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Biomedical subjects

B Roy

Publications and source records attributed to B Roy.

At least 19 recordsLinked to original sources
PubMed1995

Reexpression of retinoic acid receptor (RAR) gamma or overexpression of RAR alpha or RAR beta in RAR gamma-null F9 cells reveals a partial functional redundancy between the three RAR types.

Disruption of retinoic acid receptor (RAR) gamma in F9 embryonal carcinoma cells leads to aberrent differentiation and reduced activation of expression of several all-trans-retinoic acid (RA)-induced genes. We have analyzed the expression of several additional RA-responsive genes in RAR alpha- and RAR gamma-null F9 cells. The RA-induced activation of Cdx1, Gap43, Stra4, and Stra6 was specifically impaired in RAR gamma-null cells, supporting the idea that each RAR may regulate distinct subsets of target genes. To further investigate the role of RAR gamma in F9 cell differentiation, "rescue" cell lines reexpressing RAR gamma 2 or overexpressing either RAR alpha 1 or RAR beta 2 were established in RAR gamma-null cells. Reexpression of RAR gamma or overexpression of RAR alpha restored both target-gene activation and the differentiation potential. In contrast, over-expression of RAR beta only poorly restored differentiation, although it could replace RAR gamma for the activation of target genes. Functional redundancy between the various RARs is discussed.

Animals↗
PubMed1995

Effects of nifedipine and Bay K 8644 on myotropic responses in aortic rings of pregnant rats.

The hypothesis that Ca2+ channel function is altered during pregnancy was tested by comparing responses to potassium chloride (KCl) and phenylephrine in aortic rings of virgin and term-pregnant rats under the influence of nifedipine and Bay K 8644. Maximum response to KCl was progressively reduced by increasing nifedipine concentrations (1.0-100 nM) in both groups of tissues. Nifedipine produced a smaller inhibition of KCl-induced contraction in aortic rings of pregnant than of virgin rats. It exerted little inhibition on the concentration-response curve to phenylephrine. The Ca2+ channel antagonist (100 nM) reduced the maximum response to the alpha-adrenoceptor agonist in rings from virgin rats, but had no effect in pregnant rats. Bay K 8644, a Ca2+ channel activator, potentiated the responses to low concentrations of both phenylephrine and KCl in the tissues of both virgin and pregnant rats, but did not affect maximum responses. It also induced concentration-dependent contractions in rings of virgin but not of pregnant rats. The effects of Bay K 8644 were markedly potentiated by precontracting the aorta with 10mM KCl. Nevertheless tissues from pregnant rats were still less responsive to Bay K 8644. However, when the strips were precontracted to the same level by different concentrations of KCl, the concentration-response curves to Bay K 8644 were identical in both groups. [3H]Nitrendipine binding to membrane preparations of the thoracic aorta was similar in virgin and pregnant rats.(ABSTRACT TRUNCATED AT 250 WORDS)

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1995

Inhibition of ribonucleotide reductase by nitric oxide derived from thionitrites: reversible modifications of both subunits.

Thionitrites are spontaneous nitric oxide (NO) donors in neutral aqueous solutions. Consequently, they inhibit ribonucleotide reductase, the rate-limiting enzyme in DNA synthesis, from Escherichia coli and murine adenocarcinoma TA3 cells. They also inhibit tumor cell proliferation. Reaction of thionitrites with protein R1, the large subunit, results in the nitrosation of cysteines, as shown from the formation of a chromophore with a characteristic absorption at 340 nm. EPR spectroscopy both on whole murine R2-overexpressing L1210 cells and on the pure protein showed that the tyrosyl radical of protein R2, the small subunit, reversibly couples to the NO radical, presumably leading to nitrosotyrosine adducts. Both molecular events might be at the origin of the inhibition of ribonucleotide reductase by NO, since a number of cysteines and the tyrosyl radical are essential for catalysis. These results identify NO donors as a new class of inhibitors of ribonucleotide reductase with potential applications as anticancer or antiviral chemotherapy agents.

Adenocarcinoma↗
PubMed1995

NMR studies of binding of 5-FdUDP and dCDP to ribonucleoside-diphosphate reductase from Escherichia coli.

5-Fluoro-2'-deoxyuridine-5'-diphosphate (5-FdUDP) has been synthesised using an original route, previously applied to the synthesis of natural nucleoside diphosphates. The interaction between 5-FdUDP and the enzyme ribonucleoside-diphosphate reductase (EC 1.17.4.1) has been studied with 19F-NMR. The product analogue is shown to be in fast exchange with substrate binding sites on protein subunit 1 (R1) of ribonucleoside-diphosphate (NDP) reductase. The number of binding sites is reduced to half when the complete holoenzyme R1R2 is formed. The temperature dependence of the line broadening of 5-FdUDP was studied using 19F-NMR, and of dCDP and dUDP using 1H-NMR. The temperature dependences are complex and a molecular model in which R1 is in a temperature dependent equilibrium between at least two conformations is suggested in order to explain the observed behaviour. Binding of a ligand to the substrate binding sites affects the conformational equilibrium in a ligand specific way. Formation of the holoenzyme R1R2 also affects the equilibrium.

Binding Sites↗
PubMed1995

Inducible expression of Mad accelerates growth arrest of serum deprived human glioblastoma cells.

Mad is a basic-helix-loop-helix leucine zipper protein that heterodimerizes with Max. Mad:Max heterodimers recognize the same DNA binding sites as Myc:Max heterodimers. However, Myc and Mad are thought to influence transcription and cell proliferation in opposite ways through interaction with Max. While Myc activates transcription and cell proliferation Mad represses these activities (Ayer et. al., Cell 72, 211-222, 1993). We have constructed an expression vector containing the mad cDNA cloned downstream of an inducible viral promoter. Cell lines carrying the construct were derived by transfection into human glioblastoma cells and the effect of Mad induction on their growth rate was studied. When the cells were cultured in low serum concentrations (0.1%) Mad induction resulted in accelerated growth arrest. These findings are consistent with the proposed growth repression function of the Mad protein.

Basic Helix-Loop-Helix Leucine Zipper Transcriptio↗
PubMed1995

Some aspects of the causes of enhanced immune response of in vitro frozen ascites fibrosarcoma tumor cells in mice.

Estimation of 3 M KCl-extracted ascites fibrosarcoma (AFS) tumor cell membrane peripheral proteins in native and frozen tumor cells showed approximately a three-, four-, and fivefold increase per 1 x 10(6) cells of single-, three-, and programmed three-cycle frozen AFS tumor cells, respectively, compared to the same number of native cells, indicating an increase in surface membrane protein concentration with freezing. The 10% gel (homogeneous) electrophoretic (SDS-PAGE) study of 3 M KCl-extracted native and frozen cell membrane proteins showed (i) membrane proteins of native cells resolve into many more components compared to those of any frozen membranes, i.e., single, three, and programmed three cycle, the components decreasing in that order; (ii) the concentration of larger-molecular-weight protein fractions (> or = 75 kDa) decreases while those of smaller fractions (14 to 24 kDa) increase in frozen cells, with the maximum being in the programmed three-cycle frozen group. In contrast, the native cell membrane is rich in higher-molecular-weight proteins (> or = 75 kDa) with concentrations slowly decreasing toward lower-molecular weight fractions. Thus, the probable reasons for increased immune response of animals immunized with frozen AFS tumor cells are (i) absolute increase in cell surface protein concentrations as given by 3 M KCl extraction of cell membrane peripheral protein estimation in AFS tumor cells postfreeze; (ii) cell-surface protein pattern which is heterogeneous before freezing becomes relatively more homogeneous following freezing of AFS tumor cells; and (iii) depolymerization and breaking of higher-molecular-weight components which increase the concentration of terminal-sequence antigenic determinants and increase accessibility of determinant grouping by removing steric hindrance following freezing.

Animals↗
PubMed1995

Effect of drafting on work intensity in classical cross-country skiing.

The purpose of this study was to compare the heart rate responses during cross-country skiing as a leading skier, as well as in a drafting situation, three meters behind the leader. Eight male and two female cross-country ski racers, paired for skiing ability, skied a 2 km course (two loops of 1 km) using the diagonal stride and double-poling techniques at a fixed speed (4.75 m.s-1 and 4.45 m.s-1 for males and females respectively) on two different occasions, once as a leading skier, the other as a drafter. A recovery period of 30 minutes was allowed between the two trials. Heart rates (HR) were registered every five seconds during all performances. Results revealed that HR were significantly lower (165 vs 172 beats.min-1) when skiing behind another skier as opposed to leading. Results also revealed that projected frontal areas appeared to influence the effects of drafting such that the HR differences between the leading and the drafting situations were larger for smaller skiers drafting behind larger skiers. These results showed that skiing behind another skier in a classical cross-country ski race would be very advantageous when the situation is encountered and could help racers using this energy saving strategy.

Adult↗
PubMed1995

Survivability and leucocyte migration inhibition in mice immunized with cryotreated ascites fibrosarcoma cells using different freeze-thaw cycles.

Attempts have been made to assess as to what extent in vitro assay of cellular immunity, e.g. leucocyte migration inhibition (LMI) in mice immunized with different freeze-thaw cycles could reflect host resistance in vivo. While survivability of animals improved significantly by immunization with single cycle (P < 0.05) to three cycle (P < 0.001) and programmed three cycle (P < 0.001) cryo-treated tumor cells compared to controls, the percentage LMI in the same groups of animals decreased progressively. The KCl(3M) extracted tumor cell protein (antigen) of both viable and cryo-treated cells showed a progressively increased protein concentrations per 1 x 10(6) tumor cells with viable cells being least and programmed three cycle cryo-treated cells highest. The apparent discrepancy observed between percentage migration inhibition and survivability may be due to the fact that (1) survivability is a function of body's total immune response while LMI represents the response of one effector limb only; (2) immuno-regulatory mechanisms depend on a balance between activation and suppression and suppressor cells being more sensitive and of shorter life span, affect migration inhibition but not the survivability; (3) cryo-treatment alters tumor cell surface antigen affecting immunological balance; and (4) suppressor and antitumor activities against antigenic stimulation develop simultaneously in different organs and LMI performed with sensitized splenic cells, where, perhaps, suppressor cell activity dominates.

Animals↗
PubMed1993

Rapid selection of donor myoblast clones for muscular dystrophy therapy using cell surface expression of NCAM.

This study describes an easy 3 step-procedure to prepare rapidly and at low cost, pure myoblast cell cultures from a normal muscle biopsy. Following collagenase and trypsin treatment of the tissue (step 1), dissociated cells were cloned at a density of 10 cells/ml in MCDB 120 medium (0.2 ml/well). Clones that grew were then tested for NCAM cell surface expression by cytofluorometric analysis (CFA) using Coulter CD56-PE monoclonal antibodies (step 2). Only those clones with more than 98% strongly labelled positive cells were expanded (step 3) for further trials in cell transfer therapy for dystrophic patients. Visualization of the pattern of NCAM expression was performed by immunoperoxidase assay, while the potential ability to form myotubes was confirmed by the observation of their formation within a period of 1 to 2 weeks. The 65% of the CD56+ clones in CFA were the same clones that proved to be myogenic with positive immunoperoxidase assay and myotube formation. This method avoids the fastidious and costly approach of cell sorting (whenever available), avoids contamination hazards due to many manipulations of the clones. Moreover this approach leads to a pure myoblast population free of any contaminating fibroblast which could contribute to connective tissue implement already deleterious in dystrophic patients.

Antibodies, Monoclonal↗
PubMed1992

8-Azidoadenosine and ribonucleotide reductase.

Inhibitors of ribonucleotide reductase are potential antiproliferative agents, since they deplete cells from DNA precursors. Substrate nucleoside analogues, carrying azido groups at the base moiety, are shown to have strong cytostatic properties, as measured by the inhibition of the incorporation of thymidine into DNA. One compound, 8-azidoadenosine, inhibits CDP reduction in cytosolic extracts from cancer cells. The corresponding diphosphate behaves as a substrate for ribonucleotide reductase while the triphosphate is an allosteric effector.

Adenosine↗
PubMed1992

Seasonal prevalence of some zoonotic trematode infections in cattle and pigs in the north-east montane zone in India.

Seasonal variations in the prevalence of Fasciola gigantica and Eurytrema pancreaticum in cattle, and Opisthorchis noverca, Artyfechinostomum malayanum, Fasciolopsis buski and Gastrodiscoides hominis in pigs, were studied post-necropsy over a 1 year period in a humid, subtropical north-east hilly region in India. The overall prevalence rate was 53.02% in cattle (n = 960) and 12.92% in pigs (n = 960). Fasciola gigantica and E. pancreaticum occurred throughout the year with peaks during cold winter months. Both species showed a high intensity of infection in winter and a low intensity during summer and autumn. The rate of infection due to A. malayanum, Fasciolopsis buski and G. hominis rose to a peak during June-September and thereafter declined to a low level (November-March). Except for the month of February, O. noverca occurred throughout the year, with the highest rate of infection in late autumn and winter. The abundance of infection due to A. malayanum, Fasciolopsis buski and G. hominis was high during late summer and early autumn. Opisthorchis noverca showed a higher density during late autumn and winter.

Animals↗
PubMed1992

Production of manganic chelates by laccase from the lignin-degrading fungus Trametes (Coriolus) versicolor.

Many ligninolytic basidiomycete fungi have been shown to secrete a group of peroxidase isozymes whose sole function appears to be the peroxide-dependent oxidation of manganous [Mn(II)] to manganic [Mn(III)] ions. Manganic chelates and these Mn peroxidases have been implicated as central to the degradation of various natural and synthetic lignins and lignin-containing effluents by white rot (ligninolytic) fungi. Another group of enzymes, the laccases, are commonly secreted by wood-rotting fungi, but are generally regarded as being able to oxidize (and usually polymerize) only phenolic substrates. In this report it is shown that in the presence of appropriate oxidizable phenolic accessory substances or primary substrates, a variety of laccases and peroxidases catalyzing one-electron oxidations can also produce Mn(III) chelates from Mn(II).

Chelating Agents↗
PubMed1992

Influence of dermal equivalent maturation on the development of a cultured skin equivalent.

Histologic and immunofluorescence methods were used to analyse the presence of fibronectin, chondroitin-4-sulphate and chondroitin-6-sulphate, type III and IV collagens, laminin, and keratins to assess the maturation level of cultured dermal and skin equivalents. In a first phase, fibroblasts in monolayer culture were compared with dermal equivalents in which fibroblasts are embedded in a type I collagen gel. Different fluorescent patterns were observed depending on the culture system used. A sequential appearance of macromolecules was noticed in dermal equivalents. Fibronectin was first detected after 4 days of culture, whereas chondroitin-4-sulphate and chondroitin-6-sulphate and type III collagen were present after 7 days. In contrast, all three macromolecules were detected at 24 h of culture in fibroblastic monolayer cultures. In a second phase, the quality of our skin equivalents was evaluated according to the seeding time of epidermal cells upon dermal equivalents (1, 4, or 7 days). A satisfactory stratification was obtained when keratinocytes were seeded after 4 and 7 days of dermal equivalent culture. Laminin and fibronectin were detected at the dermo-epidermal junction, but type IV collagen was absent. Various keratins, as detected by the AE1, AE2, and AE3 antibodies, were present in the epidermal layer. Following keratinocyte confluence, a change in the organization pattern of type III collagen in the dermal fraction of the skin equivalent was also noticed. Our comparative results show that seeding of epidermal cells on a more mature dermal equivalent leads to improved differentiation status of the epidermal layer.

Cell Division↗
PubMed1992

Propulsive and gliding phases in four cross-country skiing techniques.

The purpose of this study was to compare the relative durations of the propulsive and gliding phases between three skating techniques (1-skate, 2-skate, and offset) and the diagonal stride technique in elite cross-country skiers. Nine skiers of provincial and national level were videotaped with a Panasonic AG 170 camera. The camera speed was set at 30 frames.s-1 and the shutter speed at 1/500 s. The athletes were asked to ski at approximately 80% of their maximal skiing speed on a flat (50 m long) and on an uphill course (35 m long, 5 degrees grade). The relative propulsive phases of the skating techniques were significantly longer than those of the diagonal stride. The relative gliding phases were also longer with the skating techniques. In addition, velocities obtained while skiing with the diagonal stride were about 16% slower than those attained with the skating techniques, principally related to the longer cycle lengths observed with the skating techniques, while cycle rates were quite similar between all four techniques. The results of this study suggest that the longer relative phases of propulsion with the skating techniques may explain the greater speed attained with these techniques in comparison with the diagonal stride.

Gait↗
PubMed1991

Purification and properties of the low-molecular-weight alpha-crystallin from normal goat lens: comparison with bovine lens.

Low-molecular-weight alpha-crystallin (alpha L-crystallin) isolated from decapsulated lens of goat (Capra hiscus) has been purified to an apparently homogeneous population. Goat alpha L-crystallin closely resembles its bovine counterpart in size, shape, exposition of sulfhydryl groups, subunit composition and the nature of its UV-absorption profile. Like bovine alpha L-crystallin, dissociated subunits of goat alpha L-crystallin assemble upon reassociation into a particle of almost half the size of the native one. However, subunits of goat alpha L-crystallin are found to contain more aromatic amino acid residues than those of bovine subunits leading to a higher value of extinction coefficient (E1cm1%) at 280 nm for the goat protein.

Amino Acids↗
PubMed1991

Human myoblast transplantation: a simple assay for tumorigenicity.

A simple assay for tumorigenicity of myoblasts to be transplanted to Duchenne patients has been developed. The assay is based on culture in a soft agar medium for 2-3 weeks. The tumor cell line forms large cell clusters while the normal myoblasts do not proliferate and remain isolated.

Cell Transformation, Neoplastic↗
PubMed1991

A comparison of three skating techniques and the diagonal stride on heart rate responses and speed in cross-country skiing.

The purpose of this study was to compare the heart rate responses and the speed of three different skating techniques and the diagonal stride in cross-country skiing. The subjects were ten elite male cross-country ski racers, 16 to 25 years of age. They skied a 3.04-km loop of various terrain four separate times, using a different technique for each trial. A thirty-minute recovery period was allowed between each trial. Heart rate and skiing velocities were analyzed over a flat, an uphill, and a downhill section, as well as for the total loop. No significant differences (p greater than 0.05) were found in heart rate values between the four techniques on all sections of the course, while heart rates were significantly different over the three different sections. Skiing velocities were significantly different (p less than 0.05) between the diagonal stride and all skating techniques, the diagonal stride being the slowest technique, and this, for all sections. Energy costs while skiing were estimated on the basis of individual HR/VO2 curve determined under laboratory conditions. Since no differences in HR were found between the four techniques, no differences in energy costs were found. These energy costs represented between 69 and 73% of max VO2, and between 87 and 89% of max HR for the 3.04-km loop. Thus, for the same estimated energy expenditure, greater speeds (16%) were achieved with the skating techniques than with the diagonal stride.

Acceleration↗