Mitochondrial-membrane polar-head-group composition is influenced by diet fat.

Male Sprague-Dawley rats were fed diets containing 20% (w/w) soya-bean oil, high-erucic acid rapeseed oil or low-erucic acid rapeseed oil for 0, 12 or 23 days. The type of fat present in the diet had no effect on the total phospholipid content of heart mitochondria (micrograms/mg of protein) but did influence the phospholipid class distribution. Rats fed high-erucic acid rapeseed oil for 12 or 23 days had significantly higher mitochondrial phosphatidylcholine content than rats fed soya-bean oil. Low-erucic acid rapeseed oil resulted in elevation of cardiac mitochondrial cardiolipin content after dietary treatment for 12 days. The results demonstrate in vivo that diet is a significant determinant of the phospholipid class content of subcellular membranes.     

Bacillus megaterium spore germination is influenced by inoculum size

AIMS: The effect of spore density on the germination (time-to-germination, percent germination) of Bacillus megaterium spores on tryptic soy agar was determined using direct microscopic observation. METHODS AND RESULTS: Inoculum size varied from approximately 10(3) to 10(8) cfu ml(-1) in a medium where pH=7 and the sodium chloride concentration was 0.5% w/v. Inoculum size was measured by global inoculum size (the concentration of spores on a microscope slide) and local inoculum size (the number of spores observed in a given microscope field of observation). Both global and local inoculum sizes had a significant effect on time-to-germination (TTG), but only the global inoculum size influenced the percentage germination of the observed spores. CONCLUSIONS: These results show that higher concentrations of Bacillus megaterium spores encourage more rapid germination and more spores to germinate, indicating that low spore populations do not behave similarly to high spore populations. SIGNIFICANCE AND IMPACT OF THE STUDY: A likely explanation for the inoculum size-dependency of germination would be chemical signalling or quorum sensing between Bacillus spores.     

Responsiveness of cardiometabolic-related microbiota to diet is influenced by host genetics

Intestinal microbial community structure is driven by host genetics in addition to environmental factors such as diet. In comparison with environmental influences, the effect of host genetics on intestinal microbiota, and how host-driven differences alter host metabolism is unclear. Additionally, the interaction between host genetics and diet, and the impact on the intestinal microbiome and possible down-stream effect on host metabolism is not fully understood, but represents another aspects of inter-individual variation in disease risk. The objectives of this study were to investigate how diet and genetic background shape microbial communities, and how these diet- and genetic-driven microbial differences relate to cardiometabolic phenotypes. To determine these effects, we used the 8 progenitor strains of the collaborative cross/diversity outbred mapping panels (C57BL/6J, A/J, NOD/ShiLtJ, NZO/HILtJ, WSB/EiJ, CAST/EiJ, PWK/PhJ, and 129S1/SvImJ). 16s rRNA profiling of enteric microbial communities in addition to the assessment of phenotypes central to cardiometabolic health was conducted under baseline nutritional conditions and in response to diets varying in atherogenic nutrient (fat, cholesterol, cholic acid) composition. These studies revealed strain-driven differences in enteric microbial communities which were retained with dietary intervention. Diet–strain interactions were seen for a core group of cardiometabolic-related microbial taxa. In conclusion, these studies highlight diet and genetically regulated cardiometabolic-related microbial taxa. Furthermore, we demonstrate the progenitor model is useful for nutrigenomic-based studies and screens seeking to investigate the interaction between genetic background and the phenotypic and microbial response to diet.     

Longevity is not influenced by prenatal programming of body size

Insulin‐like growth factor (IGF) signaling is essential for achieving optimal body size during fetal development, whereas, in the adult, IGFs are associated with aging and age‐related diseases. However, it is unclear as to what extent lifespan is influenced by events that occur during development. Here, we provide direct evidence that the exceptional longevity of mice with altered IGF signaling is not linked to prenatal programming of body size. Mice null for pregnancy‐associated plasma protein‐A (PAPP‐A), an IGF‐binding protein proteinase that increases local IGF bioavailability, are 60–70% the size of their wild‐type littermates at birth and have extended median and maximum lifespan of 30–40%. In this study, PAPP‐A^?/? mice whose body size was normalized during fetal development through disruption of IgfII imprinting did not lose their longevity advantage. Adult‐specific moderation of IGF signaling through PAPP‐A inhibition may present a unique opportunity to improve lifespan without affecting important aspects of early life physiology.     

Rat brain gamma-secretase activity is highly influenced by detergents

Gamma-secretase is important for the development of Alzheimer's disease, since it is a crucial enzyme for the generation of the pathogenic amyloid beta-peptide (Abeta). Most data on gamma-secretase is derived from studies in cell lines overexpressing gamma-secretase components or amyloid precursor protein (APP), and since gamma-secretase is a transmembrane protein complex, detergents have been frequently used to facilitate the studies. However, no extensive comparison of the influence of different detergents at different concentrations on gamma-secretase activity in preparations from brain has been made. Here, we establish the optimal conditions for gamma-secretase activity in rat brain, using an activity assay detecting endogenous production of the APP intracellular domain, which is generated when gamma-secretase cleaves the APP C-terminal fragments. We performed a subcellular fractionation and noted the highest gamma-secretase activity in the 100000g pellet and that the optimal pH was around 7. We found that gamma-secretase was active for at least 16 h at 37 degrees C and that the endogenous substrate levels were sufficient for activity measurements. The highest activity was obtained in 0.4% CHAPSO, which is slightly below the critical micelle concentration (0.5%) for this detergent, but the complex was not solubilized efficiently at this concentration. On the other hand, 1% CHAPSO solubilized a substantial amount of the gamma-secretase components, but the activity was low. The activity was fully restored by diluting the sample to 0.4% CHAPSO. Therefore, using 1% CHAPSO for solubilization and subsequently diluting the sample to 0.4% is an appropriate procedure for obtaining a soluble, highly active gamma-secretase from rat brain.     

Coevolving avian eye size and brain size in relation to prey capture and nocturnality

Behavioural adaptation to ecological conditions can lead to brain size evolution. Structures involved in behavioural visual information processing are expected to coevolve with enlargement of the brain. Because birds are mainly vision-oriented animals, we tested the predictions that adaptation to different foraging constraints can result in eye size evolution, and that species with large eyes have evolved large brains to cope with the increased amount of visual input. Using a comparative approach, we investigated the relationship between eye size and brain size, and the effect of prey capture technique and nocturnality on these traits. After controlling for allometric effects, there was a significant, positive correlation between relative brain size and relative eye size. Variation in relative eye and brain size were significantly and positively related to prey capture technique and nocturnality when a potentially confounding variable, aquatic feeding, was controlled statistically in multiple regression of independent linear contrasts. Applying a less robust, brunching approach, these patterns also emerged, with the exception that relative brain size did not vary with prey capture technique. Our findings suggest that relative eye size and brain size have coevolved in birds in response to nocturnal activity and, at least partly, to capture of mobile prey.     

Intestinal microbiota composition in fishes is influenced by host ecology and environment

The digestive tracts of vertebrates are colonized by complex assemblages of micro-organisms, collectively called the gut microbiota. Recent studies have revealed important contributions of gut microbiota to vertebrate health and disease, stimulating intense interest in understanding how gut microbial communities are assembled and how they impact host fitness (Sekirov et al. 2010). Although all vertebrates harbour a gut microbiota, current information on microbiota composition and function has been derived primarily from mammals. Comparisons of different mammalian species have revealed intriguing associations between gut microbiota composition and host diet, anatomy and phylogeny (Ley et al. 2008b). However, mammals constitute <10% of all vertebrate species, and it remains unclear whether similar associations exist in more diverse and ancient vertebrate lineages such as fish. In this issue, Sullam et al. (2012) make an important contribution toward identifying factors determining gut microbiota composition in fishes. The authors conducted a detailed meta-analysis of 25 bacterial 16S rRNA gene sequence libraries derived from the intestines of different fish species. To provide a broader context for their analysis, they compared these data sets to a large collection of 16S rRNA gene sequence data sets from diverse free-living and host-associated bacterial communities. Their results suggest that variation in gut microbiota composition in fishes is strongly correlated with species habitat salinity, trophic level and possibly taxonomy. Comparison of data sets from fish intestines and other environments revealed that fish gut microbiota compositions are often similar to those of other animals and contain relatively few free-living environmental bacteria. These results suggest that the gut microbiota composition of fishes is not a simple reflection of the micro-organisms in their local habitat but may result from host-specific selective pressures within the gut (Bevins & Salzman 2011).     

Interspecies avian brain chimeras reveal that large brain size differences are influenced by cell-interdependent processes

Like humans, birds that exhibit vocal learning have relatively delayed telencephalon maturation, resulting in a disproportionately smaller brain prenatally but enlarged telencephalon in adulthood relative to vocal non-learning birds. To determine if this size difference results from evolutionary changes in cell-autonomous or cell-interdependent developmental processes, we transplanted telencephala from zebra finch donors (a vocal-learning species) into Japanese quail hosts (a vocal non-learning species) during the early neural tube stage (day 2 of incubation), and harvested the chimeras at later embryonic stages (between 9-12 days of incubation). The donor and host tissues fused well with each other, with known major fiber pathways connecting the zebra finch and quail parts of the brain. However, the overall sizes of chimeric finch telencephala were larger than non-transplanted finch telencephala at the same developmental stages, even though the proportional sizes of telencephalic subregions and fiber tracts were similar to normal finches. There were no significant changes in the size of chimeric quail host midbrains, even though they were innervated by the physically smaller zebra finch brain, including the smaller retinae of the finch eyes. Chimeric zebra finch telencephala had a decreased cell density relative to normal finches. However, cell nucleus size differences between each species were maintained as in normal birds. These results suggest that telencephalic size development is partially cell-interdependent, and that the mechanisms controlling the size of different brain regions may be functionally independent.     

Bovine ovarian follicular fluid vitronectin content is influenced by the follicle size

Vitronectin was quantified in the follicular fluid aspirated from bovine follicles with diameters of 3 to 15 mm (as determined by ultrasonography) using a specific enzyme-linked immunosorbent assay (ELISA) validated for bovine vitronectin. The primary antibody was raised in rabbit against vitronectin purified from bovine plasma. Vitronectin quantified in serial dilutions of bovine plasma and ovarian follicular fluid was highly correlated with the volume of each sample assayed. In addition, known amounts of purified bovine vitronectin added to samples of plasma or follicular fluid were accurately recovered. Follicular fluid concentrations of vitronectin were positively correlated with the follicle diameter (r = 0.8; P < 0.01). These data indicate that bovine follicular fluid concentration of vitronectin is influenced by the stage of follicular development.     

The apparent target size of rat brain benzodiazepine receptor, acetylcholinesterase, and pyruvate kinase is highly influenced by experimental conditions

Radiation inactivation is a method to determine the apparent target size of molecules. In this report we examined whether radiation inactivation of various enzymes and brain receptors is influenced by the preparation of samples preceding irradiation. The apparent target sizes of endogenous acetylcholinesterase and pyruvate kinase from rat brain and from rabbit muscle and benzodiazepine receptor from rat brain were investigated in some detail. In addition the target sizes of alcohol dehydrogenase (from yeast and horse liver), beta-galactosidase (from Escherichia coli), lactate dehydrogenase (endogenous from rat brain), and 5-HT2 receptors, acetylcholine muscarine receptors, and [35S] butyl bicyclophosphorothionate tertiary binding sites from rat brain were determined. The results show that apparent target sizes are highly influenced by the procedure applied for sample preparation before irradiation. The data indicate that irradiation of frozen whole tissue as opposed to lyophilized tissue or frozen tissue homogenates will estimate the smallest and most relevant functional target size of a receptor or an enzyme.     

The conformation of apolipoprotein A-I in high-density lipoproteins is influenced by core lipid composition and particle size: a surface plasmon resonance study

Plasma high-density lipoproteins (HDL) are a heterogeneous group of particles that vary in size as well as lipid and apoprotein composition. The effect of HDL core lipid composition and particle size on apolipoprotein (apo) A-I structure was studied using surface plasmon resonance (SPR) analysis of the binding of epitope-defined monoclonal antibodies. The association and dissociation rate constants of 12 unique apo A-I-specific monoclonal antibodies for isolated plasma HDL were calculated. In addition, the association rate constants of the antibodies were determined for homogeneous preparations of spherical reconstituted HDL (rHDL) that contained apo A-I as the sole apolipoprotein and differed either in their size or in their core lipid composition. This analysis showed that lipoprotein size affected the conformation of domains dispersed throughout the apo A-I molecule, but the conformation of the central domain between residues 121 and 165 was most consistently modified. In contrast, replacement of core cholesteryl esters with triglyceride in small HDL modified almost the entire molecule, with only two key N-terminal domains of apo A-I being unaffected. This finding suggested that the central and C-terminal domains of apo A-I are in direct contact with rHDL core lipids. This immunochemical analysis has provided valuable insight into how core lipid composition and particle size affect the structure of specific domains of apo A-I on HDL.     

Pheromone production by male Tribolium castaneum (Coleoptera: Tenebrionidae) is influenced by diet quality

Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae), the red flour beetle, is a common cosmopolitan pest exploiting a variety of stored products. We experimentally manipulated diet nutritional quality by using non-nutritive filler to examine how this influenced pheromone production and olfactory attractiveness of T. castaneum adult males. Volatiles released by individual males reared on high versus low nutrition diets were collected using solid phase microextraction, and gas chromatography coupled to mass spectrometry was used to identify and quantify the Tribolium aggregation pheromone 4, 8-dimethyldecanal (DMD). Males kept on high nutrition diet showed a three-fold increase in daily DMD production, which suggests the possibility that this pheromone could act as a condition-dependent mating signal. In pitfall trap assays, there was no significant difference in the mean response of virgin females to discs kept with low versus high nutrition males, although discs carrying male cues were significantly more attractive than blank discs. These results suggest that DMD production rates by T. castaneum males will depend on the nutritional quality of various stored products, but such differences may not alter males' ability to attract females.     

The influence of prey identity and size on selection of prey by two marine fishes

Laboratory experiments were conducted with two predatory fishes, Lagodon rhomboides (Linnaeus) and Syngnathus floridae (Jordan & Gilbert), to determine if prey selection was a result of predator preference or prey accessibility. Prey consisted of two species of caridean shrimp, Tozeuma carolinense (Kingsley) and Hippolyte zostericola (Smith), that commonly inhabit seagrass meadows. Natural diets of both predators revealed that selection ofTozeuma and Hippolyte was not related to their field densities. My experiments demonstrated that natural prey selection was a consequence of prey accessibility, not predator preference. Experiments examining the role of prey size in predator preference revealed that large individuals were significantly preferred over small individuals. Observations of prey behavior indicated that prey motion affected predator choice. These results suggest that predator preference was primarily determined by prey visibility and that the combined effects of prey size and motion contributed to the visibility of these prey.     

A community-level evaluation of the impact of prey behavioural and ecological characteristics on predator diet composition

Although predation avoidance is the most commonly invoked explanation for vertebrate social evolution, there is little evidence that individuals in larger groups experience lower predation rates than those in small groups. We compare the morphological and behavioural traits of mammal prey species in the Taï forest, Ivory Coast, with the diet preferences of three of their non-human predators: leopards, chimpanzees and African crowned eagles. Individual predators show marked differences in their predation rates on prey species of different body sizes, but clear patterns with prey behaviour were apparent only when differences in prey habitat use were incorporated into the analyses. Leopard predation rates are highest for terrestrial species living in smaller groups, whereas eagle predation rates are negatively correlated with group size only among arboreal prey. When prey predation rates are summed over all three predators, terrestrial species incur higher predation rates than arboreal species and, within both categories, predation rates decline with increasing prey group size and decreasing density of groups in the habitat. These results reveal that it is necessary to consider anti-predator strategies in the context of a dynamic behavioural interaction between predators and prey.     

Improved felid embryo development by group culture is maintained with heterospecific companions

Domestic cat embryos of excellent quality appear to improve development of conspecific embryos when cultured together, providing an avenue for improving development of embryos from valuable species or individuals. To have relevance to rare species, it would be useful to understand if this advantage could be conferred by heterospecific companions because there usually are severely limited numbers of conspecific embryos available from wildlife donors. In the first study, we incubated single test cat embryos alone (controls) or with 10 cat embryos or 10 or 20 mouse embryos under similar regimented conditions (each group shared 20 microl medium). In the second study, single test cat embryos were cultured alone, with 10 conspecific or 20 mouse embryos or 10 cattle embryos (each group shared 20 microl medium). Single test embryos in all treatment groups achieved similar (P>0.05) stages of compaction and blastocyst development. In the first study, only the test embryos incubated with 10 cat or 20 mouse companion embryos achieved blastocyst expansion. The average total cell number within test embryos incubated with 10 cat or 20 mouse companions was greater (P<0.05) than controls or those placed with 10 mouse embryos. In the second study, test embryos in all groups achieved blastocyst expansion and had more (P<0.05) total cells per embryo than the solitary controls. Inner cell mass to trophoblast cell ratio did not differ among treatments in either study. Thus, companion mouse and cattle embryos selected for excellent quality confer a benefit to singleton cat embryos, although the number of companions necessary to grant an advantage may be species dependent. If this phenomenon can be extrapolated across species, this may be an avenue for 'common animal embryos' to improve developmental potential of embryos from rare, unrelated taxa.     

Intestinal immune system of young rats influenced by cocoa-enriched diet

Gut-associated lymphoid tissue (GALT) maintains mucosal homeostasis by counteracting pathogens and inducing a state of nonresponsiveness when it receives signals from food antigens and commensal bacteria. We report for the first time the influence of continuous cocoa consumption on GALT function in rats postweaning. Weaned Wistar rats were fed cocoa-enriched diets (4% or 10% food intake) for 3 weeks. The function of the primary inductive sites of GALT, such as Peyer's patches (PP) and mesenteric lymph nodes (MLN), was evaluated through an analysis of IgA-secretory ability and lymphocyte composition (T, B and natural killer cells), activation (IL-2 secretion and IL-2 receptor alpha expression) and proliferation. T-helper effector cell balance was also established based on cytokine profile (interferon gamma, IL-4 and IL-10) after mitogen activation. A 10% cocoa intake induced significant changes in PP and MLN lymphocyte composition and function, whereas a 4% cocoa diet did not cause significant modifications in either tissues. Cocoa diet strongly reduced secretory IgA (S-IgA) in the intestinal lumen, although IgA's secretory ability was only slightly decreased in PP. In addition, the 10% cocoa diet increased T-cell-antigen receptor gammadelta cell proportion in both lymphoid tissues. Thus, cocoa intake modulates intestinal immune responses in young rats, influencing gammadelta T-cells and S-IgA production.