Yoshinari Taniuchi

Developmental changes in mitochondrial activity and energy metabolism in fetal and neonatal rat brain

Experiments were undertaken to investigate mitochondrial activity and energy metabolism in the developing rat brain from the late fetal stage to the neonatal stage. Samples of cerebral cortical tissue were obtained from fetuses at 14, 16, 18, and 20 days of gestation, and from pups at 1 h, 1 day and 7 days after birth. Mitochondrial respiration was measured polarographically using homogenates. Fetal and neonatal brains were frozen in situ and fluorometric enzymatic techniques were used for the analysis of ATP, ADP, AMP, and lactate. In the fetal brain, there was a gradual increase in stimulated (+ADP) and uncoupled respiratory rates using glutamate and malate as substrates, from 14 days to 20 days of gestation, together with a moderate increase in ATP concentration and in the sum total of adenine nucleotides, and a significant decrease in lactate. Since non-stimulated (-ADP) respiratory rates did not change with increasing gestational age, the respiratory control ratio appeared to increase over the same period. An increase in mitochondrial activity was more pronounced immediately after birth, together with a marked increase in ATP concentration and in the sum total of adenine nucleotides. The highest rate of mitochondrial respiration was observed in 1-hour-old pups. These results indicate that, in the rat brain, there is maturation of oxidative metabolism in mitochondria that is initiated in late gestation. Acceleration in mitochondrial respiration occurs immediately after birth in order to maintain high-energy phosphate levels, and this may be crucial for the successful outcome of the newborn.

Effect of α-phenyl-N-tert-butyl nitrone (PBN) on fetal cerebral energy metabolism during intrauterine ischemia and reperfusion in rats

The objective of the present study was to explore whether a free radical spin trap agent, α-phenyl-N-tert-butyl nitrone (PBN), influences bioenergetic failure induced in the 20-day-old fetal brain by 30 min of intrauterine ischemia in Wistar rats. Fetal brains were frozen in situ at the end of ischemia and after 1, 2, and 4 h of recirculation for analysis of ATP, ADP, AMP, and lactate. PBN or vehicle was given 1 h after recirculation. Tissue oxygen tension was evaluated in placental and fetal cerebral tissues throughout the whole periods of 30 min of ischemia and 4 h of recirculation. Ischemia was associated with a decrease in ATP concentration and an increase in lactate concentration (p < 0.001). Recirculation (1 and 2 h) led to a recovery of ATP concentration, but continued reflow (4 h) was associated with a secondary deterioration of high-energy phosphates (p < 0.01). Lactate concentration increased during this recovery period. This deterioration was prevented by PBN (p < 0.05). After 30 min of ischemia, tissue oxygen tension in placenta and fetal brain decreased to about 30% and 50% of control, respectively. However, recirculation brought about a recovery of oxygen delivery. The results indicate that although during the early time period after ischemia fetal cerebral energy metabolism is maintained by an acceleration of the anaerobic glycolytic rate, secondary deterioration of cellular bioenergetic state develops in the immature fetal brain. This deterioration may be due to mitochondrial dysfunction, which may be induced by oxygen-derived free radicals, and not by compromised microcirculation.

Influence of mild hypothermia on delayed mitochondrial dysfunction after transient intrauterine ischemia in the immature rat brain

The aim of this study was to determine the effect of different maternal thermal conditions during transient intrauterine ischemia on the mitochondrial respiratory activities in the immature rat brain. On 17 days of gestation, transient intrauterine ischemia was induced by 30 min of right uterine artery occlusion under hypothermic (33.5-34.5 degrees C, n=6), normothermic (36.5-37.5 degrees C, n=6), and hyperthermic conditions (39.5-40.5 degrees C, n=6). All of the pups were delivered by cesarean section at 21 days of gestation and cerebral neocortical tissue was sampled 1 h after delivery. The mitochondrial respiration was measured polarographically in homogenates. In the ischemic uterine horn, ADP-stimulated respiration of the normothermia and the hyperthermia groups decreased significantly to 73 and 74% of the non-ischemic controls, respectively. Since non-stimulated respiration remained unchanged, the respiratory control ratio (RCR) of the normothermia and the hyperthermia groups decreased significantly to 59 and 54% of the non-ischemic levels, respectively. In contrast, the mitochondrial respiratory activities of the hypothermia group showed no differences between the non-ischemic and the ischemic uterine horns. The results demonstrate that mild maternal hypothermia ameliorates the cerebral mitochondrial dysfunction in neonatal rats after intrauterine ischemia due to transient uterine artery occlusion and suggest that maternal thermal conditions, particularly during uteroplacental insufficiency, have important implications for the neuropathological outcome of the newborn.

Increased Level of Granulocyte Elastase in Cervical Secretion Is an Independent Predictive Factor for Preterm Delivery

Objective: The objective of this study was to explore whether increased levels of granulocyte elastase in cervical secretion is an independent predictive factor for preterm delivery before 34 weeks of gestation in the patient with preterm labor. Methods: One hundred and sixty-one women with preterm labor at 22–28 weeks of gestation were enrolled prospectively. The level of granulocyte elastase in cervical secretions was measured by immunoassay, vaginal secretions were collected for the microscopic evaluation of Gram-stained smears, and the uterine cervix was assessed by transvaginal ultrasonography. Results: Nineteen of 161 patients (12%) delivered before 34 weeks of gestation. Granulocyte elastase assessment had a sensitivity, specificity, positive predictive value, and negative predictive value for preterm delivery of 53, 75, 22 and 92%, respectively. A positive elastase assessment was associated with a relative risk for preterm delivery of 2.9 (95% CI 1.3–6.6), whereas a positive bacterial vaginosis assessment and shorter cervical length less than 25 mm demonstrated a relative risk of 1.9 (95% CI 0.8–4.6) and 1.5 (95% CI 0.6–5.0), respectively. Conclusion: The present study demonstrates that the risk of spontaneous preterm delivery before 34 weeks of gestation is increased in the women with preterm labor who are found to have an increased level of granulocyte elastase in cervical secretions.

Vitamins ameliorate secondary mitochondrial failure in neonatal rat brain

Recirculation after transient intrauterine ischemia has previously been found to be accompanied by secondary mitochondrial dysfunction in the immature rat brain. This study was performed to assess the efficacy of combined treatment with ascorbic acid and alpha-tocopherol in improving secondary brain damage. On the 17th day of gestation, transient intrauterine ischemia was induced by 30 minutes of uterine artery occlusion. Either vehicle, ascorbic acid, alpha-tocopherol, or combination of ascorbic acid and alpha-tocopherol was randomly administered to pregnant rats before and after occlusion. The pups were delivered by cesarean section at 21 days of gestation, and cerebral neocortical tissue was sampled. The mitochondrial respiration was measured polarographically in homogenates. In the ischemia uterine horn, mitochondrial activity of the vehicle treatment decreased significantly to 56% of nonischemic controls. Treatment with ascorbic acid or alpha-tocopherol alone demonstrated a moderate improvement of the secondary mitochondrial dysfunction to 64% and 62% of nonischemic controls, respectively. The combined treatment caused a normalization of mitochondrial activity to 91% of nonischemic controls. These results indicate that combined treatment with ascorbic acid and alpha-tocopherol has a more protective effect against secondary mitochondrial dysfunction after transient intrauterine ischemia compared with the administration of ascorbic acid or alpha-tocopherol alone.

Secondary Mitochondrial Dysfunction after Transient Intrauterine Ischemia in the Fetal Rat Brain

Objective: Recirculation following transient intrauterine ischemia has previously been found to cause partial recovery and secondary deterioration of cellular bioenergetic states in the fetal rat brain. Our objective was to assess whether secondary bioenergetic failure is due to mitochondrial dysfunction.

Maternal treatment with NMDA receptor antagonist (MK-801) attenuates delayed mitochondrial dysfunction after transient intrauterine ischemia in the neonatal rat brain

AbstractPurpose. Mitochondrial respiratory activities were measured in neonatal rat brains to evaluate the influence of transient intrauterine ischemia on the near-term fetus and to assess the effect of dizocilpine maleate (MK-801), a noncompetitive N-methyl-d-aspartate (NMDA) receptor antagonist. Methods. Transient intrauterine ischemia was induced by 30 min of right uterine artery occlusion at 17 days of gestation in Wistar rats. Vehicle (saline) or 0.5 mg/kg of MK-801 was administered after 1 h of recirculation. All of the pups were delivered by cesarean section at 21 days of gestation and samples of cerebral cortical tissue were obtained from pups at 1 h after birth. Adenosine diphosphate (ADP)-stimulated, nonstimulated, and uncoupled respirations were measured polarographically in homogenates. The respiratory control ratio was defined as ADP-stimulated divided by non-stimulated respiration. Results. In the vehicle-treated group the neonatal cortical tissue exposed to ischemia showed a significant decrease in ADP-stimulated respiration and respiratory control ratio compared with these findings in normoxic control animals. The delayed mitochondrial respiratory dysfunction was prevented by MK-801, given 1 h after the start of recirculation (P < 0.05). Conclusion. The present results indicate that transient intrauterine ischemia in the near-term rat fetus is associated with delayed mitochondrial dysfunction in the neonatal brain; the results suggest that maternal treatment with MK-801 attenuates the deterioration, even when administered 1 h after the start of recirculation.

Short therapeutic window for nifedipine in transient intrauterine ischemia in fetal rat brain.

The aim of this study was to explore whether nifedipine influences the secondary deterioration of cerebral mitochondrial function after transient intrauterine ischemia in fetal rats. Intrauterine ischemia was induced by a 30-min occlusion of the right uterine artery at 20 days of gestation in Wistar rats. Nifedipine (1 mg kg(-1)) or vehicle was injected subcutaneously before the onset of ischemia or 1 h after the start of recirculation. Fetuses were delivered by cesarean section at the end of ischemia (n=6 with vehicle; n=6 with nifedipine pretreatment) or at 4 h of recirculation (n=6 with vehicle; n=6 with nifedipine pretreatment; n=6 with nifedipine posttreatment), and the cerebral mitochondrial respiration was measured polarographically. Tissue oxygen tension was evaluated in placental and fetal cerebral tissues (n=5 with vehicle; n=5 with nifedipine pretreatment). The vehicle treated animals showed a significant decrease in mitochondrial activities at the end of ischemia and 4 h of recirculation. Nifedipine attenuates the secondary deterioration at 4 h of recirculation when given just prior to ischemia, but had no neuroprotective activity when given 1 h after the start of recirculation. Nifedipine pretreatment had no influence on oxygen delivery in placenta and fetal cerebrum during and after ischemia. Despite the short therapeutic window, the treatment of nifedipine attenuates the secondary deterioration of cerebral mitochondrial function after transient intrauterine ischemia in fetal rats when given just prior to ischemia.

Maternal Treatment with α-Phenyl-N-tert-Butylnitrone Attenuates Secondary Mitochondrial Dysfunction after Transient Intrauterine Asphyxia in the Fetal Rat Brain

Recirculation following 30 min of ischemia due to transient uterine artery occlusion in pregnant rats at 20 days gestation has previously been found to cause partial recovery and secondary deterioration of the cellular bioenergetic state in the fetal brain, the subsequent damage being ameliorated by a free radical spin trap agent, α-phenyl-N-tert-butylnitrone (PBN). Our objective was to assess whether the secondary deterioration of the cellular bioenergetic state is due to mitochondrial dysfunction and to study whether PBN acts to prevent secondary damage to mitochondria in the fetal rat brain. Fetal neocortical tissues were sampled after 30 min of intrauterine ischemia and after 1, 2 or 4 h of recirculation. PBN or vehicle was given 1 h after recirculation. Homogenates were prepared, and ADP-stimulated, nonstimulated and uncoupled respiratory rates were measured polarographically. Ischemia was associated with a decrease in ADP-stimulated and uncoupled respiratory rates, with a marked fall in the respiratory control ratio, defined as ADP-stimulated divided by nonstimulated respiration (p < 0.01). Recirculation (1 h) brought about partial recovery, but continued reflow (2 and 4 h) was associated with a secondary deterioration of respiratory functions (p < 0.01). The secondary deterioration was prevented by PBN (p < 0.05). The results demonstrate that the secondary deterioration of the cellular bioenergetic state in ischemia-reperfusion is due to secondary mitochondrial dysfunction and that this deterioration may be induced by oxygen-derived free radicals in the immature fetal brain.