[X-ray structural analysis of kidney stones. Mechanism of action of pharmalith in nephrolithiasis]

The litholytic effect of soluran and pharmalith on renal calculi was studied by X-ray diffraction analysis. It is shown that pharmalith is more effective in treating nephrolithiasis, than other drugs.

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.

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.

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.

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.

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)

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.

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.

[Determination of the turbidity temperature of solutions of the nonionogenic surface-active agent LF-57 after the action on urinary calculi in uric acid]

Non-ionogenic surfactant LF-57 contributes solving of urinary calculi from uric acid and is a component of the drug Pharmalit for curing kidney-stone disease. Turbidity temperature was determined of the solution LF-57-78, 1C, and in the presence of uric acid--80.2C.

[Level of microelements in urinary stones after the action of surface-active agents]

Effect of non-ionogenic surfactant LF-57 on concrements from uric acid was studied. It was shown that the litholytic effect of this chemical was also directed on microelements. Composition of concrements and LF-57 was determined.

Expression of repetitive human calcitonin genes in Escherichia coli

In order to stabilize recombinant human calcitonin (rhCT) against Escherichia coli proteases a series of concatemeric hCT genes with varying degrees of repetition were synthesized and expressed in E. coli under the control of a constitutive synthetic phage promoter. The series of expression vectors thus constructed was used as a model to study the effect of gene repetition on the efficiency of expression (both transcription and translation), stability of mRNA, proteolytic stability of recombinant protein, genetic stability of expression plasmids, etc. The oligomerization of the hCT gene resulted in stabilization of the mRNA increasing its half-life from 60-70 s (as in the hCT monomer, dimer, and trimer genes) to 100-120 s (for the hCT tetramer gene). This effect held true as well for the proteins coded by the corresponding repetitive hCT genes. The genetic stability (segregation and recombination) of the expression plasmids containing hCT oligomeric genes also depended on the number of hCT gene repeats. The expression plasmid containing the hCT tetramer gene segregated from one of the best producers of rhCT (E. coli LE392) up to 100% after 100 cell generations in nonselective media (free of antibiotics). One of the plasmids most sensitive to recombination events was that containing the hCT pentamer gene. The series of expression plasmids bearing hCT oligomeric genes was used for transformation of various E. coli strains in order to find the optimal host for production of rhCT. The highest yield (44-100 mg rhCT per 1 liter of bacterial culture) was obtained with the strains LE392, JM107, and DH1.

Experimental immune oophoritis as a model for studying the thymus-ovary interaction: 1. Morphological studies

The experimental immune oophoritis (EIO) model was used to study the functional relationship between the ovary and organs of the immune system. EIO was developed in Balb/c mice by twofold subcutaneous injection of saline ovarian extract in complete Freund's adjuvant. The ovary, thymus, and spleen were investigated histologically, histoautoradiographically, and electromicroscopically on days 7, 14, 21, and 28 after immunization. EIO was manifested by massive atresia of follicles and perivascular mononuclear cell infiltration. The appearance of the germinal center like structures in the thymus and increased T cell mitotic activity and B cell stimulation in the spleen pointed out that EIO is mediated both by T and B cells.