Starvation Time Research Articles

Effect of defective cells on the temperature distribution of a proton exchange membrane fuel cell stack

Proton exchange membrane fuel cell (PEMFC) stacks may encounter performance degradation or even damage during long-term operations, while the influence of defective cells on the stack performance still remains inadequately understood. In this study, the effect of defective cells on the stack temperature distribution was experimentally investigated. Two defective cells of different defect degrees were prepared by controlling hydrogen starvation time and quantitively characterized by the polarization curves, electrochemical impedance spectroscopy (EIS), and galvanostatic charge method (GCM) tests. Results show that the presence of defective cells reduces the stack performance and the temperature distribution uniformity. The increment of stack temperature and decrement of stack temperature uniformity is more prominent (with 0.9 °C and 0.31 °C at 0.8 A cm−2, respectively) when the defective cell is located at central stack. The peak sub-cell regional temperature rise can even reach 2.9 °C. For defective cells with a relatively low degree of defect, the reverse current density is high, thus leading to an increased heat generation with the average sub-cell regional temperature increment of 0.5 °C and causing adjacent normal cells to operate at higher temperature. For defective cells with an excessive degree of defect, polarization reverse occurs at low current densities, resulting in significant voltage losses and reduced performance of the stack. The present results are insightful for developing thermal management strategies for the long-term operation of PEMFC stacks.

Energy Metabolism in Human Pluripotent Stem and Differentiated Cells Compared Using a Seahorse XF96 Extracellular Flux Analyzer.

Evaluating cell metabolism is crucial during pluripotent stem cell (PSC) differentiation and somatic cell reprogramming as it affects cell fate. As cultured stem cells are heterogeneous, a comparative analysis of relative metabolism using existing metabolic analysis methods is difficult, resulting in inaccuracies. In this study, we measured human PSC basal metabolic levels using a Seahorse analyzer. We used fibroblasts, human induced PSCs, and human embryonic stem cells to monitor changes in basal metabolic levels according to cell number and determine the number of cells suitable for analysis. We evaluated normalization methods using glucose and selected the most suitable for the metabolic analysis of heterogeneous PSCs during the reprogramming stage. The response of fibroblasts to glucose increased with starvation time, with oxygen consumption rate and extracellular acidification rate responding most effectively to glucose 4 hours after starvation and declining after 5 hours of starvation. Fibroblasts and PSCs achieved appropriate responses to glucose without damaging their metabolism 2∼4 and 2∼3 hours after starvation, respectively. We developed a novel method for comparing basal metabolic rates of fibroblasts and PSCs, focusing on quantitative analysis of glycolysis and oxidative phosphorylation using glucose without enzyme inhibitors. This protocol enables efficient comparison of energy metabolism among cell types, including undifferentiated PSCs, differentiated cells, and cells undergoing cellular reprogramming, and addresses critical issues, such as differences in basal metabolic levels and sensitivity to normalization, providing valuable insights into cellular energetics.

Adaptive responses of feeding and swimming behaviors in black rockfish, Sebastes schlegelii, under starvation at juvenile and young stages

Starvation is a ubiquitous stress that many fish species have to cope with. To investigate the behavioral responses under this pressure in the fry stage, black rockfish (Sebastes schlegelii) at juvenile (29 days of age, 15.2 ± 1.0 mm in total length) and young (51 days of age, 40.3 ± 1.2 mm in total length) stages were starved for 12 and 21 days, respectively. During these two periods of starvation, the starved and routinely fed individuals (serving as the control group) were sampled to be analyzed the variations in growth, survival, feeding activity, swimming ability (cruise and burst), and diet transition process. The results indicated that juveniles were more sensitive to hunger, and the point of no return (PNR) was approximately 5.5 days (19 ℃ in water temperature). In contrast, the young fish had a significantly higher tolerance to starvation because the survival rate after 21 days of starvation was still higher than 99% (20 ℃). The total length and body weight of juveniles and young fish showed different degrees of negative growth. After the starvation for 1 day, the juveniles’ feeding activity on shrimps increased significantly (p < 0.05), while their cruising speed and time changed insignificantly. Similar results were observed in young fish been starved for 1–3 days. With the prolongation of starvation, however, both the feeding and cruising activities of black rockfish became significantly lower than those of the control groups (p < 0.05). The burst swimming ability did not seem to be affected by starvation time. Although the short-term starvation would not increase the young fish’s predation on shrimp, it might be serviceable for improving their feeding vitality. These behavioral results would help us understand the adaptive processes and response mechanisms of fish under starvation.

Initial nutrient condition determines the recovery speed of quiescent cells in fission yeast

Most of microbe cells spend the majority of their times in quiescence due to unfavorable environmental conditions. The study of this dominant state is crucial for understanding the basic cell physiology. Retained recovery ability is a critical property of quiescent cells, which consists of two features: how long the cells can survive (the survivability) and how fast they can recover (the recovery activity). While the survivability has been extensively studied under the background of chronological aging, how the recovery activity depends on the quiescent time and what factors influence its dynamics have not been addressed quantitatively. In this work, we systematically quantified both the survivability and the recovery activity of long-lived quiescent fission yeast cells at the single cell level under various nutrient conditions. It provides the most profound evolutionary dynamics of quiescent cell regeneration ability described to date. We found that the single cell recovery time linearly increased with the starvation time before the survivability significantly declined. This linearity was robust under various nutrient conditions and the recovery speed was predetermined by the initial nutrient condition. Transcriptome profiling further revealed that quiescence states under different nutrient conditions evolve in a common trajectory but with different speed. Our results demonstrated that cellular quiescence has a continuous spectrum of depths and its physiology is greatly influenced by environmental conditions.

Tissue Distribution and Nutritional Regulation of Four Cholesterol Transport-Related Genes in Tiger Puffer (Takifugu rubripes)

This study characterized four cholesterol transport-related genes, namely, lcat, acat1, acat2, and mttp, in juvenile tiger puffer in terms of tissue distribution (eye, heart, brain, skin, liver, spleen, muscle, and intestine) and nutritional regulation. Three feeding trials were conducted: (i) using diets with different cholesterol levels (0.11%, 0.65%, 1.10%, 2.32%, and 4.59% of dry matter); (ii) using diets with different lipid levels (8.05%, 12.02%, and 16.36% of dry matter); and (iii) a 1-month starvation experiment with different sampling times (Days 1, 4, 9, 16, and 31). The lcat, acat1, and acat2 were the most abundantly expressed in the liver, while mttp was the most abundantly expressed in the intestine. The lcat had a medium expression level in the muscle and skin but the lowest expression level in the spleen and intestine. The acat1 and acat2 had similar tissue distribution patterns, except that acat2 had a lower expression level in the heart but a higher level in the intestine than acat1. The mttp had medium expression levels in the liver and spleen but had the lowest level in the eye and skin. Different dietary cholesterol levels did not significantly affect the expression of these cholesterol transport genes in the liver and intestine, except that higher cholesterol levels (1.10%–4.59%) significantly downregulated the acat2 expression in the liver. Dietary lipid levels also had a mild influence on the hepatic expression of these genes, except that the diet with 12.02% lipid resulted in significantly higher acat1 expression than the one with 16.36% lipid. The starvation time significantly affected the hepatic expression of these genes. Long-term starvation (16 and 31 days) generally upregulated the hepatic gene expression of lcat, acat1, and mttp but generally downregulated that of acat2. This study provided preliminary knowledge about the tissue distribution and nutritional regulation of cholesterol transport-related genes in marine teleost.

Starvation-induced autophagy modulates spermatogenesis and sperm quality in Nile tilapia

Spermatogenesis is a finely regulated process that involves the interaction of several cellular mechanisms to ensure the proper development and maturation of germ cells. This study assessed autophagy contribution and its relation to apoptosis in fish spermatogenesis during starvation. To that end, Nile tilapia males were subjected to 0 (control), 7, 14, 21, and 28 days of starvation to induce autophagy. Testes samples were obtained for analyses of spermatogenesis by histology, electron microscopy, immunohistochemistry, and western blotting. Sperm quality was assessed using a computer-assisted sperm analysis (CASA) system. Data indicated a significant reduction in gonadosomatic index, seminiferous tubule area, and spermatozoa proportion in fish subject to starvation compared to the control group. Immunoblotting revealed a reduction of Bcl2 and Beclin 1 associated with increased Bax and Caspase-3, mainly after 21 and 28 days of starvation. LC3 and P62 indicated reduced autophagic flux in these starvation times. Immunolabeling for autophagic and apoptotic proteins occurred in all development stages of the germ cells, but protein expression varied throughout starvation. Beclin 1 and Cathepsin D decreased while Bax and Caspase-3 increased in spermatocytes, spermatids, and spermatozoa after 21 and 28 days. Autophagic and lysosomal proteins colocalization indicated the fusion of autophagosomes with lysosomes and lysosomal degradation in spermatogenic cells. The CASA system indicated reduced sperm motility and velocity in animals subjected to 21 and 28 days of starvation. Altogether, the data support autophagy acting at different spermatogenesis stages in Nile tilapia, with decreased autophagy and increased apoptosis after 21 and 28 days of starvation, which results in a decrease in the spermatozoa number and sperm quality.

Spawning manipulation, broodfish diet feeding and egg production in farmed Atlantic salmon

Atlantic salmon aquaculture relies on continuous supply of high quality eggs. Broodfish nutrition and manipulation of ovulation time (photoperiod and temperature) are key factors. The optimum feeding period with broodfish diet has not been investigated before. The present study examined how feeding period with broodfish diet (9 vs. 17 months) interacted with manipulation of ovulation time (early (Nov), normal (Dec), late (Feb)) on broodstock egg production capacity and egg quality in two-sea-winter female Atlantic salmon (∼12 kg). All groups were fed until June 2021 when they were transferred to tanks and starved until ovulation.There were no measurable main or interaction effects of feeding period. Manipulation of ovulation gave several significant effects compared to normal ovulating females:1.Early ovulating females had higher viscerosomatic index, smaller eggs with higher swelling rate (early 1.36, normal 1.27, late 1.23), and lower egg quality shown as reduced survival from fertilization to the eyed egg stage (mortality: early 11%, normal 5%, late 14%).2.Late ovulating females: (i) were emaciated as shown by low condition factor calculated on gutted weight, and hepatosomatic and viscera indexes; (ii) had larger gonads caused by larger eggs; (iii) had reduced egg quality measured as elevated mortality from fertilization to first-feeding (eyed egg – first feeding: early 11%, normal 8%, late 23%).3.All groups spawned a similar number of eggs per female.The current results show that the feeding period with broodstock diet may be set to 9 months. This would make Atlantic salmon egg production more economical and environmentally sustainable. The results also show that manipulation of ovulation time reduce egg quality but not fecundity. Further research should investigate feeding periods with broodstock diet shorter than 9 months and determine the threshold for jeopardized fish welfare with respect to starvation time for manipulated late ovulating females.

Two-state swimming: Strategy and survival of a model bacterial predator in response to environmental cues

Bdellovibrio bacteriovorus is a predatory bacterium preying upon Gram-negative bacteria. As such, B. bacteriovorus has the potential to control antibiotic-resistant pathogens and biofilm populations. To survive and reproduce, B. bacteriovorus must locate and infect a host cell. However, in the temporary absence of prey, it is largely unknown how B. bacteriovorus modulate their motility patterns in response to physical or chemical environmental cues to optimize their energy expenditure. To investigate B. bacteriovorus’ predation strategy, we track and quantify their motion by measuring speed distributions as a function of starvation time. While an initial unimodal speed distribution relaxing to one for pure diffusion at long times may be expected, instead we observe a bimodal speed distribution with one mode centered around that expected from diffusion and the other centered at higher speeds. What is more, for an increasing amount of time over which B. bacteriovorus is starved, we observe a progressive reweighting from the active swimming state to an apparent diffusive state in the speed distribution. Distributions of trajectory-averaged speeds for B. bacteriovorus are largely unimodal, indicating switching between a faster swim speed and an apparent diffusive state within individual observed trajectories rather than there being distinct active swimming and apparent diffusive populations. We also find that B. bacteriovorus’ apparent diffusive state is not merely caused by the diffusion of inviable bacteria as subsequent spiking experiments show that bacteria can be resuscitated and bimodality restored. Indeed, starved B. bacteriovorus may modulate the frequency and duration of active swimming as a means of balancing energy consumption and procurement. Our results thus point to a reweighting of the swimming frequency on a trajectory basis rather than a population level basis.

MTOR Plays a Conserved Role in Regulation of Nutritional Metabolism in Bivalve Sinonovacula constricta

The mammalian target of rapamycin (mTOR) has been shown to play a central role in regulating cell growth and metabolism. However, little is known about the function of mTOR in nutrient metabolism in bivalve mollusks. In this study, the role of mTOR in the regulation of nutrient metabolism was investigated in Sinonovacula constricta. First, the activation of mTOR was assayed after starvation and refeeding. Afterwards, the role of mTOR in the regulation of nutrient metabolism was investigated using an activator (MHY1485) or inhibitor (rapamycin) of mTOR. The open reading frame of the S. constricta mTOR is 7416 bp in length and encodes a polypeptide consisting of 2471 amino acids. The mTOR amino acid sequence of S. constricta was highly conserved when compared with other species and had a close evolutionary relationship with the TOR proteins of Crassostrea gigas and Lingula anatine. mTOR was expressed in the intestine, exhalent siphon, labial palppus, muscle, inhalent siphon, gill, mantle, digestive land, and gonad tissue of S. constricta, with the highest expression in muscle. During starvation, the level of phosphorylated mTOR protein was relatively low, and the ratio of LC3II/LC3I protein and the AMPKα mRNA level significantly increased with the increase in starvation time. After feeding, the level of phosphorylated mTOR protein increased from 0.13 to 0.56, and the ratio of LC3II/I protein and AMPKα mRNA level decreased from 1.17 to 0.38. MHY1485 significantly increased the level of phosphorylated 4E-BP1 and significantly decreased the ratio of LC3II/I proteins. Furthermore, MHY1485 significantly increased the mRNA level of the glucose metabolism-related gene glucokinase (GK), significantly decreased the mRNA expression of the G6P gene, and significantly increased the mRNA expression of the lipid synthesis-related genes sterol-regulatory element-binding protein (SREBP) and stearoyl-CoA desaturase (SCD). Rapamycin significantly reduced the level of phosphorylated 4E-BP1 and the mRNA expression of mTOR, and the expression level of phosphorylated 4EBP1 decreased from 0.97 to 0.28. Meanwhile, it also significantly reduced the mRNA expression of glucose metabolism-related genes GK, pyruvate kinase (PK), glucose transporter 1 (GLUT1), and G6P, as well as lipid synthesis-related genes SCD and acetyl-CoA carboxylase (ACC). These results indicate a conserved role of mTOR in regulating nutritional metabolism, including glucose metabolism, lipid synthesis, and autophagy in S. constricta.

Predicting future production system bottlenecks with a graph neural network approach

Predicting throughput bottlenecks has received an increasing research attention in the recent years. Several statistical and machine learning models have been developed, with the objective of identifying future bottleneck locations for more efficient and cost-saving productions. However, bottleneck prediction remains a challenging task due to the complexity of manufacturing systems and the interactive effects from many impacting factors. This paper proposed the BSTAN (bottleneck spatial-temporal attention network) – an interpretable modeling framework to improve system bottlenecks prediction capability for complex manufacturing systems by: (1) characterizing line topological features using graph representations; (2) modeling spatial-temporal relationships and interactions between stations using graph attention network with gated recurrent units. In this proposed framework, the production line is first transformed into the representation of a weighted undirected graph to depict network structural information of a production line. An attention-based graph neural network with gated recurrent units is applied to capture both the temporal trends and station interactions to predict each station’s blockage and starvation. Future bottleneck stations are identified by analyzing the forecasted blockage and starvation distribution. To evaluate the model performance, an industrial case study is performed with data collected from a one-year production at an automotive powertrain assembly line. With the proper model construction, BSTAN has outperformed both statistical and machine learning benchmark models, achieving up to 15% lower root mean square error compared to the best benchmark method in predicting overall system blockage and starvation time.

Potential causes of partial-denitrification (PD) granular sludge breakdown under high nitrate loading rates

The granule instability has been frequently reported during the operation of high loading rates. While, there no research was performed on the recently developed anoxic partial-denitrification (PD) granules, a novel pathway in producing nitrite from nitrate for anammox process. Herein, this work, for the first time, investigated the influence of nitrate loading rates on the instability of PD granules and identified the key causes. Two lab-scale sequencing batch reactors (SBRs) were operated with nitrate loading rates (NLR) increased from 0.48 to 3.84 kg N/m3/d (R1, 8 cycles/d), and 0.96 to 7.68 kg N/m3/d (R2, 16 cycles/d) by gradually elevating the influent nitrate concentration. Results showed that nitrite production rates increased with the NLRs, with a maximal value of 5.26 kg N/m3/d obtained. However, the compact regular PD granules were not stable and broke down when NLR was above 3.84 kg N/m3/d, which resulted in serious sludge washing out from SBR. The high NLRs led to the extracellular polymeric substances (EPS) transformation in terms of its composition and structure, which the protein content in the EPS and the tightly bound EPS (T-EPS) fraction was significantly decreased, this was supposed to be the major reason causing the breakdown of PD granules. Besides, it was found the PD granule in R2 was more deteriorated than that in R1 under the same high NLR, suggesting the short starvation (idle) times in SBR cycle was likely another reason impairing the stability of PD granules. Overall, this research provides useful information in development of granule-based PD systems and sheds light on achieving high-rate nitrite production in SBR with great stability.

Autophagy Mediates MMP-2 Expression in Glaucomatous Trabecular Meshwork Cells.

Purpose To investigate the effect of 3-methyladenine (3-MA) and starvation on the expression of matrix metalloproteinase (MMP-2) in patients with primary open-angle glaucoma. Methods Primary TM cells were cultured and divided into three groups. The control group was treated with a normal medium, the 3-MA group was stimulated with 3-MA, and the starvation group received nutrient depletion by replacing the normal media with Earle's balanced salt solution. Cellular mRNA and protein were measured at different 3-MA concentrations and starvation time periods. The level of autophagy was accessed by monodansylcadaverine fluorescent staining and expression of specific autophagy-related genes, light chain 3 (LC3), and Beclin1. The effects of 3-MA and starvation on cell proliferation were determined with a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay kit. The mRNA and protein expression of LC3-II, Beclin1, and MMP-2 were measured by reverse transcription-polymerase chain reaction and western blot, respectively. Results Compared to the control group, starvation significantly upregulated LC3-II and Beclin1 in TM cells after 3 h of stimulation, which peaked at 6 h and 9 h, respectively. Increased MDC-labeled cells were also observed. Starvation downregulated the expression of MMP-2. On the contrary, 3-MA suppressed the activation of autophagy, as shown by the marked downregulation of LC3-II and Beclin1. The expressions of MMP-2 were higher in the 3-MA group compared to the control group, reaching a peak at a concentration of 5 mM. Conclusion Autophagy may be involved in the pathogenesis of POAG via regulating the expression of MMP-2 and, subsequently, the deposition of the extracellular matrix.

Tissue distribution and nutritional regulation of peroxisomal fatty acid β‐oxidation genes: A preliminary study in two marine teleosts, turbot ( Scophthalmus maximus ) and tiger puffer ( Takifugu rubripes )

Peroxisome plays an important role in the modulation of lipid catabolism in fish. The present study investigated the tissue distribution of five peroxisomal fatty acid β-oxidation genes, including vlcs, acox1, acox3, ehhadh and acaa1, in turbot and tiger puffer. Their expressions in response to different nutritional status (starvation and change in dietary lipid levels) were also studied. Both fish were fed diets with graded lipid levels (8%, 12% and 16%) for 9 weeks, followed by 1-month of starvation. The five genes were highly expressed in the liver, intestine and pyloric caecum of turbot, and tiger puffer intestine. High-lipid diets up-regulated the expression of vlcs and acox3 in tiger puffer liver, whereas did not affect the expression of all genes investigated in turbot. During the starvation, expression of acox1, acox3 and acaa1 in turbot liver was increased firstly from day 0 to day 10, and then was decreased, while expression of vlcs in muscle, and acaa1 in muscle and subcutaneous adipose tissue was linearly increased. In tiger puffer liver, the expression of peroxisomal β-oxidation genes increased linearly with starvation time, but the expression of acox3, ehhadh and acaa1 in the muscle firstly increased from day 0 to day 4–9, and thereafter decreased. In conclusion, the peroxisomal fatty acid β-oxidation genes were highly expressed in the liver and intestine of both turbot and tiger puffer, and starvation could stimulate and high dietary lipid levels have less impact on their expression.

Effect of starvation and refeeding on reactive oxygen species, autophagy and oxidative stress in Chinese perch (Siniperca chuatsi) muscle growth.

In skeletal muscle, autophagy regulates the development and growth of muscle fibres and maintains the normal muscle metabolism. Under starvation and refeeding conditions, the effect of reactive oxygen species (ROS) levels on skeletal muscle autophagy is still unclear, although the excessive accumulation of ROS has been shown to increase autophagy in cells. The purpose of this study was to explore the effects of starvation and diet after starvation on the autophagy of adult Chinese perch muscle, and to determine the level of ROS in the muscle. We performed zero (Normal control), three and seven starvation treatments on adult Chinese perch, and returned to normal feeding for 3 days after starvation for 7 days. In the muscles of the adult Chinese perch muscle after 3 days of starvation, the autophagy marker protein LC3 and the number of autophagosomes remained basically the same as in the normal feeding situation. However, on starvation for 7 days, the mitochondrial autophagy was sensitive and the number of autophagosomes increased, but the antioxidant-related molecules (malondialdehyde, catalase, glutathione S-transferase, glutathione and anti-superoxide anion) decreased and the accumulation of ROS was obvious. In addition, the extended starvation time also increased the level of LC3 protein. However, by refeeding after starvation this nutritional stress resulted in a decrease in ROS levels and a partial restoration of antioxidant enzyme activity. Our data show that in the adult Chinese perch muscle, starvation could reduce the antioxidant activity through the accumulation of ROS, and that the number of autophagosomes continues to increase. Refeeding after starvation could effectively compensate for the level of ROS, and restore the mRNA abundance of antioxidant genes and the activity of antioxidant enzymes to reduce autophagy and improve feed efficiency. Further research should optimize starvation conditions to reduce autophagy in muscles and maintain normal muscle metabolism.

Response of lipid-related composition of farmed tiger puffer (Takifugu rubripes) to starvation under different dietary lipid levels in the previous feeding period

Starvation is a natural process in the life cycle of wild fish, and also a means of body composition regulation for farmed fish. This study with tiger puffer was aimed at investigating the effects of starvation on lipid and fatty acid compositions in fish with different levels of lipid accumulation. Different lipid accumulation levels in tiger puffer were obtained by manipulating the dietary lipid content (8%, 12%, and 16%) in a previous feeding period for 9 weeks. Each diet was fed to sextuplicate net cages in this feeding trial. At the end of the feeding trial, fish with an average initial body weight of 68.26 g were then subjected to starvation for 31 days. Tissue samples were collected at the end of the feeding trial and at 1, 4, 9, 16, and 31 days after starvation. The results showed that the muscle lipid content decreased linearly with starvation time, but the liver lipid content increased firstly (1–16 days of starvation), and thereafter sharply declined. However, no interaction between starvation time and dietary lipid level was observed in the effects on liver and muscle lipid composition. Starvation had slight effects on muscle and liver fatty acid compositions, except that it largely increased the C22:5n-3 content in the muscle. Starvation primarily mobilized C14:0, C16:1n-7, C20:1n-9 and C22:1n-9 in the muscle, and C18:0, C18:1n-9, and EPA in the liver. Interactive effects between starvation time and dietary lipid level were observed for many fatty acids. Short-term (1–4 days) starvation increased the muscle texture parameters, but longer-term starvation decreased them. In conclusion, starvation exerts significant effects on lipid and fatty acid composition in farmed tiger puffer. Customed lipid and fatty acid composition, and possibly customed fillet quality could be obtained through manipulation of starvation time and dietary lipid level in the previous feeding period.

Influence of an R&D lot on productivity in semiconductor manufacturing

Both high productivity of finished goods and new product development are important for manufacturing firms to compete in a market successfully. High productivity is closely related to near-term profit, while new product development is imperative for long-term competitiveness. In a semiconductor fabrication facility, the final stage of new product development is testing new R&D lots in a real mass production environment. Because the test shares the same facility of mass production, if the R&D lots are processed to prioritize fast product development, it negatively influences the productivity of the lines. This study develops a stochastic model to analyze how the flow speed of R&D lots affects starvation of a bottleneck stage and the throughput of regular production lots on a semiconductor fabrication line. The model calculates the distributions of the delay time of R&D lots and the starvation time of the bottleneck stage under a given flow control policy of the R&D lots. Numerical examples are provided to illustrate how this model can be used on actual manufacturing lines to determine appropriate speeds of R&D lots.

A Simulation Study on Model-Based Optimization of Intracellular Trehalose Accumulation in Saccharomyces cerevisiae Fed-Batch Cultures

Trehalose is a reserve carbohydrate, which occurs naturally in yeast and acts as a stress protectant for cells. Due to its features, trehalose is used in many industries (food, biopharmaceuticals, cosmetics). Its production/accumulation may be triggered and enhanced by the culture operating conditions, among which the feed flow rate and the start of the starvation period play the most important role. This paper presents a simulation study based on a novel model validated with experimental data, highlighting the interplay between trehalose maximization and biomass maximization. Several single-objective and multi-objective constrained optimization problems are solved using the control vector parameterization approach. It is shown that maximizing either the trehalose concentration or the biomass amount leads to solutions which are not appealing in practice. The best solution is obtained by maximizing trehalose concentration with a lower bound on the biomass amount. A comparison of the optimal solution to experimental data reveals that, although approximately the same amount of biomass can be obtained with different feeding profiles and starvation times, the maximization of trehalose concentration requires feeding most of the culture medium in the first part of the experiment while starting the nitrogen starvation at an early stage.

Modulation of sugar feeding behavior by Gymnema sylvestre in Drosophila melanogaster.

IntroductionSugar is the main source of energy for nearly all animals. However, consumption of a high amount of sugars can lead to many metabolic disorders hence, balancing calorie intake in the form of sugar is required. Various herbs are in use to control body weight, cure diabetes and control elevated blood sugar levels. One such herb is Gymnema sylvestre commonly called Gurmar (destroyer of sugar). Gurmar selectively inhibits sugar sensation by mechanisms that are still elusive.ObjectivesThe primary objective of this study is to understand the effect of gurmar on sweet taste feeding behaviour in insects using the invertebrate model system Drosophila melanogaster.MethodsFor this study, we used feeding assays, spectrophotometry and Proboscis Extension Reflex (PER) assay to determine how flies detect gurmar. Additionally, life span analysis, egg-laying behaviour and developmental profiles were used to probe the role of gurmar on the overall health of the flies. During the whole study, we used only the raw powdered form of gurmar (dried leaves) to examine its effect on sweet taste feeding behaviour.ResultsOur data demonstrate that whole gurmar in a raw powdered form is aversive to flies and inhibits sugar evoked PER and feeding responses. Also, we observed it takes at least 24 h of starvation time to reduce the consumption of sugar in flies pre-fed on gurmar. Flies lay a fewer number of eggs on gurmar media and show developmental defects. Our data suggest that flies detect gurmar using both taste and olfactory cues.ConclusionUnderstanding how gurmar reshapes taste curves to promote reduced consumption of sugars in flies will open up avenues to help people with health issues related to high sugar consumption, but our data also highlights that its consumption should be carefully considered since gurmar is aversive to flies and has detrimental effects on development.

Response of lipid and fatty acid composition of turbot to starvation under different dietary lipid levels in the previous feeding period

The present study was aimed at investigating the interactive effects of starvation and dietary lipid level in the previous feeding period on lipid-related composition of turbot. Turbot with an average initial body weight of 26 g were firstly fed diets with different lipid levels, namely, 8%, 12%, and 16%, for 9 weeks, and then subjected to starvation for 30 days. Each diet was fed to sextuplicate tanks of 35 fish in the feeding trial. Tissue samples were collected at the end of the feeding trial and at 10, 20, and 30 days after starvation. The results showed that 30-day starvation decreased the lipid content in the liver and the subcutaneous tissue around the fin (STF), but increased the lipid content in the muscle. A synergetic increase of muscle lipid by starvation and dietary lipid level was observed. Starvation mobilized different fatty acids among the three tissues, namely, MUFA (16:1n-7 and 18:1n-9) in the muscle, SFA (14:0 and 16:0), MUFA (16:1n-7, 18:1n-9 and 20:1n-9), and 18C-PUFA (18:2n-6 and 18:3n-3) in the liver, and unexpectedly n-3 PUFA (18:3n-3, EPA, and DHA) in the STF, respectively. The 30-day starvation decreased the muscle hardness and resilience, but affected other texture parameters in a starvation time-dependent manner. Up-regulation of expression of lipolytic genes by starvation occurred later in the STF than in the liver. Interactive effects of starvation and dietary lipid level were observed mainly on tissue fatty acid compositions. Results of this study suggested that combined manipulation of starvation time and dietary lipid level could be used as an effective means of fish quality regulation in terms of lipid/fatty acid-related composition.

Effect of starvation and feeding on desiccated cover crops (Urochloa spp.), in different time periods, on the survival and biomass of Spodoptera frugiperda

In tropical agroecosystems, cover crops are an alternative toward a more diverse and sustainable production. Urochloa spp. (syn. Brachiaria spp.) are perennial grasses that are commonly used as cover crops in the no-tillage crop systems. Their residues after desiccation protect the soil and provide nutrient to the next crop cycle. However, these plants can act as a green bridge to fall armyworm (FAW) during the winter season. When summer crops are sown, late instar larvae destroy the seedlings. Therefore, one of the main issues in the management of cover crops is when to perform desiccation before the main crop sowing to avoid FAW larvae survival on the straw. In this context, we investigated the survival of S. frugiperda larvae under different starvation time periods, and assessed their survival and biomass on U. ruziziensis (Ur) and U. brizantha (Ub) desiccated over different time periods. Our results showed that FAW larvae developed into pupae only when corn was offered for twelve days and during the total larval phase. However, larvae fed for eight days survived approximately 13 days. Larval survival decreased on Ub and Ur with increasing infestation time after desiccation. However, survival was higher on Ur. Also, larval biomass was lower on Ub at 7, 14 and 21 days after desiccation. The results obtained may have direct implications for FAW management.