The formation of catalytically competent enzyme-substrate complex is not a bottleneck in lesion excision by human alkyladenine DNA glycosylase.

Human alkyladenine DNA glycosylase (AAG) protects DNA from alkylated and deaminated purine lesions. AAG flips out the damaged nucleotide from the double helix of DNA and catalyzes the hydrolysis of the N-glycosidic bond to release the damaged base. To understand better, how the step of nucleotide eversion influences the overall catalytic process, we performed a pre-steady-state kinetic analysis of AAG interaction with specific DNA-substrates, 13-base pair duplexes containing in the 7th position 1-N6-ethenoadenine (εA), hypoxanthine (Hx), and the stable product analogue tetrahydrofuran (F). The combination of the fluorescence of tryptophan, 2-aminopurine, and 1-N6-ethenoadenine was used to record conformational changes of the enzyme and DNA during the processes of DNA lesion recognition, damaged base eversion, excision of the N-glycosidic bond, and product release. The thermal stability of the duplexes characterized by the temperature of melting, Tm, and the rates of spontaneous opening of individual nucleotide base pairs were determined by NMR spectroscopy. The data show that the relative thermal stability of duplexes containing a particular base pair in position 7, (Tm(F/T) < Tm(εA/T) < Tm(Hx/T) < Tm(A/T)) correlates with the rate of reversible spontaneous opening of the base pair. However, in contrast to that, the catalytic lesion excision rate is two orders of magnitude higher for Hx-containing substrates than for substrates containing εA, proving that catalytic activity is not correlated with the stability of the damaged base pair. Our study reveals that the formation of the catalytically competent enzyme-substrate complex is not the bottleneck controlling the catalytic activity of AAG.

[The monitoring of application of dabigatran as a remedy of prevention of thromboembolic complications after hip joint arthroplasty].

The analysis was applied to the indicators of hemostasis system under application of new anticoagulant, dabigatran etexilat, after hip joint arthroplasty. It is established that among the coagulation methods analysis the most specific to the effect of dabigatran is the testing of thrombin and echitox time of coagulation. Considering low sensitivity of the echitox to anticoagulation effect of D-dimer the echitox test is optimal for laboratory monitoring of application of dabigatran after orthopedic intervention.

[Contemporary treatment of parapneumonic pleural complication in children: the role of Video - Assisted Thoracoscopic Surgery (VATS)].

AIM: To reveal the role of Video Assisted Thoracoscopic Surgery (VATS) in the treatment of different stages of pleural empyema in children. CLINICAL MATERIAL: Between 2004 and 2006, 87 children aged from 11 months to 18 years were treated at the Department of Thoracic pediatric surgery for parapneumonic pleural complications (pleural empyema). The children were admitted in a period from 5 to 30 days (mean 11.9) after the initial pulmonary symptoms. Of them 41 children were treated by means of VATS. The indications for this approach were based on clinical course, radiological features, chest ultrasound image and fluid examination. RESULTS: Primary thoracostomy underwent 22 children (53.6%). VATS was applied in a period of 3 to 12 days after the initial procedure. The indications for VATS includes: a) multiloculated pleural effusion, b) encapsulated empyema and c) failed tube drainage. According to the local finding VATS was performed for evacuation of the flocculated exudate and debridement of fibrinous adhesions in 25 children (61 %). In 16 children (39 %) VATS comprised debridement and decortication. The mean operative time amounts 74.1 min (from 50 to 125). There were 4 conversions to open thoracotomy due to evaluation of necrotic lung parenchyma. Pleural drainage lasts from 2 to 12 days (mean 4.8). The postoperative hospital stay takes from 5 to 24 days (mean 10.2). CONCLUSION: VATS is an appropriate and effective method for treatment of children with complicated parapneumonic effusion in the second (fibrino-purulent) stage as well by some indication in the third (organization) stage.

[Malignant neurogenic tumors with retroperitoneal and mediastinal locations in infants].

INTRODUCTION: Malignant neurogenic tumors /MNT/ are the third by frequency malignancies in children with mainly localization in the retroperitoneal space and posterior mediastinum. THE AIM: of this study is to compare the clinical presentation and the treatment results by young children with retroperitoneal and mediastinal MNT. CLINICAL MATERIAL: For a period of 12 years (1993 -2004) 52 children aged fron 1 month to 3 years were admitted at the Department of Pediatric surgery-University Hospital "N.I.Pirogov", Sofia. The findings of different diagnostic methods are reviewed. Age and sex of the children, the frequency of location, maturity and stage of the tumor, type of operations and survival rate are compared. RESULTS: The MNT in young children encounter more common in the retroperitoneal space and are diagnosed in advanced clinical stage due to late clinical presentation. Most of them have an unfavorable histological variant and affect predominantly the adrenal glands. The mediastinal MNT are mainly manifested in the first age of life with good prognosis. The total survival up to 2004 year is 59,6 %.

[Surgical aspects of primary tuberculosis in children: clinical presentation and indications for surgical treatment].

AIM: During the last years a trend of increasing the cases with primary pulmonary tuberculosis (PPT) in our country is observed. The aim of this study is to analyze retrospectively the pediatric cases with PPT and to determinate the specific clinical features as well the indications for surgery. MATERIAL AND METHODS: For a period of six years (2000-2005) thirteen children with PPT were treated at the Department of pediatric surgery. The patients underwent different type surgical procedures. Lobectomy was the most frequent operation. RESULTS: The initial diagnosis at admission was: chronic pneumonia, mediastinal tumor, complicated hydatid cyst, congenital lung cyst and pleural complication of PPT. The radiological features were typical for PPT in only two cases. The remaining showed atypical presentation and the diagnosis were confirmed by histopathological study of the surgery specimens. There were no postoperative complications and no late morbidity. DISCUSSION AND CONCLUSION: We classify the clinical course of children with PPT into three groups: 1) Identified PPT - two children, 2) Suspected PPT according the criteria of Migliori - six children and 3) Non identified PPT - five children. The diagnosis of the childhood pulmonary tuberculosis presents a major challenge. The most common radiological features are similar to those of other pulmonary affections and a thorough examination of symptoms of disease is necessary. Surgery has a complementary role in the complex treatment in children with PPT.

[A case of surgically removed retroperitoneal rhabdomyosarcoma in a child requiring vascular reconstruction]. / Sudovi rekonstruktsii pri radikalno otstraniavane na retroperitonealen rabdomiosarkom u dete.

Retroperitoneal tumors engaging large vessels require vascular reconstruction when surgically removed. We present a case of retroperitoneal rhabdomiosarcoma in a child, which required inferior vena cava (IVC) grafting, creating a new bifurcation of IVC, and an A-V fistula between greater saphenous vein and femoral artery as well as grafting of right common iliac artery.

The role of Ca ions in restoration of the structure of interphase and mitotic chromosomes in PK living cells after hypotonic stress.

The dynamics of mitotic chromosome and interphase chromatin recondensation in living PK cells during their adaptation to hypotonic medium was studied. The recondensation process was found to be slowed down by the modification of plasma membrane with low concentrations of glutaraldehyde, while osmotic reactions of glutaraldehyde-treated cells remain unchanged. The effect of glutaraldehyde can be rapidly reversed by the addition of Ca(2+)-ionophore A23187. Intracellular Ca(2+)measurements show that the adaptation to hypotonic shock is accompanied by restoration of free Ca concentration, whereas the delay of chromatin condensation in glutaraldehyde-treated cells is paralleled by the decrease of Ca level. The mechanisms implying the role of low concentration of Ca(2+)in chromatin compactization in vivo are discussed.

[Idiopathic perforation of the extrahepatic bile ducts in a nursing infant]. / Idiopatichna perforatsiia na ekstrakhepatalnite zhluchni putishta u kurmache.

The report concerns a two-month-old suckling, affected on the 20th day of life with occurrence of icterus, dark urine and acholic stool, and on the 34th day--fever, vomiting and enlargement of the abdomen. Bile ascites is demonstrated by abdominal puncture, and perforation of the extrahepatic biliary ducts--by hepatobiliary scintigraphy. In the course of emergency laparotomy, diffuse bile peritonitis is established against the background of punctiform perforation at the site of d. cysticus and d. hepaticus communis union. Following sanation of the abdominal cavity, a draining catheter is inserted into the perforation area. The serious postoperative course, characterized by progressive hepatic failure, results in a fatal outcome on the third postoperative day. The etiopathogenesis, clinical symptomatology, timely diagnosis and effective operative management of this exceptionally rare surgical disease in children are discussed against the background of pertinent literature data survey.

Glucose strongly stimulates rate of the rRNA synthesis in Ehrlich ascites carcinoma cells.

A change in glucose concentration in an Ehrlich ascites carcinoma cell suspension from 0.1 mM to 20 mM causes a more than 50-fold stimulation of the rate of ribosomal RNA synthesis. Such an effect occurs without any dramatic effect on the rate of protein synthesis in cells. This process parallels a decrease in intracellular pH which may be a reason of Na+/H(+)-antiport activation.

[Meckel's diverticulum in childhood]. / Mekelov divertikul v detskata vuzrast.

For a period of 12 years (1977-1988) 64 children with Meckel's diverticulum (32 boys and 32 girls) have been operated. In early childhood (younger than 3 years) were 14.1 per cent; most of the others (59.4 per cent) were in school age. Complicated Meckel's diverticulum had 31.2 per cent of the children, the most common complication being intestinal obstruction--65 per cent (intussusception 25 per cent, strangulation 25 per cent and volvulus 15 per cent). Acute diverticulitis was found in 25 per cent of the complicated cases. In the clinical picture of these complications lacked cause-pathognomonic symptoms. The Meckel's diverticulum was removed in 60 children (93.8 per cent) the operation was cuneiform resection of the diverticulum in 96.6 per cent of the operated children. Only one child (1.7 per cent) had postoperative complication. All others were discharged from the clinic in full surgical repair. Practical inferences were made, based on analysis of the clinical case material.

[Dependence of the nature of the action of metabolic inhibitors on ribosomal RNA synthesis in Ehrlich ascites carcinoma cells on cell integrity]. / Zavisimost' kharaktera deistviia metabolicheskikh ingibitorov na sintez ribosomnoi RNK v kletkakh astsitnoi kartsinomy Erlikha ot tselostnosti kletok.

Ribosomal RNA (rRNA) synthesis in the intact Ehrlich ascite carcinoma cells is selectively inhibited by papaverin (ED50 = 0.01 mM), 2,4-dinitrophenol (DPN; ED50 = 5 microM), and actinomycin D (ED50 = 0.1 microgram/ml). The inhibition of rRNA synthesis is not connected with a direct action of these agents on the rRNA synthesis apparatus, and they had no effect on isolated cell nuclei. The rRNA synthesis in cells permeabilized with triton X-100 (0.05%) becomes insensible to the action of papaverine and DPN, but is inhibited by actinomycin D in low doses. In cells permeabilized with digitonin (0.01%) the rRNA synthesis shows no sensibility to the action of low doses of actinomycin D. The results suggest that the action of these agents on the rRNA synthesis may depend on cell integrity and on the permeabilization method employed.

[Effect of hydrophobic compounds on rRNA synthesis in intact cells and isolated nuclei]. / Deistvie gidrofobnykh soedinenii na sintez rRNK v intaktnykh kletkakh i izolirovannykh iadrakh.

Papaverine, cycloheximide, 2,4-dinitrophenol (DNP) and actinomycin D at low concentration have been shown to suppress selectively rRNA synthesis in Ehrlich ascite carcinoma cells. rRNA synthesis in isolated nuclei is not sensible to wide range of concentration of papaverine (0,005-0,1 mM), cycloheximide (0,5-100 micrograms/ml) and DNP (5-500 microM). Actinomycin D at low concentration does not act on the rRNA synthesis in vitro either. To suppress rRNA synthesis in this system much higher concentration of this agent (10 micrograms/ml) producing inhibition of all classes of rRNA synthesis in intact cells is required. Selective sensitivity of rRNA synthesis in the cells to papaverine, cycloheximide, DNP and low concentration of actinomycin D does not connect with their direct action on the apparatus of rRNA synthesis.

[Inhibitor interaction in the suppression of ribosomal RNA synthesis in Ehrlich ascites carcinoma cells]. / Vzaimodeistvie ingibitorov pri podavlenii sinteza ribosomnoi RNK v kletkakh astsitnoi kartsinomy Erlikha.

Kinetic analysis of inhibitory action of papaverine, 2,4-dinitrophenol (DNP) and actinomycin D on RNA synthesis in the intact Ehrlich ascites carcinoma cells has shown that the action of these agents is mediated by their effect on the same step of rRNA synthesis.

[Effect of 2,4-dinitrophenol on the synthesis of ribosomal RNA in the cells of Ehrlich ascitic carcinoma under anaerobic conditions]. / Vliianie 2,4-dinitrofenola na sintez ribosomnoi RNK v kletkakh astsitnoi kartsinomy Erlikha v anaérobnykh usloviiakh.

It is shown that 2,4-DNP (20 mkM to 1 mM) selectively inhibited RNA synthesis in Ehrlich ascite carcinoma cells both in aerobic and in anaerobic conditions in equal extent. It is supposed that the inhibitory action of DNP is not associated with its influence on oxidative phosphorylation and intracellular ATP concentration, but may be accounted for cell reaction to non-specific actions.

[Effect of cycloheximide, 2,4-dinitrophenol and papaverine on ribosomal RNA synthesis in Ehrlich ascitic carcinoma cells]. / Vliianie tsiklogeksimida, 2,4-dinitrofenola i papaverina na sintez ribosomal'noi RNK v kletkakh astsitnoi kartsinomy Erlikha.

The influence of 2,4-dinitrophenol (DNP), papaverine and cycloheximide on RNA synthesis in Ehrlich ascites tumour cells has been investigated. All above mentioned agents inhibit selectively synthesis of high-molecular rRNA precursor, when the cell population density is 3.10(7)--5.10(7) per 1 ml of suspension. When the density of cells decreases as far as 1.10(6) cells per 1 ml. the rRNA synthesis loses the sensitivity to all these agents. The effects of both cycloheximide on the protein synthesis and DNP on ATP level do not depend on the cell population density in suspension. It is suggested that either with a decrease of cell population density the protein synthesis and ATP level cease playing the role of a rate-limiting factor in the rRNA synthesis, or the influence of agents studied is realized by means of their interaction with other cell system.