Commissurally projecting inhibitory interneurons of the rat hippocampal dentate gyrus: a colocalization study of neuronal markers and the retrograde tracer Fluoro-gold.

Improved methods for detecting neuronal markers and the retrograde tracer Fluoro-Gold (FG) were used to identify commissurally projecting neurons of the rat hippocampus. In addition to the dentate hilar mossy cells and CA3 pyramidal cells shown previously to transport retrograde tracers after injection into the dorsal hippocampus, FG-positive interneurons of the dentate granule cell layer and hilus were detected in numbers greater than previously reported. FG labeling of interneurons was variable among animals, but was as high as 96% of hilar somatostatin-positive interneurons, 84% of parvalbumin-positive cells of the granule cell layer and hilus combined, and 33% of hilar calretinin-positive cells. By comparison, interneurons of the dentate molecular layer and all hippocampal subregions were conspicuously FG-negative. Whereas hilar mossy cells and CA3 pyramidal cells were FG-labeled throughout the longitudinal axis, FG-positive interneurons exhibited a relatively homotopic distribution. "Control" injections of FG into the neocortex, septum, and ventral hippocampus demonstrated that the homotopic labeling of dentate interneurons was injection site-specific, and that the CA1-CA3 interneurons unlabeled by contralateral hippocampal FG injection were nonetheless able to transport FG from the septum. These data suggest a hippocampal organizing principle according to which virtually all commissurally projecting hippocampal neurons share the property of being monosynaptic targets of dentate granule cells. Because granule cells innervate their exclusively ipsilateral target cells in a highly lamellar pattern, these results suggest that focal granule cell excitation may result in commissural inhibition of the corresponding "twin" granule cell lamella, thereby lateralizing and amplifying the influence of the initiating discharge.

Short-term antibiotic prophylaxis for the prevention of wound infection and secondary meningitis in acoustic neuroma surgery: a ten-year experience in a regional hospital.

Wound infection and secondary meningitis are important complications for patients undergoing acoustic neuroma surgery. The Authors retrospectively evaluated the efficacy of a short-term protocol utilizing vancomycin and netilmicin. 434 patients underwent acoustic neuroma surgery in the Otorhinolaryngology Division, A.O. Ospedali Riuniti di Bergamo, from February 1987 to February 1997. Perioperative short-term prophylaxis was administered with vancomycin plus netilmicin. The utility of the prophylaxis schedule was evaluated on the basis of the occurrence of infectious episodes during the first 10-day follow-up. Only 2 episodes (0.5%) of bacterial meningitis were observed.

Meta-[123I]iodobenzylguanidine single photon emission computed tomography in chemodectomas.

Chemodectoma is a rare, slow growing neoplasm with local aggressiveness and a high rate of residuals after surgery, arising from paraganglionic tissue (neural crest) and therefore able to take up Metaiodobenzylguanidine (MIBG). The aim of this study was to evaluate the diagnostic accuracy of 123I-MIBG Single Photon Emission Computed Tomography (SPECT) in comparison to Selective Digital Angiography (SDA), Computed Tomography (CT) and Magnetic Resonance Imaging (MRI). We studied 50 patients (41 women, 9 men) mean age 56 years (range 14-79), with diagnostic suspicion of chemodectoma (CH). There were 2 groups of patients: Group A (26 patients) examined before Surgery and Group B (24 patients) examined after surgery. SPECT of the head and neck region was performed 4 hours after i.v. administration of 185 MBq of 123I-MIBG. All patients were pre-treated with iodine solution. We performed a qualitative evaluation of the reconstructed slices. In Group A, all patients with CH (24) showed accumulation of MIBG in agreement with SDA, CT and MRI: 2 patients (histologically one had a cordoma, the other metastasis of papillary thyroid carcinoma), did not show any accumulation of 123I-MIBG. In Group B, 6 patients showed accumulation of 123I-MIBG in local residuals, and 9 were negative. Six patients with a lesion smaller than 1.5 cm were negative. Three patients had a positive scan but no lesion on SDA, CT and MRI. 123I-MIBG SPECT proved to be useful procedure in the diagnosis of untreated CH. During follow-up after surgery this procedure may assume a role in the perspective of radiometabolic therapy with 131I-MIBG.

Ciliary ultrastructure and nasal mucociliary clearance in chronic and allergic rhinitis.

The authors have studied nasal specimens collected by means of nasal brushing in eight patients affected by allergic rhinitis and in eight affected by chronic rhinitis, while in other four patients affected by allergic rhinitis a lower turbinate biopsy was performed. All twenty patients showed an increased mucociliary clearance time and a reduced velocity regardless to the pathology during a previously performed saccharin test. Different ultrastructural alterations have been observed, such as: both central and peripheral microtubules alterations; absence of dynein arms; absence of radial spokes; ciliary membrane alterations; "compound" cilia; disorientation of central tubules. These alterations have been observed variously associated in both allergic and chronic rhinitis patients groups. Basing on their data, the authors state that ciliary abnormalities cannot be considered specific of a particular pathology but they can coexist in different situations. They also think that the mucociliary clearance parameters determination represents the only method to evaluate, even if in an indirect fashion, the percentage of ciliary abnormalities, as no direct quantitative method has been described. Ciliary ultrastructural alterations can be of diagnostic value only if associated with mucociliary clearance time and velocity determination.

Adenoid hypertrophy and nasal mucociliary clearance in children. A morphological and functional study.

The authors have studied nasal mucociliary function and adenoid surface characteristics in a group of 86 children, aged between 4 and 10 years, divided in two groups according to the presence or absence of clinical, instrumental and röntgenographic signs of nasal obstruction due to hypertrophied adenoids. Each group was divided into 3 age-related subgroups (group I: 4-5 years; group II: 6-7 years; group III: 8-10 years). A population of normal adults was chosen both for functional and ultrastructural characteristics. Nasal mucociliary clearance velocity values were evaluated by means of the saccharine method and the surface characteristics of the adenoid tissue by means of scanning electron microscopy. The data obtained show that the nasal mucociliary function is generally reduced in children but, while in the group with poorly developed adenoids an early and progressive improvement can be observed, the children with severely hypertrophied adenoids show an impaired function up to 10 years, without age-related improvements. At almost 10 years, children with poorly developed adenoids reach normal adult clearance values. These functional data can be related to the surface characteristics of adenoid tissue. In fact, while poorly developed adenoids are characterized by a compact layer of ciliated cells, severely hypertrophied adenoids are characterized by a metaplasic epithelium, with almost complete loss of cilia. Such findings, which are probably due to the inflammatory events frequently complicating adenoid hypertrophy, could explain, together with the obstructive effects, the impairment of the nasal mucociliary clearance in childhood.