Photo-assisted inactivation of Escherichia coli bacteria by silver functionalized titanate nanotubes, Ag/H2Ti2O5·H2O.

One-dimensional titanate nanotubes (H2Ti2O5·H2O) functionalized with silver nanoparticles (AgNPs) exhibited unique properties for the effective inactivation of the Gram-negative Escherichia coli within 45 minutes under irradiation using a 65 W halogen lamp. The pathway of the photo-assisted catalytic inactivation was examined by SEM and TEM using a reproducible biological protocol for sample preparations. The membrane integrity of the bacteria was damaged due to the oxidative stress caused by the reactive oxygen species, the bacteriostatic effect of the highly-dispersed-surface AgNPs (∼5 nm) and the sharp nanotube penetration that induced the cell death.

Validation tool for traction force microscopy.

Traction force microscopy (TFM) is commonly used to estimate cells' traction forces from the deformation that they cause on their substrate. The accuracy of TFM highly depends on the computational methods used to measure the deformation of the substrate and estimate the forces, and also on the specifics of the experimental set-up. Computer simulations can be used to evaluate the effect of both the computational methods and the experimental set-up without the need to perform numerous experiments. Here, we present one such TFM simulator that addresses several limitations of the existing ones. As a proof of principle, we recreate a TFM experimental set-up, and apply a classic 2D TFM algorithm to recover the forces. In summary, our simulator provides a valuable tool to study the performance, refine experimentally, and guide the extraction of biological conclusions from TFM experiments.

Observational Study of the Safety of a Cluster Schedule for Subcutaneous Immunotherapy in a Pediatric Population

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Numerical estimation of 3D mechanical forces exerted by cells on non-linear materials.

The exchange of physical forces in both cell-cell and cell-matrix interactions play a significant role in a variety of physiological and pathological processes, such as cell migration, cancer metastasis, inflammation and wound healing. Therefore, great interest exists in accurately quantifying the forces that cells exert on their substrate during migration. Traction Force Microscopy (TFM) is the most widely used method for measuring cell traction forces. Several mathematical techniques have been developed to estimate forces from TFM experiments. However, certain simplifications are commonly assumed, such as linear elasticity of the materials and/or free geometries, which in some cases may lead to inaccurate results. Here, cellular forces are numerically estimated by solving a minimization problem that combines multiple non-linear FEM solutions. Our simulations, free from constraints on the geometrical and the mechanical conditions, show that forces are predicted with higher accuracy than when using the standard approaches.

Pol kappa: A DNA polymerase required for sister chromatid cohesion.

Establishment of cohesion between sister chromatids is coupled to replication fork passage through an unknown mechanism. Here we report that TRF4, an evolutionarily conserved gene necessary for chromosome segregation, encodes a DNA polymerase with beta-polymerase-like properties. A double mutant in the redundant homologs, TRF4 and TRF5, is unable to complete S phase, whereas a trf4 single mutant completes a presumably defective S phase that results in a failure of cohesion between the replicated sister chromatids. This suggests that TRFs are a key link in the coordination between DNA replication and sister chromatid cohesion. Trf4 and Trf5 represent the fourth class of essential nuclear DNA polymerases (designated DNA polymerase kappa) in Saccharomyces cerevisiae and probably in all eukaryotes.

[Brachmann-de-Lange syndrome in our population: clinical and epidemiological characteristics]. / Síndrome de Brachmann de Lange en nuestro medio: características clínicas y epidemiológicas.

INTRODUCTION: We present the study of the clinical and epidemiological characteristics of Brachmann-de Lange syndrome in our population. PATIENTS AND METHODS: In this study we present the analysis of 13 cases of Brachmann-de Lange syndrome identified among 24,696 infants with congenital defects registered by the Spanish Collaborative Study of Congenital Malformations (ECEMC) between April 1976 and June 1996. RESULTS: The minimum estimation of the prevalence in our population is 0.97 per 100,000 live births. We have epidemiologically confirmed the presence of intrauterine growth retardation and have observed that parental ages tend to be relatively young. We have observed a wide range of clinical expression of this syndrome. One hundred percent of our cases have limb reduction defects, followed in frequency by craniofacial alterations (84.62%), abnormal hair distribution (76.92%) and genital defects (69.23%). Upper limbs are predominantly affected and one case of diaphragmatic hernia is worth mentioning. We underline the importance of the differential diagnosis with Fryns'syndrome. CONCLUSIONS: The cases studied correspond to the most severe form of the syndrome, reason for which the prevalence is a minimal estimate. However, the mild forms of the syndrome are more frequent and it is important to consider that the face, especially the form of the eyebrow, could be a good guide for the diagnosis of mild forms of the syndrome.

SigmaE is an essential sigma factor in Escherichia coli.

SigmaE is an alternative sigma factor that controls the extracytoplasmic stress response in Escherichia coli. SigmaE is essential at high temperatures but was previously thought to be nonessential at temperatures below 37 degrees C. We present evidence that sigmaE is an essential sigma factor at all temperatures. Cells lacking sigmaE are able to grow at low temperatures because of the presence of a frequently arising, unlinked suppressor mutation.

Evidence that rseC, a gene in the rpoE cluster, has a role in thiamine synthesis in Salmonella typhimurium.

In Salmonella typhimurium, the genetic loci and biochemical reactions necessary for the conversion of aminoimidazole ribotide (AIR) to the 4-amino-5-hydroxymethyl-2-methyl pyrimidine (HMP) moiety of thiamine remain unknown. Preliminary genetic analysis indicates that there may be more than one pathway responsible for the synthesis of HMP from AIR and that the function of these pathways depends on the availability of AIR, synthesized by the purine pathway or by the purF-independent alternative pyrimidine biosynthetic (APB) pathway (L. Petersen and D. Downs, J. Bacteriol. 178:5676-5682, 1996). An insertion in rseB, the third gene in the rpoE rseABC gene cluster at 57 min, prevented HMP synthesis in a purF mutant. Complementation analysis demonstrated that the HMP requirement of the purF rseB strain was due to polarity of the insertion in rseB on the downstream rseC gene. The role of RseC in thiamine synthesis was independent of rpoE.

The response to extracytoplasmic stress in Escherichia coli is controlled by partially overlapping pathways.

The activity of the alternate sigma-factor sigmaE of Escherichia coli is induced by several stressors that lead to the extracytoplasmic accumulation of misfolded or unfolded protein. The sigmaE regulon contains several genes, including that encoding the periplasmic protease DegP, whose products are thought to be required for maintaining the integrity of the cell envelope because cells lacking sigmaE are sensitive to elevated temperature and hydrophobic agents. Selection of multicopy suppressors of the temperature-sensitive phenotype of cells lacking sigmaE revealed that overexpression of the lipoprotein NlpE restored high temperature growth to these cells. Overexpression of NlpE has been shown previously to induce DegP synthesis by activating the Cpx two-component signal transduction pathway, and suppression of the temperature-sensitive phenotype by NlpE was found to be dependent on the Cpx proteins. In addition, a constitutively active form of the CpxA sensor/kinase also fully suppressed the temperature-sensitive defect of cells lacking sigmaE. DegP was found to be necessary, but not sufficient, for suppression. Activation of the Cpx pathway has also been shown to alleviate the toxicity of several LamB mutant proteins. Together, these results reveal the existence of two partially overlapping regulatory systems involved in the response to extracytoplasmic stress in E. coli.

The sigmaE-mediated response to extracytoplasmic stress in Escherichia coli is transduced by RseA and RseB, two negative regulators of sigmaE.

The extracytoplasmic stress response in Escherichia coli is controlled by the alternative sigma factor, sigma(E). sigma(E) activity is uniquely induced by the accumulation of outer membrane protein precursors in the periplasmic space, and leads to the increased production of several proteins, including the periplasmic protease DegP, that are thought to be required for maintaining cellular integrity under stress conditions. Genetic and biochemical experiments show that sigma(E) activity is under the control of three genes, rseABC (for regulator of sigma E), encoded immediately downstream of the sigma factor. Deletion of rseA leads to a 25-fold induction of sigma(E) activity. RseA is predicted to be an inner membrane protein, and the purified cytoplasmic domain binds to and inhibits sigma(E)-directed transcription in vitro, indicating that RseA acts as an anti-sigma factor. Deletion of rseB leads to a slight induction of sigma(E), indicating that RseB is also a negative regulator of sigma(E). RseB is a periplasmic protein and was found to co-purify with the periplasmic domain of RseA, indicating that RseB probably exerts negative activity on sigma(E) through RseA. Deletion of rseC, in contrast, has no effect on sigma(E) activity under steady-state conditions. Under induction conditions, strains lacking RseB and/or C show wild-type induction of sigma(E) activity, indicating either the presence of multiple pathways regulating sigma(E) activity, or the ability of RseA alone to both sense and transmit information to sigma(E).

rpoE, the gene encoding the second heat-shock sigma factor, sigma E, in Escherichia coli.

In Escherichia coli, the heat shock response is under the control of two alternative sigma factors: sigma 32 and sigma E. The sigma 32-regulated response is well understood, whereas little is known about that of sigma E, except that it responds to extracytoplasmic immature outer membrane proteins. To further understand this response, we located the rpoE gene at 55.5' and analyzed the role of sigma E. sigma E is required at high temperature, and controls the transcription of at least 10 genes. Some of these might contribute to the integrity of the cell since delta rpoE cells are more sensitive to SDS plus EDTA and crystal violet. sigma E controls its own transcription from a sigma E-dependent promoter, indicating that rpoE transcription plays a role in the regulation of E sigma E activity. Indeed, under steady-state conditions, the transcription from this promoter mirrors the levels of E sigma E activity in the cell. However, it is unlikely that the rapid increase in E sigma E activity following induction can be accounted for solely by increased transcription of rpoE. Based upon homology arguments, we suggest that a gene encoding a negative regulator of sigma E activity is located immediately downstream of rpoE and may function as the target of the E sigma E inducing signal.

[3 cases of postpartum acquired factor VIII inhibitor]. / Tres casos de inhibidor del factor VIII adquirido postparto.

Three cases of postpartum acquired factor VIII inhibitors were seen in our hospital between 1981 and 1989. The clinical picture, which was mild in one patient and severe in two, began several months after delivery (four to nine). After treatment with methylprednisolone, good clinical response was obtained in the three cases. However, normal values of factor VIII:C were obtained more easily with the higher doses of steroids. A new pregnancy and delivery in one of our patients did not induce the reappearance of the inhibitor after several years of follow-up.

Novel organization of the common nodulation genes in Rhizobium leguminosarum bv. phaseoli strains.

Nodulation by Rhizobium, Bradyrhizobium, and Azorhizobium species in the roots of legumes and nonlegumes requires the proper expression of plant genes and of both common and specific bacterial nodulation genes. The common nodABC genes form an operon or are physically mapped together in all species studied thus far. Rhizobium leguminosarum bv. phaseoli strains are classified in two groups. The type I group has reiterated nifHDK genes and a narrow host range of nodulation. The type II group has a single copy of the nifHDK genes and a wide host range of nodulation. We have found by genetic and nucleotide sequence analysis that in type I strain CE-3, the functional common nodA gene is separated from the nodBC genes by 20 kb and thus is transcriptionally separated from the latter genes. This novel organization could be the result of a complex rearrangement, as we found zones of identity between the two separated nodA and nodBC regions. Moreover, this novel organization of the common nodABC genes seems to be a general characteristic of R. leguminosarum bv. phaseoli type I strains. Despite the separation, the coordination of the expression of these genes seems not to be altered.