Restoring assembly and activity of cystathionine β-synthase mutants by ligands and chemical chaperones

Misfolding and aggregation of mutant enzymes have been proposed to play role in the pathogenesis of homocystinuria due to cystathionine β-synthase (CBS) deficiency. Chemical chaperones have been recently shown to facilitate proper assembly of several CBS mutants. To asses the number of patients that may respond to chaperone therapy, we examined the effect of selected CBS ligands and osmolytes on assembly and activity of 27 CBS mutants that represent 70% of known CBS alleles. The mutant enzymes were expressed in a bacterial system, and their properties were assessed by native Western blotting and sensitive liquid chromatography tandem mass spectrometry (LC-MS/MS) assay, respectively. We studied the chaperoning activity of δ-aminolevulinic acid (δ-ALA)—a heme precursor—and of three osmolytes betaine, 2-aminoethanesulfonic acid (taurine), and glycerol. Fourteen mutants responded by at least 30% increase in the amount of correctly assembled tetramers and enzymatic activity to the coexpressional presence of either 0.5 mM δ-ALA, 100 mM betaine, and/or 750 mM glycerol. Eight of these mutants (p.R266K, p.P49L, p.R125Q, p.K102N, p.R369C, p.V180A, p.P78R, p.S466L) were rescuable by all of these three substances. Four mutants showed increased formation of tetramers that was not accompanied by changes in activity. Topology of mutations appeared to determine the chaperone responsiveness, as 11 of 14 solvent-exposed mutations were substantially more responsive than three of 13 buried mutations. This study identified chaperone-responsive mutants that represent 56 of 713 known patient-derived CBS alleles and may serve as a basis for exploring pharmacological approaches aimed at correcting misfolding in homocystinuria.     

Supersaturation of body fluids,plasma and urine,with respect to biological hydroxyapatite

Supersaturation of body fluids, specifically of plasma and urine, with respect to biological hydroxyapatite was evaluated taking into account calcium complexation, fraction of total phosphorus present as hydrogen phosphate ions, solubility of carbonated hydroxyapatite and the size dependency of equilibrium solubility. Plasma is always supersaturated with respect to apatitic solid phase and thus calcific deposits are formed unless a sufficient quantity of potent inhibitors is present. When urinary pH is lower than 6.3 for normal urine hydroxyapatite cannot appear in renal stones, at higher pH apatitic renal stones can be formed. Predictions based on supersaturation calculated for different conditions correspond well with clinical observations.     

Validation of a new tool for automatic assessment of tremor frequency from video recordings

We present a validation study for TremAn--a tool for automatic detection of tremor and measurement of its frequency from video recordings. To assess the validity of TremAn we designed a study consisting of tremor assessment from video, by accelerometry and by clinical evaluation using Fahn-Tolosa-Marin scale. 26 patients with essential tremor and 5 healthy volunteers underwent the examination in four standardized positions with focus on the hand tremor. Results showed that the frequencies of tremor measured with TremAn and with accelerometry are closely related, attaining agreement with less than 0.1 Hz difference in 80% and less than 0.5 Hz in 94% of measured samples. The reproducibility of frequency measurements using TremAn was comparable to the accelerometry, with the TremAn/accelerometry ratio of measurement error standard deviations equal to 0.99 (95% confidence interval (0.84, 1.17)).     

Atrial macroreentry tachycardia in patients without obvious structural heart disease or previous cardiac surgical or catheter intervention: characterization of arrhythmogenic substrates, reentry circuits, and results of catheter ablation

Introduction: Atrial macroreentry tachycardia (AMRT) in patients without obvious structural heart disease or previous surgical or catheter intervention has not been characterized in detail.
Methods and Results: Electroanatomical mapping and ablation of right or left AMRT were performed in 33 patients. Right atrial central conduction obstacle was formed by an electrically silent area (ESA) in 15 (68%) patients and by a line of double potentials (DPs) in seven (32%) patients. Left atrial ESAs were found in all 11 patients with the left AMRT. Reentry circuit was reconstructed in 19 (86%) patients with right AMRT and seven (64%) patients with left AMRT. Of the ESA-related right AMRT, eight (50%) were double-loop reentry circuits utilizing a narrow critical isthmus within the ESA and eight (50%) were single-loop reentry circuits with a critical isthmus bounded by ESA and either ostium of the vena cava. Single-loop DP-related AMRTs had the critical isthmus between the DP line and the ostium of the inferior vena cava (IVC). Left AMRTs included a variety of single-, double-, or triple-loop reentry circuits and their critical isthmuses. During the 37 ± 15 month follow-up, atrial tachyarrhythmia-free clinical outcome was achieved in 21 (95%) patients (18 patients, 82%, without antiarrhythmic drugs) with the right AMRT and in nine (82%) patients (six patients, 55%, without antiarrhythmic drugs) with the left AMRT.
Conclusion: The majority of right and left AMRTs were related to the presence of ESA. Ablation can be successful with a favorable risk of atrial tachyarrhythmia recurrence.     

Tumor angiogenesis

Angiogenesis have shown a major role in tumor growth and metastasis formation. For tumor growth beyond the size 1-2 mm3, angiogenesis must be started to form vascular supply of tumor cells. Angiogenesis is a complex process, involving degradation of the basement membrane of preexisting vessel, proliferation of endothelial cells towards the angiogenetic stimulus, maturation of endothelial cells with formation of luminized capillary, and finally formation of a functional vessel, surrounded by basement membrane and pericytes. Angiogenesis is regulated by numerous angiogenic and anti-angiogenic factors. Hypoxia is a significant stimulus for angiogenesis. For many cancers the extent of vascularisation is a negative prognostic indicator signifying aggressive disease and increased potential for metastasis.     

Pulmonary vein isolation using segmental versus electroanatomical circumferential ablation for paroxysmal atrial fibrillation

PURPOSE: We tested the hypothesis that electroanatomic pulmonary vein (PV) antra encircling for the PV isolation will improve the outcome in treatment of paroxysmal atrial fibrillation (PAF), compared with segmental PV isolation. METHODS: Fifty-four patients underwent segmental PV isolation (group 1) and 56 patients circumferential PV isolation (group 2) for symptomatic PAF in a randomized study. RESULTS: Following single ablation procedure, at the 48 +/- 8 month follow-up, 30 (56%) and 32 (57%) patients in groups 1 and 2 remained free of arrhythmia (P = 0.41). After repeat ablation, 43 (80%) and 45 (80%) patients in groups 1 and 2 were free of arrhythmia without antiarrhythmic drugs (AADs); 48 (89%) and 51 (91%) patients in groups 1 and 2 did not have arrhythmia recurrences without or with AADs. CONCLUSION: This study demonstrates no advantage in long-term arrhythmia-free clinical outcome after circumferential PV isolation in patients with frequent PAF.     

Urinary excretion of catecholamines in patients with primary aldosteronism before and after unilateral adrenalectomy

The authors compared urinary excretion of noradrenalin (NA), adrenalin (A) and dopamine (DA) in 12 patients with primary aldosteronism (PA), 54 healthy controls and 17 patients with fixed benign essential hypertension (BEH), and in PA investigated the changes occurring in the catecholamine spectrum after removal of aldosterone-producing adrenal adenoma. The patients with PA before adrenalectomy differed from the controls and patients with BEH by low NA excretion and high DA excretion. After unilateral adrenalectomy, patients with PA presented simultaneously with BP, aldosterone and renin normalization a rise in NA excretion and a drop in urinary DA to similar or lower values than those found in the controls and BEH. The results show that changes in urinary catecholamines excretion in A may be a secondary consequence of hypermineralocorticism. High DA may be the consequence of a mobilization of contra-regulatory natriuretic mechanisms in the course of aldosterone-induced sodium retention. Low NA and A may participate in lowering the plasma renin activity which in PA in suppressed, sometimes disproportionately to the actual body sodium content.