ISSN:0031-3998    

出版商:OVID    

年代:2002

数据来源: OVID

ISSN:0031-3998    

出版商:OVID    

年代:2002

数据来源: OVID

ISSN:0031-3998    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

The perinatal development of respiratory rhythm generation and its modulation by adenosinergic drugs have been examined in rats from embryonic d 18 (E18) to postnatal d 3 using anin vitrobrain stem-spinal cord preparation. Generation of rhythmic respiratory activity in the medulla oblongata and inhibition of this activity by pontine structures were evident on E18. The adenosine A1-receptor agonist,N6-(2-phenylisopropyl) adenosine, R (−) isomer (R-PIA) (1 &mgr;M), induced an age-dependent reduction of respiratory frequency that could be reversed by the adenosine antagonist theophylline (55 &mgr;M). The effect of R-PIA was reduced 24 h after birth compared with E21 and 2 h postnatal age. In preparations from pups that had been exposed to a low dose of caffeine (0.3 g/L in drinking water to dams), pontine inhibition of respiratory rhythm generation in the medulla was more pronounced. When the pons was removed, the respiratory frequency was higher than in the control group. Adenosine A1-mRNA and A1-receptor development in pons and medulla were studied, and by E18, mRNA, receptor protein, and functional coupling to G-proteins were confirmed using guanylyl-5′-O-(&ggr;-[35S]thio)-triphosphate binding. There were no major changes in receptor numbers or distribution of A1receptors or mRNA in rat pups subjected to caffeine exposure. We conclude that respiration is already modulated by adenosine A1receptors at the level of the medulla oblongata in the fetal period in an age-dependent manner. Furthermore, long-term maternal caffeine intake during gestation seems to increase the pontine inhibition of, and the activity of, respiratory rhythm-generating neuronal networks in medulla oblongata without detectable changes in expression of A1-receptor number or A1-receptor mRNA.

ISSN:0031-3998    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Since hypothermia may be a potential treatment for perinatal cerebral hypoxic-ischemic injury, we used an established neonatal model of hypoxia-ischemia to determine the time after injury at which cooling had the best protective effect. Fourteen-day-old Wistar rats were subjected to right carotid artery ligation and hypoxia (8% O2for 90 min). Immediately at the end of hypoxia (defined as 0h), animals were either maintained at normal body temperature until sacrifice (normothermia) or subjected to hypothermia. In a preliminary study, the effects of a reduction in temperature and the duration of such cooling were investigated; animals were cooled (until brain temperature reached 33°C or 30°C) for 2, 4, or 6 h commencing immediately after hypoxia. In a second study, animals were cooled (brain temperature 30°C) for 6 h commencing at either 0, 2, 4, or 6 h after the end of hypoxia. Sham-operated animals were used as controls. Twenty-four hours after hypoxia-ischemia, cerebral energy metabolism was measured by phosphorus magnetic resonance spectroscopy, and at 5 d cerebral infarction was measured by planimetry. In normothermic animals the ratio of phosphocreatine/inorganic phosphate (PCr/Pi) had fallen markedly 24 h following hypoxia-ischemia. In contrast, animals cooled between 6 and 12 h displayed high PCr/Pi ratios similar to those in control animals. Similarly, after 5 d, infarct area was significantly reduced only in animals cooled between 6 and12 h after injury. These results indicate that cooling between 6 and 12 h after hypoxia-ischemia is more effective in reducing cerebral injury than other cooling regimes and suggest that the physiologic events during this period are critical for understanding cerebral infarction.

ISSN:0031-3998    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Our purpose was to determine factors contributing to vulnerability to antenatal periventricular leukomalacia (PVL) induced by hemorrhagic hypotension in premature fetal sheep. Systemic hypotension was induced in 10 fetal sheep by acutely withdrawing 35% to 40% of the fetoplacental blood volume at 113 d gestation. Brains were processed for histologic analysis 6 d after the insult. Statistical comparisons of physiologic parameters between fetuses suffering from PVL (n= 5) and those without PVL (n= 5) were performed. Significant correlations were found between induction of PVL and fetal brain weight, changes in fetal mean blood pressure over time, base excess, oxygen content, hematocrit, and plasma arginine vasopressin (AVP) levels in fetal abdominal aortic blood. Brain developmental stage, the magnitude of induced systemic hypotension, and baseline blood oxygen content were important intrinsic factors in the induction of antenatal PVL by hemorrhagic hypotension in premature fetal sheep.

ISSN:0031-3998    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Neonatal periventricular white matter injury is a major contributor to chronic neurologic dysfunction. In a neonatal rat stroke model, myelin basic protein (MBP) immunostaining reveals acute periventricular white matter injury. Yet, the extent to which myelin proteins can recover after neonatal hypoxic-ischemic injury is unknown. We developed a quantitative method to correlate the severity of the hypoxic-ischemic insult with the magnitude of loss of MBP immunostaining. Seven-day-old (P7) rats underwent right carotid ligation, followed by exposure to 8% oxygen for 1, 1.5, 2, or 2.5 h. On both P12 and P21, white matter integrity was evaluated by densitometric analysis of MBP immunostaining, and the amount of tissue injury was evaluated by morphometric measurements of cerebral hemisphere areas. The most severe hypoxic-ischemic insults (2.5 h) elicited marked reductions in MBP immunostaining ipsilaterally on both P12 and P21. In contrast, in mildly lesioned animals (1.5 h), MBP immunostaining was reduced ipsilaterally on P12, but 2 wk after lesioning, on P21, there was a substantial restoration of MBP immunostaining. The restoration in MBP immunostaining could reflect either functional recovery of injured oligodendroglia or proliferation and maturation of oligodendroglial precursors. Our data demonstrate that quantitative measurement of MBP immunostaining provides a sensitive indicator of acute oligodendroglial injury. Most importantly, we show that in this neonatal rodent stroke model, restoration of myelin proteins occurs after moderate, but not after more severe, cerebral hypoxia-ischemia.

ISSN:0031-3998    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Prematurity-mediated cerebral damage has been associated with oxidative stress. The aim of the present work was to study the possible role played by free oxygen radicals generated by mitochondrial respiratory function in cerebral injury in preterm neonates. Our results show that whereas total glutathione concentrations are similar in term and preterm neonates, the GSH/GSSG ratio decreases sharply in preterm neonates immediately after birth. This effect is not due to a lack of enzymes involved in GSH regeneration, such as glutathione reductase and glucose-6-phosphate dehydrogenase, but to a significant increase in free-radical generation in preterm rat brain as shown by the increase in lipoperoxidation. Because the mitochondrion is the main source of free radicals in the cell, mitochondrial respiratory function was studied in the brain of preterm neonates. Our results show that prematurity prevented the postnatal increases in complex II–III activity and ATP concentrations that occur in term neonates at 5 min after delivery. All these effects were counteracted by the oxygen supply, suggesting that the inhibition of mitochondrial function is caused by restricted oxygen availability. Consequently, cerebral damage associated with prematurity may be mediated by mitochondrial free-radical generation as a consequence of hypoxia undergone by preterm neonates at birth.

ISSN:0031-3998    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Globoid cell leukodystrophy is an autosomal recessive disease with progressive demyelination caused by a deficiency of the lysosomal enzyme galactosylceramidase. Bone marrow transplantation (BMT) is a therapeutic option for patients with late-onset disease and for patients with early onset disease that had an early diagnosis owing to an affected sibling. This therapy, however, typically is not effective for early onset disease when the diagnosis occurs after several months of life. In an effort to enable a broader range of patients to benefit from BMT, we tested whether combining substrate-reduction therapy with BMT would result in a greater benefit than either treatment alone in the twitcher mouse model of globoid cell leukodystrophy. Twitcher mice treated with l-cycloserine, an inhibitor of 3-ketodyhydrosphingosine synthase, and transplanted with 50 ± 5 × 106bone marrow cells on d 10 had a mean life-span of 112 d compared with 51 d for BMT alone (p< 0.001) or l-cycloserine alone, which was previously reported to be 56 d. l-Cycloserine treatment also was initiated neonatally to determine whether it would allow for a delayed BMT to have therapeutic value. Twitcher mice given only BMT at 18 d or only a short course of l-cycloserine died at 36 and 37 d, respectively. Twitcher mice given a short course of l-cycloserine + BMT at 18 d lived to 58 d (p= 0.0006). In conclusion, substrate-reduction therapy enhanced the value of BMT in twitcher mice, suggesting that this combination strategy might benefit patients with globoid cell leukodystrophy.

ISSN:0031-3998    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Our knowledge on the regulation of the N-mycproto-oncogene expression comes mostly fromin vitrostudies. Very fewin vivoanalyses have been performed to identify the regulatory elements involved in N-mycdevelopmental expression. In the present study, we defined DNA regions required for the regulated expression of N-mycduring early embryogenesis. We showed that the expression of N-mycdriven by the human N-mycsequences previously described to control N-mycexpression in appropriate cell typesin vitrocannot rescue the mouse N-mycmutant phenotype, suggesting that regulatory elements necessary for N-mycembryonic expression were missing. To identify the regulatory DNA regions involved in N-mycexpression, transgenic mouse lines carrying N-myc/lacZ reporter constructs were generated. &bgr;-Galactosidase staining analysis at different stages of gestation revealed that >16 kb of mouse N-mycgenomic sequences are required to recapitulate the entire spatiotemporal expression pattern of the endogenous N-mycgene between embryonic d 8.5 and 11.5. This observation supported the notion that the sequences previously identified byin vitroassays were not sufficient to reproduce the N-mycembryonic expression pattern. However, regulatory elements that can direct specific expression in the visceral arches, the limb buds, the CNS, and the dorsal root ganglia are included into the mouse N-mycgenomic sequences tested. Altogether, these findings indicated that the regulation of the spatiotemporal expression pattern of N-mycduring development necessitates multiple regulatory DNA elements.

ISSN:0031-3998    

出版商:OVID    

年代:2002

数据来源: OVID