Increased brain levels of F2-isoprostane are an early marker of behavioral sequels in a rat model of global perinatal asphyxia

Cannabidiol effectively prevents oxidative stress and stabilizes hypoxia-inducible factor-1 alpha (HIF-1α) in an animal model of global hypoxia

Cannabidiol (CBD) is a non-psychotomimetic phytocannabinoid derived from Cannabis sativa. It has therapeutic effects in different paradigms of brain injury, acting as a neuroprotectant. As oxidative stress is a primary risk factor for brain damage after neonatal hypoxia, we tested the effect of CBD on oxidative status and non-protein-bound iron accumulation in the immature brain after hypoxia. Moreover, we tested whether cannabidiol affects the accumulation of hypoxia-inducible factor-1 alpha (HIF-1α) which plays a key role in the regulation of cellular adaptation to hypoxia and oxidative stress. We used 7-day-old mice randomly assigned to hypoxic or control groups. Immediately after hypoxia or control exposure, pups were randomly assigned to a vehicle or CBD treatment. 24 h later, they were decapitated and the brains were immediately removed and stored for further biochemical analyses. We found that CBD reduced lipid peroxidation and prevented antioxidant depletion. For the first time, we also demonstrated that CBD upregulated HIF-1α protein level. This study indicates that CBD may effective agent in attenuating the detrimental consequences of perinatal asphyxia.

Small molecule biomarkers for neonatal hypoxic ischemic encephalopathy

Hypoxic Ischemic Encephalopathy (HIE) is one of the most deleterious conditions in the perinatal period and the access to small molecule biomarkers aiding accurate diagnosis and disease staging, progress monitoring, and early outcome prognosis could provide relevant advances towards the development of personalized therapies. The emergence of metabolomics, the "omics" technology enabling the holistic study of small molecules, for biomarker discovery employing different analytical platforms, animal models and study populations has drastically increased the number and diversity of small molecules proposed as candidate biomarkers. However, the use of very few compounds has been implemented in clinical guidelines and authorized medical devices. In this work we review different approaches employed for discovering HIE-related small molecule biomarkers. Their role in associated biochemical disease mechanisms as well as the way towards their translation into the clinical practice are discussed.

Distress vocalization delay in the neonate lamb as a neurobehavioral assessment tool

Acoustic features of infant distress vocalizations including latency and rate of emission are used as indices of neurological deficit and integrity in human and rodent neonates. This paper investigates the relationship between temporal characteristics of distress calls, elicited by an isolation stimulus, and indicators of neurobehavioral development over 12 hr postpartum in the neonate lamb. Delayed vocalization initiation was found to be associated with poor locomotor and orientation behavior reflecting the capacity of the lamb to reunite with and follow its dam, and a lowered rate of signal emission following commencement of vocalization. Animals demonstrating delayed vocalization initiation also appeared more likely to be of a birth weight predisposed to fetal distress, and to urinate when exposed to a novel environment. Based on these preliminary studies, we propose that compromised emission of vocal signals is indicative of neurobehavioral deficit in the neonate lamb.

25 years of research on global asphyxia in the immature rat brain

Hypoxic-ischemic encephalopathy remains a common cause of brain damage in neonates. Preterm infants have additional complications, as prematurity by itself increases the risk of encephalopathy. Currently, therapy for this subset of asphyxiated infants is limited to supportive care. There is an urgent need for therapies in preterm infants - and for representative animal models for preclinical drug development. In 1991, a novel rodent model of global asphyxia in the preterm infant was developed in Sweden. This method was based on the induction of asphyxia during the birth processes itself by submerging pups, still in the uterine horns, in a water bath followed by C-section. This insult occurs at a time-point when the rodent brain maturity resembles the brain of a 22-32 week old human fetus. This model has developed over the past 25 years as an established model of perinatal global asphyxia in the early preterm brain. Here we summarize the knowledge gained on the short- and long-term neuropathological and behavioral effects of asphyxia on the immature central nervous system.

Nitric Oxide Production in the Striatum and Cerebellum of a Rat Model of Preterm Global Perinatal Asphyxia

Encephalopathy due to perinatal asphyxia (PA) is a major cause of neonatal morbidity and mortality in the period around birth. Preterm infants are especially at risk for cognitive, attention and motor impairments. Therapy for this subgroup is limited to supportive care, and new targets are thus urgently needed. Post-asphyxic excitotoxicity is partially mediated by excessive nitric oxide (NO) release. The aims of this study were to determine the timing and distribution of nitric oxide (NO) production after global PA in brain areas involved in motor regulation and coordination. This study focused on the rat striatum and cerebellum, as these areas also affect cognition or attention, in addition to their central role in motor control. NO/peroxynitrite levels were determined empirically with a fluorescent marker on postnatal days P5, P8 and P12. The distributions of neuronal NO synthase (nNOS), cyclic guanosine monophosphate (cGMP), astroglia and caspase-3 were determined with immunohistochemistry. Apoptosis was additionally assessed by measuring caspase-3-like activity from P2-P15. On P5 and P8, increased intensity of NO-associated fluorescence and cGMP immunoreactivity after PA was apparent in the striatum, but not in the cerebellum. No changes in nNOS immunoreactivity or astrocytes were observed. Modest changes in caspase-3-activity were observed between groups, but the overall time course of apoptosis over the first 11 days of life was similar between PA and controls. Altogether, these data suggest that PA increases NO/peroxynitrite levels during the first week after birth within the striatum, but not within the cerebellum, without marked astrogliosis. Therapeutic benefits of interventions that reduce endogenous NO production would likely be greater during this time frame.

Preliminary case control study to establish the correlation between novel peroxidation biomarkers in cord serum and the severity of hypoxic ischemic encephalopathy

BACKGROUND

Hypoxic-ischemic encephalopathy (HIE) has deleterious neurological consequences. To identify patients at risk of neuronal damage deserving implementation of neuroprotective strategies clinicians have relied on prenatal sentinel events, postnatal clinical assessment (Apgar score), and blood gas analysis. This feasibility study aimed to assess if lipid peroxidation byproducts associated with neuronal damage correlated with cord blood metabolic acidemia in patients with HIE.

POPULATION AND METHODS

This is a case/control study in which cases were newborn infants with severe acidemia (pH<7.00; base excess ≥12mmol/L) while control babies exhibited normal gases (pH=7.20-7.40; base excess=-4 to +4mmol/L) in the first cord blood analysis performed immediately after birth. Concomitantly, lipid peroxidation byproducts were determined using ultra performance liquid chromatography coupled to mass spectrometry in the same cord blood sample.

RESULTS

A total of 19 controls and 20 cases were recruited. No differences in gestational characteristics were present. However, cases exhibited profound metabolic alterations as compared to controls (Cases vs.

CONTROL

pH=6.90±0.1 vs. 7.33±0.03; base excess=-15±3 vs. -1±2mmol/L), 85% were admitted to the NICU, and 50% developed symptoms of HIE. 8-iso-15(R)-PGF2α (P=0.01) and total isoprostanes (P=0.045) presented statistically significant differences between cases and control groups and correlated with level of HIE.

CONCLUSIONS

The 8-iso-15(R)-PGF2α and isoprostanes reflecting oxidative damage are significantly increased in severe postnatal acidemia. Follow up studies with adequate power are necessary to confirm if these biomarkers measured in cord blood serum could be predictive of neonatal encephalopathy.

Deferoxamine improves antioxidative protection in the brain of neonatal rats: The role of anoxia and body temperature

After hypoxic-ischemic insult iron deposited in the brain catalyzes formation of reactive oxygen species. Newborn rats, showing reduced physiological body temperature and their hyperthermic counterparts injected with deferoxamine (DF), a chelator of iron, are protected both against iron-mediated neurotoxicity and against depletion of low-molecular antioxidants after perinatal asphyxia. Therefore, we decided to study the effects of DF on activity of antioxidant enzymes (superoxide dismutase-SOD, glutathione peroxidase-GPx and catalase-CAT) in the brain of rats exposed neonatally to a critical anoxia at body temperatures elevated to 39°C. Perinatal anoxia under hyperthermic conditions intensified oxidative stress and depleted the pool of antioxidant enzymes. Both the depletion of antioxidants and lipid peroxidation were prevented by post-anoxic DF injection. The present paper evidenced that deferoxamine may act by recovering of SOD, GPx and CAT activity to reduce anoxia-induced oxidative stress.

Reduced miR-659-3p Levels Correlate with Progranulin Increase in Hypoxic Conditions: Implications for Frontotemporal Dementia

Progranulin (PGRN) is a secreted protein expressed ubiquitously throughout the body, including the brain, where it localizes in neurons and is activated microglia. Loss-of-function mutations in the GRN gene are an important cause of familial frontotemporal lobar degeneration (FTLD). PGRN has a neurotrophic and anti-inflammatory activity, and it is neuroprotective in several injury conditions, such as oxygen or glucose deprivation, oxidative injury, and hypoxic stress. Indeed, we have previously demonstrated that hypoxia induces the up-regulation of GRN transcripts. Several studies have shown microRNAs (miRNAs) involvement in hypoxia. Moreover, in FTLD patients with a genetic variant of GRN (rs5848), the reinforcement of miR-659-3p binding site has been suggested to be a risk factor. Here, we report that miR-659-3p interacts directly with GRN 3′UTR as shown by luciferase assay in HeLa cells and ELISA and Western Blot analysis in HeLa and Kelly cells. Moreover, we demonstrate the physical binding between GRN mRNA and miR-659-3p employing a miRNA capture-affinity technology in SK-N-BE and Kelly cells. In order to study miRNAs involvement in hypoxia-mediated up-regulation of GRN, we evaluated miR-659-3p levels in SK-N-BE cells after 24 h of hypoxic treatment, finding them inversely correlated to GRN transcripts. Furthermore, we analyzed an animal model of asphyxia, finding that GRN mRNA levels increased at post-natal day (pnd) 1 and pnd 4 in rat cortices subjected to asphyxia in comparison to control rats and miR-659-3p decreased at pnd 4 just when GRN reached the highest levels. Our results demonstrate the interaction between miR-659-3p and GRN transcript and the involvement of miR-659-3p in GRN up-regulation mediated by hypoxic/ischemic insults.

Effects of Arginase Inhibition in Hypertensive Hyperthyroid Rats

BACKGROUND

This study analyzed the effects of chronic administration of N[omega]-hydroxy-nor-l-arginine (nor-NOHA), an inhibitor of arginase, on the hemodynamic, oxidative stress, morphologic, metabolic, and renal manifestations of hyperthyroidism in rats.

METHODS

Four groups of male Wistar rats were used: control, nor-NOHA-treated (10 mg/kg/day), thyroxine (T4)-treated (75 μg/rat/day), and thyroxine- plus nor-NOHA-treated rats. All treatments were maintained for 4 weeks. Body weight, tail systolic blood pressure (SBP), and heart rate (HR) were recorded weekly. Finally, morphologic, metabolic, plasma, and renal variables were measured. Arginase I and II protein abundance and arginase activity were measured in aorta, heart, and kidney.

RESULTS

The T4 group showed increased arginase I and II protein abundance, arginase activity, SBP, HR, plasma nitrates/nitrites (NOx), brainstem and urinary isoprostanes, proteinuria and cardiac and renal hypertrophy in comparison to control rats. In hyperthyroid rats, chronic nor-NOHA prevented the increase in SBP and HR and decreased proteinuria in association with an increase in plasma NOx and a decrease in brainstem and urinary isoprostanes. In normal rats, nor-NOHA treatment did not significantly change any hemodynamic, morphologic, or renal variables. Acute nor-NOHA administration did not affect renal or systemic hemodynamic variables in normal or T4-treated rats.

CONCLUSION

Hyperthyroidism in rats is associated with the increased expression and activity of arginase in aorta, heart, and kidney. Chronic arginase inhibition with nor-NOHA suppresses the characteristic hemodynamic manifestations of hyperthyroidism in association with a reduced oxidative stress. These results indicate an important role for arginase pathway alterations in the cardiovascular and renal abnormalities of hyperthyroidism.

Regulation of Glial Cell Functions by PPAR-gamma Natural and Synthetic Agonists

In the recent years, the peroxisome proliferator-activated receptor-γ (PPAR-γ), a well known target for type II diabetes treatment, has received an increasing attention for its therapeutic potential in inflammatory and degenerative brain disorders. PPAR-γ agonists, which include naturally occurring compounds (such as long chain fatty acids and the cyclopentenone prostaglandin 15-deoxy Δ^12,14 prostaglandin J₂), and synthetic agonists (among which the thiazolidinediones and few nonsteroidal anti-inflammatory drugs) have shown anti-inflammatory and protective effects in several experimental models of Alzheimer's and Parkinson's diseases, amyotrophic lateral sclerosis, multiple sclerosis and stroke, as well as in few clinical studies. The pleiotropic effects of PPAR-γ agonists are likely to be mediated by several mechanisms involving anti-inflammatory activities on peripheral immune cells (macrophages and lymphocytes), as well as direct effects on neural cells including cerebral vascular endothelial cells, neurons, and glia. In the present article, we will review the recent findings supporting a major role for PPAR-γ agonists in controlling neuroinflammation and neurodegeneration through their activities on glial cells, with a particular emphasis on microglial cells as major macrophage population of the brain parenchyma and main actors in brain inflammation.

Role of sympathetic tone in BSO-induced hypertension in mice

BACKGROUND

We investigated the contribution of the sympathetic tone to the hypertension induced by chronic administration of buthionine sulfoximine (BSO) and characterized this model in mice.

METHODS

Three experiments were performed. In experiment I, four groups of CBA-C57 male mice were used: controls and three groups that received oral BSO at 5, 10, or 20 mmol/l. In experiment II, the alpha(1)-adrenergic blocker prazosin was orally administered (10 mg/100 ml) to control and BSO-treated mice. All treatments were maintained for 5 weeks. Body weight (BW), tail blood pressure (BP), and heart rate (HR) were measured weekly. Direct mean arterial pressure (MAP) and morphological, metabolic, plasma, and renal variables were measured at the end of the experiments. In experiment III, the acute response of MAP and HR to the ganglionic blocker pentolinium (10 mg/kg intravenous) was used to further evaluate the sympathetic contribution to BP and HR in control and BSO-treated mice.

RESULTS

BSO produced dose-related increases in BP (control, 115 +/- 0.5; BSO-5, 141 +/- 0.5; BSO-10, 151 +/- 0.9; BSO-20, 163 +/- 1.1 mm Hg) and HR and augmented plasma noradrenaline, brainstem isoprostane levels, and total urinary isoprostane excretion. BSO did not produce cardiac hypertrophy and did not modify metabolic or plasma variables, or creatinine clearance, proteinuria, or renal morphology. Chronic prazosin markedly reduced MAP (control, 101 +/- 4.7; prazosin, 95 +/- 1.29; BSO-10, 130 +/- 2.9; BSO-10 +/- prazosin, 98 +/- 0.9) and HR. Acute pentolinium produced a greater percentage MAP (control, 43 +/- 4.2; BSO-10, 66 +/- 4.5) and HR decrease in BSO-treated mice vs. controls.

CONCLUSION

Sympathetic tone plays a major role in the increased BP and HR of BSO hypertensive mice.

Peroxisome proliferator-activated receptor-gamma agonists promote differentiation and antioxidant defenses of oligodendrocyte progenitor cells

Several lines of evidence suggest that peroxisome proliferator-activated receptor-gamma (PPAR-gamma) agonists may control brain inflammation and, therefore, may be useful for the treatment of human CNS inflammatory conditions. The PPAR-gamma agonists delay the onset and ameliorate clinical manifestations in animal demyelinating disease models, in which the beneficial effects are thought to be mainly related to anti-inflammatory effects on peripheral and brain immune cells. Direct effects on neurons, oligodendrocytes, and other CNS resident cells cannot be excluded, however. To analyze potential direct actions of PPAR-gamma agonists on oligodendrocytes, we investigated the effects of both natural (15-deoxy Delta prostaglandin J2) and synthetic (pioglitazone) PPAR-gamma agonists in primary cultures of rat oligodendrocyte progenitor cells. The PPAR-gamma agonists promoted oligodendrocyte progenitor cell differentiation and enhanced their antioxidant defenses by increasing levels of catalase and copper-zinc superoxide dismutase while maintaining the overall homeostasis of the glutathione system. Protective effects were abolished in the presence of the specific PPAR-gamma antagonist GW9662, indicating that they are specifically dependent on PPAR-gamma. These observations suggest that in addition to their known anti-inflammatory effects, PPAR-gamma agonists may protect oligodendrocyte progenitor cells by preserving their integrity and favoring their differentiation into myelin-forming cells. Thus, PPAR-gamma may promote recovery from demyelination by direct effects on oligodendrocytes.

Can tissue oxygenation index (TOI) and cotside neurophysiological variables predict outcome in depressed/asphyxiated newborn infants?

BACKGROUND

Diagnostic tools of birth asphyxia provide only an uncertain prediction of neurological outcome.

AIMS

To assess whether TOI and DeltaCBV, combined with a set of biochemical and neurophysiological variables, have any diagnostic and prognostic value in birth depression or asphyxia.

STUDY DESIGN

Case control study at the nursery and NICU of the Padova University Children's Hospital.

SUBJECTS

22 term neonates with an Apgar score < or = 6 at 5', a 1-h umbilical artery pH value < or = 7.25 with an increased base deficit and a gestational age > or = 36 weeks; 15 healthy term infants with an Apgar score > or = 9 at 5'.

OUTCOME MEASURES

Troponin I and NIRS measurements (TOI and DeltaCBV) were assessed in both groups. Blood gases, neurological evaluation, US, NIRS, EEG and SEP were evaluated in the infants with depression or asphyxia.

RESULTS

Troponin I was higher in the study group than in controls (p=0.04), showing a correlation with base excess values. In the depressed/asphyxiated neonates with an abnormal outcome at 1 year, TOI rose to 80.1% vs 66.4% in controls (p=0.04) and 74.7% in infants with a normal 1-year outcome. A multiple regression model showed a significant multiple correlation coefficient, R=0.79, p<0.001, where the predictive variables significantly associated with outcome were SEP and BE.

CONCLUSIONS

Troponin I is a useful short-term index of birth asphyxia or perinatal depression. An increased TOI suggests a risk of abnormal neurological outcome at 1 year. Among the cotside variables, BE and evoked potential abnormalities were the best predictors of abnormal outcome in this study.

Acute perinatal asphyxia at birth has long-term effects on behavioural arousal and maternal behaviour in lactating rats

This study analysed the long-term consequences of an asphyctic event at birth on maternal behaviour and emotionality in rats. Pregnant Wistar rats were delivered by Caesarean section and the pups, still in the uterus horns, were placed into a water bath at 37 degrees C for periods of 0 (Caesarean delivery, CD) or 20 min (asphyxia, CD+20). Control subjects were born by vaginal delivery (VD). Subsequently, pups were given to surrogate mothers, weaned at 21 days, and mated at adulthood. After giving birth, differences in maternal competence and behavioural arousal were assessed observing: (i) maternal behaviour after reunion with the pups following a 3h separation, on postpartum day (PPD) 4; (ii) behaviour in an elevated plus-maze test, on postpartum day 7; and (iii) performance in a fear conditioning test, in which subjects learned to associate a conditional stimulus with an aversive unconditioned stimulus (postpartum days 7-8). Results indicate that subjects in the CD+20 group showed a deficit in maternal care, taking a longer time to retrieve the whole litter and often failing to retrieve all pups. Both CD and CD+20 groups showed higher behavioural activity in the plus-maze. In addition, when tested in the fear conditioning paradigm, the CD+20 group showed a lower latency to perform freezing behaviour in the auditory cue trial. The changes in behavioural arousal described suggest that the dopaminergic system may be a potential neurochemical target for an early hypoxic insult and indicate maternal behaviour as a useful endpoint to study the effects of early birth insult on brain function.

C-section birth per se or followed by acute global asphyxia altered emotional behaviour in neonate and adult rats

Birth complications such as perinatal asphyxia are considered risk factors for later neurobehavioural disorders. Behavioural analysis of animal models may help to clarify the contribution of particular patterns of early hypoxia and their combination to psychiatric morbidity. Wistar rats underwent caesarean section (c-section) alone or c-section followed by asphyxia, the latter induced by placing pups still in uterus horns into a water bath at 37 degrees C for 20 min. Vaginally delivered pups were used as controls. Frequency of ultrasound emissions was analysed following isolation at a lower temperature than that of the home nest (23+/-0.5 degrees C) and reunion with their mother (3 min) on postnatal day (PND) 13 (maternal potentiation test). A sex-dependent effect of hypoxia was observed, with higher production of ultrasounds in hypoxic males. Caesarean-delivered pups produced significantly more ultrasounds than those vaginally delivered. At adolescence (PND 35) rats underwent a 25 min social interaction test with a conspecific of the same sex and age. Significant alterations in investigative behaviour (inclusive of: nose, anogenital, body sniffing, and following) were evident in caesarean-delivered rats of both sexes, but not in rats experiencing perinatal asphyxia. At adulthood, auditory, and context conditioned responses, analysed in a fear conditioning test, were not markedly affected either by c-section or c-section plus hypoxia. However, hypoxic rats emitted significantly more 22 kHz ultrasounds than c-section or vaginally delivered rats during the training session. In conclusion, differential effects appear to be brought about by c-section and by hypoxia mainly related to emotional/anxious responses.

Maternal care is similar for rat pups subjected to birth hypoxia and for controls

The rat model of global anoxia during cesarean section birth has been used extensively to investigate effects of birth hypoxia on central nervous system function. This study tested whether differential maternal care mediates central nervous system alterations in this model. Maternal care of mixed litters of pups born vaginally, by cesarean section or by cesarean section with anoxia, was assessed. Frequency and duration of licking and grooming by dams were similar for all birth groups. No group differences were observed in order of retrieval, when pups were displaced from the nest. The results indicate that altered central nervous system function in anoxic animals in this model are not due to differential maternal care, but may be mediated by other mechanisms such as direct hypoxic insult to neurons.

Acute global anoxia during C-section birth affects dopamine-mediated behavioural responses and reactivity to stress

Perinatal asphyxia may induce major neurological deficits shortly after birth as well as neurological/behavioural disorders later in development. We used a rat model of global perinatal asphyxia to model acute intrauterine asphyxia around the time of birth. Caesarean section was performed in rats and their pups, still in uterus horns, were placed into a water bath at 37 degrees C for periods of 0, 10 or 20 min. Pups were then given to surrogate mothers, and examined for long-term behavioural effects of the perinatal asphyctic insult. Behavioural assessment included analysis of novelty seeking behaviour at adolescence, while spatial discrimination abilities, response to both an acute and a chronic stress, and the effects of the full D1 receptor agonist SKF 82958 on open field behaviour were assessed at adulthood. Overall, no marked abnormalities were found in the novelty seeking test, in the ability to discriminate spatial changes in the test environment and in physiological response to stress. However, adult rats subjected to severe perinatal asphyxia (20 min) showed lower activity level and lower stereotyped behaviour after the administration of SKF 82958 in an open field test. These results support the observations from human and animal studies that perinatal insult can produce long-term dysfunction of dopaminergic neurotransmission, and points to the need of more thorough examination of the potential effects of perinatal asphyxia on hypothalamic-pituitary-adrenal (HPA) axis. Altogether, the present findings suggest that the present 20 min perinatal asphyxia model might serve for the study of neurodevelopmental disorders associated with perinatal insults.

Cognitive and neurological deficits induced by early and prolonged basal forebrain cholinergic hypofunction in rats

In the present study we examined the long-term effects of neonatal lesion of basal forebrain cholinergic neurons induced by intracerebroventricular injections of the immunotoxin 192 IgG saporin. Animals were then characterised behaviourally, electrophysiologically and molecularly. Cognitive effects were evaluated in the social transmission of food preferences, a non-spatial associative memory task. Electrophysiological effects were assessed by recording of cortical electroencephalographic (EEG) patterns. In addition, we measured the levels of proteins whose abnormal expression has been associated with neurodegeneration such as amyloid precursor protein (APP), presenilin 1 and 2 (PS-1, PS-2), and cyclooxygenases (COX-1 and COX-2). In animals lesioned on postnatal day 7 and tested 6 months thereafter, memory impairment in the social transmission of food preferences was evident, as well as a significant reduction of choline acetyltransferase activity in hippocampus and neocortex. Furthermore, similar to what observed in Alzheimer-like dementia, EEG cortical patterns in lesioned rats presented changes in alpha, beta and delta activities. Levels of APP protein and mRNA were not affected by the treatment. Levels of hippocampal COX-2 protein and mRNA were significantly decreased whereas COX-1 remained unaltered. PS-1 and PS-2 transcripts were reduced in hippocampus and neocortex. These findings indicate that neonatal and permanent basal forebrain cholinergic hypofunction is sufficient to induce behavioural and neuropathological abnormalities. This animal model could represent a valid tool to evaluate the role played by abnormal cholinergic maturation in later vulnerability to neuropathological processes associated with cognitive decline and, possibly, to Alzheimer-like dementia.