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Biomedical subjects

S Maricić

Publications and source records attributed to S Maricić.

16 recordsLinked to original sources
PubMed2001

Laparoscopic management of consecutive ovarian pregnancy in a patient with infertility.

The diagnosis of ovarian pregnancy is based on the improper rise of serum beta-hCG levels, sonographic findings of an empty uterus, highly characteristic ovarian formation with double hyperechogenic ring surrounding small hypoechogenic field, and the laparoscopic verification of Spiegelberg's criteria. We present a case of ovarian pregnancy in spontaneous cycle in 34-year-old woman following two unsuccessful IVF/ET procedures and ovarian pregnancy on contralateral side laparoscopically treated seven months ago, also achieved in non-stimulated, spontaneous cycle. On admission she had a serum hCG level of 596 mIU/mL on cycle day 46 and an empty uterus. Transvaginal sonography showed a 20 mm ring-like thick-walled hyperechogenic structure within the left ovary. The echogenic ring was surrounded by irregular, hypoechogenic structures suggestive of an ovarian pregnancy with periluteal hemorrhage and blood clots. The ruptured cystic ovarian pregnancy and the corpus luteum were removed by laparoscopy. During the procedure we have seen two clips on the right ovary placed laparoscopically to achieve hemostasis after rupture of the ovarian pregnancy seven months ago. Histopathology showed isolated chorionic villi within hemorrhagic areas in the vicinity of the corpus luteum.

Adult↗
PubMed1982

Temperature-dependent conformation change in spin-labeled hemoglobin.

Hemoglobin was spin labeled at beta-93(F9)-cysteine with N-oxyl-2,2,6,6-tetramethylpiperidinylmaleimide. The inward shift of the high-field hyperfine line (delta Hx) position in the ESR spectra of the spin label was measured as a function of temperature. One can except that an abrupt change in the microenvironment around the tightly bound spin label will be reflected in the function delta Hx(T) as a discontinuity (break point). This was shown for aquo-, azido-, nitro- and oxyhemoglobin derivatives. The presented results suggest that the microenvironment around the tightly bound spin label in those methemoglobin derivatives that exhibit the mixed-spin state of the heme iron is prone to an abrupt change above a certain ligand-specific temperature. The change in microenvironment of the spin label is probably due to a temperature-dependent change in the teritary structure of the protein.

Hemoglobins↗
PubMed1979

Comparison of microsomal and solubilized monooxygenases from rat and rabbit by proton magnetic relaxation.

The paper presents results of a comparative study of the haem environment, by proton magnetic relaxation, in P-450 and P-448 monooxygenases from rat and rabbit, induced by phenobarbital and 3-methylcholanthrene, in both species. It was established that the method yields information on the accessibility of the haem iron for solvent molecules (protons), both in microsomes and in solubilized samples of various degrees of purification, i.e. association. The state of micelles in the solutions does not alter the haem iron accessibility. A slight difference was found for the microsomes suspended in a phosphate vs. pyrophosphate buffer, but this is without any consequence with regard to the species and form differences. The correlation time for the highly purified LM2 fraction of rabbit P-450 could not be determined more precisely than before for a sample of lower purity, because the relaxation rates are frequency independent. The correlation time for the rat P-448 monooxygenase was determined by dispersion measurements to be (4.1 +/- 0.4) x 10(-11) s. It was found that the PMRx behaviours of rabbit and rat monooxygenases are more alike in microsomes than in the partially purified solubilized form. The solubilization produces a pronounced alteration of the PMRx temperature dependence only for the rat 3-MC induced monooxygenase P-448. For the P-450 form the haem iron becomes less accessible on solubilization, both for the rabbit and the rat liver monooxygenases, whereas in case of rat liver P-448 the accessibility is considerably enhanced on solubilization. There is a substantial structural specificity of the haem environments from the two animal species, the one from rat being tighter. The reduced, NO-bound rabbit liver monooxygenase was studied also, but the results are not yet conclusive, except the fact that the unpaired spin from NO is thoroughly shielded from the solvent compared with the haem iron from the original sample. The following series of increased haem-iron accessibility emerges from the PMRx studies known so far: rat (P-448) less than rabbit (P-448) less than rat (P-450) less than rabbit (P-450) in microsomes, and rabbit (P-448, with 3-MC bound?) less than Pseudomonas putida (P-450) rat less than (P-448), less than rat (P-450) less than rabbit (P-450) from solubilized samples. For the latter, it appears that increased enzymic specificity goes along with a closing of the haem cleft.

Animals↗
PubMed1979

Quaternary structure, hydration, and self-association of hemoglobin. A proton magnetic relaxation study.

The hydration of oxyhemoglobin, carbonylhemoglobin, and deoxyhemoglobin does not depend on the quaternary state of the hemoglobin molecule as revealed through the concentration dependence of proton magnetic relaxation rates. The biphasic relaxation behavior of isotopically diluted solutions of hemoglobin confirms that the self-association of hemoglobin molecules at higher concentration is independent of the quaternary structure. In the case of aquomethemoglobin, a biphasic relaxation and a diminished heme accessibility at higher concentrations are observed, caused by interaction of the associating hemoglobin molecules.

Chemical Phenomena↗
PubMed1977

A proton magnetic relaxation study of ferric myoglobin and haemoglobin in water/ethanediol solutions.

Structural alterations of the haem vicinity of the high-spin derivatives of bovine ferric myoglobin (metmyoglobin) and human haemoglobin and the changes of the interaction with inositol hexaphosphate induced by ethanediol were monitored by solvent-proton magnetic relaxation. On addition of ethanediol up to 60% the fluoromet derivatives exhibit a gradual increase in the accessibility of the haem for the molecules from the solvent. In aquomethaemoglobin solutions with more than 25% ethanediol there is no unique explanation of proton magnetic relaxation. Ethanediol enhances the binding of inositol hexaphosphate to methaemoglobin, but the structural consequences of this binding on the haem-pockets seem to be diminished. The mechanisms of the observed structural and functional alterations of myoglobin as well as haemoglobin tetramer are discussed here.

Animals↗
PubMed1977

Structural studies by proton magnetic relaxation of stereochemical probes. II. Allosteric effects in human methaemoglobin.

The haem-iron accessibility to solvent molecules in human aquomet- and fluoromethaemoglobin was studied by the magnetic relaxation of protons from a stereochemical probe (methanol in deuterated solutions) in its dependence on allosteric effects induced by inositol hexaphosphate and pH between 5.5 and 8.5. The exchange of methanol with bulk solvent was observed only when inositol hexaphosphate was bound to aquomethaemoglobin, which is consistent with a widening of the haemcrevice compared to the conformation in the absence of inositol hexaphosphate. An increase in alkalinity in the physiological range of the Bohr effect results in a gradual impedence of the solvent dynamics inside the haem-pocket. The fast-relaxation phase of methyl protons indicates that a large number of methanol molecules are under the strong influence of the protein; this effect is considerably smaller with inositol hexaphosphate bound to aquomethaemoglobin. The hypothesis which implies a proton from the coordinated water molecule is responsible for the observed relaxation rates has been critically discussed. The model with a water molecule exchanging between a position next to the sixth-ligand site of the haem-iron and the bulk solvent is further substantiated experimentally. This model has been found to be the simplest and most self consistent in the interpretation of all these proton magnetic relaxation data.

Allosteric Regulation↗
PubMed1977

Self-association of oxyhaemoglobin. A nuclear magnetic relaxation study in H2O/D2O solutions.

The proton and deuterium longitudinal relaxation rates were studied at room temperature up to the highest protein concentrations in oxyhaemoglobin solutions of different H2O/D2O composition. The deuterium relaxation rates followed the experimentally well known single linear dependence on protein concentration, the slopes being little influenced by solvent (D2O/H2O) composition. The proton relaxation rates show two different linear dependences on haemoglobin concentration. The entire concentration range is described by two straight lines with the threshold concentration about 11 mM (in haem). The ratio of the slopes is 1.6 (high-to-low HB-conc). Only in the higher concentration range two T1's were observed if the solvent contained more than half of D2O. The slow relaxation phase of protons has T1's similar to those measured in solutions with less than half of D2O. The relaxation of the other phase was ten times faster. The ratio of the proton populations in these two phases was equal to 2 (slow-to-fast) and independent of protein concentration. The fast relaxing protons are attributed to water molecules encaged within two or more haemoglobin molecules which associate for times long enough on the PMR time-scale.

Chemical Phenomena↗
PubMed1976

Temperature dependence of ESR spectra of spin-labelled met-hemoglobin.

The maleimide spin-label, firmly fixed to the protein, was used to study conformation changes of various met-hemoglobin derivatives. The temperature dependence of the rotational correlation time shows a distinct conformation change in aquomet-hemoglobin at about 25 degrees C. The other met-hemoglobin derivatives studied (fluoro-, cyano-, aquomet-complexed with inositol hexaphosphate) and carbonmonoxy-hemoglobin exhibit no conformation changes in the temperature range from 0-50 degrees C.

Electron Spin Resonance Spectroscopy↗
PubMed1976

The haem-accessibility in leghaemoglobin of Lupinus luteus as observed by proton magnetic relaxation.

Using the solvent-protons' longitudinal magnetic relaxation rates (p.m.r.) for Lupinus luteus leghaemoglobin derivatives the accessibility of the haem has been evaluated by our "stereo-chemical p.m.r. titration" method with nonexchangeable protons of aliphatic lower alcohols in otherwise deuterated solutions. The haem in leghaemoglobin is more accessible and its protein environment more flexible compared with vertebrate haemoglobins. The correlation time in aquometleghaemglobin aqueous solution has been determined by measuring the frequency dispersion of the p.m.r. rates between 6.1 and 93 MHZ. Taking into account the measured value of tauc = (7.7 +/- 0.5 x 10(-10) s the iron-to-proton inter-spin distances have been calculated. The significance of these distances as well as the electronic g-factor anisotrophy for elucidation of fine structural details of the haem-environment are discussed.

Heme↗