This multifactorial study investigates the interrelationships between head circumference (HC) and intellectual quotient (IQ), learning, nutritional status and brain development in Chilean school-age children graduating from high school, of both sexes and with high and low IQ and socio-economic strata (SES). The sample consisted of 96 right-handed healthy students (mean age 18.0 +/- 0.9 years) born at term. HC was measured both in the children and their parents and was expressed as Z-score (Z-HC). In children, IQ was determined by means of the Wechsler Intelligence Scale for Adults-Revised (WAIS-R), scholastic achievement (SA) through the standard Spanish language and mathematics tests and the academic aptitude test (AAT) score, nutritional status was assessed through anthropometric indicators, brain development was determined by magnetic resonance imaging (MRI) and SES applying the Graffar modified method. Results showed that microcephalic children (Z-HC < or = 2 S.D.) had significantly lower values mainly for brain volume (BV), parental Z-HC, IQ, SA, AAT, birth length (BL) and a significantly higher incidence of undernutrition in the first year of life compared with their macrocephalic peers (Z-HC > 2S.D.). Multiple regression analysis revealed that BV, parental Z-HC and BL were the independent variables with the greatest explanatory power for child's Z-HC variance (r(2) = 0.727). These findings confirm the hypothesis formulated in this study: (1) independently of age, sex and SES, brain parameters, parental HC and prenatal nutritional indicators are the most important independent variables that determine HC and (2) microcephalic children present multiple disorders not only related to BV but also to IQ, SA and nutritional background.
The objective of the present study was to investigate the inter-relationships between nutritional status (past and current nutrition), brain development, and scholastic achievement (SA) of Chilean high-school graduates from high and low intellectual quotient (IQ) and socio-economic status (SES) (mean age 18 : 0 (SD 0 : 9) years). Results showed that independently of SES, highschool graduates with similar IQ have similar nutritional, brain development and SA variables. Multiple regression analysis between child IQ (dependent variable) and age, sex, SES, brain volume (BV), undernutrition during the first year of life, paternal and maternal IQ (independent variables) revealed that maternal IQ (P,0 : 0001), BV (P,0 : 0387) and severe undernutrition during the first year of life (P,0 : 0486), were the independent variables with the greatest explanatory power for child IQ variance (r 2 0 : 707), without interaction with age, sex or SES. Child IQ (P,0 : 0001) was the only independent variable that explained both SA variance (r 2 0 : 848) and academic aptitude test variance (r 2 0 : 876) without interaction with age, sex or SES. These results confirm the hypotheses formulated for this study that: (1) independently of SES, high-school graduates with similar IQ have similar variables of nutritional status, brain development and SA; (2) past nutritional status, brain development, child IQ and SA are strongly and significantly inter-related. These findings are relevant in explaining the complex interactions between variables that affect IQ and SA and can be useful for nutritional and educational planning.
Mild reduction in the protein content of the mother's diet from 25 to 8% casein, calorically compensated by carbohydrates, does not alter body and brain weights of rat pups at birth, but leads to significant enhancements in the concentration and release of cortical noradrenaline during early postnatal life. Since central noradrenaline and some of its receptors are critically involved in long-term potentiation (LTP) and memory formation, this study evaluated the effect of mild prenatal protein malnutrition on the a 2C -adrenoceptor density in the frontal and occipital cortices, induction of LTP in the same cortical regions and the visuo-spatial memory. Pups born from rats fed a 25% casein diet throughout pregnancy served as controls. At day 8 of postnatal age, prenatally malnourished rats showed a threefold increase in neocortical a 2C -adrenoceptor density. At 60 days-of-age, a 2C -adrenoceptor density was still elevated in the neocortex, and the animals were unable to maintain neocortical LTP and presented lower visuo-spatial memory performance. Results suggest that overexpression of neocortical a 2C -adrenoceptors during postnatal life, subsequent to mild prenatal protein malnutrition, could functionally affect the synaptic networks subserving neocortical LTP and visuo-spatial memory formation. Keywords: a 2C adrenoceptor, long-term potentiation, neocortex, protein malnutrition, visuo-spatial memory. Central nervous system noradrenaline critically influences long-term potentiation (LTP) in cerebral cortex (Nowicky et al. 1992;Kamatsu 1996) and hippocampus (Hopkins and Johnston 1988;Radisavljevic et al. 1994;Bramham et al. 1997), as well as memory formation (Sternberg et al. 1986;Crowe et al. 1990;Gibbs 1991), through balanced activation of specific receptors. For instance, animal studies have revealed that b adrenoceptor activation is associated with enhancement of LTP in the hippocampus (Hopkins and Johnston 1988;Radisavljevic et al. 1994;Bramham et al. 1997) and memory facilitation (Crowe et al. 1990;Gibbs 1991;Gibbs and Summers 2000), while activation of a 2 adrenoceptors (Sara and Devauges 1989;Devauges and Sara 1990;Bunsey and Strupp 1995), especially the a 2C subtype (Haapalinna et al. 1998 Björklund et al. 1998Björklund et al. , 1999Björklund et al. , 2000, is related to decreased memory formation. This role of b and a 2C adrenoceptors is consistent with the widespread distribution of these receptor subtypes in the hippocampus and the cerebral cortex (Lee et al. 1998;Gibbs and Summers 2000).It has been reported that perinatal malnutrition and severe forms of prenatal malnutrition in the rat, in addition to decrease body and brain weights of pups results in functional changes of central noradrenergic systems, including increased activity of brain tyrosine hydroxylase
Mild prenatal protein malnutrition, induced by reduction of the casein content of the maternal diet from 25 to 8%, calorically compensated by the addition of excess carbohydrates, leads to so-called "hidden" malnutrition in the rat. This form of malnutrition results in normal body and brain weights of pups at birth, but in significant alterations of their central nervous system neurochemical profiles. Since severe forms of prenatal malnutrition induce morpho-functional deficits on callosal interhemispheric communication together with brain neurochemical disturbances, we evaluated, in rats born from mothers submitted to an 8% casein diet, the potassium-induced release of [3H]-noradrenaline in visual cortex slices, as well as functional properties of callosal-cortical synapses by determining cerebral cortical excitability to callosal inputs and fatigability and temporal summation of transcallosal evoked responses. Rats born from mothers submitted to a 25% casein diet served as controls. At birth prenatally malnourished pups had significantly higher cortical percent net noradrenaline release (14.79 +/- 1.11) than controls (9.14 +/- 1.26). At 45-50 days of age, rehabilitated previously malnourished rats showed, when compared to controls; (i) significantly reduced percent net noradrenaline release in the visual cortex (4.50 +/- 0.52 vs 11.31 +/- 1.14); (ii) decreased cortical excitability to callosal inputs as revealed by significantly increased chronaxie (607.2 +/- 82.8 microseconds vs 351.3 +/- 47.7 microseconds); (iii) enhanced fatigability of transcallosal evoked responses as revealed by significantly decreased stimulus frequency required to fatigate the responses (4.9 +/- 0.8 Hz vs 9.2 +/- 1.3 Hz); and (iv) decreased ability of callosal-cortical synapses to perform temporal summation, as revealed by significantly reduced percent response increment to double-shock (54.2 +/- 6.2 vs 83.0 +/- 11.0, for a 3.2-ms interstimulus time interval). These changes, resulting from mild prenatal protein restriction, are discussed in relationship to developmental processes leading to the formation of synaptic contacts between callosal axons and their appropriate cortical target during perinatal age.
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