[Measles vaccination campaign among vulnerable populations during the peak of the 2011 epidemic in Marseilles]. / Campagne de vaccination hors centre contre la rougeole des populations précaires en période de pic épidémique, Marseille 2011.

BACKGROUND: From 2008 to the end of 2011, Europe experienced a major outbreak of measles. The outbreak hit France especially hard, with measles hotspots in the South-East of France. It is known that people living in precarious socio-economic conditions are more exposed to infectious diseases. Regarding the local situation, the NGO "MdM-Marseille" decided to conduct a vaccination campaign among the Roma community living in camps. METHODS: The campaign was planned with two injections of a combined measles, mumps and rubella vaccine (MMR) in a one month interval for all young people born since 1980 and over the age of one year, regardless of antecedents. Twenty-four camps were selected. The target population was estimated at 720 people. Each site was the subject of an information visit. A letter was sent to the Prefecture to inform them and ask for a moratorium on evictions for the identified camps. RESULTS: Between May 15th and September 15th 2011, 326 primary immunizations were performed during 34 visits (covering 45.3% of the target population). Over the same period, almost all the camps were evacuated, forcing teams to stop the vaccination campaign. The second injection campaign covered only 37 persons. CONCLUSION: The vaccination campaign among Roma populations in Marseilles was organized in a context of a major national outbreak of measles in the general population. Although the Prefecture was informed, camp evictions were not interrupted. This highlights the discrepancy between public health policy and security policy. In the context of an epidemic, innovative actions should be focused on vulnerable populations in partnership with health authorities. The main objective is to find procedures that can protect populations at risk in the event of a health crisis but which are also useful for routine prevention.

[Relationship between precariousness, social coverage, and vaccine coverage: survey among children consulting in pediatric emergency departments in France]. / Précarité, couverture sociale et couverture vaccinale : enquête chez les enfants consultant aux urgences pédiatriques.

UNLABELLED: Poor children are more susceptible to infectious diseases. Routine medical follow-up is infrequent in these patients, sometimes resulting in immunization delays. The aim of this study was to correlate a number of socioeconomic factors related to poverty with vaccination coverage in children visiting a pediatric emergency ward. PATIENTS AND METHODS: Previous routine vaccinations and various socioeconomic features were prospectively recorded for children aged 9 months to 7 years visiting two public pediatric emergency departments in Marseilles (southern France) from 2009 to 2010. RESULTS: Three hundred and seventy-five children were included. Vaccination coverage was 87% for diphtheria, tetanus, poliomyelitis, Haemophilus influenzae type b infections and pertussis, 69% for tuberculosis (Bacillus Calmette-Guérin), 77% for measles, mumps and rubella, 74% for pneumococcal infections (conjugate vaccine), and 55% for hepatitis B. Socioeconomic factors related to poverty were significantly associated with delays in immunizations. Children not attending school (OR=2.5), having parents who were not fluent in French (OR=5.7), living in caravans or squatting (OR=11.5), or being recipients of the national medical assistance for foreigners (OR=12.8) had significant delays with diphtheria, tetanus, and poliomyelitis vaccines. The measles-mumps-rubella vaccine was also delayed in homeless children (OR=3.4). Children who were recipients of the national medical assistance for citizens were better vaccinated against tuberculosis and hepatitis B. CONCLUSION: Poor children living in southern France had significant delays in their routine immunizations, resulting in gaps in their protection. Every medical visit, even those conducted in an emergency ward, should identify children with immunization delays and offer a catch-up schedule if necessary.

Evidence for multiple loci from a genome scan of autism kindreds.

We performed a genome-wide linkage scan using highly polymorphic microsatellite markers. To minimize genetic heterogeneity, we focused on sibpairs meeting the strict diagnosis of autism. In our primary analyses, we observed a strong linkage signal (P=0.0006, 133.16 cM) on chromosome 7q at a location coincident with other linkage studies. When a more relaxed diagnostic criteria was used, linkage evidence at this location was weaker (P=0.01). The sample was stratified into families with only male affected subjects (MO) and families with at least one female affected subject (FC). The strongest signal unique to the MO group was on chromosome 11 (P=0.0009, 83.82 cM), and for the FC group on chromosome 4 (P=0.002, 111.41 cM). We also divided the sample into regression positive and regression negative families. The regression-positive group showed modest linkage signals on chromosomes 10 (P=0.003, 0 cM) and 14 (P=0.005, 104.2 cM). More significant peaks were seen in the regression negative group on chromosomes 3 (P=0.0002, 140.06 cM) and 4 (P=0.0005, 111.41 cM). Finally, we used language acquisition data as a quantitative trait in our linkage analysis and observed a chromosome 9 signal (149.01 cM) of P=0.00006 and an empirical P-value of 0.0008 at the same location. Our work provides strong conformation for an autism locus on 7q and suggestive evidence for several other chromosomal locations. Diagnostic specificity and detailed analysis of the autism phenotype is critical for identifying autism loci.

Autism and the serotonin transporter: the long and short of it.

Autism is a neurodevelopmental disorder manifesting early in childhood. Some symptoms of autism are alleviated by treatment with selective serotonin reuptake inhibitors, which are known to interact with the serotonin transporter. Moreover, variation in the gene that encodes the transporter (SLC6A4), especially the HTTLPR locus, is known to modulate its expression. It is natural, therefore, to evaluate whether this variation plays a role in liability to autism. We investigated the impact of alleles at HTTLPR and three other loci in SLC6A4 by using a large, independent family-based sample (390 families, 1528 individuals) from the NIH Collaborative Programs of Excellence in Autism (CPEA) network. Allele transmissions to individuals diagnosed with autism were biased only for HTTLPR, both for the narrow diagnosis of autism (P=0.035) and for the broader diagnosis of autism spectrum (P=0.007). The short allele of HTTLPR was significantly overtransmitted. Investigation of haplotype transmissions suggested that, in our data, biased transmission was only due to HTTLPR. With respect to this locus, there are now seven of 12 studies reporting significant transmission bias of HTTLPR alleles, a noteworthy result in itself. However, the studies with significant findings are almost equally divided between overtransmission of short and overtransmission of long alleles. We place our results within this extremely heterogeneous field of studies. Determining the factors influencing the relationship between autism phenotypes and HTTLPR variation, as well as other loci in SLC6A4, could be an important advance in our understanding of this complex disorder.

Discovery of allelic variants of HOXA1 and HOXB1: genetic susceptibility to autism spectrum disorders.

BACKGROUND: Family studies have demonstrated that the autism spectrum disorders (ASDs) have a major genetic etiologic component, but expression and penetrance of the phenotype are variable. Mice with null mutations of Hoxa1 or Hoxb1, two genes critical to hindbrain development, have phenotypic features frequently observed in autism, but no naturally occurring variants of either gene have been identified in mammals. METHODS: By sequencing regions of genomic DNA of patients with autism spectrum disorders, we detected a substitution variant at HOXA1 and an insertion variant at HOXB1, both in coding regions of the genes. Fifty-seven individuals ascertained for a diagnosis of an ASD, along with 166 of their relatives, were typed for these variants. Two non-ASD populations were typed, and the frequency of the newly identified alleles was determined in all groups. The genotypes of the ASD families were tested for conformation to Hardy-Weinberg proportions and Mendelian expectations for gene transmission. RESULTS: The frequency of the variants was 10-25% in persons of European or African origin. In the ASD families, there was a significant deviation from the HOXA1 genotype ratios expected from Hardy-Weinberg proportions (P = 0.005). Among affected offspring, a significant deviation from Mendelian expectation in gene transmission (P = 0.011) was observed. No statistically significant effects were detected when the same analyses were applied to the HOXB1 locus, but there was evidence of an interaction between HOXA1, HOXB1, and gender in susceptibility to ASDs. CONCLUSIONS: The results support a role for HOXA1 in susceptibility to autism, and add to the existing body of evidence implicating early brain stem injury in the etiology of ASDs.

Prenatal exposure of rats to valproic acid reproduces the cerebellar anomalies associated with autism.

Abnormalities in anatomy and function of the cranial nerve motor nuclei have been demonstrated in some people with autism and can be modeled in rats by exposure to valproic acid during neural tube closure. Reductions in Purkinje cell number and cerebellar volume, particularly of the posterior lobe, have also been reported in people with autism. Thus, a stereological examination of cerebellar morphology was undertaken in valproate-exposed rats. Compared to controls, rats exposed to a single dose of 600-mg/kg sodium valproate on embryonic day 12.5 had significantly fewer Purkinje cells in the cerebellar vermis and a reduction short of significant in the hemispheres. The diminished cell numbers reflect reductions in tissue volume throughout the cerebellum, rather than cell density, which was unaffected in all regions. Within the vermis, the reduction in volume was significantly greater in the posterior lobe than in the anterior lobe. The results parallel those reported for human cases of autism.

Minor malformations and physical measurements in autism: data from Nova Scotia.

In the context of an epidemiological study of autism in Nova Scotia, subjects were evaluated for minor physical anomalies and physical measurements. Normal control children, children with autism and their siblings, and children with developmental disabilities and their siblings were compared. Posterior rotation of the external ears was found to be a characteristic related to autism specifically, rather than to developmental disabilities in general. Small feet and normal-to-large hands also were observed in the autism group. Children with autism had a significant reduction in interpupillary distance, but not intercanthic distance or head circumference. In contrast, children with other developmental disabilities were notable for general small stature, which affected the hands, feet, eyes, and head size, as well as height. Abnormal ear configuration was the minor malformation most characteristic of the developmental disability group, and the subset of Down syndrome children had single transverse creases of the palm and epicanthic folds that resulted in significantly increased rates of these anomalies in the developmentally disabled controls. Siblings of the two disabled groups were not significantly different from normal controls on any of the measures that characterized children with autism or other developmental disabilities. The results agree with those of several previous studies, which have suggested that abnormalities of the ears are the general category of minor anomalies most associated with autism. Recent evidence regarding the embryological origin of autism suggests that the ear effects may be an important marker of the initiating events that lead to the disorder.

Linking etiologies in humans and animal models: studies of autism.

Thalidomide has been shown to lead to a high rate of autism when exposure occurs during the 20th to 24th d of gestation. Both the critical period and the neurological deficits of the autistic cases indicate that they have sustained injuries to the cranial nerve motor nuclei. To determine whether such lesions characterize other cases of autism, the brain stem of an autistic case was compared to that of a control. The autopsy case showed abnormalities predicted by the thalidomide cases and evidence of shortening of the brain stem, a defect that could have occurred only during neural tube closure. To test whether animals can be similarly injured but remain viable, rats were treated with 350 mg/kg of valproic acid on day 11.5, 12, or 12.5 of gestation. Neuron counts showed reductions of cell numbers in the cranial nerve motor nuclei. Rats with motor neuron deficits also had cerebellar anomalies like those reported in studies of autistic cases, supporting the idea that these animals may be a useful model of the developmental injury that initiates autism.

Embryological origin for autism: developmental anomalies of the cranial nerve motor nuclei.

The underlying brain injury that leads to autism has been difficult to identify. The diagnostic criteria of the disease are not readily associated with any brain region or system, nor are they mimicked by vascular accidents, tumors, or degenerative neurological diseases occurring in adults. Fortuitously, a recent report of autism induced by thalidomide exposure provides evidence that the disease originates by an injury at the time of closure of the neural tube. The human data suggest that the initiating lesion includes the motor cranial nerve nuclei. To test this hypothesis, we first examined motor nuclei in the brainstem of a human autistic case. The autopsy brain exhibited near-complete absence of the facial nucleus and superior olive along with shortening of the brainstem between the trapezoid body and the inferior olive. A similar deficit has been reported in Hoxa-1 gene knockout mice in which pattern formation of the hindbrain is disrupted during neurulation. Alternatively, exposure to antimitotic agents just after neural tube closure could produce the observed pattern of deficits. Thus, the lesions observed in the autopsy case appear to match those predicted by the thalidomide cases in both time of origin and central nervous system (CNS) location. To produce similar brain lesions experimentally, we exposed rat embryos to valproic acid, a second teratogen newly linked to autism. Dams received 350 mg/kg of valproic acid (VPA) on day 11.5 (the day of neural tube closure), day 12, or day 12.5 gestation. Each treatment significantly reduced the number of motor neurons counted in matched sections of the earliest-forming motor nuclei (V, XII), and progressively later exposures affected the VIth and IIIrd cranial nerve nuclei. All treatments spared the facial nucleus, which forms still later. Counts from the mesencephalic nucleus of trigeminal, the dorsal motor nucleus of the vagus, and the locus ceruleus were not affected by exposure to VPA, even though these nuclei form during the period when exposure occurred. Despite its effects on the motor nuclei, valproic acid exposure did not alter the further development of the brain in any obvious way. Treated animals were robust and had no external malformations. The autopsy data and experimental data from rats confirm that CNS injuries occurring during or just after neural tube closure can lead to a selective loss of neurons derived from the basal plate of the rhombencephalon. The results add two new lines of evidence that place the initiating injury for autism around the time of neural tube closure.

[Long-term effects of prescription drugs in 174 patients treated for myocardial infarction, followed up from 4 to 5 years (the DEVENIR study)]. / Evolution à long terme de la prescription médicamenteuse chez 174 patients atteints d'infarctus du myocarde suivis pendant 4,5 ans (étude DEVENIR).

The aim of this study was to document changes in drug prescription after myocardial infarction. One hundred and seventy four men with typical myocardial infarction recensed by the Toulouse MONICA centre between 1989 and 1990 were followed up for 4.5 years. A copy of their drug prescription was obtained during the acute phase of infarction, at the time of discharge from hospital or clinic, after 6 months, and finally, after 4.5 years after infarction. During the acute phase, the majority of patients received nitrate derivatives, platelet antiaggregants, calcium antagonists, betablockers and antiarrhythmics. Between hospital discharge and the sixth month, the prescription of lipid lowering drugs quadrupled (from 8 to 33%; p < 0.00001) and those of platelet anti-aggregants decreased (from 82 to 70%; p < 0.01). The prescriptions of other drugs remained relatively stable. Between the 6th month and the 4th year of follow-up the only prescription to increase significantly was that of ACE inhibitors (from 14 to 23%; p < 0.03). The other prescriptions were maintained: platelet anti-aggregants (70% at 6 months vs 75% at 4.5 years), nitrate derivatives (59 vs 51%), betablockers (51 vs 52%), calcium antagonists (51 vs 48%), lipid lowering drugs (33 vs 42%), diuretics (3 vs 6%) and inotropic agents (2 vs 2%). Overall analysis showed an increase in the prescriptions of lipid-lowering agents (p < 0.00001) and ACE inhibitors (p < 0.002). On the other hand, the prescriptions of calcium antagonists and nitrate derivatives tended to decrease. These results show that the treatment of patients with coronary artery disease is based on drugs of proven efficacy, reflecting the impact of large scale therapeutic trials on everyday medical practice.

Developing brain as a target of toxicity.

The human brain forms over an unusually long period compared to other organs. While most of the basic structure is laid down before birth, neuron proliferation and migration continue in the postnatal period. The blood-brain barrier is not fully developed until the middle of the first year of life. The number of synaptic connections between neurons reaches a peak around age two and is then trimmed back by about half. Similarly, there is great postnatal activity in the development of receptors and transmitter systems as well as in the production of myelin. Many of the toxic agents known to damage the developing brain interfere with one or more of these developmental processes. Those with antimitotic action, such as X-ray and methyl mercury, have distinctly different effects on structure depending on which neurons are forming at the time of exposure. Vulnerability to agents that interfere with cell production decreases rapidly over the early postnatal period. Other toxic substances, such as psychoactive drugs and agents that alter hormone levels, are especially hazardous during synaptogenesis and the development of transmitter systems, and thus continue to be damaging for years after birth. Still other toxic substances such as lead, seem to have their greatest effects during even later stages of brain development, perhaps by interfering with the trimming back of connections. Guidelines designed to protect human populations from developmental neurotoxicity need to take into account the changing sensitivity of the brain as it passes through different developmental stages, as well as the fundamental differences in the effects of toxicants on the mature and the developing brain.

Vulnerable periods and processes during central nervous system development.

The developing central nervous system (CNS) is the organ system most frequently observed to exhibit congenital abnormalities. While the developing CNS lacks a blood brain barrier, the characteristics of known teratogens indicate that differential doses to the developing vs mature brain are not the major factor in differential sensitivity. Instead, most agents seem to act on processes that occur only during development. Thus, it appears that the susceptibility of the developing brain compared to the mature one depends to a great extent on the presence of processes sensitive to disruption. Yet cell proliferation, migration, and differentiation characterize many other developing organs, so the difference between CNS and other organs must depend on other properties of the developing CNS. The most important of these is probably the fact that nervous system development takes much longer than development of other organs, making it subject to injury over a longer period.

Patterns of growth deficiency in rats exposed in utero to undernutrition, ethanol, or the neuroteratogen methylazoxymethanol (MAM).

Children and experimental animals exposed to ethanol (EtOH) in utero commonly have low birthweights, and many remain small at maturity. Low body weight or small stature in adulthood may reflect an inability to recover from in utero growth retardation, or it may reflect a separate, postnatal growth deficiency. In this study, daily body weights (postnatal days 1 to 60) were compared among the offspring of the following groups of Long Evans rats: dams fed liquid diet containing 35% EtOH-derived calories; their pair-fed and chow-fed controls; and dams exposed to methylazoxymethanol (MAM) in two previous studies, in which offspring exhibited reduced numbers of growth hormone releasing factor (GRF) neurons. All treatments produced a number of offspring with weight deficits beginning after birth and persisting into maturity. Three distinct patterns of growth deficiency were observed: (1) weight loss relative to controls in the first weeks of life, seen in offspring exposed to EtOH, pair feeding, or MAM on gestation day 13 (G13); (2) a delay in the onset of the prepubertal growth spurt, seen in all EtOH-exposed offspring and in G13 MAM-exposed dwarfs; and (3) failure to sustain the prepubertal growth spurt, seen only after exposure to MAM on G14. The results of this study support the view that prenatal EtOH exposure is capable of affecting postnatal growth specifically; moreover, the pattern of growth deficiency seen in EtOH-exposed offspring was distinct from that of the undernourished offspring of pair-fed dams.

Changes in the reproductive system following acute prenatal exposure to ethanol or methylazoxymethanol in the rat: I. Effects on immunoreactive LHRH cell number.

It has long been recognized that ethanol (EtOH) interferes with the hypothalamo-pituitary-gonad axis in adults of many species, and recent studies have provided evidence for similar effects after prenatal EtOH exposure. Since EtOH is capable of injuring dividing cells, we investigated the possibility that a single acute in utero EtOH exposure during the period of LHRH neuron formation might change the number of immunoreactive LHRH cells in the hypothalamus. Final LHRH cell division in Long-Evans rats was determined by [3H]thymidine autoradiography to take place over a short period between gestation days 12 and 13. Subsequently, pregnant rats were treated acutely with either EtOH or methylazoxymethanol (MAM), a known neuroteratogen, and the numbers of immunoreactive LHRH cells were counted. On gestation day 22, LHRH-positive cell numbers were significantly fewer than control numbers in both EtOH- and MAM-exposed offspring. On postnatal day 60, cell numbers in EtOH-exposed offspring did not differ from control numbers, whereas cells in MAM-exposed offspring remained significantly reduced. In controls, there were 40% fewer LHRH-positive cells on postnatal day 4 than in late gestation or at maturity. We conclude that 1) acute exposure to a high dose of EtOH at a critical time in early gestation can alter the expression of LHRH in late gestation; 2) exposure to MAM in the same period alters LHRH expression before birth and in the adult; and 3) in the early postnatal period, LHRH expression decreases profoundly.

Selective vulnerability and early progression of hippocampal CA1 pyramidal cell degeneration and GFAP-positive astrocyte reactivity in the rat four-vessel occlusion model of transient global ischemia.

Selective, delayed-onset vulnerability of hippocampal CA1 pyramidal cells has been reported as a unique phenomenon in man and the rat four-vessel occlusion (4-VO) model of global ischemia. This has become of great interest for clarification of CA1 pathophysiology and pharmacological intervention after global ischemia. Studies of pathophysiology and pharmacotherapy appear to be impeded by variability in specific criteria and duration of 4-VO ischemia for producing selective CA1 and differential CA1-CA3 damage. The goals of this study were to: (1) develop specific criteria for 4-VO ischemia to ensure selective, bilaterally symmetrical CA1 pyramidal cell damage, (2) examine the effects of 15 min of ischemia on concomitant CA1 cell necrosis and presence of remaining and/or "viable" neurons postischemia, (3) compare 15 and 30 min of ischemia on differential vulnerability of CA1-CA3 subfields, and (4) evaluate the effects of 15 min of ischemia on CA1 pyramidal cell necrosis and glial fibrillary acidic protein (GFAP)-positive astrocyte reactivity in CA1. After 15 min of ischemia, hippocampal pyramidal cell damage was well delineated, with CA1 severely damaged, but leaving CA3 virtually intact. In contrast, 30 min of ischemia produced severe CA1 and less severe CA3 necrosis. Histological evaluations across Days 1, 3, 6, and 14 indicated a significant delayed onset of CA1-CA3 cell necrosis by Day 3. Counting of remaining cells indicated a detectable loss of some large pyramidal neurons even 1 day after ischemia. Compared to controls, there was a differential increase in GFAP-positive astrocytes in CA1-CA3 after ischemia. The results provided quantitative data on the effects of specific 4-VO criteria and durations on: (1) selective CA1 cell necrosis, (2) differential CA1-CA3 cell vulnerability, (3) presence of postischemic remaining and/or viable neurons, and (4) prospect of a "therapeutic window" for pharmacological treatment of CA1 neuronal injury.

The relationship of rat brain weight and pituitary weight to postnatal growth after prenatal exposure to methylazoxymethanol.

Teratogens can affect body weight in various ways, but the association of brain damage with postnatal growth abnormalities suggests a role for neuroendocrine growth-controlling systems. Growth deficiencies follow methylazoxymethanol (MAM) exposure during the period when the growth hormone releasing factor (GRF) cells of the hypothalamus form, and the pattern of growth of the animals is like that of animals deficient in growth hormone. The present studies were designed to examine the growth, body proportions, brain weight, and pituitary weight of animals treated with 20 mg/kg MAM on the 13th day of gestation, a peak period for production of GRF neurons. Among the offspring, this treatment produced about 25% dwarfs (animals smaller than the smallest control of the same sex). Significantly more females than males were categorized as dwarfs. The weight effect occurred long after birth, as is characteristic of animals and humans with growth hormone deficiency. Analyses of weights over the course of development indicated that prenatal factors, rather than factors operating between birth and weaning, predicted the adult body weight of dwarfs, while both sets of factors were significant in other animals. The growth reduction was symmetrical, as would be expected if the animals were growth hormone deficient, with an 18% reduction in weight reflecting a 6% reduction in bone length. The remaining treated animals were similar to controls in absolute weight, body proportions, and rate of growth. Neither pituitary weight nor brain weight appears to play the key role in determining which animals will exhibit growth deficiency.(ABSTRACT TRUNCATED AT 250 WORDS)

A comparison of hypothalamic cell numbers in dwarf and normal weight rats exposed prenatally to methylazoxymethanol (MAM).

Growth deficiencies follow MAM exposure during the period when the growth hormone releasing factor (GRF) cells of the hypothalamus form, while animals exposed slightly later in gestation when the inhibitors of growth hormone release are forming, exhibit giantism. Counts of sample regions of the hypothalamus have shown that rats treated in utero on the 14th day of gestation have reductions in the number of GRF cells, increases in the number of SRIF (somatotropin release inhibiting factor) cells, and alterations of pituitary structure. These effects occurred in all treated subjects, even though obvious effects on body size were present in a small fraction of the treated animals. The present study was designed to examine the effect of 20 mg/kg MAM on the 13th day of gestation (a peak period for production of GRF cells) on GRF and SRIF cell numbers, in a large sample of dwarf-treated rats, normal weight-treated rats, and controls. The results of total counts of hypothalamic cells identified by immunocytochemistry demonstrated significant reductions in GRF cells in both dwarf and normal weight rats exposed to MAM, compared to controls, with no difference between the two treated groups. Like pituitary weights, the neuron counts were significantly correlated with body weight only in dwarf animals. SRIF cell numbers were equivalent to those in controls, suggesting that the increase reported earlier may have been due to a rebound effect in proliferation rather than some response of SRIF cells to GRF cell reduction.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of prenatal exposure to methylazoxymethanol (MAM) on brain weight, hypothalamic cell number, pituitary structure, and postnatal growth in the rat.

Congenital brain damage syndromes typically are described in terms of behavioral symptoms. Many brain functions are not reflected in behavior, however, and prenatal injury to the developing nervous system could alter these functions, as well. To test the hypothesis that prenatal brain injury can result in postnatal endocrine malfunction, rats were exposed in utero to 20 mg/kg of methylazoxymethanol acetate, a potent neuroteratogen, at two stages of gestation when different sets of growth-controlling neurons of the hypothalamus are forming. The growth hormone releasing factor (GRF) neurons stimulate release of growth hormone from the somatotropes of the anterior pituitary, contributing to rapid growth in the period between weaning and puberty. The somatotropin release inhibiting factor (SRIF) neurons have the opposite effect on the pituitary and can inhibit the GRF cells directly. Growth of treated animals was monitored daily from birth to 40 days and compared to that of controls. Treatment on the 14th day of gestation produced a small number of dwarf animals characterized by normal weight at birth and a sudden decrease in growth rate at the beginning of the fourth postnatal week that led to a body weight about 50% of normal. Treatment on day 16 yielded an acceleration of postnatal growth (significant in males). In each group, most treated animals were like controls in adult size and pattern of growth. As adults, both treatment groups demonstrated massive reductions in brain weight which characterized all the subjects, whether or not they exhibited growth anomalies. The animals treated on day 14 were confirmed to have a significant, selective reduction in growth hormone releasing factor neurons. Reductions were greatest in the middle and posterior levels of the GRF cell distribution, the regions forming most actively at the time of exposure. Unexpectedly, the same group also had increased numbers of periventricular SRIF neurons. Neither type of neurons was significantly altered in the later treatment group. Examination of pituitary structure indicated that dwarfs had very small pituitaries, with an immature pattern of somatotrope distribution, and giants had very large pituitaries, with some hypertrophy of somatotropes. The results suggest that endocrine anomalies which manifest themselves long after birth may originate as birth defects of the nervous system.