Phenotypic diversification of a cultured tumor line as a function of substratum

We have found that a murine hepatoma displays a considerable phenotypic diversification in culture, which depends upon the substratum utilized, and is manifested by the formation of multicellular structures of differing geometry: Monolayer on glass and plastic, thick multilayer pads on Gelfilm, and spheroids on agar and agarose. These multicellular morphological phenotypes were assayed without disruption to ascertain their antigenicity in vitro and their tumorigenicity in vivo and to obtain quantitative information on the effect of the spatial arrangement of the hepatoma cells upon the ability of each multicellular structure to interact, as a whole, with molecules and cells in its surroundings. The antigenicity of the multicellular structures was determined with calibrated probes and a methodology that measures the total antigenicity, as well as antigenicity per unit of surface area. Antigenicity was found to differ in the following decreasing order: Monolayer on plastic > spheroids on agarose > spheroids on agar > multilayer on Gelfilm. At least part of these antigenic variants arise from different degrees of masking of the structures' surface determinants by a trypsin-sensitive material. The multicellular phenotypes also differed in tumorigenicity. When assayed in syngeneic hosts under comparable conditions, agar-grown spheroids produced the fewest tumors, whereas Gelfilm-grown multilayers produced the most. These two independent sets of data show that the various geometries that a tumor tissue is induced to acquire by the culture substratum are accompanied by a distinctive combination of surface and biological properties.     

High levels of arbuscular mycorrhizal fungus colonization on Medicago truncatula reduces plant suitability as a host for pea aphids (Acyrthosiphon pisum)

This study sheds light on a poorly understood area in insect-plant-microbe interactions,focusing on aphid probing and feeding behavior on plants with varying levels of arbuscular mycorrhizal(AM)fungus root colonization.It investigates a commonly occurring interaction of three species:pea aphid Acyrthosiphon pisum,barrel medic Medicago truncatula,and the AM fungus Rhizophagus irregularis,examining whether aphid-feeding behavior changes when insects feed on plants at different levels of AM fungus colonization(42% and 84% root length colonized).Aphid probing and feeding behavior was monitored throughout 8 h of recording using the electrical penetration graph(EPG)technique,also,foliar nutrient content and plant growth were measured.Summarizing,aphids took longer to reach their 1st sustained phloem ingestion on the 84% AM plants than on the 42% AM plants or on controls.Less aphids showed phloem ingestion on the 84% AM plants relative to the 42% AM plants.Shoots of the 84% AM plants had higher percent carbon(43.7%)relative to controls(40.5%),and the 84% AM plants had reduced percent nitrogen(5.3%)relative to the 42% AM plants(6%).In conclusion,EPG and foliar nutrient data support the hypothesis that modifications in plant anatomy(e.g.,thicker leaves),and poor food quality(reduced nitrogen)in the 84% AM plants contribute to reduced aphid success in locating phloem and ultimately to differences in phloem sap ingestion.This work suggests that M.truncatula plants benefit from AM symbiosis not only because of increased nutrient uptake but also because of reduced susceptibility to aphids.     

Feeding behavior,life history,and virus transmission ability of Bemisia tabaci Mediterranean species (Hemiptera: Aleyrodidae) under elevated CO2

The continuous rise of CO₂ concentrations in the atmosphere is reducing plant nutritional quality for herbivores and indirectly affects their performance. The whitefly (Bemisia tabaci, Gennadius) is a major worldwide pest of agricultural crops causing significant yield losses. This study investigated the plant‐mediated indirect effects of elevated CO₂ on the feeding behavior and life history of B. tabaci Mediterranean species. Eggplants were grown under elevated and ambient CO₂ concentrations for 3 weeks after which plants were either used to monitor the feeding behavior of whiteflies using the Electrical Penetration Graph technique or to examine fecundity and fertility of whiteflies. Plant leaf carbon, nitrogen, phenols and protein contents were also analyzed for each treatment. Bemisia tabaci feeding on plants exposed to elevated CO₂ showed a longer phloem ingestion and greater fertility compared to those exposed to ambient CO₂ suggesting that B. tabaci is capable of compensating for the plant nutritional deficit. Additionally, this study looked at the transmission of the virus Tomato yellow leaf curl virus (Begomovirus) by B. tabaci exposing source and receptor tomato plants to ambient or elevated CO₂ levels before or after virus transmission tests. Results indicate that B. tabaci transmitted the virus at the same rate independent of the CO₂ levels and plant treatment. Therefore, we conclude that B. tabaci Mediterranean species prevails over the difficulties that changes in CO₂ concentrations may cause and it is predicted that under future climate change conditions, B. tabaci would continue to be considered a serious threat for agriculture worldwide.     

Resprouting in the Mediterranean‐type shrub Erica australis afffected by soil resource availability

Abstract. Soil resource availability may affect plant regeneration by resprouting in disturbed environments directly, by affecting plant growth rates, or indirectly by determining allocation to storage in the resprouting organs. Allocation to storage may be higher in stressful, low resource‐supply soils, but under such conditions plant growth rates may be lower. These factors could act in opposite directions leading to poorly known effects on resprouting. This paper analyses the role played by soil resources in the production and growth of resprouts after removal of above‐ground plant tissues in the Mediterranean shrub Erica australis. At 13 sites, differing in substrate, we cut the base of the stems of six plants of E. australis and allowed them to resprout and grow for two years. Soils were chemically analysed and plant water potential measured during the summer at all sites to characterize soil resource availability. We used stepwise regression analysis to determine the relationships between the resprouting response [mean site values of the number of resprouts (RN), maximum length (RML) and biomass (RB)] and soil nutrient content and plant water potential at each site. During the first two years of resprouting there were statistically significant differences among sites in the variables characterizing the resprouting response. RML was always different among sites and had little relationship with lignotuber area. RN was less different among sites and was always positively correlated with lignotuber area. RB was different among sites after the two years of growth. During the first months of resprouting, RN and RML were highly and positively related to the water status of the plant during summer. At later dates soil fertility variables came into play, explaining significant amounts of variance of the resprouting variables. Soil extractable cations content was the main variable accounting for RML and RB. Our results indicate that resprout growth of E. australis is positively affected by high water availability at the beginning of the resprouting response and negatively so by high soil extractable cation content at later periods. Some of these factors had previously shown to be related, with an opposite sign, to the development of a relatively larger lignotuber. Indeed, RML and RB measured in the second year of resprouting were significantly and negatively correlated with some indices of biomass allocation to the lignotuber at each site. This indicates that sites favouring allocation to the resprouting organ may not favour resprout growth.     

Naloxone influences ultrasonic calling in young mice

The ultrasonic calls produced by three day old mice when separated from the nest mother and siblings increase in number when naloxone is injected.