Long-term effects of postnatal undernutrition and maternal malnutrition on mouse cerebral cortex

Quantitative analysis of cellular densities as well as an estimate of the cortical volume and of its total cell population were performed on the cortex of postnatally undernourished mice (2--21 days) and on that of pups from malnourished mothers (gestation and lactation). Animals were followed until 180 days of age after more than 5 months of nutritional rehabilitation, and data were obtained at 10, 30, 60, and 180 days of age. The neuronal density was much higher in all cortical layers of the two experimental series, suggesting a delay in cortical maturation. Moreover, layers II, III, and IV were more delayed than layers I, V, and VI. Postnatal undernutrition had more severe effects than maternal malnutrition and the degree of recovery after a long rehabilitation was much less. The increase of the cortical volume was greatly reduced in postnatal undernutrition and to a lesser degree in maternal malnutrition. The total number of glial cells was also reduced more in postnatal undernutrition than in maternal malnutrition, but the total number of neurons was never smaller than in the controls.     

Effect of undernutrition and subsequent rehabilitation on brain 5-HT (serotonin) profile of developing newborn rats

For littermate comparison, undernutrition in half of the pups of a litter was induced by 12h maternal deprivation from day 5 to day 18 postnatal. Subsequently, undernourished suckling rats were rehabilitated. Brain 5-HT concentrations and its turnover rate were measured on different days of age up to the period of 3 months. Brain 5-HT concentration was approximately half of the adult level at birth and increased progressively, except with a steep fall on day 18 postnatal, to the adult level by day 25 postnatal and thereafter it did not vary much on different days of age. Undernourished newborn rats showed significantly low level of brain 5-HT on day 9 and significantly higher concentrations on day 12 and 18 postnatal, whereas, rehabilitated rats showed comparable brain 5-HT concentrations with that of their nourished littermates. It is concluded that undernutrition had affected the brain 5-HT concentration and its turnover rate. Brain 5-HT concentration was low during early phase and was more during late phase of undernutrition. Rehabilitation of undernourished rats restored the brain 5-HT concentration similar to that of their nourished littermates.     

Morphology and dendritic maturation of developing principal neurons in the rat basolateral amygdala

The basolateral nucleus of the amygdala (BLA) assigns emotional valence to sensory stimuli, and many amygdala-dependent behaviors undergo marked development during postnatal life. We recently showed principal neurons in the rat BLA undergo dramatic changes to their electrophysiological properties during the first postnatal month, but no study to date has thoroughly characterized changes to morphology or gene expression that may underlie the functional development of this neuronal population. We addressed this knowledge gap with reconstructions of biocytin-filled principal neurons in the rat BLA at postnatal days 7 (P7), 14, 21, 28, and 60. BLA principal neurons underwent a number of morphological changes, including a twofold increase in soma volume from P7 to P21. Dendritic arbors expanded significantly during the first postnatal month and achieved a mature distribution around P28, in terms of total dendritic length and distance from soma. The number of primary dendrites and branch points were consistent with age, but branch points were found farther from the soma in older animals. Dendrites of BLA principal neurons at P7 had few spines, and spine density increased nearly fivefold by P21. Given the concurrent increase in dendritic material, P60 neurons had approximately 17 times as many total spines as P7 neurons. Together, these developmental transitions in BLA principal neuron morphology help explain a number of concomitant electrophysiological changes during a critical period in amygdala development.     

Postnatal development of the visual cortex of the mouse after enucleation at birth

Summary Quantitative data in the neocortex up to the age of 180 days (neuronal densities, number of neurones, glial cells, dendritic intersections and spines) were compared in normal mice and mice enucleated at birth.Bilateral enucleation induced an increase of neuronal density in all cortical layers of areas 17, 18a, and 41, the supragranular layers II–III being more affected than layers IV–VI. This was noticed in layer II 10 days after the operation and was maximal in all layers between 30 and 60 days; at 180 days there was some return to normal of the neuronal density in all layers. The total number of neurones and glial cells were the same in the bilaterally enucleated mice as in the controls. No reaction in dendritic branching was evident for pyramids of layers III and V in areas 17 and 41 after bilateral enucleation. In contrast the number of spines was reduced on the apical dendrites of pyramids from layers III and V in area 17, but not in area 41.After unilateral enucleation the reaction was less severe and delayed compared with bilateral enucleation, the first signs of increase of neuronal density appearing 30 days after the lesion in the contralateral hemisphere. The contralateral areas 17 and 18a were more affected than the ipsilateral ones and area 41 showed no change compared to the control. As after bilateral enucleation, layers IV and V were least affected by unilateral enucleation in both ipsi- and contralateral cortices.These results suggest that deafferentation in an immature system affects the development of all cortical layers but with a greatest intensity in supragranular layers, which are not the main direct targets of thalamo-cortical input.Supported by the Swiss National Research Foundation, Grants no. 3-641-71 and 3-434-74     

小鼠海马CA1区锥体神经元树突棘的发育

目的 对小鼠海马CA1区锥体神经元正常发育中树突棘密度及各种形态变化进行分析测定,为深入研究突触发生及突触可塑性提供直接的形态学依据.方法 分别取出生后0、5、10、20及30d 5个年龄段的C57BL/6小鼠各10只,采用基因枪对小鼠海马CA1区锥体神经元树突棘进行亲脂性荧光染料DiI标记,通过激光共焦显微镜对其进行观察分析;同时利用透射电镜技术对树突棘的超微结构进行分析.结果 树突棘的形态、大小及其密度随小鼠发育而变化,成熟树突棘内部存在滑面内质网与棘器,可能参与了突触后膜结合蛋白及其转运体的合成.结论 树突棘的发育过程与突触连接的形成以及突触可塑性密切相关.     

Fetal exposure to excess glucocorticoid is unlikely to explain the effects of periconceptional undernutrition in sheep

Periconceptional undernutrition alters fetal growth, metabolism and endocrinology in late gestation. The underlying mechanisms remain uncertain, but fetal exposure to excess maternal glucocorticoids has been hypothesized. We investigated the effects of periconceptional undernutrition on maternal hypothalamic–pituitary–adrenal axis function and placental 11β-hydroxysteroid dehydrogenase type 2 (11βHSD2) activity. Ewes received maintenance feed (N, n = 20) or decreased feed from −60 to +30 days from mating to achieve 15% weight loss after an initial 2-day fast (UN, n = 21). Baseline plasma samples and arginine vasopressin (AVP)–corticotrophin-releasing hormone (CRH) challenges were performed on days −61, −57, −29, −1, +29, 33, and 49 from mating (day 0). Maternal adrenal and placental tissue was collected at 50 days. Baseline plasma levels of adrenocorticotrophic hormone (ACTH) and cortisol decreased in the UN group ( P < 0.0001). ACTH response to AVP–CRH was greater in UN ewes during undernutrition ( P = 0.03) returning to normal levels after refeeding. Cortisol response to AVP–CRH was greater in UN ewes after the initial 2-day fast, but thereafter decreased and was lower in UN ewes from mating until the end of the experiment ( P = 0.007). ACTH receptor, StAR and p450c17 mRNA levels were down-regulated in adrenal tissue from UN ewes. Placental 11βHSD2 activity was lower in UN than N ewes at 50 days ( P = 0.014). Moderate periconceptional undernutrition results in decreased maternal plasma cortisol concentrations during undernutrition and after refeeding, and adrenal resistance to ACTH for at least 20 days after refeeding. Fetal exposure to excess maternal cortisol is unlikely during the period of undernutrition, but could occur later in gestation if maternal plasma cortisol levels return to normal while placental 11βHSD2 activity remains low.     

Effects of twin pregnancy and periconceptional undernutrition on maternal metabolism, fetal growth and glucose-insulin axis function in ovine pregnancy

Although twins have lower birthweights than singletons, they may not experience the increased disease risk in adulthood reportedly associated with low birthweight. In contrast, another periconceptional event, maternal undernutrition, does not reduce birthweight but does affect fetal and postnatal physiology in sheep. We therefore studied maternal and fetal metabolism, growth and glucose–insulin axis function in late gestation in twin and singleton sheep pregnancies, either undernourished from 60 days before until 30 days after conception or fed ad libitum . We found that twin-bearing ewes had decreased maternal food intake in late gestation and lower maternal and fetal plasma glucose and insulin levels. Twin fetuses had fewer everted placentomes, grew slower in late gestation, and had a greater insulin response to a glucose challenge, but lesser response to arginine. In contrast, periconceptional undernutrition led to increased maternal food intake and a more rapid fall in maternal glucose levels in response to fasting. Periconceptional undernutrition increased the number of everted placentomes, and abolished the difference in insulin responses to glucose between twins and singletons. Thus, the physiology of twin pregnancy is quite different from that of singleton pregnancy, and is probably determined by a combination of factors acting in both early and late gestation. The inconsistency of the relationships between low birthweight and postnatal disease risk of twins may lie in their very different fetal development. These data suggest that twin pregnancy may be another paradigm of developmental programming, and indicate that twins and singletons must be examined separately in any study of fetal or postnatal physiology.     

Dendritic spines in the visual cortex of the mouse: Introduction to a mathematical model

Summary The spines of apical dendrites of the layer V pyramidal cells of the area striata in the mouse represent a sequence of post-synaptic structures receiving a variety of contacts from terminal fibers derived fundamentally from short axon cells and superficial pyramidal cells. The study of Golgi preparations of mice 180 days old shows the existence of the most complicated terminal structures over portions of apical dendrites at the levels of layers III and IV. Observations on young mice reveals the terminations of the specific afferent fibers on the dendrites of short axon cells. A mathematical model which defines the distribution of spines along the apical dendrites is introduced. The principal equation of the model has been adjusted from the data processing of microscope countings through a series of programs written for an IBM 7070. The equation defines satisfactorily the different distributions of dendritic spines in mice 10–180 days old raised in normal conditions and in complete darkness. The equation defines also the distribution of dendritic spines in the visual cortex of mice enucleated at birth on one side, and the distribution along the apical dendrites of various cortical areas of the hamster, cat and man. The number of dendritic spines increases with the age of the subject and their distribution varies significantly according to the values of the parameters of the model.     

Intra-uterine nutrition and its effects on aggression

Prenatal zinc deficiency and prenatal undernutrition were found to have adverse effects on the food consumption and weight gain of pregnant dams and their offspring. Pups whose dams suffered prenatal zinc deficiency (ZD) consumed less food and gained less weight than pups whose dams suffered prenatal undernutrition (PF). The PF pups consumed less food and gained less weight than pups whose dams were normally fed (AL). The ZD females at age 75 days were significantly more aggressive than the PF females, while the PF females were more aggressive than the AL females. At age 105 days, ZD females were significantly more aggressive than the PF and AL females. There were no differences in aggression between the PF and AL females at 105 days. Among the ZD, PF, and AL male offspring, there were no differences in aggression at either age level except that the 75 day old PF males were significantly less aggressive than the AL males. Thus prenatal malnutrition, especially zinc deficiency, seems to have differential effects on the aggressive tendencies of female and male offspring.     

Maturation of pyramidal cell form in relation to developing afferent and efferent connections of rat somatic sensory cortex.

Golgi and axonal labeling methods were used to examine the maturation of pyramidal cells in layers III and V of the rat somatic sensory cortex. The material came from animals late in the gestation period, postnatal, ranging from 0 to 43 days of age and at maturity. Special attention was paid to the period (0–7 days of age) during which it is known that thalamic and callosal fibers grow into the cortex. It is shown that the basic features of the pyramidal cell form are established before the long afferent fibers arrive in layers III and V and before the large number of synapses are established in these layers. Nevertheless, considerable dendritic growth and spine formation occurs after the afferent fibers establish an adult-like pattern of distribution. It is also shown that even at 1 day of age, the axons of pyramidal cells in all layers have reached the vicinity of targets such as the striatum, thalamus, brainstem, spinal cord and contralateral cortex.At 0–1 day the immature pyramidal cells are essentially bipolar in the upper cortical plate, but in the developing infragranular layers they have a few short, almost spine-free, basal dendrites and, rarely, a few oblique branches of the apical dendrite. The apical dendrite extends to the pial surface and the dendritic branches end in growth cones. The dendrites of cells in all layers increase in size and complexity of branching over the first postnatal week; the maturation of dendrites in layer V leads that of dendrites in the supragranular layers by about 2–3 days. As maturation proceeds, basal dendrites acquire secondary and tertiary branches and more oblique branches appear on the apical dendrite. Dendritic spines appear after 4 days of age but remain sparse up to 7–8 days. At 14 days of age, the spine density is much higher than in 7-day-old animals but remains at a much lower density than in 4-week-old, 6-week-old, or adult animals. By 7–14 days, the difference in maturity between superficial (layer III) and deep (layer V) pyramidal cells is difficult to discern qualitatively. All the pyramidal cells now have relatively complex, highly branched dendritic trees when compared to younger cells, but the dendritic tree is still immature in terms of the number, length and complexity of branching of the apical and basal dendritic systems.It can be concluded that the growth of the long axon of cortical pyramidal neurons precedes the acquisition of afferent connections and when these afferent fibers arrive in the cortex the dendritic tree of the pyramidal cell is still highly immature. Thus it remains possible that the finer modeling of the dendritic tree and the formation of spines may be affected by extrinsic influences such as the afferent fibers.     

The ontogeny of maternal potentiation of the infant rats' isolation call

Previous studies have shown that preweanling rat pups double or triple their rates of ultrasonic vocalization (USV) when isolated immediately after brief periods of maternal interaction (potentiation). We studied the ontogenetic pattern of USV and other behavioral responses of pups to 3-min periods of isolation in a novel test chamber, from 5 to 25 days postnatal age, before, during, and after 1 min or 5 min of interaction with an anesthetized or an active dam. USV potentiation did not develop until 7–9 days postnatal, a week after the initial isolation and maternal contact quieting responses were well established. Potentiation reached a peak at 13 days, and then declined until all USV responses ceased after 21 days. Other behavioral responses to isolation were not enhanced by maternal interaction at any age. The distinct ontogenetic pattern of this unusual response to maternal separation has implications for understanding its mode of development and possible adaptive value. © 1998 John Wiley & Sons, Inc. Dev Psychobiol 33: 189–201, 1998     

Ontogeny of short- and long-term memory capacities for passive avoidance training in undernourished mice

To assess the effects of early postnatal undernutrition upon the developing abilities of infant and juvenile mice to acquire and retain a passive-avoidance response, we reared mice following birth in either “normally nourished” or “undernourished” conditions by maintaining litter sizes of 6 or 16, respectively. At ages ranging from 7 to 21 days of age, mice from each nutritional condition were trained to withhold stepping off from a small vibrating platform in order to avoid shock. Following training to a common criterion, separate groups of mice were retrained to the same criterion either 1 or 24 hr later. From the comparisons with yoked control groups at each age and retention interval, we conclude that although undernutrition results in some age-related differences in the ability to withhold responding, these are quite small during acquisition within each age group. In contrast, the retention data suggest that undernutrition delayed the development of both short- and long-term memory abilities on this task. In general, these results are similar to earlier data involving discriminated shock-escape wherein undernutrition had little apparent effect upon acquisition at the early ages but rather marked effects upon developing memory systems.     

A quantitative electron microscopic study of synaptic reorganization in the rat medial habenular nucleus after transection of the stria medullaris

Synaptic plasticity has been studied electron-microscopically in the rat medial habenular nucleus by counting the numbers of different types of synapses per unit area at various times after transection of the stria medullaris on one or both sides.Over 80% of synapses in the normal medial habenula had asymmetrical thickenings, and of these most were in contact with dendritic spines, the rest were in contact with dendritic shafts. The presynaptic terminals were complex structures frequently invaginated by slender spinules from the postsynaptic element. Each presynaptic terminal made contact with a large number of dendritic spines. The remainder of the synapses involved symmetrical contacts on dendritic shafts or neuronal somata.After transection of the ipsilateral stria medullaris the presynaptic elements of both symmetrical and asymmetrical synapses showed electron-dense degeneration. Degeneration was first seen at 24 hours after operation, reached a maximum (of 19%) at two days, and disappeared by 12 days.Non-degenerating synapses fell to around 30%, of their normal level at four days and finally recovered to around 80%, of normal by more than 100 days. Differential counts for synapses on dendritic spines, shafts and cell bodies revealed different time courses for reinnervation. Thus, synapse numbers on spines began to recover sooner than those on shafts and somata. but only the number of synapses on somata returned to almost normal (98%), whilst those on spines and shafts reached only about 70%, of normal.Membrane thickenings resembling vacant postsynaptic sites were rarely (0.3%,) found in unoperated animals. They appeared after transection of the ipsilateral stria, reached a peak of around 12%, at 4 6 days, (slightly later than the degeneration), and then fell, although not quite reaching their normal low levels even at more than 100 days.The nucleus as a whole shrank by about 17% of its normal volume. This would cause the synaptic density to increase by about 12% (calculated as³ √17²%), an effect which is not of sufficient magnitude to account for the observed recovery of synapse numbers, which involves a nearly three-fold increase —i.e. from 30% to 80% normal. The temporal coincidence between the recovery of non-degenerating synapses, and the disappearance of degenerating synapses and vacant sites favours the view that the denervated sites are reinnervated by the formation of new presynaptic terminals.Under normal circumstances the contralateral stria medullaris forms few synapses in the medial habenular nucleus (0.07%, degeneration at four days after transection). However, at long-term survivals after an ipsilateral striai lesion (when the degeneration from that lesion has been completely removed), a lesion of the contralateral stria causes appreciably more degeneration (around 2%), and a considerable fall (more than 30%,) in non-degenerating synapses. Despite the (unexplained) discrepancy between these figures, the findings still suggest that at least some of the new synapses induced after denervation by an ipsilateral strial lesion are formed by axons belonging to the contralateral stria.     

Effect of maternal separation on feeding behavior of rats in later life

Effects of maternal separation on feeding behavior, particularly on rebound hyperphagia, in adult rats were examined. Time-restricted scheduled feeding (2 h per day for 6 days), was given at the age of 3, 6, 9 or 12 weeks in rats that were maternal separated from postnatal days (PD) 1–21 and control rats. Following the time-restricted scheduled feeding, rats were fed freely for 24 h (rebound hyperphagia). Body weight, daily normal food consumption and food consumption during time-restricted scheduled feeding and rebound hyperphagia were measured. Body weight of 3-week-old maternally separated rats were less than those of control rats. There was no significant difference in normal daily food consumption. Food consumption during rebound hyperphagia was significantly increased in 6- to 9-week-old female maternally separated rats, but there was no difference observed in males. Postnatal maternal separation enhanced rebound hyperphagia of female rats in later life. These results indicate that postnatal maternal separation made rats more vulnerable to the development of abnormal feeding behavior in response to food restriction in later life.     

Locomotor activity and social behavior of old rats after preweaning undernutrition

Rat pups were undernourished from birth to 25 days of age by giving them a nipple-ligated mother and a normal lactating mother for alternate periods of 12 hr/day, thus providing adequate full-time maternal care. Male and female rats undernourished neonatally had greater locomotor activity than controls in old age (16–20 months). Females were more active than males, irrespective of neonatal undernutrition. At the age of 24 months, social behavior was recorded at various times of the day for pairs of male rats (1 previously undernourished and 1 control). With one minor exception, undernourished animals did not differ significantly from controls in the incidence of the various behavioral items that were scored. Neonatal social factors may compensate for possible negative effects of neonatal undernutrition on later social behavior.     

Low protein diet fed exclusively during mouse oocyte maturation leads to behavioural and cardiovascular abnormalities in offspring

Early embryonic development is known to be susceptible to maternal undernutrition, leading to a disease-related postnatal phenotype. To determine whether this sensitivity extended into oocyte development, we examined the effect of maternal normal protein diet (18% casein; NPD) or isocaloric low protein diet (9% casein; LPD) restricted to one ovulatory cycle (3.5 days) prior to natural mating in female MF-1 mice. After mating, all females received NPD for the remainder of gestation and all offspring were litter size adjusted and fed standard chow. No difference in gestation length, litter size, sex ratio or postnatal growth was observed between treatments. Maternal LPD did, however, induce abnormal anxiety-related behaviour in open field activities in male and female offspring ( P < 0.05). Maternal LPD offspring also exhibited elevated systolic blood pressure (SBP) in males at 9 and 15 weeks and in both sexes at 21 weeks ( P < 0.05). Male LPD offspring hypertension was accompanied by attenuated arterial responsiveness in vitro to vasodilators acetylcholine and isoprenaline ( P < 0.05). LPD female offspring adult kidneys were also smaller, but had increased nephron numbers ( P < 0.05). Moreover, the relationship between SBP and kidney or heart size or nephron number was altered by diet treatment ( P < 0.05). These data demonstrate the sensitivity of mouse maturing oocytes in vivo to maternal protein undernutrition and identify both behavioural and cardiovascular postnatal outcomes, indicative of adult disease. These outcomes probably derive from a direct effect of protein restriction, although indirect stress mechanisms may also be contributory. Similar and distinct postnatal outcomes were observed here compared with maternal LPD treatment during post-fertilization preimplantation development which may reflect the relative contribution of the paternal genome.     

Regulation of dendrite formation of Purkinje cells by serotonin through serotonin1A and serotonin2A receptors in culture

Serotonergic fibers and receptors appear in the rat cerebellum during early postnatal development. In the present study, we investigated the actions of serotonin (5-HT) and its receptors in the dendrite formation of Purkinje cells in organotypic cultures of anterior and posterior lobes of the cerebellum at postnatal day 7. In anterior lobes after 4 days in vitro (4DIV), the dendritic areas and branchings of Purkinje cells were increased by the treatment of 2 microM 5-HT, but decreased by 20 microM 5-HT. In posterior lobes after 4DIV, the dendritic areas of Purkinje cells were increased by 5-HT (2, 20 and 200 microM). In contrast, 5-HT treatment decreased dendritic areas of Purkinje cells in both anterior and posterior lobes after 7DIV. Next, we determined the actions of specific 5-HT receptors in mediating the effects of 5-HT by treatment with selective 5-HT receptor agonists. In anterior lobes after 4DIV, dendritic areas of Purkinje cells were increased by a 5-HT1A receptor agonist (8-OH-DPAT), whereas decreased by a 5-HT2A receptor agonist (DOI). The present study suggested that the dendrite formation of Purkinje cells is promoted by 5-HT through 5-HT1A receptors, but inhibited by 5-HT through 5-HT2A receptors.     

The development, ultrastructure and synaptic connections of the mossy cells of the dentate gyrus

Summary One of the most distinctive and common cell types in Golgi preparations of the hilus of the rat dentate gyrus is the mossy cell. We have used a variety of techniques including the Golgi method, the combined Golgi and electron microscopic (EM) method and the retrograde transport of horseradish peroxidase (HRP) to study the development, ultrastructure and synaptic connections of this cell type. The mossy cells identified in our light microscopic preparations are characterized by: (1) triangular or multipolar shaped somata; (2) three to four primary dendrites that arise from the soma and bifurcate once or more to produce an extensive dendritic arborization restricted, for the most part, to the hilus; (3) numerous thorny excrescences on their somata and proximal dendrites with typical spines on distal dendrites; and (4) axons that bifurcate and are directed toward the fimbria and the molecular layer of the dentate gyrus.The mossy cells have an immature appearance at birth and on subsequent days their maturation appears to lag somewhat behind that of the hippocampal pyramidal cells. On postnatal day 1, many of the dendrites bear growth cones primarily at their termini and have long, thin filipodia emanating from various points along their lengths. Many of the dendrites enter the molecular layer of the dentate gyrus, though this is rarely seen in the mature brain. Typical pedunculate spines are first commonly seen on the distal dendrites around postnatal day 7 while thorny excrescences are first commonly seen between postnatal days 11 and 14. By postnatal day 21, the dendrites have attained a mature appearance although the density of both typical spines and thorny excrescences is less than that found in adults.Two different retrograde transport methods were used to confirm that mossy cells give rise to the commissural projection to the contralateral dentate gyrus. The first method combined HRP histochemistry with a silver intensification procedure and the second method combined HRP histochemistry with Golgi staining. While the majority of commissurally projecting hilar neurons had the appearance of mossy cells, there were others that were smaller and either ovoid or fusiform.     

Some effects of protein-calorie undernutrition on the developing central nervous system of the rat

Some effects of undernutrition were noted in the brains of 21-day-old pups undernourished from birth by being reared by nursing dams fed on a low protein diet. As compared to the normally fed control pups, the body weight, brain weight, and thickness of the parietal neocortex and paravermal cerebellar cortex were significantly lower in the undernourished pups (p less than 0.001), while the thickness of the cortices of the dentate gyrus and hippocampus CA3 only reached significance at the 5% level. Again, as compared to the control pups, the number of spines per unit length on the distal dendritic segments of the pyramidal cells of lamina III of the parietal neocortex and of the hippocampus CA3 reached significance at the 5% level whereas that of the granule cells of dentate gyrus and Purkinje cells of the paravermis did not reach significance at the 5% level. The myelination of the pyramidal tract and spinal trigeminal tract in the lower medulla was less advanced in the undernourished pups. To date, the demonstration of precise functional correlates for the observed changes of morphological and physiological parameters in animals subjected to undernutrition has been elusive. An approach that may lead to unraveling this problem is suggested in a discussion of relating sources of input to the specific dendritic segments where the spine counts were made.     

Effects of paternal and maternal undernutrition on growth of offspring in rats

In adult males, undernutrition is associated with altered spermatogenesis. The present study was performed to evaluate the possible role of paternal undernutrition on growth and development of rat offspring and to compare those effects with undernutrition in pregnant animals. Male rats were fed 100%, 80% or 60% of their ad lib food intake for eight weeks and were then bred to untreated females. Pregnant rats were mated with untreated males and received their food allotments throughout pregnancy. Although male body weights and rate of successful matings were decreased by paternal undernutrition, offspring litter size, birth weights, and weights at 21 days were not significantly altered. By contrast, maternal undernutrition was associated with decreased maternal weight gain, lower offspring birth weights and body weights at weaning.