A stereological analysis of the neuronal and synaptic content of the frontal and cerebellar cortex of weanling rats undernourished from birth

Changes of Cerebellar Cortex in a Valproic Acid-Induced Rat Model of Autism

In this study, 32 male Sprague-Dawley rats (8 for each group) were used in total to examine the effects of valproic acid on rat cerebellum. It was determined that the experimental group received valproic acid (600mg/kg) on embryonic day 15 and postnatal day 11, whereas the control group was treated with saline on the same days. Moreover, on the postnatal 30^th day, the cerebellums of all pups were removed and prepared for light and electron microscopy. The numerical density of granule cells in the cerebellum of experimental groups of rats increased whereas the numerical density of Purkinje cells decreased. Furthermore, the granule cells had a smaller mean nuclear diameter in one of the experimental groups while the Purkinje cells had in both experimental groups than those in the comparison group. Thus, the numerical density of synaptic discs and their mean diameter in the cerebellar granular layer of experimental groups were significantly decreased compared to the corresponding controls; also, the synapse-to-neurons ratio, a parameter indicating interneural connectivity, was the same. Consequently, it was seen that valproic acid administration to pups in prenatal or early postnatal days causes changes in number of neurons and synapses in the cerebellum of rats.

Protein malnutrition during gestation and early life decreases neuronal size in the medial prefrontal cortex of post-pubertal rats

Retrospective studies in human populations indicate that protein deprivation during pregnancy and early life (early protein malnutrition, EPM) is associated with cognitive impairments, learning disabilities and may represent a risk factor for the late onset of some psychiatric disorders, fundamentally schizophrenia, a condition where the prefrontal cortex plays an important role. The purpose of this study was to analyze whether EPM affects structural aspects of the rat medial prefrontal cortex (mPFC), such as cortical volume, neuronal density and neuronal soma size, which seem altered in patients with schizophrenia. For this, a rat model of EPM (5% casein from conception to postnatal day 60) was adopted and the rat mPFC volume, total number of neurons and average neuronal volume were evaluated on postnatal day 60 (post-pubertal animals) by histo- and immunohistochemical techniques using unbiased stereological analysis. EPM did not alter the number of NeuN+ neurons in the rat mPFC. However, a very significant decrease in mPFC volume and average neuronal size was observed in malnourished rats. Although the present study does not establish causal relationships between malnutrition and schizophrenia, our results may indicate a similar structural phenomenon in these two situations.

Nutritional effects on neuron numbers

Undernutrition during early life is known to cause deficits and distortions of brain structure although it has remained uncertain whether or not this includes a diminution of the total numbers of neurons. Estimates of numerical density (e.g. number of cells per microscopic field, or number of cells per unit area of section, or number of cells per unit volume of tissue) are extremely difficult to interpret and do not provide estimates of total numbers of cells. However, advances in stereological techniques have made it possible to obtain unbiased estimates of total numbers of cells in well defined biological structures. These methods have been utilised in studies to determine the effects of varying periods of undernutrition during early life on the numbers of neurons in various regions of the rat brain. The regions examined so far have included the cerebellum, the dentate gyrus, the olfactory bulbs and the cerebral cortex. The only region to show, unequivocally, that a period of undernutrition during early life causes a deficit in the number of neurons was the dentate gyrus. These findings are discussed in the context of other morphological and functional deficits present in undernourished animals.

The influence of litter size on brain damage caused by hypoxic-ischemic injury in the neonatal rat

Hypoxic ischemia is a common cause of brain injury in the human neonate. This can be mimicked in the neonatal rat, but produces variable injury. The present study investigated the influence of litter size on the severity and variability of damage caused by hypoxic-ischemic injury in neonatal rats. Groups of 7-d-old pups from birth-sized litters (13-15 pups), or from litters culled to 10 on postnatal d 2, and 8- and 9-d-old pups from birth-sized litters, were exposed to common carotid artery occlusion and then, 3 h later, hypoxia (2 h 15 min, 8% oxygen). Damage was assessed histologically 72 h after injury, and graded (I-IV) according to severity. In nonculled litters, similar numbers of animals had each grade of injury. Most pups (70%) from culled litters had grade III or IV damage, and severity was significantly greater than in nonculled litters (p < 0.001). Pups from culled litters were heavier (17.6 +/- 0.4 g) than pups from nonculled litters (14.7 +/- 0.3 g, p < 0.0001). To determine whether this indicated that culled litters were more similar to older pups in their response to hypoxic-ischemic injury, we examined injury in 8- and 9-d-old pups of similar body weight to 7-d-old pups from culled litters. The severity and distribution of damage in the older pups was different from damage in the 7-d-old pups from culled litters. These data suggest that in 7-d-old rats, litter size influences damage caused by hypoxic-ischemic injury, and that the relationship between body weight, brain development, and susceptibility to hypoxic-ischemic injury is complex.

Prenatal protein malnutrition decreases mossy fibers-CA3 thorny excrescences asymmetrical synapses in adult rats

Prenatal protein malnutrition has deleterious effects on hippocampal structure and function that likely result from decreased synapse number. We thus evaluated long-term effects of prenatal protein malnutrition on the mossy fibers-CA3 thorny excrescences asymmetrical synapses in 220-day-old rats. Protein malnourished rats born from pregnant dams fed with 6% casein diet were cross-fostered to lactating control rats at birth. Control animals were fed with a 25% casein diet. Timm's stained material was used to estimate the total reference volume of the mossy fiber system suprapyramidal bundle by means of stereology. The mossy fiber-CA3 asymmetrical synapse numerical density was obtained by electron microscopy, using the physical disector method. The total number of mossy fiber-CA3 asymmetrical synapses was determined on the basis of the total reference volume of the mossy fiber system suprapyramidal bundle and the mossy fiber-CA3 asymmetrical synapse numerical density. Prenatal protein malnutrition produced long-lasting, significant decreases in the volume of the mossy fiber system suprapyramidal bundle and in the numerical density of mossy fiber-CA3 asymmetrical synapse, suggesting a reduction in the total number of this synapse type. Hence, prenatal protein malnutrition induces long lasting deleterious effects on the progression of developmental programs controlling synaptogenesis and/or synaptic consolidation, likely by affecting a myriad of cellular processes.

Estimation of the numerical densities of neurons and synapses in cerebral cortex

In this paper we discuss a stereological technique, 'the unfolding method', for a quantitative study of the nervous system [1,31]. Stereology implies a geometric analysis of structures and textures, and is a method to derive directly metric properties of structures from two-dimensional sections on the basis of geometrico-statistical reasoning [36,37]. Recent advances in the stereological method allow quantitative analysis [8,19,27,32]. Images on sections provide only two-dimensional information, but the stereological method can offer three-dimensional and quantitative information [19]. The need for quantitative analysis is more important and useful in the central nervous system (CNS) than in other organs. Two functional units, neurons and synapses, are of particular interest in evaluating CNS function. Numerical densities of neurons and synapses in rat visual cortex were estimated using the unfolding method at light and electron microscopic levels, respectively. Once the numerical densities of neurons and synapses were obtained, synapse-to-neuron ratios could be calculated. The ratios are interpreted as a means to obtain an index of interneuronal connectivity [9]. The unfolding method may become a powerful strategy in neuroscience research when numerical estimates are performed in restricted areas such as cortical layers II-IV, because this method is less time-consuming than other stereological methods [6,21,22].

Undernutrition during early life does not affect the number of granule cells in the rat olfactory bulb

Undernutrition during early life causes deficits and distortions of brain structure. However, whether or not this includes a diminution of the total numbers of neurones remains uncertain. Recent advances in stereological techniques have made it possible to obtain unbiased estimates of total numbers of cells in well-defined biological structures. Rats were undernourished from conception to 90 postnatal days of age by standardised procedures. Groups of well-fed control and undernourished rats were anaesthetised and killed by intracardiac perfusion with fixatives at 30 and 90 days of age. Each olfactory bulb was serially sectioned at a nominal thickness of 100 microns on a vibratome. These sections were analysed by the Cavalieri principle to obtain estimates of the total volume of the olfactory bulb as well as the volume of its granule cell layer. The physical "disector" method was later used on serial 1-micron-thick toluidine-blue-stained sections to estimate the numerical density of granule cell neurones in the olfactory granule cell layer. These values were used to compute estimates of the total number of olfactory granule cell neurones for each animal. Thirty-day-old control and undernourished rats had between 2.6 and 3 million granule cell neurones in the olfactory bulb. By 90 days of age the number of granule cells had increased in both groups of animals to between about 4.2 and 5.2 million cells. Analysis of variance tests showed a significant main effect of age but not nutrition in these estimates. Although the interaction term did reach statistical significance, post hoc analysis did not reveal any differential effect of undernutrition between the two age groups examined.(ABSTRACT TRUNCATED AT 250 WORDS)

Undernutrition of rats during early life does not affect the total number of cortical neurons

Undernutrition during early life is known to cause deficits and distortions in brain structure. However, it remains uncertain whether this includes a diminution of the total numbers of neurons. Recent advances in stereological techniques have made it possible to obtain unbiased estimates of total numbers of cells in well-defined biological structures. Rats were undernourished from day 16 of gestation to 30 postnatal days of age by standardized procedures. These rats and well-fed control rats were anaesthetized and killed by intracardiac perfusion with fixatives at 70 days of age. The left cerebral hemisphere from each animal was embedded in Paraplast and serially sectioned. The sections were analyzed via the Cavalieri principle to obtain the total cortical volume and by the "disector" method to estimate the numerical density of neurons in the cortex. These values were later used to compute estimates of the total number of cortical neurons for each animal. Well-fed control rats had 26.9 million cortical neurons, while the previously undernourished animals had 24.8 million. The difference between these two groups was not statistically significant. It therefore appears that undernutrition of rats during early postnatal life does not affect the total numbers of neurons in the cerebral cortex.

Successful prediction of immediate effects of undernutrition throughout the brain growth spurt on capillarity and synapse-to-neuron ratio of cerebral cortex in rats

Based on the hypothesis that undernutrition depresses the growth rate of all processes in brain contemporaneous with it to the same extent (Peeling & Smart, 1994), specific predictions were made regarding the effect of undernutrition on two quite different facets of anatomical development within visual cortex. It was predicted that severe undernutrition during the suckling period would leave capillarity unaffected, but would result in a deficit in synapse-to-neuron ratio of similar magnitude to that in brain weight. At birth rat pups were fostered and either well fed to 30 days or undernourished to the same age by underfeeding their foster mothers. Rats were killed at 30 days by perfusion with glutaraldehyde. Visual cortex was dissected out for quantitative histological study. The number of capillary profiles per unit area of section and the area of each profile were assessed with an image analysis system. Quantitative characteristics of the neuron and synapse populations were estimated by light and electron microscopy respectively. Undernutrition resulted in a 21% deficit in brain weight, and a 22% deficit in the number of synapses per neuron. Capillarity, expressed as the fraction of section area occupied by capillary lumen, appeared completely indifferent to nutrition. However, fewer capillary profiles were found per unit area of section in growth-restricted samples, and the profiles which were present were, on average, larger. Neuron density was elevated by 19% in the undernourished group. These findings are in good agreement with the hypothesis.

Locomotor development in undernourished rats

The effects of undernutrition on the development of locomotion were studied in fourteen rats. Mothers received about 40% of normal quantities of standard laboratory food from the 5th day of gestation until weaning at the 21st day after birth. Qualitative as well as quantitative aspects of locomotion were studied from the 12th to the 30th day and compared to data from ten control rats. Undernutrition leads to delayed and prolonged developmental changes in locomotion. The adult type of locomotion, which in normal rats develops from the 14th day occurs after the 15th or 16th day in undernourished rats and this development also lasts longer. Locomotion remains mildly abnormal, at least until the 30th day. Especially at lower speeds, walking is clumsy because of an unusual brisk onset, a slightly unsteady gait and non-fluent paw movements. These results are discussed in the perspective of data on brain and muscle development in rats after early undernutrition.

Intrauterine growth in children with cerebral palsy

The risk of cerebral palsy in connection with intrauterine growth retardation has been analysed in a case-control study. The case series comprised 519 children with cerebral palsy born in 1967-1982 in the west health-care region of Sweden and the control series 445 children born during the same years in the same region. The risk of cerebral palsy in small-for-gestational-age infants was significantly increased in term and moderately preterm infants. The highest proportion among infants with cerebral palsy born at term was found in tetraplegia, followed by diplegia and dyskinetic cerebral palsy. It was concluded that small for gestational age on the one hand reflects early prenatal brain damage, and on the other mediates prenatal risk factors compatible with foetal deprivation of supply and also potentiates adverse effects of birth asphyxia and neonatal hypoxia.

Body measurements, neurological and behavioural development in six-year-old children born preterm and/or small-for-gestational-age

In three groups of low birth weight (LBW) infants: full term, small-for-gestational-age (FT-SGA, N = 142); preterm, appropriate-for-gestational-age (PT-AGA, N = 47); preterm, small-for-gestational-age (PT-SGA, N = 20); and a reference group of FT-AGA infants (N = 185) the relationship between body weight, body length and head circumference and the presence of minor neurological dysfunction (MND) was studied. Non-caucasian and handicapped children were excluded from the analysis. Data were collected on behaviour and school achievement. The parameters of physical growth in the three LBW groups were reduced significantly compared to the FT-AGA group. In both preterms and full-terms body measurements were related to weight at term age; in the preterm groups no relation with gestational age at birth was found. MND was not related to body weight or length. In the group of FT severely growth retarded infants a relation was found between a skull circumference below the third centile and the presence of MND. Body measurements, behaviour at home and at school and school achievement were not related. The significance of severe intrauterine growth retardation for developmental disorders is emphasized. The data suggest a different aetiology and clinical significance of small head size for AGA and SGA born children.

Effects of protein deprivation on pyramidal cells of the visual cortex in rats of three age groups

The effect of protein deprivation on rapid Golgi impregnated pyramidal neurons in layers II/III and V of the rat visual cortex was studied at 30, 90, and 220 days of age using morphometric methods. In order to mimic human under-nutrition female rats were adapted to either an 8% or control 25% casein diet 5 weeks prior to conception and maintained on these diets during gestation and lactation. The pups were then weaned and maintained on their respective diets. The undernourished rats showed a significant decrease in brain weight only at 90 days, indicating that the protein deprivation had a mild effect on brain development. Correspondingly, the number of significant histological differences between the two diet groups were least at 30 and 220 days of age. The effect of the diet was greater on layer V than on layer II/III pyramids. At 30 days of age the effect of the diet was different on the pyramids of these two cell layers, at 90 days there was a mixture of similar and dissimilar effects, and at 220 days the pyramids of these two cell layers showed only minor differences between the two diet groups. Analysis of age-related changes indicated that the effect of the diet was different on layer II/III pyramids compared to layer V pyramidal cells. These different effects apparently accounted for the progression from a dissimilar effect of the diet at 30 days on the pyramids of the two cell layers to only minor differences between them at 220 days. Further analysis of these age-related changes shows that two prominent effects of protein deprivation are for age-related changes to occur in undernourished rats but not in controls and for age-related changes to be out-of-phase with each other in the two diet groups. From these findings, and a review of similar studies in the literature, we propose that these mechanisms are a prominent effect of undernutrition in the post-weaning period and help account for the unexpected increases in morphometric measurements noted in undernourished rats in this and other studies.

Functional development of the visual system in normal and protein-deprived rats. VII. Lamination of oxidative enzyme activity in the visual cortex during post-natal development

Lamination of activity of two mitochondrial enzymes-succinate dehydrogenase (SDH) and menadione-dependent alpha-glycerophosphate dehydrogenase (M-GPDH) - was examined in the visual cortex of control (C) and protein-deprived (PD) rats from 10 days old to adult. In C rats, lamination of enzyme activity was evident from 10 days by a band of higher activity in lamina IV. A band of higher SDH activity was seen in superficial lamina VI from 15 days. Lamination of M-GPDH activity became less pronounced with increasing age, whereas distinct bands of high SDH activity in lamina IV and VI remained also in adult rats. PD rats showed a developmental delay of approximately 5 days with regard to the general increase in neuropile activity. A band of higher enzyme activity in lamina IV was present from 10 days, but it was markedly less distinct in the PD rats compared to the C rats between 15 and 25 days. A band of higher SDH activity in superficial lamina VI was not seen until 25 days in PD rats. No apparent differences were seen between adult C and PD rats. The observed developmental alterations are discussed in relation to other delays, distortions and deficits found in the visual system of PD rats.

Undernutrition during early adult life significantly affects neuronal connectivity in rat visual cortex

Male black and white Hooded Lister rats were undernourished for 29 days during early adult life. Undernourished rats had 30% more synapses per neurone in the visual cortex than matched controls. It is suggested that undernutrition may cause a delay in the normal decline of this ratio.

Alpha fetoprotein and albumin gene transcripts are detected in distinct cell populations of the brain and kidney of the developing rat

We report the cellular localization of alpha-fetoprotein (AFP) and albumin (ALB) gene transcripts in rat kidney and brain as detected by in situ hybridization on tissue sections with [35S]-labelled alpha-fetoprotein and albumin cDNA probes. Both types of mRNA were present in distinct cell populations of the developing kidney and brain. In the kidney, both gene transcripts were distributed over all developing tubular cells in the 20-day-old fetus. During the first 3 weeks of life, a gradual decrease in the expression of AFP and ALB mRNA was apparent, the rate of decrease being greater on proximal tubules than on the other tubular cells. From the 4th week onwards, a weak signal for both mRNAs persisted in the majority of the tubular cells. In the brain, all neuronal cells expressed both genes. Transcript cellular distribution was mainly cytoplasmic during fetal and early postnatal life and became predominantly nuclear at 3, 4 and 5 weeks, suggesting that posttranscriptional mechanisms are involved in the control of AFP and ALB gene expression at these stages. In the adult brain no significant signal was recorded thereafter. Coexpression of AFP and ALB transcripts by specific cell types, together with their gradual disappearance concomitant with postnatal organ maturation, suggests a possible role for these proteins in terminal differentiation processes of tubular and neuronal cells.

Effects of a lengthy period of undernutrition from birth and subsequent nutritional rehabilitation on the synapse: granule cell neuron ratio in the rat dentate gyrus

Recent evidence showing alterations in spatial memory due to a period of undernutrition during early life has implicated the hippocampus as one of the brain centres that may be particularly adversely affected. However, there are very few quantitative morphological studies that have examined the neuronal and synaptic populations of the hippocampi from undernourished animals. We decided to carry out such experiments, paying particular attention to the granule cell of the dentate gyrus. Male rats were undernourished from the 18th day of gestation until 21, 75, or 150 days of age. Some of these previously undernourished rats were nutritionally rehabilitated between 150 and 250 days of age. Groups of well-fed control and experimental rats were killed by intracardiac perfusion with 2.5% sodium-cacodylate-buffered glutaraldehyde. The right hippocampus from each rat was dissected out and processed for electron microscopy. Stereological procedures at the light and electron microscopical levels were used to estimate the numerical densities of granular cell neurons and molecular layer synapses in the dorsal lip of the dentate gyrus. These estimates were used to calculate synapse: neuron ratios. There were 5,056 +/- 347 (mean +/- SE) and 5,002 +/- 190 synapses per neuron in 21-day-old control and undernourished rats, respectively. By 75 days these values had increased to 9,215 +/- 588 and 6,683 +/- 237. The difference was statistically significant. By 150 days of age the value for control animals had fallen once again to 6,518 +/- 209 whereas undernourished rats had increased slightly to 7,689 +/- 288 (P less than .01); 250-day-old rats, previously undernourished from birth to 150 days of age, showed a substantial increase in the synapse: neuron ratio during the period of nutritional rehabilitation. Thus these nutritionally rehabilitated rats had 9,407 +/- 365 synapses per neuron whereas age-matched controls had only 6,323 +/- 239 (P less than .01). These results indicate that the rat dentate gyrus is vulnerable to undernutrition even during the postweaning period and that a lengthy period of undernutrition can alter the developmental growth curve for synapse: neuron ratios.

Functional development of the visual system in normal and protein-deprived rats. VI. Evoked responses in adult rats, protein deprived in early life and nutritionally rehabilitated from weaning

Previous studies have shown an increase in latency of the visual evoked response (VER) recorded from the cortical surface of adult rats subjected to protein deprivation (PD) during pre- and postnatal development. This alteration has been shown to originate mainly from the cortex itself. In the present study the possibility of normalizing such VER alterations by nutritional rehabilitation after early protein deprivation (R-PD) was investigated. Male rats were subjected to pre- and early postnatal protein deprivation through their mothers. Nutritional rehabilitation was started from weaning. The rats gained weight rapidly compared with rats subjected to protein deprivation throughout postnatal development but never reached the weight of controls (C) of the same age. Food consumption in relation to body weight was similar to that of controls. Rehabilitation continued until adult age when neurophysiological experiments were performed. The VER recordings from the dorsal lateral geniculate nucleus (dLGN) showed latencies similar to those reported previously for adult C and PD rats. The latencies of onset and first peaks of the cortical response recorded from the surface were increased by 5-6 ms in R-PD compared with C rats and hence similar to the latencies of adult PD rats. Intracortical responses to electrical stimulation in the dLGN were also similar to those of adult PD rats showing an normal onset latency but an increased latency of the peaks of the monosynaptic and late responses compared with C rats. The present results imply that the increased VER latencies noted in adult PD and R-PD rats are due to changes installed by protein deprivation during early development since they can not be reversed by nutritional rehabilitation starting at weaning.

The effects of a lengthy period of environmental diversity on well-fed and previously undernourished rats. II. Synapse-to-neuron ratios

Rats were undernourished from the 16th day of gestation until 25 postnatal days of age and then weaned on to an ad libitum diet. Around 35 days of age, 12 previously undernourished male rats were assigned to an enriched environmental condition (EC) and their littermates to an isolated environmental condition (IC). A parallel set of well-fed rats was similarly assigned. After 80 days in these environmental conditions, all rats were killed by perfusion with 2% phosphate buffered glutaraldehyde. Small pieces of tissue containing the entire depth of the right visual cortex were embedded in Spurr's resin. Semithin (0.5 micron) sections were cut from these blocks and stained with toluidine blue. Photomicrographs of these sections were used to estimate the numerical density of neurons in cortical layers II to III. Ultrathin sections (approximately 70 nm) of the same region of cortex were then prepared for electron microscopy. These were used to estimate the mean synaptic disc diameter and synaptic numerical density. From these estimates of neuronal and synaptic numerical density, synapse-to-neuron ratios were calculated. The results of a two-way analysis of variance test revealed that environment had significant effects on neuronal numerical density, mean synaptic disc diameter, and synapse-to-neuron ratios. Neither nutrition nor its interaction with environment had significant effects on any of the parameters analyzed. These results suggest that environmental diversity can produce alterations in certain neuronal and synaptic characteristics in the visual cortex of both well-fed and previously undernourished rats.

Developmental protein malnutrition in the rat: effects on single-unit activity in the frontal cortex

This study evaluated the effects of developmental protein malnutrition on the spontaneous electrical activity of frontal cortex neurons in the anesthetized rat. Rats were raised prenatally and postnatally on either an 8% or 6% casein diet until adulthood. Compared to the 25% casein controls, both malnourished groups showed a 30-36% decrease in mean discharge rates and a 100-200% increase in the percentage of cells with very slow (less than 1/s) discharge rates. Most of the diet-related changes were confined to a zone 600-1200 micron below the brain surface, approximately cortical layers III, IV and V. A second set of studies in which diet reversals were introduced at birth or in adulthood found that: (a) restoration of a normal 25% casein diet at birth did not appreciably attenuate the effect of prenatal administration of an 8% casein diet; (b) introduction in adulthood of the 8% casein diet to a normally fed rat had no effect; (c) introduction of the 8% diet at birth, however, produced effects in adulthood comparable to those seen when the protein malnutrition was introduced in the prenatal period. Thus, the rat brain is sensitive to both prenatal and postnatal protein malnutrition (starting at birth). Most importantly, the effects of prenatal protein malnutrition on the activity of frontal cortex neurons do not appear to be reversible by restoration of a normal diet in adulthood or at birth.

A quantitative assessment of the development of synapses and neurons in the visual cortex of control and undernourished rats

Male rats undernourished from the 18th day of gestation until 100 days of age were nutritionally rehabilitated until 200 days of age. Six control and six experimental rats at each of 12, 25, 50, 100, and 200 days of age were killed by perfusion with buffered 2.5% glutaraldehyde. Pieces of visual cortex from each rat were postfixed in osmium tetroxide and embedded in resin. Stereological procedures at the light and electron microscope levels were used to estimate the synapse-to-neuron ratios in cortical layers II to IV. There were no statistically significant differences in the synapse-to-neuron ratio between control and undernourished rats at 12, 25, and 50 days of age. However 100-day-old undernourished rats had a significant deficit in this ratio compared to age-matched controls. Despite this, 200-day-old nutritionally rehabilitated rats were found to have, on average, 23% more synapses per neuron than controls. In both the control and the undernourished groups the synapse-to-neuron ratio increased to a peak by 50 days of age. This was followed by a significant fall in the ratio by 100 days of age. Although there was no further change in the control rats, the experimental group showed a substantial increase in the ratio by 200 days of age. This latter increase appeared to be related to the period of nutritional rehabilitation.

The effects of undernutrition during early life on the rat optic nerve fibre number and size-frequency distribution

Male rats undernourished from the 18th day of gestation till 100 days of age were nutritionally rehabilitated until 200 days of age. Six control and six experimental rats at each of 25, 50, 100, and 200 days of age were killed by perfusion with buffered 2.5% glutaraldehyde. Pieces of optic nerve from just behind the left eye of each rat were postfixed in osmium tetroxide and embedded in resin. Estimates of the total number of fibres and their mean diameter and size-frequency distributions were made for each nerve. Rats undernourished until 25 days of age had a mean +/- SE of 57,464 +/- 6,778 fibres per optic nerve. This represented a 36% deficit (P less than 0.01) compared with the 25-day-old control value of 89,778 +/- 6,625. In addition, these undernourished rats had proportionately more small fibres than the age-matched controls. This resulted in a significant deficit in mean fibre diameter at this age. These deficits and distortions disappeared in all the older rats studied, despite the continued undernourishment of some animals up to 100 days of age. It appears that even the lengthy period of undernutrition imposed in the present experiments could not produce a permanent deficit in optic nerve fibre number, size, and size distribution. It is suggested that the deficits seen initially at 25 days of age may have been due to a temporary delay in the growth and development of these nerve fibres.

Histological maturation of the neocortex in phenylketonuric rats

The histological maturation of pyramidal cells from the deeper layer of the neocortex was studied in phenylketonuric rats. The main alterations consist of a decrease in the number of span and dendritic basilar processes of large pyramidal cells, and changes in the structural organization of the cerebral cortex. It is postulated that high levels of phenylalanine induced immediately after birth disturb profoundly the process of neuronal maturation in the neocortex of the rat brain, probably with long-term effects.

The effect of advanced old age on the neurone content of the cerebral cortex. Observations with an automatic image analyser point counting method

The effect of advanced old age on the nerve cell content of the cerebral cortex was examined in 19 non-demented persons aged 69-95 years, using a Quantimet 720 image analysing computer to make area proportion measurements. Neurone loss around 1.0% per annum was found both in the neocortex and in the medial hippocampus. There was also significant shrinkage of neurones in the hippocampus. Macroscopic measurements of the cerebral hemispheres by means of point-counting morphometry showed a corresponding reduction in the volume of white matter amounting to about 0.8% per annum, but only a minor change in the cortex volume. This finding is consistent with the occurrence of dendritic growth of surviving neocortical neurones. By contrast, there appears to be no compensatory dendritic proliferation in the medial hippocampus since tissue atrophy was commensurate with cell loss in this region.

Experimental phenylketonuria: effect of phenylacetate intoxication on number of synapses in the cerebellar cortex of the rat

In experimental phenylketonuria, induced in the rat by exposure to phenylacetate during the first 21 days of life, there was a significant reduction of boutons, a decrease of an average of 25% in the whole cerebellar molecular layer. Both the density of synaptic profiles per square unit and the number of synapses per unit volume were decreased in the phenylacetate-treated rat as compared to the age-matched control. Neuronal density was unaffected. Results are interpreted to show a deficit of synapses per neuron, probably due to a decrease in synaptic formation in phenylacetate-induced phenylketonuria. Undernutrition was eliminated as a contributing factor.

Synapse-to-neuron ratios in the visual cortex of adult rats undernourished from about birth until 100 days of age

Male rats undernourished from the 18th day of gestation until 100 days of age were nutritionally rehabilitated until 200 days of age. Six control and six experimental rats at each of 100 and 200 days of age were killed by perfusion with buffered 2.5% glutaraldehyde. Pieces of visual cortex from each rat were postfixed in osmium tetroxide and embedded in resin. Stereological procedures at the light and electron microscopy levels were used to estimate the synapse-to-neuron ratios in cortical layers II to IV. Rats undernourished until 100 days of age had a mean +/- S.E. of 10,350 +/- 470 synapses associated with each neuron. This represented a 13% deficit (P less than 0.05) when compared to the control value of 11,950 +/- 530. Following nutritional rehabilitation till 200 days of age it was found that the previously undernourished rats had about 23% more (P less than 0.05) synapses-per-neuron than their age-matched controls. This was due almost entirely to a substantial increase in the ratio in the previously undernourished animals; the value of controls did not alter significantly between the two age groups. It appears that the deficit in the synapse-to-neuron ratio seen after a lengthy period of undernutrition is not permanent, at least in rats subsequently allowed nutritional rehabilitation. In fact, such animals seem to be capable of not only "catching-up" but "overshooting" the values found in age-matched controls.

Early life undernutrition in rats. 1. Quantitative histology of skeletal muscles from underfed young and refed adult animals

1. Male rats were undernourished either during the gestational and suckling periods or for a period of time immediately following weaning. Some rats were killed at the end of the period of undernutrition; others were nutritionally rehabilitated for lengthy periods of time before examination. Two muscles, the extensor digitorum longus (EDL) and soleus (SOL) were studied from each rat. Histochemically-stained transverse sections of these muscles were used to determine total number of fibres, the fibre cross-sectional areas and the relative frequency of the various fibre types. 2. All rats killed immediately following undernutrition showed significant deficits in body-weight, muscle weight and fibre cross-sectional area compared to age-matched controls. 3. Animals undernourished during gestation and suckling and then fed normally for 5 months showed persistent and significant deficits in body-weight, muscle weight, muscle weight and total fibre number. There were also significant deficits in mean fibre cross-sectional area of each fibre type except for red fibres in the EDL. No difference in the volume proportion of connective tissue was found. 4. Rats undernourished after weaning and then fed ad lib. for approximately 7 months had normal body-and muscle weights. Their muscles showed no significant differences in total fibre number, relative frequency of the various fibre types, fibre size or volume proportion of connective tissue. 5. These results indicate that, although the effects on rat skeletal muscle of a period of undernutrition after weaning can be rectified, undernutrition before weaning causes lasting deficits.

Early life undernutrition in rats. 2. Some contractile properties of skeletal muscles from adult animals

1. The contractile properties of soleus and extensor digitorum longus muscles from animals at 12 months of age whose mothers had been undernourished during pregnancy and lactation (PU rats) have been compared with those of muscles from ge-matched controls. 2. Body-weight and muscle wet weight of PU rats was significantly reduced. Muscle:body-weight values were, however, no different from controls. 3. No significant alterations in whole muscle speeds of contraction or relaxation could be detected when compared with those of age-matched controls. 4. Twitch and tetanic forces of both SOL and EDL were greater per unit weight of muscle in PU rats. Apart from SOL twitch these differences were significant. The tetanus:twitch values were, however, not different.

Developmental aspects of subacute fetal distress: behaviour problems and neurological dysfunction

A group of term infants malnourished in utero and classified as a subacute fetal distress at birth were followed up with a group of normally grown term infants matched for age, sex, birth rank and social class. Both groups were free from other perinatal morbidity and chronic diseases. At three years of age behaviour was studied using the behaviour screening questionnaire of Richman and Graham and a behaviour observation report, whereas neurological dysfunction was assessed according to the pro forma of Touwen. Both problematic behaviour and neurological dysfunction occurred more frequently in the subacute fetal distress group. Behaviour problems are comparable to neurological signs as indicators for brain dysfunction.

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.

A stereological analysis of the cerebellar granule and Purkinje cells of 30-day-old and adult rats undernourished during early postnatal life

Male rats undernourished from birth to 30 days of age were nutritionally rehabilitated till 160 days of age. Quantitative stereological procedures at the light microscope level were used to estimate, among other things, the numerical densities of cerebellar granule and Purkinje cells on a "per unit volume of cortex" basis. These were subsequently used to calculate granule-to-Purkinje cell ratios. The 30-day-old undernourished rats had a mean +/- S.E. of 290 +/- 27 granule cells for every Purkinje cell present, compared to 395 +/- 34 for the controls. This was a deficit of about 27% (p < 0.05). At 160 days of age, the previously undernourished rats still showed a persisting deficit of about 25% (p < 0.05) in this ratio, despite the lengthy nutritional rehabilitation. There were no statistically significant age-related changes in this ratio. The numerical density of Purkinje cells, but not that of granule cells, was significantly greater in the previously undernourished rats than in controls, for both age groups, Increasing age caused a fall in the numerical density of both cell types. Granule and Purkinje cell nuclear diameters were unaffected by nutrition. However, Purkinje cell nuclei decreased in size by between 7%--13% with increasing age. These results indicate that undernutrition during early life can cause a permanent distortion of the relative number of the various cell types in the cerebellum.

Synapse-to-neuron ratios of the frontal and cerebellar cortex of 30-day-old and adult rats undernourished during early postnatal life

Male rats undernourished from birth to 30 days were nutritionally rehabilitated till 160 days of age. Quantitative stereological procedures at the light and electron microscopical levels were employed to estimate, among other things, the synapse-to-neuron ratios in the frontal cortex and granular layer of the cerebellum. In the frontal cortex, the 30-day-old undernourished rat had a mean +/- SE of about 14,020 +/- 1,540 synapses-per-neuron compared with 22,270 +/- 3,250 for the controls. This was a deficit of 37% (p < 0.05). By 160 days of age the previously undernourished rats showed no statistically significant deficit in this ratio compared with controls (11,800 +/- 690 and 13,360 +/- 1,110 respectively, p > 0.1). This was due mainly to a fall in the synapse-to-neuron ratio with age. A much larger fall in the ratio occurred in the control than in the previously undernourished group. In the granular layer of the cerebellum the 30-day-old undernourished rats had 341 +/- 17 synapses-per-neuron compared with 495 +/- 25 for the controls. This was a deficit of 31% (p < 0.01). By 160 days of age the previously undernourished rats again showed no statistically significant deficit in this ratio compared with controls (627 +/- 56 and 688 +/- 38, respectively (p > 0.1). These results show that the previously undernourished rats are capable of at least some (if not complete) "catch-up" with regard to the synapse-to-neuron ratio.

Deficits in synapse-to-neuron ratio due to early undernutrition show evidence of catch-up in later life

30-day-old rats undernourished from birth are known to have large deficits in the synapse-to-neuron ratio in certain brain regions. It has not been possible to demonstrate any statistically significant deficits in this ratio in animals undernourished from birth to 30 days but then provided with an ad libitum amount of food til 6 months of age.