Concerted nitrogen inversion and hydrogen bonding to Glu451 are responsible for protein-controlled suppression of the reverse reaction in human DPP III.

Human dipeptidyl-peptidase III (h.DPP III) is a zinc-exopeptidase that hydrolyses dipeptides from the N-terminus of its substrates. Its mechanism of action was assumed to be similar to that of thermolysin, but was never thoroughly investigated. This study presents the first insight into the reaction mechanism of h.DPP III, determined on the model and real (hydrated enzyme with Leu-enkephalin bound in the active site) systems. The Glu451-assisted water addition on amide carbon atoms and nitrogen inversion (i.e. change of pyramidalization on the leaving nitrogen) are shown to be the rate-determining steps with the activation energies in a good agreement with the experimental results for the Leu-enkephalin hydrolysis. The energy barrier for nucleophilic attack is about 28 kJ mol-1, while barriers for the N-inversion differ as a consequence of the number of hydrogen bonds that have to be changed, which is smaller in the model active site than in the solvated enzyme. Although precisely defined geometry of the enzyme binding site puts an additional restraint on the hydrogen bonding interactions, at the same time it stimulates the forward reaction towards the final hydrolytic product. Namely, different from the model, the N-inversion is in a concerted fashion followed by favourable hydrogen bonding with Glu451 that immediately "locks" the system into the configuration where reversion to the enzyme-substrate complex is hardly achievable. Therefore we propose that the functional significance of DPP III is dual: to lower the energy barrier of the peptide hydrolysis and to suppress the reverse reaction.

Human 3-hydroxyanthranilate 3,4-dioxygenase () dynamics and reaction, a multilevel computational study.

3-Hydroxyanthranilate 3,4-dioxygenase () is a non-heme iron dependent enzyme. It catalyses the cleavage of the benzene ring of 3-hydroxyanthranilic acid (3-Ohaa), an intermediate in the kynurenine pathway, and therefore represents a potential target in treating numerous disorders related to the concentration of quinolinic acid (QUIN), the kynurenine pathway product, in tissues. The stability and behaviour of the enzyme in nearly physiological conditions, studied by the empirical molecular modelling methods enabled us to determine the influence of several, for the enzyme activity relevant, point mutations (Arg43Ala, Arg95Ala and Glu105Ala) on the protein structure, particularly on the active site architecture and the metal ion environment, as well as on the substrate, 3-Ohaa, binding. Besides, the water population of the active site, and the protein flexibility as well as the amino acid residues interaction networks relevant for the enzyme activity were determined for the 3-Ohaa complexes with the native and mutated enzyme variants. Finally, using the hybrid quantum-mechanics/molecular-mechanics (QM/MM) calculations the catalysed 3-Ohaa oxidation into 2-amino-3-carboxymuconic acid semialdehyde was elucidated.

C-reactive protein as an early predictor for anastomotic leakage in elective abdominal surgery.

BACKGROUND: Anastomotic leakage (AL) represents a serious complication after abdominal surgery. Therefore, it is important to detect it early before it becomes clinically apparent. The predictive value of C-reactive protein (CRP) as a marker of infective postoperative complications, particularly in the form of anastomotic leakage, has been investigated by several authors with promising results. The aim of this study was to evaluate the diagnostic accuracy of C-reactive protein in predicting anastomotic leakage. METHODS: The serum CRP level, white blood cell (WBC) count, and body temperature (BT) of 156 patients who underwent elective abdominal surgery with primary anastomosis were monitored daily until postoperative day (POD) 7. We recorded all postoperative complications and analyzed the data. Diagnostic accuracy of CRP with regard to development of AL was assessed by receiver operating characteristic curve analysis. RESULTS: Fifteen patients (9.6 %) developed anastomotic leakage. CRP was significantly higher every day during the first 7 postoperative days in patients who developed AL compared with those patients who did not develop complications, whereas the WBC count and BT were not. A CRP cutoff value of 135 mg/l on POD 3 yielded a sensitivity of 73 %, a specificity of 73 %, and a negative predictive value of 95.4 % for the detection of AL. CONCLUSIONS: According to our results, values of CRP less than 135 mg/l on POD 3 may contribute to a safe discharge from hospital. Patients with CRP values higher than 135 mg/l on POD 3 require prolonged hospitalization and an intensive search for infective complications, particularly AL.

Early prediction of symptomatic hypocalcemia after total thyroidectomy.

BACKGROUND: Hypocalcemia is the most common postoperative complication after total thyroidectomy. The aim of this prospective study was to determine biochemical parameters in the early postoperative period that could identify patients with significantly increased risk of symptomatic hypocalcemia development. METHODS: The study included 100 individuals undergoing total thyroidectomy from January to May 2009. In all patients PTH, calcium, inorganic phosphate, magnesium, and albumin levels were measured immediately preoperatively, 30 minutes postoperatively and every morning for the following five days. RESULTS: Clinically significant hypocalcemia was observed in 19% of all cases. Fall of the iPTH values by more than 88% from preoperative values, 30 min after completion of the surgery, showed 100% sensitivity and 100% specificity for the occurrence of symptomatic hypocalcemia. CONCLUSIONS: According to our results immediate postoperative measurement of the iPTH may be considered as a useful method to predict with high certainty which patients will need calcium supplementation, and to separate them from patients who can be safely and early discharged.

Changing trends in mortality of thyroid cancer in Belgrade population.

PURPOSE: Thyroid cancer patients have favorable prognosis. The aim of this study was to analyze changing trends in mortality of thyroid cancer in Belgrade, during the period between 1987 and 2006. METHODS: Mortality data were obtained from the Belgrade Office of Statistics. Mortality rates per 100,000 inhabitants were standardized according to the Segi's world population. Regression analysis was used to estimate the thyroid cancer mortality trend for the period 1987-2006. RESULTS: The average percent of deaths due to thyroid cancer among all deaths was almost 2-fold higher in females (0.11%) than in males (0.6%), as well as among deaths due to all malignancies (females 0.54% and males 0.27%). During this 20-year period, the average standardized mortality rate was 1.5 times higher in females (0.74 per 100.000) than in males (0.51 per 100.000). In the observed period, the mortality rates for thyroid cancer were increased (+0.40%) in women and decreased (-0.42%) in men. In particular, in the 60-69 years age group in males, a significant trend for mortality decrease of 3.5%/year was detected. CONCLUSION: Belgrade is classified in the regions with low risk of dying due to thyroid malignancies. The increasing trend of thyroid cancer mortality in females during the examined period calls for improvement of methods for early detection of disease and differential diagnosis of thyroid nodules, so that surgical treatment of thyroid cancer could be performed at a stage when it is not life threatening.

Hyperstrong neutral organic bases: phosphazeno azacalix[3](2,6)pyridines.

The gas-phase basicities and pKa values in acetonitrile of tris(phosphazeno)-substituted azacalix[3](2,6)pyridine and some related compounds are examined by DFT computational method. It is shown that the hexakis(phosphazeno) derivative of azacalix[3](2,6)pyridine is a hyperstrong neutral base as evidenced by the absolute proton affinity (APA) of 314.6 kcal mol(-1) and pKa(MeCN) of 37.3 units. It is a consequence of the very strong bifurcated hydrogen bond (32 kcal mol(-1)) and substantial cationic resonance effect.

Derivatives of azacalix[3](2,6)pyridine are strong neutral organic superbases: a DFT study.

The gas phase basicities and pKa values in acetonitrile of azacalix[3](2,6)pyridine and its derivatives are determined by the B3LYP DFT method. It is found that all compounds of this series are neutral organic superbases. The proton attacks the inner pyridine N(sp2) atom, thus forming a bifurcated intramolecular hydrogen bond. The most powerful superbase is provided by the hexakis(dimethylamino) derivative of the title compound. Its gas phase proton affinity is 296.6 kcal mol-1, its basicity is 291.3 kcal mol-1, and its pKa(MeCN) is 30.9 units. [structure: see text]

Basicity of some organic superbases in acetonitrile.

[structure: see text] It is shown that the pK(a) values of strong neutral organic (super)bases in acetonitrile are well described by the density functional theory (DFT) employing the isodensity polarization continuum model (IPCM) for treating solvent-solute interactions. High pK(a) values are predicted for two model compounds, and their synthesis is strongly recommended.

Autopsy material analysis at the Cardiology Clinic in 1999.

Clinico-pathological studies serve as a valuable source of information in everyday practice of most medical institutions. The aim of this study was to correlate the clinical and pathological diagnoses of principal disease and cause of death after autopsy in patients who died during 1999 at the Cardiology Clinic, Institute of Cardiovascular Diseases, Sremska Kamenica, Yugoslavia. Medical histories and autopsy reports of dead patients were analyzed: 255 (8.46%) patients died, but only 72 (28%) underwent autopsy. In 53 patients (73%) clinical cause of death was cardiac. Among these patients, consequences of coronary (atherosclerotic) artery disease prevailed in 41 patients (77%). Noncardiac cause of death was established in 19 patients (27%) and vascular causes prevailed with 17 (23%). The comparison of clinical and principal disease established by autopsy revealed a complete concordance in 62 cases, partial concordance in 1 and no concordance in 9 cases. Thus, concordance was found in 86-87.5%. The correlation coefficient was 0.48. Comparison of clinical and autopsy diagnoses of causes of death revealed concordance in 53 patients, with correlation coefficient 0.26.

[The superior vena cava syndrome as a manifestation of dissection of the ascending aorta]. / Sindrom gornje suplje vene kao manifestacija disekcije ascendentne aorte.

INTRODUCTION: Most clinical manifestations of aortic dissection are due to complications of either ischemic origin or wall rupture of pleural, pericardial, peritoneal or mediastinal cavity. Compression of other blood vessels such as pulmonary artery or superior vena cava is possible, but rarely occurs. CASE REPORT: A 60 year-old patient was admitted to hospital due to severe cyanosis and edema of the face, neck and upper thorax. Ten years ago, due to aortic insufficiency, aortic valve replacement with mechanical prosthesis (St. Jude) was performed. Diagnosis of superior vena cava syndrome was established on the basis of clinical examination, ECG and chest radiography. The etiology was confirmed by echocardiography indicating an enormous dissecting aneurysm of the ascending aorta, 9.2 cm in diameter. Lethal outcome followed 24 h after admission according to the type of electromechanical dissociation. DISCUSSION: The first case of superior vena cava syndrome was described by William Hunter in 1757. This severe disease is caused by tumors which compress or develop inside superior vena cava. In cases of rapid symptom occurrence, thrombosis or compression of vena due to hematoma (trauma, voluminous, dissecting aortic aneurysm) should be considered. Since symptoms of aortic dissection were absent (thoracic pain, aortic regurgitation, pulse asymmetry) the etiologic diagnosis of superior vena cava syndrome was confirmed by echocardiography. Surgical treatment of dissection provides repermeabilization of the superior vena cava and loss of symptoms. CONCLUSION: Superior vena cava syndrome is a rare and slightly known clinical manifestation of ascending aortic dissection. If symptoms rapidly occur, dissection should be considered, particularly in previously surgically treated patients.

[The first non-Q myocardial infarct as a clinical manifestationn of acute coronary syndrome]. / Prvi non-Q infarkt miokarda kao klinicka manifestacija akutnog koronarnog sindroma.

INTRODUCTION: Non-Q myocardial infarction is only one of the possible clinical manifestations of acute coronary syndromes. Acute coronary syndrome is the most frequent cause of hospitalization in everyday cardiological practice. OBJECTIVES: 1. To evaluate the incidence of unstable angina and myocardial infarction in the group of patients admitted to hospital with diagnosis of acute coronary syndromes; 2. To evaluate the incidence of non-Q myocardial infarction in the group with index myocardial infarction; 3. To determine the frequency of different ECG changes in the subgroup with non-Q myocardial infarction. MATERIAL AND METHODS: The study was conducted at the Institute of Cardiovascular Diseases in Sremska Kamenica in the period between Jan. 1, 1997 and Dec. 31, 1999. Hospitalized patients with acute coronary syndromes (n = 3.337) were divided into subgroups with unstable angina (chest pain, ECG changes and normal level of CK) and with myocardial infarction (chest pain, ECG with/without changes, elevation of cardiac enzymes). Myocardial infarction without Q waves on ECG was considered to be non-Q myocardial infarction. Initial ECG changes (ST elevation, ST depression, inverted T waves, abscence of changes) were evaluated in patients with non-Q myocardial infarction who were not treated with Streptase. RESULTS: During a three-year period, 3.337 patients with acute coronary syndrome were hospitalized. 65.3% of them had unstable angina, while 34.7% suffered from myocardial infarction. In the group with myocardial infarction, 12.9% (280/2179) had reinfarction. 8.8% of patients were treated with thrombolytic agents, which prevented formation of Q waves in 24.6% of patients. In the group of patients who were not treated with thrombolytics, 196 patients (11.8%) fulfilled criteria for non-Q myocardial infarction. Incidence of initial ST elevation, ST depression and inverted T waves in those patients with non-Q myocardial infarction were 11.2%, 35.2% and 52.1% respectively, whereas 1.5% had no ECG changes. CONCLUSION: Both incidence of unstable angina and non-Q myocardial infarction, as manifestations of acute coronary syndromes, and incidence of newly formed ST elevation, which is one of the forms of initial ECG changes in non-Q myocardial infarction, are significantly lower than those found in literature.

Absolute proton affinity of some polyguanides

The problem of the absolute proton affinity (APA) of some polyguanides is addressed by the MP2(fc)/6-311+G//HF/6-31G theoretical model. It is shown that the linear chain polyguanides exhibit increased basicity as a function of the number of guanide subunits. However, the saturation effect yields an asymptotic APA value of 254 kcal/mol. Branched polyguanides on the other hand have higher APAs than their linear counterparts. The largest proton affinity is found in a doubly bifurcated heptaguanide, being as high as 285 kcal/mol, thus potentially representing one of the strongest organic bases. Finally, it is found that all polyguanides protonate at imino nitrogen atoms, since they are apparently susceptible the most to the proton attack. The origin of their very high intrinsic basicity is traced down to a dramatic increase in the resonance interaction of the corresponding conjugate bases. For instance, the increase in the resonance energy in the protonated guanidine is estimated to be in a range of 24-27 kcal/mol, which is higher than the aromatic stabilization in benzene. The proton affinity of some polycyclic guanides including Schwesinger proton sponge and porphine is briefly discussed.

[Asphyxia and intracranial hemorrhage in high-risk neonates of various gestational ages]. / Asfiksija i intrakranijalno krvarenje kod vitalno ugrozene novorodencadi razlicite gestacione dobi.

The aim of this study was to compare the type and severeness of brain damage in vitally most endangered newborn infants of different gestational age. We retrospectively analyzed the records of 75 newborn infants treated and decreased at the Department of Intensive Care and Therapy of the Institute of Children's and Adolescents' Health Care in Novi Sad. Diagnoses of hypoxic-ischemic lesion and intracranial hemorrhage in the case of grade four PVH-IVH (periventricular hemorrhage-intraventricular hemorrhage) were established by ultrasonography of the brain and lumbar punction in the case of subarachnoid hemorrhage. These diagnoses were confirmed after forensic-medical expertise. The volume and degree of the damage were compared in regard to the gestational age, Apgar score and time of initial mechanical ventilation and initial parameters of the mechanical ventilation, as well as to values of acido-basic status, concentration of gases in arterialized capillary blood and type of lung damage which always occurred in these patients. In all 75 examined newborns perinatal asphyxia was the dominant etiologic factor for the course and outcome of the disease (in all patients Apgar score was 4 or less). 75% of examines were born before 32 weeks gestation and of low or very low body weight, whereas 72% had intracranial hemorrhage (periventricular-intraventricular) and hypoxic-ischemic damage of the brain parenchyma. The rest of examinees had intracranial hemorrhage or hypoxic-ischemic damage of the brain parenchyma. Although 92% of examinees received mechanical ventilation in the first 3 days of life, only 20% of newborn infants had satisfactory values of acido-basic status and gas concentrations in the blood. We concluded that in the most severe cases of perinatal asphyxia, especially in preterm newborns of low or very low body weight, both intracranial hemorrhage and hypoxic-ischemic encephalopathy develop. Damages of other organs or systems of organs, especially lungs, as a rule contribute to infaust ending.

Developing mortality patterns: robust modified generalized likelihood ratio algorithm for infant mortality rate change detection.

A new robust modified generalized likelihood ratio algorithm, which enables the changes of mortality rates to be detected automatically, is applied. The procedure is based on the calculation of discrimination function using robust least squares estimates of AR mortality rates residuals. The feasibility of the approach is demonstrated with experimental data concerning infant mortality rate in Serbia.

[Echotomographic picture of splenic rupture]. / Ehotomografska slika rupture slezine.

Over a period of four years, June 1986-June 1990, we examined 100 patients with semitraumas of the abdomen and the thorax. We sonographically confirmed rupture of the spleen in 12 patients. Sonographic verification of the ruptured spleen can offer direct or indirect sonographic indications. The indirect indication is the liquid in the abdominal cavity (haematoperitoneum). The direct sonographic indication is subcapsular haematoma of the spleen, and heterosonographic indication is the parenchyma in the form of deep unechogenic and liquid fissures of the spleen in all directions. In some patients these unechogenic parts of the spleen converge to the hilus of the spleen.