Created By: Riley Quijano
http://www.parents.com/health/autism/vaccines/health-update-more-proof-that-vaccines-dont-cause-autism/?page=1
In the late 1990s, [1] some researchers started raising concerns over the
amount of thimerosal -- a mercury-containing preservative -- found in
many children's vaccines. Although thimerosal had been used as an
anti-contamination agent for decades, until 1991 the
diphtheria-tetanus-pertussis (DTaP) vaccination was the only
thimerosal-containing shot recommended for infants
and children. The hypothesis: As more thimerosal-containing vaccines
like hepatitis B and Hib were added to the recommended schedule,
[2] researchers worried that babies were receiving too much of the chemical
in too short a timeframe, which could potentially impact brain
development.
To understand more about thimerosal safety, a brief chemistry/history
lesson is in order. [3] Thimerosal was removed from most vaccines by 2001
because researchers worried that children were being exposed to too-high
levels from receiving multiple vaccinations in a short timeframe.
[4] But this decision was based on what levels were considered safe
for methyl mercury -- the kind in fish, which is structurally very
different from the ethyl mercury found in thimerosal. Although
scientists suspected that thimerosal was much safer than methyl mercury,
they decided to remove it anyway, just to be super-careful.
[5] Now, new research published in the journal Pediatrics
shows that babies excrete thimerosal too quickly for it to build up to
dangerous amounts. In the study, researchers tested the blood mercury
levels of Argentinean babies after they received routine childhood
vaccinations (thimerosal is still used as a vaccine preservative there).
They found that infants
expel thimerosal about 10 times faster than fish mercury -- so rapidly
that it can't accumulate in the body between vaccine doses.
"This study helps to debunk a crucial basis of the
autism-vaccines theory, which held that babies were getting so many
thimerosal-containing shots that the chemical would build up in the
bloodstream and eventually cross over to the brain, where it could
theoretically impact development," says study author Michael Pichichero,
MD, a professor of microbiology/immunology and pediatrics at the
University of Rochester Medical Center. "But thimerosal leaves babies'
bodies way too quickly for that to happen, which just adds more proof
that this theory is extremely unlikely."
Category: Second Semester Research Sources | Comments: 0 | Rate:
0 Votes
You have rated this item.
Created By: Riley Quijano
http://www.wiringthebrain.com/2012/04/de-novo-mutations-in-autism.html
A trio of papers in this week’s
Nature
identifies mutations causing autism in four new genes, demonstrate the
importance of de novo mutations in the etiology of this disorder and
suggest that there may be 1,000 or more genes in which high-risk,
autism-causing mutations can occur.
These studies provide an
explanation for what seems like a paradox: on the one hand, twin studies
show that autism is very strongly genetic (identical twins are much
more likely to share a diagnosis than fraternal twins) – on the other,
many cases are sporadic, with no one else in the family affected. How
can the condition be “genetic” but not always run in the family? The
explanation is that many cases are caused by new mutations – ones that
arise in the germline of the parents. (This is similar to conditions
like Down syndrome). The studies reported in Nature are trying to find
those mutations and see which genes are affected.
They are only
possible because of the tremendous advances in our ability to sequence
DNA. The first genome cost three billion dollars to sequence and took
ten years – we can do one now for a couple thousand dollars in a few
days. That means you can scan through the entire genome in any affected
individual for mutated genes. The problem is we each carry hundreds of
such mutations, making it difficult to recognise the ones that are
really causing disease.
The solution is to sequence the DNA of
large numbers of people with the same condition and see if the same
genes pop up multiple times. That is what these studies aimed to do,
with samples of a couple hundred patients each. They also concentrated
on families where autism was present in only one child and looked
specifically for mutations in that child that were not carried by either
parent – so-called
de novo mutations,
that arise in the generation of sperm or eggs. These are the easiest
to detect because they are likely to be the most severe. (Mutations
with very severe effects are unlikely to be passed on because the people
who carry them are far less likely to have children).
[1] There is
already strong evidence that de novo mutations play an important role in
the etiology of autism – first, de novo copy number variants (deletions
or duplications of chunks of chromosomes) appear at a significantly
higher rate in autism patients compared to controls (in 8% of patients
compared to 2% of controls). [2] Second, it has been known for a while that
the risk of autism increases with paternal age – that is, older fathers
are more likely to have a child with autism. (Initial studies
suggested the risk was up to five-fold greater in fathers over forty –
these figures have been revised downwards with increasing sample sizes,
but the effect remains very significant, with risk increasing
monotonically with paternal age). This is also true of schizophrenia
and, in fact, of dominant Mendelian disorders in general (those caused
by single mutations).
[3] The reason is that the germ cells generating
sperm in men continue to divide throughout their lifetime, leading to an
increased chance of a mutation having happened as time goes on.
The
three studies in Nature were looking for a different class of mutation –
point mutations or changes in single DNA bases.
[4]They each provide a
list of genes with de novo mutations found in specific patients.
Several of these showed a mutation in more than one (unrelated) patient,
providing strong evidence that these mutations are likely to be causing
autism in those patients. [5] The genes with multiple hits include CHD8,
SCN2A, KATNAL2 and NTNG1. Mutations in the last of these, NTNG1, were
only found in two patients but have been previously implicated as a rare cause of Rett syndrome. [6] This gene encodes the protein Netrin-G1, which is involved in the guidance of growing nerves and the specification of neuronal connections. CHD8
is a chromatin-remodeling factor and is involved in Wnt signaling, a
major neurodevelopmental pathway, as well as interacting with p53, which
controls cell growth and division. SCN2A
encodes a sodium channel subunit; mutations in this gene are involved
in a variety of epilepsies. Not much is known about KATNAL2, except by
homology – it is related to proteins katanin and spastin,
which sever microtubules – mutations in spastin are associated with
hereditary spastic paraplegia. [7] How the specific mutations observed in
these genes cause the symptoms of autism in these patients (or
contribute to them) is not clear – these discoveries are just a starting
point, but they will greatly aid the quest to understand the biological
basis of this disorder.
[8] The fact that these studies only got a
few repeat hits also means that there are probably many hundreds or even
thousands of genes that can cause autism when mutated (if there were
only a small number, we would see more repeat hits). Some of these will
be among the other genes on the lists provided by these studies and
will no doubt be recognisable as more patients are sequenced.
Interestingly, many of the genes on the lists are involved in aspects of
nervous system development or function and encode proteins that
interact closely with each other – this makes it more likely that they
are really involved.
These studies reinforce the fact that
autism is not one disorder - not clinically and not genetically either.
Like intellectual disability or epilepsy or many other conditions, it
can be caused by mutations in any of a very large number of genes. The
ones we know about so far make up around 30% of cases – these new
studies add to that list and also show how far we have to go to complete
it.
We should recognise too that the picture will also get more
complex – in many cases there may be more than one mutation involved in
causing the disease. De novo mutations are likely to be the most
severe class and thus most likely to cause disease with high penetrance
themselves. But many inherited mutations may cause autism only in
combination with one or a few other mutations.
These
complexities will emerge over time, but for now we can aim to recognise
the simpler cases where a mutation in a particular gene is clearly
implicated. Each new gene discovered means that the fraction of cases
we can assign to a specific cause increases. As we learn more about the
biology of each case, those genetic diagnoses will have important
implications for prognosis, treatment and reproductive decisions. We
can aim to diagnose and treat the underlying cause in each patient and
not just the symptoms.
Category: Second Semester Research Sources | Comments: 0 | Rate:
0 Votes
You have rated this item.
Created By: Riley Quijano
http://www.mayoclinic.com/health/childhood-disintegrative-disorder/DS00801/DSECTION=symptoms
Children with childhood disintegrative disorder typically show a
[1]dramatic loss of previously acquired skills in two or more of the
following areas:
- Language, including a severe decline in the ability to speak and have a conversation
- Social skills, including significant difficulty relating to and interacting with others
- Play, including a loss of interest in imaginary play and in a variety of games and activities
- Motor skills, including a dramatic decline in the ability to walk, climb, grasp objects and perform other movements
- Bowel or bladder control, including frequent accidents in a child who was previously toilet trained
Loss of developmental milestones may occur abruptly over the course of
days to weeks or gradually over an extended period of time.
When to see a doctor
Children typically develop at their own pace, but any loss of
developmental milestones is cause for concern. If your child has
suddenly lost previously acquired language, social, motor, play,
thinking (cognitive) or self-help skills, such as toilet training and
feeding, contact your doctor. In addition, if you suspect that your
child has gradually shown a loss in any area of development, talk with
your doctor.
Category: Second Semester Research Sources | Comments: 0 | Rate:
0 Votes
You have rated this item.
Created By: Riley Quijano
Category: Second Semester Research Sources | Comments: 0 | Rate:
0 Votes
You have rated this item.
Created By: Riley Quijano
http://www.helpguide.org/mental/autism_spectrum.htm
Autism is a spectrum disorder, meaning that there is a wide degree of
variation in the way it affects people. Every child on the autism
spectrum has unique abilities, symptoms, and challenges. Learning about
the different autism spectrum disorders will help you better understand
your own child, get a handle on what all the different autism terms
mean, and make it easier to communicate with the doctors, teachers, and
therapists helping your child.
[1] Autism is not a single disorder, but a spectrum of closely-related disorders with a shared core of symptoms. Every individual on the autism spectrum has problems to some degree with social skills, empathy, communication, and flexible behavior. But the level of disability and the combination of symptoms varies tremendously from person to person. In fact, two kids with the same diagnosis may look very different when it comes to their behaviors and abilities.
If you’re a parent dealing with a child on the autism spectrum, you may hear many different terms including high-functioning autism, atypical autism, autism spectrum disorder, and pervasive developmental disorder. These terms can be confusing, not only because there are so many, but because doctors, therapists, and other parents may use them in dissimilar ways.
But no matter what doctors, teachers, and other specialists call the autism spectrum disorder, it’s your child’s unique needs that are truly important. No diagnostic label can tell you exactly what problems your child will have. Finding treatment that addresses your child’s needs, rather than focusing on what to call the problem, is the most helpful thing you can do. You don’t need a diagnosis to start getting help for your child’s symptoms.
Category: Second Semester Research Sources | Comments: 0 | Rate:
0 Votes
You have rated this item.
Created By: Riley Quijano
http://www.webmd.com/brain/autism/understanding-autism-basics
l interaction and developmental language and communication skills, and rigid, repetitive behaviors. It ranges in severity from a handicap that limits an otherwise normal life to a devastating disability that may require institutional care.
Children with autism have trouble communicating. They have trouble understanding what other people think and feel. This makes it very hard for them to express themselves either with words or through gestures, facial expressions, and touch.
A child with autism who is very sensitive may be greatly troubled -- sometimes even pained -- by sounds, touches, smells, or sights that seem normal to others.
Children who are autistic may have repeated body movements such as rocking or hand flapping. They may have unusual responses to people, attachments to objects, resistance to change in their routines, and/or aggressive or self-injurious behavior. At times they may seem not to notice people, objects, or activities in their surroundings. Some children with autism may also develop seizures, in some cases not until adolescence.
Many people with autism are mentally challenged. In contrast to mental retardation alone, which is characterized by relatively even skill development, people with autism show uneven skill development. They may have problems in certain areas, especially the ability to communicate and relate to others. But they may have unusually developed skills in other areas, such as drawing, creating music, solving math problems, or memorizing facts. For this reason, they may test higher -- perhaps even in the average or above-average range -- on nonverbal intelligence tests.
Autism typically appears during the first three years of life. Some children show signs from birth. Others seem to develop normally at first, only to slip suddenly into symptoms when they are 18 to 36 months old. Autism is four times more common in boys than in girls. It knows no racial, ethnic, or social boundaries. Family income, lifestyle, or educational levels do not affect a child's chance of being autistic.
[1] Some of the different types of autism spectrum disorders include:
[2] Autistic disorder. This is what most people think of when they hear the word "autism." It refers to problems with social interactions, communication, and imaginative play in children younger than 3 years.
[3] Asperger'ssyndrome. These children don't have a problem with language -- in fact, they tend to score in the average or above-average range on intelligence tests. But they have the same social problems and limited scope of interests as children with autistic disorder.
[4] Pervasive developmental disorder or PDD -- also known as atypical autism. This is a kind of catch-all category for children who have some autistic behaviors but who don't fit into other categories.
[5] Rett syndrome. Known to occur mainly in girls, children with Rett syndrome start developing normally but begin to lose their communication and social skills. Beginning at the age of 1 to 4 years, repetitive hand movements replace purposeful use of the hands.
[6] Childhood disintegrative disorder. These children develop normally for at least two years and then lose some or most of their communication and social skills.
Category: Second Semester Research Sources | Comments: 0 | Rate:
0 Votes
You have rated this item.