Basic Concepts of Aging Flashcards
Lectures 2-4 for exam 1
What are the 3 definitions of aging?
Mortality-based definition, functional definition, and “our” definition
Mortality-based definition
Biological aging is characterized by an increased susceptibility to die or increase in loss of vigor
What are the limitations of the mortality-based definition?
Not a complete definition because there are some changes we experience that do not increase susceptibility to death such as white hairs and wrinkles
Functional definition
Aging is the deteriorating changes with time during post-maturational life that underlie an increasing vulnerability to challenges, thereby decreasing the ability of the organism to survive
What are the limitations of the functional definition?
inaccurate and incomplete; inaccurate because aging is not always post-maturational and incomplete because it does not include cellular changes but only at an organismal level
“Our” definition
Aging is the stochastic (random) change of molecules, cells, and organisms that is caused by one’s interactions with the environment and aging increases the probability of death
What are the limitations of “our” definition?
there are none because this definition is complete and accurate
Are aging and diseases the same?
No aging and diseases are two different things; with the definitions of aging there is no mention of diseases
What are the differences between aging and diseases?
- aging occurs in every animal
- Most age-related changes occur after sexual maturity
- Age-related changes often increase vulnerability to death
- Aging takes place in both animate and inanimate objects
What are the 3 stages of aging?
Development, maturity, and senescence
Development stage
stage of lifespan in which growth takes place
Maturity stage
functions remain at optimal levels or slowly decline (sometimes)
Senescence stage
post-reproductive phase associated with a negative change to vitality and function
Life stage curves
percentage of your life span that you have in each of these stages as a percent of function of the organism
How long do humans spend in the development, maturity, and senescence stages?
30% in development, 50% in maturity, and 20% in senescence
What are the 7 model systems used for biogerontology?
- isolated cells
- fungi
- invertebrates and insects
- vertebrates
- non-human primates
- human progerias
- comparative biogerontology
Isolate cells
used for studying basic biochemistry of aging
Fungi
used to study environmental factors that affect aging
Invertebrates and insects
used to study extended cellular life, cell signaling, and genetics of aging
Vertebrates
commonly used in the investigation of physiological, genetics, and nutritional questions related to aging
Non-human primates
commonly used to investigate time-dependent physiological changes associated with aging
Human progerias
a group of genetic diseases associated with premature aging and greater risk of age-related diseases
What are the 2 types of progerias?
Werner syndrome and Hutchison-Gilford syndrome
Werner syndrome
- more prone to CVD and cancer
- symptoms appear during the 2nd-3rd decade in life
- caused by mutations in WRN gene
Hutchison-Glifford syndrome
- more prone to CVD and neurological defects
- symptoms appear at birth/young adult
Comparative biogerontology
compare models and try to see if there are similarities in regard to aging
What is the difference between quantifying ages in a population vs. individuals?
quantifying ages in a population is easier than individually; quantifying an individualized age is difficult
What are two approaches scientists use to identify a biomarker for quantifying individualized aging?
cross-sectional studies and longitundinal studies
Cross sectional studies
a variable is selected and measured in groups of individuals of different ages
Longitudinal studies
observe changes in a single individual over time
What is a limitation of cross-sectional studies?
individual values are significantly different from the mean
What is a limitation of longitudinal studies?
aging is highly specific but not only for individual humans but also for different organ systems
Why is aging so unique and individualized?
intrinsic and extrinsic aging is the main factor that contributes to aging in individuals
How do scientists quantify aging in a population?
measurement of mortality rate and survival curves
What is the mortality rate equation?
M = D/P, where M is the mortality rate, D is the number of deaths, and P is the population
What are the 2 different variations of mortality rates?
age-specific mortality rate and Gompertz mortality rate
Age-specific mortality rate
describes the probability of dying within a age-range or within a specific age
Gompertz mortality rate
describes a constant increase in mortality with age
Survival curves
representation of survival over time
What influences mean life span and max life span?
intrinsic and extrinsic aging
Mean life span
primarily influenced by extrinsic factors - a measure of extrinsic aging
Max life span
primarily influenced by genes - a measure of intrinsic aging
What is the evidence supporting contribution of genetics to human life span?
- underlying reason for increased life expectancy
- underlying reason for human’s unique trajectory in life span during 1920-1960
- continuous increase in life expectancy is attributed to better management and diagnosis of non-infectious diseases
- differences in life span of male and females
What is August Weismann’s 1st theory of aging?
described as a programmed phenomenon that was hardwired into the genes of the organisms where the elderly are eliminated for the benefit of the reproductively active individuals in an organisms
What are the flaws of the 1st theory of aging?
- Animals that live in the wild never age because they die before they can actually age (ex: predation and disease)
- Reproductively not active and cannot contribute to the gene pool (forces of natural selection do not apply if not reproductively active)
What are the 3 contemporary theories?
Antagonistic pleiotrophy, mutation accumulation, disposable soma theory
What is the difference between the 1st theory of aging and the 3 contemporary theories?
all 3 contemporary theories are accepted while the 1st theory of aging is flawed
Antagonistic pleiotropy
genes that contribute to aging convey a benefit early in life and thus are selected for by evolutionary forces…”pay later” theory
Mutation accumulation
Accumulation of mutations in late-active genes which lead to small, non-lethal effects early on and negative effects later in post-reproductive life
Disposable soma theory (“DST)
DST proposes that aging results in part from “trade-off” between reproduction and longevity
What are the 2 principles of DST?
- Environmental resources are limited
- Reproductive success of species depends on germline. Soma are disposable - their main function is to support survival of germline to the point of reproduction
What is the prediction of the DST?
organisms that invest in high fecundity, invest less in maintenance of somatic cells and experience short lifespans
What is the experimental evidence that supports DST?
- Artificial delaying onset of reproduction in fruit flies increase longevity
- Simulation of high predation leads to development of early reproducing flies
