scholarly journals Historical Perspective on the Discovery of the Quasispecies Concept

2021 ◽  
Vol 8 (1) ◽  
pp. 51-72
Author(s):  
Esteban Domingo ◽  
Carlos García-Crespo ◽  
Celia Perales
Keyword(s):  
Biological Diversity ◽  
Control Strategies ◽  
Viral Evolution ◽  
Continuous Process ◽  
Viral Population ◽  
Viral Quasispecies ◽  
Viral Genomes ◽  
The Origin Of Life ◽  
And Control ◽  
Made In

Viral quasispecies are dynamic distributions of nonidentical but closely related mutant and recombinant viral genomes subjected to a continuous process of genetic variation, competition, and selection that may act as a unit of selection. The quasispecies concept owes its theoretical origins to a model for the origin of life as a collection of mutant RNA replicators. Independently, experimental evidence for the quasispecies concept was obtained from sampling of bacteriophage clones, which revealed that the viral populations consisted of many mutant genomes whose frequency varied with time of replication. Similar findings were made in animal and plant RNA viruses. Quasispecies became a theoretical framework to understand viral population dynamics and adaptability. The evidence came at a time when mutations were considered rare events in genetics, a perception that was to change dramatically in subsequent decades. Indeed, viral quasispecies was the conceptual forefront of a remarkable degree of biological diversity, now evident for cell populations and organisms, not only for viruses. Quasispecies dynamics unveiled complexities in the behavior of viral populations,with consequences for disease mechanisms and control strategies. This review addresses the origin of the quasispecies concept, its major implications on both viral evolution and antiviral strategies, and current and future prospects.

scholarly journals Populations of Genomic RNAs Devoted to the Replication or Spread of a Bipartite Plant Virus Differ in Genetic Structure

2009 ◽  
Vol 83 (24) ◽  
pp. 12973-12983 ◽  
Author(s):  
Gloria Lozano ◽  
Ana Grande-Pérez ◽  
Jesús Navas-Castillo
Keyword(s):  
Genetic Structure ◽  
Detailed Analysis ◽  
Rna Viruses ◽  
Control Strategies ◽  
Cooperative Behavior ◽  
Viral Evolution ◽  
Continuous Process ◽  
Viral Quasispecies ◽  
Sequencing Data ◽  
Genomic Rnas

ABSTRACT RNA viruses within a host exist as dynamic distributions of closely related mutants and recombinant genomes. These closely related mutants and recombinant genomes, which are subjected to a continuous process of genetic variation, competition, and selection, act as a unit of selection, termed viral quasispecies. Characterization of mutant spectra within hosts is essential for understanding viral evolution and pathogenesis resulting from the cooperative behavior of viral mutants within viral quasispecies. Furthermore, a detailed analysis of viral variability within hosts is needed to design control strategies, because viral quasispecies are reservoirs of viral variants that potentially can emerge with increased virulence or altered tropism. In this work, we report a detailed analysis of within-host viral populations in 13 field isolates of the bipartite Tomato chlorosis virus (ToCV) (genus Crinivirus, family Closteroviridae). The intraisolate genetic structure was analyzed based on sequencing data for 755 molecular clones distributed in four genomic regions within the RNA-dependent RNA polymerase (RNA1) and Hsp70h, CP, and CPm (RNA2) open reading frames. Our results showed that populations of ToCV within a host plant have a heterogeneous and complex genetic structure similar to that described for animal and plant RNA viral quasispecies. Moreover, the structures of these populations clearly differ depending on the RNA segment considered, being more complex for RNA1 (encoding replication-associated proteins) than for RNA2 (encoding encapsidation-, systemic-movement-, and insect transmission-relevant proteins). These results support the idea that, in multicomponent RNA viruses, function can generate profound differences in the genetic structures of the different genomic segments.

scholarly journals Synthesis of novel heterocyclic Quinolone compound for anti -tubercular activity

2018 ◽  
Vol 4 (3) ◽  
pp. 44-49
Author(s):  
Rahul K. Godge ◽  
Rahul Kunkulol
Keyword(s):  
Control Strategies ◽  
Secondary Amines ◽  
Organic Reaction ◽  
Severe Problem ◽  
Mycobacterium Tuberculosis H37rv ◽  
Monitoring Tools ◽  
H37rv Strain ◽  
And Control ◽  
Quinolone Derivatives ◽  
Made In

In last few decades, though significant progress has been made in the treatment and control strategies of tubercular infections by introducing new diagnostic and monitoring tools and combination therapy, it still continues to be severe problem. The need of study was only because of there are many drugs in market to treat infection but most of the drugs are showing resistance because of the same it is difficult to treat the infection. In this study we chosen quinolone nucleus for study and over it.  Thus with the aim of developing novel molecule with improved potency for treating Mycobacterium tuberculosis H37Rv strain infections and with decreased probability of developing drug resistance. Methodology: The synthesis of Quinolone derivatives, starting from substituted aniline and ethyl acetoacetate, by conventional organic reaction and results of investigations of their anti-mycobacterial activity. Results: MICs of the synthesized compounds are compared with existing drugs Cytotoxicity. The substituted quinolones are synthesized by taking mixture of 7-substituted-2-(3-chloro-2-oxopropyl) quinolin-4(1H)-one and different secondary amines.  Many compounds have shown promising activity while some were inactive. Conclusion: It was found that Compound A1, A3, B1, B3, have shown promising anti tubercular activity whereas compound A2, A4,B2,B4 were showing moderate anti tubercular activity  against std. Streptomycin. 

scholarly journals Intercellular Transmission of Viral Populations with Vesicles

2015 ◽  
Vol 89 (24) ◽  
pp. 12242-12244 ◽  
Author(s):  
Nihal Altan-Bonnet ◽  
Ying-Han Chen
Keyword(s):  
Host Cell ◽  
Viral Pathogenesis ◽  
Viral Population ◽  
Viral Quasispecies ◽  
Susceptible Host ◽  
Infection Efficiency ◽  
Viral Genomes ◽  
Viral Particles ◽  
Cell Transmission

A common paradigm holds that during cell-to-cell transmission, viruses behave as lone soldiers. Recently, we discovered not only that enteroviruses are transmitted via vesicles as populations of viral particles but also that this type of transmission enhances their infection efficiency (Y. H. Chen et al., Cell160:619–630, 2015). This mechanism could be advantageous for the overall fitness of the viral population, promoting genetic interplay by enabling viral quasispecies to collectively infect a susceptible host cell. Here, we discuss these findings in the context of viral pathogenesis and also propose that this novel type of vesicular transmission is widespread among different virus families and includes populations of both viral particles and naked viral genomes.

scholarly journals Eradication and Control Strategies for Red Imported Fire Ants (Solenopsis invicta) in Taiwan

2020 ◽  
Vol 12 (10) ◽  
pp. 3951
Author(s):  
Helen K. Liu ◽  
Chung-Chi Lin ◽  
Li-Hsin Huang ◽  
Sin-An Huang ◽  
Rong-Nan Huang
Keyword(s):  
Large Scale ◽  
Biological Diversity ◽  
Control Strategies ◽  
Red Imported Fire Ant ◽  
New Wave ◽  
Adoption Of Technology ◽  
The Public ◽  
Effective Strategies ◽  
Horizontal Networks ◽  
And Control

Invasive alien species are one of the major threats to biological diversity, public safety, agriculture, and economics. In recent years, a new wave of the red imported fire ant (RIFA) has been detected in new regions, including Kobe (Japan), Daegu (South Korea), Kaohsiung (Taiwan), and other locations in southeast Asia. Due to the increasing number of invasions, practitioners and scientists are seeking effective strategies to respond to RIFA invasions in Pacific regions, especially in countries that have had no presence of RIFA. This study aims to identify the strategies adopted to eradicate RIFA in Taiwan and to elucidate some of the assumptions about RIFA prevention and treatment in infested areas with diverse land patterns. Through a literature review and examination of eradication cases in Taiwan, five essential eradication lessons are discussed: (1) Immediate action through partnership with universities and the private sector; (2) engagement with the public and community with an interest in RIFA control through technology; (3) establishment of multi-level horizontal networks of response teams; (4) strategy implementation ranging from large-scale prevention to precise treatment; and (5) adoption of technology and social media. These strategies will have implications and applications for east and south Asian countries that are dealing with similar challenges.

scholarly journals Antigenic Stimulation Specifically Reactivates the Replication of Archived Simian Immunodeficiency Virus Genomes in Chronically Infected Macaques

2005 ◽  
Vol 79 (17) ◽  
pp. 11231-11238 ◽  
Author(s):  
Céline Renoux ◽  
Simon Wain-Hobson ◽  
Bruno Hurtrel ◽  
Rémi Cheynier
Keyword(s):  
T Cells ◽  
Simian Immunodeficiency Virus ◽  
Viral Evolution ◽  
Direct Consequence ◽  
Viral Fitness ◽  
Viral Population ◽  
Viral Quasispecies ◽  
Cell Clones ◽  
Immunodeficiency Virus ◽  
Virus Genomes

ABSTRACT Human immunodeficiency virus/simian immunodeficiency virus (SIV) diversification is a direct consequence of viral replication and occurs principally in secondary lymphoid organs where CD4+ T cells are activated and proliferate. However, the evolution of viral quasispecies may also be driven by various nonexclusive mechanisms, including adaptation to specific immune responses and modification of viral fitness. Analysis of viral quasispecies in SIV-infected macaques subjected to repeated antigenic stimulations allowed us to demonstrate transient expansions of SIV populations that were highly dependent upon activation of antigen-specific T cells. T-cell clones expanded in response to a particular antigen were infected by a specific viral population and persisted for prolonged periods. Upon a second stimulation by encounter with the same antigen, these specific genomes were at the origin of a new burst of replication, leading to rapid but transient replacement of the viral quasispecies in blood. Finally, longitudinal analysis of SIV sequence variation during and between antigenic stimulations revealed that viral evolution is mostly constrained to periods of strong immunological activity.

Full scale parallel operation of a biological aerated filter (BAF) and activated sludge (AS) for nitrogen removal

2000 ◽  
Vol 41 (4-5) ◽  
pp. 159-168 ◽  
Author(s):  
T. Thøgersen ◽  
R. Hansen
Keyword(s):  
Activated Sludge ◽  
Control Strategies ◽  
Treatment Plant ◽  
Operating Costs ◽  
Biological Aerated Filter ◽  
Parallel Operation ◽  
Wet Weather ◽  
Aerated Filter ◽  
And Control ◽  
Made In

In connection with the reconstruction and capacity extension of the Frederikshavn Central Wastewater Treatment Plant in the period between 1989 and 1995 the existing activated sludge plant (AS) was supplemented with a biological aerated filter (BAF). The parallel operation with two wastewater flows has made a comparison of the two plants possible in relation to operating data, operating costs and experience. For the purpose of optimizing the operation, tests were conducted to increase the hydraulic capacity of the plant during rain and control strategies for the plants were considered for dry weather as well as wet weather situations. This paper discusses the experience gained from the plant operation as well as the considerations made in relation to future control strategies and possibilities of increasing the total hydraulic capacity during rain.

An Efficient Approach for Modeling and Control of a Quadrotor

2016 ◽  
Vol 4 (2) ◽  
pp. 1-16
Author(s):  
Ahmed S. Khusheef
Keyword(s):  
Pid Control ◽  
Control Method ◽  
Mechanical Design ◽  
Loop Control ◽  
Modeling And Control ◽  
Loop Control System ◽  
And Control ◽  
Close Loop Control ◽  
Close Loop Control System ◽  
Made In

 A quadrotor is a four-rotor aircraft capable of vertical take-off and landing, hovering, forward flight, and having great maneuverability. Its platform can be made in a small size make it convenient for indoor applications as well as for outdoor uses. In model there are four input forces that are essentially the thrust provided by each propeller attached to each motor with a fixed angle. The quadrotor is basically considered an unstable system because of the aerodynamic effects; consequently, a close-loop control system is required to achieve stability and autonomy. Such system must enable the quadrotor to reach the desired attitude as fast as possible without any steady state error. In this paper, an optimal controller is designed based on a Proportional Integral Derivative (PID) control method to obtain stability in flying the quadrotor. The dynamic model of this vehicle will be also explained by using Euler-Newton method. The mechanical design was performed along with the design of the controlling algorithm. Matlab Simulink was used to test and analyze the performance of the proposed control strategy. The experimental results on the quadrotor demonstrated the effectiveness of the methodology used.

Effective infection prevention and control strategies in a large accredited psychiatric facility in Singapore

2020 ◽  
Author(s):  
Daniel Poremski ◽  
Sandra Henrietta Subner ◽  
Grace Lam Fong Kin ◽  
Raveen Dev Ram Dev ◽  
Mok Yee Ming ◽  
...  
Keyword(s):  
Mental Health ◽  
Prevention And Control ◽  
Infection Prevention ◽  
Control Strategies ◽  
Infection Prevention And Control ◽  
Psychiatric Facility ◽  
Essential Services ◽  
Community Transmission ◽  
And Control

The Institute of Mental Health in Singapore continues to attempt to prevent the introduction of COVID-19, despite community transmission. Essential services are maintained and quarantine measures are currently unnecessary. To help similar organizations, strategies are listed along three themes: sustaining essential services, preventing infection, and managing human and consumable resources.

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