Distribution of intracellular and extracellular water molecules in developing rat's midbrain: comparison with fraction of multicomponent T(2) relaxation time and morphological findings from electron microscopic imaging.
OBJECTIVE
In the present study, we examined the behavior and state of water molecules in immature and mature rat brains by measuring the components of magnetic resonance (MR) water proton transverse relaxation time ( T(2)). We also performed morphological examination of immature and mature rat brains using electron microscopy (EM). We then compared the fraction of T(2) component and the EM findings.


METHODS
Midbrains of male Wistar rats were examined at various time points ranging from 4 h to 12 weeks after birth. T(2) was measured by MR, and the ratios of intra- to extracellular spaces were determined by EM in each stage.


RESULTS
T(2) consisted of two components: fast T(2) (<100 ms), and slow T(2) (>100 ms). During maturation, values of fast T(2) decreased dramatically, but slow T(2) remained constant. However, the fraction accounted for by slow T(2) decreased from 59% to 9% during maturation. Morphological examination showed that the extracellular space fraction of the midbrain decreased from 49% to 5% during maturation. Thus, morphological change correlated well with changes in slow T(2); in other words, multicomponent T(2) results showed a close correlation with tissue compartmentalization.


CONCLUSIONS
MR relaxation times obtained by means of multicomponent analysis can thus be used to measure intra- and extracellular space fractions.
Matsumae
M
M
Department of Neurosurgery, Tokai University School of Medicine, Bohseidai, Isehara, 259-1193, Kanagawa, Japan. mike@is.icc.u-tokai.ac.jp
Oi
S
S
Watanabe
H
H
Okamoto
K
K
Suzuki
Y
Y
Sato
K
K
Atsumi
H
H
Goto
T
T
Tsugane
R
R
D000818:Animals; D000831:Animals, Newborn / Q000254:growth & development; D001826:Body Fluids / Q000378:metabolism*; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008636:Mesencephalon / Q000254:growth & development* / Q000648:ultrastructure; D008854:Microscopy, Electron / Q000379:methods; D009186:Myelin Sheath / Q000378:metabolism / Q000648:ultrastructure; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors; D014867:Water / Q000378:metabolism*
D014867:Water