Barbara E. Lingwood

Glial glutamate transporter expression patterns in brains from multiple mammalian species

It is generally assumed that rodent brains can be used as representative models of neurochemical function in other species, such as humans. We have compared the distributions of the predominant glial glutamate transporters in rodents, rabbits, cats, pigs, monkeys, and humans. We identify similarities but also significant differences between species. GLT‐1v, which is abundantly expressed by rodent astrocytes, is expressed only in a rare subset of astrocytes of cats and humans, and appears to be absent from brains of rabbits and monkeys. Conversely, in the pig brain GLT‐1v is expressed only by oligodendrocytes. GLAST and GLT‐1α expression differed significantly between species; while rodents and rabbits exhibited uniform expression patterns in cortex, higher species, including cats, pigs, monkeys, and humans, exhibited heterogeneities in cortical and hippocampal expression. Patches devoid of labeling intermingling with patches of strong labeling were evident in areas such as temporal cortex and frontal cortex. In addition, we noted that in human motor cortex, there were inconsistencies in labeling for the C‐terminal of GLT‐1α and common domains of GLT‐1, suggesting that the C‐terminal region may be missing or that an unidentified splicing is present in many human astrocytes. Collectively our data suggest that assumptions as to the roles of glutamate transporters in any species may need to be tested empirically.

Body Composition From Birth to 4.5 Months in Infants Born to Non-Obese Women

Infant body composition is affected by maternal obesity, which results in increased % body fat in the infant. With the rapidly increasing incidence of obesity, it is important that normative data are available for infant body composition that is not affected by this trend in maternal obesity. This study assessed body composition in infants born at term to women with a BMI between 18.5 and 25. Infant % body fat, fat mass (FM), and fat free mass (FFM) were assessed at birth, 6 wk, 3 mo, and 4.5 mo of age by air displacement plethysmography, using the PEA POD body composition system. The effects of age, gender, GA, and feeding mode on these parameters were assessed. The % body fat doubled between birth and 6 wk of age and then increased at a slower rate. FFM was higher in male infants at all ages, whereas % body fat was higher in female infants at 4.5 mo. There was a trend to increased % fat and decreased FFM in breastfed (BF) infants. The study provides unique data regarding changes in infant body composition and growth in infants born to women in the healthy weight range.

SPRING: an RCT study of probiotics in the prevention of gestational diabetes mellitus in overweight and obese women

BackgroundObesity is increasing in the child-bearing population as are the rates of gestational diabetes. Gestational diabetes is associated with higher rates of Cesarean Section for the mother and increased risks of macrosomia, higher body fat mass, respiratory distress and hypoglycemia for the infant. Prevention of gestational diabetes through life style intervention has proven to be difficult. A Finnish study showed that ingestion of specific probiotics altered the composition of the gut microbiome and thereby metabolism from early gestation and decreased rates of gestational diabetes in normal weight women. In SPRING (the Study of Probiotics IN the prevention of Gestational diabetes), the effectiveness of probiotics ingestion for the prevention of gestational diabetes will be assessed in overweight and obese women.Methods/designSPRING is a multi-center, prospective, double-blind randomized controlled trial run at two tertiary maternity hospitals in Brisbane, Australia. Five hundred and forty (540) women with a BMI > 25.0 kg/m2 will be recruited over 2 years and receive either probiotics or placebo capsules from 16 weeks gestation until delivery. The probiotics capsules contain > 1x109 cfu each of Lactobacillus rhamnosus GG and Bifidobacterium lactis BB-12 per capsule. The primary outcome is diagnosis of gestational diabetes at 28 weeks gestation. Secondary outcomes include rates of other pregnancy complications, gestational weight gain, mode of delivery, change in gut microbiome, preterm birth, macrosomia, and infant body composition. The trial has 80% power at a 5% 2-sided significance level to detect a >50% change in the rates of gestational diabetes in this high-risk group of pregnant women.DiscussionSPRING will show if probiotics can be used as an easily implementable method of preventing gestational diabetes in the high-risk group of overweight and obese pregnant women.

Cerebral impedance and neurological outcome following a mild or severe hypoxic/ischemic episode in neonatal piglets

Multi-frequency bio-impedance has the potential to identify infants at risk of poor neurodevelopmental outcome following hypoxia by detecting cerebral edema. This study investigated the relationship between the severity of an hypoxic/ischemic episode, neurological outcome following the hypoxia and non-invasively measured cerebral bioelectrical impedance in piglets. One-day-old piglets were anaesthetised and ventilated. Hypoxia was induced by reducing the inspired oxygen concentration to 3-5%. Severe hypoxia was defined as hypoxia resulting in at least 30 min of low amplitude EEG (<5 microV) as well as hypotension and acidosis. Cerebral bio-impedance was measured before, during and for up to 6 h post-hypoxia. Neurological outcome was determined by a neurology score at 24 and 48 h after hypoxia, and by histological examination of the brain at 72 h. There was no increase in cerebral impedance in control animals. Following mild hypoxia cerebral impedance increased transiently. Following severe hypoxia, cerebral impedance increased and remained elevated. Cerebral impedance following severe hypoxia was significantly higher than after mild hypoxia at 10 min and from 2 to 6 h after resuscitation. Cerebral impedance measurements made up to 1 h and between 3 and 6 h after resuscitation were significantly correlated with neurological outcome. Results indicate that non-invasive cerebral impedance measurements are able to discriminate early between those individuals who have suffered a mild, acute hypoxic episode, and those who have suffered a severe hypoxic episode. The technique has the potential to predict which individuals will have a poor neurological outcome.

Prediction of fat-free mass and percentage of body fat in neonates using bioelectrical impedance analysis and anthropometric measures: validation against the PEA POD.

Accurate assessment of neonatal body composition is essential to studies investigating neonatal nutrition or developmental origins of obesity. Bioelectrical impedance analysis or bioimpedance analysis is inexpensive, non-invasive and portable, and is widely used in adults for the assessment of body composition. There are currently no prediction algorithms using bioimpedance analysis in neonates that have been directly validated against measurements of fat-free mass (FFM). The aim of the study was to evaluate the use of bioimpedance analysis for the estimation of FFM and percentage of body fat over the first 4 months of life in healthy infants born at term, and to compare these with estimations based on anthropometric measurements (weight and length) and with skinfolds. The present study was an observational study in seventy-seven infants. Body fat content of infants was assessed at birth, 6 weeks, 3 and 4·5 months of age by air displacement plethysmography, using the PEA POD body composition system. Bioimpedance analysis was performed at the same time and the data were used to develop and test prediction equations for FFM. The combination of weight+sex+length predicted FFM, with a bias of < 100 g and limits of agreement of 6-13 %. Before 3 months of age, bioimpedance analysis did not improve the prediction of FFM or body fat. At 3 and 4·5 months, the inclusion of impedance in prediction algorithms resulted in small improvements in prediction of FFM, reducing the bias to < 50 g and limits of agreement to < 9 %. Skinfold measurements performed poorly at all ages.

Use of the Ages and Stages Questionnaire to predict outcome after hypoxic-ischaemic encephalopathy in the neonate

Background:  Infants who suffer hypoxic‐ischaemic encephalopathy (HIE) at birth are at increased risk of developmental disability. In this at‐risk population, reliable, inexpensive and early identification of those children who are likely to require formal developmental assessment and intervention is needed.

Hypoxic/Ischemic models in newborn piglet: Comparison of constant FiO2 versus variable FiO2 delivery

A comparison of a constant (continuous delivery of 4% FiO2) and a variable (initial 5% FiO2 with adjustments to induce low amplitude EEG (LAEEG) and hypotension) hypoxic/ischemic insult was performed to determine which insult was more effective in producing a consistent degree of survivable neuropathological damage in a newborn piglet model of perinatal asphyxia. We also examined which physiological responses contributed to this outcome. Thirty-nine 1-day-old piglets were subjected to either a constant hypoxic/ischemic insult of 30- to 37-min duration or a variable hypoxic/ischemic insult of 30-min low peak amplitude EEG (LAEEG <5 microV) including 10 min of low mean arterial blood pressure (MABP <70% of baseline). Control animals (n = 6) received 21% FiO2 for the duration of the experiment. At 72 h, the piglets were euthanased, their brains removed and fixed in 4% paraformaldehyde and assessed for hypoxic/ischemic injury by histological analysis. Based on neuropathology scores, piglets were grouped as undamaged or damaged; piglets that did not survive to 72 h were grouped separately as dead. The variable insult resulted in a greater number of piglets with neuropathological damage (undamaged = 12.5%, damaged = 68.75%, dead = 18.75%) while the constant insult resulted in a large proportion of undamaged piglets (undamaged = 50%, damaged = 22.2%, dead = 27.8%). A hypoxic insult varied to maintain peak amplitude EEG <5 microV results in a greater number of survivors with a consistent degree of neuropathological damage than a constant hypoxic insult. Physiological variables MABP, LAEEG, pH and arterial base excess were found to be significantly associated with neuropathological outcome.

Noninvasive measurement of cerebral bioimpedance for detection of cerebral edema in the neonatal piglet

The association of sustained cerebral edema with poor neurological outcome following hypoxia-ischaemia in the neonate suggests that measurement of cerebral edema may allow early prediction of outcome in these infants. Direct measurements of cerebral impedance have been widely used in animal studies to monitor cerebral edema, but such invasive measurements are not possible in the human neonate. This study investigated the ability of noninvasive cerebral impedance measurements to detect cerebral edema following hypoxia-ischaemia. One-day-old piglets were anaesthetized, intubated and ventilated. Hypoxia was induced by reducing the inspired oxygen concentration to 4-6% O(2). Noninvasive cerebral bioimpedance was measured using gel electrodes attached to the scalp. Cerebral bioimpedance was also measured directly by insertion of two silver-silver chloride electrodes subdurally. Noninvasive and invasive measurements were made before, during and after hypoxia. Whole body impedance was measured to assess overall fluid movements. Intracranial pressure was measured continuously via a catheter inserted subdurally, as an index of cerebral edema. There was good agreement between noninvasive and invasive measurements of cerebral impedance although externally obtained responses were attenuated. Noninvasive measurements were also well correlated with intracranial pressure. Whole body impedance changes did not account for increases in noninvasively measured cerebral impedance. Results suggest that noninvasive cerebral impedance measurements do reflect intracranial events, and are able to detect cerebral edema following hypoxia-ischaemia in the neonate.

Measurement of extracellular fluid volume in the neonate using multiple frequency bio-impedance analysis.

Bioelectrical impedance analysis may be useful for cot-side monitoring of fluid balance in the neonatal intensive care unit (NICU). However the presence of cardio-respiratory monitoring equipment, non-ideal electrode placement and inability to obtain accurate crown-heel measurements may interfere with the ability to obtain reliable impedance data in this setting. This study aimed to investigate the effects of these factors on impedance analysis and to develop a prediction equation for extracellular fluid volume in the neonate. The study found that cardio respiratory monitoring had no significant effect on multi-frequency impedance measurements. Placement of current delivering electrodes on the ventral rather than dorsal surfaces improved separation of current and voltage electrodes but did not alter impedance results. Contralateral measurements were not significantly different to ipsilateral measurements. In 24 infants, extracellular fluid volume was measured using corrected bromide space (CBS) and simultaneous impedance analysis was performed. There was good correlation between CBS and the impedance quotient FF2/Ro where F is foot length and R0 is resistance at zero frequency. The study concludes that despite many potential difficulties associated with impedance analysis in the NICU, reliable measurements of impedance can be obtained and further work to validate prediction equations for ECF is warranted.

Rapid loss of glutamine synthetase from astrocytes in response to hypoxia: Implications for excitotoxicity

We have examined brains of neonatal pigs that were rendered hypoxic. Glutamine synthetase (GS), a key enzyme in the detoxification of glutamate and ammonia, was rapidly lost from astrocytes in regions susceptible to damage, including the CA1 of hippocampus and various cortical regions. Conversely, resilient areas such as the dentate gyrus exhibited little or no loss of GS. Onset of loss was rapid, patches of loss being evident by 1h post-insult, and loss was extensive by 24h and did not recover by 72 h. Examination of counterstained sections revealed that GS losses preceded any overt neuronal damage. Loss of GS from astrocytes would plausibly lead to a rise in intracellular glutamate, and could explain why reversal of astrocytic glutamate transport during hypoxia/ischaemia is conceptually possible.