View Full Version : "X Inactivation and Epigenetics"


mildadhd
06-15-13, 08:36 PM
X Inactivation and Epigenetics

http://www.wehi.edu.au/x_inactivation_and_epigenetics/





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Amtram
06-16-13, 12:41 PM
Excellent find, Peripheral! Using the X chromosome activation and inactivation to show how a basic epigenetic function works, and expanding that at the very end to explain how it works for other genes in different cells is a good way of explaining the process as it's programmed to work.

However, the person who decided to add the really creepy sound effects needs to be whacked upside the head. OMG, I kept laughing every time that chomping noise came on. It was like "Epigenetics! NOMNOMNOM!!!"

DcGonzo
06-16-13, 02:33 PM
Epigenetics was also explained in the video in my signature.

What does the X chromosome have to do with ADHD?

mildadhd
06-16-13, 06:42 PM
LEVELS OF HORMONAL REGULATION


1) SIMPLE HORMONAL

-Endocrine Gland Cell
-Hormone
-Target Organ Cell
-Effect Of Hormone


2) COMPLEX HORMONAL

-Pituitary Gland Cell
-Tropic Hormone
-Target Endocrine Gland Cell


3) COMPLEX NEUROHORMONAL

-Environment
-Brain
-Hypothalamus Neurosecretory Cell
-Hypothalamic Hormone


Kapit/Macey/Meisami, "The Physiology Coloring Book", (Mechanism Of Hormonal Regulation) Endocrines and Hormonal Regulation, P.115.



Focusing on ADD and brain cells..




3)COMPLEX NEUROHORMONAL

-Environment
-Brain
-Hypothalamus Neurosecretory Cell
-Hypothalamic Hormone

2)COMPLEX HORMONAL

-Pituitary Gland Cell
-Tropic Hormone
-Target Endocrine Gland Cell

1)SIMPLE HORMONAL

-Endocrine Gland Cell
-Hormone
-Target Organ Cell
-Effect Of Hormone




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mildadhd
06-16-13, 07:09 PM
..Actions of cortisol in the stress response are exerted independently from the adrenal medulla and are longer lasting.

Because cortisol is so important in defending the body against noxious and traumatic stresses,

it is considered essential for life.

Adrenalectomized animals and humans may die if exposed to sudden unexpected stresses.




..Stress induces CRH & ACTH release from hypothalamus & pituitary-

Many of stressful conditions (cold, fasting,starvation, loss of blood pressure [hypotension], hemorrhage, surgery, infections, pain from wounds and fractures, inflamations, severe exercise, and even emotional traumas) can act on the brain to release CRH (corticotropin-releasing hormone) from the hypothalamus into the hypophysial portal blood.

CRH stimulates the release of ACTH (corticotropin),

a polypeptide hormone,

from the corticotrop cells of the anterior pituitary.




ACTH stimulates cortisol secretion from adrenal cortex-

ACTH circulates in the blood and acts on the zona fasciculata of the adrenal cortex,

stimulating the synthesis and release of cortisol.

Once the cortisol level is sufficiently elevated,

CRH and ACTH secretion is decreased through the negative-feedback effect of cortisol on the hypothalamus.

This reduces the cortisol level back to the normal baseline condition.

When stress is chronic,

the brain overrides this control..





Kapit/Macey/Meisami, The PHYSIOLOGY COLORING BOOK, "Adrenal Cortex: Actions Of Cortisol", Endocrines and Hormonal Regulation, P127.



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mildadhd
06-16-13, 07:42 PM
Epigenetics




As a result of life events, chemicals attach themselves to DNA and direct gene activities.

The licking of a rat pup by the mother in the early hours of life turns on a gene in the brain that helps protect the animal from being overwhelmed by stress even as an adult.

In rats deprived of such grooming, the same gene remains dormant.

Epigenetics effects are most powerful during early development and have now been shown to be transmittable from one generation to the next,

without any change in the gene themselves. (*15)

Environmentally induced epigenetic influences powerfully modulate genetic ones.


-Gabor Mate, M.D. "In The Realm Of Hungry Ghosts", P 204.



Notes (*15)


Maternal care, gene expression, and the transmission of individual differences in stress reactivity across generations.


Abstract

Naturally occurring variations in maternal care alter the expression of genes that regulate behavioral and endocrine responses to stress, as well as hippocampal synaptic development. These effects form the basis for the development of stable, individual differences in stress reactivity and certain forms of cognition. Maternal care also influences the maternal behavior of female offspring, an effect that appears to be related to oxytocin receptor gene expression, and which forms the basis for the intergenerational transmission of individual differences in stress reactivity. Patterns of maternal care that increase stress reactivity in offspring are enhanced by stressors imposed on the mother. These findings provide evidence for the importance of parental care as a mediator of the effects of environmental adversity on neural development.
http://www.ncbi.nlm.nih.gov/pubmed/11520931




See thread, ADHD and Stress: Examining stress and the causation of neurological disorders (http://www.addforums.com/forums/showthread.php?t=146137)


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Amtram
06-16-13, 08:05 PM
I'm kind of sad now, here, Peripheral. There are a lot of videos out there that illustrate the mechanisms of epigenetics as they take place as a function of turning genetic instructions into proteins that make cells, and they are phenomenally complex by covering many more aspects of the whole process. The one you posted reduced it to something much more approachable without leaving out anything important. It was really good.

What happened in this video had nothing to do with environment, as most of the epigenetic process does. Each embryo gets four sex chromosomes (2 from mom and 2 from dad) and must end up with only two of its own. There will always be an extra X, which means that the epigenetic process has to turn that one off, just as it turns off all the genes that aren't going to be expressed on the entire chain of DNA.

Environment does not have anything to do with us turning off the extra genes so we don't end up with genetic disorders. It's not necessary for epigenetics to happen. It happens with a lot more than the extra sex chromosomes. The illustration with the striped skin is something that's been studied by biologists for some time, and can even be seen using some imaging technology whose name escapes me at the moment. It shows how the genetic information from the father and the mother is selectively expressed all over the body, even to the extent of "stripes" of skin cells built by one parent's DNA or another.

This is epigenetics picking and choosing which genes are going to be dominant and expressed, which has to happen millions of times, for each cell that's created. Imagine if you got all the DNA for a heart from only one parent, and neither parent's germ cells contained that DNA? Or if both parents' germ cells contained the DNA to build a heart, as they do, but there was nothing to turn one of them off, and you ended up with two hearts, or some crazy nonworking 8-chambered one?

This video was showing how what we used to simply call "dominant" and "recessive" genes being turned on or off, which we now know is epigenetics in action.

mildadhd
06-16-13, 09:24 PM
Amtram,

I thought you where discussing ADD, cells and epigenetics?

In my opinion external environment and internal environment are the total "environment". (not separate)



1)Do you consider the body's internal environment,

as environment?



2)In regards to ADD, are you discussing brain cells?



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DcGonzo
06-16-13, 09:37 PM
I think needs to be a significant distinction drawn between environmental influence on epigenetics on the "hardware" ( as in the example in the OP) vs the "software" ( as in the example in Peripheral's post #6). The obvious distinction to me would seem to be one of sensitivity, or "wobble" as they refer to it in the video in my signature.