Biomedical subjects

M Barcena

Publications and source records attributed to M Barcena.

3 recordsLinked to original sources

PubMed2000

Premedication with EMLA cream for ambultory surgery in children.

Objectives: The objective of this study was to confirm the ability of EMLA(R) cream (Eutectic Mixture of Local Anaesthetics, Astra, Sweden) to provide effective dermal analgesia after topical application on the skin of the dorsum of the hand 1 h before venous cannulation for anaesthetic induction. Material and Methods: Prospective, randomized, double blind study. We included 100 children, ASA I-III, distributed into three groups: Group EMLA (E, n=34), Placebo (P, n=33) and Control (C, n=33). Results: The EMLA group of patients (E) refered an evaluation of pain (visual analogical scale (mean=2.34+/-2.41), significantly smaller than the other groups (Placebo=5.54+/-3.40, Control=6.03+/-2.77). Conclusion: EMLA cream, when topically applied 1 h before venous cannulation, provides effective dermal analgesia for venous cannulation. No general or local adverse reactions were observed.

Journal Article↗

PubMed2000

Sequence-related protein export NTPases encoded by the conjugative transfer region of RP4 and by the cag pathogenicity island of Helicobacter pylori share similar hexameric ring structures.

RP4 TrbB, an essential component of the conjugative transfer apparatus of the broad-host-range plasmid RP4, is a member of the PulE protein superfamily involved in multicomponent machineries transporting macromolecules across the bacterial envelope. PulE-like proteins share several well conserved motifs, most notable a nucleoside triphosphate binding motif (P-loop). Helicobacter pylori HP0525 also belongs to the PulE superfamily and is encoded by the pathogenicity island cag, involved in the inflammatory response of infected gastric epithelial cells in mammals. The native molecular masses of TrbB and HP0525 as determined by gel filtration and glycerol gradient centrifugation suggested a homohexameric structure in the presence of ATP and Mg(2+). In the absence of nucleotides and bivalent cations, TrbB behaved as a tetramer whereas the hexameric state of HP0525 remained unaffected. Electron microscopy and image processing demonstrated that TrbB and HP0525 form ring-shaped complexes (diameter: 12 nm) with a central region (diameter: 3 nm) of low electron density when incubated in the presence of ATP and Mg(2+). However, the TrbB average image appeared to be more elliptical with strong twofold rotational symmetry whereas HP0525 complexes are regular hexagons. Six well defined triangle-shaped areas of high electron density were distinguishable in both cases. Covalent crosslinking of TrbB suggests that the hexameric ring is composed from a trimer of dimers, because only dimeric, tetrameric, and hexameric species were detectable. The toroidal structure of TrbB and HP0525 suggests that both proteins catalyze a repetitive process, most probably translocating a cognate substrate across the inner membrane.

Acid Anhydride Hydrolases↗

PubMed1999

Gold-ATP.

The synthesis, purification, and chemical analysis of two covalent conjugates between ATP and undecagold are described, one in which gold is attached to the ribose moiety of ATP and the other in which it is attached to the N-6 position of the adenine base. The former probe was then used to bind to two ATP binding proteins, the helicase DnaB and the chaperone DnaK. After purification from unbound gold by column chromatography, binding was measured by UV-Vis spectroscopy, then the protein and gold were visualized by scanning transmission electron microscopy. Binding was observed with the conjugates, and virtually no binding occurred in the control of undecagold without the ATP attached. This new probe may be useful for studying nucleotide binding sites on proteins or for labeling nucleic acids or oligonucleotides directly.

Adenosine Triphosphate↗