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Y Roux

Publications and source records attributed to Y Roux.

5 recordsLinked to original sources
PubMed1999

Simultaneous expression of NAD-dependent isocitrate dehydrogenase and other krebs cycle genes after nitrate resupply to short-term nitrogen-starved tobacco

Mitochondrial NAD-dependent (IDH) and cytosolic NADP-dependent isocitrate dehydrogenases have been considered as candidates for the production of 2-oxoglutarate required by the glutamine synthetase/glutamate synthase cycle. The increase in IDH transcripts in leaf and root tissues, induced by nitrate or NH4+ resupply to short-term N-starved tobacco (Nicotiana tabacum) plants, suggested that this enzyme could play such a role. The leaf and root steady-state mRNA levels of citrate synthase, acotinase, IDH, and glutamine synthetase were found to respond similarly to nitrate, whereas those for cytosolic NADP-dependent isocitrate dehydrogenase and fumarase responded differently. This apparent coordination occurred only at the mRNA level, since activity and protein levels of certain corresponding enzymes were not altered. Roots and leaves were not affected to the same extent either by N starvation or nitrate addition, the roots showing smaller changes in N metabolite levels. After nitrate resupply, these organs showed different response kinetics with respect to mRNA and N metabolite levels, suggesting that under such conditions nitrate assimilation was preferentially carried out in the roots. The differential effects appeared to reflect the C/N status after N starvation, the response kinetics being associated with the nitrate assimilatory capacity of each organ, signaled either by nitrate status or by metabolite(s) associated with its metabolism.

Journal Article↗
PubMed1999

Glutamine synthetase in the phloem plays a major role in controlling proline production

To inhibit expression specifically in the phloem, a 274-bp fragment of a cDNA (Gln1-5) encoding cytosolic glutamine synthetase (GS1) from tobacco was placed in the antisense orientation downstream of the cytosolic Cu/Zn superoxide dismutase promoter of Nicotiana plumbaginifolia. After Agrobacterium-mediated transformation, two transgenic N. tabacum lines exhibiting reduced levels of GS1 mRNA and GS activity in midribs, stems, and roots were obtained. Immunogold labeling experiments allowed us to verify that the GS protein content was markedly decreased in the phloem companion cells of transformed plants. Moreover, a general decrease in proline content in the transgenic plants in comparison with wild-type tobacco was observed when plants were forced to assimilate large amounts of ammonium. In contrast, no major changes in the concentration of amino acids used for nitrogen transport were apparent. A (15)NH(4)(+)-labeling kinetic over a 48-hr period confirmed that in leaves of transgenic plants, the decrease in proline production was directly related to glutamine availability. After 2 weeks of salt treatment, the transgenic plants had a pronounced stress phenotype, consisting of wilting and bleaching in the older leaves. We conclude that GS in the phloem plays a major role in regulating proline production consistent with the function of proline as a nitrogen source and as a key metabolite synthesized in response to water stress.

Journal Article↗
PubMed1999

Decrease in carotid intima-media thickness after one year growth hormone (GH) treatment in adults with GH deficiency.

An increased carotid arterial intima-media thickness (IMT) has been reported in hypopituitary adults untreated for GH deficiency. In the present study, the effect of GH replacement on IMT and cardiovascular risk factors was prospectively investigated, in GH deficiency patients treated at a mean dose of 1 UI/day during 1 yr (n = 22) and 2 yr (n = 11). The IMT measurements were performed by the same experienced physician, and the coefficient of variation (calculated in two control groups) was below 6.5%. IMT at baseline was related to conventional risk factors. After 1 yr GH treatment, IMT decreased from 0.78 +/- 0.03 mm to 0.70 +/- 0.03 mm (P < 0.001). The decrement was observed in 21 of 22 patients. After 2 yr GH treatment, IMT had stabilized at 0.70 +/- 0.04 mm and remained significantly different from baseline values (P < 0.003). GH treatment resulted in a moderate decrease in waist circumference and body fat mass and an increase in VO2 max. Conventional cardiovascular risk factors were unmodified except for a transient 10% decrease in low-density lipoprotein cholesterol at 6 months. The contrast between the limited metabolic effect of treatment and the importance and precocity of the changes in IMT suggests that the decrease in IMT was not exclusively attributable to a reversal in the atherosclerotic process. A direct parietal effect of GH replacement on the arterial wall might also be involved. The consequences, in terms of cardiovascular risk, should be established by randomized prospective trials.

Adult↗
PubMed1989

Normal brainstem auditory evoked potentials in adult hypothyroidism.

Nervous system dysfunction and hearing loss are part of the clinical picture of hypothyroidism. Several studies on visual evoked potential and two brainstem auditory evoked potential studies have shown abnormalities in this disease that are reversible with treatment. It has been suggested that visual evoked potential and brainstem auditory evoked potential could be useful to evaluate the effects of hypothyroidism on the central nervous system and to monitor the response to treatment. We recorded brainstem auditory evoked potentials in 15 adult hypothyroid patients immediately before treatment. All patients were women, ranging in age from 34 to 82 years. Fourteen also had an audiometric study. In five patients, both tests were repeated 20 to 22 months after treatment. Audiometry showed that hearing loss increased with age, suggesting that hearing loss in these patients could be secondary more to aging than to hypothyroidism. When compared to sex-matched controls of similar ages, our patients showed no statistically significant differences in brainstem auditory evoked potentials before treatment. Brainstem auditory evoked potential values were not modified in the five patients whose tests were repeated after treatment. The normality of these results raises serious objections to the clinical use of brainstem auditory evoked potential for central nervous system evaluation and therapy monitoring in adult hypothyroidism.

Adult↗