Molecular characterisation of congenital myasthenic syndromes in Southern Brazil

Objective To perform genetic testing of patients with congenital myasthenic syndromes (CMS) from the Southern Brazilian state of Parana. Patients and methods Twenty-five CMS patients from 18 independent families were included in the study. Known CMS genes were sequenced and restriction digest for the mutation RAPSN p.N88K was performed in all patients. Results We identified recessive mutations of CHRNE in ten families, mutations in DOK7 in three families and mutations in COLQ, CHRNA1 and CHRNB1 in one family each. The mutation CHRNE c. 70insG was found in six families. We have repeatedly identified this mutation in patients from Spain and Portugal and haplotype studies indicate that CHRNE c. 70insG derives from a common ancestor. Conclusions Recessive mutations in CHRNE are the major cause of CMS in Southern Brazil with a common mutation introduced by Hispanic settlers. The second most common cause is mutations in DOK7. The minimum prevalence of CMS in Parana is 0.18/100 000

Novel homozygous RARS2 mutation in two siblings without pontocerebellar hypoplasia - further expansion of the phenotypic spectrum.

BACKGROUND: Pontocerebellar hypoplasia type 6 (PCH6) is a mitochondrial disease caused by mutations in the RARS2 gene. RARS2 encodes mitochondrial arginyl transfer RNA synthetase, an enzyme involved in mitochondrial protein translation. A total of 27 patients from 14 families have been reported so far. Characteristic clinical features comprise neonatal lactic acidosis, severe encephalopathy, intractable seizures, feeding problems and profound developmental delay. Most patients show typical neuroradiologic abnormalities including cerebellar hypoplasia and progressive pontocerebellar atrophy. METHODS: We describe the clinical, biochemical and molecular features of 2 siblings with a novel homozygous mutation in RARS2. Both patients presented neonatally with lactic acidosis. While the older sibling had severe neurological symptoms with microcephaly, seizures and developmental delay, the younger patient was still neurologically asymptomatic at the age of 2 months. RESULTS: MRI studies in both children lacked pontocerebellar involvement. The expression of the OXPHOS complex proteins was decreased in both patients, whereas oxygen consumption was increased. CONCLUSIONS: Characteristic neuroradiological abnormalities of PCH6 such as vermis and cerebellar hypoplasia and progressive pontocerebellar atrophy may be missing in patients with RARS2 mutations. RARS2 testing should therefore also be performed in patients without pontocerebellar hypoplasia but otherwise typical clinical symptoms

The Coronary Microcirculation in Hamster-to-Rat Cardiac Xenografts

BACKGROUND The aim of this study was to establish a new experimental model to directly analyse the coronary microcirculation in cardiac xenografts. METHODS Intravital fluorescence microscopy (IVM) of the subepicardial microcirculation in heterotopically transplanted hamster-to-rat cardiac xenografts was performed at 30 and 90 min of reperfusion. We quantitatively assessed the microcirculatory perfusion characteristics as well as the interactions of leukocytes and platelets with the endothelium of postcapillary coronary venules in non-sensitised as well as sensitised recipients. RESULTS In this first experimental IVM study of cardiac xenografts, we successfully visualised the subepicardial microcirculation, i.e. feeding arterioles, nutritive capillaries and draining postcapillary venules, during reperfusion. Leukocyte-endothelial and platelet-endothelial cell interactions could be quantified. In the non-sensitised group, the myocardial microcirculation remained stable during the observation period of 90 min, whereas in the sensitised group, xenografts were rejected immediately. CONCLUSIONS We established a model for the assessment of the microcirculatory dysfunction and inflammation during ischaemia/reperfusion injury in hamster-to-rat cardiac xenografts

Congental myasthenic syndromes - diagnostics and treatment

Kongenitalni mijastenički sindromi (KMS) predstavljaju poremećaje granice sigurnosti neuralne transmisije na presinaptičkoj, sinaptičkoj i postinaptičkoj razini. Dijagnoza kongenitalnog mijasteničkog sindroma postavlja se na temelju kliničke slike koja uključuje mišićnu slabost uzrokovanu zamorom što se pojavljuje od ranog djetinjstva, oftalmoparezu, respiratornu insuficijenciju, poremećaj funkcije mišića inerviranih kranijalnim živcima te pad amplitude mišićnog potencijala pri repetitivnoj stimulaciji (dekrementalni odgovor) i odsutnost protutijela na acetilkolinske receptore (AchR) i mišićno specifičnu tirozinsku kinazu (MuSK). Neki kongenitalni mijastenički sindromi manifestiraju se kasnije, a mišićna slabost i dekrementalni odgovor pojavljuju se intermintentno sa selektivnom raspodjelom u određenim mišićnim skupinama. Molekularno genetska analiza je vrlo značajna u dijagnostici kongenitalnog mijasteničkog sindroma. Presinaptički kongenitalni mijastenički sindrom vezan je za recesivne mutacije gena CHAT (kolinacetiltransferaza). Sinaptički oblik uzrokovan je mutacijom podjedinice kolagenskog repa acetilkolinesteraze (AchE). Većina kongenitalnih mijasteničkih sindroma su postsinaptički, uzrokovani mutacijama gena AchR podjedinica. Najčešće su mutacije gena CHRNE za ε-podjedinicu. Općenito, besmislene ili mutacije s pomakom okvira čitanja uzrokuju kongenitalni mijastenički sindrom zbog smanjene ili odsutne ekpresije proteina i nasljeđuju se autosomno recesivno. Mutacije gena rapsina (RAPSN) uzrokuju primarni nedostatak AchR-a na završnoj ploči. U terapiji kongenitalnog mijasteničkog sindroma ponajprije se primjenjuju inhibitori AchE. Prikazujemo djecu s kongenitalnim presinaptičkim i postinaptičkim poremećajima koji su udruženi sa značajnom varijabilnošću kliničke ekspresije u okviru kongenitalnog mijasteničkog sindroma.Congenital myasthenic syndromes (CMS) are genetically determined disorders affecting safety margins of neural transmission at presynaptic, postsynaptic and synaptic level. Diagnosis of CMS is made based on clinical symptoms including fatigable muscle weakness since infancy or childhood, decremental EMG response and negative antibodies to acetylcholine receptors (AchR) and muscle specific tyrosine kinase (MuSK). In some CMS the onset is delayed, weakness and EMG abnormalities appear intermittently in restricted distribution. Molecular genetic analysis has an important role in diagnosis of CMS. Presynaptic CMS are associated with recessive CHAT (cholinacyltransferase) gene mutations. The synaptic disorder is caused by mutation of the collagenic tail subunit of the AchE gene. However most CMS are postsynaptic, mostly caused by CHRNE gene mutations of AchR ε-subunit. In general, nonsense or frame shifting mutations cause CMS by decreased or absent protein expression and are inherited in autosomal recessive traits. Rapsyn gene (RAPSN) mutations cause primary endplate AchR deficiency. AchE inhibitors are the drugs of first choice in the treatment of CMS. We present children with presynaptic and with postsynaptic defects manifesting remarkable clinical heterogeneity

Fast b-tagging at the high-level trigger of the ATLAS experiment in LHC Run 3

The ATLAS experiment relies on real-time hadronic jet reconstruction and b-tagging to record fully hadronic events containing b-jets. These algorithms require track reconstruction, which is computationally expensive and could overwhelm the high-level-trigger farm, even at the reduced event rate that passes the ATLAS first stage hardware-based trigger. In LHC Run 3, ATLAS has mitigated these computational demands by introducing a fast neural-network-based b-tagger, which acts as a low-precision filter using input from hadronic jets and tracks. It runs after a hardware trigger and before the remaining high-level-trigger reconstruction. This design relies on the negligible cost of neural-network inference as compared to track reconstruction, and the cost reduction from limiting tracking to specific regions of the detector. In the case of Standard Model HH → bb̅bb̅, a key signature relying on b-jet triggers, the filter lowers the input rate to the remaining high-level trigger by a factor of five at the small cost of reducing the overall signal efficiency by roughly 2%

AChR deficiency due to ε-subunit mutations: two common mutations in the Netherlands

Congenital myasthenic syndromes are a clinically and genetically heterogeneous group of hereditary disorders affecting neuromuscular transmission. We have identified mutations within the acetylcholine receptor (AChR) ε-subunit gene underlying congenital myasthenic syndromes in nine patients (seven kinships) of Dutch origin. Previously reported mutations ε1369delG and εR311Q were found to be common; ε1369delG was present on at least one allele in seven of the nine patients, and εR311Q in six. Phenotypes ranged from relatively mild ptosis and external ophthalmoplegia to generalized myasthenia. The common occurrence of εR311Q and ε1369delG suggests a possible founder for each of these mutations originating in North Western Europe, possibly in Holland. Knowledge of the ethnic or geographic origin within Europe of AChR deficiency patients can help in targeting genetic screening and it may be possible to provide a rapid genetic diagnosis for patients of Dutch origin by screening first for εR311Q and ε1369delG

Energetic beams of negative and neutral hydrogen from intense laser plasma interaction

One of the most striking demonstrations of intermolecular forces is the tension at the surface of liquid n-alkanes. The prediction of surface tension is important in the design of distillation towers, extraction units and tower internals such as bubble caps and trays, since it has a considerable influence on the transfer of mass and energy across interfaces. Surface tension data are needed wherever foaming emulsification, droplet formation or wetting are involved. They are also required in a number of equations for two-phase flow calculations and for determining the flow regime. Petroleum engineers are especially interested in the surface tension in the extraction of crude oil to add surfactants to modify the interfacial properties between crude oil and the geological reservoir to improve production and increase oil yields. In this work, a simple computer program using Arrhenius-type asymptotic exponential function, Vandermoned matrix and Matlab technical computing language, is developed for the estimation of surface tension of paraffin hydrocarbons as a function of molecular weight and temperature. The surface tension is calculated for temperatures in the range of 250 to 440 K and paraffin hydrocarbons molecular weights between 30 and 250. The proposed numerical technique is superior owing to its accuracy and clear numerical background, wherein the relevant coefficients can be retuned quickly if more data become available in the future. Estimations are found to be in excellent agreement with the reliable data in the literature with average absolute deviation being less than 2%

Cold non-ischemic heart preservation with continuous perfusion prevents early graft failure in orthotopic pig-to-baboon xenotransplantation

Background Successful preclinical transplantations of porcine hearts into baboon recipients are required before commencing clinical trials. Despite years of research, over half of the orthotopic cardiac xenografts were lost during the first 48 hours after transplantation, primarily caused by perioperative cardiac xenograft dysfunction (PCXD). To decrease the rate of PCXD, we adopted a preservation technique of cold non-ischemic perfusion for our ongoing pig-to-baboon cardiac xenotransplantation project. Methods Fourteen orthotopic cardiac xenotransplantation experiments were carried out with genetically modified juvenile pigs (GGTA1- KO/hCD46/hTBM) as donors and captive-bred baboons as recipients. Organ preservation was compared according to the two techniques applied: cold static ischemic cardioplegia (IC; n = 5) and cold non-ischemic continuous perfusion (CP; n = 9) with an oxygenated albumin-containing hyperoncotic cardioplegic solution containing nutrients, erythrocytes and hormones. Prior to surgery, we measured serum levels of preformed anti-non-Gal-antibodies. During surgery, hemodynamic parameters were monitored with transpulmonary thermodilution. Central venous blood gas analyses were taken at regular intervals to estimate oxygen extraction, as well as lactate production. After surgery, we measured troponine T and serum parameters of the recipient's kidney, liver and coagulation functions. Results In porcine grafts preserved with IC, we found significantly depressed systolic cardiac function after transplantation which did not recover despite increasing inotropic support. Postoperative oxygen extraction and lactate production were significantly increased. Troponin T, creatinine, aspartate aminotransferase levels were pathologically high, whereas prothrombin ratios were abnormally low. In three of five IC experiments, PCXD developed within 24 hours. By contrast, all nine hearts preserved with CP retained fully preserved systolic function, none showed any signs of PCXD. Oxygen extraction was within normal ranges; serum lactate as well as parameters of organ functions were only mildly elevated. Preformed anti-non-Gal-antibodies were similar in recipients receiving grafts from either IC or CP preservation. Conclusions While standard ischemic cardioplegia solutions have been used with great success in human allotransplantation over many years, our data indicate that they are insufficient for preservation of porcine hearts transplanted into baboons: Ischemic storage caused severe impairment of cardiac function and decreased tissue oxygen supply, leading to multi-organ failure in more than half of the xenotransplantation experiments. In contrast, cold non-ischemic heart preservation with continuous perfusion reliably prevented early graft failure. Consistent survival in the perioperative phase is a prerequisite for preclinical long-term results after cardiac xenotransplantation