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Enzyme error behind neural tube defects.



Women who supplement their diet with folic acid from the time they conceive through the first few months of pregnancy reduce the risk that their baby will develop a devastating dev·as·tate  
tr.v. dev·as·tat·ed, dev·as·tat·ing, dev·as·tates
1. To lay waste; destroy.

2. To overwhelm; confound; stun: was devastated by the rude remark.
 neural tube defect neural tube defect

Congenital defect of the brain or spinal cord from abnormal growth of their precursor, the neural tube (see embryology), usually with spine or skull defects.
. A new study shows why this B vitamin may work and suggests how to identify some of the women who need it most.

The brain and spinal cord develop from a single pancake of cells that first folds into a tube. If this neural tube does not fuse completely during the first 3 to 6 weeks of human life, the brain may fail to develop fully (anencephaly anencephaly /an·en·ceph·a·ly/ (an?en-sef´ah-le) congenital absence of the cranial vault, with the cerebral hemispheres completely missing or reduced to small masses.anencephal´ic

an·en·ceph·a·ly
n.
), certain protective structures may fail to shield the spinal cord (spina bifida) from paralyzing and potentially lethal injury, or both.

Recent studies have also linked neural tube defects Neural tube defects
A group of birth defects that affect the backbone and sometimes the spinal chord.

Mentioned in: Birth Defects
 to mothers deficient in another vitamin, [B.sub.12], notes James L. Mills of the National Institute of Child Health and Human Development in Bethesda, Md. Only one chemical reaction in the body requires both [B.sub.12] and folic acid. This reaction recycles an amino acid that does not go into proteins (homocysteine Homocysteine Definition

Homocysteine is a naturally occurring amino acid found in blood plasma. High levels of homocysteine in the blood are believed to increase the chance of heart disease, stroke, Alzheimer's disease, and osteoporosis.
) into one that does (methionine methionine (mĕthī`ənēn), organic compound, one of the 20 amino acids commonly found in animal proteins. Only the L-stereoisomer appears in mammalian protein. ). Mills and his coworkers reasoned that a defect in the enzyme driving this transformation might underlie neural tube defects.

They now offer confirmatory evidence of this from a study of pregnant women in Dublin, where the incidence of neural tube defects is nearly double that in the United States. Most of the 81 women whose babies suffered such defects had significantly higher concentrations of homocysteine in their blood than did mothers of 323 healthy babies born in the same hospitals.

Moreover, blood tests indicated that most women whose babies developed the neural tube defects were not deficient in either folic acid or [B.sub.12]. The group published its findings in the Jan. 21 LANCET.

This study "is the first to really suggest a mechanism" for neural tube defects, notes Norman W. Klein of the University of Connecticut The University of Connecticut is the State of Connecticut's land-grant university. It was founded in 1881 and serves more than 27,000 students on its six campuses, including more than 9,000 graduate students in multiple programs.

UConn's main campus is in Storrs, Connecticut.
 in Storrs. It also points out the value of someday screening women for a defect in homocysteine metabolism, he says.

Mills and his colleagues say their data reinforce the idea of supplementing women of childbearing age with folic acid and probably vitamin [B.sub.12]. Klein argues instead that "what [women] need is methionine" - an essential amino acid essential amino acid
n.
An alpha-amino acid that is required for protein synthesis but cannot be synthesized by humans and must be obtained in the diet.
 most abundant in animal proteins. For now, the Food and Drug Administration is reviewing plans to ensure that women receive enough folic acid by requiring - perhaps as early as this year - that manufacturers add the vitamin to all "enriched" grain-based products.
COPYRIGHT 1995 Science Service, Inc.
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1995, Gale Group. All rights reserved. Gale Group is a Thomson Corporation Company.

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Author:Raloff, J.
Publication:Science News
Article Type:Brief Article
Date:Jan 28, 1995
Words:424
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