Interaction between alpha- and beta-adrenergic receptor agonists modulating the slow Ca(2+)-activated K+ current IAHP in hippocampal neurons

Noradrenaline inhibits the Ca(2+)-activated K+ current IAHP, which underlies the slow afterhyperpolarization and spike frequency adaptation in hippocampal and neocortical neurons. The resulting increase in excitability probably contributes to the state control of the forebrain during arousal and attention. The modulation of IAHP by noradrenaline has previously been shown to be mediated by beta 1 receptors, cyclic AMP and protein kinase A, but not by alpha receptors. We have now tested the possibility that alpha receptors also contribute to IAHP modulation through interaction with beta receptors, by the use of whole-cell recordings in CA1 pyramidal cells of rat hippocampal slices. The alpha-receptor agonist 6-fluoro-noradrenaline strongly potentiated the effect of isoproterenol on IAHP. The synergistic effect of 6-fluoro-noradrenaline and isoproterenol was blocked by the beta-receptor antagonist timolol, but the receptor type mediating the effect of 6-fluoro-noradrenaline could not be unequivocally identified by using alpha-receptor antagonists. The effect of high concentrations of noradrenaline on IAHP was only partly blocked by the beta-receptor antagonist timolol, and was further reduced by blocking alpha receptors, again suggesting a contribution from alpha receptors. In contrast, the effect of low concentrations of noradrenaline seemed to be potentiated by the alpha-receptor antagonist phentolamine in 57% of the cells, suggesting concentration-dependent antagonistic interaction between alpha and beta receptors. Further tests indicated that the cross-talk between 6-fluoro-noradrenaline and isoproterenol occurs upstream from cyclic AMP production, and that protein kinase A serves as a final common path for the modulation of IAHP by noradrenaline, and by the combination of 6-fluoro-noradrenaline and isoproterenol.     

An anatomo-clinical case of dementia in endovascular large-cell lymphoma

Cerebral angiotropic large cell lymphoma is a rare fatal neurologic disorder characterized by multifocal intravascular proliferation of large pleomorphic cells within vessels of all caliber, predominantly skin and nervous system. Clinical manifestations in previously reported cases were dominated by focal neurologic signs, epilepsia and progressive dementia. We report a case of a 70 year-old man with subacute dementia, epileptic seizures and cerebrovascular events. There was no evidence of a systemic disease outside the nervous system. Cerebrospinal fluid contained 13 leukocytes/mm3 (49% of lymphocytic cells) and more than 100 mg/dl of protein. Cytology was negative. Cranial MRI demonstrated cerebral atrophy and an increased paraventricular signal in T 2 weighted images. A frontal brain biopsy revealed only neuronal dystrophy and astrocytic gliosis. Despite treatment with corticosteroids the patient died 18 months after the onset of the first symptoms. Autopsy was performed and revealed B cell lymphoma.     

Unilateral injury of posterior parietal cortex and spatial learning in hooded rats

The influences of bilateral or unilateral injuries within the posterior parietal cortex (PPC) upon spatial learning in a water maze were examined in three experiments. Place-learning and response-learning were investigated in a four-alley 'Greek-cross' shaped water maze with extra-maze visual cues available. No differences were detected on any of several measures sensitive to learning between the lesion groups on the place-learning task. Microanalysis of behavior within trials revealed that animals with either bilateral or right unilateral PPC injuries committed significantly more total errors, initial alley entrance ('reference memory') errors, and re-entry ('working memory') errors in the response-learning paradigm than did either the control or left PPC-injured rats. No differences were detected between the latter two groups on these measures. Unilateral lesions resulted in asymmetrical placing responses ipsilateral to the injury 10 days after surgery whereas bilateral injuries resulted in asymmetrical placing with mixed directionality. The acquisition of the response-learning problem in the absence of visual cues was studied on animals prepared with unilateral lesions and housed post-operatively either in isolation or in a 'complex environment.' In the absence of visual cues both right and left PPC-injured rats committed more errors than sham controls, and differential post-surgical housing did not attenuate these impairments. These same animals were trained on the landmark navigation task. Although no differences appeared between the lesion groups, a generalized but transient facilitation of learning was observed in animals housed in the 'complex' environment. Unilateral injuries placed in sham controls failed to disturb retention of the landmark navigation strategy. Because none of the PPC-injured animals were deficient in the landmark task, a result which is contrary to observations in other laboratories, the influence of post-surgical recovery interval upon acquisition of the landmark navigation strategy was explored. Animals were prepared with right PPC injuries and trained following either a 5 or 35 day recovery interval. Only those animals limited to the short recovery interval proved to have a spatial deficit in the landmark task. It is concluded that injuries in the PPC of either hemisphere disturb egocentric spatial functions. However, animals with left PPC injuries are able to compensate by using allocentric visual cues if they are available. It is due to the special role played by the right PPC in complex visuospatial functions that animals with this injury are unable to compensate.     

Efficacy of sonographically guided biopsy of thyroid masses and cervical lymph nodes

OBJECTIVE: We performed a prospective study in 96 patients to determine accuracy of sonographically guided fine-needle aspiration biopsy of thyroid masses and cervical lymph nodes. MATERIALS AND METHODS: Real-time sonography was used to guide biopsy of 112 cervical masses in 96 patients (71 patients with impalpable masses, 16 with failed unguided attempts, patient's or physician's preference in nine). The diameters of all masses were less than 3 cm, with a mean of 1.5 cm and a median of 1.5 cm. Twenty-nine masses measured 1 cm or less in diameter, 60 masses between 1.1 and 2.0 cm, and 23 masses between 2.1 and 3.0 cm. Cervical masses that were sampled by biopsy included 75 thyroid masses and 37 lymph nodes. RESULTS: Diagnostic specimens were obtained in 102 (91%) of 112 masses sampled. Sixty-eight (91%) of 75 biopsies of thyroid tissue and 34 (92%) of 37 biopsies of lymph nodes were diagnostic. Nondiagnostic thyroid biopsies included four of complex cysts and three of solid nodules. Sonographic follow-up (1 year) revealed no change or decrease in size of those seven lesions. Sixty of 68 diagnostic thyroid biopsies showed benign processes: 42 macrofollicular adenomas, six colloid adenomas, five microfollicular adenomas, four probable cases of thyroiditis, and three hemorrhagic cysts. The remaining eight diagnostic thyroid biopsies showed malignant processes: seven papillary carcinomas and one metastatic small-cell carcinoma. Of 34 diagnostic biopsies of lymph nodes, 26 showed malignant processes and eight showed benign processes. Surgery in the three patients with nondiagnostic biopsies of lymph nodes revealed two recurrent medullary cancers and one benign node. CONCLUSION: Sonographically guided fine-needle aspiration biopsy of neck masses has a high sensitivity (91%) and should be routinely used to evaluate indeterminate masses in the neck.     

An improved approach to delivery of enteral nutrition in the intensive care unit

Using immunohistochemistry, vasoactive intestinal peptide (VIP) was visualized in taste bud cells of the carp, Cyprinus carpio, and the European catfish, Silurus glanis, by means of light and electron microscopy. Intracellular membrane systems, presumably smooth endoplasmic reticulum, of light (sensory) cells, but not of dark (supporting) cells and basal cells, were densely labelled with antibody. In the frog (four species: Rana temporaria, R. ridibunda, R. arvalis, R. pipiens), taste bud cells did not label. However, the dense basal nerve fibre plexus, some subepithelial ganglionic cells, but no ascending intragemmal fibres, were immunoreactive. In fish, the results support evidence that VIP is involved in the modulation of taste transduction at the level of receptor cells. In the frog, an indirect, possibly vasodilatatory effect on taste perception may be considered.     

Ovarian cysts. Diagnostic and therapeutic aspects

The methods used to carry out exeresis of ovarian cysts by celioscopy are now familiar. Today, the main concern is the selection of annexial tumors appropriate for celiosurgical treatment in order to limit their use to benign organic cysts only. By comparing the results of a sery of 200 cysts which were treated surgically with cases in the literature, the authors conclude that the three-pronged use of clinical, ultrasound and macroscopic data in the diagnosis of malignant tumors is reliable. Progress remains to be made however in identifying functional cysts which are sometimes mistaken for an organic structure and all too often are still dealt with surgically. In order to reduce the incidence of such errors, new perspectives are envisaged, knowing that diagnostic error is often related to change in their ultrasound structure or their persistence despite conventional estro-progestogen treatment.     

Catecholaminergic neurons result from intracerebral implantation of embryonal carcinoma cells

A replication-defective retrovirus was used to introduce the marker gene nlsLacZ into the murine embryonal carcinoma (EC) cell line PCC7-S-aza-R-1009. Undifferentiated EC cells were implanted into the central nervous system of adult rats. One month later, the grafted cells continued to express the nlsLacZ gene. Immunohistochemical analysis demonstrated the presence of EC-derived neurons. These neurons were capable of expressing tyrosine hydroxylase and extended neurites into the host parenchyma. EC-derived glial cells could not be detected. There was no evidence of tumorigenicity. These results demonstrate the utility of EC cells for introduction of exogenous gene products into the central nervous system in experimental models of gene therapy.