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Biomedical subjects

M Ivanova

Publications and source records attributed to M Ivanova.

At least 37 records · Page 2Linked to original sources
PubMed1999

Zona pellucida autoantibodies in women undergoing ART.

The presence of ZP autoantibodies in serum and Ffl samples of 109 women attending the ART Center in Kiev was investigated using IIF and ELISA. Positive serum and Ffl samples examined by both methods were found in 20 (18.34%) and in 19 (17.43%) patients respectively; 31 (28.44%) serum samples and 33 (30.27 %) Ffl samples analyzed by IIF were positive; of the samples analyzed by ELISA 21 (19.26%) and 20 (18.34%), respectively, were positive. No relationship was found between ZP autoantibody incidence and the type and cause of infertility. A significant prevalence of ZP autoantibodies detected by ELISA in Ffl was found in patients with fertilization failure (39.13%) and with low fertilization rate (42.85%) when compared to patients with middle fertilization rate (5.71%) and high fertilization rate (8.1%). The clinical significance of ZP autoantibodies in Ffls for in vitro fertilization outcome was suggested.

Adult↗
PubMed1998

Extremely low frequency electric and magnetic fields as risk factors in chemical industry.

OBJECTIVES: The risk assessment for staff in the chemical industry is usually related to accident hazards, production emergencies, blast and fire danger, or to the adverse effects of toxic substances. The combined effect of electric and magnetic fields with other factors combined with other hazards and working conditions, has not yet been studied. In all branches of industry, the members of staff who endure the most exposure to electric and magnetic fields, are electricians. This group is considered at high risk because of the increased probability of cancer. METHODS: We studied electric and magnetic fields with low frequencies in the nitrogen chemical fertilizer plant "HIMCO", Vratza. Sources of extremely low frequency fields (50 Hz) are local thermal power plants, substations, open (110 kV) and closed (6 kV and 0.4 kV) distribution devices, transformers, compressors and turbocompressors, command halls, and video display units. The methods used for assessing exposure of low frequency electric and magnetic fields were based on the separate measurement of the electric and magnetic components of the field, using spot measurements and evaluation of the real time duration of exposure for different staff groups. RESULTS: The measured values for the different staff groups were within the limits of national and international standards. The measured magnetic flux densities in the "HIMCO" plant exceeded 3 mG, a value which is considered by many investigations in the literature, as a possible carcinogenic factor. CONCLUSIONS: The prolonged exposure to low frequency electric and magnetic fields determines the place of these physical factors in the complex of hazardous environmental factors for the staff. The simultaneous performance of combined investigations of all risk factors would result in the complete risk assessment for staff in the chemical industry. Electricians are considered to be a professional group who have an increased risk of contracting cancer. Extensive measurement and assessment of exposure of the low frequency electric and magnetic fields is needed using individual dosimeters and retrospective analysis to determine this. It is important to study all types of nonionizing radiation in the whole of the Bulgarian chemical industry, especially within petroleum refineries.

Bulgaria↗
PubMed1997

Effects of colipase and bile salts on the catalytic activity of human pancreatic lipase. A study using the oil drop tensiometer.

Using the oil drop technique, we studied the effects of colipase and bile salts on the rate of hydrolysis of soybean oil by human pancreatic lipase (HPL) as well as on the interfacial binding. Upon continuously recording the decrease in the interfacial tension with time, a 10-15-fold increase in the HPL activity was found to occur in the presence of colipase. The catalytic rate constants of hydrolysis measured at the oil drop surface were found to be of the same order of magnitude as those obtained with monomolecular films spread at the air-water interface. Biotin-labeled HPL (HPL*) was used to determine the amount of adsorbed enzyme using an ELISA test. Less than 1% of the total amount of injected HPL* molecules was found to have adsorbed to the oil-water interface, and no significant effects of colipase on HPL* binding were observed. No significant changes in the hydrolysis rates or the binding of HPL* were detected in the presence of bile salts at concentrations ranging from below their critical micellar concentration (CMC) up to 100 microM. At the oil-water interface, in the absence or presence of bile salts below their CMC, it can be concluded that the colipase is a true lipase cofactor, i.e, it increases the enzyme turnover (approximately 10-15-fold) and does not affect the interfacial lipase adsorption.

Animals↗
PubMed1996

A model for standardization of lung function parameters by height.

Lung function parameters are closely associated with the height of the individual and this is the reason why this genetically determined characteristic is present obligatorily in the equations giving their reference values. The present work studies a large group of models by analysing two groups of healthy individuals - 20 healthy boys aged 7 to 14 years (10.6 +/- 2.2; mean +/- SD) with a height of 121 to 170 cm (145.0 +/- 14.2) and 98 healthy men aged 30 to 60 years (44.7 +/- 6.7) with a height of 159 to 192 cm (171.0 +/- 9.1), all of them non-smokers. Statistical analysis shows that standardization of lung function parameters by height of healthy individuals is achieved by using a power function of the height - FEV1/2.7 and VC/H2.6 for boys aged 7 to 14 years and FEV1/H2.5 and VC/H2.4 for men aged 30 to 60 years. The model proposed for children practically neutralizes age completely and can be used as a reference equation. The graphic and correlation analysis of the residuals obtained as a difference between the actual and predicted values of the respective models indicated clearly presence of age peculiarities. In men the correlation coefficients between the residuals and the height were close to zero, and the residuals themselves were relatively evenly distributed around the zero line (a homoscedastic distribution). In children the differences scattering increased with the height, i.e. there is a heteroscedastic distribution.

Adolescent↗
PubMed1995

Interfacial properties of the polyheme cytochrome c3 superfamily from Desulfovibrio.

In order to compare the interfacial behavior of the polyheme cytochromes c which belong to the cytochrome c3 superfamily, the monomolecular film technique was used to determine whether and how these metalloproteins interact with (phospho)lipids). Measurements of the variations of surface pressure and surface potential versus time have shown differences in their penetration capacity into phosphatidylcholine, dicaprin, and phosphatidylglycerol films. The Desulfovibrio vulgaris Hildenborough cytochrome with 16 hemes (Hmc) and Desulfovibrio desulfuricans Norway tetra- and octaheme cytochromes c3, which have been assumed to be soluble periplasmic molecules, may be considered as extrinsic membrane proteins, unlike the D. vulgaris Hildenborough cytochrome c3 (Mr 13 000). The interfacial properties are discussed in terms of the available three-dimensional structural data, the electrostatic potential calculation, and the results obtained by hydrophobic cluster analysis of the cytochrome sequences. The very different behavior of the two cytochromes c3 (Mr 13 000) enlightens the role of a particular surface loop in the interaction with a model membrane. A functional interpretation is proposed assuming that the D. vulgaris Hildenborough Hmc and both cytochromes c3 (Mr 13 000) and (Mr 26 000) from the Norway strain might provide the link between periplasmic hydrogen oxidation and cytoplasmic sulfate reduction.

Amino Acid Sequence↗
PubMed1995

Interfacial binding of human gastric lipase to lipid monolayers, measured with an ELISA.

Two sandwich enzyme linked immunosorbent assays (ELISA) were developed for evaluating the surface excess at the lipid/water interface of the human gastric lipase (HGL) and two anti-HGL monoclonal antibodies (mAbs). These assays were adapted to the monomolecular film technique used previously for measuring lipase kinetics. HGL and the two anti-HGL mAbs (4-3 and 218-13) were biotinylated without any significant loss of their biological activities occurring. They were further detected by ELISA using either anti-HGL or anti-mouse IgG polyclonal antibodies as specific captors before being revealed using a streptavidin--peroxidase conjugate as tracer. The detection limit was 25 and 85 pg in the case of HGL and mAb, respectively. By combining the above sandwich ELISA technique with the monomolecular film technique, it was possible for the first time to measure the enzymatic activity of HGL on 1,2-didecanoyl-sn-glycerol (dicaprin) monolayers as well as to determine the corresponding interfacial excess of the enzyme. The HGL turnover number increased steadily with the lipid packing. The specific activities determined on dicaprin films spread at 35 mN.m-1 were found to be in the range of the values measured under optimal bulk assay conditions, using tributyrin emulsion as a substrate [i.e., 1000 mumol/(min.mg of enzyme)]. At a given lipase concentration in the water subphase, the interfacial binding of HGL to the nonhydrolyzable egg yolk phosphatidylcholine (egg PC) monolayers was found to be 10 times lower than that in the case of dicaprin monolayers.(ABSTRACT TRUNCATED AT 250 WORDS)

Adsorption↗
PubMed1994

New parameters for evaluation of oxygen transport on the dissociation curve of human blood.

Three new parameters were applied to evaluate oxygen transport using the dissociation curve of human blood. They are derived from the following equation: [formula: see text] The first parameter, beta 1,0, reflects the oxygen capacity of the curve within the range of 1.0 kPa at its "arterial section". The second parameter, beta 2,3, reflects the oxygen transport from the "arterial" point to the point of extraction of 2.3 mmol/l-1 of oxygen which is assumed as normal. The third parameter, beta 5-4 kPa, characterises the oxygen transport at the "venous" section of the curve. The parameters were studied on a cohort of 12 healthy people and 141 patients with chronic obstructive pulmonary disease at different stages of respiratory failure. A significant correlation was found between the oxygen capacity parameters, beta 1,0 and beta 2,3, and pO2(a), sO2 and the calculated transpulmonary shunt. They were not influenced by ctHb and ctO2(a). beta 5-4 showed marked correlation with the hemoglobin and total O2 concentration and the parameters that indicate a risk of tissue hypoxia-px and Qx. Standardisation of the new parameters with ctO2(a) correlates it functionally with the parameters of oxygen affinity.

Adult↗
PubMed1993

Zona-penetration in vitro test for evaluating boar sperm fertility.

We investigated the capacity of porcine sperm-zona binding and penetration by using bioassay to differentiate between spermatozoa from fertile and subfertile boars. Semen was collected from Large White boars grouped into categories of fertile and subfertile (n=5 per each group) according to the results of artificial insemination. Boars in both groups showed similarly hyperactivated sperm motility at insemination (44.72 and 43.03% respectively) regardless of the lower percentage of progressive motility observed in the ejaculates of subfertile boars. At in vitro insemination, a high proportion of the sperm population (43.76%) in the subfertile boars was without acrosomes, while in the fertile boars this proportion was only 24.35%. The sperm penetration rate of fertile boars reached 66.03% while that of subfertile boars was only 25.08%. In conclusion, the results of our study showed that the penetration rate by boar spermatozoa of the zona pellucida can be used to predict fertility and/or as an in vitro standard for describing porcine semen characteristics.

Journal Article↗
PubMed1993

Body-plethysmographic pressure-flow diagrams in chronic obstructive lung disease. II. Functional assessment.

One hundred patients with various forms of chronic obstructive lung disease (COLD) were allocated to groups according to their body-plethysmographic pressure-flow diagrams. Group I comprised 30 patients with resistance curves displaying linear relationship between pressure and flow. The second group (n = 30) was formed by patients who had a markedly pronounced hysteresis in the central parts of their resistance curves. Group III consisted of 30 patients who exhibited resistance curves with distended expiratory sections. Group IV's patients (n = 10) had eight-shaped resistance curves. The lung function profiles of these patients were obtained by measuring the parameters of forced expiration and static lung volumes, the diffusion, blood-gas and acid-base parameters. The analysis of the results shows progressive aggravation of airway obstructions from Group I to Groups III and IV the latter two groups having similar lung function characteristics. Another corollary is that the resistance curve configuration reflects to a great extent the severity of the lung mechanics disorders, but does not correspond entirely to the clinically established forms of the chronic obstructive lung disease.

Adult↗
PubMed1993

Body-plethysmographic pressure-flow diagrams in chronic obstructive lung disease. I. Comparative measurements.

One hundred patients with various forms of chronic obstructive lung disease were allocated to groups according to their body-plethysmographic pressure-flow diagrams. Group I comprised 30 patients with resistance curves displaying linear relationship between pressure and flow. The second group (n = 30) was formed by patients who had a markedly pronounced hysteresis in the central parts of their resistance curves. Group III consisted of 30 patients who exhibited resistance curves with distended expiratory parts. Group IV's patients (n = 30) had eight-shaped resistance curves. The comparative measurements on these 4 types of body-plethysmographic pressure-flow diagrams included all kinds of airway resistances, as well as their components and ratios (Raw, Rpeak, R, Raw(in), Raw(ex), R(ex), R(in), Raw/R, Raw(ex)/R(ex), Raw(in)/R(in), Raw(ex)/Raw(in), R(ex)/R(in)). The analysis of the results shows that the quantitative criteria used in the assessment undergo the greatest change in the eight-shaped loops and in those resistance curves whose expiratory parts are considerably distended. The difference between the absolute values obtained by using the basic methods of calculating airway resistance is the greater the weaker is the linear relationship between pressure and flow.

Adult↗
PubMed1993

Relationships between blood oxygen parameters in patients with chronic obstructive lung disease.

The hemoglobin-oxygen dissociation curve and the relationships between the parameters of tension, saturation, capacity, affinity and concentration of oxygen in the course of respiratory failure in chronic obstructive lung diseases (COLD) were studied. The study included 141 patients divided into four basic groups according to the value of pO2 (a): patients with normoxia, mild, moderate and severe arterial hypoxia. The blood-gas status was determined using the ABL-330 and OSM-3 analyzers (Radiometer A/S, Denmark). It is concluded that: 1. Presence of normoxia (pO2 and sO2 in norm) in COLD patients does not exclude abnormalities in their arterial blood oxygen transport and increased risk of tissue hypoxia. 2. Total oxygen concentration in respiratory failure is relatively stable and "independent" from the stepwise decrease of the arterial pO2, which results from the compensatory increase of the total and effective hemoglobin. 3. There are phase fluctuations of the ctO2/pO2 dissociation curve in the reference interval, expressed in the "lowering" of P50 and p90 in mild hypoxia and the "centering" or "raising" of their values in severe hypoxia. Such fluctuations are more pronounced in the p90 than in the p50. 4. The oxygen extraction tension lowers progressively (without reaching the anaerobic threshold) and the oxygen compensation factor elevates with the pO2 (a) reduction and the arising of hypercapnia and acidemia. 5. The calculated 2,3-diphosphoglycerate (2,3-DPG) concentration values are significantly higher in hypercapnics with COHb > 1% than in those with COHb < 1%. The relationships between hypoxia, oxygen affinity, hemoglobinemia and oxygen affinity as well as the dissociation curve properties in chronic respiratory failure are discussed.

Acid-Base Equilibrium↗
PubMed1992

Comparative analysis of some methods for standardizing the maximal expiratory flows.

Maximal expiratory flows were obtained in 40 patients with chronic non-specific pulmonary diseases displaying mild obstruction of air flows and in 35 clinically healthy subjects with normal ventilatory functions and similar anthropometric characteristics. The flows for the two groups and their standardized values by referring to FVC, TLC, H and H3 were compared. The u-criterion and V% were used as measures for the diagnostic value of the flows and their standardized values. In the patients with mild airflow obstruction the highest u-criterion and the lowest V% were obtained by standardizing the maximal expiratory flows through referring to H3. This is an indication that this method of standardization is to be preferred to other methods in the functional diagnostics of mild obstructive disorders.

Adult↗
PubMed1992

Relationships between some oxygen and carbon dioxide indices in patients with chronic lung and cardiovascular diseases.

A total of 281 patients were divided into groups according to their clinical diagnosis and were examined using capnography, spirometry and blood-gas analysis. The highest percentage of patients with arterial hypoxemia was found in the group with chronic bronchitis and emphysema. The same group had the highest number of patients with moderate hypoxemia and was the only group containing patients with severe hypoxemia. Alveolar hypoventilation and increased ventilation-perfusion ratio were most pronounced in patients with chronic bronchitis and emphysema. The greatest negative correlation between PaO2 and PaCO2 was found, again, in this group. We also found the greatest direct correlation between the oxygen and carbon dioxide gradients in this group. These results suggest that the relationships between the partial pressures of O2 and CO2 depend on the type of the pulmonary and cardiovascular diseases. The relationships between the partial pressures of O2 and CO2 as well as between their gradients, become stronger with the increase of the ventilation-perfusion ratio. The relationships between the expired alveolar gases are approximately the same as those of these gases in blood.

Adult↗
PubMed1991

Identification and characterization of human acrosomal antigen defined by a monoclonal antibody with blocking effect on in vitro fertilization.

A monoclonal anti-human sperm antibody (Mab 1A1) has been produced by fusion of myeloma cells with splenocytes from a BALB/c mouse immunized with in vitro capacitated human spermatozoa. Immunofluorescence studies with Mab 1A1 show that it recognizes an antigen(s) (Ag 1A1) which is located in the acrosome of human spermatozoa. As shown by Western blotting experiments, 1A1 antigen represents a family of proteins with Mr ranging from 20 kDa to 34 kDa. Immunofluorescence observations on epitope exposure and location suggest that during in vitro capacitation of human spermatozoa, Mab 1A1 epitope-bearing molecules are concentrated in regularly arranged granules in the acrosome. After long-term incubation the epitope is exposed on the apical acrosome surface exhibiting a spot-like arrangement. The 1A1 epitope is widely distributed among mammalian species: boar, ram, mouse and rat acrosome is intensively stained by Mab 1A1. The antibody inhibits in vitro fertilization mainly by blocking sperm attachment to and penetration through the zona pellucida when included in the medium for the in vitro fertilization of mouse, porcine and human oocytes.

Acrosome↗
PubMed1990

[A test for determining hydrogen sulfide in waste waters].

An express quantitative test is recommended for determination of hydrogen sulfide in waste waters, based on linear colorimetric principle, which could be used for concentration scopes: 20-400 mg/l with sensitivity 10 mg/l; 10-250 mg/l with sensitivity 5 mg/l. The reproduction of the test is very good--the coefficient of variation do not surpass +/- 10%.

Calibration↗