I of the cockroach Diploptera punctata was used to establish a competitive enzyme-linked immunosorbent assay for quantification of allatostatin-like peptides in the hindgut of the adult male earwig, Euborellia annulipes. Hindguts of 0-day males contained significantly more allatostatin-positive material than those of 8-day males fed on catfood. However, males starved for the first 8 days of adult life had significantly higher levels of allatostatin-positive material than those of either 0-day or of 8-day fed males. Hindguts from 0-day old males exhibited lower spontaneous motility in vitro than those from 8-day males. Hindguts from males at both ages responded to allostatin with reversible, dosage-dependent decreases in hindgut motility, and responded to proctolin with reversible, dosage-dependent increases in hindgut motility. When both allatostatin and proctolin were applied to hindgut preparations simultaneously and in equal concentrations, the response varied with the stage of the male. Starvation enhanced hindgut motility and abolished the response to allatostatin, but not to proctolin. These results indicate the presence of material similar to cockroach allatostatins in male earwigs, and that the levels change with age and physiological stage. Furthermore, such peptides may indeed be regulatory neuropeptides and could modulate hindgut contraction. There was an increase in sensitivity to exogenous allatostatin in the hindgut during development from day 0 to day 8 in feeding males, but a loss in sensitivity in response to starvation; sensitivity to exogenous proctolin also increased with age, but such responsiveness was not diminished by starvation. [source] The effect of ram-pressure stripping and starvation on the star formation properties of cluster galaxiesASTRONOMISCHE NACHRICHTEN, Issue 9-10 2009A. Boselli Abstract We have combined UV to radio centimetric observations of resolved galaxies in the Virgo cluster with multizone, chemospectrophotometric models of galaxy evolution especially tailored to take into account the effects of the cluster environment (ram pressure stripping and starvation). This exercise has shown that anemic spirals with truncated radial profiles of the gas component and of the young stellar populations, typical in rich clusters of galaxies, have been perturbed by a recent (,100 Myr) ram pressure stripping event induced by their interaction with the cluster intergalactic medium. Starvation is not able to reproduce the observed truncated radial profiles. Both ram pressure and starvation induce a decrease of the stellar surface brightness of the perturbed disc, and thus can hardly be invoked to explain the formation of lenticular galaxies inhabiting rich clusters, which are characterised by higher surface brightnesses than early type spirals of similar luminosity. In dwarfs the ram pressure stripping event is so efficient to totally remove their gas thus stopping on short time scales (<2 Gyr) their star formation activity. Low luminosity star forming discs can be transformed in dE galaxies (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Schemes for avoiding starvation in transactional memory systemsCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 7 2009M. M. Waliullah Abstract Transactional memory systems trade ease of programming with run-time performance losses in handling transactions. This paper focuses on starvation effects that show up in systems where unordered transactions are committed on a demand-driven basis. Such simple commit arbitration policies are prone to starvation. The design issues for commit arbitration policies are analyzed and novel policies that reduce the amount of wasted computation due to roll-back and, most important, that avoid starvation are proposed. We analyze in detail how to incorporate them in the transactional coherence and consistency protocol as well as a scalable version of it. The proposed schemes are shown to have no impact on the common-case performance and add quite modest complexity to the baseline protocol. Copyright © 2008 John Wiley & Sons, Ltd. [source] Differentiation inducing factors in Dictyostelium discoideum: A novel low molecular factor functions at an early stage(s) of differentiationDEVELOPMENT GROWTH & DIFFERENTIATION, Issue 9 2009Akiko A. Oohata There are reports that secreted factor(s) are involved in prespore cell differentiation in Dictyostelium discoideum, but the structures and functions of the various factors have not been elucidated. Previously, we described two prespore cell-inducing factors in conditioned medium; one was a glycoprotein named prespore cell-inducing factor (, factor, or PSI-1), and the other, a heat stable dialyzable factor(s). In the present paper, we purified and characterized the most potent prespore cell-inducing activity in dialysates. The factor began to be secreted after the onset of starvation and stopped being secreted once the cells had aggregated, which was earlier than the onset of the , factor gene expression. In addition, unlike , factor, its secretion did not appear to depend on activation of protein kinase A. Interestingly, the purified factor not only induced prespore cell specific genes such as pspA and cotC but also a prestalk-cell specific gene, ecmB in vitro. The purified factor is tentatively designated polyketide-like factor (PLF), because it seems to be a novel polyketide with 208 Da. Half maximal induction of prespore cell was obtained with 26 nmol/L of PLF. We propose that PLF plays a key role in the acquisition of differentiation commitment, before the , factor induces specifically prespore cell differentiation. [source] Novel functions of ribosomal protein S6 in growth and differentiation of Dictyostelium cellsDEVELOPMENT GROWTH & DIFFERENTIATION, Issue 6 2009Kazutaka Ishii We have previously shown that in Dictyostelium cells a 32 kDa protein is rapidly and completely dephosphorylated in response to starvation that is essential for the initiation of differentiation (Akiyama & Maeda 1992). In the present work, this phosphoprotein was identified as a homologue (Dd-RPS6) of ribosomal protein S6 (RPS6) that is an essential member for protein synthesis. As expected, Dd-RPS6 seems to be absolutely required for cell survival, because we failed to obtain antisense-RNA mediated cells as well as Dd-rps6 -null cells by homologous recombination in spite of many trials. In many kinds of cell lines, RPS6 is known to be located in the nucleus and cytosol, but Dd-RPS6 is predominantly located in the cell cortex with cytoskeletons, and in the contractile ring of just-dividing cells. In this connection, the overexpression of Dd-RPS6 greatly impairs cytokinesis during axenic shake-cultures in growth medium, resulting in the formation of multinucleate cells. Much severe impairment of cytokinesis was observed when Dd-RPS6-overexpressing cells (Dd-RPS6OE cells) were incubated on a living Escherichia coli lawn. The initiation of differentiation triggered by starvation was also delayed in Dd-RPS6OE cells. In addition, Dd-RPS6OE cells exhibit defective differentiation into prespore cells and spores during late development. Thus, it is likely that the proper expression of Dd-RPS6 may be of importance for the normal progression of late differentiation as well as for the initiation of differentiation. [source] Inter-sexual differences in the immune response of Eurasian kestrel nestlings under food shortageECOLOGY LETTERS, Issue 1 2002Juan A. Fargallo When resources are limited, parents should decide the optimal number, size, and sex of progeny, and offspring should decide the optimal allocation of resources to different costly functions, such as growth and immunity. We manipulated clutch sizes of Eurasian kestrels by one egg to estimate possible cumulative effects of incubation and chick rearing costs on parental body condition, feeding effort, and offspring viability. No obvious effects of clutch size manipulations on feeding effort were found while feeding effort was adjusted to the original clutch size. Enlarged and control nests suffered from higher nestling mortality than reduced nests, and chicks of the enlarged group were in poorer body condition than chicks of the reduced group. Controlling for body mass, male chicks exhibited lower cell-mediated immunity assessed by a cutaneous hypersensitivity response than females, but only in treatments suffering from food restrictions, as indicated by chick starvation. These novel results reveal inter-sexual differences in physiological strategies in early life, suggesting sex-related differences in susceptibility to disease and consequently in survival prospects of offspring. [source] Survival and oviposition of a western corn rootworm variant feeding on soybeanENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 2 2003Timothy R. Mabry Abstract The role of soybean, Glycine max (L.) Merril (Fabaceae), in the circumvention of crop rotation was evaluated by observing the effects of soybean herbivory on western corn rootworm, Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae) survival and oviposition. Field collected D. virgifera adults resistant to annual rotation of corn, Zea mays (L.) (Poaceae), and soybean were given the opportunity to feed on a soybean pre-treatment diet prior to diet combinations of corn, soybean, and/or water. The number of days that the adults survived after removal of the diet combinations was used as a measure of insect vigor and diet quality. Willingness to feed on a soybean foliage pre-treatment did not indicate greater ability to benefit nutritionally from soybean herbivory. Adult D. virgifera previously feeding on corn, soybean, or water survived starvation for 8.3 ± 0.15 days, 5.1 ± 0.13 days, and 3.9 ± 0.14 days, respectively. Diabrotica virgifera recover from 2 days of starvation or poor diet if subsequently given access to corn tissues for 2 days. Eggs were laid within 1 day of access to poor diet or starvation. Other D. virgifera, captured as they flew from a cornfield into a soybean field, were maintained on soybean foliage or only water until they died. Of the beetles with access to soybean foliage, 24% fed within 24 h after capture and survived 1 day longer than insects given only water. Only 20% of these D. virgifera were able to lay eggs without consuming additional corn prior to death. Few D. virgifera enter soybean fields capable of immediate oviposition. Female reproductive status and diet quality influence the likelihood of oviposition following exposure to stress. The effects of soybean herbivory may contribute to the proximate mechanism of resistance to crop rotation. [source] Effects of hunger level and nutrient balance on survival and acetylcholinesterase activity of dimethoate exposed wolf spidersENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 3 2002Lars-Flemming Pedersen Abstract The influence of two nutritional factors (food quantity and quality) on the responses of a wolf spider, Pardosa prativaga (L.K.), to a high dose of the insecticide dimethoate, was investigated in a fully factorial experimental design. Spider groups with different (good and bad) nutrient balance were created by feeding them fruit flies of either high or low nutrient content for 28 days. Both groups were then split into satiated and 14 days starved subgroups. Each of these was further divided into insecticide treated and control halves. Survivorship and acetylcholinesterase (AChE) activity measured on the survivors were used as response variables. Survivorship after topical dimethoate exposure (LD50; 48 h) was influenced by spider body weight, nutrient balance, and starvation. Furthermore, AChE activity was significantly inhibited by dimethoate exposure. A significant interaction between nutrient balance, starvation, and dimethoate exposure revealed synergistic effects of starvation and nutrient imbalance on AChE inhibition by dimethoate in surviving spiders. These results show that the tolerance of non-target arthropods to dimethoate may vary depending on the nutritional history of the animal. [source] Prior encounters modulate subsequent choices in host acceptance behavior by the bark beetle Ips piniENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 3 2002Kimberly F. Wallin Abstract Laboratory bioassays indicate that the bark beetle Ips pini employs flexible, rather than absolute, responses to phytochemicals in its host acceptance behavior. Each beetle's decision to enter substrate was influenced by the types and concentrations of monoterpenes present. However, previous rejection of a simulated host containing a moderate concentration of monoterpenes increased the likelihood that the same concentration would be accepted upon a second or third encounter. This flexibility more than offsets any loss of vigor due to starvation and age that accompanies a process of trial and error. Starvation decreased beetles' total lipid content, but beetles can recover some energetic losses by a small amount of feeding during each trial. In addition to its adaptive value, a flexible host acceptance strategy may yield population level consequences. That is, bark beetles preferentially enter trees having low concentrations of monoterpenes, but may modify their acceptance thresholds when cues associated with stressed trees are not available. This could partially explain how some tree-killing bark beetles colonize a broader physiological range of trees during outbreaks. The adaptive value of relating individual decisions to population density may arise from two ecological relationships: first, as populations rise, the pool of stressed trees is rapidly depleted; secondly, healthy trees are attainable through pheromone , mediated mass attacks when adequate numbers of beetles are present. Flexible host acceptance behaviors may also reduce the advantage of relying exclusively on pre-landing cues to distinguish between susceptible and non-susceptible trees. [source] Transcriptional control of the pvdS iron starvation sigma factor gene by the master regulator of sulfur metabolism CysB in Pseudomonas aeruginosaENVIRONMENTAL MICROBIOLOGY, Issue 6 2010Francesco Imperi Summary In the Gram-negative pathogen Pseudomonas aeruginosa, the alternative sigma factor PvdS acts as a key regulator of the response to iron starvation. PvdS also controls P. aeruginosa virulence, as it drives the expression of a large set of genes primarily implicated in biogenesis and transport of the pyoverdine siderophore and synthesis of extracellular factors, such as protease PrpL and exotoxin A. Besides the ferric uptake regulatory protein Fur, which shuts off pvdS transcription under iron-replete conditions, no additional regulatory factor(s) controlling the pvdS promoter activity have been characterized so far. Here, we used the promoter region of pvdS as bait to tentatively capture, by DNA-protein affinity purification, P. aeruginosa proteins that are able to bind specifically to the pvdS promoter. This led to the identification and functional characterization of the LysR-like transcription factor CysB as a novel regulator of pvdS transcription. The CysB protein directly binds to the pvdS promoter in vitro and acts as a positive regulator of PvdS expression in vivo. The absence of a functional CysB protein results in about 50% reduction of expression of PvdS-dependent virulence phenotypes. Given the role of CysB as master regulator of sulfur metabolism, our findings establish a novel molecular link between the iron and sulfur regulons in P. aeruginosa. [source] Molecular analysis of the phosphorus starvation response in Trichodesmium spp.ENVIRONMENTAL MICROBIOLOGY, Issue 9 2009Elizabeth D. Orchard Summary The marine diazotroph Trichodesmium is a major contributor to primary production and nitrogen fixation in the tropical and subtropical oceans. These regions are often characterized by low phosphorus (P) concentrations, and P starvation of Trichodesmium could limit growth, and potentially constrain nitrogen fixation. To better understand how this genus responds to P starvation we examined four genes involved in P acquisition: two copies of a high-affinity phosphate binding protein (pstS and sphX) and two putative alkaline phosphatases (phoA and phoX). Sequence analysis of these genes among cultured species of Trichodesmium (T. tenue, T. erythraeum, T. thiebautii and T. spiralis) showed that they all are present and conserved within the genus. In T. erythraeum IMS101, the expression of sphX, phoA and phoX were sensitive to P supply whereas pstS was not. The induction of alkaline phosphatase activity corresponded with phoA and phoX expression, but enzyme activity persisted after the expression of these genes returned to basal levels. Additionally, nifH (nitrogenase reductase; involved in nitrogen fixation) expression was downregulated under P starvation conditions. These data highlight molecular level responses to low P and lay a foundation for better understanding the dynamics of Trichodesmium P physiology in low-P environments. [source] Iron availability affects mcyD expression and microcystin-LR synthesis in Microcystis aeruginosa PCC7806ENVIRONMENTAL MICROBIOLOGY, Issue 10 2008Emma Sevilla Summary Microcystins are toxins produced by cyanobacteria that entail serious health and environmental problems. They are cyclic heptapeptides synthesized via a mixed polyketide synthase/non-ribosomal peptide synthetase system called microcystin synthetase. Environmental and nutritional factors that trigger microcystin synthesis are still debated and this work deals with the study of the influence of iron nutritional status on the microcystin synthesis. The results indicate that iron deficiency could be one of the inducing factors of the microcystin synthesis. For the first time, increased transcription of an essential mcy gene and correlative microcystin synthesis has been established. Real-time PCR analysis of mcyD, and microcystin-LR synthesis were studied on Microcystis aeruginosa PCC7806 grown in iron-replete and iron-deplete media. Iron starvation causes an increase of mcyD transcription, correlative to the increase of microcystin-LR levels. Four transcription start points were identified for mcyD and two for mcyA, and they are not changed as a consequence of iron deficiency. [source] Stationary phase mutagenesis: mechanisms that accelerate adaptation of microbial populations under environmental stressENVIRONMENTAL MICROBIOLOGY, Issue 10 2003Maia Kivisaar Summary Microorganisms are exposed to constantly changing environmental conditions. In a growth-restricting environment (e.g. during starvation), mutants arise that are able to take over the population by a process known as stationary phase mutation. Genetic adaptation of a microbial population under environmental stress involves mechanisms that lead to an elevated mutation rate. Under stressful conditions, DNA synthesis may become more erroneous because of the induction of error-prone DNA polymerases, resulting in a situation in which DNA repair systems are unable to cope with increasing amounts of DNA lesions. Transposition may also increase genetic variation. One may ask whether the rate of mutation under stressful conditions is elevated as a result of malfunctioning of systems responsible for accuracy or are there specific mechanisms that regulate the rate of mutations under stress. Evidence for the presence of mutagenic pathways that have probably been evolved to control the mutation rate in a cell will be discussed. [source] Caloric Restriction Inhibits Seizure Susceptibility in Epileptic EL Mice by Reducing Blood GlucoseEPILEPSIA, Issue 11 2001Amanda E. Greene Summary: ,Purpose: Caloric restriction (CR) involves underfeeding and has long been recognized as a dietary therapy that improves health and increases longevity. In contrast to severe fasting or starvation, CR reduces total food intake without causing nutritional deficiencies. Although fasting has been recognized as an effective antiseizure therapy since the time of the ancient Greeks, the mechanism by which fasting inhibits seizures remains obscure. The influence of CR on seizure susceptibility was investigated at both juvenile (30 days) and adult (70 days) ages in the EL mouse, a genetic model of multifactorial idiopathic epilepsy. Methods: The juvenile EL mice were separated into two groups and fed standard lab chow either ad libitum (control, n = 18) or with a 15% CR diet (treated, n = 17). The adult EL mice were separated into three groups; control (n = 15), 15% CR (n = 6), and 30% CR (n = 3). Body weights, seizure susceptibility, and the levels of blood glucose and ketones (,-hydroxybutyrate) were measured over a 10-week treatment period. Simple linear regression and multiple logistic regression were used to analyze the relations among seizures, glucose, and ketones. Results: CR delayed the onset and reduced the incidence of seizures at both juvenile and adult ages and was devoid of adverse side effects. Furthermore, mild CR (15%) had a greater antiepileptogenic effect than the well-established high-fat ketogenic diet in the juvenile mice. The CR-induced changes in blood glucose levels were predictive of both blood ketone levels and seizure susceptibility. Conclusions: We propose that CR may reduce seizure susceptibility in EL mice by reducing brain glycolytic energy. Our preclinical findings suggest that CR may be an effective antiseizure dietary therapy for human seizure disorders. [source] Mimicking Natural Nursing Conditions Promotes Early Pup Survival in Domestic RabbitsETHOLOGY, Issue 3 2000Gérard Coureaud In the wild rabbit, Oryctolagus cuniculus, mother,young relationships are based on restricted, once-per-day nursing interactions. Correspondingly, pups have evolved an efficient strategy of energy saving. Here we investigate under breeding conditions, whether matching or not, the once-daily nursing visit by the rabbit females has an effect on pup survival and growth. Two nursing regimen were applied to 89 primiparous (P) and to 78 multiparous (M) does: (a) one that matched the once daily nursing pattern (closed nest-box during the whole day except for a few minutes devoted to nursing) and (b) one that did not match it (24 h free nest access). In P females, the controlled nest access resulted in lower mortality between birth and weaning (8.1%) as compared to the free nest-access (18%). This effect was recorded from postnatal d 3,4 onwards. Both treatments induced different death causes (starvation (63%) in controlled-access regimen, and wounds and nest-soiling (29%) in free-access regimen). While both experimental nest-access regimens differentially affected pup survival in P or M females, they were without influence on pup growth rate in does of either parity. It is concluded that repeated nest visits by the female increase risks of injury to pups, and of out-of-time pup activation or sucking, and that, more generally, it plays against the ethophysiologigal strategy of biomass conservation evolved by rabbit newborns. The fact that the nest-access regimen no longer affected pup survival from the second parity suggests that the behaviour of multiparous does more adequately models the offspring demands. [source] Eating disorders in Italy: a historical reviewEUROPEAN EATING DISORDERS REVIEW, Issue 5 2001Giovanni Maria Ruggiero This paper reviews the history of medical knowledge of eating disorders in Italy. It starts with the first examples of the medical interpretation of starvation during the Middle and Renaissance Ages, continues with the seminal figure of Brugnoli in the late XIX century, describes the neurological interpretations of the 1930s, the return to psychiatry in the 1940s and 1950s, the rise to international prominence of Mara Selvini Palazzoli in the 1960s and 1970s and ends with a description of the present state of the art. Copyright © 2001 John Wiley & Sons, Ltd and Eating Disorders Association. [source] Strength Effects in Micropillars of a Dispersion Strengthened Superalloy,ADVANCED ENGINEERING MATERIALS, Issue 5 2010Baptiste Girault The present paper investigates the uniaxial compression behavior of highly alloyed, focused ion beam (FIB) manufactured micropillars, ranging from 200 up to 4000,nm in diameter. The material used was the Ni-based oxide-dispersion strengthened (ODS) alloy Inconel MA6000. Stress,strain curves show a change in slip behavior comparable to those observed in pure fcc metals. Contrary to pure Ni pillar experiments, high critical resolved shear stress (CRSS) values were found independent of pillar diameter. This suggests that the deformation behavior is primarily controlled by the internal obstacle spacing, overwhelming any pillar-size-dependent mechanisms such as dislocation source action or starvation. [source] Expression of Pit2 sodium-phosphate cotransporter during murine odontogenesis is developmentally regulatedEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 6 2006Dawei Zhao Different sodium-dependent inorganic phosphate (Pi) uptake mechanisms play a major role in cellular Pi homeostasis. The function and detailed distribution patterns of the type III Na+ -phosphate cotransporter, PiT-2, in different organs during development are still largely unknown. We therefore examined the temporospatial expression patterns of Pit2 during murine odontogenesis. Odontoblasts were always devoid of Pit2 expression, whereas a transient, but strong, expression was detected in young secretory ameloblasts. However, the stratum intermedium and, later on, the papillary layer and cells of the subodontoblastic layer, exhibited high levels of Pit2 mRNA, which increased gradually as the tooth matured. Hormonal treatment or Pi starvation of tooth germs in vitro did not alter Pit2 levels or patterns of expression, indicating mechanisms of regulation different from those of PiT-1 or other cell types. PiT-2 also functions as a retroviral receptor, and functional membrane-localized protein was confirmed throughout the dental papilla/pulp by demonstrating cellular permissiveness to infection by a gammaretrovirus that uses PiT-2 as a receptor. The distinct pattern of Pit2 expression during odontogenesis suggests that its Pi -transporter function may be important for homeostasis of dental cells and not specifically for mineralization of the dental extracellular matrices. The expression of viral receptors in enamel-forming cells and the dental pulp may be of pathological significance. [source] Ontogenetic selection on hatchery salmon in the wild: natural selection on artificial phenotypesEVOLUTIONARY APPLICATIONS (ELECTRONIC), Issue 4 2010Michael M. Bailey Abstract Captive rearing often alters the phenotypes of organisms that are destined for release into the wild. Natural selection on these unnatural phenotypes could have important consequences for the utility of captive rearing as a restoration approach. We show that normal hatchery practices significantly advance the development of endangered Atlantic salmon (Salmo salar) fry by 30+ days. As a result, hatchery fry might be expected to face strong natural selection resulting from their developmental asynchrony. We investigated patterns of ontogenetic selection acting on hatchery produced salmon fry by experimentally manipulating fry development stage at stocking. Contrary to simple predictions, we found evidence for strong stabilizing selection on the ontogeny of unfed hatchery fry, with weaker evidence for positive directional selection on the ontogeny of fed fry. These selection patterns suggest a seasonally independent tradeoff between abiotic or biotic selection favoring advanced development and physiological selection linked to risk of starvation in unfed fry. We show, through a heuristic exercise, how such selection on ontogeny may exacerbate problems in restoration efforts by impairing fry productivity and reducing effective population sizes by 13,81%. [source] | ||||||||||||||||||||||||||||||||||||||||