Diet and foraging effort of Adélie penguins in relation to pack-ice conditions in the southern Ross Sea

We investigated the diet and aspects of foraging effort among Adélie penguins (Pygoscelis adeliae) breeding at three colonies on Ross Island, in the southwestern Ross Sea – Capes Royds, Bird and Crozier – during the chick-provisioning period of three austral summers, 1994–1995, 1995–1996 and 1996–1997. During the study period, pack-ice cover differed in waters offshore of these colonies, by colony, seasons and year. Diet differed among colonies only slightly. The fish Pleuragramma antarcticum was the most important prey, especially during years or periods within years when little pack ice was present. With respect to krill, which composed the remainder of diet, juvenile Euphausia crystallorophias were consumed predominantly in a year of heavy pack-ice cover; more adult krill were consumed in 2 years when pack ice was sparse. Foraging trip duration differed by colony, season and year and was related directly to distance from the colony to the nearest pack ice. The amount of food brought to chicks increased as trip duration increased, to a point (2 days), but then decreased as duration increased further (up to 4 days). On the basis of data on mass of parents and of meal sizes to chicks, it appeared that on the longest trips more of the food gathered by parents was used for self maintenance; on the longest trips, parents lost body mass. Successful foraging during chick rearing, the period when adult foraging is most intense, appears to depend on the proximity of pack ice to nesting colonies for this penguin species. Received: 1 October 1997 / Accepted: 25 April 1998     

Remodeling of Proteostasis Upon Transition to Adulthood is Linked to Reproduction Onset

Protein folding and clearance networks sense and respond to misfolded and aggregation-prone proteins by activating cytoprotective cell stress responses that safeguard the proteome against damage, maintain the health of the cell, and enhance lifespan. Surprisingly, cellular proteostasis undergoes a sudden and widespread failure early in Caenorhabditis elegans adulthood, with marked consequences on proteostasis functions later in life. These changes in the regulation of quality control systems, such as chaperones, the ubiquitin proteasome system and cellular stress responses, are controlled cell-nonautonomously by the proliferation of germline stem cells. Here, we review recent studies examining changes in proteostasis upon transition to adulthood and how proteostasis is modulated by reproduction onset, focusing on C. elegans. Based on these and our own findings, we propose that the regulation of quality control systems is actively remodeled at the point of transition between development and adulthood to influence the subsequent course of aging.     

A deep nursery for juveniles of the zebra angelfish <Emphasis Type="Italic">Genicanthus caudovittatus</Emphasis>

Juveniles of many coral reef fish species are thought to either follow the same bathymetric distribution patterns as the adults, or to occupy shallower waters. However, our knowledge base suffers a dearth of data from the deep reefs (>40 m). In a recent survey of the deep reefs of the northern Gulf of Aqaba (<65 m), we examined the bathymetric distribution of 26 diurnal zooplanktivorous species. In sharp contrast to the general trend known from the literature and from this research, the abundance of juvenile zebra angelfish, Genicanthus caudovittatus, peaked at deeper waters (60–65 m) compared with the adults (30 m). This suggests that the deeper reefs may serve as nursery grounds for the zebra angelfish. Peak juvenile abundance coincided with relatively low predator abundances. This raises the question, which factors constrain the bathymetric distribution of the remaining species. Our findings stress the potential importance of deep coral reef research for understanding the ecological patterns and processes that govern reef community structure.     

Exocytosis by vesicle crumpling maintains apical membrane homeostasis during exocrine secretion

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Biomechanical stimulation effects on the metabolism of adipocyte

Adipose tissue plays a leading role in obesity, which, in turn, can lead to Type 2 diabetes. Adipocytes (AD) respond to the biomechanical stimulation experienced in fat tissue under static stretch during prolonged sitting or lying. To investigate the effect of such chronic stimulation on adipocyte cell metabolism, we used an in vitro system to mimic the static stretch conditions. Under in vitro culture stretching, cells were analyzed at the single-cell level and we measured an increase in the projected area of the AD and higher content of lipid droplets. A decrease in the projected area of these cells’ nucleus is associated with peroxisome proliferator-activated receptor-gamma expression and heterochromatin. This is the first study to reveal proteins that were altered under static stretch following a mass spectrometry analysis and main pathways that affect cell fate and metabolism. Bioinformatics analysis of the proteins indicated an increase in mitochondrial activity and associated pathways under static stretch stimulation. Quantification of the mitochondrial activity by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) assay and the ATPase related proteins specifically measured ATP5B indicated an increase in adipogenesis which points to a higher rate of cell metabolism under static stretch. In summary, our results elaborate on the metabolism of AD exposed to biomechanical stimulation, that is, associated with altered cellular protein profile and thereby influenced cell fate. The static stretch stimulation accelerated adipocyte differentiation through increased mitochondrial activity. Hence, in this study, we introduce a new perspective in understanding the molecular regulation of mechano-transduction in adipogenesis.     

Analysis of protein synthesis dynamic model in eukaryotic cells: Input control

This paper presents the analysis of initiation control model of protein synthesis via eukaryotic initiation factor (eIF)-2 unit, introduced by [N.S. Bar, D.R. Morris, Dynamic model of the process of protein synthesis in eukaryoric cells, Bulletin of Mathematical Biology 69 (2007) 361-393, doi:10.1007/s11538-006-9128-2.] and propose methods to control it.Linearization of the model is presented as a measure to simplify the analysis and control application. The properties of the linear model were investigated and compared to the non-linear model using simulations. It was shown that the linear model is (marginally) stable and the states converge to a finite value. Linear optimal control theory can then be applied to the model under the value range where the linearized model is accurate. The effect of the input signals GCN2·tRNA and eIF-2 on the non-linear system was investigated. A few characteristics known from in vitro experiments of the initiation process were proven from a mathematical aspect and some conclusions about the function of the initiation complexes such as eIF2B and the ternary complex were derived. Consistent with published experiments, it was shown that overexpression of eIF-2 increases the concentration of 48S initiation complex and promote initiation rate. A state feedback control was applied in order to manipulate the initiation rate and it was proven that the 48S initiation complex can be driven to a desired value by calculating an input control law using measurement techniques available today. If this strategy can be implemented de facto, then a genuine control on protein synthesis process can be obtained.     

Long-term prediction of fish growth under varying ambient temperature using a multiscale dynamic model

Background  

Feed composition has a large impact on the growth of animals, particularly marine fish. We have developed a quantitative dynamic model that can predict the growth and body composition of marine fish for a given feed composition over a timespan of several months. The model takes into consideration the effects of environmental factors, particularly temperature, on growth, and it incorporates detailed kinetics describing the main metabolic processes (protein, lipid, and central metabolism) known to play major roles in growth and body composition.     

Apparent recruitment failure for the vast majority of coral species at Eilat,Red Sea

Coral Reefs - The status of coral reefs is often portrayed by parameters (e.g., coverage, bleaching, diseases, nutrients and rugosity) assigned to adult populations. Yet, coral recruitment is...