PubMed Health⌕ Search

Biomedical subjects

J Mazur

Publications and source records attributed to J Mazur.

At least 19 recordsLinked to original sources
PubMed1997

[Territorial distribution of neural tube defects in Poland].

Neural tube defects (ntd) remain unresolved therapeutic problems, even for contemporary health services. Prophylactic measures are the best methods for limitation of the problem. In many countries, the number of children born with ntd has been reduced significantly, even in 4-5 folds. Authors found that the situation in Poland remains stable since last 20 years. Epidemiological evaluation of the ntd morbidity in Poland is very difficult. There is no National Register of Inherited Defects. Authors observed and analysed mortality and hospitalisation due to ntd in Poland, in early ninetees, and compared these data with information originated from Regional (Wielkopolska) Inherited Defects Register. It was found that ntd mortality and hospitalisation in Wielkopolska was similar to average in Poland. It has been estimated that the rate of children born with ntd in Poland, in 1995 was 2.68 per 1000 live and stillbriths (in 1972-1974 was 2.04). Especially high rates of ntd's have been found in north-eastern part of Country. Incidence of ntd's was higher in rural, than in urban population of the Country.

Adult↗
PubMed1996

Prognostic significance of proliferative and apoptotic fractions in low grade follicle center cell-derived non-Hodgkin's lymphomas.

BACKGROUND: The biologic parameters, DNA ploidy and proliferative activity, have been suggested as prognostic factors in non-Hodgkin's lymphoma (NHL). However, reports on the prognostic importance of these factors in follicle center cell-derived (FCC) centroblastic/centrocytic (CB/CC) NHL patients with long follow-up are scarce. METHODS: Apoptotic fractions were quantified in 60 patients with CB/CC NHL by in situ labeling of DNA strand breaks in nuclei [TdT-mediated dUTP/dATP in situ 3'OH--end labeling (TUNEL)]. The findings were related to S-phase and MIB-1 counts, DNA ploidy, and clinical outcome. RESULTS: In CB/CC NHL, the percentages of proliferating and apoptotic cells were lower than in reactive germinal centers (GC; P < 0.05; mean, 0.188 vs 3.263% and 19.05 vs. 69.4% for TUNEL and MIB-1 positive cells in CB/CC and GC, respectively). Significantly higher percentages of MIB-1 and TUNEL positive cells were observed in patients with complete remission when compared with the partial remission / no response group (P < 0.01). The size of proliferative and apoptotic fractions did not correlate with the overall survival of the patients. However, follicular and diffuse growth pattern, elevated serum lactic dehydrogenase, advanced stage, and age indicated a lower probability of 5- and 10-year survival. CONCLUSIONS: The investigation of proliferative and apoptotic fractions in FCC lymphomas may help to define groups of patients to who would benefit from aggressive, high dose therapy protocols and patients to whom less aggressive strategies can be applied safely.

Adult↗
PubMed1996

Constructing optimal backbone segments for joining fixed DNA base pairs.

A method is presented to link a sequence of space-fixed base pairs by the sugar-phosphate segments of single nucleotides and to evaluate the effects in the backbone caused by this positioning of the bases. The entire computational unit comprises several nucleotides that are energy-minimized, subject to constraints imposed by the sugar-phosphate backbone segments being anchored to space-fixed base pairs. The minimization schemes are based on two stages, a conjugate gradient method followed by a Newton-Raphson algorithm. Because our purpose is to examine the response, or relaxation, of an artificially stressed backbone, it is essential to be able to obtain, as closely as possible, a lowest minimum energy conformation of the backbone segment in conformational space. For this purpose, an algorithm is developed that leads to the generation of an assembly of many local energy minima. From these sets of local minima, one conformation corresponding to the one with the lowest minimum is then selected and designated to represent the backbone segment at its minimum. The effective electrostatic potential of mean force is expressed in terms of adjustable parameters that incorporate solvent screening action in the Coulombic interactions between charged backbone atoms; these parameters are adjusted to obtain the best fit of the nearest-neighbor phosphorous atoms in an x-ray structure.

Algorithms↗
PubMed1996

Interdependence of conformational variables in double-helical DNA.

DNA exhibits conformational polymorphism, with the details depending on the sequence and its environment. To understand the mechanisms of conformational polymorphism and these transitions, we examine the interrelationships among the various conformational variables of DNA. In particular, we examine the stress-strain relation among conformational variables, describing base-pair morphology and their effects on the backbone conformation. For the calculation of base pairs, we use the method previously developed to calculate averages over conformational variables of DNA. Here we apply this method to calculate the Boltzmann averages of conformational variables for fixed values of one particular conformational variable, which reflects the strain in the structure responding to a particular driving stress. This averaging over all but one driving variable smooths the usual rough energy surface to permit observation of the effects of one conformational variable at a time. The stress-strain analyses of conformational variables of base pair slide, twist, and roll, which exhibit characteristic changes during the conformational transition of DNA, have shown that the conformational changes of base pairs are strongly correlated with one another. Furthermore, the stress-strain relations are not symmetrical with respect to these variables, i.e., the response of one coordinate to another is different from the reverse direction. We also examine the effect of conformational changes in base-pair variables on the sugar-backbone conformation by using the minimization method we developed. The conformational changes of base pairs affect the sugar pucker and other dihedral angles of the backbone of DNA, but each variable affects the sugar-backbone differently. In particular, twist is found to have the most influence in affecting the sugar pucker and backbone conformation. These calculated conformational changes in base pairs and backbone segments are consistent with experimental observations and serve to validate the calculation method.

Base Composition↗
PubMed1996

[Barriers in breast feeding: cesarean section].

The rate of cesarean sections in Poland is about 15%. The post partum practice conductive to breast-feeding are less frequently introduced in after caesarean delivery even after adjustment for newborn birth weight. Measures to foster and facilitate successful breast-feeding after caesarean delivery are recommended.

Breast Feeding↗
PubMed1995

Comparison of rotation models for describing DNA conformations: application to static and polymorphic forms.

A new method, based on a space-fixed rotation axis, or local helix axis, is proposed for the calculation of the relative orientation variables for a sequence of base pairs. With this method, orientation variables are determined through the rotation of a base pair about this axis. These variables uniquely determine a set of helical variables, similar to the roll, tilt, and twist, commonly used for a description of spatial orientations of internally rigid base pairs. The proposed identification of roll and tilt with the direction cosines of the space-fixed rotation axis agrees well with their customary definitions as the openings of the angles between adjoining base pairs toward the minor groove and toward the ascending (5' to 3') backbone strand, respectively. These new variables permit a more direct physical comprehension of DNA conformations and also the behavior of self-complementary sequences. These direction cosines, together with the rotation angle about the space-fixed axis, form a set of three independent orientation variables of the bases that afford some advantages over the variously defined twist, roll, and tilt angles, either for static or average forms. An example for the static form of these variables is shown through their use to interpret crystal coordinates. An example for the average of orientation variables is based on statistical calculations. In this example, the orientation variables, together with the translational variables that describe the relative displacements of a pair of adjacent base pairs, form a canonically distributed ensemble in phase space spanned by these variables. Two sets of conformational variables are generated by using two different methods for performing rotation operations on the sequences of base pairs. The first method is based on the new single rotation about a space-fixed axis of rotation. This space-fixed axis of rotation is, in fact, the local helical axis as constructed previously by others. The second method is based on three consecutive rotations by Euler angles. Because of large flexibilities and anisotropies along various conformational variables of DNA base pairs, the two sets of generated conformational variables, based on these two different methods of performing rotation operations, lead to slightly different sets of structurally different, but energetically equivalent, spatial arrangements of the base pairs.

Base Composition↗
PubMed1995

DNA image cytometry and the expression of proliferative markers (proliferating cell nuclear antigen and Ki67) in non-Hodgkin's lymphomas.

We have analyzed DNA content and proliferative activity in morphologically defined cell subpopulations of 74 non-Hodgkin's lymphomas (NHL) and 29 reactive lymph nodes using DNA image cytometry and antibodies to proliferative markers (proliferating cell nuclear antigen (PCNA) and Ki67). Thirteen (18.6%) of 70 NHL cases were aneuploid. The follicular center cell-derived lymphomas with DNA aneuploidy had DNA indices (DI) predominantly in the tetraploid region, whereas aneuploid high-grade (HG) NHL presented DNA histograms with multiple aneuploid stemlines. In aneuploid centrocytic-centroblastic (CB/CC) NHLs, DNA aneuploidy was found exclusively in centroblasts, whereas centrocytes in these cases were diploid. Percentages of cells in S and G2/M phase in chronic lymphocytic leukemia (CLL), immunocytoma (IC), centrocytic NHL (CC), and centrocytes from CB/CC were low (< 5%), whereas the respective values for centroblasts in CB/CC and in malignant cells of HG NHL were similar to those of large lymphoid cells in the reactive lymph nodes (mean, 39.5%, 36.6%, and 53.5%, respectively). The mean percentage of PCNA positive cells in CLL, IC, and CC was 4.9%. In the follicles of CB/CC NHLs there was, on average, 56.9% of PCNA positive centroblasts and 8.1% of PCNA positive centrocytes. In HG NHL, the mean percentage of PCNA positive lymphoma cells was 27.9%. A positive correlation was found between percentages of cells in S and G2/M phase and cells positive for PCNA (P < 0.001). There was also a significant correlation between percentages of Ki67 (mean, 19.2%) and PCNA positive cells (mean, 17.7%) (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1993

Remedies to the problem of child labor: the situation in the apparel industry.

When you realize how long the problem of child labor has been around, anyone who ventures into the terrain of remedies obviously needs a long memory and not a little optimism. What have we tried? What has worked? And what has not worked? To answer these questions, we must first look at how we have diagnosed the problem. Some say that the return of child labor is due to the present recession. Hard-pressed businesses are looking for cheap and cheaper labor. Sweatshops proliferate. When the recession recedes, so will child labor. If it were that simple, we could all congratulate ourselves on having conducted this enlightened symposium and go home without worrying much more about the problem. The magic hand of the market, in due course, will straighten it all out. Let me tell you something about the apparel industry in New York where new laws and strict enforcement make the only difference. Over 80% of OSHA inspections were triggered by the state's Apparel Task Force.

Adolescent↗
PubMed1991

Distance-dependent dielectric constants and their application to double-helical DNA.

Detailed studies of structures of biological macromolecules, even in simplified models, involve many costly and time-consuming calculations. Any thorough methods require sampling of an extremely large conformation and momentum space. Calculations of electrostatic interactions, which depend on many physical factors, such as the details of solvent, solvent accessibility in macromolecules, and molecular polarizability, are always developed in a compromise between more rigorous, detailed models and the need for immediate application to complicated biological systems. In this paper, a middle ground is taken between the more exact theoretical models and the simplest constant values for the dielectric constant. The effects of solvent, counterions, and molecular polarizability are incorporated through a set of adjustable parameters that should be determined from experimental conditions. Several previous forms for the dielectric function are compared with the new ones. The present methods use Langevin functions to span the region of dielectric constant between bulk solvent and cavity values. Application of such dielectric models to double-helical DNA is important because base-stacking preferences were previously demonstrated [A. Sarai, J. Mazur, R. Nussinov, and R. L. Jernigan (1988) Biochemistry, vol. 27, pp. 8498-8502] to be sensitive to the electrostatic formulation. Here we find that poly(dG).poly(dC) can be A form for high screening and B form for low screening. By contrast, poly(dA).poly(dT) can only take the B form. Base stacking is more sensitive to the form of the dielectric function than are the sugar-phosphate backbone conformations. Also in B form, the backbone conformations are not so affected by the base types as in A form.

Base Sequence↗
PubMed1991

[Preliminary results of the treatment of acute leukemia with mitoxantrone].

Mitoxantrone is a new anthracenodione derivative with a high antineoplastic activity in proliferative diseases of the haemopoietic system. In the Institute of Haematology in Warsaw and in the Department of Haematology, Silesian Medical Academy in Katowice this agent was used in combination with cytarabine in 49 cases of acute leukaemia (35 with acute myeloid leukaemia and 14 with acute lymphoblastic leukaemia). The preparations used were Mitoxantrone (POLFA Works in Jelenia Góra) and Novantrone (Lederle). These agents were given intravenously in doses of 10-20 mg/m2 for 3 days in combination with cytarabine in three doses: 100 mg/m2 on days 1 through 7, and 1 g/m2 or 3 g/m2 every 12 hours on days 1 through 4 of the treatment. Complete remission was obtained in 17 cases (35%), including 13 with acute myeloid leukaemia (37%) and 4 with acute lymphoblastic leukaemia (29). The most frequent side effects were: long-lasting pancytopenia (in 100% of cases), hair loss (39%) and gastrointestinal toxicity (33%). No significant differences were noted in the effectiveness and toxicity between these two preparations. In the light of the presented results it may be accepted that the combination of mitoxantrone with cytarabine is an important advance in the treatment of acute leukaemias.

Adolescent↗
PubMed1989

Sequence dependence of DNA conformational flexibility.

By using conformational free energy calculations, we have studied the sequence dependence of flexibility and its anisotropy along various conformational variables of DNA base pairs. The results show the AT base step to be very flexible along the twist coordinate. On the other hand, homonucleotide steps, GG(CC) and AA(TT), are among the most rigid sequences. For the roll motion that would correspond to a bend, the TA step is most flexible, while the GG(CC) step is least flexible. The flexibility of roll is quite anisotropic; the ratio of fluctuations toward the major and minor grooves is the largest for the GC step and the smallest for the AA(TT) and CG steps. Propeller twisting of base pairs is quite flexible, especially of A.T base pairs; propeller twist can reach 19 degrees by thermal fluctuation. We discuss the effect of electrostatic parameters, comparison with available experimental results, and biological relevance of these results.

Base Sequence↗
PubMed1989

Sequence dependence of the B-A conformational transition of DNA.

We have studied, by conformational analysis, the sequence dependence of DNA conformational transition between B- and A-forms. We have considered intramolecular interactions between base pairs, without backbone, to examine their role in the conformational transition between B- and A-forms, and found that base pairs themselves usually have intrinsic conformational preferences for the B- or A-form. Calculation of all ten possible base steps shows that the base combinations, CC (or GG), GC, AT, and TA, have tendencies to assume the A-conformation. Results show that it is particularly easy to slide along the long axis of the base pair for these steps, with AT and CC showing especially flat energies. These calculations show that a preference for the B- or A-conformation depends on the electrostatic energy parameters, in particular, on dielectric and shielding constants; the A-conformation is preferred for low dielectric constant or low shielding. Both the A- and B-conformations are mainly stabilized by electrostatic interactions between favorably juxtaposed atomic charges on base pairs; however, the B-conformation generally has more favorable van der Waals interactions than the A-form. These sequence-dependent conformational preference and environmental effects agree roughly with experimental observations, suggesting that the origin of the conformational polymorphism is attributable to the intrinsic conformational preference of base pairs.

Base Sequence↗
PubMed1988

Origin of DNA helical structure and its sequence dependence.

Conformational analysis of DNA shows that the origin of the B-form double helix can be attributed in large part to the atomic charge pattern in the base pairs. The charge patterns favor specific helical stacking of the base pairs. Base pairs alone--without backbones--have a strong tendency to form helix, indicating that the backbones play a rather passive role in determining the basic helical structure of DNA. It is mainly the electrostatic interactions determined by the charge pattern on base pairs that stabilize a particular helical conformation. The charge pattern in the base pairs appears to be responsible for much of the sequence dependence of DNA conformation, rather than steric clashes.

Base Composition↗
PubMed1985

Dissolution rate measurements of sparingly soluble compounds with the Coulter Counter model TAII.

A Coulter Counter, Model TAII was used to determine both solubility and dissolution rate from suspensions of griseofulvin and hydrocortisone acetate, where the initial particle size and shape had been characterized. The method assesses the weights and surface areas of particles remaining undissolved as a function of time. A comparison with a conventional method, assessing dissolved quantities of materials, showed that solubility data of the same order of magnitude can be obtained. The TAII data fitted a previously established equation that linearly relates log solubility and log of the intrinsic dissolution rate and indicated that the dissolution process was not diffusion controlled. The TAII method described is a rapid and convenient means of estimating the solubility and dissolution rate where no adequate technique for analysing the dissolved fraction exists.

Chromatography, High Pressure Liquid↗