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F T Dionne

Publications and source records attributed to F T Dionne.

36 records · Page 2Linked to original sources
PubMed1993

Mitochondrial DNA sequence polymorphism, VO2max, and response to endurance training.

Mitochondrial DNA sequence variation was determined in 46 sedentary young adult males who took part in ergocycle endurance training programs in two laboratories to assess whether mitochondrial DNA variants were associated with individual differences in maximal oxygen uptake (VO2max) and its response to training. VO2max was obtained from a progressive ergocycle test to exhaustion. White blood cell mitochondrial DNA was characterized with the restriction fragment length polymorphism (RFLP) technique using 22 restriction enzymes and human mitochondrial DNA as a probe for hybridization. Multiple mitochondrial DNA variants were detected with 15 of the enzymes. Some subjects exhibited many RFLPs, while others showed no variation. These RFLPs (morphs) were generated by base substitutions located in gene regions coding for mitochondrial proteins as well as in the noncoding regions. Carriers of three mitochondrial DNA morphs, two in the subunit 5 of the NADH dehydrogenase gene and one in the tRNA for threonine, had a VO2max (ml.kg-1.min-1) in the untrained state significantly higher than noncarriers, while carriers of one mitochondrial DNA morph in subunit 2 of NADH dehydrogenase had a lower initial VO2max. Endurance training increased VO2max by a mean of 0.5 l of O2, with individual differences ranging from gains of 0.06 to 1.03. After adjustment for training site and initial VO2max, a lower response was observed for three carriers of a variant in subunit 5 of the NADH dehydrogenase detected with HincII (mean gain of 0.28 l; P < 0.05). These results suggest that sequence variation in mitochondrial DNA may contribute to individual difference in VO2max and its response to training.

Adolescent↗
PubMed1991

Mitochondrial DNA sequence polymorphism, VO2max, and response to endurance training.

Mitochondrial DNA sequence variation was determined in 46 sedentary young adult males who took part in ergocycle endurance training programs in two laboratories to assess whether mitochondrial DNA variants were associated with individual differences in maximal oxygen uptake (VO2max) and its response to training. VO2max was obtained from a progressive ergocycle test to exhaustion. White blood cell mitochondrial DNA was characterized with the restriction fragment length polymorphism (RFLP) technique using 22 restriction enzymes and human mitochondrial DNA as a probe for hybridization. Multiple mitochondrial DNA variants were detected with 15 of the enzymes. Some subjects exhibited many RFLPs, while others showed no variation. These RFLPs (morphs) were generated by base substitutions located in gene regions coding for mitochondrial proteins as well as in the noncoding regions. Carriers of three mitochondrial DNA morphs, two in the subunit 5 of the NADH dehydrogenase gene and one in the tRNA for threonine, had a VO2max (ml.kg-1.min-1) in the untrained state significantly higher than noncarriers, while carriers of one mitochondrial DNA morph in subunit 2 of NADH dehydrogenase had a lower initial VO2max. Endurance training increased VO2max by a mean of 0.51 of O2, with individual differences ranging from gains of 0.06 to 1.03. After adjustment for training site and initial VO2max, a lower response was observed for three carriers of a variant in subunit 5 of the NADH dehydrogenase detected with HincII (mean gain of 0.28 I; P less than 0.05). These results suggest that sequence variation in mitochondrial DNA may contribute to individual difference in VO2max and its response to training.

Adolescent↗
PubMed1989

Mitochondrial DNA polymorphism detected with the restriction enzymes BstNI and BclI in a French Canadian population.

The enzymes BstNI and BclI were used to detect various human mitochondrial DNA RFLPs in a sample of 104 unrelated French Canadians. These sequence variations were found in total white blood cell DNA probed with whole human mitochondrial DNA. With BstNI, 6 mitochondrial DNA restriction patterns (morphs) were identified. BstNI morphs 2-6 each differ from morph 1 by one single distinct restriction site gain or loss on the mitochondrial DNA molecule. Although BstNI morph 1 was found in most of the subjects (80%), each other morph was observed at a frequency of at least 3%. With the enzyme BclI, 4 different morphs were detected. Morphs 2-4 also result from different single restriction site alteration as compared with BclI morph 1. The morph 1 was clearly the most frequent (95%) while morphs 3 and 4 were present in only 1% of the subjects. These data indicate that the enzyme BstNI and, to a much lesser extent, the enzyme BclI detect mitochondrial DNA polymorphism in Caucasians. They are therefore of interest for population genetics studies.

Canada↗
PubMed1986

Recovery of biologically functional messenger RNA from agarose gels by passive elution.

A general method for isolating biologically active messenger RNA (mRNA) from agarose gels is reported. Purified cellular RNA is resolved by preparative agarose gel electrophoresis and recovered in high yields (80%) by passive diffusion. Polyadenylated mRNA isolated from the eluted RNA is functionally intact based on the ability of the RNA to serve as a template in cell-free translation systems and complementary DNA synthesis reactions. The entire procedure is simple and rapid. A substantial purification of the mRNAs coding for skeletal muscle myosin heavy chain, light chain subunits and carbonic anhydrase III has been achieved employing this method.

Animals↗
PubMed1983

Induction of acid phosphatase synthesis in canine prostatic epithelial cells in vitro.

The increase in acid phosphatase (AP) activity in cultured canine prostatic epithelial cells was investigated as a biochemical marker of in vitro cellular differentiation. The enzyme was studied in secretory and non-secretory epithelial cell populations obtained from control and cycloheximide-treated cultures over a period of 3 weeks and compared to the AP present in tissue and cellular extracts from normal canine prostates. The progressive increase in AP activity with the duration of culture was strongly inhibited by cycloheximide in both cell populations. The degree of inhibition was more pronounced late in the culture when AP activity increased at a faster rate in secretory cells. Cycloheximide inhibited protein biosynthesis by 70-80% as evidenced by a reduction in the incorporation of amino acids into acid-insoluble material. However, the specific activities of AP in the cellular extracts were similar in control and cycloheximide-treated cultures and increased sharply by 3-4-fold in the secretory cells after 12 days of culture. When extracts derived from control and cycloheximide-treated cells of various duration were submitted to electrophoresis in polyacrylamide gels (PAGE), a unique pattern of three bands of AP activity with Rf values of 0.18, 0.27 and 0.38 was obtained. In controls the AP activity in the band with an Rf of 0.18 increased preferentially during the culture period and was more important quantitatively in secretory cells. In cycloheximide-treated cultures the increase of AP activity associated with the band with an Rf of 0.18 was more strongly inhibited. The addition of tartrate to the staining mixture inhibited all three bands of AP activity. Similar results were obtained when extracts derived from freshly dispersed cells as well as from normal canine prostatic tissue were submitted to PAGE; the AP activity was resolved into 3 bands with Rf values of 0.15-0.18, 0.23-0.27 and 0.33-0.38; all three bands were inhibited by the addition of tartrate and the first band was predominant. Thus, the increase in AP activity in prostatic epithelial cells in a culture medium supplemented with serum and deprived of sex steroids is due to the de novo synthesis of a major form of the enzyme by the secretory cells.

Acid Phosphatase↗
PubMed1983

Regulation of the pro-opiomelanocortin mRNA levels in rat pituitary by dopaminergic compounds.

Dopamine-containing neurons directly innervate the intermediate lobe of the pituitary and dopaminergic compounds exert inhibitory effects on the secretion and the content of alpha-melanocyte-stimulating hormone and beta-endorphin in this tissue. In this study, we have investigated the effects of dopamine receptor agonists and antagonists on the level of pro-opiomelanocortin (POMC) mRNA in rat pituitary. RNAs isolated from neurointermediate pituitary (NIP) or anterior pituitary were spotted on nitrocellulose filters and the levels of POMC mRNA were quantified by hybridization to a POMC-specific complementary DNA probe coupled with autoradiography and densitometry. Administration of a dopamine receptor antagonist, haloperidol (2 mg/kg per day), to adult female rats resulted in a 3- to 5-fold increase in POMC mRNA level in the NIP. Treatment with the dopamine agonist 2-Br-alpha-ergocryptine (1 mg/kg per day) decreased significantly the content of POMC mRNA in the NIP. These drugs had no apparent effect on the POMC mRNA levels in the anterior pituitary. The effect of haloperidol and ergocryptine on POMC mRNA in the NIP is time- and dose-dependent. The elevation of POMC mRNA content in the NIP by haloperidol can be observed as early as 6 hr after treatment. These effects of dopaminergic compounds can also be demonstrated in adult male and ovariectomized female rats. The beta-endorphin content of the NIP, as measured by radioimmunoassay, and the de novo synthesis of POMC, as determined by radioactive amino acid labeling and two-dimensional gel electrophoresis analysis, also show negative regulation by dopaminergic compounds.

Animals↗
PubMed1979

Interaction of spironolactone with rat skin androgen receptor.

Some characteristics of the dorsal skin cytoplasmic androgen receptor (AR) have been studied in male rats. The affinity constant, the binding specificity, and the sedimentation profile of the receptor have been found to be similar to the rat prostate AR. The measurement of the number of binding sites in various hormonal conditions (deprivation) led to the conclusion that this receptor was largely occupied by endogeneous hormones from gonadal and (or) adrenal sources. Administration of spironolactone or canrenone to 7-day-castrated rats was accompanied by a rapid and drastic decrease of available binding sites. This diminution was ascribed to the competitive inhibition of canrenone, the active in vivo metabolite of spironolactone. It is postulated that the antiandrogenic action of spironolactone, at the skin level, is mediated by canrenone which inhibits the formation of specific testosterone and (or) 5 alpha-dihydrotestosterone receptor complex in cytoplasm and consequently in nuclei.

Adrenalectomy↗
PubMed1978

Progestin binding in testes from three siblings with the syndrome of male pseudohermaphroditism with testicular feminization.

We have found a specific binding protein for synthetic progestins 6,7-[3H]methyltrienolone (R1881) and 17,21-dimethyl-19-norpregna-4,9-diene-3,20-dione (R5020) and in the testis cytosol from three "sisters" with the complete form of the testicular feminization syndrome. The binding component sediments in the 8S region of sucrose gradients. It is saturable. The apparent affinity constant (Ka) for R5020 was determined in two cases and found to be 1.8 and 0.6 X 10(8) M-1. The number of binding sites calculated from Scatchard plots is relatively high: 572 and 826 fmol/mg protein. Competition studies indicate that this putative receptor is specific for natural and synthetic progestins but not for 5 alpha-dihydrotestosterone and cortisol. Similar progestin binding could not be found in normal human and rat testes.

Adult↗
PubMed1977

Apparent saturability of a 4S dihydrotestosterone-binding protein in rat muscle cytosol: role of 3 alpha-hydroxysteroid dehydrogenase and albumin.

In our studies of the binding of steroids in rat skeletal muscles, we have shown the existence of a saturable '4S' dihydrotestosterone-binding protein of low affinity (Kd = 1.16 X 10(-6) M). Competition studies led us to believe that the binding of dihydrotesterone (DHT) was due to 3 alpha-hydroxysteroid dehydrogenase (3 alpha-OHSD) enzyme responsible for the conversion of DHT to androstanediol (Adiol). Indeed, both the binding and the enzymatic activity are inhibited by various 3-keto steroids. In addition, the dissociation constant (Kd) and the Michaelis constant (Km) of the enzyme are similar. However, experiments with ammonium sulfate fractions of the cytosol have shown a partial separation of the binding and of the enzymatic activity. On the other hand, we have established that DHT (3 micrometer) is almost completely metabolized to Adiol during a 2-h incubation of 0 degrees C even in the absence of added coenzymes. Furthermore the '4S' protein binds Adiol more strongly than DHT and this binding is not saturable. Finally the binding behaviour of both DHT and Adiol with either muscle cytosol or rat albumin is similar when subjected to ammonium sulfate fractionation and sucrose density gradient centrifugation. In conclusion, the skeletal muscle 3 alpha-OHSD rapidly metabolizes DHT into Adiol which then binds strongly to a nonspecific binding protein, presumably rat serum albumin. Thus it can be said that the observed saturability of DHT binding is only apparent.

3-Hydroxysteroid Dehydrogenases↗