Biomedical subjects

T Lavoie

Publications and source records attributed to T Lavoie.

5 recordsLinked to original sources

PubMed2001

Sustained-release potassium chloride overdose.

BACKGROUND: Although ingestion of sustained-release potassium supplements can cause life-threatening hyperkalemia in patients with abnormal renal function, only a few previous reports suggest that this may occur in patients with normal renal function. We report 2 cases of hyperkalemia in patients with normal renal function who developed hyperkalemia after ingesting sustained-release potassium preparations and describe the use of radiography and whole-bowel irrigation in their care. CASE REPORTS: The first patient is a 50-year-old woman who ingested 100 K-Dur tablets (each tablet containing 750 mg KCl or 10 mEq potassium) in a suicide attempt 1 hour prior to presenting to the emergency department. She developed a peak serum potassium level of 9.7 mEq/L and had transient, potentially life-threatening electrocardiographic changes. The second patient was a 17-year-old man who ingested 20 to 30 Klor-Con tablets (each tablet containing 750 mg KCl or 10 mEq potassium) in a suicide attempt 10 hours prior to presentation. Although he developed a peak serum potassium level of 6.1 mEq/L, he had a persistently normal electrocardiogram. In both patients, the tablets were visualized on abdominal radiographs and the gastrointestinal tracts of both were successfully decontaminated using whole-bowel irrigation. DISCUSSION: Although the sensitivity and specificity are unknown, the abdominal radiograph appears to be useful in detecting sustained-release potassium tablets. Whole-bowel irrigation as a primary method of gastrointestinal decontamination also appears to be effective although its use is not previously reported for sustained-release potassium overdoses.

Adolescent↗

PubMed1997

Normal intrauterine pregnancy is unlikely in emergency department patients with either menstrual days > 38 days or beta-hCG > 3,000 mIU/mL, but without a gestational sac on ultrasonography.

OBJECTIVE: To determine whether the absence of a gestational sac on transvaginal ultrasonography in patients with a quantitative beta-human chorionic gonadotropin (beta-hCG) > 3,000 mIU/mL and/or menstrual days > 38 excludes the diagnosis of a normal intrauterine pregnancy (IUP). METHODS: A retrospective analysis was performed of ED patients evaluated from August 1991 to December 1994 at an urban teaching hospital. Patients presented with abdominal pain and/or vaginal bleeding and had a positive serum beta-hCG test. Patients who had transvaginal ultrasonographies performed during the ED visit that were read as indeterminate were reviewed. Menstrual days were determined by subtracting the date of the last normal menstrual period (LMP) from the ED visit date. ED beta-hCGs were quantified. Patients were excluded if the LMP or quantitative beta-hCG result was not available or if the final diagnosis could not be definitively determined. RESULTS: 248 patients met eligibility criteria; of these, 54 were excluded. Therefore, 194 patients were enrolled. Menstrual days ranged from 5 to 151, with a median of 54 days. Of 143 patients with menstrual days > 38 and no gestational sac by ultrasonography, only 4 (2.8%) had a final diagnosis of normal IUP. The menstrual days for the 4 normal IUPs were 39, 41, 42, and 59 days. beta-hCGs ranged from 19 to 151,926 mIU/mL, with a median of 2,410 mIU/mL. None of the 74 patients with a beta-hCG > 3,000 mIU/mL and no gestational sac by ultrasonography had a final diagnosis of normal IUP. CONCLUSION: In patients with either a beta-hCG > 3,000 mIU/mL or menstrual days > 38 and no gestational sac by transvaginal ultrasonography, the likelihood of a normal IUP is low.

Adult↗

PubMed1996

Crystallization and preliminary crystallographic analysis of E. coli uridine 5'-diphospho-N-acetylenolpyruvylglucosamine reductase in two new crystal forms.

Uridine 5'-diphospho-N-acetylenolpyruvylglucosamine reductase (MurB), the second enzyme in the peptidoglycan synthetic pathway of Escherichia coli, has been crystallized in two previously unreported forms, one orthorhombic and the other monoclinic. MurB (molecular mass 38 kDa) crystallizes in a range of conditions that utilize polyethylene glycol fractions as precipitants, and crystals can be grown with or without the enzyme's substrate, uridine 5'-diphospho-N-acetylenolpyruvylglucosamine. X-ray diffraction from crystals of the orthorhombic form extends to 2 A resolution and shows the symmetry and systematic absences of space group P2(1)2(1)2(1). These crystals show significant variations in cell dimensions at room temperature and at 100 K. A crystal used to collect a 2.0 A resolution data set at a synchrotron source showed cell dimensions at ca 100 K of a = 51.0, b = 79.3 and c = 87.1 A, indicating one molecule peroasymmetric unit. The monoclinic crystals scatter X-rays to 3.0 A resolution consistent with space group P2(1), unit-cell dimensions (ca 100 K) a = 50.7, b = 92.4, c = 85.5 A, and beta = 104 degrees, and two molecules per asymmetric unit. Mercury derivatives have been prepared with both orthorhombic and monoclinic forms, and efforts are underway to exploit these derivatives to determine the structure of this protein.

Journal Article↗

PubMed1995

Refined solution structure of human profilin I.

Profilin is a ubiquitous eukaryotic protein that binds to both cytosolic actin and the phospholipid phosphatidylinositol-4,5-bisphosphate. These dual competitive binding capabilities of profilin suggest that profilin serves as a link between the phosphatidyl inositol cycle and actin polymerization, and thus profilin may be an essential component in the signaling pathway leading to cytoskeletal rearrangement. The refined three-dimensional solution structure of human profilin I has been determined using multidimensional heteronuclear NMR spectroscopy. Twenty structures were selected to represent the solution conformational ensemble. This ensemble of structures has root-mean-square distance deviations from the mean structure of 0.58 A for the backbone atoms and 0.98 A for all non-hydrogen atoms. Comparison of the solution structure of human profilin to the crystal structure of bovine profilin reveals that, although profilin adopts essentially identical conformations in both states, the solution structure is more compact than the crystal structure. Interestingly, the regions that show the most structural diversity are located at or near the actin-binding site of profilin. We suggest that structural differences are reflective of dynamical properties of profilin that facilitate favorable interactions with actin. The global folding pattern of human profilin also closely resembles that of Acanthamoeba profilin I, reflective of the 22% sequence identity and approximately 45% sequence similarity between these two proteins.

Actins↗

PubMed1994

Orientation of peptide fragments from Sos proteins bound to the N-terminal SH3 domain of Grb2 determined by NMR spectroscopy.

NMR spectroscopy has been used to characterize the protein-protein interactions between the mouse Grb2 (mGrb2) N-terminal SH3 domain complexed with a 15-residue peptide (SPLLPKLPP-KTYKRE) corresponding to residues 1264-1278 of the mouse Sos-2 (mSos-2) protein. Intermolecular interactions between the peptide and 13C-15N-labeled SH3 domain were identified in half-reverse-filtered 2D and 3D NOESY experiments. Assignments for the protons involved in interactions between the peptide and the SH3 domain were confirmed in a series of NOESY experiments using a set of peptides in which different leucine positions were fully deuterated. The peptide ligand-binding site of the mGrb2 N-terminal SH3 domain is defined by the side chains of specific aromatic residues (Tyr7, Phe9, Trp36, Tyr52) that form two hydrophobic subsites contacting the side chains of the peptide Leu4 and Leu7 residues. An adjacent negatively charged subsite on the SH3 surface is likely to interact with the side chain of a basic residue at peptide position 10 that we show to be involved in binding. The peptide-binding site of the SH3 is characterized by large perturbations of amide chemical shifts when the peptide is added to the SH3 domain. The mGrb2 N-terminal SH3 domain structure in the complex is well-defined (backbone RMSD of 0.56 +/- 0.21 calculated over the backbone N, C alpha, and C atoms of residues 1-54). The structure of the peptide in the complex is less well-defined but displays a distinct orientation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptor Proteins, Signal Transducing↗