PubMed Health⌕ Search

Biomedical subjects

M Hamdan

Publications and source records attributed to M Hamdan.

At least 55 records · Page 3Linked to original sources
PubMed1996

Postextrasystolic U wave augmentation, a new marker of increased arrhythmic risk in patients without the long QT syndrome.

OBJECTIVES: We attempted to determine the correlation between the presence of postextrasystolic changes in the STU segment and a history of sustained ventricular arrhythmias. BACKGROUND: Postextrasystolic U wave augmentation (a marked increment in U wave amplitude after premature ventricular complexes [PVCs]) is an adverse prognostic sign in the "pause-dependent long QT syndrome." However, the prevalence of postextrasystolic changes in patients without the long QT syndrome is unknown. METHODS: We compared the configuration of the STU segment of the postextrasystolic beat (the sinus beat after a PVC) with the STU configuration during sinus rhythm in three patient groups: 1) 41 patients with spontaneous ventricular tachycardia/fibrillation (VT/VF) (VT/VF group), 2) 63 patients with heart disease and high grade ventricular arrhythmias (control group), and 3) 29 patients with high grade ventricular arrhythmias but no heart disease (reference group). RESULTS: Postextrasystolic T wave changes did not correlate with a history of ventricular tachyarrhythmias. However, postextrasystolic U wave changes were more common among the patients with VT/VF than among control subjects (39% vs. 8.7%, p < 0.001). By logistic multiple regression analysis, a low left ventricular ejection fraction (p < 0.001) and postextrasystolic U wave changes (p < 0.005) were independent predictors of ventricular tachyarrhythmias. CONCLUSIONS: Postextrasystolic T wave changes are common and lack predictive value. Postextrasystolic U wave changes may be a specific marker of a tendency to the development of spontaneous ventricular arrhythmias. Prospective studies should be performed to confirm this association.

Aged↗
PubMed1995

Investigation of complexes between some glycopeptide antibiotics and bacterial cell-wall analogues by electrospray- and capillary zone electrophoresis/electrospray-mass spectrometry.

Complexation in aqueous solutions between vancomycin, ristocetin A, teicoplanin and two bacterial cell-wall analogues, Ac2-L-Lys-D-Ala-D-Ala (tripeptide) and Ac-D-Ala-D-Ala (dipeptide) has been examined by positive-ion electrospray mass spectrometry (ES-MS) and capillary zone electrophoresis (CZE)/ES-MS. The ES-MS data demonstrate that as well as complexes between monomeric antibiotics and either peptide, the investigated solutions contained complexes ranging from the simple homodimer of the antibiotic to a more complex association giving ions of the type [2(antibiotic) + 3(tripeptide) + 3H]3+. The same data also demonstrate that the homodimers of the investigated antibiotics are significantly suppressed in the presence of the tripeptide. The use of CZE/ES-MS made it evident that the complexes between the antibiotic and the tripeptide were present in the solution prior to their introduction into the ion source. The two sets of data are compared with existing UV difference spectroscopy and nuclear magnetic resonance data on complexation and dimerization.

Amino Acid Sequence↗
PubMed1995

Investigation of crudes of synthesis of [Leu31, Pro34]-neuropeptide Y by capillary zone electrophoresis/mass spectrometry.

[Leu31, Pro34]-Neuropeptide Y is a thirty-six amino-acid peptide which has a measured relative molecular mass of 4222. Solid-phase synthesis of this peptide resulted in complex crudes of synthesis which were examined by capillary zone electrophoresis (CZE)/electrospray ionization mass spectrometry (ES-MS). The separation efficiency of CZE combined with the mass specificity of mass spectrometry yielded rapid and reliable information on the target peptide and a number of associated side products, which were mainly acetylated peptide sequences having relative molecular masses in the range 2240-4101. Such incomplete or, as they are commonly called, difficult sequences are provoked by problems of swelling and aggregation of the growing peptide chains in the course of synthesis. The use of mass spectrometry is indispensable for obtaining reliable information on the inevitable side products. Initial tuning of the ion source and optimization of the coupling between the CZE system and the mass spectrometer were achieved by performing a number of measurements pertaining to artificially made mixtures of commercial neuropeptides.

Amino Acid Sequence↗
PubMed1995

Current approaches in patients with ventricular tachyarrhythmias.

The article has summarized the studies and ongoing trials looking at the significance and treatment of ventricular tachyarrhythmias. In most instances, the presence of these arrhythmias is associated with an increased risk of future arrhythmic events. Electrophysiologic studies are helpful in risk stratification in patients with coronary artery disease but can be misleading in the setting of dilated cardiomyopathy and often produce nonspecific results in patients with HCM. The need for an invasive electrophysiologic study is crucial in the diagnosis of certain ventricular arrhythmias that are amenable to cure with radiofrequency catheter ablation, such as idiopathic ventricular tachycardia and BBR-VT. The correct approach for patients with SVT not amenable to catheter ablation remains to be determined. In deciding whether to use a device or drug therapy, however, one should take into consideration the degree of left ventricular dysfunction and the overall health status of the patient. For example, device implantation clearly reduces sudden death in patients with severe left ventricular dysfunction but may not change total mortality because these same patients may die of congestive heart failure. Device therapy might be more cost-effective for patients with less severe depression of left ventricular function.

Cardiac Complexes, Premature↗
PubMed1995

Antisense oligodeoxyribonucleotide down-regulation of bcl-2 gene expression inhibits growth of the low-grade non-Hodgkin's lymphoma cell line WSU-FSCCL.

The BCL-2 gene product is involved in preventing apoptosis. The t(14,18) chromosomal translocation, which results in a fusion messenger RNA containing the entire coding region of BCL-2 and a portion of the immunoglobulin heavy chain gene, is commonly found in follicular lymphoma and appears to play a role in lymphomagenesis by inhibiting cell death. We tested the hypothesis that downregulation of BCL-2 would decrease accumulation of follicular lymphoma cells by treating the t(14,18)-carrying follicular lymphoma cell line WSU-FSCCL in vitro with antisense oligodeoxyribonucleotides (ODNs) directed against BCL-2. We found dose-dependent, sequence-specific inhibition of cell accumulation by an antisense unmodified ODN directed at codons 2 to 7, which downregulated BCL-2 protein levels. This effect was near maximal at an ODN concentration of 40 micrograms/mL (6.9 mumol/L), with minimal toxicity by control sense, reverse, and mutated antisense ODN at the same concentration. The pre-B leukemia cell line REH showed no sequence-specific growth inhibition by the antisense ODN at these concentrations, and BCL-2 protein levels were not altered. These data suggest that WSU-FSCCL may be useful in a murine model to optimize antisense ODN for potential therapeutic utility.

Base Sequence↗
PubMed1994

Collision-induced dissociation of some protonated peptides with and without mass selection.

Collision-induced dissociation (CID) of several protonated peptides formed by positive-ion electrospray (ES+) and by Cs+ fast-ion bombardment are reported. The CID spectra of ions formed by the first ionization method were effected at elevated extraction cone voltages within the ion source of a single quadrupole instrument, while linked-fields-scan measurements at constant B/E of ions formed by the latter technique were performed within the collision cell of a trisector instrument. For molecular masses below 1000 Da, the two sets of spectra yielded identical sequencing information; however, for higher molecular masses the similarity was less evident. This divergence between the two sets of measurements is partially attributed to dominant doubly charged ions and less efficient dissociation of sodium adduct ions at elevated cone voltages.

Amino Acid Sequence↗
PubMed1993

Propagation of Waldenström's macroglobulinemia cells in vitro and in severe combined immune deficient mice: utility as a preclinical drug screening model.

Waldenström's macroglobulinemia (WM) represents an indolent incurable human B-cell tumor. We have successfully established a permanent cell line, WSU-WM, without growth factors or viral transformation, from the pleural effusion of a 60-year-old man with IgM kappa WM. Phenotypic characterization of WSU-WM shows IgM lambda and expression of other B-cell markers. Karyotypic analysis shows a male chromosome complement with several clonal aberrations, including t(8;14)(q24;q32). Molecular characterization shows deletion of kappa and rearrangement of lambda light chain genes indicating a class switching. Both the secretory (s mu) and membrane (m mu) components of IgM are expressed. In addition, the breakpoint on 8q24 is downstream of exon 3 of the c-myc oncogene. WSU-WM grows in liquid culture and soft agar. When cells were injected subcutaneously in immune deficient mice, six of seven SCID mice developed subcutaneous tumors as opposed to three of seven in the athymic nude mice. When a WSU-WM SCID tumor was passaged in vivo in the SCID mice, the take rate was 100%. This xenograft model and a soft agar disk-diffusion assay were used to test the efficacy of standard chemotherapy agents against this tumor in vivo and in vitro, respectively. The cell line and the assays described herein can be used as a model to facilitate the discovery of new therapeutic agents or modalities for this disease.

Animals↗
PubMed1993

Effects of target identity and collision energy on the fragmentation of some mass-selected protonated neuropeptides.

A number of protonated neuropetides formed by 10 keV Cs+ ion bombardment are mass selected and their collision-induced dissociations (CID) with helium, argon, xenon and isobutane are monitored using a collision energy of 200 eV. Data obtained by fixing the collision gas and using translational energies in the range 50-250 eV are also presented. The present data imply that optimization of the CID spectra presented can be achieved through a judicious choice of both the target gas and the translational energy of the mass-selected ion. The combined effect of the two experimental parameters on the relative abundances of the major sequence ions and on the loss of side-chain moieties is discussed.

Argon↗
PubMed1993

Effect of TGF-alpha on growth of normal human breast epithelial cells in serum-free primary culture using 3-dimensional collagen gels.

The mitogenic effect of TGF-alpha, acidic-FGF, basic-FGF and lithium on normal human breast epithelial cells was studied in a collagen gel culture system using a serum-free 1:1 mixture of Ham's F12 and DME medium containing insulin, cholera toxin and bovine serum albumin. TGF-alpha elicited a strong mitogenic response in a dose dependent manner. Addition of cortisol to TGF-alpha stimulated growth over and above that achieved with TGF-alpha alone. A consistent observation has been the effect of a combination of TGF-alpha and cortisol on growth stimulation of normal human breast epithelial cells resulting in 3-12 fold growth after 11-13 days in culture. Acidic-FGF, basic-FGF and lithium were not growth promoting.

Breast↗
PubMed1992

[The aorto-esophageal fistula. A rare cause of digestive hemorrhage].

The authors report a new case of aortoesophageal fistula caused by a giant ulcer of the esophagus. Success of the surgical treatment during the bleeding period couldn't occult the seriousness of this fistula which is almost fatal. Only an early diagnosis permitting a surgical treatment in better conditions could improve the prognosis of this condition.

Aortic Diseases↗