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.