Comparison of the Cathepsin D from Mackerel (Scomber australasicus) and Milkfish (Chanos chanos) Muscle

Muscle proteases from mackerel and milkfish were purified to electrophoretical homogeneity by concanavalin A-Sepharose and Sephadex G-100 chromatographies. Both proteases appear to be an aspartic protease, cathepsin D (EC 3.4.23.5). The molecular weights of the purified cathepsin D’s from mackerel and milkfish were 51,000 and 54,000, estimated by Sephadex G-100, and 59,000 and 61,000 by SDS–PAGE, respectively. Both cathepsin D’s were completely inhibited by pepstatin, but not affected by leupeptin, N-ethylmaleimide, dithiothreitol, or glutathione. ß-Mercaptoethanol, iodoacetic acid, p-chloromercuri-benzoate, phenylmethylsulfonyl fluoride, and sodium dodecyl sulfate partially or completely inhibited both cathepsin D’s. Na⁺ and K⁺ partially activated the cathepsin D from milkfish. Both cathepsin D’s were inhibited by Mg²⁺, Sr²⁺, Fe²⁺, and H²⁺, but activated by Ca²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, and Cd²⁺. The pI and optimal temperature of the cathepsin D’s from mackerel and milkfish were 5.04 and 4.91, 45°, and 50°C, respectively. The temperatures for inactivating 50% activity of the cathepsin D’s from mackerel and milkfish during 20 min of incubation were 53° and 48°C, respectively. Both cathepsin D’s had similar optimal pHs near 3. The activity of that from milkfish markedly decreased when the pH was higher than 4, and was almost completely lost at pH above 6, while that from mackerel still had at least 40% activity at pH 6.     

Comparative Effects of Dietary Fat Types on Hepatic Enzyme Activities Related to the Synthesis and Oxidation of Fatty Acid and to Lipogenesis in Rats

The effects of different types of dietary fat on the activities of hepatic enzymes related to fatty acid synthesis {glucose-6-phosphate dehydrogenase (G6PDH) and acetyl-CoA carboxylase ACC)}, oxidation {acyl-CoA synthetase (AST), carnitine palmitoyl transferase (CPT), and peroxisomal β-oxidation (P βOX)}, and lipogenesis {phosphatidate phosphohydrolase (PAP), diacylglycerol acyltransferase (DGAT), and phosphocholine diacylglycerol transferase (PCDGT)}, and plasma and liver lipid levels were investigated in male Wistar rats. The animals were 6 weeks old and about 120 g of body weight, and were fed on test diets containing 20% of a mixture of tripalmitin, tristearin and corn oil (SFA), olive oil (OLI), sunflower oil (SUN), linseed oil (LIS), and sardine oil (SAR) for 2 weeks. The concentrations of plasma total cholesterol (T-CHOL), high-density lipoprotein-cholesterol (HDL-CHOL), triacylglycerol (TG) and phospholipid (PL) were generally higher in the rats fed on SEA and OLI than in those given SUN, LIS and SAR. The rats fed on OLI had a higher level of liver T-CHOL than those fed on the other fats. The liver TG content was nearly higher from the intake of SFA and OLI than from SUN, LIS and SAR, although the liver PL level was not affected by the type of dietary fat. The SFA and OLI groups had the highest activities of hepatic G6PDH and ACC, and the SAR group, the lowest activities. The activities of AST and CPT, and peroxisomal P βOX in the liver were higher in the rats fed on the LIS and SAR diets than in those given the other diets. The hepatic PAP activity was higher from the intake of OLI and SUN, and tended to be higher from SFA than from LIS and SAR. The activity of liver DGAT was higher from SFA and inclined to be higher from OLI, SUN, and LIS than from SAR, while the PCDGT activity in the liver was not effected by the type of dietary fat. The concentrations of plasma and liver TG were generally positively correlated with the activities of liver enzymes related to the synthesis of fatty acids and lipids, and negatively with those involved in fatty acid oxidation. Based on these results, it is suggested that the levels of plasma and liver TG were controlled by different types of dietary fat through changes in the hepatic enzyme activities related to fatty acid synthesis, lipogenesis, and fatty acid oxidation.     

Antioxidative and Prooxidative Activity of Caffeic Acid toward H2O2-induced DNA Strand Breakage Dependent on the State of the Fe Ion in the Medium

Hen egg lysozyme–carboxymethyl dextran (HEL–CMD) conjugate was prepared by using water-soluble carbodiimide as a model protein-acidic polysaccharide conjugate for improving the protein function. An acid-amide bond between HEL and CMD was confirmed by SDS-PAGE, isoelectric focusing and IR spectra. The molar ratio of CMD to HEL in the conjugate was 1:1. The isoelectric point of the conjugate was 5.5–6.0, which is much lower than that of HEL. Spectroscopic studies suggested that the conformation around the Trp residue had not changed but the α-helix content had decreased to about 1/3 that for native HEL. The conjugate maintained about 60% of the enzymatic activity of native HEL at 40–60°C, while it was about 1.4 times as active as native HEL at 4°C and 80°C. The conjugate was more stable to proteolysis than native HEL. The denaturation temperature of the conjugate was about 73°C, which is almost the same as that of native HEL. However, the enthalpy for denaturation of the conjugate was about 1/3 that of native HEL, which corresponds to the decrease in α-helix content.     

Condition‐dependent expression of pre‐ and postcopulatory sexual traits in guppies

Female choice can impose persistent directional selection on male sexually selected traits, yet such traits often exhibit high levels of phenotypic variation. One explanation for this paradox is that if sexually selected traits are costly, only the fittest males are able to acquire and allocate the resources required for their expression. Furthermore, because male condition is dependent on resource allocation, condition dependence in sexual traits is expected to underlie trade‐offs between reproduction and other life‐history functions. In this study we test these ideas by experimentally manipulating diet quality (carotenoid levels) and quantity in the guppy (Poecilia reticulata), a livebearing freshwater fish that is an important model for understanding relationships between pre‐ and post‐copulatory sexually selected traits. Specifically, we test for condition dependence in the expression of pre‐ and postcopulatory sexual traits (behavior, ornamentation, sperm traits) and determine whether diet manipulation mediates relationships among these traits. Consistent with prior work we found a significant effect of diet quantity on the expression of both pre‐ and postcopulatory male traits; diet‐restricted males performed fewer sexual behaviors and exhibited significant reductions in color ornamentation, sperm quality, sperm number, and sperm length than those fed ad libitum. However, contrary to our expectations, we found no significant effect of carotenoid manipulation on the expression of any of these traits, and no evidence for a trade‐off in resource allocation between pre‐ and postcopulatory episodes of sexual selection. Our results further underscore the sensitivity of behavioral, ornamental, and ejaculate traits to dietary stress, and highlight the important role of condition dependence in maintaining the high variability in male sexual traits.     

A simple model predicting individual weight change in humans

Excessive weight in adults is a national concern with over 2/3 of the US population deemed overweight. Because being overweight has been correlated to numerous diseases such as heart disease and type 2 diabetes, there is a need to understand mechanisms and predict outcomes of weight change and weight maintenance. A simple mathematical model that accurately predicts individual weight change offers opportunities to understand how individuals lose and gain weight and can be used to foster patient adherence to diets in clinical settings. For this purpose, we developed a one-dimensional differential equation model of weight change based on the energy balance equation paired to an algebraic relationship between fat-free mass and fat mass derived from a large nationally representative sample of recently released data collected by the Centers for Disease Control. We validate the model's ability to predict individual participants’ weight change by comparing model estimates of final weight data from two recent underfeeding studies and one overfeeding study. Mean absolute error and standard deviation between model predictions and observed measurements of final weights are less than 1.8±1.3 kg for the underfeeding studies and 2.5±1.6 kg for the overfeeding study. Comparison of the model predictions to other one-dimensional models of weight change shows improvement in mean absolute error, standard deviation of mean absolute error, and group mean predictions. The maximum absolute individual error decreased by approximately 60% substantiating reliability in individual weight-change predictions. The model provides a viable method for estimating individual weight change as a result of changes in intake and determining individual dietary adherence during weight-change studies.     

Phylogenetic beta diversity in bacterial assemblages across ecosystems: deterministic versus stochastic processes

Increasing evidence has emerged for non-random spatial distributions of microbes, but knowledge of the processes that cause variation in microbial assemblage among ecosystems is lacking. For instance, some studies showed that deterministic processes such as habitat specialization are important, while other studies hold that bacterial communities are assembled by stochastic forces. Here we examine the relative influence of deterministic and stochastic processes for bacterial communities from subsurface environments, stream biofilm, lake water, lake sediment and soil using pyrosequencing of the 16S ribosomal RNA gene. We show that there is a general pattern in phylogenetic signal in species ecological niches across recent evolutionary time for all studied habitats, enabling us to infer the influences of community assembly processes from patterns of phylogenetic turnover in community composition. The phylogenetic dissimilarities among-habitat types were significantly higher than within them, and the communities were clustered according to their original habitat types. For communities within-habitat types, the highest phylogenetic turnover rate through space was observed in subsurface environments, followed by stream biofilm on mountainsides, whereas the sediment assemblages across regional scales showed the lowest turnover rate. Quantifying phylogenetic turnover as the deviation from a null expectation suggested that measured environmental variables imposed strong selection on bacterial communities for nearly all sample groups. For three sample groups, spatial distance reflected unmeasured environmental variables that impose selection, as opposed to spatial isolation. Such characterization of spatial and environmental variables proved essential for proper interpretation of partial Mantel results based on observed beta diversity metrics. In summary, our results clearly indicate a dominant role of deterministic processes on bacterial assemblages and highlight that bacteria show strong habitat associations that have likely emerged through evolutionary adaptation.     

Morphological and niche divergence of pinyon pines

The environmental variables that define a species ecological niche should be associated with the evolutionary patterns present in the adaptations that resulted from living in these conditions. Thus, when comparing across species, we can expect to find an association between phylogenetically independent phenotypic characters and ecological niche evolution. Few studies have evaluated how organismal phenotypes might mirror patterns of niche evolution if these phenotypes reflect adaptations. Doing so could contribute on the understanding of the origin and maintenance of phenotypic diversity observed in nature. Here, we show the pattern of niche evolution of the pinyon pine lineage (Pinus subsection Cembroides); then, we suggest morphological adaptations possibly related to niche divergence, and finally, we test for correlation between ecological niche and morphology. We demonstrate that niche divergence is the general pattern within the clade and that it is positively correlated with adaptation.     

Horseshoe crab phylogeny and independent colonizations of fresh water: ecological invasion as a driver for morphological innovation

Xiphosurids are an archaic group of aquatic chelicerate arthropods, generally known by the colloquial misnomer of ‘horseshoe crabs’. Known from marine environments as far back as the early Ordovician, horseshoe crabs are generally considered ‘living fossils’ – descendants of a bradytelic lineage exhibiting little morphological or ecological variation throughout geological time. However, xiphosurids are known from freshwater sediments in the Palaeozoic and Mesozoic; furthermore, the contention that xiphosurids show little morphological variation has never been tested empirically. Attempts to test this are hampered by the lack of a modern phylogenetic framework with which to explore different evolutionary scenarios. Here, I present a phylogenetic analysis of Xiphosurida and explore patterns of morphospace and environmental occupation of the group throughout the Phanerozoic. Xiphosurids are shown to have invaded non‐marine environments independently at least five times throughout their evolutionary history, twice resulting in the radiation of major clades – bellinurines and austrolimulids – that occupied novel regions of morphospace. These clades show a convergent ecological pattern of differentiation, speciation and subsequent extinction. Horseshoe crabs are shown to have a more dynamic and complex evolutionary history than previously supposed, with the extant species representing only a fraction of the group's past ecological and morphological diversity.