UMLS:C0022116 - FACTA Search

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Query: UMLS:C0022116 (ischemia)
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Despite extensive adverse publicity, tobacco use continues in approximately 25% of all pregnancies in the United States, overshadowing illicit drugs of abuse, including cocaine. The societal cost of maternal smoking is seen most readily in underweight newborns, in high rates of perinatal morbidity, mortality and Sudden Infant Death Syndrome and in persistent deficits in learning and behavior. We have designed animal models of nicotine exposure to prove that nicotine itself is a neuroteratogen, thus providing a causative link between tobacco exposure and adverse perinatal outcomes. In particular, nicotine infusion paradigms that, like the transdermal patch used in man, produce drug exposure without the confounds of other components of tobacco or of episodic hypoxic-ischemic insult, have enabled a mechanistic dissection of the role played by nicotine in fetal brain damage. Nicotine targets specific neurotransmitter receptors in the fetal brain, eliciting abnormalities of cell proliferation and differentiation, leading to shortfalls in the number of cells and eventually to altered synaptic activity. Because of the close regulatory association of cholinergic and catecholaminergic systems, adverse effects of nicotine involve multiple transmitter pathways and influence not only the immediate developmental events in fetal brain, but also the eventual programming of synaptic competence. Accordingly, defects may appear after a prolonged period of apparent normality, leading to cognitive and learning defects that appear in childhood or adolescence. Comparable alterations occur in peripheral autonomic pathways, leading to increased susceptibility to hypoxia-induced brain damage, perinatal mortality and Sudden Infant Death. Identifying the receptor-driven mechanisms that underlie the neurobehavioral damage caused by fetal nicotine exposure provides a rational basis for decisions about nicotine substitution therapy for smoking cessation in pregnancy. In contrast to the effects of nicotine, animal models of crack cocaine use in pregnancy indicate a more restricted spectrum of effects, a reflection of differences both in pharmacokinetics and pharmacodynamics of the two drugs. Notably, although cocaine, like nicotine, also targets cell replication, its effects are short-lived, permitting recovery to occur in between doses, so that the eventual consequences are much less severe. To some extent, the effects of cocaine on brain development resemble those of nicotine because the two share cardiovascular actions (vasoconstriction) that, under some circumstances, elicit fetal hypoxia-ischemia. In light of the fact that nearly all crack cocaine users smoke cigarettes, the identification of specific developmental effects of cocaine may prove difficult to detect. Although scientists and the public continue to pay far more attention to fetal cocaine effects than to those of nicotine or tobacco use, a change of focus to concentrate on tobacco could have a disproportionately larger impact on human health.
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PMID:Fetal nicotine or cocaine exposure: which one is worse? 961 92

The catecholaminergic systems of sudden infant death syndrome victims were examined in the diencephalon and basal ganglia, in addition to the midbrain, pons, and medulla oblongata, using the immuno-histochemical method involving tyrosine hydroxylase. A significant decrease in tyrosine hydroxylase immunoreactivity was demonstrated in the basal ganglia of sudden infant death syndrome victims between 2 to 12 months of age compared with age-matched control subjects. This change in the basal ganglia may be a secondary finding induced by chronic hypoxia or repeated ischemia in sudden infant death syndrome but suggests impairment of the development of the neuronal connection from the brainstem to the upper cardiorespiratory control in sudden infant death syndrome.
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PMID:Catecholaminergic neurons in the diencephalon and basal ganglia of SIDS. 1042 33

Sudden infant death syndrome (SIDS) occurs silently usually during sleep and, though remaining unexplained after autopsy, leaves footprints creating a pattern analogous to that which follows a flood of nitric acid (NO). These footprints in SIDS are associated with serious pathological changes, viz. elevated hepatic iron, bone marrow hyperplasia, hypomyelinated respiratory control centres, elevated lung immunoglobulins, cerebral hypoperfusion resembling lesions induced by chronic hypoxemia, ischemia, congenital heart disease and congenital myopathy. Hypoxia stimulates the immune response and the over-arousal of the immune response triggers a flood of NO. Adenosine triggers sleep. NO and adenosine are additive as dilators of coronary blood vessels. Blood pressure collapses. Selenium increases the activity of the enzyme ferrochelatase during incorporation of heme into cytochrome oxidase. NO binds to cytochrome oxidase, inhibiting respiration. When NO reaches dangerous levels, the cell turns on production of heme oxygenase. Heme is broken down to iron (Fe) carbon monoxide (CO) and bile pigments. NO has a huge affinity for hemoglobin which catalyses NO degradation to nitrate. Furthermore, NO is a product of smoke and SIDS incidence is higher in smoking mothers.
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PMID:Association of sudden infant death syndrome with grossly deranged iron metabolism and nitric oxide overload. 1079 Jul 39

Sudden infant death syndrome or "cot death" has until the late eighties been a significant cause of death in children between the ages of 1 month and 1 year. Approximately two per 1000 children born alive dies of sudden infant death syndrome each year in Western Europe, North America, and Australia. The vulnerability of the infant brain stem to ischemia has been suggested to be a conceivable cause of sudden infant death syndrome. This is compatible with a hypothesis that genetic risk factors for cerebral thrombosis could cause microinfarction in the brain stem during the first month of life, affecting vital centers or their blood supply. The presence of three common point mutations seen in families with thrombophilia (1691G-->A in the coagulation factor V gene, 677C-->T in the methylenetetrahydrofolate reductase gene, and the 20210G-->A mutation in the prothrombin gene) could increase the risk for thrombosis in the child. This prompted us to investigate these genetic markers of thromboembolic disease in 121 cases of sudden infant death syndrome and in relevant controls, in the expectation of a more frequent occurrence of these markers if thrombosis is an etiological factor in sudden infant death syndrome. The frequency of homozygous 1691G-->A mutation in SIDS cases was higher than expected (odds ratio: 7.3, 95% confidence interval, 1.2-45.8). The allele frequencies (theta;) in cases of sudden infant death syndrome of the 1691G-->A, 677C-->T, and 20210G-->A alleles was 2.6% (1.0-5.5), 32.6% (26.8-38.9), and 0.9% (0.1-3.4), respectively. None of the allele frequencies found in the background population (3.4% for the 1691G-->A allele, 29% for the 677C-->T allele, and 1% for the 20210G-->A allele) differed significantly from that in cases of sudden infant death syndrome. In 5,251,027 inhabitants in Denmark, the incidence of venous thromboembolism was 0.9 per 1000 per year in the background population, and less than one-thousandth of these were children. Consequently it is not likely that venous thrombosis is a major cause of sudden infant death syndrome. On the other hand, this does not exclude other known or unknown risk factors for thrombosis as possible etiological factors for sudden infant death syndrome. It is likely that we must continuously employ the exclusion principle on possible etiological causes in genetic material from a large group of victims of sudden infant death syndrome if the phenomenon of sudden infant death syndrome is to be ascribed to a specific hereditary disorder.
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PMID:Sudden infant death syndrome, childhood thrombosis, and presence of genetic risk factors for thrombosis. 1082 69

It has been hypothesized that some cases of sudden infant death syndrome (SIDS) are a result of neck extension and/or rotation that causes vertebral artery (VA) compression and brain stem ischemia. There is a paucity of relevant literature on this topic. Therefore, our aim was to compare neck rotation and extension in SIDS and other natural infant deaths. Cases of SIDS and other natural infant deaths within the San Diego SIDS Research Project database were analyzed retrospectively with respect to neck and body position as reported by the trained, experienced scene investigators and/or the caretakers who discovered the infants. Information was used from 246 SIDS cases and 56 cases of other natural deaths. Simultaneous neck extension and rotation was not reported in either group. When data regarding neutral/flexed/extended position and rotation of the neck were combined, no significant differences were found between the two groups (P = 0.94); 40% of the SIDS cases and 41% of the other natural death cases were found with the neck either extended or rotated (odds ratio [OR] 0.97, [reference group = neck either neutral or flexed, and not rotated], 95% confidence interval [CI] 0.45, 2.11). There were also no significant differences between the groups when neck rotation and neck extension were analyzed independent of one another. Neck rotation among cases found in the prone position was common and was not significantly different between the two groups (49% of 146 SIDS cases, 58% of 24 other natural death cases, P = 0.38, OR 0.68, 95% CI 0.28, 1.62). Neck rotation among infants found in the supine position occurred one-third as often in the SIDS group (9% of 33 cases) as in the other natural death group (29% of 14 cases); however, the difference was not significant (P = 0.17; OR 0.25, 95% CI 0.05, 1.31). Although our analysis does not exclude VA compression and brain stem ischemia in some cases of SIDS, we found no evidence to affirm its importance. This study demonstrates the importance of meticulous scene descriptions, including neck position.
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PMID:Neck extension and rotation in sudden infant death syndrome and other natural infant deaths. 1117 31

Neuropathologic findings in stillbirths oftentimes provide insight into the specific mechanisms leading to death. Examination of the brains of stillborn infants may also identify pathophysiologic processes that result in prenatal brain injury in liveborn as well as stillborn infants and that lead to neurologic disorders in liveborn infants, such as cerebral palsy or the sudden infant death syndrome (SIDS). A variety of abnormalities are found in the brains of stillborns, the most common including cerebral white matter necrosis (periventricular leukomalacia) or gliosis, germinal matrix or intraventricular hemorrhage, cerebral infarcts, pontosubicular necrosis, and spinal cord or brainstem necrosis. The 2 major hypotheses that have been proposed for the pathophysiology of cerebral white matter injury in the perinatal period are hypoxia/ischemia and infection/cytokines as the basis for injury. The fetal brain may be selectively vulnerable to various insults at specific stages of development.
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PMID:Neuropathology associated with stillbirth. 1187 72

We compared the developmental changes of 5-hydroxytryptamine (5-HT) 1 A and 5-HT2 A receptor immunoreactivity in the nuclei in relation to the cardiorespiratory or autonomic function in the human brain stem in sudden infant death syndrome (SIDS) and congenital central hypoventilation syndrome (CCHS) patients and age-matched controls by means of immunohistochemical methods. There were significant decreases in 5-HT1 A and 5-HT2 A receptor immunoreactivity in the dorsal nucleus of the vagus, solitary nucleus and ventrolateral medulla in the medulla oblongata, and significant increases in the periaqueductal gray matter (PAG) of the midbrain in SIDS victims, but there were no significant differences between those in CCHS patients and controls. The decreased immunoreactivity of the receptors in the medulla oblongata was accompanied by brain stem gliosis. Therefore, the decreases in the receptors may be secondary to chronic hypoxia or repeated ischemia, but may be causally related to some impairment of the developing cardiorespiratory neuronal system. As 5-HT1 A and 5-HT2 A receptors were the most abundant in the fetal period and then decreased with subsequent development, the increases in 5-HT1 A and 5-HT2 A receptor immunoreactivity in PAG may reflect delayed neuronal maturation, but may also reflect compensatory changes in response to hypofunctioning serotonergic neurons in the medulla oblongata in SIDS. There was no abnormal expression of 5-HT1 A and 5-HT2 A receptors in CCHS brain stems, and so the pathophysiology seems to be different between SIDS and CCHS patients.
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PMID:Alteration of serotonergic receptors in the brain stems of human patients with respiratory disorders. 1220 Jul 44

Sudden infant death syndrome (SIDS) victims were regarded as normal as a matter of definition (Beckwith 1970) until 1952 when Kinney and colleagues argued for elimination of the clause, "unexpected by history." They argued that "not all SIDS victims were normal," and referred to their hypothesis that SIDS results from brain abnormalities, which they postulated "to originate in utero and lead to sudden death during a vulnerable postnatal period." Bergman (1970) argued that SIDS did not depend on any "single characteristic that ordains a infant for death," but on an interaction of risk factors with variable probabilities. Wedgwood (1972) agreed and grouped risk factors into the first "triple risk hypothesis" consisting of general vulnerability, age-specific risks, and precipitating factors. Raring (1975), based on a bell-shaped curve of age of death (log-transformed), concluded that SIDS was a random process with multifactorial causation. Rognum and Saugstad (1993) developed a "fatal triangle" in 1993, with groupings similar to those of Wedgwood, but included mucosal immunity under a vulnerable developmental stage of the infant. Filiano and Kinney (1994) presented the best known triple risk hypothesis and emphasized prenatal injury of the brainstem. They added a qualifier, "in at least a subset of SIDS," but, the National Institute of Child Health and Development SIDS Strategic Plan 2000, quoting Kinney's work, states unequivocally that "SIDS is a developmental disorder. Its origins are during fetal development." Except for the emphasis on prenatal origin, all 3 triple risk hypotheses are similar. Interest in the brainstem of SIDS victims began with Naeye's 1976 report of astrogliosis in 50% of all victims. He concluded that these changes were caused by hypoxia and were not the cause of SIDS. He noted an absence of astrogliosis in some older SIDS victims, compatible with a single, terminal episode of hypoxia without previous hypoxic episodes, prenatal or postnatal. Kinney and colleagues (1983) reported gliosis in 22% of their SIDS victims. Subsequently, they instituted studies of neurotransmitter systems in the brainstem, particularly the muscarinic (1995) and serotenergic systems (2001). The major issue is when did the brainstem abnormalities, astrogliosis, or neurotransmitter changes occur and whether either is specific to SIDS. There is no published method known to us of determining the time of origin of these markers except that the injury causing astrogliosis must have occurred at least 4 days before death (Del Bigio and Becker, 1994). Because the changes in neurotransmitter systems found in the arcuate nucleus in SIDS victims were also found in the chronic controls with known hypoxia, specificity of these markers for SIDS has not been established. It seems likely that the "acute control" group of Kinney et al (1995) died too quickly to develop gliosis or severe depletion of the neurotransmitter systems. We can conclude that the acute controls had no previous episodes of severe hypoxia, unlike SIDS or their "chronic controls." Although the average muscarinic cholinergic receptor level in the SIDS victim was significantly less than in the acute controls, the difference was only 27%, and only 21 of 41 SIDS victims had values below the mean of the acute controls. The study of the medullary serotonergic network by Kinney et al (2001) revealed greater reductions in the SIDS victims than in acute controls, but the questions of cause versus effect of the abnormalities, and whether they occurred prenatally or postnatally, remain unanswered. Hypoplasia of the arcuate nucleus was stated to occur in 5% of their SIDS cases by Kinney et al (2001), but this is a "primary developmental defect" according to Matturri et al (2002) with a larger series, many of whom were stillbirths. These cases should not be included under the rubric of SIDS, by definition. There are difficulties with Filiano and Kinney's (1994) explanation of the age at death distribution of SIDS. They postulate that the period between 1 and 6 months represents an unstable time for virtually all physiologic systems. However, this period demonstrates much less instability than does the neonatal period, when most deaths from congenital defects and severe maternal anemia occur. We present data for infants born to mothers who were likely to have suffered severe anemia as a consequence of placenta previa, abruptio placentae, and excessive bleeding during pregnancy; these infants presumably are at increased risk of hypoxia and brainstem injury. The total neonatal mortality rate in these 3 groups of infants is 4 times greater than the respective postneonatal mortality, and in the postneonatal period the non-SIDS mortality rate is between 14 and 22 times greater than the postneonatal SIDS rate in these 3 groups. A preponderance of deaths in the neonatal period is also found for congenital anomalies, a category that logically should include infants who experienced prenatal hypoxia or ischemia; this distribution of age of death is very different from that for SIDS, which mostly spares the first month and peaks between 2 and 3 months of age. Finally, evidence inconsistent with prenatal injury as a frequent cause of SIDS comes from prospective studies of ventilatory control in neonates who subsequently died of SIDS; no significant respiratory abnormalities in these infants have been found (Waggener et al 1990; Schectman et al 1991). We conclude that none of the triple risk hypotheses presented so far have significantly improved our understanding of the cause of SIDS. Bergman's and Raring's concepts of multifactorial causation with interaction of risk factors with variable probabilities is less restrictive and more in keeping with the large number of demonstrated risk factors and their varying prevalence. If prenatal hypoxic damage of the brainstem occurred, it seems likely that the infant so afflicted would be at risk for SIDS, but it is even more likely that their death would occur in the neonatal period, as we have demonstrated in infants who have known maternal risk factors that involve severe anemia. This is in contrast to the delay until the postneonatal period of most SIDS deaths. A categorical statement that the origin of SIDS is prenatal is unwarranted by the evidence. Brainstem abnormalities have not been shown to cause SIDS, but are more likely a nonspecific effect of hypoxia.
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PMID:The triple risk hypotheses in sudden infant death syndrome. 1241 70

The immature brain is more resistant to hypoxia/ischemia than the mature brain. Although chronic hypoxia can induce adaptive-changes on the developing brain, the mechanisms underlying such adaptive changes are poorly understood. To further elucidate some of the adaptive changes during postnatal hypoxia, we determined the activities of four enzymes of glucose oxidative metabolism in eight brain regions of hypoxic and normoxic rats. Litters of Sprague-Dawley rats were put into the hypoxic chamber (oxygen level maintained at 9.5%) with their dams starting on day 3 postnatal (P3). Age-matched normoxic rats were use as control animals. In P10 hypoxic rats, lactate dehydrogenase (LDH) activity in cerebral cortex, striatum, olfactory bulb, hippocampus, hypothalamus, pons and medulla, and cerebellum was significantly increased (by 100%-370%) compared to those in P10 normoxic rats. In P10 hypoxic rats, hexokinase (HK) activity in hypothalamus, hippocampus, olfactory bulb, midbrain, and cerebral cortex was significantly decreased (by 15%-30%). Neither alpha-ketoglutarate dehydrogenase complex (KGDHC, which is believed to have an important role in the regulation of the tricarboxylic acid [TCA] cycle flux) nor citrate synthase (CS) activity was significantly decreased in the eight regions of P10 hypoxic rats compared to those in P10 normoxic rats. In P30 hypoxic rats, LDH activity was only increased in striatum (by 19%), whereas HK activity was only significantly decreased (by 30%) in this region. However, KGDHC activity was significantly decreased in olfactory bulb, hippocampus, hypothalamus, cerebral cortex, and cerebellum (by 20%-40%) in P30 hypoxic rats compared to those in P30 normoxic rats. Similarly, CS activity was decreased, but only in olfactory bulb, hypothalamus, and midbrain (by 9%-21%) in P30 hypoxic rats. Our results suggest that at least some of the mechanisms underlying the hypoxia-induced changes in activities of glycolytic enzymes implicate the upregulation of HIF-1. Moreover, our observation that chronic postnatal hypoxia induces differential effects on brain glycolytic and TCA cycle enzymes may have pathophysiological implications (e.g., decreased in energy metabolism) in childhood diseases (e.g., sudden infant death syndrome) in which hypoxia plays a role.
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PMID:Chronic hypoxia in development selectively alters the activities of key enzymes of glucose oxidative metabolism in brain regions. 1271 48

The hypothesis that unexplained stillbirth arises in a similar manner as the sudden infant death syndrome (SIDS) is based in part on shared neuropathologic features between the two entities, including hypoxic-ischemic lesions such as white matter and brainstem gliosis, as well as aplasia or hypoplasia of the arcuate nucleus on the ventral surface of the medulla. The arcuate nucleus is the putative homologue of the respiratory chemosensory region at the ventral medullary surface in animals that is involved in central chemosensitivity. To determine arcuate nucleus pathology in stillbirth, and its co-occurrence with evidence of hypoxia-ischemia, we reviewed brain specimens from the archives of our hospitals from 22 consecutive stillbirths from 22 to 41 gestational weeks. Explained causes of death (n=17) included nuchal cord, acute chorioamnionitis, placental abruption, and fetal glomerulosclerosis; 5 cases were unexplained. In 12 brains, we observed nuclear karyorrhexis and/or pyknosis with cytoplasmic hypereosinophilia in neurons in the arcuate nucleus in both explained (n=8) and unexplained (n=4) cases (54.5% of total cases). Three additional cases had arcuate aplasia (n=1) or hypoplasia (n=2) (13.6% of total cases); one of the latter cases also had neuronal necrosis in the hypoplastic arcuate. The degree of gliosis in the region of the arcuate nucleus was variable across all cases, without statistically significant differences between groups with and without arcuate nucleus necrosis. Other lesions in association with (n=14) and without (n=8) arcuate nucleus abnormalities were diffuse cerebral white matter gliosis, periventricular leukomalacia (PVL), and neuronal necrosis in the hippocampus, basal ganglia, thalamus, basis pontis, and brainstem tegmentum. In 16/20 (80.0%) cases (with or without histologic necrosis of the arcuate), immunostaining with caspase-3 demonstrated positive neurons. Our findings suggest that neuronal pathology in the arcuate nucleus may be both developmental (13.6%) and acquired (54.5%). The association of neuronal necrosis and apoptosis in the arcuate nucleus with systemic entities involving fetal ischemia, and with other brain lesions consistent with ischemia, e.g., cerebral white matter gliosis, suggests that ischemia plays a role in the arcuate nucleus damage as well. Thus, the underpopulation of arcuate neurons detected postnatally in some SIDS infants may be secondary to an acquired insult in mid- or late gestation, and in other cases, a primary developmental lesion in early gestation, or both. The role of arcuate nucleus pathology in the pathogenesis of fetal demise remains to be determined.
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PMID:Neuronal cell death in the arcuate nucleus of the medulla oblongata in stillbirth. 1795 May 58

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