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S Petrović

Publications and source records attributed to S Petrović.

At least 19 recordsLinked to original sources
PubMed2000

Estradiol affect Na-dependent Ca2+ efflux from synaptosomal mitochondria.

The effects of gonadal steroid hormone, 17beta-estradiol (E2), in vitro on rat brain mitochondria Ca2+ movement were investigated. Intrasynaptosomal mitochondria Ca2+ uptake via an energy-driven Ca2+ uniporter have Km = 112.73 +/- 7.3 micromol x l(-1) and Vmax = 21.97 +/- 1.7 nmol 45Ca2+ mg(-1). Ca2+ release trough a Na+/Ca2+ antiporter was measured with a Km for Na+ of 43.7 +/- 2.6 mmol x l(-1), and Vmax of 1.5 +/- 0.3 nmol 45Ca2+ mg(-1). Addition of estradiol in preincubation mixture did not affect the uptake of Ca2+ mediated by the ruthenium red-sensitive uniporter, while it produced biphasic effect on Na-dependent Ca2+ efflux. Estradiol at concentrations up to 1 nmol x l(-1) decreased the efflux significantly (63% inhibition with respect to the control), and at concentrations above 10 nmol x l(-1) increased it exponentially. The maximum inhibiting concentration of estradiol (0.5 nmol x l(-1)) increased the affinity of the uniporter (Km reduced by about 30%), without affecting significantly the capacity (Vmax) for Na+. The results presented suggest that estradiol inhibits Na-dependent Ca2+ efflux from mitochondria and acts on mitochondrial retention of Ca2+, which may modulate mitochondrial and consequently synaptosomal content of Ca2+, and in this way exerts its role in the homeostasis of calcium in nerve terminals.

Animals↗
PubMed1999

Selective determination of fish aspartate aminotransferase isoenzymes by their differential sensitivity to proteases.

Various proteases (proteinase K, subtilisin, trypsin and chymotrypsin) were used to study the selective inactivation of the aspartate aminotransferase (EC 2.6.1.1) isoenzymes of grey mullet (Mugil auratus Risso; Osteichthyes). The cytosolic isoenzyme was significantly inactivated by proteinase K, subtilisin and chymotrypsin, while the mitochondrial isoenzyme was sensitive only to proteinase K and to high doses of trypsin. Further identification of the aspartate aminotransferase isoenzymes was based on their discrete sensitivity toward chymotrypsin. Chymotrypsin (1 mg/ml) successfully inhibited purified cytosolic aspartate aminotransferase as well as cytosolic isoenzyme from plasma, whereas the mitochondrial form persisted unaffected. Similar results were obtained when examining liver and red muscle homogenates. This method revealed that the increased total activity of aspartate aminotransferase in fish plasma with induced acute liver injury, was partially a result of the mitochondrial isoenzyme leakage from damaged tissue.

Animals↗
PubMed1999

Physicochemical and immunologic characterization of low-molecular-weight allergoids of Dactylis glomerata pollen proteins.

BACKGROUND: Orchard grass (Dactylis glomerata) pollen proteins were chemically modified by means of acid anhydrides (maleic and succinic anhydride) to obtain low-molecular-weight allergoids. Chemical modification in both cases led to the replacement of one positive charge (epsilon amino group of Lys) by one negative charge, yielding proteins with changed physicochemical properties in comparison to the native orchard grass-pollen proteins. METHODS: Physicochemical characterization of derivatives was done by gel chromatography, SDS-PAGE, and isoelectric focusing. To examine the IgE-binding properties of these derivatives, we carried out immunoblotting. To examine the ability of derivatives to induce IgG production, we immunized rabbits. Skin prick testing with the allergoids was performed on 15 individuals allergic to orchard grass pollens and on two healthy subjects. RESULTS: It was shown that the modified proteins retain their original molecular weights, but change pI to more acidic values. In the case of allergoids, a strong reduction in IgE binding was found. Immunization of rabbits with allergoids showed that the derivatives retain the ability to induce IgG production, and that the antisera obtained in such a way react to native (unmodified) extract. The ability of derivatives to induce allergic reaction was significantly reduced. The patients (86.6%) included in our study exhibited less than 50% of native extract response. Among them, 53.3% had no response to one or both allergoids. CONCLUSIONS: These modification procedures yield allergoids with a reduced allergenic activity and preserved immunogenic potential suitable for use in immunotherapy.

Allergens↗
PubMed1998

Biochemical and genetic characterization of the membrane-associated malate dehydrogenase (acceptor) from Corynebacterium glutamicum.

In addition to a cytoplasmic, NAD-dependent malate dehydrogenase (EC 1.1.1.37), Corynebacterium glutamicum possesses a highly active membrane-associated malate dehydrogenase (acceptor) (EC 1.1.99.16). This enzyme also takes part in the citric acid cycle. It oxidizes L-malate to oxaloacetate and donates electrons to ubiquinone-1 and other artificial acceptors or, via the electron transfer chain, to oxygen. NAD is not an acceptor and the natural direct acceptor for the enzyme is most likely a quinone. The enzyme is therefore called malate:quinone oxidoreductase, abbreviated to Mqo. Mqo is a peripheral membrane protein and can be released from the membrane by addition of chelators. The solubilized form was partially purified and characterized biochemically. FAD is probably a tightly but non-covalently bound prosthetic group, and the enzyme is activated by lipids. A C. glutamicum mutant completely lacking Mqo activity was isolated. It grows poorly on several substrates tested. The mutant possesses normal levels of cytoplasmic NAD-dependent malate dehydrogenase. A plasmid containing the gene from C. glutamicum coding for Mqo was isolated by complementation of the Mqo-negative phenotype. It leads to overexpression of Mqo activity in the mutant. The nucleotide sequence of the mqo gene was determined and is the first sequence known for this enzyme. The derived protein sequence is similar to hypothetical proteins from Escherichia coli, Klebsiella pneumoniae, and Mycobacterium tuberculosis.

Amino Acid Sequence↗
PubMed1997

Comparison of allergenic potentials of timothy (Phleum pratense) pollens from different pollen seasons collected in the Belgrade area.

We investigated extracts of timothy grass pollen from four seasons (1989, 1990, 1991, and 1994) by protein content, SDS-PAGE, immunoblot, RAST, RAST inhibition, and crossed immunoelectrophoresis. Extract of the pollen from 1991 showed the lowest yield in quantitative assays. SDS-PAGE, crossed immunoelectrophoresis, RAST, and RAST inhibition expressed approximately comparable patterns for all extracts except that from 1991. Obviously, the quality of grass pollens, as shown for some ragweed (Ambrosia elatior) pollens depend on year of collection. Our findings are partially in agreement with some earlier examinations of the quality of timothy pollen from different pollen seasons.

Allergens↗
PubMed1995

[Undescended testes and paratesticular anomalies].

In the field of developmental paratesticular anomalies there are numerous questions without answers. The goal of this paper is to give some information on embryology of normal and disturbed development parallely, as well as to describe the occurrence of certain anomalies with a special review on anomalies of epididymis and deferent ductus considering their importance in urology. Results and statistical data from our work have been reported.

Adolescent↗
PubMed1994

Isolation and properties of mitochondrial aspartate aminotransferase from red muscle of grey mullet, Mugil auratus Risso.

Following the chromatographic separation of the grey mullet (Mugil auratus Risso) red muscle extract, two fractions with aspartate aminotransferase activity were detected. One of the anticipated enzymes was purified to homogeneity. The isolated enzyme was a dimeric protein composed of identical subunits with the overall M(r) of about 65,000. It consisted of three electrophoretically distinct subforms with isoelectric points at pH 8.50, 8.70 and 8.85, respectively. The Michaelis-Menten constants of the substrates L-aspartate and 2-oxoglutarate were estimated to be 0.29 +/- 0.012 mM and 0.45 +/- 0.016 mM, respectively. For the reverse reaction, the Km for L-glutamate was 8.57 +/- 2.1 mM and for oxaloacetate it was 0.13 +/- 0.035 mM. The inhibition of the isolated enzyme by hydroxylamine was of a mixed linear noncompetitive type for L-aspartate as a substrate, whereas with 2-oxoglutarate hyperbolic uncompetitive inhibition was observed. The inhibition by aminooxyacetic acid and D,L-glyceraldehyde 3-phosphate was of a mixed linear noncompetitive type with respect to L-aspartate and 2-oxoglutarate. The isolated enzyme was slightly affected by maleate and succinate and no effects were produced by adipate. According to its subcellular distribution, susceptibility to inhibitors molecular and catalytic properties the isolated enzyme belonged to the mitochondrial form of aspartate aminotransferase.

Animals↗
PubMed1993

Peritubular Na-K exchange ion pump in maleate-treated frog kidney proximal tubular cells.

1. After perfusion of isolated frog kidneys for 1 hr with 10(-3) or 10(-2) M maleate Ringer, the peritubular membrane potential gradually declined in a dose-dependent manner. 2. The ouabain-like effects of maleate on cell Na and K activities were dose-dependent and smaller than the effects of zero K or 10(-4) M ouabain. Intracellular pH was not altered in the presence of 10(-2) M maleate. 3. The driving force for Na entry into the cell was reduced, respectively, to 81.4 and 58.4% (of control) in the presence of 10(-3) and 10(-2) M maleate. 4. There was no histochemically detectable inhibition of proximal tubule Na-K ATPase activity during 3 hr of perfusion with 10(-2) M maleate.

Animals↗
PubMed1993

[Pulmonary neuroblastoma--a rare type of manifestation].

We report a case of pulmonary manifestation of neuroblastoma, one of the most common malignant, solid tumors in children. Diagnostic approach and results of a combined cytostatic therapy are described. The nature of the tumor makes prognosis unpredictable.

Adolescent↗
PubMed1990

Seminal antisperm antibodies and genitourinary infection.

A total of 326 infertile men, 126 with genitourinary tract infection, and 200 without infection, were compared with 60 fertile men. Seminal plasma antisperm antibody with other clinical and microbiologic investigations were performed in all. Infertile men with genitourinary tract infection had antisperm antibody in 11.9 percent, infertile men without infection in 14.5 percent, and fertile men in 5 percent; these differences were not significant. The most common causes of these infections were gram-negative organisms and Chlamydia. Comparison of the levels of the titers of seminal plasma antisperm antibodies showed no significant difference between infertile and fertile men. This study shows no significant relationship between genitourinary tract infection and formation of the seminal antisperm antibody.

Antibodies↗
PubMed1990

Purification and properties of glutamyl aminopeptidase from chicken egg-white.

Hydrolytic activities characteristic for different aminopeptidases were detected in the egg-white of unfertilized chicken eggs, and one aminopeptidase was isolated in an electrophoretically homogeneous form. The isolated aminopeptidase preferentially hydrolyzed bonds of alpha-glutamyl residue at the NH(2)-end of synthetic substrates and peptides. The enzyme is a dimer with an M(r) of 320,000 and pI of 4.2. Its optimal pH and temperature are 7.6 and 60 degrees C, respectively. EDTA, amastatin, and N-bromosuccinimide are inhibitors, while Ca2++ and Mn2+ are activators of the enzyme Ca2+ also stabilizes the enzyme. According to the observed properties, the isolated chicken egg-white aminopeptidase belongs to the glutamyl aminopeptidases.

Aminopeptidases↗
PubMed1989

[Modern aspects of diagnosis and therapy of Wilm's tumor].

Real-time sonography of 12 cases with Wilms' tumour confirmed by the pathohistological finding was presented according to the ultrasonographic picture and the possibilities of radiotherapeutic treatment in dependence of the degree of disease. Uniform, irregularly reflective appearance of the tumourous tissue was observed in 58.3% of the patients, while the areas of necrosis and/or hemorrhage and cystic degeneration in the tumour accounted for 41.7%. Clear determination between the tumour and the normal parenchyma of the kidney was confirmed in 66.6% of the cases, while visualization of the normal tissue of the kidney was not possible in 25% of the patients. The treatment of patients with Wilms' tumour was narrowly coordinated by the program consisting of the surgical extirpation of the tumour, postoperative irradiation of the tumorous area at degrees II, III, IV and V and intensive adjuvant chemiotherapy.

Child↗