the aging process in humans is gradual
present-day life expectancy of 70 yrs or more in Western societies
from 1900 to 1980, the expectancy rose more than 25 yrs to the present levels
almost 13% of the present population is over the age of 65 and the number within this age group is steadily rising
so why has there been this huge increase in longevity?
it has been argued that the upper limit to the span of human life has yet to be achieved
life span
there is documentation of people surviving to the age of 115-120 yrs old
is this the maximum intrinsic life span?
if deaths from vascular diseases and cancers can be reduced, then life expectancies will
in order to approach the genetically determined life span, it would appear necessary to
What factors affect longevity?
a person’s sex has much to do with longevity
females on the other hand, are affected more often than males with
there is evidence that a whole host of other factors influence longevity
also been determined that temperature affects aging
metabolism slows down
interesting to note that the human female has a metabolic rate that is 6% lower
than the male….is there significance to this?
evidence that cell loss does occur in tissues and organs in the body
ex:
simply put, aging is the progressive deterioration in structure and function
ex:
experimental proof that the death of cells is a normal, pre-programmed event
or if take an “old” cell and transfer it to a young organism
each cell has a finite lifetime in terms of the number of divisions it can undergo
collectively the cells set an upper limit on the
this idea of programmed cell death (apoptosis)
in a general sense, a cell presumably switches on its “suicide” program and this activates
the production of self-destruction proteins
ex:
one factor that may activate this programmed cell death is an oncogene protein
oncogene =
production of highly reactive free radicals by many normal biological reactions in the body
ex: H2O2 (hydrogen peroxide), OH (hydroxyl radical), O2 (superoxide anion)
these free radicals are highly toxic to cells
degraded by a protective enzyme system
the free radical reactions occur continually in cells
it has been suggested that human longevity could be increased 5-10 yrs
tocopherols or carotenes
not much data to support this use in humans, but has helped mice, rats, fruit flies
health food stores try to sell you selenium or superoxide dismutase
does this help or hurt?
estimated by American Cancer Society that about one in three people will develop cancer
about one in four will die from cancer
each year about 500,000 people die of cancer
currently over 10 million people are receiving medical treatment for cancer
cancer is a complex group of diseases that affects
characterized by the uncontrolled growth and division of cells
due to dramatic changes in the cell surface or cell membrane
cancer cells can grow in culture in low concentrations of serum and without known
growth factors
these cells have the ability to spread or metastasize
unchecked, the growth and metastasis result in death
as we increase our life span, this benefit has also help make cancer a major cause of illness and death in our society
because
cancer is not a recent disease
the link between cancer and mutation was suggested earlier this century
found that certain types of cancer are inherited
specific chromosomal changes are found in particular forms of cancer
specific translocations
mutation is a common feature of all cancers
in most cases, these mutational events take place in somatic cells
mutant alleles (alternate forms of a gene)
in other cases the mutations take place in germ cells
so if mutations are the spark, and we know mutations can be spontaneous, then there will always be a baseline rate of mutation
other factors can contribute to or accelerate the rate of mutation
ex: the environment
ex: behavior
estimated new cases of cancer in the US (1996)
benign tumors – self-contained
these tumors usually cause problems by
malignant tumors – cancer-forming tumors
cells can detach from the primary tumor
cancers develop in a series of steps over time
there is a series of genetic alterations
cancers are usually clonal in origin
malignant transformation