A bilateral model integrating vergence and the vestibulo-ocular reflex

The majority of previous modelling studies of vergence and the vestibulo-ocular reflex (VOR) have postulated arbitrary structures mainly on the basis of input-output behavioural relationships. Such models were developed following traditional schemes of oculomotor organization, based upon the notion of independence between different oculomotor subsystems. This impedes the simulation of complex binocular interactions and associated central activities. In contrast to preceding studies, the mathematical model for binocular control presented here was developed fully on physiological and anatomical grounds which reflect the organization and functional properties of known vergence and VOR premotor centres. Computer simulations show the model properly simulates the mainobserved characteristics in the discharge of several premotor and motor nuclei during slow vergence and the VOR in the dark. In particular, the model reproduces the activity profiles of abducens internuclear neurons, secondary vestibular cells, tonic prepositus hypoglossi neurons and ocular motoneurons during vergence and the VOR. It also simulates the activity of mesencephalic neurons whose discharge is modulated by vergence parameters alone. It is shown that given recent neurophysiological and behavioural findings, ocular reflexes cannot be properly modelled as separate independent subsystems whereas a single, unified modelling approach can produce results consistent with observed data. This study also shows how changes in the functional activity of shared pathways in a single two-sided structure produce vergence and conjugate integrators whose function relies on coupled loops across the brainstem: separate, dedicated operators are not necessary to replicate data. This provides evidence that challenges previous studies supporting the existence of separate vergence and conjugate integrators to transform velocity to position signals in the brainstem. A major implication of this study is that it questions the validity of testing conjugate and vergence systems independently, neglecting potential interactions.     

Contribution of magnetic resonance cholangiopancreatography to the diagnosis of biliary tract disease

The aim of the study was to assess the role of magnetic resonance cholangiopan-creatography (MRCP) in the diagnosis of biliary tract and pancreatic duct diseases, also in relation to the data reported in the literature. Over the period from Februrary 2002 to July 2004, 252 consecutive patients, with a clinical or instrumental suspicion of biliary disease were submitted to magnetic resonance to investigate the biliary tract. The definitive diagnosis of disease was obtained by surgery and/or endoscopic retrtograde cholangiopancreatography (ERCP) in patients with clinical or diagnostic evidence of disease and by means of follow-up in the remaining cases. MRCP, combined with T2-weighted FSE sequence on the axial plane yielded positive findings in 191/252 patients (75.79%); in 75/191 (39.26%) either ERCP was indispensable (n = 33) or surgery proved necessary (n = 42). MRCP and surgical sample findings proved discordant in 3/42 cases operated on (7.14%); MRCP and ERCP yielded discordant findings in 11/33 cases (33.33%) submitted to ERCP. With the exception of the limitations associated with the difficulty in obtaining dynamic information relating to functional diseases of Oddi's sphincter, for which, moreover, a progressive tecnological updating is underway, MRCP is the diagnostic reference procedure in biliopancreatic disease, reserving a therapeutic role for ERCP.     

Prolonged lymphocyte depletion by single-dose rabbit anti-thymocyte globulin and alemtuzumab in kidney transplantation

Although antibody induction has gained in popularity, two agents are rarely combined. We retrospectively analyzed peripheral lymphocyte phenotypes of renal transplant recipients who received induction therapy with a different antibody/combination: alemtuzumab(C1H), Thymoglobulin(rATG), daclizumab(Dac), rATG+C1H, and rATG+Dac. CD4+ T-cells were suppressed by C1H and rATG+C1H, as well as by rATG and rATG+Dac but to a lesser extent. The effect lasted for 3 years at around 40% of baseline values. CD8+ T-cells showed a similar trend but had a more rapid recovery to baseline. CD19+ B-cells were effectively suppressed for 2 months by C1H and rATG+C1H, and abruptly returned to baseline afterwards; suppression by rATG(7 doses) was modest but lasted longer. A higher proportion of CD56+CD16+ Natural Killer cells in C1H treated patients suggested a relatively spared effect of C1H on this cell type. Low CD25+ T-cells by 5-dose Dac returned to baseline around 6 months, whereas rATG+C1H and rATG+Dac showed persistent effect. CD4+CD25hi T-cells were suppressed by both rATG+C1H and rATG+Dac, but the initial proportion of CD4+CD25hi T-cells among CD4+ T-cells and CD4+CD25hi/CD4+CD25lo ratio were significantly higher in rATG+C1H. Overall, with extensive and persistent lymphocyte suppression by a simple administration of agents, single-dose rATG+C1H induction can be an alternative in renal transplantation.     

Multimodal approach to the endovascular treatment of embolisation or exclusion of the renal arteries and their distal and/or polar branches: personal experience

Purpose

This study reviews our experience over the last 10 years with procedures of embolisation and/or exclusion of the renal arteries, their parenchymal branches and the polar arteries [renal artery embolisation (RAE)].

Materials and methods

Twenty-seven patients (19 men and eight women; age range 37?C93 years; mean 74 years) underwent RAE. The indications were: symptomatic gross haematuria in nine patients (33.3%) (tumour-related in seven and iatrogenic in two), symptomatic inoperable renal tumour in five (18.5%), large subcapsular or perirenal haematoma in three (11.1%) and aneurysm of the main renal artery in two (7.4%). Eight patients (29.6%) scheduled for endovascular aneurysm repair (EVAR) of the abdominal aorta underwent prophylactic embolisation of the renal polar branch arising from the aneurysmal sac or the subrenal aortic neck to prevent the possible revascularisation of the sac. Different embolisation agents were used: coils (17 cases), embolisation particles (14 cases), glue (one case), coated stent (two cases) and mechanical occlusion devices (two cases). In 11 cases, two to three different embolisation agents were used together.

Results

Technical success was achieved in 26/27 patients (96.3%); in one case, embolisation of a polar artery arising from the aneurysmal sac was not possible. One case of gross haematuria recurred 13 months after the procedure and was re-treated with success. There were no cases of major or minor complications.

Conclusions

RAE is an effective and minimally invasive procedure in the treatment of neoplastic/iatrogenic symptomatic gross haematuria and in the palliative treatment of inoperable renal tumours. One possible new indication is the prophylactic exclusion of the polar artery arising from the neck or the sac of an abdominal aortic aneurysm in patients who are candidates for EVAR. In our experience, we observed very low morbidity and a short hospital stay. This procedure requires the availability of various materials for performing embolisation and experience in their use.     

Prolonged duck hepatitis B virus replication in duck hepatocytes cocultivated with rat epithelial cells: a useful system for antiviral testing

Duck cultured hepatocytes from Pekin ducks naturally infected by duck hepatitis B virus can remain functional twice longer if a coculture system with rat liver epithelial cells is used instead of ordinary primary culture. The use of a selective medium in which ornithine and lactate replaced arginine and glucose, respectively, allowed viral replication initiated in vivo to be maintained in the coculture for 2 months. Several antiviral compounds including the pyrophosphate analog (phosphonoformic acid) or nucleoside analogs (9 beta-arabinofuranosyl AMP, 1-(2'-deoxy-2'-fluoro-beta-D-arabinofuranosyl)-5-iodocytosine, 1,2'-deoxy-2'-fluoro-beta-D-arabinofuranosyl-5-ethyluracil and 1,2'-deoxy-2'-fluoro-beta-D-arabinofuranosyl thymine) were studied in both culture systems for their ability to inhibit duck hepatitis B virus replication. Hepatocytes were treated for 7 days with 1,2'-deoxy-2'-fluoro-beta-D-arabinofuranosyl-5-ethyluracil (10 microM) and 1,2'-deoxy-2'-fluoro-beta-D-arabinofuranosyl thymine (0.5 microM) or for 14 days with 9 beta-arabinofuranosyl AMP (90 microM), phosphonoformic acid (100 microM) and 1-(2'-deoxy-2'-fluoro-beta-D-arabinofuranosyl)-5-iodocytosine (6 microM). The effects of the drugs on viral replication were monitored by testing for duck hepatitis B virus DNA in the culture supernatant and in the cells by molecular hybridization.(ABSTRACT TRUNCATED AT 250 WORDS)     

Early predictors of dysphagia in ischaemic stroke patients

Background and purpose

Post-stroke dysphagia affects outcome. In acute stroke patients, the aim was to evaluate clinical, cognitive and neuroimaging features associated with dysphagia and develop a predictive score for dysphagia.

Methods

Ischaemic stroke patients underwent clinical, cognitive and pre-morbid function evaluations. Dysphagia was retrospectively scored on admission and discharge with the Functional Oral Intake Scale.

Results

In all, 228 patients (mean age 75.8 years; 52% males) were included. On admission, 126 (55%) were dysphagic (Functional Oral Intake Scale ≤6). Age (odds ratio [OR] 1.03, 95% confidence interval [CI] 1.00–1.05), pre-event modified Rankin scale (mRS) score (OR 1.41, 95% CI 1.09–1.84), National Institutes of Health Stroke Scale (NIHSS) score (OR 1.79, 95% CI 1.49–2.14), frontal operculum lesion (OR 8.53, 95% CI 3.82–19.06) and Oxfordshire total anterior circulation infarct (TACI) (OR 1.47, 95% CI 1.05–2.04) were independently associated with dysphagia at admission. Education (OR 0.91, 95% CI 0.85–0.98) had a protective role. At discharge, 82 patients (36%) were dysphagic. Pre-event mRS (OR 1.28, 95% CI 1.04–1.56), admission NIHSS (OR 1.88, 95% CI 1.56–2.26), frontal operculum involvement (OR 15.53, 95% CI 7.44–32.43) and Oxfordshire classification TACI (OR 3.82, 95% CI 1.95–7.50) were independently associated with dysphagia at discharge. Education (OR 0.89, 95% CI 0.83–0.96) and thrombolysis (OR 0.77, 95% CI 0.23–0.95) had a protective role. The 6-point “NOTTEM” (NIHSS, opercular lesion, TACI, thrombolysis, education, mRS) score predicted dysphagia at discharge with good accuracy. Cognitive scores had no role in dysphagia risk.

Conclusions

Dysphagia predictors were defined and a score was developed to evaluate dysphagia risk during stroke unit stay. In this setting, cognitive impairment is not a predictor of dysphagia. Early dysphagia assessment may help in planning future rehabilitative and nutrition strategies.     

Comparison between the efficacy of dimeric and monomeric non-ionic contrast media (iodixanol vs iopromide) in urography in patients with mild to moderate renal insufficiency

Non-ionic dimers induce less diuresis than non-ionic monomers, resulting in increased opacification of the urinary tract in intravenous (i.v.) urography. This double blind, comparative, randomized, parallel trial compared the efficacy of iodixanol (non-ionic dimer) and iopromide (non-ionic monomer) in 100 patients with mild to moderate renal insufficiency (serum creatinine of 135 to 265 mumol l-1) who underwent i.v. urography. A total dose of 600 mgI kg-1 bw of iodixanol (320 mgI ml-1) or iopromide (300 mgI ml-1) was injected. Radiographs were blindly evaluated by three radiologists who analysed different parameters (renal border visualization, nephrogram density, calyceal filling and density, papillary blush detection, delineation of collecting ducts, renal pelvis opacification, visualization of ureters, bladder density, bladder distention). Densitometric evaluation on the renal pelvis and bladder was also performed. Iodixanol showed better filling and density of the calyces (p = 0.004), more frequent detection of papillary blush (p = 0.003) and better opacification of the renal pelvis (p = 0.006). No significant differences between the two contrast media were found in regard to other parameters. In conclusion, the results confirmed theoretical expectations. The non-ionic dimer iodixanol is to be preferred to a non-ionic monomer such as iopromide in i.v. urography on patients with impaired renal function.     

Magnetic resonance imaging of articular cartilage: ex vivo study on normal cartilage correlated with magnetic resonance microscopy

The aims of this study were (a) to compare the MR appearance of normal articular cartilage in ex vivo MR imaging (MRI) and MR microscopy (MRM) images of disarticulated human femoral heads, (b) to evaluate by MRM the topographic variations in articular cartilage of disarticulated human femoral heads, and subsequently, (c) to compare MRM images with histology. Ten disarticulated femoral heads were examined. Magnetic resonance images were obtained using spin-echo (SE) and gradient-echo (GE) sequences. Microimages were acquired on cartilage–bone cylindrical plugs excised from four regions (superior, inferior, anterior, posterior) of one femoral head, using a modified SE sequence. Both MRI and MRM images were obtained before and after a 90 ° rotation of the specimen, around the axis perpendicular to the examined cartilage surface. Finally, MRM images were correlated with histology. A trilaminar appearance of articular cartilage was observed with MRI and with a greater detail with MRM. A good correlation between MRI and MRM features was demonstrated. Both MRI and MRM showed a loss of the trilaminar cartilage appearance after specimen rotation, with greater evidence on MRM images. Cartilage excised from the four regions of the femoral head showed a different thickness, being thickest in the samples excised from the superior site. The MRM technique confirms the trilaminar MRI appearance of human articular cartilage, showing good correlation with histology. The loss of the trilaminar appearance of articular cartilage induced by specimen rotation suggests that this feature is partially related to the collagen-fiber orientation within the different layers. The MRM technique also shows topographic variations in thickness of human articular cartilage. Received 28 July 1997; Revision received 31 December 1997; Accepted 6 January 1998