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P Dudley

Publications and source records attributed to P Dudley.

10 recordsLinked to original sources
PubMed1999

Expression of a higher-plant chloroplast psbD promoter in a cyanobacterium (Synechococcus sp. strain PCC7942) reveals a conserved cis-element, designated PGT, that differentially interacts with sequence-specific binding factors during leaf development.

The chloroplast psbD gene, which encodes the D2 subunit of photosystem II, is regulated by a blue light-responsive promoter (BLRP). We tested the ability of different regions of the barley (Hordeum vulagare) BLRP to drive transcription of the lacZ reporter gene in genomic transformants of Synechococcus sp. strain PCC7942. The barley BLRP was transcribed in Synechococcus from the same initiation sites that are used in plant chloroplasts in vivo. A region of the BLRP, residing between -83 and -112 bp upstream from the transcription initiation sites, functioned as a negative element in Synechococcus. Nucleotide sequences within this region are conserved among the psbD genes of several monocots and dicots, and with the nuclear negative regulatory element GT. Thus this new cis-element was designated Plastid GT, PGT. Proteins from chloroplasts of barley and Arabidopsis thaliana interacted with PGT in a sequence-specific and developmental-dependent manner. The DNA-protein complexes from Arabidopsis chloroplasts are composed of 60- and 38-kDa polypeptides. We postulate that GT and PGT have evolved in the nucleus and chloroplast, respectively, from a common ancestral regulatory element.

Arabidopsis↗
PubMed1997

Developmental regulation of the plant mitochondrial matrix located HSP70 chaperone and its role in protein import.

Changes in the level of the mitochondrial chaperone mtHSP70 have been investigated in pea (Pisum sativum) leaf mitochondria by Western blot analysis and quantified by scanning densitometry. As pea leaves develop (from 6 days to 30 days of age) the levels of mtHSP70 decrease. Analysis of the levels of the alpha subunit of the F1ATPase show that the levels of this protein remain constant throughout the same developmental period, whereas the levels of the alternative oxidase increase. In vitro import of the alternative oxidase precursor protein into pea leaf mitochondria from day 6 to day 30 leaves and quantification by scanning densitometry indicates that protein import efficiency decreases with increasing maturity of the plant cell. Results are discussed in terms of how changing levels of the mtHSP70 chaperone, as a result of plant cell development, influence the efficiency of protein import.

Blotting, Western↗
PubMed1996

Targeting the plant alternative oxidase protein to Schizosaccharomyces pombe mitochondria confers cyanide-insensitive respiration.

The Sauromatum guttatum alternative oxidase has been expressed in Schizosaccharomyces pombe under the control of the thiamine-repressible nmt1 promoter. Alternative oxidase protein and activity were detected both in spheroplasts and isolated mitochondria, indicating that the enzyme is expressed in a functional form and confers cyanide-resistant respiration to S. pombe, which is sensitive to inhibition by octyl-gallate. Protein import studies revealed that the precursor form of the alternative oxidase protein is efficiently imported into isolated mitochondria and processed to its mature form comparable to that observed with potato mitochondria. Western blot analysis and respiratory studies revealed that the alternative oxidase protein is expressed in the inner mitochondrial membrane in its reduced (active) form. Treatment of mitochondria with diamide and dithiothreitol resulted in interconversion of the reduced and oxidized species and modulation of respiratory activity. The addition of pyruvate did not effect either the respiratory rate or expression of the reduced species of the protein. To our knowledge this is the first time that the alternative oxidase has been effectively targeted to and integrated into the inner mitochondrial membrane of S. pombe, and we conclude that the expression of a single polypeptide is sufficient for alternative oxidase activity.

Antimycin A↗
PubMed1989

Computer-aided self-instruction training with hearing-impaired impulsive students.

This study explored the utility of computer-aided, self-instruction training for enhancing reflective problem-solving among impulsive hearing-impaired adolescent students. Sixteen moderate to severely hearing-impaired students were randomly assigned to either a treatment or control condition. The self-instruction treatment condition consisted of training to solve visual problems using a modified version of the LOGO computer language (REFLECT) and videotape feedback. The control condition consisted of LOGO problem-solving without self-instruction. Instruction took place over 12 weeks. On two dependent measures of impulsive problem-solving behaviors, students in the treatment condition demonstrated significantly improved problem-solving ability.

Adolescent↗
PubMed1984

The effect of oxygen inhalation and intravenous naftidrofuryl on the transcutaneous partial oxygen pressure in ischaemic lower limbs.

The effect of oxygen inhalation at atmospheric pressure and Naftidrofuryl infusion (N) on the TCpO2 is shown. At the central control site--5 cm below the midclavicular line--oxygen inhalation produced a significant increase in TCpO2, whereas there was no change after Naftidrofuryl infusion. At the 10 cm below-knee site, there were significant rises after oxygen inhalation alone, Naftidrofuryl alone and both combined. The study was conducted on 20 patients (23 legs). It is suggested that this study can form the basis for a regimen to improve the viability of ischaemic limbs showing borderline TCpO2 readings, and increase the chances of a successful below-knee amputation.

Adolescent↗
PubMed1983

Relationship between untreated and insulin-treated diabetes and vascular relaxation.

The effects of untreated and insulin-treated streptozotocin-induced diabetes on the ability of the rat aorta maximally contracted with either 10(-4) M phenylephrine (PE) or 70 mM KCl to relax in response to 10(-5) to 10(-2) M theophylline (Theo) were examined. No significant differences between Theo-induced relaxation of the PE-contracture in control, untreated diabetic and insulin-treated diabetic aortas were observed until 12 weeks after the induction of diabetes. Twelve weeks after the induction of diabetes, the untreated diabetic aortas exhibited less relaxation in response to Theo than did the controls. This diabetes-induced decrease in relaxation of the PE-contracture was not reversed by insulin-treatment. Diabetes increased the ability of the K-contracted aortas to relax in response to Theo 4 weeks after the induction of diabetes. This diabetes-induced increase in the Theo-induced relaxation of the K-contracture was reversed by insulin-treatment. Even though there was no difference in the sensitivity of the PE-contracted tissues to Theo, the K-stimulated tissues from the untreated diabetic animals were more susceptible to the relaxing effects of Theo than either the control or insulin-treated aortas. These results indicate that diabetes affects the ability of the vascular smooth muscle to relax in response to theophylline, depending on the length of time in the diabetic state, the type of stimulus (PE or KCl) and whether or not insulin-treatment is applied.

Animals↗