Natural variation in decision-making behavior in Drosophila melanogaster

There has been considerable recent interest in using Drosophila melanogaster to investigate the molecular basis of decision-making behavior. Deciding where to place eggs is likely one of the most important decisions for a female fly, as eggs are vulnerable and larvae have limited motility. Here, we show that many natural genotypes of D. melanogaster prefer to lay eggs near nutritious substrate, rather than in nutritious substrate. These preferences are highly polymorphic in both degree and direction, with considerable heritability (0.488) and evolvability.Relative preferences are modulated by the distance between options and the overall concentration of ethanol, suggesting Drosophila integrate many environmental factors when making oviposition decisions. As oviposition-related decisions can be efficiently assessed by simply counting eggs, oviposition behavior is an excellent model for understanding information processing in insects. Associating natural genetic polymorphisms with decision-making variation will shed light on the molecular basis of host choice behavior, the evolutionary maintenance of genetic variation, and the mechanistic nature of preference variation in general.     

The influence of gibberellic acid and sulfur fertilization rate on growth and S-use efficiency of mustard (<Emphasis Type="Italic">Brassica juncea</Emphasis>)

Earlier research has shown that exogenous gibberellic acid (GA₃) application increases shoot growth, photosynthesis and soil nitrogen (N) utilisation in mustard (Brassica juncea L. Czern & Coss.). Mustard has a high sulfur (S) requirement. Its assimilatory pathway is well coordinated with N and dependent on photosynthesis. Thus, the higher photosynthate production and an efficient use of N with the use of GA₃ could result in an increase in S-use efficiency of the crop. The research was, therefore, carried out to study the effects of 10~M GA₃ spray on specific leaf area, plant dry mass, leaf carbon dioxide exchange rate (CER), plant growth rate (PGR), relative growth rate (RGR), net assimilation rate (NAR) and S-use efficiency (SUE) of mustard treated with 0, 100 or 200 mg S kg^–1 soil levels. Plants treated with 100~mg S kg^–1 soil and receiving GA₃ treatment showed increased specific leaf area and dry mass accumulation compared to the control. At 0~mg S kg^–1 soil, N and S concentrations were reduced. They increased with increasing S supply. GA₃ application significantly increased N and S concentrations further. A two-fold increase in SUE in GA₃-treated plants at 100~mg S kg^–1 soil was noted in comparison to the control. SUE was not increased under excess S conditions beyond 100~mg S kg^–1 soil. The increase in SUE was through increase in the growth, CER and use efficiency of N by the crop due to GA₃ application.     

Fenretinide prevents lipid-induced insulin resistance by blocking ceramide biosynthesis

Fenretinide is a synthetic retinoid that is being tested in clinical trials for the treatment of breast cancer and insulin resistance, but its mechanism of action has been elusive. Recent in vitro data indicate that fenretinide inhibits dihydroceramide desaturase, an enzyme involved in the biosynthesis of lipotoxic ceramides that antagonize insulin action. Because of this finding, we assessed whether fenretinide could improve insulin sensitivity and glucose homeostasis in vitro and in vivo by controlling ceramide production. The effect of fenretinide on insulin action and the cellular lipidome was assessed in a number of lipid-challenged models including cultured myotubes and isolated muscles strips incubated with exogenous fatty acids and mice fed a high-fat diet. Insulin action was evaluated in the various models by measuring glucose uptake or disposal and the activation of Akt/PKB, a serine/threonine kinase that is obligate for insulin-stimulated anabolism. The effects of fenretinide on cellular lipid levels were assessed by LC-MS/MS. Fenretinide negated lipid-induced insulin resistance in each of the model systems assayed. Simultaneously, the drug depleted cells of ceramide, while promoting the accumulation of the precursor dihydroceramide, a substrate for the reaction catalyzed by Des1. These data suggest that fenretinide improves insulin sensitivity, at least in part, by inhibiting Des1 and suggest that therapeutics targeting this enzyme may be a viable therapeutic means for normalizing glucose homeostasis in the overweight and diabetic.     

Identification and regulation of a molecular module for bleb-based cell motility

Single-cell migration is a key process in development, homeostasis, and disease. Nevertheless, the control over basic cellular mechanisms directing cells into motile behavior in?vivo is largely unknown. Here, we report on the identification of a minimal set of parameters the regulation of which confers proper morphology and cell motility. Zebrafish primordial germ cells rendered immotile by knockdown of Dead end, a negative regulator of miRNA function, were used as a platform for identifying processes restoring motility. We have defined myosin contractility, cell adhesion, and cortex properties as factors whose proper regulation is sufficient for restoring cell migration of this cell type. Tight control over the level of these cellular features, achieved through a balance between miRNA-430 function and the action of the RNA-binding protein Dead end, effectively transforms immotile primordial germ cells into polarized cells that actively migrate relative to cells in their environment.     

Photosynthetic Rate, Growth, and Yield of Mustard Plants Sprayed with 28-Homobrassinolide

Thirty-day-old plants of mustard (Brassica juncea L.) were sprayed with 10⁻¹⁰, 10⁻⁸, or 10⁻⁶ M aqueous solution of 28-homobrassinolide (HBR). The HBR-treated plants were healthier than those treated with water and yielded more. Maximum increase over control was found in 60-d-old, 10⁻⁸ M-HBR-treated plants in fresh and dry mass per plant, carbonic anhydrase (CA, E.C. 4.2.1.1) activity, and net photosynthetic rate (P _N), at harvest in number of pods per plant and seed yield per plant (the respective values were 25, 30, 34, 69, 24, and 29 %). A further increase in the concentration of HBR (10⁻⁶ M) did not make any additional impact on the growth and yield. Increased CA activity and P _N were correlated with growth and seed yield. This revised version was published online in August 2006 with corrections to the Cover Date.     

MPDB 1.0: a medicinal plant database of Bangladesh

The term of medicinal plants include a various types of plants used in herbalism with medicinal activities. These plants are considered as rich resources of ingredients which can be used as complementary and alternative medicines and, also in drug developments and synthesis. In addition, some plants regarded as valuable origin of nutrition. Thus, all these plants are recommended as therapeutic agents. Information related to medicinal plants and herbal drugs accumulated over the ages are scattered and unstructured which make it prudent to develop a curated database for medicinal plants. MPDB 1.0 database is dedicated to provide the first window to find the plants around Bangladesh claimed to have medicinal and/or nutritive values by accumulating data from the published literatures. This database contains 406 medicinal plants with their corresponding scientific, family and local names as well as utilized parts for treatment from different districts of Bangladesh. Information regarding ailments is available for 353 plants. In addition, we have found active compounds for 78 plants with their corresponding PubMed ID.

Availability

www.medicinalplantbd.net     

Cattle selectivity by leopards suggests ways to mitigate human–leopard conflict

Addressing widespread livestock losses to carnivores requires information on which livestock categories are preferentially selected. We analyzed an individual‐based database of cattle grazing in forest (n = 932) and having been killed (n = 70) by leopards (Panthera pardus) in the Hyrcanian forest, Iran. We calculated Jacobs’ selectivity index for cattle age, sex, and coloration across four scales: the study area as a whole, three sites, nine villages, and 60 cattle owners. Naturally colored cattle were significantly preferred by leopards at all scales in comparison with black and black‐and‐white cattle, and there was also a preference for males and juveniles at the study area level. More research is needed to see whether cattle losses would decrease if the share of naturally colored individuals in local holdings was reduced and males and juveniles had limited access to forest. We conclude that phenotypic and biologic characteristics of livestock can affect depredation and appeal for more research in this direction, particularly within the predator–prey framework.     

Effects of sucrose, inoculum density, auxins, and aeration volume on ceil growth ofGymnema sylvestre

To improve the cell protocol forCymnema sylvestre, we investigated the influence of initial sucrose concentration, inoculum density, and optimal concentrations of auxins (IBA and NAA) in flask cultures, as well as the role of aeration volume in bioreactor cultures. Cell growth was enhanced 9-fold when the medium was supplemented with 3% sucrose versus a sucrose-free environment. Increasing the inoculum density to 60 g (wet weight) L^-1, but no further, greatly improved the growth of these cultures. All concentrations of IBA proved inhibitory while supplementation with 5 nig L^-1 NAA was associated with significantly higher dry-cell weights. In our bioreactor cultures, a step-wise increase in aeration volume from 0.05 to 0.40 wm was optimal for cell growth. Although biomass (i.e., fresh weight) accumulated in the bioreactor up until Day 20, the dry-cell weights increased 10-fold, but only through Day 15. The internal dynamics of our culture media indicated that sucrose was preferentially utilized and that its concentration steeply decreased at the log phase. In contrast, both glucose and fructose supplies were exhausted only at the beginning of the declining phase. Our findings suggest that a 15-d culture period is optimal for G.sylvestre cell growth in a bioreactor.     

Ceramides and Glucosylceramides Are Independent Antagonists of Insulin Signaling

Inhibitors of sphingolipid synthesis protect mice from diet induced-insulin resistance, and sphingolipids such as ceramides and glucosylated-ceramides (e.g., GM3) are putative nutritional intermediates linking obesity to diabetes risk. Herein we investigated the role of each of these sphingolipids in muscle and adipose tissue and conclude that they are independent and separable antagonists of insulin signaling. Of particular note, ceramides antagonize insulin signaling in both myotubes and adipocytes, whereas glucosyceramides are only efficacious in adipocytes: 1) In myotubes exposed to saturated fats, inhibitors of enzymes required for ceramide synthesis enhance insulin signaling, but those targeting glucosylceramide synthase have no effect. 2) Exogenous ceramides antagonize insulin signaling in myotubes, whereas ganglioside precursors do not. 3) Overexpression of glucosylceramide synthase in myotubes induces glucosylceramide but enhances insulin signaling. In contrast, glucosylated ceramides have profound effects in adipocytes. For example, either ganglioside addition or human glucosylceramide synthase overexpression suppresses insulin signaling in adipocytes. These data have important mechanistic implications for understanding how these sphingolipids contribute to energy sensing and the disruption of anabolism under conditions of nutrient oversupply.