Biomedical subjects

B W Row

Publications and source records attributed to B W Row.

4 recordsLinked to original sources

PubMed2006

High fat/refined carbohydrate diet enhances the susceptibility to spatial learning deficits in rats exposed to intermittent hypoxia.

BACKGROUND: Intermittent hypoxia during sleep (IH), as occurs in sleep disordered breathing (SDB), induces spatial learning deficits associated with regulation of transcription factors associated with learning and memory in the hippocampal CA1 region in rats. high fat refined carbohydrate diet (HF/RC) can induce similar deficits and associated changes in signaling pathways under normoxic conditions. METHODS: Sprague-Dawley adult male rats were fed either with (HF/RC) or low fat/complex carbohydrate diet (LF/CC) starting at post-natal day 30 for 90 days, and were then exposed for 14 days during light phase (12 h/day) to either normoxia (RA) or IH (21% and 10% O2 alternations every 90 s). Place-training reference memory task deficits were assessed in the Morris water maze. Total and ser-133 phosphorylated CREB were assessed in different brain regions by Western blotting and immunostaining in rats exposed to normoxia or IH and to LF/CC or HF/RC. RESULTS: Substantial decreases in CREB phosphorylation occurred in CA1 but not in motor cortex following either IH, HF/RC, and HF/RC + IH. Place-training reference memory task deficits were observed in rats exposed to IH and to HF/RC, and to a much greater extent in rats exposed to HF/RC + IH. CONCLUSIONS: Nutritional factors alter recruitment of transcription factors, possibly via oxidative-related pathways, and modulate the vulnerability of the CA1 region of the hippocampus to the episodic hypoxia that characterizes SDB, thereby enhancing neurocognitive susceptibility in SDB patients.

Animals↗

PubMed2004

Increased oxidative stress is associated with chronic intermittent hypoxia-mediated brain cortical neuronal cell apoptosis in a mouse model of sleep apnea.

Chronic intermittent hypoxia (CIH), as occurs in obstructive sleep apnea (SA), is associated with substantial cortico-hippocampal damage leading to impairments of neurocognitive, respiratory and cardiovascular functions. Previous studies in a rat model have shown that CIH increases brain cortical neuronal cell death. However, the molecular events leading to CIH-mediated neuronal cell death remain largely undefined. The oscillation of O2 concentrations during CIH remarkably mimics the processes of ischemia/re-oxygenation and could therefore increase cellular production of reactive oxygen species (ROS). We extended the CIH paradigm to a mouse model of SA to identify the molecular mechanisms underlying cortical neuronal cell death. A significant increase of ROS production in mouse brain cortex and cortical neuronal cells was detected by fluorescent oxidation assays upon exposure of mice to CIH, followed by increased expression of oxidative stress response markers, c-Fos, c-Jun and NF-kappaB in mouse brain cortex, as revealed by immunohistochemical and LacZ reporter assays respectively. Long-term exposure of mice to CIH increased the levels of protein oxidation, lipid peroxidation and nucleic acid oxidation in mouse brain cortex. Furthermore, exposure of mice to CIH induced caspase-3 activation and increased some cortical neuronal cell apoptosis. On the other hand, transgenic mice overexpressing Cu,Zn-superoxide dismutase exposed to CIH conditions had a lower level of steady-state ROS production and reduced neuronal apoptosis in brain cortex compared with that of normal control mice. Taken together, these findings suggest that the increased ROS production and oxidative stress propagation contribute, at least partially, to CIH-mediated cortical neuronal apoptosis and neurocognitive dysfunction.

Animals↗

PubMed2003

Intermittent hypoxic exposure during light phase induces changes in cAMP response element binding protein activity in the rat CA1 hippocampal region: water maze performance correlates.

Intermittent hypoxia (IH) during sleep, a characteristic feature of sleep-disordered breathing (SDB) is associated with time-dependent apoptosis and spatial learning deficits in the adult rat. The mechanisms underlying such neurocognitive deficits remain unclear. Activation of the cAMP-response element binding protein (CREB) transcription factor mediates critical components of neuronal survival and memory consolidation in mammals. CREB phosphorylation and DNA binding, as well as the presence of apoptosis in the CA1 region of the hippocampus were examined in Sprague-Dawley male rats exposed to IH. Spatial reference task learning was assessed with the Morris water maze. IH induced significant decreases in Ser-133 phosphorylated CREB (pCREB) without changes in total CREB, starting as early as 1 h IH, peaking at 6 h-3 days, and returning toward normoxic levels by 14-30 days. Double-labeling immunohistochemistry for pCREB and Neu-N (a neuronal marker) confirmed these findings. The expression of cleaved caspase 3 (cC3) in the CA1, a marker of apoptosis, peaked at 3 days and returned to normoxic values at 14 days. Initial IH-induced impairments in spatial learning were followed by partial functional recovery starting at 14 days of IH exposure. We postulate that IH elicits time-dependent changes in CREB phosphorylation and nuclear binding that may account for decreased neuronal survival and spatial learning deficits in the adult rat. We suggest that CREB changes play an important role in the neurocognitive morbidity of SDB patients.

Animals↗

PubMed2001

Developmental differences in cortical and hippocampal vulnerability to intermittent hypoxia in the rat.

Obstructive sleep apnea is characterized by intermittent hypoxic events during sleep, and is associated with substantial neurocognitive morbidity, particularly in children. Intermittent hypoxia (IH) leads to increases in apoptosis in the cortex and hippocampus of the adult rat, peaking at 48 h of exposure. To examine whether the susceptibility to IH exhibits developmental differences, rats were exposed to 48 h of IH at ages 2, 5, 10, 15, 20, 25, 30, 60, and 120-day postnatally, and apoptosis was determined by terminal deoxy-nucleotidyl transferase-mediated in situ end labeling and immunohistochemical staining for single-stranded DNA. Although IH induced apoptosis at all postnatal ages, smaller increases were apparent in 2 and 5-day old (P < 0.01 vs. any other age) while peak apoptosis occurred at 10-25 days (P < 0.001 vs. 30, 60, and 120 days). We conclude that a unique window of vulnerability to IH is present in the cortex and hippocampus during post-natal maturation, and may underlie the high frequency of neurobehavioral deficits associated with obstructive sleep apnea in children.

Aging↗