STD-Dependent and Independent Encoding of Input Irregularity as Spike Rate in a Computational Model of a Cerebellar Nucleus Neuron

Neurons in the cerebellar nuclei (CN) receive inhibitory inputs from Purkinje cells in the cerebellar cortex and provide the major output from the cerebellum, but their computational function is not well understood. It has recently been shown that the spike activity of Purkinje cells is more regular than previously assumed and that this regularity can affect motor behaviour. We use a conductance-based model of a CN neuron to study the effect of the regularity of Purkinje cell spiking on CN neuron activity. We find that increasing the irregularity of Purkinje cell activity accelerates the CN neuron spike rate and that the mechanism of this recoding of input irregularity as output spike rate depends on the number of Purkinje cells converging onto a CN neuron. For high convergence ratios, the irregularity induced spike rate acceleration depends on short-term depression (STD) at the Purkinje cell synapses. At low convergence ratios, or for synchronised Purkinje cell input, the firing rate increase is independent of STD. The transformation of input irregularity into output spike rate occurs in response to artificial input spike trains as well as to spike trains recorded from Purkinje cells in tottering mice, which show highly irregular spiking patterns. Our results suggest that STD may contribute to the accelerated CN spike rate in tottering mice and they raise the possibility that the deficits in motor control in these mutants partly result as a pathological consequence of this natural form of plasticity.     

Chronic hepatitis D in intravenous drug addicts and non-addicts. A comparative clinico-pathological study

In recent years chronic infection by the hepatitis delta virus (HDV) has become an important cause of chronic liver disease among drug addicts. To evaluate the influence of addiction to i.v. drugs on the course of this disease we have analyzed the clinical, histopathological, virological and evolutive features in 18 addicts and 11 non-addicts with chronic delta infection. Recent acute hepatitis D, documented as HDV superinfection, was observed in 14 addicts (77%) and in 2 non-addicts (18%) (P less than 0.02). At the time of evaluation for chronic liver disease, the frequency of symptoms, the degree of biochemical disturbances and the histopathological severity were similar in the two groups but the duration of HDV infection was probably shorter in drug addicts. HBV replication, as indicated by the presence of HBeAg and HBV-DNA in serum and HBcAg in liver, was more frequent in addicts. The amount of HDAg in liver tissue was also greater in addicts (P less than 0.005). Antibodies against the human immunodeficiency virus were detected in all of the addicts (P less than 0.001). Although most patients remained asymptomatic, significant histological worsening occurred in one half of the cases after a relatively short period of follow-up (25.1 +/- 16.3 months). The tendency to deteriorate in addicts (61% of cases) was greater than in non-addicts (36%). These observations suggest that the prognosis of chronic HDV infection is particularly poor in drug addicts in whom rapid deterioration may be related to simultaneous and inadequately controlled replication of hepatotropic viruses.     

Esophageal dysfunction in primary biliary cirrhosis

To investigate esophageal involvement of scleroderma in primary biliary cirrhosis, esophageal, manometry was performed in 18 patients (16 females, two males) with primary biliary cirrhosis and in a control group of 18 subjects matched by age and sex. All patients were screened for clinical manifestations of scleroderma and for the presence of Sj?gren's syndrome. Four patients had scleroderma (all of them with Sj?rgren's syndrome), nine had Sj?gren's syndrome without scleroderma, and five had neither scleroderma nor Sj?gren's syndrome. Three patients with scleroderma had aperistalsis and diminished lower sphincter pressure. Five patients with Sj?rgren's syndrome without scleroderma also had esophageal manometric disturbances. Furthermore, lower esophageal sphincter pressure (LESP) and distal mean wave pressure (DMWP) were significantly reduced in patients with scleroderma (LESP: 7.5 +/- 1.4 mmHg; DMWP: 29.5 +/- 5.9 mmHg) and in patients with Sj?gren's syndrome without scleroderma (LESP: 14.8 +/- 0.8 mmHg; DMWP: 54.3 +/- 7.5 mmHg) compared to controls (LESP: 18.0 +/- 0.7 mmHg; DMWP: 83.9 +/- 5.1 mmHg). By contrast, LESP and DMWP were similar in patients without Sj?gren's syndrome (LESP: 17.6 +/- 0.9 mmHg; DMWP: 78.2 +/- 10.9 mmHg) and controls. These results indicate that esophageal motility dysfunction is often present in patients with primary biliary cirrhosis who have scleroderma, and also in those with Sj?gren's syndrome without scleroderma, suggesting that some esophageal motor disturbances could be related to association with Sj?gren's syndrome.     

Hyperglucagonism and glucagon resistance in cirrhosis. Paradoxical effect of propranolol on plasma glucagon levels

Propranolol, a non-selective beta-blocker, is known to decrease glucagon release in normal subjects. The present study was aimed at investigating the effects of propranolol on the hyperglucagonism commonly observed in patients with cirrhosis. Eight cirrhotic patients and 6 matched healthy controls were studied. The plasma concentrations of glucagon, insulin, c-peptide and glucose were measured in basal conditions and after stimulating glucagon secretion by an i.v. infusion of arginine (0.4 g/kg/30 min). The study was repeated 24 h later after inducing beta-blockade by the i.v. infusion of propranolol (10 mg). In baseline conditions, patients with cirrhosis, despite normal levels of insulin and glucose, had a marked hyperglucagonism (654 +/- 303 pg/ml vs. 269 +/- 90 in controls, P less than 0.01). Prior to propranolol, arginine infusion caused greater glucagon release in cirrhotics (71 +/- 31 ng.h.ml-1) than in controls (33 +/- 17 ng.h.ml-1, P less than 0.02), but despite a similar insulin secretion (assessed from c-peptide), blood glucose did not increase. After propranolol, glucagon secretion decreased as expected in controls (29 +/- 12 ng.h.ml-1, P less than 0.05) but experienced a paradoxical increase in cirrhotics (113 +/- 64 ng.h.ml-1, P less than 0.05). Again, despite the marked increase in glucagon release, there was no increase in glucose production, providing further evidence of the glucagon resistance that accompanies hyperglucagonism in cirrhosis. Our results suggest that hyperglucagonism with glucagon resistance might be the initial disturbance in carbohydrate metabolism in patients with cirrhosis. Contrary to what could be expected, propranolol does not correct but further accentuates this disturbance.     

Human gut microbiota in obesity and after gastric bypass

Recent evidence suggests that the microbial community in the human intestine may play an important role in the pathogenesis of obesity. We examined 184,094 sequences of microbial 16S rRNA genes from PCR amplicons by using the 454 pyrosequencing technology to compare the microbial community structures of 9 individuals, 3 in each of the categories of normal weight, morbidly obese, and post-gastric-bypass surgery. Phylogenetic analysis demonstrated that although the Bacteria in the human intestinal community were highly diverse, they fell mainly into 6 bacterial divisions that had distinct differences in the 3 study groups. Specifically, Firmicutes were dominant in normal-weight and obese individuals but significantly decreased in post-gastric-bypass individuals, who had a proportional increase of Gammaproteobacteria. Numbers of the H₂-producing Prevotellaceae were highly enriched in the obese individuals. Unlike the highly diverse Bacteria, the Archaea comprised mainly members of the order Methanobacteriales, which are H₂-oxidizing methanogens. Using real-time PCR, we detected significantly higher numbers of H₂-utilizing methanogenic Archaea in obese individuals than in normal-weight or post-gastric-bypass individuals. The coexistence of H₂-producing bacteria with relatively high numbers of H₂-utilizing methanogenic Archaea in the gastrointestinal tract of obese individuals leads to the hypothesis that interspecies H₂ transfer between bacterial and archaeal species is an important mechanism for increasing energy uptake by the human large intestine in obese persons. The large bacterial population shift seen in the post-gastric-bypass individuals may reflect the double impact of the gut alteration caused by the surgical procedure and the consequent changes in food ingestion and digestion.     

Anatomo‐functional organization of the ventral primary motor and premotor cortex in the macaque monkey

The ventral agranular frontal cortex of the macaque monkey is formed by a mosaic of anatomically distinct areas. Although each area has been explored by several neurophysiological studies, most of them focused on small sectors of single areas, thus leaving to be clarified which is the general anatomo‐functional organization of this wide region. To fill this gap, we studied the ventral convexity of the frontal cortex in two macaque monkeys (Macaca nemestrina) using intracortical microstimulation and extracellular recording. Functional data were then matched with the cytoarchitectonic parcellation of the recorded region. The results demonstrated the existence of a dorso‐ventral functional border, encompassing the anatomical boundary between areas F4 and F1, and a rostro‐caudal anatomo‐functional border between areas F5 and F4. The ventral subdivision of areas F4 and F1 was highly electrically excitable, represented simple mouth movements and lacked visual properties; in contrast, their dorsal counterpart showed a higher stimulation threshold, represented forelimb and mouth motor acts and hosted different types of visual properties. The data also showed that area F5 was scarcely excitable, and displayed various motor specificity (e.g. for the type of grip) and complex visual (i.e. mirror responses) properties. Overall, the posterior areas F4 and F1 appear to be involved in organizing and controlling goal‐directed mouth motor acts and simple movements within different parts of the external (dorsal sector) and internal (ventral sector) space, whereas area F5 code motor acts at a more abstract level, thus enabling the emergence of higher order socio‐cognitive functions.     

Long-term effects of ursodeoxycholic acid in primary biliary cirrhosis: results of a double-blind controlled multicentric trial. UDCA-Cooperative Group from the Spanish Association for the Study of the Liver

BACKGROUND/AIM: The aim of this study was to assess the efficacy of ursodeoxycholic acid (UDCA) for primary biliary cirrhosis in a randomized, double-blind placebo-controlled trial. METHODS: Consecutive patients (n=192) were randomized to receive 14-16 mg UDCA/kg/day or placebo. Patients underwent a complete history, physical examination, liver chemistries, immunological determinations and liver biopsy at entry and at the end of the trial, which lasted for at least 2 years. Patients were seen every 3 months and the median follow-up was 3.4 years (range 0.3 to 6.1 years). RESULTS: Patients receiving UDCA (99) or placebo (93) were comparable with regard to age, sex, biochemical parameters and liver histology. UDCA treatment was associated with decreases in alkaline phosphatase, gammaglutamyl transferase, alanine aminotransferase, and cholesterol levels, effects which were conspicuous after 3 months of treatment and remained similar during the follow-up. During the study 31 patients (10 receiving UDCA and 21 placebo) discontinued the trial because of noncompliance (n=11), voluntary withdrawal (n=19) or adverse effects (n=1). Treatment failure (death or liver transplantation) was observed in 17 patients receiving UDCA and in 11 patients receiving placebo. Times to death or liver transplantation and to clinical complications were not significantly different in patients receiving UDCA or placebo. Histological analysis indicates that UDCA improved portal inflammation and prevented histological stage progression. By contrast, histological stage as well as ductular proliferation and ductopenia progressed in patients receiving placebo. CONCLUSIONS: Although UDCA treatment did not significantly affect time to death or liver transplantation and to clinical complications, the effects on both cholestasis and liver histology suggest that UDCA is safe and may be useful for preventing the progression of primary biliary cirrhosis.