Isoflurane-induced apoptosis of oligodendrocytes in the neonatal primate brain.

OBJECTIVE: Previously we reported that exposure of 6-day-old (P6) rhesus macaques to isoflurane for 5 hours triggers a robust neuroapoptosis response in developing brain. We have also observed (unpublished data) that isoflurane causes apoptosis of cellular profiles in the white matter that resemble glia. We analyzed the cellular identity of the apoptotic white matter profiles and determined the magnitude of this cell death response to isoflurane. METHODS: Neonatal (P6) rhesus macaques were exposed for 5 hours to isoflurane anesthesia according to current clinical standards in pediatric anesthesia. Brains were collected 3 hours later and examined immunohistochemically to analyze apoptotic neuronal and glial death. RESULTS: Brains exposed to isoflurane displayed significant apoptosis in both the white and gray matter throughout the central nervous system. Approximately 52% of the dying cells were glia, and 48% were neurons. Oligodendrocytes (OLs) engaged in myelinogenesis were selectively vulnerable, in contrast to OL progenitors, astrocytes, microglia, and interstitial neurons. When adjusted for control rates of OL apoptosis, the percentage of OLs that degenerated in the forebrain white matter of the isoflurane-treated group was 6.3% of the total population of myelinating OLs. INTERPRETATION: Exposure of the infant rhesus macaque brain to isoflurane for 5 hours is sufficient to cause widespread apoptosis of neurons and OLs throughout the developing brain. Deletion of OLs at a stage when they are just beginning to myelinate axons could potentially have adverse long-term neurobehavioral consequences that might be additive to the potential consequences of isoflurane-induced neuroapoptosis.

Strain-specific differences in perinatal rodent oligodendrocyte lineage progression and its correlation with human.

Progress in the development of rat models of human periventricular white matter injury (WMI) has been hampered by uncertainty about the developmental window in different rodent strains that coincides with cerebral white matter development in human premature infants. To define strain-specific differences in rat cerebral white matter maturation, we analyzed oligodendrocyte (OL) lineage maturation between postnatal days (P)2 and P14 in three widely studied strains of rat: Sprague-Dawley, Long-Evans and Wistar (W). We previously reported that late OL progenitors (preOL) are the major vulnerable cell type in human periventricular WMI. Strain-specific differences in preOL maturation were found at P2, such that the W rat had the highest percentage and density of preOL relative to the other strains. Overall, at P2, the state of OL maturation was similar to preterm human cerebral white matter. However, by P5, all three strains displayed a similar magnitude and extent of OL maturation that persisted with progressive myelination between P7 and P14. PreOL were the predominant OL lineage stage present in the cerebral cortex through P14, and thus OL lineage maturation occurred latter than in white matter. The hippocampus also displayed a later onset of preOL maturation in all three strains, such that OL lineage maturation and early myelination was not observed to occur until about P14. This timing of preOL maturation in rat cortical gray matter coincided with a similar timing in human cerebral cortex, where preOL also predominated until at least 8 months after full-term birth. These studies support that strain-specific differences in OL lineage immaturity were present in the early perinatal period at about P2, and they define a narrow window of preterm equivalence with human that diminishes by P5. Later developmental onset of preOL maturation in both cerebral cortex and hippocampus coincides with an extended window of potential vulnerability of the OL lineage to hypoxia-ischemia in these gray matter regions.

Diffusion characteristics associated with neuronal injury and glial activation following hypoxia-ischemia in the immature brain.

To identify quantitative MRI indices of injury in the brain following neonatal hypoxic-ischemic brain injury, we subjected mouse pups to hypoxia-ischemia on postnatal day 7 and obtained conventional and diffusion-weighted in vivo images of the brain 24 h later followed by histological assessment. T(2)-weighted images showed increased signal intensity in the CA1 and CA2 regions of the hippocampus ipsilateral to the injury and adjacent white matter. In contrast, diffusion imaging showed reduced apparent diffusion coefficient (ADC) values in CA1 and CA2, but increased values in the adjacent white matter. Histological analysis showed widespread gliosis with degenerating oligodendrocytes in the ipsilateral hippocampus. In addition, white matter areas that were abnormal by MRI showed an increase in the number of activated microglia (CD45 positive cells). Activated caspase-3 immunostaining showed a marked increase in neurons in the hippocampal regions corresponding to those with reduced ADC, and a quantitative measure of staining showed a statistically significant correlation with the ADC. In contrast, ADC was higher in adjacent white matter, where histology showed activation of microglia and reactive oligodendrocytes but not caspase-3 activation. These results suggest that the ADC response differs between areas of neuronal injury as compared with those showing glial changes without marked cell death.

Prevalence of colon polyps detected by colonoscopy screening in asymptomatic black and white patients.

CONTEXT: Compared with white individuals, black men and women have a higher incidence and mortality from colorectal cancer and may develop cancer at a younger age. Colorectal cancer screening might be less effective in black individuals, if there are racial differences in the age-adjusted prevalence and location of cancer precursor lesions. OBJECTIVES: To determine and compare the prevalence rates and location of polyps sized more than 9 mm in diameter in asymptomatic black and white individuals who received colonoscopy screening. DESIGN, SETTING, AND PATIENTS: Colonoscopy data were prospectively collected from 67 adult gastrointestinal practice sites in the United States using a computerized endoscopic report generator between January 1, 2004, and December 31, 2005. Data were transmitted to a central data repository, where all asymptomatic white (n = 80 061) and black (n = 5464) patients who had received screening colonoscopy were identified. MAIN OUTCOME MEASURES: Prevalence and location of polyps sized more than 9 mm, adjusted for age, sex, and family history of colorectal cancer in a multivariate analysis. RESULTS: Both black men and women had a higher prevalence of polyps sized more than 9 mm in diameter compared with white men and women (422 [7.7%] vs 4964 [6.2%]; P < .001). Compared with white patients, the adjusted odds ratio (OR) for black men was 1.16 (95% confidence interval [CI], 1.01-1.34) and the adjusted OR for black women was 1.62 (95% CI, 1.39-1.89). Black and white patients had a similar risk of proximal polyps sized more than 9 mm (OR, 1.13;95% CI, 0.93-1.38). However, in a subanalysis of patients older than 60 years, proximal polyps sized more than 9 mm were more likely prevalent in black men (P = .03) and women (P < .001) compared with white men and women. CONCLUSION: Compared with white individuals, black men and women undergoing screening colonoscopy have a higher risk of polyps sized more than 9 mm, and black individuals older than 60 years are more likely to have proximal polyps sized more than 9 mm.