Phenotyping calcium and contraction in a zebrafish model of phospholamban R9C mutation

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Ministry of Science, Innovation and Universities, Spain by Consejería de Educación, Cultura y Deportes. Junta de Comunidades de Castilla-La Mancha.

Background

Phospholamban regulates SERCA2a pump activity by reducing its calcium affinity in the heart. Under β-adrenergic stimulation, protein kinase A (PKA) phosphorylates phospholamban attenuating its inhibitory effect on SERCA2a. The phospholamban mutation Arg 9 to Cys (R9C) was firstly identified in an American family with ventricular dilatation and premature death, and subsequently in a cohort of dilated cardiomyopathy patients in South Africa. Emerging evidence suggests that phospholamban R9C is a loss-of-function mutation with autosomal dominant inheritance. In vitro studies revealed that it enhances pentamer assembly by disulfide bridge formation, reducing the availability of phospholamban monomers to regulate SERCA2a.

Purpose

The present study aimed to investigate defects in Ca2+ handling and cardiac function of phospholamban R9C mutation in an in vivo zebrafish model.

Methods

We generated transgenic zebrafish lines overexpressing phospholamban wild-type (TgPLNwt) and phospholamban R9C (TgPLNR9C) in the heart of zebrafish. To measure calcium kinetics in 3 day-old larvae, TgPLNwt and TgPLNR9C fish were outcrossed with transgenic zebrafish lines expressing the fluorescent calcium biosensor mCyRFP1-GCaMP6f (TgRFP-GcaMP6f) and the bioluminescence calcium biosensor GFP-Aequorin (TgGA) in the heart.

Results

Overexpression of phospholamban wild-type and R9C did not alter the heart rate compared to sibling larvae, and no differences were observed in the upstroke and recovery time of the calcium transients.  However, atrial and ventricular calcium transient amplitude were higher in TgPLNR9C larvae with respect to TgPLNwt larvae. Contractile force of the heart, assessed as the fractional shortening, increased in TgPLNR9C larvae compared to siblings and TgPLNwt. Furthermore, stroke volume and cardiac output were also higher in TgPLNR9C larvae. Bioluminescence experiments were performed to estimate the average calcium levels in the heart. We found that TgPLNR9C larvae showed higher calcium levels than sibling and TgPLNwt larvae. To evaluate the responsiveness to β-adrenergic stimulation, larvae were treated with the β-agonist isoproterenol. Calcium transient amplitude and contractile force increased in sibling and TgPLNwt larvae after treatment. However, this response was absent in TgPLNR9C larvae, suggesting that they were hyper-stimulated in basal conditions, displaying amplitude and contractile force similar to sibling and TgPLNwt larvae treated with isoproterenol.

Conclusion

TgPLNR9C larvae exhibited aberrant calcium handling in the heart with higher calcium levels and contractility, consistent with a lack of inhibition of SERCA2a. Consequently, TgPLNR9C larvae did not respond to β-adrenergic stimulation. These results were consistent with previous in vitro studies carried out in cardiomyocites infected with phospholamban R9C and highlighted the pathological defects of phospholamban R9C at early stages of the disease.

Calcium, contraction, and hemodynamic alterations induced by arrhythmogenic drugs in the zebrafish larvae

Funding Acknowledgements

Type of funding sources: Public grant(s) – EU funding. Main funding source(s): MCIN/AEI/ 10.13039/501100011033 and “ERDF A way of making Europe” by the European Union

Background

Ca2+ ion is pivotal in excitation-contraction coupling. The dysregulation of Ca2+ fluxes is at the core of inherited and acquired arrhythmias. In recent years zebrafish have become an attractive vertebrate model to study heart development, cardiotoxicity, and heart diseases. We recently reported that the transgenic zebrafish line Tg(myl7:Twitch-4) expressing the ratiometric Ca2+ indicator Twitch-4 in the heart, allowed imaging Ca2+ transients (CaT) simultaneously with heart contraction in zebrafish larvae, thus maintaining the physiological mechano-electrical feedback.

Purpose

This study aimed to detect subtle disturbances in Ca2+ cycling, contractility, and hemodynamics induced by arrhythmogenic drugs in zebrafish larvae.

Methods

We have used the zebrafish transgenic line Tg(myl7:Twitch-4) and a custom software to acquire and analyze fluorescence emission ratio images of the heart. Larvae of 3- and 5-days post-fertilization (dpf) were incubated with arrhythmogenic drugs, and their effects on the systolic and diastolic Ca2+ and the CaT amplitude in the atrium and ventricle were determined. As the ventricular diameter was assessed in the same fluorescence images, a simultaneous, real-time, measurement of contraction correlated with Ca2+ was obtained. The systolic and diastolic areas, measured independently, were used to estimate hemodynamic parameters.

Results

Dofetilide caused time-dependent bradycardia and ultimately a 2:1 arrhythmia in 3 and 5 dpf larvae, with an increase in the CaT amplitude. the ejection fraction and the stroke volume increased, but the cardiac output decreased due to the low heart rate (2:1 arrhythmia). The T-type Ca2+ channel antagonist ML218 induced bradycardia and decreased systolic and diastolic Ca2+ levels in 3 dpf larvae, but the CaT amplitude did not change. Interestingly, some larvae (3 out of 14) displayed a progressive lengthening of the time between the start of atrial and ventricular CaT, analogous to increased PR interval of the electrocardiogram, until a ventricular systole failed. This is reminiscent of a second-degree atrioventricular block in humans. At higher ML218 concentration, a 2:1 arrhythmia was observed and increased ventricular CaT amplitude in all larvae.

Conclusions

We characterized Ca2+ changes induced by arrhythmogenic drugs and correlated them with contractility and hemodynamic parameters. The zebrafish line Tg(myl7:Twitch-4) allowed investigating drug-induced arrhythmias in this animal model with unprecedented detail. This transgenic line will serve to screen cardiotoxicity during drug development and to study conduction and rhythm defects in zebrafish, and their correlation with human disease.

Impact of COVID-19 Infection on the Outcome of Patients With Ischemic Stroke

Supplemental Digital Content is available in the text.

We evaluated whether stroke severity, functional outcome, and mortality are different in patients with ischemic stroke with or without coronavirus disease 2019 (COVID-19) infection.

Patterns of African and Asian admixture in the Afrikaner population of South Africa

BACKGROUND

The Afrikaner population of South Africa is the descendants of European colonists who started to colonize the Cape of Good Hope in the 1600s. In the early days of the colony, mixed unions between European males and non-European females gave rise to admixed children who later became incorporated into either the Afrikaner or the Coloured populations of South Africa. Differences in ancestry, social class, culture, sex ratio and geographic structure led to distinct and characteristic admixture patterns in the Afrikaner and Coloured populations. The Afrikaner population has a predominant European composition, whereas the Coloured population has more diverse ancestries. Genealogical records previously estimated the contribution of non-Europeans into the Afrikaners to be between 5.5 and 7.2%.

RESULTS

To investigate the genetic ancestry of the Afrikaner population today (11-13 generations after initial colonization), we genotyped approximately five million genome-wide markers in 77 Afrikaner individuals and compared their genotypes to populations across the world to determine parental source populations and admixture proportions. We found that the majority of Afrikaner ancestry (average 95.3%) came from European populations (specifically northwestern European populations), but that almost all Afrikaners had admixture from non-Europeans. The non-European admixture originated mostly from people who were brought to South Africa as slaves and, to a lesser extent, from local Khoe-San groups. Furthermore, despite a potentially small founding population, there is no sign of a recent bottleneck in the Afrikaner compared to other European populations. Admixture amongst diverse groups from Europe and elsewhere during early colonial times might have counterbalanced the effects of a small founding population.

CONCLUSIONS

While Afrikaners have an ancestry predominantly from northwestern Europe, non-European admixture signals are ubiquitous in the Afrikaner population. Interesting patterns and similarities could be observed between genealogical predictions and our genetic inferences. Afrikaners today have comparable inbreeding levels to current-day European populations.

Surgical repair versus conservative treatment and subacromial decompression for the treatment of rotator cuff tears

Aims

The purpose of this study was to compare the effectiveness of surgical repair to conservative treatment and subacromial decompression for the treatment of chronic/degenerative tears of the rotator cuff.

Materials and Methods

PubMed, Cochrane database, and Medline were searched for randomized controlled trials published until March 2018. Included studies were assessed for methodological quality, and data were extracted for statistical analysis. The systematic review was conducted following PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines.

Results

Six studies were included. Surgical repair resulted in a statistically significantly better Constant–Murley Score (CMS) at one year compared with conservative treatment (mean difference 6.15; p = 0.002) and subacromial decompression alone (mean difference 5.81; p = 0.0004). In the conservatively treated group, 11.9% of patients eventually crossed over to surgical repair.

Conclusion

The results of this review show that surgical repair results in significantly improved outcomes when compared with either conservative treatment or subacromial decompression alone for degenerative rotator cuff tears in older patients. However, the magnitude of the difference in outcomes between surgery and conservative treatment may be small and the ‘success rate’ of conservative treatment may be high, allowing surgeons to be judicious in choosing those patients who are most likely to benefit from surgery. Cite this article: Bone Joint J 2019;101-B:1100–1106.

Silk flow-diverter stent for the treatment of complex intracranial aneurysms: A one-year follow-up multicenter study

Background Flow-diverter stents have been successfully used in the treatment of complex aneurysms with limited therapeutic alternatives. We report our experience using the Silk flow diverter (SFD; Balt Extrusion, Montmorency, France) for the treatment of complex aneurysms in four Argentine centers. Methods We conducted a retrospective review of 246 consecutive patients who were treated with the SFD at four Argentine centers between January 2009 and January 2017. The patient and aneurysm characteristics, as well as the details of the procedure, were analyzed. The angiographic and clinical findings were recorded during and immediately after the procedure and at 12-month follow-up. Results Angiography follow-up at 12 months was possible in 235 patients (95.5%) with 282 aneurysms. A total of 265 aneurysms (93.9%) presented with complete occlusion of the aneurysmal sac (class 1) and 17 aneurysms (6.1%) presented with partial occlusion (class 2). The 12-month clinical follow-up showed 11 patients with major events (seven, scale 2; five, scale 3; and two, scale 4). The morbidity and mortality rates were 4.2% (11/289) and 2.1% (5/289), respectively. Conclusions The treatment of aneurysms with the SFD was associated with a low rate of complications and a high percentage of aneurysmal occlusion. These findings suggest that SFD is an effective and safe alternative in the endovascular treatment of complex aneurysms.

Business Process Modelling is an Essential Part of a Requirements Analysis

To perform a requirements analysis of the barriers to conducting research linking of primary care, genetic and cancer data.

We extended our initial data-centric approach to include socio-culturalandbusinessrequirements.Wecreatedreferencemodels of core data requirements common to most studies using unified modelling language (UML), dataflow diagrams (DFD) and business process modelling notation (BPMN). We conducted a stakeholder analysis and constructed DFD and UML diagrams for use cases based on simulated research studies. We used research output as a sensitivity analysis.

Differences between the reference model and use cases identified study specific data requirements. The stakeholder analysis identified: tensions, changes in specification, some indifference from data providers and enthusiastic informaticians urging inclusion of socio-cultural context. We identified requirements to collect information at three levels: microdata items, which need to be semantically interoperable, meso-the medical record and data extraction, and macro-the health system and socio-cultural issues. BPMN clarified complex business requirements among data providers and vendors; and additional geographical requirements for patients to be represented in both linked datasets. High quality research output was the norm for most repositories.

Reference models provide high-level schemata of the core data requirements. However, business requirements’ modelling identifies stakeholder issues and identifies what needs to be addressed to enable participation.

Key Concepts to Assess the Readiness of Data for International Research: Data Quality, Lineage and Provenance, Extraction and Processing Errors, Traceability, and Curation

To define the key concepts which inform whether a system for collecting, aggregating and processing routine clinical data for research is fit for purpose.

Literature review and shared experiential learning from research using routinely collected data. We excluded socio-cultural issues, and privacy and security issues as our focus was to explore linking clinical data.

Six key concepts describe data: (1) Data quality: the core Overarching concept – Are these data fit for purpose? (2) Data provenance: defined as how data came to be; incorporating the concepts of lineage and pedigree. Mapping this process requires metadata. New variables derived during data analysis have their own provenance. (3) Data extraction errors and (4) Data processing errors, which are the responsibility of the investigator extracting the data but need quantifying. (5) Traceability: the capability to identify the origins of any data cell within the final analysis table essential for good governance, and almost impossible without a formal system of metadata; and (6) Curation: storing data and look-up tables in a way that allows future researchers to carry out further research or review earlier findings.

There are common distinct steps in processing data; the quality of any metadata may be predictive of the quality of the process. Outputs based on routine data should include a review of the process from data origin to curation and publish information about their data provenance and processing method.

How 3D patient-specific instruments improve accuracy of pelvic bone tumour resection in a cadaveric study

OBJECTIVES

To assess the accuracy of patient-specific instruments (PSIs) versus standard manual technique and the precision of computer-assisted planning and PSI-guided osteotomies in pelvic tumour resection.

METHODS

CT scans were obtained from five female cadaveric pelvises. Five osteotomies were designed using Mimics software: sacroiliac, biplanar supra-acetabular, two parallel iliopubic and ischial. For cases of the left hemipelvis, PSIs were designed to guide standard oscillating saw osteotomies and later manufactured using 3D printing. Osteotomies were performed using the standard manual technique in cases of the right hemipelvis. Post-resection CT scans were quantitatively analysed. Student's t-test and Mann-Whitney U test were used.

RESULTS

Compared with the manual technique, PSI-guided osteotomies improved accuracy by a mean 9.6 mm (p < 0.008) in the sacroiliac osteotomies, 6.2 mm (p < 0.008) and 5.8 mm (p < 0.032) in the biplanar supra-acetabular, 3 mm (p < 0.016) in the ischial and 2.2 mm (p < 0.032) and 2.6 mm (p < 0.008) in the parallel iliopubic osteotomies, with a mean linear deviation of 4.9 mm (p < 0.001) for all osteotomies. Of the manual osteotomies, 53% (n = 16) had a linear deviation > 5 mm and 27% (n = 8) were > 10 mm. In the PSI cases, deviations were 10% (n = 3) and 0 % (n = 0), respectively. For angular deviation from pre-operative plans, we observed a mean improvement of 7.06° (p < 0.001) in pitch and 2.94° (p < 0.001) in roll, comparing PSI and the standard manual technique.

CONCLUSION

In an experimental study, computer-assisted planning and PSIs improved accuracy in pelvic tumour resections, bringing osteotomy results closer to the parameters set in pre-operative planning, as compared with standard manual techniques.Cite this article: A. Sallent, M. Vicente, M. M. Reverté, A. Lopez, A. Rodríguez-Baeza, M. Pérez-Domínguez, R. Velez. How 3D patient-specific instruments improve accuracy of pelvic bone tumour resection in a cadaveric study. Bone Joint Res 2017;6:577-583. DOI: 10.1302/2046-3758.610.BJR-2017-0094.R1.

Seizures and electroencephalography findings in 61 patients with fetal alcohol spectrum disorders

Fetal alcohol spectrum disorders (FASD) cause neurodevelopmental abnormalities. However, publications about epilepsy and electroencephalographic features are scarce. In this study, we prospectively performed electroencephalography (EEG) and brain magnetic resonance (MR) imaging in 61 patients with diagnosis of FASD. One patient had multiple febrile seizures with normal EEGs. Fourteen children showed EEG anomalies, including slow background activity and interictal epileptiform discharges, focal and/or generalized, and 3 of them had epilepsy. In one patient, seizures were first detected during the EEG recording and one case had an encephalopathy with electrical status epilepticus during slow sleep (ESES). Focal interictal discharges in our patients did not imply the presence of underlying visible focal brain lesions in the neuroimaging studies, such as cortical dysplasia or polymicrogyria. However, they had nonspecific brain MR abnormalities, including corpus callosum hypoplasia, vermis hypoplasia or cavum septum pellucidum. The latter was significantly more frequent in the group with EEG abnormal findings (p < 0.01).

Evaluation of risk factors for vancomycin-resistant Enterococcus bacteremia among previously colonized hematopoietic stem cell transplant patients

BACKGROUND

Hematopoietic stem cell transplantation (HSCT) recipients colonized with vancomycin-resistant Enterococcus (VRE) may have an increased risk of developing VRE bacteremia. Identification of risk factors for the development of subsequent VRE bacteremia among colonized HSCT recipients is necessary to predict which patients may benefit the most from receiving anti-VRE antibiotic therapy as part of an initial antimicrobial regimen when gram-positive bacteremia is suspected.

METHODS

This study was a retrospective chart review conducted from May 2008 to May 2011. Adult HSCT patients admitted to the hospital found to have positive VRE surveillance cultures were included. A multivariate analysis was completed to identify risk factors for the development of VRE bacteremia in the study population.

RESULTS

Of 152 patients, 19 (13%) patients developed subsequent VRE bacteremia. Risk factors identified for patients with current VRE colonization for VRE bacteremia were the utilization of vancomycin subsequent to VRE surveillance culture positivity (P = 0.017), prolonged duration of neutropenia (P = 0.001), immunosuppression (P < 0.001), and timing of first VRE surveillance screen positivity at week 1 (P = 0.005). A history of VRE colonization on a prior admission was not an independent risk factor for bacteremia in HSCT patients (P = 1.0). HSCT patients with VRE bacteremia had a 30-day all-cause inpatient mortality rate of 29% (P = 0.001).

CONCLUSION

HSCT patients receiving immunosuppressive therapy, who have been exposed to vancomycin subsequent to surveillance culture positivity, have had prolonged neutropenia of >30 days, or first surveillance culture positive at week 1 of admission are potential candidates for early implementation of anti-VRE therapy when a gram-positive bacteremia is suspected.

Membrane reconstitution of FtsZ-ZipA complex inside giant spherical vesicles made of E. coli lipids: large membrane dilation and analysis of membrane plasticity

During the division process of Escherichia coli, the globular protein FtsZ is early recruited at the constriction site. The Z-ring, based on FtsZ filaments associated to the inner cell membrane, has been postulated to exert constriction forces. Membrane anchoring is mediated by ZipA, an essential transmembrane protein able to specifically bind FtsZ. In this work, an artificial complex of FtsZ-ZipA has been reconstituted at the inner side of spherical giant unilamellar vesicles made of E. coli lipids. Under these conditions, FtsZ polymerization, triggered when a caged GTP analogue is UV-irradiated, was followed by up to 40% vesicle inflation. The homogeneous membrane dilation was accompanied by the visualization of discrete FtsZ assemblies at the membrane. Complementary rheological data revealed enhanced elasticity under lateral dilation. This explains why vesicles can undergo large dilations in the regime of mechanical stability. A mechanical role for FtsZ polymers as promoters of membrane softening and plasticization is hypothesized.

Cucumber anaphylaxis in a latex-sensitized patient

We report the case of a 76-year-old woman who experienced dizziness, vomiting, dyspnea, thoracic erythema, and vaginal itching within 5 minutes of eating cucumber. She had been diagnosed 3 months earlier with papaya urticaria and latex sensitization. The results of skin prick tests were positive for cucumber, watermelon, papaya, and latex and negative for melon and profilin extracts. ImmunoCAP for latex-specific serum immunoglobulin (Ig) E was positive. Cucumber-specific serum IgE was negative. Immunoblot analysis using patient serum revealed a 30- to 32-kDa protein band in the cucumber (peel) and papaya extracts. Immunoblot inhibition with latex extract demonstrated inhibition of the band in both extracts. Immunoblot inhibition with cucumber-papaya and papaya-cucumber revealed inhibition of the same band in the cucumber and papaya extracts, respectively. We present a case of IgE-mediated allergy to cucumber and papaya. Our results strongly suggest that the allergen(s) implicated are associated with latex sensitization. To our knowledge, this is the first report of cucumber-latex and cucumber-papaya cross-reactivity.

Monitoring influenza activity in Europe with Google Flu Trends: comparison with the findings of sentinel physician networks - results for 2009-10

The number of Internet searches has recently been used by Google to estimate the influenza incidence in the United States. We examined the correlation between the Google Flu Trends tool and sentinel networks estimates in several European countries during the 2009 influenza A(H1N1) pandemic and found a good correlation between estimates and peak incidence timing, with the highest peaks in countries where Internet is most frequently used for health-related searching. Although somehow limited, Google could be a valuable tool for syndromic surveillance.

Fracturas en el plano coronal del húmero distal

Son lesiones que comprenden las fracturas del cóndilo y/o de la tróclea humeral. Suponen el 1% de las fracturas del codo y el 6% de las fracturas del húmero distal. Las más frecuentes son las fracturas del cóndilo humeral tipo I según la clasificación de Bryan y Morrey. Analizamos 16 casos de este tipo de lesiones tratadas con reducción abierta y osteosíntesis con tornillos y valoramos los resultados funcionales. Obtuvimos la consolidación en el 100 % de los casos con ausencia de dolor o dolor leve. El 87,5 % de los casos presentaron una movilidad activa en flexión entre 120º y 140º, en extensión de –10º a –30º. Prono-supinación completa en 15 casos y un déficit de pronación de 60º y de supinación de 50º en un caso. El 100 % volvieron a su actividad laboral sin restricciones en 11 semanas. En el seguimiento (11,3 meses de media, rango: 4-29), 2 pacientes (12,5%), necesitaron de cirugía por rigidez articular (artrolisis abierta). No hubo ningún caso de necrosis avascular. Subrayamos la importancia de obtener una reducción anatómica suficientemente estable, siendo la osteosíntesis abierta el mejor método para conseguirlo y así permitir la movilización precoz del codo y una la correcta recuperación funcional.

Carotid bifurcation atherosclerosis in the over-65s: a prevalence study

AIM

The aim of this study was to determine the prevalence of carotid stenosis (CS) in the over-65 population segment residing in a catchment area (Gijón) served by the Asturias Health Service (Spain) as a necessary step in planning medical care for treating cerebrovascular disease in the elderly.

METHODS

In this descriptive transversal study, 232 subjects (114 men and 118 women) randomly chosen from health card data underwent colour-flow duplex scanning of the supra-aortic trunks.

RESULTS

The prevalence of CS in this sample was 21.5%. When stratified by sex and age (65-74 and >75 years of age), the CS rate was 5 points higher in the older than in the younger group, and 4 points higher among males (23.6%) than among females (19.2%).

CONCLUSION

Approximately one in every 5 subjects over 65 years of age presents with CS; CS prevalence was higher in the over-75s and among males, although the differences were not statistically significant.

Biogeochemical processes and nutrient cycling within an artificial reef off Southern Portugal

This study (2002/2004) examines the effect of artificial reef (AR) structures off the southern coast of Portugal on biogeochemical process and nutrient cycling. Organic and inorganic carbon, nitrogen, phosphorus and chlorophyll a were determined monthly in sediment cores and settled particles for a two-year period. Ammonium, nitrates, phosphates, silicates, total organic nitrogen and phosphorus, chlorophyll a and phaeopigments were also determined monthly in water samples within AR and control sites. Results of the two-year study showed that: (i) there was a significant exponential fit between organic carbon and chlorophyll a (r2=0.91; p<0.01) in reef sediment suggesting an increase of benthic productivity; (ii) organic carbon and nitrogen content in settled particles within AR environment was about four times higher two years after reef deployment; (iii) nutrients and chlorophyll a in the water column were higher at AR than control site. Two years after AR deployment, dissolved organic and inorganic compounds in near bottom water were 30-60% higher, emphasizing benthic remineralization processes at AR's organically rich sediment. Marked chemical changes in the ecosystem were observed during the two-year study period, reinforcing the importance of these structures for sandy coastal areas rehabilitation through trophic chain pull-out.

Osteosíntesis percutánea de las fracturas de escafoides

Objetivos: Valoración del resultado de la osteosíntesis percutánea del escafoides y evaluación de la reincorporación precoz de los pacientes a su actividad habitual.

Material y métodos: Osteosínteis percutánea con tornillo canulado tanto por vía palmar como dorsal en 51 casos, describiendo ambas técnicas quirúrgicas.

Resultados: Se consiguió la consolidación de la fractura en todos los pacientes en un tiempo medio de 33 días desde la intervención, empezando a utilizar la mano durante la primera o segunda semana tras la cirugía y permitiéndose la actividad sin restricciones a partir de los 35 días. La movilidad media de la muñeca fue de una flexión entre 50 y 70º y la extensión conseguida fue de entre 65 y 80º, con una buena fuerza de prensión al cabo de 8 semanas. El grado de satisfacción de los pacientes fue considerado como muy bueno en el 100% de los casos. No hubo complicaciones de importancia. El gasto del tratamiento se redujo aproximadamente en torno al 50% respecto del tratamiento conservador.

Conclusiones: La osteosíntesis percutánea del escafoides es una técnica sencilla, rápida y con escasa morbilidad que permite una rápida reincorporación del paciente a su vida habitual con las mínimas molestias.

Analysis of the S-locus structure in Prunus armeniaca L. Identification of S-haplotype specific S-RNase and F-box genes

The gametophytic self-incompatibility (GSI) system in Rosaceae has been proposed to be controlled by two genes located in the S -locusan S-RNase and a recently described pollen expressed S -haplotype specific F-box gene (SFB). However, in apricot (Prunus armeniaca L.) these genes had not been identified yet. We have sequenced 21 kb in total of the S -locus region in 3 different apricot S -haplotypes. These fragments contain genes homologous to the S-RNase and F-box genes found in other Prunus species, preserving their basic gene structure features and defined amino acid domains. The physical distance between the F-box and the S-RNase genes was determined exactly in the S2-haplotype (2.9 kb) and inferred approximately in the S 1-haplotype (< 49 kb) confirming that these genes are linked. Sequence analysis of the 5' flanking regions indicates the presence of a conserved region upstream of the putative TATA box in the S-RNase gene. The three identified S-RNase alleles (S1, S2 and S4) had a high allelic sequence diversity (75.3 amino acid identity), and the apricot F-box allelic variants (SFB1, SFB2 and SFB4) were also highly haplotype-specific (79.4 amino acid identity). Organ specific-expression was also studied, revealing that S1- and S2-RNases are expressed in style tissues, but not in pollen or leaves. In contrast, SFB1 and SFB2 are only expressed in pollen, but not in styles or leaves. Taken together, these results support these genes as candidates for the pistil and pollen S-determinants of GSI in apricot.

Escherichia coli FtsZ polymers contain mostly GTP and have a high nucleotide turnover

The cell division protein FtsZ is a GTPase structurally related to tubulin and, like tubulin, it assembles in vitro into filaments, sheets and other structures. To study the roles that GTP binding and hydrolysis play in the dynamics of FtsZ polymerization, the nucleotide contents of FtsZ were measured under different polymerizing conditions using a nitrocellulose filter-binding assay, whereas polymerization of the protein was followed in parallel by light scattering. Unpolymerized FtsZ bound 1 mol of GTP mol(-1) protein monomer. At pH 7.5 and in the presence of Mg(2+) and K(+), there was a strong GTPase activity; most of the bound nucleotide was GTP during the first few minutes but, later, the amount of GTP decreased in parallel with depolymerization, whereas the total nucleotide contents remained invariant. These results show that the long FtsZ polymers formed in solution contain mostly GTP. Incorporation of nucleotides into the protein was very fast either when the label was introduced at the onset of the reaction or subsequently during polymerization. Molecular modelling of an FtsZ dimer showed the presence of a cleft between the two subunits maintaining the nucleotide binding site open to the medium. These results show that the FtsZ polymers are highly dynamic structures that quickly exchange the bound nucleotide, and this exchange can occur in all the subunits.

Activation of cell division protein FtsZ. Control of switch loop T3 conformation by the nucleotide gamma-phosphate

The effect of bound nucleotide on the conformation of cell division protein FtsZ from Methanococcus jannaschii has been investigated using molecular dynamics and site-directed mutagenesis. The molecular dynamics indicate that the gamma-phosphate of GTP induces a conformational perturbation in loop T3 (Gly88-Gly99 segment), in a position structurally equivalent to switch II of Ha-ras-p21. In the simulated GTP-bound state, loop T3 is pulled by the gamma-phosphate into a more compact conformation than with GDP, related to that observed in the homologous proteins alpha- and beta-tubulin. The existence of a nucleotide-induced structural change in loop T3 has been confirmed by mutating Thr92 into Trp (T92W-W319Y FtsZ). This tryptophan (12 A away from gamma-phosphate) shows large differences in fluorescence emission, depending on which nucleotide is bound to FtsZ monomers. Loop T3 is located at a side of the contact interface between two FtsZ monomers in the current model of FtsZ filament. Such a structural change may bend the GDP filament upon hydrolysis by pushing against helix H8 of next monomer, thus, generating force on the membrane during cell division. A related curvature mechanism may operate in tubulin activation.

Bringing gene order into bacterial shape

A different arrangement of a cluster of genes involved in division and cell-wall synthesis separates bacilli from other bacteria in a phylogenetic analysis. We conclude that the relationships between these genes are not random and might reflect significant events in the evolution of the coupling between growth and division in bacteria.

Transcription of the Escherichia coli dcw cluster: evidence for distal upstream transcripts being involved in the expression of the downstream ftsZ gene

Escherichia coli strains VIP596 and VIP597 have been constructed to compare the amount of transcription of the ftsZ gene derived from proximal promoters in the ddlB-ftsZ region with that originating in the upstream regions of the dcw cluster. Both strains have in common a beta-galactosidase reporter fusion located at the ddlB locus, but differ in that VIP597 has a transcription terminator Omega interposon located downstream from lacZ. In addition, these strains have the ddlB, ftsQ, ftsA and ftsZ genes under the control of the IPTG-inducible promoter P(tac), allowing to control artificially ftsZ expression for normal cell division to take place. When beta-galactosidase activity was measured in VIP596 and VIP597 and compared to the levels measured in strain VIP407, in which the lacZ reporter fusion is located in the ftsZ gene, they were found to account for nearly 66% of the total transcription entering into ftsZ. This result indicates that the reduction in ftsZ transcription observed when the promoters in the ddlB-ftsA region are disconnected from the upstream sequences of the dcw cluster (as observed by Flärdh et al., Mol. Microbiol. 30 (1998) 305-316) in strain VIP490) is the direct consequence of the interruption in the transcription originated upstream and not due to the effect of such sequences on the promoters proximal to ftsZ.