Starvation affects pre-dispersal behaviour of Erigone spiders

Population studies often focus on demographic and genetic consequences of dispersal strategies, generally within an evolutionary framework. Adaptive investment in dispersal is generally assessed from single types of (pre-)dispersal behaviour that are presumed to reliably reflect the dispersal strategy adopted. Various spider families show a striking and quantifiable display, known as tiptoe behaviour that prepares individuals for take-off prior to (passive) aerial dispersal (ballooning). The lack of efficient control mechanisms during ballooning prevents individuals from actively selecting a suitable habitat for landing. Ballooning dispersal is therefore often regarded as a wind lottery preceded by individual-based risk assessment. Our laboratory experiments showed that the duration of tiptoe behaviour can be used as an indicator of silk thread length, which is related to the potential dispersal distance. For two related species, Erigone arctica and E. dentiplapis, tiptoe duration decreased independently of sex after starvation, while more complex reaction norms were observed for tiptoe frequency.

Because these two aspects of dispersal behaviours show different responses towards a simple stress-factor (starvation) in two related spider species, we conclude that the level of plasticity in dispersal investment can be subject to selective forces affecting different dispersal properties in different ways. Our results, hence, plead for a more holistic approach when addressing evolutionary and applied questions related to dispersal.     

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.     

The limits to genomic predictions: role of sigma(N) in environmental stress survival of Pseudomonas putida

Based on genomic data and on the phenotypes of an FlhF mutant of Pseudomonas putida, the alternative sigma factor sigma(N) (sigma(54)) has been proposed to play a key role in survival to various nutritional and environmental stresses in this bacterium. Quite in contrast, we show that unlike sigma(S) (sigma(38)) the loss of sigma(N) does not impair to any significant extent the ability of P. putida to survive long-term starvation. rpoN mutants (lacking sigma(N)) are indistinguishable from the wild-type with respect to solvent tolerance, resistance to heat shock or sensitivity to hydrogen peroxide. These data suggest that while sigma(N) is a key component of expression of alternative biodegradative pathways for unusual carbon sources (i.e. m-xylene or dimethylphenols), its loss does not compromise bacterial endurance to gross types of environmental stress. Moreover, these results point out the limitations, if not the deception, of genomic predictions when confronted with experimental data.     

捕食风险对不同饥饿状态下艾虎取食行为的影响

在室内条件下,将大鵟作为艾虎的天敌动物,通过双通道选择实验确定6 只成体艾虎在3 个捕食风险水平和4 种饥饿状态条件下的取食行为,探讨艾虎在取食过程中对饥饿风险与捕食风险的权衡策略。研究结果表明:在无捕食风险存在时,艾虎被剥夺食物0 d 和1 d 后对食物量不同的两个斑块中的取食量和利用频次均无明显不同(P > 0. 05),但对高食物量斑块的利用时间均明显高于低食物量斑块的(P <0.05),而艾虎被剥夺食物2 d和3 d后对高食物量斑块中的取食量和利用时间均明显高于低食物量斑块中的(P < 0.05),但在利用频次上均无明显差异(P > 0.05)。在面临低风险时,艾虎在4 种饥饿状态下均只利用无天敌动物存在的低食物量斑块,而基本不利用有天敌动物存在的高食物量斑块。在面临高风险时,艾虎不得不利用有天敌动物存在的食物斑块,被剥夺食物0 d 时艾虎对无风险、无食物量斑块的利用时间基本相同于对高风险、有食物量斑块的利用时间(P>0.05),而被剥夺食物1d、2 d 和3 d 后艾虎对高风险、有食物量斑块的利用时间明显高于无风险、无食物量斑块的(P< 0. 05)。在相同风险条件下,随着饥饿程度增加,艾虎在斑块中的取食量均明显增加(P< 0.05),而对斑块的利用时间和利用频次明显降低(P<0.05)。在相同的饥饿状态下,不同风险水平时,艾虎在斑块中的取食量无明显的差异(P>0.05),但在低风险和高风险时对斑块的利用时间和频次均明显低于无风险时的(P <0.05)。以上结果说明艾虎能够根据食物摄取率和自身的能量需求在捕食风险和饥饿风险之间做出权衡,当饥饿风险小于捕食风险时,艾虎趋于躲避捕食风险,当饥饿风险大于捕食风险时,艾虎趋于面对捕食风险,所采用的取食策略是减少活动时间和能量消耗,最大程度地提高单位时间内获得的能量。     

饥饿对南方鲇仔稚鱼消化系统的形态和组织学影响

在实验室饲养条件下,对南方鲇仔、稚鱼进行饥饿,观察了消化系统的形态和组织学变化。仔鱼肝脏萎缩,肠管缩短、变细,失去变曲形状。组织学结构与功能明显衰退：肝组织变得疏松,细胞缩小,仔鱼肝细胞内无脂质积累,到饥饿后期,部分细胞核仁解体;稚鱼肝细胞内贮存的脂质迅速消失,细胞由多角形变为圆形。胰脏组织变得致密,腺泡小叶分界不清,腺泡萎缩,其内分泌物减少或消失。消化道上皮细胞的高度下降,微绒毛退化,胃腺下发达     

The liver-enriched transcription factor CREBH is nutritionally regulated and activated by fatty acids and PPARα

To elucidate the physiological role of CREBH, the hepatic mRNA and protein levels of CREBH were estimated in various feeding states of wild and obesity mice. In the fast state, the expression of CREBH mRNA and nuclear protein were high and profoundly suppressed by refeeding in the wild-type mice. In ob/ob mice, the refeeding suppression was impaired. The diet studies suggested that CREBH expression was activated by fatty acids. CREBH mRNA levels in the mouse primary hepatocytes were elevated by addition of the palmitate, oleate and eicosapenonate. It was also induced by PPARα agonist and repressed by PPARα antagonist. Luciferase reporter gene assays indicated that the CREBH promoter activity was induced by fatty acids and co-expression of PPARα. Deletion studies identified the PPRE for PPARα activation. Electrophoretic mobility shift assay and chromatin immunoprecipitation (ChIP) assay confirmed that PPARα directly binds to the PPRE. Activation of CREBH at fasting through fatty acids and PPARα suggest that CREBH is involved in nutritional regulation.     

Thermodynamic and kinetic studies of a stoichiometric model of energetic metabolism under starvation conditions

Abstract A stoichiometric model of anaerobic glycolysis is presented and the influence on its dynamics by the ATP-consuming membrane transport processes and substrate input rate are studied. The model is represented by a system of four ODE (ordinary differential equations), mass conservation equations and functions of state variables, such as thermodynamic efficiency. A low substrate input rate provokes damped oscillations while a high enrgy load determines sustained oscillations in all the metabolites and in thermodynamic efficiency. Due to the lack of linearity between fluxes and forces in the oscillatory region it may be stated that oscillations appear when the system is kinetically controlled.     

Starvation induced cholesterogenesis in hepatic and extra hepatic tissues of climbing Perch,Anabas testudineus (Bloch)

Cholesterol is a structural lipid, which may be differentially utilized or synthesized in response to stress or during insulin deficient states such as starvation. In the present investigation we estimated the levels of cholesterol in Anabas testudineus, which was subjected to brief (15 days) and prolonged fasting (60 days). Tissues such as liver, kidney, brain, accessory respiratory organ, pectoral and lateral line muscle were selected for the study. Cholesterol content was estimated by the Crawford method (1958). Both the starvation regimes showed a significant increase in cholesterol levels in almost all the tissues, but for liver, which strangely showed an insignificant decline during the short-term starvation. This overall upsurge in cholesterol levels observed in all extra hepatic tissues may be attributed to the synthesis of stress hormones such as glucocorticoids, which may promote gluconeogenesis and adrenocorticoids, which may help the animal to combat the stressful condition of starvation. Anabas adapted well to starvation stress and survived all throughout the experimental period.     

Enzymatic,outer membrane proteins and plasmid alterations of starved <Emphasis Type="Italic">Vibrio parahaemolyticus</Emphasis> and <Emphasis Type="Italic">Vibrio alginolyticus</Emphasis> cells in seawater

The marine bacteria Vibrio parahaemolyticus and V. alginolyticus were incubated in seawater for 8 months to evaluate their adaptative responses to starvation. The starved cells showed an altered biochemical and enzymatic profiles, respectively, on Api 20E and Api ZYM systems and an evolution to the filterable minicells state capable to pass membrane pore size 0.45 μm. Outer membrane proteins patterns of stressed bacteria were also altered. Indeed, these modifications were manifested by the appearance and/or disappearance of bands as well as in the level of expression of certain proteins. Plasmids profiles analysis showed that V. alginolyticus ATCC 33787 lost three plasmids, whereas other tested strains conserved their initial profiles.