An uncommon case of spontaneous conversion from AV re-entry tachycardia to AV nodal re-entry tachycardia in a patient with dual tachycardia

We report the case of a 46-year old patient in whom an electrophysiology study (EP) was performed due to paroxysmal supraventricular tachycardia documented in 12-lead ECG. During the EP study, supraventricular tachycardia was induced easily and it corresponded to orthodromic AV reentry tachycardia (AVRT) using a concealed left free wall accessory pathway. However, during the study AVRT spontaneously and repeatedly converted to the typical slow-fast AV node reentry tachycardia (AVNRT). Both accessory and AV nodal slow pathways were ablated, due to the finding that both AVRT and AVNRT were independently inducible during the EP study.     

Emergency epicardial dissection of the accessory pathway in a patient with atrioventricular nodal reentrant tachycardia]

Diagnostic and therapeutic problems in 14 year old patient with concealed WPW syndrome were presented. Paroxysms of atrio-ventricular reentrant tachycardia 180-220/min were frequently recurring, usually with normal QRS pattern. Tachycardias often had to be terminated by intravenous administration of antiarrhythmic drugs. Long term treatment with various antiarrhythmic agents did not prevent recurrence of tachycardias but they became sustained and were recurring more often. Their other side effects manifested with sinus node disfunction and depression of the heart muscle. The electrophysiologic study revealed right anterior septal accessory pathway. Epicardial dissection of the accessory pathway was urgently performed. The control electrophysiologic study revealed no evidence of conduction through the accessory pathway. The patient did not require antiarrhythmic treatment. During the 12 months follow up no tachycardia occurred.     

Interaction centres of purine nucleotides: adenosine-5'-diphosphate and adenosine-5'-triphosphate in their reactions with tetramines and Cu(II) ions

The interactions between the nucleotides: adenosine-5'-diphosphate (ADP) and adenosine-5'-triphosphate (ATP) with spermine (Spm) and 1,11-diamine-4,8-diazaundecane (3,3,3-tet), as well as Cu(II) ions are studied. In the metal-free systems nucleotide-polyamine molecular complexes have been found to form, in which the interaction centres are the nitrogen atoms of the purine ring N(1) and N(7), oxygen atoms of the phosphate group of the nucleotide (for 3,3,3-tet) and protonated nitrogen atoms of the polyamine. Significant differences in the mode of metallation between the systems with Spm and 3,3,3-tet have been established. In the systems with Spm, the main products are protonated species with [N(7),O] chromophore and the nitrogen N(1) is involved in the intramolecular interaction additionally stabilising the complex. In the systems with 3,3,3-tet the formation of metal-ligand-ligand (MLL) species has been observed, in which the oxygen atoms from the phosphate group and the nitrogen atoms from the polyamine are involved in the metallation, while the N(1) and N(7) atoms from the purine ring of the nucleotide remain outside the inner coordination sphere of the copper ion. The main centre of metallation in the nucleotide, both with Spm and 3,3,3-tet, is the phosphate group of the nucleotide.     

Mechanism of stimulation of globin synthesis by adenosine-3',5'-monophosphate and guanosine 5'-triphosphate in a rabbit reticulocyte lysate system

The inhibition of globin synthesis in hemin-deficient rabbit reticulocyte lysates is due to the activation of a hemin-controlled translational inhibitor (HCI) that specifically phosphorylates eIF-2 alpha. High concentrations of cAMP (5-10 mM) and GTP (1-2 mM) stimulated the globin synthesis in hemin-deficient lysates when these compounds were added at the initial stage of incubation. The mechanism of the stimulation by cAMP and GTP was studied using hemin-deficient lysates, the N-ethylmaleimide (NEM)-treated HCI-supplemented lysates and a partially purified initiation factor, eIF-2. As the stimulation of globin synthesis by these compounds must be due to the prevention of the inhibition of globin synthesis, or due to the restoration of globin synthesis, or both, the preventive and restorative effects of these compounds were examined. As for the preventive effect, it was observed that a) the activation of HCI in the postribosomal supernatant of reticulocytes was prevented by GTP, but not by cAMP, and b) cAMP and GTP inhibited the phosphorylation of eIF-2 alpha in hemin-deficient lysates. As for the restorative effect of cAMP and GTP, it was observed that c) these compounds restored the globin synthesis and the binding of [35S]Met-tRNAf to the 40S ribosomal subunits, and promoted the dephosphorylation of eIF-2(alpha P), d) the rates of the restored synthesis of globin were lower than the control, and e) cAMP promoted the release of [3H]GDP from the eIF-2(alpha P) X [3H]GDP complex and the formation of eIF-2(alpha P) X eIF-2B complex. Finding (d) indicates that steps involved in the restorative effect of these compounds may not contribute to the stimulation of the globin synthesis in hemin-deficient lysates. The data on the preventive and restorative effects of cAMP and GTP showed that these compounds affected multiple steps. That is, cAMP inhibited the phosphorylation of eIF-2 alpha and promoted both the release of GDP from eIF-2 and the formation of eIF-2(alpha P) X eIF-2B complex, and GTP prevented both the activation of HCI and the phosphorylation of eIF-2 alpha. Though cAMP and GTP affected multiple steps, it is suggested that cAMP stimulates the globin synthesis by inhibiting the phosphorylation of eIF-2 alpha and that GTP stimulates the globin synthesis chiefly by preventing the activation of HCI in hemin-deficient lysates.     

Transient kinetics of the interaction of 1,N6-ethenoadenosine 5'-triphosphate with myosin subfragment 1 under normal and cryoenzymic conditions: a comparison with adenosine 5'-triphosphate

The kinetics of the interaction of the fluorescent analogue 1,N6-ethenoadenosine 5'-triphosphate (epsilon-ATP) with myosin subfragment 1 (S1) were studied at 15 and -7.5 degrees C with 40% ethylene glycol as cryosolvent. Two techniques were used: fluorescence stopped flow and rapid flow-quench. When S1 is mixed with epsilon-ATP in a stopped-flow apparatus, biphasic fluorescence transients are obtained which are difficult to assign. Chemical sampling by the rapid-flow-quench method led to the chemical identity and the kinetics of interconversion of key intermediates, and by this method the optical signals were assigned and information about the cleavage and release of products was obtained. The data were interpreted by a shortened form of the Bagshaw-Trentham scheme for myosin adenosinetriphosphatase: M + ATP K1 in equilibrium M.ATP k2----M*.ATP k3 in equilibrium k3 M**.ADP.Pi k4----M + ADP + Pi The constants obtained were compared with those for ATP under identical conditions. In agreement with Rosenfeld and Taylor [Rosenfeld, S. S., & Taylor, E. W. (1984) J. Biol. Chem. 259, 11920-11929] we find that epsilon-ATP is bound tightly to S1 and that the chemical step is slower than with ATP. We show that the fast fluorescence transient is due to the tight binding of epsilon-ATP with K1 = 32 microM and k2 = 58 s-1 at 15 degrees C. With ATP these values are 8 microM and 16 s-1, respectively. There is a large difference in the delta H for k2: 50 kJ.mol-1 for epsilon-ATP and 119 kJ.mol-1 for ATP.(ABSTRACT TRUNCATED AT 250 WORDS)     

Localization of the high-affinity ATP site in adenosine-3':5'-monophosphate-dependent protein kinase type I. Photoaffinity labelling studies with 8-azidoadenosine 5'-triphosphate.

8-Azido-adenosine 5'-triphosphate (n8(3)ATP) appeared to be a suitable photoaffinity label for the protein kinase dependent on adenosine 3':5'-monophosphate (cAMP). It competes with ATP for the high-affinity ATP site in the undissociated form of the kinase and in the phosphotransferase reaction catalyzed by the catalytic subunit. Furthermore, it is accepted as a substrate in the phosphotransfer reaction. n8(3)ATP incorporated into the holoenzyme is covalently bound irradiation. Protection experiments with ATP indicated that this covalent attachment occurs in the high-affinity ATP site of the enzyme. Polyacrylamide gel electrophoresis in the presence of sodium dodecylsulfate shows that n8(3)ATP is bound to the catalytic subunit. After irradiation the enzyme was dissociated by cAMP. Proportional to the incorporated [gamma-32P]n8(3)ATP, a loss in phosphotransferase activity was found. These results support our model that both ATP sites coincide with respect to their adenine binding part. Thus binding of the regulatory subunit to the catalytic subunit would then transform the low-affinity catalytically active ATP site into a high-affinity inactive site.     

Mechanisms of initiation and termination of signalling by neuropeptide receptors: a comparison with the proteinase-activated receptors

Biological responses to neuropeptides are rapidly attenuated by overlapping mechanisms that include peptide degradation by cell-surface proteases, receptor uncoupling from heterotrimeric G-proteins and receptor endocytosis. We have investigated the mechanisms that terminate the proinflammatory effects of the neuropeptide substance P (SP), which are mediated by the neurokinin 1 receptor (NK1R). Neutral endopeptidase degrades SP in the extracellular fluid and is one of the first mechanisms to terminate signalling. G-protein receptor kinases and second-messenger kinases phosphorylate the NK1R to permit interaction with beta-arrestins, which uncouple the receptor from G-proteins to terminate the signal. SP-induces NK1R endocytosis by a beta-arrestin-dependent mechanism, which also involves the GTPases dynamin and Rab5a. Endocytosis contributes to desensitization by depleting receptors from the cell surface. Disruption of these mechanisms results in uncontrolled stimulation and disease. Thus the deletion of neutral endopeptidase in mice exacerbates inflammation of many tissues. There are similarities and distinct differences in the mechanisms that regulate signalling by neuropeptide receptors and other G-protein-coupled receptors, in particular those that are activated irreversibly by proteolysis.     

Microbody proliferation in liver induced by nafenopin, a new hypolipidemic drug: comparison with CPIB

Nafenopin (2-methyl-2[P-(1,2,3,4-tetrahydro-1 naphthyl) phenoxy]- propionic acid, a phenolic ether with hypolipidemic properties, when administered by gavage at 100 mg/kg b wt daily for 1 to 2 weeks, caused a significant increase in the number of microbody profiles and simultaneous increase in catalase activity in livers of male rats. The concentration of catalase protein and the rate of incorporation of H³-δ-aminolevulinic acid into catalase fraction, as determined by immunochemical methods were approximately twice that of controls. The microbody proliferation resulting from nafenopin treatment was comparable to that induced by CPIB.     

Downmodulation of mitochondrial F0F1 ATP synthase by diazoxide in cardiac myoblasts: a dual effect of the drug

Similar to ischemic preconditioning, diazoxide was documented to elicit beneficial bioenergetic consequences linked to cardioprotection. Inhibition of ATPase activity of mitochondrial F(0)F(1) ATP synthase may have a role in such effect and may involve the natural inhibitor protein IF(1). We recently documented, using purified enzyme and isolated mitochondrial membranes from beef heart, that diazoxide interacts with the F(1) sector of F(0)F(1) ATP synthase by promoting IF(1) binding and reversibly inhibiting ATP hydrolysis. Here we investigated the effects of diazoxide on the enzyme in cultured myoblasts. Specifically, embryonic heart-derived H9c2 cells were exposed to diazoxide and mitochondrial ATPase was assayed in conditions maintaining steady-state IF(1) binding (basal ATPase activity) or detaching bound IF(1) at alkaline pH. Mitochondrial transmembrane potential and uncoupling were also investigated, as well as ATP synthesis flux and ATP content. Diazoxide at a cardioprotective concentration (40 muM cell-associated concentration) transiently downmodulated basal ATPase activity, concomitant with mild mitochondria uncoupling and depolarization, without affecting ATP synthesis and ATP content. Alkaline stripping of IF(1) from F(0)F(1) ATP synthase was less in diazoxide-treated than in untreated cells. Pretreatment with glibenclamide prevented, together with mitochondria depolarization, inhibition of ATPase activity under basal but not under IF(1)-stripping conditions, indicating that diazoxide alters alkaline IF(1) release. Diazoxide inhibition of ATPase activity in IF(1)-stripping conditions was observed even when mitochondrial transmembrane potential was reduced by FCCP. The results suggest that diazoxide in a model of normoxic intact cells directly promotes binding of inhibitor protein IF(1) to F(0)F(1) ATP synthase and enhances IF(1) binding indirectly by mildly uncoupling and depolarizing mitochondria.     

Folate decorated dual drug loaded nanoparticle: role of curcumin in enhancing therapeutic potential of nutlin-3a by reversing multidrug resistance

Retinoblastoma is the most common intraocular tumor in children. Malfunctioning of many signaling pathways regulating cell survival or apoptosis, make the disease more vulnerable. Notably, resistance to chemotherapy mediated by MRP-1, lung-resistance protein (LRP) is the most challenging aspect to treat this disease. Presently, much attention has been given to the recently developed anticancer drug nutlin-3a because of its non-genotoxic nature and potency to activate tumor suppressor protein p53. However, being a substrate of multidrug resistance protein MRP1 and Pgp its application has become limited. Currently, research has step towards reversing Multi drug resistance (MDR) by using curcumin, however its clinical relevance is restricted by plasma instability and poor bioavailability. In the present investigation we tried to encapsulate nutlin-3a and curcumin in PLGA nanoparticle (NPs) surface functionalized with folate to enhance therapeutic potential of nutlin-3a by modulating MDR. We document that curcumin can inhibit the expression of MRP-1 and LRP gene/protein in a concentration dependent manner in Y79 cells. In vitro cellular cytotoxicity, cell cycle analysis and apoptosis studies were done to compare the effectiveness of native drugs (single or combined) and single or dual drug loaded nanoparticles (unconjugated/folate conjugated). The result demonstrated an augmented therapeutic efficacy of targeted dual drug loaded NPs (Fol-Nut-Cur-NPs) over other formulation. Enhanced expression or down regulation of proapoptotic/antiapoptotic proteins respectively and down-regulation of bcl2 and NFκB gene/protein by Fol-Nut-Cur-NPs substantiate the above findings. This is the first investigation exploring the role of curcumin as MDR modulator to enhance the therapeutic potentiality of nutlin-3a, which may opens new direction for targeting cancer with multidrug resistance phenotype.     

Hepatic and nonhepatic sterol synthesis and tissue distribution following administration of a liver selective HMG-CoA reductase inhibitor, CI-981: comparison with selected HMG-CoA reductase inhibitors.

Since cholesterol biosynthesis is an integral part of cellular metabolism, several HMG-CoA reductase inhibitors were systematically analyzed in in vitro, ex vivo and in vivo sterol synthesis assays using [14C]acetate incorporation into digitonin precipitable sterols as a marker of cholesterol synthesis. Tissue distribution of radiolabeled CI-981 and lovastatin was also performed. In vitro, CI-981 and PD134967-15 were equipotent in liver, spleen, testis and adrenal, lovastatin was more potent in extrahepatic tissues than liver and BMY21950, pravastatin and PD135023-15 were more potent in liver than peripheral tissues. In ex vivo assays, all inhibitors except lovastatin preferentially inhibited liver sterol synthesis; however, pravastatin and BMY22089 were strikingly less potent in the liver. CI-981 inhibited sterol synthesis in vivo in the liver, spleen and adrenal while not affecting the testis, kidney, muscle and brain. Lovastatin inhibited sterol synthesis to a greater extent than CI-981 in the spleen, adrenal and kidney while pravastatin and BMY22089 primarily affected liver and kidney. The tissue distribution of radiolabeled CI-981 and lovastatin support the changes observed in tissue sterol synthesis. Thus, we conclude that a spectrum of liver selective HMG-CoA reductase inhibitors exist and that categorizing agents as liver selective is highly dependent upon method of analysis.     

Crystal structure of tryptophanyl-tRNA synthetase complexed with adenosine-5' tetraphosphate: evidence for distributed use of catalytic binding energy in amino acid activation by class I aminoacyl-tRNA synthetases

Tryptophanyl-tRNA synthetase (TrpRS) is a functionally dimeric ligase, which specifically couples hydrolysis of ATP to AMP and pyrophosphate to the formation of an ester bond between tryptophan and the cognate tRNA. TrpRS from Bacillus stearothermophilus binds the ATP analogue, adenosine-5' tetraphosphate (AQP) competitively with ATP during pyrophosphate exchange. Estimates of binding affinity from this competitive inhibition and from isothermal titration calorimetry show that AQP binds 200 times more tightly than ATP both under conditions of induced-fit, where binding is coupled to an unfavorable conformational change, and under exchange conditions, where there is no conformational change. These binding data provide an indirect experimental measurement of +3.0 kcal/mol for the conformational free energy change associated with induced-fit assembly of the active site. Thermodynamic parameters derived from the calorimetry reveal very modest enthalpic changes, consistent with binding driven largely by a favorable entropy change. The 2.5 A structure of the TrpRS:AQP complex, determined de novo by X-ray crystallography, resembles that of the previously described, pre-transition state TrpRS:ATP complexes. The anticodon-binding domain untwists relative to the Rossmann-fold domain by 20% of the way toward the orientation observed for the Products complex. An unexpected tetraphosphate conformation allows the gamma and deltad phosphate groups to occupy positions equivalent to those occupied by the beta and gamma phosphates of ATP. The beta-phosphate effects a 1.11 A extension that relocates the alpha-phosphate toward the tryptophan carboxylate while the PPi mimic moves deeper into the KMSKS loop. This configuration improves interactions between enzyme and nucleotide significantly and uniformly in the adenosine and PPi binding subsites. A new hydrogen bond forms between S194 from the class I KMSKS signature sequence and the PPi mimic. These complementary thermodynamic and structural data are all consistent with the conclusion that the tetraphosphate mimics a transition-state in which the KMSKS loop develops increasingly tight bonds to the PPi leaving group, weakening linkage to the Palpha as it is relocated by an energetically favorable domain movement. Consistent with extensive mutational data on Tyrosyl-tRNA synthetase, this aspect of the mechanism develops high transition-state affinity for the adenosine and pyrophosphate moieties, which move significantly, relative to one another, during the catalytic step.     

Existence of a light-sensitive phase in the photoperiodic termination of diapause inPieris brassicae L. (Insecta:Lepidoptera) and comparison with diapause induction

Summary Pupal diapause ofPieris brassicae can be terminated experimentally by the sole action of photoperiod. Curves gave evidence of similar effect of photoperiod within a broad range of regimes in both diapause induction and termination. However, they showed opposite responses to ultra-short and ultra-long days and to continuous light and darkness. In diapause termination, the critical daylength is longer than in diapause induction by about 1.20 h.Results of night interruption experiments (asymmetrical skeleton photoperiods) provided the first reliable evidence of the involvement of a particular light-sensitive phase in photoperiodic diapause termination. A light pulse delivered at this moment elicited a complete long-day effect (i.e. diapause termination). Only one single point of long-day effect (lying in the early night) was disclosed in diapause termination whereas two points (A and B) characterize diapause induction in this species. Results of experimental designs where the period of the photoperiodic cycles differed from 24 h indicated that photoperiodic clock likely makes a nightlength measurement in both diapause induction and termination. This is discussed in relation to the formal properties of the clock, especially those derived from the time distribution of points of long-day effect.     

Loss of consciousness and convulsion induced by a ventricular tachycardia mimicking epilepsy in a patient with noncompaction cardiomyopathy: a case report

Convulsions and loss of consciousness can be caused by, among other things, arrhythmias, conduction disorders or epilepsy. In clinical practice it can be difficult to distinguish between these causes of syncope, even for well-trained specialists. Patients with cardiac syncope have a substantial risk of subsequent sudden death. We present a patient with previously unknown noncompaction cardiomyopathy in whom syncope induced by ventricular tachycardia was misinterpreted as epilepsy. We present this case report in order to underline the necessity for cardiological assessment in patients with assumed mild epilepsy or syncope of unknown origin.     

Effects of 5 rounds of mass drug administration with diethylcarbamazine and albendazole on filaria-specific IgG4 titers in urine: 6-year follow-up study in Sri Lanka

ELISA for filaria-specific IgG4 in urine (urine ELISA) was applied to children in 7 schools in Sri Lanka, before and after 5 rounds of annual mass drug administration (MDA). The pre-treatment IgG4 prevalence in 2002 was 3.20%, which decreased to 0.91% in 2003 after the first MDA (P<0.001), and finally to 0.36% in 2007 after the 5th MDA. Among 5-10 year-old children, the prevalence decreased from 3.37% in 2002 to 0.51% in 2003 (P=0.009). A pattern of IgG4 titer distribution according to age and its yearly change could also provide useful information in drug efficacy analysis. In 2008, new samples from eleven 2006/07 urine ELISA-positive students and their family members (total n=56) were examined by ICT antigen test, microfilaria test, and urine ELISA. No infection was confirmed among them. Urine ELISA will be useful in monitoring elimination/resurgence in a post-MDA low endemic situation.