Feedback topology and XOR-dynamics in Boolean networks with varying input structure.

We analyze a model of fixed in-degree random Boolean networks in which the fraction of input-receiving nodes is controlled by the parameter gamma. We investigate analytically and numerically the dynamics of graphs under a parallel XOR updating scheme. This scheme is interesting because it is accessible analytically and its phenomenology is at the same time under control and as rich as the one of general Boolean networks. We give analytical formulas for the dynamics on general graphs, showing that with a XOR-type evolution rule, dynamic features are direct consequences of the topological feedback structure, in analogy with the role of relevant components in Kauffman networks. Considering graphs with fixed in-degree, we characterize analytically and numerically the feedback regions using graph decimation algorithms (Leaf Removal). With varying gamma , this graph ensemble shows a phase transition that separates a treelike graph region from one in which feedback components emerge. Networks near the transition point have feedback components made of disjoint loops, in which each node has exactly one incoming and one outgoing link. Using this fact, we provide analytical estimates of the maximum period starting from topological considerations.

Use of radioisotopic esophageal transit in the assessment of patients with symptoms of reflux and non-specific esophageal motor disorders.

The purposes of this study were to assess the esophageal clearance of a radioisotopic bolus in patients with symptoms of reflux and evaluate the impact of manometric abnormalities on scintigraphic esophageal transit. Esophageal clearance was assessed in a supine position and indicated by the retained radioactivity in the esophagus at 10, 20, 30 and 40 s after the ingestion of a liquid bolus labeled with 2 mCi 99 mTc-SC. The study included 214 consecutive patients with symptoms of reflux and 11 normal controls. The results were compared to the motility findings detected on manometry performed on a separate occasion. Esophageal manometry was normal in 93 patients. Nonspecific esophageal motor disorders were identified in 121 patients and were classified into: 'predominantly nonpropagated activity', 'predominantly low-amplitude peristaltic contractions' and 'miscellaneous disorders' diagnosed in 27, 47 and 47 patients, respectively. The radionuclide clearance was significantly delayed in the overall group of patients compared with that of normal controls (P < 0.001); in patients with reflux symptoms and nonspecific esophageal motor disorders compared with patients with reflux symptoms and 'normal manometry' (P < 0.01 at 20 s); and in patients with reflux symptoms and 'normal manometry' compared with the control group (P < 0.01 at 20 s). Abnormal radioisotope clearances were detected in 88% of patients with 'predominantly nonpropagated activity', in 70% of patients with 'predominantly low-amplitude peristaltic contractions' and in 57% of patients with 'miscellaneous disorders'. Radioisotopic esophageal clearance abnormalities are frequently observed in patients with reflux symptoms and are more likely to be associated to hypomotility disorders, i.e. nonpropagated motor activity or low-amplitude contractions.

Recurrent gastric carcinoma causing pseudoachalasia: case report.

We report the case of a patient with a gastric remnant relapse of an antral carcinoma resected 5 years before and presenting with the clinical feature of a secondary achalasia (pseudoachalasia). In spite of the patient's 4-month history of dysphagia and weight loss that suggested a malignant lesion, barium swallow, repeated endoscopic biopsies and computed tomography (CT) scan of the upper abdomen did not reveal any abnormalities to indicate a recurrence. However, in the following months, because of worsening symptoms, a further CT scan was performed and revealed thickening of the cardia and gastric wall. The patient underwent an exploratory laparotomy that showed an unresectable lesion involving the gastric fundus, the diaphragm and penetrating into the mediastinum, and therefore a palliative jejunostomy was performed.

Differential neural projections to regions of the inferior colliculus of the cat responsive to high frequency sounds.

Iontophoretic injections of horseradish peroxidase were made in the vicinity of high best frequency neurons in the central nucleus of the inferior colliculus of the cat. Retrogradely labelled cells were found in most major auditory nuclei known to provide afferent input to the central nucleus, and were distributed in accordance with the known tonotopic organization of these nuclei. However, different injection sites gave rise to patterns of brain stem labelling that differed from one experiment to the next, in spite of the similarities in injection site best frequency. With each injection a small group of nuclei contained the majority of labelled cells. The results confirm previous anatomical findings of convergence of ascending input in relation to the tonotopic organization of the central nucleus. Additionally it is suggested that different subregions of the central nucleus may have different roles in the integration of acoustic information because of the varying patterns of brain stem terminations in each region.