Basic Concepts of Aging

Question 1

What are the 3 definitions of aging?

Answer 1

Mortality-based definition, functional definition, and “our” definition

Question 2

Mortality-based definition

Answer 2

Biological aging is characterized by an increased susceptibility to die or increase in loss of vigor

Question 3

What are the limitations of the mortality-based definition?

Answer 3

Not a complete definition because there are some changes we experience that do not increase susceptibility to death such as white hairs and wrinkles

Question 4

Functional definition

Answer 4

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

Question 5

What are the limitations of the functional definition?

Answer 5

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

Question 6

“Our” definition

Answer 6

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

Question 7

What are the limitations of “our” definition?

Answer 7

there are none because this definition is complete and accurate

Question 8

Are aging and diseases the same?

Answer 8

No aging and diseases are two different things; with the definitions of aging there is no mention of diseases

Question 9

What are the differences between aging and diseases?

Answer 9

1. aging occurs in every animal
2. Most age-related changes occur after sexual maturity
3. Age-related changes often increase vulnerability to death
4. Aging takes place in both animate and inanimate objects

Question 10

What are the 3 stages of aging?

Answer 10

Development, maturity, and senescence

Question 11

Development stage

Answer 11

stage of lifespan in which growth takes place

Question 12

Maturity stage

Answer 12

functions remain at optimal levels or slowly decline (sometimes)

Question 13

Senescence stage

Answer 13

post-reproductive phase associated with a negative change to vitality and function

Question 14

Life stage curves

Answer 14

percentage of your life span that you have in each of these stages as a percent of function of the organism

Question 15

How long do humans spend in the development, maturity, and senescence stages?

Answer 15

30% in development, 50% in maturity, and 20% in senescence

Question 16

What are the 7 model systems used for biogerontology?

Answer 16

1. isolated cells
2. fungi
3. invertebrates and insects
4. vertebrates
5. non-human primates
6. human progerias
7. comparative biogerontology

Question 17

Isolate cells

Answer 17

used for studying basic biochemistry of aging

Question 18

Fungi

Answer 18

used to study environmental factors that affect aging

Question 19

Invertebrates and insects

Answer 19

used to study extended cellular life, cell signaling, and genetics of aging

Question 20

Vertebrates

Answer 20

commonly used in the investigation of physiological, genetics, and nutritional questions related to aging

Question 21

Non-human primates

Answer 21

commonly used to investigate time-dependent physiological changes associated with aging

Question 22

Human progerias

Answer 22

a group of genetic diseases associated with premature aging and greater risk of age-related diseases

Question 23

What are the 2 types of progerias?

Answer 23

Werner syndrome and Hutchison-Gilford syndrome

Question 24

Werner syndrome

Answer 24

• more prone to CVD and cancer
• symptoms appear during the 2nd-3rd decade in life
• caused by mutations in WRN gene

Question 25

Hutchison-Glifford syndrome

Answer 25

• more prone to CVD and neurological defects
• symptoms appear at birth/young adult

Question 26

Comparative biogerontology

Answer 26

compare models and try to see if there are similarities in regard to aging

Question 27

What is the difference between quantifying ages in a population vs. individuals?

Answer 27

quantifying ages in a population is easier than individually; quantifying an individualized age is difficult

Question 28

What are two approaches scientists use to identify a biomarker for quantifying individualized aging?

Answer 28

cross-sectional studies and longitundinal studies

Question 29

Cross sectional studies

Answer 29

a variable is selected and measured in groups of individuals of different ages

Question 30

Longitudinal studies

Answer 30

observe changes in a single individual over time

Question 31

What is a limitation of cross-sectional studies?

Answer 31

individual values are significantly different from the mean

Question 32

What is a limitation of longitudinal studies?

Answer 32

aging is highly specific but not only for individual humans but also for different organ systems

Question 33

Why is aging so unique and individualized?

Answer 33

intrinsic and extrinsic aging is the main factor that contributes to aging in individuals

Question 34

How do scientists quantify aging in a population?

Answer 34

measurement of mortality rate and survival curves

Question 35

What is the mortality rate equation?

Answer 35

M = D/P, where M is the mortality rate, D is the number of deaths, and P is the population

Question 36

What are the 2 different variations of mortality rates?

Answer 36

age-specific mortality rate and Gompertz mortality rate

Question 37

Age-specific mortality rate

Answer 37

describes the probability of dying within a age-range or within a specific age

Question 38

Gompertz mortality rate

Answer 38

describes a constant increase in mortality with age

Question 39

Survival curves

Answer 39

representation of survival over time

Question 40

What influences mean life span and max life span?

Answer 40

intrinsic and extrinsic aging

Question 41

Mean life span

Answer 41

primarily influenced by extrinsic factors - a measure of extrinsic aging

Question 42

Max life span

Answer 42

primarily influenced by genes - a measure of intrinsic aging

Question 43

What is the evidence supporting contribution of genetics to human life span?

Answer 43

1. underlying reason for increased life expectancy
2. underlying reason for human’s unique trajectory in life span during 1920-1960
3. continuous increase in life expectancy is attributed to better management and diagnosis of non-infectious diseases
4. differences in life span of male and females

Question 44

What is August Weismann’s 1st theory of aging?

Answer 44

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

Question 45

What are the flaws of the 1st theory of aging?

Answer 45

1. Animals that live in the wild never age because they die before they can actually age (ex: predation and disease)
2. Reproductively not active and cannot contribute to the gene pool (forces of natural selection do not apply if not reproductively active)

Question 46

What are the 3 contemporary theories?

Answer 46

Antagonistic pleiotrophy, mutation accumulation, disposable soma theory

Question 47

What is the difference between the 1st theory of aging and the 3 contemporary theories?

Answer 47

all 3 contemporary theories are accepted while the 1st theory of aging is flawed

Question 48

Antagonistic pleiotropy

Answer 48

genes that contribute to aging convey a benefit early in life and thus are selected for by evolutionary forces…”pay later” theory

Question 49

Mutation accumulation

Answer 49

Accumulation of mutations in late-active genes which lead to small, non-lethal effects early on and negative effects later in post-reproductive life

Question 50

Disposable soma theory (“DST)

Answer 50

DST proposes that aging results in part from “trade-off” between reproduction and longevity

Question 51

What are the 2 principles of DST?

Answer 51

1. Environmental resources are limited
2. Reproductive success of species depends on germline. Soma are disposable - their main function is to support survival of germline to the point of reproduction

Question 52

What is the prediction of the DST?

Answer 52

organisms that invest in high fecundity, invest less in maintenance of somatic cells and experience short lifespans

Question 53

What is the experimental evidence that supports DST?

Answer 53

1. Artificial delaying onset of reproduction in fruit flies increase longevity
2. Simulation of high predation leads to development of early reproducing flies