Persistence to anti-cancer treatments in the stationary to proliferating transition

The heterogeneous responses of clonal cancer cells to treatment is understood to be caused by several factors, including stochasticity, cell-cycle dynamics, and different micro-environments. In a tumor, cancer cells may encounter fluctuating conditions and transit from a stationary culture to a proliferating state, for example this may occur following treatment. Here, we undertake a quantitative evaluation of the response of single cancerous lymphoblasts (L1210 cells) to various treatments administered during this transition. Additionally, we developed an experimental system, a “Mammalian Mother Machine,” that tracks the fate of thousands of mammalian cells over several generations under transient exposure to chemotherapeutic drugs. Using our developed system, we were able to follow the same cell under repeated treatments and continuously track many generations. We found that the dynamics of the transition between stationary and proliferative states are highly variable and affect the response to drug treatment. Using cell-cycle markers, we were able to isolate a subpopulation of persister cells with distinctly higher than average survival probability. The higher survival rate encountered with cell-cycle phase specific drugs was associated with a significantly longer time-till-division, and was reduced by a non cell-cycle specific drug. Our results suggest that the variability of transition times from the stationary to the proliferating state may be an obstacle hampering the effectiveness of drugs and should be taken into account when designing treatment regimens.     

Effects of Hydroxyurea on the Ultrastructure of Giant Cells in Galls Induced by Meloidogyne javanica

Hydroxyurea (HU) at concentrations of 10 or 20 mg/liter was included in a medium on which excised tomato roots infected with the root-knot nematode Meloidogyne javanica were grown. In the HU, treated roots, giant cells were small and contained large vacuoles. Giant cell nuclei were amoeboidal with relatively small nucleoli in treated roots, compared with giant cells of nontreated galls. In treated-root giant cells, the cytoplasm was diffuse and few organelles such as mitochondria, dictyosomes, and endoplasmic reticulum were detected; also, walls of giant cells were thin with less extensive ingrowths than in nontreated roots. We conclude that HU suppressed normal giant cell formation interfering with its function as a feeding cell.     

New hydrazone derivatives of adriamycin and their immunoconjugates--a correlation between acid stability and cytotoxicity

New N-substituted hydrazine linkers were synthesized and their hydrazone derivatives of adriamycin were prepared. These functionalized adriamycin derivatives were conjugated with a monoclonal antibody, 5E9. The release rate of adriamycin from the hydrazones and from some of the conjugates was studied, and their relationship to the IC50's of the conjugate against 5E9-positive Daudi cells was investigated.     

A socio‐ecological model for predicting impacts of land‐use and climate change on regional plant diversity in the Austrian Alps

Climate and land‐use change jointly affect the future of biodiversity. Yet, biodiversity scenarios have so far concentrated on climatic effects because forecasts of land use are rarely available at appropriate spatial and thematic scales. Agent‐based models (ABMs) represent a potentially powerful but little explored tool for establishing thematically and spatially fine‐grained land‐use scenarios. Here, we use an ABM parameterized for 1,329 agents, mostly farmers, in a Central European model region, and simulate the changes to land‐use patterns resulting from their response to three scenarios of changing socio‐economic conditions and three scenarios of climate change until the mid of the century. Subsequently, we use species distribution models to, first, analyse relationships between the realized niches of 832 plant species and climatic gradients or land‐use types, respectively, and, second, to project consequent changes in potential regional ranges of these species as triggered by changes in both the altered land‐use patterns and the changing climate. We find that both drivers determine the realized niches of the studied plants, with land use having a stronger effect than any single climatic variable in the model. Nevertheless, the plants' future distributions appear much more responsive to climate than to land‐use changes because alternative future socio‐economic backgrounds have only modest impact on land‐use decisions in the model region. However, relative effects of climate and land‐use changes on biodiversity may differ drastically in other regions, especially where landscapes are still dominated by natural or semi‐natural habitat. We conclude that agent‐based modelling of land use is able to provide scenarios at scales relevant to individual species distribution and suggest that coupling ABMs with models of species' range change should be intensified to provide more realistic biodiversity forecasts.     

Reconstructing geographical parthenogenesis: effects of niche differentiation and reproductive mode on Holocene range expansion of an alpine plant

Asexual taxa often have larger ranges than their sexual progenitors, particularly in areas affected by Pleistocene glaciations. The reasons given for this ‘geographical parthenogenesis’ are contentious, with expansion of the ecological niche or colonisation advantages of uniparental reproduction assumed most important in case of plants. Here, we parameterized a spread model for the alpine buttercup Ranunculus kuepferi and reconstructed the joint Holocene range expansion of its sexual and apomictic cytotype across the European Alps under different simulation settings. We found that, rather than niche broadening or a higher migration rate, a shift of the apomict's niche towards colder conditions per se was crucial as it facilitated overcoming of topographical barriers, a factor likely relevant for many alpine apomicts. More generally, our simulations suggest potentially strong interacting effects of niche differentiation and reproductive modes on range formation of related sexual and asexual taxa arising from their differential sensitivity to minority cytotype disadvantage.     

Prevalence of and risk factors for quinolone-resistant Neisseria gonorrhoeae infection in Ontario

Background

Quinolone-resistant Neisseria gonorrhoeae has swiftly emerged in Canada. We sought to determine its prevalence in the province of Ontario and to investigate risk factors for quinolone-resistant N. gonorrhoeae infection in a Canadian setting.

Methods

We used records from the Public Health Laboratory of the Ontario Agency for Health Protection and Promotion in Toronto, Ontario, and the National Microbiology Laboratory in Winnipeg, Manitoba, to generate epidemic curves for N. gonorrhoeae infection. We extracted limited demographic data from 2006 quinolone-resistant N. gonorrhoeae isolates and from a random sample of quinolone-susceptible isolates. We also extracted minimum inhibitory concentrations for commonly tested antibiotics.

Results

Between 2002 and 2006, the number of N. gonorrhoeae infections detected by culture decreased by 26% and the number of cases detected by nucleic acid amplification testing increased 6-fold. The proportion of N. gonorrhoeae isolates with resistance to quinolones increased from 4% to 28% over the same period. Analysis of 695 quinolone-resistant N. gonorrhoeae isolates and 688 quinolone-susceptible control isolates from 2006 showed a higher proportion of men (odds ratio [OR] 3.1, 95% confidence interval [CI] 2.3–4.1) and patients over 30 years of age (OR 3.1, 95% CI 2.4–3.8) in the quinolone-resistant group. The proportion of men who have sex with men appeared to be relatively similar in both groups (OR 1.4, 95% CI 1.1–1.8). Quinolone-resistant strains were more resistant to penicillin (p < 0.001), tetracycline (p < 0.001) and erythromycin (p < 0.001). All isolates were susceptible to cefixime, ceftriaxone, azithromycin and spectinomycin.

Interpretation

During 2006 in Ontario, 28% of N. gonorrhoeae isolates were resistant to quinolones. Infections in heterosexual men appear to have contributed significantly to the quinolone resistance rate. Medical practitioners should be aware of the widespread prevalence of quinolone-resistant N. gonorrhoeae and avoid quinolone use for empiric therapy.After declining for a number of years, Neisseria gonorrhoeae infections are once more on the rise in Canada. Between 1997 and 2007, reported incidence of the disease more than doubled, from 15 to 35 cases per 100 000.¹ To address the emergence of quinolone-resistant N. gonorrhoeae strains, the empiric treatment regimens for N. gonorrhoeae infection were recently revised in the 2006 Canadian Guidelines on Sexually Transmitted Infections.^2,3 Quinolones are no longer recommended for empiric therapy for N. gonorrhoeae infection.³In Canada, quinolone resistance in N. gonorrhoeae isolates increased from an estimated 2% in 2001 to 16% in 2005.⁴ Demographic risk factors for quinolone-resistant N. gonorrhoeae infection have not been studied. American studies have associated quinolone-resistant N. gonorrhoeae infection with men who have sex with men,^5,6 antibiotic use,^5,7 age above 35 years,⁵ HIV infection⁵ and travel to Asia.⁶ Public health data from the provinces of Quebec⁸ and Alberta² have also suggested an association between quinolone-resistant infection and men who have sex with men. In this study we generated epidemic curves for N. gonorrhoeae and quinolone-resistant N. gonorrhoeae infection in the province of Ontario. We also investigated demographic risk factors for quinolone-resistant N. gonorrhoeae infection.     

Arbovirus detection in insect vectors by rapid, high-throughput pyrosequencing

Background

Despite the global threat caused by arthropod-borne viruses, there is not an efficient method for screening vector populations to detect novel viral sequences. Current viral detection and surveillance methods based on culture can be costly and time consuming and are predicated on prior knowledge of the etiologic agent, as they rely on specific oligonucleotide primers or antibodies. Therefore, these techniques may be unsuitable for situations when the causative agent of an outbreak is unknown.

Methodology/Principal Findings

In this study we explored the use of high-throughput pyrosequencing for surveillance of arthropod-borne RNA viruses. Dengue virus, a member of the positive strand RNA Flavivirus family that is transmitted by several members of the Aedes genus of mosquitoes, was used as a model. Aedes aegypti mosquitoes experimentally infected with dengue virus type 1 (DENV-1) were pooled with noninfected mosquitoes to simulate samples derived from ongoing arbovirus surveillance programs. Using random-primed methods, total RNA was reverse-transcribed and resulting cDNA subjected to 454 pyrosequencing.

Conclusions/Significance

In two types of samples, one with 5 adult mosquitoes infected with DENV-1- and the other with 1 DENV-1 infected mosquito and 4 noninfected mosquitoes, we identified DENV-1 DNA sequences. DENV-1 sequences were not detected in an uninfected control pool of 5 adult mosquitoes. We calculated the proportion of the Ae. aegypti metagenome contributed by each infecting Dengue virus genome (p^IP), which ranged from 2.75×10⁻⁸ to 1.08×10⁻⁷. DENV-1 RNA was sufficiently concentrated in the mosquito that its detection was feasible using current high-throughput sequencing instrumentation. We also identified some of the components of the mosquito microflora on the basis of the sequence of expressed RNA. This included members of the bacterial genera Pirellula and Asaia, various fungi, and a potentially uncharacterized mycovirus.     

International Code of Phytosociological Nomenclature. 4th edition

The fourth edition of the International Code of Phytosociological Nomenclature (ICPN) was prepared by the Steering Committee of the IAVS Working Group for Phytosociological Nomenclature (GPN). The edition consists of 14 Definitions, 7 Principles, 53 Articles, and 7 Appendices. When compared with the previous edition, the main amendments are: (a) the acceptance of electronic publications (Art. 1); (b) the introduction of binding decisions (Definition XIV, Principle II, Articles 1, 2b, 3c, 29b, 40, 42, 44, Appendices 6 and 7); (c) the mandatory use of the English or Latin terminology for syntaxonomic novelties (Definition II, Principle II, Articles 3d and 3i); (d) the introduction of autonyms for the main ranks when the corresponding secondary ranks are created (Articles 13b and 24); (e) the automatic correction of the taxon names (name-giving taxa) used in the names of syntaxa in accordance with the International Code of Nomenclature for algae, fungi, and plants (ICN) (Article 44); (f) the possibility to mutate the name of a syntaxon in using other correct, alternative names for the name-giving taxa (Article 45); (g) the introduction of inadequate names, a new category of rejected names (Definition V, Articles 43 through 45); and (h) the introduction of a conserved type (Definition XIII, Article 53). The fourth edition of ICPN was approved by the GPN on 25 May 2019 and becomes effectively binding on 1 January 2021.