Effects of perinatal undernourishment on neuronal development of the facial motor nucleus in the rat

Preterm nutritional intake and MRI phenotype at term age: a prospective observational study

OBJECTIVE

To describe (1) the relationship between nutrition and the preterm-at-term infant phenotype, (2) phenotypic differences between preterm-at-term infants and healthy term born infants and (3) relationships between somatic and brain MRI outcomes.

DESIGN

Prospective observational study.

SETTING

UK tertiary neonatal unit.

PARTICIPANTS

Preterm infants (<32 weeks gestation) (n=22) and healthy term infants (n=39) MAIN OUTCOME MEASURES: Preterm nutrient intake; total and regional adipose tissue (AT) depot volumes; brain volume and proximal cerebral arterial vessel tortuosity (CAVT) in preterm infants and in term infants.

RESULTS

Preterm nutrition was deficient in protein and high in carbohydrate and fat. Preterm nutrition was not related to AT volumes, brain volume or proximal CAVT score; a positive association was noted between human milk intake and proximal CAVT score (r=0.44, p=0.05). In comparison to term infants, preterm infants had increased total adiposity, comparable brain volumes and reduced proximal CAVT scores. There was a significant negative correlation between deep subcutaneous abdominal AT volume and brain volume in preterm infants (r=-0.58, p=0.01).

CONCLUSIONS

Though there are significant phenotypic differences between preterm infants at term and term infants, preterm macronutrient intake does not appear to be a determinant. Our preliminary data suggest that (1) human milk may exert a beneficial effect on cerebral arterial vessel tortuosity and (2) there is a negative correlation between adiposity and brain volume in preterm infants at term. Further work is warranted to see if our findings can be replicated and to understand the causal mechanisms.

Early undernourishment interferes with the maternal aggressive response triggered by an intruder entering the homing cage

The maternal aggressive response (MAR) against intruders is temporarily expressed during lactation in association with the rearing and protection of offspring to promote their survival and growth in the nest. This normal component of maternal behaviour requires both the hormonal changes occurring at the end of pregnancy and the presence of pups for its establishment. Because early food restriction in the rat results in long-term maternal deficiencies, we analysed in Wistar rats the effects of perinatal undernutrition on the MAR to an intruder at days 1, 4, and 8 postpartum. The data showed that undernourished dams exhibited significant reductions of sniffing frequency on days 4 and 8 and significant increases of biting on day 4 and of lateral attacks on postpartum days 4 and 8. The finding of an altered MAR during the lactating period may be relevant for the survival and long-term behavioural development of the progeny.

Neonatal Food Restriction Induces Hypoplasia in Developing Facial Motor Neurons of Rats

The effects of neonatal food restriction upon the dendritic development of facial nucleus (FN) motor neurons of Wistar rats were analyzed. Rats neonatally underfed by daily (12 h) mother-litter separation in an incubator from 5-30 days after birth exhibited, in brain stem Golgi-Cox sections, significant reductions in the number and extension of stellate, triangular and bipolar FN neuronal dendritic prolongations with negligible effects upon perikarya measurements. Data suggest that in the underfed newborn, the ability of FN neurons to establish synaptic contacts with afferent fibers is reduced, which then interferes with their capacities for the integration and triggering of nerve impulses to modulate facial motor expression in response to sensory cues.

Alterations in the Solitary Tract Nucleus of the Rat Following Perinatal Food Restriction and Subsequent Nutritional Rehabilitation

Newborn of altricial species maintain functional gustatory communication with the mother because the neural substrate and the capacity to discriminate and promote gustofacial responses are already operating. Because little is known about the effects of perinatal food restriction upon gustatory neuronal brain stem structures, we characterized neuronal Golgi-Cox alterations of the solitary tract rostral portion (NSTr) where gustatory information is known to convey in neonatal Wistar rats. Pre-and neonatally undernourished rats exhibited a general reduction in the number and extension of distal dendrites particularly in small neurons but little effect upon perikarya measurements of the NSTr neuronal population. By contrast, in nutritional and sensory rehabilitated rats the number of distal dendrites increased, although the dendritic extensions were less affected compared to perinatally underfed and control subjects. The data indicate that perinatal food restriction interferes with the NSTr dendritic arbor organization, while nutritional and sensorial rehabilitation given by normally lactating dams induced plastic changes presumably modifying the integrative processes underlying early taste discriminative capabilities. Moreover, since perinatal food restriction is a powerful stressor influence and the NST forms a part of a complex system underlying adaptive stress responses, the neuronal alterations observed here may be partly due to this noxious perinatal influence.

Prenatal nicotine exposure alters neuroanatomical organization of the developing brain

Although there has been considerable research conducted regarding the long-term effects of prenatal exposure to nicotine, there has been little examination of how this experience influences brain development. This study was designed to examine if there are morphological changes (dendritic branching, dendritic length, and spine density) in medial prefrontal cortex, orbital frontal cortex, parietal cortex, and nucleus accumbens associated with exposure to nicotine during gestation. Nicotine or saline was administered to pregnant Long Evans dams for the duration of pregnancy. Golgi-Cox techniques were used to examine neuroanatomy of offspring at postnatal day 21. The dendritic changes identified in rats exposed to nicotine prenatally resembled neuroanatomical changes that are identified in rats administered with nicotine in adulthood. Of the 18 anatomical parameters measured, 11 exhibited significant modification, with two parameters apical and basilar spine density in parietal cortex demonstrating sex-dependent modification. These early changes in anatomy and behavior have important implications for later plasticity and long-term well-being.

Gene expression in the placenta: maternal stress and epigenetic responses

Successful placental development is crucial for optimal growth, development, maturation and survival of the embryo/fetus into adulthood. Numerous epidemiologic and experimental studies have demonstrated the profound influence of intrauterine environment on life, and the diseases to which one is subject as an adult. For the most part, these invidious influences, whether maternal hypoxia, protein or caloric deficiency or excess, and others, represent types of maternal stress. In the present review, we examine certain aspects of gene expression in the placenta as a consequence of maternal stressors. To examine these issues in a controlled manner, and in a species in which the genome has been sequenced, most of these reported studies have been performed in the mouse. Although each individual maternal stress is characterized by up- or down-regulation of specific genes in the placenta, functional analysis reveals some patterns of gene expression common to the several forms of stress. Of critical importance, these genes include those involved in DNA methylation and histone modification, cell cycle regulation, and related global pathways of great relevance to epigenesis and the developmental origins of adult health and disease.

Assessing the impact of preterm nutrition

Growth is the traditional means of assessing the impact of newborn nutrition. We argue that this approach is flawed as the optimum pattern of postnatal growth after extremely preterm birth is unknown and both growth restraint and growth acceleration are associated with beneficial as well as adverse outcomes. Clinical trials examining nutritional regimens should be designed to achieve specific patterns of postnatal growth. Clinical practice should include the systematic capture of neonatal nutritional intake. As the ultimate goals are adult health and wellbeing, long-term follow-up is essential.

A component of BRAF-HDAC complex, BHC80, is required for neonatal survival in mice

BHC80 is a component of BRAF-HDAC complex (BHC) involved in transcriptional repression of neuron-specific genes in non-neuronal cells. However, BHC80 is present in both neuronal and non-neuronal cells. To explore the physiological importance of BHC80 in vivo, and the precise mechanism underlying neuron-specific gene repression by BHC80, we have produced mutant mice lacking Bhc80. The loss of Bhc80 resulted in neonatal lethality without sucking mother's breast milk sufficiently. Although Bhc80-deficient mice showed no developmental defect in the neuronal and non-neuronal tissues, Bhc80 is indispensable for the survival of neonatal pups.

Movements restriction and alterations of the number of spines distributed along the apical shafts of layer V pyramids in motor and primary sensory cortices of the peripubertal and adult rat

The number and distribution of spines along apical shafts of rapid-Golgi-stained layer V pyramidal cells from visual, motor and somatosensory cortical areas were analyzed in control and movement-restricted (beginning at 20 days old) Wistar rats killed at 30, 40, 80 and 120 days of age (experiment A). In other group of rats, spine density was analyzed when restriction initiates on day 40 and the animals were killed at 50, 60 and 80 days postpartum, or after restriction starting on day 80 and killed at 120 days of age (experiment B). It has been found that the restriction of movements significantly reduces the total number of spines on apical shafts in the three cortical areas, when this condition starts at 20, 40 or 80 days without changing the overall distribution of spines. Also present findings indicate that the effects of movements restriction are attenuated when they were concurrent with maturational brain processes (20-40 days) than when they occurred later in life. The question remains open of which part of the measured reduction on the number of spines is due to the immobilization and which to the stress associated with this maneuver.

Undernutrition and food rehabilitation effects on the locus coeruleus in the rat

Perinatal nutrition plays a fundamental role on the morphological organization and function of a number of brain stem structures. Because little is known of the effects of perinatal undernutrition upon sexually dimorphic structures underlying reproductive behavior, the locus coeruleus morphology of 60-day-old male and female Wistar rats was analyzed. Perinatal food deprivation until weaning significantly decreased the volume and neuronal number of locus coerulus in male and female rats, while nutritional rehabilitation ameliorated these alterations in males but not in females. Data suggest that perinatal undernutrition interferes with the neuroendocrine mechanisms underlying the establishment of sex differences of the locus coeruleus.

A paradigm of undernourishing and neonatal rehabilitation in the newborn rat

Perinatal undernutrition as a deficiency of nutrient availability, affects body and brain developmental processes and promotes recurrent health problems. Thus, altered mother-litter bonds and deficient environmental interactions may interfere with the brain pluripotential capabilities of the newborn. To gather information concerning the mechanisms underlying perinatal undernutrition we designed a paradigm of undernutrition and neonatal rehabilitation in the rat. An underfed group came from pregnant Wistar rats fed with 50% of the diet from G6 to G12 and with 60% from G13 until G21. After birth, pups were daily undernourished during 12 h daily by rotating a pair of lactating well-nourished dams which had one of their nipples subcutaneously ligated. The rehabilitated animals were undernourished pups neonatally fed by a pair of normally lactating dams. Controls received plenty of food during the pre- and neonatal periods. Pups were sacrificed at 12, 20 and 30 days of age. Perinatal underfeeding significantly reduced body and brain weights and neuronal morphometric parameters. Normal neonatal feeding in the newborn ameliorated the damages associated to food deprivation. The current undernourishing paradigm may be helpful to assess brain development alterations, as well as to study the compensatory mechanisms associated to salutary epigenetic influences.

Carotid body denervation effect on cytochrome oxidase activity in pre-Botzinger complex of developing rats

Previously, we found that the rat pre-Bötzinger complex (PBC) exhibited reduced cytochrome oxidase (CO) activity on postnatal days (P) 3-4 and especially on P12, with a concomitant decrease in glutamate and N-methyl-d-aspartate receptor subunit 1, and an increase in GABA, GABA(B), glycine receptor, and glutamate subunit 2. We hypothesized that the PBC would be more affected by carotid body denervation (CBD) during the two critical windows than at other times. Pairs of CBD and sham animals at each postnatal day from P2 to P14 and at P21 were operated on and survived for 3 days. Brain stems were processed for CO and neurokinin-1 receptor for the identification of PBC. Results indicate that CBD caused a significant loss in body weight in all animals and a reduction in PBC somal size when the surgery was between P2 and P7. CBD also induced a significant decrease in CO activity of the PBC in most animals and a distinct delay, as well as prolongation of the maturational process, especially when induced close to P3 and P11-P13.

Neonatal nutritional rehabilitation of morphological features in facial motoneurons altered by prenatally food deprivation in the rat

Undernutrition alters facial motoneurons development. Here, we evaluated the plastic characteristics of facial motoneurons in response to neonatal rehabilitation. Prenatally undernourished rat pups derived from pregnant rats fed with 50% of the diet from gestational days G6 to G12, and with 60% of food from G13 to G21 and rehabilitated after birth by a pair of control lactating foster dams. Morphological features of 640 Golgi-Cox impregnated motoneurons from 12, 20 and 30 days old pups were analyzed. Neonatal food rehabilitation increased the number and extension of the dendritic branches (main neuronal reception area) without altering significantly soma measurements (main neuronal firing area), suggesting that food and sensory maternal disponibility after birth ameliorates the damage due to prenatal deprivation. Findings showed that neonatal rehabilitation in addition to intense maternal polysensorial stimuli from the foster mothers partially diminished the morphological alterations associated to prenatal undernutrition, and provide evidence of plastic properties of facial motoneurons to the influence of environmental cues.