Cellular signaling by an agonist-activated receptor/Gs alpha fusion protein.

The consequences of agonist-dependent activation of guanine nucleotide-binding protein (G protein)-coupled receptors vary from cell to cell, depending on a complex network of regulations between components of the signaling cascade. Specific interactions between receptors, G proteins, and effectors are difficult to analyze in intact cells. Engineering of receptor-transducer fusion proteins might be an effective strategy to target cellular effectors more efficiently and specifically. As a model, we evaluated the ability of a fusion protein of beta 2-adrenergic receptor bound to the alpha subunit of adenylyl cyclase-stimulatory G protein (Gs alpha) to restore the defective activation of adenylyl cyclase in S49 cyc- cells that lack endogenous Gs alpha. The coupling between the two partners of the fusion protein was functional, and the agonist-dependent activation of the effector was more potent and more productive in transfected than in wild-type S49 cells. The covalent link between receptor and Gs alpha could thus convey an advantage over freely interacting components. Such receptor-G alpha fusion proteins may help to elucidate the complex interactions between members of signaling pathways and may also constitute a useful tool for studying the effects of single effector activation.     

Pyruvate and creatine prevent oxidative stress and behavioral alterations caused by phenylalanine administration into hippocampus of rats

Phenylketonuria is characterized by a variable degree of mental retardation and other neurological features whose mechanisms are not fully understood. In the present study we investigated the effect of intrahippocampal administration of phenylalanine, isolated or associated with pyruvate or creatine, on rat behavior and on oxidative stress. Sixty-day-old male Wistar rats were randomly divided into 6 groups: saline; phenylalanine; pyruvate; creatine; phenylalanine + pyruvate; phenylalanine + creatine. Phenylalanine was administered bilaterally in the hippocampus one hour before training; pyruvate, at the same doses, was administered in the hippocampus one hour before phenylalanine; creatine was administered intraperitoneally twice a day for 5 days before training; controls received saline solution at same volumes than the other substances. Parameters of exploratory behavior and of emotionality were assessed in both training and test sessions in the open field task. Rats receiving phenylalanine did not habituate to the open field along the sessions, indicating deficit of learning/memory, but parameters of emotionality were normal, not interfering in the habituation process. Pyruvate or creatine administration prevented the lack of habituation caused by phenylalanine. Pyruvate and creatine also prevented alterations provoked by phenylalanine on lipid peroxidation, total content of sulfhydryls, total radical-trapping antioxidant potential and total antioxidant reactivity. The results suggest that the behavioral alterations provoked by intra-hippocampal administration of phenylalanine may be caused, at least in part, by oxidative stress and/or energy deficit. If this also occurs in PKU, it is possible that pyruvate and creatine supplementation to the phenylalanine-restricted diet might be beneficial to phenylketonuric patients.     

IRM après radiochimiothérapie néoadjuvante du cancer du rectum

MRI is the optimal imaging technique to restage rectal cancer after neoadjuvant treatment, which is becoming a very relevant issue for tailoring of treatment. For optimal MRI, no bowel preparation is required; a standard protocol comprises T2-weighted sequences without fat suppression in three planes, and diffusion-weighted sequences. Gadolinium contrast administration has not proven to be beneficial. Interpretation criteria are morphologic, volumetric and functional (diffusion-weighted sequences). Overstaging is the most encountered problem because fibrosis cannot be distinguished from residual tumor. Especially, accuracy of identification of complete responders is only 30-35%, and MRI has to be correlated to clinical examination and endoscopy.     

Early bronchial airflow impairment in patients with persistent allergic rhinitis and bronchial hyperreactivity

BACKGROUND: Allergic rhinitis and its impact on asthma (ARIA) document underlines the link between upper and lower airways. Patients suffering from allergic rhinitis frequently (up to 80%) show bronchial hyperreactivity (BHR). OBJECTIVES: This study aimed at evaluating a group of subjects suffering from persistent allergic rhinitis, with BHR but with nasal symptoms only, to investigate the type and intensity of nasal symptoms, nasal and bronchial airflow, and BHR grade during the pollen season. METHODS: One hundred and twenty one polysensitized rhinitics were investigated. Total symptom score (TSS) was assessed in all patients. Rhinomanometry, spirometry and methacholine bronchial challenge were performed in all patients. RESULTS: 65 (53.7%) patients had impaired FEF 25-75 values. TSS correlated with nasal airflow (P<0.001) and BHR grade (P<0.001). Nasal airflow correlated with FEF 25-75 values (P<0.05) and BHR (P<0.001). FEF 25-75 values correlated with FEV(1) levels (P<0.003), BHR grade (P<0.001), and nasal obstruction symptom (P<0.05). Severe BHR correlated with FEV(1) (P<0.05) and FEF 25-75 (P<0.03) values, nasal airflow (P<0.05) and nasal symptoms (P<0.001). CONCLUSIONS: This study evidences that early bronchial impairment is frequently detectable in patients with persistent allergic rhinitis and BHR. Moreover, nasal function is strictly related with bronchial calibre and BHR grade. Therefore, careful evaluation of lower airways should be investigated in all rhinitics as suggested by the ARIA document.