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Biomedical subjects

T N Popova

Publications and source records attributed to T N Popova.

At least 19 recordsLinked to original sources
PubMed2006

Regulation of 2-oxoglutarate metabolism in rat liver by NADP-isocitrate dehydrogenase and aspartate aminotransferase.

Kinetic and regulatory properties of NADP-isocitrate dehydrogenase (NADP-IDH) and aspartate aminotransferase (AsAT) responsible for 2-oxoglutarate metabolism in the cytoplasm and mitochondria of rat liver were studied. Based on the subcellular location of these enzymes and their kinetic parameters (Km, Ksi) obtained with highly purified enzyme preparations, it is suggested that synthesis of 2-oxoglutarate should be mainly determined by cytoplasmic NADP-IDH (86% of the total activity in the cell), whereas its utilization should depend on cytoplasmic AsAT (78% of the total activity). AsAT from the rat liver was specified by substrate inhibition and also by changes in the enzyme affinity for the substrates under the influence of some intermediates of the tricarboxylic acid cycle: isocitrate, succinate, fumarate, and citrate. Key intermediates of nitrogen metabolism (glutamate, glutamine, and aspartate) are involved in the regulation of NADP-IDH and AsAT. These enzymes are regulated oppositely, and the catalytic activity of one enzyme can be stimulated concurrently with a decrease in the activity of the other. Obviously, carbon and nitrogen metabolism in the rat liver can be controlled through redistribution of 2-oxoglutarate between different metabolic processes via regulatory mechanisms influencing differently located forms of NADP-IDH and AsAT.

Animals↗
PubMed2005

Function of cytoplasmic NAD-dependent malate dehydrogenase from rat myocardium under conditions of ischemia.

NAD-dependent malate dehydrogenase activity decreased by 2.7 times in the myocardium of rats with experimental ischemia. Cytoplasmic NAD-dependent malate dehydrogenase from intact and ischemic rat heart was purified by 91.4 and 95.5 times. We compared kinetic characteristics and regulation of enzyme activity by Fe(2+), Cu(2+), Ca(2+), hydrogen peroxide, and glutathione under normal and pathological conditions.

Animals↗
PubMed2004

Free radical oxidation and catalytic activity of aconitate hydratase in rat liver under normal conditions and during toxic hepatitis.

We observed intensification of free radical oxidation, decrease in activity, and changes in catalytic properties of aconitate hydratase in the liver of rats with toxic hepatitis. The total yield and maximum flash intensity of biochemiluminescence increased by 2.2 and 1.7 times, respectively. Differences were revealed in the regulation of aconitate hydratase activity with Fe(2+), Ca(2+), H(2)O(2), and oxidized and reduced glutathione in the liver of rats with toxic hepatitis and control animals.

Aconitate Hydratase↗
PubMed2003

[Therapy of synchronous multiple primary malignancies].

The data on 526 patients treated for primary multiple synchronous malignancies were evaluated. The total number of detected tumors was 1,069; concomitant pathology was identified in 377 out of 490 (76.9 +/- 1.9%). Removal of all synchronous tumors was considered radical--and palliative or symptomatic when, whatever the modality, two or at least one tumor was treated. Most of primary multiple synchronous tumors were removed radically (56.4 +/- 2.3%). The best results were obtained when combined therapy was used for early-stage tumors while surgical treatment of advanced cancer was complemented with radiochemotherapy. Radical treatment was contraindicated in 30.3 +/- 3.8% because of concomitant pathology.

Aged↗
PubMed2002

Intensity of free radical processes and regulation of cytoplasmic NADP-isocitrate dehydrogenase in rat cardiomyocytes under normal and ischemic conditions.

The intensity of free radical processes and the regulation of NADP-isocitrate dehydrogenase (EC 1.1.1.42; NADP-IDH) activity have been studied in the cytoplasmic fraction of normal and ischemized rat myocardium. Chemiluminescence parameters, such as the light sum (S) of slow flash and the tangent of the kinetic curve slope angle (tanalpha1), which characterize the intensity of free radical processes, were increased in ischemia 2.1- and 20.0-fold, respectively. The slow flash intensity (Imax) was increased 22-fold. The contents of lipid peroxidation products--diene conjugates and malonic dialdehyde--were increased 11.9- and 4.7-fold, respectively, suggesting pronounced oxidative stress. Using homogenous enzyme preparations of NADP-IDH isolated from the normal and experimentally ischemized rat myocardium, a number of catalytic properties of the enzyme were characterized for normal and pathologic conditions. NADP-IDH from the normal and ischemized myocardium had the same electrophoretic mobility and was regulated similarly by Fe2+, Cu2+, Zn2+, and also with succinate and fumarate. However, under normal and pathologic conditions NADP-IDH was different in the affinity for substrates and in the sensitivity to inhibitory effects of hydrogen peroxide, reduced glutathione, and of Ca2+. The degree of synergy in the enzyme inhibition with Fe2+ and H2O2 was less pronounced in ischemia. The inhibitory effect of the reaction product 2-oxoglutarate was higher under normal conditions than in ischemia (the Ki values were 0.22 and 0.75 mM, respectively). The specific features of the NADP-IDH regulation in ischemia are suggested to promote the stimulation of the enzyme functioning during increased level of free radical processes, and this seems to be important for NADPH supplying for the glutathione reductase/glutathione peroxidase antioxidant system of cardiomyocytes.

Animals↗
PubMed2002

Oxidative status and distribution of NADP-dependent isocitrate dehydrogenase and aconitate hydratase in rat cardiomyocytes under normal conditions and during ischemia.

Oxidative status of rat cardiomyocytes during ischemia induced by occlusion of the descending branch of the coronary artery was studied by the methods of Fe-induced chemiluminescence and spectrophotometry of primary and secondary lipid peroxidation product. The concentrations of low-molecular-weight antioxidants a-tocopherol and citrate and activities of NADP-dependent isocitrate dehydrogenase (EC 1.1.1.41) and aconitate hydratase (EC 4.2.1.3) were also measured. Ischemia was associated with intensification of free radical processes, increased antioxidant activity in subcellular fractions of the myocardium, activation of NADP-isocitrate dehydrogenase, accumulation of citrate, and inhibition of aconitate hydratase. Differential centrifugation, ion exchange chromatography on various ion exchangers, and electrophoresis in polyacrylamide gel revealed no redistribution of enzyme activity between the cytoplasmic and mitochondrial cardiomyocyte fractions during ischemia.

Aconitate Hydratase↗
PubMed2002

[Surgical treatment of multiple primary neoplasms].

Comparison of two groups of patients with polyneoplasia was carried out: in group 1 surgeries were performed simultaneously, in group 2--at different time. Choice of surgical technique seems to depend on the time between detection of the tumors. When polyneoplasias were revealed at the same time, surgeries were performed simultaneously. These operations were conducted more often when the tumors were localized in organs accessible by one surgical approach. When multiple synchronous tumors located in various anatomic regions consecutive operations were performed more often. The stage of the tumor does not influence the choice of time of operation for the first and second tumor. Simultaneous operations are preferable for young patients without concomitant diseases.

Abdominal Neoplasms↗
PubMed2001

[Specifics of diagnosis in primary-multiple synchronous tumors of the head and neck].

The data of 100 case histories of primary-multiple synchronous malignancies of the head and neck have been analyzed. A second tumor was not detected during examination of the first one in every third case. The presence of tumor and pain were reported mostly by patients with neoplasms of the tongue, oral mucosa and, less frequently, laryngopharynx. In more than half the cases (48%), head and neck tumors were detected by physical examination. The most frequent were laryngeal tumors (30%), followed by those of the thyroid gland (26%). Second tumor incidence in the lung was (31%), breast (19%) and gastrointestinal tract (18%).

Breast Neoplasms↗
PubMed1999

[Application of suturing devices in gastrointestinal surgery].

Suturing devices of the firm "Auto Suture" have been widely used for two last years in Saratov Medical University clinic of surgery at pediatric faculty. 131 patients with gastrointestinal diseases (54 had cancer of the stomach, 35--ulcer of the stomach and the duodenum and 42--oncoproctologic diseases) were operated on with their help. Application of the suturing devices results in improved quality of the operations as the devices warrant excellent functional qualities of the anastomoses and their reliability. The duration of the operation decreases considerably. It works well in rectal surgery to increase significantly the number of organ-saving operations.

Adult↗
PubMed1999

Catalytic properties of phosphoglucomutase from pea chloroplasts.

Electrophoretically homogeneous phosphoglucomutase (PGM) with specific activity of 3.6 units/mg protein was isolated from pea (Pisum sativum L.) chloroplasts. The molecular mass of this PGM determined by gel-filtration is 125 +/- 4 kD. According to SDS-PAGE, the molecular mass of subunits is 65 +/- 3 kD. The Km for glucose-1-phosphate is 18.0 +/- 0.5 microM, and for glucose-1, 6-diphosphate it is 33 +/- 0.7 microM. At glucose-1-phosphate and glucose-1,6-diphosphate concentrations above 0.5 and 0.2 mM, respectively, substrate inhibition is observed. The enzyme has optimum activity at pH 7.9 and 35 degrees C. Mg2+ activates the PGM. Mn2+ activates the enzyme at concentrations below 0.2 mM, while higher concentrations have an inhibitory effect. The activity of the PGM is affected by 6-phosphogluconate, fructose-6-phosphate, NAD+, ATP, ADP, citrate, and isocitrate.

Catalysis↗
PubMed1999

Catalytic properties of glucose-6-phosphate dehydrogenase from pea leaves.

A homogeneous preparation of glucose-6-phosphate dehydrogenase (G6PDH, EC 1.1.1.49) with a specific activity of 3.88 U/mg protein was isolated from pea (Pisum sativum L.) leaves. The molecular mass of the G6PDH is 79 +/- 2 kD. According to SDS-PAGE, the molecular mass of the enzyme subunit is 40 +/- 3 kD. The Km values for glucose-6-phosphate and NADP are 2 and 0.5 mM, respectively. The enzyme has a pH optimum of 8.0. Mg2+, Mn2+, and Ca2+ activate the enzyme at concentrations above 1 mM. Galactose-6-phosphate and fructose-6-phosphate inhibit the G6PDH from pea leaves. Fructose-1, 6-bisphosphate and galactose-1-phosphate are enzyme activators. NADPH is a competitive inhibitor of the G6PDH with respect to glucose-6-phosphate (Ki = 0.027 mM). ATP, ADP, AMP, UTP, NAD, and NADH have no effect on the activity of the enzyme.

Chromatography, DEAE-Cellulose↗
PubMed1998

Citrate and isocitrate in plant metabolism.

The relevance of citrate and isocitrate metabolism in plants is discussed in connection with the different pathways for their conversions. The routes for citrate and isocitrate conversions are incorporated into the system of cross-linked metabolic processes and may provide carbon skeletons for nitrogen assimilation and reducing equivalents for biosynthetic reactions, support the functioning of the glyoxylate cycle and play an important role in the TCA and energy metabolism as a whole. The possibility of the coupling of citrate and isocitrate metabolism with various electron transport systems is discussed from the point of view of the efficiency of the balancing cellular NAD(P)H/NAD(P)+ and ATP/ADP ratios. The role of citrate and isocitrate and their derivations as potent effectors of some enzymes is considered. Special attention is paid to the enzymes associated with citrate and isocitrate metabolism and to the mechanisms which regulate their activity. The possibilities of the coordination of the main processes of energy and biosynthetic metabolism at the level of citrate and isocitrate distribution are discussed.

Citric Acid↗
PubMed1998

Purification, separation and characterization of phosphoglucomutase and phosphomannomutase from maize leaves.

Different phosphomutases-phosphoglucomutase (EC 2.7.5.1; PGM) and phosphomannomutase (EC 2.7.5.7; PMM) from maize (Zea mays L.) leaves have been purified. PGM and PMM were completely separated from each other. The purified PGM was shown to be electrophoretically homogeneous. The PGM from maize leaves was found to be a homodimer with an apparent molecular mass of 132 kDa, the size of the subunits was 66 kDa. The PGM is a bifunctional enzyme, which can use both glucose-1-phosphate and mannose-1-phosphate as substrates. In contrast, the PMM appears to be monospecific for mannose-1-phosphate. Evidence is presented that PMM differs from PGM. Some properties of the maize leaves PGM and PMM differ in many respects (K(m) for substrates, pH optimum). However, some properties of PGM and PMM were similar (influence of Mg2+ and Mn2+ ions).

Chromatography↗
PubMed1993

[Isocitrate dehydrogenases: forms, localization, properties, and regulation].

The literary and original data concerning the localization, properties, activity regulation and physiological role of NAD- and NADP-dependent isocitrate dehydrogenases are reviewed. Possible mechanisms of regulation of anabolic and catabolic cellular processes at the isocitrate dehydrogenase level are discussed. The data on the structure and chemical modification of the active center functional groups suggest that isocitrate dehydrogenases isolated from various sources differ in their catalytic properties. The pathways and prospectives in practical application of the enzymes are considered.

Adsorption↗
PubMed1989

[Diagnostic possibilities of laparoscopy in the assessment of the stage in stomach cancer].

The authors employed laparoscopy as a method of final examination for identifying the stage of a neoplastic process in 259 patients. Obvious signs of generalization of the process were found in 110 patients (42.5 +/- 6.0%). An unnecessary additional trauma--diagnostic laparotomy was avoided in this case. The informativeness of laparoscopic examination was 97.3 +/- 3.6% in metastases to the liver, 96.1 +/- 5.3% in metastatic involvement of the parietal peritoneum, and 87.7 +/- 8.5% in ascites. The diagnosis was verified morphologically.

Adult↗