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Biomedical subjects

D J Oliver

Publications and source records attributed to D J Oliver.

At least 19 recordsLinked to original sources
PubMed1995

Glycine decarboxylase: protein chemistry and molecular biology of the major protein in leaf mitochondria.

The four component proteins of the glycine decarboxylase multienzyme complex (the P-, H-, T-, and L-proteins) comprise over one-third of the soluble proteins in mitochondria isolated from the leaves of C3 plants. Together with serine hydroxymethyltransferase, glycine decarboxylase converts glycine to serine and is the site of photorespiratory CO2 and NH3 release. The component proteins of the complex are encoded on nuclear genes with N-terminal presequences that target them to the mitochondria. The isolated complex readily dissociates into its component proteins and reassociates into the intact complex in vitro. Because of the intimate association between photosynthesis and photorespiration, the proteins of the complex are present at higher levels in leaves in the light. The expression of these genes is controlled at the transcriptional level and the kinetics of expression are closely related to those of the small subunit of Rubisco. Deletion analysis of fusions between the promoter of the H-protein of the complex and the reporter gene beta-glucuronidase in transgenic tobacco has identified a region responsible for the tissue specificity and light dependence of gene expression. Gel shift experiments show that a nuclear protein in leaves binds to this region. Glycine decarboxylase has proven to be an excellent system for studying problems in plant biochemistry ranging from protein-protein interactions to control of gene expression.

Amino Acid Oxidoreductases↗
PubMed1995

Timing of surgery during the menstrual cycle for breast cancer: possible role of growth factors.

Premenopausal patients undergoing surgery for breast cancer were prospectively studied. Data regarding menstrual history, pathological parameters and hormone receptor status were collected. Serum oestradiol, prolactin and progesterone levels, tumour epidermal growth factor receptor (EGFR) levels, tumour epidermal growth factor (EGF) levels and flow cytometry were measured. Patients were allocated to the follicular or luteal phase of their cycle both by history and progesterone level. No significant differences were seen in hormone receptor levels, pathological parameters or EGF levels between the two groups. EGFR levels were significantly higher in women undergoing surgery during the follicular phase of their cycle, when classified by menstrual history. Patients operated on during this phase have previously been found to have a poorer prognosis, and these results may provide a basis for this finding. This may have implications for prognosis and timing of surgery, and further investigation is warranted.

Adult↗
PubMed1995

Light-dependent and tissue-specific expression of the H-protein of the glycine decarboxylase complex.

Glycine decarboxylase is a mitochondrial enzyme complex, which is the site of photorespiratory CO2 and NH3 release. Although the proteins that constitute the complex are located within the mitochondria, because of their intimate association with photosynthesis their expression is controlled by light. Comparisons of the kinetics of mRNA accumulation between the small subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase and the H-protein of glycine decarboxylase during the greening of etiolated Arabidopsis thaliana suggest that their expression is controlled in parallel. A genomic clone for the H-protein (gdcH) was isolated from Arabidopsis and sequenced. The upstream region from -856 to +62 was fused to the beta-glucuronidase (GUS) reporter gene, and this construct was transformed into tobacco. This 5' upstream regulatory region appears to control GUS expression in a manner very similar to that of the endogenous H-protein gene. Constructs with deletions in the 5' upstream region were transformed into tobacco. These deletions revealed that light-dependent and tissue-specific expression was largely controlled by a 259-bp region between -376 and -117 bp. This region contains several putative GT boxes with the GGTTAA consensus core sequence. Once these strong light-dependent elements were removed, a second level of control was revealed. In constructs in which the gdcH 5' regulatory region was shortened to -117 bp or less, there was more GUS activity in the roots than in the leaves, and in dark-grown plants than in light-grown plants. This suggests that more proximal control elements may be responsible for the constitutive low levels of gene expression noted in all nonphotosynthetic tissues.

Amino Acid Oxidoreductases↗
PubMed1992

Stereotactic fine needle biopsy of the breast.

The experience of the use of the TRC-Mammotest machine for stereotactic fine needle biopsy (SFNB) of the breast in Perth is presented. During the period 20 October 1988 to 10 January 1990, 404 SFNB were performed on 389 women with impalpable, mammographically detected lesions of the breast. Surgical biopsy was performed in 73 cases, of which 38 were malignant, giving a benign to malignant ratio in less than 1:1. The sensitivity for detecting cancer was 95%, with a positive predictive value of 100%. Using a combination of the mammographic and cytologic rating for the likelihood of cancer, all the cancers were detected and no cancers have developed in those considered mammographically and cytologically benign. The importance of a combined assessment of mammography and cytology in the management of patients with mammographically detected abnormalities is stressed.

Biopsy, Needle↗
PubMed1990

Molecular cloning, transcriptional characterization, and sequencing of cDNA encoding the H-protein of the mitochondrial glycine decarboxylase complex in peas.

The glycine decarboxylase multienzyme complex is located in the mitochondrial matrix and catalyzes a key reaction of the photorespiratory C-2 cycle of C3 plants. The cDNA encoding the smallest subunit, the 13,900-dalton H-protein, of the glycine decarboxylase complex from pea (Pisum sativum) leaves was cloned, identified, characterized, and sequenced. The 678-nucleotide sequence contained a 495-nucleotide open reading frame capable of encoding the 165-amino-acid H-protein precursor. The N terminus of this protein contains a 34-amino-acid sequence which does not appear in the mature protein. This presequence resembles the amphiphilic helices observed with mitochondrial leader sequences in yeast. The 131-amino-acid mature protein from peas shares substantial homology with the enzyme isolated from chicken liver. The abundance of the H-protein mRNA was about 5-fold greater in light-grown pea seedlings compared to dark-grown seedlings. The amount of H-protein transcript increased within 4 h after the plants were transferred to white light and continued to increase up to 24 h. The time course for the accumulation of the H-protein mRNA was similar to that for the mRNA of the small subunit of ribulose-1,5-bisphosphate carboxylase.

Amino Acid Oxidoreductases↗
PubMed1990

Villous adenomas of the duodenum and an unusual variant.

We report two cases of villous adenoma of the duodenum, one arising from the main papilla and the other from the accessory papilla. Both were managed by local resection. In one case endoscopic biopsies and intraoperative frozen sections were negative for carcinoma but histology of the locally resected specimen revealed a focus of invasive adenocarcinoma. Villous adenomas of the duodenum have a high risk of malignant change and foci of carcinoma can be missed on endoscopic biopsy. The literature is reviewed and the clinical, diagnostic, pathological and therapeutic aspects of villous adenomas of the duodenum are discussed.

Adenocarcinoma↗
PubMed1988

Monoclonal antibodies as tools in membrane biochemistry. Identification and partial characterization of the dicarboxylate transporter from pea leaf mitochondria.

Monoclonal antibodies specific for the dicarboxylate transporter of pea mitochondria were prepared and used to identify this substrate carrier. The hybridoma library was derived from mice that had been immunized with total mitochondrial membranes. The monoclonal antibodies specific for the dicarboxylate transporter were selected by screening hybridoma supernatants for their ability to inhibit malate- and succinate-dependent oxalacetate reduction by osmotically shocked pea leaf mitochondria. Three monoclonal antibodies were shown to be specific for the dicarboxylate transporter by their ability to 1) inhibit malate and succinate metabolism without affecting alpha-ketoglutarate, citrate, pyruvate, glycine, glutamate, or aspartate metabolism by mitochondria and 2) inhibit malate uptake by a partially purified transporter fraction reconstituted into asolectin vesicles. The dicarboxylate transporter was identified by Western blotting and immunoprecipitation and had an apparent molecular mass of 26,000 Da. The techniques described should prove useful for identifying a number of membrane proteins that can be assayed in situ but are difficult to assay following dissolution of the membrane.

Aminomethyltransferase↗
PubMed1988

Sulfur-dependent inhibition of protein and RNA synthesis by iron-grown Thiobacillus ferrooxidans.

The addition of sulfur to iron-grown Thiobacillus ferrooxidans resulted in a rapid inhibition in the rates of protein synthesis and RNA synthesis. The inhibition of both functions was measured within 15 to 30 min and was maximal between 70 and 90% compared to the iron-grown controls. DNA synthesis, carbon dioxide fixation, and short-term ferrous oxidation rates of the bacteria growing on ferrous ions were not effected by sulfur addition, indicating that the sulfur addition was not perturbing general cellular energy metabolism. The inhibition caused by sulfur mimicked the effect of the RNA synthesis inhibitor, rifampicin, which inhibited both RNA and protein synthesis, but did not correspond with the translational inhibitor, chloramphenicol, which inhibited only protein synthesis in the first hour. Since chloramphenicol pretreatment did not block the sulfur effect, the inhibition of RNA synthesis following sulfur addition was not mediated through protein synthesis.

Bacterial Proteins↗
PubMed1986

Light-induced increases in the glycine decarboxylase multienzyme complex from pea leaf mitochondria.

The rates of mitochondrial glycine oxidation estimated by CO2-release and glycine-bicarbonate exchange activities in fully greened tissues are approximately 10 times greater than those of etiolated pea leaves and potato tuber mitochondria. The release of CO2 from glycine in intact mitochondria isolated from dark-grown and nonphotosynthetic tissues was sensitive to inhibitors of mitochondrial electron transport, glycine transport, and glycine decarboxylase activities. The CO2-release and glycine-bicarbonate exchange activities in crude mitochondrial protein extracts from light-grown versus dark-grown tissues exhibited light/dark ratios of 12 and 21, respectively. This suggests that the differences in capacity to oxidize glycine reside with the glycine decarboxylase enzyme complex itself. The complex is composed of four subunit enzymes, the P, H, T, and L proteins, which can be isolated individually and reconstituted into the active enzyme. The activities of P and T proteins were at least 10 times higher in fully greened pea leaves than in the etiolated tissue, while the H and L protein activities were four times higher in these same tissues. The levels of P and T proteins detected immunochemically were substantially lower in total mitochondrial extracts prepared from leaves of dark-grown pea seedlings. Labeling of whole pea seedlings and in vitro protein synthesis with isolated mitochondria indicated that the entire glycine decarboxylase enzyme complex is cytoplasmically synthesized and therefore encoded by the nucleus. Polypeptides synthesized from total leaf polyadenylated mRNA isolated from leaves of both the dark-grown and light-treated peas indicated the presence of P protein. This implies that translatable messages for this enzyme are present at some level throughout leaf development.

Amino Acid Oxidoreductases↗
PubMed1986

Glycine decarboxylase multienzyme complex. Purification and partial characterization from pea leaf mitochondria.

The P, H, and T proteins of the glycine cleavage system have been purified separately from pea leaf mitochondria and demonstrate molecular weights of 98,000, 15,500, and 45,000, respectively, by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The molecular weight of P protein by gel filtration was 210,000, indicating that this enzyme has a native homodimer conformation. Reconstitution assays containing purified P, H, and T proteins and yeast lipoamide dehydrogenase catalyze the oxidation of glycine and demonstrate a strict dependence on pyridoxal phosphate, tetrahydrofolate, NAD+, and dithiothreitol. The released CO2, methylamine-H protein intermediate, and methylenetetrahydrofolate are produced in stoichiometric amounts from glycine during the cleavage reaction. H protein acts as co-substrate with glycine during the decarboxylation reaction, demonstrating an apparent Km value of 2.2 microM. P and H protein alone jointly catalyze the glycine carboxyl-14 CO2 exchange reaction in the presence of pyridoxal phosphate and dithiothreitol. L protein of the glycine cleavage system was immunopurified using monoclonal antibodies. Antigenic and molecular weight similarities of the L protein with the lipoamide dehydrogenase component of the pyruvate dehydrogenase complex were shown suggesting the possibility of common isomers of lipoamide dehydrogenase for the two enzyme complexes.

Amino Acid Oxidoreductases↗
PubMed1985

Medical management of intestinal obstruction in patients with advanced malignant disease. A clinical and pathological study.

A clinical and pathological study was made of 40 patients with intestinal obstruction due to far-advanced abdominal and/or pelvic malignant disease. Surgical intervention was feasible in only 2 cases. The remaining 38 patients were managed medically without intravenous fluids and nasogastric suction. Obstructive symptoms such as intestinal colic, vomiting, and diarrhoea were effectively controlled by drugs.

Abdominal Neoplasms↗