Increased cortical neuronal responses to NMDA and improved attentional set-shifting performance in rats following prebiotic (B-GOS®) ingestion

We have previously shown that prebiotics (dietary fibres that augment the growth of indigenous beneficial gut bacteria) such as Bimuno^? galacto-oligosaccharides (B-GOS^®), increased N-methyl-D-aspartate (NMDA) receptor levels in the rat brain. The current investigation examined the functional correlates of these changes in B-GOS^®-fed rats by measuring cortical neuronal responses to NMDA using in vivo NMDA micro-iontophoresis electrophysiology, and performance in the attentional set-shifting task. Adult male rats were supplemented with B-GOS^® in the drinking water 3 weeks prior to in vivo iontophoresis or behavioural testing. Cortical neuronal responses to NMDA iontophoresis, were greater (+30%) in B-GOS^® administered rats compared to non-supplemented controls. The intake of B-GOS^® also partially hindered the reduction of NMDA responses by the glycine site antagonist, HA-966. In the attentional set-shifting task, B-GOS^® -fed rats shifted from an intra-dimensional to an extra-dimensional set in fewer trials than controls, thereby indicating greater cognitive flexibility. An initial exploration into the mechanisms revealed that rats ingesting B-GOS^® had increased levels of plasma acetate, and cortical GluN2B subunits and Acetyl Co-A Carboxylase mRNA. These changes were also observed in rats fed daily for 3 weeks with glyceryl triacetate, though unlike B-GOS^®, cortical histone deacetylase (HDAC1, HDAC2) mRNAs were also increased which suggested an additional epigenetic action of direct acetate supplementation. Our data demonstrate that a pro-cognitive effect of B-GOS^® intake in rats is associated with an increase in cortical NMDA receptor function, but the role of circulating acetate derived from gut bacterial fermentation of this prebiotic requires further investigation.     

A murine model of type 2 autoimmune hepatitis: Xenoimmunization with human antigens

Autoimmune hepatitis (AIH) is characterized by an immune-mediated injury of the hepatic parenchyma of unknown pathogenesis. Type 2 AIH is identified by the presence of anti-liver-kidney microsomes type 1 (anti-LKM1) and anti-liver cytosol type 1 (anti-LC1) autoantibodies. The current study shows that a murine model of AIH can be generated by DNA immunization against type 2 AIH self-antigens (P450 2D6 and formiminotransferase-cyclodeaminase). A pCMV plasmid containing the N-terminal region of mouse CTLA-4 and the antigenic region of human CYP2D6 (672-1,377 bp) and human formiminotransferase cyclodeaminase (FTCD; 1,232-1,668 bp) was used for DNA immunization of C57BL/6 female mice. Immunized mice showed elevated levels of alanine aminotransferase (ALT), with peaks at 4 and 7 months postinjection. Periportal, portal, and intralobular liver inflammatory infiltrates were observed at histology. Mainly CD4+ lymphocytes, but also CD8+ and B lymphocytes, were found in the liver. Cytotoxic-specific T cells were found in both the liver and spleen of these animals. Mice developed anti-LKM1 and anti-LC1 antibodies of immunoglobulin G2 (IgG2) subclass, against specific mouse autoantigens. The ALT levels correlated with both the presence of anti-LKM1/anti-LC1 antibodies and the presence of liver necroinflammation. In conclusion, in mice, DNA immunization against human autoantigens breaks tolerance and induces an autoimmune liver disease. Molecular mimicry between foreign and self-antigens explains the liver injury. This model of AIH resembles human type 2 AIH and will be helpful for the study of its pathogenesis.     

Positional abnormalities of atrioventricular valves in transposition of the great arteries including double outlet right ventricle, atrioventricular valve straddling and malattachment.

Positional abnormalities (straddling or overriding) of the atrioventricular (A-V) valves were studied using angiographic, sector scan echocardiographic and postmortem anatomic data in 10 patients with transposition of the great arteries including double outlet right ventricle. Group I included six patients with tricuspid valve abnormalities. This group was further classified into: (a) patients with anular straddling and abnormal attachment of portions of the tricuspid leaflets in the left ventricle (malattachment) or on the ventricular septum, or both (four patients with d-transposition of the great arteries and hypoplastic right ventricle); and (2) patients with malattachment of portions of the tricuspid valve leaflet to the crest or left ventricular surface of the septum (septal malattachment) without significant anular straddling (two patients with d-transposition of the great arteries).Group II included four patients with mitral valve abnormalities without significant anular straddling, further classified into: (1) patients with septal malattachment of the portions of the mitral valve to the crest and right ventricular surface of the ventricular septum (two patients with double outlet right ventricle); and (2) patients with ventricular malattachment of portions of the mitral valve leaflets to the papillary muscles in the right ventricle (two patients with ventricular septal defect and discordant criss-cross atrioventricular connections).On the basis of these observations and reported experience, two main types of positional abnormalities of the A-V valves were recognized: (1) anular straddling in which the A-V anulus straddled the ventricular septum above the contralateral ventricle, together with ventricular leaflet malattachments, and (2) leaflet malattachment of either the septal or ventricular type without significant straddling of the valve anulus. Angiocardiography and sector scan echocardiography helped to identify these abnormalities of the A-V valves.     

Factors influencing coronary vascular resistance during hypothermia

Factors influencing total coronary vascular resistance (CVR) during hypothermia were studied in 30 mongrel dogs. Complete isolation of the heart in situ was achieved by transection of all cardiac neural and vascular connections in 15 dogs (denervated, Group I). Cardiac innervation was maintained in the other 15 dogs using systemic normothermic cardiopulmonary bypass (innervated, Group II). The aortic root was perfused with heparinized oxygenated blood at a constant flow rate at variable myocardial temperatures. Electromechanical arrest was achieved using potassium chloride (KCl) (25 meq/liter) added to the coronary perfusate. In each group, 5 dogs were maintained at a flow rate of 10 cc/kg/min without KCl and allowed to beat spontaneously, another 5 at a flow rate of 10 cc/kg/min and arrested with KCl, and the remaining 5 at a flow rate of 5 cc/kg/min with KCl. Total coronary vascular resistance was calculated from aortic root pressure, right atrial pressure, and flow rate and expressed in units per 100 grams of cardiac tissue. At 37 degrees C, resistance was lower in the denervated arrested (1.3 +/- 0.2) than in the innervated arrested hearts (2.1 +/- 0.2) (P less than 0.001). Preservation of spontaneous electromechanical activity in the innervated hearts resulted in a lower resistance (0.4 +/- 0.1) (P less than 0.001). A progressive decrease in myocardial temperature to 15 degrees C resulted in a corresponding decrease in coronary vascular resistance to a plateau value (0.5 to 0.7 U) in all arrested groups. The data suggest that at normothermia, innervation increases vascular tone in the coronary vascular bed, while electromechanical activity decreases it.(ABSTRACT TRUNCATED AT 250 WORDS)     

Implication of tumor necrosis factor alpha receptor 1 and hexosaminidase: relationship to pathogenesis of liver diseases

Liver disease is the main cause of morbidity and mortality worldwide. The spectrum of the disease ranged from fatty liver to hepatic inflammation, necrosis, progressive fibrosis, and hepatocellular carcinoma. We evaluated the serum levels of soluble tumor necrosis factor alpha receptor 1, total B-hexosaminidase and its isoenzymes Hex A and B activities, and nitric oxide in patients with liver diseases and their association with aminotransferase level. Seventy patients and 12 healthy subjects were recruited. Patients were divided into three groups: chronic hepatitis group (20 patients), liver cirrhosis group (30 patients), and malignant liver group (20 patients). Serum levels of soluble tumor necrosis factor alpha receptor 1, total B-hexosaminidase and its isoenzymes Hex A and B activities, and nitric oxide were measured. Serum levels of soluble tumor necrosis factor alpha receptor 1, total B-hexosaminidase activity, and nitric oxide were significantly higher in the liver disease patients. Serum levels of isoenzymes Hex A and B were significantly higher in malignant liver patients. Total B-hexosaminidase and its isoenzyme Hex A activity levels were significantly higher in positive HBsAg and positive anti-HCV patients. Serum levels of soluble tumor necrosis factor alpha receptor 1 were positively correlated with aminotransferase level. Taken together, these findings suggested that these biochemical indices might reflect ongoing disease activity and played an important role in the pathophysiology of liver diseases.     

Selective modulation of P-glycoprotein's ATPase and anion efflux regulation activities with PKC α and PKC ɛ in Sf9 cells

The modulation of P-glycoprotein's (Pgp) ATPase activity and its ability to regulate swelling-activated ¹²⁵I efflux, by PKC α and PKC ɛ, was examined in insect cells. Recombinant baculovirus was used to express human Pgp in Sf9 cells and Pgp was also co-expressed with either PKC α or PKC ɛ. ATPase assays showed the enzyme activity of Pgp to be elevated during co-expression with the Ca²⁺ dependent isoform PKC α, but not with the Ca²⁺ independent variant PKC ɛ. Furthermore, neither isoform, when co-expressed with Pgp, altered the swelling-activated efflux of ¹²⁵I from Sf9 cells. However, in cells co-expressing Pgp/PKC (α or ɛ), pre-treatment with the phorbol ester TPA significantly reduced the swelling-activated ¹²⁵I efflux with both PKC isoforms. Our results suggest that phosphorylation with the Ca²⁺ independent variant PKC ɛ does not regulate the ATPase activity of Pgp and that stimulation of PKC with TPA alters the swelling-activated efflux of anions from insect cells expressing Pgp. Received: 8 March 2000 / Accepted: 5 June 2000     

Feasibility study of real-time three-dimensional intracardiac echocardiography for guidance of interventional electrophysiology

The authors tested the feasibility of real-time three-dimensional intracardiac echocardiography for guidance of interventional electrophysiological studies. The three-dimensional scanner uses a matrix array ultrasound transducer of 64 channels operating at 5 MHz in a 12 Fr catheter. The system features real-time three-dimensional image rendering and produces up to 60 volumetric scans per second. Using an open-chest sheep model, real-time three-dimensional images of anatomic landmarks were obtained, including the pulmonary veins and coronary sinus, which are of value in electrophysiological procedures. In vivo radio frequency ablation procedures in the right ventricle were also monitored, which yielded lesions of high image contrast.