The document discusses the effects of low-level lead exposure on the developing brain and blood-brain barrier (BBB) function in young rats. Rats exposed to lead through their mother's milk showed lead levels of 20-80 micrograms per deciliter in their blood but no effects on growth. The BBB integrity was unchanged, but some regions showed alterations in nutrient transport across the BBB that could impact central nervous system development and maturation. The document also reviews how lead exposure can disrupt the BBB and impact cognitive development in children by blocking receptors involved in brain plasticity and learning.

1. Name:Pavan Barot
:Megha Patel Group 218
CFU

2. • Lead has been recognized as a poison for millennia and has been
the focus of public health regulation in much of the developed
world for the better part of the past century. The nature of
regulation has evolved in response to increasing information
provided by vigorous scientific investigation of lead’s effects. In
recognition of the particular sensitivity of the developing brain to
lead’s pernicious effects, much of this legislation has been
addressed to the prevention of childhood lead poisoning.

3. • The present review discusses the current state of knowledge
concerning the effects of lead on the cognitive development of
children. Addressed are the reasons for the child’s exquisite
sensitivity, the behavioural effects of lead, how these effects are
best measured, and the long‐term outlook for the poisoned child.
Of particular importance are the accumulating data suggesting
that there are toxicological effects with behavioural concomitants
at exceedingly low levels of exposure.

4. • In addition, there is also evidence that certain genetic and environmental
factors can increase the detrimental effects of lead on neural development,
thereby rendering certain children more vulnerable to lead neurotoxicity. The
public health implications of these findings are discussed.

5. Blood-brain barrier (BBB) function was assessed in 19-21-day-old rats
exposed to low level lead from birth. Newborn rats received lead via milk
from lactating dams given drinking water containing 0.1% lead acetate
[Pb(Ac)2]. The treatment regime produced lead levels in the neonates
within the range 20-80 micrograms dl-1 blood, without affecting growth.
Cerebrovascular permeability (PS-product) to the diffusion-limited solute
mannitol was unchanged in six regions of the cerebral hemisphere, the
cerebellum and the brainstem, suggesting that barrier integrity was not
affected by the low dose lead treatment. Regional cerebrovascular
permeability to nutrient tracers representing seven BBB transport classes
was not impaired by lead treatment. However, the PS estimates for the
amino acids lysine and histidine and for thiamine were greater than control
in some regions of the cerebral hemisphere. These alterations in nutrient
supply to the brain may reflect altered substrate utilization associated with
repair processes or delayed maturation of the CNS.

6. Altitude
 In the nervous system, lead blocks the receptor know as N-
methyl-D-aspartate, an effective receptor involved in the
maturation of brain plasticity, which are changes that occur in
brain organization. The blockage of this receptor in the brain leads
to the interruption of long-term potentiation, which, in turn, limits
the permanent intake and storage of newly learned knowledge.
Also, elevated blood lead levels (BLLs) impair the blood-brain
barrier function (1).

7. • The blood-brain barrier is made up of many endothelial cells connected by
tight junctions. These endothelial cells become surrounded by astrocytes,
which actually outnumber neurons in brain; in the process, the astrocytes
weave their way in between the axons and dendrites. Studies have shown that
the toxicity of lead plays a major role in the communication between the
astrocytes and the endothelial cells (1)

8. Conclusion
• The blood-brain barrier has a very important function in maintaining
the fluid environment of the nervous system. While other organs in
the body transport molecules by the simple method of diffusion, the
blood-brain barrier is very persnickety in that it selects only certain and
essential water-soluble molecules (essential amino acids, glucose,
calcium, sodium, and potassium) to be transported by carriers in the
plasma membrane. This intricacy in the transportation of molecules
through the blood-brain barrier explains the barrier’s susceptibility to
trauma due to dangerous toxicants (see Figure 1) (2).

9. • When the blood-brain barrier is exposed to high levels of lead concentration,
plasma moves into the interstitial spaces of the brain, resulting in edema. High
blood lead toxicity of the CNS results in encephalopathy and edema that mainly
affects the cerebellum of the brain (3). Edema causes extreme pressure increases in
the brain, which can lead to irreversible brain damage (4). This type of brain
damage includes decreased attention, affects visual-motor reasoning skills and social
behavior and can damage mathematic skills and reading abilities (5). Studies have
also shown that lead intoxication drastically decreases cognitive ability, resulting in a
loss of IQ points anywhere from 0 to 5 per increase of 10 μg/dl in BLLs