Molecular modelling and site-directed mutagenesis of the active site of endothelin-converting enzyme

Mammalian endothelin-converting enzyme is a membrane-bound metalloprotease; its C-terminal domain contains sequence motifs characteristic of zinc metalloproteases. We examined residues expected from molecular modelling to be important for substrate binding using selectively mutated recombinant rat ECE-1alpha expressed in CHO cells. A conserved N-A-Ar-Ar (Ar = aromatic) motif is likely to be important for substrate binding. Mutating N550 to Gln or Y552 to Phe reduces Vmax/Km by 8- and 18-fold, respectively. The equivalent residue to Y553 in thermolysin binds the inhibitor through its NH group. Removing this putative interaction by mutating Tyr to Pro destroys activity, but mutating it to Ala or Phe also removes most activity. Mutating G583 (in a conserved GGI motif N-terminal of the zinc-binding helix) to Ala has no measurable effect, but mutating G584 to Ala destroys activity. Changing V583 in the zinc-binding helix to Met, to mimic the sequence pattern in bovine ECE-2, increases Vmax/Km to 1.7-fold that of the wild- type. Assays of phosphoramidon binding follow the pattern of those of substrate binding, but the IC50 of the more potent ECE inhibitor CGS 26303 was not significantly altered by any of these mutations, suggesting that this compound may bind to ECE in a different mode from phosphoramidon.      

Catalytic dehydrogenation of cyclohexane over Ag-M/ACC catalysts for hydrogen supply

Dehydrogenation of cyclohexane to benzene has been carried out over Ag supported on activated carbon cloth (Ag/ACC) catalysts using a spray- pulse reactor. Hydrogen evolution was studied for hydrogen storage and supply system applications. The maximum rate of hydrogen evolution rate using monometallic Ag/ACC catalysts was 6.9 mmol/g_met/min for Ag loading of 10 wt%. An enhanced hydrogen evolution was observed by adding a small amount of noble metal (1 wt% Pt, Pd, Rh) to the Ag based catalysts. A synergistic effect was observed in the case of the Pt promoted catalysts on the hydrogen production were twice as compared to 10 wt% Ag catalyst only.     

Design development and testing of a solar PV pump based drip system for orchards

A Solar Photovoltaic (PV) pump operated drip irrigation system has been designed and developed for growing orchards in arid region considering different design parameters like pumps size, water requirements, the diurnal variation in the pressure of the pump due to change in irradiance and pressure compensation in the drippers. The system comprising a PV pump with 900 W_p PV array and 800 W dc motor-pump mono-block, micro filter, main and sub-mains and three open-able low-pressure compensating drippers on each plant was field tested. The emission uniformity was observed to be 92–94% with discharge of 3.8 l/h in the pressure range of 70–100 kPa provided by the pump and thus the system could irrigate some 1 ha area within 2 h. Based on the performance of the PV pump and the drip system, it was inferred that about 5 ha area of orchard could be covered. The projected benefit–cost ratio for growing pomegranate orchards with such a system was evaluated to be above 2 even with the costly PV pump and therefore the system was considered to be an appropriate technology for the development of arid region.     

Bases of surgical treatment of bilateral suppurative processes in the lungs

In dogs subjected to gravitational overloadings (+Gx) according to a special training schedule the wall structure of the main arteries (carotid, humeral, femoral and aorta) was studied by histological methods. The amount of catecholamines (adrenaline and noradrenaline) in the venous blood plasma and in the adrenal tissue was the index of the sympathoadrenal system condition. It was demonstrated that in trained animals the tolerance threshold to continuously increasing overloadings (+Gx) rose. It was accompanied by an elevated amount of catecholamines in blood and the adrenals In the walls of the main arteries studied a moderate hyperelastosis and a slight collagenization of the adventitia was noted. All parts of the microcirculatory bed were moderately dilated, which favoured a better blood outflow. The data obtained demonstrate adaptational changes, which can be interpreted as indices of training and reliability of the organism.     

Purification, crystallisation and preliminary X-ray diffraction study of ribosome inactivating protein: saporin

OBJECTIVES: To compare transesophageal atrial pacing stress echocardiography with dobutamine stress echocardiography for feasibility, safety, duration, patient acceptance and concordance in inducing wall motion abnormalities. BACKGROUND: Transesophageal atrial pacing is an effective method of increasing heart rate and has been used in the assessment of coronary artery disease. METHODS: Both tests were performed in sequence on the same patients in random order. Transesophageal atrial pacing stress echocardiography began at a heart rate of 10 beats/min above the baseline value and was increased by 20 beats/min every two min until 85% of the age-predicted maximum heart rate or another end point was reached. Dobutamine echocardiography was performed using three-min stages and a maximum dose of 40 microg/kg per min. Atropine (total dose < or =2 mg) was administered at the start of the 40 microg/kg per min stage if needed to augment heart rate or during pacing if Wenckebach heart block occurred. RESULTS: Transesophageal atrial pacing stress echocardiography was feasible in 100 of 104 patients (96%); the duration (8.6+/-3.6 min) was significantly shorter than that of dobutamine stress echocardiography (15.1+/-3.9 min) (p = 0.0001). With transesophageal atrial pacing stress echocardiography, the recovery period was shorter, symptoms and dysrhythmias were fewer, hypertension and hypotension were less common and target heart rate was more frequently achieved. No complications occurred with either test. Patient acceptance was satisfactory. Agreement between results of both tests was good for segmental wall motion scoring with a 16-segment model, scores 1 to 5 (kappa: rest, 0.79; peak, 0.57) and test interpretation (normal, ischemia, infarction or resting wall motion abnormality with ischemia) (kappa: 0.77). CONCLUSIONS: Transesophageal atrial pacing stress echocardiography is a feasible, well-tolerated alternative to dobutamine stress echocardiography. It can be performed rapidly and shows good agreement with dobutamine stress echocardiography in the induction of myocardial ischemia.     

Chronic abdominal pain: role of video-laparoscopic adhesiolysis

Adhesions have been suggested as a possible cause of chronic abdominal pain, but the reports of their etiological role conflict. Lysis of adhesions has been proposed as the therapeutic modality of choice, although the reports of success are controversial. The aim our prospective study was to determine whether laparoscopic adhesiolysis ameliorates chronic abdominal pain in patients with abdominal adhesions. Forty-one patients with chronic abdominal pain lasting for more than 6 months, but with no abnormal findings other than adhesions found at laparoscopy, underwent laparoscopic adhesiolysis. 37 patients (90.2%) were available for follow-up after a median time interval of 18 months (range: 12-41 months). Twenty-two patients (59.4%) were free from abdominal pain and 9 (24.3%) patients reported significant amelioration of their pain. Six (16.2%) patients had no amelioration. In conclusion the laparoscopy is an effective tool for the evaluation of patients with chronic abdominal pain, and laparoscopic adhesiolysis cures of ameliorates chronic abdominal pain in more than 80% of patients.     

Acute toxicity of several organophosphorous insecticides and protection by cholinergic antagonists and 2-PAM on Artemia salina larvae

Western blot analysis and indirect immunofluorescence microscopy were used to evaluate the fate of the aryl-hydrocarbon receptor (AhR) and aryl-hydrocarbon receptor nuclear translocator (Arnt) protein in culture cell models exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). In wild-type (WT) murine Hepa-1c1c7 cells, AhR protein was depleted by 85% after 4 hr of TCDD treatment as measured in total cell lysates. In contrast, the concentration of Arnt protein was unaffected by TCDD treatment in WT cells. Analysis of the AhR with immunofluorescence microscopy revealed that nuclear translocation of the liganded AhR preceded its depletion from cells. AhR protein was depleted from Hepa-1 type I variants (that contain a concentration of AhR that is 10% of WT) with a similar time course and to the same maximal level observed in WT cells (85%). The EC50 for AhR depletion in Hepa-1 cells was 39 pm TCDD and correspond to the EC50 for induction of P4501A1 protein. Murine embryonic fibroblasts (NIH-3T3), rat aortic smooth muscle cells (A7), and murine skeletal muscle cells (C2C12) all exhibited >90% depletion of the AhR after 2-4 hr of TCDD treatment. Arnt concentration was not affected by TCDD in these cell lines. These results indicate that the liganded AhR is rapidly depleted within the nuclear compartment of hepatic and nonhepatic cells in a manner independent of the Arnt protein.