High-dose cutaneous exposure to mite allergen induces IgG-mediated protection against anaphylaxis.

BACKGROUND: The relationship among natural allergen exposure, induction of blocking antibody and the occurrence of atopic allergy-particularly in the presence of IgE production-is debatable. OBJECTIVE: To clarify the relationship between the dose of cutaneous exposure to dust mite allergen and susceptibility to the IgE-mediated allergic response in relation to IgG production. METHODS: NC/Nga mice were epicutaneously exposed to various doses of Dermatophagoides pteronyssinus allergen to induce atopic dermatitis-like skin lesions. We then evaluated the skin lesions, induction of mite-specific immune responses, and susceptibility to anaphylaxis. RESULTS: Dose-dependent exacerbation of atopic dermatitis-like skin lesions and increases in mite-specific IgG and IgE production were observed. However, mice exposed to relatively low doses of mite allergen showed hypersusceptibility to mite allergen-specific anaphylaxis. We also showed that adoptive transfer of total IgG from Dp-sensitized mice rescued mice from the hypersusceptibility seen in those exposed to low doses of mite allergen. CONCLUSIONS AND CLINICAL RELEVANCE: High-dose cutaneous exposure to dust mites induced effective blocking IgG production, even if accompanied by IgE production. Our data might support the concept that an increase in IgG titre, not a decrease in IgE titre, is a marker of clinical improvement in allergen-specific immunotherapy.

Impairment of gastrointestinal motility by nitrate administration: evaluation based on electrogastrographic changes and autonomic nerve activity.

BACKGROUND: Nitrates decrease the tone of the lower oesophageal sphincter, and may thus induce gastro-oesophageal reflux. AIM: In the present study, we evaluated electrogastrographic changes and heart-rate variability before and after the administration of nitrates. METHODS: In 15 patients with chest pain treated with nitrates, electrocardiography and percutaneous electrogastrography were performed before and after administration of nitrates. Autonomic nervous system function was evaluated by spectral analysis of heart-rate variability and serial changes in low frequency and high frequency power, and the low frequency/high frequency ratio were compared. Electrogastrograms were analysed by obtaining peak power amplitudes and their dominant frequencies. RESULTS: After the administration of nitrates (isosorbide dinitrate), high frequency power, an index of parasympathetic nervous activity, was significantly decreased, whereas the low frequency/high frequency ratio, an index of sympathetic nervous activity, was significantly increased. The mean peak amplitude of the electrogastrogram significantly increased postprandially both before and after treatment. After isosorbide dinitrate treatment, however, mean peak amplitudes after a meal were significantly lower than those obtained before treatment. The mean dominant frequency of the electrogastrogram did not vary before and after treatment. CONCLUSIONS: The present study suggests that nitrates inhibit gastrointestinal motility by decreasing autonomic nervous activity.

Evaluation of myocardial sympathetic nerve function in patients with mitral valve prolapse using iodine-123-metaiodobenzylguanidine myocardial scintigraphy.

Mitral valve prolapse (MVP) is closely related to myocardial sympathetic nerve function. This study evaluated the presence of impaired myocardial sympathetic nerve function by Iodine-123-metaiodobenzylguanidine (MIBG) scintigraphy in ten patients with MVP. For comparison, 15 healthy subjects without heart disease were investigated (control group). Single photon emission computed tomography (SPECT) and anterior planar myocardial scintigraphy were performed 15 min (initial images) and 3 hours (delayed images) after injection of MIBG (111 MBq). The location and degrees of reduced tracer uptake were evaluated. Myocardial MIBG uptake was quantified by uptake ratio of the heart (H) to upper mediastinum (M) on the anterior planar images (H/M). Percentage washout of MIBG in nine sectors of all oblique slices along the short-axis was calculated. The washout rates were higher at the inferoposterior and septal segments in patients with anterior leaflet prolapse, and at inferoposterior and lateral segments in patients with posterior leaflet prolapse. The bull's eye map showed increased washout rate in the apical and posteroseptal basal segments. There was no significant difference in the H/M ratio between MVP patients and the control group. These results indicate that MIBG can be used to evaluate localized myocardial sympathetic nerve function in MVP.

Amyloid beta-peptide inhibits neuronal glucose uptake by preventing exocytosis.

Amyloid beta peptide (Abeta) is suspected as a contributing factor for decreased glucose utilization in the brain of Alzheimer's patients; however, little is known about the regulatory mechanism of neuronal glucose uptake and how Abeta affects such a mechanism. We report that membrane depolarization by 40 mM KCl increases both neuronal glucose uptake and immunolabeling of the exofacial epitope of glucose transporter isoform GLUT3, suggesting that fusion of GLUT3 vesicles with the plasma membrane increases glucose uptake. Abeta25-35 decreased neuronal glucose uptake and this decrease was prevented by exocytosis-enhancing compounds (40 mM KCl, 50 microM ruthenium red). Abeta25-35 also inhibited exocytosis of the fluorescent membrane dye FM1-43 at neuronal cell bodies; however, 40 mM KCl was effective in overcoming this Abeta inhibition. Furthermore, GLUT3 colocalized with SNARE (N-ethylmaleimide-sensitive factor attached protein receptor) complex proteins (SNAP-25 and Syntaxin 1), and cleavage of the v-SNARE, VAMP, reduced glucose uptake. Our findings suggest that neuronal glucose uptake is regulated by SNARE complex-dependent docking and fusion of GLUT3 vesicles with the plasma membrane and that Abeta decreases glucose uptake by inhibiting fusion of these vesicles.

Consumption coagulopathy associated with aneurysms of the abdominal aorta and the bilateral femoral arteries. Report of a case.

The authors report a case of a 70-year-old man, with repeating episodes of systemic subdermal hematoma due to consumption coagulopathy associated with abdominal aortic aneurysm and the bilateral femoral arterial aneurysms. Prior to the first operation for abdominal aortic repair, anticoagulation therapy was applied to treat thrombocytopenia and hypofibrinogenemia. Five years following the first surgery, the same treatment was required before resection of the femoral lesions. Consumption coagulopathy is seen in approximately 1-4% population of aortic aneurysms, however, repeated appearance of symptomatic coagulopathy is rarely reported. Anticoagulation therapy was effective to normalize the coagulation and fibrinolytic system and followed by uneventful surgical resection of the aneurysms.

G protein and cAMP-dependent protein kinase mediate amyloid beta-peptide inhibition of neuronal glucose uptake.

The mechanism by which amyloid beta-peptide (Abeta) inhibits glucose uptake in cultured cells is not known. Here we demonstrated a signaling pathway in which Abeta25-35, a neurotoxic portion of the Abeta peptide corresponding to amino acids 25-35, inhibits neuronal glucose uptake by hippocampal neurons. The GP antagonist-2, which blocks Gs, prevented the inhibitory effect of Abeta on the glucose uptake. Exposure of cells to Abeta resulted in a transitory increase in intracellular levels of cAMP. To assess the role of cAMP in neuronal glucose uptake, cultured neurons were exposed to dibutyryl cAMP (Bt2cAMP) or an adenylyl cyclase activator, forskolin. Both Bt2cAMP and forskolin inhibited neuronal glucose uptake, and cAMP-dependent protein kinase (PKA) inhibitor KT5720 blocked the Abeta-mediated inhibition of glucose uptake. Cholera toxin, which stimulates adenylyl cyclase by activating Gs protein, also inhibited neuronal glucose uptake, and Abeta potentiated this inhibitory effect of cholera toxin on glucose uptake. Thus, our findings suggest that Abeta inhibits glucose uptake by activating the Gs-coupled receptors and involves the cAMP-PKA system.

[Neurocysticercosis. A tomographic diagnosis in neurological patients]. / Neurocisticercose. Diagnóstico tomográfico em pacientes neurológicos.

Neurocysticercosis (NC) is the most common parasitic disease of the central nervous system and accounts for a significant proportion of morbidity and mortality, in special epilepsy. The authors reviewed 3093 computed tomography scans out of 2554 randomized neurological patients evaluated during a one year period. Most patients (77.3%) were living in Curitiba, Paraná, Brazil. 1821 (58.9%) CT scans were normal. NC was diagnosed in 236 patients based on tomographic criteria; the sex ratio was F:M 1.6:1. 219 (92.8%) patients had the inactive form of NC: 195 (89%) had only isolated intraparenchymal calcifications, and 24 calcifications plus hydrocephalus. Active forms were observed in 14 patients: 8 with degenerating cysts, 4 with viable cysts, 1 with intraventricular cyst, and 1 with racemose form. Three patients had both forms, active (cysts) and inactive (calcifications). The most common clinical finding among patients with tomographic diagnosis of NC was headache alone (35.5%), followed by epilepsy (20.9%). There is a potential role of NC as a causal factor of epilepsy in most of our patients, but surely not in all of them. On the other hand, the finding of inactive NC (calcifications without hydrocephalus and/or meningitic reaction) in patients with headache is probably fortuitous in most cases. In fact, the occasional finding of isolated calcifications in general population is not quite rare, as it was observed in 3.3% of another series of 973 patients with head trauma submitted to CT scan and without epilepsy previous history. The presence of CT findings compatible with NC, especially calcifications, must be carefully correlated with the clinical context in each case. Only then, an unequivocal cause-effect with all its medical and epidemiological implications role can be established.

Neurocisticercose: diagnóstico tomográfico em pacientes neurológicos / Neurocysticercosis: a tomographic diagnosis in neurological patients

Neurocisticercose (NC) é a parasitose mais comum do sistema nervoso central no nosso meio. Foram analisadas 3093 tomografias computadorizadas (TC) de 2554 pacientes neurológicos durante o período de um ano. A maioria dos pacientes era procedente de Curitiba (77,3 por cento). 1821 (58,9 por cento) das TC foram normais. Do total destes pacientes, 236 (9,2 por cento) possuíam achados tomográficos compatíveis com NC; a proporçao feminino:masculino foi 1,6:1. Duzentos e dezenove casos (92,8 por cento) apresentavam a forma inativa, 13 (5,5 por cento) ativa, 3 (1,3 por cento) ambas, e apenas 1 caso a forma racemosa. Calcificaçoes intraparenquimatosas foram o achado mais comum (89 por cento). Cefaléia foi o achado clínico mais frequente (35,5 por cento), seguida de epilepsia isolada (20,9 por cento) ou associada a outros achados neurológicos (9 por cento). Achados tomográficos compatíveis com NC, especialmente a forma inativa, sao achados relativamente comuns em uma populaçao nao selecionada de pacientes neurológicos. Com exceçao parcial dos pacientes epilépticos, a relaçao destes achados com o quadro clínico neurológico deve ser cuidadosamente analisada individualmente, pois a presença casual de calcificaçoes isoladas intraparenquimatosas ocorre em uma proporçao significativa de pacientes com queixas ou doenças neurológicas sem relaçao com a NC.

Integrin Mac-1 and beta-amyloid in microglial release of nitric oxide.

The beta-amyloid protein associated with Alzheimer's disease (AD) has been well characterized biochemically; however, its primary biological function and mode of action in AD has not been determined. We have shown previously that beta-amyloid (beta25-35), in combination with interferon-gamma (IFN-gamma), can induce nitric oxide release from cultured hippocampal microglial cells. In the present study, binding of beta-amyloid with the leukocyte integrin Mac-1, a cell surface receptor on microglia, was studied by observing (1) inhibition of beta-amyloid (beta25-35)-mediated release of nitric oxide from cultured microglial cells following exposure to monoclonal antibodies against Mac-1 (anti-CD18 and anti-CD11b) and (2) competitive binding of fluorochrome-labeled beta25-35 with anti-CD18 or anti-CD11b using fluorescent flow cytometry. Wt.3 (anti-CD18 antibody) and OX42 (anti-CD11b antibody) were as effective as opsonized zymosan at inducing the release of nitric oxide from microglia. Furthermore, Wt.3 and OX42 acted synergistically to induce maximum nitric oxide release. An interaction between beta-amyloid and CD18 of Mac-1 was evidenced by the suppressive action of beta25-35 on Wt.3-mediated release of nitric oxide and the synergistic action between OX42 and beta25-35 in inducing nitric oxide release from microglia. The tissue culture study was supported by competitive binding assays of fluorochrome-labeled beta25-35 and Mac-1 antibodies (Wt.3 or OX42). The majority of microglial cells (71%) did bind biotinylated beta-amyloid in the presence of cytochalasin B, suggesting that beta-amyloid binding to microglia is a receptor-mediated event. Furthermore, pre-exposure to Wt.3, but not OX42, significantly decreased binding of biotinylated beta25-35 to microglia. These findings suggest that CD18 of Mac-1 may play a role in beta-amyloid-mediated release of nitric oxide.

The inhibitory effects of beta-amyloid on glutamate and glucose uptakes by cultured astrocytes.

beta-Amyloid is the primary protein component of neuritic plaques, which are degenerative foci in brains of patients with Alzheimer's disease (AD). The effects of this naturally occurring beta-amyloid on the cells of the central nervous system have not been completely understood. beta-Amyloid increases the vulnerability of cultured neurons to glutamate-induced excitotoxic damage. Because astrocytes play a key role in uptake of extracellular glutamate and glutamate uptake is ATP-dependent, we studied the effect of beta25-35 on glutamate and glucose uptake in cultured hippocampal astrocytes following 7 days of exposure to beta25-35. Astrocytic glutamate uptake was studied at 1, 5, 10, 15, 20, and 60 min following the addition of [3H]glutamate (5 nM) to the culture media, and astrocytic glucose uptake was assessed at 60 min after the addition of [14C]glucose (600 and 640 nM) to the media. Glutamate uptake by control astrocytes was time-dependent. Astrocytes exposed to beta25-35, however, showed significantly lower glutamate uptake at all sampling times. Similarly, [14C]glucose uptake by astrocytes was inhibited by beta25-35. When glucose uptake was blocked by phloretin (10 mM), astrocytic [3H]glutamate uptake was also blocked, suggesting that the inhibitory effect of beta-amyloid on glutamate uptake is caused by diminished glucose uptake. Thus, our present study suggests a possible link between two proposed mechanisms of pathogenesis of the Alzheimer's disease: glutamate neurotoxicity and global defect in cerebral energy metabolism.

Microglial release of nitric oxide by the synergistic action of beta-amyloid and IFN-gamma.

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized histopathologically by a loss of neurons and an accumulation of beta-amyloid plaques, neurofibrillary tangles, dystrophic neurites, and reactive glial cells. While most previous studies on the neurodegeneration of AD have focused on neuronal cells and direct beta-amyloid-mediated neurotoxicity, few have focused on the role of reactive glial cells in beta-amyloid-mediated neurotoxicity. In the present study nitric oxide release from cultured rat microglia was examined by exposing the cells to synthetic beta-amyloid peptides (beta 25-35 and beta 1-40) alone and in combination with the cytokines IFN-alpha/beta (100 U/ml), IL-1 beta (100 U/ml), TNF-alpha (100 U/ml), TNF-beta (100 U/ml), or IFN-gamma (10, 100, 500, or 1000 U/ml). Assessment of microglial release of nitric oxide was based on the colorimetric assay for nitrite in the culture medium and histochemistry for nitric oxide synthase. Of the cytokines tested, only IFN-gamma (1000 U/ml) induced nitric oxide release from microglia. beta 25-35 did not stimulate nitric oxide release by itself, but it did induce nitric oxide release when co-exposed with IFN-gamma (100, 500, and 1000 U/ml). In contrast, beta 1-40 did induce microglial release of nitric oxide by itself, and this effect was enhanced significantly by co-exposure with IFN-gamma (100 U/ml). These findings warrant a further investigation into the role of microglia in the neurodegeneration of Alzheimer's disease via nitric oxide toxicity induced by the synergistic action of beta-amyloid and a costimulatory factor.

Mathematical modeling of dendritic growth in vitro.

The dendritic branching pattern of cultured hippocampal neurons was analyzed to obtain mathematical parameters that fit the time-dependent growth of dendrites under limited extrinsic influence. Cultured neurons were stained with a non-toxic carbocyanine dye (diO) and pyramidal-shaped neurons that were physically separated from one another were analyzed at post-plating days 1, 2, 3, 4, 6 and 7. The geometric branching pattern of the dendrites was analyzed using a mathematical model that incorporates random effects in the form of a Galton-Watson branching process where splitting of one branch is statistically independent of the splitting of all other branches, and deterministic effects in the form of a parameter that measures the extent to which dense patterns (clusters) or sparse patterns (elongated trees) are formed. The geometric branching pattern of the dendrites was analyzed using a mathematical model that incorporates random and deterministic effects. The model parameters were estimated via the method of maximum likelihood. The data suggest that in vitro basal dendrites grow according to a purely random branching process without pronounced dense or sparse patterns, while apical dendrites tend to form elongated trees with fewer secondary bifurcations. This trend is quantified, and it depends on the culture conditions in which the neurons are grown. The quantitative assessment of various influences on dendritic growth patterns are discussed.

Aluminum induces neurite elongation and sprouting in cultured hippocampal neurons.

It has been reported that the aluminum content in the human brain increases with age, and it is particularly high in those with Alzheimer's disease. In this study, we found that a low aluminum concentration (100 mumol/L) in the culture media of opossum hippocampal neurons can induce extensive neurite outgrowth (ie, elongation and branching of neurites) and sprouting (ie, outgrowth of filiform processes from neurite varicosities) within 48 hours. Such changes in neurite morphology were remarkably similar to those described in the aged or Alzheimer's disease brain. Neurites that responded to aluminum varied greatly in length, thickness, and branching pattern. Many neurites appeared to have no clear directional growth pattern because they frequently changed their course and formed a meshwork of neurites with others originating from the same cell body. Sprouting neurites varied in length, thickness, and branching pattern, but they always originated from a globular enlargement of neurites along the neurite shaft or at the terminal end. Such growth pattern and extensive sprouting of neurites did not fit the growth pattern displayed by the control neurons. Our findings suggest that aluminum may be involved in the neuronal remodeling characteristic of aging and Alzheimer's disease.

The effect of halothane on cultured fibroblasts and neuroblastoma cells.

Halothane exposure over the cultured cells (100 and 1,000 ppm) caused a disruption of the pattern of actin distribution in both fibroblasts and neuroblastoma cells. Neuroblastoma cells exposed to halothane also lost microspikes; however, neurite elongation was not affected by halothane. The present study suggests that halothane induces the functional disruption of actin, resulting in an interference of normal neural development in vivo.

Enhanced neurite growth in cultured neuroblastoma cells exposed to aluminum.

Patients with aluminum-induced encephalopathy syndromes have been shown to have a high level of aluminum concentration in the brain. In the present study, the effects of aluminum were studied in mouse neuroblastoma cells (N-2A) grown in medium supplemented with aluminum (100 microM). It was found that aluminum enhanced neurite growth within 2 days of exposure. The mean total length of neurites in the control after 14 days in culture was 29.8 +/- 4.7 microns, whereas the neurite length of cells pre-exposed to aluminum for 2 days and then maintained in normal media for an additional 12 days was 56.4 +/- 8.9 microns. Further, the duration of exposure did not significantly promote a greater neurite response. The neurite length of cells exposed to aluminum for 14 days (60.7 +/- 9.6 microns) was not statistically different from that of cells exposed to aluminum for 2 days. Using morin stain, intracellular aluminum was detected within 24 h of exposure in the majority of aluminum-exposed cells. Intracellular aluminum did not disappear from those cells even after they were grown for 12 days in control medium. Our finding suggests that a brief exposure (2 days) to low level aluminum (100 microM) is sufficient to cause long-lasting effects on the morphology of neuroblastoma cells in culture. Such neurite behavior associated with aluminum exposure may suggest a morphological basis for the dementia seen in aluminum encephalopathy.

Dietary aluminum selectively decreases MAP-2 in brains of developing and adult rats.

Administration of 0.3% aluminum in drinking water elevated serum aluminum concentrations 8-fold in rats. Further, chronic treatment with aluminum for 2-3 mon, in both developing and adult rats, significantly decreased the levels of MAP-2 in brain, as determined by quantitative immunoblot analysis. Aluminum treatment also decreased the level of brain spectrin, but only in the hippocampus of adult rats. These were selective effects, since the levels of tubulin, tau and the three proteins of the neurofilament triplet were unaltered. In the aluminum-treated adult rats MAP-2 levels were significantly decreased in the hippocampus and brainstem to 71% and 56% of control values, respectively. In developing rats, MAP-2 levels were significantly decreased in the cortex and brainstem (65 and 64% of control values, respectively) but not in the hippocampus. In support of these findings, immunohistochemical examination revealed that the intensity of hippocampal MAP-2 immunoreactivity was significantly decreased to 88% of control values with aluminum treatment in adult rats. To determine a possible mechanism by which MAP-2 levels are reduced, the effect of aluminum on calpain-induced proteolysis of MAP-2 was examined in vitro. At the aluminum concentrations tested, there was no apparent effect on calpain-induced proteolysis of MAP-2. In the developing rats, aluminum administration significantly increased the hippocampal cyclic AMP concentration, as reported previously in adult aluminum-treated rats, and decreased the inositol 1,4,5-trisphosphate concentration. These results demonstrate that chronic oral aluminum administration to rats selectively decreases the levels of MAP-2 in specific brain regions independent of calpain proteolysis. This decrease may be associated with increased cyclic AMP and protein phosphorylation, and the impairment of cognition previously observed in this model of aluminum intoxication.

Neurobehavioral toxicology of halothane in rats.

Halothane, a commonly used general anesthetic, is considered to be relatively safe for that purpose. Chronic exposure, however, has been found to cause long-lasting damage to neural structure and impairment of behavioral function. In rats, behavioral alterations are particularly evident after developmental exposure, but they can also be seen with adult exposure, especially when halothane is given during the period of neural regrowth following a brain lesion. The pattern of neural damage includes retarded synaptogenesis, impaired dendritic branching and disruption of organelle structure. The behavioral syndrome includes learning impairment, decreased exploratory behavior and decreased nociceptive reactivity. In general, the neural pathology is more pronounced and more easily discernible than the behavioral effects. Neural damage, particularly to the hippocampus, can be clearly seen at points when behavioral impairments have not been found. This demonstrates that in some cases changes in neural structure can be more sensitive indicators of toxic damage than behavioral dysfunction. Halothane exposure has proved to be quite useful as an experimental tool in the study of neural and behavioral recovery after brain lesions. For example, after unilateral entorhinal cortical lesions, behavioral recovery and reactive synaptogenesis occur contemporaneously. It has not been demonstrated whether the behavioral recovery is due to this reinnervation. Postlesion halothane exposure almost completely suppresses reactive synaptogenesis, however, behavioral recovery of T-maze alternation behavior occurs in the halothane-treated rats as well as in controls. This suggests that recovery of spatial performance after such a lesion is not due to recovery of innervation in the dentate, but to some other process such as other neural systems taking over the functions lost with the brain lesion. The studies reviewed highlight the dangers of halothane exposure, especially during development or when recovering from brain injury. They also provide a good case study for comparing the relative sensitivity of morphological and behavioral measures in toxicology and point to the potential use of halothane as an experimental tool for examining the relationships between neural structure and behavioral function.

Statistical evaluation of dendritic growth models.

A mathematical model (Kliemann, W. 1987. Bull. math. Biol. 49, 135-152.) that predicts the quantitative branching pattern of dendritic tree was evaluated using the apical and basal dendrites of rat hippocampal neurons. The Wald statistic for chi 2-test was developed for the branching pattern of dendritic trees and for the distribution of the maximal order of the tree. Using this statistic, we obtained a reasonable, but not excellent, fit of the mathematical model for the dendritic data. The model's predictability of branching pattern was greatly enhanced by replacing one of the assumptions used for the original method "splitting of branches for all dendritic orders is stochastically independent", with a new assumption "branches are more likely to split in areas where there is already a high density of branches". The modified model delivered an excellent fit for basal dendrites and for the apical dendrites of hippocampal neurons from young rats (30-34 days postpartum). This indicates that for these cells the development of dendritic patterns is the result of a purely random and a systematic component, where the latter one depends on the density of dendritic branches in the brain area considered. For apical dendrites there is a trend towards decreasing pattern predictability with increasing age. This appears to reflect the late arrival of afferents and subsequent synaptogenesis proximal on the apical dendritic tree of hippocampal neurons.

Long-term effects of developmental halothane exposure on radial arm maze performance in rats.

Chronic exposure of rats to low levels of halothane during development, a treatment which retards synaptogenesis, was found to cause a long-term impairment of choice accuracy in the radial-arm maze. In Expt. 1, the relative importance of dose level and dosing regimen was examined. Dose level seemed the more critical variable for causing impaired choice accuracy. Exposure to 100 parts per million (ppm) of halothane in the air either on an intermittent or continuous schedule from day two of conception until 60 days after birth significantly impaired choice accuracy, whereas exposure to 25 ppm on a continuous schedule did not cause a deficit, even though with this condition the total amount of halothane exposure was about the same as with 100 ppm given intermittently. In Expt. 2, the 100 ppm intermittent exposure regimen was used to examine the relative importance of exposure during early and late developmental periods for producing the cognitive effects of halothane. Groups were divided into those exposed to halothane during gestation and until 30 days after birth (early exposure), those exposed from day 31 until day 90 (late exposure) and those exposed during both early and late periods (combined exposure). Adverse effects on choice accuracy were seen with all 3 types of exposure, but surprisingly, it was the late exposure that caused the most severe effects. These results show that developmental exposure to halothane which impairs synaptogenesis also causes long-lasting cognitive impairment. Halothane exposure can be a useful experimental tool for examining the relationship between synaptic and behavioral development.

Neuronal RNA in nucleus ambiguus and nucleus hypoglossus of patients with amyotrophic lateral sclerosis.

To establish objectively the involvement of neurons in the medulla oblongata in patients with amyotrophic lateral sclerosis (ALS), ribonucleic acid (RNA) content was determined in neurons of the hypoglossal nucleus and the nucleus ambiguus. Neurons from those two nuclei showed a significant loss of RNA content in patients with ALS; only 57% and 38% of the normal RNA content was found in hypoglossal and ambiguus neurons, respectively. This marked loss of neuronal RNA suggests changes in functional states of neurons, which may contribute to fasciculations in the tongue and difficulties in swallowing often associated with ALS.