Biomedical subjects

Lajos Nagy

Publications and source records attributed to Lajos Nagy.

9 recordsLinked to original sources

PubMed2006

A simple method for estimating activation energies using the fragmentation yield: collision-induced dissociation of iron(II)-phenanthroline complexes in an electrospray ionization mass spectrometer.

The gas-phase stabilities of Fe(Phi)3(2+) complexes, where Phi represents the 1,10-phenanthroline, 5-chloro-1,10-phenanthroline, 5-methyl-1,10-phenanthroline, 3,4,7,8-tetramethyl-1,10-phenanthroline, and 4,7-diphenyl-1,10-phenanthroline ligands were investigated by collision-induced dissociation (CID) in the capillary-first skimmer region upon changing the voltage difference between the capillary and the skimmer. The loss of only one ligand from the Fe(Phi)3(2+) complexes was observed with each of the phenanthroline ligands studied. An increase in the voltage difference between the capillary and the skimmer resulted in a higher fragmentation yield as calculated from the intensity of the precursor and the fragment ion. The fragmentation yield versus capillary-skimmer voltage difference plots were evaluated by means of the Arrhenius and the Rice-Ramsperger-Kassel (RRK) model by fitting the model parameters to the experimental data. Both models yielded practically the same results. In addition, if the internal energy gained through the capillary-skimmer region is estimated correctly, the approximate value of the critical energy (activation energy) for fragmentation can be extracted from the fragmentation yield versus capillary-skimmer voltage difference plots. It was found that the gas-phase stabilities of the Fe(Phi)3(2+) complexes are nearly identical except for the more stable Fe(II)-4,7-diphenyl-1,10-phenanthroline complex. The critical energy for fragmentation was estimated to be approximately 1.2 and 0.9 eV for the Fe(II)- 4,7-diphenyl-1,10-phenanthroline, and the other complexes, respectively.

Journal Article↗

PubMed2005

Matrix-assisted laser desorption/ionization and electrospray ionization mass spectrometric study of 2,3-dihydro-1,4-benzoxazepines.

Fragmentations of the protonated adduct ions [M+H](+) of seven 1,4-benzoxazepine derivatives were studied using 'post-source decay' matrix-assisted laser desorption/ionization (PSD MALDI) and electrospray nozzle-skimmer collisionally induced dissociation (ESI-CID) mass spectrometric methods. It was found that both methods generated mainly product ions arising from the cross-ring cleavages of the benzoxazepine ring. Similar product ions were generated under MALDI and ESI conditions; however, it was observed that the loss of the alkylene unit from the N-substituted benzoxazepine, and the loss of a H(2)X molecule (where X = O or S), are more preferred under ESI conditions. Based on the experimental results a mechanism is also proposed for the fragmentation of the oxazepines studied.

Journal Article↗

PubMed2005

Multiple charging of poly(propylene glycol) by binary mixtures of cations in electrospray.

Single, double and triple charging of poly(propylene glycol) (PPG) (Mn = 1900 g/mol) in the presence of binary mixtures of cations (Li+, Na+, K+, Cs+, and NH4+) under electrospray ionization (ESI) conditions were investigated. For these studies, sodium ion was selected as the reference cation, and the resulting ion-intensities were evaluated as a function of the [Na+]/[C+] ratio (where C+ is the other cation, i.e., Li+, K+, Cs+ and NH4+). A linear relationship was found between INa+/IC+)and [Na+]/[C+] (INa+ and IC+ stand for the intensity of the singly charged PPG molecules cationized with Na+ and C+ ions, respectively). The slope of the INa+/IC+--[Na+]/[C+] plot (alpha) indicates the binding selectivity of Na+ ions to PPG chains with respect to cation C+. In the case of the doubly charged PPG chains, the INaNa2+/INaC2+ and INaC2+/ICC2+ versus [Na+]/[C+] ratio also yield straight lines with slopes of approximately alpha/2 and 2alpha, respectively (INaNa2+, INaC2+ and ICC2+ are the intensity of the doubly charged PPG chains cationized with two Na+ ions, Na+ and C+ ions, and two C+ ions, respectively). Similarly, linear dependences with the [Na+]/[C+] ratio for the corresponding intensity ratios of the triply charged PPG were found. Based on the value of alpha, the selectivity of the cations was found to increase in the order of Li+ < Cs+ approximately Na+ < K+ approximately NH4+. The observed relative ion intensities are interpreted on the basis of the solution state equilibrium between PPG and the cations. In addition, the investigations showed that the abundances of the doubly and triply charged PPG-containing mixed cations can be optimized in a simple way using the value of alpha.

Journal Article↗

PubMed2004

[Necrotising fasciitis in hyper-IgE syndrome].

Hyper-IgE syndrome is a rare primary immunodeficiency disease characterized by recurrent staphylococcal skin abscesses, chronic eczematoid dermatitis, pneumonia, pneumatoceles, and extreme elevation of serum IgE. The most common pathogens are S. aureus, and C. albicans. Abnormalities of dentition, bone manifestations, and connective tissue disorders are also common features of the disease. The authors report here a 19-year-old female with hyper-IgE syndrome who developed necrotising fasciitis and toxic shock syndrome. Methicillin resistant S. aureus and S. pyogenes cultured from the skin lesions. Association of hyper-IgE syndrome with necrotising fasciitis is a rarity in the medical literature. In addition to the case report, the authors describe here the major immunologic and clinical manifestations of hyper-IgE syndrome.

Adult↗

PubMed2004

Post-source decay matrix-assisted laser desorption/ionization mass spectrometric study of tetracyclic 2,3-dihydro-1,5-benzothiazepines.

The fragmentation behavior of six tetracyclic 2,3-dihydro-1,5-benzothiazepine derivatives cationized with protons and silver ions under post-source decay (PSD) matrix-assisted laser desorption/ionization (MALDI) conditions is reported. The protonated adduct ions decompose into several structurally important fragment ions, including substituted cyclopropane and benzohydrothiazole cations. Elimination of Ag and H and/or AgH from the silver-cationized adduct ions of these ([M+Ag](+)) compounds was observed. It was also found that [M+Ag](+) produced silver-depleted fragment ions exclusively. Based on the PSD results a fragmentation pathway is proposed for the [M+H](+) and [M+Ag](+) precursor ions.

Spectrometry, Mass, Matrix-Assisted Laser Desorpti↗

PubMed2004

Cationization of simple organic molecules by singly-charged Ag3+ cluster ions in matrix-assisted laser desorption/ionization mass spectrometry: metal cluster-molecule interactions.

It was found earlier that under matrix-assisted laser desorption/ionization (MALDI) conditions several organic compounds which produce adduct with silver ions, are also capable of forming adducts with Ag(3)(+) cluster ions under appropriate conditions. The Ag(3)(+) cluster ion can be in situ generated under the MALDI analysis conditions from silver trifluoroacetate cationization agent in the presence of organic MALDI matrices. In this article the fragmentation of a commercial plasticizer, a peracetylated isoflavone glycoside and a pyrazolylphenyl disulfide derivative cationized with silver ions and Ag(3)(+) cluster ions are compared. It was observed that the complexes of Ag(3)(+) are less fragmented than the corresponding adduct ions with Ag(+). The presumable fragmentation channel of [M + Ag(3)(+)] is the elimination of Ag(2) units from these complexes. No significant dissociation of [M + Ag(3)(+)], into M and Ag(3)(+) takes place, indicating a tight connection between the corresponding molecule and Ag(3)(+) cluster ion. However, with a compound carrying very labile groups, such as the pyrazolylphenyl disulfide derivative, intramolecular cleavages can occur prior to significant dissociation of the Ag(3)(+) cluster ion.

Journal Article↗

PubMed2004

Bimetallic silver-gold clusters by matrix-assisted laser desorption/ionization.

Pure gold clusters (Aun+) were produced up to the cluster size of n = 100 by matrix-assisted laser desorption/ionization (MALDI). The mass spectrum of the resulting clusters showed alteration in the ion intensity at odd-even clusters size. On the other hand, intensity drops at cluster size predicted by the jellium model theory was also observed. Positively and negatively charged bimetallic silver-gold clusters were produced under MALDI conditions from the mixture of HAuCl4/silver trifluoroacetate and the 2-(4-hydroxyphenylazo)benzoic acid (HABA) matrix. A linear correlation was found between the intensity ratio of AunAgm+ to Au(n+1)Ag(m-1)+ cluster ions and the molar ratio of the gold to silver salt. It was observed that the composition and the distribution of the clusters can be varied with the molar ratio of the silver and gold salts. It was also found that the resulting cluster sizes obey the lognormal distribution.

Journal Article↗

PubMed2004

Analgesic nephropathy in Hungary: the HANS study.

BACKGROUND: The diagnosis of analgesic nephropathy has improved significantly with modern imaging techniques. We reviewed a large portion of the Hungarian dialysis population to obtain additional insight into the problem. METHODS: Twenty-two participating dialysis units enrolled 1400 patients on renal replacement therapy between 1 January 1995 and 1 January 1998. Patients with no known aetiology (n = 284) were interviewed and studied with renal imaging. We assessed the presence of decreased renal mass combined with either bumpy contours, papillary calcification, or both. The subjects studied were interrogated extensively. RESULTS: Our survey suggested analgesic nephropathy in 47 of 1400 patients (3.3%), 3-fold higher than the EDTA database estimate for Hungary. The analgesics most commonly abused were phenacetin-containing mixtures. The driving symptoms were mainly headache and joint pain. Cardiovascular complications were more common than in the rest of the dialysis population, independent of smoking and lipid values (P<0.01). CONCLUSIONS: Phenacetin should be banned. Our study results support the need for longitudinal cohort and case-control studies in Hungary.

Analgesics, Non-Narcotic↗

PubMed2003

The effect of frequent or occasional dialysis-associated hypotension on survival of patients on maintenance haemodialysis.

BACKGROUND: While frequent or occasional symptomatic intradialytic hypotension (IDH) may influence patient well-being, its effects on survival-independent of comorbidities-has not previously been investigated. In this study, therefore, our objective was to assess the effect of frequent IDH (f-IDH) or occasional IDH (o-IDH) on survival. METHODS: During a 10 month run-in period in 1998, 77 patients with f-IDH (> or =10 hypotensive events/10 months, responding only to medical intervention) and 101 patients with o-IDH (1 or 2 events/10 months) were identified among all 958 patients of a dialysis network. Eighty-five patients who had no hypotensive episodes (no-IDH) during this run-in phase served as controls. Patients were followed for a median of 27 months (range: 0.3-37) and survival of patients in the three groups was compared by log-rank test. Independent association of f-IDH and o-IDH with survival, compared with no-IDH, was assessed by a proportional hazards model that included patient demographics, laboratory data and antihypertensive medication as well as comorbidity. RESULTS: Forty-five patients (58%) with f-IDH, 47 (47%) with o-IDH and 33 (39%) with no-IDH died during the follow-up. Mortality rates (deaths/100 patient years) were 37 (log-rank P = 0.013 vs no-IDH), 26 (log-rank P = 0.375 vs no-IDH) and 21 in the three groups, respectively. This indicates significantly decreased survival in patients with f-IDH as compared to those with no-IDH. In multivariate proportional hazards regression, however, where age, sex, time spent on dialysis, presence of coronary heart disease, diabetes, Kt/V, albumin level and use of beta-blockers, calcium-channel blockers and long-acting nitrates has been adjusted for, neither f-IDH nor o-IDH was associated with survival. CONCLUSIONS: Mortality in patients with f-IDH is significantly higher than in those without such events. After adjustments for covariates, however, there is no independent effect of frequent or occasional episodes of IDH on mortality.

Adult↗