Passive avoidance training and recall are associated with increased glutamate levels in the intermediate medial hyperstriatum ventrale of the day-old chick

In the young chick, the intermediate medial hyperstriatum ventrale is involved in learning paradigms, including imprinting and passive avoidance learning. Biochemical changes in the intermediate medial hyperstriatum ventrale following learning include an up-regulation of amino-acid transmitter levels and receptor activity. To follow the changes of extracellular amino acid levels during passive avoidance training, we used an in vivo microdialysis technique. Probes were implanted in chicks before training the animals, either on a methylanthranylate- or water-coated bead. One hour later, recall was tested in both groups by presenting a similar bead. An increase of extracellular glutamate levels accompanied training and testing in both groups; during training, glutamate release was higher in methylanthranylate-trained than in water-trained chicks. When compared with the methylanthranylate-trained chicks during testing, the water-trained chicks showed enhanced extra-cellular glutamate levels. No other amino acid examined showed significant changes. After testing, the chicks were anesthetized and release-stimulated with an infusion of 50 mM potassium. Extracellular glutamate and taurine levels were significantly increased in both methylanthranylate- and water-trained chicks. The presentation of methylanthranylate as an olfactory stimulus significantly enhanced glutamate levels, especially in methylanthranylate-trained chicks. The results suggest that such changes in extracellular glutamate levels in the intermediate medial hyperstriatum ventrale accompany pecking at either the water- or the methylanthranylate-bead. The taste of the aversant may be responsible for the greater increases found in methylanthranylate-trained birds.     

Extended durability of external metal mirror reflector of side-firing Nd:YAG laser fiber used for prostatic ablation

The effect on Pseudomonas aeruginosa virulence factors (elastase and proteinase) after short-time treatment (30 min) with suprainhibitory (2x or 4x MIC) as well as with supra-subinhibitory concentrations (2x MIC + sub-MICs or 4x MIC + sub-MICs) of pefloxacin was studied. An effective decrease of elastase activity (to 42.6% of the control value) was observed only after higher suprainhibitory antibiotic concentration. More significant depression of the activities tested was found after the postantibiotic effect of subinhibitory concentrations. Elastase as well as proteinase activity were suppressed by supra-subinhibitory concentration of 4x MIC + 0.1x MIC to 13.1% or 37.9%, as compared to controls.     

Endothelin induces dopamine release from rat striatum via endothelin-B receptors

The aim of the present study was to determine whether local administration of endothelin induces the release of dopamine in the rat striatum and to characterize and localize endothelin receptors in this brain region. Local injection of endothelin-1 (10 pmol) into the ventral striatum of urethane-anaesthetized rats caused an increase of 8 microM in the extracellular concentration of dopamine as measured by in vivo chronoamperometry. The peak increase in dopamine concentration occurred within 5 min of endothelin injection. Injection of the selective endothelin-B receptor agonist [Ala1.3,11.15]endothelin-1 (10 pmol) also caused an increase in extracellular dopamine concentration, suggesting that endothelin is acting at the endothelin-B receptor to elicit its effect. In rats with unilateral 6-hydroxydopamine lesions of the nigrostriatal pathway, the response to local injection of endothelin-1 (10 pmol) was significantly inhibited on the lesioned side as compared to the non-lesioned side. In contrast, pretreatment of the rats with the N-methyl-D-aspartate receptor antagonist dizocilpine maleate (5 mg/kg, i.p.) or the nitric oxide synthase inhibitor NG-nitro-L-arginine (3 mg/kg, i.p.) did not alter the endothelin-induced release of dopamine. In binding studies, addition of endothelin-1 displaced [125I]endothelin-1 with a Ki of 220 pM. The endothelin-B receptor antagonist BQ788 displaced [125I]endothelin-1 with a Ki of 120 nM, whereas the endothelin-A receptor antagonist BQ123 produced only a 25% displacement at 10 microM, suggesting that endothelin receptors in the striatum are of the endothelin-B subtype. In rats with unilateral 6-hydroxydopamine lesions of the nigrostriatal dopamine system, [125I]endothelin-1 binding was reduced by 53% in lesioned striatum compared to non-lesioned striatum, with no difference in the Kd. These data provide evidence that endothelin acts on a homogeneous population of endothelin-B receptors within the striatum to cause the release of dopamine and that a significant proportion of these receptors is located on dopaminergic neurons.     

Pneumococcal trafficking across the blood-brain barrier. Molecular analysis of a novel bidirectional pathway

Although Streptococcus pneumoniae is a major cause of meningitis in humans, the mechanisms underlying its traversal from the circulation across the blood-brain barrier (BBB) into the subarachnoid space are poorly understood. One mechanism might involve transcytosis through microvascular endothelial cells. In this study we investigated the ability of pneumococci to invade and transmigrate through monolayers of rat and human brain microvascular endothelial cells (BMEC). Significant variability was found in the invasive capacity of clinical isolates. Phase variation to the transparent phenotype increased invasion as much as 6-fold and loss of capsule approximately 200-fold. Invasion of transparent pneumococci required choline in the pneumococcal cell wall, and invasion was partially inhibited by antagonists of the platelet-activating factor (PAF) receptor on the BMEC. Pneumococci that gained access to an intracellular vesicle from the apical side of the monolayer subsequently were subject to three fates. Most opaque variants were killed. In contrast, the transparent phase variants were able to transcytose to the basal surface of rat and human BMEC in a manner dependent on the PAF receptor and the presence of pneumococcal choline-binding protein A. The remaining transparent bacteria entering the cell underwent a previously unrecognized recycling to the apical surface. Transcytosis eventually becomes a dominating process accounting for up to 80% of intracellular bacteria. Our data suggest that interaction of pneumococci with the PAF receptor results in sorting so as to transcytose bacteria across the cell while non-PAF receptor entry shunts bacteria for exit and reentry on the apical surface in a novel recycling pathway.     

Contrast-enhanced gradient-echo MR imaging of the head and neck: experimental and clinical assessment

To clarify the enhancement pattern of gradient-echo (GE) MR imaging, phantom experiments and 24 clinical examinations of the head and neck region were performed. Both long repetition time (TR) GE and short TR GE pulse sequences demonstrated an enhancement pattern similar to T1-weighted spin-echo imaging in phantom experiments, although the signal intensity of water and gadopentetate dimeglumine (Gd) solution was higher and the signal intensity of fat was lower with the GE technique. In clinical examinations, contrast-enhanced GE imaging was beneficial for tumors within fatty tissue, and for tumors with calcification or other magnetic susceptibility difference.     

Systematic ultrasonography in asymptomatic dense breasts

Case report of a 64-year-old woman with increasing dyspnea and cough. She cared at home for 8 parakeets (Melopsittacus undulatus). Subsequent studies revealed a restrictive pulmonary defect and transbronchial biopsy, a histological bronchiolitis obliterans (BO). No significant elevated anti-avian IgG could be detected, probably because of a transient hypogammaglobulinaemia. The implication of antigenic exposure to avian antigens in the pathogenesis of BO is discussed.     

Immunological characterization of Asp f 2, a major allergen from Aspergillus fumigatus associated with allergic bronchopulmonary aspergillosis

The 37-kDa recombinant protein Asp f 2, encoding an allergen of Aspergillus fumigatus, was expressed in a prokaryotic expression system and immunologically evaluated for its functional and structural properties. The open reading frame for a 310-amino-acid-long protein was shown to encode a signal peptide of 31 amino acids. A native 37-kDa culture filtrate protein and a 55-kDa mycelial glycoprotein (gp55) exhibited complete N-terminal sequence homology to Asp f 2. A GenBank search for homologous proteins revealed 60 and 44% sequence homologies to the cytosolic protein ASPND1 from Aspergillus nidulans and fibrinogen binding protein from Candida albicans, respectively. The glycosylation sites and cysteine molecules are conserved in all the three proteins. The extracellular matrix protein laminin showed a dose-dependent interaction with Asp f 2. This protein, expressed as a major cell-associated protein within 24 h of in vitro fungal culture, comprises 20 to 40% of total fungal protein. Furthermore, both native and recombinant Asp f 2 exhibited specific immunoglobulin (IgE) binding with allergic bronchopulmonary aspergillosis (ABPA) and cystic fibrosis-ABPA patients, whereas A. fumigatus-sensitized allergic asthma and normal control subjects failed to show IgE binding with Asp f 2. These results indicate that Asp f 2 is a major allergen of A. fumigatus exhibiting IgE antibody binding with sera from patients with ABPA. The antigen should be explored further for its potential role in the differential diagnosis of A. fumigatus-associated allergic diseases.