Ixtli wrote:
This is good. Thimerosal--which is now absent in most if not all vaccines anyway--doesn't cause or trigger autism, a genetic condition. I agree with Dr. Offit--it's great to see proper science have its victory in court.
It is generally wrong to think of Autism as a genetic disease - it is a developmental disease. Genes can greatly increase the risk of autism, but environmental factors are also recognized as important. Chemicals that increase birth defects (without causing mutations) can cause autism. So can viral infections when the mother is pregnant.
Quote:
J Neurosci. 2006 May 3;26(18):4752-62.
Comment in:
J Neurosci. 2006 Jul 26;26(30):7777-8.
The time of prenatal immune challenge determines the specificity of inflammation-mediated brain and behavioral pathology.
Meyer U, Nyffeler M, Engler A, Urwyler A, Schedlowski M, Knuesel I, Yee BK, Feldon J.
Laboratory of Behavioural Neurobiology, Swiss Federal Institute of Technology Zurich, CH-8603 Schwerzenbach, Switzerland.
Disturbance to early brain development is implicated in several neuropsychiatric disorders including autism, schizophrenia, and mental retardation. Epidemiological studies have indicated that the risk of developing these disorders is enhanced by prenatal maternal infection, presumably as a result of neurodevelopmental defects triggered by cytokine-related inflammatory events. Here, we demonstrate that the effects of maternal immune challenge between middle and late gestation periods in mice are dissociable in terms of fetal brain cytokine responses to maternal inflammation and the pathological consequences in brain and behavior. Specifically, the relative expression of pro- and anti-inflammatory cytokines in the fetal brains in response to maternal immune challenge may be an important determinant among other developmental factors for the precise pathological profile emerging in later life. Thus, the middle and late gestation periods correspond to two windows with differing vulnerability to adult behavioral dysfunction, brain neuropathology in early adolescence, and of the acute cytokine responses in the fetal brain.
Quote:
Brain Behav Immun. 2009 Jan;23(1):116-23. Epub 2008 Aug 9.
Activation of the maternal immune system alters cerebellar development in the offspring.
Shi L, Smith SE, Malkova N, Tse D, Su Y, Patterson PH.
Biology Division, California Institute of Technology, 391 S. Holliston Avenue, M/C 216-76 Pasadena, CA 91125, USA.
A common pathological finding in autism is a localized deficit in Purkinje cells (PCs). Cerebellar abnormalities have also been reported in schizophrenia. Using a mouse model that exploits a known risk factor for these disorders, maternal infection, we asked if the offspring of pregnant mice given a mid-gestation respiratory infection have cerebellar pathology resembling that seen in these disorders. We also tested the effects of maternal immune activation in the absence of virus by injection of the synthetic dsRNA, poly(I:C). We infected pregnant mice with influenza on embryonic day 9.5 (E9.5), or injected poly(I:C) i.p. on E12.5, and assessed the linear density of PCs in the cerebellum of adult or postnatal day 11 (P11) offspring. To study granule cell migration, we also injected BrdU on P11. Adult offspring of influenza- or poly(I:C)-exposed mice display a localized deficit in PCs in lobule VII of the cerebellum, as do P11 offspring. Coincident with this are heterotopic PCs, as well as delayed migration of granule cells in lobules VI and VII. The cerebellar pathology observed in the offspring of influenza- or poly(I:C)-exposed mice is strikingly similar to that observed in autism. The poly(I:C) findings indicate that deficits are likely caused by the activation of the maternal immune system. Finally, our data suggest that cerebellar abnormalities occur during embryonic development, and may be an early deficit in autism and schizophrenia.
Certainly, genetic have a big effect on the mother's immune system ... but exposure or lack of exposure to a virus can change the brain in ways that are quite similar to autism, and that is an environmental effect.
There is also a significant body of research that shows that the hormone levels of the mother while carrying the child influences the brain, and can contribute to autism. Some mothers may be genetically hard wired to have unusual testosterone levels, but often this is not determined genetically - various environmental factors flip switches that lead to autism.
Quote:
Br J Psychol. 2009 Feb;100(Pt 1):1-22. Epub 2008 Jun 10.
Fetal testosterone and autistic traits.
Auyeung B, Baron-Cohen S, Ashwin E, Knickmeyer R, Taylor K, Hackett G.
Autism Research Centre, Department of Psychiatry, University of Cambridge, Cambridge, UK.
Studies of amniotic testosterone in humans suggest that fetal testosterone (fT) is related to specific (but not all) sexually dimorphic aspects of cognition and behaviour. It has also been suggested that autism may be an extreme manifestation of some male-typical traits, both in terms of cognition and neuroanatomy. In this paper, we examine the possibility of a link between autistic traits and fT levels measured in amniotic fluid during routine amniocentesis. Two instruments measuring number of autistic traits (the Childhood Autism Spectrum Test (CAST) and the Child Autism Spectrum Quotient (AQ-Child)) were completed by these women about their children (N=235), ages 6-10 years. Intelligence Quotient (IQ) was measured in a subset of these children (N=74). fT levels were positively associated with higher scores on the CAST and AQ-Child. This relationship was seen within sex as well as when the sexes were combined, suggesting this is an effect of fT rather than of sex per se. No relationships were found between overall IQ and the predictor variables, or between IQ and CAST or AQ-Child. These findings are consistent with the hypothesis that prenatal androgen exposure is related to children exhibiting more autistic traits. These results need to be followed up in a much larger sample to test if clinical cases of ASC have elevated fT.
12 Feb 2009, 2:36 pm
I am not a jigsaw, I am a free man ! 
