30 Introduction to Autism Spectrum Disorders
vasopressin‐ and oxytocin‐positive receptors positive neurons is not as pro
nounced in the fetal neuronal cell lines of females as compared with males.
These specific neuron types are known to play key roles in male brain develop
ment. As we explain below, ASD results from degenerations of specific types of
neurons at the early stages of human brain development when exposed to
certain synthetic chemicals that are commonly found in fragrances and other
chemicals. We will discuss this in detail in Chapter 4.Why Do Certain Chemicals Induce Specific Depletions
of Certain Brain Compartments?
The brain of ASD children is a complex mosaic. The typical newborn human
brain possesses hundreds, perhaps even thousands, of different faculties, and is
comparable with the Amazon Jungle in which millions of species thrive indi
vidually. Yet this individualized existence takes place within a complex ecosys
tem that involves complex patterns of interaction and communication. In the
jungle that is the developing human brain, the speed of communication is
exceptionally rapid.
The human body develops from an extremely small genesis of a single ferti
lized egg. Growth takes place quickly and through a series of cell divisions,
body mass expands to include, at maturity, approximately 3.7 trillion cells.
However, far from being uniformly homogeneous, these cells are beautifully
apportioned throughout the various bodily organs, each of which contains
various distinct tissue layers, which in turn contain one or more histologically
recognizable cell types. The human brain is the leading organ in terms of het
erogeneity and complexity, and includes the greatest cellular diversity in terms
of length, shape, size, and function. In spite of modern molecular and immu
nological characterization methods, the human brain is still to a significant
degree a mystery to researchers – a true black box. During the period of early
fetal development, stem cells proliferation and development facilitates distinc
tive neural progenitor cells; these further differentiate into a variety of precur
sor cells that then further differentiate and enable the creation of numerous
specialized populations within the human brain. Eventually, the brain becomes
home to over 100 billion neurons. Many cell divisions are requisite to the pro
cess of manufacturing the large variety of neuronal types that make up the
varied faculties present in the fully developed human brain. At any point in
these complicated processes, mutations can occur. Fortuitously, most human
DNA is composed of noncoding genes, and this renders many mutations of
little or no significance. Thus, if the coding genes that represent only 1 or 2%
of the entire human DNA genome are not damaged, then the countless other
potential mutations can occur without producing negative phenotypic effects.