Biomedical subjects

Attila Kovács

Publications and source records attributed to Attila Kovács.

15 recordsLinked to original sources

PubMed2006

A theoretical study of the structure and bonding of UOX4 (X = F, Cl, Br, I) molecules: the importance of inverse trans influence.

During nitroxide-mediated polymerization (NMP) in the presence of a nitroxide R2(R1)NO*, the reversible formation of N-alkoxyamines [P-ON(R1)R2] reduces significantly the concentration of polymer radicals (P*) and their involvement in termination reactions. The control of the livingness and polydispersity of the resulting polymer depends strongly on the magnitude of the bond dissociation energy (BDE) of the C-ON(R1)R2 bond. In this study, theoretical BDEs of a large series of model N-alkoxyamines are calculated with the PM3 method. In order to provide a predictive tool, correlations between the calculated BDEs and the cleavage temperature (T(c)), and the dissociation rate constant (k(d)), of the N-alkoxyamines are established. The homolytic cleavage of the N-OC bond is also investigated at the B3P86/6-311++G(d,p)//B3LYP/6-31G(d), level. Furthermore, a natural bond orbital analysis is carried out for some N-alkoxyamines with a O-C-ON(R1)R2 fragment, and the strengthening of their C-ON(R1)R2 bond is interpreted in terms of stabilizing anomeric interactions.

Journal Article↗

PubMed2006

[Assessment of suicidal behaviour in general practice].

AIM: To assess the prevalence of suicidal behavior (wish to die, suicidal thoughts, suicide attempts) and to determine the characteristics of suicide attempters in primary care, including screening for major mental disorders. METHOD: A Hungarian urban general practitioner's district with 1248 inhabitants was screened for suicidal behavior as well as for major mental disorders. All the patients (n=382) who visited their general practitioner within a two-week period were asked to participate. 277 patients completed the Prime-MD questionnaire, an easy-to-use diagnostic instrument developed for general practitioners to recognize the most common psychiatric disorders, like depressive (major depressive disorder, minor depressive disorder), anxiety (panic disorder, generalized anxiety disorder), somatoform, eating and alcohol related disorders. Detailed data about suicidal thoughts and attempts were also collected by the structured questions of MINI-Plus diagnostic interview. RESULTS: Prevalence of suicide attempts in primary care was 2.9%. 9% of the patients had either suicidal thoughts or suicide attempts in the previous month. Suicidal patients were more ready to use psychotropic drugs, they assessed their health status more poorly, and had more mental symptoms than the control group (non-suicidal patients). 60% of suicidal patients and 11.5% of the investigated population had a current depressive episode. Beside depressive symptoms, anxiety disorders and alcohol problems were also more common among suicidal patients. The rate of previous psychiatric treatments was also higher in suicidal patients, who generally visited their general practitioners less frequently than non-suicidal patients. According to multivariate logistic regression, suicidal patients are more ready to take antidepressants, they tend to have more previous psychiatric treatments and suicidal attempts, and they visit their general practitioners less frequently and have a current depressive episode. CONCLUSION: Suicidal behavior and mental disorders are frequent in primary care. Since almost every tenth patient visiting their general practitioner has suicidal thoughts or depressive or anxiety disorder, the recognition of suicide risk and mental disorders is very important in primary care. As for preventing suicides, the diagnosing and treating of mental disorders -especially affective disorders- are very important for general practitioners. In addition to pharmacotherapy, psychotherapies are also important in treating patients in crisis situations, or with suicidal thoughts or depressive disorder. The modified Prime-MD questionnaire can be an effective, easy-to-use method in the hand of the general practitioners to identify suicidal risk and to recognize the most common mental disorders in the average population.

Adult↗

PubMed2005

Endotoxin can decrease isolated rat parotid acinar cell amylase secretion in a nitric oxide-independent manner.

Salivary mucus and amylase have an anti-bacterial nature. Bacterial endotoxin is considered to decrease mucus secreting cell activity by nitric oxide-dependent mechanisms. In this study, the actions of endotoxin on amylase secreting cell activity have been studied. Endotoxin (Escherichia coli lipopolysaccharide; 3 mg/kg, i.v., 5 h) evoked nitric oxide synthase 2 (NOS2) induction in the rat whole parotid tissue (assessed by Western blot and the citrulline assay) and in rat isolated parotid acinar cells (assessed by Western blot and immunohistochemistry), and reduced basal and acetylcholine-stimulated amylase secretion from these isolated cells. However, N(G)-nitro-L-arginine methyl ester (0.1 mg/ml, 4 days in drinking water, yielding a dose of 25 mg/kg/day) did not affect amylase release under basal or acetylcholine-stimulated conditions, either in control acinar cells or those from endotoxin challenged rats. Thus, basal, acetylcholine-evoked or endotoxin-decreased cellular amylase secretion from rat isolated parotid acinar cells does not appear to be modulated by endogenous nitric oxide.

Acetylcholine↗

PubMed2005

[The attendance of the first screening round (2002-2003) of the Hungarian organized breast cancer screening program and its effect on the number of diagnostic and screening mammography].

AIM: Organised, nationwide screening for breast cancer with mammography in the age group 45-65 years with 2 years screening interval started in Hungary in January 2002. The aim of this study is to analyze the attendance rate of breast screening programme, including the analysis of the ratio of screening and diagnostic mammography examinations. DATA AND METHODS: The data derive from the financial database of the National Health Insurance Fund Administration (NHIFA) covering the period 2000-2003. The ratio of women was calculated in the age group 45-65 years having either a screening mammography or a diagnostic mammography. The analysis was carried out for the years 2000-2001 (mainly opportunistic screening) before and 2002-2003 after the implementation of nationwide organized programme. RESULTS: In the years 2000-2001 7,26% of the women aged 45-65 had an opportunistic screening mammography while in 2002-2003 33,95% of the target population had screening mammography within the organized programme. During the same periods 19,67% (2000-2001) and 22,05% (2002-2003) of women aged 45-65 had a diagnostic mammography. Thus the total (screening and diagnostic) coverage of mammography increased from 25,85% (2000-2001) to 53,46% (2002-2003). CONCLUSIONS: The attendance of the Hungarian organized breast cancer screening programme - compared to the previous period before the implementation of the organized screening programme - is promising, although to achieve the expected results in mortality decrease a further improvement of the uptake is necessary.

Breast Neoplasms↗

PubMed2005

The nature of the chemical bond revisited: an energy-partitioning analysis of nonpolar bonds.

The nature of the chemical bond in nonpolar molecules has been investigated by energy-partitioning analysis (EPA) of the ADF program using DFT calculations. The EPA divides the bonding interactions into three major components, that is, the repulsive Pauli term, quasiclassical electrostatic interactions, and orbital interactions. The electrostatic and orbital terms are used to define the nature of the chemical bond. It is shown that nonpolar bonds between main-group elements of the first and higher octal rows of the periodic system, which are prototypical covalent bonds, have large attractive contributions from classical electrostatic interactions, which may even be stronger than the attractive orbital interactions. Fragments of molecules with totally symmetrical electron-density distributions, like the nitrogen atoms in N(2), may strongly attract each other through classical electrostatic forces, which constitute 30.0 % of the total attractive interactions. The electrostatic attraction can be enhanced by anisotropic charge distribution of the valence electrons of the atoms that have local areas of (negative) charge concentration. It is shown that the use of atomic partial charges in the analysis of the nature of the interatomic interactions may be misleading because they do not reveal the topography of the electronic charge distribution. Besides dinitrogen, four groups of molecules have been studied. The attractive binding interactions in H(n)E-EH(n) (E=Li to F; n=0-3) have between 20.7 (E=F) and 58.4 % (E=Be) electrostatic character. The substitution of hydrogen by fluorine does not lead to significant changes in the nature of the binding interactions in F(n)E-EF(n) (E=Be to O). The electrostatic contributions to the attractive interactions in F(n)E-EF(n) are between 29.8 (E=O) and 55.3 % (E=Be). The fluorine substituents have a significant effect on the Pauli repulsion in the nitrogen and oxygen compounds. This explains why F(2)N-NF(2) has a much weaker bond than H(2)N-NH(2), whereas the interaction energy in FO-OF is much stronger than in HO-OH. The orbital interactions make larger contributions to the double bonds in HB=BH, H(2)C=CH(2), and HN=NH (between 59.9 % in B(2)H(2) and 65.4 % in N(2)H(2)) than to the corresponding single bonds in H(n)E-EH(n). The orbital term Delta E(orb) (72.4 %) makes an even greater contribution to the HC triple bond CH triple bond. The contribution of Delta E(orb) to the H(n)E=EH(n) bond increases and the relative contribution of the pi bonding decreases as E becomes more electronegative. The pi-bonding interactions in HC triple bond CH amount to 44.4 % of the total orbital interactions. The interaction energy in H(3)E-EH(3) (E=C to Pb) decreases monotonically as the element E becomes heavier. The electrostatic contributions to the E-E bond increases from E=C (41.4 %) to E=Sn (55.1 %) but then decreases when E=Pb (51.7 %). A true understanding of the strength and trends of the chemical bonds can only be achieved when the Pauli repulsion is considered. In an absolute sense the repulsive Delta E(Pauli) term is in most cases the largest term in the EPA.

Journal Article↗

PubMed2005

Density functional study of the conformational space of 4C1 D-glucuronic acid.

The conformational space of (4)C(1) alpha- and beta-d-glucuronic acid was scanned by HF/3-21G(p) calculations followed by optimization of the 15 most stable structures for each, using the B3LYP density functional theory method in conjunction with a diffuse polarized valence triple-zeta basis set. We found a general preference of the alpha anomers in the isolated molecules in agreement with the large endo-anomeric hyperconjugation effects in these structures. From the other intramolecular interactions (exo-anomeric hyperconjugation, hydrogen-bonding, dipole-dipole, and steric interactions), the effect of the hydrogen bonding is the most pronounced and plays a major role in determining the stability order within the alpha and beta series. The most stable conformer of both alpha and beta (4)C(1) d-glucuronic acid is the structure with the maximum number (5) of intramolecular hydrogen bonds. Introduction of solvent (water) effects by the SCI-PCM model resulted in two characteristic changes of the energetic properties: the gas-phase stability order changed considerably, and the energy range of the 15 most stable conformers decreased from 30 to 15 kJ/mol. The geometrical parameters reflect well the superimposed effects of hyperconjugation and hydrogen-bonding interactions. Most characteristics are the variations of the C-O bond distances (within a range of 0.04 A) upon the combined intramolecular effects.

Carbon↗

PubMed2005

Suicide attempt and melancholic depression in a male with erotomania: case report.

Erotomania is a delusional disorder, which is more common among women. A case of erotomania in a 34-year-old male associated with depression and suicidal behavior is presented. At the time he attempted suicide his erotomania fulfilled the diagnostic criteria of "pure" erotomania, described by de Clérambault. A depressive picture with melancholic features emerged four months later. Antidepressant medication was given and two months later he became euthymic. The erotomanic delusion disappeared in the third month of the euthymic state. In this case primary erotomania was associated with a depressive illness, presumably unipolar depression. The patient developed delusional guilt and suicidal ideation before the unequivocal change in his mood. To the authors' knowledge this is the first reported case where the erotomanic symptomatology led to suicidal attempt.

Adult↗

PubMed2005

[The role of pneumoperitoneum and the "chimney effect" on the development of port site metastasis. A new experimental animal model using Furka's spleen tissue suspension].

Following the introduction of laparoscopic cholecystectomy, laparoscopic technology has been applied in many other fields of surgery, including surgery for malignancies, even before prospective, randomised trials were available. Many authors observed development of port site metastases following laparoscopic surgery in malignancies (1-2%). The studies report about the pathomechanism of the development of port site metastasis, some describe the role of pneumoperitoneum. We developed a new model to show the role of pneumoperitoneum and the "chimney effect" on the development of port site metastasis, using a large experimental animal with a suspension of its own spleen tissue. On follow up histology viable spleen tissue was found between the layers of the trocar incisions.

Abdominal Neoplasms↗

PubMed2003

Cardiovascular autonomic dysfunction in primary Sjögren's syndrome.

OBJECTIVE: To assess the occurrence and clinical significance of a cardiovascular autonomic nervous system dysfunction in primary Sjögren's syndrome (pSS). METHODS: Fifty-one pSS patients participated in this case-control study. Heart rate and blood pressure variability measurements, spontaneous baroreflex sensitivity examinations and cardiovascular reflex tests were performed. RESULTS: The results of the heart rate and blood pressure variability measurements and also the baroreflex sensitivity parameters of the pSS patients peaked in the lowest percentile ranges of a database on 559 healthy control subjects (P < 0.05). In three of the five cardiovascular reflex tests, the frequencies of abnormal results were significantly higher among the patients than among the controls (P < 0.05), and the median autonomic neuropathy score was also elevated (3 vs 0 in the controls; P < 0.0001). CONCLUSION: Signs of an autonomic nervous system dysfunction involving the cardiovascular system can be discerned in the majority of pSS patients.

Adult↗

PubMed2003

Theoretical study of mixed MLaX(4) (M = Na, K, Cs; X = F, Cl, Br, I) rare earth/alkali metal halide complexes.

The structure, bonding, and vibrational properties of the mixed MLaX(4) (M = Na, K, Cs; X = F, Cl, Br, I) rare earth/alkali metal halide complexes have been studied using the MP2 method in conjunction with polarized triple-zeta valence basis sets and quasi-relativistic effective core potentials for the heavy atoms. From the three characteristic structures, possessing 1- (C(3)(v)), 2- (C(2)(v)), or 3-fold coordination (C(3)(v)) between the alkali metal and the bridging halide atoms, the bi- and tridentate forms are stable isomers with close dissociation energies. In general, for the complexes existing of lighter alkali metals and halogens, the bidentate structure corresponds to the global minimum of the potential energy surface, while the heavier analogues favor the tridentate structure. At experimentally relevant temperatures (T > 800 K), however, the isomerization entropy leads to a domination of the bidentate structures over the tridentate forms for all complexes. An important effect of the size of the alkali metal is manifested in the larger stabilities of the K and Cs complexes. The natural atomic charges are in agreement with strong electrostatic interactions in the title complexes. The marginal covalent contributions show a slight increasing trend in the heavier analogues. The calculated vibrational data indicate that infrared spectroscopy may be an effective tool for experimental investigation and characterization of MLaX(4) molecules.

Journal Article↗

PubMed2003

Energy decomposition analysis of the chemical bond in main group and transition metal compounds.

The nature of the chemical bond in the main group diborane(4) compounds X2B-BX2 (X = H,F,Cl,Br,I) and in the Fischer- and Schrock-type transition metal carbene and carbyne complexes and heavier homologues (CO)5W-CH2, (CO)5W-E(OH)2, Cl4W-EH2, Cl(CO)4W-EH and Cl3W-EH (E = C,Si,Ge,Sn,Pb) have been investigated with an energy decomposition analysis (EDA). The results give a deep insight into the nature of the chemical interactions. The EDA results can be used as a bridge between the heuristic models of experimental chemists which have been proven as useful ordering schemes for experimental observations and the physical mechanism which leads to a chemical bond. At the time the data give a well defined qantitative answer to the questions about the strength of the covalent and electrostatic interactions and about the contributions of sigma and pi electrons to the covalent bond.

Journal Article↗

PubMed2002

[Psychiatric sequelae of interferon-alpha therapy].

INTRODUCTION: Psychopathologic conditions commonly complicate the treatment with the interferon-alpha. The most important among them is depression, which can induce suicidal attempt. The outcome of mental side effects of interferon-alpha necessitate the discontinuation of therapy and, in more severe cases, psychiatric treatment. AIM AND METHOD: A brief literature review presents the biology of interferon-alpha with emphasis on the central nervous system effects which are probably closely related to mental side effects. Three case reports demonstrate the interdisciplinary nature of interferon induced psychiatric conditions. RESULTS: The appearance of neuropsychiatric side effects of interferon-alpha are frequent, the consequences of which can prove dramatic: involvement of the vital prognosis, psychiatric morbidity, especially depressions, and suicidal risk. CONCLUSION: The close collaboration of clinical practitioners and psychiatrists, from the pre-therapeutical evaluation to the follow up care is required.

Anxiety↗

PubMed2002

Antioxidant enzyme activities are decreased in preterm infants and in neonates born via caesarean section.

OBJECTIVES: To investigate the antioxidant defense potential of human neonates according to gestational age and mode of delivery. STUDY DESIGN: Four study groups were established, full-term normal spontaneous vaginal delivery (FT-NSVD, n=24), full-term caesarean section (FT-CS, n=19), preterm normal spontaneous vaginal delivery (PT-NSVD, n=15) preterm caesarean section (PT-CS, n=21). The activity of catalase (CAT), glutathion peroxidase (GPX), Cu/Zn superoxide dismutase (Cu/Zn-SOD) were determined from cord blood. Statistical analysis was made by ANOVA. RESULTS: CAT activity was significantly higher in full-term than in preterm newborns. In both the categories, neonates born via caesarean section had significantly lower CAT activities. GPX activity was significantly higher in the FT-NSVD group than in any other group. Cu/Zn-SOD activity was significantly higher in full-term neonates than in preterms and no difference was found related to the mode of delivery. CONCLUSIONS: Prematurity and caesarean section may cause a deficiency of antioxidant defense in human newborn.

Antioxidants↗

PubMed2002

Chemical vapor deposition of gallium nitride from the GaCl(3)+NH(3) system. Theoretical study of the structure and thermodynamics of potential intermediates formed in the gaseous phase.

Quantum chemical calculations at the B3P86/6-311G(d,p) level have been performed on potential intermediate molecules in the chemical vapor deposition (CVD) of GaN from the GaCl(3) + NH(3) system. The investigated molecules included the monomer (Cl(x)GaNH(x), x = 1-3) and oligomer species (Cl(2)GaNH(2))(n) with n = 1-3 and (ClGaNH)(n) with n = 1-4 as well as the respective chain dimers and trimers. The calculations revealed the importance of intramolecular Cl...H hydrogen bonding and dipole-dipole interactions in determining the conformational properties of the larger species. Except for the ClGaNH monomer, the Ga[bond]N bonding has a single bond character with a strong ionic contribution. Our thermodynamic study of the composition of the gaseous phase supported the predominance of the Cl(3)GaNH(3) complex under equilibrium conditions. Additionally, the calculated Gibbs free energies of various GaCl(3) + NH(3) reactions imply the favored formation of "saturated" chain and cyclic oligomers below 1000 K.

Journal Article↗

PubMed2002

Structural characteristics of intramolecular hydrogen bonding in benzene derivatives.

In this Account, the intramolecular hydrogen bonding (HB) properties of various proton acceptor groups (BX(n): C=N, NO(2), C=O, P=O, F, CF(3)) with OH and NH(2) (AH) in benzene derivatives are assessed on the basis of gas electron diffraction, spectroscopic, and quantum chemical results. The most important properties are the HB energy, the characteristic geometrical changes in the interacting groups (lengthening of the A-H and B-X, shortening of the C-A and C-B bonds) and in the benzene ring, and the vibrational properties of the AH groups. These properties are characteristic of the particular HB interaction (in particular of the AH and BX(n) pair in single and multiple hydrogen-bonded systems); however, they cannot be related directly to the computed HB energies.

Journal Article↗