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Biomedical subjects

R Durand

Publications and source records attributed to R Durand.

At least 73 records · Page 4Linked to original sources
PubMed1985

Mitochondrial DNA expression in Drosophila melanogaster: neosynthesized polypeptides in isolated mitochondria.

The expression of mitochondrial genome of D. melanogaster in isolated mitochondria was followed by incorporation of 35S methionine in neosynthesized polypeptides. A high level of protein synthesis was obtained after optimization of all the incubation parameters. Two kinds of energy-generating systems were used: an endogenous system where an oxidizable substrate were added for ATP synthesis; an exogenous system with an energy-rich compound for ATP regeneration, the latter proved to be the most effective. The effect of the oxidative phosphorylation uncoupler (Clccp), and an ATPase inhibitor (oligomycine) allow us to postulate the role of the electrochemical potential in the expression of the mitochondrial genome. Electrophoresis and autoradiography of neosynthesized mitochondrial proteins exhibits 18 to 24 protein bands, ranging from 6.5 to 65 Kd; incubation of KC 0% drosophila cells with 35S methionine and cycloheximide gave similar results. Both our results and those published elsewhere suggest that the expression of mitochondrial genome in higher organisms could be more complex than simple translation of the 13 genes presents on these genomes.

Animals↗
PubMed1984

Complex RNA chain elongation kinetics by wheat germ RNA polymerase II.

Kinetics of RNA chain elongation catalyzed by wheat germ RNA polymerase II have been studied using various synthetic DNA templates in the presence of excess dinucleotide monophosphate primers. With single- or double-stranded homopolymer templates, the double reciprocal plots 1/(velocity) as a function of 1/(nucleotide substrate) exhibit positive, negative or no curvature. With poly(dAT) as template, the mechanism of nucleoside monophosphate incorporation into RNA is not the ping-pong kinetic mechanism which was derived for E. coli RNA polymerase (6). Noncomplementary nucleoside triphosphates inhibit RNA transcription allosterically. Cordycepin triphosphate behaves as ATP, and not only inhibits AMP incorporation but also that of UMP and GMP on appropriate templates. The reason for this complex kinetic behavior is not yet understood. Possibilities are raised that there are several nucleoside triphosphate binding sites on wheat germ RNA polymerase II, that additional nucleoside triphosphate dependent enzymatic activities are required for reaction to occur or that the Km value for incorporation of a given nucleoside monophosphate into RNA is dependent on the length of the RNA chain and/or the nucleotide sequence surrounding the complementary base on the DNA template.

Kinetics↗
PubMed1984

[Isolation of the RNA-poly A+ fraction from mitochondria of Drosophila melanogaster embryos. Incorporation of methionine-35S into newly-synthesized proteins in whole and lysed mitochondria].

The poly A+ RNA fraction of embryos mitochondria of Drosophila melanogaster was prepared by fractionation by oligo dT-cellulose chromatography. It accounted for 5% of total insoluble RNA. 15 bands were identified by electrophoresis, from 500 to 2,000 base pairs. This poly A+ RNA fraction hybridizes with mitochondrial DNA clones. It contains mitochondrial transcripts: messenger RNA and the large ribosomal RNA. The sum of the transcripts (29 kb) exceed the coding capacities of the mitochondrial DNA. Some of the transcripts may be precursors, greater in size, of the mRNA corresponding to a gene. Our results are compared to those previously published (9, 11, 12). The relationship between mitochondrial transcripts and proteins was studied in whole and lysed isolated mitochondria. In the former, incubated in the presence of 35S-methionine, 20 to 30 radioactive bands were identified (M. Wt. 100 to 16 kd). This incorporation was totally inhibited by chloramphenicol. When the mitochondria were opened in the presence of detergent (lysis). 35S-methionine incorporation was markedly enhanced. In all cases the number of proteins identified was greater than the number of potential genes (12). This finding is discussed.

Animals↗
PubMed1984

Newborn ethical dilemmas: intensive care and intermediate care nursing attitudes.

A self-administered questionnaire concerning various neonatal ethical issues was completed by 39 ICU and 36 intermediate care unit (INT) nurses. Guttman scale analysis indicated that ICU nurses were more reluctant than INT nurses to resuscitate certain high-risk newborn infants. Work experience and a stated religious preference accentuated an INT nurse's disinclination to resuscitate high-risk babies. ICU nurses were more likely than INT nurses to favor passive and active euthanasia. Further, ICU nurses were more likely than INT nurses to view termination of life support for a sick infant as a necessity. ICU nurses were less likely than INT nurses to favor physician intervention in the care of all acutely sick neonates. ICU and INT nurses agreed, however, that the decision to terminate a baby's life support should be made jointly by the child's parents and physicians. Although differences in ICU and INT nursing attitudes may reflect quantitative and qualitative differences in work experience, these findings suggest a common need for emotional support and continuing education programs for nurses who care for high-risk newborns.

Adult↗
PubMed1983

Comparative transcription of right- and left-handed poly[d(G-C)] by wheat germ RNA polymerase II.

The template properties of left-handed synthetic polymers, the Z* form of poly[d(G-C)] and the Z form of poly[d(G-m5C)], have been investigated using an eucaryotic RNA polymerase, the class II enzyme from wheat germ. Results from a comparative kinetic study of transcription using the polynucleotide substrates in the B and Z conformations are reported. Optimal conditions for enzyme activity compatible with the preservation of the desired template conformation were determined. On the basis of several criteria, both physical (c.d. spectra of the polymers, sedimentability of the Z* form) and biochemical, it was demonstrated that the left-handed conformations of poly[d(G-C)] and poly[d(G-m5C)] serve as templates for wheat germ RNA polymerase II. The level of incorporation was less than that exhibited by the B form of poly[d(G-C)], the relative activity being a function of the precise experimental conditions. Activity ratios (Z*/B or Z/B) ranged from 0.1 to 0.5. The effect of various incubation parameters, including pH, salt concentration, temperature, and the presence of dinucleoside monophosphate primers were investigated. The Km values for nucleoside triphosphate substrates were slightly smaller for the Z* form of poly[d(G-C)] than for the B conformation. Titration of DNA (Z* or B) with enzyme and reciprocal experiments suggested that the reduced activity of left-handed templates might derive from the availability of fewer and/or lower affinity sites for initiation and/or translocation on these templates. Specific antibodies raised against left-handed DNA strongly inhibited the observed transcription of Z* and Z DNAs by wheat germ RNA polymerase II.

Ammonium Sulfate↗
PubMed1983

High-performance liquid chromatographic analysis of MTX, 7-OH-MTX and MTX derivatives: application to intracellular metabolism in tumor cells (HT 29).

In order to study the intracellular metabolism of Methotrexate (MTX) and the cytotoxicity of the antifolates, a specific paired-ion HPLC method has been developed which permits the simultaneous determination of DAMPA, MTX, 7-OH-MTX, MTX-G1, MTX-G2 and MTX-G3. Cells were incubated with 3H-MTX. The MTX metabolites were extracted, purified on SEP-PAK cartridges and further analysed by high-performance liquid chromatography (HPLC). The stationary phase was constituted by a C18 muBondapak and the mobile phase by 5 mM phosphate buffer (pH 7.4) containing 2.5 mM tetrabutylammonium nitrate. The elution was performed with a linear methanol gradient (20--30%). HPLC fractions were collected and radioactivity evaluated by beta counting (retention times: DAMPA = 12.93 min; MTX = 18.29 min; 7-OH-MTX = 21.13 min; MTX-G1 = 22.69 min; MTX-G2 = 26.81 min; MTX-G3 = 30.61 min). This analytical procedure was applied to separate and characterize multiple forms of MTX polyglutamate derivatives in HT 29, a human adenocarcinoma cell line varying the incubation time (4--18 h) and MTX concentration (0.6--10.6 micrometer). The incorporation process seems to be characteristic of a cell line resistant to MTX. The incorporation were very low and after a 4-h exposure time only 5% of the MTX was converted to polyglutamates. Between 1.6 and 10.6 microM MTX, no difference was observed in the polyglutamization. The defect in the incorporation of the drug and in the metabolization process in vitro could partially explain the failure of the MTX treatment in colorectal cancer.

Adenocarcinoma↗
PubMed1982

Non-processive transcription of poly[d(A-T)] by wheat germ RNA polymerase II.

RNA product distribution obtained during the transcription of poly[d(A-T)] by wheat germ RNA polymerase IIA under various experimental conditions was analyzed by high resolution polyacrylamide gel electrophoresis. Poly[r(A-U)] synthesis proceeded as if wheat germ RNA polymerase II was a non-processive enzyme: a ladder of RNA products of increasing lengths was obtained, which apparently, terminated at every other nucleotide. RNA release was not dependent upon nucleoside triphosphate substrate concentrations. A likely explanation would be that ternary complexes enzyme: DNA: RNA were very much unstable; moreover, oligonucleotides released were not re-used for further elongation by the enzyme.

DNA-Directed RNA Polymerases↗
PubMed1982

Metabolic type of muscles of the sheep. III. evolution with age and influence of sex.

Myofibrillar ATPase activity (in the presence of Ca2+ and Mg2+), activities of various glycolytic and mitochondrial enzymes, and haemin iron, glycogen, ATP and lactic acid levels were determined in the heart and five skeletal muscles of the sheep as a function of age and sex. During growth from 2 to 13 months, ATPase activity remained stable whereas most mitochondrial and glycolytic activities tended to decrease, particularly between 2 and 6 months. The isoenzyme composition of lactic dehydrogenase evolved markedly, with in particular a rise in the percentage of M4. Haemin iron level rose from 6 months. These modifications occurred in most of the skeletal muscles but rarely in the heart. Glycogen and ATP decreased progressively between 2 and 13 months. Overall, results indicated a regression of the metabolic differentiation among muscles between 2 and 13 months, particularly marked before 6 months. At 3 and 7 months, sex had practically no influence on the enzyme activities studied.

Adenosine Triphosphatases↗
PubMed1982

Intergovernmental relations in physician education and health planning: state adoption decisions and the impact of federal programs.

This study seeks to explain states' adoptions of programs in health planning and in physician education. It also seeks to further understanding of the impact of federal health planning and education programs on the states. Several theories and models are employed in analyzing the actions of state decision-makers. These include incremental theory, models of the diffusion of innovations, economic resources theory, and a theory of competitive partisanship. The data utilized in this research were principally derived from intensive interviews with "key" state actors and from historical, documentary materials. Only minimal federal impact appears on states' goals in physician education and health planning. Rather, there is evidence of considerable innovativeness among the states prior to Federal program initiatives. A problem-generated search for solutions seems to be a major source of this innovation. Finally, federal program implementation requirements appear to be a major source of federal--state conflict and opposition.

Diffusion of Innovation↗
PubMed1982

Enzymatic properties and cooperative effects in the kinetics of wheat-germ RNA polymerases. A comparative study of the three nuclear enzyme classes.

Some of the enzymatic properties of the three classes of RNA polymerase purified from wheat germ were studied. Although the four enzyme species exhibited different template specificities using synthetic polydeoxyribonucleotides, poly(dC) was the most efficiently transcribed. Furthermore, with this matrix all enzyme forms had nearly the same specific activity (approximately equal to 5500 units/mg). A comparative kinetic study of RNA synthesis catalyzed by the wheat germ RNA polymerases lead to the following results: when rate measurements were effected as a function of the concentration of purine nucleoside triphosphates, non-linear double-reciprocal plots were obtained for polymerases I and IIB, whereas linear plots were obtained for RNA polymerases IIA and III. The reaction rates were also measured as a function of UTP concentration (a nucleoside triphosphate which can only be used in the elongation step): the kinetics of the reactions catalyzed by RNA polymerases IIA and III can be accounted for by a simple ping-pong kinetic model; in contrast, negative cooperativity was obtained for enzymes I and IIB. This kinetic behaviour may signify that RNA polymerases I and IIB are allosterically regulated enzymes.

Cell Nucleus↗
PubMed1981

Metabolic types of muscle in the sheep: I. Myosin ATPase, glycolytic, and mitochondrial enzyme activities.

The metabolic characteristics of 12 skeletal muscles of the sheep were studied. Glycolytic activities (hexokinase, glycogen synthetase I and D, phosphorylase a and b, phosphofructokinase) were measured. Myofibrillar ATPase activity was evaluated. Oxygen consumption, respiratory control and carnitine palmityl transferase, isocitrate dehydrogenase, succinate dehydrogenase and cytochrome oxidase activities were measured in isolated mitochondria. Three metabolic types could be distinguished; (1) essentially oxidative slow twitch muscles, typified by the supraspinatus and infraspinatus, having low ATPase activity, (2) fast twitch red muscles, typified by the longissimus dorsi and the semimembranosus, having a higher ATPase activity and both high oxidative and high glycolytic activity, and (3) essentially glycolytic fast twitch muscles, typified by the tensor fascia lata and the semitendinosus, having the highest ATPase activity.

Adenosine Triphosphatases↗
PubMed1981

Metabolic types of muscle in the sheep: II. Lactate dehydrogenase activity and LDH isoenzyme distribution.

Lactate dehydrogenase activity and isoenzyme distribution were measured in fast-twitch red, slow-twitch red and fast-twitch white muscles in the sheep. Total enzyme activity is higher in fast-twitch muscles irrespective of their colour type. Isoenzymes M4 and H4 bear an inverse relationship, M4 being predominant in fast-twitch red and white muscles, and H4 in heart muscle and slow-twitch red muscles.

Animals↗