Transient NMDA receptor-mediated hypoperfusion following umbilical cord occlusion in preterm fetal sheep

Exposure to severe hypoxia leads to delayed cerebral and peripheral hypoperfusion. There is evidence in the very immature brain that transient abnormal glutaminergic receptor activity can occur during this phase of recovery. We therefore examined the role of N-methyl-D-aspartate (NMDA) receptor activity in mediating secondary hypoperfusion in preterm fetal sheep at 70% of gestation. Fetuses received either sham asphyxia or asphyxia and were studied for 12 h recovery. The specific, non-competitive NMDA receptor antagonist dizocilpine maleate (2 mg kg-1 bolus plus 0.07 mg kg h-1i.v.) or saline (vehicle) was infused from 15 min after asphyxia until 4 h. In the asphyxia-vehicle group abnormal epileptiform EEG transients were observed during the first 4 h of reperfusion, the peak of which corresponded approximately to the nadir in peripheral and cerebral hypoperfusion. Dizocilpine significantly suppressed this activity (2.7+/-1.3 versus 11.2+/-2.7 counts min-1 at peak frequency, P<0.05) and markedly delayed and attenuated the rise in vascular resistance in both peripheral and cerebral vascular beds observed after asphyxia, effectively preventing the initial deep period of hypoperfusion in carotid blood flow and femoral blood flow (P<0.01). However, while continued infusion did attenuate subsequent transient tachycardia, it did not prevent the development of a secondary phase of persistent but less profound hypoperfusion. In conclusion, the present studies suggest that in the immature brain the initial phase of delayed cerebral and peripheral hypoperfusion following exposure to severe hypoxia is mediated by NMDA receptor activity. The timing of this effect in the cerebral circulation corresponds closely to abnormal EEG activity, suggesting a pathological glutaminergic activation that we speculate is related to evolving brain injury.

Biochemical analysis and immunohistochemical determination of cardiac troponin for the postmortem diagnosis of myocardial damage

Cardiac disease is the most common cause of sudden death in Western nations. In forensic practice there is a need for more sensitive diagnostic methods for the postmortem diagnosis of myocardial damage. The aim of this study was to analyse the diagnostic efficacy of biochemical markers in cadaver fluids in conjunction with histological studies and the immunohistochemical determination of cardiac troponin C (cTnC) and cardiac troponin T (cTnT) levels in myocardial tissue fixed in formol and included in paraffin. We studied 50 cadavers (43 males and 7 females) with a mean age of 47.5 years (SD 19.2; range 12 to 87 years). Cases were chosen according to the postmortem interval, cause of death, and circumstances of death. Pericardial fluid and serum were tested in duplicate for cardiac troponin I (cTn I), myoglobin and CKMB by immunoassay system using commercial kits. In myocardial tissue, histological studies were performed with hematoxylin and eosin (HE), Masson's trichrome staining and immunohistochemical techniques involving streptavidin-biotin-peroxidase were performed. The results pointed to statistically significant differences for all the biochemical markers in pericardial fluid. The highest levels were obtained in the group of cadavers who had died from myocardial infarction. The immunohistochemical expression of cTnC was detected in 86% of cases; it was strongly positive and usually diffuse. The expression of cTnT, was much less frequent (46% of cases) and less intense. It was concluded that the immunohistochemical determination of cTnC and cTnT levels in myocardial tissue may be used as an index of myocardium damage.

Cortisol and ACTH responses to severe asphyxia in preterm fetal sheep

It has been hypothesized that the hypothalamic-pituitary-adrenal (HPA) axis is immature in the preterm fetus and that this compromises their ability to adapt to hypoxic stress; however, there are few direct data. We therefore examined the effects of asphyxia on HPA responses in chronically instrumented preterm fetal sheep (104 days of gestation; term is 147 days), allocated to a sham control group (n = 7) or 25 min of complete umbilical cord occlusion (n = 8), followed by recovery for 72 h. During umbilical cord occlusion there was a rapid rise in ACTH levels (230.4 +/- 63.5 versus 14.1 +/- 1.8 ng ml(-1) in sham controls, 16-fold) and cortisol levels (7.4 +/- 4.9 versus 0.2 +/- 0.1 ng ml(-1), 31-fold), with further increases after release of cord occlusion. ACTH levels were normalized by 24 h, while plasma cortisol levels returned to sham control values 72 h after asphyxia. Fetal arterial blood pressure was elevated in the first 36 h, with a marked increase in femoral vascular resistance, and correlated positively with cortisol levels after asphyxia (P = 0.05). In conclusion, the preterm fetus shows a brisk, substantial HPA response to severe hypoxia.

Cerebral oxygenation during postasphyxial seizures in near-term fetal sheep

After exposure to asphyxia, infants may develop both prolonged, clinically evident seizures and shorter, clinically silent seizures; however, their effect on cerebral tissue oxygenation is unclear. We therefore examined the hypothesis that the increase in oxygen delivery during postasphyxial seizures might be insufficient to meet the needs of increased metabolism, thus causing a fall in tissue oxygenation, in unanesthetized near-term fetal sheep in utero (gestational age 125+/-1 days). Fetuses were administered an infusion of the specific adenosine A1 receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine, followed by 10 mins of asphyxia induced by complete umbilical cord occlusion. The fetuses then recovered for 3 days. Sixty-one episodes of electrophysiologically defined seizures were identified in five fetuses. Tissue PO(2) (tPO(2)) did not change significantly during short seizures (<3.5 mins), 5.2+/-0.2 versus baseline 5.6+/-0.1 mm Hg (NS), but fell to 2.2+/-0.2 mm Hg during seizures lasting more than 3.5 mins (P<0.001). During prolonged seizures, cortical blood flow did not begin to increase until tPO(2) had begun to fall, and then rose more slowly than the increase in metabolism, with a widening of the brain to blood temperature gradient. In conclusion, in the immature brain, during prolonged, but not short seizures, there is a transient mismatch between cerebral blood flow and metabolism leading to significant cerebral deoxygenation.

Quantitative analysis of ubiquitin-immunoreactivity in the midbrain periaqueductal gray matter with regard to the causes of death in forensic autopsy

The aim of the present study was to examine Ub-immunoreactivity in the midbrain periaqueductal gray matter (PGM), which is involved in pain processing and modulation, in forensic autopsy cases (n=273) in relation to the causes of death: acute deaths from blunt injuries (n=75), sharp weapon injuries (n=36), fatal asphyxiation (n=22), drownings (n=16: freshwater, n=9; saltwater, n=7), fire fatalities (n=64), poisoning (n=12), hyperthermia (n=5), hypothermia (n=5), delayed deaths from blunt head injury (n=8), acute cardiac deaths (n=24), and acute cerebrovascular strokes (n=6). The Ub-immunoreactivity was clearly observed in the nuclei of the PGM neurons, showing no postmortem interference or age-dependency. A higher value was observed in blunt injuries, fire fatalities and also in saltwater drowning, hyperthermia and delayed head injury deaths. These findings suggest a complicated mechanism for the ubiquitination of PGM neurons, to which multiple factors including the intensity and duration of pains possibly under alert consciousness, traumatic and metabolic neurodegeneration may contribute.

Free fatty acid metabolism in the air-breathing African catfish (Clarias gariepinus) during asphyxia

In several waterbreathing fish species, hypoxia induces a decrease in plasma free fatty acid (FFA) levels as opposed to an increase in air-breathing mammals. We hypothesised that this change is coupled to the mode of breathing. Therefore, we followed the metabolic response of cannulated air-breathing African catfish to an 8-h asphyxia period. The hematocrit and hemoglobin increased significantly upon asphyxia. However, no change was observed in the mean cellular hemoglobin concentration, indicating that more erythrocytes were brought into circulation. A continuous increase in plasma lactate concentration during asphyxia showed permanent activation of anaerobic glycolysis, pointing to a persistent oxygen shortage. Plasma glucose levels did not change, but FFA levels decreased significantly upon asphyxia with a concomitant increase in plasma noradrenaline levels. Thus, these results suggest that in the air-breathing African catfish noradrenaline mediated a decrease in plasma FFA levels similar to that in waterbreathing fish species.

Quantitative morphometry of granular ‘dot-like’ ubiquitin-immunoreactivity in the crus cerebri in asphyxiation and fire fatalities

In the central nervous system (CNS), a variety of ubiquitinated structures have been reported, usually as pathological alterations of the brain related to degenerative diseases or aging. However, previous studies showed an increase in the ubiquitin (Ub)-immunoreactive intranuclear inclusion of the pigmented neurons of the substantia nigra in the midbrain in asphyxiation and fire fatalities in the adult subjects. The aim of the present study was to examine granular 'dot-like' Ub-immunoreactivity in the crus cerebri (cortico-spinal tracts) in related fatalities (over 35 years of age, n=169), including fatal asphyxiation (n=27), drownings (n=14), fire fatalities (n=60), and control groups (n=68). Dot-like Ub-immunoreactivity was clearly observed in the descending tract of the crus cerebri. Morphometric analysis of the positive granular area (dot-like Ub-area) showed a higher value in strangulation and fire fatalities and a lower value in hemorrhagic and head injury deaths, as was observed for the inclusion-type neuronal Ub-positivity. However, there was a difference between those markers: a low value was seen for the inclusion-type neuronal Ub-positivity in hanging and drownings, and a difference in the dot-like Ub-area was detected between fire fatalities with lower and higher COHb levels. Our findings suggested the possible usefulness of these markers for examination of CNS stress responses in traumas, at least in middle-aged and elderly victims and a partial difference in stress reaction between the cortico-spinal tracts and dopaminergic neurons.

Effects of perinatal asphyxia on cell survival, neuronal phenotype and neurite growth evaluated with organotypic triple cultures

The effect of perinatal asphyxia on brain development was studied with organotypic cultures from substantia nigra, neostriatum and neocortex. Asphyxia was induced by immersing foetuses-containing uterine horns removed from ready-to-deliver rats into a water bath for 20 min. Following asphyxia, the pups were nursed by a surrogate dam and sacrificed after three days for preparing organotypic cultures. Non-asphyxiated caesarean-delivered pups were used as controls. Morphological features and cell viability were recorded during in vitro development. At day in vitro (DIV) 24, the cultures were treated for immunocytochemistry using antibodies against the N-methyl-D-aspartate receptor subunit 1 (NR1) and tyrosine hydroxylase (TH). While in vitro survival was similar in cultures from both asphyxiated and control animals, differences were observed when the neuronal phenotype was assessed. Compared to controls, the total number of NR1-positive neurons in substantia nigra, as well as the number of secondary to higher level branching of TH-positive neurites from asphyxiated pups were decreased, illustrating the vulnerability of the dopaminergic systems to perinatal asphyxia.

Ontogenetic changes and developmental adjustments in lactate dehydrogenase isozymes of an obligate air-breathing fish Channa punctatus during deprivation of air access

In air-breathing snakehead Channa punctatus, Ldh-B is expressed at all ontogenetic and developmental stages, while Ldh-A is expressed temporally in pre-hatchlings 12-13 days ahead of bimodal respiration marked by air-breathing. Remarkable differences are observed in the LDH isozyme expression among various ontogenetic and developmental stages upon denying air access. When denied air access, water-breathing larvae show two distinct characteristics: (i) they survive longer than transitory air-breathers due to independence from air-breathing and (ii) there is more transient induction of Ldh-B than Ldh-A. Transition to bimodal breathing, which occurred post-hatching in 15-day old larvae, is coincidental with inducibility of Ldh-A and concomitant down-regulation of Ldh-B. Heart tissue from air-breathing adults denied air access shows a preferential expression of LDH-A subunit and slight down-regulation of LDH-B. Heterotetramers of A and B subunits participate in adjusting LDH levels among those stages which either precede air-breathing switchover, or are subsequent to this transition. The contribution of heterotetramers depends on the stage-specific levels of LDH homotetramers A(4) or B(4). Scaling of muscle mass during growth, tolerance to extended deprivation of air access and induction of Ldh-A are correlated. Response to restoring air contact indicated that advanced air-breathing stages of C. punctatus possess an inherent capacity to sense surface air. In kinetic properties, LDH isozymes of C. punctatus are teleost-like but species specificity is displayed in oxidative potential by cardiac muscle and in L-lactate reduction by skeletal muscle.

Endolymphatic Perfusion with EGTA-Acetoxymethyl Ester Inhibits Asphyxia- and Furosemide-Induced Decrease in Endocochlear Potential in Guinea Pigs

We examined the effect of the Ca(2+) concentration in the endolymph ([Ca](e)) or in the endolymphatic surface cells ([Ca](i)) on the endocochlear potential (EP) by using an endolymphatic or perilymphatic perfusion technique, respectively. (i) A large increase in [Ca](e) up to approximately 10(-3) M with a fall in the EP was induced by transient asphyxia ( approximately 2 min) or by the intravenous administration of furosemide (60 mg/kg), and a significant correlation was obtained between the EP and p[Ca](e) (= -log [Ca](e), r = 0.998). (ii) Perfusion of the endolymph with 10 mM EGTA for 5 min neither produced any significant change in the EP nor altered the asphyxia-induced change in EP (DeltaEP(asp)), suggesting that neither [Ca](e) nor the Ca(2+) concentration gradient across the stria vascularis contributed directly to the generation of the EP in the condition of low [Ca](e). In contrast, endolymphatic perfusion with high Ca(2+) (more than 10 mM) produced a decrease in EP and a significant correlation was obtained between the EP and the Ca(2+) concentration of perfusion solution (r = 0.982), suggesting that Ca(2+) permeability may exist across the stria vascularis. (iii) The administration of a Ca(2+) chelator, EGTA-acetoxymethyl ester (AM, 0.3 mM), to the endolymph, which produced a gradual increase in EP, suppressed significantly, by 60-80%, DeltaEP(asp) or furosemide-induced changes in EP. In contrast, perilymphatic administration of 0.5 mM EGTA-AM caused no significant suppression of the DeltaEP(asp). These findings suggest that [Ca](i) plays an important role in generating/maintaining a large positive EP.

[Five fatalities due to inhalation of "asphyxiant gases": pathophysiological analysis in autopsy cases]

Five autopsy cases were examined to investigate fatal factors involved in inhalation of "asphyxiant gases": carbon monoxide (CO, n=3), fluorocarbons (n=1) and butane (n=1). In all cases, there was severe pulmonary edema and congestion in all viscera, suggesting advanced circulatory failure. The airway was filled with bloody froth in cases of fluorocarbons and butane inhalation. In CO intoxication, a marked increase in serum cardiac troponins suggested severe myocardial damage. There were also biochemical findings of respiratory distress (an evident increase in intra-alveolar pulmonary surfactant protein A), alveolar injury (an increase in serum surfactant protein A and D), rhabdomyolysis (myoglobinuria) and prolonged hypoxia (myogenic hyperuricemia) in cases of inhaling incomplete combustion gases. In a case of fluorocarbons gas inhalation, biochemical findings suggested respiratory distress, myocardial ischemia (an increase in serum CK-MB) and advanced hypoxia. Similar findings were observed in a case of butane inhalation, although cardiac troponin levels were low in the peripheral blood. These observations suggested that myocardial damage was prominent in CO intoxication, accompanied by respiratory distress in cases of inhaling incomplete combustion gases, whereas respiratory distress and hypoxia were major findings in cases of fluorocarbons and butane gas inhalation.

Postischemic mild hypothermia reduces neurotransmitter release and astroglial cell proliferation during reperfusion after asphyxial cardiac arrest in rats

The present study investigated whether postischemic mild hypothermia attenuates the ischemia-induced striatal glutamate (GLU) and dopamine (DA) release, as well as astroglial cell proliferation in the brain. Anesthetized rats were exposed to 8 min of asphyxiation, including 5 min of cardiac arrest. The cardiac arrest was reversed to restoration of spontaneous circulation (ROSC), by brief external heart massage and ventilation within a period of 2 min. After the insult and during reperfusion, the extracellular glutamate and dopamine overflow increased to, respectively, 3000% and 5000% compared with the baseline values in the normothermic group and resulted in brain damage, ischemic neurons and gliosis. However, when hypothermia was induced for a period of 60 min after the insult and restoration of spontaneous circulation, the glutamate and dopamine overflows were not significantly different from that in the sham group. Histological analysis of the brain showed that postischemic mild hypothermia reduced brain damage, ischemic neurons, as well as astroglial cell proliferation. Thus, postischemic mild hypothermia reduces the excitotoxic process, brain damage, as well as astroglial cell proliferation during reperfusion. Moreover, these results emphasize the trigger effect of dopamine on the excitotoxic pathway.

[Function of actin in renal tubular epithelial cell of newborn swine during ATP deficiency]

OBJECTIVE

To investigate the variations of actin of newborn porcine Renal Tubalar Epithelial (RTE) cell during ATP deficiency and shed light on the possible mechanisms of renal deficiency during newborn asphyxia.

METHODS

After the establishment of ATP deficiency cell-model, the ATP content of the RTE cell of the control and hypoxic groups was determined. And the variations of actin in newborn porcine RTE cell during ATP deficiency were detected using flow-cytometry.

RESULTS

It was found that the ATP content of new-born porcine RTE cell decreased with the continuance of hypoxia, and the changes in G-actin and F-actin contents of RTE cell both appeared at the time of one-minute ATP deficiency. The G-actin decreased first and then increased, and the F-actin decreased step by step.

CONCLUSION

As the ATP deficiency time elongated, G-actin of the newborn porcine RTE cell decreased first and then increased, and the F-actin decreased step by step. This may destruct the cell bone-skeleton of the newborn RTE cell and maybe one of the important mechanisms of renal deficiency during newborn asphyxia.

Association between brain tissue pH and brain injury during asphyxia in piglets

BACKGROUND

Acidosis may contribute to brain injury from asphyxia, but its role is unclear. In order to evaluate the association between brain acidosis and cerebral injury, we subjected piglets to hypoxia and hypotension (HYP-HOTN) or hypoxia alone (HYP) to inflict varying amounts of brain damage. We hypothesized that piglets with a more severe brain injury would have a lower brain pH.

METHODS

Piglets had a pH microprobe inserted into the cerebral cortex. HYP animals breathed 5-8% O(2)/7% CO(2) for 30 min with mean arterial pressure (MAP) maintained at >40 mmHg. HYP-HOTN animals breathed the same gas for 30 min, but during the last 15 min, MAP was reduced to 25-30 mmHg by withdrawing blood. After 4 h of recovery, the animals were perfusion-fixed and pathology assessed. Somatosensory-evoked potentials (SEP) were also monitored.

RESULTS

HYP-HOTN piglets had more neuropathology than HYP animals. During the last 15 min of injury, brain pH in the HYP-HOTN group was significantly higher than that in HYP. However, recovery of brain pH was prolonged in the HYP-HOTN animals. The amount of time for brain pH to recover to > or =7.00 correlated very well with both the degree of neuropathology and SEP recovery. The reduction in brain pH, either absolute or relative to baseline, was not associated with the severity of damage.

CONCLUSIONS

The time needed for brain pH to recover after asphyxia, but not its severity, was associated with the amount of brain injury. Further study is warranted to determine whether immediate restoration of brain pH will reduce brain damage.

The role of fetal breathing motions compared with gasping motions in pulmonary airway uptake of intra-amniotic iron dextran

OBJECTIVE

We hypothesized that normal fetal breathing, not acute asphyxial gasping, results in the movement of iron dextran from the amniotic cavity into the fetal lungs. In addition, the amount of iron dextran moving into the fetal lungs is cumulative with time.

STUDY DESIGN

Twelve pregnant New Zealand White rabbits at 25 days of gestation were sedated and underwent ultrasound-guided injections of iron dextran into the amniotic cavities of the rabbit fetuses in both horns of each pregnant doe. Oxygen saturation was maintained at >90% in the pregnant does. The 12 does were then equally assigned to four groups on the basis of the duration of fetal exposure to the dextran (0, 8, 16, and 24 hours). At the end of each time point, one half of the fetuses received an intracardiac injection of potassium chloride to induce gasping just before necropsy. Gasping was confirmed by ultrasound scanning. At necropsy, the fetal lungs were evaluated grossly and underwent histomorphometry for iron distribution and quantification in the fetal airways.

RESULTS

In the animals that received iron dextran, there was no significant difference in iron accumulation at any time point between those animals that did and did not receive potassium chloride, which suggests that acute gasping does not increase the accumulation of amniotic fluid substances in the lungs. The amount of iron in the fetal airways increased significantly with progressive length of exposure.

CONCLUSION

We conclude that normal fetal breathing, not acute asphyxial gasping, resulted in the movement of intra-amniotic iron dextran into the fetal lungs and that the amount of substances that move into the fetal lungs accumulated with time.

Perinatal asphyxia exerts lifelong effects on neuronal responsiveness to stress in specific brain regions in the rat

BACKGROUND

Perinatal asphyxia (PA) causes irreversible damage to the brain of newborns and can produce neurologic and behavioral changes later in life. To identify neuronal substrates underlying the effects of PA, we investigated whether and how neuronal responsiveness to an established stress challenge is affected.

METHODS

We used Fos expression as a marker of neuronal activation and examined the pattern of Fos expression in response to acute swim stress in 24-month-old rats exposed to a 20-minute PA insult.

RESULTS

Swim stress produced a similar pattern of Fos expression in control and asphyxiated rats in 34 brain areas. Asphyxiated rats displayed a higher number of stress-induced Fos-positive cells in the nucleus of the solitary tract, parabrachial nucleus, periaqueductal gray, paraventricular hypothalamic nucleus, nucleus accumbens, caudate-putamen, and prelimbic cortex. No differences in the Fos response to stress were observed in other regions, including the locus ceruleus, amygdala, hippocampus, or septum.

CONCLUSION

These data provide functional anatomic evidence that PA has lifelong effects on neuronal communication and leads to an abnormal, augmented neuronal responsiveness to stress in specific brain areas, particularly in the main telencephalic target regions of the mesencephalic dopamine projections, as well as in a functionally related set of brain regions associated with autonomic and neuroendocrine regulation.

Cerebral metabolism during cord occlusion and hypoxia in the fetal sheep: a novel method of continuous measurement based on heat production

This study was undertaken to validate a new method of measuring cerebral metabolic rate in the fetal sheep based on heat production in a local region of the brain. Heat production was compared to oxygen use in 20 near-term fetuses during basal conditions, moderate hypoxia and cord occlusion. Thermocouples were placed to measure core and brain temperature and a composite probe placed in the parietal cortex to measure changes in cortical blood flow (CBF) using laser Doppler flowmetry and tissue PO2 using fluorescent decay. Catheters were inserted in a brachiocephalic artery and sagittal sinus for blood sampling. With moderate hypoxia, induced by administering 10-12 % oxygen to the ewes, fetal arterial PO2 declined from 23 +/- 1 to 11 +/- 1 Torr and brain tissue PO2 fell from 7.6+/- 0.7 to a nadir of 0.8 +/- 0.4 Torr, while CBF increased to 139 +/- 5 % of baseline. Cortical heat production, calculated as the product of CBF, the temperature gain from artery to brain tissue, and the specific heat of blood, decreased by 45 +/- 11 % in parallel to similar declines in oxygen uptake. With severe asphyxia induced by complete cord occlusion for 10 min, fetal arterial PO2 declined from 23 +/- 1 to 9 +/- 2 Torr and brain tissue PO2 fell from 7.0 +/- 0.7 to essentially 0 Torr while CBF decreased 40 +/- 5 %. Cortical heat production decreased by 78 +/- 6 % while oxygen use declined by 90 +/- 3 %. Glucose uptake increased significantly relative to oxygen use and lactate concentration increased in sagittal sinus blood. We conclude that local measurements of heat production in the brain provide a useful index of overall metabolic rate, closely reflecting oxygen use in moderate hypoxia and indicating a significant contribution from anaerobic metabolism during severe asphyxia.

Key neuroprotective role for endogenous adenosine A1 receptor activation during asphyxia in the fetal sheep

BACKGROUND AND PURPOSE

The fetus is well known to be able to survive prolonged exposure to asphyxia with minimal injury compared with older animals. We and others have observed a rapid suppression of EEG intensity with the onset of asphyxia, suggesting active inhibition that may be a major neuroprotective adaptation to asphyxia. Adenosine is a key regulator of cerebral metabolism in the fetus.

METHODS

We therefore tested the hypothesis that infusion of the specific adenosine A1 receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX), given before 10 minutes of profound asphyxia in near-term fetal sheep, would prevent neural inhibition and lead to increased brain damage.

RESULTS

DPCPX treatment was associated with a transient rise and delayed fall in EEG activity in response to cord occlusion (n=8) in contrast with a rapid and sustained suppression of EEG activity in controls (n=8). DPCPX was also associated with an earlier and greater increase in cortical impedance, reflecting earlier onset of primary cytotoxic edema, and a significantly smaller reduction in calculated cortical heat production after the start of cord occlusion. After reperfusion, DPCPX-treated fetuses but not controls developed delayed onset of seizures, which continued for 24 hours, and sustained greater selective hippocampal, striatal, and parasagittal neuronal loss after 72-hour recovery.

CONCLUSIONS

These data support the hypothesis that endogenous activation of the adenosine A1 receptor during severe asphyxia mediates the initial suppression of neural activity and is an important mechanism that protects the fetal brain.

Blockade of D1 dopaminergic transmission alleviates c-fos induction and cleaved caspase-3 expression in the brains of rat pups exposed to prenatal cocaine or perinatal asphyxia

Hypoxia due to uterine vasoconstriction may be an important cause of the teratogenic consequences of prenatal cocaine exposure. We used immediate-early gene and cleaved caspase-3 expression patterns to monitor fetal brain regions affected by intrauterine hypoxia and prenatal cocaine and pretreatment with the D1 dopamine receptor antagonist SCH 23390 to determine how much of the induction observed was due to dopamine. Both cocaine binge (3 x 15 mg/kg) and perinatal asphyxia on embryonic day 22 (E22) induced c-fos in the striatum as well as in several other brain regions within 3 h after treatment. Maternal administration of a D1 dopamine antagonist, SCH 23390, before either cocaine or asphyxia exposure dramatically reduced the numbers of Fos-immunoreactive cells in the striatum as well as in many other brain regions. Cells immunoreactive for cleaved caspase-3 expression were more numerous after perinatal asphyxia than after prenatal cocaine exposure in most brain regions 24 h after C-section. SCH 23390 decreased caspase-3 expression after both birth insults, indicating that the increased incidence of apoptosis is related to overactivation of dopaminergic pathways.

[The function of integrin beta 1 in the hypoxic cellular damage mechanism of renal tubular epithelial cell of newborn porcine]

OBJECTIVE

To inquire into the mechanism of renal deficiency in neonatal asphyxia.

METHODS

The 30, 60, 90, 120 min hypoxic renal cell model was made by use of DMEM/F-12 with antimycine A. ATP content was detected by reversed-phase HPLC. The levels of integrin beta 1 of renal tubular epithelial(RTE) cell of the groups were detected using flow cytometry.

RESULTS

ATP deficiency cellular model of newborn porcine RTE cell was successfully set up. The levels of ATP of the newborn porcine RET cell during 30, 60, 90, 120 min hypoxia time significantly decreased as compared with normal control (P < 0.001). The levels of integrin beta 1 of newborn porcine RTE cell decreased as the ATP deficiency time increased and the differences between the groups were statistically significant (P < 0.001).

CONCLUSION

The decreased level of integrin beta 1 in the newborn porcine RTE cell during anoxia may play an important role in the newborn renal deficiency during asphyxia.

Impact of perinatal asphyxia on the GABAergic and locomotor system

Perinatal asphyxia can cause neuronal loss and depletion of neurotransmitters within the striatum. The striatum plays an important role in motor control, sensorimotor integration and learning. In the present study we investigated whether perinatal asphyxia leads to motor deficits related to striatal damage, and in particular to the loss of GABAergic neurons. Perinatal asphyxia was induced in time-pregnant Wistar rats on the day of delivery by placing the uterus horns, containing the pups, in a 37 degrees C water bath for 20 min. Three motor performance tasks (open field, grip test and walking pattern) were performed at 3 and 6 weeks of age. Antibodies against calbindin and parvalbumin were used to stain GABAergic striatal projection neurons and interneurons, respectively. The motor tests revealed subtle effects of perinatal asphyxia, i.e. small decrease in motor activity. Analysis of the walking pattern revealed an increase in stride width at 6 weeks of age after perinatal asphyxia. Furthermore, a substantial loss of calbindin-immunoreactive (-22%) and parvalbumin-immunoreactive (-43%) cells was found in the striatum following perinatal asphyxia at two months of age. GABA(A) receptor autoradiography revealed no changes in GABA binding activity within the striatum, globus pallidus or substantia nigra. We conclude that perinatal asphyxia resulted in a loss of GABAergic projection neurons and interneurons in the striatum without alteration of GABA(A) receptor affinity. Despite a considerable loss of striatal neurons, only minor deficits in motor performance were found after perinatal asphyxia.

Long term production of reactive oxygen species during perinatal asphyxia in the rat central nervous system: effects of hypothermia

The formation of oxygen-derived free radicals in hypoxic and ischemic/reperfused brains has been proposed as an important step that links brain injury to neuronal death. Previously, we have demonstrated that reactive oxygen species (ROS) production was significantly increased in rat neostriatum during acute perinatal asphyxia (PA) in pups. In this article, we have studied the time course of ROS production in the neostriatum and neocortex of adult rats subjected to PA using electron spin resonance spectrometry (ESR) in order to record ROS production. Further more, we analyzed the actions of hypothermia on ROS release in pups and adult rats. We used for this study 6-month-old rats that suffered sub-severe and severe PA when they were pups. The most significant production of ROS was detected either in the neostriatum or neocortex at 19 and 20 min of PA. Hypothermia during 20 and 100 min at 15 degrees C prevented ROS formation either in pups and adult rats. These data further support the concept that free radicals may contribute to the brain injury alterations and that hypothermia can prevent long-term sequelae induced by PA.

Maternal milk reduces severity of necrotizing enterocolitis and increases intestinal IL-10 in a neonatal rat model

Necrotizing enterocolitis (NEC) is a devastating intestinal disease of premature infants. Maternal milk has been suggested to be partially protective against NEC; however, the mechanisms of this protection are not defined. The aim of this study was to examine the effect(s) of artificial feeding of rat milk (RM)-versus cow milk-based rat milk substitute (RMS) on the development of NEC in a neonatal rat model and elucidate the role of inflammatory cytokines in NEC pathogenesis. Newborn rats were artificially fed with either collected RM or RMS. Experimental NEC was induced by exposure to asphyxia and cold stress and evaluated by histologic scoring of damage in ileum. Intestinal cytokine mRNA expression was determined by real-time PCR. Cytokine histologic localization was performed by confocal microscopy. Similar to human NEC, artificial feeding of RM reduces the incidence and severity of NEC injury in neonatal rats. Freezing and thawing of collected RM did not eliminate the protective effect of maternal milk. Ileal IL-10 expression was significantly increased in the RM group compared with RMS. Increased IL-10 peptide production was detected in the RM group with signal localized predominantly in the cytoplasm of villus epithelial cells. These results suggest that the protective effect of maternal milk is associated with increased production of anti-inflammatory IL-10 in the site of injury. Better understanding of the mechanisms underlying these protective effects could be beneficial either in the prevention of NEC or in the development of future therapeutic strategies to cure NEC.