Selective Defecation and Selective Foraging: Antiparasite Behavior in Wild Ungulates?

Selective defecation and selective foraging are two potential antiparasite behaviors used by grazing ungulates to reduce infection by fecal–oral transmitted parasites. While there is some evidence that domestic species use these strategies, less is known about the occurrence and efficacy of these behaviors in wild ungulates. In this study, I examined whether wild antelope use selective defecation and selective foraging strategies to reduce exposure to gastrointestinal nematode parasites. By quantifying parasite levels in the environment in relation to the defecation patterns of three species, dik‐dik (Madoqua kirkii), Grant's gazelle (Gazella granti), and impala (Aepyceros melampus), I found that nematode larval concentrations in pasture were higher in the vicinity of clusters of feces (dung middens) compared to single fecal pellet groups or dung‐free areas. In addition, experimental feeding trials in free‐ranging dik‐dik showed that individuals selectively avoided feeding near concentrations of feces. Given that increased parasite contamination was found in the immediate vicinity of fecal clusters, fecal avoidance could help reduce host consumption of parasites and may therefore be an effective antiparasite behavior for certain species. On the other hand, while the concentration of parasite larvae in the vicinity of middens coupled with host avoidance of these areas during grazing could reduce host contact with parasites, results showing a positive correlation between the number of middens in a habitat and larval abundance at control sites suggest that dung middens might increase and not decrease overall host exposure to parasites. If this is the case, dung midden formation may not be a viable antiparasite strategy.     

The Occurence of δ-Tocopherylquinone in Higher Plants and Its Relation to Senescence

δ-Tocopherylquinone (δTQ) content was determined in tobacco and yellow maple leaves, green ivy leaves and cactus tissues. It was found that the concentration of δ-TQ was highest in mature or senescent tissues, such as white tobacco leaves (0.02 μmole/g dry wt) while its detection was uncertain in young, green leaves from the apex of tobacco plants. Fractionation by centrifugation of senescent tobacco leaves showed that the osmiophilic globule fraction was enriched in δ-TQ. Electron microscope studies of young, mature and senescent tobacco tissues showed progressive changes in the size and number of osmiophilic globules. After chloroplast breakdown in senescent tobacco leaves, these globules became the predominant constituents of the organelle. δ-TQ which is associated with osmiophilic globules may play a role in the development of plants, particularly during senescence.     

Breast Tumor Heterogeneity: Cancer Stem Cells or Clonal Evolution?

Breast tumors are composed of a variety of cell types with distinct morphologies and behaviors. It is not clear how this tumor heterogeneity comes about. Two popular concepts that attempt to explain this are the cancer stem cell hypothesis and the clonal evolution model. Each of these ideas has been investigated for some time, leading to the accumulation of numerous findings that are used to support one or the other. Although the two views share some similarities, they are fundamentally different notions with very different clinical implications. Analysis of the research backing each concept, along with a review of the results of our recent study investigating putative breast cancer stem cells, suggests how the cancer stem cell hypothesis and the clonal evolution model may be involved in generating breast tumor heterogeneity. An understanding of this process will allow the development of more effective ways to treat and prevent breast cancer.     

Do Physiological Integration and Soil Heterogeneity Influence the Clonal Growth and Foraging of <Emphasis Type="Italic">Schoenoplectus pungens</Emphasis>?

Physiological integration and foraging behavior have both been proposed as advantages for clonal growth in heterogeneous environments. We tested three predictions concerning their short- and long-term effects on the growth of the clonal perennial sedge Schoenoplectus pungens (Pers.) Volk. ex Schinz and R. Keller: (1) growth would be greatest for clones with connected rhizomes and on heterogeneous soil, (2) clones would preferentially place biomass in the nutrient-rich patches of a spatially heterogeneous environment, and (3) physiological integration would decrease a clone’s ability to forage. We tested our predictions by growing S. pungens clones for 2 years in an experimental garden with two severing treatments (connected and severed rhizomes) crossed with two soil treatments (homogeneous and heterogeneous nutrient distribution). Severing treatments were only carried out in the first year. As predicted, severing significantly decreased total biomass and per capita growth rate in year one and individual ramet biomass both in year one and the year after severing stopped. This reduction in growth was most likely caused by severing damage, because the total biomass and growth rate in severed treatments did not vary with soil heterogeneity. Contrary to our prediction, total biomass and number of ramets were highest on homogeneous soil at the end of year two, regardless of severing treatment, possibly because ramets in heterogeneous treatments were initially planted in a nutrient-poor patch. Finally, as predicted, S. pungens concentrated ramets in the nutrient-rich patches of the heterogeneous soil treatment. This foraging behavior seemed enhanced by physiological integration in the first year, but any possible enhancement disappeared the year after severing stopped. It seems that over time, individual ramets become independent, and parent ramets respond independently to the conditions of their local microsite when producing offspring, a life-history pattern that may be the rule for clonal species with the spreading “guerrilla” growth form.     

The Development of Sociobiology in Relation to Animal Behavior Studies, 1946–1975

This paper aims at bridging a gap between the history of American animal behavior studies and the history of sociobiology. In the post-war period, ecology, comparative psychology and ethology were all investigating animal societies, using different approaches ranging from fieldwork to laboratory studies. We argue that this disunity in “practices of place” (Kohler, Robert E. Landscapes & Labscapes: Exploring the Lab-Field Border in Biology. Chicago: University of Chicago Press, 2002) explains the attempts of dialogue between those three fields and early calls for unity through “sociobiology” by J. Paul Scott. In turn, tensions between the naturalist tradition and the rising reductionist approach in biology provide an original background for a history of Edward Wilson’s own version of sociobiology, much beyond the William Hamilton’s papers (Journal of Theoretical Biology 7: 1–16, 17–52, 1964) usually considered as its key antecedent. Naturalists were in a defensive position in the geography of the fields studying animal behavior, and in reaction were a driving force behind the various projects of synthesis called “sociobiology”.     

Does Physiological Integration Enable Clonal Herbs to Integrate the Effects of Environmental Heterogeneity?

Abstract The effects of physiological integration on clone behaviour are examined at various structural scales, using data from the stoloniferous herb Glechoma hederacea . The consequences for clone expansion of traumatic fragmentation of the connections between clonal ramets are also illustrated. These results, together with information from other species, are used to refute the commonly-quoted view that physiological integration between the ramets of clonal herbs evens out the effects of variation in environmental quality, and promotes equitable ramet performance. Instead, clonal species are responsive, at a variety of structural scales, to environmental quality. Therefore, in a heterogeneous habitat, within-clone variation in the performance of ramets and clonal sub-structures is to be expected. The seminal study which purports to demonstrate environmental averaging in clonal herbs is shown to be both inadequately designed and inappropriately analysed to accomplish its aim.
Physiological and architectural reasons for the local responses to environmental quality seen in the majority of clonal herbs are discussed.     

Foraging in honeybees--when does it pay to dance?

Honeybees are unique in that they are the only social insectsthat are known to recruit nest mates using the waggle dance.This waggle dance is used by successful foragers to convey informationabout both the direction and distance to food sources. Nestmates can use this spatial information, increasing their chancesof locating the food source. But how effective is the bees'dance communication? Previous work has shown that dancing doesnot benefit a honeybee colony under all foraging conditionsand that the benefits of dancing are small. We used an individual-basedsimulation model to investigate under which foraging conditionsit pays to dance. We compared the net nectar intake of 3 typesof colonies: 1) colonies that use dance communication; 2) coloniesthat did dance but could not use the dance's spatial information;and 3) colonies that did not dance. Our results show that dancingis beneficial when the probability of independent discoveryof food sources is low. Low independent discovery rates occurwhen patches are very small or very far away. Under these conditions,dancing is beneficial as only a single individual needs to finda patch for the whole colony to benefit. The main benefit ofthe honeybee's dance communication, however, seems to be thatit enables the colony to forage at the most profitable patchesonly, ignoring forage patches that are of low quality. Thus,dancing allows the colony to rapidly exploit high-quality patches,thereby preventing both intra- and interspecific competitorsfrom using that same patch.     

Progress of Study on Chitosan in Regulating Plants’Growth and Eliciting Plants’Defense Responses

Important effect of chitosan on regulating plant growth , eliciting plant resistance to disease and it’s possible operating mechanism are reviewed . Chitosan shows evidence physiological effect on the key enzymes of ammonia assimilation and enhances the amination capacity in plant, which is in favor of biology synthesize and accumulation of protein . Thus , chitosan improves nutrition quality and horticulture properties of plant . Moreover , chitosan rapidly stimulates plant defense responses , then startups defensive system and elevates resistance to disease . To a further understanding of the mechanism of chitosan on plant , we have isolated and determined some biochemical properties of a chitosan-bingding protein .     

Resource Capture by Localized Root Proliferation: Why Do Plants Bother?

Using data from a well-known, published experiment [Drew (1975)TheNew Phytologist75: 479–490], the potential exploitationof locally available nutrients by barley roots is calculated.Local proliferation of lateral roots does not necessarily achievesignificantly greater exploitation of mobile soil resourceslike nitrate, but it does for less mobile ones such as phosphate.Despite this, the magnitude of the proliferative response isas great to locally available nitrate as it is to phosphate.This implies an ‘over-production’ of roots in responseto localized nitrate availability, prompting a re-evaluationof the nature and implications of the response mechanism(s)of roots to soil heterogeneity. Hordeum vulgare; barley; carbon; heterogeneity; lateral root; nitrate; localized nutrient supply; phosphate; proliferation; root     

PIP Aquaporin Gene Expression in Arbuscular Mycorrhizal Glycine max and Lactuca sativa Plants in Relation to Drought Stress Tolerance

Although the discovery of aquaporins in plants has resulted in a paradigm shift in the understanding of plant water relations, the relationship between aquaporins and plant responses to drought still remains elusive. Moreover, the contribution of aquaporin genes to the enhanced tolerance to drought in arbuscular mycorrhisal (AM) plants has never been investigated. Therefore, we studied, at a molecular level, whether the expression of aquaporin-encoding genes in roots is altered by the AM symbiosis as a mechanism to enhance host plant tolerance to water deficit. In this study, genes encoding plasma membrane aquaporins (PIPs) from soybean and lettuce were cloned and their expression pattern studied in AM and nonAM plants cultivated under well-watered or drought stressed conditions. Results showed that AM plants responded to drought stress by down-regulating the expression of the PIP genes studied and anticipating its down-regulation as compared to nonAM plants. The possible physiological implications of this down-regulation of PIP genes as a mechanism to decrease membrane water permeability and to allow cellular water conservation is further discussed.     

Foraging in surfperches: resource partitioning or individualistic responses?

Synopsis On Naples Reef off southern California, five sympatric species of surfperch (Embiotocidae) eat small animal prey associated with algal turf and other benthos. Although they tend to select different foods in different microhabitats, their different foraging traits are probably individualistic responses (non-interactive or autecological species responses to resources) because the species' pairwise resource overlaps are neither uniformly small nor generally complementary. Mean overlap in both food and foraging microhabitat was significantly greater than random as most species converged in resource use. Only two exploiters of extremes in the available spectra of prey types and microhabitats had significantly narrow overlap. Thus, resource overlaps may simply reflect similarities and differences in the species' independently evolved foraging traits, which were rendered more or less inflexible as different morphological specializations for picking, crunching, or winnowing prey. Therefore, any one species may occur about the reef to its best advantage independently of the others. Its distribution and abundance may simply reflect its tolerance of the local environment. The evidence indicates that the surfperches are not concertedly partitioning resources on Naples Reef, i.e., that the five species had not all coevolved to avoid interspecific competition in the past nor have they all mutually shifted their niches to minimize it in the present.     

Recruitment Behavior During Foraging in the Neotropical Ant Gnamptogenys moelleri (Formicidae: Ponerinae): Does the Type of Food Matter?

Gnamptogenys moelleri nests in bromeliads and feeds on an array of food items, including dead and live animals, and nectar. Field data in Brazilian forests indicate that G. moelleri hunts solitarily, while retrieving is performed both by solitary workers for small items, or by a group of recruited workers for large items. This flexible foraging strategy was investigated in the laboratory through a series of experiments to assess the context in which recruitment is elicited. Three types of food were used: 50% honey solution, large insect prey, and cluster of small insects. For all food types the first encounter by a scout resulted in increased numbers of ants leaving the nest and finding the food in the arena. After finding liquid food or large prey, the forager returns to the nest and transmits information to nestmates about food location on the substrate. The successful scout repeatedly taps the sting on the ground, and recruited ants collectively retrieve the large insect to the nest. On the other hand, there is no transmission of information to nestmates about the location of small clumped prey, although the returning scout induces nestmates to leave the nest and hunt. Because foraging in G. moelleri is restricted mostly to the nest bromeliad, and small worker size (0.5 cm) precludes capturing large prey solitarily, recruitment behavior widens the spectrum of food items consumed by this ant species. Although recruitment behavior in ponerines has already been reported to vary with the type and size of a food source, this study also shows that the transmission of information about food location depends on the type of food found (large prey or liquid food versus cluster of small prey).     

Cadmium Toxicity in Plants: Is There any Analogy to its Carcinogenic Effect in Mammalian Cells?

Cadmium is a heavy metal, which is classified as a human carcinogen and is known to be toxic to plants. However, plants do not respond to this metal by massive cell proliferation. In this review the various aspects of cadmium toxicity in plants are compared to related processes in mammalian cells. The following issues are discussed: cellular uptake of Cd ions, their intracellular transport, the effects on cellular signaling, nucleic acids and proteins, modification of gene expression, cell cycle control and apoptosis. Reviewed data suggest that such features as: ability to remove the oxidized proteins, slightly different regulation of cell cycle genes, specific pattern of apoptosis, makes plants resistant to Cd²⁺-induced uncontrolled cell proliferation.     

Negative Regulation of Human Astrocytes by Interferon (IFN) α in Relation to Growth Inhibition and Impaired Glucose Utilization

The present study assessed the direct effects of IFNs on human astrocytes. Human astrocytes were exposed to human recombinant IFNs, and the proliferation of cells was measured. Type I IFN receptor mRNA and protein expression, the phosphoprotein levels of signaling molecules including JNK, ERK1/2, IκB, p38MAPK, Stat3, and the expression of cytokines were determined respectively. In addition, cellular glucose consumption was measured as well as Glut-1 protein and activation of GSK-3β/mTOR signal were determined. The expression of Type I IFN receptor was detected in cultured human astrocytes. 2?IU/ml IFNα2a and IFNα2b significantly decreased the proliferation of human astrocytes respectively, compared to control. IFNβ had no significant effect on the proliferation of the cells. The phosphorylation of JNK stimulated by all IFNs detected was more pronounced and sustained than ERK1/2 and IκB. No effects were observed on the activation of p38MAPK and Stat3. Moreover, Treatment with IFNα, especially with IFNα2b, decreased glucose consumption and stimulated phosphorylation of GSK-3β and mTOR, but decreased the expression of Glut-1. In contrast, IFNβ had no significant effect on either glucose consumption or activation of GSK-3β/mTOR signals. INFα2b significantly decreased the levels of IL-8 whereas the levels of GM-CSF were increased. The present study demonstrates direct inhibitory effects of IFNα on cell proliferation, cell signaling and glucose utilization in human astrocytes.     

Inhibitory Effects of Cycasin on Germination,Growth and α-Amylase Biosynthesis in Rice Plants

Cycasin, the toxic glycoside of cycad plants, interfered with seed germination and seedling growth of Gramineae, Crucifereae and Leguminosae. The shoots and roots of seedlings showed wilting, chlorosis and necrosis. Rice plants were most sensitive and soybean plants rather tolerant.

Respiration and α-amylase activity were markedly low in the rice seedlings treated with cycasin. Both cycasin and its aglycone, methylazoxymethanol, did not inhibit the activity of α-amylase, but did suppress the formation of α-amylase in rice endosperms. Exogenous gibberellin considerably reversed the inhibition of germination and growth, and the suppression of α-amylase formation caused by these toxins.     

Growth-Defense Tradeoffs in Plants： A Balancing Act to Optimize Fitness

Growth-defense tradeoffs are thought to occur in plants due to resource restrictions, which demand prior- itization towards either growth or defense, depending on external and internal factors. These tradeoffs have profound implications in agriculture and natural ecosystems, as both processes are vital for plant survival, reproduction, and, ulti- mately, plant fitness. While many of the molecular mechanisms underlying growth and defense tradeoffs remain to be elucidated, hormone crosstalk has emerged as a major player in regulating tradeoffs needed to achieve a balance. In this review, we cover recent advances in understanding growth-defense tradeoffs in plants as well as what is known regard- ing the underlying molecular mechanisms. Specifically, we address evidence supporting the growth-defense tradeoff concept, as well as known interactions between defense signaling and growth signaling. Understanding the molecular basis of these tradeoffs in plants should provide a foundation for the development of breeding strategies that optimize the growth-defense balance to maximize crop yield to meet rising global food and biofuel demands.     

Heterogeneity of depolymerized heparin SEC fractions: to pool or not to pool?

In the structural analysis of heparin and heparan sulfate, it is customary to combine or pool like-sized fractions obtained by size-exclusion chromatography (SEC) of enzymatically derived heparin oligosaccharides. In this study, we examine the heterogeneity of preparative-scale SEC fractions obtained from enzymatic digests of porcine intestinal mucosa heparin. Each fraction was profiled by capillary electrophoresis with UV detection (CE−UV) using a 60 mM formic acid running buffer at pH 3.43. Differences in the composition and relative concentration of components of the SEC fractions were observed for disaccharides and larger oligosaccharides. The heterogeneity of the fractions becomes more pronounced when heparin is digested using a heparin lyase cocktail. The heterogeneity of preparative SEC fractions was further investigated by reversed-phase ion-pairing ultraperformance liquid chromatography coupled with mass spectrometry (RPIP−UPLC−MS) using the ion-pairing reagent, tributylamine (Bu₃N). Our results suggest that preliminary profiling of preparative SEC fractions prior to pooling may simplify efforts to identify and/or isolate rare structures.     

Does ABA in the Xylem Control the Rate of Leaf Growth in Soil-Dried Maize and Sunflower Plants?

Maize (Zea mays L.) and sunflower (Helianthus annuus L.) plantswere grown in large volumes of soil and leaf growth rate wasmonitored on a daily basis. Half the plants were given a soildrying treatment and when they showed a significant restrictionof growth rate (compared to both their daily growth rate beforedrying and the average growth rate of well-watered plants onthe same day), leaf water relations were measured and xylemsap was extracted using several techniques. There was a significant negative log-linear relationship betweenthe rate of leaf growth and the concentration of ABA in thexylem for both species. There was no clear relationship betweenleaf growth rate and leaf water potential or turgor for eitherspecies. Assessment of different methods for sampling xylemsap suggests that exudates collected from stem stumps or samplescollected by pressurizing the whole root system are suitablefor estimating ABA concentration in xylem, at least with largeplants of maize or sunflower, provided the first few hundredcubic millimetres of collected sap are used for the assay. Centrifugationof sections of stems resulted in dilution of ABA in the xylemsap with sap squeezed from parenchyma tissue. This is because,at least in plants subjected to mild soil drying, the concentrationof the ABA in the xylem is far higher than that in the cellsap of stem tissue. Results support the proposal that ABA plays a major role asa chemical signal involved in the root-to-shoot communicationof the effects of soil drying. The non-hydraulic restrictionof leaf growth by a chemical signal can be explained by theextra root-sourced ABA in the xylem and may be an importantcomponent of the modification of growth and development whichresults from prolonged soil drought. Key words: Soil drying, ABA, leaf growth, Zea mays L., Helianthus annuus L.