Polyamine metabolism in BHK21/C13 cells : Loss of spermidine from cells following transfer to serum-depleted medium

The growth rate of BHK21/C13 cells in culture was slowed down by transferring growing cells to serum-depleted medium Following deprivation of serum, the intracellular concentration of polyamines decreased. The amount of spermidine relative to spermine decreased, and this change was the result of the spermidine content per cell decreasing more than the spermine content. The decrease in cell content of polyamines was accompanied by release of polyamines from the cells into the culture medium. The polyamines released were examined using cells whose polyamines had been labelled by prior incubation of the cells with radioactive putrescine. Almost all of the radioactivity released into the medium was found in spermidine, even though the cells contained most of their radioactivity in spermine. It is suggested that specific release of spermidine may be an important mechanism by which these cells can regulate their intracellular content of polyamines.     

Calmodulin activity in yeast and mycelial phases of Ceratocystis ulmi

Abstract The yeast and mycelial phases of Ceratocystis ulmi contained roughly equivalent levels of calmodulin activity as determined by their ability to stimulate calmodulin-deficient bovine brain cAMP phosphodiesterase. This stimulation was calcium-dependent and could be inhibited by either dibucaine or trifluoperazine. Also, the concentration of dibucaine necessary to achieve the mycelium-to-yeast morphological conversion was found to be 3-fold greater in the presence of exogenous calcium. A model is presented in which only 30% of the cellular calmodulin need be complexed with calcium ions for mycelial development.     

Stable transformation of papaya via microprojectile bombardment

Summary Stable transformation of papaya (Carica papaya L.) has been achieved following DNA delivery via high velocity microprojectiles. Three types of embryogenic tissues, including immature zygotic embryos, freshly explanted hypocotyl sections, and somatic embryos derived from both, were bombarded with tungsten particles carrying chimeric NPTII and GUS genes. All tissue types were cultured prior to and following bombardment on half-strength MS medium supplemented with 10 mg 1^–1 2,4-D, 400 mg 1^–1 glutamine, and 6% sucrose. Upon transfer to 2,4-D-free medium containing 150 mg 1^–1 kanamycin sulfate, ten putative transgenic isolates produced somatic embryos and five regenerated leafy shoots. Leafy shoots were produced six to nine months following bombardment. Tissues from 13 of these isolates were assayed for NPTII activity, and 10 were positive. Six out of 15 isolates assayed for GUS expression were positive. Three isolates were positive for both NPTII and GUS,Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid - GUS -glucuronidase - X-gluc 5-Br-4-Cl-3-indolyl--D-glucuronic acid - CaMV cauliflower mosaic virus - NOS nopaline synthase - NPTII neomycin phosphotransferase II Journal Series no. 3448 of the Hawaii Institute of Tropical Agriculture and Human Resources     

Effects of plant odor on oviposition by the black swallowtail butterfly,Papilio polyxenes (Lepidoptera: Papilionidae)

Black swallowtail females laid more eggs on plant models treated with contact stimulants and volatiles from carrot leaves than on models treated only with contact stimulants. The volatiles enhanced landing rates and females alighted more frequently on artificial leaves treated with host volatiles than on adjacent control leaves. Volatiles from cabbage, a nonhost, inhibited landing rates on artificial leaves treated with carrot contact stimulants. Examination of antennae revealed two major types of sensilla, believed to be olfactory in function. Electroantennogram preparations responded more strongly to carrot volatiles than to cabbage volatiles and several shared responses at particular retention times to carrot volatile components eluting from a gas chromatograph. Our results are consistent with a long-standing hypothesis that behavioral responses to essential oil components characteristic of the larval food plants have facilitated host shifts in the genus Papilio.     

Deriving phylogenetic trees from the similarity analysis of metabolic pathways

MOTIVATION: Comparative analysis of metabolic pathways in different genomes can give insights into the understanding of evolutionary and organizational relationships among species. This type of analysis allows one to measure the evolution of complete processes (with different functional roles) rather than the individual elements of a conventional analysis. We present a new technique for the phylogenetic analysis of metabolic pathways based on the topology of the underlying graphs. A distance measure between graphs is defined using the similarity between nodes of the graphs and the structural relationship between them. This distance measure is applied to the enzyme-enzyme relational graphs derived from metabolic pathways. Using this approach, pathways and group of pathways of different organisms are compared to each other and the resulting distance matrix is used to obtain a phylogenetic tree. RESULTS: We apply the method to the Citric Acid Cycle and the Glycolysis pathways of different groups of organisms, as well as to the Carbohydrate metabolic networks. Phylogenetic trees obtained from the experiments were close to existing phylogenies and revealed interesting relationships among organisms.     

High-resolution molecular epidemiology and evolutionary history of HIV-1 subtypes in Albania

Background

HIV-1 epidemic in Western Europe is largely due to subtype B. Little is known about the HIV-1 in Eastern Europe, but a few studies have shown that non-B subtypes are quite common. In Albania, where a recent study estimated a ten-fold increase of AIDS incidence during the last six years, subtype A and B account for 90% of the know infections.

Methodology/Principal Findings

We investigated the demographic history of HIV-1 subtype A and B in Albania by using a statistical framework based on coalescent theory and phylogeography. High-resolution phylogenetic and molecular clock analysis showed a limited introduction to the Balkan country of subtype A during the late 1980s followed by an epidemic outburst in the early 1990s. In contrast, subtype B was apparently introduced multiple times between the mid-1970s and mid-1980s. Both subtypes are growing exponentially, although the HIV-1A epidemic displays a faster growth rate, and a significantly higher basic reproductive number R₀. HIV-1A gene flow occurs primarily from the capital Tirane, in the center of the country, to the periphery, while HIV-1B flow is characterized by a balanced exchange between center and periphery. Finally, we calculated that the actual number of infections in Albania is at least two orders of magnitude higher than previously thought.

Conclusions/Significance

Our analysis demonstrates the power of recently developed computational tools to investigate molecular epidemiology of pathogens, and emphasize the complex factors involved in the establishment of HIV-1 epidemics. We suggest that a significant correlation exists between HIV-1 exponential spread and the socio-political changes occurred during the Balkan wars. The fast growth of a relatively new non-B epidemic in the Balkans may have significant consequences for the evolution of HIV-1 epidemiology in neighboring countries in Eastern and Western Europe.     

The roles of integration in molecular systems biology

A common way to think about scientific practice involves classifying it as hypothesis- or data-driven. We argue that although such distinctions might illuminate scientific practice very generally, they are not sufficient to understand the day-to-day dynamics of scientific activity and the development of programmes of research. One aspect of everyday scientific practice that is beginning to gain more attention is integration. This paper outlines what is meant by this term and how it has been discussed from scientific and philosophical points of view. We focus on methodological, data and explanatory integration, and show how they are connected. Then, using some examples from molecular systems biology, we will show how integration works in a range of inquiries to generate surprising insights and even new fields of research. From these examples we try to gain a broader perspective on integration in relation to the contexts of inquiry in which it is implemented. In today's environment of data-intensive large-scale science, integration has become both a practical and normative requirement with corresponding implications for meta-methodological accounts of scientific practice. We conclude with a discussion of why an understanding of integration and its dynamics is useful for philosophy of science and scientific practice in general.     

The role of monocyte/macrophages as vehicles of dissemination of Simkania negevensis: an in vitro simulation model

Exposure to Simkania negevensis (Sn), an intracellular microorganism that has been associated with respiratory tract infections in infants and adults, is prevalent. Sn can multiply within free-living amoebae and has been detected in domestic water supplies, which may constitute a source of infection with the organism. Its path of transport from its portal of entry to the body to its target organs is unknown. In this study, the possibility that monocytes/macrophages may serve as vehicles of transmission was examined. In vitro cocultivation of Sn-infected Acanthamoeba polyphaga with the monocyte/macrophage cell line U937 resulted in the death of the amoebae and infection of the U937 cells. Sn entered and multiplied in U937 cells within short periods of time, and the microorganism could be transferred from U937 cells to cell cultures of various origins. Uninfected monocyte/macrophages could become infected when in contact with either actively or persistently Sn-infected cell cultures. Persistently infected cultures in contact with uninfected U937 cells became actively infected. The results of this study provide a basis for determination of the molecular mechanisms of monocyte/macrophage-cell interactions in transfer of infection and may contribute to a better understanding of the pathogenesis of Sn infections in vivo.