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Biomedical subjects

Z Simon

Publications and source records attributed to Z Simon.

At least 19 recordsLinked to original sources
PubMed2002

Steric and electrostatic effects in dye-cellulose interactions by the MTD and CoMFA approaches.

This paper presents the application of the MTD (minimal steric difference) analysis and CoMFA (comparative molecular field analysis) to series of anthraquinone vat, mono and disazo and disperses dyes with known affinities for cellulose fiber. A comparison of the results demonstrates that these methods usually agree with the prediction of structural features favorable for dyeing. A series of n = 49 anthraquinone vat dyes was studied by MTD with r2 between 0.903 and 0.941 and r2CV values in the range of 0.827-0.878. For CoMFA, r2 = 0.992, r2CV = 0.841 were obtained; the CoMFA field is in rather good agreement with vertex attributions, by MTD for attractive and repulsive vertices. Anionic disazo dyes were studied by the CoMFA method (n = 21, r2 = 0.999, r2CV = 0.703). Monoazo dyes (several series) were studied by CoMFA and MTD. The effect of lipophilicity on dye fiber affinity was, also, studied for these dyes. Disperse dye adsorption was analyzed by MTD and CoMFA (n = 27, r2 = 0.925, r2CV = 0.776). Conclusions refer to the effect of structural features of dye molecules upon adsorption on cellulose fibers.

Adsorption↗
PubMed2001

MTD-PLS: a PLS-based variant of the MTD method. A 3D-QSAR analysis of receptor affinities for a series of halogenated dibenzoxin and biphenyl derivatives.

MTD-PLS, the Partial Least Squares (PLS) variant of the Minimum Topological Difference (MTD) method is described. In MTD-PLS, molecules are characterised not only by the occupancy or nonoccupancy of the hypermolecular vertices (as in classical MTD), but also by additional descriptors for each vertex: fragmental van der Waals volumes, fragmental hydrophobicities, partial atomic charges, etc. This method was applied to a series of 73 polyhalogenated derivatives of dibenzo-p-dioxine, dibenzofuran and biphenyl (induction of aryl hydrocarbon hydrolase and affinities to rat cytosolic receptor), previously studied by MTD. The separation of steric, hydrophobic, and electrostatic effects was achieved retranslating from the latent variable space into a linear combination of the initial structural variables. The MTD-PLS method yields more detailed results compared to classical MTD, indicating the importance of electrostatic effects at some substituent positions.

Binding Sites↗
PubMed2001

Significance of MTD and other descriptors in lipophilicity models for chlorinated aromatic compounds.

The lipophilicity of chlorinated benzenes and 20 biphenyls has been modeled using the minimum topological difference method and MTD indices. The MTD descriptor has been optimized on its own or together with nCl (number of chlorine atoms per molecule), 2D- and 3D-descriptors such as van der Waals surface area and volume, solvent accessible surface area and solvent-accessible surface-bounded molecular volume, and the inter-planar angle of the substituted biphenyls. In lipophilicity models of chlorinated aromatic compounds the majority of descriptors, including MTD, contain essentially the information of nCl. MTD is a good lipophilicity descriptor of chlorinated aromatic compounds either alone or in association with other descriptors. For chlorobenzenes it gives r = 0.998, s = 0.069, F = 2281, and for the set of chlorinated biphenyls r = 0.974, s = 0.255, F = 338, a better result than gives the nCl descriptor (r = 0.967). The significance of MTD descriptor in different models is discussed. Beside nCl, the MTD index encodes ortho and para effects.

Benzene Derivatives↗
PubMed1999

MOBISIM--package for simulation in molecular biology.

A computer program for simulation of protein synthesis regulatory processes is described. A short theoretical background reveals the requirements of a simulation program. Our program, MOBISIM, offers several facilities and a user-friendly interface for molecular biologists. An example illustrates the graphical representation both as time evolution of the system or as phase diagram.

Artificial Intelligence↗
PubMed1999

Eosinophilic cystitis in view of two cases.

Authors present their experiences with eosinophilic cystitis. In both of their cases the preoperative evaluation presumed bladder cancer, the histologic examination, however, showed eosinophilic cystitis. In this report a discussion is given on the diagnostic and treatment possibilities of the entity.

Aged↗
PubMed1998

Immunologic tolerance: self-nonself discrimination versus costimulatory factors and second signals.

An attempt is made to assess the total number of the theoretically possible antigenic epitopes, the number of lymphocyte clones and the number of epitopes on cell surface antibody of a clone may be able to recognize. We suggest that the structures of recognizing antibody sites of a human are far from random and derived from a limited number of structures adapted to the recognition of pathogenic agents. The probability of recognition for a random epitope-like structure is likely to be very small. Discriminative power of BCR and TCR binding sites, together with T-helper control, should be sufficient for prevention of peripheral autoimmune response, but second-signal-type controls should not be neglected as supplementary mechanisms to prevent such response.

Antibodies↗
PubMed1998

MTD-ADJ: a multiconformational minimal topologic difference for determining bioactive conformers using adjusted biological activities.

The active conformation is part of a conformational mixture with experimental activity Yexp, and is used in QSAR studies to extract more information regarding the ligand-receptor interaction. To reflect the relative amount (alpha) of the active conformation, we adjust Yexp: Yadj = Yexp - log alpha. We establish a quantitative structure-activity relationship (QSAR) between Yadj and 3D conformational characteristics for the acetylcholinesterase (AChE) hydrolysis rates of 25 acetic esters. The 3D-QSAR model was obtained using the adjusted multiconformational minimal steric/topologic difference (MTD-ADJ) method, optimizing the receptor map based on Yadj for each conformer. Yadj was updated during each step of the optimization process. alpha and Yadj are based on the Boltzmann distribution calculated using AMI (MOPAC 6.0) relative energies of the COSMIC 90 derived conformers. The MTD-ADJ results are: (i) the 3D-QSAR models obtained by this procedure have significant statistical parameters and are similar to the unadjusted (MTD-MC, using Yexp) models; (ii) the selected bioactive conformations are extended, occupy cavity vertices and, for the same structures, have the same MTD value; and (iii) the optimized conformational map of the neutral ligands obtained from the MTD-ADJ model fits well in the active site of the crystallographic structure of AChE (from Torpedo californica). We propose a neutral ligands binding site model for AChE. Our results show that MTD-ADJ, which can be implemented in any 3D-QSAR method, is capable of providing additional information regarding the active conformations, and can be used to gain further insight into the ligand-receptor models for which no structural data are available.

Acetylcholinesterase↗
PubMed1993

Acute gastric dilatation causing respiratory failure and "tension pneumothorax" in an elderly women with a diaphragmatic hernia.

The occurrence of respiratory failure as a result of a large diaphragmatic hernia is a well-described entity in infants with congenital hernias. On reviewing the literature, the authors did not find a similar clinical presentation in the adult population. They report the case of an elderly patient with a large hiatus hernia who developed recurrent episodes of life-threatening respiratory failure and hemodynamic compromise due to recurrent gastric dilatation. Decompression with nasogastric suction resulted in dramatic and immediate relief of the respiratory distress. One should keep in mind the possibility of intrathoracic gastric dilatation as a cause of acute respiratory insufficiency in patients with hiatal hernia.

Acute Disease↗
PubMed1993

Continuous therapy with intravenous prostacyclin for primary pulmonary hypertension: a bridge to heart-lung transplantation.

Primary pulmonary hypertension (PPH) continues to be a major problem. Vasodilator therapy has been of variable success in selected patients. Recently, with the introduction of prostacyclin (Prostaglandin I2, epoprostenon) as a potent vasodilator, several reports have shown a positive effect in primary pulmonary hypertension. We report here two patients with PPH who responded favorably to continuous intravenous therapy with prostacyclin. Both patients responded with a reduction in pulmonary vascular resistance, increase in cardiac output and dramatic improvement of right heart failure. Although therapy with prostacyclin is extremely expensive it may be used as a bridge to heart-lung transplantation in patients with end-stage PPH who do not respond adequately to alternative therapy.

Adult↗
PubMed1986

HLA antigens, jejunal morphology and associated diseases in children with dermatitis herpetiformis.

Forty-five Hungarian and Finnish children from 1.5 to 15 years with dermatitis herpetiformis were studied for HLA antigens, jejunal morphology on gluten-containing diet and associated diseases in the patients and their relatives. A strong association with HLA-B8 was found in patients of both nationalities, the relative risks were 12.8 and 9.6, respectively. The Hungarian patients were also typed for HLA-DR locus, and an association with DR3 but not with DR7 was observed. Patients with subtotal villous atrophy had slightly more often HLA-B8 and DR3 than those with milder intestinal lesions. Atopic eczema occurred in 20% of the patients and family history of atopy seemed to have an inverse correlation with HLA-B8 and DR3.

Adolescent↗
PubMed1986

Electrical stimulation of the bladder and gravidity.

Following experimental investigations, the authors have performed bladder stimulator implantation for paralyzed bladder patients since 1969. Up to 1983 altogether 32 operations were carried out for bladder paralysis following 21 peripheral and 11 central neural lesions. The patients urinated without residue after the operation. The observations showed that regular use of the stimulator led to the elimination of reflux in patients who had vesicoureteral reflux before the operation. It was found that, if the stimulator had to be removed for any reason after a period of 1 or 2 years, the urinating ability was maintained. Of the 7 female patients operated, 2 became pregnant. During pregnancy and delivery, the patients did not experience any problem with the implanted stimulator, and the children were born healthy and at term.

Adolescent↗
PubMed1986

Importance of the urodynamic examination of aged patients.

Urodynamic studies have been made since 1980 in aged patients treated for micturition disorders. Impaired micturition reflex action was found in 37% of the cases. The importance of the combined use of cystometry with sphincter electromyography is emphasized.

Aged↗
PubMed1985

QSAR application in chemical carcinogenesis. II. QSAR analysis of a class of carcinogenesis inhibitor: retinoids.

Quantitative structure-activity relationships for the reversion of keratinization of hamster tracheal cell organ culture by structurally related retinoids were formulated. Their biological activities (ED50 . M) were correlated with the following parameters: the minimal topological difference (describing the fit of the considered molecules with a possible receptor site) and the lipophilicity constants. For computation purposes the retinoids were divided in three series (A, B and C) according to structural modifications in the cyclic moiety of the molecule, in the polienic chain and in the terminal functional group, respectively. The computed regression equations suggested the importance of the stereochemical features of cyclic moiety (for series A, eq. 1, n = 19, r = 0.926, F = 48.19) and of the uninterrupted conjugation for the polienic chain (for series B, eq. 6, n = 11, r = 0.954, F = 39.39) for the biological activity. In order to check the prediction potential of the regression equation computed for the overall set of compounds (eq. 10, n = 53, r = 0.853, F = 32.11), it was used to calculate the ED50 for a test series of 15 retinoids. The correlation obtained between ED50 exp and ED50 calc for this series was r = 0.916, F = 60.25. The nature of the receptor site possibly involved in the interaction with retinoids was discussed.

Animals↗
PubMed1985

Cryocaustics in view of the complications.

The authors compared the complications of cryocaustic operations in hyperplastic patients with those of transvesical prostatectomy, TUR and of cryosurgical procedures. They have found that, considering its complications, cryocaustics is the intervention incurring the smallest risk to patients of bad general condition.

Aged↗
PubMed1985

Quantitative structure-activity relationship (QSAR) applications in chemical carcinogenesis. III. QSAR analysis of some phenolic antioxidants.

Quantitative structure-activity relationships (QSAR) were formulated for a series of 22 phenolic inhibitors of carcinogenesis, taking into account: a) the inhibition of forestomach tumor induction in benzo(a)pyrene fed mice, as biological parameter and b) minimal topological differences (MTD), lipophilicities, quantum mechanic indices (epsilon LE, epsilon HO, and delta E1) and Hammett constants, as structural and physicochemical ones. Significant multilinear regression equations were found for a set of 22 compounds, two 2,6-di-tert-butyl derivatives (4 and 22) diverting from the general correlations. The obtained correlations support the conclusion that the antioxidizing potential is not directly responsible (in a rate determining step) for the inhibitory properties of the investigated phenols.

Animals↗