Dynamic structure of lipid-bound synaptobrevin suggests a nucleation-propagation mechanism for trans-SNARE complex formation

The synaptic vesicle protein synaptobrevin engages with syntaxin and SNAP-25 to form the SNARE complex, which drives membrane fusion in neuronal exocytosis. In the SNARE complex, the SNARE motif of synaptobrevin forms a 55-residue helix, but it has been assumed to be mostly unstructured in its prefusion form. NMR data for full-length synaptobrevin in dodecylphosphocholine micelles reveals two transient helical segments flanked by natively disordered regions and a third more stable helix. Transient helix I comprises the most N-terminal part of the SNARE motif, transient helix II extends the SNARE motif into the juxtamembrane region, and the more stable helix III is the transmembrane domain. These helices may have important consequences for SNARE complex folding and fusion: helix I likely forms a nucleation site, the C-terminal disordered SNARE motif may act as a folding arrest signal, and helix II likely couples SNARE complex folding and fusion.     

Primary coronary angioplasty with stent implantation in a patient with dextrocardia - a case report

A case of a 45-year-old male with acute myocardial infarction and dextrocardia is presented. The patient underwent successful primary coronary angioplasty with direct stenting. Difficulties in establishing diagnosis and treating patients with dextrocardia and chest pain are discussed.     

Polymorphism of the sulfonylurea receptor gene in type 2 diabetes mellitus

Sulfonylureas are used in treatment of diabetes. Resistance to these derivatives is a therapeutical problem. Sulfonylureas act through sulfonylurea receptor 1 (SUR1) in the beta cell. SUR1 also enhances a physiological secretion of insulin induced by an increase of glucose concentration. It may be expected that polymorphism of SUR1 gene can lead to beta cell dysfunction and resistance to sulfonylureas. The aim of this study was to examine the frequency of polymorphism in exon 22 of SUR1 gene and its correlation with type 2 diabetes mellitus and sulfonylurea treatment failure. The group consisted of 42 patients with type 2 diabetes. The controls were 46 persons with proper glucose tolerance. Polymorphism was found in 5 patients and in 1 control person. Neither statistically significant difference of polymorphism frequency nor correlation between polymorphism and sulfonylurea failure was found due to a low number of cases. Polymorphism of exon 22 of SUR1 gene appeared more frequent in diabetic than in non-diabetic subjects but this was statistically not significant.     

Impact of cardiac resynchronisation therapy on adaptation of circulatory and respiratory systems to exercise assessed by cardiopulmonary exercise test in patients with chronic heart failure

BACKGROUND: Cardiac resynchronisation therapy (CRT) has become a valuable therapeutic tool in patients with advanced chronic heart failure (CHF). The search for optimal methods for the assessment of CRT efficacy is still underway. AIM: To evaluate the impact of implantation of CRT devices in patients with CHF on adaptation of circulatory and respiratory systems to maximal exercise assessed by cardiopulmonary exercise tests (CPX) and 6-minute walking tests (6MWT). METHODS: We investigated 27 patients (22 males, 5 females, 61.2+/-9.1 years) with a CRT device implanted due to advanced CHF, which resulted from ischaemic or dilated cardiomyopathy. All patients before implantation underwent echocardiography, CPX with expired gas analysis and 6MWT. Investigations were repeated at 3-6 months after CRT implantation. In CPX we evaluated peak oxygen uptake (peak VO2), oxygen pulse, maximal minute ventilation-carbon dioxide production (VE/VCO2 (max)), and its slope (VE/VCO2 slope) and VE/VO2 slope, VO2 in anaerobic threshold (AT), and cardiac and respiratory reserve. In 6MWT we evaluated walking distance and heart rate and blood pressure response to exercise. RESULTS: We noted statistically higher mean peak VO2 after CRT implantation in the studied group: 11.34+/-3.38 vs. 14.56+/-3.99 ml/kg/min (p<0.0001) and 1.01 +/-0.44 vs. 1.4+/-0.55 l/min (p=0.003) and higher values of expired CO2: 1.00+/-0.43 vs. 1.43+/-0.67 l/min (p=0.004). The O2 pulse rose from 9.65+/-3.39 to 13.23+/-5.43 ml/beat (p=0.015). We also observed a significant reduction of VE/VCO2 slope from 42.34+/-13.35 before CRT to 34.77+/-6.04 after CRT (p=0.0196) and a significant decrease of VE/VO2 slope from 41.32 +/-15.46 to 34.01+/-6.27 (p=0.037). VE/VCO2 (max) fell from 58.02+/-15.86 to 50.1+/-13.14 (p=0.009). Patients estimated their dyspnoea on the Borg scale at peak exercise at 4.75+/-0.75 points before CRT and at 3.67+/-1.15 points (p=0.002) after CRT. Patients could walk a longer distance during 6MWT than before CRT (367+/-154.9 vs. 231.1+/-170.3 m, p<0.001). CONCLUSIONS: Cardiac resynchronisation therapy improves exercise tolerance measured by means of CPX and 6MWT, improves respiratory system efficiency and restores its adaptive mechanisms during exercise in patients with advanced CHF. Better exercise adaptation after CRT may be objectively measured with CPX parameters, and correlates with improvement of clinical symptoms. CPX seems to be a very helpful tool in assessing the results of CRT.     

Comparison of the effect of nitroglycerine and pentaerithritol compositum on exercise time restricted by anginal pain or objective parameters of ischaemia in patients with stable angina

Short acting nitrates are commonly used to prevent the anginal pain. The purpose of the study was to compare antianginal efficacy of Pentaerythritol compositum (20 mg of pentaerythritol tetranitrate and 0.5 mg of nitroglicerine) and 0,5 mg of nitroglycerine. Twenty patients aged 45-75 years with stable angina were enrolled. Antianginal effectiveness was evaluated during treadmill test. Time to ischemic pain and/or electrocardiographic parameters of ischemia were measured. It was found that Pentaerythritol compositum was superior to nitroglycerine in preventing angina with the difference disappearing 60 minutes after drug administration. Both drugs were well tolerated. Achieved results show that Pentaerythritol compositum can be effective as antianginal drug in patients with stable angina.     

First heart sound and opening snap in patients with mitral valve disease. Phonocardiographic and pathomorphologic study

Patients with exercise angina >2 months (n:13) showed significantly lower SigmaST elevation during 120 s balloon coronary occlusion than those with =<2 months (n:7), or those with angina at rest <=2 days (n:8) but similar to patients with angina at rest >2 days (n:7). These results underscore the importance of the kind and duration of angina in limiting the extent of ischemia during coronary occlusion.     

Type A aortic intramural haematoma--clinical course in two patients

Aortic intramural haematoma (AIH) is a variation of aortic dissection where blood collects within the aortic media without the presence of an intimal flap. The natural history of the disease has not yet been definitely established. Two cases of AIH type A are presented--an 81-year-old hypertensive male, and a 60-year-old male, both admitted to the hospital with sudden-onset severe chest pain. In both cases AIH type A was confirmed using computed tomography. One patient underwent successful conservative treatment, whereas another one had urgent surgery.     

Pharmacological versus invasive treatment in patients with atrial fibrillation

Aim of this prospective study was to assess quality of life (QoL), left ventricular (LV) function and exercise performance in two groups of patients (pts) with atrial fibrillation (Af) treated with: radiofrequency catheter ablation (RFA) and antiarrhythmic drugs (AA). Between 1996 and 2000 - 74 patients, 28 women, with drug refractory Af were enrolled by clinical indications for two modes of therapy: RFA and AA. RFA group consisted of 38 pts, 63.7 +/- 11.5 years old: 28 pts with RF AV Node ablation and pacemaker implantation (PI) and 10 pts with AV Node modification or right atrial isthmus RF ablation due to Af conversion to atrial flutter (Aflu) during medical therapy. AA group consisted of 36 pts, aged 59.7 +/- 13.8 years. Patients from RFA group suffered significantly more serious diseases than pts from AA group. No significant (sign.) differences between two groups were found in age, gender, arrhythmia history and number of AA taken. Pts were analyzed before entry, after 3 and 12 months of follow-up (3 mo. FU, 12 mo. FU) with following indices: LV function (Echo: EF & FS), exercise performance (treadmill test), QoL questionnaires, number of hospital admissions connected to arrhythmia or procedures (RFA & PI), number of AA drugs taken in RFA group. RFA group: Two deaths occurred due to end stage respiratory insufficiency (COPD), one pt required reposition of pacemaker lead. AA group: 3 pts required RFA due to uncontrolled Af/Aflu (AV Node ablation with PI - 1 pt, right atrial isthmus ablation - 2 pts). Analysis of two patients groups: LV function: Sign. improvement (EF & FS) in both groups in 12 mo. FU; Exercise performance: no sign. changes in 3 and 12 mo. FU. QoL: Arrhythmia scale: 3 mo. FU sign. reduction in both groups; 12 mo. FU reduction in RFA group only; Anxiety scale: 3 and 12 mo. FU sign. reduction of anxiety level in RFA group; Exercise and activity scales: 3 and 12 mo. FU sign. improvement in RFA group. During 3 and 12 mo. FU sign. less pts from RFA group required hospital admission versus pts from AA group. Sign. reduction in AA was noted in RFA group. Patients with symptomatic Af treated with RFA benefit from this kind of therapy more than patients treated with AA. Quality of life improvement visible in short term observation in patients from RFA group is still present after one year observation. Improvement in LV function is observed after one year in both groups of pts with Af.