Effect of traumatic brain injury on mouse spatial and nonspatial learning in the Barnes circular maze

In order to evaluate the functional role of chemotactic cytokines in the regulation of brain function, we examined the effects of acidosis on the production of IL-8 in cultured neurons and/or astrocyte-rich cerebellar granule cells as assessed by the ELISA method. A time-dependent and significant production of IL-8 was detected in the extracellular fluid of astrocyte-rich cultured cells at 2, 3 and 6 hrs after treatment with acidified Krebs-HEPES buffer (pH 6.9), although such production did not appear in the fluid of neuron-rich cells. Additionally, microglia were detected by microscopic examination in both cultured cells under acidotic conditions. Only astrocyte-containing cultured cells produced a marked increase in intracellular IL-8 under acidotic conditions, although this production was much less than that seen in the extracellular fluid at 6 hrs under acidosis. The increase of IL-8 in astrocyte-rich cultures induced by acidosis was potentiated by treatment with glutamate, which enhanced the increase of cytosolic Ca2+ levels under acidosis, and was affected by extracellular Ca2+ conditions, by cyclosporine A, an inhibitor of calcineurin, and by trifluoperazine, an inhibitor of phospholipase A2. Significant inhibition of IL-8 production was detected after 6 hrs of pretreatment with trifluoperazine. Furthermore, the production of IL-8 under acidosis was associated with the appearance of astrocyte damage. These results suggest that Ca2+-dependent IL-8 is produced by astrocytes, but not neuronal cells, under acidosis, and that this production may be related to the process of cell dysfunction resulting from membrane destruction induced by acidosis.     

Hypothalamic dopamine D1 receptors are involved in the stimulation of prolactin secretion by high environmental temperature in the female sheep

Recent evidence suggests that dopamine, acting via its D1 receptors, may function as a neurotransmitter in intrahypothalamic pathways involved in the stimulation of prolactin secretion. Functional dopamine D1 receptors are present in the ventromedial hypothalamic nucleus (VMH) and we hypothesized that they might be part of a prolactin-stimulatory pathway activated by stress. We tested this hypothesis in a series of experiments on sheep involving two different forms of stressors, audiovisual (barking dog) and high environmental temperature. We attempted to block the stimulation of prolactin secretion by infusion into the VMH of an antagonist specific for the D1 receptor. Ovariectomised, oestradiol-implanted merino ewes were surgically implanted with bilateral guide tubes directed at the VMH. After a 180 min pretreatment period, the ewes either were or were not exposed to a stressor (30 min of barking dog or 120 min at 35 degrees C, 65% relative humidity). D1 receptor antagonist, SCH23390 or vehicle (0.9% saline) was infused into the VMH (1.7 microliters/h, 120 nmol/h) for 60 min prior to and during the stressor period. Blood was sampled every 15 min via jugular cannulae and the plasma was assayed for prolactin, cortisol and growth hormone (GH). Both stressors significantly increased prolactin concentrations over control levels. SCH23390 infusion significantly attenuated the prolactin response to high environmental temperature, but had no effect on the prolactin response to audiovisual stress. Cortisol concentrations were significantly increased by audiovisual stress only and were not affected by SCH23390. GH concentrations were not changed by either stressor or infusion. Drug infusion alone did not affect the concentration of the hormones. The data suggest that the VMH D1 receptors are involved in a prolactin stimulatory pathway in response to high environmental temperature. The inability of the D1 antagonist to affect the response to the barking dog indicates that this pathway is stress-specific, implying that there is more than one mechanism or pathway involved in the prolactin response to different stressors.     

Mechanism of action of beta-bungarotoxin, a presynaptically acting phospholipase A2 neurotoxin: its effect on protein phosphorylation in rat brain synaptosomes

The snake venom phospholipase A2 neurotoxin, beta-bungarotoxin, acts presynaptically to alter acetylcholine release in both the peripheral and central nervous systems. In investigating the mechanism of this action, we found that beta-bungarotoxin inhibited phosphorylation of synapsin I, GAP-43 and MARCKS in rat brain synaptosomes. This inhibition was not due to the inhibition of ATP synthesis, action of arachidonic acid metabolites, or stimulation of phosphatase activities. Furthermore, the activities of Ca2+/calmodulin-kinase II, cAMP-kinase and protein kinase C were not altered by beta-bungarotoxin in either synaptic plasma membranes or cytosol. When synaptic plasma membranes were treated with beta-bungarotoxin, MARCKS phosphorylation was inhibited, and this inhibition was overcome by the addition of exogenous protein kinase C. These results suggest that the interaction between MARCKS and endogenous protein kinase C is altered by beta-bungarotoxin. In contrast, Naja naja atra phospholipase A2, a typical phospholipase A2 enzyme, had effects on phosphorylation which were different from those of beta-bungarotoxin: (1) inhibition of phosphorylation of synapsin I in intact synaptosomes was less potent than that by beta-bungarotoxin; (2) it stimulated basal phosphorylation of GAP-43 and MARCKS; and (3) it increased the activity of protein kinase C. The inhibition of synapsin I phosphorylation by N. n. atra phospholipase A2 in intact synaptosomes may be due to the inhibition of ATP synthesis. The stimulation of GAP-43 and MARCKS by N. n. atra phospholipase A2 can be explained by the production of arachidonic acid, which stimulated protein kinase C activity to a similar extent as that caused by N. n. atra phospholipase A2. Thus, the mechanism of action of beta-bungarotoxin appears to be quite different from that of a phospholipase A2 enzyme, suggesting that phospholipase A2 activity of beta-bungarotoxin may not be essential for its action. beta-Bungarotoxin may be a useful tool to study the physiological role of phosphorylation of synaptosomal proteins in neurotransmitter release.     

Suprasellar osteolipoma: case report

BACKGROUND: Osteolipomas are distinguished from other intracranial lipomas by their arrangement of central adipose and peripheral osseous tissues and by characteristically arising in the suprasellar/interpeduncular region. METHODS: We report computed tomography (CT), magnetic resonance imaging (MRI), and pathology findings from this 34-year-old man who underwent surgical removal of this benign lesion. RESULTS: This case displays the distinctive histopathology that has been reported in 13 of 31 (42%) lipomas in this region. In contrast, ossification of lipomas at other intracranial sites is relatively rare. CONCLUSIONS: Ossification should be expected in many suprasellar/interpeduncular lipomas, and osteolipoma should be included in the radiologic differential diagnosis of fat-intensity masses with calcification in this region.     

Multiplexing and double band filtering with common-multimodecavities

A novel multiplexing and double band filtering (DBF) method is established. DBF refers to two-port equipment which serves two transmit frequency channels simultaneously. The methods build on frequency-independent resonance modes, excited within a common multimode cavity (CMC), which are assigned to different channel filters. The design principles are presented for cylindrical CMCs by way of example. It is shown that combining CMCs with advanced coupling methods produces a multitude of new design variants. Initial experimental results are presented for a diplexer and DBF equipment that are both realized with only two double-dual TE₁₁₂/TM₁₁₀ CMCs and a novel iris-providing four intercavity couplings-to perform two four-pole elliptic function filter responses     

Inline TM/sub 110/-mode filters with high-design flexibility by utilizing bypass couplings of nonresonating TE/sub 10/01/ modes

This paper presents a new class of pseudoelliptic function filters that are based on compact inline TM/sub 110/-mode cavity configurations. No structural folding is required. The bypass couplings are implemented through the nonresonating TE/sub 10/01/ modes so that arbitrarily positioned transmission zeros can be implemented. Design guidelines to generate a given transmission zero on the desired side of the passband and how to control it are presented. To demonstrate its flexibility, the approach is illustrated at examples of four-pole inline filters providing Chebyshev, elliptic-function-type, and asymmetric characteristics. Performance comparisons with different numerical codes validate the designs. A fourth-order pseudoelliptic filter with four transmission zeros is then designed, constructed, and measured. Excellent agreement between simulated and experimental results verifies the approach.     

Effect of nitrogen dioxide and other combustion products on asthmatic subjects in a home-like environment

Nitrogen dioxide (NO2) is one of a number of nitrogen compounds that are by-products of combustion and occur in domestic environments following the use of gas or other fuels for heating and cooking. In this study, we examined the effect of two levels of NO2 on symptoms, lung function and airway hyperresponsiveness (AHR) in asthmatic adults and children. In addition, in the same subjects, we examined the effects of the same levels of NO2 mixed with combustion by-products from a gas space heater. The subjects were nine adults, aged 19-65 yrs, and 11 children, aged 7-15 yrs, with diagnosed asthma which was severe enough to require daily medication. All subjects had demonstrable AHR to histamine. Exposures were for 1 h on five separate occasions, 1 week apart, to: 1) ambient air, drawn from outside the building; 2) 0.3 parts per million (ppm) NO2 in ambient air; 3) 0.6 ppm NO2 in ambient air; 4) ambient air+combustion by-products+NO2 to give a total of 0.3 ppm; and 5) ambient air+combustion by-products+NO2 to give a total of 0.6 ppm. Effects were measured as changes in lung function and symptoms during and 1 h after exposure, in AHR 1 h and 1 week after exposure, and in lung function and symptoms during the week following exposure. Exposure to NO2 either in ambient air or mixed with combustion by-products from a gas heater, had no significant effect on symptoms or lung function in adults or in children. There was a small, but statistically significant, increase in AHR after exposure to 0.6 ppm NO2 in ambient air. However, there was no effect of 0.6 ppm NO2 on AHR when the combustion by-products were included in the test atmosphere nor of 0.3 ppm NO2 under either exposure condition. We conclude that a 1 h exposure to 0.3 or 0.6 ppm NO2 has no clinically important effect on the airways of asthmatic adults or children, but that 0.6 ppm may cause a slight increase in airway hyperresponsiveness.