Intrauterine growth restriction due to uteroplacental vascular insufficiency leads to increased hypoxia-induced cerebral apoptosis in newborn piglets

Uteroplacental vascular insufficiency in humans is a common cause of intrauterine growth restriction (IUGR) and is associated with an increased incidence of perinatal asphyxia and neurodevelopmental disorders compared to normal weight newborns. Experimental models that provide an opportunity to analyze the pathogenesis of these relationships are limited. Here, we used neonatal pigs from large litters in which there were piglets of normal birth weight (for controls) and of low birth weight (for uteroplacental vascular insufficiency). Hypoxia was induced in paired littermates by reducing the fraction of inspired oxygen to 4% for 25 min. Brain tissue was collected 4 h post-hypoxia. Cerebral levels of apoptosis were quantified morphologically and verified with caspase-3 activity and TUNEL. Expression of Bcl-2, BcI-XL and Bax proteins was investigated using immunohistochemistry. Cellular positivity for Bcl-2 was consistently higher in the non-apoptotic white matter of the hypoxic IUGR animals compared with their littermates and reached significance at P < 0.05 in several pairs of littermates. Alterations in Bax showed a trend towards higher expression in the hypoxic IUGR littermates but rarely reached significance. The IUGR piglets showed a significantly greater amount of apoptosis in response to the hypoxia than the normal weight piglets, suggesting an increased vulnerability to apoptosis in the IUGR piglets. (c) 2006 Elsevier B.V. All rights reserved.

White and gray matter development in human fetal, newborn and pediatric brains

Brain anatomy is characterized by dramatic growth from the end of the second trimester through the neonatal stage. The characterization of normal axonal growth of the white matter tracts has not been well-documented to date and could provide important clues to understanding the extensive inhomogeneity of white matter injuries in cerebral palsy (CP) patients. However, anatomical studies of human brain development during this period are surprisingly scarce and histology-based atlases have become available only recently. Diffusion tensor magnetic resonance imaging (DTMRI) can reveal detailed anatomy of white matter. We acquired diffusion tensor images (DTI) of postmortem fetal brain samples and in vivo neonates and children. Neural structures were annotated in two-dimensional (2D) slices, segmented, measured, and reconstructed three-dimensionally (3D). The growth status of various white matter tracts was evaluated on cross-sections at 19-20 gestational weeks, and compared with 0-month-old neonates and 5- to 6-year-old children. Limbic, commissural, association, and projection white matter tracts and gray matter structures were illustrated in 3D and quantitatively characterized to assess their dynamic changes. The overall pattern of the time courses for the development of different white matter is that limbic fibers develop first and association fibers last and commissural and projection fibers are forming from anterior to posterior part of the brain. The resultant DTNIRI-based 3D human brain data will be a valuable resource for human brain developmental study and will provide reference standards for diagnostic radiology of premature newborns. (c) 2006 Elsevier Inc. All rights reserved.

Heart rate variability characterization using a time-frequency based instantaneous frequency estimation technique

In this paper, a new method for characterizing the newborn heart rate variability (HRV) is proposed. The central of the method is the newly proposed technique for instantaneous frequency (IF) estimation specifically designed for nonstationary multicomponen signals such as HRV. The new method attempts to characterize the newborn HRV using features extracted from the time–frequency (TF) domain of the signal. These features comprise the IF, the instantaneous bandwidth (IB) and instantaneous energy (IE) of the different TF components of the HRV. Applied to the HRV of both normal and seizure suffering newborns, this method clearly reveals the locations of the spectral peaks and their time-varying nature. The total energy of HRV components, ET and ratio of energy concentrated in the low-frequency (LF) to that in high frequency (HF) components have been shown to be significant features in identifying the HRV of newborn with seizures.