A Test of Evolutionary Theories of Senescence

2002 ◽  
Vol 2002 (37) ◽  
Author(s):  
Michael Rose ◽  
Brian Charlesworth
Keyword(s):  
Age Of Onset ◽  
Genetic Diseases ◽  
Mutation Accumulation ◽  
Deleterious Mutations ◽  
Fitness Components ◽  
Mean Values ◽  
Evolutionary Theories ◽  
Beneficial Effects ◽  
Effect Of Age ◽  
Selection Of

Senescence is the post-maturation decline in survivorship and fecundity that accompanies advancing age. Two main evolutionary theories have been proposed to account for senescence. (1) The mutation-accumulation theory. Deleterious mutations exerting their effects only late in life would tend to accumulate, because of their minimal effects on fitness. More precisely, exclusively late-acting deleterious mutations will attain higher equilibrium frequencies under mutation-selection balance than will mutations that act early, resulting in lower mean values for fitness components late in life (ref. 3 , p. 218). Medawar emphasized the possibility that this effect would be enhanced by selection of modifiers that postpone the age of onset of genetic diseases. (2) The pleiotropy theory. Williams suggested that many of the genes with beneficial effects on early fitness components have pleiotropy deleterious effects on late fitness components, but are nevertheless favoured by natural selection. (These theories are based on the decline with age in the effect of age-specific fitness-component changes on total fitness (ref. 3 , pp. 206-214 and refs 4, 5 ). Either or both of these theories could apply in any particular population.) Selection experiments in Drosophila and Tribolium support the pleiotropy theory, although one such experiment gave results that only bordered on significance, but the mutation-accumulation theory has never been tested. The present results provide evidence for the pleiotropy theory, but do not support the mutation-accumulation theory. Reproduced by permission. Michael Rose, Brian Charlesworth, A Test of Evolutionary Theories of Senescence. Nature 287 , 141-142 (1980).

Microencapsulation: A Prospective to Protect Probiotics

2020 ◽  
Vol 16 (6) ◽  
pp. 891-899 ◽  
Author(s):  
Wissam Zam
Keyword(s):  
Gastrointestinal Tract ◽  
Food Industry ◽  
Health Benefits ◽  
Probiotic Bacteria ◽  
Bacterial Cells ◽  
Beneficial Effects ◽  
Host Health ◽  
Resistant Strains ◽  
Selection Of

Probiotics are viable microorganisms widely used for their claimed beneficial effects on the host health. A wide number of researchers proved that the intake of probiotic bacteria has numerous health benefits which created a big market of probiotic foods worldwide. The biggest challenge in the development of these products is to maintain the viability of bacterial cells during the storage of the product as well as throughout the gastrointestinal tract transit after consumption, so that the claimed health benefits can be delivered to the consumer. Different approaches have been proposed for increasing the resistance of these sensitive microorganisms, including the selection of resistant strains, incorporation of micronutrients, and most recently the use of microencapsulation techniques. Microencapsulation has resulted in enhancing the viability of these microorganisms which allows its wide use in the food industry. In this review, the most common techniques used for microencapsulation of probiotics will be presented, as well as the most usual microcapsule shell materials.

scholarly journals On the Rate and Linearity of Viability Declines in Drosophila Mutation-Accumulation Experiments: Genomic Mutation Rates and Synergistic Epistasis Revisited

Genetics ◽  
2004 ◽  
Vol 166 (2) ◽  
pp. 797-806 ◽  
Author(s):  
James D Fry
Keyword(s):  
Mutation Rate ◽  
Average Rate ◽  
Natural Populations ◽  
Mutation Accumulation ◽  
High Rate ◽  
Deleterious Mutations ◽  
Order Of Magnitude ◽  
Contamination Event ◽  
Genomic Mutation ◽  
The 1960S

Abstract High rates of deleterious mutations could severely reduce the fitness of populations, even endangering their persistence; these effects would be mitigated if mutations synergize each others’ effects. An experiment by Mukai in the 1960s gave evidence that in Drosophila melanogaster, viability-depressing mutations occur at the surprisingly high rate of around one per zygote and that the mutations interact synergistically. A later experiment by Ohnishi seemed to support the high mutation rate, but gave no evidence for synergistic epistasis. Both of these studies, however, were flawed by the lack of suitable controls for assessing viability declines of the mutation-accumulation (MA) lines. By comparing homozygous viability of the MA lines to simultaneously estimated heterozygous viability and using estimates of the dominance of mutations in the experiments, I estimate the viability declines relative to an appropriate control. This approach yields two unexpected conclusions. First, in Ohnishi’s experiment as well as in Mukai’s, MA lines showed faster-than-linear declines in viability, indicative of synergistic epistasis. Second, while Mukai’s estimate of the genomic mutation rate is supported, that from Ohnishi’s experiment is an order of magnitude lower. The different results of the experiments most likely resulted from differences in the starting genotypes; even within Mukai’s experiment, a subset of MA lines, which I argue probably resulted from a contamination event, showed much slower viability declines than did the majority of lines. Because different genotypes may show very different mutational behavior, only studies using many founding genotypes can determine the average rate and distribution of effects of mutations relevant to natural populations.

scholarly journals Harmful mutation load in the mitochondrial genomes of cattle breeds

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Sankar Subramanian
Keyword(s):  
Population Size ◽  
Artificial Selection ◽  
Deleterious Mutation ◽  
Genetic Diseases ◽  
Mitochondrial Genomes ◽  
Deleterious Mutations ◽  
Founder Population ◽  
Mutation Load ◽  
Effective Population ◽  
Cattle Breeds

Abstract Objective Domestication of wild animals results in a reduction in the effective population size, and this could affect the deleterious mutation load of domesticated breeds. Furthermore, artificial selection will also contribute to the accumulation of deleterious mutations due to the increased rate of inbreeding among these animals. The process of domestication, founder population size, and artificial selection differ between cattle breeds, which could lead to a variation in their deleterious mutation loads. We investigated this using mitochondrial genome data from 364 animals belonging to 18 cattle breeds of the world. Results Our analysis revealed more than a fivefold difference in the deleterious mutation load among cattle breeds. We also observed a negative correlation between the breed age and the proportion of deleterious amino acid-changing polymorphisms. This suggests a proportionally higher deleterious SNPs in young breeds compared to older breeds. Our results highlight the magnitude of difference in the deleterious mutations present in the mitochondrial genomes of various breeds. The results of this study could be useful in predicting the rate of incidence of genetic diseases in different breeds.

scholarly journals A qualitative study among patients with an inherited retinal disease on the meaning of genomic unsolicited findings

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Marlies Saelaert ◽  
Heidi Mertes ◽  
Tania Moerenhout ◽  
Caroline Van Cauwenbergh ◽  
Bart P. Leroy ◽  
...  
Keyword(s):  
Qualitative Study ◽  
Interpretative Phenomenological Analysis ◽  
Age Of Onset ◽  
Genetic Diseases ◽  
Retinal Disease ◽  
Clinical Approach ◽  
Inherited Retinal Disease ◽  
Illness Experiences ◽  
Meaning Structure ◽  
Main Components

AbstractExome-based testing for genetic diseases can reveal unsolicited findings (UFs), i.e. predispositions for diseases that exceed the diagnostic question. Knowledge of patients’ interpretation of possible UFs and of motives for (not) wanting to know UFs is still limited. This lacking knowledge may impede effective counselling that meets patients’ needs. Therefore, this article examines the meaning of UFs from a patient perspective. A qualitative study was conducted and an interpretative phenomenological analysis was made of 14 interviews with patients with an inherited retinal disease. Patients assign a complex meaning to UFs, including three main components. The first component focuses on result-specific qualities, i.e. the characteristics of an UF (inclusive of actionability, penetrance, severity and age of onset) and the consequences of disclosure; the second component applies to a patient’s lived illness experiences and to the way these contrast with reflections on presymptomatic UFs; the third component addresses a patient’s family embedding and its effect on concerns about disease prognosis and genetic information’s family relevance. The complex meaning structure of UFs suggests the need for counselling procedures that transcend a strictly clinical approach. Counselling should be personalised and consider patients’ lived illness experiences and family context.

Supergene degeneration opposes polymorphism: The curious case of balanced lethals

2021 ◽  
Author(s):  
Emma Berdan ◽  
Alexandre Blanckaert ◽  
Roger K Butlin ◽  
Thomas Flatt ◽  
Tanja Slotte ◽  
...  
Keyword(s):  
Equilibrium State ◽  
Balancing Selection ◽  
Mutation Accumulation ◽  
Small Population ◽  
Quasi Equilibrium ◽  
Deleterious Mutations ◽  
Critical Factors ◽  
Critical Aspect ◽  
Allopatric Divergence

Supergenes offer some of the most spectacular examples of long-term balancing selection in nature but their origin and maintenance remain a mystery. A critical aspect of supergenes is reduced recombination between arrangements. Reduced recombination protects adaptive multi-trait phenotypes, but can also lead to degeneration through mutation accumulation. Mutation accumulation can stabilize the system through the emergence of associative overdominance (AOD), destabilize the system, or lead to new evolutionary outcomes. One such outcome is the formation of balanced lethal systems, a maladaptive system where both supergene arrangements have accumulated deleterious mutations to the extent that both homozygotes are inviable, leaving only heterozygotes to reproduce. Here, we perform a simulation study to understand the conditions under which these different outcomes occur, assuming a scenario of introgression after allopatric divergence. We found that AOD aids the invasion of a new supergene arrangement and the establishment of a polymorphism. However, this polymorphism is easily destabilized by further mutation accumulation. While degradation may strengthen AOD, thereby stabilizing the supergene polymorphism, it is often asymmetric, which is the key disrupter of the quasi-equilibrium state of the polymorphism. Furthermore, mechanisms that accelerate degeneration also tend to amplify asymmetric mutation accumulation between the supergene arrangements and vice versa. As the evolution of a balanced lethal system requires symmetric degradation of both arrangements, this leaves highly restricted conditions under which such a system could evolve. We show that small population size and low dominance coefficients are critical factors, as these reduce the efficacy of selection. The dichotomy between the persistence of a polymorphism and degradation of supergene arrangements likely underlies the rarity of balanced lethal systems in nature.

scholarly journals New Perspectives on Dystonia

2003 ◽  
Vol 30 (S1) ◽  
pp. S34-S44 ◽  
Author(s):  
Mélanie Langlois ◽  
Francois Richer ◽  
Sylvain Chouinard
Keyword(s):  
Age Of Onset ◽  
Clinical Investigation ◽  
Genetic Data ◽  
Therapeutic Agents ◽  
Anatomical Distribution ◽  
Beneficial Effects ◽  
Physiological Abnormalities ◽  
Primary Torsion ◽  
Primary Torsion Dystonia ◽  
Deep Brain

Dystonia is a syndrome of sustained muscular contractions with numerous underlying etiologies. This review examines the varied phenomenology of dystonias, its evolving classification including recent genetic data as well as its clinical investigation and treatment. Although age of onset, anatomical distribution and family history are key elements of the investigation of dystonia, classification increasingly relies on etiologic and genetic criteria. Physiological abnormalities in striatocortical circuits are common in dystonia but the pathophysiology is still unclear. In recent years, a great deal has been learned on the more common primary dystonias such as primary torsion dystonia and on dystonia-plus syndromes such as dopamine responsive dystonia. Treatment of dystonia has also evolved and there are now a number of therapeutic agents with clear beneficial effects including anticholinergics, benzodiazepines, and botulinum toxin and there is growing interest in neurofunctional surgery including deep brain stimulation.

scholarly journals Antler growth in male roe deer in field hunting grounds in Vojvodina: Effect of age on trophy value

2006 ◽  
pp. 109-122
Author(s):  
Dragan Gacic
Keyword(s):  
Old Age ◽  
Representative Sample ◽  
Roe Deer ◽  
Age Groups ◽  
Capreolus Capreolus ◽  
Mean Values ◽  
Antler Growth ◽  
Study Results ◽  
Effect Of Age ◽  
Healthy Males

Antler growth in male roe deer (Capreolus capreolus L) was studied on the representative sample consisting of 546 trophies (227 from Backa and 319 from Banat) hunted in the period 19982005. No significant differences in antler characters and trophy values were noted between Backa and Banat (except weight of antlers for 5 year old males), and the data for both regions were pooled. Antler growth is a curvilinear function of age. Mean values of length, weight and volume of antlers, and total trophy score varied significantly between the males in different age groups. The study results prove that in Vojvodina field hunting grounds, healthy males attain the culmination in antler growth and trophy value at the age of six years but already after the age of seven years, they show the first sign of old age and decline.

scholarly journals Antioxidant Activity and Polyphenolic Profile of Walnut (Juglans regia L.) Green Husks and Liqueurs

2020 ◽  
Vol 69 (1-2) ◽  
pp. 5-11
Author(s):  
Dijana Kulačanin ◽  
Sandra Bijelić ◽  
Jovana Šućur ◽  
Borivoje Bogdanović ◽  
Sezai Ercisli ◽  
...  
Keyword(s):  
Antioxidant Activity ◽  
Growth And Development ◽  
Juglans Regia ◽  
Flavonoid Content ◽  
Beneficial Effects ◽  
Cultivar Selection ◽  
Polyphenolic Content ◽  
Polyphenolic Profile ◽  
Selection Of ◽  
Time Point

SummaryThe beneficial effects of walnuts and walnut products on human health, due primarily to their rich polyphenolic content, have been appreciated as an empirical fact for centuries. The purpose of this study is to determine the polyphenolic contents of liqueurs made from the walnut selections ‘Rasna’ and ‘Sava’ and the walnut cultivar ‘Šampion’ (all harvested at three different times), as well as the polyphenolic contents of their green husks. The walnut liqueurs were prepared according to two traditional recipes using young walnut fruits. The highest antioxidant capacity was recorded in the liqueur made from the ‘Rasna’ walnut selection (89.94%), whereas the highest contents of phenols (83.28 mg GAE/g FW), flavonoids (0.83 mg QE/g FW) and proanthocyanidins were found in the liqueur made from the ‘Šampion’ cultivar (14.75 mg CE/g FW). The youngest ‘Rasna’ walnuts, harvested at the first experimental time point, exhibited the highest phenolic and tannin contents, whereas the highest flavonoid content was observed in the ‘Šampion’ cultivar. The biochemical results obtained indicate a decrease in the polyphenolic content of walnut fruits with their growth and development. Moreover, the polyphenolic profiles of the walnut liqueurs considered were found to be greatly affected by the method of preparation and the cultivar/selection of walnuts.

scholarly journals Modelling of Metallic Particle Binders for Increased Part Density in Binder Jet Printed Components

2019 ◽  
Author(s):  
Joseph Roberts ◽  
Peter Green ◽  
Kate Black ◽  
Christopher Sutcliffe
Keyword(s):  
Particle Size ◽  
Critical Radius ◽  
Detailed Knowledge ◽  
Particle Sizes ◽  
Powder Bed ◽  
Beneficial Effects ◽  
Drop Tests ◽  
Maximum Particle ◽  
Packing Efficiency ◽  
Selection Of

Binder jet printed components typically have low overall density in the green state and high shrinkage and deformation after heat treatment. It has previously been demonstrated that, by including nanoparticles of the same material in the binder, these properties can be improved as the nanoparticles can fill the interstices and pore throats between the bed particles. The beneficial effects from using these additive binder particles can be improved by maximising the binder particle size, enabling the space within the powder bed to be filled with a higher packing efficiency. The selection of maximum particle size for a binder requires detailed knowledge of the pores and pore throats between the powder bed particles. In this paper, a raindrop model is developed to determine the critical radius at which binder particles can pass between pores and penetrate the bed. The model is validated against helium pycnometry measurements and binder particle drop tests. It is found that the critical radius can be predicted, with acceptable accuracy, using a linear function of the mean and standard deviation of the particle radii. Percolation theory concepts have been employed in order to generalise the results for powder beds that have different mean particle sizes and size distributions. The results of this work can be employed to inform the selection of particle sizes required for binder formulations, to optimise density and reduce shrinkage in printed binder jet components.

scholarly journals WILLINGNESS TO BE VACCINATED AGAINST COVID-19 AMONG HIGHER EDUCATION INSTITUTION

2021 ◽  
Vol 13 (2) ◽  
Author(s):  
Joel Rey Acob ◽  
Moises Neil V. Seriño ◽  
Reyvin N. Sabanal ◽  
Therese C. Ratilla ◽  
Elwin Jay Yu ◽  
...  
Keyword(s):  
Medical Profession ◽  
Education Institution ◽  
Faculty Members ◽  
Descriptive Statistics ◽  
Pharmaceutical Companies ◽  
Health Crisis ◽  
Beneficial Effects ◽  
Convenience Sampling ◽  
Increase Success Rate ◽  
Selection Of

Background: The increasing COVID-19 cases worldwide ignite pharmaceutical companies’ effort to discover safe vaccines have been eyed globally. Informed perspectives across medical profession explaining beneficial effects of inoculation, however, various personal views persist which lead to confusion among general public. Objectives: To describe demographic characteristics among education institutions and their willingness to be vaccinated. Methods: Data were collected by google forms, in February 2021. The online form was then pre-tested on 10 respondents to refine questions prior to commencing the survey. Convenience sampling was administered for the selection of voluntary respondents. Data cleaning was done prior to the data analysis. Recoding of string variables and omittion of invalid responses were also done. Descriptive statistics was undertaken in a genuine licensed software of IBM SPSS Statistics version 26. Results: A total of 401 respondents answered the survey. More than half of the respondents are female constituting 62.1% of the sample, whereas males constitute 37.9%, mostly faculty members, single (63.1%), earning 20,000 (54.2%) per month. More than half of the respondents are willing to get vaccinated against COVID-19 (54.6%) and have no preference for a specific type of COVID-19 vaccine (54.9%). Around 30.4% are still unsure if they should get vaccinated or not and 15% have indicated negatively. Comparing both sexes, a larger frequency of males is willing to get vaccinated constituting 69.1% and females (45.8%). Conclusion: Males showed more willingness to be inoculated regardless of COVID-19 vaccine types. Education and continuous campaign on the importance of vaccination program is a must to increase success rate to end the health crisis.

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