Presence of the cfxA gene in Bacteroides distasonis

In this study we investigated the presence of the cfxA gene (encoding a class A beta-lactamase) in 73 strains of the Bacteroides fragilis group belonging to the species B. distasonis (34), B. vulgatus (14), B. thetaiotaomicron (8), B. merdae (6), B. caccae (9) and B. ovatus (2) isolated from human intestinal microflora of healthy children and adults. Employing specific primers to the cfxA gene, a 312-bp amplified fragment was obtained in 2 strains of B. vulgatus and 9 strains, the majority from children, of B. distasonis. The expression of this enzyme was analysed by determining the MICs to cefoxitin and cefotaxime and values varied from 2 to >256 microg/ml of both cefoxitin and cefotaxime. Sequence analysis of the amplicons corresponding to the cfxA gene from B. distasonis and B. vulgatus revealed identical sequences between these isolates and high similarity with other beta-lactamase genes of anaerobes such as cfxA of B. vulgatus (99%) and cfxA2 of Prevotella intermedia (99%), both sequences of which deposited in Genbank under accession numbers U38243 and AF118110, respectively. However, a fragment obtained from a B. distasonis strain (EC17-4) showed a unique RFLP profile and 87% nucleotide similarity with cfxA and cfxA2 genes. These results seem to suggest a dissemination of these resistance determinants among Bacteroides species.     

Molecular analysis of Bruton’s tyrosine kinase gene in Spain

Mutations in Bruton’s tyrosine kinase (BTK) gene result in X linked agammaglobulinemia (XLA). Using Single Strand Conformation Polymorphism (SSCP) followed by direct sequencing 21 mutations were found in 27 patients with an XLA phenotype from 21 unrelated families. We identified 13 novel and 8 known mutations: seven missense (R288W, R544G, P566S, K430E; K374N, L512P, R544S), 5 nonsense (Q196X, Y361X, L249X, Q612X, Q466X), 2 deletions of one nucleotide (A207fsX216, Q612fsX648), 2 deletion‐insertions (V219fsX227, K218fsX228), one insertion of two nucleotides (S572fsX587) and 4 point mutations in donor/acceptor splice sites (g.IVS1+1G>C, g.IVS6+5G>A, g.IVS10+1G>T, g.IVS13‐1GG>CT). Carrier detection was performed in 18 mothers. Only in one case the mutation was found to be de novo. Additionally, BTK mutations were not found in four patients without family history, but with XLA‐compatible phenotype. Hum Mutat 18:84, 2001. © 2001 Wiley‐Liss, Inc.     

E-cadherin germline missense mutations and cell phenotype: evidence for the independence of cell invasion on the motile capabilities of the cells

In Hereditary Diffuse Gastric Cancer syndrome, E-cadherin germline mutations of the missense type harbour significant functional consequences. In this study, we have characterised the effect of T340A, A617T, A634V and V832M E-cadherin germline missense mutations on cell morphology, motility and proliferation. Wild-type E-cadherin and A617T expressing cells have an epithelial-like morphology, with polarised cells migrating unidirectionally. T340A and A634V expressing cells, fibroblast-like, have a high motile phenotype. We show that this phenotype is dependent on an increased level of active RhoA. V832M expressing cells grow in piled-up structure of round cells, as an effect of the disturbance of the binding between alpha-catenin and beta-catenin. The destabilisation of the adhesion complex is shown to hamper the motile capabilities of these cells. We did not observe any effect of the E-cadherin mutations on cell proliferation. We show the existence of a genotype-phenotype correlation between different E-cadherin mutations and cell behaviour. However, we demonstrate that the ability of cells expressing the different E-cadherin mutations to invade is independent on their motile capabilities, providing evidence that motility is neither necessary nor sufficient for cells to invade. Our data give new insights into the understanding of the mechanisms linking invasion and E-cadherin mutations in diffuse gastric cancer.     

Sequential Flow Cytometry and Fluorescence In Situ Hybridization for the Study of Formalin-Fixed, Paraffin-Embedded Breast Cancer Cells

Both flow cytometry and fluorescence in situ hybridization (FISH) are useful techniques in the analysis of cancer tissues. When the two are used in the study of the same specimens, they are usually performed in parallel, separately. This is problematic where there is a scarcity of material, making completion of both studies impossible. Fluorescence in situ hybridization procedures that will utilize excess material discarded from flow cytometry would be advantageous. The present report describes an optimized protocol for performing sequential flow cytometry and FISH using formalin-fixed paraffin-embedded archival material. Although breast cancer tissues were used in this initial study, the protocol is applicable to other cancer tissues as well.     

Can energy drinks reduce the depressor effect of ethanol? An experimental study in mice

Although the popularization of the combined use of alcoholic beverages and energy drinks (ED) containing caffeine, taurine and other substances has increased, there are no controlled experimental studies on the effects of ED alone or combined with ethanol. This work aimed at evaluating the effects of different doses of ED combined or not with ethanol, on the locomotor activity of Swiss mice. The administration of 3.57, 10.71 or 17.86 ml/kg of ED alone increased the locomotor activity of the animals in relation to a control group. Low doses of ethanol (0.5, 1.0 and 1.5 g/kg) alone or in combination with 10.71 ml/kg of ED did not affect their locomotor activity. However, the reduction of activity observed after 2.5 g/kg of ethanol was antagonized by 10.71 ml/kg of ED. Further studies on the mechanisms of this interaction are still needed.     

Anatomic study of the tricuspid valve in children

We performed an anatomic study of the right atrioventricular valve in children under one year of age using a conservative method of dissection of the heart valve. The main aspects studied were the number of cusps and their morphometric characteristics, such as the width of the base and the depth of the cusps. Other parameters studied were the number of papillary muscles, number of tendinous cords, and diameter of the fibrous ring and the last one were divided in three regions, anterior, posterior and septal for localization of cusps. Our results showed that the number of cusps varied from two to four. Three cusps was the commonest finding and the fourth cusp, if present, was classified as anterolateral in location. The anterior and septal cusps had bases bigger than those of the posterior and anterolateral cusps; the septal cusp was deeper than the others; and the number of tendinous cords was greater for the anterior and septal cusps than for the posterior and anterolateral cusps. In addition, the posterior region showed great variability: in 35.7% it was occupied by undeveloped valve tissue and the posterior valve in these cases was located anteriorly.     

Distribution of cytoskeletal structures and organelles of the host cell during evolution of the intracellular parasitism by Trypanosoma cruzi

The distribution of microtubules, microfilaments, mitochondria, Golgi complex and endosomes/lysosomes was analyzed in Vero cells allowed to interact for different periods of time with the pathogenic protozoan Trypanosoma cruzi and observed by confocal laser scanning microscopy. Microtubules were revealed using a mouse monoclonal anti-alpha-tubulin antibody. Actin filaments were revealed using phalloidin-rhodamine. To identify mitochondria, endosomes/lysosomes and the Golgi complex the cells were labelled with Rhodamine 123, Lucifer yellow and C6-NBD-ceramide, respectively. During cell invasion actin filaments concentrate at the site of parasite penetration in some, but not in all cells, probably depending upon the mechanism used by the trypomastigote form to penetrate into the host cells. Following internalization the trypomastigote form gradually changes into the amastigote form, disruption of the parasitophorous vacuole membrane takes place and the amastigote form enters in direct contact with host cell structures and organelles, and starts to divide. The presence of the parasite in the cytoplasm of the host cell did not induce significant changes in the distribution of actin filaments, microtubules, the Golgi complex, mitochondria and endosomes/lysosomes during the first 48 h of infection. Amastigote forms were seen close to the microtubules. After 72 h of interaction, the number of microtubules and microfilaments around the parasites was reduced and lysosomes and mitochondria were seen in between the parasites.     

Learning of olfactory cues is not necessary for early lamb recognition by the mother

Ewes identify their young through the use of different sensory modalities. Olfactory recognition, which mediates selective acceptance at the udder, is established at 4 h postpartum (pp). Visual and auditory cues are involved in recognition at a distance, which is evident at 12 h pp. This study investigates whether anosmic ewes are able (a) to develop visual and auditory recognition and (b) to restore selective acceptance of their lamb at the udder. Visual and auditory recognition was assessed in anosmic and intact ewes at 12 h and 24 h pp by a test of two choices: their own and an alien lamb. Selectivity at allowing suckling was tested by presenting successively an alien and the familiar lamb at 4 h, 3 days, and 1 month pp. In the two-choice recognition test, at both 12 h and 24 h pp, anosmic as well as intact ewes showed a preference for their familiar lamb. Although anosmic ewes showed no difference in their acceptance of alien and familiar lambs for suckling at 4 h and 3 days pp, they nursed the alien lamb less at 1 month pp and showed more rejection behaviors toward it. Thus, visual, auditory, or both those types of recognition can be rapidly established, independent of olfactory recognition. Moreover, differential behavior of anosmic ewes toward their own versus an alien lamb at the udder at 1 month suggests that vision and audition may compensate to some extent for the loss of olfaction.     

Role of resident macrophages in canatoxin-induced in vivo neutrophil migration

Canatoxin (Cntx), a toxic protein purified fromCanavalia ensiformis seeds, was shown to have lipoxygenase-mediated effects either in vivo or in vitro. Data here show that Cntx induced a dose-dependent migration of neutrophils and mononuclear cells when injected into rat peritoneal cavities. Furthermore, Cntx was able to induce neutrophil migration into pleural cavities and into air pouches. These effects were inhibited by dexamethasone but not by inhibitors of arachidonic acid metabolism (indomethacin, NDGA, and BW-755c) or by a PAF antagonist (BN 52021). In the peritoneal cavity Cntx caused an increase in vascular permeability inhibited by dexamethasone and BW-755c. Neutrophil migration induced by this toxin was dependent on the number of resident macrophages, since the migratory effect was enhanced by increasing the peritoneal macrophage population with thioglycollate pretreatmen; and was diminished when this population was reduced by peritoneal wash. It was also observed that Cntx induced release of a chemotactic factor from macrophage monolayers in vitro. Dexamethasone blocked this release but did not affect in vivo neutrophil recruitment induced by that factor. These data suggest that Cntx-induced neutrophil migration may be mediated by the same macrophage-derived neutrophil chemotactic factor released by other stimuli such as LPS, IL-1, and INF-gamma.     

Conformational changes in Sindbis virions resulting from exposure to low pH and interactions with cells suggest that cell penetration may occur at the cell surface in the absence of membrane fusion

Alphaviruses have the ability to induce cell-cell fusion after exposure to acid pH. This observation has served as an article of proof that these membrane-containing viruses infect cells by fusion of the virus membrane with a host cell membrane upon exposure to acid pH after incorporation into a cell endosome. We have investigated the requirements for the induction of virus-mediated, low pH-induced cell-cell fusion and cell-virus fusion. We have correlated the pH requirements for this process to structural changes they produce in the virus by electron cryo-microscopy. We found that exposure to acid pH was required to establish conditions for membrane fusion but that membrane fusion did not occur until return to neutral pH. Electron cryo-microscopy revealed dramatic changes in the structure of the virion as it was moved to acid pH and then returned to neutral pH. None of these treatments resulted in the disassembly of the virus protein icosahedral shell that is a requisite for the process of virus membrane-cell membrane fusion. The appearance of a prominent protruding structure upon exposure to acid pH and its disappearance upon return to neutral pH suggested that the production of a "pore"-like structure at the fivefold axis may facilitate cell penetration as has been proposed for polio (J. Virol. 74 (2000) 1342) and human rhino virus (Mol. Cell 10 (2002) 317). This transient structural change also provided an explanation for how membrane fusion occurs after return to neutral pH. Examination of virus-cell complexes at neutral pH supported the contention that infection occurs at the cell surface at neutral pH by the production of a virus structure that breaches the plasma membrane bilayer. These data suggest an alternative route of infection for Sindbis virus that occurs by a process that does not involve membrane fusion and does not require disassembly of the virus protein shell.