Lipid Storage and Utilization in Reptiles

Lipids represent a biochemically efficient mechanism for storingenergy to be used at a later date for maintenance and/or reproduction.This storage and utilization at different times results in seasonalpatterns of lipid cycling. Reptiles exhibit a number of lipidcycling patterns which can be explained by seasonal patternsof food availability. Seasonality in food availability determinesthe quantity of lipids stored, when lipids are stored, and forwhat purposes these lipids are utilized. Lipid cycling patternsare in turn correlated with life histories.     

Physiological Considerations of Lipid Storage and Utilization

Normally, rats and mice eat chow-type rations. When fed sucha ration, body fat usually ranges between 11 and 18%. If a semi-purifieddiet high in fat is fed instead of the chow-type ration, somestrains of rats and mice respond by accumulating abnormal amountsof weight and fat. Their bodies now contain as much as 40% fatand fat depots are enlarged. Rats which respond to a high fatdiet with excessive weight and fat gain consume more kilocaloriesin the same time interval and are more efficient in energy utilizationthan rats of the same strain which consume a grain diet. Forthese rats, if medium-chain triglycerides are substituted forthe long-chain triglycerides in the high fat diet, there isa depression in food intake, accretion of body weight and fatas well as energy utilization. Blood makes up 3.5 to 5.1% of the fat organ weight. The lowervalue represents the quantity present in adipose tissue of obeserats while the higher value is for "normal-weight" rats. Thetriglyceride content of perirenal and epididymal fat depotsis around 90%. On the other hand, the triglyceride content ofinguinal fat tissue ranges from 56 to 80% and is affected bystrain, age and diet. If diets are high in fat, the proportionaldistribution of fatty acids in the adipose tissue reflects theproportional distribution in dietary fat, except when medium-chaintriglycerides are fed.     

Translocation and Utilization of Fungal Storage Lipid in the Arbuscular Mycorrhizal Symbiosis

The arbuscular mycorrhizal (AM) symbiosis is responsible for huge fluxes of photosynthetically fixed carbon from plants to the soil. Carbon is transferred from the plant to the fungus as hexose, but the main form of carbon stored by the mycobiont at all stages of its life cycle is triacylglycerol. Previous isotopic labeling experiments showed that the fungus exports this storage lipid from the intraradical mycelium (IRM) to the extraradical mycelium (ERM). Here, in vivo multiphoton microscopy was used to observe the movement of lipid bodies through the fungal colony and to determine their sizes, distribution, and velocities. The distribution of lipid bodies along fungal hyphae suggests that they are progressively consumed as they move toward growing tips. We report the isolation and measurements of expression of an AM fungal expressed sequence tag that encodes a putative acyl-coenzyme A dehydrogenase; its deduced amino acid sequence suggests that it may function in the anabolic flux of carbon from lipid to carbohydrate. Time-lapse image sequences show lipid bodies moving in both directions along hyphae and nuclear magnetic resonance analysis of labeling patterns after supplying 13C-labeled glycerol to either extraradical hyphae or colonized roots shows that there is indeed significant bidirectional translocation between IRM and ERM. We conclude that large amounts of lipid are translocated within the AM fungal colony and that, whereas net movement is from the IRM to the ERM, there is also substantial recirculation throughout the fungus.     

Aspects of Lipid Metabolism in Crustaceans

Lipid is the predominant organic reserve of many crustaceansand is important in the metabolism of many of these animals.Ingested lipid is digested by gastric lipase and apparentlyabsorbed into depot-lipid as rß-monoglycerides. Thevariation in the content and composition of the depot-lipidis a function of both the external environment and internalcontrol systems. Evidence suggests that lipids from marine organismscontain more long-chain polyunsaturated fatty acids than doesthe lipid of fresh water organisms which in turn have a highproportion of C₁₆ and C₁₈ fatty acids. The fatty-acid compositionof the sub-tropical land crab,Gecarcinns lateralis, resemblesthat of the fresh-water crustaceans. In addition, our studiesindicate that aspects of lipid metabolism may be under endocrinecontrol. The induction of premolt by destalking markedly increasesthe synthesis of lipid from metabolic precursors and its subsequentincorporation into the depot-lipid of the hepatopancreas. Inthe late premolt stages there is a decrease in the lipid contentof the hepatopancreas. This occurs as the lipid is mobilizedfrom the hepatopancreas to meet the energy demands of all thoseprocesses resulting in ecdysis. This sinusoidal variation inthe lipid metabolism of the hepatopancreas is influenced byan eyestalk factor (s).     

Provocative Aspects of Pictures of Animals in Confined Settings

Abstract

The perceptual aspects of various animal pictures were studied to assess their aesthetic appeal in a high-fidelity interior mock-up of the proposed International Space Station. We examined a variety of mammals in light of two ecologically important attributes—the direction of their gazes and their apparent distance from the viewer—that could conceivably promote differences in subjective attitudes and sympathetic nervous system arousal, the latter reflected by changes in pupillary dilation. Another point of examination was the amount of picture area occupied by various birds and mammals. Slides were projected on a simulated video monitor, and subjects rated the images using scales of preference, interest, familiarity, and mock-up enhancement. Results showed that nearby, staring animals elicited more physiological arousal and less favorable attitudes than did nearby animals averting their gazes; animals staring from greater distances were clearly the most preferred, interesting, and provided the greatest mock-up enhancement. Animals occupying larger picture areas were more arousing than those occupying smaller areas, and, irrespective of scale, birds enhanced the mock-up more than mammals did. These findings suggest that pictures of animals, especially birds, can enhance the aesthetic appeal of confined, technical settings, though large pictures of nearby, staring mammals might create an inappropriately threatening context.     

Physiological and Biochemical Aspects of Halophyte Ecology

Physiological and biochemical features of euhalophytes, сrinohalophytes, and glycohalophytes growing in natural conditions in El’ton Lake area were studied. The water content in tissues, intensity of lipid peroxidation, and membrane permeability were found to determine the differentiation of plants by their salt accumulation strategy. The concentration of pigments and their ratio are related to the mesostructure of leaves and are dependent on the salt accumulation strategy and life form. The membrane complex is connected with the cell structure and photosynthetic apparatus. The specificity of ion transportation depends on the specific features of plants.     

Spider Venoms: Biochemical Aspects

SYNOPSIS. The venoms of spiders are quite complex and containan array of biologically active components. The majority ofstudies on the biochemical aspects of these venoms have utilizedfour species: Phoneutria fera, Lycosa erythrognatha, Atrax robustus,and Latrodectus mactans. They produce venoms which are lethalto mammals as well as arthropods. The following substances havebeen isolated from one or more of their venoms: a-aminobutyricacid, histamine, 5-hydroxytryptamine, spermine, proteases, hyaluronidase,phosphodiesterase, and toxic and lethal polypeptides. With thepossible exception of spermine, the lethality of these venomsappears to be the result of the actions of the polypeptides.The other substances apparently play a subsidiary role.     

Lysosomal Lipid Storage Diseases

Lysosomal lipid storage diseases, or lipidoses, are inherited metabolic disorders in which typically lipids accumulate in cells and tissues. Complex lipids, such as glycosphingolipids, are constitutively degraded within the endolysosomal system by soluble hydrolytic enzymes with the help of lipid binding proteins in a sequential manner. Because of a functionally impaired hydrolase or auxiliary protein, their lipid substrates cannot be degraded, accumulate in the lysosome, and slowly spread to other intracellular membranes. In Niemann-Pick type C disease, cholesterol transport is impaired and unesterified cholesterol accumulates in the late endosome. In most lysosomal lipid storage diseases, the accumulation of one or few lipids leads to the coprecipitation of other hydrophobic substances in the endolysosomal system, such as lipids and proteins, causing a “traffic jam.” This can impair lysosomal function, such as delivery of nutrients through the endolysosomal system, leading to a state of cellular starvation. Therapeutic approaches are currently restricted to mild forms of diseases with significant residual catabolic activities and without brain involvement.Lysosomal lipid storage diseases are a group of inherited catabolic disorders in which typically large amounts of complex lipids accumulate in cells and tissues. Macromolecules such as complex lipids and oligosaccharides are constitutively degraded in the acidic compartments of the cell, the endosomes, and lysosomes, into their building blocks. The resulting catabolites are exported to the cytosol and reused in cellular metabolism. When lysosomal function is impaired because of a defect in a catabolic step, degradation cannot proceed normally and undegraded compounds accumulate. Lysosomal lipid storage diseases comprise mainly the sphingolipidoses, Niemann-Pick type C disease (NPC), and Wolman disease, including the less severe form of this disease, called cholesteryl ester storage. NPC is a complex lipid storage disease mainly characterized by the accumulation of unesterified cholesterol in the late endosomal/lysosomal compartment (Bi and Liao 2010). The sphingolipidoses are caused by defects in genes encoding proteins involved in the lysosomal degradation of sphingolipids (Kolter and Sandhoff 2006). First reports on these diseases were given more than a century ago. Already in 1881, Warren Tay described the clinical symptoms of a disease, which is today called Tay-Sachs disease (Tay 1881). After Christian de Duve discovered the lysosome in 1955 (de Duve 2005), Henri-Géry Hers established the first correlation between an enzyme deficiency and a lysosomal storage disorder (Pompe’s disease) in 1963 (Hers 1963). In the following decades, the enzymes and cofactors deficient in the sphingolipidoses have been identified. Though lysosomal lipid storage diseases have been known for a long time, treatment is only available for a few mild forms of the diseases, such as the adult forms of Gaucher disease (Barton et al. 1991). For several lysosomal storage diseases, therapies like enzyme replacement or bone marrow transplantation are in the clinical trial stage (Platt and Lachmann 2009). For a long time, lysosomal diseases have been considered a problem of superabundance (storage) in which the storage material can slowly spread to other cellular membranes, impairing their function. More recently, it came into focus that massive storage prevents lysosomal functions such as nutrition delivery through the endolysosomal system, leading to a state of cellular starvation. In mouse models of both GM1 and GM2 gangliosidoses iron is progressively depleted in brain tissue. Administration of iron prolonged survival in the diseased mice by up to 38% (Jeyakumar et al. 2009).