饥饿胁迫对小鼠学习记忆、SOD和心肌丙二醛的影响

给小鼠断绝食物,观察小鼠学习记忆能力的变化及生理应激反应。结果表明,饥饿后小鼠的体重明显减轻,学习能力明显增强,记忆能力和大脑5－羟色胺含量无明显改变,心肌丙二醛含量下降,肝组织超氧化物歧化酶（SOD）活性无明显改变,血浆SOD活性提高,血浆SOD同工酶变带无明显改变。提示饥饿胁迫使小鼠产生适应性的生理反应,使小鼠学习能力提高,加强延缓机体衰退的生理功能;这些应激反应有利于小鼠在逆境下的生存。     

饥饿与重摄食对河蟹肠道菌群结构的影响

研究采用16S rRNA测序研究饥饿以及重摄食的河蟹(Eriocheir sinensis)肠道菌群结构变化, 结果显示, 在饥饿胁迫下, 河蟹肠道细菌群落Alpha多样性指数下降, 重摄食后仍未改变肠道菌群多样性指数下降的趋势, 但与对照组无显著差异(P>0.05); 而在菌门组成方面, 随着饥饿时间的增加, 4个优势菌门占比呈现了相应的变化, 变形菌门、厚壁菌门以及拟杆菌门占比逐渐增加, 软壁菌门占比逐渐下降, 但在重摄食后, 4个优势菌门恢复至对照组水平; 而通过对比不同状态下差异菌群, 在科属水平下筛选出8个具有显著差异(P< 0.05)的菌群, 其中Candidatus Bacilloplasma菌属因具有较高的菌群丰度, 且对饥饿以及重摄食响应较为显著, 其菌群的特定功能值得进一步深究。研究首次报道了饥饿状态以及重摄食后河蟹肠道菌群的变化, 对于后续探究菌群的特定功能提供基础数据。     

Environmental stress responses in Lactobacillus: a review

Environmental stress responses in Lactobacillus, which have been investigated mainly by proteomics approaches, are reviewed. The physiological and molecular mechanisms of responses to heat, cold, acid, osmotic, oxygen, high pressure and starvation stresses are described. Specific examples of the repercussions of these effects in food processing are given. Molecular mechanisms of stress responses in lactobacilli and other bacteria are compared.     

How Vibrio cholerae survive during starvation

Vibrio cholerae, a Gram-negative, motile, aquatic bacterium, is the causal agent of the diarrheal disease cholera. Cholera is a serious epidemic disease that has killed millions of people and continues to be a major health problem world-wide. The hypothesis that V. cholerae occupies an ecological niche in the estuarine environment requires that this organism is able to survive the dynamics of physiochemical stresses, including nutrient starvation. As a result of these stresses, bacteria in nature often exist in non-growth or very slow growth states with a low metabolic activity. Because microorganisms have little ability to control their environment, environmental changes have led to changes in cell function and structure. Such cellular responses can originate in one of two ways: by changes in genetic constitution or by phenotypic adaptation. In this review, we will focus on the phenotypic responses of V. cholerae of a given genotype to starvation stress.     

Quantifying food limitation of arthropod predators in the field

A method for quantifying food limitation of arthropod predators in the field is presented and applied to species of ground beetles (Carabidae) and sheet-web spiders (Linyphiidae) from a cereal field. Food limitation is expressed quantitatively as accumulated hunger (=starvation) by transforming 24-h food consumption at 20°C of animals newly collected in the field into days of starvation at 20°C. This is done by means of a reference curve relating 24-h food intake at 20°C to starvation periods (days) at 20°C. Such a reference curve was obtained for the carabid beetle Agonum dorsale in the laboratory. For other species the reference curve was modified with species-specific data. The procedure makes it possible to compare the feeding conditions of different species populations that are part of the same community. Hunger levels in the field for females of A.␣dorsale were equivalent to c. 15 days of starvation in early spring, c. 5 days in June, increasing to c. 10 days in late summer. Two ground beetles occurring during summer also showed increasing hunger levels from June to July, probably the result of a dry summer. Two spider species experienced a hunger level in the range of 4–8 days of starvation. Received: 15 August 1997 / Accepted: 22 January 1998     

Starvation-survival of deep subsurface isolates

Six deep, subsurface endolithic isolates were subjected to starvation conditions for up to 100 days in artificial pore water, formulated to mimic in situ geochemical conditions in the nearly saturated rock. Most isolates demonstrated the typical starvation-survival curve for chemoheterotrophic bacteria, and all became miniaturized during starvation. Starvation indices were developed to compare changes in viable cell counts between isolates. Two isolates retained higher viability after 100 days of starvation-survival. High survival correlated with sustained respiration, measured by iodonitrotetrazolium-formazan production, during starvation. In all but one case, isolates plated on two nutritionally dilute media, metal-containing and antibioticcontaining media, showed similar viable counts.     

Survival and Recovery of Methanotrophic Bacteria Starved under Oxic and Anoxic Conditions

The effects of carbon deprivation on survival of methanotrophic bacteria were compared in cultures incubated in the presence and absence of oxygen in the starvation medium. Survival and recovery of the examined methanotrophs were generally highest for cultures starved under anoxic conditions as indicated by poststarvation measurements of methane oxidation, tetrazolium salt reduction, plate counts, and protein synthesis. Methylosinus trichosporium OB3b survived up to 6 weeks of carbon deprivation under anoxic conditions while maintaining a physiological state that allowed relatively rapid (hours) methane oxidation after substrate addition. A small fraction of cells starved under oxic and anoxic conditions (4 and 10%, respectively) survived more than 10 weeks but required several days for recovery on plates and in liquid medium. A non-spore-forming methanotroph, strain WP 12, displayed 36 to 118% of its initial methane oxidation capacity after 5 days of carbon deprivation. Oxidation rates varied with growth history prior to the experiments as well as with starvation conditions. Strain WP 12 starved under anoxic conditions showed up to 90% higher methane oxidation activity and 46% higher protein production after starvation than did cultures starved under oxic conditions. Only minor changes in biomass and morphology were seen for methanotrophic bacteria starved under anoxic conditions. In contrast, starvation under oxic conditions resulted in morphology changes and an initial 28 to 35% loss of cell protein. These data suggest that methanotrophic bacteria can survive carbon deprivation under anoxic conditions by using maintenance energy derived solely from an anaerobic endogenous metabolism. This capability could partly explain a significant potential for methane oxidation in environments not continuously supporting aerobic methanotrophic growth.     

Phosphate sensing in higher plants

Phosphate (Pi) plays a central role as reactant and effector molecule in plant cell metabolism. However, Pi is the least accessible macronutrient in many ecosystems and its low availability often limits plant growth. Plants have evolved an array of molecular and morphological adaptations to cope with Pi limitation, which include dramatic changes in gene expression and root development to facilitate Pi acquisition and recycling. Although physiological responses to Pi starvation have been increasingly studied and understood, the initial molecular events that monitor and transmit information on external and internal Pi status remain to be elucidated in plants. This review summarizes molecular and developmental Pi starvation responses of higher plants and the evidence for coordinated regulation of gene expression, followed by a discussion of the potential involvement of plant hormones in Pi sensing and of molecular genetic approaches to elucidate plant signalling of low Pi availability. Complementary genetic strategies in Arabidopsis thaliana have been developed that are expected to identify components of plant signal transduction pathways involved in Pi sensing. Innovative screening methods utilize reporter gene constructs, conditional growth on organophosphates and the inhibitory properties of the Pi analogue phosphite, which hold the promise for significant advances in our understanding of the complex mechanisms by which plants regulate Pi-starvation responses.     

Stress induced cross-protection against environmental challenges on prokaryotic and eukaryotic microbes

Prokaryotic and eukaryotic microbes thrive successfully in stressful environments such as high osmolarity, acidic or alkali, solar heat and u.v. radiation, nutrient starvation, oxidative stress, and several others. To live under these continuous stress conditions, these microbes must have mechanisms to protect their proteins, membranes, and nucleic acids, as well as other mechanisms that repair nucleic acids. The stress responses in bacteria are controlled by master regulators, which include alternative sigma factors, such as RpoS and RpoH. The sigma factor RpoS integrates multiple signals, such as the general stress response regulators and the sigma factor RpoH regulates the heat shock proteins. These response pathways extensively overlap and are induced to various extents by the same environmental stresses. In eukaryotes, two major pathways regulate the stress responses: stress proteins, termed heat shock proteins (HSP), which appear to be required only for growth during moderate stress, and stress response elements (STRE), which are induced by different stress conditions and these elements result in the acquisition of a tolerant state towards any stress condition. In this review, the mechanisms of stress resistance between prokaryotic and eukaryotic microbes will be described and compared.     

Aerobic and Anaerobic Starvation Metabolism in Methanotrophic Bacteria

The capacity for anaerobic metabolism of endogenous and selected exogenous substrates in carbon- and energy-starved methanotrophic bacteria was examined. The methanotrophic isolate strain WP 12 survived extended starvation under anoxic conditions while metabolizing 10-fold less endogenous substrate than did parallel cultures starved under oxic conditions. During aerobic starvation, the cell biomass decreased by 25% and protein and lipids were the preferred endogenous substrates. Aerobic protein degradation (24% of total protein) took place almost exclusively during the initial 24 h of starvation. Metabolized carbon was recovered mainly as CO(inf2) during aerobic starvation. In contrast, cell biomass decreased by only 2.4% during anaerobic starvation, and metabolized carbon was recovered mainly as organic solutes in the starvation medium. During anaerobic starvation, only the concentration of intracellular low-molecular-weight compounds decreased, whereas no significant changes were measured for cellular protein, lipids, polysaccharides, and nucleic acids. Strain WP 12 was also capable of a limited anaerobic glucose metabolism in the absence of added electron acceptors. Small amounts of CO(inf2) and organic acids, including acetate, were produced from exogenous glucose under anoxic conditions. Addition of potential anaerobic electron acceptors (fumarate, nitrate, nitrite, or sulfate) to starved cultures of the methanotrophs Methylobacter albus BG8, Methylosinus trichosporium OB3b, and strain WP 12 did not stimulate anaerobic survival. However, anaerobic starvation of these bacteria generally resulted in better survival than did aerobic starvation. The results suggest that methanotrophic bacteria can enter a state of anaerobic dormancy accompanied by a severe attenuation of endogenous metabolism. In this state, maintenance requirements are presumably provided for by fermentation of certain endogenous substrates. In addition, low-level catabolism of exogenous substrates may support long-term anaerobic survival of some methanotrophic bacteria.     

ppGpp介导的抗生素胁迫应答机制研究进展

抗生素是由微生物在生长发育后期产生的次级代谢产物,具有杀死或抑制细菌生长的能力,因此被广泛应用于细菌感染的临床治疗。在长期的进化过程中,细菌采取多种方式应对环境中抗生素的威胁。除了广为人知的抗生素耐药性(resistance)之外,细菌还能对抗生素产生耐受性(tolerance)和持留性(persistence),严重影响抗生素的临床疗效。鸟苷四磷酸(guanosine tetraphosphate, ppGpp)和鸟苷五磷酸(guanosine pentaphosphate, pppGpp) (本文统称ppGpp)是细菌应对营养饥饿等不利环境时产生的"报警"信号分子,其能够在全局水平调控基因的表达,使细菌适应不利的环境。越来越多的研究表明,ppGpp与细菌应对抗生素胁迫密切相关。基于此,本文综述了细菌中ppGpp的合成与水解及其作用机制,并重点阐述了ppGpp介导抗生素胁迫应答的分子机制,以期为新型抗生素的开发提供新思路。     

Evidence for a robust sex-specific trade-off between cold resistance and starvation resistance in Drosophila melanogaster

In insects changes in lipid metabolism may underlie a trade-off between cold resistance and starvation resistance. To test this we examined correlated responses in independent sets of Drosophila melanogaster lines selected for increased cold resistance and increased starvation resistance. The starvation lines showed correlated patterns found in other D. melanogaster populations selected for this trait, including higher lipid levels and increased resistance to desiccation, although the selected lines did not show a longer development time as found in some other studies. Consistent with the trade-off hypothesis, selected lines with increased starvation resistance showed decreased resistance to a cold stress as measured by mortality, whereas selected lines with increased cold resistance showed a decrease in starvation resistance. To counter the possibility of inadvertent selection accounting for these patterns, selected and control lines from both selection regimes were crossed to form mass bred populations, which were left for four generations prior to establishing isofemale lines. By scoring starvation and cold resistance in these lines derived from both sets of selection regimes, we confirmed the negative association between resistance to these stresses in females but not in males. Potential implications of this trade-off for surviving cold conditions when food resources are limiting are discussed.     

Cycles of famine and feast: the starvation and outgrowth strategies of a marineVibrio

Studies of starvation survival in non-differentiating bacteria have largely focused on physiological changes and regulatory aspects of a few master regulators such as the signal molecule ppGpp and the stationary phase alternative sigma factor, sigma S. Recent findings have implicated a series of novel key events for the entry as well as exit from starvation. The importance of alternative sigma factors other than sigma S is emerging. In addition, low molecular weight extracellular signals have been demonstrated to be essential for the induction and mediation of several adaptive responses. The importance of mRNA modification and stability for starvation survival as well as outgrowth is receiving renewedinterest. In this paper, we present the results obtained from studies of starvation survival and recovery ofVibrio sp. strain S14.     

The effect of hunger on mating behaviour and sexual selection for male body size in Gerris buenoi

The set of mating behaviours expressed by an individual may depend upon the state of that individual and local environmental conditions. Understanding how these factors affect mating behaviours may elucidate how a mating system operates, and its consequences for the form and strength of sexual selection. We conducted two experiments on the water striderGerris buenoi to (1) determine the effect of hunger on the mating behaviour of both sexes and (2) examine female choice for large males. In our first experiment, we manipulated hunger (20 h starvation) in both sexes and recorded mating, male harassment, copulation duration and guarding duration. We predicted that hunger would increase female reluctance to mate because mating conflicts with foraging. Female hunger (20 h starvation) decreased mating rate by two-thirds but had no significant effect on male mating behaviour. In a second experiment, we examined the effect of female hunger, and resulting reluctance, on sexual selection for large male size. Hungry females (5 h starvation) were placed with two fed males (one large, one small) and we recorded male premating and mating behaviours. We observed significant large-male mating advantage when females were hungry, but not when satiated. Mating efforts (harassment, premating struggles) were similar for both male phenotypes in both female hunger treatments, suggesting that the mating advantage of large males resulted from increased reluctance of hungry females to mate. Neither male body size nor female hunger explained a significant amount of variation in copulation duration or guarding duration. We discuss our results in light of two competing hypotheses for female choice (active and passive) on male body size and suggest that passive choice for large males acts in this system. Copyright 2002 Published by Elsevier Science Ltd on behalf of The Association for the Study of Animal Behaviour     

Effect of sex,hunger and relative body size on the use of ripple signals in the interactions among water striders Gerris latiabdominis

Water striders use ripple signals in aggressive interactions between individuals for access to food. We asked whether water striders produce ripple signals more frequently when they are hungrier and when the value of food resources is higher. We also asked if and how the use of signals depends on the size difference between interacting individuals. We found that females used ripple signals more often than males did. The experiment suggested that use of aggressive ripple signals is affected by hunger in females – the sex with high demands for food resources. Among females, but not males, we found out that the probability of using signals in response to the approaching intruder depended both on the degree of hunger and on the size of the focal animal relative to the size of the intruder. Before starvation, the probability of a female using a signal in an interaction with an intruder was higher when the individual's size was larger relative to the intruder. After starvation, the focal individuals were more likely to signal when their size was smaller relative to the intruder. The results are consistent with the idea that these signals may reveal information about the signalers weight or hunger level, and specific hypotheses are suggested for the future studies.     

Genetic and genomic evidence that sucrose is a global regulator of plant responses to phosphate starvation in Arabidopsis

Plants respond to phosphate (Pi) starvation by exhibiting a suite of developmental, biochemical, and physiological changes to cope with this nutritional stress. To understand the molecular mechanism underlying these responses, we isolated an Arabidopsis (Arabidopsis thaliana) mutant, hypersensitive to phosphate starvation1 (hps1), which has enhanced sensitivity in almost all aspects of plant responses to Pi starvation. Molecular and genetic analyses indicated that the mutant phenotype is caused by overexpression of the SUCROSE TRANSPORTER2 (SUC2) gene. As a consequence, hps1 has a high level of sucrose (Suc) in both its shoot and root tissues. Overexpression of SUC2 or its closely related family members SUC1 and SUC5 in wild-type plants recapitulates the phenotype of hps1. In contrast, the disruption of SUC2 functions greatly inhibits plant responses to Pi starvation. Microarray analysis further indicated that 73% of the genes that are induced by Pi starvation in wild-type plants can be induced by elevated levels of Suc in hps1 mutants, even when they are grown under Pi-sufficient conditions. These genes include several important Pi signaling components and those that are directly involved in Pi transport, mobilization, and distribution between shoot and root. Interestingly, Suc and low-Pi signals appear to interact with each other both synergistically and antagonistically in regulating gene expression. Our genetic and genomic studies provide compelling evidence that Suc is a global regulator of plant responses to Pi starvation. This finding will help to further elucidate the signaling mechanism that controls plant responses to this particular nutritional stress.     

Effects of age, sex and hunger on the antennal olfactory sensitivity of tsetse flies

Abstract The effects of age on electroantennogram (EAG) responses were investigated in male and female Glossina morsitans morsitans and comparative studies on the effects of starvation and sex on the EAG in G.m. morsitans, G.austeni, G.tachinoides and G.fuscipes fuscipes were made. Stimuli were the vapours of l-octen-3-ol, 4-heptanone, 3-nonanone and acetone. EAG decreased with age in both sexes of G.m.morsitans , responses in 5-day-old flies already being significantly lower than those in 1-day-old flies. In G.m.morsitans and G.tachinoides , EAG responses of males were higher than those of females. In G.austeni and G.f.fuscipes , however, the reverse was found. With increasing starvation EAG sensitivity increased in both sexes of G.m.morsitans and G.tachinoides. In G.austeni and in G.f.fuscipes no clear effects of starvation were observed. Response spectra of the individual species to the four odour substances did not change with increasing hunger. It is concluded that receptor sensitivity may be modulated depending on the insect's needs. Possible mechanisms of regulation and significance of this modulation are discussed.     

Physiological and morphological changes during short term starvation of marine bacterial islates

Three marine bacteria were examined for physiological and morphological changes in the initial phase of starvation. It was found that the starvation process was induced in a similar way irrespective of whether the cells were suspended in nutrient and energy free artificial seawater (NSS) or NSS supplemented with nitrogen and phosphorus. An initial phase of increased activity was consistent with a decreased response to added nutrients. Recovery from starvation exhibited the same response in both these starvation regimes, measured throughout the starvation period. Cells in nitrogen or phosphorus deprived starvation regimes, showed a high and rapid increased activity, followed by a delayed and more pronounced decline in respiratory activity. The initial phase of starvation also included a loss of poly--hydroybutyrate as observed by transmission electron microscopy (TEM). Two bacterial strains showed formation of small vesicles on the outer cell layer when examined by TEM. This formation and release of vesicles was related to the continuous size reduction during starvation survival. The results are discussed in terms of defining the mechanisms of initial cellular responses to nutrient deprivation.Abbreviation NSS nine salt solution     

Ethylene signalling is involved in regulation of phosphate starvation-induced gene expression and production of acid phosphatases and anthocyanin in Arabidopsis

? With the exception of root hair development, the role of the phytohormone ethylene is not clear in other aspects of plant responses to inorganic phosphate (Pi) starvation. ? The induction of AtPT2 was used as a marker to find novel signalling components involved in plant responses to Pi starvation. Using genetic and chemical approaches, we examined the role of ethylene in the regulation of plant responses to Pi starvation. ? hps2, an Arabidopsis mutant with enhanced sensitivity to Pi starvation, was identified and found to be a new allele of CTR1 that is a key negative regulator of ethylene responses. 1-aminocyclopropane-1-carboxylic acid (ACC), the precursor of ethylene, increases plant sensitivity to Pi starvation, whereas the ethylene perception inhibitor Ag+ suppresses this response. The Pi starvation-induced gene expression and acid phosphatase activity are also enhanced in the hps2 mutant, but suppressed in the ethylene-insensitive mutant ein2-5. By contrast, we found that ethylene signalling plays a negative role in Pi starvation-induced anthocyanin production. ? These findings extend the roles of ethylene in the regulation of plant responses to Pi starvation and will help us to gain a better understanding of the molecular mechanism underlying these responses.