PubMed Health⌕ Search

Biomedical subjects

O Markovic

Publications and source records attributed to O Markovic.

At least 19 recordsLinked to original sources
PubMed2005

Plasmacytoma of the lung: an indolent disease resistant to conventional myeloma treatment: report of a case.

Solitary lung plasmacytoma is a rare form of plasma cell tumors. The case of a 56-yr-old man is presented, who had a massive tumor of the right pulmonary apex. Percutaneous transthoracic lung biopsy demonstrated a tumor-cell population consisting of mature plasma cells, proplasmacytes, and rare plasmablasts. Immunohistochemically, the cells were CD79a+, kappa+, cyclin D1-, p53-, MDR-. Proliferative index was low (number of Ki-67+ tumor cells was 8%). Serum and urine immunoelectrophoresis did not show the presence of paraprotein. Screening for multiple myeloma with skeletal X-ray survey and bone marrow biopsy were negative. Radiotherapy and chemotherapy with alkylating agents were ineffective. However, the course of the disease is indolent and the patient is well, alive, and with no signs of multiple myeloma >5 yr after the diagnosis was established. Some pathogenetic aspects of tumor resistance to conventional myeloma treatment in this case are discussed.

Drug Resistance, Neoplasm↗
PubMed2004

Immunohistochemical analysis of cyclin D1 and p53 in multiple myeloma: relationship to proliferative activity and prognostic significance.

Conflicting data are reported on the clinical significance of cyclin D1 deregulation in multiple myeloma. The aim of this study was to evaluate the incidence and prognostic significance of cyclin D1 expression and p53 mutations in multiple myeloma, as well as the relationship of their expression with selected clinical data, histological features, and proliferative activity of myeloma cells. We analyzed bone marrow biopsy specimens obtained from 59 patients with newly diagnosed multiple myeloma. Expression of cyclin D1 and p53 was analyzed using standard immunohistochemical method of B5-fixed and routinely processed paraffin-embedded bone marrow specimens. Cyclin D1 was overexpressed in 14/59 (27%) and p53 in 5/59 (8.5%) specimens. There was no significant correlation between cyclin D1 overexpression and age, gender, clinical stage (Durie-Salmon classification), extent of osteolytic lesions, type of monoclonal protein, hemoglobin concentration, platelet count, serum concentration of creatinine, calcium, C-reactive protein, and beta2-microglobulin. No association was observed between the expression of cyclin D1 and the extent of bone marrow infiltration, histological grade, proliferative activity index (measured with Ki-67 immunoreactivity) and response to therapy. No significant difference was observed regarding overall survival between cyclin D1 positive and cyclin D1 negative patients (29 vs 36 mo, p = 0.76). Results of this study did not revealed prognostic significance of cyclin D1 overexpression in multiple myeloma. Mutations of p53 gene are rare events in myeloma, suggesting their limited role in the pathogenesis of the disease.

Adult↗
PubMed2002

Characterization of carrot pectin methylesterase.

The most alkaline form of pectin methylesterase was purified from ripe carrot roots and used for structural analysis. Determination of an N-terminal blocking group and of the primary structure allowed comparisons with other forms, and facilitated crystallographic determination of the three-dimensional structure. The mature enzyme has 319 residues and the N-terminal blocking group was shown to be a pyroglutamyl residue derived from a glutaminyl cyclization. Few other methylesterases have been isolated and assigned to exact mature forms, and together with the present enzyme, only two have been analyzed in three-dimensional structure. However, comparison of 39 forms, mainly from GenBank data, reveals clear relationships and identifies subgroups of this enzyme type, deviating in structure but centering around two functionally important and conserved Asp residues at positions 136 and 157 in the carrot enzyme.

Amino Acid Sequence↗
PubMed2001

Pectin degrading glycoside hydrolases of family 28: sequence-structural features, specificities and evolution.

Family 28 belongs to the largest families of glycoside hydrolases. It covers several enzyme specificities of bacterial, fungal, plant and insect origins. This study deals with all available amino acid sequences of family 28 members. First, it focuses on the detailed analysis of 115 sequences of polygalacturonases yielding their evolutionary tree. The large data set allowed modification of some of the existing family 28 sequence characteristics and to draw the sequence features specific for bacterial and fungal exopolygalacturonases discriminating them from the endopolygalacturonases. The evolutionary tree reflects both the taxonomy and specificity so that bacterial, fungal and plant enzymes form their own clusters, the endo- and exo-mode of action being respected, too. The only insect (animal) representative is most related to fungal endopolygalacturonases. The present study brings further: (i) the analysis of available rhamnogalacturonase sequences; (ii) the elucidation of relatedness between the recently added member, the endo-xylogalacturonan hydrolase and the rest of the family; and (iii) revealing the sequence features characteristic of the individual enzyme specificities and the evolutionary relationships within the entire family 28. The disulfides common for the individual enzyme groups were also proposed. With regard to functionally important residues of polygalacturonases, xylogalacturonan hydrolase possesses all of them, while the rhamnogalacturonases, known to lack the histidine residue (His223; Aspergillus niger polygalacturonase II numbering), have a further tyrosine (Tyr291) replaced by a conserved tryptophan. Evolutionarily, the xylogalacturonan hydrolase is most related to fungal exopolygalacturonases and the rhamnogalacturonases form their own cluster on the adjacent branch.

Amino Acid Sequence↗
PubMed1998

Cell cross-contamination in cell cultures: the silent and neglected danger.

Cell cross-contamination in cell cultures is a common problem during cell culturing and use. Contamination invalidates research results, compromises the comparison of results between laboratories, reduces reproducibility required in industrial production of cell lines, and may lead to unusable therapeutic products. The problem can be solved by increasing the awareness of its seriousness and by introducing regular quality control of cell cross-contamination in every laboratory where cells are grown and used.

Animals↗
PubMed1998

The glycoprotein character of multiple forms of Aspergillus polygalacturonase.

Comparisons of known primary structures of polygalacturonases show that extent and localization of potential N-glycosylation sites differ. Some sites are similar in position and adjacent to strictly conserved residues at the potential active site. The presence of N-acetylglucosamine and mannose in the molecules of two homogeneous, major Aspergillus sp. polygalacturonase forms was confirmed by IR spectroscopy. The purification method, based on interaction of the carbohydrate part with concanavalin A immobilized on chlorotriazine bead cellulose, was optimized. Deglycosylation with N-glycosidase F under denaturating and nondenaturating conditions led to molecular mass decreases followed by complete inactivation of the polygalacturonase enzyme activity. These results show the importance of glycosylation in these protein forms, while the comparative patterns establish both variability and some similarities in overall glycosylation architectures.

Amino Acid Sequence↗
PubMed1996

An essential tyrosine residue of Aspergillus polygalacturonase.

Based on strict conservation of a tyrosine residue in 24 polygalacturonases, tyrosine modification was assessed in two different forms of the Aspergillus enzyme. The second subform was unknown in structure but submitted to sequence analysis and was found also to have the conserved tyrosine residue. Results of chemical modifications are consistent in showing inactivation of the proteins with all tyrosine-reactive agents tested, acetic anhydride, N-acetyl imidazole, and tetranitromethane. Furthermore, after acetylation, regeneration of enzyme activity was possible with hydroxylamine. Spectrophotometric pH titration showed that one accessible tyrosine residue is ionized at pH 9.3-9.5, whereas the remaining, masked residues are all ionized at pH 10.5. It is concluded that one tyrosine residue is catalytically important, in agreement with the inactivation and reactivation data, that this residue is accessible, and that it is likely to correspond to the strictly conserved residue observed in all forms.

Acetic Anhydrides↗
PubMed1996

Modification of tomato and Aspergillus niger pectinesterases with diethyl pyrocarbonate.

The role of histidine residues in pectinesterases was evaluated by monitoring the sensitivity to modification with diethyl pyrocarbonate in the tomato and Aspergillus niger enzymes. Different and incomplete losses of enzyme activity were obtained. Inactivation of the enzymes was proportional to the histidine content (two in the tomato T1 form, six in the Aspergillus form), suggesting that accessible histidine residues do not have active-site functions in these pectinesterases, but contribute to the overall structural stability. Lack of His roles in common between the enzyme forms is in agreement with the structures of pectinesterases having no conserved His residues.

Aspergillus niger↗
PubMed1994

A new assay for intracellular measurement of inosine monophosphate dehydrogenase activity: a guide for better selection of patients for enzyme-targeted chemotherapy.

We developed a new cytochemical assay for identification of cells containing inosine monophosphate dehydrogenase (IMPDH) and measurement of tumor cell sensitivity to the escalating dose/schedule of the IMPDH pattern-targeting drugs. The assay is based on cytochemical principles for development of DH activity markers inside morphologically classified cells, image analysis for measuring the amount of this marker, and computer assistance for data management. The assay was optimized on a human leukemia cell line (K562-NS) and reference values for enzyme activity were established. Assay specificity was determined with different substrates and enzyme inhibitors. Sensitivity depends on the measuring instrument (image analyzing system), and the precision of the biological model used for assessment of reference values was high. IMPDH-positive malignant cells were found in all specimens obtained from acute leukemia and solid tumor patients (13/13 and 29/29) and in four human tumor cell lines (K562, K562-NS, HL60, and HL60-M). Cells of the K562-NS line were exposed to tiazofurin and ribavirin in conventional assays for assessment of drug-induced acute and subacute toxicity/sensitivity. A reduction of IMPDH activity was recorded at drug concentrations below the range at which cell damage appeared.

Acute Disease↗
PubMed1993

Pectinase Aspergillus sp. polygalacturonase: multiplicity, divergence, and structural patterns linking fungal, bacterial, and plant polygalacturonases.

Nine forms of Aspergillus sp. polygalacturonase were purified from a commercial preparation of pectinase Rohament P using chromatographies and chromatofocusing. Individual forms differ in isoelectric point, and at least five differ in structure; whereas molecular masses and enzymatic properties are largely identical. Four forms with free alpha-amino groups have identical start positions but internal amino acid replacements. Therefore, the multiplicity is derived from true heterogeneities and not from N-terminal truncations. Peptide analysis of the major polygalacturonase reveals large variations toward the enzyme from other Aspergillus species (72-75% residue differences, depending on species) but additional similarities with the enzyme from bacterial and plant sources (only 66-71% residue differences toward the Erwinia, tomato, and peach enzymes). Combined with previous data, these facts show polygalacturonase to exhibit extensive multiplicity and much variability, but also unexpected similarities between distantly related forms with conserved functional properties.

Amino Acid Sequence↗
PubMed1993

Potentiation of metaphit-induced audiogenic seizures by REM sleep deprivation in rats.

The possibility that REM sleep deprivation (REMD) induced increased susceptibility of rats to the convulsive effects of metaphit was investigated. Metaphit-induced audiogenic seizures were studied in three groups of animals: 1) caged controls; 2) large platform animals; and 3) small platform, REMD animals. After 48 h of confinement to their environments the rats from all three groups were injected with metaphit (10 mg kg-1, IP) and the procedures continued for the next 24 h. Immediately after removal from platforms and at 3-h intervals thereafter all rats were individually subjected to intense sound stimulation. Convulsive responses were recorded and analyzed with respect to incidence, intensity, and duration. The REMD rats were found to be more sensitive to the convulsive effects of metaphit compared to nondeprived rats. This was manifested in significantly shorter latencies to seizures, and significantly higher incidence, severity, and duration of seizures, especially of the most severe seizure component-tonic extensor convulsion. Inducing rats to convulse while they were being REM sleep deprived eliminated the REM sleep rebound observed in REMD rats that did not convulse. The occurrence of spontaneous EEG seizures during the undisturbed recovery period reduced REM sleep rebound. The results demonstrate a reciprocal relation between seizure behavior and REM sleep.

Acoustic Stimulation↗
PubMed1992

Disulfide bridges in tomato pectinesterase: variations from pectinesterases of other species; conservation of possible active site segments.

Analysis of tomato pectinesterase by carboxymethylation, with and without reduction, shows that the enzyme has two intrachain disulfide bridges. Analysis of fragments obtained from the native enzyme after digestion with pepsin identified bridges connecting Cys-98 with Cys-125, and Cys-166 with Cys-200. The locations of disulfide bridges in tomato pectinesterase are not identical to those in three distantly related pectinesterases (18-33% residue identities) from microorganisms. However, one half-Cys (i.e., Cys-166) position is conserved in all four enzymes. Sequence comparisons of the overall structures suggest a special importance for three short segments of the entire protein. One segment is at the N-terminal part of the tomato pectinesterase, another in the C-terminal portion near the distal end of the second disulfide loop, and the third segment is located in the central part between the two disulfide bridges. The latter segment, encompassing only 40 residues of the entire protein, appears to high-light a functional site in a midchain segment.

Amino Acid Sequence↗
PubMed1992

Antiserum to prolactin decreases rapid eye movement sleep (REM sleep) in the male rat.

Previous reports suggest that blood-born prolactin (PRL) may selectively promote rapid eye movement sleep (REMS). To study the possible involvement of endogenous PRL in sleep regulation, rats were systemically injected with either antiserum to PRL or normal rabbit serum, and the sleep-wake activity was determined during the subsequent 12-h light cycle. The administration of normal rabbit serum in physiological saline did not alter sleep-wake activity compared to control recordings, whereas the PRL antiserum caused a modest and selective suppression in REMS. Immunoreactive PRL was eliminated from the serial plasma samples obtained between 6 to 11 h after the injection of the antiserum. Brain temperature was not affected by the antiserum. The results indicate that physiological pituitary PRL secretion has a slight REMS-promoting activity in the male rat. It is speculated that an increased release of pituitary PRL or the PRL-like substance previously demonstrated in the brain may significantly stimulate REMS.

Animals↗
PubMed1990

Tomato and Aspergillus niger pectinesterases. Correlation of differences in existing reports: large species variations.

Existing reports on the enzyme tomato pectinesterase differ in alignments of two internal segments and in many single-residue replacements. The alignment from cDNA data, with a 317-residue mature protein, is correct, but protein analyses also show at least 18 single-residue replacements, suggesting the presence of many native or (less likely) cloning-derived microheterogeneities. Purification of Aspergillus niger pectinesterase and N-terminal sequence analysis of this enzyme reveal a different structure and indicate an extensive protein divergence.

Amino Acid Sequence↗
PubMed1988

A new chromogenic substrate for assay and detection of alpha-amylase.

A new soluble chromogenic substrate for alpha-amylase was prepared by coupling partially hydrolyzed starch with a dye, Ostazin brilliant red H-3B. The substrate is precipitable from buffered solutions with ethanol and is equally suitable for assay of alpha-amylase, detection of separated alpha-amylase isoenzymes in gels, and selection of microbial producers of the enzyme.

Chromogenic Compounds↗