Seven in absentia homolog 1A mediates ubiquitination and degradation of group 1 metabotropic glutamate receptors

Seven in absentia homolog 1A (Siah1A) is a member of the RING-finger-containing E3 ubiquitin ligases and has been shown to bind to the Siah-interacting domain (SID) at the carboxyl-terminal tails of the long splice forms of group 1 metabotropic glutamate receptors (mGluR1a and mGluR5). We examined the function of Siah1A in ubiquitination and degradation of group 1 mGluRs in heterologously expressing cell lines. Coexpression of Siah1A markedly decreased the SID-containing splice forms of group 1 mGluRs but not the SID-lacking mGluR1b splice form or the SID-deleted mGluR1a mutant. The decrease of mGluR1a resulted from accelerated protein turnover, as revealed by pulse-chase experiments. The Siah1A-mediated degradation of group 1 mGluRs was abrogated by not only mutations at the RING-finger domain of Siah1A but also treatment with a proteasome inhibitor. Siah1A coexpression induced strong ubiquitination of group 1 mGluRs. Replacements of lysine residues with arginine showed that Siah1A-mediated ubiquitination occurs at multiple lysine residues spanning both the seven-transmembrane region and carboxyl-terminal tail of mGluR5. In situ hybridization histochemistry showed a wide-spread distribution of Siah1 mRNAs, with high expression in the hippocampal pyramidal neurons and cerebellar Purkinje cells. Group 1 mGluRs play critical roles in the neural plasticity in both the hippocampal neurons and Purkinje cells. This investigation indicates that Siah1A serves as a selective ubiquitin ligase that mediates ubiquitination-dependent degradation of long splice variants of group 1 mGluRs and would contribute to posttranslational down-regulation of group 1 mGluRs.     

Pharmacoangiographic diagnosis of venous invasion of carcinoma of the colon with reference to liver metastases

Angiography using prostaglandin E1 was performed on 34 patients with carcinoma of the colon in order to define the degree of venous invasion. Venous findings on angiogram (occlusion and/or encasement) were classified into three groups: AG-V2, above-mentioned venous findings up to marginal vein; AG-V1, these findings up to the vasa recta; AG-V0, no distinct findings on the vein. These venous findings were compared with histologic subserosal venous invasion that was diagnosed with both hematoxylin and eosin and elastica van Gieson's staining. When angiographic findings were compared with histologic subserosal venous invasion, the results of AG-V2, AG-V1, and AG-V0 showed a positive correlation of 92.3 percent, 46.7 percent, and 16.7 percent, respectively. The angiographic findings were also correlated with the degree of fibrosis around the carcinoma of the colon. The incidence rate of liver metastasis in a group of AG-V2 was 46.2 percent. In AG-V1 it was 26.7 percent and in AG-V0 0 percent. In the course of the postoperative follow-up, liver metastases appeared in two cases of AG-V2 and AG-V1, respectively. This finding may suggest the presence of liver micrometastases at the time of surgery.     

Differential diagnosis of benign versus malignant nonfunctioning islet cell tumors of the pancreas: the roles of EUS and ERCP.

BACKGROUND: Differentiation between benign and malignant nonfunctioning islet cell tumors of the pancreas before surgery is often difficult. The roles of EUS and ERCP were evaluated in the differential diagnosis of these tumors. METHODS: Seven patients with histologically confirmed nonfunctioning islet cell tumors (4 benign, 3 malignant) underwent EUS and ERCP. OBSERVATIONS: EUS demonstrated a homogeneous hypoechoic mass or a hypoechoic mass with a regular central echogenic area in the 4 cases of benign tumor, and a hypoechoic mass with an irregular central echogenic area in all 3 cases of malignant tumor. The irregular central echogenic area corresponded to severe hemorrhage, necrosis, or fibrosis with hyalinosis (hyaline degeneration) on pathologic examination. ERCP demonstrated displacement or complete obstruction (because of ductal invasion) of the main pancreatic duct in 2 patients with malignant tumors and no abnormalities in the other 5 cases. CONCLUSIONS: In patients with nonfunctioning islet cell tumors, a hypoechoic mass with an irregular central echogenic area on EUS or complete obstruction of the main pancreatic duct on ERCP suggests malignancy.     

TNF-alpha rapidly antagonizes the beta-adrenergic responses of the chloride current in guinea-pig ventricular myocytes.

The purpose of this study was to test the hypothesis that tumor necrosis factor-alpha (TNF-alpha) rapidly antagonizes the beta-adrenergic responses of the chloride current and to clarify the intracellular mechanisms responsible for the anti-adrenergic action. The whole-cell patch-clamp technique was used to monitor the anti-adrenergic effects of TNF-alpha on the cAMP-dependent chloride current (I(Cl)) recorded from isolated guinea-pig ventricular myocytes. Ramp pulses (+/-120 mV; dv/dt = +/-0.4 V/s) were applied from the holding potential of -40 mV. TNF-alpha rapidly (<15 min) inhibited the isoproterenol (Iso, 0.1 micromol/L)-induced I(Cl) in a concentration-dependent manner (30-1,000 U/ml, IC (50) = 144 U/ml, n=30). The inhibitory action of TNF-alpha was also observed when I(Cl) had been previously stimulated by 1 micromol/L forskolin (n=5). Prior exposure of myocytes to 5 microg/ml pertussis toxin (PTX) hardly affected the anti-adrenergic action of TNF-alpha (n=4). However, when I(Cl) was induced by both 8-bromo-cAMP (100 micromol/L) and isobutylmethylxanthine (0.1 mmol/L), TNF-alpha (1,000 U/ml) failed to decrease I(Cl) amplitude (n=5). Prior exposure of myocytes to 5 mg/ml pertussis toxin (PTX) hardly affected the anti-adrenergic action of TNF-alpha (n=4). Furthermore, despite of the presence of nitro-L-arginine methyl ester (0.1 mmol/L), a nitric oxide synthase (NOS) inhibitor, TNF-alpha reversed the Iso-induced increase in I(Cl) (n=5). These results suggest that TNF-alpha rapidly antagonizes the beta-adrenergic responses of I(Cl) by reducing cAMP concentration. This anti-adrenergic action is mediated by neither the PTX-sensitive G proteins regulatory pathway nor constitutive NOS activation.     

Improvement in physiological outcomes and health-related quality of life following cardiac rehabilitation in patients with acute myocardial infarction.

BACKGROUND: The present study examined the impact of an 8-week cardiac rehabilitation (CR) program on physiological outcomes and health-related quality of life (HRQOL) of patients with acute myocardial infarction (AMI). METHODS AND RESULTS: A total of 124 consecutive AMI patients were divided into a supervised outpatient CR group (n=82) and a non-CR group as a control (n=42). Peak oxygen uptake, handgrip strength, and knee extension muscular strength were used as physiological outcome measures. HRQOL outcomes were assessed by the Medical Outcome Study Short Form 36 (SF-36). CR group patients performed both aerobic exercise and moderate resistance training from 1 month (T1) to 3 months (T2) after AMI onset. Age, sex, body mass index, medications, and ejection fraction were similar in both groups. Significantly greater increases in overall physiological outcomes from T1 to T2 were measured in the CR group compared with those of the non-CR group. There were also significantly greater improvements in 4 of the 8 SF-36 health status subscales (physical functioning, role-physical, general health, and vitality) in the CR group compared with the non-CR group. CONCLUSIONS: Eight weeks of exercise training have specific effects on improvement in HRQOL and physiological outcomes in Japanese patients.