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]

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.

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.

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.

Suppressive effects of halothane on reactive synaptogenesis in the dentate gyrus of rats

Reactive synaptogenesis was studied in the dentate gyrus of rats exposed to 100 parts per million of halothane for 15 days starting on the day after unilateral entorhinal lesioning. Halothane exposure markedly affected the replacement of synapses. Only 17% of the lost synapses were restored by day 15 postlesion in rats exposed to halothane, while 73% of the lost synapses were recovered in rats not exposed to halothane. However, this suppression in initial reactive synaptogenesis did not result in permanent deficits in synaptic population. After halothane exposure was stopped, reactive synaptogenesis resumed, and by day 30 after the lesion, the synaptic population of the experimental group caught up to the control level. This suppressive action of halothane suggests its utility as a research tool for delaying synaptogenesis during selected developmental epochs to study the relationship between synaptic and behavioral recovery.

The influence of prenatal phenobarbital exposure on the growth of dendrites in the rat hippocampus

Barbiturates, such as phenobarbital (PHB), are often used during pregnancy and early neonatal life to prevent epileptic seizures, hyperbilirubinemia and the stressful effects of labor. However, the long-term consequences of barbiturate exposure during the prenatal and neonatal periods have not been fully investigated. Several studies have indicated that phenobarbital does affect the resulting morphology and neurochemistry of various components of the central nervous system. In the present study we have investigated the effects of 3 days of prenatal phenobarbital administration (days 18-20 of gestation) on the growth and development of dendrites within the CA1 region of the hippocampus in the rat. Pups were sacrificed on days 5, 10, 23, and 35 of postnatal age and the brains were processed for Golgi impregnation of neurons. The terminal and non-terminal segments of apical and basal dendrites of neurons within the CA1 region of the hippocampus were analyzed with the aid of a scanning stage on a Zeiss universal photomicroscope and a PDP 11/23 microcomputer. In general, results indicated that 3 days of prenatal PHB severely suppresses the development of the dendritic tree which normally takes place during the first 35 days of postnatal life. There are significantly less branch points and the overall dendritic length of both apical and basal dendrites is reduced. These results indicate that prenatal PHB, even for short periods of time, affects the normal morphological development of the hippocampus. Thus, the utilization of PHB in the treatment of various human prenatal disorders should be questioned.

Morphometric studies of the rat hippocampus following chronic delta-9-tetrahydrocannabinol (THC)

Persistent behavioral effects resembling those of hippocampal brain lesions have been reported following chronic administration of marijuana or its major psychoactive constituent, delta-9-tetrahydrocannabinol (THC) to rats. We used morphometric techniques to investigate the effects of chronic THC on the anatomical integrity of the hippocampus. Rats dosed orally for 90 days with 10 to 60 mg/kg THC or vehicle were evaluated by light and electron microscopy up to 7 months after their last dose of drug. Electron micrographs revealed a striking ultrastructural appearance and statistically significant decreases in mean volume of neurons and their nuclei sampled from the hippocampal CA3 region of rats treated with the highest doses of THC. A 44% reduction in the number of synapses per unit volume was demonstrated in these same rats. Golgi impregnation studies of additional groups of rats treated with 10 or 20 mg/kg/day THC and sacrificed 2 months after their last treatment with THC revealed a reduction in the dendritic length of CA3 pyramidal neurons, despite normal appearing ultrastructure and no changes in synaptic density. The hippocampal changes reported here may constitute a morphological basis for behavioral effects after chronic exposure to marijuana.

Neurobehavioral effects of chronic halothane exposure during developmental and juvenile periods in the rat

Chronic exposure of rats to the surgical anesthetic agent halothane during development has been found to cause both neural and behavioral impairment. Among the halothane-induced deficits are retarded synaptogenesis and impaired spontaneous alternation. It is unclear how long after birth the susceptibility to the neurotoxic effects of halothane persists. The present study compared in rats the effects of halothane exposure on synaptic density and spontaneous alternation during early and late periods of maturation. All three experimental groups were exposed to 100 parts per million of halothane for 8 h/day, 5 days/week. One group (early exposure) was exposed from day 2 of conception until 30 days after birth. The second group (late exposure) was exposed to the same amounts from day 31 until day 90 after birth. The third group (continued exposure) received both periods. The control group was treated in the same way, but was not exposed to halothane. As found in the previous study, there were greater effects of halothane on synaptogenesis than on spontaneous alternation; impairment of spontaneous alternation behavior was found only with the early exposure. Deficits in synaptic density were found with both early and late exposure, although the early exposure had more severe effects. Halting the exposure to halothane on day 30 reinstated control-like rates of synaptogenesis, but the deficit in synaptic density from the early exposure persisted into adulthood. The potent neurotoxic effect of halothane in suppressing synaptogenesis highlights not only its potential as a hazard but also its potential as an experimental tool for manipulating the rate of synaptogenesis and examining the relationship between synaptic development and behavioral maturation.

Effects of halothane on the development of rat brain: a golgi study of dendritic growth

Dendritic growth was studied in rats exposed to halothane in utero for the entire gestation period and 60 days after birth. The exposure conditions were control, intermittent halothane (25 +/- 5 ppm or 100 +/- 5 ppm, 8 h/day, 5 days/week), or continuous halothane (25 +/- 5 ppm, 24 h/day, 7 days/week). Dendritic growth in terms of branch numbers and length was most advanced in the control groups, followed by those groups exposed to 25 +/- 5 ppm halothane intermittently, 25 +/- 5 ppm halothane continuously, and 100 +/- 5 ppm halothane intermittently. The latter two exposure conditions exerted identical effects on dendritic growth. The order of this dendritic growth level established at 5 postnatal days remained the same throughout the first 95 postnatal days in both the entorhinal cortex and subiculum. The effect of halothane on dendritic growth appeared to be enduring, and the delay in the initial dendritic growth caused by halothane was not compensated for by an increased rate of dendritic growth.

Effects of halothane on synaptogenesis and learning behavior in rats

Synaptic density was quantitated in the entorhinal cortex and subiculum of rats at 5, 21, 34, and 95 postnatal days. These rats were offspring of mothers that had been subjected to four different concentrations of halothane during gestation and for 60 days after birth. The exposure conditions were control, intermittent halothane (25 +/- 5 ppm or 100 +/- 5 ppm, 8 h/day, 5 days/week) and continuous halothane (25 +/- 5 ppm, 24 h/day, 7 days/week). Synaptic density in rats exposed to halothane was significantly less than in control rats. Animals exposed intermittently to 25 +/- 5 ppm halothane had higher synaptic density than animals exposed continuously to 25 +/- 5 ppm halothane or intermittently to 100 +/- 5 ppm halothane. The latter two exposure conditions exerted similar effects. The lag in synaptic development was established at 5 days postnatal and remained the same throughout the first 95 postnatal days in both the entorhinal cortex and subiculum. Delayed synaptogenesis caused by halothane was indicated by the presence of growth cones in halothane-exposed rats to 34 days compared with 21 days in the control rats. The spontaneous alternation test indicated that the delayed synaptogenesis by halothane was sufficient to suppress behavioral development. Thus, the delay in the initial synaptic maturation caused by halothane exposure in utero may result in permanent morphologic and functional deficits of the brain.

Dendritic alterations in chronic animals with experimental neurofibrillary changes

Dendritic changes were quantitated in the cerebral cortex and subiculum of rabbits injected with aluminum tartrate for 90 days (5 days/week) at 100, 200, and 300 days after the last injection of aluminum. Both apical and basal dendrites of the cerebral cortex and subiculum responded similarly to aluminum tartrate. The dendrites were fewer and shorter in the animals examined at 200 and 300 days postinjection of aluminum tartrate. Such dendritic changes were more prominent at longer postinjection times and in dendrites that were more peripheral from the cell body. Aluminum-induced changes in apical dendrites were more prominent in the subiculum than in the cerebral cortex. Aluminum-induced changes in basal dendrites, however, were more prominent in the cerebral cortex than in the subiculum. The results suggest a time delay between the initial accumulation of neurofibrillary changes and the subsequent loss of peripheral dendritic branches, which appears to be long-lasting.

A mathematical model for the growth of dendritic trees

A theoretical model for calculating the total length of dendritic trees is presented. Predictions of velocity of dendritic growth, time when branching begins and mean maximal extent of dendritic tree derived from the model for apical dendrites in entorhinal cortex of the rat are presented.

Age-related changes in the subiculum of Macaca mulatta: synaptic density

Dendritic spines and synapses were quantitated in the subiculum of 12 Macaca mulatta from 7 to 29 years of age. Dendritic spines were analyzed in six dendritic foci of pyramidal neurons impregnated by the Golgi-Cox method. The dendritic foci examined were the apical shaft, apical oblique, apical tuft, apical terminal, basal terminal, and basal dendrites. Electron microscopic observations were made on synapses stained with ethanolic phosphotungstic acid. There was no difference in spine density between a group of young (7 to 12 years of age) and middle-aged (18 to 21 years) animals. The mean spine density was 1.09/microns for the young and 1.15/microns for the middle-aged animals. In contrast, the spine density of the old animals was 0.87/microns, which was significantly lower than the spine density found in the young and middle-aged animals. A loss of dendritic spines in the old animals occurred equally in all six dendritic foci. A decline in synaptic density in the aged animals were further evidenced by an ultrastructural analysis. The synaptic density of the old animals was 8.3 X 10(8)/mm3, significantly lower than 9.5 X 10(8)/mm3 and 10.2 X 10(8)/mm3 found in the young and middle-aged animals, respectively. This study on synaptic density demonstrated the decline in synaptic number as a function of age in M. mulatta.

Age-related changes in the subiculum of Macaca mulatta: dendritic branching pattern

The dendritic branching pattern was studied in the subiculum of nine Macaca mulatta from 7 to 28 years of age. Morphometric analysis of pyramidal neurons revealed significant age-related differences at various designated branch orders in both the centrifugal and centripetal ordering methods. There was continued branching and growth of the apical dendrites in adulthood. Basal dendrites did not show any added complexity, but rather showed continued growth of existing terminal branches. The three oldest animals showed a preferential loss of whole terminal branches on the apical portion of the dendritic tree, whereas shortening of existing terminal branches was the characteristic feature of the basal dendrites. Data obtained from the subiculum provide quantitative evidence indicating the considerable potential for dendritic plasticity beyond the early developmental stages and eventual loss of dendritic complexity in the old M. mulatta.

Intranuclear aluminum accumulation in chronic animals with experimental neurofibrillary changes

Young New Zealand white rabbits (1.5 kg body weight) subjected to daily subcutaneous injection of aluminum tartrate (7.7 mg/kg body weight) developed neurofibrillary tangles (NFTs) in specific areas of the central nervous system. The NFTs were initially observed in the spinal cord and brain stem. The hippocampus was the last region to show NFTs. Animals neither died nor showed any neurologic signs. Their growth pattern during and following the aluminum injection was comparable to that of controls. Energy-dispersive X-ray spectrometry detected aluminum within the nucleus of a high percentage of NFT-bearing neurons in the spinal cord and hippocampus. Aluminum was not detected in NFT-free neurons. These findings suggest the association of intranuclear aluminum with NFTs induced experimentally in the chronic animals.

Synaptic density in chronic animals with experimental neurofibrillary changes

Synaptic density was quantitated in the cerebral cortex and subiculum of rabbits with experimental neurofibrillary changes. Animals were subjected to subcutaneous injection of aluminum tartrate for 90 days, and synapses stained with ethanolic phosphotungstic acid were analyzed in animals killed 100, 200, or 300 days postinjection with aluminum tartrate. A significant difference was found in synaptic density between animals injected with aluminum tartrate and their age-matched controls. This difference was a result of a low synaptic density present in animals killed 200 or 300 days postinjection of aluminum tartrate. In contrast, animals killed 100 days postinjection revealed the same synaptic density as their control. The data suggest that the synaptic depopulation associated with experimental neurofibrillary changes is a gradual process, and such changes are demonstrable only long after the initial appearance of neurofibrillary changes.

Studies on regression of atherosclerosis--role of lipid containers

The appearance of the aortic wall of rabbits fed a lanolin containing diet was examined by scanning (SEM) and transmission electron microscopy (TEM) in order to clarify the mechanism of removal of lipids deposited in the aorta. SEM study showed that circulating leukocytes penetrated into the arterial wall in the early phase of the experimental atherosclerosis. In some specimens, spherical bodies with a diameter of 10-30 mu were observed along the cleavage of the marginal folds between the endothelial cells. TEM demonstrated that these bodies contained many lipid particles, and numerous active microvilli were seen on the body surface. In the deeper subendothelial space, villi of each body interdigitated. From these results, it is postulated that the circulating leukocytes penetrate under the endothelium and take up the deposited lipids. Then, they return to the blood stream, containing lipid rich particles. The deposited lipids in the atherosclerotic lesion would be removed by this process. We named this phenomenon as "exo-tissuesis with lipid containers". While lipids are believed to be removed from the atherosclerotic lesion by HDL, lecithin cholesterol acyltransferase and others at the molecular level, we suggest that lipid containers play important roles in the regression and prevention of atherosclerosis on a major scale-cellular and tissue level.

Age-related changes in neuronal RNA content in rhesus monkeys (Macaca mulatta)

The prefrontal cortex and subiculum of the hippocampal formation was sampled from 10 Macaca mulatta aged 7 to 30 years. There was no significant difference in RNA content of frontal and subicular neurons between 7 and 20 years. The mean RNA content was 22.86 pg for the cortical and 45.14 pg for the subicular neuron. Contrarily, a significant decrease in neuronal RNA content in both the prefrontal cortex and the subiculum was found for the four M. mulatta of advanced age. The oldest M. mulatta aged 27 to 30 years revealed a mean RNA content of 16.8 pg for the prefrontal cortex and 33.5 pg for the subiculum. Age-related RNA changes in M. mulatta was discussed in relation to that in the human brain.

Quantitative studies of neuronal RNA on the subiculum of demented old individuals

Autopsied human brains from three patients with senile dementia were studied for the effect of neurofibrillary tangles on neuronal RNA content. Nerve cell bodies were dissected out from the subiculum under the phase contrast microscope and were separated into two groups based on the presence or absence of neurofibrillary tangles within the perikaryon. It was found that the mean RNA content of the tangle-bearing cells was 28.61 pg, whereas that measured in nerve cell bodies considered as free from the tangles was 41.21 pg. Thus, a significant decrease in neuronal RNA content could be correlated to an excess accumulation of neurofibrillary tangles.

Menetrier's disease in a rhesus monkey (Macaca mulatta)

Gross and microscopic features closely resembling those found in Menetrier's disease in man are described in a 20-month-old rhesus monkey. The gastric lining was characterized by greatly enlarged rugae caused by mucosal hypertrophy and hyperplasia along with outfolding of the muscularis mucosa and the submucosa. The mucosa and submucosa were infiltrated with inflammatory cells, mainly lymphocytes and plasma cells.

Strongyloidiasis in an infant orangutan (Pongo pygmaeus)

Necropsy of a 15-month-old male orangutan (Pongo pygmaeus) showed multiple nodular elevations of the mucosa of the colon, petechial hemorrhages in both lungs, and mucosal ulcerations in the cecum, appendix, and proximal colon. Light microscopy revealed filariform larvae of Strongyloides in the lung, colon, and mesenteric lymph nodes. Rhabditiform larvae were also observed in sections of colon.

RNA content and volume of nerve cell bodies in human brain. I. Prefrontal cortex in aging normal and demented patients

The age-related change in the neuronal RNA content, volume, and the RNA concentration of 2,160 single cell bodies was examined from the prefrontal cortex. Human brains from 15 normal and 3 demented patients of ages ranging from 8 months to 94 years were obtained at post-mortem examination. The neuronal RNA showed an adult level at age 9 years and remained unchanged until age 66; the mean RNA content was 27.15 pg during this period of time. A decline in the RNA content followed with increasing ages, but it leveled off to an average of 17.97 pg after the age of 80 years. A comparative observation of morphological changes of normal and demented patients reveal the quantitative spectrum of senile plaques. In spite of the presence of significantly more senile plaques, patients with senile dementia showed the RNA content and the volume of the cell body like those of normal patients of similar age. There seems to be no criterion which is characteristic of senile dementia in terms of the RNA content in cortical cell bodies.

Distribution of lumbar and sacral afferent axons in submucosa of cat urinary bladder

Lumbar and sacral afferent axons in the submucosa of the urinary bladder were recognized by degeneration in seven cats subjected to spinal ganglionectomies. Of 2,935 observed terminating axon profiles, 145 were found degenerating. Lumber afferent axons were 3.7 times more numerous than sacral afferent axons in the submucosa, a reversal of the ratio reported for the muscle coat of the bladder. Sacral afferent axons were evenly distributed to different regions of the bladder, but lumbar afferents were concentrated in the bladder neck. Apparent afferent endings in the submucosa of the urinary bladder were principally free nerve endings. Synaptic vesicles were found in 57% of observed terminating axon profiles. The bladder neck had more terminating axon profiles of all kinds than other regions of the urinary bladder.