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Re: Genetic comparisons
It makes sense that insects are genetically closer to
humans than nematodes. This result will probably
disappoint some gerontologists who have been using
_Caenorhabditis elegans_ (a nematode) as a model of
longevity.
I remember my insect morphology professor stating
numerous times that the arthropods, in particular the
Class Insecta, are the most evolutionarily advanced
line of invertebrates. [Nematodes are less advanced].
Obviously there is a very large split in the lineage
between invertebrates and vertebrates, but the insects
are at the top of the invertebrate lineage. Insects
are often cheap and easy to rear and are a reasonably
good model for general information.
Insects really aren't very close to humans [compared
with vertebrate models like mice] in the specifics of
biological response to toxicants or radiation, but
they can yield comparative general information.
There have been quite a few studies of radiation with
insects (too many to list here). Many use doses on
the order of 100's of Gy.
Models of stress response and adaptation (hormesis)
involving insects, particularly fruit flies?
P.A. Parsons has spent much of his life investigating
responses to abiotic stress (heat, desiccation,
ethanol titre, radiation) in a couple of species of
fruit flies that live in rotting fruit. From this he
has derived theories about the evolutionary
significance of stress adaptation.
More of Parsons' articles can be found in PubMed by
typing "Parsons PA Drosophila"
In the interest of humor, here is an article that
found that radiation increased longevity of male
houseflies but decreased longevity among the
girl-flies! Quite high doses were used. I don't know
what would have happened had they flypapered the flies
with lower doses (500 R? 1 kR?).
~Ruth 2 (material below is titles and abstracts)
=====================================================
A FEW CITATIONS
=====================================================
Allen RG, Sohal RS. 1982. Life-lengthening effects
of gamma-radiation on the adult housefly, Musca
domestica. Mech Ageing Dev. 1982 Dec;20(4):369-375.
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7166985&dopt=Abstract
Effects of gamma-irradiation on the life span of the
adult housefly (Musca domestica) were examined in
order to elucidate the relationship between metabolic
rate, irradiation and longevity. Adult houseflies of
both sexes, exposed to 0, 20, 40 and 66 kR of
gammma-radiation, were housed under conditions of
relatively high or low physical activity. The mean
longevity of high activity males exposed to 20 and 40
kR exhibited a significant increase, whereas the
average life span of all female populations, low
activity males, and high activity males exposed to 66
kR was significantly decreased following irradiation.
Radiation exposure caused a reduction in the rate of
oxygen consumption in both sexes as well as a decrease
in the incidence of wing loss in the male flies.
Analysis of the results suggests that
radiation-induced life-lengthening in the housefly is
a consequence of reduced metabolic activity.
"DROSOPHILA RESEARCH"
Parsons PA. 1995. Inherited stress resistance and
longevity: a stress theory of ageing. Heredity. 1995
Aug;75 ( Pt 2):216-221.
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7558889&dopt=Abstract
Parsons PA. 1993. Evolutionary adaptation and
stress: energy budgets and habitats preferred. Behav
Genet. 1993 May;23(3):231-238. Review.
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8352716&dopt=Abstract
Hoffmann AA, Parsons PA. 1989. Selection for
increased desiccation resistance in Drosophila
melanogaster: additive genetic control and correlated
responses for other stresses. Genetics. 1989
Aug;122(4):837-845.
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=2503423&dopt=Abstract
Previously we found that Drosophila melanogaster lines
selected for increased desiccation resistance have
lowered metabolic rate and behavioral activity levels,
and show correlated responses for resistance to
starvation and a toxic ethanol level. These results
were consistent with a prediction that increased
resistance to many environmental stresses may be
genetically correlated because of a reduction in
metabolic energy expenditure. Here we present
experiments on the genetic basis of the selection
response and extend the study of correlated responses
to other stresses. The response to selection was not
sex-specific and involved X-linked and autosomal genes
acting additively. Activity differences contributed
little to differences in desiccation resistance
between selected and control lines. Selected lines had
lower metabolic rates than controls in darkness when
activity was inhibited. Adults from selected lines
showed increased resistance to a heat shock,
60Co-gamma-radiation, and acute ethanol and acetic
acid stress. The desiccation, ethanol and starvation
resistance of isofemale lines set up from the F2s of a
cross between one of the selected and one of the
control lines were correlated. Selected and control
lines did not differ in ether-extractable lipid
content or in resistance to acetone, ether or a cold
shock.
Zimmermann KC, Ricci JE, Droin NM, Green DR.
The role of ARK in stress-induced apoptosis in
Drosophila cells. J Cell Biol. 2002 Mar
18;156(6):1077-1087.
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11901172&dopt=Abstract
"THEORY/HYPOTHESES"
These articles have as their basis Parsons' work with
stresses on Drosophila (heat, desiccation, as well as
radiation).
Parsons, P.A. 2001. The hormetic zone: an ecological
and evolutionary perspective based upon habitat
characteristics and fitness selection. Q. Rev. Biol.
76(4):459-467.
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11783398&dopt=Abstract
Parsons, P.A. 1999. Low level exposure to ionizing
radiation: do ecological and evolutionary
considerations imply phantom risks? Perspect Biol
Med. Autumn;43(1):57-68. (no abstract)
Parsons PA. 2002. Radiation hormesis: challenging
LNT theory via ecological and evolutionary
considerations.
Health Phys. 2002 Apr;82(4):513-516.
===================================================
--- "Jacobus, John (OD/ORS)" <jacobusj@ors.od.nih.gov>
wrote:
> I received this from a National Science Foundation
> news server. I would
> expect that when you compare the beneficial effects
> to radiation to humans,
> it is better to use fruit flies than nematodes. I
> wonder how yeast compare?
>
> -- John
> John Jacobus, MS
> Certified Health Physicist
> 3050 Traymore Lane
> Bowie, MD 20715-2024
>
> E-mail: jenday1@email.msn.com (H)
>
> Gene Study Determines How Humans are Related to
> Fruit Flies and Nematode
> Worms
>
> The most comprehensive genetic study of evolutionary
> relationships among
> those animals whose genes have been completely
> sequenced - the human, the
> fruit fly, and the nematode worm - has determined
> that the human species is
> more closely related to the fruit fly than to the
> nematode.
>
> "We compared 100 genes that are common among these
> three species - the
> largest data set ever used to address this question
> - and obtained a result
> that is unambiguous," says S. Blair Hedges, an
> evolutionary biologist at
> Penn State University.
>
> Hedges and his colleagues overturn a popular
> hypothesis that was based
> primarily on the study of a single gene. The
> research team, comprising
> scientists from Penn State and Japan, was funded by
> the National Science
> Foundation (NSF). Two of these species represent
> much larger groups of
> animals, with humans representing vertebrates and
> the fruit fly representing
> arthropods.
>
> The study impacts any field that is concerned with
> the inheritance of traits
> in major groups of animals, Hedges says. The results
> - expected to affect
> the content of biology textbooks - have important
> implications for research
> in fields such as medicine and developmental
> biology. The results of the
> study were published in the web-based journal BMC
> Evolutionary Biology.
>
> The researchers tapped into the wealth of data now
> available in the
> completely sequenced genomes of the three species.
> The nematode and fruit
> fly are among the most widely used model organisms
> in medical and genetics
> research because they can be bred easily and produce
> new generations
> quickly.
>
> "A lot of our understanding of human medicine is
> based on these species
> because we can do experiments with them that you
> wouldn't do with humans,"
> Hedges says. Scientists' understanding of how the
> species are related will
> determine how to reconstruct their histories and
> whether a mutational change
> is interpreted as relatively recent or ancient.
> [Cheryl Dybas]
>
> http://www.nsf.gov/od/lpa/news/02/tip020507.htm
>
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