Effects of Umbilical Cord Occlusion in Late Gestation on the Ovine Fetal Brain and Retina

Brief hypoxia in late gestation sheep causes prolonged disruption of fetal electrographic, breathing behaviours and can result in early labour

KEY POINTS

Brief episodes of severe fetal hypoxia can arise in late gestation as a result of interruption of normal umbilical blood flow Systemic parameters and blood chemistry indicate complete recovery within 1-2 hours, although the long-term effects on fetal brain functions are unknown Fetal sheep were subjected to umbilical cord occlusion (UCO) for 10 min at 131 days of gestation, and then monitored intensively until onset of labour or delivery (<145 days of gestation) Normal patterns of fetal behaviour, including breathing movements, episodes of high and low voltage electorcortical activity, eye movements and postural (neck) muscle activity, were disrupted for 3-10 days after the UCO Preterm labour and delivery occurred in a significant number of the pregnancies after UCO compared to the control (sham-UCO) cohort.

ABSTRACT

Complications arising from antepartum events such as impaired umbilical blood flow can cause significant fetal hypoxia. These complications can be unpredictable, as well as difficult to detect, and thus we lack a detailed understanding of the (patho)physiological changes that occur between the antenatal in utero event and birth. In the present study, we assessed the consequences of brief (∼10 min) umbilical cord occlusion (UCO) in fetal sheep at ∼0.88 gestation on fetal plasma cortisol concentrations and fetal behaviour [electrocortical (EcoG), electo-oculargram (EOG), nuchal muscle electromyography (EMG) and breathing activities] in the days following UCO. UCO caused a rapid onset of fetal hypoxaemia, hypercapnia, and acidosis; however, by 6 h, all blood parameters and cardiovascular status were normalized and not different from the control (Sham-UCO) cohort. Subsequently, the incidence of fetal breathing movements decreased compared to the control group, and abnormal behavioural patterns developed over the days following UCO and leading up to the onset of labour, which included increased high voltage and sub-low voltage ECoG and EOG activities, as well as decreased nuchal EMG activity. Fetuses subjected to UCO went into labour 7.9 ± 3.6 days post-UCO (139.5 ± 3.2 days of gestation) compared to the control group fetuses at 13.6 ± 3.3 days post-sham UCO (144 ± 2.2 days of gestation; P < 0.05), despite comparable increases in fetal plasma cortisol and a similar body weight at birth. Thus, a single transient episode of complete UCO late in gestation in fetal sheep can result in prolonged effects on fetal brain activity and premature labour, suggesting persisting effects on fetal cerebral metabolism.

Experimental modelling of the consequences of brief late gestation asphyxia on newborn lamb behaviour and brain structure

Brief but severe asphyxia in late gestation or at the time of birth may lead to neonatal hypoxic ischemic encephalopathy and is associated with long-term neurodevelopmental impairment. We undertook this study to examine the consequences of transient in utero asphyxia in late gestation fetal sheep, on the newborn lamb after birth. Surgery was undertaken at 125 days gestation for implantation of fetal catheters and placement of a silastic cuff around the umbilical cord. At 132 days gestation (0.89 term), the cuff was inflated to induce umbilical cord occlusion (UCO), or sham (control). Fetal arterial blood samples were collected for assessment of fetal wellbeing and the pregnancy continued until birth. At birth, behavioral milestones for newborn lambs were recorded over 24 h, after which the lambs were euthanased for brain collection and histopathology assessments. After birth, UCO lambs displayed significant latencies to (i) use all four legs, (ii) attain a standing position, (iii) find the udder, and (iv) successfully suckle - compared to control lambs. Brains of UCO lambs showed widespread pathologies including cell death, white matter disruption, intra-parenchymal hemorrhage and inflammation, which were not observed in full term control brains. UCO resulted in some preterm births, but comparison with age-matched preterm non-UCO control lambs showed that prematurity per se was not responsible for the behavioral delays and brain structural abnormalities resulting from the in utero asphyxia. These results demonstrate that a single, brief fetal asphyxic episode in late gestation results in significant grey and white matter disruption in the developing brain, and causes significant behavioral delay in newborn lambs. These data are consistent with clinical observations that antenatal asphyxia is causal in the development of neonatal encephalopathy and provide an experimental model to advance our understanding of neuroprotective therapies.

In utero exposure to ischemic-hypoxic conditions and attention-deficit/hyperactivity disorder

OBJECTIVE

To examine the association between ischemic-hypoxic conditions (IHCs) and attention-deficit/hyperactivity disorder (ADHD) by gestational age and race/ethnicity.

METHODS

Nested case-control study using the Kaiser Permanente Southern California (KPSC) medical records. The study cohort included children aged 5 to 11 years who were delivered and cared for in the KPSC between 1995 and 2010 (N = 308,634). Case children had a diagnosis of ADHD and received ≥ 2 prescriptions specific to ADHD during the follow-up period. For each case, 5 control children were matched by age at diagnosis. Exposures were defined by using International Classification of Diseases, Ninth Revision codes. A conditional regression model was used to estimate adjusted odds ratios (ORs).

RESULTS

Among eligible children, 13,613 (4.3%) had a diagnosis of ADHD. Compared with control children, case children were more likely to be male and of white or African American race/ethnicity. Case children were more likely to be exposed to IHCs (OR = 1.16, 95% confidence interval [CI] 1.11-1.21). When stratified by gestational age, cases born at 28 to 33, 34 to 36, and 37 to 42 weeks of gestation, were more likely to be exposed to IHCs (ORs, 1.6 [95% CI 1.2-2.1], 1.2 [95% CI 1.1-1.3], and 1.1 [95% CI 1.0-1.2], respectively) compared with controls. IHC was associated with increased odds of ADHD across all race/ethnicity groups.

CONCLUSIONS

These findings suggest that IHCs, especially birth asphyxia, respiratory distress syndrome, and preeclampsia, are independently associated with ADHD. This association was strongest in preterm births.

The biological basis of injury and neuroprotection in the fetal and neonatal brain

A compromised intrauterine environment that delivers low levels of oxygen and/or nutrients, or is infected or inflammatory, can result in fetal brain injury, abnormal brain development and in cases of chronic compromise, intrauterine growth restriction. Preterm birth can also be associated with injury to the developing brain and affect the normal trajectory of brain growth. This review will focus on the effects that episodes of perinatal hypoxia (acute, chronic, associated with inflammation or as an antecedent of preterm birth) can have on the developing brain. In animal models of these conditions we have found that relatively brief (acute) periods of fetal hypoxemia can have significant effects on the fetal brain, for example death of susceptible neuronal populations (cerebellum, hippocampus, cortex) and cerebral white matter damage. Chronic placental insufficiency which includes fetal hypoxemia, nutrient restriction and altered endocrine status can result in fetal growth restriction and long-term deficits in neural connectivity in addition to altered postnatal function, for example in the auditory and visual systems. Maternal/fetal inflammation can result in fetal brain damage, particularly but not exclusively in the white matter; injury is more pronounced when associated with fetal hypoxemia. In the baboon, in which the normal trajectory of growth is affected by preterm birth, there is a direct correlation between a higher flux in oxygen saturation and a greater extent of neuropathological damage. Currently, the only established therapy for neonatal encephalopathy in full term neonates is moderate hypothermia although this only offers some protection to moderately but not severely affected brains. There is no accepted therapy for injured preterm brains. Consequently the search for more efficacious treatments continues; we discuss neuroprotective agents (erythropoietin, N-acetyl cysteine, melatonin, creatine, neurosteroids) which we have trialed in appropriate animal models. The possibility of combining hypothermia with such agents or growth factors is now being considered. A deeper understanding of causal pathways in brain injury is essential for the development of efficacious strategies for neuroprotection.

Danqi Piantan Jiaonang does not modify hemostasis, hematology, and biochemistry in normal subjects and stroke patients

BACKGROUND AND OBJECTIVE

Previous studies on Danqi Piantan Jiaonang (DPJ, NeuroAid), a traditional Chinese medicine, in stroke patients showed promising results. Our aim was to determine the safety of DPJ in normal subjects and stroke patients through a series of studies assessing its immediate and long-term effects, alone and in combination with aspirin, on hematological, hemostatic, and biochemical parameters.

METHODS

We conducted 3 studies from December 2004 to May 2006. Study 1 was a case series which recruited 32 healthy volunteers who were given 2 oral doses of 4 DPJ capsules (0.4 g/capsule) 6 h apart. Study 2 was a randomized controlled trial of 22 healthy volunteers who received either 1 oral dose of aspirin 300 mg alone or a combination of 1 dose of aspirin 300 mg and 2 doses of 4 DPJ capsules taken 6 h apart. For both studies 1 and 2, hemostatic parameters (prothrombin time, activated partial thromboplastin time, fibrinogen, platelet aggregation, D-dimer) were tested at baseline, and after 2 and 8 h. Study 3 was a case series which recruited 10 patients with recent ischemic stroke (within 7 days) who were given 4 DPJ capsules taken orally 3 times a day for 1 month. Blood tests for hemostatic, hematological (complete blood count), and biochemical parameters (glucose, creatinine, alanine aminotransferase, aspartate transaminase, C-reactive protein) were performed at baseline, and after 1 and 4 weeks.

RESULTS

Apart from the expected changes in platelet aggregation in subjects taking aspirin, no significant differences were detected in hemostatic parameters at baseline, and 2 and 8 h after oral intake of DPJ alone or in combination with aspirin. Likewise, no significant differences were observed in hematological, hemostatic, and biochemical parameters at baseline, and after 1 and 4 weeks of oral intake of DPJ.

CONCLUSION

DPJ does not significantly modify hematological, hemostatic, and biochemical parameters in normal subjects and stroke patients.

An adverse intrauterine environment: implications for injury and altered development of the brain

Abnormal development of the brain during fetal life is now thought to contribute to the aetiology of many functional and behavioural disorders that manifest throughout life. Many factors are likely to underlie such abnormal development including genetic makeup and an adverse intrauterine environment. This review will focus on prenatal hypoxic-ischemic injury and inflammatory/infective insults. A range of experimental models have been used to characterise lesions formed in response to these insults and to determine mechanisms of damage resulting from such events. Relatively brief periods of fetal hypoxia result in neuronal death (cerebellum, hippocampus, and cerebral cortex), white matter damage and reduced growth of neural processes. These effects are more profound at mid than late gestation. Chronic mild placental insufficiency can result in fetal growth restriction and deficits in neural connectivity and myelination. Exposure of the preterm fetus to inflammatory agents causes brain damage particularly in the white matter and this is exacerbated by hypoxia. These studies show that the timing, severity and nature of specific insults are critical in determining the pattern of injury and thus the extent to which neurological function will be affected postnatally. Defining the causes, patterns and mechanisms of brain injury is crucial if we are to develop rational neuroprotective strategies to reduce the burden of altered brain growth and poor functional and behavioural outcomes.

Inhibition of neurosteroid synthesis increases asphyxia-induced brain injury in the late gestation fetal sheep

Allopregnanolone (AP) is a potent GABAergic agonist that suppresses CNS activity, seizure threshold, and excitotoxicity in the adult brain. AP is present in the fetal sheep brain and increases rapidly after asphyxial insult due to increased 5alpha-reductase type-2 (5alphaR-2) expression. The aim of this study was to use finasteride to suppress fetal neurosteroid synthesis, and then determine the effect on brain injury, particularly in the hippocampus, of asphyxia induced in utero by brief occlusion of the umbilical cord. Catheters and an inflatable umbilical cord cuff were implanted in fetal sheep at approximately 125 days gestation. Five days later the fetuses received either finasteride (20 mg/kg/h) or vehicle (40% hydroxypropyl-beta-cyclodextrin) for 2 h. The umbilical cord was occluded (UCO) for 5 min at 30 min after starting the infusion. The fetal brain was obtained 24 h later for examination of activated caspase-3 expression as an index of apoptosis, and to measure AP content. Finasteride treatment alone significantly reduced AP content and increased the number of caspase-3 positive cells in the hippocampus, cerebellum, and the subcallosal bundle, indicating that AP modulates the normal rate of apoptosis in the developing brain. UCO in vehicle and finasteride-treated fetuses produced a similar, marked decrease in O2 saturation (5.8+/-0.6%), but after finasteride treatment UCO caused a significantly greater increase in the number of caspase-3 positive cells in the hippocampal cornu ammonis 3 (CA3) (57.3+/-1.6%) compared with the vehicle-treated fetuses. Thus, 5alpha-reduced steroids such as AP may be protective in reducing cell death following acute fetal asphyxia. Perturbation of normal fetal neurosteroid levels in late gestation (e.g. due to preterm birth, or maternal synthetic steroid treatment to induce fetal lung maturation) could adversely affect brain development and increase its vulnerability to injury.